WorldWideScience

Sample records for imrt dose optimization

  1. A Method for Correcting IMRT Optimizer Heterogeneity Dose Calculations

    International Nuclear Information System (INIS)

    Zacarias, Albert S.; Brown, Mellonie F.; Mills, Michael D.

    2010-01-01

    Radiation therapy treatment planning for volumes close to the patient's surface, in lung tissue and in the head and neck region, can be challenging for the planning system optimizer because of the complexity of the treatment and protected volumes, as well as striking heterogeneity corrections. Because it is often the goal of the planner to produce an isodose plan with uniform dose throughout the planning target volume (PTV), there is a need for improved planning optimization procedures for PTVs located in these anatomical regions. To illustrate such an improved procedure, we present a treatment planning case of a patient with a lung lesion located in the posterior right lung. The intensity-modulated radiation therapy (IMRT) plan generated using standard optimization procedures produced substantial dose nonuniformity across the tumor caused by the effect of lung tissue surrounding the tumor. We demonstrate a novel iterative method of dose correction performed on the initial IMRT plan to produce a more uniform dose distribution within the PTV. This optimization method corrected for the dose missing on the periphery of the PTV and reduced the maximum dose on the PTV to 106% from 120% on the representative IMRT plan.

  2. A fast dose calculation method based on table lookup for IMRT optimization

    International Nuclear Information System (INIS)

    Wu Qiuwen; Djajaputra, David; Lauterbach, Marc; Wu Yan; Mohan, Radhe

    2003-01-01

    This note describes a fast dose calculation method that can be used to speed up the optimization process in intensity-modulated radiotherapy (IMRT). Most iterative optimization algorithms in IMRT require a large number of dose calculations to achieve convergence and therefore the total amount of time needed for the IMRT planning can be substantially reduced by using a faster dose calculation method. The method that is described in this note relies on an accurate dose calculation engine that is used to calculate an approximate dose kernel for each beam used in the treatment plan. Once the kernel is computed and saved, subsequent dose calculations can be done rapidly by looking up this kernel. Inaccuracies due to the approximate nature of the kernel in this method can be reduced by performing scheduled kernel updates. This fast dose calculation method can be performed more than two orders of magnitude faster than the typical superposition/convolution methods and therefore is suitable for applications in which speed is critical, e.g., in an IMRT optimization that requires a simulated annealing optimization algorithm or in a practical IMRT beam-angle optimization system. (note)

  3. Study of dose calculation and beam parameters optimization with genetic algorithm in IMRT

    International Nuclear Information System (INIS)

    Chen Chaomin; Tang Mutao; Zhou Linghong; Lv Qingwen; Wang Zhuoyu; Chen Guangjie

    2006-01-01

    Objective: To study the construction of dose calculation model and the method of automatic beam parameters selection in IMRT. Methods: The three-dimension convolution dose calculation model of photon was constructed with the methods of Fast Fourier Transform. The objective function based on dose constrain was used to evaluate the fitness of individuals. The beam weights were optimized with genetic algorithm. Results: After 100 iterative analyses, the treatment planning system produced highly conformal and homogeneous dose distributions. Conclusion: the throe-dimension convolution dose calculation model of photon gave more accurate results than the conventional models; genetic algorithm is valid and efficient in IMRT beam parameters optimization. (authors)

  4. Evaluation of dose prediction errors and optimization convergence errors of deliverable-based head-and-neck IMRT plans computed with a superposition/convolution dose algorithm

    International Nuclear Information System (INIS)

    Mihaylov, I. B.; Siebers, J. V.

    2008-01-01

    The purpose of this study is to evaluate dose prediction errors (DPEs) and optimization convergence errors (OCEs) resulting from use of a superposition/convolution dose calculation algorithm in deliverable intensity-modulated radiation therapy (IMRT) optimization for head-and-neck (HN) patients. Thirteen HN IMRT patient plans were retrospectively reoptimized. The IMRT optimization was performed in three sequential steps: (1) fast optimization in which an initial nondeliverable IMRT solution was achieved and then converted to multileaf collimator (MLC) leaf sequences; (2) mixed deliverable optimization that used a Monte Carlo (MC) algorithm to account for the incident photon fluence modulation by the MLC, whereas a superposition/convolution (SC) dose calculation algorithm was utilized for the patient dose calculations; and (3) MC deliverable-based optimization in which both fluence and patient dose calculations were performed with a MC algorithm. DPEs of the mixed method were quantified by evaluating the differences between the mixed optimization SC dose result and a MC dose recalculation of the mixed optimization solution. OCEs of the mixed method were quantified by evaluating the differences between the MC recalculation of the mixed optimization solution and the final MC optimization solution. The results were analyzed through dose volume indices derived from the cumulative dose-volume histograms for selected anatomic structures. Statistical equivalence tests were used to determine the significance of the DPEs and the OCEs. Furthermore, a correlation analysis between DPEs and OCEs was performed. The evaluated DPEs were within ±2.8% while the OCEs were within 5.5%, indicating that OCEs can be clinically significant even when DPEs are clinically insignificant. The full MC-dose-based optimization reduced normal tissue dose by as much as 8.5% compared with the mixed-method optimization results. The DPEs and the OCEs in the targets had correlation coefficients greater

  5. Reducing dose calculation time for accurate iterative IMRT planning

    International Nuclear Information System (INIS)

    Siebers, Jeffrey V.; Lauterbach, Marc; Tong, Shidong; Wu Qiuwen; Mohan, Radhe

    2002-01-01

    A time-consuming component of IMRT optimization is the dose computation required in each iteration for the evaluation of the objective function. Accurate superposition/convolution (SC) and Monte Carlo (MC) dose calculations are currently considered too time-consuming for iterative IMRT dose calculation. Thus, fast, but less accurate algorithms such as pencil beam (PB) algorithms are typically used in most current IMRT systems. This paper describes two hybrid methods that utilize the speed of fast PB algorithms yet achieve the accuracy of optimizing based upon SC algorithms via the application of dose correction matrices. In one method, the ratio method, an infrequently computed voxel-by-voxel dose ratio matrix (R=D SC /D PB ) is applied for each beam to the dose distributions calculated with the PB method during the optimization. That is, D PB xR is used for the dose calculation during the optimization. The optimization proceeds until both the IMRT beam intensities and the dose correction ratio matrix converge. In the second method, the correction method, a periodically computed voxel-by-voxel correction matrix for each beam, defined to be the difference between the SC and PB dose computations, is used to correct PB dose distributions. To validate the methods, IMRT treatment plans developed with the hybrid methods are compared with those obtained when the SC algorithm is used for all optimization iterations and with those obtained when PB-based optimization is followed by SC-based optimization. In the 12 patient cases studied, no clinically significant differences exist in the final treatment plans developed with each of the dose computation methodologies. However, the number of time-consuming SC iterations is reduced from 6-32 for pure SC optimization to four or less for the ratio matrix method and five or less for the correction method. Because the PB algorithm is faster at computing dose, this reduces the inverse planning optimization time for our implementation

  6. Peripheral doses from pediatric IMRT

    International Nuclear Information System (INIS)

    Klein, Eric E.; Maserang, Beth; Wood, Roy; Mansur, David

    2006-01-01

    Peripheral dose (PD) data exist for conventional fields (≥10 cm) and intensity-modulated radiotherapy (IMRT) delivery to standard adult-sized phantoms. Pediatric peripheral dose reports are limited to conventional therapy and are model based. Our goal was to ascertain whether data acquired from full phantom studies and/or pediatric models, with IMRT treatment times, could predict Organ at Risk (OAR) dose for pediatric IMRT. As monitor units (MUs) are greater for IMRT, it is expected IMRT PD will be higher; potentially compounded by decreased patient size (absorption). Baseline slab phantom peripheral dose measurements were conducted for very small field sizes (from 2 to 10 cm). Data were collected at distances ranging from 5 to 72 cm away from the field edges. Collimation was either with the collimating jaws or the multileaf collimator (MLC) oriented either perpendicular or along the peripheral dose measurement plane. For the clinical tests, five patients with intracranial or base of skull lesions were chosen. IMRT and conventional three-dimensional (3D) plans for the same patient/target/dose (180 cGy), were optimized without limitation to the number of fields or wedge use. Six MV, 120-leaf MLC Varian axial beams were used. A phantom mimicking a 3-year-old was configured per Center for Disease Control data. Micro (0.125 cc) and cylindrical (0.6 cc) ionization chambers were appropriated for the thyroid, breast, ovaries, and testes. The PD was recorded by electrometers set to the 10 -10 scale. Each system set was uniquely calibrated. For the slab phantom studies, close peripheral points were found to have a higher dose for low energy and larger field size and when MLC was not deployed. For points more distant from the field edge, the PD was higher for high-energy beams. MLC orientation was found to be inconsequential for the small fields tested. The thyroid dose was lower for IMRT delivery than that predicted for conventional (ratio of IMRT/cnventional ranged from

  7. GPU-Monte Carlo based fast IMRT plan optimization

    Directory of Open Access Journals (Sweden)

    Yongbao Li

    2014-03-01

    Full Text Available Purpose: Intensity-modulated radiation treatment (IMRT plan optimization needs pre-calculated beamlet dose distribution. Pencil-beam or superposition/convolution type algorithms are typically used because of high computation speed. However, inaccurate beamlet dose distributions, particularly in cases with high levels of inhomogeneity, may mislead optimization, hindering the resulting plan quality. It is desire to use Monte Carlo (MC methods for beamlet dose calculations. Yet, the long computational time from repeated dose calculations for a number of beamlets prevents this application. It is our objective to integrate a GPU-based MC dose engine in lung IMRT optimization using a novel two-steps workflow.Methods: A GPU-based MC code gDPM is used. Each particle is tagged with an index of a beamlet where the source particle is from. Deposit dose are stored separately for beamlets based on the index. Due to limited GPU memory size, a pyramid space is allocated for each beamlet, and dose outside the space is neglected. A two-steps optimization workflow is proposed for fast MC-based optimization. At first step, a rough dose calculation is conducted with only a few number of particle per beamlet. Plan optimization is followed to get an approximated fluence map. In the second step, more accurate beamlet doses are calculated, where sampled number of particles for a beamlet is proportional to the intensity determined previously. A second-round optimization is conducted, yielding the final result.Results: For a lung case with 5317 beamlets, 105 particles per beamlet in the first round, and 108 particles per beam in the second round are enough to get a good plan quality. The total simulation time is 96.4 sec.Conclusion: A fast GPU-based MC dose calculation method along with a novel two-step optimization workflow are developed. The high efficiency allows the use of MC for IMRT optimizations.--------------------------------Cite this article as: Li Y, Tian Z

  8. Automated IMRT planning with regional optimization using planning scripts.

    Science.gov (United States)

    Xhaferllari, Ilma; Wong, Eugene; Bzdusek, Karl; Lock, Michael; Chen, Jeff

    2013-01-07

    Intensity-modulated radiation therapy (IMRT) has become a standard technique in radiation therapy for treating different types of cancers. Various class solutions have been developed for simple cases (e.g., localized prostate, whole breast) to generate IMRT plans efficiently. However, for more complex cases (e.g., head and neck, pelvic nodes), it can be time-consuming for a planner to generate optimized IMRT plans. To generate optimal plans in these more complex cases which generally have multiple target volumes and organs at risk, it is often required to have additional IMRT optimization structures such as dose limiting ring structures, adjust beam geometry, select inverse planning objectives and associated weights, and additional IMRT objectives to reduce cold and hot spots in the dose distribution. These parameters are generally manually adjusted with a repeated trial and error approach during the optimization process. To improve IMRT planning efficiency in these more complex cases, an iterative method that incorporates some of these adjustment processes automatically in a planning script is designed, implemented, and validated. In particular, regional optimization has been implemented in an iterative way to reduce various hot or cold spots during the optimization process that begins with defining and automatic segmentation of hot and cold spots, introducing new objectives and their relative weights into inverse planning, and turn this into an iterative process with termination criteria. The method has been applied to three clinical sites: prostate with pelvic nodes, head and neck, and anal canal cancers, and has shown to reduce IMRT planning time significantly for clinical applications with improved plan quality. The IMRT planning scripts have been used for more than 500 clinical cases.

  9. Inverse planning IMRT

    International Nuclear Information System (INIS)

    Rosenwald, J.-C.

    2008-01-01

    The lecture addressed the following topics: Optimizing radiotherapy dose distribution; IMRT contributes to optimization of energy deposition; Inverse vs direct planning; Main steps of IMRT; Background of inverse planning; General principle of inverse planning; The 3 main components of IMRT inverse planning; The simplest cost function (deviation from prescribed dose); The driving variable : the beamlet intensity; Minimizing a 'cost function' (or 'objective function') - the walker (or skier) analogy; Application to IMRT optimization (the gradient method); The gradient method - discussion; The simulated annealing method; The optimization criteria - discussion; Hard and soft constraints; Dose volume constraints; Typical user interface for definition of optimization criteria; Biological constraints (Equivalent Uniform Dose); The result of the optimization process; Semi-automatic solutions for IMRT; Generalisation of the optimization problem; Driving and driven variables used in RT optimization; Towards multi-criteria optimization; and Conclusions for the optimization phase. (P.A.)

  10. Incorporating multi-leaf collimator leaf sequencing into iterative IMRT optimization

    International Nuclear Information System (INIS)

    Siebers, Jeffrey V.; Lauterbach, Marc; Keall, Paul J.; Mohan, Radhe

    2002-01-01

    Intensity modulated radiation therapy (IMRT) treatment planning typically considers beam optimization and beam delivery as separate tasks. Following optimization, a multi-leaf collimator (MLC) or other beam delivery device is used to generate fluence patterns for patient treatment delivery. Due to limitations and characteristics of the MLC, the deliverable intensity distributions often differ from those produced by the optimizer, leading to differences between the delivered and the optimized doses. Objective function parameters are then adjusted empirically, and the plan is reoptimized to achieve a desired deliverable dose distribution. The resulting plan, though usually acceptable, may not be the best achievable. A method has been developed to incorporate the MLC restrictions into the optimization process. Our in-house IMRT system has been modified to include the calculation of the deliverable intensity into the optimizer. In this process, prior to dose calculation, the MLC leaf sequencer is used to convert intensities to dynamic MLC sequences, from which the deliverable intensities are then determined. All other optimization steps remain the same. To evaluate the effectiveness of deliverable-based optimization, 17 patient cases have been studied. Compared with standard optimization plus conversion to deliverable beams, deliverable-based optimization results show improved isodose coverage and a reduced dose to critical structures. Deliverable-based optimization results are close to the original nondeliverable optimization results, suggesting that IMRT can overcome the MLC limitations by adjusting individual beamlets. The use of deliverable-based optimization may reduce the need for empirical adjustment of objective function parameters and reoptimization of a plan to achieve desired results

  11. Investigation of effective decision criteria for multiobjective optimization in IMRT.

    Science.gov (United States)

    Holdsworth, Clay; Stewart, Robert D; Kim, Minsun; Liao, Jay; Phillips, Mark H

    2011-06-01

    To investigate how using different sets of decision criteria impacts the quality of intensity modulated radiation therapy (IMRT) plans obtained by multiobjective optimization. A multiobjective optimization evolutionary algorithm (MOEA) was used to produce sets of IMRT plans. The MOEA consisted of two interacting algorithms: (i) a deterministic inverse planning optimization of beamlet intensities that minimizes a weighted sum of quadratic penalty objectives to generate IMRT plans and (ii) an evolutionary algorithm that selects the superior IMRT plans using decision criteria and uses those plans to determine the new weights and penalty objectives of each new plan. Plans resulting from the deterministic algorithm were evaluated by the evolutionary algorithm using a set of decision criteria for both targets and organs at risk (OARs). Decision criteria used included variation in the target dose distribution, mean dose, maximum dose, generalized equivalent uniform dose (gEUD), an equivalent uniform dose (EUD(alpha,beta) formula derived from the linear-quadratic survival model, and points on dose volume histograms (DVHs). In order to quantatively compare results from trials using different decision criteria, a neutral set of comparison metrics was used. For each set of decision criteria investigated, IMRT plans were calculated for four different cases: two simple prostate cases, one complex prostate Case, and one complex head and neck Case. When smaller numbers of decision criteria, more descriptive decision criteria, or less anti-correlated decision criteria were used to characterize plan quality during multiobjective optimization, dose to OARs and target dose variation were reduced in the final population of plans. Mean OAR dose and gEUD (a = 4) decision criteria were comparable. Using maximum dose decision criteria for OARs near targets resulted in inferior populations that focused solely on low target variance at the expense of high OAR dose. Target dose range, (D

  12. Optimization of dose distributions for adjuvant locoregional radiotherapy of gastric cancer by IMRT

    International Nuclear Information System (INIS)

    Lohr, F.; Dobler, B.; Mai, S.; Hermann, B.; Tiefenbacher, U.; Wieland, P.; Steil, V.; Wenz, F.

    2003-01-01

    Background and Purpose: Locoregional relapse is a problem frequently encountered with advanced gastric cancer. Data from the randomized Intergroup trial 116 suggest effectiveness of adjuvant radiochemotherapy, albeit with significant toxicity. The potential of intensity-modulated radiotherapy (IMRT) to reduce toxicity by significantly reducing maximum and median doses to organs at risk while still applying sufficient dose to the target volume in the upper abdomen was studied. Patient and Methods: For a typical configuration of target volumes and organs, a step-and-shoot IMRT plan (eight beam orientations), developed as a class solution for treatment of tumors in the upper abdomen (Figures 1 to 3), a conventional plan, a combination of the conventional plan with a kidney-sparing boost plan, and a conventional plan with noncoplanar ap and pa fields for improved kidney sparing were compared with respect to coverage of target volume and dose to organs at risk with a dose of 45 Gy delivered as the median dose to the target volume. Results: When using the conventional three-dimensionally planned box techniques, the right kidney could be kept below tolerance, but median dose to the left kidney amounted to between 14.8 and 26.9 Gy, depending on the plan. IMRT reduced the median dose to the left kidney to 10.5 Gy, while still keeping the dose to the right kidney 90% of prescription dose were delivered to > 90% of target volume with IMRT (Table 1). Conclusion: IMRT has the potential to deliver efficient doses to target volumes in the upper abdomen, while delivering dose to organs at risk in a more advantageous fashion than a conventional technique. For clinical implementation, the possibility of extensive organ motion in the upper abdomen has to be taken into account for treatment planning and patient positioning. The multitude of potential risks related to its application has to be the subject of thorough follow-up and further studies. (orig.)

  13. Is uniform target dose possible in IMRT plans in the head and neck?

    International Nuclear Information System (INIS)

    Vineberg, K.A.; Eisbruch, A.; Coselmon, M.M.; McShan, D.L.; Kessler, M.L.; Fraass, B.A.

    2002-01-01

    Purpose: Various published reports involving intensity-modulated radiotherapy (IMRT) plans developed using automated optimization (inverse planning) have demonstrated highly conformal plans. These reported conformal IMRT plans involve significant target dose inhomogeneity, including both overdosage and underdosage within the target volume. In this study, we demonstrate the development of optimized beamlet IMRT plans that satisfy rigorous dose homogeneity requirements for all target volumes (e.g., ±5%), while also sparing the parotids and other normal structures. Methods and Materials: The treatment plans of 15 patients with oropharyngeal cancer who were previously treated with forward-planned multisegmental IMRT were planned again using an automated optimization system developed in-house. The optimization system allows for variable sized beamlets computed using a three-dimensional convolution/superposition dose calculation and flexible cost functions derived from combinations of clinically relevant factors (costlets) that can include dose, dose-volume, and biologic model-based costlets. The current study compared optimized IMRT plans designed to treat the various planning target volumes to doses of 66, 60, and 54 Gy with varying target dose homogeneity while using a flexible optimization cost function to minimize the dose to the parotids, spinal cord, oral cavity, brainstem, submandibular nodes, and other structures. Results: In all cases, target dose uniformity was achieved through steeply varying dose-based costs. Differences in clinical plan evaluation metrics were evaluated for individual cases (eight different target homogeneity costlets), and for the entire cohort of plans. Highly conformal plans were achieved, with significant sparing of both the contralateral and ipsilateral parotid glands. As the homogeneity of the target dose distributions was allowed to decrease, increased sparing of the parotids (and other normal tissues) may be achieved. However, it

  14. TH-E-BRE-08: GPU-Monte Carlo Based Fast IMRT Plan Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y; Tian, Z; Shi, F; Jiang, S; Jia, X [The University of Texas Southwestern Medical Ctr, Dallas, TX (United States)

    2014-06-15

    Purpose: Intensity-modulated radiation treatment (IMRT) plan optimization needs pre-calculated beamlet dose distribution. Pencil-beam or superposition/convolution type algorithms are typically used because of high computation speed. However, inaccurate beamlet dose distributions, particularly in cases with high levels of inhomogeneity, may mislead optimization, hindering the resulting plan quality. It is desire to use Monte Carlo (MC) methods for beamlet dose calculations. Yet, the long computational time from repeated dose calculations for a number of beamlets prevents this application. It is our objective to integrate a GPU-based MC dose engine in lung IMRT optimization using a novel two-steps workflow. Methods: A GPU-based MC code gDPM is used. Each particle is tagged with an index of a beamlet where the source particle is from. Deposit dose are stored separately for beamlets based on the index. Due to limited GPU memory size, a pyramid space is allocated for each beamlet, and dose outside the space is neglected. A two-steps optimization workflow is proposed for fast MC-based optimization. At first step, rough beamlet dose calculations is conducted with only a small number of particles per beamlet. Plan optimization is followed to get an approximated fluence map. In the second step, more accurate beamlet doses are calculated, where sampled number of particles for a beamlet is proportional to the intensity determined previously. A second-round optimization is conducted, yielding the final Result. Results: For a lung case with 5317 beamlets, 10{sup 5} particles per beamlet in the first round, and 10{sup 8} particles per beam in the second round are enough to get a good plan quality. The total simulation time is 96.4 sec. Conclusion: A fast GPU-based MC dose calculation method along with a novel two-step optimization workflow are developed. The high efficiency allows the use of MC for IMRT optimizations.

  15. Direct aperture optimization for IMRT using Monte Carlo generated beamlets

    International Nuclear Information System (INIS)

    Bergman, Alanah M.; Bush, Karl; Milette, Marie-Pierre; Popescu, I. Antoniu; Otto, Karl; Duzenli, Cheryl

    2006-01-01

    This work introduces an EGSnrc-based Monte Carlo (MC) beamlet does distribution matrix into a direct aperture optimization (DAO) algorithm for IMRT inverse planning. The technique is referred to as Monte Carlo-direct aperture optimization (MC-DAO). The goal is to assess if the combination of accurate Monte Carlo tissue inhomogeneity modeling and DAO inverse planning will improve the dose accuracy and treatment efficiency for treatment planning. Several authors have shown that the presence of small fields and/or inhomogeneous materials in IMRT treatment fields can cause dose calculation errors for algorithms that are unable to accurately model electronic disequilibrium. This issue may also affect the IMRT optimization process because the dose calculation algorithm may not properly model difficult geometries such as targets close to low-density regions (lung, air etc.). A clinical linear accelerator head is simulated using BEAMnrc (NRC, Canada). A novel in-house algorithm subdivides the resulting phase space into 2.5x5.0 mm 2 beamlets. Each beamlet is projected onto a patient-specific phantom. The beamlet dose contribution to each voxel in a structure-of-interest is calculated using DOSXYZnrc. The multileaf collimator (MLC) leaf positions are linked to the location of the beamlet does distributions. The MLC shapes are optimized using direct aperture optimization (DAO). A final Monte Carlo calculation with MLC modeling is used to compute the final dose distribution. Monte Carlo simulation can generate accurate beamlet dose distributions for traditionally difficult-to-calculate geometries, particularly for small fields crossing regions of tissue inhomogeneity. The introduction of DAO results in an additional improvement by increasing the treatment delivery efficiency. For the examples presented in this paper the reduction in the total number of monitor units to deliver is ∼33% compared to fluence-based optimization methods

  16. SU-E-T-488: An Iso-Dose Curve Based Interactive IMRT Optimization System for Physician-Driven Plan Tuning

    International Nuclear Information System (INIS)

    Shi, F; Tian, Z; Jia, X; Jiang, S; Zarepisheh, M; Cervino, L

    2014-01-01

    Purpose: In treatment plan optimization for Intensity Modulated Radiation Therapy (IMRT), after a plan is initially developed by a dosimetrist, the attending physician evaluates its quality and often would like to improve it. As opposed to having the dosimetrist implement the improvements, it is desirable to have the physician directly and efficiently modify the plan for a more streamlined and effective workflow. In this project, we developed an interactive optimization system for physicians to conveniently and efficiently fine-tune iso-dose curves. Methods: An interactive interface is developed under C++/Qt. The physician first examines iso-dose lines. S/he then picks an iso-dose curve to be improved and drags it to a more desired configuration using a computer mouse or touchpad. Once the mouse is released, a voxel-based optimization engine is launched. The weighting factors corresponding to voxels between the iso-dose lines before and after the dragging are modified. The underlying algorithm then takes these factors as input to re-optimize the plan in near real-time on a GPU platform, yielding a new plan best matching the physician's desire. The re-optimized DVHs and iso-dose curves are then updated for the next iteration of modifications. This process is repeated until a physician satisfactory plan is achieved. Results: We have tested this system for a series of IMRT plans. Results indicate that our system provides the physicians an intuitive and efficient tool to edit the iso-dose curves according to their preference. The input information is used to guide plan re-optimization, which is achieved in near real-time using our GPU-based optimization engine. Typically, a satisfactory plan can be developed by a physician in a few minutes using this tool. Conclusion: With our system, physicians are able to manipulate iso-dose curves according to their preferences. Preliminary results demonstrate the feasibility and effectiveness of this tool

  17. Direct aperture optimization of breast IMRT and the dosimetric impact of respiration motion

    International Nuclear Information System (INIS)

    Zhang Guowei; Jiang Ziping; Shepard, David; Zhang Bin; Yu, Cedric

    2006-01-01

    We have studied the application of direct aperture optimization (DAO) as an inverse planning tool for breast IMRT. Additionally, we have analysed the impact of respiratory motion on the quality of the delivered dose distribution. From this analysis, we have developed guidelines for balancing the desire for a high-quality optimized plan with the need to create a plan that will not degrade significantly in the presence of respiratory motion. For a DAO optimized breast IMRT plan, the tangential fields incorporate a flash field to cover the range of respiratory motion. The inverse planning algorithm then optimizes the shapes and weights of additional segments that are delivered in combination with the open fields. IMRT plans were generated using DAO with the relative weights of the open segments varied from 0% to 95%. To assess the impact of breathing motion, the dose distribution for the optimized IMRT plan was recalculated with the isocentre sampled from a predefined distribution in a Monte Carlo convolution/superposition dose engine with the breast simulated as a rigid object. The motion amplitudes applied in this study ranged from 0.5 to 2.0 cm. For a range of weighting levels assigned to the open field, comparisons were made between the static plans and the plans recalculated with motion. For the static plans, we found that uniform dose distributions could be generated with relative weights for the open segments equal to and below 80% and unacceptable levels of underdosage were observed with the weights larger than 80%. When simulated breathing motion was incorporated into the dose calculation, we observed a loss in dose uniformity as the weight of the open field was decreased to below 65%. More quantitatively, for each 1% decrease in the weight, the per cent volume of the target covered by at least 95% of the prescribed dose decreased by approximately 0.10% and 0.16% for motion amplitudes equal to 1.5 cm and 2.0 cm, respectively. When taking into account the

  18. Multiple local minima in IMRT optimization based on dose-volume criteria

    International Nuclear Information System (INIS)

    Wu Qiuwen; Mohan, Radhe

    2002-01-01

    Multiple local minima traps are known to exist in dose-volume and dose-response objective functions. Nevertheless, their presence and consequences are not considered impediments in finding satisfactory solutions in routine optimization of IMRT plans using gradient methods. However, there is often a concern that a significantly superior solution may exist unbeknownst to the planner and that the optimization process may not be able to reach it. We have investigated the soundness of the assumption that the presence of multiple minima traps can be ignored. To find local minima, we start the optimization process a large number of times with random initial intensities. We investigated whether the occurrence of local minima depends upon the choice of the objective function parameters and the number of variables and whether their existence is an impediment in finding a satisfactory solution. To learn about the behavior of multiple minima, we first used a symmetric cubic phantom containing a cubic target and an organ-at-risk surrounding it to optimize the beam weights of two pairs of parallel-opposed beams using a gradient technique. The phantom studies also served to test our software. Objective function parameters were chosen to ensure that multiple minima would exist. Data for 500 plans, optimized with random initial beam weights, were analyzed. The search process did succeed in finding the local minima and showed that the number of minima depends on the parameters of the objective functions. It was also found that the consequences of local minima depended on the number of beams. We further searched for the multiple minima in intensity-modulated treatment plans for a head-and-neck case and a lung case. In addition to the treatment plan scores and the dose-volume histograms, we examined the dose distributions and intensity patterns. We did not find any evidence that multiple local minima affect the outcome of optimization using gradient techniques in any clinically

  19. SU-E-T-21: A Novel Sampling Algorithm to Reduce Intensity-Modulated Radiation Therapy (IMRT) Optimization Time

    International Nuclear Information System (INIS)

    Tiwari, P; Xie, Y; Chen, Y; Deasy, J

    2014-01-01

    Purpose: The IMRT optimization problem requires substantial computer time to find optimal dose distributions because of the large number of variables and constraints. Voxel sampling reduces the number of constraints and accelerates the optimization process, but usually deteriorates the quality of the dose distributions to the organs. We propose a novel sampling algorithm that accelerates the IMRT optimization process without significantly deteriorating the quality of the dose distribution. Methods: We included all boundary voxels, as well as a sampled fraction of interior voxels of organs in the optimization. We selected a fraction of interior voxels using a clustering algorithm, that creates clusters of voxels that have similar influence matrix signatures. A few voxels are selected from each cluster based on the pre-set sampling rate. Results: We ran sampling and no-sampling IMRT plans for de-identified head and neck treatment plans. Testing with the different sampling rates, we found that including 10% of inner voxels produced the good dose distributions. For this optimal sampling rate, the algorithm accelerated IMRT optimization by a factor of 2–3 times with a negligible loss of accuracy that was, on average, 0.3% for common dosimetric planning criteria. Conclusion: We demonstrated that a sampling could be developed that reduces optimization time by more than a factor of 2, without significantly degrading the dose quality

  20. Improving IMRT-plan quality with MLC leaf position refinement post plan optimization

    International Nuclear Information System (INIS)

    Niu Ying; Zhang Guowei; Berman, Barry L.; Parke, William C.; Yi Byongyong; Yu, Cedric X.

    2012-01-01

    Purpose: In intensity-modulated radiation therapy (IMRT) planning, reducing the pencil-beam size may lead to a significant improvement in dose conformity, but also increase the time needed for the dose calculation and plan optimization. The authors develop and evaluate a postoptimization refinement (POpR) method, which makes fine adjustments to the multileaf collimator (MLC) leaf positions after plan optimization, enhancing the spatial precision and improving the plan quality without a significant impact on the computational burden. Methods: The authors’ POpR method is implemented using a commercial treatment planning system based on direct aperture optimization. After an IMRT plan is optimized using pencil beams with regular pencil-beam step size, a greedy search is conducted by looping through all of the involved MLC leaves to see if moving the MLC leaf in or out by half of a pencil-beam step size will improve the objective function value. The half-sized pencil beams, which are used for updating dose distribution in the greedy search, are derived from the existing full-sized pencil beams without need for further pencil-beam dose calculations. A benchmark phantom case and a head-and-neck (HN) case are studied for testing the authors’ POpR method. Results: Using a benchmark phantom and a HN case, the authors have verified that their POpR method can be an efficient technique in the IMRT planning process. Effectiveness of POpR is confirmed by noting significant improvements in objective function values. Dosimetric benefits of POpR are comparable to those of using a finer pencil-beam size from the optimization start, but with far less computation and time. Conclusions: The POpR is a feasible and practical method to significantly improve IMRT-plan quality without compromising the planning efficiency.

  1. Phantoms for IMRT dose distribution measurement and treatment verification

    International Nuclear Information System (INIS)

    Low, Daniel A.; Gerber, Russell L.; Mutic, Sasa; Purdy, James A.

    1998-01-01

    Background: The verification of intensity-modulated radiation therapy (IMRT) patient treatment dose distributions is currently based on custom-built or modified dose measurement phantoms. The only commercially available IMRT treatment planning and delivery system (Peacock, NOMOS Corp.) is supplied with a film phantom that allows accurate spatial localization of the dose distribution using radiographic film. However, measurements using other dosimeters are necessary for the thorough verification of IMRT. Methods: We have developed a phantom to enable dose measurements using a cylindrical ionization chamber and the localization of prescription isodose curves using a matrix of thermoluminescent dosimetry (TLD) chips. The external phantom cross-section is identical to that of the commercial phantom, to allow direct comparisons of measurements. A supplementary phantom has been fabricated to verify the IMRT dose distributions for pelvis treatments. Results: To date, this phantom has been used for the verification of IMRT dose distributions for head and neck and prostate cancer treatments. Designs are also presented for a phantom insert to be used with polymerizing gels (e.g., BANG-2) to obtain volumetric dose distribution measurements. Conclusion: The phantoms have proven useful in the quantitative evaluation of IMRT treatments

  2. Peripheral doses of cranial pediatric IMRT performed with attenuator blocks; Doses perifericas de IMRT cranial pediatrica realizada com blocos atenuadores

    Energy Technology Data Exchange (ETDEWEB)

    Soboll, Danyel Scheidegger; Schitz, Ivette; Schelin, Hugo Reuters, E-mail: soboll@utfpr.edu.b, E-mail: iveteschitz@yahoo.com.b, E-mail: schelin@utfpr.edu.b [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Silva, Ricardo Goulart da, E-mail: ricardo.goulart@ymail.co [Hospital Angelina Caron, Campina Grande do Sul, PR (Brazil); Viamonte, Alfredo, E-mail: aviamonte@inca.gov.b [Instituto Nacional do Cancer (INCa), Rio de Janeiro, RJ (Brazil)

    2011-10-26

    This paper presents values of peripheral doses measured at six vital points of simulator objects which represent the ages of 2, 5 and 10 years old, submitted to a cranial IMRT procedure that applied compensator blocks interposed to 6 MV beams. The found values indicate that there is independence of dose with position of measurements and age of the patient, as the peripheral dose at the points nearest and the 2 year old simulator object where larger. The doses in thyroid reached the range of 1.4 to 2.9% of the dose prescribed in the isocenter, indicating that the peripheral doses for IMRT that employ compensator blocks can be greater than for the IMRT produced with sliding window technique

  3. Multiple fields may offer better esophagus sparing without increased probability of lung toxicity in optimized IMRT of lung tumors

    International Nuclear Information System (INIS)

    Chapet, Olivier; Fraass, Benedick A.; Haken, Randall K. ten

    2006-01-01

    Purpose: To evaluate whether increasing numbers of intensity-modulated radiation therapy (IMRT) fields enhance lung-tumor dose without additional predicted toxicity for difficult planning geometries. Methods and Materials: Data from 8 previous three dimensional conformal radiation therapy (3D-CRT) patients with tumors located in various regions of each lung, but with planning target volumes (PTVs) overlapping part of the esophagus, were used as input. Four optimized-beamlet IMRT plans (1 plan that used the 3D-CRT beam arrangement and 3 plans with 3, 5, or 7 axial, but predominantly one-sided, fields) were compared. For IMRT, the equivalent uniform dose (EUD) in the whole PTV was optimized simultaneously with that in a reduced PTV exclusive of the esophagus. Normal-tissue complication probability-based costlets were used for the esophagus, heart, and lung. Results: Overall, IMRT plans (optimized by use of EUD to judiciously allow relaxed PTV dose homogeneity) result in better minimum PTV isodose surface coverage and better average EUD values than does conformal planning; dose generally increases with the number of fields. Even 7-field plans do not significantly alter normal-lung mean-dose values or lung volumes that receive more than 13, 20, or 30 Gy. Conclusion: Optimized many-field IMRT plans can lead to escalated lung-tumor dose in the special case of esophagus overlapping PTV, without unacceptable alteration in the dose distribution to normal lung

  4. Coverage-based constraints for IMRT optimization

    Science.gov (United States)

    Mescher, H.; Ulrich, S.; Bangert, M.

    2017-09-01

    Radiation therapy treatment planning requires an incorporation of uncertainties in order to guarantee an adequate irradiation of the tumor volumes. In current clinical practice, uncertainties are accounted for implicitly with an expansion of the target volume according to generic margin recipes. Alternatively, it is possible to account for uncertainties by explicit minimization of objectives that describe worst-case treatment scenarios, the expectation value of the treatment or the coverage probability of the target volumes during treatment planning. In this note we show that approaches relying on objectives to induce a specific coverage of the clinical target volumes are inevitably sensitive to variation of the relative weighting of the objectives. To address this issue, we introduce coverage-based constraints for intensity-modulated radiation therapy (IMRT) treatment planning. Our implementation follows the concept of coverage-optimized planning that considers explicit error scenarios to calculate and optimize patient-specific probabilities q(\\hat{d}, \\hat{v}) of covering a specific target volume fraction \\hat{v} with a certain dose \\hat{d} . Using a constraint-based reformulation of coverage-based objectives we eliminate the trade-off between coverage and competing objectives during treatment planning. In-depth convergence tests including 324 treatment plan optimizations demonstrate the reliability of coverage-based constraints for varying levels of probability, dose and volume. General clinical applicability of coverage-based constraints is demonstrated for two cases. A sensitivity analysis regarding penalty variations within this planing study based on IMRT treatment planning using (1) coverage-based constraints, (2) coverage-based objectives, (3) probabilistic optimization, (4) robust optimization and (5) conventional margins illustrates the potential benefit of coverage-based constraints that do not require tedious adjustment of target volume objectives.

  5. PARETO: A novel evolutionary optimization approach to multiobjective IMRT planning.

    Science.gov (United States)

    Fiege, Jason; McCurdy, Boyd; Potrebko, Peter; Champion, Heather; Cull, Andrew

    2011-09-01

    In radiation therapy treatment planning, the clinical objectives of uniform high dose to the planning target volume (PTV) and low dose to the organs-at-risk (OARs) are invariably in conflict, often requiring compromises to be made between them when selecting the best treatment plan for a particular patient. In this work, the authors introduce Pareto-Aware Radiotherapy Evolutionary Treatment Optimization (pareto), a multiobjective optimization tool to solve for beam angles and fluence patterns in intensity-modulated radiation therapy (IMRT) treatment planning. pareto is built around a powerful multiobjective genetic algorithm (GA), which allows us to treat the problem of IMRT treatment plan optimization as a combined monolithic problem, where all beam fluence and angle parameters are treated equally during the optimization. We have employed a simple parameterized beam fluence representation with a realistic dose calculation approach, incorporating patient scatter effects, to demonstrate feasibility of the proposed approach on two phantoms. The first phantom is a simple cylindrical phantom containing a target surrounded by three OARs, while the second phantom is more complex and represents a paraspinal patient. pareto results in a large database of Pareto nondominated solutions that represent the necessary trade-offs between objectives. The solution quality was examined for several PTV and OAR fitness functions. The combination of a conformity-based PTV fitness function and a dose-volume histogram (DVH) or equivalent uniform dose (EUD) -based fitness function for the OAR produced relatively uniform and conformal PTV doses, with well-spaced beams. A penalty function added to the fitness functions eliminates hotspots. Comparison of resulting DVHs to those from treatment plans developed with a single-objective fluence optimizer (from a commercial treatment planning system) showed good correlation. Results also indicated that pareto shows promise in optimizing the number

  6. IMRT optimization with pseudo-biologic objective function

    International Nuclear Information System (INIS)

    Yi, B. Y.; Ahn, S. D.; Kim, J. H.; Lee, S. W.; Choi, E. K.

    2002-01-01

    The pseudo-biologic objective function has been proposed for the IMRT optimization. It is similar to the biological objective function in mathematical shape, but uses physical parameters. The pseudo-biologic objective function concept is consisted of the target coverage index (TCI) and the organ score index (OSI), was introduced. The TCI was expressed as the sum of all of the weighted bins of target dose volume histogram (DVH). The weights were given as the normal distribution of which the average is 100 % and the standard deviation is ±. The OSI was expressed as similar way. The average of the normal distribution was 0% of the dose and that of standard deviation was selected as a function of limiting dose and its importance. The objective function could be calculated as the product of the TCI and OSI's. The RTP Tool Box (RTB) was used for this study. The constraints applied in the optimization was intuitively clinical experience based numbers, while the physical objective function asks just numbers which are not necessarily based on the clinic, and the parameters for the biologic objective functions are uncertain. The OSI's from the pseudo-biological function showed better results than from the physical functions, while TCI's showed similar tendency. We could show that the pseudo-biologic function can be used for an IMRT objective function on behalf of the biological objective function

  7. Optimization of the primary collimator settings for fractionated IMRT stereotactic radiotherapy

    International Nuclear Information System (INIS)

    Tobler, Matt; Leavitt, Dennis D.; Watson, Gordon

    2004-01-01

    Advances in field-shaping techniques for stereotactic radiosurgery/radiotherapy have allowed dynamic adjustment of field shape with gantry rotation (dynamic conformal arc) in an effort to minimize dose to critical structures. Recent work evaluated the potential for increased sparing of dose to normal tissues when the primary collimator setting is optimized to only the size necessary to cover the largest shape of the dynamic micro multi leaf field. Intensity-modulated radiotherapy (IMRT) is now a treatment option for patients receiving stereotactic radiotherapy treatments. This multisegmentation of the dose delivered through multiple fixed treatment fields provides for delivery of uniform dose to the tumor volume while allowing sparing of critical structures, particularly for patients whose tumor volumes are less suited for rotational treatment. For these segmented fields, the total number of monitor units (MUs) delivered may be much greater than the number of MUs required if dose delivery occurred through an unmodulated treatment field. As a result, undesired dose delivered, as leakage through the leaves to tissues outside the area of interest, will be proportionally increased. This work will evaluate the role of optimization of the primary collimator setting for these IMRT treatment fields, and compare these results to treatment fields where the primary collimator settings have not been optimized

  8. On the role of modeling parameters in IMRT plan optimization

    International Nuclear Information System (INIS)

    Krause, Michael; Scherrer, Alexander; Thieke, Christian

    2008-01-01

    The formulation of optimization problems in intensity-modulated radiotherapy (IMRT) planning comprises the choice of various values such as function-specific parameters or constraint bounds. In current inverse planning programs that yield a single treatment plan for each optimization, it is often unclear how strongly these modeling parameters affect the resulting plan. This work investigates the mathematical concepts of elasticity and sensitivity to deal with this problem. An artificial planning case with a horse-shoe formed target with different opening angles surrounding a circular risk structure is studied. As evaluation functions the generalized equivalent uniform dose (EUD) and the average underdosage below and average overdosage beyond certain dose thresholds are used. A single IMRT plan is calculated for an exemplary parameter configuration. The elasticity and sensitivity of each parameter are then calculated without re-optimization, and the results are numerically verified. The results show the following. (1) elasticity can quantify the influence of a modeling parameter on the optimization result in terms of how strongly the objective function value varies under modifications of the parameter value. It also can describe how strongly the geometry of the involved planning structures affects the optimization result. (2) Based on the current parameter settings and corresponding treatment plan, sensitivity analysis can predict the optimization result for modified parameter values without re-optimization, and it can estimate the value intervals in which such predictions are valid. In conclusion, elasticity and sensitivity can provide helpful tools in inverse IMRT planning to identify the most critical parameters of an individual planning problem and to modify their values in an appropriate way

  9. PARETO: A novel evolutionary optimization approach to multiobjective IMRT planning

    International Nuclear Information System (INIS)

    Fiege, Jason; McCurdy, Boyd; Potrebko, Peter; Champion, Heather; Cull, Andrew

    2011-01-01

    Purpose: In radiation therapy treatment planning, the clinical objectives of uniform high dose to the planning target volume (PTV) and low dose to the organs-at-risk (OARs) are invariably in conflict, often requiring compromises to be made between them when selecting the best treatment plan for a particular patient. In this work, the authors introduce Pareto-Aware Radiotherapy Evolutionary Treatment Optimization (pareto), a multiobjective optimization tool to solve for beam angles and fluence patterns in intensity-modulated radiation therapy (IMRT) treatment planning. Methods: pareto is built around a powerful multiobjective genetic algorithm (GA), which allows us to treat the problem of IMRT treatment plan optimization as a combined monolithic problem, where all beam fluence and angle parameters are treated equally during the optimization. We have employed a simple parameterized beam fluence representation with a realistic dose calculation approach, incorporating patient scatter effects, to demonstrate feasibility of the proposed approach on two phantoms. The first phantom is a simple cylindrical phantom containing a target surrounded by three OARs, while the second phantom is more complex and represents a paraspinal patient. Results: pareto results in a large database of Pareto nondominated solutions that represent the necessary trade-offs between objectives. The solution quality was examined for several PTV and OAR fitness functions. The combination of a conformity-based PTV fitness function and a dose-volume histogram (DVH) or equivalent uniform dose (EUD) -based fitness function for the OAR produced relatively uniform and conformal PTV doses, with well-spaced beams. A penalty function added to the fitness functions eliminates hotspots. Comparison of resulting DVHs to those from treatment plans developed with a single-objective fluence optimizer (from a commercial treatment planning system) showed good correlation. Results also indicated that pareto shows

  10. Investigating multi-objective fluence and beam orientation IMRT optimization

    Science.gov (United States)

    Potrebko, Peter S.; Fiege, Jason; Biagioli, Matthew; Poleszczuk, Jan

    2017-07-01

    Radiation Oncology treatment planning requires compromises to be made between clinical objectives that are invariably in conflict. It would be beneficial to have a ‘bird’s-eye-view’ perspective of the full spectrum of treatment plans that represent the possible trade-offs between delivering the intended dose to the planning target volume (PTV) while optimally sparing the organs-at-risk (OARs). In this work, the authors demonstrate Pareto-aware radiotherapy evolutionary treatment optimization (PARETO), a multi-objective tool featuring such bird’s-eye-view functionality, which optimizes fluence patterns and beam angles for intensity-modulated radiation therapy (IMRT) treatment planning. The problem of IMRT treatment plan optimization is managed as a combined monolithic problem, where all beam fluence and angle parameters are treated equally during the optimization. To achieve this, PARETO is built around a powerful multi-objective evolutionary algorithm, called Ferret, which simultaneously optimizes multiple fitness functions that encode the attributes of the desired dose distribution for the PTV and OARs. The graphical interfaces within PARETO provide useful information such as: the convergence behavior during optimization, trade-off plots between the competing objectives, and a graphical representation of the optimal solution database allowing for the rapid exploration of treatment plan quality through the evaluation of dose-volume histograms and isodose distributions. PARETO was evaluated for two relatively complex clinical cases, a paranasal sinus and a pancreas case. The end result of each PARETO run was a database of optimal (non-dominated) treatment plans that demonstrated trade-offs between the OAR and PTV fitness functions, which were all equally good in the Pareto-optimal sense (where no one objective can be improved without worsening at least one other). Ferret was able to produce high quality solutions even though a large number of parameters

  11. Fluence map optimization (FMO) with dose-volume constraints in IMRT using the geometric distance sorting method.

    Science.gov (United States)

    Lan, Yihua; Li, Cunhua; Ren, Haozheng; Zhang, Yong; Min, Zhifang

    2012-10-21

    A new heuristic algorithm based on the so-called geometric distance sorting technique is proposed for solving the fluence map optimization with dose-volume constraints which is one of the most essential tasks for inverse planning in IMRT. The framework of the proposed method is basically an iterative process which begins with a simple linear constrained quadratic optimization model without considering any dose-volume constraints, and then the dose constraints for the voxels violating the dose-volume constraints are gradually added into the quadratic optimization model step by step until all the dose-volume constraints are satisfied. In each iteration step, an interior point method is adopted to solve each new linear constrained quadratic programming. For choosing the proper candidate voxels for the current dose constraint adding, a so-called geometric distance defined in the transformed standard quadratic form of the fluence map optimization model was used to guide the selection of the voxels. The new geometric distance sorting technique can mostly reduce the unexpected increase of the objective function value caused inevitably by the constraint adding. It can be regarded as an upgrading to the traditional dose sorting technique. The geometry explanation for the proposed method is also given and a proposition is proved to support our heuristic idea. In addition, a smart constraint adding/deleting strategy is designed to ensure a stable iteration convergence. The new algorithm is tested on four cases including head-neck, a prostate, a lung and an oropharyngeal, and compared with the algorithm based on the traditional dose sorting technique. Experimental results showed that the proposed method is more suitable for guiding the selection of new constraints than the traditional dose sorting method, especially for the cases whose target regions are in non-convex shapes. It is a more efficient optimization technique to some extent for choosing constraints than the dose

  12. Compensating for the impact of non-stationary spherical air cavities on IMRT dose delivery in transverse magnetic fields

    International Nuclear Information System (INIS)

    Bol, G H; Lagendijk, J J W; Raaymakers, B W

    2015-01-01

    With the development of the 1.5 T MRI linear accelerator and the clinical introduction of the 0.35 T ViewRay™ system, delivering intensity-modulated radiotherapy (IMRT) in a transverse magnetic field becomes increasingly important. When delivering dose in the presence of a transverse magnetic field, one of the most prominent phenomena occurs around air cavities: the electron return effect (ERE). For stationary, spherical air cavities which are centrally located in the phantom, the ERE can be compensated by using opposing beams configurations in combination with IMRT. In this paper we investigate the effects of non-stationary spherical air cavities, centrally located within the target in a phantom containing no organs at risk, on IMRT dose delivery in 0.35 T and 1.5 T transverse magnetic fields by using Monte Carlo simulations. We show that IMRT can be used for compensating ERE around those air cavities, except for intrafraction appearing or disappearing air cavities. For these cases, gating or plan re-optimization should be used. We also analyzed the option of using IMRT plans optimized at 0 T to be delivered in the presence of 0.35 T and 1.5 T magnetic field. When delivering dose at 0.35 T, IMRT plans optimized at 0 T and 0.35 T perform equally well regarding ERE compensation. Within a 1.5 T environment, the 1.5 T optimized plans perform slightly better for the static and random intra- and interfraction air cavity movement cases than the 0 T optimized plans. For non-stationary spherical air cavities with a baseline shift (intra- and interfraction) the 0 T optimized plans perform better. These observations show the intrinsic ERE compensation by equidistant and opposing beam configurations for spherical air cavities within the target area. IMRT gives some additional compensation, but only in case of correct positioning of the air cavity according to the IMRT compensation. For intrafraction appearing or disappearing air cavities this correct

  13. Advantages and limitations of navigation-based multicriteria optimization (MCO) for localized prostate cancer IMRT planning

    International Nuclear Information System (INIS)

    McGarry, Conor K.; Bokrantz, Rasmus; O’Sullivan, Joe M.; Hounsell, Alan R.

    2014-01-01

    Efficacy of inverse planning is becoming increasingly important for advanced radiotherapy techniques. This study’s aims were to validate multicriteria optimization (MCO) in RayStation (v2.4, RaySearch Laboratories, Sweden) against standard intensity-modulated radiation therapy (IMRT) optimization in Oncentra (v4.1, Nucletron BV, the Netherlands) and characterize dose differences due to conversion of navigated MCO plans into deliverable multileaf collimator apertures. Step-and-shoot IMRT plans were created for 10 patients with localized prostate cancer using both standard optimization and MCO. Acceptable standard IMRT plans with minimal average rectal dose were chosen for comparison with deliverable MCO plans. The trade-off was, for the MCO plans, managed through a user interface that permits continuous navigation between fluence-based plans. Navigated MCO plans were made deliverable at incremental steps along a trajectory between maximal target homogeneity and maximal rectal sparing. Dosimetric differences between navigated and deliverable MCO plans were also quantified. MCO plans, chosen as acceptable under navigated and deliverable conditions resulted in similar rectal sparing compared with standard optimization (33.7 ± 1.8 Gy vs 35.5 ± 4.2 Gy, p = 0.117). The dose differences between navigated and deliverable MCO plans increased as higher priority was placed on rectal avoidance. If the best possible deliverable MCO was chosen, a significant reduction in rectal dose was observed in comparison with standard optimization (30.6 ± 1.4 Gy vs 35.5 ± 4.2 Gy, p = 0.047). Improvements were, however, to some extent, at the expense of less conformal dose distributions, which resulted in significantly higher doses to the bladder for 2 of the 3 tolerance levels. In conclusion, similar IMRT plans can be created for patients with prostate cancer using MCO compared with standard optimization. Limitations exist within MCO regarding conversion of navigated plans to

  14. Radiobiological impact of dose calculation algorithms on biologically optimized IMRT lung stereotactic body radiation therapy plans

    International Nuclear Information System (INIS)

    Liang, X.; Penagaricano, J.; Zheng, D.; Morrill, S.; Zhang, X.; Corry, P.; Griffin, R. J.; Han, E. Y.; Hardee, M.; Ratanatharathom, V.

    2016-01-01

    The aim of this study is to evaluate the radiobiological impact of Acuros XB (AXB) vs. Anisotropic Analytic Algorithm (AAA) dose calculation algorithms in combined dose-volume and biological optimized IMRT plans of SBRT treatments for non-small-cell lung cancer (NSCLC) patients. Twenty eight patients with NSCLC previously treated SBRT were re-planned using Varian Eclipse (V11) with combined dose-volume and biological optimization IMRT sliding window technique. The total dose prescribed to the PTV was 60 Gy with 12 Gy per fraction. The plans were initially optimized using AAA algorithm, and then were recomputed using AXB using the same MUs and MLC files to compare with the dose distribution of the original plans and assess the radiobiological as well as dosimetric impact of the two different dose algorithms. The Poisson Linear-Quadatric (PLQ) and Lyman-Kutcher-Burman (LKB) models were used for estimating the tumor control probability (TCP) and normal tissue complication probability (NTCP), respectively. The influence of the model parameter uncertainties on the TCP differences and the NTCP differences between AAA and AXB plans were studied by applying different sets of published model parameters. Patients were grouped into peripheral and centrally-located tumors to evaluate the impact of tumor location. PTV dose was lower in the re-calculated AXB plans, as compared to AAA plans. The median differences of PTV(D 95% ) were 1.7 Gy (range: 0.3, 6.5 Gy) and 1.0 Gy (range: 0.6, 4.4 Gy) for peripheral tumors and centrally-located tumors, respectively. The median differences of PTV(mean) were 0.4 Gy (range: 0.0, 1.9 Gy) and 0.9 Gy (range: 0.0, 4.3 Gy) for peripheral tumors and centrally-located tumors, respectively. TCP was also found lower in AXB-recalculated plans compared with the AAA plans. The median (range) of the TCP differences for 30 month local control were 1.6 % (0.3 %, 5.8 %) for peripheral tumors and 1.3 % (0.5 %, 3.4 %) for centrally located tumors. The lower

  15. Prostate Dose Escalation by a Innovative Inverse Planning-Driven IMRT

    National Research Council Canada - National Science Library

    Xing, Lei

    2008-01-01

    ...) Developed a voxel-specific penalty scheme for TRV-based inverse planning; (iv) Established a cine-EPID image retrospective dose reconstruction in IMRT dose delivery for adaptive planning and IMRT dose verification. These works are both timely and important and should lead to widespread impact on prostate cancer management.

  16. The MLC tongue-and-groove effect on IMRT dose distributions

    Energy Technology Data Exchange (ETDEWEB)

    Deng Jun [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305 (United States). E-mail: jun@reyes.stanford.edu; Pawlicki, Todd; Chen Yan; Li Jinsheng; Jiang, Steve B.; Ma, C.-M. [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305 (United States)

    2001-04-01

    We have investigated the tongue-and-groove effect on the IMRT dose distributions for a Varian MLC. We have compared the dose distributions calculated using the intensity maps with and without the tongue-and-groove effect. Our results showed that, for one intensity-modulated treatment field, the maximum tongue-and-groove effect could be up to 10% of the maximum dose in the dose distributions. For an IMRT treatment with multiple gantry angles ({>=} 5), the difference between the dose distributions with and without the tongue-and-groove effect was hardly visible, less than 1.6% for the two typical clinical cases studied. After considering the patient setup errors, the dose distributions were smoothed with reduced and insignificant differences between plans with and without the tongue-and-groove effect. Therefore, for a multiple-field IMRT plan ({>=} 5), the tongue-and-groove effect on the IMRT dose distributions will be generally clinically insignificant due to the smearing effect of individual fields. The tongue-and-groove effect on an IMRT plan with small number of fields (<5) will vary depending on the number of fields in a plan (coplanar or non-coplanar), the MLC leaf sequences and the patient setup uncertainty, and may be significant (>5% of maximum dose) in some cases, especially when the patient setup uncertainty is small ({<=} 2 mm). (author)

  17. Head-and-neck IMRT treatments assessed with a Monte Carlo dose calculation engine

    International Nuclear Information System (INIS)

    Seco, J; Adams, E; Bidmead, M; Partridge, M; Verhaegen, F

    2005-01-01

    IMRT is frequently used in the head-and-neck region, which contains materials of widely differing densities (soft tissue, bone, air-cavities). Conventional methods of dose computation for these complex, inhomogeneous IMRT cases involve significant approximations. In the present work, a methodology for the development, commissioning and implementation of a Monte Carlo (MC) dose calculation engine for intensity modulated radiotherapy (MC-IMRT) is proposed which can be used by radiotherapy centres interested in developing MC-IMRT capabilities for research or clinical evaluations. The method proposes three levels for developing, commissioning and maintaining a MC-IMRT dose calculation engine: (a) development of a MC model of the linear accelerator, (b) validation of MC model for IMRT and (c) periodic quality assurance (QA) of the MC-IMRT system. The first step, level (a), in developing an MC-IMRT system is to build a model of the linac that correctly predicts standard open field measurements for percentage depth-dose and off-axis ratios. Validation of MC-IMRT, level (b), can be performed in a rando phantom and in a homogeneous water equivalent phantom. Ultimately, periodic quality assurance of the MC-IMRT system is needed to verify the MC-IMRT dose calculation system, level (c). Once the MC-IMRT dose calculation system is commissioned it can be applied to more complex clinical IMRT treatments. The MC-IMRT system implemented at the Royal Marsden Hospital was used for IMRT calculations for a patient undergoing treatment for primary disease with nodal involvement in the head-and-neck region (primary treated to 65 Gy and nodes to 54 Gy), while sparing the spinal cord, brain stem and parotid glands. Preliminary MC results predict a decrease of approximately 1-2 Gy in the median dose of both the primary tumour and nodal volumes (compared with both pencil beam and collapsed cone). This is possibly due to the large air-cavity (the larynx of the patient) situated in the centre

  18. Patient specific quality assurance of IMRT: quantitative approach using film dosimetry and optimization

    International Nuclear Information System (INIS)

    Shin, Kyung Hwan; Park, Sung Yong; Park, Dong Hyun

    2005-01-01

    Film dosimetry an a part of patient specific intensity modulated radiation therapy quality assurance (IMRT QA) was performed to develop a new optimization method of film isocenter offset and to then suggest new quantitative criteria for film dosimetry. Film dosimetry was performed on 14 IMRT patients with head and neck cancers. An optimization method for obtaining the local minimum was developed to adjust for the error in the film isocenter offset, which is the largest part of the systemic errors. The adjust value of the film isocenter offset under optimization was 1 mm in 12 patients, while only two patients showed 2 mm translation. The means of absolute average dose difference before and after optimization were 2.36 and 1.56%, respectively, and the mean radios over a 5% tolerance were 9.67 and 2.88%. After optimization, the differences in the dose decreased dramatically. A low dose range cutoff (L-Cutoff) had been suggested for clinical application. New quantitative criteria of a ratio of over a 5%, but less than 10% tolerance, and for an absolute average dose difference less than 3% have been suggested for the verification of film dosimetry. The new optimization method was effective in adjusting for the film dosimetry error, and the newly quantitative criteria suggested in this research are believed to be sufficiently accurate and clinically useful

  19. Robust optimization methods for cardiac sparing in tangential breast IMRT

    Energy Technology Data Exchange (ETDEWEB)

    Mahmoudzadeh, Houra, E-mail: houra@mie.utoronto.ca [Mechanical and Industrial Engineering Department, University of Toronto, Toronto, Ontario M5S 3G8 (Canada); Lee, Jenny [Radiation Medicine Program, UHN Princess Margaret Cancer Centre, Toronto, Ontario M5G 2M9 (Canada); Chan, Timothy C. Y. [Mechanical and Industrial Engineering Department, University of Toronto, Toronto, Ontario M5S 3G8, Canada and Techna Institute for the Advancement of Technology for Health, Toronto, Ontario M5G 1P5 (Canada); Purdie, Thomas G. [Radiation Medicine Program, UHN Princess Margaret Cancer Centre, Toronto, Ontario M5G 2M9 (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario M5S 3S2 (Canada); Techna Institute for the Advancement of Technology for Health, Toronto, Ontario M5G 1P5 (Canada)

    2015-05-15

    Purpose: In left-sided tangential breast intensity modulated radiation therapy (IMRT), the heart may enter the radiation field and receive excessive radiation while the patient is breathing. The patient’s breathing pattern is often irregular and unpredictable. We verify the clinical applicability of a heart-sparing robust optimization approach for breast IMRT. We compare robust optimized plans with clinical plans at free-breathing and clinical plans at deep inspiration breath-hold (DIBH) using active breathing control (ABC). Methods: Eight patients were included in the study with each patient simulated using 4D-CT. The 4D-CT image acquisition generated ten breathing phase datasets. An average scan was constructed using all the phase datasets. Two of the eight patients were also imaged at breath-hold using ABC. The 4D-CT datasets were used to calculate the accumulated dose for robust optimized and clinical plans based on deformable registration. We generated a set of simulated breathing probability mass functions, which represent the fraction of time patients spend in different breathing phases. The robust optimization method was applied to each patient using a set of dose-influence matrices extracted from the 4D-CT data and a model of the breathing motion uncertainty. The goal of the optimization models was to minimize the dose to the heart while ensuring dose constraints on the target were achieved under breathing motion uncertainty. Results: Robust optimized plans were improved or equivalent to the clinical plans in terms of heart sparing for all patients studied. The robust method reduced the accumulated heart dose (D10cc) by up to 801 cGy compared to the clinical method while also improving the coverage of the accumulated whole breast target volume. On average, the robust method reduced the heart dose (D10cc) by 364 cGy and improved the optBreast dose (D99%) by 477 cGy. In addition, the robust method had smaller deviations from the planned dose to the

  20. Simultaneous optimization of sequential IMRT plans

    International Nuclear Information System (INIS)

    Popple, Richard A.; Prellop, Perri B.; Spencer, Sharon A.; Santos, Jennifer F. de los; Duan, Jun; Fiveash, John B.; Brezovich, Ivan A.

    2005-01-01

    Radiotherapy often comprises two phases, in which irradiation of a volume at risk for microscopic disease is followed by a sequential dose escalation to a smaller volume either at a higher risk for microscopic disease or containing only gross disease. This technique is difficult to implement with intensity modulated radiotherapy, as the tolerance doses of critical structures must be respected over the sum of the two plans. Techniques that include an integrated boost have been proposed to address this problem. However, clinical experience with such techniques is limited, and many clinicians are uncomfortable prescribing nonconventional fractionation schemes. To solve this problem, we developed an optimization technique that simultaneously generates sequential initial and boost IMRT plans. We have developed an optimization tool that uses a commercial treatment planning system (TPS) and a high level programming language for technical computing. The tool uses the TPS to calculate the dose deposition coefficients (DDCs) for optimization. The DDCs were imported into external software and the treatment ports duplicated to create the boost plan. The initial, boost, and tolerance doses were specified and used to construct cost functions. The initial and boost plans were optimized simultaneously using a gradient search technique. Following optimization, the fluence maps were exported to the TPS for dose calculation. Seven patients treated using sequential techniques were selected from our clinical database. The initial and boost plans used to treat these patients were developed independently of each other by dividing the tolerance doses proportionally between the initial and boost plans and then iteratively optimizing the plans until a summation that met the treatment goals was obtained. We used the simultaneous optimization technique to generate plans that met the original planning goals. The coverage of the initial and boost target volumes in the simultaneously optimized

  1. Peripheral doses of cranial pediatric IMRT performed with attenuator blocks

    International Nuclear Information System (INIS)

    Soboll, Danyel Scheidegger; Schitz, Ivette; Schelin, Hugo Reuters; Silva, Ricardo Goulart da; Viamonte, Alfredo

    2011-01-01

    This paper presents values of peripheral doses measured at six vital points of simulator objects which represent the ages of 2, 5 and 10 years old, submitted to a cranial IMRT procedure that applied compensator blocks interposed to 6 MV beams. The found values indicate that there is independence of dose with position of measurements and age of the patient, as the peripheral dose at the points nearest and the 2 year old simulator object where larger. The doses in thyroid reached the range of 1.4 to 2.9% of the dose prescribed in the isocenter, indicating that the peripheral doses for IMRT that employ compensator blocks can be greater than for the IMRT produced with sliding window technique

  2. Fraction-variant beam orientation optimization for non-coplanar IMRT

    Science.gov (United States)

    O'Connor, Daniel; Yu, Victoria; Nguyen, Dan; Ruan, Dan; Sheng, Ke

    2018-02-01

    Conventional beam orientation optimization (BOO) algorithms for IMRT assume that the same set of beam angles is used for all treatment fractions. In this paper we present a BOO formulation based on group sparsity that simultaneously optimizes non-coplanar beam angles for all fractions, yielding a fraction-variant (FV) treatment plan. Beam angles are selected by solving a multi-fraction fluence map optimization problem involving 500-700 candidate beams per fraction, with an additional group sparsity term that encourages most candidate beams to be inactive. The optimization problem is solved using the fast iterative shrinkage-thresholding algorithm. Our FV BOO algorithm is used to create five-fraction treatment plans for digital phantom, prostate, and lung cases as well as a 30-fraction plan for a head and neck case. A homogeneous PTV dose coverage is maintained in all fractions. The treatment plans are compared with fraction-invariant plans that use a fixed set of beam angles for all fractions. The FV plans reduced OAR mean dose and D 2 values on average by 3.3% and 3.8% of the prescription dose, respectively. Notably, mean OAR dose was reduced by 14.3% of prescription dose (rectum), 11.6% (penile bulb), 10.7% (seminal vesicle), 5.5% (right femur), 3.5% (bladder), 4.0% (normal left lung), 15.5% (cochleas), and 5.2% (chiasm). D 2 was reduced by 14.9% of prescription dose (right femur), 8.2% (penile bulb), 12.7% (proximal bronchus), 4.1% (normal left lung), 15.2% (cochleas), 10.1% (orbits), 9.1% (chiasm), 8.7% (brainstem), and 7.1% (parotids). Meanwhile, PTV homogeneity defined as D 95/D 5 improved from .92 to .95 (digital phantom), from .95 to .98 (prostate case), and from .94 to .97 (lung case), and remained constant for the head and neck case. Moreover, the FV plans are dosimetrically similar to conventional plans that use twice as many beams per fraction. Thus, FV BOO offers the potential to reduce delivery time for non-coplanar IMRT.

  3. SU-E-T-163: Evaluation of Dose Distributions Recalculated with Per-Field Measurement Data Under the Condition of Respiratory Motion During IMRT for Liver Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Song, J; Yoon, M; Nam, T; Ahn, S; Chung, W [Chonnam National University Hwasun Hospital, Hwasun-kun, Chonnam (Korea, Republic of)

    2014-06-01

    Purpose: The dose distributions within the real volumes of tumor targets and critical organs during internal target volume-based intensity-modulated radiation therapy (ITV-IMRT) for liver cancer were recalculated by applying the effects of actual respiratory organ motion, and the dosimetric features were analyzed through comparison with gating IMRT (Gate-IMRT) plan results. Methods: The 4DCT data for 10 patients who had been treated with Gate-IMRT for liver cancer were selected to create ITV-IMRT plans. The ITV was created using MIM software, and a moving phantom was used to simulate respiratory motion. The period and range of respiratory motion were recorded in all patients from 4DCT-generated movie data, and the same period and range were applied when operating the dynamic phantom to realize coincident respiratory conditions in each patient. The doses were recalculated with a 3 dose-volume histogram (3DVH) program based on the per-field data measured with a MapCHECK2 2-dimensional diode detector array and compared with the DVHs calculated for the Gate-IMRT plan. Results: Although a sufficient prescription dose covered the PTV during ITV-IMRT delivery, the dose homogeneity in the PTV was inferior to that with the Gate-IMRT plan. We confirmed that there were higher doses to the organs-at-risk (OARs) with ITV-IMRT, as expected when using an enlarged field, but the increased dose to the spinal cord was not significant and the increased doses to the liver and kidney could be considered as minor when the reinforced constraints were applied during IMRT plan optimization. Conclusion: Because Gate-IMRT cannot always be considered an ideal method with which to correct the respiratory motional effect, given the dosimetric variations in the gating system application and the increased treatment time, a prior analysis for optimal IMRT method selection should be performed while considering the patient's respiratory condition and IMRT plan results.

  4. SU-F-T-378: Evaluation of Dose-Volume Variability and Parameters Between Prostate IMRT and VMAT Plans

    Energy Technology Data Exchange (ETDEWEB)

    Chow, J [Princess Margaret Cancer Centre, Toronto, ON (Canada); Jiang, R [Grand River Regional Cancer Centre, Kitchener, ON (Canada); Kiciak, A [University of Waterloo, Waterloo, ON (Canada)

    2016-06-15

    Purpose: This study compared the rectal dose-volume consistency, equivalent uniform dose (EUD) and normal tissue complication probability (NTCP) in prostate intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). Methods: For forty prostate IMRT and fifty VMAT patients treated using the same dose prescription (78 Gy/39 fraction) and dose-volume criteria in inverse planning optimization, the rectal EUD and NTCP were calculated for each patient. The rectal dose-volume consistency, showing the variability of dose-volume histogram (DVH) among patients, was defined and calculated based on the deviation between the mean and corresponding rectal DVH. Results: From both the prostate IMRT and VMAT plans, the rectal EUD and NTCP were found decreasing with the rectal volume. The decrease rates for the IMRT plans (EUD = 0.47 × 10{sup −3} Gy cm{sup −3} and NTCP = 3.94 × 10{sup −2} % cm{sup −3}) were higher than those for the VMAT (EUD = 0.28 × 10{sup −3} Gy cm{sup −3} and NTCP = 2.61 × 10{sup −2} % cm{sup −3}). In addition, the dependences of the rectal EUD and NTCP on the dose-volume consistency were found very similar between the prostate IMRT and VMAT plans. This shows that both delivery techniques have similar variations of the rectal EUD and NTCP on the dose-volume consistency. Conclusion: Dependences of the dose-volume consistency on the rectal EUD and NTCP were compared between the prostate IMRT and VMAT plans. It is concluded that both rectal EUD and NTCP decreased with an increase of the rectal volume. The variation rates of the rectal EUD and NTCP on the rectal volume were higher for the IMRT plans than VMAT. However, variations of the rectal dose-volume consistency on the rectal EUD and NTCP were found not significant for both delivery techniques.

  5. A two isocenter IMRT technique with a controlled junction dose for long volume targets

    International Nuclear Information System (INIS)

    Zeng, G G; Heaton, R K; Catton, C N; Chung, P W; O'Sullivan, B; Lau, M; Parent, A; Jaffray, D A

    2007-01-01

    Most IMRT techniques have been designed to treat targets smaller than the field size of conventional linac accelerators. In order to overcome the field size restrictions in applying IMRT, we developed a two isocenter IMRT technique to treat long volume targets. The technique exploits an extended dose gradient throughout a junction region of 4-6 cm to minimize the impact of field match errors on a junction dose and manipulates the inverse planning and IMRT segments to fill in the dose gradient and achieve dose uniformity. Techniques for abutting both conventional fields with IMRT ('Static + IMRT') and IMRT fields ('IMRT + IMRT') using two separate isocenters have been developed. Five long volume sarcoma cases have been planned in Pinnacle (Philips, Madison, USA) using Elekta Synergy and Varian 2100EX linacs; two of the cases were clinically treated with this technique. Advantages were demonstrated with well-controlled junction target uniformity and tolerance to setup uncertainties. The junction target dose heterogeneity was controlled at a level of ±5%; for 3 mm setup errors at the field edges, the junction target dose changed less than 5% and the dose sparing to organs at risk (OARs) was maintained. Film measurements confirmed the treatment planning results

  6. An absorbed dose calorimeter for IMRT dosimetry

    International Nuclear Information System (INIS)

    Duane, S.; Aldehaybes, M.; Bailey, M.; Lee, N.D.; Thomas, C.G.; Palmans, H.

    2012-01-01

    A new calorimeter for dosimetry in small and complex fields has been built. The device is intended for the direct determination of absorbed dose to water in moderately small fields and in composite fields such as IMRT treatments, and as a transfer instrument calibrated against existing absorbed dose standards in conventional reference conditions. The geometry, materials and mode of operation have been chosen to minimize detector perturbations when used in a water phantom, to give a reasonably isotropic response and to minimize the effects of heat transfer when the calorimeter is used in non-reference conditions in a water phantom. The size of the core is meant to meet the needs of measurement in IMRT treatments and is comparable to the size of the air cavity in a type NE2611 ionization chamber. The calorimeter may also be used for small field dosimetry. Initial measurements in reference conditions and in an IMRT head and neck plan, collapsed to gantry angle zero, have been made to estimate the thermal characteristics of the device, and to assess its performance in use. The standard deviation (estimated repeatability) of the reference absorbed dose measurements was 0.02 Gy (0.6%). (authors)

  7. First application of quantum annealing to IMRT beamlet intensity optimization

    International Nuclear Information System (INIS)

    Nazareth, Daryl P; Spaans, Jason D

    2015-01-01

    Optimization methods are critical to radiation therapy. A new technology, quantum annealing (QA), employs novel hardware and software techniques to address various discrete optimization problems in many fields. We report on the first application of quantum annealing to the process of beamlet intensity optimization for IMRT.We apply recently-developed hardware which natively exploits quantum mechanical effects for improved optimization. The new algorithm, called QA, is most similar to simulated annealing, but relies on natural processes to directly minimize a system’s free energy. A simple quantum system is slowly evolved into a classical system representing the objective function. If the evolution is sufficiently slow, there are probabilistic guarantees that a global minimum will be located.To apply QA to IMRT-type optimization, two prostate cases were considered. A reduced number of beamlets were employed, due to the current QA hardware limitations. The beamlet dose matrices were computed using CERR and an objective function was defined based on typical clinical constraints, including dose-volume objectives, which result in a complex non-convex search space. The objective function was discretized and the QA method was compared to two standard optimization methods, simulated annealing and Tabu search, run on a conventional computing cluster.Based on several runs, the average final objective function value achieved by the QA was 16.9 for the first patient, compared with 10.0 for Tabu and 6.7 for the simulated annealing (SA) method. For the second patient, the values were 70.7 for the QA, 120.0 for Tabu and 22.9 for the SA. The QA algorithm required 27–38% of the time required by the other two methods.In this first application of hardware-enabled QA to IMRT optimization, its performance is comparable to Tabu search, but less effective than the SA in terms of final objective function values. However, its speed was 3–4 times faster than the other two methods

  8. Dosimetry investigation of MOSFET for clinical IMRT dose verification.

    Science.gov (United States)

    Deshpande, Sudesh; Kumar, Rajesh; Ghadi, Yogesh; Neharu, R M; Kannan, V

    2013-06-01

    In IMRT, patient-specific dose verification is followed regularly at each centre. Simple and efficient dosimetry techniques play a very important role in routine clinical dosimetry QA. The MOSFET dosimeter offers several advantages over the conventional dosimeters such as its small detector size, immediate readout, immediate reuse, multiple point dose measurements. To use the MOSFET as routine clinical dosimetry system for pre-treatment dose verification in IMRT, a comprehensive set of experiments has been conducted, to investigate its linearity, reproducibility, dose rate effect and angular dependence for 6 MV x-ray beam. The MOSFETs shows a linear response with linearity coefficient of 0.992 for a dose range of 35 cGy to 427 cGy. The reproducibility of the MOSFET was measured by irradiating the MOSFET for ten consecutive irradiations in the dose range of 35 cGy to 427 cGy. The measured reproducibility of MOSFET was found to be within 4% up to 70 cGy and within 1.4% above 70 cGy. The dose rate effect on the MOSFET was investigated in the dose rate range 100 MU/min to 600 MU/min. The response of the MOSFET varies from -1.7% to 2.1%. The angular responses of the MOSFETs were measured at 10 degrees intervals from 90 to 270 degrees in an anticlockwise direction and normalized at gantry angle zero and it was found to be in the range of 0.98 ± 0.014 to 1.01 ± 0.014. The MOSFETs were calibrated in a phantom which was later used for IMRT verification. The measured calibration coefficients were found to be 1 mV/cGy and 2.995 mV/cGy in standard and high sensitivity mode respectively. The MOSFETs were used for pre-treatment dose verification in IMRT. Nine dosimeters were used for each patient to measure the dose in different plane. The average variation between calculated and measured dose at any location was within 3%. Dose verification using MOSFET and IMRT phantom was found to quick and efficient and well suited for a busy radiotherapy

  9. IMRT fluence map editing to control hot and cold spots

    International Nuclear Information System (INIS)

    Taylor Cook, J.; Tobler, Matt; Leavitt, Dennis D.; Watson, Gordon

    2005-01-01

    Manually editing intensity-modulated radiation therapy (IMRT) fluence maps effectively controls hot and cold spots that the IMRT optimization cannot control. Many times, re-optimizing does not reduce the hot spots or increase the cold spots. In fact, re-optimizing only places the hot and cold spots in different locations. Fluence-map editing provides manual control of dose delivery and provides the best treatment plan possible. Several IMRT treatments were planned using the Varian Eclipse planning system. We compare the effects on dose distributions between fluence-map editing and re-optimization, discuss techniques for fluence-map editing, and analyze differences between fluence editing on one beam vs. multiple beams. When editing a beam's fluence map, it is essential to choose a beam that least affects dose to the tumor and critical structures. Editing fluence maps gives an advantage in treatment planning and provides controlled delivery of IMRT dose

  10. Dose-volume based ranking of incident beam direction and its utility in facilitating IMRT beam placement

    International Nuclear Information System (INIS)

    Schreibmann, Eduard; Xing Lei

    2005-01-01

    Purpose: Beam orientation optimization in intensity-modulated radiation therapy (IMRT) is computationally intensive, and various single beam ranking techniques have been proposed to reduce the search space. Up to this point, none of the existing ranking techniques considers the clinically important dose-volume effects of the involved structures, which may lead to clinically irrelevant angular ranking. The purpose of this work is to develop a clinically sensible angular ranking model with incorporation of dose-volume effects and to show its utility for IMRT beam placement. Methods and Materials: The general consideration in constructing this angular ranking function is that a beamlet/beam is preferable if it can deliver a higher dose to the target without exceeding the tolerance of the sensitive structures located on the path of the beamlet/beam. In the previously proposed dose-based approach, the beamlets are treated independently and, to compute the maximally deliverable dose to the target volume, the intensity of each beamlet is pushed to its maximum intensity without considering the values of other beamlets. When volumetric structures are involved, the complication arises from the fact that there are numerous dose distributions corresponding to the same dose-volume tolerance. In this situation, the beamlets are not independent and an optimization algorithm is required to find the intensity profile that delivers the maximum target dose while satisfying the volumetric constraints. In this study, the behavior of a volumetric organ was modeled by using the equivalent uniform dose (EUD). A constrained sequential quadratic programming algorithm (CFSQP) was used to find the beam profile that delivers the maximum dose to the target volume without violating the EUD constraint or constraints. To assess the utility of the proposed technique, we planned a head-and-neck and abdominal case with and without the guidance of the angular ranking information. The qualities of the

  11. A silicon strip detector dose magnifying glass for IMRT dosimetry

    International Nuclear Information System (INIS)

    Wong, J. H. D.; Carolan, M.; Lerch, M. L. F.; Petasecca, M.; Khanna, S.; Perevertaylo, V. L.; Metcalfe, P.; Rosenfeld, A. B.

    2010-01-01

    Purpose: Intensity modulated radiation therapy (IMRT) allows the delivery of escalated radiation dose to tumor while sparing adjacent critical organs. In doing so, IMRT plans tend to incorporate steep dose gradients at interfaces between the target and the organs at risk. Current quality assurance (QA) verification tools such as 2D diode arrays, are limited by their spatial resolution and conventional films are nonreal time. In this article, the authors describe a novel silicon strip detector (CMRP DMG) of high spatial resolution (200 μm) suitable for measuring the high dose gradients in an IMRT delivery. Methods: A full characterization of the detector was performed, including dose per pulse effect, percent depth dose comparison with Farmer ion chamber measurements, stem effect, dose linearity, uniformity, energy response, angular response, and penumbra measurements. They also present the application of the CMRP DMG in the dosimetric verification of a clinical IMRT plan. Results: The detector response changed by 23% for a 390-fold change in the dose per pulse. A correction function is derived to correct for this effect. The strip detector depth dose curve agrees with the Farmer ion chamber within 0.8%. The stem effect was negligible (0.2%). The dose linearity was excellent for the dose range of 3-300 cGy. A uniformity correction method is described to correct for variations in the individual detector pixel responses. The detector showed an over-response relative to tissue dose at lower photon energies with the maximum dose response at 75 kVp nominal photon energy. Penumbra studies using a Varian Clinac 21EX at 1.5 and 10.0 cm depths were measured to be 2.77 and 3.94 mm for the secondary collimators, 3.52 and 5.60 mm for the multileaf collimator rounded leaf ends, respectively. Point doses measured with the strip detector were compared to doses measured with EBT film and doses predicted by the Philips Pinnacle treatment planning system. The differences were 1.1%

  12. An IMRT dose distribution study using commercial verification software

    International Nuclear Information System (INIS)

    Grace, M.; Liu, G.; Fernando, W.; Rykers, K.

    2004-01-01

    Full text: The introduction of IMRT requires users to confirm that the isodose distributions and relative doses calculated by their planning system match the doses delivered by their linear accelerators. To this end the commercially available software, VeriSoft TM (PTW-Freiburg, Germany) was trialled to determine if the tools and functions it offered would be of benefit to this process. The CMS Xio (Computer Medical System) treatment planning system was used to generate IMRT plans that were delivered with an upgraded Elekta SL15 linac. Kodak EDR2 film sandwiched in RW3 solid water (PTW-Freiburg, Germany) was used to measure the IMRT fields delivered with 6 MV photons. The isodose and profiles measured with the film generally agreed to within ± 3% or ± 3 mm with the planned doses, in some regions (outside the IMRT field) the match fell to within ± 5%. The isodose distributions of the planning system and the film could be compared on screen and allows for electronic records of the comparison to be kept if so desired. The features and versatility of this software has been of benefit to our IMRT QA program. Furthermore, the VeriSoft TM software allows for quick and accurate, automated planar film analysis.Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

  13. IMRT for Image-Guided Single Vocal Cord Irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Osman, Sarah O.S., E-mail: s.osman@erasmusmc.nl [Department of Radiation Oncology, Erasmus Medical Center-Daniel den Hoed Cancer Center, Rotterdam (Netherlands); Astreinidou, Eleftheria; Boer, Hans C.J. de; Keskin-Cambay, Fatma; Breedveld, Sebastiaan; Voet, Peter; Al-Mamgani, Abrahim; Heijmen, Ben J.M.; Levendag, Peter C. [Department of Radiation Oncology, Erasmus Medical Center-Daniel den Hoed Cancer Center, Rotterdam (Netherlands)

    2012-02-01

    Purpose: We have been developing an image-guided single vocal cord irradiation technique to treat patients with stage T1a glottic carcinoma. In the present study, we compared the dose coverage to the affected vocal cord and the dose delivered to the organs at risk using conventional, intensity-modulated radiotherapy (IMRT) coplanar, and IMRT non-coplanar techniques. Methods and Materials: For 10 patients, conventional treatment plans using two laterally opposed wedged 6-MV photon beams were calculated in XiO (Elekta-CMS treatment planning system). An in-house IMRT/beam angle optimization algorithm was used to obtain the coplanar and non-coplanar optimized beam angles. Using these angles, the IMRT plans were generated in Monaco (IMRT treatment planning system, Elekta-CMS) with the implemented Monte Carlo dose calculation algorithm. The organs at risk included the contralateral vocal cord, arytenoids, swallowing muscles, carotid arteries, and spinal cord. The prescription dose was 66 Gy in 33 fractions. Results: For the conventional plans and coplanar and non-coplanar IMRT plans, the population-averaged mean dose {+-} standard deviation to the planning target volume was 67 {+-} 1 Gy. The contralateral vocal cord dose was reduced from 66 {+-} 1 Gy in the conventional plans to 39 {+-} 8 Gy and 36 {+-} 6 Gy in the coplanar and non-coplanar IMRT plans, respectively. IMRT consistently reduced the doses to the other organs at risk. Conclusions: Single vocal cord irradiation with IMRT resulted in good target coverage and provided significant sparing of the critical structures. This has the potential to improve the quality-of-life outcomes after RT and maintain the same local control rates.

  14. IMRT for Image-Guided Single Vocal Cord Irradiation

    International Nuclear Information System (INIS)

    Osman, Sarah O.S.; Astreinidou, Eleftheria; Boer, Hans C.J. de; Keskin-Cambay, Fatma; Breedveld, Sebastiaan; Voet, Peter; Al-Mamgani, Abrahim; Heijmen, Ben J.M.; Levendag, Peter C.

    2012-01-01

    Purpose: We have been developing an image-guided single vocal cord irradiation technique to treat patients with stage T1a glottic carcinoma. In the present study, we compared the dose coverage to the affected vocal cord and the dose delivered to the organs at risk using conventional, intensity-modulated radiotherapy (IMRT) coplanar, and IMRT non-coplanar techniques. Methods and Materials: For 10 patients, conventional treatment plans using two laterally opposed wedged 6-MV photon beams were calculated in XiO (Elekta-CMS treatment planning system). An in-house IMRT/beam angle optimization algorithm was used to obtain the coplanar and non-coplanar optimized beam angles. Using these angles, the IMRT plans were generated in Monaco (IMRT treatment planning system, Elekta-CMS) with the implemented Monte Carlo dose calculation algorithm. The organs at risk included the contralateral vocal cord, arytenoids, swallowing muscles, carotid arteries, and spinal cord. The prescription dose was 66 Gy in 33 fractions. Results: For the conventional plans and coplanar and non-coplanar IMRT plans, the population-averaged mean dose ± standard deviation to the planning target volume was 67 ± 1 Gy. The contralateral vocal cord dose was reduced from 66 ± 1 Gy in the conventional plans to 39 ± 8 Gy and 36 ± 6 Gy in the coplanar and non-coplanar IMRT plans, respectively. IMRT consistently reduced the doses to the other organs at risk. Conclusions: Single vocal cord irradiation with IMRT resulted in good target coverage and provided significant sparing of the critical structures. This has the potential to improve the quality-of-life outcomes after RT and maintain the same local control rates.

  15. Simulation of respiratory motion during IMRT dose delivery

    International Nuclear Information System (INIS)

    Mohn, Silje; Wasboe, Ellen

    2011-01-01

    Background. When intensity modulated radiation therapy (IMRT) is realised with dynamic multi-leaf collimators (MLC) and given under respiratory motion, dosimetric errors may occur. These errors are a consequence of the dose blurring and the interplay between the organ motion and the leaf motion. In the present study, a model for evaluating these dosimetric effects for patient-specific cases has been developed and tested. Material and methods. In the purpose written software, three dimensional (3D) dose distributions can be calculated both with and without a generated breathing cycle. To validate the presented model and illustrate its application, periodic breathing cycles were generated, where the starting phase was set randomly for each field during the calculations. Respiration in the anterior-posterior (AP), superior-inferior (SI) and left-right (LR) direction was tested and verified. To illustrate the application of the presented model, two 5-fields IMRT plans with different complexity were calculated with a 2 cm peak-to-peak motion in the AP direction for one fraction and for 25 fractions. Results. The results showed that the calculation method is of good accuracy, in particular for IMRT plans consisting of several fields, where 97% of the pixels within the body fulfilled a tolerance set to 4% dose difference and 4 mm distance to agreement (DTA). For the two IMRT plans with different complexity, pronounced respiratory induced dose errors, which increased with increasing complexity, were found for both one fraction and 25 fractions, but due to the random stating phase the interplay effect was considerably reduced for the plans consisting of 25 fractions. This illustrates how the dosimetric effects will vary depending on the dose plan and on the number of fractions investigated. Conclusion. For patient specific cases, the model can with good accuracy calculate 3D dose distributions both with and without respiratory motion, and evaluate the dosimetric effects

  16. Dose domain regularization of MLC leaf patterns for highly complex IMRT plans

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Dan; Yu, Victoria Y.; Ruan, Dan; Cao, Minsong; Low, Daniel A.; Sheng, Ke, E-mail: ksheng@mednet.ucla.edu [Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California 90095 (United States); O’Connor, Daniel [Department of Mathematics, University of California Los Angeles, Los Angeles, California 90095 (United States)

    2015-04-15

    Purpose: The advent of automated beam orientation and fluence optimization enables more complex intensity modulated radiation therapy (IMRT) planning using an increasing number of fields to exploit the expanded solution space. This has created a challenge in converting complex fluences to robust multileaf collimator (MLC) segments for delivery. A novel method to regularize the fluence map and simplify MLC segments is introduced to maximize delivery efficiency, accuracy, and plan quality. Methods: In this work, we implemented a novel approach to regularize optimized fluences in the dose domain. The treatment planning problem was formulated in an optimization framework to minimize the segmentation-induced dose distribution degradation subject to a total variation regularization to encourage piecewise smoothness in fluence maps. The optimization problem was solved using a first-order primal-dual algorithm known as the Chambolle-Pock algorithm. Plans for 2 GBM, 2 head and neck, and 2 lung patients were created using 20 automatically selected and optimized noncoplanar beams. The fluence was first regularized using Chambolle-Pock and then stratified into equal steps, and the MLC segments were calculated using a previously described level reducing method. Isolated apertures with sizes smaller than preset thresholds of 1–3 bixels, which are square units of an IMRT fluence map from MLC discretization, were removed from the MLC segments. Performance of the dose domain regularized (DDR) fluences was compared to direct stratification and direct MLC segmentation (DMS) of the fluences using level reduction without dose domain fluence regularization. Results: For all six cases, the DDR method increased the average planning target volume dose homogeneity (D95/D5) from 0.814 to 0.878 while maintaining equivalent dose to organs at risk (OARs). Regularized fluences were more robust to MLC sequencing, particularly to the stratification and small aperture removal. The maximum and

  17. Intensity-modulated radiotherapy (IMRT) and conventional three-dimensional conformal radiotherapy for high-grade gliomas: Does IMRT increase the integral dose to normal brain?

    International Nuclear Information System (INIS)

    Hermanto, Ulrich; Frija, Erik K.; Lii, MingFwu J.; Chang, Eric L.; Mahajan, Anita; Woo, Shiao Y.

    2007-01-01

    Purpose: To determine whether intensity-modulated radiotherapy (IMRT) treatment increases the total integral dose of nontarget tissue relative to the conventional three-dimensional conformal radiotherapy (3D-CRT) technique for high-grade gliomas. Methods and Materials: Twenty patients treated with 3D-CRT for glioblastoma multiforme were selected for a comparative dosimetric evaluation with IMRT. Original target volumes, organs at risk (OAR), and dose-volume constraints were used for replanning with IMRT. Predicted isodose distributions, cumulative dose-volume histograms of target volumes and OAR, normal tissue integral dose, target coverage, dose conformity, and normal tissue sparing with 3D-CRT and IMRT planning were compared. Statistical analyses were performed to determine differences. Results: In all 20 patients, IMRT maintained equivalent target coverage, improved target conformity (conformity index [CI] 95% 1.52 vs. 1.38, p mean by 19.8% and D max by 10.7%), optic chiasm (D mean by 25.3% and D max by 22.6%), right optic nerve (D mean by 37.3% and D max by 28.5%), and left optic nerve (D mean by 40.6% and D max by 36.7%), p ≤ 0.01. This was achieved without increasing the total nontarget integral dose by greater than 0.5%. Overall, total integral dose was reduced by 7-10% with IMRT, p < 0.001, without significantly increasing the 0.5-5 Gy low-dose volume. Conclusions: These results indicate that IMRT treatment for high-grade gliomas allows for improved target conformity, better critical tissue sparing, and importantly does so without increasing integral dose and the volume of normal tissue exposed to low doses of radiation

  18. Temporo-spatial IMRT optimization: concepts, implementation and initial results

    International Nuclear Information System (INIS)

    Trofimov, Alexei; Rietzel, Eike; Lu Hsiaoming; Martin, Benjamin; Jiang, Steve; Chen, George T Y; Bortfeld, Thomas

    2005-01-01

    With the recent availability of 4D-CT, the accuracy of information on internal organ motion during respiration has improved significantly. We investigate the utility of organ motion information in IMRT treatment planning, using an in-house prototype optimization system. Four approaches are compared: (1) planning with optimized margins, based on motion information; (2) the 'motion kernel' approach, in which a more accurate description of the dose deposit from a pencil beam to a moving target is achieved either through time-weighted averaging of influence matrices, calculated for different instances of anatomy (subsets of 4D-CT data, corresponding to various phases of motion) or through convolution of the pencil beam kernel with the probability density function describing the target motion; (3) optimal gating, or tracking with beam intensity maps optimized independently for each instance of anatomy; and (4) optimal tracking with beam intensity maps optimized simultaneously for all instances of anatomy. The optimization is based on a gradient technique and can handle both physical (dose-volume) and equivalent uniform dose constraints. Optimization requires voxel mapping from phase to phase in order to score the dose in individual voxels as they move. The results show that, compared to the other approaches, margin expansion has a significant disadvantage by substantially increasing the integral dose to patient. While gating or tracking result in the best dose conformation to the target, the former elongates treatment time, and the latter significantly complicates the delivery procedure. The 'motion kernel' approach does not provide a dosimetric advantage, compared to optimal tracking or gating, but might lead to more efficient delivery. A combination of gating with the 'motion kernel' or margin expansion approach will increase the duty cycle and may provide one with the most efficient solution, in terms of complexity of the delivery procedure and dose conformality to

  19. Does IMRT increase the peripheral radiation dose? A comparison of treatment plans 2000 and 2010

    International Nuclear Information System (INIS)

    Salz, Henning; Eichner, Regina; Wiezorek, Tilo

    2012-01-01

    It has been reported in several papers and textbooks that IMRT treatments increase the peripheral dose in comparison with non-IMRT fields. But in clinical practice not only open fields have been used in the pre-IMRT era, but also fields with physical wedges or composed fields. The aim of this work is to test the hypothesis of increased peripheral dose when IMRT is used compared to standard conformal radiotherapy. Furthermore, the importance of the measured dose differences in clinical practice is discussed and compared with other new technologies for the cases where an increase of the peripheral dose was observed. For cancers of the head and neck, the cervix, the rectum and for the brain irradiation due to acute leukaemia, one to four plans have been calculated with IMRT or conformal standard technique (non-IMRT). In an anthropomorphic phantom the dose at a distance of 30 cm in cranio-caudal direction from the target edge was measured with TLDs using a linear accelerator Oncor registered (Siemens) for both techniques. IMRT was performed using step-and-shoot technique (7 to 11 beams), non-IMRT plans with different techniques. The results depended on the site of irradiation. For head and neck cancers IMRT resulted in an increase of 0.05 - 0.09% of the prescribed total dose (Dptv) or 40 - 70 mGy (Dptv = 65 Gy), compared to non-IMRT technique without wedges or a decrease of 0.16% (approx. 100 mGy) of the prescribed total dose compared to non-IMRT techniques with wedges. For the cervical cancer IMRT resulted in an increased dose in the periphery (+ 0.07% - 0.15% of Dptv or 30 - 70 mGy at Dptv = 45 Gy), for the rectal cancer in a dose reduction (0.21 - 0.26% of Dptv or 100 - 130 mGy at Dptv = 50 Gy) and for the brain irradiation in an increase dose (+ 0.05% of Dptv = 18 Gy or 9 mSv). In summary IMRT does not uniformly cause increased radiation dose in the periphery in the model used. It can be stated that these dose values are smaller than reported in earlier papers

  20. Per-beam, planar IMRT QA passing rates do not predict clinically relevant patient dose errors

    International Nuclear Information System (INIS)

    Nelms, Benjamin E.; Zhen Heming; Tome, Wolfgang A.

    2011-01-01

    Purpose: The purpose of this work is to determine the statistical correlation between per-beam, planar IMRT QA passing rates and several clinically relevant, anatomy-based dose errors for per-patient IMRT QA. The intent is to assess the predictive power of a common conventional IMRT QA performance metric, the Gamma passing rate per beam. Methods: Ninety-six unique data sets were created by inducing four types of dose errors in 24 clinical head and neck IMRT plans, each planned with 6 MV Varian 120-leaf MLC linear accelerators using a commercial treatment planning system and step-and-shoot delivery. The error-free beams/plans were used as ''simulated measurements'' (for generating the IMRT QA dose planes and the anatomy dose metrics) to compare to the corresponding data calculated by the error-induced plans. The degree of the induced errors was tuned to mimic IMRT QA passing rates that are commonly achieved using conventional methods. Results: Analysis of clinical metrics (parotid mean doses, spinal cord max and D1cc, CTV D95, and larynx mean) vs IMRT QA Gamma analysis (3%/3 mm, 2/2, 1/1) showed that in all cases, there were only weak to moderate correlations (range of Pearson's r-values: -0.295 to 0.653). Moreover, the moderate correlations actually had positive Pearson's r-values (i.e., clinically relevant metric differences increased with increasing IMRT QA passing rate), indicating that some of the largest anatomy-based dose differences occurred in the cases of high IMRT QA passing rates, which may be called ''false negatives.'' The results also show numerous instances of false positives or cases where low IMRT QA passing rates do not imply large errors in anatomy dose metrics. In none of the cases was there correlation consistent with high predictive power of planar IMRT passing rates, i.e., in none of the cases did high IMRT QA Gamma passing rates predict low errors in anatomy dose metrics or vice versa. Conclusions: There is a lack of correlation between

  1. IMRT optimization: Variability of solutions and its radiobiological impact

    International Nuclear Information System (INIS)

    Mattia, Maurizio; Del Giudice, Paolo; Caccia, Barbara

    2004-01-01

    We aim at (1) defining and measuring a 'complexity' index for the optimization process of an intensity modulated radiation therapy treatment plan (IMRT TP), (2) devising an efficient approximate optimization strategy, and (3) evaluating the impact of the complexity of the optimization process on the radiobiological quality of the treatment. In this work, for a prostate therapy case, the IMRT TP optimization problem has been formulated in terms of dose-volume constraints. The cost function has been minimized in order to achieve the optimal solution, by means of an iterative procedure, which is repeated for many initial modulation profiles, and for each of them the final optimal solution is recorded. To explore the complexity of the space of such solutions we have chosen to minimize the cost function with an algorithm that is unable to avoid local minima. The size of the (sub)optimal solutions distribution is taken as an indicator of the complexity of the optimization problem. The impact of the estimated complexity on the probability of success of the therapy is evaluated using radiobiological indicators (Poissonian TCP model [S. Webb and A. E. Nahum, Phys. Med. Biol. 38(6), 653-666 (1993)] and NTCP relative seriality model [Kallman et al., Int. J. Radiat. Biol. 62(2), 249-262 (1992)]). We find in the examined prostate case a nontrivial distribution of local minima, which has symmetry properties allowing a good estimate of near-optimal solutions with a moderate computational load. We finally demonstrate that reducing the a priori uncertainty in the optimal solution results in a significant improvement of the probability of success of the TP, based on TCP and NTCP estimates

  2. Variable beam dose rate and DMLC IMRT to moving body anatomy

    International Nuclear Information System (INIS)

    Papiez, Lech; Abolfath, Ramin M.

    2008-01-01

    Derivation of formulas relating leaf speeds and beam dose rates for delivering planned intensity profiles to static and moving targets in dynamic multileaf collimator (DMLC) intensity modulated radiation therapy (IMRT) is presented. The analysis of equations determining algorithms for DMLC IMRT delivery under a variable beam dose rate reveals a multitude of possible delivery strategies for a given intensity map and for any given target motion patterns. From among all equivalent delivery strategies for DMLC IMRT treatments specific subclasses of strategies can be selected to provide deliveries that are particularly suitable for clinical applications providing existing delivery devices are used. Special attention is devoted to the subclass of beam dose rate variable DMLC delivery strategies to moving body anatomy that generalize existing techniques of such deliveries in Varian DMLC irradiation methodology to static body anatomy. Few examples of deliveries from this subclass of DMLC IMRT irradiations are investigated to illustrate the principle and show practical benefits of proposed techniques.

  3. Variable beam dose rate and DMLC IMRT to moving body anatomy

    Energy Technology Data Exchange (ETDEWEB)

    Papiez, Lech; Abolfath, Ramin M. [Department of Radiation Oncology, UTSouthwestern Medical Center, Dallas, Texas 75390 (United States)

    2008-11-15

    Derivation of formulas relating leaf speeds and beam dose rates for delivering planned intensity profiles to static and moving targets in dynamic multileaf collimator (DMLC) intensity modulated radiation therapy (IMRT) is presented. The analysis of equations determining algorithms for DMLC IMRT delivery under a variable beam dose rate reveals a multitude of possible delivery strategies for a given intensity map and for any given target motion patterns. From among all equivalent delivery strategies for DMLC IMRT treatments specific subclasses of strategies can be selected to provide deliveries that are particularly suitable for clinical applications providing existing delivery devices are used. Special attention is devoted to the subclass of beam dose rate variable DMLC delivery strategies to moving body anatomy that generalize existing techniques of such deliveries in Varian DMLC irradiation methodology to static body anatomy. Few examples of deliveries from this subclass of DMLC IMRT irradiations are investigated to illustrate the principle and show practical benefits of proposed techniques.

  4. Per-beam, planar IMRT QA passing rates do not predict clinically relevant patient dose errors

    Energy Technology Data Exchange (ETDEWEB)

    Nelms, Benjamin E.; Zhen Heming; Tome, Wolfgang A. [Canis Lupus LLC and Department of Human Oncology, University of Wisconsin, Merrimac, Wisconsin 53561 (United States); Department of Medical Physics, University of Wisconsin, Madison, Wisconsin 53705 (United States); Departments of Human Oncology, Medical Physics, and Biomedical Engineering, University of Wisconsin, Madison, Wisconsin 53792 (United States)

    2011-02-15

    Purpose: The purpose of this work is to determine the statistical correlation between per-beam, planar IMRT QA passing rates and several clinically relevant, anatomy-based dose errors for per-patient IMRT QA. The intent is to assess the predictive power of a common conventional IMRT QA performance metric, the Gamma passing rate per beam. Methods: Ninety-six unique data sets were created by inducing four types of dose errors in 24 clinical head and neck IMRT plans, each planned with 6 MV Varian 120-leaf MLC linear accelerators using a commercial treatment planning system and step-and-shoot delivery. The error-free beams/plans were used as ''simulated measurements'' (for generating the IMRT QA dose planes and the anatomy dose metrics) to compare to the corresponding data calculated by the error-induced plans. The degree of the induced errors was tuned to mimic IMRT QA passing rates that are commonly achieved using conventional methods. Results: Analysis of clinical metrics (parotid mean doses, spinal cord max and D1cc, CTV D95, and larynx mean) vs IMRT QA Gamma analysis (3%/3 mm, 2/2, 1/1) showed that in all cases, there were only weak to moderate correlations (range of Pearson's r-values: -0.295 to 0.653). Moreover, the moderate correlations actually had positive Pearson's r-values (i.e., clinically relevant metric differences increased with increasing IMRT QA passing rate), indicating that some of the largest anatomy-based dose differences occurred in the cases of high IMRT QA passing rates, which may be called ''false negatives.'' The results also show numerous instances of false positives or cases where low IMRT QA passing rates do not imply large errors in anatomy dose metrics. In none of the cases was there correlation consistent with high predictive power of planar IMRT passing rates, i.e., in none of the cases did high IMRT QA Gamma passing rates predict low errors in anatomy dose metrics or vice versa

  5. Incorporating prior knowledge into beam orientation optimization in IMRT

    International Nuclear Information System (INIS)

    Pugachev, Andrei M.S.; Lei Xing

    2002-01-01

    Purpose: Selection of beam configuration in currently available intensity-modulated radiotherapy (IMRT) treatment planning systems is still based on trial-and-error search. Computer beam orientation optimization has the potential to improve the situation, but its practical implementation is hindered by the excessive computing time associated with the calculation. The purpose of this work is to provide an effective means to speed up the beam orientation optimization by incorporating a priori geometric and dosimetric knowledge of the system and to demonstrate the utility of the new algorithm for beam placement in IMRT. Methods and Materials: Beam orientation optimization was performed in two steps. First, the quality of each possible beam orientation was evaluated using beam's-eye-view dosimetrics (BEVD) developed in our previous study. A simulated annealing algorithm was then employed to search for the optimal set of beam orientations, taking into account the BEVD scores of different incident beam directions. During the calculation, sampling of gantry angles was weighted according to the BEVD score computed before the optimization. A beam direction with a higher BEVD score had a higher probability of being included in the trial configuration, and vice versa. The inclusion of the BEVD weighting in the stochastic beam angle sampling process made it possible to avoid spending valuable computing time unnecessarily at 'bad' beam angles. An iterative inverse treatment planning algorithm was used for beam intensity profile optimization during the optimization process. The BEVD-guided beam orientation optimization was applied to an IMRT treatment of paraspinal tumor. The advantage of the new optimization algorithm was demonstrated by comparing the calculation with the conventional scheme without the BEVD weighting in the beam sampling. Results: The BEVD tool provided useful guidance for the selection of the potentially good directions for the beams to incident and was used

  6. SU-F-J-133: Adaptive Radiation Therapy with a Four-Dimensional Dose Calculation Algorithm That Optimizes Dose Distribution Considering Breathing Motion

    Energy Technology Data Exchange (ETDEWEB)

    Ali, I; Algan, O; Ahmad, S [University of Oklahoma Health Sciences, Oklahoma City, OK (United States); Alsbou, N [University of Central Oklahoma, Edmond, OK (United States)

    2016-06-15

    Purpose: To model patient motion and produce four-dimensional (4D) optimized dose distributions that consider motion-artifacts in the dose calculation during the treatment planning process. Methods: An algorithm for dose calculation is developed where patient motion is considered in dose calculation at the stage of the treatment planning. First, optimal dose distributions are calculated for the stationary target volume where the dose distributions are optimized considering intensity-modulated radiation therapy (IMRT). Second, a convolution-kernel is produced from the best-fitting curve which matches the motion trajectory of the patient. Third, the motion kernel is deconvolved with the initial dose distribution optimized for the stationary target to produce a dose distribution that is optimized in four-dimensions. This algorithm is tested with measured doses using a mobile phantom that moves with controlled motion patterns. Results: A motion-optimized dose distribution is obtained from the initial dose distribution of the stationary target by deconvolution with the motion-kernel of the mobile target. This motion-optimized dose distribution is equivalent to that optimized for the stationary target using IMRT. The motion-optimized and measured dose distributions are tested with the gamma index with a passing rate of >95% considering 3% dose-difference and 3mm distance-to-agreement. If the dose delivery per beam takes place over several respiratory cycles, then the spread-out of the dose distributions is only dependent on the motion amplitude and not affected by motion frequency and phase. This algorithm is limited to motion amplitudes that are smaller than the length of the target along the direction of motion. Conclusion: An algorithm is developed to optimize dose in 4D. Besides IMRT that provides optimal dose coverage for a stationary target, it extends dose optimization to 4D considering target motion. This algorithm provides alternative to motion management

  7. Generalized field-splitting algorithms for optimal IMRT delivery efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Kamath, Srijit [Department of Radiation Oncology, University of Florida, Gainesville, FL (United States); Sahni, Sartaj [Department of Computer and Information Science and Engineering, University of Florida, Gainesville, FL (United States); Li, Jonathan [Department of Radiation Oncology, University of Florida, Gainesville, FL (United States); Ranka, Sanjay [Department of Computer and Information Science and Engineering, University of Florida, Gainesville, FL (United States); Palta, Jatinder [Department of Radiation Oncology, University of Florida, Gainesville, FL (United States)

    2007-09-21

    Intensity-modulated radiation therapy (IMRT) uses radiation beams of varying intensities to deliver varying doses of radiation to different areas of the tissue. The use of IMRT has allowed the delivery of higher doses of radiation to the tumor and lower doses to the surrounding healthy tissue. It is not uncommon for head and neck tumors, for example, to have large treatment widths that are not deliverable using a single field. In such cases, the intensity matrix generated by the optimizer needs to be split into two or three matrices, each of which may be delivered using a single field. Existing field-splitting algorithms used the pre-specified arbitrary split line or region where the intensity matrix is split along a column, i.e., all rows of the matrix are split along the same column (with or without the overlapping of split fields, i.e., feathering). If three fields result, then the two splits are along the same two columns for all rows. In this paper we study the problem of splitting a large field into two or three subfields with the field width as the only constraint, allowing for an arbitrary overlap of the split fields, so that the total MU efficiency of delivering the split fields is maximized. Proof of optimality is provided for the proposed algorithm. An average decrease of 18.8% is found in the total MUs when compared to the split generated by a commercial treatment planning system and that of 10% is found in the total MUs when compared to the split generated by our previously published algorithm. For more information on this article, see medicalphysicsweb.org.

  8. SU-E-T-593: Clinical Evaluation of Direct Aperture Optimization in Head/Neck and Prostate IMRT Treatment

    Energy Technology Data Exchange (ETDEWEB)

    Hosini, M [King Saud University Hospitals, Riyadh (Saudi Arabia); GALAL, M [Hermitage Medical Clinic, Dublin (Ireland); Emam, I [Ain Shams University, Cairo (France); Kamal, G; Algohary, M [Al Azhar University, Cairo (Egypt)

    2014-06-01

    Purpose: To investigate the planning and dosimetric advantages of direct aperture optimization (DAO) over beam-let optimization in IMRT treatment of head and neck (H/N) and prostate cancers. Methods: Five Head and Neck as well as five prostate patients were planned using the beamlet optimizer in Elekta-Xio ver 4.6 IMRT treatment planning system. Based on our experience in beamlet IMRT optimization, PTVs in H/N plans were prescribed to 70 Gy delivered by 7 fields. While prostate PTVs were prescribed to 76 Gy with 9 fields. In all plans, fields were set to be equally spaced. All cases were re-planed using Direct Aperture optimizer in Prowess Panther ver 5.01 IMRT planning system at same configurations and dose constraints. Plans were evaluated according to ICRU criteria, number of segments, number of monitor units and planning time. Results: For H/N plans, the near maximum dose (D2) and the dose that covers 95% D95 of PTV has improved by 4% in DAO. For organs at risk (OAR), DAO reduced the volume covered by 30% (V30) in spinal cord, right parotid, and left parotid by 60%, 54%, and 53% respectively. This considerable dosimetric quality improvement achieved using 25% less planning time and lower number of segments and monitor units by 46% and 51% respectively. In DAO prostate plans, Both D2 and D95 for the PTV were improved by only 2%. The V30 of the right femur, left femur and bladder were improved by 35%, 15% and 3% respectively. On the contrary, the rectum V30 got even worse by 9%. However, number of monitor units, and number of segments decreased by 20% and 25% respectively. Moreover the planning time reduced significantly too. Conclusion: DAO introduces considerable advantages over the beamlet optimization in regards to organs at risk sparing. However, no significant improvement occurred in most studied PTVs.

  9. Analysis of Radiation Treatment Planning by Dose Calculation and Optimization Algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dae Sup; Yoon, In Ha; Lee, Woo Seok; Baek, Geum Mun [Dept. of Radiation Oncology, Asan Medical Center, Seoul (Korea, Republic of)

    2012-09-15

    Analyze the Effectiveness of Radiation Treatment Planning by dose calculation and optimization algorithm, apply consideration of actual treatment planning, and then suggest the best way to treatment planning protocol. The treatment planning system use Eclipse 10.0. (Varian, USA). PBC (Pencil Beam Convolution) and AAA (Anisotropic Analytical Algorithm) Apply to Dose calculation, DVO (Dose Volume Optimizer 10.0.28) used for optimized algorithm of Intensity Modulated Radiation Therapy (IMRT), PRO II (Progressive Resolution Optimizer V 8.9.17) and PRO III (Progressive Resolution Optimizer V 10.0.28) used for optimized algorithm of VAMT. A phantom for experiment virtually created at treatment planning system, 30x30x30 cm sized, homogeneous density (HU: 0) and heterogeneous density that inserted air assumed material (HU: -1,000). Apply to clinical treatment planning on the basis of general treatment planning feature analyzed with Phantom planning. In homogeneous density phantom, PBC and AAA show 65.2% PDD (6 MV, 10 cm) both, In heterogeneous density phantom, also show similar PDD value before meet with low density material, but they show different dose curve in air territory, PDD 10 cm showed 75%, 73% each after penetrate phantom. 3D treatment plan in same MU, AAA treatment planning shows low dose at Lung included area. 2D POP treatment plan with 15 MV of cervical vertebral region include trachea and lung area, Conformity Index (ICRU 62) is 0.95 in PBC calculation and 0.93 in AAA. DVO DVH and Dose calculation DVH are showed equal value in IMRT treatment plan. But AAA calculation shows lack of dose compared with DVO result which is satisfactory condition. Optimizing VMAT treatment plans using PRO II obtained results were satisfactory, but lower density area showed lack of dose in dose calculations. PRO III, but optimizing the dose calculation results were similar with optimized the same conditions once more. In this study, do not judge the rightness of the dose

  10. Analysis of Radiation Treatment Planning by Dose Calculation and Optimization Algorithm

    International Nuclear Information System (INIS)

    Kim, Dae Sup; Yoon, In Ha; Lee, Woo Seok; Baek, Geum Mun

    2012-01-01

    Analyze the Effectiveness of Radiation Treatment Planning by dose calculation and optimization algorithm, apply consideration of actual treatment planning, and then suggest the best way to treatment planning protocol. The treatment planning system use Eclipse 10.0. (Varian, USA). PBC (Pencil Beam Convolution) and AAA (Anisotropic Analytical Algorithm) Apply to Dose calculation, DVO (Dose Volume Optimizer 10.0.28) used for optimized algorithm of Intensity Modulated Radiation Therapy (IMRT), PRO II (Progressive Resolution Optimizer V 8.9.17) and PRO III (Progressive Resolution Optimizer V 10.0.28) used for optimized algorithm of VAMT. A phantom for experiment virtually created at treatment planning system, 30x30x30 cm sized, homogeneous density (HU: 0) and heterogeneous density that inserted air assumed material (HU: -1,000). Apply to clinical treatment planning on the basis of general treatment planning feature analyzed with Phantom planning. In homogeneous density phantom, PBC and AAA show 65.2% PDD (6 MV, 10 cm) both, In heterogeneous density phantom, also show similar PDD value before meet with low density material, but they show different dose curve in air territory, PDD 10 cm showed 75%, 73% each after penetrate phantom. 3D treatment plan in same MU, AAA treatment planning shows low dose at Lung included area. 2D POP treatment plan with 15 MV of cervical vertebral region include trachea and lung area, Conformity Index (ICRU 62) is 0.95 in PBC calculation and 0.93 in AAA. DVO DVH and Dose calculation DVH are showed equal value in IMRT treatment plan. But AAA calculation shows lack of dose compared with DVO result which is satisfactory condition. Optimizing VMAT treatment plans using PRO II obtained results were satisfactory, but lower density area showed lack of dose in dose calculations. PRO III, but optimizing the dose calculation results were similar with optimized the same conditions once more. In this study, do not judge the rightness of the dose

  11. Single-Arc IMRT?

    International Nuclear Information System (INIS)

    Bortfeld, Thomas; Webb, Steve

    2009-01-01

    The idea of delivering intensity-modulated radiation therapy (IMRT) with a multileaf collimator in a continuous dynamic mode during a single rotation of the gantry has recently gained momentum both in research and industry. In this note we investigate the potential of this Single-Arc IMRT technique at a conceptual level. We consider the original theoretical example case from Brahme et al that got the field of IMRT started. Using analytical methods, we derive deliverable intensity 'landscapes' for Single-Arc as well as standard IMRT and Tomotherapy. We find that Tomotherapy provides the greatest flexibility in shaping intensity landscapes and that it allows one to deliver IMRT in a way that comes close to the ideal case in the transverse plane. Single-Arc and standard IMRT make compromises in different areas. Only in relatively simple cases that do not require substantial intensity modulation will Single-Arc be dosimetrically comparable to Tomotherapy. Compared with standard IMRT, Single-Arc could be dosimetrically superior in certain cases if one is willing to accept the spreading of low dose values over large volumes of normal tissue. In terms of treatment planning, Single-Arc poses a more challenging optimization problem than Tomotherapy or standard IMRT. We conclude that Single-Arc holds potential as an efficient IMRT technique especially for relatively simple cases. In very complex cases, Single-Arc may unduly compromise the quality of the dose distribution, if one tries to keep the treatment time below 2 min or so. As with all IMRT techniques, it is important to explore the tradeoff between plan quality and the efficiency of its delivery carefully for each individual case. (note)

  12. Fast online Monte Carlo-based IMRT planning for the MRI linear accelerator

    Science.gov (United States)

    Bol, G. H.; Hissoiny, S.; Lagendijk, J. J. W.; Raaymakers, B. W.

    2012-03-01

    The MRI accelerator, a combination of a 6 MV linear accelerator with a 1.5 T MRI, facilitates continuous patient anatomy updates regarding translations, rotations and deformations of targets and organs at risk. Accounting for these demands high speed, online intensity-modulated radiotherapy (IMRT) re-optimization. In this paper, a fast IMRT optimization system is described which combines a GPU-based Monte Carlo dose calculation engine for online beamlet generation and a fast inverse dose optimization algorithm. Tightly conformal IMRT plans are generated for four phantom cases and two clinical cases (cervix and kidney) in the presence of the magnetic fields of 0 and 1.5 T. We show that for the presented cases the beamlet generation and optimization routines are fast enough for online IMRT planning. Furthermore, there is no influence of the magnetic field on plan quality and complexity, and equal optimization constraints at 0 and 1.5 T lead to almost identical dose distributions.

  13. Comparison of direct machine parameter optimization versus fluence optimization with sequential sequencing in IMRT of hypopharyngeal carcinoma

    International Nuclear Information System (INIS)

    Dobler, Barbara; Pohl, Fabian; Bogner, Ludwig; Koelbl, Oliver

    2007-01-01

    To evaluate the effects of direct machine parameter optimization in the treatment planning of intensity-modulated radiation therapy (IMRT) for hypopharyngeal cancer as compared to subsequent leaf sequencing in Oncentra Masterplan v1.5. For 10 hypopharyngeal cancer patients IMRT plans were generated in Oncentra Masterplan v1.5 (Nucletron BV, Veenendal, the Netherlands) for a Siemens Primus linear accelerator. For optimization the dose volume objectives (DVO) for the planning target volume (PTV) were set to 53 Gy minimum dose and 59 Gy maximum dose, in order to reach a dose of 56 Gy to the average of the PTV. For the parotids a median dose of 22 Gy was allowed and for the spinal cord a maximum dose of 35 Gy. The maximum DVO to the external contour of the patient was set to 59 Gy. The treatment plans were optimized with the direct machine parameter optimization ('Direct Step & Shoot', DSS, Raysearch Laboratories, Sweden) newly implemented in Masterplan v1.5 and the fluence modulation technique ('Intensity Modulation', IM) which was available in previous versions of Masterplan already. The two techniques were compared with regard to compliance to the DVO, plan quality, and number of monitor units (MU) required per fraction dose. The plans optimized with the DSS technique met the DVO for the PTV significantly better than the plans optimized with IM (p = 0.007 for the min DVO and p < 0.0005 for the max DVO). No significant difference could be observed for compliance to the DVO for the organs at risk (OAR) (p > 0.05). Plan quality, target coverage and dose homogeneity inside the PTV were superior for the plans optimized with DSS for similar dose to the spinal cord and lower dose to the normal tissue. The mean dose to the parotids was lower for the plans optimized with IM. Treatment plan efficiency was higher for the DSS plans with (901 ± 160) MU compared to (1151 ± 157) MU for IM (p-value < 0.05). Renormalization of the IM plans to the mean of the

  14. Maximizing dosimetric benefits of IMRT in the treatment of localized prostate cancer through multicriteria optimization planning

    International Nuclear Information System (INIS)

    Wala, Jeremiah; Craft, David; Paly, Jon; Zietman, Anthony; Efstathiou, Jason

    2013-01-01

    We examine the quality of plans created using multicriteria optimization (MCO) treatment planning in intensity-modulated radiation therapy (IMRT) in treatment of localized prostate cancer. Nine random cases of patients receiving IMRT to the prostate were selected. Each case was associated with a clinically approved plan created using Corvus. The cases were replanned using MCO-based planning in RayStation. Dose-volume histogram data from both planning systems were presented to 2 radiation oncologists in a blinded evaluation, and were compared at a number of dose-volume points. Both physicians rated all 9 MCO plans as superior to the clinically approved plans (p −5 ). Target coverage was equivalent (p = 0.81). Maximum doses to the prostate and bladder and the V50 and V70 to the anterior rectum were reduced in all MCO plans (p<0.05). Treatment planning time with MCO took approximately 60 minutes per case. MCO-based planning for prostate IMRT is efficient and produces high-quality plans with good target homogeneity and sparing of the anterior rectum, bladder, and femoral heads, without sacrificing target coverage

  15. Maximizing dosimetric benefits of IMRT in the treatment of localized prostate cancer through multicriteria optimization planning

    Energy Technology Data Exchange (ETDEWEB)

    Wala, Jeremiah; Craft, David [Harvard Medical School, Boston, MA (United States); Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA (United States); Paly, Jon [Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA (United States); Zietman, Anthony [Harvard Medical School, Boston, MA (United States); Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA (United States); Efstathiou, Jason, E-mail: jefstathiou@partners.org [Harvard Medical School, Boston, MA (United States); Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA (United States)

    2013-10-01

    We examine the quality of plans created using multicriteria optimization (MCO) treatment planning in intensity-modulated radiation therapy (IMRT) in treatment of localized prostate cancer. Nine random cases of patients receiving IMRT to the prostate were selected. Each case was associated with a clinically approved plan created using Corvus. The cases were replanned using MCO-based planning in RayStation. Dose-volume histogram data from both planning systems were presented to 2 radiation oncologists in a blinded evaluation, and were compared at a number of dose-volume points. Both physicians rated all 9 MCO plans as superior to the clinically approved plans (p<10{sup −5}). Target coverage was equivalent (p = 0.81). Maximum doses to the prostate and bladder and the V50 and V70 to the anterior rectum were reduced in all MCO plans (p<0.05). Treatment planning time with MCO took approximately 60 minutes per case. MCO-based planning for prostate IMRT is efficient and produces high-quality plans with good target homogeneity and sparing of the anterior rectum, bladder, and femoral heads, without sacrificing target coverage.

  16. Direct aperture optimization: A turnkey solution for step-and-shoot IMRT

    International Nuclear Information System (INIS)

    Shepard, D.M.; Earl, M.A.; Li, X.A.; Naqvi, S.; Yu, C.

    2002-01-01

    IMRT treatment plans for step-and-shoot delivery have traditionally been produced through the optimization of intensity distributions (or maps) for each beam angle. The optimization step is followed by the application of a leaf-sequencing algorithm that translates each intensity map into a set of deliverable aperture shapes. In this article, we introduce an automated planning system in which we bypass the traditional intensity optimization, and instead directly optimize the shapes and the weights of the apertures. We call this approach 'direct aperture optimization'. This technique allows the user to specify the maximum number of apertures per beam direction, and hence provides significant control over the complexity of the treatment delivery. This is possible because the machine dependent delivery constraints imposed by the MLC are enforced within the aperture optimization algorithm rather than in a separate leaf-sequencing step. The leaf settings and the aperture intensities are optimized simultaneously using a simulated annealing algorithm. We have tested direct aperture optimization on a variety of patient cases using the EGS4/BEAM Monte Carlo package for our dose calculation engine. The results demonstrate that direct aperture optimization can produce highly conformal step-and-shoot treatment plans using only three to five apertures per beam direction. As compared with traditional optimization strategies, our studies demonstrate that direct aperture optimization can result in a significant reduction in both the number of beam segments and the number of monitor units. Direct aperture optimization therefore produces highly efficient treatment deliveries that maintain the full dosimetric benefits of IMRT

  17. Dose discrepancies in the buildup region and their impact on dose calculations for IMRT fields

    International Nuclear Information System (INIS)

    Hsu, Shu-Hui; Moran, Jean M.; Chen Yu; Kulasekere, Ravi; Roberson, Peter L.

    2010-01-01

    Purpose: Dose accuracy in the buildup region for radiotherapy treatment planning suffers from challenges in both measurement and calculation. This study investigates the dosimetry in the buildup region at normal and oblique incidences for open and IMRT fields and assesses the quality of the treatment planning calculations. Methods: This study was divided into three parts. First, percent depth doses and profiles (for 5x5, 10x10, 20x20, and 30x30 cm 2 field sizes at 0 deg., 45 deg., and 70 deg. incidences) were measured in the buildup region in Solid Water using an Attix parallel plate chamber and Kodak XV film, respectively. Second, the parameters in the empirical contamination (EC) term of the convolution/superposition (CVSP) calculation algorithm were fitted based on open field measurements. Finally, seven segmental head-and-neck IMRT fields were measured on a flat phantom geometry and compared to calculations using γ and dose-gradient compensation (C) indices to evaluate the impact of residual discrepancies and to assess the adequacy of the contamination term for IMRT fields. Results: Local deviations between measurements and calculations for open fields were within 1% and 4% in the buildup region for normal and oblique incidences, respectively. The C index with 5%/1 mm criteria for IMRT fields ranged from 89% to 99% and from 96% to 98% at 2 mm and 10 cm depths, respectively. The quality of agreement in the buildup region for open and IMRT fields is comparable to that in nonbuildup regions. Conclusions: The added EC term in CVSP was determined to be adequate for both open and IMRT fields. Due to the dependence of calculation accuracy on (1) EC modeling, (2) internal convolution and density grid sizes, (3) implementation details in the algorithm, and (4) the accuracy of measurements used for treatment planning system commissioning, the authors recommend an evaluation of the accuracy of near-surface dose calculations as a part of treatment planning commissioning.

  18. SU-E-T-478: Sliding Window Multi-Criteria IMRT Optimization

    International Nuclear Information System (INIS)

    Craft, D; Papp, D; Unkelbach, J; Bokrantz, R

    2014-01-01

    Purpose: To demonstrate a method for what-you-see-is-what-you-get multi-criteria Pareto surface navigation for step and shoot IMRT treatment planning. Methods: We show mathematically how multiple sliding window treatment plans can be averaged to yield a single plan whose dose distribution is the dosimetric average of the averaged plans. This is incorporated into the Pareto surface navigation based approach to treatment planning in such a way that as the user navigates the surface, the plans he/she is viewing are ready to be delivered (i.e. there is no extra ‘segment the plans’ step that often leads to unacceptable plan degradation in step and shoot Pareto surface navigation). We also describe how the technique can be applied to VMAT. Briefly, sliding window VMAT plans are created such that MLC leaves paint out fluence maps every 15 degrees or so. These fluence map leaf trajectories are averaged in the same way the static beam IMRT ones are. Results: We show mathematically that fluence maps are exactly averaged using our leaf sweep averaging algorithm. Leaf transmission and output factor corrections effects, which are ignored in this work, can lead to small errors in terms of the dose distributions not being exactly averaged even though the fluence maps are. However, our demonstrations show that the dose distributions are almost exactly averaged as well. We demonstrate the technique both for IMRT and VMAT. Conclusions: By turning to sliding window delivery, we show that the problem of losing plan fidelity during the conversion of an idealized fluence map plan into a deliverable plan is remedied. This will allow for multicriteria optimization that avoids the pitfall that the planning has to be redone after the conversion into MLC segments due to plan quality decline. David Craft partially funded by RaySearch Laboratories

  19. SU-E-T-478: Sliding Window Multi-Criteria IMRT Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Craft, D; Papp, D; Unkelbach, J [Massachusetts General Hospital, Boston, MA (United States); Bokrantz, R [RaySearch Laboratories, Stockholm (Sweden)

    2014-06-01

    Purpose: To demonstrate a method for what-you-see-is-what-you-get multi-criteria Pareto surface navigation for step and shoot IMRT treatment planning. Methods: We show mathematically how multiple sliding window treatment plans can be averaged to yield a single plan whose dose distribution is the dosimetric average of the averaged plans. This is incorporated into the Pareto surface navigation based approach to treatment planning in such a way that as the user navigates the surface, the plans he/she is viewing are ready to be delivered (i.e. there is no extra ‘segment the plans’ step that often leads to unacceptable plan degradation in step and shoot Pareto surface navigation). We also describe how the technique can be applied to VMAT. Briefly, sliding window VMAT plans are created such that MLC leaves paint out fluence maps every 15 degrees or so. These fluence map leaf trajectories are averaged in the same way the static beam IMRT ones are. Results: We show mathematically that fluence maps are exactly averaged using our leaf sweep averaging algorithm. Leaf transmission and output factor corrections effects, which are ignored in this work, can lead to small errors in terms of the dose distributions not being exactly averaged even though the fluence maps are. However, our demonstrations show that the dose distributions are almost exactly averaged as well. We demonstrate the technique both for IMRT and VMAT. Conclusions: By turning to sliding window delivery, we show that the problem of losing plan fidelity during the conversion of an idealized fluence map plan into a deliverable plan is remedied. This will allow for multicriteria optimization that avoids the pitfall that the planning has to be redone after the conversion into MLC segments due to plan quality decline. David Craft partially funded by RaySearch Laboratories.

  20. Independent calculation-based verification of IMRT plans using a 3D dose-calculation engine

    International Nuclear Information System (INIS)

    Arumugam, Sankar; Xing, Aitang; Goozee, Gary; Holloway, Lois

    2013-01-01

    Independent monitor unit verification of intensity-modulated radiation therapy (IMRT) plans requires detailed 3-dimensional (3D) dose verification. The aim of this study was to investigate using a 3D dose engine in a second commercial treatment planning system (TPS) for this task, facilitated by in-house software. Our department has XiO and Pinnacle TPSs, both with IMRT planning capability and modeled for an Elekta-Synergy 6 MV photon beam. These systems allow the transfer of computed tomography (CT) data and RT structures between them but do not allow IMRT plans to be transferred. To provide this connectivity, an in-house computer programme was developed to convert radiation therapy prescription (RTP) files as generated by many planning systems into either XiO or Pinnacle IMRT file formats. Utilization of the technique and software was assessed by transferring 14 IMRT plans from XiO and Pinnacle onto the other system and performing 3D dose verification. The accuracy of the conversion process was checked by comparing the 3D dose matrices and dose volume histograms (DVHs) of structures for the recalculated plan on the same system. The developed software successfully transferred IMRT plans generated by 1 planning system into the other. Comparison of planning target volume (TV) DVHs for the original and recalculated plans showed good agreement; a maximum difference of 2% in mean dose, − 2.5% in D95, and 2.9% in V95 was observed. Similarly, a DVH comparison of organs at risk showed a maximum difference of +7.7% between the original and recalculated plans for structures in both high- and medium-dose regions. However, for structures in low-dose regions (less than 15% of prescription dose) a difference in mean dose up to +21.1% was observed between XiO and Pinnacle calculations. A dose matrix comparison of original and recalculated plans in XiO and Pinnacle TPSs was performed using gamma analysis with 3%/3 mm criteria. The mean and standard deviation of pixels passing

  1. A planning and delivery study of a rotational IMRT technique with burst delivery

    International Nuclear Information System (INIS)

    Kainz, Kristofer; Chen, Guang-Pei; Chang, Yu-Wen; Prah, Douglas; Sharon Qi, X.; Shukla, Himanshu P.; Stahl, Johannes; Allen Li, X.

    2011-01-01

    Purpose: A novel rotational IMRT (rIMRT) technique using burst delivery (continuous gantry rotation with beam off during MLC repositioning) is investigated. The authors evaluate the plan quality and delivery efficiency and accuracy of this dynamic technique with a conventional flat 6 MV photon beam. Methods: Burst-delivery rIMRT was implemented in a planning system and delivered with a 160-MLC linac. Ten rIMRT plans were generated for five anonymized patient cases encompassing head and neck, brain, prostate, and prone breast. All plans were analyzed retrospectively and not used for treatment. Among the varied plan parameters were the number of optimization points, number of arcs, gantry speed, and gantry angle range (alpha) over which the beam is turned on at each optimization point. Combined rotational/step-and-shoot rIMRT plans were also created by superimposing multiple-segment static fields at several optimization points. The rIMRT trial plans were compared with each other and with plans generated using helical tomotherapy and VMAT. Burst-mode rotational IMRT plans were delivered and verified using a diode array, ionization chambers, thermoluminescent dosimeters, and film. Results: Burst-mode rIMRT can achieve plan quality comparable to helical tomotherapy, while the former may lead to slightly better OAR sparing for certain cases and the latter generally achieves slightly lower hot spots. Few instances were found in which increasing the number of optimization points above 36, or superimposing step-and-shoot IMRT segments, led to statistically significant improvements in OAR sparing. Using an additional rIMRT partial arc yielded substantial OAR dose improvements for the brain case. Measured doses from the rIMRT plan delivery were within 4% of the plan calculation in low dose gradient regions. Delivery time range was 228-375 s for single-arc rIMRT 200-cGy prescription with a 300 MU/min dose rate, comparable to tomotherapy and VMAT. Conclusions: Rotational IMRT

  2. SU-E-T-500: Initial Implementation of GPU-Based Particle Swarm Optimization for 4D IMRT Planning in Lung SBRT

    International Nuclear Information System (INIS)

    Modiri, A; Hagan, A; Gu, X; Sawant, A

    2015-01-01

    Purpose 4D-IMRT planning, combined with dynamic MLC tracking delivery, utilizes the temporal dimension as an additional degree of freedom to achieve improved OAR-sparing. The computational complexity for such optimization increases exponentially with increase in dimensionality. In order to accomplish this task in a clinically-feasible time frame, we present an initial implementation of GPU-based 4D-IMRT planning based on particle swarm optimization (PSO). Methods The target and normal structures were manually contoured on ten phases of a 4DCT scan of a NSCLC patient with a 54cm3 right-lower-lobe tumor (1.5cm motion). Corresponding ten 3D-IMRT plans were created in the Eclipse treatment planning system (Ver-13.6). A vendor-provided scripting interface was used to export 3D-dose matrices corresponding to each control point (10 phases × 9 beams × 166 control points = 14,940), which served as input to PSO. The optimization task was to iteratively adjust the weights of each control point and scale the corresponding dose matrices. In order to handle the large amount of data in GPU memory, dose matrices were sparsified and placed in contiguous memory blocks with the 14,940 weight-variables. PSO was implemented on CPU (dual-Xeon, 3.1GHz) and GPU (dual-K20 Tesla, 2496 cores, 3.52Tflops, each) platforms. NiftyReg, an open-source deformable image registration package, was used to calculate the summed dose. Results The 4D-PSO plan yielded PTV coverage comparable to the clinical ITV-based plan and significantly higher OAR-sparing, as follows: lung Dmean=33%; lung V20=27%; spinal cord Dmax=26%; esophagus Dmax=42%; heart Dmax=0%; heart Dmean=47%. The GPU-PSO processing time for 14940 variables and 7 PSO-particles was 41% that of CPU-PSO (199 vs. 488 minutes). Conclusion Truly 4D-IMRT planning can yield significant OAR dose-sparing while preserving PTV coverage. The corresponding optimization problem is large-scale, non-convex and computationally rigorous. Our initial results

  3. SU-E-T-500: Initial Implementation of GPU-Based Particle Swarm Optimization for 4D IMRT Planning in Lung SBRT

    Energy Technology Data Exchange (ETDEWEB)

    Modiri, A; Hagan, A; Gu, X; Sawant, A [UT Southwestern Medical Center, Dallas, TX (United States)

    2015-06-15

    Purpose 4D-IMRT planning, combined with dynamic MLC tracking delivery, utilizes the temporal dimension as an additional degree of freedom to achieve improved OAR-sparing. The computational complexity for such optimization increases exponentially with increase in dimensionality. In order to accomplish this task in a clinically-feasible time frame, we present an initial implementation of GPU-based 4D-IMRT planning based on particle swarm optimization (PSO). Methods The target and normal structures were manually contoured on ten phases of a 4DCT scan of a NSCLC patient with a 54cm3 right-lower-lobe tumor (1.5cm motion). Corresponding ten 3D-IMRT plans were created in the Eclipse treatment planning system (Ver-13.6). A vendor-provided scripting interface was used to export 3D-dose matrices corresponding to each control point (10 phases × 9 beams × 166 control points = 14,940), which served as input to PSO. The optimization task was to iteratively adjust the weights of each control point and scale the corresponding dose matrices. In order to handle the large amount of data in GPU memory, dose matrices were sparsified and placed in contiguous memory blocks with the 14,940 weight-variables. PSO was implemented on CPU (dual-Xeon, 3.1GHz) and GPU (dual-K20 Tesla, 2496 cores, 3.52Tflops, each) platforms. NiftyReg, an open-source deformable image registration package, was used to calculate the summed dose. Results The 4D-PSO plan yielded PTV coverage comparable to the clinical ITV-based plan and significantly higher OAR-sparing, as follows: lung Dmean=33%; lung V20=27%; spinal cord Dmax=26%; esophagus Dmax=42%; heart Dmax=0%; heart Dmean=47%. The GPU-PSO processing time for 14940 variables and 7 PSO-particles was 41% that of CPU-PSO (199 vs. 488 minutes). Conclusion Truly 4D-IMRT planning can yield significant OAR dose-sparing while preserving PTV coverage. The corresponding optimization problem is large-scale, non-convex and computationally rigorous. Our initial results

  4. Verification of eye lens dose in IMRT by MOSFET measurement.

    Science.gov (United States)

    Wang, Xuetao; Li, Guangjun; Zhao, Jianling; Song, Ying; Xiao, Jianghong; Bai, Sen

    2018-04-17

    The eye lens is recognized as one of the most radiosensitive structures in the human body. The widespread use of intensity-modulated radiotherapy (IMRT) complicates dose verification and necessitates high standards of dose computation. The purpose of this work was to assess the computed dose accuracy of eye lens through measurements using a metal-oxide-semiconductor field-effect transistor (MOSFET) dosimetry system. Sixteen clinical IMRT plans of head and neck patients were copied to an anthropomorphic head phantom. Measurements were performed using the MOSFET dosimetry system based on the head phantom. Two MOSFET detectors were imbedded in the eyes of the head phantom as the left and the right lens, covered by approximately 5-mm-thick paraffin wax. The measurement results were compared with the calculated values with a dose grid size of 1 mm. Sixteen IMRT plans were delivered, and 32 measured lens doses were obtained for analysis. The MOSFET dosimetry system can be used to verify the lens dose, and our measurements showed that the treatment planning system used in our clinic can provide adequate dose assessment in eye lenses. The average discrepancy between measurement and calculation was 6.7 ± 3.4%, and the largest discrepancy was 14.3%, which met the acceptability criterion set by the American Association of Physicists in Medicine Task Group 53 for external beam calculation for multileaf collimator-shaped fields in buildup regions. Copyright © 2018 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.

  5. IMRT delivers lower radiation doses to dental structures than 3DRT in head and neck cancer patients.

    Science.gov (United States)

    Fregnani, Eduardo Rodrigues; Parahyba, Cláudia Joffily; Morais-Faria, Karina; Fonseca, Felipe Paiva; Ramos, Pedro Augusto Mendes; de Moraes, Fábio Yone; da Conceição Vasconcelos, Karina Gondim Moutinho; Menegussi, Gisela; Santos-Silva, Alan Roger; Brandão, Thais B

    2016-09-07

    Radiotherapy (RT) is frequently used in the treatment of head and neck cancer, but different side-effects are frequently reported, including a higher frequency of radiation-related caries, what may be consequence of direct radiation to dental tissue. The intensity-modulated radiotherapy (IMRT) was developed to improve tumor control and decrease patient's morbidity by delivering radiation beams only to tumor shapes and sparing normal tissue. However, teeth are usually not included in IMRT plannings and the real efficacy of IMRT in the dental context has not been addressed. Therefore, the aim of this study is to assess whether IMRT delivers lower radiation doses to dental structures than conformal 3D radiotherapy (3DRT). Radiation dose delivery to dental structures of 80 patients treated for head and neck cancers (oral cavity, tongue, nasopharynx and oropharynx) with IMRT (40 patients) and 3DRT (40 patients) were assessed by individually contouring tooth crowns on patients' treatment plans. Clinicopathological data were retrieved from patients' medical files. The average dose of radiation to teeth delivered by IMRT was significantly lower than with 3DRT (p = 0.007); however, only patients affected by nasopharynx and oral cavity cancers demonstrated significantly lower doses with IMRT (p = 0.012 and p = 0.011, respectively). Molars received more radiation with both 3DRT and IMRT, but the latter delivered significantly lower radiation in this group of teeth (p dental groups. Maxillary teeth received lower doses than mandibular teeth, but only IMRT delivered significantly lower doses (p = 0.011 and p = 0.003). Ipsilateral teeth received higher doses than contralateral teeth with both techniques and IMRT delivered significantly lower radiation than 3DRT for contralateral dental structures (p radiation doses to teeth than 3DRT, but only for some groups of patients and teeth, suggesting that this decrease was more likely due to the protection of

  6. Effectiveness of noncoplanar IMRT planning using a parallelized multiresolution beam angle optimization method for paranasal sinus carcinoma

    International Nuclear Information System (INIS)

    Wang Xiaochun; Zhang Xiaodong; Dong Lei; Liu, Helen; Gillin, Michael; Ahamad, Anesa; Ang Kian; Mohan, Radhe

    2005-01-01

    Purpose: To determine the effectiveness of noncoplanar beam configurations and the benefit of plans using fewer but optimally placed beams designed by a parallelized multiple-resolution beam angle optimization (PMBAO) approach. Methods and Materials: The PMBAO approach uses a combination of coplanar and noncoplanar beam configurations for intensity-modulated radiation therapy (IMRT) treatment planning of paranasal sinus cancers. A smaller number of beams (e.g. 3) are first used to explore the solution space to determine the best and worst beam directions. The results of this exploration are then used as a starting point for determining an optimum beam orientation configuration with more beams (e.g. 5). This process is parallelized using a message passing interface, which greatly reduces the overall computation time for routine clinical practice. To test this approach, treatment for 10 patients with paranasal sinus cancer was planned using a total of 5 beams from a pool of 46 possible beam angles. The PMBAO treatment plans were also compared with IMRT plans designed using 9 equally spaced coplanar beams, which is the standard approach in our clinic. Plans with these two different beam configurations were compared with respect to dose conformity, dose heterogeneity, dose-volume histograms, and doses to organs at risk (i.e., eyes, optic nerve, optic chiasm, and brain). Results: The noncoplanar beam configuration was superior in most paranasal sinus carcinoma cases. The target dose homogeneity was better using a PMBAO 5-beam configuration. However, the dose conformity using PMBAO was not improved and was case dependent. Compared with the 9-beam configuration, the PMBAO configuration significantly reduced the mean dose to the eyes and optic nerves and the maximum dose to the contralateral optical path (e.g. the contralateral eye and optic nerve). The maximum dose to the ipsilateral eye and optic nerve was also lower using the PMBAO configuration than using the 9-beam

  7. Conventional patient specific IMRT QA and 3DVH verification of dose distribution for helical tomotherapy

    International Nuclear Information System (INIS)

    Sharma, Prabhat Krishna; Joshi, Kishore; Epili, D.; Gavake, Umesh; Paul, Siji; Reena, Ph.; Jamema, S.V.

    2016-01-01

    In recent years, patient-specific IMRT QA has transitioned from point dose measurements by ion chambers to films to 2D array measurements. 3DVH software has taken this transition a step further by estimating the 3D dose delivered to the patient volume from 2D diode measurements using a planned dose perturbation (PDP) algorithm. This algorithm was developed to determine, if the conventional IMRT QA though sensitive at detecting errors, has any predictive power in detecting dose errors of clinical significance related to dose to the target volume and organs at risk (OAR). The aim of this study is to compare the conventional IMRT patient specific QA and 3DVH dose distribution for patients treated with helical tomotherapy (HT)

  8. Verification of IMRT dose distributions using a water beam imaging system

    International Nuclear Information System (INIS)

    Li, J.S.; Boyer, Arthur L.; Ma, C.-M.

    2001-01-01

    A water beam imaging system (WBIS) has been developed and used to verify dose distributions for intensity modulated radiotherapy using dynamic multileaf collimator. This system consisted of a water container, a scintillator screen, a charge-coupled device camera, and a portable personal computer. The scintillation image was captured by the camera. The pixel value in this image indicated the dose value in the scintillation screen. Images of radiation fields of known spatial distributions were used to calibrate the device. The verification was performed by comparing the image acquired from the measurement with a dose distribution from the IMRT plan. Because of light scattering in the scintillator screen, the image was blurred. A correction for this was developed by recognizing that the blur function could be fitted to a multiple Gaussian. The blur function was computed using the measured image of a 10 cmx10 cm x-ray beam and the result of the dose distribution calculated using the Monte Carlo method. Based on the blur function derived using this method, an iterative reconstruction algorithm was applied to recover the dose distribution for an IMRT plan from the measured WBIS image. The reconstructed dose distribution was compared with Monte Carlo simulation result. Reasonable agreement was obtained from the comparison. The proposed approach makes it possible to carry out a real-time comparison of the dose distribution in a transverse plane between the measurement and the reference when we do an IMRT dose verification

  9. The impact of direct aperture optimization on plan quality and efficiency in complex head and neck IMRT

    Directory of Open Access Journals (Sweden)

    Sabatino Marcello

    2012-01-01

    Full Text Available Abstract Background Conventional step&shoot intensity modulated radio therapy (IMRT approaches potentially lead to treatment plans with high numbers of segments and monitor units (MU and, therefore, could be time consuming at the linear accelerator. Direct optimization methods are able to reduce the complexity without degrading the quality of the plan. The aim of this study is the evaluation of different IMRT approaches at standardized conditions for head and neck tumors. Method For 27 patients with carcinomas in the head and neck region a planning study with a 2-step-IMRT system (KonRad, a direct optimization system (Panther DAO and a mixture of both approaches (MasterPlan DSS was created. In order to avoid different prescription doses for boost volumes a simple standardization was realized. The dose was downscaled to 50 Gy to the planning target volume (PTV which included the primary tumor as well as the bilateral lymphatic drainage (cervical and supraclavicular. Dose restrictions for the organs at risk (OAR were downscaled to this prescription from high dose concepts up to 72 Gy. Those limits were defined as planning objectives while reaching definable PTV coverage with a standardized field setup. The parameters were evaluated from the corresponding dose volume histogram (DVH. Special attention was paid to the efficiency of the method, measured by means of calculated MU and required segments. Statistical tests of significance were applied to quantify the differences between the evaluated systems. Results PTV coverage for all systems in terms of V90% and V95% fell short of the requested 100% and 95%, respectively, but were still acceptable (range: 98.7% to 99.1% and 94.2% to 94.7%. Overall for OAR sparing and the burden of healthy tissue with low doses no technique was superior for all evaluated parameters. Differences were found for the number of segments where the direct optimization systems generated less segments. Lowest average numbers of

  10. The impact of direct aperture optimization on plan quality and efficiency in complex head and neck IMRT

    International Nuclear Information System (INIS)

    Sabatino, Marcello; Kretschmer, Matthias; Zink, Klemens; Würschmidt, Florian

    2012-01-01

    Conventional step&shoot intensity modulated radio therapy (IMRT) approaches potentially lead to treatment plans with high numbers of segments and monitor units (MU) and, therefore, could be time consuming at the linear accelerator. Direct optimization methods are able to reduce the complexity without degrading the quality of the plan. The aim of this study is the evaluation of different IMRT approaches at standardized conditions for head and neck tumors. For 27 patients with carcinomas in the head and neck region a planning study with a 2-step-IMRT system (KonRad), a direct optimization system (Panther DAO) and a mixture of both approaches (MasterPlan DSS) was created. In order to avoid different prescription doses for boost volumes a simple standardization was realized. The dose was downscaled to 50 Gy to the planning target volume (PTV) which included the primary tumor as well as the bilateral lymphatic drainage (cervical and supraclavicular). Dose restrictions for the organs at risk (OAR) were downscaled to this prescription from high dose concepts up to 72 Gy. Those limits were defined as planning objectives while reaching definable PTV coverage with a standardized field setup. The parameters were evaluated from the corresponding dose volume histogram (DVH). Special attention was paid to the efficiency of the method, measured by means of calculated MU and required segments. Statistical tests of significance were applied to quantify the differences between the evaluated systems. PTV coverage for all systems in terms of V 90% and V 95% fell short of the requested 100% and 95%, respectively, but were still acceptable (range: 98.7% to 99.1% and 94.2% to 94.7%). Overall for OAR sparing and the burden of healthy tissue with low doses no technique was superior for all evaluated parameters. Differences were found for the number of segments where the direct optimization systems generated less segments. Lowest average numbers of MU were 308 by Panther DAO calculated for

  11. IMRT delivers lower radiation doses to dental structures than 3DRT in head and neck cancer patients

    International Nuclear Information System (INIS)

    Fregnani, Eduardo Rodrigues; Parahyba, Cláudia Joffily; Morais-Faria, Karina; Fonseca, Felipe Paiva; Ramos, Pedro Augusto Mendes; Moraes, Fábio Yone de; Conceição Vasconcelos, Karina Gondim Moutinho da; Menegussi, Gisela; Santos-Silva, Alan Roger; Brandão, Thais B.

    2016-01-01

    Radiotherapy (RT) is frequently used in the treatment of head and neck cancer, but different side-effects are frequently reported, including a higher frequency of radiation-related caries, what may be consequence of direct radiation to dental tissue. The intensity-modulated radiotherapy (IMRT) was developed to improve tumor control and decrease patient’s morbidity by delivering radiation beams only to tumor shapes and sparing normal tissue. However, teeth are usually not included in IMRT plannings and the real efficacy of IMRT in the dental context has not been addressed. Therefore, the aim of this study is to assess whether IMRT delivers lower radiation doses to dental structures than conformal 3D radiotherapy (3DRT). Radiation dose delivery to dental structures of 80 patients treated for head and neck cancers (oral cavity, tongue, nasopharynx and oropharynx) with IMRT (40 patients) and 3DRT (40 patients) were assessed by individually contouring tooth crowns on patients’ treatment plans. Clinicopathological data were retrieved from patients’ medical files. The average dose of radiation to teeth delivered by IMRT was significantly lower than with 3DRT (p = 0.007); however, only patients affected by nasopharynx and oral cavity cancers demonstrated significantly lower doses with IMRT (p = 0.012 and p = 0.011, respectively). Molars received more radiation with both 3DRT and IMRT, but the latter delivered significantly lower radiation in this group of teeth (p < 0.001), whereas no significant difference was found for the other dental groups. Maxillary teeth received lower doses than mandibular teeth, but only IMRT delivered significantly lower doses (p = 0.011 and p = 0.003). Ipsilateral teeth received higher doses than contralateral teeth with both techniques and IMRT delivered significantly lower radiation than 3DRT for contralateral dental structures (p < 0.001). IMRT delivered lower radiation doses to teeth than 3DRT, but only for some groups of patients and

  12. Evaluation of homogeneity and dose conformity in IMRT planning in prostate radiotherapy; Avaliacao da homogeneidade e conformidade de dose em planejamentos de IMRT de prostata em radioterapia

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, Juliane S.; Leidens, Matheus; Estacio, Daniela R., E-mail: juliane.lopes@pucrs.br [Hospital Sao Lucas (PUC-RS), Porto Alegre, RS (Brazil). Servico de Radioterapia; Razera, Ricardo A.Z.; Streck, Elaine E.; Silva, Ana M.M. da [Pontificia Universidade Catolica do Rio Grande do Sul (PUC-RS), Porto Alegre, RS (Brazil). Faculdade de Fisica

    2015-12-15

    The goal of this study was to evaluate the dose distribution homogeneity and conformity of radiation therapy plans of prostate cancer using IMRT. Data from 34 treatment plans of Hospital Sao Lucas of PUCRS, where those plans were executed, were retrospectively analyzed. All of them were done with 6MV X-rays from a linear accelerator CLINAC IX, and the prescription doses varied between 60 and 74 Gy. Analyses showing the homogeneity and conformity indices for the dose distribution of those plans were made. During these analyses, some comparisons with the traditional radiation therapy planning technic, the 3D-CRT, were discussed. The results showed that there is no correlation between the prescribed dose and the homogeneity and conformity indices, indicating that IMRT works very well even for higher doses. Furthermore, a comparison between the results obtained and the recommendations of ICRU 83 was carried out. It has also been observed that the indices were really close to the ideal values. 82.4% of the cases showed a difference below 5% of the ideal value for the index of conformity, and 88.2% showed a difference below 10% for the homogeneity index. Concluding, it is possible to confirm the quality of the analyzed radiation therapy plans of prostate cancer using IMRT. (author)

  13. IMRT in a pregnant patient: how to reduce the fetal dose?

    DEFF Research Database (Denmark)

    Josipovic, Mirjana; Nyström, Håkan; Kjaer-Kristoffersen, Flemming

    2008-01-01

    dose distribution. The peripheral dose originating from the final IMRT plan was measured at distances reaching from the most proximal to the most distal fetal position, along the accelerator's longitudinal axis, using an anthropomorphic phantom extended with water-equivalent plastic. The measured...... was built and placed beneath the accelerator head, extending caudally from the field edge, to function as an extra collimator jaw. This shield reduced the fetal dose by a factor of 3.5. The peripheral dose components were also measured for simple rectangular fields and also here the collimator scatter...... was the greatest contributor to the peripheral dose. Therefore, the shielding used for the IMRT treatment of our patient could also be used when shielding in conventional radiotherapy. It is important for a radiation therapy department to be prepared for treatment of a pregnant patient to shield the fetus...

  14. Degeneracy, frequency response and filtering in IMRT optimization

    International Nuclear Information System (INIS)

    Llacer, Jorge; Agazaryan, Nzhde; Solberg, Timothy D; Promberger, Claus

    2004-01-01

    This paper attempts to provide an answer to some questions that remain either poorly understood, or not well documented in the literature, on basic issues related to intensity modulated radiation therapy (IMRT). The questions examined are: the relationship between degeneracy and frequency response of optimizations, effects of initial beamlet fluence assignment and stopping point, what does filtering of an optimized beamlet map actually do and how could image analysis help to obtain better optimizations? Two target functions are studied, a quadratic cost function and the log likelihood function of the dynamically penalized likelihood (DPL) algorithm. The algorithms used are the conjugate gradient, the stochastic adaptive simulated annealing and the DPL. One simple phantom is used to show the development of the analysis tools used and two clinical cases of medium and large dose matrix size (a meningioma and a prostate) are studied in detail. The conclusions reached are that the high number of iterations that is needed to avoid degeneracy is not warranted in clinical practice, as the quality of the optimizations, as judged by the DVHs and dose distributions obtained, does not improve significantly after a certain point. It is also shown that the optimum initial beamlet fluence assignment for analytical iterative algorithms is a uniform distribution, but such an assignment does not help a stochastic method of optimization. Stopping points for the studied algorithms are discussed and the deterioration of DVH characteristics with filtering is shown to be partially recoverable by the use of space-variant filtering techniques

  15. Degeneracy, frequency response and filtering in IMRT optimization

    Energy Technology Data Exchange (ETDEWEB)

    Llacer, Jorge [EC Engineering Consultants LLC, 130 Forest Hill Drive, Los Gatos, CA 95032 (United States); Agazaryan, Nzhde [Department of Radiation Oncology, University of California, Los Angeles, CA 90095 (United States); Solberg, Timothy D [Department of Radiation Oncology, University of California, Los Angeles, CA 90095 (United States); Promberger, Claus [BrainLAB AG, Ammerthalstrasse 8, 85551 Heimstetten (Germany)

    2004-07-07

    This paper attempts to provide an answer to some questions that remain either poorly understood, or not well documented in the literature, on basic issues related to intensity modulated radiation therapy (IMRT). The questions examined are: the relationship between degeneracy and frequency response of optimizations, effects of initial beamlet fluence assignment and stopping point, what does filtering of an optimized beamlet map actually do and how could image analysis help to obtain better optimizations? Two target functions are studied, a quadratic cost function and the log likelihood function of the dynamically penalized likelihood (DPL) algorithm. The algorithms used are the conjugate gradient, the stochastic adaptive simulated annealing and the DPL. One simple phantom is used to show the development of the analysis tools used and two clinical cases of medium and large dose matrix size (a meningioma and a prostate) are studied in detail. The conclusions reached are that the high number of iterations that is needed to avoid degeneracy is not warranted in clinical practice, as the quality of the optimizations, as judged by the DVHs and dose distributions obtained, does not improve significantly after a certain point. It is also shown that the optimum initial beamlet fluence assignment for analytical iterative algorithms is a uniform distribution, but such an assignment does not help a stochastic method of optimization. Stopping points for the studied algorithms are discussed and the deterioration of DVH characteristics with filtering is shown to be partially recoverable by the use of space-variant filtering techniques.

  16. After low and high dose-rate interstitial brachytherapy followed by IMRT radiotherapy for intermediate and high risk prostate cancer

    International Nuclear Information System (INIS)

    Nakamura, Satoshi; Murakami, Naoya; Inaba, Koji; Wakita, Akihisa; Kobayashi, Kazuma; Takahashi, Kana; Okamoto, Hiroyuki; Umezawa, Rei; Morota, Madoka; Sumi, Minako; Igaki, Hiroshi; Ito, Yoshinori; Itami, Jun

    2016-01-01

    The study aimed to compare urinary symptoms in patients with clinically localized prostate cancer after a combination of either low-dose-rate or high-dose-rate interstitial brachytherapy along with intensity-modulated radiation therapy (LDR-ISBT + IMRT or HDR-ISBT + IMRT). From June 2009 to April 2014, 16 and 22 patients were treated with LDR-ISBT + IMRT and HDR-ISBT + IMRT, respectively. No patient from these groups was excluded from this study. The prescribed dose of LDR-ISBT, HDR-ISBT, and IMRT was 115 Gy, 20 Gy in 2 fractions, and 46 Gy in 23 fractions, respectively. Obstructive and irritative urinary symptoms were assessed by the International Prostate Symptom Score (IPSS) examined before and after treatments. After ISBT, IPSS was evaluated in the 1st and 4th weeks, then every 2–3 months for the 1st year, and every 6 months thereafter. The median follow-up of the patients treated with LDR-ISBT + IMRT and HDR-ISBT + IMRT was 1070.5 days and 1048.5 days, respectively (p = 0.321). The IPSS-increment in the LDR-ISBT + IMRT group was greater than that in the HDR-ISBT + IMRT between 91 and 180 days after ISBT (p = 0.015). In the LDR-ISBT + IMRT group, the IPSS took longer time to return to the initial level than in the HDR-ISBT + IMRT group (in LDR-ISBT + IMRT group, the recovery time was 90 days later). The dose to urethra showed a statistically significant association with the IPSS-increment in the irritative urinary symptoms (p = 0.011). Clinical outcomes were comparable between both the groups. Both therapeutic modalities are safe and well suited for patients with clinically localized prostate cancer; however, it took patients longer to recover from LDR-ISBT + IMRT than from HDR-ISBT + IMRT. It is possible that fast dose delivery induced early symptoms and early recovery, while gradual dose delivery induced late symptoms and late recovery. Urethral dose reductions were associated with small increments in IPSS

  17. Four-dimensional dose distributions of step-and-shoot IMRT delivered with real-time tumor tracking for patients with irregular breathing: Constant dose rate vs dose rate regulation

    International Nuclear Information System (INIS)

    Yang Xiaocheng; Han-Oh, Sarah; Gui Minzhi; Niu Ying; Yu, Cedric X.; Yi Byongyong

    2012-01-01

    Purpose: Dose-rate-regulated tracking (DRRT) is a tumor tracking strategy that programs the MLC to track the tumor under regular breathing and adapts to breathing irregularities during delivery using dose rate regulation. Constant-dose-rate tracking (CDRT) is a strategy that dynamically repositions the beam to account for intrafractional 3D target motion according to real-time information of target location obtained from an independent position monitoring system. The purpose of this study is to illustrate the differences in the effectiveness and delivery accuracy between these two tracking methods in the presence of breathing irregularities. Methods: Step-and-shoot IMRT plans optimized at a reference phase were extended to remaining phases to generate 10-phased 4D-IMRT plans using segment aperture morphing (SAM) algorithm, where both tumor displacement and deformation were considered. A SAM-based 4D plan has been demonstrated to provide better plan quality than plans not considering target deformation. However, delivering such a plan requires preprogramming of the MLC aperture sequence. Deliveries of the 4D plans using DRRT and CDRT tracking approaches were simulated assuming the breathing period is either shorter or longer than the planning day, for 4 IMRT cases: two lung and two pancreatic cases with maximum GTV centroid motion greater than 1 cm were selected. In DRRT, dose rate was regulated to speed up or slow down delivery as needed such that each planned segment is delivered at the planned breathing phase. In CDRT, MLC is separately controlled to follow the tumor motion, but dose rate was kept constant. In addition to breathing period change, effect of breathing amplitude variation on target and critical tissue dose distribution is also evaluated. Results: Delivery of preprogrammed 4D plans by the CDRT method resulted in an average of 5% increase in target dose and noticeable increase in organs at risk (OAR) dose when patient breathing is either 10% faster or

  18. SU-G-TeP4-02: A Method for Evaluating the Direct Impact of Failed IMRT QAs On Patient Dose

    International Nuclear Information System (INIS)

    Geneser, S; Butkus, M

    2016-01-01

    Purpose: We developed a method to calculate patient doses corresponding to IMRT QA measurements in order to determine and assess the actual dose delivered for plans with failed (or borderline) IMRT QA. This work demonstrates the feasibility of automatically computing delivered patient dose from portal dosimetry measurements in the Varian TPS system, which would provide a valuable and clinically viable IMRT QA tool for physicists and physicians. Methods: IMRT QA fluences were measured using portal dosimetry, processed using in-house matlab software, and imported back into Eclipse to calculate dose on the planning CT. To validate the proposed workflow, the Eclipse calculated portal dose for a 5-field sliding window prostate boost plan was processed as described above. The resulting dose was compared to the planned dose and found to be within 0.5 Gy. Two IMRT QA results for the prostate boost plan (one that failed and one that passed) were processed and the resulting patient doses were evaluated. Results: The max dose difference between IMRT QA #1 and the original planned and approved dose is 4.5 Gy, while the difference between the planned and IMRT QA #2 dose is 4.0 Gy. The inferior portion of the PTV is slightly underdosed in both plans, and the superior portion is slightly overdosed. The patient dose resulting from IMRT QA #1 and #2 differs by only 0.5 Gy. With this new information, it may be argued that the evaluated plan alteration to obtain passing gamma analysis produced clinically irrelevant differences. Conclusion: Evaluation of the delivered QA dose on the planning CT provides valuable information about the clinical relevance of failed or borderline IMRT QAs. This particular workflow demonstrates the feasibility of pushing the measured IMRT QA portal dosimetry results directly back onto the patient planning CT within the Varian system.

  19. SU-G-TeP4-02: A Method for Evaluating the Direct Impact of Failed IMRT QAs On Patient Dose

    Energy Technology Data Exchange (ETDEWEB)

    Geneser, S; Butkus, M [Yale University School of Medicine/YNHH Radiology, New Haven, CT (United States)

    2016-06-15

    Purpose: We developed a method to calculate patient doses corresponding to IMRT QA measurements in order to determine and assess the actual dose delivered for plans with failed (or borderline) IMRT QA. This work demonstrates the feasibility of automatically computing delivered patient dose from portal dosimetry measurements in the Varian TPS system, which would provide a valuable and clinically viable IMRT QA tool for physicists and physicians. Methods: IMRT QA fluences were measured using portal dosimetry, processed using in-house matlab software, and imported back into Eclipse to calculate dose on the planning CT. To validate the proposed workflow, the Eclipse calculated portal dose for a 5-field sliding window prostate boost plan was processed as described above. The resulting dose was compared to the planned dose and found to be within 0.5 Gy. Two IMRT QA results for the prostate boost plan (one that failed and one that passed) were processed and the resulting patient doses were evaluated. Results: The max dose difference between IMRT QA #1 and the original planned and approved dose is 4.5 Gy, while the difference between the planned and IMRT QA #2 dose is 4.0 Gy. The inferior portion of the PTV is slightly underdosed in both plans, and the superior portion is slightly overdosed. The patient dose resulting from IMRT QA #1 and #2 differs by only 0.5 Gy. With this new information, it may be argued that the evaluated plan alteration to obtain passing gamma analysis produced clinically irrelevant differences. Conclusion: Evaluation of the delivered QA dose on the planning CT provides valuable information about the clinical relevance of failed or borderline IMRT QAs. This particular workflow demonstrates the feasibility of pushing the measured IMRT QA portal dosimetry results directly back onto the patient planning CT within the Varian system.

  20. Contralateral breast doses measured by film dosimetry: tangential techniques and an optimized IMRT technique

    International Nuclear Information System (INIS)

    Saur, S; Frengen, J; Fjellsboe, L M B; Lindmo, T

    2009-01-01

    The contralateral breast (CLB) doses for three tangential techniques were characterized by using a female thorax phantom and GafChromic EBT film. Dose calculations by the pencil beam and collapsed cone algorithms were included for comparison. The film dosimetry reveals a highly inhomogeneous dose distribution within the CLB, and skin doses due to the medial fields that are several times higher than the interior dose. These phenomena are not correctly reproduced by the calculation algorithms. All tangential techniques were found to give a mean CLB dose of approximately 0.5 Gy. All wedged fields resulted in higher CLB doses than the corresponding open fields, and the lateral open fields resulted in higher CLB doses than the medial open fields. More than a twofold increase in the mean CLB dose from the medial open field was observed for a 90 deg. change of the collimator orientation. Replacing the physical wedge with a virtual wedge reduced the mean dose to the CLB by 35% and 16% for the medial and lateral fields, respectively. Lead shielding reduced the skin dose for a tangential technique by approximately 50%, but the mean CLB dose was only reduced by approximately 11%. Finally, a technique based on open medial fields in combination with several IMRT fields is proposed as a technique for minimizing the CLB dose. With and without lead shielding, the mean CLB dose using this technique was found to be 0.20 and 0.27 Gy, respectively.

  1. A comparison of HDR brachytherapy and IMRT techniques for dose escalation in prostate cancer: A radiobiological modeling study

    Energy Technology Data Exchange (ETDEWEB)

    Fatyga, M.; Williamson, J. F.; Dogan, N.; Todor, D.; Siebers, J. V.; George, R.; Barani, I.; Hagan, M. [Department of Radiation Oncology, Virginia Commonwealth University Medical Center, 401 College Street, Richmond, Virginia 23298 (United States)

    2009-09-15

    A course of one to three large fractions of high dose rate (HDR) interstitial brachytherapy is an attractive alternative to intensity modulated radiation therapy (IMRT) for delivering boost doses to the prostate in combination with additional external beam irradiation for intermediate risk disease. The purpose of this work is to quantitatively compare single-fraction HDR boosts to biologically equivalent fractionated IMRT boosts, assuming idealized image guided delivery (igIMRT) and conventional delivery (cIMRT). For nine prostate patients, both seven-field IMRT and HDR boosts were planned. The linear-quadratic model was used to compute biologically equivalent dose prescriptions. The cIMRT plan was evaluated as a static plan and with simulated random and setup errors. The authors conclude that HDR delivery produces a therapeutic ratio which is significantly better than the conventional IMRT and comparable to or better than the igIMRT delivery. For the HDR, the rectal gBEUD analysis is strongly influenced by high dose DVH tails. A saturation BED, beyond which no further injury can occur, must be assumed. Modeling of organ motion uncertainties yields mean outcomes similar to static plan outcomes.

  2. TH-A-9A-02: BEST IN PHYSICS (THERAPY) - 4D IMRT Planning Using Highly- Parallelizable Particle Swarm Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Modiri, A; Gu, X; Sawant, A [UT Southwestern Medical Center, Dallas, TX (United States)

    2014-06-15

    Purpose: We present a particle swarm optimization (PSO)-based 4D IMRT planning technique designed for dynamic MLC tracking delivery to lung tumors. The key idea is to utilize the temporal dimension as an additional degree of freedom rather than a constraint in order to achieve improved sparing of organs at risk (OARs). Methods: The target and normal structures were manually contoured on each of the ten phases of a 4DCT scan acquired from a lung SBRT patient who exhibited 1.5cm tumor motion despite the use of abdominal compression. Corresponding ten IMRT plans were generated using the Eclipse treatment planning system. These plans served as initial guess solutions for the PSO algorithm. Fluence weights were optimized over the entire solution space i.e., 10 phases × 12 beams × 166 control points. The size of the solution space motivated our choice of PSO, which is a highly parallelizable stochastic global optimization technique that is well-suited for such large problems. A summed fluence map was created using an in-house B-spline deformable image registration. Each plan was compared with a corresponding, internal target volume (ITV)-based IMRT plan. Results: The PSO 4D IMRT plan yielded comparable PTV coverage and significantly higher dose—sparing for parallel and serial OARs compared to the ITV-based plan. The dose-sparing achieved via PSO-4DIMRT was: lung Dmean = 28%; lung V20 = 90%; spinal cord Dmax = 23%; esophagus Dmax = 31%; heart Dmax = 51%; heart Dmean = 64%. Conclusion: Truly 4D IMRT that uses the temporal dimension as an additional degree of freedom can achieve significant dose sparing of serial and parallel OARs. Given the large solution space, PSO represents an attractive, parallelizable tool to achieve globally optimal solutions for such problems. This work was supported through funding from the National Institutes of Health and Varian Medical Systems. Amit Sawant has research funding from Varian Medical Systems, VisionRT Ltd. and Elekta.

  3. Dose sculpting with generalized equivalent uniform dose

    International Nuclear Information System (INIS)

    Wu Qiuwen; Djajaputra, David; Liu, Helen H.; Dong Lei; Mohan, Radhe; Wu, Yan

    2005-01-01

    With intensity-modulated radiotherapy (IMRT), a variety of user-defined dose distribution can be produced using inverse planning. The generalized equivalent uniform dose (gEUD) has been used in IMRT optimization as an alternative objective function to the conventional dose-volume-based criteria. The purpose of this study was to investigate the effectiveness of gEUD optimization to fine tune the dose distributions of IMRT plans. We analyzed the effect of gEUD-based optimization parameters on plan quality. The objective was to determine whether dose distribution to selected structures could be improved using gEUD optimization without adversely altering the doses delivered to other structures, as in sculpting. We hypothesized that by carefully defining gEUD parameters (EUD 0 and n) based on the current dose distributions, the optimization system could be instructed to search for alternative solutions in the neighborhood, and we could maintain the dose distributions for structures already satisfactory and improve dose for structures that need enhancement. We started with an already acceptable IMRT plan optimized with any objective function. The dose distribution was analyzed first. For structures that dose should not be changed, a higher value of n was used and EUD 0 was set slightly higher/lower than the EUD value at the current dose distribution for critical structures/targets. For structures that needed improvement in dose, a higher to medium value of n was used, and EUD 0 was set to the EUD value or slightly lower/higher for the critical structure/target at the current dose distribution. We evaluated this method in one clinical case each of head and neck, lung and prostate cancer. Dose volume histograms, isodose distributions, and relevant tolerance doses for critical structures were used for the assessment. We found that by adjusting gEUD optimization parameters, the dose distribution could be improved with only a few iterations. A larger value of n could lead to

  4. Intensity-modulated radiotherapy (IMRT) for carcinoma of the maxillary sinus: A comparison of IMRT planning systems

    International Nuclear Information System (INIS)

    Ahmed, Raef S.; Ove, Roger; Duan, Jun; Popple, Richard; Cobb, Glenn

    2006-01-01

    The treatment of maxillary sinus carcinoma with forward planning can be technically difficult when the neck also requires radiotherapy. This difficulty arises because of the need to spare the contralateral face while treating the bilateral neck. There is considerable potential for error in clinical setup and treatment delivery. We evaluated intensity-modulated radiotherapy (IMRT) as an improvement on forward planning, and compared several inverse planning IMRT platforms. A composite dose-volume histogram (DVH) was generated from a complex forward planned case. We compared the results with those generated by sliding window fixed field dynamic multileaf collimator (MLC) IMRT, using sets of coplanar beams. All setups included an anterior posterior (AP) beam, and 3-, 5-, 7-, and 9-field configurations were evaluated. The dose prescription and objective function priorities were invariant. We also evaluated 2 commercial tomotherapy IMRT delivery platforms. DVH results from all of the IMRT approaches compared favorably with the forward plan. Results for the various inverse planning approaches varied considerably across platforms, despite an attempt to prescribe the therapy similarly. The improvement seen with the addition of beams in the fixed beam sliding window case was modest. IMRT is an effective means of delivering radiotherapy reliably in the complex setting of maxillary sinus carcinoma with neck irradiation. Differences in objective function definition and optimization algorithms can lead to unexpected differences in the final dose distribution, and our evaluation suggests that these factors are more significant than the beam arrangement or number of beams

  5. Dose distribution of IMRT and 3D-CRT on treating central non-small-cell lung cancer

    International Nuclear Information System (INIS)

    Zhu Xiaoyang; Yu Guangwei

    2010-01-01

    3D-CRT and IMRT were used in the radiation therapy of Central Non-small-cell lung cancer (NSCLC), and the dose difference of the methods was estimated. Thirty-two patients suffering with II class NSCLC were selected. Based on CT images, each patient was given 1 3D-CRT (3 dimensional conformal radiotherapy) and 2 IMRT(intensity modulated radiation therapy) treatment plans (5 fields and 7 fields), respectively, and the dose distribution was evaluated too. The results showed that PTVD mean and the PTV max , PTVD max (%) and CI of IMRT were both higher than those of 3D-CRT, but the uniformity was not as good as 3D-CRT. All indexes of lung and spinal cord treated with IMRT were lower than that treated with 3D-CRT. Moreover, there was no significance of the difference between 5 fields and 7 fields. In a conclusion, IMRT could not only decrease the target dose of NSCLC, but it can protect normal tissue from radiation damage effectively. And when IMRT was used, 5 fields might be enough. (authors)

  6. Prostate Dose Escalation by Innovative Inverse Planning-Driven IMRT

    National Research Council Canada - National Science Library

    Xing, Lei

    2005-01-01

    .... Because of the tacit ignorance of intra-structural tradeoff, the IMRT plans generated by these systems for prostate treatment are, at best, sub-optimal and our endeavor of providing the best possible...

  7. Toward IMRT 2D dose modeling using artificial neural networks: A feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Kalantzis, Georgios; Vasquez-Quino, Luis A.; Zalman, Travis; Pratx, Guillem; Lei, Yu [Radiation Oncology Department, University of Texas, Health Science Center San Antonio, Texas 78229 and Radiation Oncology Department, Stanford University School of Medicine, Stanford, California 94305 (United States); Radiation Oncology Department, University of Texas, Health Science Center San Antonio, Texas 78229 (United States); Radiation Oncology Department, Stanford University School of Medicine, Stanford, California 94305 (United States); Radiation Oncology Department, University of Texas, Health Science Center San Antonio, Texas 78229 (United States)

    2011-10-15

    Purpose: To investigate the feasibility of artificial neural networks (ANN) to reconstruct dose maps for intensity modulated radiation treatment (IMRT) fields compared with those of the treatment planning system (TPS). Methods: An artificial feed forward neural network and the back-propagation learning algorithm have been used to replicate dose calculations of IMRT fields obtained from PINNACLE{sup 3} v9.0. The ANN was trained with fluence and dose maps of IMRT fields for 6 MV x-rays, which were obtained from the amorphous silicon (a-Si) electronic portal imaging device of Novalis TX. Those fluence distributions were imported to the TPS and the dose maps were calculated on the horizontal midpoint plane of a water equivalent homogeneous cylindrical virtual phantom. Each exported 2D dose distribution from the TPS was classified into two clusters of high and low dose regions, respectively, based on the K-means algorithm and the Euclidian metric in the fluence-dose domain. The data of each cluster were divided into two sets for the training and validation phase of the ANN, respectively. After the completion of the ANN training phase, 2D dose maps were reconstructed by the ANN and isodose distributions were created. The dose maps reconstructed by ANN were evaluated and compared with the TPS, where the mean absolute deviation of the dose and the {gamma}-index were used. Results: A good agreement between the doses calculated from the TPS and the trained ANN was achieved. In particular, an average relative dosimetric difference of 4.6% and an average {gamma}-index passing rate of 93% were obtained for low dose regions, and a dosimetric difference of 2.3% and an average {gamma}-index passing rate of 97% for high dose region. Conclusions: An artificial neural network has been developed to convert fluence maps to corresponding dose maps. The feasibility and potential of an artificial neural network to replicate complex convolution kernels in the TPS for IMRT dose calculations

  8. Toward IMRT 2D dose modeling using artificial neural networks: A feasibility study

    International Nuclear Information System (INIS)

    Kalantzis, Georgios; Vasquez-Quino, Luis A.; Zalman, Travis; Pratx, Guillem; Lei, Yu

    2011-01-01

    Purpose: To investigate the feasibility of artificial neural networks (ANN) to reconstruct dose maps for intensity modulated radiation treatment (IMRT) fields compared with those of the treatment planning system (TPS). Methods: An artificial feed forward neural network and the back-propagation learning algorithm have been used to replicate dose calculations of IMRT fields obtained from PINNACLE 3 v9.0. The ANN was trained with fluence and dose maps of IMRT fields for 6 MV x-rays, which were obtained from the amorphous silicon (a-Si) electronic portal imaging device of Novalis TX. Those fluence distributions were imported to the TPS and the dose maps were calculated on the horizontal midpoint plane of a water equivalent homogeneous cylindrical virtual phantom. Each exported 2D dose distribution from the TPS was classified into two clusters of high and low dose regions, respectively, based on the K-means algorithm and the Euclidian metric in the fluence-dose domain. The data of each cluster were divided into two sets for the training and validation phase of the ANN, respectively. After the completion of the ANN training phase, 2D dose maps were reconstructed by the ANN and isodose distributions were created. The dose maps reconstructed by ANN were evaluated and compared with the TPS, where the mean absolute deviation of the dose and the γ-index were used. Results: A good agreement between the doses calculated from the TPS and the trained ANN was achieved. In particular, an average relative dosimetric difference of 4.6% and an average γ-index passing rate of 93% were obtained for low dose regions, and a dosimetric difference of 2.3% and an average γ-index passing rate of 97% for high dose region. Conclusions: An artificial neural network has been developed to convert fluence maps to corresponding dose maps. The feasibility and potential of an artificial neural network to replicate complex convolution kernels in the TPS for IMRT dose calculations have been

  9. Effects of intra-fraction motion on IMRT dose delivery: statistical analysis and simulation

    International Nuclear Information System (INIS)

    Bortfeld, Thomas; Jokivarsi, Kimmo; Goitein, Michael; Kung, Jong; Jiang, Steve B.

    2002-01-01

    There has been some concern that organ motion, especially intra-fraction organ motion due to breathing, can negate the potential merit of intensity-modulated radiotherapy (IMRT). We wanted to find out whether this concern is justified. Specifically, we wanted to investigate whether IMRT delivery techniques with moving parts, e.g., with a multileaf collimator (MLC), are particularly sensitive to organ motion due to the interplay between organ motion and leaf motion. We also wanted to know if, and by how much, fractionation of the treatment can reduce the effects. We performed a statistical analysis and calculated the expected dose values and dose variances for volume elements of organs that move during the delivery of the IMRT. We looked at the overall influence of organ motion during the course of a fractionated treatment. A linear-quadratic model was used to consider fractionation effects. Furthermore, we developed software to simulate motion effects for IMRT delivery with an MLC, with compensators, and with a scanning beam. For the simulation we assumed a sinusoidal motion in an isocentric plane. We found that the expected dose value is independent of the treatment technique. It is just a weighted average over the path of motion of the dose distribution without motion. If the treatment is delivered in several fractions, the distribution of the dose around the expected value is close to a Gaussian. For a typical treatment with 30 fractions, the standard deviation is generally within 1% of the expected value for MLC delivery if one assumes a typical motion amplitude of 5 mm (1 cm peak to peak). The standard deviation is generally even smaller for the compensator but bigger for scanning beam delivery. For the latter it can be reduced through multiple deliveries ('paintings') of the same field. In conclusion, the main effect of organ motion in IMRT is an averaging of the dose distribution without motion over the path of the motion. This is the same as for treatments

  10. Evaluation of homogeneity and dose conformity in IMRT planning in prostate radiotherapy

    International Nuclear Information System (INIS)

    Lopes, Juliane S.; Leidens, Matheus; Estacio, Daniela R.; Razera, Ricardo A.Z.; Streck, Elaine E.; Silva, Ana M.M. da

    2015-01-01

    The goal of this study was to evaluate the dose distribution homogeneity and conformity of radiation therapy plans of prostate cancer using IMRT. Data from 34 treatment plans of Hospital Sao Lucas of PUCRS, where those plans were executed, were retrospectively analyzed. All of them were done with 6MV X-rays from a linear accelerator CLINAC IX, and the prescription doses varied between 60 and 74 Gy. Analyses showing the homogeneity and conformity indices for the dose distribution of those plans were made. During these analyses, some comparisons with the traditional radiation therapy planning technic, the 3D-CRT, were discussed. The results showed that there is no correlation between the prescribed dose and the homogeneity and conformity indices, indicating that IMRT works very well even for higher doses. Furthermore, a comparison between the results obtained and the recommendations of ICRU 83 was carried out. It has also been observed that the indices were really close to the ideal values. 82.4% of the cases showed a difference below 5% of the ideal value for the index of conformity, and 88.2% showed a difference below 10% for the homogeneity index. Concluding, it is possible to confirm the quality of the analyzed radiation therapy plans of prostate cancer using IMRT. (author)

  11. Beam intensity scanner system for three dimensional dose verification of IMRT

    International Nuclear Information System (INIS)

    Vahc, Young W.; Kwon, Ohyun; Park, Kwangyl; Park, Kyung R.; Yi, Byung Y.; Kim, Keun M.

    2003-01-01

    Patient dose verification is clinically one of the most important parts in the treatment delivery of radiation therapy. The three dimensional (3D) reconstruction of dose distribution delivered to target volume helps to verify patient dose and determine the physical characteristics of beams used in IMRT. Here we present beam intensity scanner (BInS) system for the pre-treatment dosimetric verification of two dimensional photon intensity. The BInS is a radiation detector with a custom-made software for dose conversion of fluorescence signals from scintillator. The scintillator is used to produce fluorescence from the irradiation of 6 MV photons on a Varian Clinac 21EX. The digitized fluoroscopic signals obtained by digital video camera-based scintillator (DVCS) will be processed by our custom made software to reproduce 3D- relative dose distribution. For the intensity modulated beam (IMB), the BInS calculates absorbed dose in absolute beam fluence which is used for the patient dose distribution. Using BInS, we performed various measurements related to IMRT and found the following: (1) The 3D-dose profiles of the IMBs measured by the BInS demonstrate good agreement with radiographic film, pin type ionization chamber and Monte Carlo simulation. (2) The delivered beam intensity is altered by the mechanical and dosimetric properties of the collimation of dynamic and/or step MLC system. This is mostly due to leaf transmission, leaf penumbra scattered photons from the round edges of leaves, and geometry of leaf. (3) The delivered dose depends on the operational detail of how to make multi leaf opening. These phenomena result in a fluence distribution that can be substantially different from the initial and calculated intensity modulation and therefore, should be taken into account by the treatment planning for accurate dose calculations delivered to the target volume in IMRT. (author)

  12. SU-F-BRD-13: Quantum Annealing Applied to IMRT Beamlet Intensity Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Nazareth, D [Roswell Park Cancer Institute, Buffalo, NY (United States); Spaans, J [Hawarden, IA (United States)

    2014-06-15

    Purpose: We report on the first application of quantum annealing (QA) to the process of beamlet intensity optimization for IMRT. QA is a new technology, which employs novel hardware and software techniques to address various discrete optimization problems in many fields. Methods: We apply the D-Wave Inc. proprietary hardware, which natively exploits quantum mechanical effects for improved optimization. The new QA algorithm, running on this hardware, is most similar to simulated annealing, but relies on natural processes to directly minimize the free energy of a system. A simple quantum system is slowly evolved into a classical system, representing the objective function. To apply QA to IMRT-type optimization, two prostate cases were considered. A reduced number of beamlets were employed, due to the current QA hardware limitation of ∼500 binary variables. The beamlet dose matrices were computed using CERR, and an objective function was defined based on typical clinical constraints, including dose-volume objectives. The objective function was discretized, and the QA method was compared to two standard optimization Methods: simulated annealing and Tabu search, run on a conventional computing cluster. Results: Based on several runs, the average final objective function value achieved by the QA was 16.9 for the first patient, compared with 10.0 for Tabu and 6.7 for the SA. For the second patient, the values were 70.7 for the QA, 120.0 for Tabu, and 22.9 for the SA. The QA algorithm required 27–38% of the time required by the other two methods. Conclusion: In terms of objective function value, the QA performance was similar to Tabu but less effective than the SA. However, its speed was 3–4 times faster than the other two methods. This initial experiment suggests that QA-based heuristics may offer significant speedup over conventional clinical optimization methods, as quantum annealing hardware scales to larger sizes.

  13. SU-F-BRD-13: Quantum Annealing Applied to IMRT Beamlet Intensity Optimization

    International Nuclear Information System (INIS)

    Nazareth, D; Spaans, J

    2014-01-01

    Purpose: We report on the first application of quantum annealing (QA) to the process of beamlet intensity optimization for IMRT. QA is a new technology, which employs novel hardware and software techniques to address various discrete optimization problems in many fields. Methods: We apply the D-Wave Inc. proprietary hardware, which natively exploits quantum mechanical effects for improved optimization. The new QA algorithm, running on this hardware, is most similar to simulated annealing, but relies on natural processes to directly minimize the free energy of a system. A simple quantum system is slowly evolved into a classical system, representing the objective function. To apply QA to IMRT-type optimization, two prostate cases were considered. A reduced number of beamlets were employed, due to the current QA hardware limitation of ∼500 binary variables. The beamlet dose matrices were computed using CERR, and an objective function was defined based on typical clinical constraints, including dose-volume objectives. The objective function was discretized, and the QA method was compared to two standard optimization Methods: simulated annealing and Tabu search, run on a conventional computing cluster. Results: Based on several runs, the average final objective function value achieved by the QA was 16.9 for the first patient, compared with 10.0 for Tabu and 6.7 for the SA. For the second patient, the values were 70.7 for the QA, 120.0 for Tabu, and 22.9 for the SA. The QA algorithm required 27–38% of the time required by the other two methods. Conclusion: In terms of objective function value, the QA performance was similar to Tabu but less effective than the SA. However, its speed was 3–4 times faster than the other two methods. This initial experiment suggests that QA-based heuristics may offer significant speedup over conventional clinical optimization methods, as quantum annealing hardware scales to larger sizes

  14. A hybrid electron and photon IMRT planning technique that lowers normal tissue integral patient dose using standard hardware.

    Science.gov (United States)

    Rosca, Florin

    2012-06-01

    To present a mixed electron and photon IMRT planning technique using electron beams with an energy range of 6-22 MeV and standard hardware that minimizes integral dose to patients for targets as deep as 7.5 cm. Ten brain cases, two lung, a thyroid, an abdominal, and a parotid case were planned using two planning techniques: a photon-only IMRT (IMRT) versus a mixed modality treatment (E+IMRT) that includes an enface electron beam and a photon IMRT portion that ensures a uniform target coverage. The electron beam is delivered using a regular cutout placed in an electron cone. The electron energy was chosen to provide a good trade-off between minimizing integral dose and generating a uniform, deliverable plan. The authors choose electron energies that cover the deepest part of PTV with the 65%-70% isodose line. The normal tissue integral dose, the dose for ring structures around the PTV, and the volumes of the 75%, 50%, and 25% isosurfaces were used to compare the dose distributions generated by the two planning techniques. The normal tissue integral dose was lowered by about 20% by the E+IMRT plans compared to the photon-only IMRT ones for most studied cases. With the exception of lungs, the dose reduction associated to the E+IMRT plans was more pronounced further away from the target. The average dose ratio delivered to the 0-2 cm and the 2-4 cm ring structures for brain patients for the two planning techniques were 89.6% and 70.8%, respectively. The enhanced dose sparing away from the target for the brain patients can also be observed in the ratio of the 75%, 50%, and 25% isodose line volumes for the two techniques, which decreases from 85.5% to 72.6% and further to 65.1%, respectively. For lungs, the lateral electron beams used in the E+IMRT plans were perpendicular to the mostly anterior/posterior photon beams, generating much more conformal plans. The authors proved that even using the existing electron delivery hardware, a mixed electron/photon planning

  15. Segment-based dose optimization using a genetic algorithm

    International Nuclear Information System (INIS)

    Cotrutz, Cristian; Xing Lei

    2003-01-01

    Intensity modulated radiation therapy (IMRT) inverse planning is conventionally done in two steps. Firstly, the intensity maps of the treatment beams are optimized using a dose optimization algorithm. Each of them is then decomposed into a number of segments using a leaf-sequencing algorithm for delivery. An alternative approach is to pre-assign a fixed number of field apertures and optimize directly the shapes and weights of the apertures. While the latter approach has the advantage of eliminating the leaf-sequencing step, the optimization of aperture shapes is less straightforward than that of beamlet-based optimization because of the complex dependence of the dose on the field shapes, and their weights. In this work we report a genetic algorithm for segment-based optimization. Different from a gradient iterative approach or simulated annealing, the algorithm finds the optimum solution from a population of candidate plans. In this technique, each solution is encoded using three chromosomes: one for the position of the left-bank leaves of each segment, the second for the position of the right-bank and the third for the weights of the segments defined by the first two chromosomes. The convergence towards the optimum is realized by crossover and mutation operators that ensure proper exchange of information between the three chromosomes of all the solutions in the population. The algorithm is applied to a phantom and a prostate case and the results are compared with those obtained using beamlet-based optimization. The main conclusion drawn from this study is that the genetic optimization of segment shapes and weights can produce highly conformal dose distribution. In addition, our study also confirms previous findings that fewer segments are generally needed to generate plans that are comparable with the plans obtained using beamlet-based optimization. Thus the technique may have useful applications in facilitating IMRT treatment planning

  16. Intensity-modulated radiation therapy for nasopharyngeal carcinoma parotid sparing with euivalent uiform dose optimization

    International Nuclear Information System (INIS)

    Yue Weiyou; Dai Jianrong; Gao Li

    2006-01-01

    Objective: The aim of this study was to evaluate the role of an euivalent uiform dose (EUD) based optimization algorithm in sparing the parotids of patients with nasopharyngeal carcinoma (NPC) when they are treated with intensity-modulated radiation therapy (IMRT). Methods: 12 patients were randomly selected from the NPC patients who received IMRT treatments. For these patients, the treatment plans were designed with physical optimization constraints (dose/dose-volume constraints). Based on these plans, new plans were designed through replacing the physical constraints with maximum EUD for parotids, while keeping the physical objectives for targets and other organs at risk(OARs) unchanged. Comparison was then made between the new plan, which had EUD constraints to parotids, and the former for each individual patient. Results: While maintaining the dose to the targets and the other OARs un- changed, optimization with EUD constraints to parotids decreased the mean dose and V 30 of parotids significantly, simultaneously, the dose of target volume and other organs at risk keep stable, the values of probability were less than 0.05 by T-test. Conclusions: The doses to parotids can be reduced through optimization with EUD constraints. This finding is quite helpful to reduce the occurrence rate of parotid complications, and to provide spaces for escalating target dose. (authors)

  17. Three-dimensional portal image-based dose reconstruction in a virtual phantom for rapid evaluation of IMRT plans

    International Nuclear Information System (INIS)

    Ansbacher, W.

    2006-01-01

    A new method for rapid evaluation of intensity modulated radiation therapy (IMRT) plans has been developed, using portal images for reconstruction of the dose delivered to a virtual three-dimensional (3D) phantom. This technique can replace an array of less complete but more time-consuming measurements. A reference dose calculation is first created by transferring an IMRT plan to a cylindrical phantom, retaining the treatment gantry angles. The isocenter of the fields is placed on or near the phantom axis. This geometry preserves the relative locations of high and low dose regions and has the required symmetry for the dose reconstruction. An electronic portal image (EPI) is acquired for each field, representing the dose in the midplane of a virtual phantom. The image is convolved with a kernel to correct for the lack of scatter, replicating the effect of the cylindrical phantom surrounding the dose plane. This avoids the need to calculate fluence. Images are calibrated to a reference field that delivers a known dose to the isocenter of this phantom. The 3D dose matrix is reconstructed by attenuation and divergence corrections and summed to create a dose matrix (PI-dose) on the same grid spacing as the reference calculation. Comparison of the two distributions is performed with a gradient-weighted 3D dose difference based on dose and position tolerances. Because of its inherent simplicity, the technique is optimally suited for detecting clinically significant variances from a planned dose distribution, rather than for use in the validation of IMRT algorithms. An analysis of differences between PI-dose and calculation, δ PI , compared to differences between conventional quality assurance (QA) and calculation, δ CQ , was performed retrospectively for 20 clinical IMRT cases. PI-dose differences at the isocenter were in good agreement with ionization chamber differences (mean δ PI =-0.8%, standard deviation σ=1.5%, against δ CQ =0.3%, σ=1.0%, respectively). PI-dose

  18. Independent dose calculation in IMRT for the Tps Iplan using the Clarkson modified integral

    International Nuclear Information System (INIS)

    Adrada, A.; Tello, Z.; Garrigo, E.; Venencia, D.

    2014-08-01

    Intensity-Modulated Radiation Therapy (IMRT) treatments require a quality assurance (Q A) specific patient before delivery. These controls include the experimental verification in dose phantom of the total plan as well as dose distributions. The use of independent dose calculation (IDC) is used in 3D-Crt treatments; however its application in IMRT requires the implementation of an algorithm that allows considering a non-uniform intensity beam. The purpose of this work was to develop IDC software in IMRT with MLC using the algorithm proposed by Kung (Kung et al. 2000). The software was done using Matlab programming. The Clarkson modified integral was implemented on each flowing, applying concentric rings for the dose determination. From the integral of each field was calculated the dose anywhere. One time finished a planning; all data are exported to a phantom where a Q A plan is generated. On this is calculated the half dose in a representative volume of the ionization chamber and the dose at the center of it. Until now 230 IMRT planning were analyzed carried out ??in the treatment planning system (Tps) Iplan. For each one of them Q A plan was generated, were calculated and compared calculated dose with the Tps, IDC system and measurement with ionization chamber. The average difference between measured and calculated dose with the IDC system was 0.4% ± 2.2% [-6.8%, 6.4%]. The difference between the measured and the calculated doses by the pencil-beam algorithm (Pb) of Tps was 2.6% ± 1.41% [-2.0%, 5.6%] and with the Monte Carlo algorithm was 0.4% ± 1.5% [-4.9%, 3.7%]. The differences of the carried out software are comparable to the obtained with the ionization chamber and Tps in Monte Carlo mode. (author)

  19. Evaluation of treatment plan quality of IMRT and VMAT with and without flattening filter using Pareto optimal fronts.

    Science.gov (United States)

    Lechner, Wolfgang; Kragl, Gabriele; Georg, Dietmar

    2013-12-01

    To investigate the differences in treatment plan quality of IMRT and VMAT with and without flattening filter using Pareto optimal fronts, for two treatment sites of different anatomic complexity. Pareto optimal fronts (POFs) were generated for six prostate and head-and-neck cancer patients by stepwise reduction of the constraint (during the optimization process) of the primary organ-at-risk (OAR). 9-static field IMRT and 360°-single-arc VMAT plans with flattening filter (FF) and without flattening filter (FFF) were compared. The volume receiving 5 Gy or more (V5 Gy) was used to estimate the low dose exposure. Furthermore, the number of monitor units (MUs) and measurements of the delivery time (T) were used to assess the efficiency of the treatment plans. A significant increase in MUs was found when using FFF-beams while the treatment plan quality was at least equivalent to the FF-beams. T was decreased by 18% for prostate for IMRT with FFF-beams and by 4% for head-and-neck cases, but increased by 22% and 16% for VMAT. A reduction of up to 5% of V5 Gy was found for IMRT prostate cases with FFF-beams. The evaluation of the POFs showed an at least comparable treatment plan quality of FFF-beams compared to FF-beams for both treatment sites and modalities. For smaller targets the advantageous characteristics of FFF-beams could be better exploited. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  20. Virtual couch shift (VCS): accounting for patient translation and rotation by online IMRT re-optimization

    International Nuclear Information System (INIS)

    Bol, G H; Lagendijk, J J W; Raaymakers, B W

    2013-01-01

    When delivering conventional intensity modulated radiotherapy (IMRT), discrepancies between the pre-treatment CT/MRI/PET based patient geometry and the daily patient geometry are minimized by performing couch translations and/or small rotations. However, full compensation of, in particular, rotations is usually not possible. In this paper, we introduce an online ‘virtual couch shift (VCS)’: we translate and/or rotate the pre-treatment dose distribution to compensate for the changes in patient anatomy and generate a new plan which delivers the transformed dose distribution automatically. We show for a phantom and a cervical cancer patient case that VCS accounts for both translations and large rotations equally well in terms of DVH results and 2%/2 mm γ analyses and when the various aspects of the clinical workflow can be implemented successfully, VCS can potentially outperform physical couch translations and/or rotations. This work is performed in the context of our hybrid 1.5 T MRI linear accelerator, which can provide translations and rotations but also deformations of the anatomy. The VCS is the first step toward compensating all of these anatomical changes by online re-optimization of the IMRT dose distribution. (paper)

  1. Dose planning objectives in anal canal cancer IMRT: the TROG ANROTAT experience

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Elizabeth, E-mail: elizabeth@mebrown.net [Princess Alexandra Hospital, Brisbane, Queensland (Australia); Cray, Alison [Peter MacCallum Cancer Cancer Centre, Box Hill, Victoria (Australia); Haworth, Annette [Peter MacCallum Cancer Cancer Centre, Box Hill, Victoria (Australia); University of Melbourne, Melbourne, Victoria (Australia); Chander, Sarat [Peter MacCallum Cancer Cancer Centre, Box Hill, Victoria (Australia); Lin, Robert [Medica Oncology, Hurstville, New South Wales (Australia); Subramanian, Brindha; Ng, Michael [Radiation Oncology Victoria, Melbourne, Victoria (Australia); Princess Alexandra Hospital, Brisbane, Queensland (Australia)

    2015-06-15

    Intensity modulated radiotherapy (IMRT) is ideal for anal canal cancer (ACC), delivering high doses to irregular tumour volumes whilst minimising dose to surrounding normal tissues. Establishing achievable dose objectives is a challenge. The purpose of this paper was to utilise data collected in the Assessment of New Radiation Oncology Treatments and Technologies (ANROTAT) project to evaluate the feasibility of ACC IMRT dose planning objectives employed in the Australian situation. Ten Australian centres were randomly allocated three data sets from 15 non-identifiable computed tomography data sets representing a range of disease stages and gender. Each data set was planned by two different centres, producing 30 plans. All tumour and organ at risk (OAR) contours, prescription and dose constraint details were provided. Dose–volume histograms (DVHs) for each plan were analysed to evaluate the feasibility of dose planning objectives provided. All dose planning objectives for the bone marrow (BM) and femoral heads were achieved. Median planned doses exceeded one or more objectives for bowel, external genitalia and bladder. This reached statistical significance for bowel V30 (P = 0.04), V45 (P < 0.001), V50 (P < 0.001), external genitalia V20 (P < 0.001) and bladder V35 (P < 0.001), V40 (P = 0.01). Gender was found to be the only significant factor in the likelihood of achieving the bowel V50 (P = 0.03) and BM V30 constraints (P = 0.04). The dose planning objectives used in the ANROTAT project provide a good starting point for ACC IMRT planning. To facilitate clinical implementation, it is important to prioritise OAR objectives and recognise factors that affect the achievability of these objectives.

  2. Comparison of dose distribution between 3DCRT and IMRT in middle thoracic and under thoracic esophageal carcinoma

    International Nuclear Information System (INIS)

    Li Dingjie; Liu Hailong; Mao Ronghu; Liu Ru; Guo Xiaoqi; Lei Hongchang; Wang Jianhua

    2011-01-01

    Objective: To compare the dose distribution between three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) in treating esophageal carcinoma (middle thoracic section and under thoracic section) and to select reasonable treatment methods for esophagus cancer. Methods: Ten cases with cancer of the middle thoracic section and under thoracic section esophagus were chosen for a retrospective treatment-planning study. 3DCRT and IMRT plans were created for each patient: Some critical indicators were evolved in evaluating the treatment plans of IMRT (5B and 7B) and 3DCRT (3B), such as, PTV coverage and dose-volumes to irradiated normal structures. Evaluation indicators: prescription of 50 Gy. total lung volume (V5, V10, V20), mean lung dose (MLD), spinal cord (Dmax), heart (V40) and conformality index (CI). Each plan was evaluated with respect to dose distribution,dose-volume histograms (DVHs), and additional dosimetric endpoints described below. Results: There is no significance of CRT and IMRT technique in protection of total lung volume,mean lung dose, spinal cord (Dmax), target, CI and heart. Conclusion: As To radiotherapy of esophagus cancer of the middle thoracic section and under thoracic section, IMRT has no advantage compared with 3DCRT, the selection of plan should be adapted to the situations of every patient. (authors)

  3. Intensity modulated radiation therapy (IMRT: differences in target volumes and improvement in clinically relevant doses to small bowel in rectal carcinoma

    Directory of Open Access Journals (Sweden)

    Delclos Marc E

    2011-06-01

    Full Text Available Abstract Background A strong dose-volume relationship exists between the amount of small bowel receiving low- to intermediate-doses of radiation and the rates of acute, severe gastrointestinal toxicity, principally diarrhea. There is considerable interest in the application of highly conformal treatment approaches, such as intensity-modulated radiation therapy (IMRT, to reduce dose to adjacent organs-at-risk in the treatment of carcinoma of the rectum. Therefore, we performed a comprehensive dosimetric evaluation of IMRT compared to 3-dimensional conformal radiation therapy (3DCRT in standard, preoperative treatment for rectal cancer. Methods Using RTOG consensus anorectal contouring guidelines, treatment volumes were generated for ten patients treated preoperatively at our institution for rectal carcinoma, with IMRT plans compared to plans derived from classic anatomic landmarks, as well as 3DCRT plans treating the RTOG consensus volume. The patients were all T3, were node-negative (N = 1 or node-positive (N = 9, and were planned to a total dose of 45-Gy. Pairwise comparisons were made between IMRT and 3DCRT plans with respect to dose-volume histogram parameters. Results IMRT plans had superior PTV coverage, dose homogeneity, and conformality in treatment of the gross disease and at-risk nodal volume, in comparison to 3DCRT. Additionally, in comparison to the 3DCRT plans, IMRT achieved a concomitant reduction in doses to the bowel (small bowel mean dose: 18.6-Gy IMRT versus 25.2-Gy 3DCRT; p = 0.005, bladder (V40Gy: 56.8% IMRT versus 75.4% 3DCRT; p = 0.005, pelvic bones (V40Gy: 47.0% IMRT versus 56.9% 3DCRT; p = 0.005, and femoral heads (V40Gy: 3.4% IMRT versus 9.1% 3DCRT; p = 0.005, with an improvement in absolute volumes of small bowel receiving dose levels known to induce clinically-relevant acute toxicity (small bowel V15Gy: 138-cc IMRT versus 157-cc 3DCRT; p = 0.005. We found that the IMRT treatment volumes were typically larger than that

  4. Cardiac dose-sparing effects of deep-inspiration breath-hold in left breast irradiation : Is IMRT more beneficial than VMAT?

    Science.gov (United States)

    Sakka, Mazen; Kunzelmann, Leonie; Metzger, Martin; Grabenbauer, Gerhard G

    2017-10-01

    Given the reduction in death from breast cancer, as well as improvements in overall survival, adjuvant radiotherapy is considered the standard treatment for breast cancer. However, left-sided breast irradiation was associated with an increased rate of fatal cardiovascular events due to incidental irradiation of the heart. Recently, considerable efforts have been made to minimize cardiac toxicity of left-sided breast irradiation by new treatment methods such as deep-inspiration breath-hold (DIBH) and new radiation techniques, particularly intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). The primary aim of this study was to evaluate the effect of DIBH irradiation on cardiac dose compared with free-breathing (FB) irradiation, while the secondary objective was to compare the advantages of IMRT versus VMAT plans in both the FB and the DIBH position for left-sided breast cancer. In all, 25 consecutive left-sided breast cancer patients underwent CT simulation in the FB and DIBH position. Five patients were excluded with no cardiac displacement following DIBH-CT simulation. The other 20 patients were irradiated in the DIBH position using respiratory gating. Four different treatment plans were generated for each patient, an IMRT and a VMAT plan in the DIBH and in the FB position, respectively. The following parameters were used for plan comparison: dose to the heart, left anterior descending coronary artery (mean dose, maximum dose, D25% and D45%), ipsilateral, contralateral lung (mean dose, D20%, D30%) and contralateral breast (mean dose). The percentage in dose reduction for organs at risk achieved by DIBH for both IMRT and VMAT plans was calculated and compared for each patient by each treatment plan. DIBH irradiation significantly reduced mean dose to the heart and left anterior descending coronary artery (LADCA) using both IMRT (heart -20%; p = 0.0002, LADCA -9%; p = 0.001) and VMAT (heart -23%; p = 0.00003, LADCA -16%; p = 0

  5. Patient-specific IMRT verification using independent fluence-based dose calculation software: experimental benchmarking and initial clinical experience

    International Nuclear Information System (INIS)

    Georg, Dietmar; Stock, Markus; Kroupa, Bernhard; Olofsson, Joergen; Nyholm, Tufve; Ahnesjoe, Anders; Karlsson, Mikael

    2007-01-01

    Experimental methods are commonly used for patient-specific intensity-modulated radiotherapy (IMRT) verification. The purpose of this study was to investigate the accuracy and performance of independent dose calculation software (denoted as 'MUV' (monitor unit verification)) for patient-specific quality assurance (QA). 52 patients receiving step-and-shoot IMRT were considered. IMRT plans were recalculated by the treatment planning systems (TPS) in a dedicated QA phantom, in which an experimental 1D and 2D verification (0.3 cm 3 ionization chamber; films) was performed. Additionally, an independent dose calculation was performed. The fluence-based algorithm of MUV accounts for collimator transmission, rounded leaf ends, tongue-and-groove effect, backscatter to the monitor chamber and scatter from the flattening filter. The dose calculation utilizes a pencil beam model based on a beam quality index. DICOM RT files from patient plans, exported from the TPS, were directly used as patient-specific input data in MUV. For composite IMRT plans, average deviations in the high dose region between ionization chamber measurements and point dose calculations performed with the TPS and MUV were 1.6 ± 1.2% and 0.5 ± 1.1% (1 S.D.). The dose deviations between MUV and TPS slightly depended on the distance from the isocentre position. For individual intensity-modulated beams (total 367), an average deviation of 1.1 ± 2.9% was determined between calculations performed with the TPS and with MUV, with maximum deviations up to 14%. However, absolute dose deviations were mostly less than 3 cGy. Based on the current results, we aim to apply a confidence limit of 3% (with respect to the prescribed dose) or 6 cGy for routine IMRT verification. For off-axis points at distances larger than 5 cm and for low dose regions, we consider 5% dose deviation or 10 cGy acceptable. The time needed for an independent calculation compares very favourably with the net time for an experimental approach

  6. SU-E-T-49: A Multi-Institutional Study of Independent Dose Verification for IMRT

    International Nuclear Information System (INIS)

    Baba, H; Tachibana, H; Kamima, T; Takahashi, R; Kawai, D; Sugawara, Y; Yamamoto, T; Sato, A; Yamashita, M

    2015-01-01

    Purpose: AAPM TG114 does not cover the independent verification for IMRT. We conducted a study of independent dose verification for IMRT in seven institutes to show the feasibility. Methods: 384 IMRT plans in the sites of prostate and head and neck (HN) were collected from the institutes, where the planning was performed using Eclipse and Pinnacle3 with the two techniques of step and shoot (S&S) and sliding window (SW). All of the institutes used a same independent dose verification software program (Simple MU Analysis: SMU, Triangle Product, Ishikawa, JP), which is Clarkson-based and CT images were used to compute radiological path length. An ion-chamber measurement in a water-equivalent slab phantom was performed to compare the doses computed using the TPS and an independent dose verification program. Additionally, the agreement in dose computed in patient CT images between using the TPS and using the SMU was assessed. The dose of the composite beams in the plan was evaluated. Results: The agreement between the measurement and the SMU were −2.3±1.9 % and −5.6±3.6 % for prostate and HN sites, respectively. The agreement between the TPSs and the SMU were −2.1±1.9 % and −3.0±3.7 for prostate and HN sites, respectively. There was a negative systematic difference with similar standard deviation and the difference was larger in the HN site. The S&S technique showed a statistically significant difference between the SW. Because the Clarkson-based method in the independent program underestimated (cannot consider) the dose under the MLC. Conclusion: The accuracy would be improved when the Clarkson-based algorithm should be modified for IMRT and the tolerance level would be within 5%

  7. A dose planning study on applicator guided stereotactic IMRT boost in combination with 3D MRI based brachytherapy in locally advanced cervical cancer

    International Nuclear Information System (INIS)

    Assenholt, Marianne S.; Petersen, Joergen B.; Nielsen, Soeren K.; Lindegaard, Jacob C.; Tanderup, Kari

    2008-01-01

    Purpose. Locally advanced cervical cancer is usually treated with external beam radiotherapy followed by brachytherapy (BT). However, if response or tumour topography is unfavourable it may be difficult to reach a sufficient BT dose. The purpose of this study was to explore whether an applicator guided stereotactic IMRT boost could be combined with brachytherapy to improve dose volume parameters. Material and methods. Dose plans of 6 patients with HR CTV volumes of 31-100cc at the time of BT were analysed. MRI was performed with a combined intracavitary (IC)-interstitial (IS) ring applicator in situ. A radiotherapy schedule consisting of 45Gy (1.8Gyx25) IMRT followed by boost of 28Gy (7Gyx4fx) was modelled. Four different boost techniques were evaluated: IC-BT, IC/IS-BT, IC-BT+IMRT and IMRT. Dose plans were optimised for maximal tumour dose (D90) and coverage (V85Gy) while respecting DVH constraints in organs at risk: D2cc <75Gy in rectum and sigmoid and <90Gy in bladder (EQD2). In combined BT+IMRT dose plans, the IMRT plan was optimised on top of the BT dose distribution. Volumes irradiated to more than 60 Gy EQD2 (V60Gy) were evaluated. Results. Median dose coverage in IC plans was 74% [66-93%]. By using IC/IS or IC-BT+IMRT boost, the median coverage was improved to 95% [78-99%], and to 96% [69-99%] respectively. For IMRT alone, a median coverage of 98% [90-100%] was achieved, but V60Gy volumes were significantly increased by a median factor of 2.0 [1.4-2.3] as compared to IC/IS. It depended on the individual tumour topography whether IC/IS-BT or IC-BT+IMRT boost was the most favourable technique. Conclusion. It is technically possible to create dose plans that combine image guided BT and IMRT. In this study the dose coverage could be significantly increased by adding IS-BT or IMRT boost to the intracavitary dose. Using IMRT alone for boost cannot be advocated since this results in a significant increase of the volume irradiated to 60Gy

  8. Clinical Evaluation of Direct Aperture Optimization When Applied to Head-And-Neck IMRT

    International Nuclear Information System (INIS)

    Jones, Stephen; Williams, Matthew

    2008-01-01

    Direct Machine Parameter Optimization (DMPO) is a leaf segmentation program released as an optional item of the Pinnacle planning system (Philips Radiation Oncology Systems, Milpitas, CA); it is based on the principles of direct aperture optimization where the size, shape, and weight of individual segments are optimized to produce an intensity modulated radiation treatment (IMRT) plan. In this study, we compare DMPO to the traditional method of IMRT planning, in which intensity maps are optimized prior to conversion into deliverable multileaf collimator (MLC) apertures, and we determine if there was any dosimetric improvement, treatment efficiency gain, or planning advantage provided by the use of DMPO. Eleven head-and-neck patients treated with IMRT had treatment plans generated using each optimization method. For each patient, the same planning parameters were used for each optimization method. All calculations were performed using Pinnacle version 7.6c software and treatments were delivered using a step-and-shoot IMRT method on a Varian 2100EX linear accelerator equipped with a 120-leaf Millennium MLC (Varian Medical Systems, Palo Alto, CA). Each plan was assessed based on the calculation time, a conformity index, the composite objective value used in the optimization, the number of segments, monitor units (MUs), and treatment time. The results showed DMPO to be superior to the traditional optimization method in all areas. Considerable advantages were observed in the dosimetric quality of DMPO plans, which also required 32% less time to calculate, 42% fewer MUs, and 35% fewer segments than the conventional optimization method. These reductions translated directly into a 29% decrease in treatment times. While considerable gains were observed in planning and treatment efficiency, they were specific to our institution, and the impact of direct aperture optimization on plan quality and workflow will be dependent on the planning parameters, planning system, and

  9. Dosimetric comparison of treatment techniques IMRT and VMAT for breast cancer; Comparacion dosimetrica de las tecnicas de tratamiento IMRT y VMAT para cancer en mama

    Energy Technology Data Exchange (ETDEWEB)

    Urbina, G. L. [Universidad Nacional de Ingenieria, Maestria en Fisica Medica, Av. Tupac Amaru s/n, Rimac, Lima 25 (Peru); Garcia, B. G., E-mail: gerlup@hotmail.com [Red AUNA, Clinica Delgado, Av. Angamos Cdra. 4 esquina Gral. Borgono, Miraflores, Lima (Peru)

    2015-10-15

    In this study the dosimetric distribution was compared in the different treatment techniques such as Volumetric Modulated Arc Therapy (VMAT) and Intensity Modulated Radiation Therapy (IMRT) in female patients with breast cancer with stage II-B and III-A, 6 cases (both calculated on VMAT and IMRT) were studied, comparison parameter that are taken into account are: compliance rate, homogeneity index, monitor units, volume dose 50 Gy (D-50%) and 5 Gy (D-5%) volume dose. Comparisons are made in primary tumor volume to optimize treatment in patients with breast cancer, with IMRT using Step, Shoot and VMAT Monte Carlo algorithm, in addition to the organs at risk; the concern to make this work is due to technological advances in radiotherapy and the application of new treatment techniques, that increase the accuracy allowing treatment dose climbing delivering a higher dose to the patient. (Author)

  10. Effect of beamlet step-size on IMRT plan quality

    International Nuclear Information System (INIS)

    Zhang Guowei; Jiang Ziping; Shepard, David; Earl, Matt; Yu, Cedric

    2005-01-01

    We have studied the degree to which beamlet step-size impacts the quality of intensity modulated radiation therapy (IMRT) treatment plans. Treatment planning for IMRT begins with the application of a grid that divides each beam's-eye-view of the target into a number of smaller beamlets (pencil beams) of radiation. The total dose is computed as a weighted sum of the dose delivered by the individual beamlets. The width of each beamlet is set to match the width of the corresponding leaf of the multileaf collimator (MLC). The length of each beamlet (beamlet step-size) is parallel to the direction of leaf travel. The beamlet step-size represents the minimum stepping distance of the leaves of the MLC and is typically predetermined by the treatment planning system. This selection imposes an artificial constraint because the leaves of the MLC and the jaws can both move continuously. Removing the constraint can potentially improve the IMRT plan quality. In this study, the optimized results were achieved using an aperture-based inverse planning technique called direct aperture optimization (DAO). We have tested the relationship between pencil beam step-size and plan quality using the American College of Radiology's IMRT test case. For this case, a series of IMRT treatment plans were produced using beamlet step-sizes of 1, 2, 5, and 10 mm. Continuous improvements were seen with each reduction in beamlet step size. The maximum dose to the planning target volume (PTV) was reduced from 134.7% to 121.5% and the mean dose to the organ at risk (OAR) was reduced from 38.5% to 28.2% as the beamlet step-size was reduced from 10 to 1 mm. The smaller pencil beam sizes also led to steeper dose gradients at the junction between the target and the critical structure with gradients of 6.0, 7.6, 8.7, and 9.1 dose%/mm achieved for beamlet step sizes of 10, 5, 2, and 1 mm, respectively

  11. Step-and-Shoot versus Compensator-based IMRT: Calculation and Comparison of Integral Dose in Non-tumoral and Target Organs in Prostate Cancer

    Directory of Open Access Journals (Sweden)

    Kaveh Shirani Tak Abi

    2015-05-01

    Full Text Available Introduction Intensity-Modulated Radiotherapy (IMRT is becoming an increasingly routine treatment method. IMRT can be delivered by use of conventional Multileaf Collimators (MLCs and/or physical compensators. One of the most important factors in selecting an appropriate IMRT technique is integral dose. Integral dose is equal to the mean energy deposited in the total irradiated volume of the patient. The aim of the present study was to calculate and compare the integral dose in normal and target organs in two different procedures of IMRT: Step-and-Shoot (SAS and compensator-based IMRT. Materials and Methods In this comparative study, five patients with prostate cancer were selected. Module Integrated Radiotherapy System was applied, using three energy ranges. In both treatment planning methods, the integral dose dramatically decreased by increasing energy. Results Comparison of two treatment methods showed that on average, the integral dose of body in SAS radiation therapy was about 1.62% lower than that reported in compensator-based IMRT. In planning target volume, rectum, bladder, and left and right femoral heads, the integral doses for SAS method were 1.01%, 1.02%, 1.11%, 1.47%, and 1.40% lower than compensator-based IMRT, respectively. Conclusion Considering the treatment conditions, the definition of dose volume constraints for healthy tissues, and the equal volume of organs in both treatment methods, SAS radiation therapy by providing a lower integral dose seems to be more advantageous and efficient for prostate cancer treatment, compared to compensator-based IMRT.

  12. Dosimetric comparison of standard three-dimensional conformal radiotherapy followed by intensity-modulated radiotherapy boost schedule (sequential IMRT plan) with simultaneous integrated boost-IMRT (SIB IMRT) treatment plan in patients with localized carcinoma prostate.

    Science.gov (United States)

    Bansal, A; Kapoor, R; Singh, S K; Kumar, N; Oinam, A S; Sharma, S C

    2012-07-01

    DOSIMETERIC AND RADIOBIOLOGICAL COMPARISON OF TWO RADIATION SCHEDULES IN LOCALIZED CARCINOMA PROSTATE: Standard Three-Dimensional Conformal Radiotherapy (3DCRT) followed by Intensity Modulated Radiotherapy (IMRT) boost (sequential-IMRT) with Simultaneous Integrated Boost IMRT (SIB-IMRT). Thirty patients were enrolled. In all, the target consisted of PTV P + SV (Prostate and seminal vesicles) and PTV LN (lymph nodes) where PTV refers to planning target volume and the critical structures included: bladder, rectum and small bowel. All patients were treated with sequential-IMRT plan, but for dosimetric comparison, SIB-IMRT plan was also created. The prescription dose to PTV P + SV was 74 Gy in both strategies but with different dose per fraction, however, the dose to PTV LN was 50 Gy delivered in 25 fractions over 5 weeks for sequential-IMRT and 54 Gy delivered in 27 fractions over 5.5 weeks for SIB-IMRT. The treatment plans were compared in terms of dose-volume histograms. Also, Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) obtained with the two plans were compared. The volume of rectum receiving 70 Gy or more (V > 70 Gy) was reduced to 18.23% with SIB-IMRT from 22.81% with sequential-IMRT. SIB-IMRT reduced the mean doses to both bladder and rectum by 13% and 17%, respectively, as compared to sequential-IMRT. NTCP of 0.86 ± 0.75% and 0.01 ± 0.02% for the bladder, 5.87 ± 2.58% and 4.31 ± 2.61% for the rectum and 8.83 ± 7.08% and 8.25 ± 7.98% for the bowel was seen with sequential-IMRT and SIB-IMRT plans respectively. For equal PTV coverage, SIB-IMRT markedly reduced doses to critical structures, therefore should be considered as the strategy for dose escalation. SIB-IMRT achieves lesser NTCP than sequential-IMRT.

  13. Dosimetric verification and evaluation of segmental multileaf collimator (SMLC)-IMRT for quality assurance. The second report. Absolute dose

    International Nuclear Information System (INIS)

    Tateoka, Kunihiko; Hareyama, Masato; Oouchi, Atsushi; Nakata, Kensei; Nagase, Daiki; Saikawa, Tsunehiko; Shimizume, Kazunari; Sugimoto, Harumi; Waka, Masaaki

    2003-01-01

    Intensity-modulated radiation therapy (IMRT) was developed to irradiate the target are more conformally, sparing organs at risk (OARs). Since the beams are sequentially delivered by many, small, irregular, and off-center fields in IMRT, dosimetric quality assurance (QA) is an extremely important issue. QA is performed by verifying both the dose distribution and doses at arbitrary points. In this work, we describe the verification of doses at arbitrary points in our hospital for Segmental multileaf collimator (SMLC)-IMRT. In general, verification of the absolute doses for IMRT is performed by comparison between the calculated doses using Radiation Treatment Planning Systems (RTP) and the measured doses using an ionization chamber with a small volume at arbitrary points in relatively flat regions of the dose gradients. However, no clear definitions of the dose gradients and the flat regions have yet been reported. We carried out verification by comparison of the measured doses with the average dose and the central point dose in a virtual Farmer type ionization chamber (V-F) and a virtual PinPoint ionization chamber (V-P) equal to the Farmer-type ionization chamber volume and PinPoint ionization chamber volumes using the RTP. Furthermore, we defined the dose gradients as the deviation of the maximum dose from the minimum dose in the virtual ionization chamber volume. In IMRT, the dose gradients may be as high as 80% or more in the virtual ionization chamber volume. Therefore, it is thought that the effective center of the ionization chamber varies by segment for IMRT fields (i.e., the variation of the ionization chamber replacement effect). Additionally, in regions with a higher dose gradient, uncertainty in the measured doses is influenced by the variations in the ionization chamber replacement effect and the ionization chamber positioning error. We more objectively examined the verification method for the absolute dose in IMRT using the virtual ionization chamber

  14. SU-E-T-521: Feasibility Study of a Rotational Step-And-Shoot IMRT Treatment Planning Approach

    International Nuclear Information System (INIS)

    Zhu, X; Chang, S; Cullip, T; Yuan, L; Zhang, X; Lian, J; Tang, X; Tracton, G; Dooley, J

    2014-01-01

    Purpose: Rotational step-and-shot IMRT (r-IMRT) could improve delivery efficiency with good dose conformity, especially if it can leverage the burst mode of the accelerator where radiation is turned on/off momentarily while the gantry rotates continuously. The challenge for the r-IMRT planning is to minimize the number of beams to achieve a fast and smooth rotational delivery. Methods: Treatment plans for r-IMRT were created using an in-house treatment planning system. To generate the plan using a very few beams, gantry angle was optimized by weighting the beam monitoring unit (MU), and beam shape optimization was a combination of column search with k-means clustering. A prostate case and a head and neck case were planned using r-IMRT. The dosimetry is compared to s-IMRT planned with Varian Eclipse treatment planning system. Results: With the same PTV dose coverage D95=100%, the r-IMRT plans shows comparable sparing as the s-IMRT plans in the prostate for the rectum D10cc and the bladder Dmean, and in the head and neck for the spinal cord Dmax, the brain stem Dmax, the left/right parotid Dmean, the larynx Dmean, and the mandible Dmean. Both plans meet the established institutional clinical dosimetric criteria. The r-IMRT plan uses 19 beam/405 MU for the prostate, and 68 beam/880 MU for the head and neck, while the s-IMRT uses 7 beam/724 MU and 9 beam/1812 MU, respectively. Compared to the corresponding s-IMRT, r-IMRT has a reduction of MUs of 44% for the prostate case and 41% for the head and neck case. Conclusions: We have demonstrated the feasibility of a rotational step and shoot IMRT treatment planning approach that significantly shortens the conventional IMRT treatment beam-on time without degrading the dose comformity

  15. SU-E-T-521: Feasibility Study of a Rotational Step-And-Shoot IMRT Treatment Planning Approach

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, X [Univ. of North Carolina at Chapel Hill, Chapel Hill, NC (United States); Chang, S [UNC School of Medicine, Chapel Hill, NC (United States); Cullip, T [UNC Hospitals, Chapel Hill, NC (United States); Yuan, L; Zhang, X [Duke University, Durham, NC (United States); Lian, J; Tang, X [UniversityNorth Carolina, Chapel Hill, NC (United States); Tracton, G; Dooley, J [University of North Carolina, Chapel Hill, NC (United States)

    2014-06-01

    Purpose: Rotational step-and-shot IMRT (r-IMRT) could improve delivery efficiency with good dose conformity, especially if it can leverage the burst mode of the accelerator where radiation is turned on/off momentarily while the gantry rotates continuously. The challenge for the r-IMRT planning is to minimize the number of beams to achieve a fast and smooth rotational delivery. Methods: Treatment plans for r-IMRT were created using an in-house treatment planning system. To generate the plan using a very few beams, gantry angle was optimized by weighting the beam monitoring unit (MU), and beam shape optimization was a combination of column search with k-means clustering. A prostate case and a head and neck case were planned using r-IMRT. The dosimetry is compared to s-IMRT planned with Varian Eclipse treatment planning system. Results: With the same PTV dose coverage D95=100%, the r-IMRT plans shows comparable sparing as the s-IMRT plans in the prostate for the rectum D10cc and the bladder Dmean, and in the head and neck for the spinal cord Dmax, the brain stem Dmax, the left/right parotid Dmean, the larynx Dmean, and the mandible Dmean. Both plans meet the established institutional clinical dosimetric criteria. The r-IMRT plan uses 19 beam/405 MU for the prostate, and 68 beam/880 MU for the head and neck, while the s-IMRT uses 7 beam/724 MU and 9 beam/1812 MU, respectively. Compared to the corresponding s-IMRT, r-IMRT has a reduction of MUs of 44% for the prostate case and 41% for the head and neck case. Conclusions: We have demonstrated the feasibility of a rotational step and shoot IMRT treatment planning approach that significantly shortens the conventional IMRT treatment beam-on time without degrading the dose comformity.

  16. Implementation of a Monte Carlo based inverse planning model for clinical IMRT with MCNP code

    International Nuclear Information System (INIS)

    He, Tongming Tony

    2003-01-01

    Inaccurate dose calculations and limitations of optimization algorithms in inverse planning introduce systematic and convergence errors to treatment plans. This work was to implement a Monte Carlo based inverse planning model for clinical IMRT aiming to minimize the aforementioned errors. The strategy was to precalculate the dose matrices of beamlets in a Monte Carlo based method followed by the optimization of beamlet intensities. The MCNP 4B (Monte Carlo N-Particle version 4B) code was modified to implement selective particle transport and dose tallying in voxels and efficient estimation of statistical uncertainties. The resulting performance gain was over eleven thousand times. Due to concurrent calculation of multiple beamlets of individual ports, hundreds of beamlets in an IMRT plan could be calculated within a practical length of time. A finite-sized point source model provided a simple and accurate modeling of treatment beams. The dose matrix calculations were validated through measurements in phantoms. Agreements were better than 1.5% or 0.2 cm. The beamlet intensities were optimized using a parallel platform based optimization algorithm that was capable of escape from local minima and preventing premature convergence. The Monte Carlo based inverse planning model was applied to clinical cases. The feasibility and capability of Monte Carlo based inverse planning for clinical IMRT was demonstrated. Systematic errors in treatment plans of a commercial inverse planning system were assessed in comparison with the Monte Carlo based calculations. Discrepancies in tumor doses and critical structure doses were up to 12% and 17%, respectively. The clinical importance of Monte Carlo based inverse planning for IMRT was demonstrated

  17. Does IGRT ensure target dose coverage of head and neck IMRT patients?

    International Nuclear Information System (INIS)

    Graff, Pierre; Hu Weigang; Yom, Sue S.; Pouliot, Jean

    2012-01-01

    Purpose: To determine if image-guided radiotherapy (IGRT) ensures dose coverage to the target, and to assess the dosimetric impact of anatomic changes using megavoltage cone-beam CT (MVCBCT) for patient positioning during head and neck IMRT. Methods and materials: Forty-eight MVCBCT from 10 head and neck IMRT/IGRT patients were analyzed off-line. Target volumes and organs at risk (OARs) contours delineated on CT were transferred and adjusted on MVCBCT images. Each MVCBCT was processed to allow dose recalculation, resulting in 469 dose–volume histograms (DVHs). The concept of dosimetric latitude was introduced to provide a clinical perspective. Results: MVCBCT target DVHs showed a moderate level of difference in D95 (dose to ⩾95% of volume), generally less than a 5% difference from the planned dose. Delivered-dose increases to the spinal cord and brainstem showed no apparent time trend. The 4 mm margin around OARs was a useful precaution to prevent exceeding critical dose thresholds. The parotid glands showed progressive increases in mean dose related to shrinkage of the external contours. Conclusion: IGRT repositioning ensured target volume coverage, but significant dose variations were observed for OARs. The dosimetric impact of anatomic changes during radiotherapy was of lesser importance than the effects of IGRT repositioning.

  18. Integration method of 3D MR spectroscopy into treatment planning system for glioblastoma IMRT dose painting with integrated simultaneous boost

    International Nuclear Information System (INIS)

    Ken, Soléakhéna; Cassol, Emmanuelle; Delannes, Martine; Celsis, Pierre; Cohen-Jonathan, Elizabeth Moyal; Laprie, Anne; Vieillevigne, Laure; Franceries, Xavier; Simon, Luc; Supper, Caroline; Lotterie, Jean-Albert; Filleron, Thomas; Lubrano, Vincent; Berry, Isabelle

    2013-01-01

    To integrate 3D MR spectroscopy imaging (MRSI) in the treatment planning system (TPS) for glioblastoma dose painting to guide simultaneous integrated boost (SIB) in intensity-modulated radiation therapy (IMRT). For sixteen glioblastoma patients, we have simulated three types of dosimetry plans, one conventional plan of 60-Gy in 3D conformational radiotherapy (3D-CRT), one 60-Gy plan in IMRT and one 72-Gy plan in SIB-IMRT. All sixteen MRSI metabolic maps were integrated into TPS, using normalization with color-space conversion and threshold-based segmentation. The fusion between the metabolic maps and the planning CT scans were assessed. Dosimetry comparisons were performed between the different plans of 60-Gy 3D-CRT, 60-Gy IMRT and 72-Gy SIB-IMRT, the last plan was targeted on MRSI abnormalities and contrast enhancement (CE). Fusion assessment was performed for 160 transformations. It resulted in maximum differences <1.00 mm for translation parameters and ≤1.15° for rotation. Dosimetry plans of 72-Gy SIB-IMRT and 60-Gy IMRT showed a significantly decreased maximum dose to the brainstem (44.00 and 44.30 vs. 57.01 Gy) and decreased high dose-volumes to normal brain (19 and 20 vs. 23% and 7 and 7 vs. 12%) compared to 60-Gy 3D-CRT (p < 0.05). Delivering standard doses to conventional target and higher doses to new target volumes characterized by MRSI and CE is now possible and does not increase dose to organs at risk. MRSI and CE abnormalities are now integrated for glioblastoma SIB-IMRT, concomitant with temozolomide, in an ongoing multi-institutional phase-III clinical trial. Our method of MR spectroscopy maps integration to TPS is robust and reliable; integration to neuronavigation systems with this method could also improve glioblastoma resection or guide biopsies

  19. Hybrid IMRT plans-concurrently treating conventional and IMRT beams for improved breast irradiation and reduced planning time

    International Nuclear Information System (INIS)

    Mayo, Charles S.; Urie, Marcia M.; Fitzgerald, Thomas J.

    2005-01-01

    Purpose: To evaluate a hybrid intensity modulated radiation therapy (IMRT) technique as a class solution for treatment of the intact breast. Methods and materials: The following five plan techniques were compared for 10 breast patients using dose-volume histogram analysis: conventional wedged-field tangents (Tangents), forward-planned field-within-a-field tangents (FIF), IMRT-only tangents (IMRT tangents), conventional open plus IMRT tangents (4-field hybrid), and conventional open plus IMRT tangents with 2 anterior oblique IMRT beams (6-field hybrid). Results: The 4-field hybrid and FIF achieved dose distributions better than Tangents and IMRT tangents. The volume of tissue outside the planning target volume receiving ≥110% of prescribed dose was largest for IMRT tangents (average 158 cc) and least for 6-field hybrid (average 1 cc); the FIF and 4-field hybrid were comparable (average 15 cc). Heart volume ≥30 Gy averaged 13 cc for all techniques, except Tangents, for which it was 32 cc. Average total lung volume ≥20 Gy was 7% for all. Contralateral breast doses were < 3% for all. Planning time for hybrid techniques was significantly less than for conventional FIF technique. Conclusions: The 4-field hybrid technique is a viable class solution. The 6-field hybrid technique creates the most conformal dose distribution at the expense of more normal tissue receiving low dose

  20. Evaluation of the 'dose of the day' for IMRT prostate cancer patients derived from portal dose measurements and cone-beam CT

    International Nuclear Information System (INIS)

    Zijtveld, Mathilda van; Dirkx, Maarten; Breuers, Marcel; Kuipers, Ruud; Heijmen, Ben

    2010-01-01

    Purpose: High geometrical and dosimetrical accuracies are required for radiotherapy treatments where IMRT is applied in combination with narrow treatment margins in order to minimize dose delivery to normal tissues. As an overall check, we implemented a method for reconstruction of the actually delivered 3D dose distribution to the patient during a treatment fraction, i.e., the 'dose of the day'. In this article results on the clinical evaluation of this concept for a group of IMRT prostate cancer patients are presented. Materials and methods: The actual IMRT fluence maps delivered to a patient were derived from measured EPID-images acquired during treatment using a previously described iterative method. In addition, the patient geometry was obtained from in-room acquired cone-beam CT images. For dose calculation, a mapping of the Hounsfield Units from the planning CT was applied. With the fluence maps and the modified cone-beam CT the 'dose of the day' was calculated. The method was validated using phantom measurements and evaluated clinically for 10 prostate cancer patients in 4 or 5 fractions. Results: The phantom measurements showed that the delivered dose could be reconstructed within 3%/3 mm accuracy. For prostate cancer patients, the isocenter dose agreed within -0.4 ± 1.0% (1 SD) with the planned value, while for on average 98.1% of the pixels within the 50% isodose surface the actually delivered dose agreed within 3% or 3 mm with the planned dose. For most fractions, the dose coverage of the prostate volume was slightly deteriorated which was caused by small prostate rotations and small inaccuracies in fluence delivery. The dose that was delivered to the rectum remained within the constraints used during planning. However, for two patients a large degrading of the dose delivery was observed in two fractions. For one patient this was related to changes in rectum filling with respect to the planning CT and for the other to large intra-fraction motion during

  1. Letter to the Editor on 'Single-Arc IMRT?'.

    Science.gov (United States)

    Otto, Karl

    2009-04-21

    In the note 'Single Arc IMRT?' (Bortfeld and Webb 2009 Phys. Med. Biol. 54 N9-20), Bortfeld and Webb present a theoretical investigation of static gantry IMRT (S-IMRT), single-arc IMRT and tomotherapy. Based on their assumptions they conclude that single-arc IMRT is inherently limited in treating complex cases without compromising delivery efficiency. Here we present an expansion of their work based on the capabilities of the Varian RapidArc single-arc IMRT system. Using the same theoretical framework we derive clinically deliverable single-arc IMRT plans based on these specific capabilities. In particular, we consider the range of leaf motion, the ability to rapidly and continuously vary the dose rate and the choice of collimator angle used for delivery. In contrast to the results of Bortfeld and Webb, our results show that single-arc IMRT plans can be generated that closely match the theoretical optimum. The disparity in the results of each investigation emphasizes that the capabilities of the delivery system, along with the ability of the optimization algorithm to exploit those capabilities, are of particular importance in single-arc IMRT. We conclude that, given the capabilities available with the RapidArc system, single-arc IMRT can produce complex treatment plans that are delivered efficiently (in approximately 2 min).

  2. IMRT: Improvement in treatment planning efficiency using NTCP calculation independent of the dose-volume-histogram

    International Nuclear Information System (INIS)

    Grigorov, Grigor N.; Chow, James C.L.; Grigorov, Lenko; Jiang, Runqing; Barnett, Rob B.

    2006-01-01

    The normal tissue complication probability (NTCP) is a predictor of radiobiological effect for organs at risk (OAR). The calculation of the NTCP is based on the dose-volume-histogram (DVH) which is generated by the treatment planning system after calculation of the 3D dose distribution. Including the NTCP in the objective function for intensity modulated radiation therapy (IMRT) plan optimization would make the planning more effective in reducing the postradiation effects. However, doing so would lengthen the total planning time. The purpose of this work is to establish a method for NTCP determination, independent of a DVH calculation, as a quality assurance check and also as a mean of improving the treatment planning efficiency. In the study, the CTs of ten randomly selected prostate patients were used. IMRT optimization was performed with a PINNACLE3 V 6.2b planning system, using planning target volume (PTV) with margins in the range of 2 to 10 mm. The DVH control points of the PTV and OAR were adapted from the prescriptions of Radiation Therapy Oncology Group protocol P-0126 for an escalated prescribed dose of 82 Gy. This paper presents a new model for the determination of the rectal NTCP ( R NTCP). The method uses a special function, named GVN (from Gy, Volume, NTCP), which describes the R NTCP if 1 cm 3 of the volume of intersection of the PTV and rectum (R int ) is irradiated uniformly by a dose of 1 Gy. The function was 'geometrically' normalized using a prostate-prostate ratio (PPR) of the patients' prostates. A correction of the R NTCP for different prescribed doses, ranging from 70 to 82 Gy, was employed in our model. The argument of the normalized function is the R int , and parameters are the prescribed dose, prostate volume, PTV margin, and PPR. The R NTCPs of another group of patients were calculated by the new method and the resulting difference was <±5% in comparison to the NTCP calculated by the PINNACLE3 software where Kutcher's dose

  3. Cardiac dose-sparing effects of deep-inspiration breath-hold in left breast irradiation. Is IMRT more beneficial than VMAT

    Energy Technology Data Exchange (ETDEWEB)

    Sakka, Mazen; Grabenbauer, Gerhard G. [Coburg Cancer Center, Department of Radiation Oncology, Coburg (Germany); Friedrich-Alexander University of Erlangen-Nuernberg, Faculty of Medicine, Erlangen (Germany); Kunzelmann, Leonie; Metzger, Martin [Coburg Cancer Center, Department of Radiation Oncology, Coburg (Germany)

    2017-10-15

    Given the reduction in death from breast cancer, as well as improvements in overall survival, adjuvant radiotherapy is considered the standard treatment for breast cancer. However, left-sided breast irradiation was associated with an increased rate of fatal cardiovascular events due to incidental irradiation of the heart. Recently, considerable efforts have been made to minimize cardiac toxicity of left-sided breast irradiation by new treatment methods such as deep-inspiration breath-hold (DIBH) and new radiation techniques, particularly intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). The primary aim of this study was to evaluate the effect of DIBH irradiation on cardiac dose compared with free-breathing (FB) irradiation, while the secondary objective was to compare the advantages of IMRT versus VMAT plans in both the FB and the DIBH position for left-sided breast cancer. In all, 25 consecutive left-sided breast cancer patients underwent CT simulation in the FB and DIBH position. Five patients were excluded with no cardiac displacement following DIBH-CT simulation. The other 20 patients were irradiated in the DIBH position using respiratory gating. Four different treatment plans were generated for each patient, an IMRT and a VMAT plan in the DIBH and in the FB position, respectively. The following parameters were used for plan comparison: dose to the heart, left anterior descending coronary artery (mean dose, maximum dose, D25% and D45%), ipsilateral, contralateral lung (mean dose, D20%, D30%) and contralateral breast (mean dose). The percentage in dose reduction for organs at risk achieved by DIBH for both IMRT and VMAT plans was calculated and compared for each patient by each treatment plan. DIBH irradiation significantly reduced mean dose to the heart and left anterior descending coronary artery (LADCA) using both IMRT (heart -20%; p = 0.0002, LADCA -9%; p = 0.001) and VMAT (heart -23%; p = 0.00003, LADCA -16%; p = 0

  4. Dosimetric comparison of treatment techniques IMRT and VMAT for breast cancer

    International Nuclear Information System (INIS)

    Urbina, G. L.; Garcia, B. G.

    2015-10-01

    In this study the dosimetric distribution was compared in the different treatment techniques such as Volumetric Modulated Arc Therapy (VMAT) and Intensity Modulated Radiation Therapy (IMRT) in female patients with breast cancer with stage II-B and III-A, 6 cases (both calculated on VMAT and IMRT) were studied, comparison parameter that are taken into account are: compliance rate, homogeneity index, monitor units, volume dose 50 Gy (D-50%) and 5 Gy (D-5%) volume dose. Comparisons are made in primary tumor volume to optimize treatment in patients with breast cancer, with IMRT using Step, Shoot and VMAT Monte Carlo algorithm, in addition to the organs at risk; the concern to make this work is due to technological advances in radiotherapy and the application of new treatment techniques, that increase the accuracy allowing treatment dose climbing delivering a higher dose to the patient. (Author)

  5. Optimization of equivalent uniform dose using the L-curve criterion

    International Nuclear Information System (INIS)

    Chvetsov, Alexei V; Dempsey, James F; Palta, Jatinder R

    2007-01-01

    Optimization of equivalent uniform dose (EUD) in inverse planning for intensity-modulated radiation therapy (IMRT) prevents variation in radiobiological effect between different radiotherapy treatment plans, which is due to variation in the pattern of dose nonuniformity. For instance, the survival fraction of clonogens would be consistent with the prescription when the optimized EUD is equal to the prescribed EUD. One of the problems in the practical implementation of this approach is that the spatial dose distribution in EUD-based inverse planning would be underdetermined because an unlimited number of nonuniform dose distributions can be computed for a prescribed value of EUD. Together with ill-posedness of the underlying integral equation, this may significantly increase the dose nonuniformity. To optimize EUD and keep dose nonuniformity within reasonable limits, we implemented into an EUD-based objective function an additional criterion which ensures the smoothness of beam intensity functions. This approach is similar to the variational regularization technique which was previously studied for the dose-based least-squares optimization. We show that the variational regularization together with the L-curve criterion for the regularization parameter can significantly reduce dose nonuniformity in EUD-based inverse planning

  6. Optimization of equivalent uniform dose using the L-curve criterion

    Energy Technology Data Exchange (ETDEWEB)

    Chvetsov, Alexei V; Dempsey, James F; Palta, Jatinder R [Department of Radiation Oncology, University of Florida, Gainesville, FL 32610-0385 (United States)

    2007-09-21

    Optimization of equivalent uniform dose (EUD) in inverse planning for intensity-modulated radiation therapy (IMRT) prevents variation in radiobiological effect between different radiotherapy treatment plans, which is due to variation in the pattern of dose nonuniformity. For instance, the survival fraction of clonogens would be consistent with the prescription when the optimized EUD is equal to the prescribed EUD. One of the problems in the practical implementation of this approach is that the spatial dose distribution in EUD-based inverse planning would be underdetermined because an unlimited number of nonuniform dose distributions can be computed for a prescribed value of EUD. Together with ill-posedness of the underlying integral equation, this may significantly increase the dose nonuniformity. To optimize EUD and keep dose nonuniformity within reasonable limits, we implemented into an EUD-based objective function an additional criterion which ensures the smoothness of beam intensity functions. This approach is similar to the variational regularization technique which was previously studied for the dose-based least-squares optimization. We show that the variational regularization together with the L-curve criterion for the regularization parameter can significantly reduce dose nonuniformity in EUD-based inverse planning.

  7. Optimization of equivalent uniform dose using the L-curve criterion.

    Science.gov (United States)

    Chvetsov, Alexei V; Dempsey, James F; Palta, Jatinder R

    2007-10-07

    Optimization of equivalent uniform dose (EUD) in inverse planning for intensity-modulated radiation therapy (IMRT) prevents variation in radiobiological effect between different radiotherapy treatment plans, which is due to variation in the pattern of dose nonuniformity. For instance, the survival fraction of clonogens would be consistent with the prescription when the optimized EUD is equal to the prescribed EUD. One of the problems in the practical implementation of this approach is that the spatial dose distribution in EUD-based inverse planning would be underdetermined because an unlimited number of nonuniform dose distributions can be computed for a prescribed value of EUD. Together with ill-posedness of the underlying integral equation, this may significantly increase the dose nonuniformity. To optimize EUD and keep dose nonuniformity within reasonable limits, we implemented into an EUD-based objective function an additional criterion which ensures the smoothness of beam intensity functions. This approach is similar to the variational regularization technique which was previously studied for the dose-based least-squares optimization. We show that the variational regularization together with the L-curve criterion for the regularization parameter can significantly reduce dose nonuniformity in EUD-based inverse planning.

  8. Plan averaging for multicriteria navigation of sliding window IMRT and VMAT

    International Nuclear Information System (INIS)

    Craft, David; Papp, Dávid; Unkelbach, Jan

    2014-01-01

    Purpose: To describe a method for combining sliding window plans [intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT)] for use in treatment plan averaging, which is needed for Pareto surface navigation based multicriteria treatment planning. Methods: The authors show that by taking an appropriately defined average of leaf trajectories of sliding window plans, the authors obtain a sliding window plan whose fluence map is the exact average of the fluence maps corresponding to the initial plans. In the case of static-beam IMRT, this also implies that the dose distribution of the averaged plan is the exact dosimetric average of the initial plans. In VMAT delivery, the dose distribution of the averaged plan is a close approximation of the dosimetric average of the initial plans. Results: The authors demonstrate the method on three Pareto optimal VMAT plans created for a demanding paraspinal case, where the tumor surrounds the spinal cord. The results show that the leaf averaged plans yield dose distributions that approximate the dosimetric averages of the precomputed Pareto optimal plans well. Conclusions: The proposed method enables the navigation of deliverable Pareto optimal plans directly, i.e., interactive multicriteria exploration of deliverable sliding window IMRT and VMAT plans, eliminating the need for a sequencing step after navigation and hence the dose degradation that is caused by such a sequencing step

  9. Plan averaging for multicriteria navigation of sliding window IMRT and VMAT.

    Science.gov (United States)

    Craft, David; Papp, Dávid; Unkelbach, Jan

    2014-02-01

    To describe a method for combining sliding window plans [intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT)] for use in treatment plan averaging, which is needed for Pareto surface navigation based multicriteria treatment planning. The authors show that by taking an appropriately defined average of leaf trajectories of sliding window plans, the authors obtain a sliding window plan whose fluence map is the exact average of the fluence maps corresponding to the initial plans. In the case of static-beam IMRT, this also implies that the dose distribution of the averaged plan is the exact dosimetric average of the initial plans. In VMAT delivery, the dose distribution of the averaged plan is a close approximation of the dosimetric average of the initial plans. The authors demonstrate the method on three Pareto optimal VMAT plans created for a demanding paraspinal case, where the tumor surrounds the spinal cord. The results show that the leaf averaged plans yield dose distributions that approximate the dosimetric averages of the precomputed Pareto optimal plans well. The proposed method enables the navigation of deliverable Pareto optimal plans directly, i.e., interactive multicriteria exploration of deliverable sliding window IMRT and VMAT plans, eliminating the need for a sequencing step after navigation and hence the dose degradation that is caused by such a sequencing step.

  10. Plan averaging for multicriteria navigation of sliding window IMRT and VMAT

    Energy Technology Data Exchange (ETDEWEB)

    Craft, David, E-mail: dcraft@partners.org; Papp, Dávid; Unkelbach, Jan [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States)

    2014-02-15

    Purpose: To describe a method for combining sliding window plans [intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT)] for use in treatment plan averaging, which is needed for Pareto surface navigation based multicriteria treatment planning. Methods: The authors show that by taking an appropriately defined average of leaf trajectories of sliding window plans, the authors obtain a sliding window plan whose fluence map is the exact average of the fluence maps corresponding to the initial plans. In the case of static-beam IMRT, this also implies that the dose distribution of the averaged plan is the exact dosimetric average of the initial plans. In VMAT delivery, the dose distribution of the averaged plan is a close approximation of the dosimetric average of the initial plans. Results: The authors demonstrate the method on three Pareto optimal VMAT plans created for a demanding paraspinal case, where the tumor surrounds the spinal cord. The results show that the leaf averaged plans yield dose distributions that approximate the dosimetric averages of the precomputed Pareto optimal plans well. Conclusions: The proposed method enables the navigation of deliverable Pareto optimal plans directly, i.e., interactive multicriteria exploration of deliverable sliding window IMRT and VMAT plans, eliminating the need for a sequencing step after navigation and hence the dose degradation that is caused by such a sequencing step.

  11. Dose evaluation of TPS according to treatment sites in IMRT

    International Nuclear Information System (INIS)

    Kim, Jin Man; Kim, Jong Sik; Hong, Chae Seon; Park, Ju Young; Park, Su Yeon; Ju, Sang Gyu

    2013-01-01

    This study executed therapy plans on prostate cancer (homogeneous density area) and lung cancer (non-homogeneous density area) using radiation treatment planning systems such as Pinnacle 3 (version 9.2, Philips Medical Systems, USA) and Eclipse (version 10.0, Varian Medical Systems, USA) in order to quantify the difference between dose calculation according to density in IMRT. The subjects were prostate cancer patients (n=5) and lung cancer patients (n=5) who had therapies in our hospital. Identical constraints and optimization process according to the Protocol were administered on the subjects. For the therapy plan of prostate cancer patients, 10 MV and 7Beam were used and 2.5 Gy was prescribed in 28 fx to make 70 Gy in total. For lung cancer patients, 6 MV and 6Beam were used and 2 Gy was prescribed in 33 fx to make 66 Gy in total. Through two therapy planning systems, maximum dose, average dose, and minimum dose of OAR (Organ at Risk) of CTV, PTV and around tumor were investigated. In prostate cancer, both therapy planning systems showed within 2% change of dose of CTV and PTV and normal organs (Bladder, Both femur and Rectum out) near the tumor satisfied the dose constraints. In lung cancer, CTV and PTV showed less than 2% changes in dose and normal organs (Esophagus, Spinal cord and Both lungs) satisfied dose restrictions. However, the minimum dose of Eclipse therapy plan was 1.9% higher in CTV and 3.5% higher in PTV, and in case of both lungs there was 3.0% difference at V5 Gy. Each TPS according to the density satisfied dose limits of our hospital proving the clinical accuracy. It is considered more accurate and precise therapy plan can be made if studies on treatment planning for diverse parts and the application of such TPS are made

  12. Is ad-hoc plan adaptation based on 2-Step IMRT feasible?

    International Nuclear Information System (INIS)

    Bratengeier, Klaus; Polat, Buelent; Gainey, Mark; Grewenig, Patricia; Meyer, Juergen; Flentje, Michael

    2009-01-01

    Background: The ability of a geometry-based method to expeditiously adapt a '2-Step' step and shoot IMRT plan was explored. Both changes of the geometry of target and organ at risk have to be balanced. A retrospective prostate planning study was performed to investigate the relative benefits of beam segment adaptation to the changes in target and organ at risk coverage. Methods: Four patients with six planning cases with extraordinarily large deformations of rectum and prostate were chosen for the study. A 9-field IMRT plan (A) using 2-Step IMRT segments was planned on an initial CT study. The plan had to fulfil all the requirements of a conventional high-quality step and shoot IMRT plan. To adapt to changes of the anatomy in a further CT data set, three approaches were considered: the original plan with optimized isocentre position (B), a newly optimized plan (C) and the original plan, adapted using the 2-Step IMRT optimization rules (D). DVH parameters were utilized for quantification of plan quality: D 99 for the CTV and the central planning target volume (PTV), D 95 for an outer PTV, V 95 , V 80 and V 50 for rectum and bladder. Results: The adapted plan (D) achieved almost the same target coverage as the newly optimized plan (C). Target coverage for plan B was poor and for the organs at risk, the rectum V 80 was slightly increased. The volume with more than 95% of the target dose (V 95 ) was 1.5 ± 1.5 cm 3 for the newly optimized plan (C), compared to 2.2 ± 1.3 cm 3 for the original plan (A) and 7.2 ± 4.8 cm 3 (B) on the first and the second CT, respectively. The adapted plan resulted in 4.3 ± 2.1 cm 3 (D), an intermediate dose load to the rectum. All other parameters were comparable for the newly optimized and the adapted plan. Conclusions: The first results for adaptation of interfractional changes using the 2-Step IMRT algorithm are encouraging. The plans were superior to plans with optimized isocentre position and only marginally inferior to a newly

  13. IMRT dose fractionation for head and neck cancer: Variation in current approaches will make standardisation difficult

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Kean F. (Academic Dept. of Radiation Oncology, Univ. of Manchester, Manchester (United Kingdom)); Fowler, Jack F. (Dept. of Human Oncology and Medical Physics, Univ. of Wisconsin, Wisconsin (United States)); Sykes, Andrew J.; Yap, Beng K.; Lee, Lip W.; Slevin, Nick J. (Dept. of Clinical Oncology, Christie Hospital NHS Foundation Trust, Manchester (United Kingdom))

    2009-04-15

    Introduction. Altered fractionation has demonstrated clinical benefits compared to the conventional 2 Gy/day standard of 70 Gy. When using synchronous chemotherapy, there is uncertainty about optimum fractionation. IMRT with its potential for Simultaneous Integrated Boost (SIB) adds further to this uncertainty. This survey will examine international practice of IMRT fractionation and suggest possible reasons for diversity in approach. Material and methods. Fourteen international cancer centres were surveyed for IMRT dose/fractionation practised in each centre. Results. Twelve different types of dose fractionation were reported. Conventional 70-72 Gy (daily 2 Gy/fraction) was used in 3/14 centres with concurrent chemotherapy while 11/14 centres used altered fractionation. Two centres used >1 schedule. Reported schedules and number of centres included 6 fractions/week DAHANCA regime (3), modest hypofractionation (=2.2 Gy/fraction) (3), dose-escalated hypofractionation (=2.3 Gy/fraction) (4), hyperfractionation (1), continuous acceleration (1) and concomitant boost (1). Reasons for dose fractionation variability include (i) dose escalation; (ii) total irradiated volume; (iii) number of target volumes; (iv) synchronous systemic treatment; (v) shorter overall treatment time; (vi) resources availability; (vii) longer time on treatment couch; (viii) variable GTV margins; (ix) confidence in treatment setup; (x) late tissue toxicity and (xi) use of lower neck anterior fields. Conclusions. This variability in IMRT fractionation makes any meaningful comparison of treatment results difficult. Some standardization is needed particularly for design of multi-centre randomized clinical trials.

  14. A Phase I Dose-Escalation Study (ISIDE-BT-1) of Accelerated IMRT With Temozolomide in Patients With Glioblastoma

    International Nuclear Information System (INIS)

    Morganti, Alessio G.; Balducci, Mario; Salvati, Maurizio; Esposito, Vincenzo; Romanelli, Pantaleo; Ferro, Marica; Calista, Franco; Digesu, Cinzia; Macchia, Gabriella; Ianiri, Massimo; Deodato, Francesco; Cilla, Savino; Piermattei, Angelo M.P.; Valentini, Vincenzo; Cellini, Numa; Cantore, Gian Paolo

    2010-01-01

    Purpose: To determine the maximum tolerated dose (MTD) of fractionated intensity-modulated radiotherapy (IMRT) with temozolomide (TMZ) in patients with glioblastoma. Methods and Materials: A Phase I clinical trial was performed. Eligible patients had surgically resected or biopsy-proven glioblastoma. Patients started TMZ (75 mg/day) during IMRT and continued for 1 year (150-200 mg/day, Days 1-5 every 28 days) or until disease progression. Clinical target volume 1 (CTV1) was the tumor bed ± enhancing lesion with a 10-mm margin; CTV2 was the area of perifocal edema with a 20-mm margin. Planning target volume 1 (PTV1) and PTV2 were defined as the corresponding CTV plus a 5-mm margin. IMRT was delivered in 25 fractions over 5 weeks. Only the dose for PTV1 was escalated (planned dose escalation: 60 Gy, 62.5 Gy, 65 Gy) while maintaining the dose for PTV2 (45 Gy, 1.8 Gy/fraction). Dose limiting toxicities (DLT) were defined as any treatment-related nonhematological adverse effects rated as Grade ≥3 or any hematological toxicity rated as ≥4 by Radiation Therapy Oncology Group (RTOG) criteria. Results: Nineteen consecutive glioblastoma were treated with step-and-shoot IMRT, planned with the inverse approach (dose to the PTV1: 7 patients, 60 Gy; 6 patients, 62.5 Gy; 6 patients, 65 Gy). Five coplanar beams were used to cover at least 95% of the target volume with the 95% isodose line. Median follow-up time was 23 months (range, 8-40 months). No patient experienced DLT. Grade 1-2 treatment-related neurologic and skin toxicity were common (11 and 19 patients, respectively). No Grade >2 late neurologic toxicities were noted. Conclusion: Accelerated IMRT to a dose of 65 Gy in 25 fractions is well tolerated with TMZ at a daily dose of 75 mg.

  15. Derivative-free generation and interpolation of convex Pareto optimal IMRT plans

    Science.gov (United States)

    Hoffmann, Aswin L.; Siem, Alex Y. D.; den Hertog, Dick; Kaanders, Johannes H. A. M.; Huizenga, Henk

    2006-12-01

    In inverse treatment planning for intensity-modulated radiation therapy (IMRT), beamlet intensity levels in fluence maps of high-energy photon beams are optimized. Treatment plan evaluation criteria are used as objective functions to steer the optimization process. Fluence map optimization can be considered a multi-objective optimization problem, for which a set of Pareto optimal solutions exists: the Pareto efficient frontier (PEF). In this paper, a constrained optimization method is pursued to iteratively estimate the PEF up to some predefined error. We use the property that the PEF is convex for a convex optimization problem to construct piecewise-linear upper and lower bounds to approximate the PEF from a small initial set of Pareto optimal plans. A derivative-free Sandwich algorithm is presented in which these bounds are used with three strategies to determine the location of the next Pareto optimal solution such that the uncertainty in the estimated PEF is maximally reduced. We show that an intelligent initial solution for a new Pareto optimal plan can be obtained by interpolation of fluence maps from neighbouring Pareto optimal plans. The method has been applied to a simplified clinical test case using two convex objective functions to map the trade-off between tumour dose heterogeneity and critical organ sparing. All three strategies produce representative estimates of the PEF. The new algorithm is particularly suitable for dynamic generation of Pareto optimal plans in interactive treatment planning.

  16. Derivative-free generation and interpolation of convex Pareto optimal IMRT plans

    International Nuclear Information System (INIS)

    Hoffmann, Aswin L; Siem, Alex Y D; Hertog, Dick den; Kaanders, Johannes H A M; Huizenga, Henk

    2006-01-01

    In inverse treatment planning for intensity-modulated radiation therapy (IMRT), beamlet intensity levels in fluence maps of high-energy photon beams are optimized. Treatment plan evaluation criteria are used as objective functions to steer the optimization process. Fluence map optimization can be considered a multi-objective optimization problem, for which a set of Pareto optimal solutions exists: the Pareto efficient frontier (PEF). In this paper, a constrained optimization method is pursued to iteratively estimate the PEF up to some predefined error. We use the property that the PEF is convex for a convex optimization problem to construct piecewise-linear upper and lower bounds to approximate the PEF from a small initial set of Pareto optimal plans. A derivative-free Sandwich algorithm is presented in which these bounds are used with three strategies to determine the location of the next Pareto optimal solution such that the uncertainty in the estimated PEF is maximally reduced. We show that an intelligent initial solution for a new Pareto optimal plan can be obtained by interpolation of fluence maps from neighbouring Pareto optimal plans. The method has been applied to a simplified clinical test case using two convex objective functions to map the trade-off between tumour dose heterogeneity and critical organ sparing. All three strategies produce representative estimates of the PEF. The new algorithm is particularly suitable for dynamic generation of Pareto optimal plans in interactive treatment planning

  17. Three-dimensional dose accumulation in pseudo-split-field IMRT and brachytherapy for locally advanced cervical cancer.

    Science.gov (United States)

    Sun, Baozhou; Yang, Deshan; Esthappan, Jackie; Garcia-Ramirez, Jose; Price, Samantha; Mutic, Sasa; Schwarz, Julie K; Grigsby, Perry W; Tanderup, Kari

    2015-01-01

    Dose accumulation of split-field external beam radiotherapy (EBRT) and brachytherapy (BT) is challenging because of significant EBRT and BT dose gradients in the central pelvic region. We developed a method to determine biologically effective dose parameters for combined split-field intensity-modulated radiation therapy (IMRT) and image-guided BT in locally advanced cervical cancer. Thirty-three patients treated with split-field-IMRT to 45.0-51.2 Gy in 1.6-1.8 Gy per fraction to the elective pelvic lymph nodes and to 20 Gy to the central pelvis region were included in this study. Patients received six weekly fractions of high-dose rate BT to 6.5-7.3 Gy per fraction. A dose tracker software was developed to compute the equivalent dose in 2-Gy fractions (EQD2) to gross tumor volume (GTV), organs-at-risk and point A. Total dose-volume histogram parameters were computed on the 3D combined EQD2 dose based on rigid image registration. The dose accumulation uncertainty introduced by organ deformations between IMRT and BT was evaluated. According to International Commission on Radiation Unit and Measurement and GEC European Society for Therapeutic Radiology and Oncology recommendations, D98, D90, D50, and D2cm3 EQD2 dose-volume histogram parameters were computed. GTV D98 was 84.0 ± 26.5 Gy and D2cc was 99.6 ± 13.9 Gy, 67.4 ± 12.2 Gy, 75.0 ± 10.1 Gy, for bladder, rectum, and sigmoid, respectively. The uncertainties induced by organ deformation were estimated to be -1 ± 4 Gy, -3 ± 5 Gy, 2 ± 3 Gy, and -3 ± 5 Gy for bladder, rectum, sigmoid, and GTV, respectively. It is feasible to perform 3D EQD2 dose accumulation to assess high and intermediate dose regions for combined split-field IMRT and BT. Copyright © 2015 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

  18. On the degeneracy of the IMRT optimization problem

    International Nuclear Information System (INIS)

    Alber, M.; Meedt, G.; Nuesslin, F.; Reemtsen, R.

    2002-01-01

    One approach to the computation of photon IMRT treatment plans is the formulation of an optimization problem with an objective function that derives from an objective density. An investigation of the second-order properties of such an objective function in a neighborhood of the minimizer opens an intuitive access to many traits of this approach. A general finding is that only a small subset of the parameter space has nonzero curvature, while the objective function is entirely flat in a neighborhood of the minimizer in most directions. The dimension of the subspace of vanishing curvature serves as a measure for the degeneracy of the solution. This finding is important both for algorithm design and evaluation of the mathematical model of clinical intuition, expressed by the objective function. The structure of the subspace of great curvature is found to be imposed on the problem by conflicts between objectives of target and critical structures. These conflicts and their corresponding modes of resolution form a common trait between all reasonable treatment plans of a given case. The high degree of degeneracy makes the use of a conjugate gradient optimization algorithm particularly favorable since the number of iterations to convergence is equivalent to the number of different eigenvalues of the curvature tensor and is hence independent from the number of optimization parameters. A high level of degeneracy of the fluence profiles implies that it should be possible to stipulate further delivery-related conditions without causing severe deterioration of the dose distribution

  19. Total dural irradiation: RapidArc versus static-field IMRT: A case study

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, Paul J., E-mail: paulj.kelly@hse.ie [Department of Radiation Oncology, Dana Farber/Brigham and Women' s Cancer Center, Harvard Medical School, Boston, MA (United States); Mannarino, Edward; Lewis, John Henry; Baldini, Elizabeth H.; Hacker, Fred L. [Department of Radiation Oncology, Dana Farber/Brigham and Women' s Cancer Center, Harvard Medical School, Boston, MA (United States)

    2012-07-01

    The purpose of this study was to compare conventional fixed-gantry angle intensity-modulated radiation therapy (IMRT) with RapidArc for total dural irradiation. We also hypothesize that target volume-individualized collimator angles may produce substantial normal tissue sparing when planning with RapidArc. Five-, 7-, and 9-field fixed-gantry angle sliding-window IMRT plans were generated for comparison with RapidArc plans. Optimization and normal tissue constraints were constant for all plans. All plans were normalized so that 95% of the planning target volume (PTV) received at least 100% of the dose. RapidArc was delivered using 350 Degree-Sign clockwise and counterclockwise arcs. Conventional collimator angles of 45 Degree-Sign and 315 Degree-Sign were compared with 90 Degree-Sign on both arcs. Dose prescription was 59.4 Gy in 33 fractions. PTV metrics used for comparison were coverage, V{sub 107}%, D1%, conformality index (CI{sub 95}%), and heterogeneity index (D{sub 5}%-D{sub 95}%). Brain dose, the main challenge of this case, was compared using D{sub 1}%, Dmean, and V{sub 5} Gy. Dose to optic chiasm, optic nerves, globes, and lenses was also compared. The use of unconventional collimator angles (90 Degree-Sign on both arcs) substantially reduced dose to normal brain. All plans achieved acceptable target coverage. Homogeneity was similar for RapidArc and 9-field IMRT plans. However, heterogeneity increased with decreasing number of IMRT fields, resulting in unacceptable hotspots within the brain. Conformality was marginally better with RapidArc relative to IMRT. Low dose to brain, as indicated by V5Gy, was comparable in all plans. Doses to organs at risk (OARs) showed no clinically meaningful differences. The number of monitor units was lower and delivery time was reduced with RapidArc. The case-individualized RapidArc plan compared favorably with the 9-field conventional IMRT plan. In view of lower monitor unit requirements and shorter delivery time, Rapid

  20. Three-dimensional dose accumulation in pseudo-split-field IMRT and brachytherapy for locally advanced cervical cancer

    DEFF Research Database (Denmark)

    Sun, Baozhou; Yang, Deshan; Esthappan, Jackie

    2015-01-01

    -field intensity-modulated radiation therapy (IMRT) and image-guided BT in locally advanced cervical cancer. METHODS AND MATERIALS: Thirty-three patients treated with split-field-IMRT to 45.0-51.2 Gy in 1.6-1.8 Gy per fraction to the elective pelvic lymph nodes and to 20 Gy to the central pelvis region were...... included in this study. Patients received six weekly fractions of high-dose rate BT to 6.5-7.3 Gy per fraction. A dose tracker software was developed to compute the equivalent dose in 2-Gy fractions (EQD2) to gross tumor volume (GTV), organs-at-risk and point A. Total dose-volume histogram parameters were...

  1. Comparison of testicular dose delivered by intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in patients with prostate cancer

    International Nuclear Information System (INIS)

    Martin, Jeffrey M.; Handorf, Elizabeth A.; Price, Robert A.; Cherian, George; Buyyounouski, Mark K.; Chen, David Y.; Kutikov, Alexander; Johnson, Matthew E.; Ma, Chung-Ming Charlie; Horwitz, Eric M.

    2015-01-01

    A small decrease in testosterone level has been documented after prostate irradiation, possibly owing to the incidental dose to the testes. Testicular doses from prostate external beam radiation plans with either intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT) were calculated to investigate any difference. Testicles were contoured for 16 patients being treated for localized prostate cancer. For each patient, 2 plans were created: 1 with IMRT and 1 with VMAT. No specific attempt was made to reduce testicular dose. Minimum, maximum, and mean doses to the testicles were recorded for each plan. Of the 16 patients, 4 received a total dose of 7800 cGy to the prostate alone, 7 received 8000 cGy to the prostate alone, and 5 received 8000 cGy to the prostate and pelvic lymph nodes. The mean (range) of testicular dose with an IMRT plan was 54.7 cGy (21.1 to 91.9) and 59.0 cGy (25.1 to 93.4) with a VMAT plan. In 12 cases, the mean VMAT dose was higher than the mean IMRT dose, with a mean difference of 4.3 cGy (p = 0.019). There was a small but statistically significant increase in mean testicular dose delivered by VMAT compared with IMRT. Despite this, it unlikely that there is a clinically meaningful difference in testicular doses from either modality

  2. Comparison of testicular dose delivered by intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in patients with prostate cancer

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Jeffrey M. [Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA (United States); Handorf, Elizabeth A. [Department of Biostatistics, Fox Chase Cancer Center, Philadelphia, PA (United States); Price, Robert A.; Cherian, George [Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA (United States); Buyyounouski, Mark K. [Department of Radiation Oncology, Stanford University, Stanford, CA (United States); Chen, David Y.; Kutikov, Alexander [Department of Urologic Oncology, Fox Chase Cancer Center, Philadelphia, PA (United States); Johnson, Matthew E.; Ma, Chung-Ming Charlie [Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA (United States); Horwitz, Eric M., E-mail: eric.horwitz@fccc.edu [Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA (United States)

    2015-10-01

    A small decrease in testosterone level has been documented after prostate irradiation, possibly owing to the incidental dose to the testes. Testicular doses from prostate external beam radiation plans with either intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT) were calculated to investigate any difference. Testicles were contoured for 16 patients being treated for localized prostate cancer. For each patient, 2 plans were created: 1 with IMRT and 1 with VMAT. No specific attempt was made to reduce testicular dose. Minimum, maximum, and mean doses to the testicles were recorded for each plan. Of the 16 patients, 4 received a total dose of 7800 cGy to the prostate alone, 7 received 8000 cGy to the prostate alone, and 5 received 8000 cGy to the prostate and pelvic lymph nodes. The mean (range) of testicular dose with an IMRT plan was 54.7 cGy (21.1 to 91.9) and 59.0 cGy (25.1 to 93.4) with a VMAT plan. In 12 cases, the mean VMAT dose was higher than the mean IMRT dose, with a mean difference of 4.3 cGy (p = 0.019). There was a small but statistically significant increase in mean testicular dose delivered by VMAT compared with IMRT. Despite this, it unlikely that there is a clinically meaningful difference in testicular doses from either modality.

  3. Application of biological dose concept in dose optimization for conformal radiotherapy of prostate carcinoma

    International Nuclear Information System (INIS)

    Li Yunhai; Liao Yuan; Zhou Lijun; Pan Ziqiang; Feng Yan

    2003-01-01

    Objective: On basis of physical dose optimization, LQ model was used to investigate the difference between the curves of biological effective dose and physical isodose. The influence of applying the biological dose concept on three dimensional conformal radiotherapy of prostate carcinoma was discussed. Methods: Four treatment plannings were designed for physical dose optimization: three fields, four-box fields, five fields and six fields. Target dose uniformity and protection of the critical tissue-rectum were used as the principal standard for designing the treatment planning. Biological effective dose (BED) was calculated by LQ model. The difference between the BED curve drawn in the central layer and the physical isodose curve was studied. The difference between the adjusted physical dose (APD) and the physical dose was also studied. Results: Five field planning was the best in target dose uniformity and protection of the critical tissue-rectum. The physical dose was uniform in the target, but the biological effective doses revealed great discrepancy in the biological model. Adjusted physical dose distribution also displayed larger discrepancy than the physical dose unadjusted. Conclusions: Intensified Modulated Radiotherapy (IMRT) technique with inversion planning using biological dose concept may be much more advantageous to reach a high tumor control probability and low normal tissue complication probability

  4. Comparison of 3D anatomical dose verification and 2D phantom dose verification of IMRT/VMAT treatments for nasopharyngeal carcinoma

    International Nuclear Information System (INIS)

    Lin, Hailei; Huang, Shaomin; Deng, Xiaowu; Zhu, Jinhan; Chen, Lixin

    2014-01-01

    The two-dimensional phantom dose verification (2D-PDV) using hybrid plan and planar dose measurement has been widely used for IMRT treatment QA. Due to the lack of information about the correlations between the verification results and the anatomical structure of patients, it is inadequate in clinical evaluation. A three-dimensional anatomical dose verification (3D-ADV) method was used in this study to evaluate the IMRT/VMAT treatment delivery for nasopharyngeal carcinoma and comparison with 2D-PDV was analyzed. Twenty nasopharyngeal carcinoma (NPC) patients treated with IMRT/VMAT were recruited in the study. A 2D ion-chamber array was used for the 2D-PDV in both single-gantry-angle composite (SGAC) and multi-gantry-angle composite (MGAC) verifications. Differences in the gamma pass rate between the 2 verification methods were assessed. Based on measurement of irradiation dose fluence, the 3D dose distribution was reconstructed for 3D-ADV in the above cases. The reconstructed dose homogeneity index (HI), conformity index (CI) of the planning target volume (PTV) were calculated. Gamma pass rate and deviations in the dose-volume histogram (DVH) of each PTV and organ at risk (OAR) were analyzed. In 2D-PDV, the gamma pass rate (3%, 3 mm) of SGAC (99.55% ± 0.83%) was significantly higher than that of MGAC (92.41% ± 7.19%). In 3D-ADV, the gamma pass rates (3%, 3 mm) were 99.75% ± 0.21% in global, 83.82% ± 16.98% to 93.71% ± 6.22% in the PTVs and 45.12% ± 32.78% to 98.08% ± 2.29% in the OARs. The maximum HI increment in PTVnx was 19.34%, while the maximum CI decrement in PTV1 and PTV2 were -32.45% and -6.93%, respectively. Deviations in dose volume of PTVs were all within ±5%. D2% of the brainstem, spinal cord, left/right optic nerves, and the mean doses to the left/right parotid glands maximally increased by 3.5%, 6.03%, 31.13%/26.90% and 4.78%/4.54%, respectively. The 2D-PDV and global gamma pass rate might be insufficient to provide an accurate assessment for

  5. SU-F-T-522: Dosimetric Study of Junction Dose in Double Isocenter Flatten and Flatten Filter Free IMRT and VMAT Plan Delivery

    Energy Technology Data Exchange (ETDEWEB)

    Samuvel, K; Yadav, G; Bhushan, M; Tamilarasu, S; Kumar, L; Suhail, M [Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, Delhi (India)

    2016-06-15

    Purpose: To quantify the dosimetric accuracy of junction dose in double isocenter flattened and flatten filter free(FFF) intensity modulated radiation therapy(IMRT) and volumetric modulated arc therapy(VMAT) plan delivery using pelvis phantom. Methods: Five large field pelvis patients were selected for this study. Double isocenter IMRT and VMAT treatment plans were generated in Eclipse Treatment planning System (V.11.0) using 6MV FB and FFF beams. For all the plans same distance 17.0cm was kept between one isocenter to another isocenter. IMRT Plans were made with 7 coplanar fields and VMAT plans were made with full double arcs. Dose calculation was performed using AAA algorithms with dose grid size of 0.25 cm. Verification plans were calculated on Scanditronix Wellhofer pelvis slab phantom. Measurement point was selected and calculated, where two isocenter plan fields are overlapping, this measurement point was kept at distance 8.5cm from both isocenter. The plans were delivered using Varian TrueBeamTM machine on pelvis slab phantom. Point dose measurements was carried out using CC13 ion chamber volume of 0.13cm3. Results: The measured junction point dose are compared with TPS calculated dose. The mean difference observed was 4.5%, 6.0%, 4.0% and 7.0% for IMRT-FB,IMRT-FFF, VMAT-FB and VMAT-FFF respectively. The measured dose results shows closer agreement with calculated dose in Flatten beam planning in both IMRT and VMAT, whereas in FFF beam plan dose difference are more compared with flatten beam plan. Conclusion: Dosimetry accuracy of Large Field junction dose difference was found less in Flatten beam compared with FFF beam plan delivery. Even though more dosimetric studies are required to analyse junction dose for FFF beam planning using multiple point dose measurements and fluence map verification in field junction area.

  6. SU-E-J-239: IMRT Planning of Prostate Cancer for a MRI-Linac Based On MRI Only

    Energy Technology Data Exchange (ETDEWEB)

    Chen, X; Prior, P; Paulson, E; Lawton, C; Li, X [Medical College of Wisconsin, Milwaukee, WI (United States)

    2014-06-01

    Purpose: : To investigate dosimetric differences between MRI- and CT-based IMRT planning for prostate cancer, the impact of a magnetic field in a MRI-Linac, and to explore the feasibility of IMRT planning based on MRI alone. Methods: IMRT plans were generated based on CT and MRI images acquired on two representative prostate-cancer patients using clinical dose volume constraints. A research planning system (Monaco, Elekta), which employs a Monte Carlo dose engine and includes a perpendicular magnetic field of 1.5T from an MRI-Linac, was used. Bulk electron density assignments based on organ-specific values from ICRU 46 were used to convert MRI (T2) to pseudo CT. With the same beam configuration as in the original CT plan, 5 additional plans were generated based on CT or MRI, with or without optimization (i.e., just recalculation) and with or without the magnetic field. The plan quality in terms of commonly used dose volume (DV) parameters for all plans was compared. The statistical uncertainty on dose was < 1%. Results: For plans with the same contour set but without re-optimization, the DV parameters were different from those for the original CT plan, mostly less than 5% with a few exceptions. These differences were reduced to mostly less than 3% when the plans were re-optimized. For plans with contours from MRI, the differences in the DV parameters varied depending on the difference in the contours as compared to CT. For the optimized plans with contours from MR, the differences for PTV were less than 3%. Conclusion: The prostate IMRT plans based on MRI-only for a MR-Linac were practically similar as compared to the CT plan under the same beam and optimization configuration if the difference on the structure delineation is excluded, indicating the feasibility of using MRI-only for prostate IMRT.

  7. 3-D dose verification for IMRT using optical CT based polymer gel dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Wuu, C [Department of Radiation Oncology, Columbia University, New York, New York (United States); Xu, Y [Department of Radiation Oncology, Columbia University, New York, New York (United States); Maryanski, M J [Department of Radiation Oncology, Columbia University, New York, New York (United States); MGS Research Inc., Madison, Connecticut (United States)

    2004-01-01

    In this study BANG[reg] polymer gels in conjunction with OCTOPUS{sup TM} optical CT scanner (MGS Research Inc., Madison, CT) was employed to measure the relative 3D dose distribution of an IMRT treatment. Measured relative dose distributions from the gel measurement were compared with those from treatment planning system calculations and EDR2 film measurements with regard to planar dose distributions in axial, coronal, and sagittal orientations.

  8. 3-D dose verification for IMRT using optical CT based polymer gel dosimetry

    International Nuclear Information System (INIS)

    Wuu, C; Xu, Y; Maryanski, M J

    2004-01-01

    In this study BANG[reg] polymer gels in conjunction with OCTOPUS TM optical CT scanner (MGS Research Inc., Madison, CT) was employed to measure the relative 3D dose distribution of an IMRT treatment. Measured relative dose distributions from the gel measurement were compared with those from treatment planning system calculations and EDR2 film measurements with regard to planar dose distributions in axial, coronal, and sagittal orientations

  9. Evaluation of dose coverage to target volume and normal tissue sparing in the adjuvant radiotherapy of gastric cancers: 3D-CRT compared with dynamic IMRT.

    Science.gov (United States)

    Murthy, Kk; Shukeili, Ka; Kumar, Ss; Davis, Ca; Chandran, Rr; Namrata, S

    2010-01-01

    To assess the potential advantage of intensity-modulated radiotherapy (IMRT) over 3D-conformal radiotherapy (3D-CRT) planning in postoperative adjuvant radiotherapy for patients with gastric carcinoma. In a retrospective study, for plan comparison, dose distribution was recalculated in 15 patients treated with 3D-CRT on the contoured structures of same CT images using an IMRT technique. 3D-conformal plans with three fields and four-fields were compared with seven-field dynamic IMRT plans. The different plans were compared by analyzing the dose coverage of planning target volume using TV(95), D(mean), uniformity index, conformity index and homogeneity index parameters. To assess critical organ sparing, D(mean), D(max), dose to one-third and two-third volumes of the OARs and percentage of volumes receiving more than their tolerance doses were compared. The average dose coverage values of PTV with 3F-CRT and 4F-CRT plans were comparable, where as IMRT plans achieved better target coverage(p3D-CRT plans. The doses to the liver and bowel reduced significantly (p3D-CRT plans. For all OARs the percentage of volumes receiving more than their tolerance doses were reduced with the IMRT plans. This study showed that a better target coverage and significant dose reduction to OARs could be achieved with the IMRT plans. The IMRT can be preferred with caution for organ motion. The authors are currently studying organ motion in the upper abdomen to use IMRT for patient treatment.

  10. Interior point algorithms: guaranteed optimality for fluence map optimization in IMRT

    Energy Technology Data Exchange (ETDEWEB)

    Aleman, Dionne M [Department of Mechanical and Industrial Engineering, University of Toronto, 5 King' s College Road, Toronto, ON M5S 3G8 (Canada); Glaser, Daniel [Division of Optimization and Systems Theory, Department of Mathematics, Royal Institute of Technology, Stockholm (Sweden); Romeijn, H Edwin [Department of Industrial and Operations Engineering, University of Michigan, Ann Arbor, MI 48109-2117 (United States); Dempsey, James F, E-mail: aleman@mie.utoronto.c, E-mail: romeijn@umich.ed, E-mail: jfdempsey@viewray.co [ViewRay, Inc. 2 Thermo Fisher Way, Village of Oakwood, OH 44146 (United States)

    2010-09-21

    One of the most widely studied problems of the intensity-modulated radiation therapy (IMRT) treatment planning problem is the fluence map optimization (FMO) problem, the problem of determining the amount of radiation intensity, or fluence, of each beamlet in each beam. For a given set of beams, the fluences of the beamlets can drastically affect the quality of the treatment plan, and thus it is critical to obtain good fluence maps for radiation delivery. Although several approaches have been shown to yield good solutions to the FMO problem, these solutions are not guaranteed to be optimal. This shortcoming can be attributed to either optimization model complexity or properties of the algorithms used to solve the optimization model. We present a convex FMO formulation and an interior point algorithm that yields an optimal treatment plan in seconds, making it a viable option for clinical applications.

  11. Interior point algorithms: guaranteed optimality for fluence map optimization in IMRT

    International Nuclear Information System (INIS)

    Aleman, Dionne M; Glaser, Daniel; Romeijn, H Edwin; Dempsey, James F

    2010-01-01

    One of the most widely studied problems of the intensity-modulated radiation therapy (IMRT) treatment planning problem is the fluence map optimization (FMO) problem, the problem of determining the amount of radiation intensity, or fluence, of each beamlet in each beam. For a given set of beams, the fluences of the beamlets can drastically affect the quality of the treatment plan, and thus it is critical to obtain good fluence maps for radiation delivery. Although several approaches have been shown to yield good solutions to the FMO problem, these solutions are not guaranteed to be optimal. This shortcoming can be attributed to either optimization model complexity or properties of the algorithms used to solve the optimization model. We present a convex FMO formulation and an interior point algorithm that yields an optimal treatment plan in seconds, making it a viable option for clinical applications.

  12. Tl and OSL dose response of LiF:Mg, Ti and Al{sub 2}O{sub 3}:C dosimeters using a PMMA phantom for IMRT technique quality assurance

    Energy Technology Data Exchange (ETDEWEB)

    Matsushima, L. C.; Veneziani, G. R.; Campos, L. L. [Instituto de Pesquisas Energeticas e Nucleares, Gerencia de Metrologia das Radiacoes / CNEN, Av. Lineu Prestes 2242, Cidade Universitaria, 05508-000 Sao Paulo (Brazil); Sakuraba, R. K.; Cruz, J. C., E-mail: lmatsushima@usp.br [Sociedade Beneficente Israelita Brasileira - Hospital Albert Einstein, Av. Albert Einstein 627/701, Morumbi, 05652-000 Sao Paulo (Brazil)

    2014-08-15

    The principle of IMRT is to treat a patient from a number of different directions (or continuous arcs) with beams of nonuniform fluences, which have been optimized to deliver a high dose to the target volume and an acceptably low dose to the surrounding normal structures (Khan, 2010). This study intends to provide information to the physicist regarding the application of different dosimeters type, phantoms and analysis technique for Intensity Modulated Radiation Therapy (IMRT) dose distributions evaluation. The measures were performed using dosimeters of LiF:Mg,Ti and Al{sub 2}O{sub 3}:C evaluated by techniques of thermoluminescent (Tl) and Optically Stimulated Luminescence (OSL). A polymethylmethacrylate (PMMA) phantom with five cavities, two principal target volumes considered like tumours to be treated and other three cavities to measure the scattered radiation dose was developed to carried out the measures. (Author)

  13. Independent dose calculation in IMRT for the Tps Iplan using the Clarkson modified integral; Calculo independiente de dosis en IMRT para el TPS Iplan usando la integral modificada de Clarkson

    Energy Technology Data Exchange (ETDEWEB)

    Adrada, A.; Tello, Z.; Garrigo, E.; Venencia, D., E-mail: jorge.alberto.adrada@gmail.com [Instituto Privado de Radioterapia, Obispo Oro 423, X5000BFI Cordoba (Argentina)

    2014-08-15

    Intensity-Modulated Radiation Therapy (IMRT) treatments require a quality assurance (Q A) specific patient before delivery. These controls include the experimental verification in dose phantom of the total plan as well as dose distributions. The use of independent dose calculation (IDC) is used in 3D-Crt treatments; however its application in IMRT requires the implementation of an algorithm that allows considering a non-uniform intensity beam. The purpose of this work was to develop IDC software in IMRT with MLC using the algorithm proposed by Kung (Kung et al. 2000). The software was done using Matlab programming. The Clarkson modified integral was implemented on each flowing, applying concentric rings for the dose determination. From the integral of each field was calculated the dose anywhere. One time finished a planning; all data are exported to a phantom where a Q A plan is generated. On this is calculated the half dose in a representative volume of the ionization chamber and the dose at the center of it. Until now 230 IMRT planning were analyzed carried out ??in the treatment planning system (Tps) Iplan. For each one of them Q A plan was generated, were calculated and compared calculated dose with the Tps, IDC system and measurement with ionization chamber. The average difference between measured and calculated dose with the IDC system was 0.4% ± 2.2% [-6.8%, 6.4%]. The difference between the measured and the calculated doses by the pencil-beam algorithm (Pb) of Tps was 2.6% ± 1.41% [-2.0%, 5.6%] and with the Monte Carlo algorithm was 0.4% ± 1.5% [-4.9%, 3.7%]. The differences of the carried out software are comparable to the obtained with the ionization chamber and Tps in Monte Carlo mode. (author)

  14. Therapeutic treatment plan optimization with probability density-based dose prescription

    International Nuclear Information System (INIS)

    Lian Jun; Cotrutz, Cristian; Xing Lei

    2003-01-01

    The dose optimization in inverse planning is realized under the guidance of an objective function. The prescription doses in a conventional approach are usually rigid values, defining in most instances an ill-conditioned optimization problem. In this work, we propose a more general dose optimization scheme based on a statistical formalism [Xing et al., Med. Phys. 21, 2348-2358 (1999)]. Instead of a rigid dose, the prescription to a structure is specified by a preference function, which describes the user's preference over other doses in case the most desired dose is not attainable. The variation range of the prescription dose and the shape of the preference function are predesigned by the user based on prior clinical experience. Consequently, during the iterative optimization process, the prescription dose is allowed to deviate, with a certain preference level, from the most desired dose. By not restricting the prescription dose to a fixed value, the optimization problem becomes less ill-defined. The conventional inverse planning algorithm represents a special case of the new formalism. An iterative dose optimization algorithm is used to optimize the system. The performance of the proposed technique is systematically studied using a hypothetical C-shaped tumor with an abutting circular critical structure and a prostate case. It is shown that the final dose distribution can be manipulated flexibly by tuning the shape of the preference function and that using a preference function can lead to optimized dose distributions in accordance with the planner's specification. The proposed framework offers an effective mechanism to formalize the planner's priorities over different possible clinical scenarios and incorporate them into dose optimization. The enhanced control over the final plan may greatly facilitate the IMRT treatment planning process

  15. Esophagus sparing with IMRT in lung tumor irradiation: An EUD-based optimization technique

    International Nuclear Information System (INIS)

    Chapet, Olivier; Thomas, Emma; Kessler, Marc L.; Fraass, Benedick A.; Ten Haken, Randall K.

    2005-01-01

    Purpose: The aim of this study was to evaluate (1) the use of generalized equivalent uniform dose (gEUD) to optimize dose escalation of lung tumors when the esophagus overlaps the planning target volume (PTV) and (2) the potential benefit of further dose escalation in only the part of the PTV that does not overlap the esophagus. Methods and Materials: The treatment-planning computed tomography (CT) scans of patients with primary lung tumors located in different regions of the left and right lung were used for the optimization of beamlet intensity modulated radiation therapy (IMRT) plans. In all cases, the PTV overlapped part of the esophagus. The dose in the PTV was maximized according to 7 different primary cost functions: 2 plans that made use of mean dose (MD) (the reference plan, in which the 95% isodose surface covered the PTV and a second plan that had no constraint on the minimum isodose), 3 plans based on maximizing gEUD for the whole PTV with ever increasing assumptions for tumor aggressiveness, and 2 plans that used different gEUD values in 2 simultaneous, overlapping target volumes (the whole PTV and the PTV minus esophagus). Beam arrangements and NTCP-based costlets for the organs at risk (OARs) were kept identical to the original conformal plan for each case. Regardless of optimization method, the relative ranking of the resulting plans was evaluated in terms of the absence of cold spots within the PTV and the final gEUD computed for the whole PTV. Results: Because the MD-optimized plans lacked a constraint on minimum PTV coverage, they resulted in cold spots that affected approximately 5% of the PTV volume. When optimizing over the whole PTV volume, gEUD-optimized plans resulted in higher equivalent uniform PTV doses than did the reference plan while still maintaining normal-tissue constraints. However, only under the assumption of extremely aggressive tumors could cold spots in the PTV be avoided. Generally, high-level overall results are obtained

  16. Evaluation of IMRT plans for prostate treatment using energies of 6 MV and 15 MV; Avaliacao de planejamentos de IMRT para tratamento de prostata utilizando energias de 6 MV e 15 MV

    Energy Technology Data Exchange (ETDEWEB)

    Guimaraes, Lucas Francisco C.; Silva, Murilo C. da; Silveira, Paula J.; Flosi, Adriana A.; Boccaletti, Karina W., E-mail: mcollete@gmail.com [A. C. Camargo Cancer Center, Sao Paulo, SP (Brazil). Servico de Radioterapia

    2013-08-15

    This study aims to evaluate and compare radiotherapy plans with intensity-modulated radiation therapy (IMRT) for prostate cancer treatments optimized for photon energies of 6 MV and 15 MV. We retrospectively evaluated 29 patients with prostate cancer, planned with IMRT technique with prescribed dose of 78 Gy. The initial plan was done for the two photon energies, keeping the same optimization parameters and comparing maximum, minimum and modal PTV doses, conformity and homogeneity indexes, dose gradients, isodoses volumes of 30, 40, 50, 60, and 70 Gy, and the total number of monitor units. It was found that the plans are equivalent regarding higher isodose volumes, conformity and homogeneity indexes, maximum, minimum and modal PTV doses. However, for 6 MV plans there was a considerable increase in both number of monitor units and volume lower isodose volumes, especially the 30 Gy. (author)

  17. Clinical experience transitioning from IMRT to VMAT for head and neck cancer

    Energy Technology Data Exchange (ETDEWEB)

    Studenski, Matthew T., E-mail: matthew.studenski@jeffersonhospital.org [Department of Radiation Oncology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA (United States); Bar-Ad, Voichita; Siglin, Joshua [Department of Radiation Oncology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA (United States); Cognetti, David; Curry, Joseph [Department of Otolaryngology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA (United States); Tuluc, Madalina [Department of Pathology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA (United States); Harrison, Amy S. [Department of Radiation Oncology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA (United States)

    2013-07-01

    To quantify clinical differences for volumetric modulated arc therapy (VMAT) versus intensity modulated radiation therapy (IMRT) in terms of dosimetric endpoints and planning and delivery time, twenty head and neck cancer patients have been considered for VMAT using Nucletron Oncentra MasterPlan delivered via an Elekta linear accelerator. Differences in planning time between IMRT and VMAT were estimated accounting for both optimization and calculation. The average delivery time per patient was obtained retrospectively using the record and verify software. For the dosimetric comparison, all contoured organs at risk (OARs) and planning target volumes (PTVs) were evaluated. Of the 20 cases considered, 14 had VMAT plans approved. Six VMAT plans were rejected due to unacceptable dose to OARs. In terms of optimization time, there was minimal difference between the two modalities. The dose calculation time was significantly longer for VMAT, 4 minutes per 358 degree arc versus 2 minutes for an entire IMRT plan. The overall delivery time was reduced by 9.2 ± 3.9 minutes for VMAT (51.4 ± 15.6%). For the dosimetric comparison of the 14 clinically acceptable plans, there was almost no statistical difference between the VMAT and IMRT. There was also a reduction in monitor units of approximately 32% from IMRT to VMAT with both modalities demonstrating comparable quality assurance results. VMAT provides comparable coverage of target volumes while sparing OARs for the majority of head and neck cases. In cases where high dose modulation was required for OARs, a clinically acceptable plan was only achievable with IMRT. Due to the long calculation times, VMAT plans can cause delays during planning but marked improvements in delivery time reduce patient treatment times and the risk of intra-fraction motion.

  18. SU-E-J-193: Feasibility of MRI-Only Based IMRT Planning for Pancreatic Cancer

    International Nuclear Information System (INIS)

    Prior, P; Botros, M; Chen, X; Paulson, E; Erickson, B; Li, X

    2014-01-01

    Purpose: With the increasing use of MRI simulation and the advent of MRI-guided delivery, it is desirable to use MRI only for treatment planning. In this study, we assess the dosimetric difference between MRI- and CTbased IMRT planning for pancreatic cancer. Methods: Planning CTs and MRIs acquired for a representative pancreatic cancer patient were used. MRI-based planning utilized forced relative electron density (rED) assignment of organ specific values from IRCU report 46, where rED = 1.029 for PTV and a rED = 1.036 for non-specified tissue (NST). Six IMRT plans were generated with clinical dose-volume (DV) constraints using a research Monaco planning system employing Monte Carlo dose calculation with optional perpendicular magnetic field (MF) of 1.5T. The following five plans were generated and compared with the planning CT: 1.) CT plan with MF and dose recalculation without optimization; 2.) MRI (T2) plan with target and OARs redrawn based on MRI, forced rED, no MF, and recalculation without optimization; 3.) Similar as in 2 but with MF; 4.) MRI plan with MF but without optimization; and 5.) Similar as in 4 but with optimization. Results: Generally, noticeable differences in PTV point doses and DV parameters (DVPs) between the CT-and MRI-based plans with and without the MF were observed. These differences between the optimized plans were generally small, mostly within 2%. Larger differences were observed in point doses and mean doses for certain OARs between the CT and MRI plan, mostly due to differences between image acquisition times. Conclusion: MRI only based IMRT planning for pancreatic cancer is feasible. The differences observed between the optimized CT and MRI plans with or without the MF were practically negligible if excluding the differences between MRI and CT defined structures

  19. Superiority of Equivalent Uniform Dose (EUD)-Based Optimization for Breast and Chest Wall

    International Nuclear Information System (INIS)

    Mihailidis, Dimitris N.; Plants, Brian; Farinash, Lloyd; Harmon, Michael; Whaley, Lewis; Raja, Prem; Tomara, Pelagia

    2010-01-01

    We investigate whether IMRT optimization based on generalized equivalent uniform dose (gEUD) objectives for organs at risk (OAR) results in superior dosimetric outcomes when compared with multiple dose-volume (DV)-based objectives plans for patients with intact breast and postmastectomy chest wall (CW) cancer. Four separate IMRT plans were prepared for each of the breast and CW cases (10 patients). The first three plans used our standard in-house, physician-selected, DV objectives (phys-plan); gEUD-based objectives for the OARs (gEUD-plan); and multiple, 'very stringent,' DV objectives for each OAR and PTV (DV-plan), respectively. The fourth plan was only beam-fluence optimized (FO-plan), without segmentation, which used the same objectives as in the DV-plan. The latter plan was to be used as an 'optimum' benchmark without the effects of the segmentation for deliverability. Dosimetric quantities, such as V 20Gy for the ipsilateral lung and mean dose (D mean ) for heart, contralateral breast, and contralateral lung were used to evaluate the results. For all patients in this study, we have seen that the gEUD-based plans allow greater sparing of the OARs while maintaining equivalent target coverage. The average ipsilateral lung V 20Gy reduced from 22 ± 4.4% for the FO-plan to 18 ± 3% for the gEUD-plan. All other dosimetric quantities shifted towards lower doses for the gEUD-plan. gEUD-based optimization can be used to search for plans of different DVHs with the same gEUDs. The use of gEUD allows selective optimization and reduction of the dose for each OAR and results in a truly individualized treatment plan.

  20. Restricted Field IMRT Dramatically Enhances IMRT Planning for Mesothelioma

    International Nuclear Information System (INIS)

    Allen, Aaron M.; Schofield, Deborah; Hacker, Fred; Court, Laurence E.; Czerminska, Maria M.S.

    2007-01-01

    Purpose: To improve the target coverage and normal tissue sparing of intensity-modulated radiotherapy (IMRT) for mesothelioma after extrapleural pneumonectomy. Methods and Materials: Thirteen plans from patients previously treated with IMRT for mesothelioma were replanned using a restricted field technique. This technique was novel in two ways. It limited the entrance beams to 200 o around the target and three to four beams per case had their field apertures restricted down to the level of the heart or liver to further limit the contralateral lung dose. New constraints were added that included a mean lung dose of <9.5 Gy and volume receiving ≥5 Gy of <55%. Results: In all cases, the planning target volume coverage was excellent, with an average of 97% coverage of the planning target volume by the target dose. No change was seen in the target coverage with the new technique. The heart, kidneys, and esophagus were all kept under tolerance in all cases. The average mean lung dose, volume receiving ≥20 Gy, and volume receiving ≥5 Gy with the new technique was 6.6 Gy, 3.0%, and 50.8%, respectively, compared with 13.8 Gy, 15%, and 90% with the previous technique (p < 0.0001 for all three comparisons). The maximal value for any case in the cohort was 8.0 Gy, 7.3%, and 57.5% for the mean lung dose, volume receiving ≥20 Gy, and volume receiving ≥5 Gy, respectively. Conclusion: Restricted field IMRT provides an improved method to deliver IMRT to a complex target after extrapleural pneumonectomy. An upcoming Phase I trial will provide validation of these results

  1. Poster — Thur Eve — 33: The Influence of a Modeled Treatment Couch on Dose Distributions During IMRT and RapidArc Treatment Delivery

    International Nuclear Information System (INIS)

    Aldosary, Ghada; Nobah, Ahmad; Al-Zorkani, Faisal; Moftah, Belal; Devic, Slobodan

    2014-01-01

    Treatment couches have been known to perturb dose delivery in patients. This effect is most pronounced in techniques such as IMRT and RapidArc. Although modern treatment planning systems (TPS) include data for a “default” treatment couch, actual couches are not manufactured identically. Thus, variations in their Hounsfield Unit (HU) values may exist. This study demonstrates a practical and simple method of acquiring reliable HU data for any treatment couch. We also investigate the effects of both the default and modeled treatment couches on absorbed dose. Experimental verifications show that by neglecting to incorporate the treatment couch in the TPS, dose differences of up to 9.5% and 7.3% were present for 4 MV and 10 MV photon beams, respectively. Furthermore, a clinical study based on a cohort of 20 RapidArc and IMRT (brain, pelvis and abdominal) cases is performed. 2D dose distributions show that without the couch in the planning phase, differences ≤ 4.6% and 5.9% for RapidArc and IMRT cases are present for the same cases that the default couch was added to. Additionally, in comparison to the default couch, employing the modeled couch in the calculation process influences dose distributions by ≤ 2.7% and 8% for RapidArc and IMRT cases, respectively. This result was found to be site specific; where an accurate couch proves to be preferable for IMRT brain plans. As such, adding the couch during dose calculation decreases dose calculation errors, and a precisely modeled treatment couch offers higher dose delivery accuracy for brain treatment using IMRT

  2. Poster — Thur Eve — 33: The Influence of a Modeled Treatment Couch on Dose Distributions During IMRT and RapidArc Treatment Delivery

    Energy Technology Data Exchange (ETDEWEB)

    Aldosary, Ghada [Medical Physics Unit, Montreal General Hospital, McGill University, Montreal, Quebec (Canada); Nobah, Ahmad; Al-Zorkani, Faisal; Moftah, Belal [Biomedical Physics Department, King Faisal Specialist Hospital and Research Center, Riyadh (Saudi Arabia); Devic, Slobodan [Department of Radiation Oncology, Jewish General Hospital, McGill University, Montreal, Quebec (Canada)

    2014-08-15

    Treatment couches have been known to perturb dose delivery in patients. This effect is most pronounced in techniques such as IMRT and RapidArc. Although modern treatment planning systems (TPS) include data for a “default” treatment couch, actual couches are not manufactured identically. Thus, variations in their Hounsfield Unit (HU) values may exist. This study demonstrates a practical and simple method of acquiring reliable HU data for any treatment couch. We also investigate the effects of both the default and modeled treatment couches on absorbed dose. Experimental verifications show that by neglecting to incorporate the treatment couch in the TPS, dose differences of up to 9.5% and 7.3% were present for 4 MV and 10 MV photon beams, respectively. Furthermore, a clinical study based on a cohort of 20 RapidArc and IMRT (brain, pelvis and abdominal) cases is performed. 2D dose distributions show that without the couch in the planning phase, differences ≤ 4.6% and 5.9% for RapidArc and IMRT cases are present for the same cases that the default couch was added to. Additionally, in comparison to the default couch, employing the modeled couch in the calculation process influences dose distributions by ≤ 2.7% and 8% for RapidArc and IMRT cases, respectively. This result was found to be site specific; where an accurate couch proves to be preferable for IMRT brain plans. As such, adding the couch during dose calculation decreases dose calculation errors, and a precisely modeled treatment couch offers higher dose delivery accuracy for brain treatment using IMRT.

  3. Dosimetric comparison of helical tomotherapy, RapidArc, and a novel IMRT and Arc technique for esophageal carcinoma

    International Nuclear Information System (INIS)

    Martin, Spencer; Chen, Jeff Z.; Rashid Dar, A.; Yartsev, Slav

    2011-01-01

    Purpose: To compare radiotherapy treatment plans for mid- and distal-esophageal cancer with primary involvement of the gastroesophageal (GE) junction using a novel IMRT and Arc technique (IMRT and Arc), helical tomotherapy (HT), and RapidArc (RA1 and RA2). Methods and materials: Eight patients treated on HT for locally advanced esophageal cancer with radical intent were re-planned for RA and IMRT and Arc. RA plans employed single and double arcs (RA1 and RA2, respectively), while IMRT and Arc plans had four fixed-gantry IMRT fields and a conformal arc. Dose-volume histogram statistics, dose uniformity, and dose homogeneity were analyzed to compare treatment plans. Results: RA2 plans showed significant improvement over RA1 plans in terms of OAR dose and PTV dose uniformity and homogeneity. HT plan provided best dose uniformity (p = 0.001) and dose homogeneity (p = 0.002) to planning target volume (PTV), while IMRT and Arc and RA2 plans gave lowest dose to lungs among four radiotherapy techniques with acceptable PTV dose coverage. Mean V 10 of the lungs was significantly reduced by the RA2 plans compared to IMRT and Arc (40.3%, p = 0.001) and HT (66.2%, p 15 of the lungs for the RA2 plans also showed significant improvement over the IMRT and Arc (25.2%, p = 0.042) and HT (34.8%, p = 0.027) techniques. These improvements came at the cost of higher doses to the heart volume compared to HT and IMRT and Arc techniques. Mean lung dose (MLD) for the IMRT and Arc technique (21.2 ± 5.0% of prescription dose) was significantly reduced compared to HT (26.3%, p = 0.004), RA1 (23.3%, p = 0.028), and RA2 (23.2%, p = 0.017) techniques. Conclusion: The IMRT and Arc technique is a good option for treating esophageal cancer with thoracic involvement. It achieved optimal low dose to the lungs and heart with acceptable PTV coverage. HT is a good option for treating esophageal cancer with little thoracic involvement as it achieves superior dose conformality and uniformity. The RA2

  4. COMPARISON OF THE PERIPHERAL DOSES FROM DIFFERENT IMRT TECHNIQUES FOR PEDIATRIC HEAD AND NECK RADIATION THERAPY.

    Science.gov (United States)

    Toyota, Masahiko; Saigo, Yasumasa; Higuchi, Kenta; Fujimura, Takuya; Koriyama, Chihaya; Yoshiura, Takashi; Akiba, Suminori

    2017-11-01

    Intensity-modulated radiation therapy (IMRT) can deliver high and homogeneous doses to the target area while limiting doses to organs at risk. We used a pediatric phantom to simulate the treatment of a head and neck tumor in a child. The peripheral doses were examined for three different IMRT techniques [dynamic multileaf collimator (DMLC), segmental multileaf collimator (SMLC) and volumetric modulated arc therapy (VMAT)]. Peripheral doses were evaluated taking thyroid, breast, ovary and testis as the points of interest. Doses were determined using a radio-photoluminescence glass dosemeter, and the COMPASS system was used for three-dimensional dose evaluation. VMAT achieved the lowest peripheral doses because it had the highest monitor unit efficiency. However, doses in the vicinity of the irradiated field, i.e. the thyroid, could be relatively high, depending on the VMAT collimator angle. DMLC and SMLC had a large area of relatively high peripheral doses in the breast region. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  5. Monte Carlo investigation of collapsed versus rotated IMRT plan verification.

    Science.gov (United States)

    Conneely, Elaine; Alexander, Andrew; Ruo, Russell; Chung, Eunah; Seuntjens, Jan; Foley, Mark J

    2014-05-08

    IMRT QA requires, among other tests, a time-consuming process of measuring the absorbed dose, at least to a point, in a high-dose, low-dose-gradient region. Some clinics use a technique of measuring this dose with all beams delivered at a single gantry angle (collapsed delivery), as opposed to the beams delivered at the planned gantry angle (rotated delivery). We examined, established, and optimized Monte Carlo simulations of the dosimetry for IMRT verification of treatment plans for these two different delivery modes (collapsed versus rotated). The results of the simulations were compared to the treatment planning system dose calculations for the two delivery modes, as well as to measurements taken. This was done in order to investigate the validity of the use of a collapsed delivery technique for IMRT QA. The BEAMnrc, DOSXYZnrc, and egs_chamber codes were utilized for the Monte Carlo simulations along with the MMCTP system. A number of different plan complexity metrics were also used in the analysis of the dose distributions in a bid to qualify why verification in a collapsed delivery may or may not be optimal for IMRT QA. Following the Alfonso et al. formalism, the kfclin,frefQclin,Q correction factor was calculated to correct the deviation of small fields from the reference conditions used for beam calibration. We report on the results obtained for a cohort of 20 patients. The plan complexity was investigated for each plan using the complexity metrics of homogeneity index, conformity index, modulation complexity score, and the fraction of beams from a particular plan that intersect the chamber when performing the QA. Rotated QA gives more consistent results than the collapsed QA technique. The kfclin,frefQclin,Qfactor deviates less from 1 for rotated QA than for collapsed QA. If the homogeneity index is less than 0.05 then the kfclin,frefQclin,Q factor does not deviate from unity by more than 1%. A value this low for the homogeneity index can only be obtained

  6. Poster - Thur Eve - 57: Craniospinal irradiation with jagged-junction IMRT approach without beam edge matching for field junctions.

    Science.gov (United States)

    Cao, F; Ramaseshan, R; Corns, R; Harrop, S; Nuraney, N; Steiner, P; Aldridge, S; Liu, M; Carolan, H; Agranovich, A; Karva, A

    2012-07-01

    Craniospinal irradiation were traditionally treated the central nervous system using two or three adjacent field sets. A intensity-modulated radiotherapy (IMRT) plan (Jagged-Junction IMRT) which overcomes problems associated with field junctions and beam edge matching, improves planning and treatment setup efficiencies with homogenous target dose distribution was developed. Jagged-Junction IMRT was retrospectively planned on three patients with prescription of 36 Gy in 20 fractions and compared to conventional treatment plans. Planning target volume (PTV) included the whole brain and spinal canal to the S3 vertebral level. The plan employed three field sets, each with a unique isocentre. One field set with seven fields treated the cranium. Two field sets treated the spine, each set using three fields. Fields from adjacent sets were overlapped and the optimization process smoothly integrated the dose inside the overlapped junction. For the Jagged-Junction IMRT plans vs conventional technique, average homogeneity index equaled 0.08±0.01 vs 0.12±0.02, and conformity number equaled 0.79±0.01 vs 0.47±0.12. The 95% isodose surface covered (99.5±0.3)% of the PTV vs (98.1±2.0)%. Both Jagged-Junction IMRT plans and the conventional plans had good sparing of the organs at risk. Jagged-Junction IMRT planning provided good dose homogeneity and conformity to the target while maintaining a low dose to the organs at risk. Jagged-Junction IMRT optimization smoothly distributed dose in the junction between field sets. Since there was no beam matching, this treatment technique is less likely to produce hot or cold spots at the junction in contrast to conventional techniques. © 2012 American Association of Physicists in Medicine.

  7. Application of monomer/polymer gel dosimetry to study the effects of tissue inhomogeneities on intensity-modulated radiation therapy (IMRT) dose distributions.

    Science.gov (United States)

    Vergote, Koen; De Deene, Yves; Claus, Filip; De Gersem, Werner; Van Duyse, Bart; Paelinck, Leen; Achten, Eric; De Neve, Wilfried; De Wagter, Carlos

    2003-04-01

    When planning an intensity-modulated radiation therapy (IMRT) treatment in a heterogeneous region (e.g. the thorax), the dose computation algorithm of a treatment planning system may need to account for these inhomogeneities in order to obtain a reliable prediction of the dose distribution. An accurate dose verification technique such as monomer/polymer gel dosimetry is suggested to verify the outcome of the planning system. The effects of low-density structures: (a) on narrow high-energy (18 MV) photon beams; and (b) on a class-solution IMRT treatment delivered to a thorax phantom have been examined using gel dosimetry. The used phantom contained air cavities that could be filled with water to simulate a homogeneous or heterogeneous configuration. The IMRT treatment for centrally located lung tumors was delivered on both cases, and gel derived dose maps were compared with computations by both the GRATIS and Helax-TMS planning system. Dose rebuildup due to electronic disequilibrium in a narrow photon beam is demonstrated. The gel measurements showed good agreement with diamond detector measurements. Agreement between measured IMRT dose maps and dose computations was demonstrated by several quantitative techniques. An underdosage of the planning target volume (PTV) was revealed. The homogeneity of the phantom had only a minor influence on the dose distribution in the PTV. An expansion of low-level isodoses in the lung volume was predicted by collapsed cone computations in the heterogeneous case. For the class-solution described, the dose in centrally located mediastinal tumors can be computed with sufficient accuracy, even when neglecting the lower lung density. Polymer gel dosimetry proved to be a valuable technique to verify dose calculation algorithms for IMRT in 3D in heterogeneous configurations.

  8. Comparison of IMRT Treatment Plans Between Linac and Helical Tomotherapy Based on Integral Dose and Inhomogeneity Index

    International Nuclear Information System (INIS)

    Shi Chengyu; Penagaricano, Jose; Papanikolaou, Niko

    2008-01-01

    Intensity modulated radiotherapy (IMRT) is an advanced treatment technology for radiation therapy. There are several treatment planning systems (TPS) that can generate IMRT plans. These plans may show different inhomogeneity indices to the planning target volume (PTV) and integral dose to organs at risk (OAR). In this study, we compared clinical cases covering different anatomical treatment sites, including head and neck, brain, lung, prostate, pelvis, and cranio-spinal axis. Two treatment plans were developed for each case using Pinnacle 3 and helical tomotherapy (HT) TPS. The inhomogeneity index of the PTV and the non-tumor integral dose (NTID) were calculated and compared for each case. Despite the difference in the number of effective beams, in several cases, NTID did not increase from HT as compared to the step-and-shoot delivery method. Six helical tomotherapy treatment plans for different treatment sites have been analyzed and compared against corresponding step-and-shoot plans generated with the Pinnacle 3 planning system. Results show that HT may produce plans with smaller integral doses to healthy organs, and fairly homogeneous doses to the target as compared to linac-based step-and-shoot IMRT planning in special treatment site such as cranio-spinal

  9. Evaluation of the effect of patient dose from cone beam computed tomography on prostate IMRT using Monte Carlo simulation.

    Science.gov (United States)

    Chow, James C L; Leung, Michael K K; Islam, Mohammad K; Norrlinger, Bernhard D; Jaffray, David A

    2008-01-01

    The aim of this study is to evaluate the impact of the patient dose due to the kilovoltage cone beam computed tomography (kV-CBCT) in a prostate intensity-modulated radiation therapy (IMRT). The dose distributions for the five prostate IMRTs were calculated using the Pinnacle treatment planning system. To calculate the patient dose from CBCT, phase-space beams of a CBCT head based on the ELEKTA x-ray volume imaging system were generated using the Monte Carlo BEAMnr code for 100, 120, 130, and 140 kVp energies. An in-house graphical user interface called DOSCTP (DOSXYZnrc-based) developed using MATLAB was used to calculate the dose distributions due to a 360 degrees photon arc from the CBCT beam with the same patient CT image sets as used in Pinnacle. The two calculated dose distributions were added together by setting the CBCT doses equal to 1%, 1.5%, 2%, and 2.5% of the prescription dose of the prostate IMRT. The prostate plan and the summed dose distributions were then processed in the CERR platform to determine the dose-volume histograms (DVHs) of the regions of interest. Moreover, dose profiles along the x- and y-axes crossing the isocenter with and without addition of the CBCT dose were determined. It was found that the added doses due to CBCT are most significant at the femur heads. Higher doses were found at the bones for a relatively low energy CBCT beam such as 100 kVp. Apart from the bones, the CBCT dose was observed to be most concentrated on the anterior and posterior side of the patient anatomy. Analysis of the DVHs for the prostate and other critical tissues showed that they vary only slightly with the added CBCT dose at different beam energies. On the other hand, the changes of the DVHs for the femur heads due to the CBCT dose and beam energy were more significant than those of rectal and bladder wall. By analyzing the vertical and horizontal dose profiles crossing the femur heads and isocenter, with and without the CBCT dose equal to 2% of the

  10. Evaluation of the effect of patient dose from cone beam computed tomography on prostate IMRT using Monte Carlo simulation

    International Nuclear Information System (INIS)

    Chow, James C. L.; Leung, Michael K. K.; Islam, Mohammad K.; Norrlinger, Bernhard D.; Jaffray, David A.

    2008-01-01

    The aim of this study is to evaluate the impact of the patient dose due to the kilovoltage cone beam computed tomography (kV-CBCT) in a prostate intensity-modulated radiation therapy (IMRT). The dose distributions for the five prostate IMRTs were calculated using the Pinnacle3 treatment planning system. To calculate the patient dose from CBCT, phase-space beams of a CBCT head based on the ELEKTA x-ray volume imaging system were generated using the Monte Carlo BEAMnrc code for 100, 120, 130, and 140 kVp energies. An in-house graphical user interface called DOSCTP (DOSXYZnrc-based) developed using MATLAB was used to calculate the dose distributions due to a 360 deg. photon arc from the CBCT beam with the same patient CT image sets as used in Pinnacle3. The two calculated dose distributions were added together by setting the CBCT doses equal to 1%, 1.5%, 2%, and 2.5% of the prescription dose of the prostate IMRT. The prostate plan and the summed dose distributions were then processed in the CERR platform to determine the dose-volume histograms (DVHs) of the regions of interest. Moreover, dose profiles along the x- and y-axes crossing the isocenter with and without addition of the CBCT dose were determined. It was found that the added doses due to CBCT are most significant at the femur heads. Higher doses were found at the bones for a relatively low energy CBCT beam such as 100 kVp. Apart from the bones, the CBCT dose was observed to be most concentrated on the anterior and posterior side of the patient anatomy. Analysis of the DVHs for the prostate and other critical tissues showed that they vary only slightly with the added CBCT dose at different beam energies. On the other hand, the changes of the DVHs for the femur heads due to the CBCT dose and beam energy were more significant than those of rectal and bladder wall. By analyzing the vertical and horizontal dose profiles crossing the femur heads and isocenter, with and without the CBCT dose equal to 2% of the

  11. Clinically Applicable Monte Carlo–based Biological Dose Optimization for the Treatment of Head and Neck Cancers With Spot-Scanning Proton Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Wan Chan Tseung, Hok Seum, E-mail: wanchantseung.hok@mayo.edu; Ma, Jiasen; Kreofsky, Cole R.; Ma, Daniel J.; Beltran, Chris

    2016-08-01

    Purpose: Our aim is to demonstrate the feasibility of fast Monte Carlo (MC)–based inverse biological planning for the treatment of head and neck tumors in spot-scanning proton therapy. Methods and Materials: Recently, a fast and accurate graphics processor unit (GPU)–based MC simulation of proton transport was developed and used as the dose-calculation engine in a GPU-accelerated intensity modulated proton therapy (IMPT) optimizer. Besides dose, the MC can simultaneously score the dose-averaged linear energy transfer (LET{sub d}), which makes biological dose (BD) optimization possible. To convert from LET{sub d} to BD, a simple linear relation was assumed. By use of this novel optimizer, inverse biological planning was applied to 4 patients, including 2 small and 1 large thyroid tumor targets, as well as 1 glioma case. To create these plans, constraints were placed to maintain the physical dose (PD) within 1.25 times the prescription while maximizing target BD. For comparison, conventional intensity modulated radiation therapy (IMRT) and IMPT plans were also created using Eclipse (Varian Medical Systems) in each case. The same critical-structure PD constraints were used for the IMRT, IMPT, and biologically optimized plans. The BD distributions for the IMPT plans were obtained through MC recalculations. Results: Compared with standard IMPT, the biologically optimal plans for patients with small tumor targets displayed a BD escalation that was around twice the PD increase. Dose sparing to critical structures was improved compared with both IMRT and IMPT. No significant BD increase could be achieved for the large thyroid tumor case and when the presence of critical structures mitigated the contribution of additional fields. The calculation of the biologically optimized plans can be completed in a clinically viable time (<30 minutes) on a small 24-GPU system. Conclusions: By exploiting GPU acceleration, MC-based, biologically optimized plans were created for

  12. Evaluation of IMRT plans for prostate treatment using energies of 6 MV and 15 MV

    International Nuclear Information System (INIS)

    Guimaraes, Lucas Francisco C.; Silva, Murilo C. da; Silveira, Paula J.; Flosi, Adriana A.; Boccaletti, Karina W.

    2013-01-01

    This study aims to evaluate and compare radiotherapy plans with intensity-modulated radiation therapy (IMRT) for prostate cancer treatments optimized for photon energies of 6 MV and 15 MV. We retrospectively evaluated 29 patients with prostate cancer, planned with IMRT technique with prescribed dose of 78 Gy. The initial plan was done for the two photon energies, keeping the same optimization parameters and comparing maximum, minimum and modal PTV doses, conformity and homogeneity indexes, dose gradients, isodoses volumes of 30, 40, 50, 60, and 70 Gy, and the total number of monitor units. It was found that the plans are equivalent regarding higher isodose volumes, conformity and homogeneity indexes, maximum, minimum and modal PTV doses. However, for 6 MV plans there was a considerable increase in both number of monitor units and volume lower isodose volumes, especially the 30 Gy. (author)

  13. Is the dose distribution distorted in IMRT and RapidArc treatment when patient plans are swapped across beam‐matched machines?

    Science.gov (United States)

    Radha, Chandrasekaran Anu; Subramani, Vendhan; Gunasekaran, Madhan Kumar

    2016-01-01

    The purpose of this study is to evaluate the degree of dose distribution distortion in advanced treatments like IMRT and RapidArc when patient plans are swapped across dosimetrically equivalent so‐called “beam‐matched” machines. For this purpose the entire work is divided into two stages. At forefront stage all basic beam properties of 6 MV X‐rays like PDD, profiles, output factors, TPR20/10 and MLC transmission of two beam‐matched machines — Varian Clinac iX and Varian 600 C/D Unique — are compared and evaluated for differences. At second stage 40 IMRT and RapidArc patient plans from the pool of head and neck (H&N) and pelvis sites are selected for the study. The plans are swapped across the machines for dose recalculation and the DVHs of target and critical organs are evaluated for dose differences. Following this, the accuracy of the beam‐matching at the TPS level for treatments like IMRT and RapidArc are compared. On PDD, profile (central 80%) and output factor comparison between the two machines, a maximum percentage disagreement value of −2.39%,−2.0% and −2.78%, respectively, has been observed. The maximum dose difference observed at volumes in IMRT and RapidArc treatments for H&N dose prescription of 69.3 Gy/33 fractions is 0.88 Gy and 0.82 Gy, respectively. Similarly, for pelvis, with a dose prescription of 50 Gy/25 fractions, a maximum dose difference of 0.55 Gy and 0.53 Gy is observed at volumes in IMRT and RapidArc treatments, respectively. Overall results of the swapped plans between two machines' 6 MV X‐rays are well within the limits of accepted clinical tolerance. PACS number(s): 87.56.bd PMID:27685106

  14. Dose-mass inverse optimization for minimally moving thoracic lesions

    Science.gov (United States)

    Mihaylov, I. B.; Moros, E. G.

    2015-05-01

    In the past decade, several different radiotherapy treatment plan evaluation and optimization schemes have been proposed as viable approaches, aiming for dose escalation or an increase of healthy tissue sparing. In particular, it has been argued that dose-mass plan evaluation and treatment plan optimization might be viable alternatives to the standard of care, which is realized through dose-volume evaluation and optimization. The purpose of this investigation is to apply dose-mass optimization to a cohort of lung cancer patients and compare the achievable healthy tissue sparing to that one achievable through dose-volume optimization. Fourteen non-small cell lung cancer (NSCLC) patient plans were studied retrospectively. The range of tumor motion was less than 0.5 cm and motion management in the treatment planning process was not considered. For each case, dose-volume (DV)-based and dose-mass (DM)-based optimization was performed. Nine-field step-and-shoot IMRT was used, with all of the optimization parameters kept the same between DV and DM optimizations. Commonly used dosimetric indices (DIs) such as dose to 1% the spinal cord volume, dose to 50% of the esophageal volume, and doses to 20 and 30% of healthy lung volumes were used for cross-comparison. Similarly, mass-based indices (MIs), such as doses to 20 and 30% of healthy lung masses, 1% of spinal cord mass, and 33% of heart mass, were also tallied. Statistical equivalence tests were performed to quantify the findings for the entire patient cohort. Both DV and DM plans for each case were normalized such that 95% of the planning target volume received the prescribed dose. DM optimization resulted in more organs at risk (OAR) sparing than DV optimization. The average sparing of cord, heart, and esophagus was 23, 4, and 6%, respectively. For the majority of the DIs, DM optimization resulted in lower lung doses. On average, the doses to 20 and 30% of healthy lung were lower by approximately 3 and 4%, whereas lung

  15. Novel method based on Fricke gel dosimeters for dose verification in IMRT techniques

    International Nuclear Information System (INIS)

    Aon, E.; Brunetto, M.; Sansogne, R.; Castellano, G.; Valente, M.

    2008-01-01

    Modern radiotherapy is becoming increasingly complex. Conformal and intensity modulated (IMRT) techniques are nowadays available for achieving better tumour control. However, accurate methods for 3D dose verification for these modern irradiation techniques have not been adequately established yet. Fricke gel dosimeters consist, essentially, in a ferrous sulphate (Fricke) solution fixed to a gel matrix, which enables spatial resolution. A suitable radiochromic marker (xylenol orange) is added to the solution in order to produce radiochromic changes within the visible spectrum range, due to the chemical internal conversion (oxidation) of ferrous ions to ferric ions. In addition, xylenol orange has proved to slow down the internal diffusion effect of ferric ions. These dosimeters suitably shaped in form of thin layers and optically analyzed by means of visible light transmission imaging have recently been proposed as a method for 3D absorbed dose distribution determinations in radiotherapy, and tested in several IMRT applications employing a homogeneous plane (visible light) illuminator and a CCD camera with a monochromatic filter for sample analysis by means of transmittance images. In this work, the performance of an alternative read-out method is characterized, consisting on visible light images, acquired before and after irradiation by means of a commercially available flatbed-like scanner. Registered images are suitably converted to matrices and analyzed by means of dedicated 'in-house' software. The integral developed method allows performing 1D (profiles), 2D (surfaces) and 3D (volumes) dose mapping. In addition, quantitative comparisons have been performed by means of the Gamma composite criteria. Dose distribution comparisons between Fricke gel dosimeters and traditional standard dosimetric techniques for IMRT irradiations show an overall good agreement, supporting the suitability of the method. The agreement, quantified by the gamma index (that seldom

  16. Conformal intensity-modulated radiotherapy (IMRT) delivered by robotic linac-conformality versus efficiency of dose delivery

    International Nuclear Information System (INIS)

    Webb, Steve

    2000-01-01

    Intensity-modulated radiotherapy (IMRT) may be delivered with a high-energy-photon linac mounted on a robotic gantry and executing a complex trajectory. In a previous paper an inverse-planning technique was developed for such an application. Here the work is extended to demonstrate the dependence of conformality on the size of the elemental pencil beam, on the complexity of the trajectory and on the sampling of azimuth and elevation of the collimated source. The improved conformality of complex trajectories is demonstrated and benchmarked relative to simpler trajectories, more representative of existing non-robotic IMRT techniques. Specifically, by choosing a very fine pencil beam, exquisitely conformal dose distributions have been obtained. Important sampling considerations have been determined. Expressions have been derived for the dosimetry and monitor-unit efficiency of robotic IMRT. Equivalent trajectories were computed for executing the complex robotic trajectories instead by using a conventional linac. The work benchmarks an ideal in IMRT against which more practical and more common techniques may be measured. (author)

  17. Rotational IMRT techniques compared to fixed gantry IMRT and Tomotherapy: multi-institutional planning study for head-and-neck cases

    International Nuclear Information System (INIS)

    Wiezorek, Tilo; Schubert, Kai; Wagner, Daniela; Wendt, Thomas G; Brachwitz, Tim; Georg, Dietmar; Blank, Eyck; Fotina, Irina; Habl, Gregor; Kretschmer, Matthias; Lutters, Gerd; Salz, Henning

    2011-01-01

    Recent developments enable to deliver rotational IMRT with standard C-arm gantry based linear accelerators. This upcoming treatment technique was benchmarked in a multi-center treatment planning study against static gantry IMRT and rotational IMRT based on a ring gantry for a complex parotid gland sparing head-and-neck technique. Treatment plans were created for 10 patients with head-and-neck tumours (oropharynx, hypopharynx, larynx) using the following treatment planning systems (TPS) for rotational IMRT: Monaco (ELEKTA VMAT solution), Eclipse (Varian RapidArc solution) and HiArt for the helical tomotherapy (Tomotherapy). Planning of static gantry IMRT was performed with KonRad, Pinnacle and Panther DAO based on step&shoot IMRT delivery and Eclipse for sliding window IMRT. The prescribed doses for the high dose PTVs were 65.1Gy or 60.9Gy and for the low dose PTVs 55.8Gy or 52.5Gy dependend on resection status. Plan evaluation was based on target coverage, conformity and homogeneity, DVHs of OARs and the volume of normal tissue receiving more than 5Gy (V 5Gy ). Additionally, the cumulative monitor units (MUs) and treatment times of the different technologies were compared. All evaluation parameters were averaged over all 10 patients for each technique and planning modality. Depending on IMRT technique and TPS, the mean CI values of all patients ranged from 1.17 to 2.82; and mean HI values varied from 0.05 to 0.10. The mean values of the median doses of the spared parotid were 26.5Gy for RapidArc and 23Gy for VMAT, 14.1Gy for Tomo. For fixed gantry techniques 21Gy was achieved for step&shoot+KonRad, 17.0Gy for step&shoot+Panther DAO, 23.3Gy for step&shoot+Pinnacle and 18.6Gy for sliding window. V 5Gy values were lowest for the sliding window IMRT technique (3499 ccm) and largest for RapidArc (5480 ccm). The lowest mean MU value of 408 was achieved by Panther DAO, compared to 1140 for sliding window IMRT. All IMRT delivery technologies with their associated TPS

  18. Dosimetric Comparison of Manual and Beam Angle Optimization of Gantry Angles in IMRT

    International Nuclear Information System (INIS)

    Srivastava, Shiv P.; Das, Indra J.; Kumar, Arvind; Johnstone, Peter A.S.

    2011-01-01

    Dosimetric comparison of manual beam angle selection (MBS) and beam angle optimization (BAO) for IMRT plans is investigated retrospectively for 15 head and neck and prostate patients. The head and neck and prostate had planning target volumes (PTVs) ranging between 96.0 and 319.9 cm 3 and 153.6 and 321.3 cm 3 , whereas OAR ranged between 8.3 and 47.8 cm 3 and 68.3 and 469.2 cm 3 , respectively. In MBS, a standard coplanar 7-9 fields equally spaced gantry angles were used. In BAO, the selection of gantry angle was optimized by the algorithm for the same number of beams. The optimization and dose-volume constraints were kept the same for both techniques. Treatment planning was performed on the Eclipse treatment planning system. Our results showed that the dose-volume histogram for PTV are nearly identical in both techniques but BAO provided superior sparing of the organs at risk compared with the MBS. Also, MBS produced statistically significant higher monitor units (MU) and segments than the BAO; 13.1 ± 6.6% (p = 0.012) and 10.4 ± 13.6% (p = 0.140), and 14.6 ± 5.6% (p = 1.003E-5) and 12.6 ± 7.4% (p = 0.76E-3) for head and neck and prostate cases, respectively. The reduction in MU translates into the reduction in total body and integral dose. It is concluded that BAO provides advantage over MBS for most intenisty-modulated radiation therapy cases.

  19. SU-E-T-368: Evaluating Dosimetric Outcome of Modulated Photon Radiotherapy (XMRT) Optimization for Head and Neck Patients

    Energy Technology Data Exchange (ETDEWEB)

    McGeachy, P; Villarreal-Barajas, JE; Khan, R [University of Calgary, Calgary, AB (Canada); Tom Baker Cancer Centre, Calgary, AB (Canada); Zinchenko, Y [University of Calgary, Calgary, AB (Canada)

    2015-06-15

    Purpose: The dosimetric outcome of optimized treatment plans obtained by modulating the photon beamlet energy and fluence on a small cohort of four Head and Neck (H and N) patients was investigated. This novel optimization technique is denoted XMRT for modulated photon radiotherapy. The dosimetric plans from XMRT for H and N treatment were compared to conventional, 6 MV intensity modulated radiotherapy (IMRT) optimization plans. Methods: An arrangement of two non-coplanar and five coplanar beams was used for all four H and N patients. Both XMRT and IMRT were subject to the same optimization algorithm, with XMRT optimization allowing both 6 and 18 MV beamlets while IMRT was restricted to 6 MV only. The optimization algorithm was based on a linear programming approach with partial-volume constraints implemented via the conditional value-at-risk method. H and N constraints were based off of those mentioned in the Radiation Therapy Oncology Group 1016 protocol. XMRT and IMRT solutions were assessed using metrics suggested by International Commission on Radiation Units and Measurements report 83. The Gurobi solver was used in conjunction with the CVX package to solve each optimization problem. Dose calculations and analysis were done in CERR using Monte Carlo dose calculation with VMC{sub ++}. Results: Both XMRT and IMRT solutions met all clinical criteria. Trade-offs were observed between improved dose uniformity to the primary target volume (PTV1) and increased dose to some of the surrounding healthy organs for XMRT compared to IMRT. On average, IMRT improved dose to the contralateral parotid gland and spinal cord while XMRT improved dose to the brainstem and mandible. Conclusion: Bi-energy XMRT optimization for H and N patients provides benefits in terms of improved dose uniformity to the primary target and reduced dose to some healthy structures, at the expense of increased dose to other healthy structures when compared with IMRT.

  20. Esophagus and contralateral lung-sparing IMRT for locally advanced lung cancer in the community hospital setting

    Directory of Open Access Journals (Sweden)

    Johnny eKao

    2015-06-01

    Full Text Available Background: The optimal technique for performing lung IMRT remains poorly defined. We hypothesize that improved dose distributions associated with normal tissue sparing IMRT can allow for safe dose escalation resulting in decreased acute and late toxicity. Methods: We performed a retrospective analysis of 82 consecutive lung cancer patients treated with curative intent from 1/10 to 9/14. From 1/10 to 4/12, 44 patients were treated with the community standard of 3-dimensional conformal radiotherapy or IMRT without specific esophagus or contralateral lung constraints (standard RT. From 5/12 to 9/14, 38 patients were treated with normal tissue-sparing IMRT with selective sparing of contralateral lung and esophagus. The study endpoints were dosimetry, toxicity and overall survival.Results: Despite higher mean prescribed radiation doses in the normal tissue-sparing IMRT cohort (64.5 Gy vs. 60.8 Gy, p=0.04, patients treated with normal tissue-sparing IMRT had significantly lower lung V20, V10, V5, mean lung, maximum esophagus and mean esophagus doses compared to patients treated with standard RT (p≤0.001. Patients in the normal tissue-sparing IMRT group had reduced acute grade ≥3 esophagitis (0% vs. 11%, p<0.001, acute grade ≥2 weight loss (2% vs. 16%, p=0.04, late grade ≥2 pneumonitis (7% vs. 21%, p=0.02. The 2-year overall survival was 52% with normal tissue-sparing IMRT arm compared to 28% for standard RT (p=0.015.Conclusion: These data provide proof of principle that suboptimal radiation dose distributions are associated with significant acute and late lung and esophageal toxicity that may result in hospitalization or even premature mortality. Strict attention to contralateral lung and esophageal dose volume constraints are feasible in the community hospital setting without sacrificing disease control.

  1. Intensity-modulated radiation therapy (IMRT) of cancers of the head and neck: Comparison of split-field and whole-field techniques

    International Nuclear Information System (INIS)

    Dabaja, Bouthaina; Salehpour, Mohammad R.; Rosen, Isaac; Tung, Sam; Morrison, William H.; Ang, K. Kian; Garden, Adam S.

    2005-01-01

    Background: Oropharynx cancers treated with intensity-modulated radiation (IMRT) are often treated with a monoisocentric or half-beam technique (HB). IMRT is delivered to the primary tumor and upper neck alone, while the lower neck is treated with a matching anterior beam. Because IMRT can treat the entire volume or whole field (WF), the primary aim of the study was to test the ability to plan cases using WF-IMRT while obtaining an optimal plan and acceptable dose distribution and also respecting normal critical structures. Methods and Materials: Thirteen patients with early-stage oropharynx cancers had treatment plans created with HB-IMRT and WF-IMRT techniques. Plans were deemed acceptable if they met the planning guidelines (as defined or with minor violations) of the Radiation Therapy Oncology Group protocol H0022. Comparisons included coverage to the planning target volume (PTV) of the primary (PTV66) and subclinical disease (PTV54). We also compared the ability of both techniques to respect the tolerance of critical structures. Results: The volume of PTV66 treated to >110% was less in 9 of the 13 patients in the WF-IMRT plan as compared to the HB-IMRT plan. The calculated mean volume receiving >110% for all patients planned with WF-IMRT was 9.3% (0.8%-25%) compared to 13.7% (2.7%-23.7%) with HB-IMRT (p = 0.09). The PTV54 volume receiving >110% of dose was less in 10 of the 13 patients planned with WF-IMRT compared to HB-IMRT. The mean doses to all critical structures except the larynx were comparable with each plan. The mean dose to the larynx was significantly less (p = 0.001), 18.7 Gy, with HB-IMRT compared to 47 Gy with WF-IMRT. Conclusions: Regarding target volumes, acceptable plans can be generated with either WF-IMRT or HB-IMRT. WF-IMRT has an advantage if uncertainty at the match line is a concern, whereas HB-IMRT, particularly in cases not involving the base of tongue, can achieve much lower doses to the larynx

  2. Method to account for dose fractionation in analysis of IMRT plans: Modified equivalent uniform dose

    International Nuclear Information System (INIS)

    Park, Clinton S.; Kim, Yongbok; Lee, Nancy; Bucci, Kara M.; Quivey, Jeanne M.; Verhey, Lynn J.; Xia Ping

    2005-01-01

    Purpose: To propose a modified equivalent uniform dose (mEUD) to account for dose fractionation using the biologically effective dose without losing the advantages of the generalized equivalent uniform dose (gEUD) and to report the calculated mEUD and gEUD in clinically used intensity-modulated radiotherapy (IMRT) plans. Methods and Materials: The proposed mEUD replaces the dose to each voxel in the gEUD formulation by a biologically effective dose with a normalization factor. We propose to use the term mEUD D o /n o that includes the total dose (D o ) and number of fractions (n o ) and to use the term mEUD o that includes the same total dose but a standard fraction size of 2 Gy. A total of 41 IMRT plans for patients with nasopharyngeal cancer treated at our institution between October 1997 and March 2002 were selected for the study. The gEUD and mEUD were calculated for the planning gross tumor volume (pGTV), planning clinical tumor volume (pCTV), parotid glands, and spinal cord. The prescription dose for these patients was 70 Gy to >95% of the pGTV and 59.4 Gy to >95% of the pCTV in 33 fractions. Results: The calculated average gEUD was 72.2 ± 2.4 Gy for the pGTV, 54.2 ± 7.1 Gy for the pCTV, 26.7 ± 4.2 Gy for the parotid glands, and 34.1 ± 6.8 Gy for the spinal cord. The calculated average mEUD D o /n o using 33 fractions was 71.7 ± 3.5 Gy for mEUD 70/33 of the pGTV, 49.9 ± 7.9 Gy for mEUD 59.5/33 of the pCTV, 27.6 ± 4.8 Gy for mEUD 26/33 of the parotid glands, and 32.7 ± 7.8 Gy for mEUD 45/33 of the spinal cord. Conclusion: The proposed mEUD, combining the gEUD with the biologically effective dose, preserves all advantages of the gEUD while reflecting the fractionation effects and linear and quadratic survival characteristics

  3. Domestic comparison of radiation treatment techniques for breast cancer: 3D-CRT, IMRT and VMAT

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Bo Ram; Yoon, Myong Geun [Dept. of Bio-convergence Engineering, College of Health Science, Korea University, Seoul (Korea, Republic of); Lee, Sun Young [Dept. of Radiation Oncology, Yusung Sun Medical Center, Daejeon (Korea, Republic of)

    2013-09-15

    The purpose of this study is to compare method in the treatment of breast cancer using dose index. And, it is to find the optimized treatment technique to the patient. The phantom filled with tissue-equivalent material were used simulation and treatment as techniques of 3D-CRT, IMRT, VMAT was planned using Eclipse v10. By using HI(homogeneity index), CI(Conformity index), OE (Organ equivalent dose), EAR(Excess Absolute Risk), were assessed for each treatment plans. HI and CI of 3D-CRT, IMRT, VMAT were calculated 16.89, 11.21, 9.55 and 0.59, 0.61, 0.83. The organ average doses of Lt lung, Rt lung, liver, heart, esophagus, cord, Lt breast, trachea and stomach were 0.01 ∼ 2.02 Gy, 0.36 ∼ 5.01 Gy, 0.25 ∼ 2.49 Gy, 0.14 ∼ 6.92 Gy, 0.03 ∼ 2.02 Gy, 0.01 ∼ 1.06 Gy, 0.25 ∼ 6.08 Gy, 0.08 ∼ 0.59 Gy, 0.01 ∼ 1.34 Gy, respectively. The OED, EAR of the IMRT and VMAT show higher than 3D-CRT. As the result of this study, we could confirm being higher dose index(HI, CI) in IMRT and VMAT than 3D-CRT, but doses of around normal organs was higher IMRT, VMAT than 3D-CRT.

  4. Influence of daily setup measurements and corrections on the estimated delivered dose during IMRT treatment of prostate cancer patients

    International Nuclear Information System (INIS)

    Haaren, Paul M.A. van; Bel, Arjan; Hofman, Pieter; Vulpen, Marco van; Kotte, Alexis N.T.J.; Heide, Uulke A. van der

    2009-01-01

    Purpose: To evaluate the impact of marker-based position verification, using daily imaging and an off-line correction protocol, by calculating the delivered dose to prostate, rectum and bladder. Methods: Prostate cancer patients (n = 217) were treated with IMRT, receiving 35 daily fractions. Plans with five beams were optimized taking target coverage (CTV, boost) and organs-at-risk (rectum and bladder) into account. PTV margins were 8 mm. Prostate position was verified daily using implanted fiducial gold markers by imaging the first segment of all the five beams on an EPID. Setup deviations were corrected off-line using an adapted shrinking-action-level protocol. The estimated delivered dose, including daily organ movements, was calculated using a version of PLATO's dose engine, enabling batch processing of large numbers of patients. The dose was calculated ± inclusion of setup corrections, and was evaluated relative to the original static plan. The marker-based measurements were considered representative for all organs. Results: Daily organ movements would result in an underdosage of 2-3 Gy to CTV and boost volume relative to the original plan, which was prevented by daily setup corrections. The dose to rectum and bladder was on average unchanged, but a large spread was introduced by organ movements, which was reduced by including setup corrections. Conclusions: Without position verification and setup corrections, margins of 8mm would be insufficient to account for position uncertainties during IMRT of prostate cancer. With the daily off-line correction protocol, the remaining variations are accommodated adequately

  5. Use experience and problems in the optimization of intensity modulated radiation therapy (IMRT). Focus on head and neck

    International Nuclear Information System (INIS)

    Ariji, Takaki; Ueda, Takashi; Kitoh, Satoshi; Goka, Tomonori; Kameoka, Satoru; Kohno, Ryosuke; Nishio, Teiji; Kawashima, Mitsuhiko

    2010-01-01

    We present the main points of the optimization in IMRT. The skin surface of the planned target volume was reduced by a few millimeters, in view of the limitations of a calculation grid in accurately estimating the influence of build-up or contamination of electrons. Air cavities such as nasal or oral cavities were, in general, filled with water equivalent density in the dose calculation. Planned target volume was contracted by 5 mm when planning target volume (PTV) of a higher prescribed dose was delineated adjacent to it. The 5 mm width of ring-shaped region of interest (ROI) was set at 5 mm outside of the entire PTV to eliminate hot spots. Physical quality assurance is extremely important to eradicate unexpected dose inhomogeneity, and meticulous efforts are required. (author)

  6. Spatial resolution of 2D ionization chamber arrays for IMRT dose verification: single-detector size and sampling step width

    International Nuclear Information System (INIS)

    Poppe, Bjoern; Djouguela, Armand; Blechschmidt, Arne; Willborn, Kay; Ruehmann, Antje; Harder, Dietrich

    2007-01-01

    The spatial resolution of 2D detector arrays equipped with ionization chambers or diodes, used for the dose verification of IMRT treatment plans, is limited by the size of the single detector and the centre-to-centre distance between the detectors. Optimization criteria with regard to these parameters have been developed by combining concepts of dosimetry and pattern analysis. The 2D-ARRAY Type 10024 (PTW-Freiburg, Germany), single-chamber cross section 5 x 5 mm 2 , centre-to-centre distance between chambers in each row and column 10 mm, served as an example. Additional frames of given dose distributions can be taken by shifting the whole array parallel or perpendicular to the MLC leaves by, e.g., 5 mm. The size of the single detector is characterized by its lateral response function, a trapezoid with 5 mm top width and 9 mm base width. Therefore, values measured with the 2D array are regarded as sample values from the convolution product of the accelerator generated dose distribution and this lateral response function. Consequently, the dose verification, e.g., by means of the gamma index, is performed by comparing the measured values of the 2D array with the values of the convolution product of the treatment planning system (TPS) calculated dose distribution and the single-detector lateral response function. Sufficiently small misalignments of the measured dose distributions in comparison with the calculated ones can be detected since the lateral response function is symmetric with respect to the centre of the chamber, and the change of dose gradients due to the convolution is sufficiently small. The sampling step width of the 2D array should provide a set of sample values representative of the sampled distribution, which is achieved if the highest spatial frequency contained in this function does not exceed the 'Nyquist frequency', one half of the sampling frequency. Since the convolution products of IMRT-typical dose distributions and the single

  7. Tomotherapy: IMRT and tomographic verification

    International Nuclear Information System (INIS)

    Mackie, T.R.

    2000-01-01

    Full text: External beam radiation therapy delivery began around the turn of the century with the use of one or a few kilovoltage beams directed to the presumed site of the tumor. Often the treatment lasted until erythema dose was reached. Delivering the beams rotationally allowed the dose to be focused on the tumor and the skin to be spared. With the advent of megavoltage radiation therapy in the 1950's, using Co-60 teletherapy and betatrons, the treatment could once again be delivered from only a few beam directions and the dose to the skin would be kept below tolerance. Fields were shaped by lead blocks and later by custom-made blocks fabricated from low-melting temperature heavy metal. Linear accelerators did not fundamentally change the way in which radiation was delivered. It is likely that this delivery paradigm would not have changed had it not been for the advent of computers. Brahme and Cormack showed in the late 1980's that highly conformal treatments could be delivered with non-uniform intensity beams. At that time the only way in which the intensity modulated beams could be delivered was using custom-milled compensators. Fabricating and using compensators for multiple fields is time-consuming and labor-intensive. Serial tomotherapy was the first successful delivery method for IMRT and went back to the earlier practice of rotation therapy. The NOMOS Peacock system uses a binary (on-off) multileaf collimator (MLC) system to modulate a fan beam of radiation. It uses an optimization system to determine when leaves should be opened and closed. The system delivers two beam slices at once and the couch is indexed to the next slices by precisely translating the couch. This approach was first used in 1994 and to-date has treated several thousand patients. Prior to the advent of IMRT, accelerator vendors introduced the multileaf collimator (MLC) to provide field shaping without the need to fabricate custom blocking. Most new linear accelerator purchases today

  8. SU-F-T-356: DosimetricComparison of VMAT Vs Step and Shoot IMRT Plans for Stage III Lung CancerPatients with Mediastinal Involvement

    Energy Technology Data Exchange (ETDEWEB)

    Pearson, D; Bogue, J [University of Toledo, Toledo, OH (United States)

    2016-06-15

    Purpose: For Stage III lung cancers that entail treatment of some or all of the mediastinum, anterior-posterior focused Step and Shoot IMRT (SS-IMRT) and VMAT plans have been clinically used to deliver the prescribed dose while working to minimize lung dose and avoid other critical structures. A comparison between the two planning methods was completed to see which treatment method is superior and minimizes dose to healthy lung tissue. Methods: Ten patients who were recently treated with SS-IMRT or VMAT plans for Stage III lung cancer with mediastinal involvement were selected. All patients received a simulation CT for treatment planning, as well as a 4D CT and PET/CT fusion for target delineation. Plans were prescribed 6250 cGy in 25 fractions and normalized such that 100% of the prescription dose covered 95% of the PTV. Clinically approved SS-IMRT or VMAT plans were then copied and planned using the alternative modality with identical optimization criteria. SS-IMRT plans utilized seven to nine beams distributed around the patient while the VMAT plans consisted of two full 360 degree arcs. Plans were compared for the lung volume receiving 20 Gy (V20). Results: Both SS-IMRT and VMAT can be used to achieve clinical treatment plans for patients with Stage III Lung cancer with targets encompassing the mediastinum. VMAT plans produced an average V20 of 23.0+/−8.3% and SS-IMRT produced an average of 24.2+/−10.0%. Conclusion: Results indicate that either method can achieve comparable dose distributions, however, VMAT can allow the optimizer to distribute dose over paths of minimal lung tissue and reduce the V20. Therefore, creating a VMAT with constraints identical to an SS-IMRT plan could help to reduce the V20 in clinical treatment plans.

  9. SU-F-T-356: DosimetricComparison of VMAT Vs Step and Shoot IMRT Plans for Stage III Lung CancerPatients with Mediastinal Involvement

    International Nuclear Information System (INIS)

    Pearson, D; Bogue, J

    2016-01-01

    Purpose: For Stage III lung cancers that entail treatment of some or all of the mediastinum, anterior-posterior focused Step and Shoot IMRT (SS-IMRT) and VMAT plans have been clinically used to deliver the prescribed dose while working to minimize lung dose and avoid other critical structures. A comparison between the two planning methods was completed to see which treatment method is superior and minimizes dose to healthy lung tissue. Methods: Ten patients who were recently treated with SS-IMRT or VMAT plans for Stage III lung cancer with mediastinal involvement were selected. All patients received a simulation CT for treatment planning, as well as a 4D CT and PET/CT fusion for target delineation. Plans were prescribed 6250 cGy in 25 fractions and normalized such that 100% of the prescription dose covered 95% of the PTV. Clinically approved SS-IMRT or VMAT plans were then copied and planned using the alternative modality with identical optimization criteria. SS-IMRT plans utilized seven to nine beams distributed around the patient while the VMAT plans consisted of two full 360 degree arcs. Plans were compared for the lung volume receiving 20 Gy (V20). Results: Both SS-IMRT and VMAT can be used to achieve clinical treatment plans for patients with Stage III Lung cancer with targets encompassing the mediastinum. VMAT plans produced an average V20 of 23.0+/−8.3% and SS-IMRT produced an average of 24.2+/−10.0%. Conclusion: Results indicate that either method can achieve comparable dose distributions, however, VMAT can allow the optimizer to distribute dose over paths of minimal lung tissue and reduce the V20. Therefore, creating a VMAT with constraints identical to an SS-IMRT plan could help to reduce the V20 in clinical treatment plans.

  10. SU-F-T-336: A Quick Auto-Planning (QAP) Method for Patient Intensity Modulated Radiotherapy (IMRT)

    International Nuclear Information System (INIS)

    Peng, J; Zhang, Z; Wang, J; Xie, J; Lu, S; Zhao, J; Hu, W

    2016-01-01

    Purpose: The aim of this study is to develop a quick auto-planning system that permits fast patient IMRT planning with conformal dose to the target without manual field alignment and time-consuming dose distribution optimization. Methods: The planning target volume (PTV) of the source and the target patient were projected to the iso-center plane in certain beameye- view directions to derive the 2D projected shapes. Assuming the target interior was isotropic for each beam direction boundary analysis under polar coordinate was performed to map the source shape boundary to the target shape boundary to derive the source-to-target shape mapping function. The derived shape mapping function was used to morph the source beam aperture to the target beam aperture over all segments in each beam direction. The target beam weights were re-calculated to deliver the same dose to the reference point (iso-center) as the source beam did in the source plan. The approach was tested on two rectum patients (one source patient and one target patient). Results: The IMRT planning time by QAP was 5 seconds on a laptop computer. The dose volume histograms and the dose distribution showed the target patient had the similar PTV dose coverage and OAR dose sparing with the source patient. Conclusion: The QAP system can instantly and automatically finish the IMRT planning without dose optimization.

  11. Conformal intensity-modulated radiotherapy (IMRT) delivered by robotic linac - testing IMRT to the limit?

    International Nuclear Information System (INIS)

    Webb, S.

    1999-01-01

    In this paper it is proposed that intensity-modulated radiotherapy (IMRT) could be delivered optimally by a short-length linac mounted on a robotic arm. The robot would allow the linac to 'plant' narrow pencils of photon radiation with any orientation (excluding zones within which the linac and couch might collide) relative to the planning target volume (PTV). The treatment is specified by the trajectory of the robot and by the number of monitor units (MUs) delivered at each robotic orientation. An inverse-planning method to determine the optimum robotic trajectory is presented. It is shown that for complex PTVs, specifically those with concavities in their outline, the conformality of the treatment is improved by the use of a complex trajectory in comparison with a less complex constrained trajectory and this improvement is quantified. It is concluded that robotic linac delivery would lead to a great flexibility in those IMRT treatments requiring very complicated dose distributions with complex 3D shapes. However, even using very fast computers, the goal of determining whether robotic linac delivery is the ultimate IMRT cannot be conclusively reached at present. (author)

  12. Prostate Dose Escalation by Innovative Inverse Planning-Driven IMRT

    Science.gov (United States)

    2006-11-01

    fLJ and at each step, we find the minimizer u,\\ of J’. The Euler-Lagrange equation for the regularized J’ functional is u- div ( 1 Vu )= f E S1,2A...GD, Agazaryan N, Solberg TD . 2003. The effects of tumor motion on planning and delivery of respiratory-gated IMRT. Med Phys 30:1052-1066. Jaffray DA...modulated) radiation therapy: a review. Phys Med Biol 51 :R403-425. Wink NM, McNitt-Gray MF, Solberg TD . 2005. Optimization of multi-slice helical

  13. SU-F-T-428: An Optimization-Based Commissioning Tool for Finite Size Pencil Beam Dose Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y; Tian, Z; Song, T; Jia, X; Gu, X; Jiang, S [UT Southwestern Medical Center, Dallas, TX (United States)

    2016-06-15

    Purpose: Finite size pencil beam (FSPB) algorithms are commonly used to pre-calculate the beamlet dose distribution for IMRT treatment planning. FSPB commissioning, which usually requires fine tuning of the FSPB kernel parameters, is crucial to the dose calculation accuracy and hence the plan quality. Yet due to the large number of beamlets, FSPB commissioning could be very tedious. This abstract reports an optimization-based FSPB commissioning tool we have developed in MatLab to facilitate the commissioning. Methods: A FSPB dose kernel generally contains two types of parameters: the profile parameters determining the dose kernel shape, and a 2D scaling factors accounting for the longitudinal and off-axis corrections. The former were fitted using the penumbra of a reference broad beam’s dose profile with Levenberg-Marquardt algorithm. Since the dose distribution of a broad beam is simply a linear superposition of the dose kernel of each beamlet calculated with the fitted profile parameters and scaled using the scaling factors, these factors could be determined by solving an optimization problem which minimizes the discrepancies between the calculated dose of broad beams and the reference dose. Results: We have commissioned a FSPB algorithm for three linac photon beams (6MV, 15MV and 6MVFFF). Dose of four field sizes (6*6cm2, 10*10cm2, 15*15cm2 and 20*20cm2) were calculated and compared with the reference dose exported from Eclipse TPS system. For depth dose curves, the differences are less than 1% of maximum dose after maximum dose depth for most cases. For lateral dose profiles, the differences are less than 2% of central dose at inner-beam regions. The differences of the output factors are within 1% for all the three beams. Conclusion: We have developed an optimization-based commissioning tool for FSPB algorithms to facilitate the commissioning, providing sufficient accuracy of beamlet dose calculation for IMRT optimization.

  14. Can All Centers Plan Intensity-Modulated Radiotherapy (IMRT) Effectively? An External Audit of Dosimetric Comparisons Between Three-Dimensional Conformal Radiotherapy and IMRT for Adjuvant Chemoradiation for Gastric Cancer

    International Nuclear Information System (INIS)

    Chung, Hans T.; Lee, Brian; Park, Eileen; Lu, Jiade J.; Xia Ping

    2008-01-01

    Purpose: To compare dosimetric endpoints between three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) at our center with limited IMRT experience, and to perform an external audit of the IMRT plans. Methods and Materials: Ten patients, who received adjuvant chemoradiation for gastric cancer, formed the study cohort. For standardization, the planning target volume (PTV) and organs at risk were recontoured with the assistance of a study protocol radiologic atlas. The cohort was replanned with CMS Xio to generate coplanar 3D-CRT and IMRT plans. All 10 datasets, including volumes but without the plans (i.e., blinded), were transmitted to an experienced center where IMRT plans were designed using Nomos Corvus (IMRT-C) and ADAC Pinnacle (IMRT-P). All IMRT plans were normalized to D95% receiving 45 Gy. Results: Intensity-modulated radiotherapy yielded higher PTV V45 (volume that receives ≥45 Gy) (p < 0.001) than 3D-CRT. No difference in V20 was seen in the right (p = 0.9) and left (p 0.3) kidneys, but the liver mean dose (p < 0.001) was superior with IMRT. For the external audit, IMRT-C (p = 0.002) and IMRT-P (p < 0.001) achieved significantly lower left kidney V20 than IMRT, and IMRT-P (p < 0.001) achieved lower right kidney V20 than IMRT. The IMRT-C (p = 0.003) but not IMRT-P (p = 0.6) had lower liver mean doses than IMRT. Conclusions: At our institution with early IMRT experience, IMRT improved PTV dose coverage and liver doses but not kidney doses. An external audit of IMRT plans showed that an experienced center can yield superior IMRT plans

  15. SU-F-T-335: Piecewise Uniform Dose Prescription and Optimization Based On PET/CT Images

    Energy Technology Data Exchange (ETDEWEB)

    Liu, G; Liu, J [Hunan University, Changsha, Hunan (China)

    2016-06-15

    Purpose: In intensity modulated radiation therapy (IMRT), the tumor target volume is given a uniform dose prescription, which does not consider the heterogeneous characteristics of tumor such as hypoxia, clonogen density, radiosensitivity, tumor proliferation rate and so on. Our goal is to develop a nonuniform target dose prescription method which can spare organs at risk (OARs) better and does not decrease the tumor control probability (TCP). Methods: We propose a piecewise uniform dose prescription (PUDP) based on PET/CT images of tumor. First, we propose to delineate biological target volumes (BTV) and sub-biological target volumes (sub-BTVs) by our Hierarchical Mumford-Shah Vector Model based on PET/CT images of tumor. Then, in order to spare OARs better, we make the BTV mean dose minimized while restrict the TCP to a constant. So, we can get a general formula for determining an optimal dose prescription based on a linearquadratic model (LQ). However, this dose prescription is high heterogeneous, it is very difficult to deliver by IMRT. Therefore we propose to use the equivalent uniform dose (EUD) in each sub-BTV as its final dose prescription, which makes a PUDP for the BTV. Results: We have evaluated the IMRT planning of a patient with nasopharyngeal carcinoma respectively using PUDP and UDP. The results show that the highest and mean doses inside brain stem are 48.425Gy and 19.151Gy respectively when the PUDP is used for IMRT planning, while they are 52.975Gy and 20.0776Gy respectively when the UDP is used. Both of the resulting TCPs(0.9245, 0.9674) are higher than the theoretical TCP(0.8739), when 70Gy is delivered to the BTV. Conclusion: Comparing with the UDP, the PUDP can spare the OARs better while the resulting TCP by PUDP is not significantly lower than by UDP. This work was supported in part by National Natural Science Foundation of China undergrant no.61271382 and by the foundation for construction of scientific project platform forthe cancer

  16. SU-F-T-335: Piecewise Uniform Dose Prescription and Optimization Based On PET/CT Images

    International Nuclear Information System (INIS)

    Liu, G; Liu, J

    2016-01-01

    Purpose: In intensity modulated radiation therapy (IMRT), the tumor target volume is given a uniform dose prescription, which does not consider the heterogeneous characteristics of tumor such as hypoxia, clonogen density, radiosensitivity, tumor proliferation rate and so on. Our goal is to develop a nonuniform target dose prescription method which can spare organs at risk (OARs) better and does not decrease the tumor control probability (TCP). Methods: We propose a piecewise uniform dose prescription (PUDP) based on PET/CT images of tumor. First, we propose to delineate biological target volumes (BTV) and sub-biological target volumes (sub-BTVs) by our Hierarchical Mumford-Shah Vector Model based on PET/CT images of tumor. Then, in order to spare OARs better, we make the BTV mean dose minimized while restrict the TCP to a constant. So, we can get a general formula for determining an optimal dose prescription based on a linearquadratic model (LQ). However, this dose prescription is high heterogeneous, it is very difficult to deliver by IMRT. Therefore we propose to use the equivalent uniform dose (EUD) in each sub-BTV as its final dose prescription, which makes a PUDP for the BTV. Results: We have evaluated the IMRT planning of a patient with nasopharyngeal carcinoma respectively using PUDP and UDP. The results show that the highest and mean doses inside brain stem are 48.425Gy and 19.151Gy respectively when the PUDP is used for IMRT planning, while they are 52.975Gy and 20.0776Gy respectively when the UDP is used. Both of the resulting TCPs(0.9245, 0.9674) are higher than the theoretical TCP(0.8739), when 70Gy is delivered to the BTV. Conclusion: Comparing with the UDP, the PUDP can spare the OARs better while the resulting TCP by PUDP is not significantly lower than by UDP. This work was supported in part by National Natural Science Foundation of China undergrant no.61271382 and by the foundation for construction of scientific project platform forthe cancer

  17. Expected treatment dose construction and adaptive inverse planning optimization: Implementation for offline head and neck cancer adaptive radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Yan Di; Liang Jian [Department of Radiation Oncology, Beaumont Health System, Royal Oak, Michigan 48073 (United States)

    2013-02-15

    Purpose: To construct expected treatment dose for adaptive inverse planning optimization, and evaluate it on head and neck (h and n) cancer adaptive treatment modification. Methods: Adaptive inverse planning engine was developed and integrated in our in-house adaptive treatment control system. The adaptive inverse planning engine includes an expected treatment dose constructed using the daily cone beam (CB) CT images in its objective and constrains. Feasibility of the adaptive inverse planning optimization was evaluated retrospectively using daily CBCT images obtained from the image guided IMRT treatment of 19 h and n cancer patients. Adaptive treatment modification strategies with respect to the time and the number of adaptive inverse planning optimization during the treatment course were evaluated using the cumulative treatment dose in organs of interest constructed using all daily CBCT images. Results: Expected treatment dose was constructed to include both the delivered dose, to date, and the estimated dose for the remaining treatment during the adaptive treatment course. It was used in treatment evaluation, as well as in constructing the objective and constraints for adaptive inverse planning optimization. The optimization engine is feasible to perform planning optimization based on preassigned treatment modification schedule. Compared to the conventional IMRT, the adaptive treatment for h and n cancer illustrated clear dose-volume improvement for all critical normal organs. The dose-volume reductions of right and left parotid glands, spine cord, brain stem and mandible were (17 {+-} 6)%, (14 {+-} 6)%, (11 {+-} 6)%, (12 {+-} 8)%, and (5 {+-} 3)% respectively with the single adaptive modification performed after the second treatment week; (24 {+-} 6)%, (22 {+-} 8)%, (21 {+-} 5)%, (19 {+-} 8)%, and (10 {+-} 6)% with three weekly modifications; and (28 {+-} 5)%, (25 {+-} 9)%, (26 {+-} 5)%, (24 {+-} 8)%, and (15 {+-} 9)% with five weekly modifications. Conclusions

  18. General strategy for the protection of organs at risk in IMRT therapy of a moving body

    International Nuclear Information System (INIS)

    Abolfath, Ramin M.; Papiez, Lech

    2009-01-01

    We investigated protection strategies of organs at risk (OARs) in intensity modulated radiation therapy (IMRT). These strategies apply to delivery of IMRT to moving body anatomies that show relative displacement of OAR in close proximity to a tumor target. We formulated an efficient genetic algorithm which makes it possible to search for global minima in a complex landscape of multiple irradiation strategies delivering a given, predetermined intensity map to a target. The optimal strategy was investigated with respect to minimizing the dose delivered to the OAR. The optimization procedure developed relies on variability of all parameters available for control of radiation delivery in modern linear accelerators, including adaptation of leaf trajectories and simultaneous modification of beam dose rate during irradiation. We showed that the optimization algorithms lead to a significant reduction in the dose delivered to OAR in cases where organs at risk move relative to a treatment target.

  19. General strategy for the protection of organs at risk in IMRT therapy of a moving body

    Energy Technology Data Exchange (ETDEWEB)

    Abolfath, Ramin M.; Papiez, Lech [Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390 (United States)

    2009-07-15

    We investigated protection strategies of organs at risk (OARs) in intensity modulated radiation therapy (IMRT). These strategies apply to delivery of IMRT to moving body anatomies that show relative displacement of OAR in close proximity to a tumor target. We formulated an efficient genetic algorithm which makes it possible to search for global minima in a complex landscape of multiple irradiation strategies delivering a given, predetermined intensity map to a target. The optimal strategy was investigated with respect to minimizing the dose delivered to the OAR. The optimization procedure developed relies on variability of all parameters available for control of radiation delivery in modern linear accelerators, including adaptation of leaf trajectories and simultaneous modification of beam dose rate during irradiation. We showed that the optimization algorithms lead to a significant reduction in the dose delivered to OAR in cases where organs at risk move relative to a treatment target.

  20. SU-E-T-256: Development of a Monte Carlo-Based Dose-Calculation System in a Cloud Environment for IMRT and VMAT Dosimetric Verification

    Energy Technology Data Exchange (ETDEWEB)

    Fujita, Y [Tokai University School of Medicine, Isehara, Kanagawa (Japan)

    2015-06-15

    Purpose: Intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) are techniques that are widely used for treating cancer due to better target coverage and critical structure sparing. The increasing complexity of IMRT and VMAT plans leads to decreases in dose calculation accuracy. Monte Carlo simulations are the most accurate method for the determination of dose distributions in patients. However, the simulation settings for modeling an accurate treatment head are very complex and time consuming. The purpose of this work is to report our implementation of a simple Monte Carlo simulation system in a cloud-computing environment for dosimetric verification of IMRT and VMAT plans. Methods: Monte Carlo simulations of a Varian Clinac linear accelerator were performed using the BEAMnrc code, and dose distributions were calculated using the DOSXYZnrc code. Input files for the simulations were automatically generated from DICOM RT files by the developed web application. We therefore must only upload the DICOM RT files through the web interface, and the simulations are run in the cloud. The calculated dose distributions were exported to RT Dose files that can be downloaded through the web interface. The accuracy of the calculated dose distribution was verified by dose measurements. Results: IMRT and VMAT simulations were performed and good agreement results were observed for measured and MC dose comparison. Gamma analysis with a 3% dose and 3 mm DTA criteria shows a mean gamma index value of 95% for the studied cases. Conclusion: A Monte Carlo-based dose calculation system has been successfully implemented in a cloud environment. The developed system can be used for independent dose verification of IMRT and VMAT plans in routine clinical practice. The system will also be helpful for improving accuracy in beam modeling and dose calculation in treatment planning systems. This work was supported by JSPS KAKENHI Grant Number 25861057.

  1. SU-E-T-256: Development of a Monte Carlo-Based Dose-Calculation System in a Cloud Environment for IMRT and VMAT Dosimetric Verification

    International Nuclear Information System (INIS)

    Fujita, Y

    2015-01-01

    Purpose: Intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) are techniques that are widely used for treating cancer due to better target coverage and critical structure sparing. The increasing complexity of IMRT and VMAT plans leads to decreases in dose calculation accuracy. Monte Carlo simulations are the most accurate method for the determination of dose distributions in patients. However, the simulation settings for modeling an accurate treatment head are very complex and time consuming. The purpose of this work is to report our implementation of a simple Monte Carlo simulation system in a cloud-computing environment for dosimetric verification of IMRT and VMAT plans. Methods: Monte Carlo simulations of a Varian Clinac linear accelerator were performed using the BEAMnrc code, and dose distributions were calculated using the DOSXYZnrc code. Input files for the simulations were automatically generated from DICOM RT files by the developed web application. We therefore must only upload the DICOM RT files through the web interface, and the simulations are run in the cloud. The calculated dose distributions were exported to RT Dose files that can be downloaded through the web interface. The accuracy of the calculated dose distribution was verified by dose measurements. Results: IMRT and VMAT simulations were performed and good agreement results were observed for measured and MC dose comparison. Gamma analysis with a 3% dose and 3 mm DTA criteria shows a mean gamma index value of 95% for the studied cases. Conclusion: A Monte Carlo-based dose calculation system has been successfully implemented in a cloud environment. The developed system can be used for independent dose verification of IMRT and VMAT plans in routine clinical practice. The system will also be helpful for improving accuracy in beam modeling and dose calculation in treatment planning systems. This work was supported by JSPS KAKENHI Grant Number 25861057

  2. Influence of MLC leaf width on biologically adapted IMRT plans

    Energy Technology Data Exchange (ETDEWEB)

    Roedal, Jan; Soevik, Aaste; Malinen, Eirik (Dept. of Medical Physics, The Norwegian Radium Hospital, Oslo Univ. Hospital, Oslo (Norway)), E-mail: jan.rodal@radiumhospitalet.no

    2010-10-15

    Introduction. High resolution beam delivery may be required for optimal biology-guided adaptive therapy. In this work, we have studied the influence of multi leaf collimator (MLC) leaf widths on the treatment outcome following adapted IMRT of a hypoxic tumour. Material and methods. Dynamic contrast enhanced MR images of a dog with a spontaneous tumour in the nasal region were used to create a tentative hypoxia map following a previously published procedure. The hypoxia map was used as a basis for generating compartmental gross tumour volumes, which were utilised as planning structures in biologically adapted IMRT. Three different MLCs were employed in inverse treatment planning, with leaf widths of 2.5 mm, 5 mm and 10 mm. The number of treatment beams and the degree of step-and-shoot beam modulation were varied. By optimising the tumour control probability (TCP) function, optimal compartmental doses were derived and used as target doses in the inverse planning. Resulting IMRT dose distributions and dose volume histograms (DVHs) were exported and analysed, giving estimates of TCP and compartmental equivalent uniform doses (EUDs). The impact of patient setup accuracy was simulated. Results. The MLC with the smallest leaf width (2.5 mm) consistently gave the highest TCPs and compartmental EUDs, assuming no setup error. The difference between this MLC and the 5 mm MLC was rather small, while the MLC with 10 mm leaf width gave considerably lower TCPs. When including random and systematic setup errors, errors larger than 5 mm gave only small differences between the MLC types. For setup errors larger than 7 mm no differences were found between non-uniform and uniform dose distributions. Conclusions. Biologically adapted radiotherapy may require MLCs with leaf widths smaller than 10 mm. However, for a high probability of cure it is crucial that accurate patient setup is ensured.

  3. Rotational IMRT techniques compared to fixed gantry IMRT and Tomotherapy: multi-institutional planning study for head-and-neck cases

    Directory of Open Access Journals (Sweden)

    Lutters Gerd

    2011-02-01

    Full Text Available Abstract Background Recent developments enable to deliver rotational IMRT with standard C-arm gantry based linear accelerators. This upcoming treatment technique was benchmarked in a multi-center treatment planning study against static gantry IMRT and rotational IMRT based on a ring gantry for a complex parotid gland sparing head-and-neck technique. Methods Treatment plans were created for 10 patients with head-and-neck tumours (oropharynx, hypopharynx, larynx using the following treatment planning systems (TPS for rotational IMRT: Monaco (ELEKTA VMAT solution, Eclipse (Varian RapidArc solution and HiArt for the helical tomotherapy (Tomotherapy. Planning of static gantry IMRT was performed with KonRad, Pinnacle and Panther DAO based on step&shoot IMRT delivery and Eclipse for sliding window IMRT. The prescribed doses for the high dose PTVs were 65.1Gy or 60.9Gy and for the low dose PTVs 55.8Gy or 52.5Gy dependend on resection status. Plan evaluation was based on target coverage, conformity and homogeneity, DVHs of OARs and the volume of normal tissue receiving more than 5Gy (V5Gy. Additionally, the cumulative monitor units (MUs and treatment times of the different technologies were compared. All evaluation parameters were averaged over all 10 patients for each technique and planning modality. Results Depending on IMRT technique and TPS, the mean CI values of all patients ranged from 1.17 to 2.82; and mean HI values varied from 0.05 to 0.10. The mean values of the median doses of the spared parotid were 26.5Gy for RapidArc and 23Gy for VMAT, 14.1Gy for Tomo. For fixed gantry techniques 21Gy was achieved for step&shoot+KonRad, 17.0Gy for step&shoot+Panther DAO, 23.3Gy for step&shoot+Pinnacle and 18.6Gy for sliding window. V5Gy values were lowest for the sliding window IMRT technique (3499 ccm and largest for RapidArc (5480 ccm. The lowest mean MU value of 408 was achieved by Panther DAO, compared to 1140 for sliding window IMRT. Conclusions All

  4. SU-E-T-29: A Web Application for GPU-Based Monte Carlo IMRT/VMAT QA with Delivered Dose Verification

    International Nuclear Information System (INIS)

    Folkerts, M; Graves, Y; Tian, Z; Gu, X; Jia, X; Jiang, S

    2014-01-01

    Purpose: To enable an existing web application for GPU-based Monte Carlo (MC) 3D dosimetry quality assurance (QA) to compute “delivered dose” from linac logfile data. Methods: We added significant features to an IMRT/VMAT QA web application which is based on existing technologies (HTML5, Python, and Django). This tool interfaces with python, c-code libraries, and command line-based GPU applications to perform a MC-based IMRT/VMAT QA. The web app automates many complicated aspects of interfacing clinical DICOM and logfile data with cutting-edge GPU software to run a MC dose calculation. The resultant web app is powerful, easy to use, and is able to re-compute both plan dose (from DICOM data) and delivered dose (from logfile data). Both dynalog and trajectorylog file formats are supported. Users upload zipped DICOM RP, CT, and RD data and set the expected statistic uncertainty for the MC dose calculation. A 3D gamma index map, 3D dose distribution, gamma histogram, dosimetric statistics, and DVH curves are displayed to the user. Additional the user may upload the delivery logfile data from the linac to compute a 'delivered dose' calculation and corresponding gamma tests. A comprehensive PDF QA report summarizing the results can also be downloaded. Results: We successfully improved a web app for a GPU-based QA tool that consists of logfile parcing, fluence map generation, CT image processing, GPU based MC dose calculation, gamma index calculation, and DVH calculation. The result is an IMRT and VMAT QA tool that conducts an independent dose calculation for a given treatment plan and delivery log file. The system takes both DICOM data and logfile data to compute plan dose and delivered dose respectively. Conclusion: We sucessfully improved a GPU-based MC QA tool to allow for logfile dose calculation. The high efficiency and accessibility will greatly facilitate IMRT and VMAT QA

  5. SU-E-T-29: A Web Application for GPU-Based Monte Carlo IMRT/VMAT QA with Delivered Dose Verification

    Energy Technology Data Exchange (ETDEWEB)

    Folkerts, M [The University of Texas Southwestern Medical Ctr, Dallas, TX (United States); University of California, San Diego, La Jolla, CA (United States); Graves, Y [University of California, San Diego, La Jolla, CA (United States); Tian, Z; Gu, X; Jia, X; Jiang, S [The University of Texas Southwestern Medical Ctr, Dallas, TX (United States)

    2014-06-01

    Purpose: To enable an existing web application for GPU-based Monte Carlo (MC) 3D dosimetry quality assurance (QA) to compute “delivered dose” from linac logfile data. Methods: We added significant features to an IMRT/VMAT QA web application which is based on existing technologies (HTML5, Python, and Django). This tool interfaces with python, c-code libraries, and command line-based GPU applications to perform a MC-based IMRT/VMAT QA. The web app automates many complicated aspects of interfacing clinical DICOM and logfile data with cutting-edge GPU software to run a MC dose calculation. The resultant web app is powerful, easy to use, and is able to re-compute both plan dose (from DICOM data) and delivered dose (from logfile data). Both dynalog and trajectorylog file formats are supported. Users upload zipped DICOM RP, CT, and RD data and set the expected statistic uncertainty for the MC dose calculation. A 3D gamma index map, 3D dose distribution, gamma histogram, dosimetric statistics, and DVH curves are displayed to the user. Additional the user may upload the delivery logfile data from the linac to compute a 'delivered dose' calculation and corresponding gamma tests. A comprehensive PDF QA report summarizing the results can also be downloaded. Results: We successfully improved a web app for a GPU-based QA tool that consists of logfile parcing, fluence map generation, CT image processing, GPU based MC dose calculation, gamma index calculation, and DVH calculation. The result is an IMRT and VMAT QA tool that conducts an independent dose calculation for a given treatment plan and delivery log file. The system takes both DICOM data and logfile data to compute plan dose and delivered dose respectively. Conclusion: We sucessfully improved a GPU-based MC QA tool to allow for logfile dose calculation. The high efficiency and accessibility will greatly facilitate IMRT and VMAT QA.

  6. Dosimetric Comparison Between 3DCRT and IMRT Using Different Multileaf Collimators in the Treatment of Brain Tumors

    International Nuclear Information System (INIS)

    Ding Meisong; Newman, Francis M.S.; Chen Changhu; Stuhr, Kelly; Gaspar, Laurie E.

    2009-01-01

    We investigated the differences between 3-dimensional conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT), and the impact of collimator leaf-width on IMRT plans for the treatment of nonspherical brain tumors. Eight patients treated by 3DCRT with Novalis were selected. We developed 3 IMRT plans with different multileaf collimators (Novalis m3, Varian MLC-120, and Varian MLC-80) with the same treatment margins, number of beams, and gantry positions as in the 3DCRT treatment plans. Treatment planning utilized the BrainLAB treatment planning system. For each patient, the dose constraints and optimization parameters remained identical for all plans. The heterogeneity index, the percentage target coverage, critical structures, and normal tissue volumes receiving 50% of the prescription dose were calculated to compare the dosimetric difference. Equivalent uniform dose (EUD) and tumor control probability (TCP) were also introduced to evaluate the radiobiological effect for different plans. We found that IMRT significantly improved the target dose homogeneity compared to the 3DCRT. However, IMRT showed the same radiobiological effect as 3DCRT. For the brain tumors adjacent to (or partially overlapping with) critical structures, IMRT dramatically spared the volume of the critical structures to be irradiated. In IMRT plans, the smaller collimator leaf width could reduce the volume of critical structures irradiated to the 50% level for those partially overlapping with the brain tumors. For relatively large and spherical brain tumors, the smaller collimator leaf widths give no significant benefit

  7. Fluence map optimization (FMO) with dose–volume constraints in IMRT using the geometric distance sorting method

    International Nuclear Information System (INIS)

    Lan Yihua; Li Cunhua; Ren Haozheng; Zhang Yong; Min Zhifang

    2012-01-01

    A new heuristic algorithm based on the so-called geometric distance sorting technique is proposed for solving the fluence map optimization with dose–volume constraints which is one of the most essential tasks for inverse planning in IMRT. The framework of the proposed method is basically an iterative process which begins with a simple linear constrained quadratic optimization model without considering any dose–volume constraints, and then the dose constraints for the voxels violating the dose–volume constraints are gradually added into the quadratic optimization model step by step until all the dose–volume constraints are satisfied. In each iteration step, an interior point method is adopted to solve each new linear constrained quadratic programming. For choosing the proper candidate voxels for the current dose constraint adding, a so-called geometric distance defined in the transformed standard quadratic form of the fluence map optimization model was used to guide the selection of the voxels. The new geometric distance sorting technique can mostly reduce the unexpected increase of the objective function value caused inevitably by the constraint adding. It can be regarded as an upgrading to the traditional dose sorting technique. The geometry explanation for the proposed method is also given and a proposition is proved to support our heuristic idea. In addition, a smart constraint adding/deleting strategy is designed to ensure a stable iteration convergence. The new algorithm is tested on four cases including head–neck, a prostate, a lung and an oropharyngeal, and compared with the algorithm based on the traditional dose sorting technique. Experimental results showed that the proposed method is more suitable for guiding the selection of new constraints than the traditional dose sorting method, especially for the cases whose target regions are in non-convex shapes. It is a more efficient optimization technique to some extent for choosing constraints than

  8. Intensity modulated radiotherapy (IMRT) in bilateral retinoblastoma

    International Nuclear Information System (INIS)

    Atalar, Banu; Ozyar, Enis; Gunduz, Kaan; Gungor, Gorkem

    2010-01-01

    External beam radiotherapy (EBRT) for retinoblastoma has traditionally been done with conventional radiotherapy techniques which resulted high doses to the surrounding normal tissues. A 20 month-old girl with group D bilateral retinoblastoma underwent intensity modulated radiotherapy (IMRT) to both eyes after failing chemoreduction and focal therapies including cryotherapy and transpupillary thermotherapy. In this report, we discuss the use of IMRT as a method for reducing doses to adjacent normal tissues while delivering therapeutic doses to the tumour tissues compared with 3-dimensional conformal radiotherapy (3DCRT). At one year follow-up, the patient remained free of any obvious radiation complications. Image guided IMRT provides better dose distribution than 3DCRT in retinoblastoma eyes, delivering the therapeutic dose to the tumours and minimizing adjacent tissue damage

  9. Reducing dose to the lungs through loosing target dose homogeneity requirement for radiotherapy of non small cell lung cancer.

    Science.gov (United States)

    Miao, Junjie; Yan, Hui; Tian, Yuan; Ma, Pan; Liu, Zhiqiang; Li, Minghui; Ren, Wenting; Chen, Jiayun; Zhang, Ye; Dai, Jianrong

    2017-11-01

    It is important to minimize lung dose during intensity-modulated radiation therapy (IMRT) of nonsmall cell lung cancer (NSCLC). In this study, an approach was proposed to reduce lung dose by relaxing the constraint of target dose homogeneity during treatment planning of IMRT. Ten NSCLC patients with lung tumor on the right side were selected. The total dose for planning target volume (PTV) was 60 Gy (2 Gy/fraction). For each patient, two IMRT plans with six beams were created in Pinnacle treatment planning system. The dose homogeneity of target was controlled by constraints on the maximum and uniform doses of target volume. One IMRT plan was made with homogeneous target dose (the resulting target dose was within 95%-107% of the prescribed dose), while another IMRT plan was made with inhomogeneous target dose (the resulting target dose was more than 95% of the prescribed dose). During plan optimization, the dose of cord and heart in two types of IMRT plans were kept nearly the same. The doses of lungs, PTV and organs at risk (OARs) between two types of IMRT plans were compared and analyzed quantitatively. For all patients, the lung dose was decreased in the IMRT plans with inhomogeneous target dose. On average, the mean dose, V5, V20, and V30 of lung were reduced by 1.4 Gy, 4.8%, 3.7%, and 1.7%, respectively, and the dose to normal tissue was also reduced. These reductions in DVH values were all statistically significant (P target dose could protect lungs better and may be considered as a choice for treating NSCLC. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

  10. The role and strategy of IMRT in radiotherapy of pelvic tumors: Dose escalation and critical organ sparing in prostate cancer

    International Nuclear Information System (INIS)

    Liu, Y.-M.; Shiau, C.-Y.; Lee, M.-L.; Huang, P.-I.; Hsieh, C.-M.; Chen, P.-H.; Lin, Y.-H.; Wang, L.-W.; Yen, S.-H.

    2007-01-01

    Purpose: To investigate the intensity-modulated radiotherapy (IMRT) strategy in dose escalation of prostate and pelvic lymph nodes. Methods and Materials: Plan dosimetric data of 10 prostate cancer patients were compared with two-dimensional (2D) or IMRT techniques for pelvis (two-dimensional whole pelvic radiation therapy [2D-WPRT] or IM-WPRT) to receive 50 Gy or 54 Gy and additional prostate boost by three-dimensional conformal radiation therapy or IMRT (3D-PBRT or IM-PBRT) techniques up to 72 Gy or 78 Gy. Dose-volume histograms (DVHs), normal tissue complication probabilities (NTCP) of critical organ, and conformity of target volume in various combinations were calculated. Results: In DVH analysis, the plans with IM-WPRT (54 Gy) and additional boost up to 78 Gy had lower rectal and bladder volume percentage at 50 Gy and 60 Gy, compared with those with 2D-WPRT (50 Gy) and additional boost up to 72 Gy or 78 Gy. Those with IM-WPRT (54 Gy) also had better small bowel sparing at 30 Gy and 50 Gy, compared with those with 2D-WPRT (50 Gy). In NTCP, those with IM-WPRT and total dose of 78 Gy achieved lower complication rates in rectum and small bowel, compared with those of 2D-WPRT with total dose of 72 Gy. In conformity, those with IM-WPRT had better conformity compared with those with 2D-WPRT with significance (p < 0.005). No significant difference in DVHs, NTCP, or conformity was found between IM-PBRT and 3D-PBRT after IM-WPRT. Conclusions: Initial pelvic IMRT is the most important strategy in dose escalation and critical organ sparing. IM-WPRT is recommended for patients requiring WPRT. There is not much benefit for critical organ sparing by IMRT after 2D-WPRT

  11. Inverse vs. forward breast IMRT planning

    International Nuclear Information System (INIS)

    Mihai, Alina; Rakovitch, Eileen; Sixel, Katharina; Woo, Tony; Cardoso, Marlene; Bell, Chris; Ruschin, Mark; Pignol, Jean-Philippe

    2005-01-01

    Breast intensity-modulated radiation therapy (IMRT) improves dose distribution homogeneity within the whole breast. Previous publications report the use of inverse or forward dose optimization algorithms. Because the inverse technique is not widely available in commercial treatment planning systems, it is important to compare the 2 algorithms. The goal of this work is to compare them on a prospective cohort of 30 patients. Dose distributions were evaluated on differential dose-volume histograms using the volumes receiving more than 105% (V 105 ) and 110% (V 110 ) of the prescribed dose, and on the maximum dose (D max ) or hot spot and the sagittal dose gradient (SDG) being the gradient between the dose on inframammary crease and the dose prescribed. The data were analyzed using Wilcoxon signed rank test. The inverse planning significantly improves the V 105 (mean value 9.7% vs. 14.5%, p = 0.002), and the V 110 (mean value 1.4% vs. 3.2%, p = 0.006). However, the SDG is not statistically significantly different for either algorithm. Looking at the potential impact on skin acute reaction, although there is a significant reduction of V 110 using an inverse algorithm, it is unlikely this 1.6% volume reduction will present a significant clinical advantage over a forward algorithm. Both algorithms are equivalent in removing the hot spots on the inframammary fold, where acute skin reactions occur more frequently using a conventional wedge technique. Based on these results, we recommend that both forward and inverse algorithms should be considered for breast IMRT planning

  12. MRI-based treatment planning for radiotherapy: Dosimetric verification for prostate IMRT

    International Nuclear Information System (INIS)

    Chen, Lili; Price, Robert A.; Wang Lu; Li Jinsheng; Qin Lihong; McNeeley, Shawn; Ma, C.-M. Charlie; Freedman, Gary M.; Pollack, Alan

    2004-01-01

    Purpose: Magnetic resonance (MR) and computed tomography (CT) image fusion with CT-based dose calculation is the gold standard for prostate treatment planning. MR and CT fusion with CT-based dose calculation has become a routine procedure for intensity-modulated radiation therapy (IMRT) treatment planning at Fox Chase Cancer Center. The use of MRI alone for treatment planning (or MRI simulation) will remove any errors associated with image fusion. Furthermore, it will reduce treatment cost by avoiding redundant CT scans and save patient, staff, and machine time. The purpose of this study is to investigate the dosimetric accuracy of MRI-based treatment planning for prostate IMRT. Methods and materials: A total of 30 IMRT plans for 15 patients were generated using both MRI and CT data. The MRI distortion was corrected using gradient distortion correction (GDC) software provided by the vendor (Philips Medical System, Cleveland, OH). The same internal contours were used for the paired plans. The external contours were drawn separately between CT-based and MR imaging-based plans to evaluate the effect of any residual distortions on dosimetric accuracy. The same energy, beam angles, dose constrains, and optimization parameters were used for dose calculations for each paired plans using a treatment optimization system. The resulting plans were compared in terms of isodose distributions and dose-volume histograms (DVHs). Hybrid phantom plans were generated for both the CT-based plans and the MR-based plans using the same leaf sequences and associated monitor units (MU). The physical phantom was then irradiated using the same leaf sequences to verify the dosimetry accuracy of the treatment plans. Results: Our results show that dose distributions between CT-based and MRI-based plans were equally acceptable based on our clinical criteria. The absolute dose agreement for the planning target volume was within 2% between CT-based and MR-based plans and 3% between measured dose

  13. Stereotactic IMRT using a MMLC

    International Nuclear Information System (INIS)

    Hoban, P.; Short, R.; Biggs, D.; Rose, A.; Smee, R.; Schneider, M.

    2001-01-01

    Full text: The leaf width of the multileaf collimator (MLC) used for intensity modulated radiotherapy (IMRT ) largely determines the resolution of the intensity maps that define the entire profile of each beam. In turn it is this resolution, and consequently the achievable degree of beam modulation, that determines the ability to conform the 3D dose distribution to complex target volumes. As such, the leaf width is of more importance than in fixed-field MLC treatments where only the beam edges are affected.A Radionics micro-multileaf collimator (MMLC) with 4 mm leaf width, attached to a Siemens Primus linear accelerator, is in use for stereotactic IMRT at PbWH. Treatment planning is performed with the XPlan system including an integrated IMRT module. Cases treated have so far been with conventional fractionation, including both malignant and benign cranial lesions. Meningiomas in particular often require a complex dose distribution because of their en-plaque nature and/or proximity to the brainstem. Stereotactic localisation and fixation is with the Gill-Thomas-Cosman head-ring or Head and Neck localiser. Cases are typically planned both for fixed-field treatment and IMRT, with IMRT being used if significant benefit is seen. IMRT treatment with the Siemens MLC is also an option. A quality assurance system has been set up, including a flowchart/checklist and phantom dosimetry using TLDs. As expected, treatment plans show IMRT with the MMLC to consistently be the best option dosimetrically. In particular, for a given target coverage there is always better sparing of nearby organs at risk (OARs) with MMLC rather than MLC-based IMRT. Adjustments such as the inclusion of a margin around the target volume or an increase in the penalty for target underdosage improve coverage for MLC plans but generally at the expense of increased OAR involvement. MMLC IMRT treatments commonly require 30-50 fields and can be delivered in approximately 10-15 minutes using an autosequence

  14. WE-AB-303-06: Combining DAO with MV + KV Optimization to Improve Skin Dose Sparing with Real-Time Fluoroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Grelewicz, Z; Wiersma, R [The University of Chicago, Chicago, IL (United States)

    2015-06-15

    Purpose: Real-time fluoroscopy may allow for improved patient positioning and tumor tracking, particularly in the treatment of lung tumors. In order to mitigate the effects of the imaging dose, previous studies have demonstrated the effect of including both imaging dose and imaging constraints into the inverse treatment planning object function. That method of combined MV+kV optimization may Result in plans with treatment beams chosen to allow for more gentle imaging beam-on times. Direct-aperture optimization (DAO) is also known to produce treatment plans with fluence maps more conducive to lower beam-on times. Therefore, in this work we demonstrate the feasibility of a combination of DAO and MV+kV optimization for further optimized real-time kV imaging. Methods: Therapeutic and imaging beams were modeled in the EGSnrc Monte Carlo environment, and applied to a patient model for a previously treated lung patient to provide dose influence matrices from DOSXYZnrc. An MV + kV IMRT DAO treatment planning system was developed to compare DAO treatment plans with and without MV+kV optimization. The objective function was optimized using simulated annealing. In order to allow for comparisons between different cases of the stochastically optimized plans, the optimization was repeated twenty times. Results: Across twenty optimizations, combined MV+kV IMRT resulted in an average of 12.8% reduction in peak skin dose. Both non-optimized and MV+kV optimized imaging beams delivered, on average, mean dose of approximately 1 cGy per fraction to the target, with peak doses to target of approximately 6 cGy per fraction. Conclusion: When using DAO, MV+kV optimization is shown to Result in improvements to plan quality in terms of skin dose, when compared to the case of MV optimization with non-optimized kV imaging. The combination of DAO and MV+kV optimization may allow for real-time imaging without excessive imaging dose. Financial support for the work has been provided in part by NIH

  15. Optimization of the temporal pattern of applied dose for a single fraction of radiation: Implications for radiation therapy

    Science.gov (United States)

    Altman, Michael B.

    The increasing prevalence of intensity modulated radiation therapy (IMRT) as a treatment modality has led to a renewed interest in the potential for interaction between prolonged treatment time, as frequently associated with IMRT, and the underlying radiobiology of the irradiated tissue. A particularly relevant aspect of radiobiology is cell repair capacity, which influences cell survival, and thus directly relates to the ability to control tumors and spare normal tissues. For a single fraction of radiation, the linear quadratic (LQ) model is commonly used to relate the radiation dose to the fraction of cells surviving. The LQ model implies a dependence on two time-related factors which correlate to radiobiological effects: the duration of radiation application, and the functional form of how the dose is applied over that time (the "temporal pattern of applied dose"). Although the former has been well studied, the latter has not. Thus, the goal of this research is to investigate the impact of the temporal pattern of applied dose on the survival of human cells and to explore how the manipulation of this temporal dose pattern may be incorporated into an IMRT-based radiation therapy treatment planning scheme. The hypothesis is that the temporal pattern of applied dose in a single fraction of radiation can be optimized to maximize or minimize cell kill. Furthermore, techniques which utilize this effect could have clinical ramifications. In situations where increased cell kill is desirable, such as tumor control, or limiting the degree of cell kill is important, such as the sparing of normal tissue, temporal sequences of dose which maximize or minimize cell kill (temporally "optimized" sequences) may provide greater benefit than current clinically used radiation patterns. In the first part of this work, an LQ-based modeling analysis of effects of the temporal pattern of dose on cell kill is performed. Through this, patterns are identified for maximizing cell kill for a

  16. Experimental verification of the Acuros XB and AAA dose calculation adjacent to heterogeneous media for IMRT and RapidArc of nasopharygeal carcinoma.

    Science.gov (United States)

    Kan, Monica W K; Leung, Lucullus H T; So, Ronald W K; Yu, Peter K N

    2013-03-01

    To compare the doses calculated by the Acuros XB (AXB) algorithm and analytical anisotropic algorithm (AAA) with experimentally measured data adjacent to and within heterogeneous medium using intensity modulated radiation therapy (IMRT) and RapidArc(®) (RA) volumetric arc therapy plans for nasopharygeal carcinoma (NPC). Two-dimensional dose distribution immediately adjacent to both air and bone inserts of a rectangular tissue equivalent phantom irradiated using IMRT and RA plans for NPC cases were measured with GafChromic(®) EBT3 films. Doses near and within the nasopharygeal (NP) region of an anthropomorphic phantom containing heterogeneous medium were also measured with thermoluminescent dosimeters (TLD) and EBT3 films. The measured data were then compared with the data calculated by AAA and AXB. For AXB, dose calculations were performed using both dose-to-medium (AXB_Dm) and dose-to-water (AXB_Dw) options. Furthermore, target dose differences between AAA and AXB were analyzed for the corresponding real patients. The comparison of real patient plans was performed by stratifying the targets into components of different densities, including tissue, bone, and air. For the verification of planar dose distribution adjacent to air and bone using the rectangular phantom, the percentages of pixels that passed the gamma analysis with the ± 3%/3mm criteria were 98.7%, 99.5%, and 97.7% on the axial plane for AAA, AXB_Dm, and AXB_Dw, respectively, averaged over all IMRT and RA plans, while they were 97.6%, 98.2%, and 97.7%, respectively, on the coronal plane. For the verification of planar dose distribution within the NP region of the anthropomorphic phantom, the percentages of pixels that passed the gamma analysis with the ± 3%/3mm criteria were 95.1%, 91.3%, and 99.0% for AAA, AXB_Dm, and AXB_Dw, respectively, averaged over all IMRT and RA plans. Within the NP region where air and bone were present, the film measurements represented the dose close to unit density water

  17. Experimental verification of the Acuros XB and AAA dose calculation adjacent to heterogeneous media for IMRT and RapidArc of nasopharygeal carcinoma

    International Nuclear Information System (INIS)

    Kan, Monica W. K.; Leung, Lucullus H. T.; So, Ronald W. K.; Yu, Peter K. N.

    2013-01-01

    Purpose: To compare the doses calculated by the Acuros XB (AXB) algorithm and analytical anisotropic algorithm (AAA) with experimentally measured data adjacent to and within heterogeneous medium using intensity modulated radiation therapy (IMRT) and RapidArc ® (RA) volumetric arc therapy plans for nasopharygeal carcinoma (NPC). Methods: Two-dimensional dose distribution immediately adjacent to both air and bone inserts of a rectangular tissue equivalent phantom irradiated using IMRT and RA plans for NPC cases were measured with GafChromic ® EBT3 films. Doses near and within the nasopharygeal (NP) region of an anthropomorphic phantom containing heterogeneous medium were also measured with thermoluminescent dosimeters (TLD) and EBT3 films. The measured data were then compared with the data calculated by AAA and AXB. For AXB, dose calculations were performed using both dose-to-medium (AXB Dm ) and dose-to-water (AXB Dw ) options. Furthermore, target dose differences between AAA and AXB were analyzed for the corresponding real patients. The comparison of real patient plans was performed by stratifying the targets into components of different densities, including tissue, bone, and air. Results: For the verification of planar dose distribution adjacent to air and bone using the rectangular phantom, the percentages of pixels that passed the gamma analysis with the ± 3%/3mm criteria were 98.7%, 99.5%, and 97.7% on the axial plane for AAA, AXB Dm , and AXB Dw , respectively, averaged over all IMRT and RA plans, while they were 97.6%, 98.2%, and 97.7%, respectively, on the coronal plane. For the verification of planar dose distribution within the NP region of the anthropomorphic phantom, the percentages of pixels that passed the gamma analysis with the ± 3%/3mm criteria were 95.1%, 91.3%, and 99.0% for AAA, AXB Dm , and AXB Dw , respectively, averaged over all IMRT and RA plans. Within the NP region where air and bone were present, the film measurements represented the

  18. Lhermitte's Sign Developing after IMRT for Head and Neck Cancer

    Directory of Open Access Journals (Sweden)

    Dong C. Lim

    2010-01-01

    Full Text Available Background. Lhermitte's sign (LS is a benign form of myelopathy with neck flexion producing an unpleasant electric-shock sensation radiating down the extremities. Although rare, it can occur after head and neck radiotherapy. Results. We report a case of Lhermitte's developing after curative intensity-modulated radiotherapy (IMRT for a patient with locoregionally advanced oropharyngeal cancer. IMRT delivers a conformal dose of radiation in head and neck cancer resulting in a gradient of radiation dose throughout the spinal cord. Using IMRT, more dose is delivered to the anterior spinal cord than the posterior cord. Conclusions. Lhermitte's sign can develop after IMRT for head and neck cancer. We propose an anterior spinal cord structure, the spinothalamic tract to be the target of IMRT-caused LS.

  19. Dosimetry tools and techniques for IMRT

    International Nuclear Information System (INIS)

    Low, Daniel A.; Moran, Jean M.; Dempsey, James F.; Dong Lei; Oldham, Mark

    2011-01-01

    Intensity modulated radiation therapy (IMRT) poses a number of challenges for properly measuring commissioning data and quality assurance (QA) radiation dose distributions. This report provides a comprehensive overview of how dosimeters, phantoms, and dose distribution analysis techniques should be used to support the commissioning and quality assurance requirements of an IMRT program. The proper applications of each dosimeter are described along with the limitations of each system. Point detectors, arrays, film, and electronic portal imagers are discussed with respect to their proper use, along with potential applications of 3D dosimetry. Regardless of the IMRT technique utilized, some situations require the use of multiple detectors for the acquisition of accurate commissioning data. The overall goal of this task group report is to provide a document that aids the physicist in the proper selection and use of the dosimetry tools available for IMRT QA and to provide a resource for physicists that describes dosimetry measurement techniques for purposes of IMRT commissioning and measurement-based characterization or verification of IMRT treatment plans. This report is not intended to provide a comprehensive review of commissioning and QA procedures for IMRT. Instead, this report focuses on the aspects of metrology, particularly the practical aspects of measurements that are unique to IMRT. The metrology of IMRT concerns the application of measurement instruments and their suitability, calibration, and quality control of measurements. Each of the dosimetry measurement tools has limitations that need to be considered when incorporating them into a commissioning process or a comprehensive QA program. For example, routine quality assurance procedures require the use of robust field dosimetry systems. These often exhibit limitations with respect to spatial resolution or energy response and need to themselves be commissioned against more established dosimeters. A chain of

  20. Feasibility of a unified approach to intensity-modulated radiation therapy and volume-modulated arc therapy optimization and delivery

    International Nuclear Information System (INIS)

    Hoover, Douglas A.; Chen, Jeff Z.; MacFarlane, Michael; Wong, Eugene; Battista, Jerry J.

    2015-01-01

    Purpose: To study the feasibility of unified intensity-modulated arc therapy (UIMAT) which combines intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) optimization and delivery to produce superior radiation treatment plans, both in terms of dose distribution and efficiency of beam delivery when compared with either VMAT or IMRT alone. Methods: An inverse planning algorithm for UIMAT was prototyped within the PINNACLE treatment planning system (Philips Healthcare). The IMRT and VMAT deliveries are unified within the same arc, with IMRT being delivered at specific gantry angles within the arc. Optimized gantry angles for the IMRT and VMAT phases are assigned automatically by the inverse optimization algorithm. Optimization of the IMRT and VMAT phases is done simultaneously using a direct aperture optimization algorithm. Five treatment plans each for prostate, head and neck, and lung were generated using a unified optimization technique and compared with clinical IMRT or VMAT plans. Delivery verification was performed with an ArcCheck phantom (Sun Nuclear) on a Varian TrueBeam linear accelerator (Varian Medical Systems). Results: In this prototype implementation, the UIMAT plans offered the same target dose coverage while reducing mean doses to organs at risk by 8.4% for head-and-neck cases, 5.7% for lung cases, and 3.5% for prostate cases, compared with the VMAT or IMRT plans. In addition, UIMAT can be delivered with similar efficiency as VMAT. Conclusions: In this proof-of-concept work, a novel radiation therapy optimization and delivery technique that interlaces VMAT or IMRT delivery within the same arc has been demonstrated. Initial results show that unified VMAT/IMRT has the potential to be superior to either standard IMRT or VMAT

  1. A Phase I Dose Escalation Study of Hypofractionated IMRT Field-in-Field Boost for Newly Diagnosed Glioblastoma Multiforme

    Energy Technology Data Exchange (ETDEWEB)

    Monjazeb, Arta M., E-mail: arta.monjazeb@ucdmc.ucdavis.edu [U.C. Davis School of Medicine, Department of Radiation Oncology, Sacramento, CA (United States); Ayala, Deandra; Jensen, Courtney [Radiation Oncology, Wake Forest University Health Sciences, Winston-Salem, NC (United States); Case, L. Douglas [Biostatistical Sciences, Wake Forest University Health Sciences, Winston-Salem, NC (United States); Bourland, J. Daniel; Ellis, Thomas L. [Neurosurgery, Wake Forest University Health Sciences, Winston-Salem, NC (United States); McMullen, Kevin P.; Chan, Michael D. [Radiation Oncology, Wake Forest University Health Sciences, Winston-Salem, NC (United States); Tatter, Stephen B. [Neurosurgery, Wake Forest University Health Sciences, Winston-Salem, NC (United States); Lesser, Glen J. [Hematology Oncology, Wake Forest University Health Sciences, Winston-Salem, NC (United States); Shaw, Edward G. [Radiation Oncology, Wake Forest University Health Sciences, Winston-Salem, NC (United States)

    2012-02-01

    Objectives: To describe the results of a Phase I dose escalation trial for newly diagnosed glioblastoma multiforme (GBM) using a hypofractionated concurrent intensity-modulated radiotherapy (IMRT) boost. Methods: Twenty-one patients were enrolled between April 1999 and August 2003. Radiotherapy consisted of daily fractions of 1.8 Gy with a concurrent boost of 0.7 Gy (total 2.5 Gy daily) to a total dose of 70, 75, or 80 Gy. Concurrent chemotherapy was not permitted. Seven patients were enrolled at each dose and dose limiting toxicities were defined as irreversible Grade 3 or any Grade 4-5 acute neurotoxicity attributable to radiotherapy. Results: All patients experienced Grade 1 or 2 acute toxicities. Acutely, 8 patients experienced Grade 3 and 1 patient experienced Grade 3 and 4 toxicities. Of these, only two reversible cases of otitis media were attributable to radiotherapy. No dose-limiting toxicities were encountered. Only 2 patients experienced Grade 3 delayed toxicity and there was no delayed Grade 4 toxicity. Eleven patients requiring repeat resection or biopsy were found to have viable tumor and radiation changes with no cases of radionecrosis alone. Median overall and progression-free survival for this cohort were 13.6 and 6.5 months, respectively. One- and 2-year survival rates were 57% and 19%. At recurrence, 15 patients received chemotherapy, 9 underwent resection, and 5 received radiotherapy. Conclusions: Using a hypofractionated concurrent IMRT boost, we were able to safely treat patients to 80 Gy without any dose-limiting toxicity. Given that local failure still remains the predominant pattern for GBM patients, a trial of dose escalation with IMRT and temozolomide is warranted.

  2. A Phase I Dose Escalation Study of Hypofractionated IMRT Field-in-Field Boost for Newly Diagnosed Glioblastoma Multiforme

    International Nuclear Information System (INIS)

    Monjazeb, Arta M.; Ayala, Deandra; Jensen, Courtney; Case, L. Douglas; Bourland, J. Daniel; Ellis, Thomas L.; McMullen, Kevin P.; Chan, Michael D.; Tatter, Stephen B.; Lesser, Glen J.; Shaw, Edward G.

    2012-01-01

    Objectives: To describe the results of a Phase I dose escalation trial for newly diagnosed glioblastoma multiforme (GBM) using a hypofractionated concurrent intensity-modulated radiotherapy (IMRT) boost. Methods: Twenty-one patients were enrolled between April 1999 and August 2003. Radiotherapy consisted of daily fractions of 1.8 Gy with a concurrent boost of 0.7 Gy (total 2.5 Gy daily) to a total dose of 70, 75, or 80 Gy. Concurrent chemotherapy was not permitted. Seven patients were enrolled at each dose and dose limiting toxicities were defined as irreversible Grade 3 or any Grade 4–5 acute neurotoxicity attributable to radiotherapy. Results: All patients experienced Grade 1 or 2 acute toxicities. Acutely, 8 patients experienced Grade 3 and 1 patient experienced Grade 3 and 4 toxicities. Of these, only two reversible cases of otitis media were attributable to radiotherapy. No dose-limiting toxicities were encountered. Only 2 patients experienced Grade 3 delayed toxicity and there was no delayed Grade 4 toxicity. Eleven patients requiring repeat resection or biopsy were found to have viable tumor and radiation changes with no cases of radionecrosis alone. Median overall and progression-free survival for this cohort were 13.6 and 6.5 months, respectively. One- and 2-year survival rates were 57% and 19%. At recurrence, 15 patients received chemotherapy, 9 underwent resection, and 5 received radiotherapy. Conclusions: Using a hypofractionated concurrent IMRT boost, we were able to safely treat patients to 80 Gy without any dose-limiting toxicity. Given that local failure still remains the predominant pattern for GBM patients, a trial of dose escalation with IMRT and temozolomide is warranted.

  3. Comparison of various online IGRT strategies: The benefits of online treatment plan re-optimization

    International Nuclear Information System (INIS)

    Schulze, Derek; Liang, Jian; Yan, Di; Zhang Tiezhi

    2009-01-01

    Purpose: To compare the dosimetric differences of various online IGRT strategies and to predict potential benefits of online re-optimization techniques in prostate cancer radiation treatments. Materials and methods: Nine prostate patients were recruited in this study. Each patient has one treatment planning CT images and 10-treatment day CT images. Five different online IGRT strategies were evaluated which include 3D conformal with bone alignment, 3D conformal re-planning via aperture changes, intensity modulated radiation treatment (IMRT) with bone alignment, IMRT with target alignment and IMRT daily re-optimization. Treatment planning and virtual treatment delivery were performed. The delivered doses were obtained using in-house deformable dose mapping software. The results were analyzed using equivalent uniform dose (EUD). Results: With the same margin, rectum and bladder doses in IMRT plans were about 10% and 5% less than those in CRT plans, respectively. Rectum and bladder doses were reduced as much as 20% if motion margin is reduced by 1 cm. IMRT is more sensitive to organ motion. Large discrepancies of bladder and rectum doses were observed compared to the actual delivered dose with treatment plan predication. The therapeutic ratio can be improved by 14% and 25% for rectum and bladder, respectively, if IMRT online re-planning is employed compared to the IMRT bone alignment approach. The improvement of target alignment approach is similar with 11% and 21% dose reduction to rectum and bladder, respectively. However, underdosing in seminal vesicles was observed on certain patients. Conclusions: Online treatment plan re-optimization may significantly improve therapeutic ratio in prostate cancer treatments mostly due to the reduction of PTV margin. However, for low risk patient with only prostate involved, online target alignment IMRT treatment would achieve similar results as online re-planning. For all IGRT approaches, the delivered organ-at-risk doses may be

  4. Optimization in radiotherapy treatment planning thanks to a fast dose calculation method

    International Nuclear Information System (INIS)

    Yang, Mingchao

    2014-01-01

    This thesis deals with the radiotherapy treatments planning issue which need a fast and reliable treatment planning system (TPS). The TPS is composed of a dose calculation algorithm and an optimization method. The objective is to design a plan to deliver the dose to the tumor while preserving the surrounding healthy and sensitive tissues. The treatment planning aims to determine the best suited radiation parameters for each patient's treatment. In this thesis, the parameters of treatment with IMRT (Intensity modulated radiation therapy) are the beam angle and the beam intensity. The objective function is multi-criteria with linear constraints. The main objective of this thesis is to demonstrate the feasibility of a treatment planning optimization method based on a fast dose-calculation technique developed by (Blanpain, 2009). This technique proposes to compute the dose by segmenting the patient's phantom into homogeneous meshes. The dose computation is divided into two steps. The first step impacts the meshes: projections and weights are set according to physical and geometrical criteria. The second step impacts the voxels: the dose is computed by evaluating the functions previously associated to their mesh. A reformulation of this technique makes possible to solve the optimization problem by the gradient descent algorithm. The main advantage of this method is that the beam angle parameters could be optimized continuously in 3 dimensions. The obtained results in this thesis offer many opportunities in the field of radiotherapy treatment planning optimization. (author) [fr

  5. Motion-induced dose artifacts in helical tomotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Bryan; Chen, Jeff; Battista, Jerry [London Regional Cancer Program, London Health Sciences Centre, London, ON (Canada); Kron, Tomas [Peter MacCallum Cancer Center, Melbourne (Australia)], E-mail: bryan.kim@lhsc.on.ca

    2009-10-07

    Tumor motion is a particular concern for a complex treatment modality such as helical tomotherapy, where couch position, gantry rotation and MLC leaf opening all change with time. In the present study, we have investigated the impact of tumor motion for helical tomotherapy, which could result in three distinct motion-induced dose artifacts, namely (1) dose rounding, (2) dose rippling and (3) IMRT leaf opening asynchronization effect. Dose rounding and dose rippling effects have been previously described, while the IMRT leaf opening asynchronization effect is a newly discovered motion-induced dose artifact. Dose rounding is the penumbral widening of a delivered dose distribution near the edges of a target volume along the direction of tumor motion. Dose rippling is a series of periodic dose peaks and valleys observed within the target region along the direction of couch motion, due to an asynchronous interplay between the couch motion and the longitudinal component of tumor motion. The IMRT leaf opening asynchronization effect is caused by an asynchronous interplay between the temporal patterns of leaf openings and tumor motion. The characteristics of each dose artifact were investigated individually as functions of target motion amplitude and period for both non-IMRT and IMRT helical tomotherapy cases, through computer simulation modeling and experimental verification. The longitudinal dose profiles generated by the simulation program agreed with the experimental data within {+-}0.5% and {+-}1.5% inside the PTV region for the non-IMRT and IMRT cases, respectively. The dose rounding effect produced a penumbral increase up to 20.5 mm for peak-to-peak target motion amplitudes ranging from 1.0 cm to 5.0 cm. Maximum dose rippling magnitude of 25% was calculated, when the target motion period approached an unusually high value of 10 s. The IMRT leaf opening asynchronization effect produced dose differences ranging from -29% to 7% inside the PTV region. This information

  6. SU-E-T-393: Evaluation of Large Field IMRT Versus RapidArc Planning for Carcinoma Cervix with Para-Aotic Node Irradiation

    International Nuclear Information System (INIS)

    Raman, S Kothanda; Girigesh, Y; MISHRA, M; Lalit, K

    2015-01-01

    Purpose: The objective of this work is to evaluate and compare Large field IMRT and RapidArc planning for Carcinoma Cervix and Para-aotic node irradiation. Methods: In this study, ten patients of Cervix with para-aotic node have been selected with PTV length 35+2cm. All plans were generated in Eclipse TPS V10.0 with Dynamic IMRT and RapidArc technique using 6MV photon energy. In IMRT planning, 7 fields were chosen to get optimal plan and in RapidArc, double Full arc clockwise and counter clockwise were used for planning. All the plans were generated with single isocenter and calculated using AAA dose algorithm. For all the cases the prescribed dose to PTV was same and the plan acceptance criteria is; 95% of the PTV volume should receive 100% prescribed dose. The tolerance doses for the OAR’s is also taken in to account. The evaluation criteria used for analysis are; 1) Homogeneity Index, 2) Conformity Index, 3) Mean Dose to OAR’s, 4)Total monitor units delivered. Results: DVH analysis were performed for both IMRT and RapidArc planning. In both the plans, 95% of PTV volume receives prescribed dose and maximum dose are less than 107%. The conformity index are same in both the techniques. The mean Homogeneity index are 1.036 and 1.053 for IMRT and RapidArc plan. The mean (mean + SD) dose of bladder and rectum in IMRT is 44.2+1.55, 42.05+2.52 and RapidArc is 46.66+1.6, 44.2+2.75 respectively. There is no significant difference found in Right Femoral head, Left Femoral head and Kidney doses. It is found that total MU’s are more in IMRT compared with RapidArc planning. Conclusion: In the case of cervix with Para-arotic node single isocenter irradiation, IMRT planning in large-field is better compared to RapidArc planning in terms of Homogeneity Index and mean dose of Bladder and Rectum

  7. SU-E-T-393: Evaluation of Large Field IMRT Versus RapidArc Planning for Carcinoma Cervix with Para-Aotic Node Irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Raman, S Kothanda; Girigesh, Y; MISHRA, M; Lalit, K [Rajiv Gandhi Cancer Institute & Research Centre, New Delhi (India)

    2015-06-15

    Purpose: The objective of this work is to evaluate and compare Large field IMRT and RapidArc planning for Carcinoma Cervix and Para-aotic node irradiation. Methods: In this study, ten patients of Cervix with para-aotic node have been selected with PTV length 35+2cm. All plans were generated in Eclipse TPS V10.0 with Dynamic IMRT and RapidArc technique using 6MV photon energy. In IMRT planning, 7 fields were chosen to get optimal plan and in RapidArc, double Full arc clockwise and counter clockwise were used for planning. All the plans were generated with single isocenter and calculated using AAA dose algorithm. For all the cases the prescribed dose to PTV was same and the plan acceptance criteria is; 95% of the PTV volume should receive 100% prescribed dose. The tolerance doses for the OAR’s is also taken in to account. The evaluation criteria used for analysis are; 1) Homogeneity Index, 2) Conformity Index, 3) Mean Dose to OAR’s, 4)Total monitor units delivered. Results: DVH analysis were performed for both IMRT and RapidArc planning. In both the plans, 95% of PTV volume receives prescribed dose and maximum dose are less than 107%. The conformity index are same in both the techniques. The mean Homogeneity index are 1.036 and 1.053 for IMRT and RapidArc plan. The mean (mean + SD) dose of bladder and rectum in IMRT is 44.2+1.55, 42.05+2.52 and RapidArc is 46.66+1.6, 44.2+2.75 respectively. There is no significant difference found in Right Femoral head, Left Femoral head and Kidney doses. It is found that total MU’s are more in IMRT compared with RapidArc planning. Conclusion: In the case of cervix with Para-arotic node single isocenter irradiation, IMRT planning in large-field is better compared to RapidArc planning in terms of Homogeneity Index and mean dose of Bladder and Rectum.

  8. An analysis of tolerance levels in IMRT quality assurance procedures

    International Nuclear Information System (INIS)

    Basran, Parminder S.; Woo, Milton K.

    2008-01-01

    Increased use of intensity modulated radiation therapy (IMRT) has resulted in increased efforts in patient quality assurance (QA). Software and detector systems intended to streamline the IMRT quality assurance process often report metrics, such as percent discrepancies between measured and computed doses, which can be compared to benchmark or threshold values. The purpose of this work is to examine the relationships between two different types of IMRT QA processes in order to define, or refine, appropriate tolerances values. For 115 IMRT plans delivered in a 3 month period, we examine the discrepancies between (a) the treatment planning system (TPS) and results from a commercial independent monitor unit (MU) calculation program; (b) TPS and results from a commercial diode-array measurement system; and (c) the independent MU calculation and the diode-array measurements. Statistical tests were performed to assess significance in the IMRT QA results for different disease site and machine models. There is no evidence that the average total dose discrepancy in the monitor unit calculation depends on the disease site. Second, the discrepancies in the two IMRT QA methods are independent: there is no evidence that a better --or worse--monitor unit validation result is related to a better--or worse--diode-array measurement result. Third, there is marginal benefit in repeating the independent MU calculation with a more suitable dose point, if the initial IMRT QA failed a certain tolerance. Based on these findings, the authors conclude at some acceptable tolerances based on disease site and IMRT QA method. Specifically, monitor unit validations are expected to have a total dose discrepancy of 3% overall, and 5% per beam, independent of disease site. Diode array measurements are expected to have a total absolute dose discrepancy of 3% overall, and 3% per beam, independent of disease site. The percent of pixels exceeding a 3% and 3 mm threshold in a gamma analysis should be

  9. Software for simulating IMRT protocol

    Energy Technology Data Exchange (ETDEWEB)

    Fonseca, Thelma C.F.; Campos, Tarcisio P.R. de, E-mail: tcff@ufmg.b, E-mail: campos@nuclear.ufmg.b [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Nuclear

    2009-07-01

    The Intensity Modulated Radiation Therapy - IMRT is an advanced technique to cancer treatment widely used on oncology around the world. The present paper describes the SOFT-RT software which is a tool for simulating IMRT protocol. Also, it will be present a cerebral tumor case of studied in which three irradiation windows with distinct orientation were applied. The SOFT-RT collect and export data to MCNP code. This code simulates the photon transport on the voxel model. Later, a out-module from SOFT-RT import the results and express the dose-response superimposing dose and voxel model in a tree-dimensional graphic representation. The present paper address the IMRT software and its function as well a cerebral tumor case of studied is showed. The graphic interface of the SOFT-RT illustrates the example case. (author)

  10. Software for simulating IMRT protocol

    International Nuclear Information System (INIS)

    Fonseca, Thelma C.F.; Campos, Tarcisio P.R. de

    2009-01-01

    The Intensity Modulated Radiation Therapy - IMRT is an advanced technique to cancer treatment widely used on oncology around the world. The present paper describes the SOFT-RT software which is a tool for simulating IMRT protocol. Also, it will be present a cerebral tumor case of studied in which three irradiation windows with distinct orientation were applied. The SOFT-RT collect and export data to MCNP code. This code simulates the photon transport on the voxel model. Later, a out-module from SOFT-RT import the results and express the dose-response superimposing dose and voxel model in a tree-dimensional graphic representation. The present paper address the IMRT software and its function as well a cerebral tumor case of studied is showed. The graphic interface of the SOFT-RT illustrates the example case. (author)

  11. Intensity-modulated radiation therapy (IMRT) for locally advanced paranasal sinus tumors: incorporating clinical decisions in the optimization process

    International Nuclear Information System (INIS)

    Tsien, Christina; Eisbruch, Avraham; McShan, Daniel; Kessler, Marc; Marsh, Robin C.; Fraass, Benedick

    2003-01-01

    Purpose: Intensity-modulated radiotherapy (IMRT) plans require decisions about priorities and tradeoffs among competing goals. This study evaluates the incorporation of various clinical decisions into the optimization system, using locally advanced paranasal sinus tumors as a model. Methods and Materials: Thirteen patients with locally advanced paranasal sinus tumors were retrospectively replanned using inverse planning. Two clinical decisions were assumed: (1) Spare both optic pathways (OP), or (2) Spare only the contralateral OP. In each case, adequate tumor coverage (treated to 70 Gy in 35 fractions) was required. Two beamlet IMRT plans were thus developed for each patient using a class solution cost function. By altering one key variable at a time, different levels of risk of OP toxicity and planning target volume (PTV) compromise were compared in a systematic manner. The resulting clinical tradeoffs were analyzed using dosimetric criteria, tumor control probability (TCP), equivalent uniform dose (EUD), and normal tissue complication probability. Results: Plan comparisons representing the two clinical decisions (sparing both OP and sparing only the contralateral OP), with respect to minimum dose, TCP, V 95 , and EUD, demonstrated small, yet statistically significant, differences. However, when individual cases were analyzed further, significant PTV underdosage (>5%) was present in most cases for plans sparing both OP. In 6/13 cases (46%), PTV underdosage was between 5% and 15%, and in 3 cases (23%) was greater than 15%. By comparison, adequate PTV coverage was present in 8/13 cases (62%) for plans sparing only the contralateral OP. Mean target EUD comparisons between the two plans (including 9 cases where a clinical tradeoff between PTV coverage and OP sparing was required) were similar: 68.6 Gy and 69.1 Gy, respectively (p=0.02). Mean TCP values for those 9 cases were 56.5 vs. 61.7, respectively (p=0.006). Conclusions: In IMRT plans for paranasal sinus tumors

  12. Study of the IMRT interplay effect using a 4DCT Monte Carlo dose calculation.

    Science.gov (United States)

    Jensen, Michael D; Abdellatif, Ady; Chen, Jeff; Wong, Eugene

    2012-04-21

    Respiratory motion may lead to dose errors when treating thoracic and abdominal tumours with radiotherapy. The interplay between complex multileaf collimator patterns and patient respiratory motion could result in unintuitive dose changes. We have developed a treatment reconstruction simulation computer code that accounts for interplay effects by combining multileaf collimator controller log files, respiratory trace log files, 4DCT images and a Monte Carlo dose calculator. Two three-dimensional (3D) IMRT step-and-shoot plans, a concave target and integrated boost were delivered to a 1D rigid motion phantom. Three sets of experiments were performed with 100%, 50% and 25% duty cycle gating. The log files were collected, and five simulation types were performed on each data set: continuous isocentre shift, discrete isocentre shift, 4DCT, 4DCT delivery average and 4DCT plan average. Analysis was performed using 3D gamma analysis with passing criteria of 2%, 2 mm. The simulation framework was able to demonstrate that a single fraction of the integrated boost plan was more sensitive to interplay effects than the concave target. Gating was shown to reduce the interplay effects. We have developed a 4DCT Monte Carlo simulation method that accounts for IMRT interplay effects with respiratory motion by utilizing delivery log files.

  13. IMRT for adjuvant radiation in gastric cancer: A preferred plan?

    International Nuclear Information System (INIS)

    Ringash, Jolie; Perkins, Greg; Brierley, James; Lockwood, Gina; Islam, Mohammad; Catton, Pamela; Cummings, Bernard; Kim, John; Wong, Rebecca; Dawson, Laura

    2005-01-01

    Purpose: To assess the potential advantage of intensity-modulated radiotherapy (IMRT) over conformal planning for postoperative adjuvant radiotherapy in patients with gastric carcinoma. Methods and Materials: Twenty patients who had undergone treatment planning with conformal beam arrangements for 4500 cGy adjuvant radiotherapy between 2000 and 2001 underwent repeat planning using IMRT techniques. Conformal five-field plans were compared with seven- to nine-field coplanar sliding-window IMRT plans. For each patient, the cumulative dose-volume histograms and organ-dose summaries (without distributions or digitally reconstructed radiographs) were provided to two independent, 'blinded' GI radiation oncologists. The oncologists indicated which plan provided better planning target volume coverage and critical organ sparing, any safety concerns with either plan, and which plan they would choose to treat the patient. Results: In 18 (90%) of 20 cases, both oncologists chose the same plan. Cases with disagreement were given to a third 'blinded' reviewer. A 'preferred plan' could be determined in 19 (95%) of 20 cases. IMRT was preferred in 17 (89%) of 19 cases. In 4 (20%) of 20 IMRT plans at least one radiation oncologist had safety concerns because of the spinal cord dose (3 cases) or small bowel dose (2 cases). Of 42 ratings, IMRT was thought to provide better planning target volume coverage in 36 (86%) and better sparing of the spinal cord in 31 (74%) of 42, kidneys in 29 (69%), liver in 30 (71%), and heart in 29 (69%) of 42 ratings. The median underdose volume (1.7 vs. 4.1 cm 3 ), maximal dose to the spinal cord (36.85 vs. 45.65 Gy), and dose to 50% of the liver (17.29 vs. 27.97), heart (12.89 vs. 15.50 Gy), and left kidney (15.50 vs. 16.06 Gy) were lower with IMRT than with the conformal plans. Conclusion: Compared with the conformal plans, oncologists frequently preferred IMRT plans when using dose-volume histogram data. The advantages of IMRT plans include both

  14. SU-E-T-182: Feasibility of Dose Painting by Numbers in Proton Therapy with Contour-Driven Plan Optimization

    International Nuclear Information System (INIS)

    Montero, A Barragan; Differding, S; Lee, J; Sterpin, E

    2014-01-01

    Purpose: The work aims to 1) prove the feasibility of dose painting by numbers (DPBN) in proton therapy with usual contour-driven plan optimization and 2) compare the achieved plan quality to that of rotational IMRT. Methods: For two patients with head and neck cancers, voxel-by-voxel prescription to the target volume (PTV-PET) was calculated from 18 FDG-PET images and converted to contour-based prescription by defining several sub-contours. Treatments were planned with RayStation (RaySearch Laboratories, Sweden) and proton pencil beam scanning modality. In order to determine the optimal plan parameters to approach the DPBN prescription, the effect of the number of fields, number of sub-contours and use of range shifter were tested separately on each patient. The number of sub-contours were increased from 3 to 11 while the number of fields were set to 3, 5, 7 and 9. Treatment plans were also optimized on two rotational IMRT systems (TomoTherapy and Varian RapidArc) using previously published guidelines. Results: For both patients, more than 99% of the PTV-PET received at least 95% of the prescribed dose while less than 1% of the PTV-PET received more than 105%, which demonstrates the feasibility of the treatment. Neither the use of a range shifter nor the increase of the number of fields had a significant influence on PTV coverage. Plan quality increased when increasing number of fields up to 7 or 9 and slightly decreased for a bigger number of sub-contours. Good OAR sparing is achieved while keeping high plan quality. Finally, proton therapy achieved significantly better plan quality than rotational IMRT. Conclusion: Voxel-by-voxel prescriptions can be approximated accurately in proton therapy using a contour-driven optimization. Target coverage is nearly insensitive to the number of fields and the use of a range shifter. Finally, plan quality assessment confirmed the superiority of proton therapy compared to rotational IMRT

  15. SU-E-T-16: A Hybrid VMAT/IMRT Technique for the Treatment of Nasopharyngeal Carcinoma

    International Nuclear Information System (INIS)

    Zhao, N; Yang, R; Wang, J

    2014-01-01

    Purpose: To investigate a Hybrid VMAT/IMRT technique which combines volumetric modulated arc therapy (VMAT) and intensity modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC). Methods: 2 full arcs VMAT, 9-field IMRT and Hybrid VMAT/IMRT plans were created for 10 patients with NPC. The Hybrid VMAT/IMRT technique consisted of 1 full VMAT arc and 7 IMRT fields. The dose distribution of planning target volume (PTV) and organs at risk (OARs) for Hybrid VMAT/IMRT was compared with IMRT and VMAT. The monitor units (MUs) were also evaluated. Results: The Hybrid VMAT/IMRT technique significantly improved target dose homogeneity compared with IMRT and VMAT for PTV70 and PTV54. For PTV70 and PTV60, the Hybrid VMAT/IMRT technique significantly improved target dose conformity compared with IMRT (0.62 vs 0.47; p<0.05 and 0.64 vs 0.58; p<0.05, respectively) and VMAT (0.62 vs 0.43; p<0.05 and 0.64 vs 0.6; p<0.05, respectively). The near maximum dose (D2%) of temporomandibular joint (TMJ), temporal lobe and mandible for Hybrid plans were 5.5%, 7.9% and 5.2% lower than IMRT plans (p<0.05). The mean dose of TMJ, temporal lobe, mandible and unspecified tissue for Hybrid plans were 12.8%, 11.4%, 4.2% and 4.1% lower than IMRT plans (p<0.05). The mean dose of right parotid, mandible and unspecified tissue for Hybrid plans were 3.3%, 2.4% and 3.1% lower than VMAT plans (p<0.05). The mean MUs needed for IMRT, VMAT and Hybrid plans were 2256, 507 and 1394, respectively. Conclusion: Hybrid VMAT/IMRT technique significantly improved the target dose homogeneity and conformity compared with IMRT and VMAT and reduced the dose of OARs and unspecified tissue compared with IMRT with fewer MUs. Compared with VMAT, Hybrid VMAT/IMRT technique can better protect parotid gland, mandible and unspecified tissue. Ruijie Yang was funded by the grant project: National Natural Science Foundation of China (No. 81071237). Other authors have no competing interest for this work

  16. SU-E-T-16: A Hybrid VMAT/IMRT Technique for the Treatment of Nasopharyngeal Carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, N; Yang, R; Wang, J [Peking University Third Hospital, Beijing, Beijing (China)

    2014-06-01

    Purpose: To investigate a Hybrid VMAT/IMRT technique which combines volumetric modulated arc therapy (VMAT) and intensity modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC). Methods: 2 full arcs VMAT, 9-field IMRT and Hybrid VMAT/IMRT plans were created for 10 patients with NPC. The Hybrid VMAT/IMRT technique consisted of 1 full VMAT arc and 7 IMRT fields. The dose distribution of planning target volume (PTV) and organs at risk (OARs) for Hybrid VMAT/IMRT was compared with IMRT and VMAT. The monitor units (MUs) were also evaluated. Results: The Hybrid VMAT/IMRT technique significantly improved target dose homogeneity compared with IMRT and VMAT for PTV70 and PTV54. For PTV70 and PTV60, the Hybrid VMAT/IMRT technique significantly improved target dose conformity compared with IMRT (0.62 vs 0.47; p<0.05 and 0.64 vs 0.58; p<0.05, respectively) and VMAT (0.62 vs 0.43; p<0.05 and 0.64 vs 0.6; p<0.05, respectively). The near maximum dose (D2%) of temporomandibular joint (TMJ), temporal lobe and mandible for Hybrid plans were 5.5%, 7.9% and 5.2% lower than IMRT plans (p<0.05). The mean dose of TMJ, temporal lobe, mandible and unspecified tissue for Hybrid plans were 12.8%, 11.4%, 4.2% and 4.1% lower than IMRT plans (p<0.05). The mean dose of right parotid, mandible and unspecified tissue for Hybrid plans were 3.3%, 2.4% and 3.1% lower than VMAT plans (p<0.05). The mean MUs needed for IMRT, VMAT and Hybrid plans were 2256, 507 and 1394, respectively. Conclusion: Hybrid VMAT/IMRT technique significantly improved the target dose homogeneity and conformity compared with IMRT and VMAT and reduced the dose of OARs and unspecified tissue compared with IMRT with fewer MUs. Compared with VMAT, Hybrid VMAT/IMRT technique can better protect parotid gland, mandible and unspecified tissue. Ruijie Yang was funded by the grant project: National Natural Science Foundation of China (No. 81071237). Other authors have no competing interest for this work.

  17. Towards biologically conformal radiation therapy (BCRT): Selective IMRT dose escalation under the guidance of spatial biology distribution

    International Nuclear Information System (INIS)

    Yang Yong; Xing Lei

    2005-01-01

    It is well known that the spatial biology distribution (e.g., clonogen density, radiosensitivity, tumor proliferation rate, functional importance) in most tumors and sensitive structures is heterogeneous. Recent progress in biological imaging is making the mapping of this distribution increasingly possible. The purpose of this work is to establish a theoretical framework to quantitatively incorporate the spatial biology data into intensity modulated radiation therapy (IMRT) inverse planning. In order to implement this, we first derive a general formula for determining the desired dose to each tumor voxel for a known biology distribution of the tumor based on a linear-quadratic model. The desired target dose distribution is then used as the prescription for inverse planning. An objective function with the voxel-dependent prescription is constructed with incorporation of the nonuniform dose prescription. The functional unit density distribution in a sensitive structure is also considered phenomenologically when constructing the objective function. Two cases with different hypothetical biology distributions are used to illustrate the new inverse planning formalism. For comparison, treatments with a few uniform dose prescriptions and a simultaneous integrated boost are also planned. The biological indices, tumor control probability (TCP) and normal tissue complication probability (NTCP), are calculated for both types of plans and the superiority of the proposed technique over the conventional dose escalation scheme is demonstrated. Our calculations revealed that it is technically feasible to produce deliberately nonuniform dose distributions with consideration of biological information. Compared with the conventional dose escalation schemes, the new technique is capable of generating biologically conformal IMRT plans that significantly improve the TCP while reducing or keeping the NTCPs at their current levels. Biologically conformal radiation therapy (BCRT

  18. Phase I Trial of Pelvic Nodal Dose Escalation With Hypofractionated IMRT for High-Risk Prostate Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Adkison, Jarrod B.; McHaffie, Derek R.; Bentzen, Soren M.; Patel, Rakesh R.; Khuntia, Deepak [Department of Human Oncology, University of Wisconsin Carbone Cancer Center, School of Medicine and Public Health, Madison, WI (United States); Petereit, Daniel G. [Department of Radiation Oncology, John T. Vucurevich Regional Cancer Care Institute, Rapid City Regional Hospital, Rapid City, SD (United States); Hong, Theodore S.; Tome, Wolfgang [Department of Human Oncology, University of Wisconsin Carbone Cancer Center, School of Medicine and Public Health, Madison, WI (United States); Ritter, Mark A., E-mail: ritter@humonc.wisc.edu [Department of Human Oncology, University of Wisconsin Carbone Cancer Center, School of Medicine and Public Health, Madison, WI (United States)

    2012-01-01

    Purpose: Toxicity concerns have limited pelvic nodal prescriptions to doses that may be suboptimal for controlling microscopic disease. In a prospective trial, we tested whether image-guided intensity-modulated radiation therapy (IMRT) can safely deliver escalated nodal doses while treating the prostate with hypofractionated radiotherapy in 5 Vulgar-Fraction-One-Half weeks. Methods and Materials: Pelvic nodal and prostatic image-guided IMRT was delivered to 53 National Comprehensive Cancer Network (NCCN) high-risk patients to a nodal dose of 56 Gy in 2-Gy fractions with concomitant treatment of the prostate to 70 Gy in 28 fractions of 2.5 Gy, and 50 of 53 patients received androgen deprivation for a median duration of 12 months. Results: The median follow-up time was 25.4 months (range, 4.2-57.2). No early Grade 3 Radiation Therapy Oncology Group or Common Terminology Criteria for Adverse Events v.3.0 genitourinary (GU) or gastrointestinal (GI) toxicities were seen. The cumulative actuarial incidence of Grade 2 early GU toxicity (primarily alpha blocker initiation) was 38%. The rate was 32% for Grade 2 early GI toxicity. None of the dose-volume descriptors correlated with GU toxicity, and only the volume of bowel receiving {>=}30 Gy correlated with early GI toxicity (p = 0.029). Maximum late Grades 1, 2, and 3 GU toxicities were seen in 30%, 25%, and 2% of patients, respectively. Maximum late Grades 1 and 2 GI toxicities were seen in 30% and 8% (rectal bleeding requiring cautery) of patients, respectively. The estimated 3-year biochemical control (nadir + 2) was 81.2 {+-} 6.6%. No patient manifested pelvic nodal failure, whereas 2 experienced paraaortic nodal failure outside the field. The six other clinical failures were distant only. Conclusions: Pelvic IMRT nodal dose escalation to 56 Gy was delivered concurrently with 70 Gy of hypofractionated prostate radiotherapy in a convenient, resource-efficient, and well-tolerated 28-fraction schedule. Pelvic nodal dose

  19. Dose and volume effects of gastrointestinal toxicity during neoadjuvant IMRT for rectal cancer

    DEFF Research Database (Denmark)

    Appelt, A. L.; Vogelius, I. R.; Jakobsen, Anders

    2015-01-01

    . Materials and Methods: We explored dose metrics correlating with acute diarrhea and chemotherapy compliance for a single-institution cohort of rectal cancer patients (n=115) treated with IMRT. Acute diarrhea during treatment was scored prospectively by trained RT nurses (CTCAE v3.0). The highest toxicity.......03) and patients with diabetes (OR=7.29, 1.21-43.8, p=0.03). Age, brachytherapy boost, prior abdominal surgery, smoking history, or domestic status had no influence on any of the two endpoints, nor had concurrent chemotherapy on the risk of acute diarrhea. Conclusions: We found that dose to the intestinal cavity...

  20. A systematic benchmark method for analysis and comparison of IMRT treatment planning algorithms.

    Science.gov (United States)

    Mayo, Charles S; Urie, Marcia M

    2003-01-01

    Tools and procedures for evaluating and comparing different intensity-modulated radiation therapy (IMRT) systems are presented. IMRT is increasingly in demand and there are numerous systems available commercially. These programs introduce significantly different software to dosimetrists and physicists than conventional planning systems, and the options often seem initially overwhelmingly complex to the user. By creating geometric target volumes and critical normal tissues, the characteristics of the algorithms may be investigated, and the influence of the different parameters explored. Overall optimization strategies of the algorithm may be characterized by treating a square target volume (TV) with 2 perpendicular beams, with and without heterogeneities. A half-donut (hemi-annulus) TV with a "donut hole" (central cylinder) critical normal tissue (CNT) on a CT of a simulated quality assurance phantom is suggested as a good geometry to explore the IMRT algorithm parameters. Using this geometry, the order of varying parameters is suggested. First is to determine the effects of the number of stratifications of optimized intensity fluence on the resulting dose distribution, and selecting a fixed number of stratifications for further studies. To characterize the dose distributions, a dose-homogeneity index (DHI) is defined as the ratio of the dose received by 90% of the volume to the minimum dose received by the "hottest" 10% of the volume. The next step is to explore the effects of priority and penalty on both the TV and the CNT. Then, choosing and fixing these parameters, the effects of varying the number of beams can be looked at. As well as evaluating the dose distributions (and DHI), the number of subfields and the number of monitor units required for different numbers of stratifications and beams can be evaluated.

  1. Image guided IMRT dosimetry using anatomy specific MOSFET configurations.

    Science.gov (United States)

    Amin, Md Nurul; Norrlinger, Bern; Heaton, Robert; Islam, Mohammad

    2008-06-23

    We have investigated the feasibility of using a set of multiple MOSFETs in conjunction with the mobile MOSFET wireless dosimetry system, to perform a comprehensive and efficient quality assurance (QA) of IMRT plans. Anatomy specific MOSFET configurations incorporating 5 MOSFETs have been developed for a specially designed IMRT dosimetry phantom. Kilovoltage cone beam computed tomography (kV CBCT) imaging was used to increase the positional precision and accuracy of the detectors and phantom, and so minimize dosimetric uncertainties in high dose gradient regions. The effectiveness of the MOSFET based dose measurements was evaluated by comparing the corresponding doses measured by an ion chamber. For 20 head and neck IMRT plans the agreement between the MOSFET and ionization chamber dose measurements was found to be within -0.26 +/- 0.88% and 0.06 +/- 1.94% (1 sigma) for measurement points in the high dose and low dose respectively. A precision of 1 mm in detector positioning was achieved by using the X-Ray Volume Imaging (XVI) kV CBCT system available with the Elekta Synergy Linear Accelerator. Using the anatomy specific MOSFET configurations, simultaneous measurements were made at five strategically located points covering high dose and low dose regions. The agreement between measurements and calculated doses by the treatment planning system for head and neck and prostate IMRT plans was found to be within 0.47 +/- 2.45%. The results indicate that a cylindrical phantom incorporating multiple MOSFET detectors arranged in an anatomy specific configuration, in conjunction with image guidance, can be utilized to perform a comprehensive and efficient quality assurance of IMRT plans.

  2. Automatic learning-based beam angle selection for thoracic IMRT

    International Nuclear Information System (INIS)

    Amit, Guy; Marshall, Andrea; Purdie, Thomas G.; Jaffray, David A.; Levinshtein, Alex; Hope, Andrew J.; Lindsay, Patricia; Pekar, Vladimir

    2015-01-01

    Purpose: The treatment of thoracic cancer using external beam radiation requires an optimal selection of the radiation beam directions to ensure effective coverage of the target volume and to avoid unnecessary treatment of normal healthy tissues. Intensity modulated radiation therapy (IMRT) planning is a lengthy process, which requires the planner to iterate between choosing beam angles, specifying dose–volume objectives and executing IMRT optimization. In thorax treatment planning, where there are no class solutions for beam placement, beam angle selection is performed manually, based on the planner’s clinical experience. The purpose of this work is to propose and study a computationally efficient framework that utilizes machine learning to automatically select treatment beam angles. Such a framework may be helpful for reducing the overall planning workload. Methods: The authors introduce an automated beam selection method, based on learning the relationships between beam angles and anatomical features. Using a large set of clinically approved IMRT plans, a random forest regression algorithm is trained to map a multitude of anatomical features into an individual beam score. An optimization scheme is then built to select and adjust the beam angles, considering the learned interbeam dependencies. The validity and quality of the automatically selected beams evaluated using the manually selected beams from the corresponding clinical plans as the ground truth. Results: The analysis included 149 clinically approved thoracic IMRT plans. For a randomly selected test subset of 27 plans, IMRT plans were generated using automatically selected beams and compared to the clinical plans. The comparison of the predicted and the clinical beam angles demonstrated a good average correspondence between the two (angular distance 16.8° ± 10°, correlation 0.75 ± 0.2). The dose distributions of the semiautomatic and clinical plans were equivalent in terms of primary target volume

  3. An investigation of PRESAGE® 3D dosimetry for IMRT and VMAT radiation therapy treatment verification

    International Nuclear Information System (INIS)

    Jackson, Jake; Juang, Titania; Oldham, Mark; Adamovics, John

    2015-01-01

    The purpose of this work was to characterize three formulations of PRESAGE ® dosimeters (DEA-1, DEA-2, and DX) and to identify optimal readout timing and procedures for accurate in-house 3D dosimetry. The optimal formulation and procedure was then applied for the verification of an intensity modulated radiation therapy (IMRT) and a volumetric modulated arc therapy (VMAT) treatment technique. PRESAGE ® formulations were studied for their temporal stability post-irradiation, sensitivity, and linearity of dose response. Dosimeters were read out using a high-resolution optical-CT scanner. Small volumes of PRESAGE ® were irradiated to investigate possible differences in sensitivity for large and small volumes (‘volume effect’). The optimal formulation and read-out technique was applied to the verification of two patient treatments: an IMRT plan and a VMAT plan. A gradual decrease in post-irradiation optical-density was observed in all formulations with DEA-1 exhibiting the best temporal stability with less than 4% variation between 2–22 h post-irradiation. A linear dose response at the 4 h time point was observed for all formulations with an R 2 value >0.99. A large volume effect was observed for DEA-1 with sensitivity of the large dosimeter being ∼63% less than the sensitivity of the cuvettes. For the IMRT and VMAT treatments, the 3D gamma passing rates for 3%/3 mm criteria using absolute measured dose were 99.6 and 94.5% for the IMRT and VMAT treatments, respectively. In summary, this work shows that accurate 3D dosimetry is possible with all three PRESAGE ® formulations. The optimal imaging windows post-irradiation were 3–24 h, 2–6 h, and immediately for the DEA-1, DEA-2, and DX formulations, respectively. Because of the large volume effect, small volume cuvettes are not yet a reliable method for calibration of larger dosimeters to absolute dose. Finally, PRESAGE ® is observed to be a useful method of 3D verification when careful

  4. Current status of intensity-modulated radiation therapy (IMRT)

    International Nuclear Information System (INIS)

    Hatano, Kazuo; Araki, Hitoshi; Sakai, Mitsuhiro

    2007-01-01

    External-beam radiation therapy has been one of the treatment options for prostate cancer. The dose response has been observed for a dose range of 64.8-81 Gy. The problem of external-beam radiotherapy (RT) for prostate cancer is that as the dose increases, adverse effects also increase. Three-dimensional conformal radiation therapy (3D-CRT) has enabled us to treat patients with up to 72-76 Gy to the prostate, with a relatively acceptable risk of late rectal bleeding. Recently, intensity-modulated radiation therapy (IMRT) has been shown to deliver a higher dose to the target with acceptable low rates of rectal and bladder complications. The most important things to keep in mind when using an IMRT technique are that there is a significant trade-off between coverage of the target, avoidance of adjacent critical structures, and the inhomogeneity of the dose within the target. Lastly, even with IMRT, it should be kept in mind that a ''perfect'' plan that creates completely homogeneous coverage of the target volume and zero or small dose to the adjacent organs at risk is not always obtained. Participating in many treatment planning sessions and arranging the beams and beam weights create the best approach to the best IMRT plan. (author)

  5. Experimental validation of deterministic Acuros XB algorithm for IMRT and VMAT dose calculations with the Radiological Physics Center's head and neck phantom

    International Nuclear Information System (INIS)

    Han Tao; Mourtada, Firas; Kisling, Kelly; Mikell, Justin; Followill, David; Howell, Rebecca

    2012-01-01

    Purpose: The purpose of this study was to verify the dosimetric performance of Acuros XB (AXB), a grid-based Boltzmann solver, in intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT). Methods: The Radiological Physics Center (RPC) head and neck (H and N) phantom was used for all calculations and measurements in this study. Clinically equivalent IMRT and VMAT plans were created on the RPC H and N phantom in the Eclipse treatment planning system (version 10.0) by using RPC dose prescription specifications. The dose distributions were calculated with two different algorithms, AXB 11.0.03 and anisotropic analytical algorithm (AAA) 10.0.24. Two dose report modes of AXB were recorded: dose-to-medium in medium (D m,m ) and dose-to-water in medium (D w,m ). Each treatment plan was delivered to the RPC phantom three times for reproducibility by using a Varian Clinac iX linear accelerator. Absolute point dose and planar dose were measured with thermoluminescent dosimeters (TLDs) and GafChromic registered EBT2 film, respectively. Profile comparison and 2D gamma analysis were used to quantify the agreement between the film measurements and the calculated dose distributions from both AXB and AAA. The computation times for AAA and AXB were also evaluated. Results: Good agreement was observed between measured doses and those calculated with AAA or AXB. Both AAA and AXB calculated doses within 5% of TLD measurements in both the IMRT and VMAT plans. Results of AXB Dm,m (0.1% to 3.6%) were slightly better than AAA (0.2% to 4.6%) or AXB Dw,m (0.3% to 5.1%). The gamma analysis for both AAA and AXB met the RPC 7%/4 mm criteria (over 90% passed), whereas AXB Dm,m met 5%/3 mm criteria in most cases. AAA was 2 to 3 times faster than AXB for IMRT, whereas AXB was 4-6 times faster than AAA for VMAT. Conclusions: AXB was found to be satisfactorily accurate when compared to measurements in the RPC H and N phantom. Compared with AAA, AXB results were equal

  6. Efficient and reliable 3D dose quality assurance for IMRT by combining independent dose calculations with measurements

    International Nuclear Information System (INIS)

    Visser, R.; Wauben, D. J. L.; Godart, J.; Langendijk, J. A.; Veld, A. A. van't; Korevaar, E. W.; Groot, M. de

    2013-01-01

    Purpose: Advanced radiotherapy treatments require appropriate quality assurance (QA) to verify 3D dose distributions. Moreover, increase in patient numbers demand efficient QA-methods. In this study, a time efficient method that combines model-based QA and measurement-based QA was developed; i.e., the hybrid-QA. The purpose of this study was to determine the reliability of the model-based QA and to evaluate time efficiency of the hybrid-QA method. Methods: Accuracy of the model-based QA was determined by comparison of COMPASS calculated dose with Monte Carlo calculations for heterogeneous media. In total, 330 intensity modulated radiation therapy (IMRT) treatment plans were evaluated based on the mean gamma index (GI) with criteria of 3%/3mm and classification of PASS (GI ≤ 0.4), EVAL (0.4 0.6), and FAIL (GI ≥ 0.6). Agreement between model-based QA and measurement-based QA was determined for 48 treatment plans, and linac stability was verified for 15 months. Finally, time efficiency improvement of the hybrid-QA was quantified for four representative treatment plans. Results: COMPASS calculated dose was in agreement with Monte Carlo dose, with a maximum error of 3.2% in heterogeneous media with high density (2.4 g/cm 3 ). Hybrid-QA results for IMRT treatment plans showed an excellent PASS rate of 98% for all cases. Model-based QA was in agreement with measurement-based QA, as shown by a minimal difference in GI of 0.03 ± 0.08. Linac stability was high with an average GI of 0.28 ± 0.04. The hybrid-QA method resulted in a time efficiency improvement of 15 min per treatment plan QA compared to measurement-based QA. Conclusions: The hybrid-QA method is adequate for efficient and accurate 3D dose verification. It combines time efficiency of model-based QA with reliability of measurement-based QA and is suitable for implementation within any radiotherapy department.

  7. SU-F-T-590: Modeling PTV Dose Fall-Off for Cervical Cancer SBRT Treatment Planning Using VMAT and Step-And-Shoot IMRT

    Energy Technology Data Exchange (ETDEWEB)

    Delgado, A Brito; Cohen, D; Eng, T; Gutierrez, A [University of Texas Health Science Center San Antonio, San Antonio, TX (United States)

    2016-06-15

    Purpose: Due to the high dose per fraction in SBRT, dose conformity and dose fall-off are critical. In patients with cervical cancer, rapid dose fall-off is particularly important to limit dose to the nearby rectum, small bowel, and bladder. This study compares the target volume dose fall-off for two radiation delivery techniques, fixed-field IMRT & VMAT, using non-coplanar beam geometries. Further comparisons are made between 6 and 10MV photon beam energies. Methods: Eleven (n=11) patients were planned in Pinnacle3 v9.10 with a NovalisTx (HD120 MLC) machine model using 6 and 10 MV photons. The following three techniques were used: (1) IMRT (10 non-coplanar beams) (2) Dual, coplanar 360° VMAT arcs (4° spacing), and (3) Triple, non-coplanar VMAT arcs (1 full arc and dual partial arcs). All plans were normalized such that 98% of the PTV received at least 28Gy/4Fx. Dose was calculated using a 2.0mm isotropic dose grid. To assess dose fall-off, twenty concentric 2mm thick rings were created around the PTV. The maximum dose in each ring was recorded and the data was fitted to model dose fall-off. A separate analysis was performed by separating target volumes into small (0–50cc), medium (51–80cc), and large (81–110cc). Results: Triple, non-coplanar VMAT arcs showed the best dose fall-off for all patients evaluated. All fitted regressions had an R{sup 2}≥0.99. At 10mm from the PTV edge, 10 MV VMAT3-arc had an absolute improvement in dose fall-off of 3.8% and 6.9% over IMRT and VMAT2-arc, respectively. At 30mm, 10 MV VMAT3-arc had an absolute improvement of 12.0% and 7.0% over IMRT and VMAT2-arc, respectively. Faster dose fall-off was observed for small volumes as opposed to medium and large ones—9.6% at 20mm. Conclusion: Triple, non-coplanar VMAT arcs offer the sharpest dose fall-off for cervical SBRT plans. This improvement is most pronounced when treating smaller target volumes.

  8. Parotid-sparing intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma: Preserved parotid function after IMRT on quantitative salivary scintigraphy, and comparison with historical data after conventional radiotherapy

    International Nuclear Information System (INIS)

    Hsiung, C.-Y.; Ting, H.-M.; Huang, H.-Y.; Lee, C.-H.; Huang, E.-Y.; Hsu, H.-C.

    2006-01-01

    Purpose: To evaluate the parotid function after parotid-sparing intensity-modulated radiotherapy (IMRT) in patients with nasopharyngeal carcinoma (NPC). Methods and Materials: From March 2003 to May 2004, 16 patients with nonmetastatic NPC underwent parotid-sparing IMRT. Eight of these patients had Stage III or IV NPC based on the 1997 American Joint Committee on Cancer staging system. The post-IMRT parotid function was evaluated by quantitative salivary scintigraphy and represented by the maximal excretion ratio (MER) of the parotid gland after sialogogue stimulation. The parotid function of 16 NPC patients who were previously treated with conventional radiotherapy was reviewed as the historical control. Results: In the parotid-sparing IMRT group, all 16 patients were alive and without cancer at the end of follow-up period (median, 24.2 months). The mean parotid MER was 53.5% before radiotherapy, 10.7% at 1 month post-IMRT, and 23.3% at 9 months post-IMRT. In the conventional radiotherapy group, the mean parotid MER was 0.6% at 6 to 12 months postradiotherapy. The difference was statistically significant (23.3% vs. 0.6%, p < 0.001, Mann-Whitney test). In the IMRT group, the mean parotid doses ranged from 33.2 Gy to 58.8 Gy (average, 43.9 Gy). The correlation between the mean parotid dose and the percentage decrease of parotid MER at 9 months post-IMRT (dMER) was statically significant (p = 0.008, Pearson correlation). Conclusions: Although the mean parotid doses are relatively high, the significant preservation of parotid function is achieved with IMRT for NPC patients. The significant correlation between mean parotid dose and parotid dMER demonstrates the dose-function relationship of the parotid gland

  9. SU-E-T-427: Feasibility Study for Evaluation of IMRT Dose Distribution Using Geant4-Based Automated Algorithms

    International Nuclear Information System (INIS)

    Choi, H; Shin, W; Testa, M; Min, C; Kim, J

    2015-01-01

    Purpose: For intensity-modulated radiation therapy (IMRT) treatment planning validation using Monte Carlo (MC) simulations, a precise and automated procedure is necessary to evaluate the patient dose distribution. The aim of this study is to develop an automated algorithm for IMRT simulations using DICOM files and to evaluate the patient dose based on 4D simulation using the Geant4 MC toolkit. Methods: The head of a clinical linac (Varian Clinac 2300 IX) was modeled in Geant4 along with particular components such as the flattening filter and the multi-leaf collimator (MLC). Patient information and the position of the MLC were imported from the DICOM-RT interface. For each position of the MLC, a step- and-shoot technique was adopted. PDDs and lateral profiles were simulated in a water phantom (50×50×40 cm 3 ) and compared to measurement data. We used a lung phantom and MC-dose calculations were compared to the clinical treatment planning used at the Seoul National University Hospital. Results: In order to reproduce the measurement data, we tuned three free parameters: mean and standard deviation of the primary electron beam energy and the beam spot size. These parameters for 6 MV were found to be 5.6 MeV, 0.2378 MeV and 1 mm FWHM respectively. The average dose difference between measurements and simulations was less than 2% for PDDs and radial profiles. The lung phantom study showed fairly good agreement between MC and planning dose despite some unavoidable statistical fluctuation. Conclusion: The current feasibility study using the lung phantom shows the potential for IMRT dose validation using 4D MC simulations using Geant4 tool kits. This research was supported by Korea Institute of Nuclear safety and Development of Measurement Standards for Medical Radiation funded by Korea research Institute of Standards and Science. (KRISS-2015-15011032)

  10. SU-E-T-417: The Impact of Normal Tissue Constraints On PTV Dose Homogeneity for Intensity Modulated Radiotherapy (IMRT), Volume Modulated Arc Therapy (VMAT) and Tomotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Peng, J; McDonald, D; Ashenafi, M; Ellis, A; Vanek, K [Medical University of South Carolina, Charleston, SC (United States)

    2014-06-01

    Purpose: Complex intensity modulated arc therapy tends to spread low dose to normal tissue(NT)regions to obtain improved target conformity and homogeneity and OAR sparing.This work evaluates the trade-offs between PTV homogeneity and reduction of the maximum dose(Dmax)spread to NT while planning of IMRT,VMAT and Tomotherapy. Methods: Ten prostate patients,previously planned with step-and-shoot IMRT,were selected.To fairly evaluate how PTV homogeneity was affected by NT Dmax constraints,original IMRT DVH objectives for PTV and OARs(femoral heads,and rectal and bladder wall)applied to 2 VMAT plans in Pinnacle(V9.0), and Tomotherapy(V4.2).The only constraint difference was the NT which was defined as body contours excluding targets,OARs and dose rings.NT Dmax constraint for 1st VMAT was set to the prescription dose(Dp).For 2nd VMAT(VMAT-NT)and Tomotherapy,it was set to the Dmax achieved in IMRT(~70-80% of Dp).All NT constraints were set to the lowest priority.Three common homogeneity indices(HI),RTOG-HI=Dmax/Dp,moderated-HI=D95%/D5% and complex-HI=(D2%-D98%)/Dp*100 were calculated. Results: All modalities with similar dosimetric endpoints for PTV and OARs.The complex-HI shows the most variability of indices,with average values of 5.9,4.9,9.3 and 6.1 for IMRT,VMAT,VMAT-NT and Tomotherapy,respectively.VMAT provided the best PTV homogeneity without compromising any OAR/NT sparing.Both VMAT-NT and Tomotherapy,planned with more restrictive NT constraints,showed reduced homogeneity,with VMAT-NT showing the worst homogeneity(P<0.0001)for all HI.Tomotherapy gave the lowest NT Dmax,with slightly decreased homogeneity compared to VMAT. Finally, there was no significant difference in NT Dmax or Dmean between VMAT and VMAT-NT. Conclusion: PTV HI is highly dependent on permitted NT constraints. Results demonstrated that VMAT-NT with more restrictive NT constraints does not reduce Dmax NT,but significantly receives higher Dmax and worse target homogeneity.Therefore, it is critical

  11. Fast optimization and dose calculation in scanned ion beam therapy

    International Nuclear Information System (INIS)

    Hild, S.; Graeff, C.; Trautmann, J.; Kraemer, M.; Zink, K.; Durante, M.; Bert, C.

    2014-01-01

    Purpose: Particle therapy (PT) has advantages over photon irradiation on static tumors. An increased biological effectiveness and active target conformal dose shaping are strong arguments for PT. However, the sensitivity to changes of internal geometry complicates the use of PT for moving organs. In case of interfractionally moving objects adaptive radiotherapy (ART) concepts known from intensity modulated radiotherapy (IMRT) can be adopted for PT treatments. One ART strategy is to optimize a new treatment plan based on daily image data directly before a radiation fraction is delivered [treatment replanning (TRP)]. Optimizing treatment plans for PT using a scanned beam is a time consuming problem especially for particles other than protons where the biological effective dose has to be calculated. For the purpose of TRP, fast optimization and fast dose calculation have been implemented into the GSI in-house treatment planning system (TPS) TRiP98. Methods: This work reports about the outcome of a code analysis that resulted in optimization of the calculation processes as well as implementation of routines supporting parallel execution of the code. To benchmark the new features, the calculation time for therapy treatment planning has been studied. Results: Compared to the original version of the TPS, calculation times for treatment planning (optimization and dose calculation) have been improved by a factor of 10 with code optimization. The parallelization of the TPS resulted in a speedup factor of 12 and 5.5 for the original version and the code optimized version, respectively. Hence the total speedup of the new implementation of the authors' TPS yielded speedup factors up to 55. Conclusions: The improved TPS is capable of completing treatment planning for ion beam therapy of a prostate irradiation considering organs at risk in this has been overseen in the review process. Also see below 6 min

  12. IMRT limits nephrotoxicity after chemoradiotherapy for gastric cancer.

    Science.gov (United States)

    Trip, Anouk Kirsten; Nijkamp, Jasper; van Tinteren, Harm; Cats, Annemieke; Boot, Henk; Jansen, Edwin Petrus Marianus; Verheij, Marcel

    2014-08-01

    This observational study compares the effect of different radiotherapy techniques on late nephrotoxicity after postoperative chemoradiotherapy for gastric cancer. Dosimetric parameters were compared between AP-PA, 3D-conformal and IMRT techniques. Renal function was measured by (99m)Tc-MAG-3 renography, glomerular filtration rate (GFR) and the development of hypertension. Mixed effects models were used to compare renal function over time. Eighty-seven patients treated between 2002 and 2010 were included, AP-PA (n=31), 3D-conformal (n=25) and IMRT (n=31), all 45 Gy in 25 fractions. Concurrent chemotherapy: 5FU/leucovorin (n=4), capecitabine (n=37), and capecitabine/cisplatin (n=46). Median follow-up time was 4.7 years (range 0.2-8). With IMRT, the mean dose to the left kidney was significantly lower. Left kidney function decreased progressively in the total study population, however with IMRT this occurred at a lower rate. A dose-effect relationship was present between mean dose to the left kidney and the left kidney function. GFR decreased only moderately in time, which was not different between techniques. Six patients developed hypertension, of whom none in the IMRT group. This study confirms progressive late nephrotoxicity in patients treated with postoperative chemoradiotherapy by different techniques for gastric cancer. Nephrotoxicity was less severe with IMRT and should be considered the preferred technique. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  13. Matching tomographic IMRT fields with static photon fields

    International Nuclear Information System (INIS)

    Sethi, A.; Leybovich, L.; Dogan, N.; Emami, B.

    2001-01-01

    The matching of abutting radiation fields presents a challenging problem in radiation therapy. Due to sharp penumbra of linear accelerator beams, small (1-2 mm) errors in field positioning can lead to large (>30%) hot or cold spots in the abutment region. With head and neck immobilization devices (thermoplastic mask/aquaplast) an average setup error of 3 mm has been reported. Therefore hot or cold spots approaching 50% of the prescription dose may occur along the matchline. Although abutting radiation fields have been investigated for static fields, there is no reported study regarding matching of tomographic IMRT and static fields. Compared to static fields, the matching of tomographic IMRT fields with static fields is more complicated. Since IMRT and static fields are planned on separate treatment planning computers, the dose in the abutment region is not specified. In addition, commonly used techniques for matching fields, such as feathering of junctions, are not practical. We have developed a method that substantially reduces dose inhomogeneity in the abutment region. In this method, a 'buffer zone' around the matchline was created and was included as part of the target for both IMRT and static field plans. In both fields, a small dose gradient (≤3%/mm) in the buffer zone was created. In the IMRT plan, the buffer zone was divided into three sections with dose varying from 83% to 25% of prescription dose. The static field dose profile was modified using either a specially designed physical (hard) or a dynamic (soft) wedge. When these modified fields were matched, the combined dose in the abutment region varied by ≤10% in the presence of setup errors spanning 4 mm (±2 mm) when the hard wedge was used and 10 mm (±5 mm) with the soft wedge

  14. On the sensitivity of IMRT dose optimization to the mathematical form of a biological imaging-based prescription function

    International Nuclear Information System (INIS)

    Bowen, Stephen R; Bentzen, Soeren M; Jeraj, Robert; Flynn, Ryan T

    2009-01-01

    Voxel-based prescriptions of deliberately non-uniform dose distributions based on molecular imaging, so-called dose painting or theragnostic radiation therapy, require specification of a transformation that maps the image data intensities to prescribed doses. However, the functional form of this transformation is currently unknown. An investigation into the sensitivity of optimized dose distributions resulting from several possible prescription functions was conducted. Transformations between the radiotracer activity concentrations from Cu-ATSM PET images, as a surrogate of tumour hypoxia, and dose prescriptions were implemented to yield weighted distributions of prescribed dose boosts in high uptake regions. Dose escalation was constrained to reflect clinically realistic whole tumour doses and constant normal tissue doses. Optimized heterogeneous dose distributions were found by minimizing a voxel-by-voxel quadratic objective function in which all tumour voxels were given equal weight. Prescriptions based on a polynomial mapping function were found to be least constraining on their optimized plans, while prescriptions based on a sigmoid mapping function were the most demanding to deliver. A prescription formalism that fixed integral dose was less sensitive to errors in the choice of the mapping function than one that boosted integral dose. Integral doses to normal tissue and critical structures were insensitive to the shape of the prescription function. Planned target dose conformity improved with smaller beamlet dimensions until the inherent spatial resolution of the functional image was matched. Clinical implementation of dose painting depends on advances in absolute quantification of functional images and improvements in delivery techniques over smaller spatial scales.

  15. Planning issues for IMRT

    International Nuclear Information System (INIS)

    Hoban, P.; Schneider, M.; Smee, R.

    2001-01-01

    Full text: Despite the 'inverse planning' stage of an intensity modulated radiotherapy (IMRT) treatment there remains a large number of variables that can, and must, be set manually. These variables can significantly affect the quality of the dose distribution arrived at by the optimisation. Clinical IMRT planning with the Radionics XPlan system for micro-multileaf collimator (MMLC) delivery has allowed for important lessons to be learned regarding the best beam and organ configurations prior to optimisation of beamlet weights. Important user-definable variables are beam directions, organ parameters (dose goals/penalties), and the margin (if any) around the planning target volume (PTV) used to aid coverage. Conventional stereotactic radiotherapy (SRT) treatments typically involve non-coplanar beams since there is often an advantage in terms of cranial organ at risk (OAR) sparing. IMRT can also benefit from such a configuration. The balance between target coverage and OAR sparing is largely controlled by user-defined goal doses and penalties. Once optimisation has been performed, intensity maps can be discretised into a selected number of levels. Less levels means less field segments and thus a shorter treatment time. Although IMRT beams attempt to spare structures which are in the 'beam's eye view' (BEV) of the target volume, sparing is greater if beams which minimise the involvement of OARs in their view are used. It has been found that the use of a margin is an effective way to ensure adequate PTV coverage. Alternatively the PTV penalties can be made larger. The best result is often obtained by the use of a 3-4 mm margin, whose penalty for underdosage is somewhat less than that for the PTV. Discretising the intensity maps to 4 or 5 levels is typically a good balance between shortening treatment time and not overly degrading the dose distribution. Beam configuration is still an important step in IMRT planning, even though optimisation of intensity maps is

  16. Radiotherapy through intensity modulation (IMRT). A new modality in the treatment of head and neck cancer

    International Nuclear Information System (INIS)

    Besa de C, Pelayo; Venencia M, Daniel

    2006-01-01

    Objective: To describe the treatment and evaluate the advantages of IMRT in the treatment of head and neck cancer. Material and methods: Four years ago, at the Cancer Center of the Pontificia Universidad Catolica, the IMRT technique for the treatment of head and neck tumors was implemented. The IMRT technique is based on modifying the intensity of the radiation beam through a multisheet collimator in order to produce a more exact distribution in the radiation doses. The results are evaluated with dose/ volume histograms. The distributions of doses and toxicity for tridimensional con formed therapy (CRT-3D) and IMRT are compared. Results: The distribution of the dose in the dose/volume histograms showed a better coverage of the white volume (PTV), with IMRT. The doses received by the organs under risk: salivary glands, eyes, ears and brain diminish with IMRT. The spinal marrow is protected with IMRT without dividing the treatment area, preventing points with lower dosage that could reduce control of the tumor. Conclusions: IMRT achieves a better conformation of the dose obtaining a better coverage of the tumor and higher protection of the organs under risk

  17. Fast, multiple optimizations of quadratic dose objective functions in IMRT

    International Nuclear Information System (INIS)

    Breedveld, Sebastiaan; Storchi, Pascal R M; Keijzer, Marleen; Heijmen, Ben J M

    2006-01-01

    Inverse treatment planning for intensity-modulated radiotherapy may include time consuming, multiple minimizations of an objective function. In this paper, methods are presented to speed up the process of (repeated) minimization of the well-known quadratic dose objective function, extended with a smoothing term that ensures generation of clinically acceptable beam profiles. In between two subsequent optimizations, the voxel-dependent importance factors of the quadratic terms will generally be adjusted, based on an intermediate plan evaluation. The objective function has been written in matrix-vector format, facilitating the use of a recently published, fast quadratic minimization algorithm, instead of commonly applied gradient-based methods. This format also reduces the calculation time in between subsequent minimizations, related to adjustment of the voxel-dependent importance factors. Sparse matrices are used to limit the required amount of computer memory. For three patients, comparisons have been made with a gradient method. Mean speed improvements of up to a factor of 37 have been achieved

  18. Intensity-Modulated Radiotherapy (IMRT) vs Helical Tomotherapy (HT) in Concurrent Chemoradiotherapy (CRT) for Patients with Anal Canal Carcinoma (ACC): an analysis of dose distribution and toxicities

    International Nuclear Information System (INIS)

    Yeung, Rosanna; McConnell, Yarrow; Warkentin, Heather; Graham, Darren; Warkentin, Brad; Joseph, Kurian; Doll, Corinne M

    2015-01-01

    Intensity-modulated radiotherapy (IMRT) and helical tomotherapy (HT) have been adopted for radiotherapy treatment of anal canal carcinoma (ACC) due to better conformality, dose homogeneity and normal-tissue sparing compared to 3D-CRT. To date, only one published study compares dosimetric parameters of IMRT vs HT in ACC, but there are no published data comparing toxicities. Our objectives were to compare dosimetry and toxicities between these modalities. This is a retrospective study of 35 ACC patients treated with radical chemoradiotherapy at two tertiary cancer institutions from 2008–2010. The use of IMRT vs HT was primarily based on center availability. The majority of patients received fluorouracil (5-FU) and 1–2 cycles of mitomycin C (MMC); 2 received 5-FU and cisplatin. Primary tumor and elective nodes were prescribed to ≥54Gy and ≥45Gy, respectively. Patients were grouped into two cohorts: IMRT vs HT. The primary endpoint was a dosimetric comparison between the cohorts; the secondary endpoint was comparison of toxicities. 18 patients were treated with IMRT and 17 with HT. Most IMRT patients received 5-FU and 1 MMC cycle, while most HT patients received 2 MMC cycles (p < 0.01), based on center policy. HT achieved more homogenous coverage of the primary tumor (HT homogeneity and uniformity index 0.14 and 1.02 vs 0.29 and 1.06 for IMRT, p = 0.01 and p < 0.01). Elective nodal coverage did not differ. IMRT achieved better bladder, femoral head and peritoneal space sparing (V30 and V40, p ≤ 0.01), and lower mean skin dose (p < 0.01). HT delivered lower bone marrow (V10, p < 0.01) and external genitalia dose (V20 and V30, p < 0.01). Grade 2+ hematological and non-hematological toxicities were similar. Febrile neutropenia and unscheduled treatment breaks did not differ (both p = 0.13), nor did 3-year overall and disease-free survival (p = 0.13, p = 0.68). Chemoradiotherapy treatment of ACC using IMRT vs HT results in differences in dose homogenity and

  19. Consequences of leaf calibration errors on IMRT delivery

    International Nuclear Information System (INIS)

    Sastre-Padro, M; Welleweerd, J; Malinen, E; Eilertsen, K; Olsen, D R; Heide, U A van der

    2007-01-01

    IMRT treatments using multi-leaf collimators may involve a large number of segments in order to spare the organs at risk. When a large proportion of these segments are small, leaf positioning errors may become relevant and have therapeutic consequences. The performance of four head and neck IMRT treatments under eight different cases of leaf positioning errors has been studied. Systematic leaf pair offset errors in the range of ±2.0 mm were introduced, thus modifying the segment sizes of the original IMRT plans. Thirty-six films were irradiated with the original and modified segments. The dose difference and the gamma index (with 2%/2 mm criteria) were used for evaluating the discrepancies between the irradiated films. The median dose differences were linearly related to the simulated leaf pair errors. In the worst case, a 2.0 mm error generated a median dose difference of 1.5%. Following the gamma analysis, two out of the 32 modified plans were not acceptable. In conclusion, small systematic leaf bank positioning errors have a measurable impact on the delivered dose and may have consequences for the therapeutic outcome of IMRT

  20. A fast 4D IMRT/VMAT planning method based on segment aperture morphing.

    Science.gov (United States)

    Klawikowski, Slade; Tai, An; Ates, Ozgur; Ahunbay, Ergun; Li, X Allen

    2018-04-01

    Four-dimensional volumetric modulated arc therapy (4D VMAT) and four-dimensional intensity-modulated radiotherapy (4D IMRT) are developing radiation therapy treatment strategies designed to maximize dose conformality, minimize normal tissue dose, and deliver the treatment as efficiently as possible. The patient's entire breathing cycle is captured through 4D imaging modalities and then separated into individual breathing phases for planning purposes. Optimizing multiphase VMAT and IMRT plans is computationally demanding and currently impractical for clinical application. The purpose of this study is to assess a new planning process decreasing the upfront computational time required to optimize multiphased treatment plans while maintaining good plan quality. Optimized VMAT and IMRT plans were created on the end-of-exhale (EOE) breathing phase of 10-phase 4D CT scans with planning tumor volume (PTV)-based targets. These single-phase optimized plans are analogous to single-phase gated treatment plans. The simulated tracked plans were created by deformably registering EOE contours to the remaining breathing phases, recalculating the optimized EOE plan onto the other individual phases and realigning the MLC's relative positions to the PTV border in each of the individual breathing phases using a segment aperture morphing (SAM) algorithm. Doses for each of the 10 phases were calculated with the treatment planning system and deformably transferred back onto the EOE phase and averaged with equal weighting simulating the actual delivered dose a patient would potentially receive in a tracked treatment plan. Plan DVH quality for the 10-phase 4D SAM plans were comparable with the individual EOE optimized treatment plans for the PTV structures as well as the organ at risk structures. SAM-based algorithms out performed simpler isocenter-shifted only approaches. SAM-based 4D planning greatly reduced plan computation time vs individually optimizing all 10 phases. In addition

  1. Dose verification in HDR brachytherapy and IMRT with Fricke gel-layer dosimeters

    International Nuclear Information System (INIS)

    Gambarini, G.; Negri, A.; Bartesaghi, G.; Pirola, L.; Carrara, M.; Gambini, I.; Tomatis, S.; Fallai, C.; Zonca, G.; Stokucova, J.

    2009-10-01

    At the Department of Physics of the Universita degli Studi di Milano in collaboration with the Medical Physics Unit and the Radiotherapy Unit of the Fondazione IRCCS Istituto Nazionale dei Tumori di Milano the research of a dosimetric technique based on Fricke gel layers and optical analysis in under study. In fact, Fricke gel layer dosimeters (FGLD) have various advantages such as the tissue-equivalence for photons in the clinical energy interval, the possibility to obtain the spatial information about continuous dose distribution and not only a point dose distribution as it is for example in the case of ionization chambers, TLD or diodes and the possibility to obtain the information about 3D dose distributions. In this work, specific applications of FGLD to absolute dosimetry in radiotherapy have been studied, i.e. in-phantom measurements of complex intensity modulated radiation therapy fields (IMRT) and complex brachytherapy fields. (Author)

  2. SU-E-T-621: Planning Methodologies for Cancer of the Anal Canal: Comparing IMRT, Rapid Arc, and Pencil Beam Scanning Proton Beam

    International Nuclear Information System (INIS)

    McGlade, J; Kassaee, A

    2015-01-01

    Purpose: To evaluate planning methods for anal canal cancer and compare the results of 9-field Intensity Modulated Radiotherapy (IMRT), Volumetric Modulated Arc Therapy (Varian, RapidArc), and Proton Pencil Beam Scanning (PBS). Methods: We generated plans with IMRT, RapidArc (RA) and PBS for twenty patients for both initial phase including nodes and cone down phase of treatment using Eclipe (Varian). We evaluated the advantage of each technique for each phase. RA plans used 2 to 4 arcs and various collimator orientations. PBS used two posterior oblique fields. We evaluated the plans comparing dose volume histogram (DVH), locations of hot spots, and PTV dose conformity. Results: Due to complex shape of target, for RA plans, multiple arcs (>2) are required to achieve optimal PTV conformity. When the PTV exceeds 15 cm in the superior-inferior direction, limitations of deliverability start to dominate. The PTV should be divided into a superior and an inferior structure. The optimization is performed with fixed jaws for each structure and collimator set to 90 degrees for the inferior PTV. Proton PBS plans show little advantage in small bowel sparing when treating the nodes. However, PBS plan reduces volumetric dose to the bladder at the cost of higher doses to the perineal skin. IMRT plans provide good target conformity, but they generate hot spots outside of the target volume. Conclusion: When using one planning technique for entire course of treatment, Multiple arc (>2) RA plans are better as compared to IMRT and PBS plans. When combining techniques, RA for the initial phase in combination with PBS for the cone down phase results in the most optimal plans

  3. SU-E-T-621: Planning Methodologies for Cancer of the Anal Canal: Comparing IMRT, Rapid Arc, and Pencil Beam Scanning Proton Beam

    Energy Technology Data Exchange (ETDEWEB)

    McGlade, J; Kassaee, A [University of Pennsylvenia, Philadelphia, PA (United States)

    2015-06-15

    Purpose: To evaluate planning methods for anal canal cancer and compare the results of 9-field Intensity Modulated Radiotherapy (IMRT), Volumetric Modulated Arc Therapy (Varian, RapidArc), and Proton Pencil Beam Scanning (PBS). Methods: We generated plans with IMRT, RapidArc (RA) and PBS for twenty patients for both initial phase including nodes and cone down phase of treatment using Eclipe (Varian). We evaluated the advantage of each technique for each phase. RA plans used 2 to 4 arcs and various collimator orientations. PBS used two posterior oblique fields. We evaluated the plans comparing dose volume histogram (DVH), locations of hot spots, and PTV dose conformity. Results: Due to complex shape of target, for RA plans, multiple arcs (>2) are required to achieve optimal PTV conformity. When the PTV exceeds 15 cm in the superior-inferior direction, limitations of deliverability start to dominate. The PTV should be divided into a superior and an inferior structure. The optimization is performed with fixed jaws for each structure and collimator set to 90 degrees for the inferior PTV. Proton PBS plans show little advantage in small bowel sparing when treating the nodes. However, PBS plan reduces volumetric dose to the bladder at the cost of higher doses to the perineal skin. IMRT plans provide good target conformity, but they generate hot spots outside of the target volume. Conclusion: When using one planning technique for entire course of treatment, Multiple arc (>2) RA plans are better as compared to IMRT and PBS plans. When combining techniques, RA for the initial phase in combination with PBS for the cone down phase results in the most optimal plans.

  4. Small bowel protection in IMRT for rectal cancer. A dosimetric study on supine vs. prone position

    Energy Technology Data Exchange (ETDEWEB)

    Koeck, Julia; Kromer, Katharina; Siebenlist, Kerstin; Mai, Sabine; Fleckenstein, Jens; Wenz, Frederik [University of Heidelberg, Department of Radiation Oncology, University Medical Center Mannheim, Mannheim (Germany); Lohr, Frank [Az. Ospedaliero-Universitaria di Modena, Unita Operativa di Radioterapia, Dipartimento di Oncologia, Modena (Italy); Baack, Tobias [GRN Clinic Weinheim, Department of Internal Medicine, Weinheim (Germany); Buettner, Sylvia [University of Heidelberg, Department of Biomathematics and Medical Statistics, University Medical Center Mannheim, Mannheim (Germany)

    2017-07-15

    This treatment planning study analyzes dose coverage and dose to organs at risk (OAR) in intensity-modulated radiotherapy (IMRT) of rectal cancer and compares prone vs. supine positioning as well as the effect of dose optimization for the small bowel (SB) by additional dose constraints in the inverse planning process. Based on the CT datasets of ten male patients in both prone and supine position, a total of four different IMRT plans were created for each patient. OAR were defined as the SB, bladder, and femoral heads. In half of the plans, two additional SB cost functions were used in the inverse planning process. There was a statistically significant dose reduction for the SB in prone position of up to 41% in the high and intermediate dose region, compared with the supine position. Furthermore, the femoral heads showed a significant dose reduction in prone position in the low dose region. Regarding the additional active SB constraints, the dose in the high dose region of the SB was significantly reduced by up to 14% with the additional cost functions. There were no significant differences in the dose distribution of the planning target volume (PTV) and the bladder. Prone positioning can significantly reduce dose to the SB in IMRT for rectal cancer and therefore should not only be used in 3D conformal radiotherapy but also in IMRT of rectal cancer. Further protection of the SB can be achieved by additional dose constraints in inverse planning without jeopardizing the homogeneity of the PTV. (orig.) [German] Diese Planungsstudie analysiert die Dosisverteilung im Zielvolumen und in den Risikoorganen (''organs at risk'', OAR) bei der intensitaetsmodulierten Strahlentherapie (''intensity-modulated radiotherapy'', IMRT) des Rektumkarzinoms und vergleicht hierbei Bauch- und Rueckenlagerung sowie die Effekte der Dosisoptimierung fuer den Duenndarm (DD) durch zusaetzliche Dosiseinschraenkungen bei der inversen Planung. Anhand der

  5. Genital marginal failures after intensity-modulated radiation therapy (IMRT) in squamous cell anal cancer: no higher risk with IMRT when compared to 3DCRT.

    Science.gov (United States)

    Dell'Acqua, V; Kobiela, J; Kraja, F; Leonardi, M C; Surgo, A; Zerella, M A; Arculeo, S; Fodor, C; Ricotti, R; Zampino, M G; Ravenda, S; Spinoglio, G; Biffi, R; Bazani, A; Luraschi, R; Vigorito, S; Spychalski, P; Orecchia, R; Glynne-Jones, R; Jereczek-Fossa, B A

    2018-03-28

    Intensity-modulated radiotherapy (IMRT) is considered the preferred option in squamous cell canal cancer (SCAC), delivering high doses to tumor volumes while minimizing dose to surrounding normal tissues. IMRT has steep dose gradients, but the technique is more demanding as deep understanding of target structures is required. To evaluate genital marginal failure in a cohort of patients with non-metastatic SCAC treated either with IMRT or 3DCRT and concurrent chemotherapy, 117 patients with SCAC were evaluated: 64 and 53 patients were treated with IMRT and 3DCRT techniques, respectively. All patients underwent clinical and radiological examination during their follow-up. Tumor response was evaluated with response evaluation criteria in solid tumors v1.1 guideline on regular basis. All patients' data were analyzed, and patients with marginal failure were identified. Concomitant chemotherapy was administered in 97 and 77.4% of patients in the IMRT and 3DCRT groups, respectively. In the IMRT group, the median follow-up was 25 months (range 6-78). Progressive disease was registered in 15.6% of patients; infield recurrence, distant recurrence and both infield recurrence and distant recurrence were identified in 5, 4 and 1 patient, respectively. Two out of 64 patients (3.1%) had marginal failures, localized at vagina/recto-vaginal septum and left perineal region. In the 3DCRT group, the median follow-up was 71.3 months (range 6-194 months). Two out of 53 patients (3.8%) had marginal failures, localized at recto-vaginal septum and perigenital structures. The rate of marginal failures was comparable in IMRT and 3DCRT groups (χ 2 test p = 0.85). In this series, the use of IMRT for the treatment of SCAC did not increase the rate of marginal failures offering improved dose conformity to the target. Dose constraints should be applied with caution-particularly in females with involvement of the vagina or the vaginal septum.

  6. Poster - 53: Improving inter-linac DMLC IMRT dose precision by fine tuning of MLC leaf calibration

    International Nuclear Information System (INIS)

    Nakonechny, Keith; Tran, Muoi; Sasaki, David; Beck, James; Poirier, Yannick; Malkoske, Kyle

    2016-01-01

    Purpose: To develop a method to improve the inter-linac precision of DMLC IMRT dosimetry. Methods: The distance between opposing MLC leaf banks (“gap size”) can be finely tuned on Varian linacs. The dosimetric effect due to small deviations from the nominal gap size (“gap error”) was studied by introducing known errors for several DMLC sliding gap sizes, and for clinical plans based on the TG119 test cases. The plans were delivered on a single Varian linac and the relationship between gap error and the corresponding change in dose was measured. The plans were also delivered on eight Varian 2100 series linacs (at two institutions) in order to quantify the inter-linac variation in dose before and after fine tuning the MLC calibration. Results: The measured dose differences for each field agreed well with the predictions of LoSasso et al. Using the default MLC calibration, the variation in the physical MLC gap size was determined to be less than 0.4 mm between all linacs studied. The dose difference between the linacs with the largest and smallest physical gap was up to 5.4% (spinal cord region of the head and neck TG119 test case). This difference was reduced to 2.5% after fine tuning the MLC gap calibration. Conclusions: The inter-linac dose precision for DMLC IMRT on Varian linacs can be improved using a simple modification of the MLC calibration procedure that involves fine adjustment of the nominal gap size.

  7. Poster - 53: Improving inter-linac DMLC IMRT dose precision by fine tuning of MLC leaf calibration

    Energy Technology Data Exchange (ETDEWEB)

    Nakonechny, Keith; Tran, Muoi; Sasaki, David; Beck, James; Poirier, Yannick; Malkoske, Kyle [Simcoe-Muskoka Regional Cancer Centre (Canada)

    2016-08-15

    Purpose: To develop a method to improve the inter-linac precision of DMLC IMRT dosimetry. Methods: The distance between opposing MLC leaf banks (“gap size”) can be finely tuned on Varian linacs. The dosimetric effect due to small deviations from the nominal gap size (“gap error”) was studied by introducing known errors for several DMLC sliding gap sizes, and for clinical plans based on the TG119 test cases. The plans were delivered on a single Varian linac and the relationship between gap error and the corresponding change in dose was measured. The plans were also delivered on eight Varian 2100 series linacs (at two institutions) in order to quantify the inter-linac variation in dose before and after fine tuning the MLC calibration. Results: The measured dose differences for each field agreed well with the predictions of LoSasso et al. Using the default MLC calibration, the variation in the physical MLC gap size was determined to be less than 0.4 mm between all linacs studied. The dose difference between the linacs with the largest and smallest physical gap was up to 5.4% (spinal cord region of the head and neck TG119 test case). This difference was reduced to 2.5% after fine tuning the MLC gap calibration. Conclusions: The inter-linac dose precision for DMLC IMRT on Varian linacs can be improved using a simple modification of the MLC calibration procedure that involves fine adjustment of the nominal gap size.

  8. Clinical implementation of dose-volume histogram predictions for organs-at-risk in IMRT planning

    International Nuclear Information System (INIS)

    Moore, K L; Appenzoller, L M; Tan, J; Michalski, J M; Thorstad, W L; Mutic, S

    2014-01-01

    True quality control (QC) of the planning process requires quantitative assessments of treatment plan quality itself, and QC in IMRT has been stymied by intra-patient anatomical variability and inherently complex three-dimensional dose distributions. In this work we describe the development of an automated system to reduce clinical IMRT planning variability and improve plan quality using mathematical models that predict achievable OAR DVHs based on individual patient anatomy. These models rely on the correlation of expected dose to the minimum distance from a voxel to the PTV surface, whereby a three-parameter probability distribution function (PDF) was used to model iso-distance OAR subvolume dose distributions. DVH models were obtained by fitting the evolution of the PDF with distance. Initial validation on clinical cohorts of 40 prostate and 24 head-and-neck plans demonstrated highly accurate model-based predictions for achievable DVHs in rectum, bladder, and parotid glands. By quantifying the integrated difference between candidate DVHs and predicted DVHs, the models correctly identified plans with under-spared OARs, validated by replanning all cases and correlating any realized improvements against the predicted gains. Clinical implementation of these predictive models was demonstrated in the PINNACLE treatment planning system by use of existing margin expansion utilities and the scripting functionality inherent to the system. To maintain independence from specific planning software, a system was developed in MATLAB to directly process DICOM-RT data. Both model training and patient-specific analyses were demonstrated with significant computational accelerations from parallelization.

  9. SU-F-T-391: Comparative Study of Treatment Planning Between IMRT and IMAT for Malignant Pleural Mesothelioma

    International Nuclear Information System (INIS)

    Duan, J

    2016-01-01

    Purpose: The purpose of this study was to compare the dosimetric differences between intensitymodulated radiation therapy (IMRT) and intensity modulated arc therapy (IMAT) for malignant pleural mesothelioma (MPM) patients with regard to the sparing effect on organs at risk (OARs), plan quality, and delivery efficiency. Methods: Ten MPM patients were recruited in this study. To avoid the inter-operator variability, IMRT and IMAT plans for each patient were performed by one experienced dosimetrist. The treatment planning optimization process was carried out using the Eclipse 13.0 software. For a fair comparison, the planning target volume (PTV) coverage of the two plans was normalized to the same level. The treatment plans were evaluated on the following dosimetric variables: conformity index (CI) and homogeneity index (HI) for PTV, OARs dose, and the delivery efficiency for each plan. Results: All plans satisfied clinical requirements. The IMAT plans gained better CI and HI. The IMRT plans performed better sparing for heart and lung. Less MUs and control points were found in the IMAT plans. IMAT shortened delivery time compared with IMRT. Conclusion: For MPM, IMAT gains better conformity and homogeneity for PTV with IMRT, but increases the irradiation dose for OARs. IMAT shows an advantage in delivery efficiency.

  10. SU-F-T-391: Comparative Study of Treatment Planning Between IMRT and IMAT for Malignant Pleural Mesothelioma

    Energy Technology Data Exchange (ETDEWEB)

    Duan, J [Shandong Cancer Hospital and Institute, Jinan, Shandong province (China)

    2016-06-15

    Purpose: The purpose of this study was to compare the dosimetric differences between intensitymodulated radiation therapy (IMRT) and intensity modulated arc therapy (IMAT) for malignant pleural mesothelioma (MPM) patients with regard to the sparing effect on organs at risk (OARs), plan quality, and delivery efficiency. Methods: Ten MPM patients were recruited in this study. To avoid the inter-operator variability, IMRT and IMAT plans for each patient were performed by one experienced dosimetrist. The treatment planning optimization process was carried out using the Eclipse 13.0 software. For a fair comparison, the planning target volume (PTV) coverage of the two plans was normalized to the same level. The treatment plans were evaluated on the following dosimetric variables: conformity index (CI) and homogeneity index (HI) for PTV, OARs dose, and the delivery efficiency for each plan. Results: All plans satisfied clinical requirements. The IMAT plans gained better CI and HI. The IMRT plans performed better sparing for heart and lung. Less MUs and control points were found in the IMAT plans. IMAT shortened delivery time compared with IMRT. Conclusion: For MPM, IMAT gains better conformity and homogeneity for PTV with IMRT, but increases the irradiation dose for OARs. IMAT shows an advantage in delivery efficiency.

  11. IMRT delivery verification using a spiral phantom

    International Nuclear Information System (INIS)

    Richardson, Susan L.; Tome, Wolfgang A.; Orton, Nigel P.; McNutt, Todd R.; Paliwal, Bhudatt R.

    2003-01-01

    In this paper we report on the testing and verification of a system for IMRT delivery quality assurance that uses a cylindrical solid water phantom with a spiral trajectory for radiographic film placement. This spiral film technique provides more complete dosimetric verification of the entire IMRT treatment than perpendicular film methods, since it samples a three-dimensional dose subspace rather than using measurements at only one or two depths. As an example, the complete analysis of the predicted and measured spiral films is described for an intracranial IMRT treatment case. The results of this analysis are compared to those of a single field perpendicular film technique that is typically used for IMRT QA. The comparison demonstrates that both methods result in a dosimetric error within a clinical tolerance of 5%, however the spiral phantom QA technique provides a more complete dosimetric verification while being less time consuming. To independently verify the dosimetry obtained with the spiral film, the same IMRT treatment was delivered to a similar phantom in which LiF thermoluminescent dosimeters were arranged along the spiral trajectory. The maximum difference between the predicted and measured TLD data for the 1.8 Gy fraction was 0.06 Gy for a TLD located in a high dose gradient region. This further validates the ability of the spiral phantom QA process to accurately verify delivery of an IMRT plan

  12. Surviving Hypopharynx-Larynx Carcinoma in the Era of IMRT

    International Nuclear Information System (INIS)

    Studer, Gabriela; Peponi, Evangelia; Kloeck, Stephan; Dossenbach, Thomas; Huber, Gerhard; Glanzmann, Christoph

    2010-01-01

    Purpose: Outcome in locoregionally advanced laryngeal carcinoma and hypopharyngeal carcinoma after conventional radiation techniques is known for modest disease control and considerable late toxicity. Considering the lack of standardization in prescription dose for intensity-modulated radiotherapy (IMRT), we aimed to compare the results after our methods of simultaneously integrated boost IMRT with published results. Methods and Materials: Between March 2002 and December 2008, 65 hypopharyngeal, 31 supraglottic, and 27 locoregionally advanced glottic tumor patients underwent definitive IMRT (with simultaneous chemotherapy in 86%). Of these, 64% presented with locoregionally advanced disease. Mean follow-up was 26 months (range, 3-83 months), with a median of 21 months. Treatment (2.0-2.2Gy per fraction, 66-72.6Gy) followed a prospectively defined protocol. If the boost volume included more than half of the larynx or a substantial part of the pharynx, dose was limited to 2.0Gy per fraction. Results: The 2-year local, nodal, and locoregional control (LRC) rates for the entire cohort were 82%, 90%, and 77%, respectively; the disease-free and overall survival rates were 75% and 83%, respectively. The ultimate 2-year LRC rate, including salvage surgery, was 86%. Laryngectomy was required in 2 LRC patients needing tracheostoma already before; 2 further LRC patients needed tracheostomy before IMRT and remained tracheostoma dependent, and 3 patients remained feeding tube dependent after IMRT. Salvage laryngectomy was successful in 8 of 11. Of all 123 patients, 91 patients (74%) are locoregionally controlled and live with a functional laryngopharynx. Conclusions: Simultaneously integrated boost IMRT with limited acceptance of dose inhomogeneity resulted in very satisfactory disease control despite a slight left shift of planning target volume curves on the dose-volume histogram. Considering the treatment tolerance, a careful increase in dose in our patients seems possible

  13. Evaluation tools of quality control for patients submitted to IMRT

    International Nuclear Information System (INIS)

    Lavor, Milton

    2011-01-01

    Intensity modulated radiation therapy (IMRT) is currently been implemented in a rapidly growing number of centers in Brazil. As consequence many institutions are now facing the problem of performing a comprehensive quality control program before and during the implementation of IMRT in the clinical routine practice. The aim of this work is to evaluate and propose a methodology for quality assurance in IMRT treatments. An ionization chamber and a two-dimensional array detector were performed to assess the absolute value of the total dose of all fields in one specific point. The relative total dose distribution of all fields was measured with a radiochromic film and a two-dimensional array at one depth in a phantom. A comparison between measured and calculated dose distributions was performed using the gamma-index method, assessing the percentage of points that meet the criteria of +-3% dose difference and +-3 mm distance to agreement. As a result of 113 tested IMRT beams using ionization chamber and 81 using two-dimensional array, the proposal was to take an action level of about +- 5% compared to the treatment planning systems and measurements, for the verification of the dose in a single point at the low gradient dose region. Analysis of the two-dimensional array measurements showed that the gamma value was <1 for 97.7% of the data and for the film the gamma value was <1 for 96.6% of the data. This can be concluded that for an accurate delivery of dose in 'sliding-window' IMRT with micro multileaf collimator, the absolute value of the total dose and the relative total dose distribution should be checked by absolute and relative dosimetry respectively. (author)

  14. Dose-volume histogram comparison between static 5-field IMRT with 18-MV X-rays and helical tomotherapy with 6-MV X-rays.

    Science.gov (United States)

    Hayashi, Akihiro; Shibamoto, Yuta; Hattori, Yukiko; Tamura, Takeshi; Iwabuchi, Michio; Otsuka, Shinya; Sugie, Chikao; Yanagi, Takeshi

    2015-03-01

    We treated prostate cancer patients with static 5-field intensity-modulated radiation therapy (IMRT) using linac 18-MV X-rays or tomotherapy with 6-MV X-rays. As X-ray energies differ, we hypothesized that 18-MV photon IMRT may be better for large patients and tomotherapy may be more suitable for small patients. Thus, we compared dose-volume parameters for the planning target volume (PTV) and organs at risk (OARs) in 59 patients with T1-3 N0M0 prostate cancer who had been treated using 5-field IMRT. For these same patients, tomotherapy plans were also prepared for comparison. In addition, plans of 18 patients who were actually treated with tomotherapy were analyzed. The evaluated parameters were homogeneity indicies and a conformity index for the PTVs, and D2 (dose received by 2% of the PTV in Gy), D98, Dmean and V10-70 Gy (%) for OARs. To evaluate differences by body size, patients with a known body mass index were grouped by that index ( 25 kg/m(2)). For the PTV, all parameters were higher in the tomotherapy plans compared with the 5-field IMRT plans. For the rectum, V10 Gy and V60 Gy were higher, whereas V20 Gy and V30 Gy were lower in the tomotherapy plans. For the bladder, all parameters were higher in the tomotherapy plans. However, both plans were considered clinically acceptable. Similar trends were observed in 18 patients treated with tomotherapy. Obvious trends were not observed for body size. Tomotherapy provides equivalent dose distributions for PTVs and OARs compared with 18-MV 5-field IMRT. Tomotherapy could be used as a substitute for high-energy photon IMRT for prostate cancer regardless of body size. © The Author 2015. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  15. SU-E-T-538: Evaluation of IMRT Dose Calculation Based on Pencil-Beam and AAA Algorithms.

    Science.gov (United States)

    Yuan, Y; Duan, J; Popple, R; Brezovich, I

    2012-06-01

    To evaluate the accuracy of dose calculation for intensity modulated radiation therapy (IMRT) based on Pencil Beam (PB) and Analytical Anisotropic Algorithm (AAA) computation algorithms. IMRT plans of twelve patients with different treatment sites, including head/neck, lung and pelvis, were investigated. For each patient, dose calculation with PB and AAA algorithms using dose grid sizes of 0.5 mm, 0.25 mm, and 0.125 mm, were compared with composite-beam ion chamber and film measurements in patient specific QA. Discrepancies between the calculation and the measurement were evaluated by percentage error for ion chamber dose and γ〉l failure rate in gamma analysis (3%/3mm) for film dosimetry. For 9 patients, ion chamber dose calculated with AAA-algorithms is closer to ion chamber measurement than that calculated with PB algorithm with grid size of 2.5 mm, though all calculated ion chamber doses are within 3% of the measurements. For head/neck patients and other patients with large treatment volumes, γ〉l failure rate is significantly reduced (within 5%) with AAA-based treatment planning compared to generally more than 10% with PB-based treatment planning (grid size=2.5 mm). For lung and brain cancer patients with medium and small treatment volumes, γ〉l failure rates are typically within 5% for both AAA and PB-based treatment planning (grid size=2.5 mm). For both PB and AAA-based treatment planning, improvements of dose calculation accuracy with finer dose grids were observed in film dosimetry of 11 patients and in ion chamber measurements for 3 patients. AAA-based treatment planning provides more accurate dose calculation for head/neck patients and other patients with large treatment volumes. Compared with film dosimetry, a γ〉l failure rate within 5% can be achieved for AAA-based treatment planning. © 2012 American Association of Physicists in Medicine.

  16. Imaging and concomitant dose in radiotherapy

    International Nuclear Information System (INIS)

    Negi, P.S.

    2008-01-01

    Image guidance in radiotherapy now involves multiple imaging procedures for planning, simulation, set-up inter and intrafraction monitoring. Presently ALARA (i.e. as low as reasonable achievable) is the principle of management of dose to radiation workers and patients in any diagnostic imaging procedures including image guided surgery. The situation is different in repeated radiographic/fluoroscopic imaging performed for simulation, dose planning, patient positioning and set-up corrections during preparation/execution of Image guided radiotherapy (IGRT) as well as for Intensity Modulated Radiotherapy (IMRT). Reported imaging and concomitant doses will be highlighted and discussed for the management and optimization of imaging techniques in IMRT and IGRT

  17. Evaluation of quality control tools for patients submitted to IMRT; Avaliacao das ferramentas de controle da qualidade para pacientes submetidos ao IMRT

    Energy Technology Data Exchange (ETDEWEB)

    Lavor, Milton; Rodrigues, Laura N.; Silva, Marco A., E-mail: miltonlavor@gmail.com [Universidade de Sao Paulo (HCFMRP/USP), Sao Paulo, SP (Brazil). Hospital das Clinicas. Servico de Radioterapia

    2013-04-15

    Intensity modulated radiation therapy (IMRT) is currently being implemented in a rapidly growing number of centers in Brazil. As consequence many institutions are now facing the problem of performing a comprehensive quality control program before and during the implementation of IMRT in the clinical practice. This paper proposes a methodology for quality control and presents the results and evaluations of the data obtained from the proposed methodology. Ionization chamber and two-dimensional array detector were performed in IMRT treatment planning in order to assess the absolute value of the total dose of all fields. The relative total dose distribution of all fields was measured with a radiochromic film and a two-dimensional array in a phantom. A comparison between measured and calculated dose distributions was performed using the gamma-index method, assessing the percentage of points that meet the criteria of ±3% dose difference and ±3mm distance to agreement. As a result and review of 113 tested IMRT beams using ionization chamber and 81 using two-dimensional array, the proposal was to take an action level of about ±5% compared to the treatment planning systems and measurements, for the verification of the dose in a single point at the low gradient dose region. Analysis of the two-dimensional array measurements showed that the gamma value was <1 for 97.7% of the data and for the film the gamma value was <1 for 96.6% of the data. This work can establish action levels required for quality control program proposed and implemented in the Department of Radiotherapy - Hospital das Clinicas in Sao Paulo that allows an accurate delivery of dose in 'sliding-window' IMRT with micro multi leaf collimator. (author)

  18. Serial tomotherapy vs. MLC-IMRT (Multileaf Collimator Intensity Modulated Radiotherapy) for simultaneous boost treatment large intracerebral lesions

    International Nuclear Information System (INIS)

    Wolff, Dirk; Lohr, Frank; Mai, Sabine; Polednik, Martin; Wenz, Frederik; Dobler, Barbara

    2009-01-01

    Introduction: Recent data suggest that a radiosurgery boost treatment for up to three brain metastases in addition to whole brain radiotherapy (WBRT) is beneficial. Sequential treatment of multiple metastatic lesions is time-consuming and optimal normal tissue sparing is not trivial for larger metastases when separate plans are created and are only superimposed afterwards. Sequential Tomotherapy with noncoplanar arcs and Multi-field IMRT may streamline the process and enable easy simultaneous treatment. We compared plans for 2-3 intracerebral targets calculated with Intensity Modulated Radiotherapy (IMRT) based on treatment with MLC or sequential Tomotherapy using the Peacock-System. Treatment time was not to exceed 90 min on a linac with standart dose rate. MIMiC plans without treatment-time restrictions were created as a benchmark. Materials and methods: Calculations are based on a Siemens KD2 linac with a dose rate of 200 MU/min. Step-and-Shoot IMRT is performed with a standard MLC (2 x 29 leaves, 1 cm), serial Tomotherapy with the Multivane-Collimator MIMiC (NOMOS Inc. USA). Treatment plans are created with Corvus 5.0. To create plans with good conformity we chose a noncoplanar beam- and arc geometry for each approach (IMRT 4-, MIMiC 5-couch angles). The benchmark MIMiC plans with maximally steep dose gradients had 9 couch angles. For plan comparison reasons, 10Gy were prescribed to 90% of the PTV. Steepness of dose gradients, homogeneity and conformity were assessed by the following parameters: Volume encompassed by certain isodoses outside the target as well as homogeneity and conformity as indicated by Homogeneity- and Conformity-Index. Results: Plans without treatment-time restrictions had slightest dose to organ at risk (OAR), normal tissue and least Conformity-index. MIMiC- and MLC-IMRT based plans can be treated within the intended period of 90 min, all plans met the required dose. MLC based plans resulted in higher dose to organs at risk (OAR) and dose

  19. IMRT in hypopharyngeal tumors

    Energy Technology Data Exchange (ETDEWEB)

    Studer, G.; Luetolf, U.M.; Davis, J.B.; Glanzmann, C. [Dept. of Radiation Oncology, Univ. Hospital, Zurich (Switzerland)

    2006-06-15

    Background and purpose: intensity-modulated radiation therapy (IMRT) data on hypopharyngeal cancer (HC) are scant. In this study, the authors report on early results in an own HC patient cohort treated with IMRT. A more favorable outcome as compared to historical data on conventional radiation techniques was expected. Patients and methods: 29 consecutive HC patients were treated with simultaneous integrated boost (SIB) IMRT between 01/2002 and 07/2005 (mean follow-up 16 months, range 4-44 months). Doses of 60-71 Gy with 2.0-2.2 Gy/fraction were applied. 26/29 patients were definitively irradiated, 86% received simultaneous cisplatin-based chemotherapy. 60% presented with locally advanced disease (T3/4 Nx, Tx N2c/3). Mean primary tumor volume measured 36.2 cm{sup 3} (4-170 cm{sup 3}), mean nodal volume 16.6 cm{sup 3} (0-97 cm{sup 3}). Results: 2-year actuarial local, nodal, distant control, and overall disease-free survival were 90%, 93%, 93%, and 90%, respectively. In 2/4 patients with persistent disease (nodal in one, primary in three), salvage surgery was performed. The mean dose to the spinal cord (extension of > 5-15 mm) was 26 Gy (12-38 Gy); the mean maximum (point) dose was 44.4 Gy (26-58.9 Gy). One grade (G) 3 dysphagia and two G4 reactions (laryngeal fibrosis, dysphagia), both following the schedule with 2.2 Gy per fraction, have been observed so far. Larynx preservation was achieved in 25/26 of the definitively irradiated patients (one underwent a salvage laryngectomy); 23 had no or minimal dysphagia (G0-1). Conclusion: excellent early disease control and high patient satisfaction with swallowing function in HC following SIB IMRT were observed; these results need to be confirmed based on a longer follow-up period. In order to avoid G4 reactions, SIB doses of < 2.2 Gy/fraction are recommended for large tumors involving laryngeal structures. (orig.)

  20. Monte Carlo simulations to replace film dosimetry in IMRT verification

    International Nuclear Information System (INIS)

    Goetzfried, Thomas; Trautwein, Marius; Koelbi, Oliver; Bogner, Ludwig; Rickhey, Mark

    2011-01-01

    Patient-specific verification of intensity-modulated radiation therapy (IMRT) plans can be done by dosimetric measurements or by independent dose or monitor unit calculations. The aim of this study was the clinical evaluation of IMRT verification based on a fast Monte Carlo (MC) program with regard to possible benefits compared to commonly used film dosimetry. 25 head-and-neck IMRT plans were recalculated by a pencil beam based treatment planning system (TPS) using an appropriate quality assurance (QA) phantom. All plans were verified both by film and diode dosimetry and compared to MC simulations. The irradiated films, the results of diode measurements and the computed dose distributions were evaluated, and the data were compared on the basis of gamma maps and dose-difference histograms. Average deviations in the high-dose region between diode measurements and point dose calculations performed with the TPS and MC program were 0.7 ± 2.7% and 1.2 ± 3.1%, respectively. For film measurements, the mean gamma values with 3% dose difference and 3 mm distance-to-agreement were 0.74 ± 0.28 (TPS as reference) with dose deviations up to 10%. Corresponding values were significantly reduced to 0.34 ± 0.09 for MC dose calculation. The total time needed for both verification procedures is comparable, however, by far less labor intensive in the case of MC simulations. The presented study showed that independent dose calculation verification of IMRT plans with a fast MC program has the potential to eclipse film dosimetry more and more in the near future. Thus, the linac-specific QA part will necessarily become more important. In combination with MC simulations and due to the simple set-up, point-dose measurements for dosimetric plausibility checks are recommended at least in the IMRT introduction phase. (orig.)

  1. Micro ionization chamber dosimetry in IMRT verification: Clinical implications of dosimetric errors in the PTV

    International Nuclear Information System (INIS)

    Sanchez-Doblado, Francisco; Capote, Roberto; Rosello, Joan V.; Leal, Antonio; Lagares, Juan I.; Arrans, Rafael; Hartmann, Guenther H.

    2005-01-01

    Background and purpose: Absolute dose measurements for Intensity Modulated Radiotherapy (IMRT) beamlets is difficult due to the lack of lateral electron equilibrium. Recently we found that the absolute dosimetry in the penumbra region of the IMRT beamlet, can suffer from significant errors (Capote et al., Med Phys 31 (2004) 2416-2422). This work has the goal to estimate the error made when measuring the Planning Target Volume's (PTV) absolute dose by a micro ion chamber (μIC) in typical IMRT treatment. The dose error comes from the assumption that the dosimetric parameters determining the absolute dose are the same as for the reference conditions. Materials and Methods: Two IMRT treatment plans for common prostate carcinoma case, derived by forward and inverse optimisation, were considered. Detailed geometrical simulation of the μIC and the dose verification set-up was performed. The Monte Carlo (MC) simulation allows us to calculate the delivered dose to water and the dose delivered to the active volume of the ion chamber. However, the measured dose in water is usually derived from chamber readings assuming reference conditions. The MC simulation provides needed correction factors for ion chamber dosimetry in non reference conditions. Results: Dose calculations were carried out for some representative beamlets, a combination of segments and for the delivered IMRT treatments. We observe that the largest dose errors (i.e. the largest correction factors) correspond to the smaller contribution of the corresponding IMRT beamlets to the total dose delivered in the ionization chamber within PTV. Conclusion: The clinical impact of the calculated dose error in PTV measured dose was found to be negligible for studied IMRT treatments

  2. SU-E-J-125: A Novel IMRT Planning Technique to Spare Sacral Bone Marrow in Pelvic Cancer Patients

    Energy Technology Data Exchange (ETDEWEB)

    McGuire, S; Bhatia, S; Sun, W; Menda, Y; Ponto, L; Gross, B; Buatti, J [University Of Iowa, Iowa City, IA (United States)

    2015-06-15

    Purpose: Develop an IMRT planning technique that can preferentially spare sacral bone marrow for pelvic cancer patients. Methods: Six pelvic cancer patients (two each with anal, cervical, and rectal cancer) were enrolled in an IRB approved protocol to obtain FLT PET images at simulation, during, and post chemoradiation therapy. Initially, conventional IMRT plans were created to maintain target coverage and reduce dose to OARs such as bladder, bowel, rectum, and femoral heads. Simulation FLT PET images were used to create IMRT plans to spare bone marrow identified as regions with SUV of 2 or greater (IMRT-BMS) within the pelvic bones from top of L3 to 5mm below the greater trochanter without compromising PTV coverage or OAR sparing when compared to the initial IMRT plan. IMRT-BMS plans used 8–10 beam angles that surrounded the subject. These plans were used for treatment. Retrospectively, the same simulation FLT PET images were used to create IMRT plans that spared bone marrow located in the sacral pelvic bone region (IMRT-FAN) also without compromising PTV coverage or OAR sparing. IMRT-FAN plans used 16 beam angles every 12° anteriorly from 90° – 270°. Optimization objectives for the sacral bone marrow avoidance region were weighted to reduce ≥V10. Results: IMRT-FAN reduced dose to the sacral bone marrow for all six subjects. The average V5, V10, V20, and V30 differences from the IMRT-BMS plan were −2.2 ± 1.7%, −11.4 ± 3.6%, −17.6 ± 5.1%, and −19.1 ± 8.1% respectively. Average PTV coverage change was 0.5% ± 0.8% from the conventional IMRT plan. Conclusion: An IMRT planning technique that uses beams from the anterior and lateral directions reduced the volume of sacral bone marrow that receives ≤10Gy while maintaining PTV coverage and OAR sparing. Additionally, the volume of sacral bone marrow that received 20 or 30 Gy was also reduced.

  3. Evaluation of a commercial biologically based IMRT treatment planning system

    International Nuclear Information System (INIS)

    Semenenko, Vladimir A.; Reitz, Bodo; Day, Ellen; Qi, X. Sharon; Miften, Moyed; Li, X. Allen

    2008-01-01

    A new inverse treatment planning system (TPS) for external beam radiation therapy with high energy photons is commercially available that utilizes both dose-volume-based cost functions and a selection of cost functions which are based on biological models. The purpose of this work is to evaluate quality of intensity-modulated radiation therapy (IMRT) plans resulting from the use of biological cost functions in comparison to plans designed using a traditional TPS employing dose-volume-based optimization. Treatment planning was performed independently at two institutions. For six cancer patients, including head and neck (one case from each institution), prostate, brain, liver, and rectal cases, segmental multileaf collimator IMRT plans were designed using biological cost functions and compared with clinically used dose-based plans for the same patients. Dose-volume histograms and dosimetric indices, such as minimum, maximum, and mean dose, were extracted and compared between the two types of treatment plans. Comparisons of the generalized equivalent uniform dose (EUD), a previously proposed plan quality index (fEUD), target conformity and heterogeneity indices, and the number of segments and monitor units were also performed. The most prominent feature of the biologically based plans was better sparing of organs at risk (OARs). When all plans from both institutions were combined, the biologically based plans resulted in smaller EUD values for 26 out of 33 OARs by an average of 5.6 Gy (range 0.24 to 15 Gy). Owing to more efficient beam segmentation and leaf sequencing tools implemented in the biologically based TPS compared to the dose-based TPS, an estimated treatment delivery time was shorter in most (five out of six) cases with some plans showing up to 50% reduction. The biologically based plans were generally characterized by a smaller conformity index, but greater heterogeneity index compared to the dose-based plans. Overall, compared to plans based on dose

  4. SU-F-T-288: Impact of Trajectory Log Files for Clarkson-Based Independent Dose Verification of IMRT and VMAT

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, R; Kamima, T [Cancer Institute Hospital of Japanese Foundation for Cancer Research, Koto, Tokyo (Japan); Tachibana, H [National Cancer Center, Kashiwa, Chiba (Japan)

    2016-06-15

    Purpose: To investigate the effect of the trajectory files from linear accelerator for Clarkson-based independent dose verification in IMRT and VMAT plans. Methods: A CT-based independent dose verification software (Simple MU Analysis: SMU, Triangle Products, Japan) with a Clarksonbased algorithm was modified to calculate dose using the trajectory log files. Eclipse with the three techniques of step and shoot (SS), sliding window (SW) and Rapid Arc (RA) was used as treatment planning system (TPS). In this study, clinically approved IMRT and VMAT plans for prostate and head and neck (HN) at two institutions were retrospectively analyzed to assess the dose deviation between DICOM-RT plan (PL) and trajectory log file (TJ). An additional analysis was performed to evaluate MLC error detection capability of SMU when the trajectory log files was modified by adding systematic errors (0.2, 0.5, 1.0 mm) and random errors (5, 10, 30 mm) to actual MLC position. Results: The dose deviations for prostate and HN in the two sites were 0.0% and 0.0% in SS, 0.1±0.0%, 0.1±0.1% in SW and 0.6±0.5%, 0.7±0.9% in RA, respectively. The MLC error detection capability shows the plans for HN IMRT were the most sensitive and 0.2 mm of systematic error affected 0.7% dose deviation on average. Effect of the MLC random error did not affect dose error. Conclusion: The use of trajectory log files including actual information of MLC location, gantry angle, etc should be more effective for an independent verification. The tolerance level for the secondary check using the trajectory file may be similar to that of the verification using DICOM-RT plan file. From the view of the resolution of MLC positional error detection, the secondary check could detect the MLC position error corresponding to the treatment sites and techniques. This research is partially supported by Japan Agency for Medical Research and Development (AMED)

  5. SU-E-P-47: Evaluation of Improvement of Esophagus Sparing in SBRT Lung Patients with Biologically Based IMRT Optimization

    International Nuclear Information System (INIS)

    Liang, X; Penagaricano, J; Paudel, N; Zhang, X; Morrill, S; Corry, P; Han, E; Hardee, M; Ratanatharathorn, V

    2015-01-01

    Purpose: To study the potential of improving esophageal sparing for stereotactic body radiation therapy (SBRT) lung cancer patients by using biological optimization (BO) compared to conventional dose-volume based optimization (DVO) in treatment planning. Methods: Three NSCLC patients (PTV (62.3cc, 65.1cc, and 125.1cc) adjacent to the heart) previously treated with SBRT were re-planned using Varian Eclipse TPS (V11) using DVO and BO. The prescription dose was 60 Gy in 5 fractions normalized to 95% of the PTV volume. Plans were evaluated by comparing esophageal maximum doses, PTV heterogeneity (HI= D5%/D95%), and Paddick’s conformity (CI) indices. Quality of the plans was assessed by clinically-used IMRT QA procedures. Results: By using BO, the maximum dose to the esophagus was decreased 1384 cGy (34.6%), 502 cGy (16.5%) and 532 cGy (16.2%) in patient 1, 2 and 3 respectively. The maximum doses to spinal cord and the doses to 1000 cc and 1500 cc of normal lung were comparable in both plans. The mean doses (Dmean-hrt) and doses to 15cc of the heart (V15-hrt) were comparable for patient 1 and 2. However for patient 3, with the largest PTV, Dmean-hrt and V15-hrt increased by 62.2 cGy (18.3%) and 549.9 cGy (24.9%) respectively for the BO plans. The mean target HI of BO plans (1.13) was inferior to the DVO plans (1.07). The same trend was also observed for mean CI in BO plans (0.77) versus DVO plans (0.83). The QA pass rates (3%, 3mm) were comparable for both plans. Conclusion: This study demonstrated that the use of biological models in treatment planning optimization can substantially improve esophageal sparing without compromising spinal cord and normal lung doses. However, for the large PTV case (125.1cc) we studied here, Dmean-hrt and V15-hrt increased substantially. The target HI and CI were inferior in the BO plans

  6. Volumetric modulated arc therapy: IMRT in a single gantry arc

    International Nuclear Information System (INIS)

    Otto, Karl

    2008-01-01

    In this work a novel plan optimization platform is presented where treatment is delivered efficiently and accurately in a single dynamically modulated arc. Improvements in patient care achieved through image-guided positioning and plan adaptation have resulted in an increase in overall treatment times. Intensity-modulated radiation therapy (IMRT) has also increased treatment time by requiring a larger number of beam directions, increased monitor units (MU), and, in the case of tomotherapy, a slice-by-slice delivery. In order to maintain a similar level of patient throughput it will be necessary to increase the efficiency of treatment delivery. The solution proposed here is a novel aperture-based algorithm for treatment plan optimization where dose is delivered during a single gantry arc of up to 360 deg. The technique is similar to tomotherapy in that a full 360 deg. of beam directions are available for optimization but is fundamentally different in that the entire dose volume is delivered in a single source rotation. The new technique is referred to as volumetric modulated arc therapy (VMAT). Multileaf collimator (MLC) leaf motion and number of MU per degree of gantry rotation is restricted during the optimization so that gantry rotation speed, leaf translation speed, and dose rate maxima do not excessively limit the delivery efficiency. During planning, investigators model continuous gantry motion by a coarse sampling of static gantry positions and fluence maps or MLC aperture shapes. The technique presented here is unique in that gantry and MLC position sampling is progressively increased throughout the optimization. Using the full gantry range will theoretically provide increased flexibility in generating highly conformal treatment plans. In practice, the additional flexibility is somewhat negated by the additional constraints placed on the amount of MLC leaf motion between gantry samples. A series of studies are performed that characterize the relationship

  7. Overview of IMRT - definitions and basic concepts

    International Nuclear Information System (INIS)

    Mackie, T.R.

    2008-01-01

    A detailed advanced outline of the title topic is presented. Summary is formulated as follows: (i) Conventional MLC, developed for block replacement, require corrections and careful QA when when used for IMRT; (ii) There are both advantages and disadvantages of static or dynamic MLC delivery; (iii) Tomotherapy uses binary MLC systems specifically designed for IMRT; (iv) There are two types of optimization, grid of beamlets and direct aperture methods; (v) Optimization is controlled by objective functions. (P.A.)

  8. Dosimetric comparison of IMRT rectal and anal canal plans generated using an anterior dose avoidance structure

    Energy Technology Data Exchange (ETDEWEB)

    Leicher, Brian, E-mail: bleicher@wpahs.org [Department of Radiation Oncology, Allegheny General Hospital, Pittsburgh, PA (United States); Day, Ellen [Department of Radiation Oncology, Allegheny General Hospital, Pittsburgh, PA (United States); Colonias, Athanasios; Gayou, Olivier [Department of Radiation Oncology, Allegheny General Hospital, Pittsburgh, PA (United States); Drexel University College of Medicine, Allegheny Campus, Philadelphia, PA (United States)

    2014-10-01

    To describe a dosimetric method using an anterior dose avoidance structure (ADAS) during the treatment planning process for intensity-modulated radiation therapy (IMRT) for patients with anal canal and rectal carcinomas. A total of 20 patients were planned on the Elekta/CMS XiO treatment planning system, version 4.5.1 (Maryland Heights MO) with a superposition algorithm. For each patient, 2 plans were created: one employing an ADAS (ADAS plan) and the other replanned without an ADAS (non-ADAS plan). The ADAS was defined to occupy the volume between the inguinal nodes and primary target providing a single organ at risk that is completely outside of the target volume. Each plan used the same beam parameters and was analyzed by comparing target coverage, overall plan dose conformity using a conformity number (CN) equation, bowel dose-volume histograms, and the number of segments, daily treatment duration, and global maximum dose. The ADAS and non-ADAS plans were equivalent in target coverage, mean global maximum dose, and sparing of small bowel in low-dose regions (5, 10, 15, and 20 Gy). The mean difference between the CN value for the non-ADAS plans and ADAS plans was 0.04 ± 0.03 (p < 0.001). The mean difference in the number of segments was 15.7 ± 12.7 (p < 0.001) in favor of ADAS plans. The ADAS plan delivery time was shorter by 2.0 ± 1.5 minutes (p < 0.001) than the non-ADAS one. The ADAS has proven to be a powerful tool when planning rectal and anal canal IMRT cases with critical structures partially contained inside the target volume.

  9. Dosimetric comparison of IMRT rectal and anal canal plans generated using an anterior dose avoidance structure

    International Nuclear Information System (INIS)

    Leicher, Brian; Day, Ellen; Colonias, Athanasios; Gayou, Olivier

    2014-01-01

    To describe a dosimetric method using an anterior dose avoidance structure (ADAS) during the treatment planning process for intensity-modulated radiation therapy (IMRT) for patients with anal canal and rectal carcinomas. A total of 20 patients were planned on the Elekta/CMS XiO treatment planning system, version 4.5.1 (Maryland Heights MO) with a superposition algorithm. For each patient, 2 plans were created: one employing an ADAS (ADAS plan) and the other replanned without an ADAS (non-ADAS plan). The ADAS was defined to occupy the volume between the inguinal nodes and primary target providing a single organ at risk that is completely outside of the target volume. Each plan used the same beam parameters and was analyzed by comparing target coverage, overall plan dose conformity using a conformity number (CN) equation, bowel dose-volume histograms, and the number of segments, daily treatment duration, and global maximum dose. The ADAS and non-ADAS plans were equivalent in target coverage, mean global maximum dose, and sparing of small bowel in low-dose regions (5, 10, 15, and 20 Gy). The mean difference between the CN value for the non-ADAS plans and ADAS plans was 0.04 ± 0.03 (p < 0.001). The mean difference in the number of segments was 15.7 ± 12.7 (p < 0.001) in favor of ADAS plans. The ADAS plan delivery time was shorter by 2.0 ± 1.5 minutes (p < 0.001) than the non-ADAS one. The ADAS has proven to be a powerful tool when planning rectal and anal canal IMRT cases with critical structures partially contained inside the target volume

  10. Tools for the analysis of dose optimization: I. Effect-volume histogram

    International Nuclear Information System (INIS)

    Alber, M.; Nuesslin, F.

    2002-01-01

    With the advent of dose optimization algorithms, predominantly for intensity-modulated radiotherapy (IMRT), computer software has progressed beyond the point of being merely a tool at the hands of an expert and has become an active, independent mediator of the dosimetric conflicts between treatment goals and risks. To understand and control the internal decision finding as well as to provide means to influence it, a tool for the analysis of the dose distribution is presented which reveals the decision-making process performed by the algorithm. The internal trade-offs between partial volumes receiving high or low doses are driven by functions which attribute a weight to each volume element. The statistics of the distribution of these weights is cast into an effect-volume histogram (EVH) in analogy to dose-volume histograms. The analysis of the EVH reveals which traits of the optimum dose distribution result from the defined objectives, and which are a random consequence of under- or misspecification of treatment goals. The EVH can further assist in the process of finding suitable objectives and balancing conflicting objectives. If biologically inspired objectives are used, the EVH shows the distribution of local dose effect relative to the prescribed level. (author)

  11. SU-E-T-105: An FMEA Survey of Intensity Modulated Radiation Therapy (IMRT) Step and Shoot Dose Delivery Failure Modes

    International Nuclear Information System (INIS)

    Faught, J Tonigan; Johnson, J; Stingo, F; Kry, S; Court, L; Balter, P; Followill, D

    2015-01-01

    Purpose: To assess the perception of TG-142 tolerance level dose delivery failures in IMRT and the application of FMEA process to this specific aspect of IMRT. Methods: An online survey was distributed to medical physicists worldwide that briefly described 11 different failure modes (FMs) covered by basic quality assurance in step- and-shoot IMRT at or near TG-142 tolerance criteria levels. For each FM, respondents estimated the worst case H&N patient percent dose error and FMEA scores for Occurrence, Detectability, and Severity. Demographic data was also collected. Results: 181 individual and three group responses were submitted. 84% were from North America. Most (76%) individual respondents performed at least 80% clinical work and 92% were nationally certified. Respondent medical physics experience ranged from 2.5–45 years (average 18 years). 52% of individual respondents were at least somewhat familiar with FMEA, while 17% were not familiar. Several IMRT techniques, treatment planning systems and linear accelerator manufacturers were represented. All FMs received widely varying scores ranging from 1–10 for occurrence, at least 1–9 for detectability, and at least 1–7 for severity. Ranking FMs by RPN scores also resulted in large variability, with each FM being ranked both most risky (1st ) and least risky (11th) by different respondents. On average MLC modeling had the highest RPN scores. Individual estimated percent dose errors and severity scores positively correlated (p<0.10) for each FM as expected. No universal correlations were found between the demographic information collected and scoring, percent dose errors, or ranking. Conclusion: FMs investigated overall were evaluated as low to medium risk, with average RPNs less than 110. The ranking of 11 FMs was not agreed upon by the community. Large variability in FMEA scoring may be caused by individual interpretation and/or experience, thus reflecting the subjective nature of the FMEA tool

  12. A Comprehensive Comparison of IMRT and VMAT Plan Quality for Prostate Cancer Treatment

    International Nuclear Information System (INIS)

    Quan, Enzhuo M.; Li Xiaoqiang; Li Yupeng; Wang Xiaochun; Kudchadker, Rajat J.; Johnson, Jennifer L.; Kuban, Deborah A.; Lee, Andrew K.; Zhang Xiaodong

    2012-01-01

    Purpose: We performed a comprehensive comparative study of the plan quality between volumetric-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) for the treatment of prostate cancer. Methods and Materials: Eleven patients with prostate cancer treated at our institution were randomly selected for this study. For each patient, a VMAT plan and a series of IMRT plans using an increasing number of beams (8, 12, 16, 20, and 24 beams) were examined. All plans were generated using our in-house–developed automatic inverse planning (AIP) algorithm. An existing eight-beam clinical IMRT plan, which was used to treat the patient, was used as the reference plan. For each patient, all AIP-generated plans were optimized to achieve the same level of planning target volume (PTV) coverage as the reference plan. Plan quality was evaluated by measuring mean dose to and dose–volume statistics of the organs at risk, especially the rectum, from each type of plan. Results: For the same PTV coverage, the AIP-generated VMAT plans had significantly better plan quality in terms of rectum sparing than the eight-beam clinical and AIP-generated IMRT plans (p < 0.0001). However, the differences between the IMRT and VMAT plans in all the dosimetric indices decreased as the number of beams used in IMRT increased. IMRT plan quality was similar or superior to that of VMAT when the number of beams in IMRT was increased to a certain number, which ranged from 12 to 24 for the set of patients studied. The superior VMAT plan quality resulted in approximately 30% more monitor units than the eight-beam IMRT plans, but the delivery time was still less than 3 min. Conclusions: Considering the superior plan quality as well as the delivery efficiency of VMAT compared with that of IMRT, VMAT may be the preferred modality for treating prostate cancer.

  13. Compensating for the impact of non-stationary spherical air cavities on IMRT dose delivery in transverse magnetic fields

    NARCIS (Netherlands)

    Bol, G H; Lagendijk, J J W; Raaymakers, B W

    2015-01-01

    With the development of the 1.5 T MRI linear accelerator and the clinical introduction of the 0.35 T ViewRay™ system, delivering intensity-modulated radiotherapy (IMRT) in a transverse magnetic field becomes increasingly important. When delivering dose in the presence of a transverse magnetic field,

  14. 2-Step IMAT and 2-Step IMRT in three dimensions

    International Nuclear Information System (INIS)

    Bratengeier, Klaus

    2005-01-01

    In two dimensions, 2-Step Intensity Modulated Arc Therapy (2-Step IMAT) and 2-Step Intensity Modulated Radiation Therapy (IMRT) were shown to be powerful methods for the optimization of plans with organs at risk (OAR) (partially) surrounded by a target volume (PTV). In three dimensions, some additional boundary conditions have to be considered to establish 2-Step IMAT as an optimization method. A further aim was to create rules for ad hoc adaptations of an IMRT plan to a daily changing PTV-OAR constellation. As a test model, a cylindrically symmetric PTV-OAR combination was used. The centrally placed OAR can adapt arbitrary diameters with different gap widths toward the PTV. Along the rotation axis the OAR diameter can vary, the OAR can even vanish at some axis positions, leaving a circular PTV. The width and weight of the second segment were the free parameters to optimize. The objective function f to minimize was the root of the integral of the squared difference of the dose in the target volume and a reference dose. For the problem, two local minima exist. Therefore, as a secondary criteria, the magnitude of hot and cold spots were taken into account. As a result, the solution with a larger segment width was recommended. From plane to plane for varying radii of PTV and OAR and for different gaps between them, different sets of weights and widths were optimal. Because only one weight for one segment shall be used for all planes (respectively leaf pairs), a strategy for complex three-dimensional (3-D) cases was established to choose a global weight. In a second step, a suitable segment width was chosen, minimizing f for this global weight. The concept was demonstrated in a planning study for a cylindrically symmetric example with a large range of different radii of an OAR along the patient axis. The method is discussed for some classes of tumor/organ at risk combinations. Noncylindrically symmetric cases were treated exemplarily. The product of width and weight of

  15. A dose homogeneity and conformity evaluation between ViewRay and pinnacle-based linear accelerator IMRT treatment plans

    International Nuclear Information System (INIS)

    Saenz, Daniel L.; Paliwal, Bhudatt R.; Bayouth, John E.

    2014-01-01

    ViewRay, a novel technology providing soft-tissue imaging during radiotherapy is investigated for treatment planning capabilities assessing treatment plan dose homogeneity and conformity compared with linear accelerator plans. ViewRay offers both adaptive radiotherapy and image guidance. The combination of cobalt-60 ( 60 Co) with 0.35 Tesla magnetic resonance imaging (MRI) allows for magnetic resonance (MR)-guided intensity-modulated radiation therapy (IMRT) delivery with multiple beams. This study investigated head and neck, lung, and prostate treatment plans to understand what is possible on ViewRay to narrow focus toward sites with optimal dosimetry. The goal is not to provide a rigorous assessment of planning capabilities, but rather a first order demonstration of ViewRay planning abilities. Images, structure sets, points, and dose from treatment plans created in Pinnacle for patients in our clinic were imported into ViewRay. The same objectives were used to assess plan quality and all critical structures were treated as similarly as possible. Homogeneity index (HI), conformity index (CI), and volume receiving 60 Co ViewRay treatments planned with its Monte Carlo treatment planning software were comparable with 6 MV plans computed with convolution superposition algorithm on Pinnacle treatment planning system. (author)

  16. A dose homogeneity and conformity evaluation between ViewRay and pinnacle-based linear accelerator IMRT treatment plans.

    Science.gov (United States)

    Saenz, Daniel L; Paliwal, Bhudatt R; Bayouth, John E

    2014-04-01

    ViewRay, a novel technology providing soft-tissue imaging during radiotherapy is investigated for treatment planning capabilities assessing treatment plan dose homogeneity and conformity compared with linear accelerator plans. ViewRay offers both adaptive radiotherapy and image guidance. The combination of cobalt-60 (Co-60) with 0.35 Tesla magnetic resonance imaging (MRI) allows for magnetic resonance (MR)-guided intensity-modulated radiation therapy (IMRT) delivery with multiple beams. This study investigated head and neck, lung, and prostate treatment plans to understand what is possible on ViewRay to narrow focus toward sites with optimal dosimetry. The goal is not to provide a rigorous assessment of planning capabilities, but rather a first order demonstration of ViewRay planning abilities. Images, structure sets, points, and dose from treatment plans created in Pinnacle for patients in our clinic were imported into ViewRay. The same objectives were used to assess plan quality and all critical structures were treated as similarly as possible. Homogeneity index (HI), conformity index (CI), and volume receiving ViewRay treatments planned with its Monte Carlo treatment planning software were comparable with 6 MV plans computed with convolution superposition algorithm on Pinnacle treatment planning system.

  17. Planner concepts in IMRT planning

    International Nuclear Information System (INIS)

    Sahoo, Suvendu Kr.; Rath, A.K.; Patnaik, S.; Mishra, S.K.

    2008-01-01

    IMRT is the most sophisticated, innovative, three- dimensional conformal radiation treatment that delivers highly focused radiation with minimal impact to surrounding normal tissue. As it is a computer control technique, the planar should have adequate knowledge to execute the plan in proper way other wise it is very difficult to get the optimal plan. In this article we want to high light, planner should have the basic concepts before starting the IMRT planning

  18. Multicriteria optimization informed VMAT planning

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Huixiao; Craft, David L.; Gierga, David P., E-mail: dgierga@partners.org

    2014-04-01

    We developed a patient-specific volumetric-modulated arc therapy (VMAT) optimization procedure using dose-volume histogram (DVH) information from multicriteria optimization (MCO) of intensity-modulated radiotherapy (IMRT) plans. The study included 10 patients with prostate cancer undergoing standard fractionation treatment, 10 patients with prostate cancer undergoing hypofractionation treatment, and 5 patients with head/neck cancer. MCO-IMRT plans using 20 and 7 treatment fields were generated for each patient on the RayStation treatment planning system (clinical version 2.5, RaySearch Laboratories, Stockholm, Sweden). The resulting DVH of the 20-field MCO-IMRT plan for each patient was used as the reference DVH, and the extracted point values of the resulting DVH of the MCO-IMRT plan were used as objectives and constraints for VMAT optimization. Weights of objectives or constraints of VMAT optimization or both were further tuned to generate the best match with the reference DVH of the MCO-IMRT plan. The final optimal VMAT plan quality was evaluated by comparison with MCO-IMRT plans based on homogeneity index, conformity number of planning target volume, and organ at risk sparing. The influence of gantry spacing, arc number, and delivery time on VMAT plan quality for different tumor sites was also evaluated. The resulting VMAT plan quality essentially matched the 20-field MCO-IMRT plan but with a shorter delivery time and less monitor units. VMAT plan quality of head/neck cancer cases improved using dual arcs whereas prostate cases did not. VMAT plan quality was improved by fine gantry spacing of 2 for the head/neck cancer cases and the hypofractionation-treated prostate cancer cases but not for the standard fractionation–treated prostate cancer cases. MCO-informed VMAT optimization is a useful and valuable way to generate patient-specific optimal VMAT plans, though modification of the weights of objectives or constraints extracted from resulting DVH of MCO-IMRT

  19. IMRT limits nephrotoxicity after chemoradiotherapy for gastric cancer

    International Nuclear Information System (INIS)

    Trip, Anouk Kirsten; Nijkamp, Jasper; Tinteren, Harm van; Cats, Annemieke; Boot, Henk; Jansen, Edwin Petrus Marianus; Verheij, Marcel

    2014-01-01

    Objective: This observational study compares the effect of different radiotherapy techniques on late nephrotoxicity after postoperative chemoradiotherapy for gastric cancer. Patients and methods: Dosimetric parameters were compared between AP–PA, 3D-conformal and IMRT techniques. Renal function was measured by 99m Tc-MAG-3 renography, glomerular filtration rate (GFR) and the development of hypertension. Mixed effects models were used to compare renal function over time. Results: Eighty-seven patients treated between 2002 and 2010 were included, AP–PA (n = 31), 3D-conformal (n = 25) and IMRT (n = 31), all 45 Gy in 25 fractions. Concurrent chemotherapy: 5FU/leucovorin (n = 4), capecitabine (n = 37), and capecitabine/cisplatin (n = 46). Median follow-up time was 4.7 years (range 0.2–8). With IMRT, the mean dose to the left kidney was significantly lower. Left kidney function decreased progressively in the total study population, however with IMRT this occurred at a lower rate. A dose–effect relationship was present between mean dose to the left kidney and the left kidney function. GFR decreased only moderately in time, which was not different between techniques. Six patients developed hypertension, of whom none in the IMRT group. Conclusions: This study confirms progressive late nephrotoxicity in patients treated with postoperative chemoradiotherapy by different techniques for gastric cancer. Nephrotoxicity was less severe with IMRT and should be considered the preferred technique

  20. Tolerance limits and methodologies for IMRT measurement-based verification QA: Recommendations of AAPM Task Group No. 218.

    Science.gov (United States)

    Miften, Moyed; Olch, Arthur; Mihailidis, Dimitris; Moran, Jean; Pawlicki, Todd; Molineu, Andrea; Li, Harold; Wijesooriya, Krishni; Shi, Jie; Xia, Ping; Papanikolaou, Nikos; Low, Daniel A

    2018-04-01

    Patient-specific IMRT QA measurements are important components of processes designed to identify discrepancies between calculated and delivered radiation doses. Discrepancy tolerance limits are neither well defined nor consistently applied across centers. The AAPM TG-218 report provides a comprehensive review aimed at improving the understanding and consistency of these processes as well as recommendations for methodologies and tolerance limits in patient-specific IMRT QA. The performance of the dose difference/distance-to-agreement (DTA) and γ dose distribution comparison metrics are investigated. Measurement methods are reviewed and followed by a discussion of the pros and cons of each. Methodologies for absolute dose verification are discussed and new IMRT QA verification tools are presented. Literature on the expected or achievable agreement between measurements and calculations for different types of planning and delivery systems are reviewed and analyzed. Tests of vendor implementations of the γ verification algorithm employing benchmark cases are presented. Operational shortcomings that can reduce the γ tool accuracy and subsequent effectiveness for IMRT QA are described. Practical considerations including spatial resolution, normalization, dose threshold, and data interpretation are discussed. Published data on IMRT QA and the clinical experience of the group members are used to develop guidelines and recommendations on tolerance and action limits for IMRT QA. Steps to check failed IMRT QA plans are outlined. Recommendations on delivery methods, data interpretation, dose normalization, the use of γ analysis routines and choice of tolerance limits for IMRT QA are made with focus on detecting differences between calculated and measured doses via the use of robust analysis methods and an in-depth understanding of IMRT verification metrics. The recommendations are intended to improve the IMRT QA process and establish consistent, and comparable IMRT QA

  1. SU-F-T-266: Dynalogs Based Evaluation of Different Dose Rate IMRT Using DVH and Gamma Index

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, S [Aga Khan University Hospital, Karachi, Sindh (Pakistan); Ahmed, S [Pakistan Inst of Eng Applied Sciences, Islamabad (Pakistan); Ahmed, F; Hussain, A

    2016-06-15

    Purpose: This work investigates the impact of low and high dose rate on IMRT through Dynalogs by evaluating Gamma Index and Dose Volume Histogram. Methods: The Eclipse™ treatment planning software was used to generate plans on prostate and head and neck sites. A range of dose rates 300 MU/min and 600 MU/min were applied to each plan in order to investigate their effect on the beam ON time, efficiency and accuracy. Each plan had distinct monitor units per fraction, delivery time, mean dose rate and leaf speed. The DVH data was used in the assessment of the conformity and plan quality.The treatments were delivered on Varian™ Clinac 2100C accelerator equipped with 120 leaf millennium MLC. Dynalogs of each plan were analyzed by MATLAB™ program. Fluence measurements were performed using the Sun Nuclear™ 2D diode array and results were assessed, based on Gamma analysis of dose fluence maps, beam delivery statistics and Dynalogs data. Results: Minor differences found by adjusted R-squared analysis of DVH’s for all the plans with different dose rates. It has been also found that more and larger fields have greater time reduction at high dose rate and there was a sharp decrease in number of control points observed in dynalog files by switching dose rate from 300 MU/min to 600 MU/min. Gamma Analysis of all plans passes the confidence limit of ≥95% with greater number of passing points in 300 MU/min dose rate plans. Conclusion: The dynalog files are compatible tool for software based IMRT QA. It can work perfectly parallel to measurement based QA setup and stand-by procedure for pre and post delivery of treatment plan.

  2. SU-F-T-266: Dynalogs Based Evaluation of Different Dose Rate IMRT Using DVH and Gamma Index

    International Nuclear Information System (INIS)

    Ahmed, S; Ahmed, S; Ahmed, F; Hussain, A

    2016-01-01

    Purpose: This work investigates the impact of low and high dose rate on IMRT through Dynalogs by evaluating Gamma Index and Dose Volume Histogram. Methods: The Eclipse™ treatment planning software was used to generate plans on prostate and head and neck sites. A range of dose rates 300 MU/min and 600 MU/min were applied to each plan in order to investigate their effect on the beam ON time, efficiency and accuracy. Each plan had distinct monitor units per fraction, delivery time, mean dose rate and leaf speed. The DVH data was used in the assessment of the conformity and plan quality.The treatments were delivered on Varian™ Clinac 2100C accelerator equipped with 120 leaf millennium MLC. Dynalogs of each plan were analyzed by MATLAB™ program. Fluence measurements were performed using the Sun Nuclear™ 2D diode array and results were assessed, based on Gamma analysis of dose fluence maps, beam delivery statistics and Dynalogs data. Results: Minor differences found by adjusted R-squared analysis of DVH’s for all the plans with different dose rates. It has been also found that more and larger fields have greater time reduction at high dose rate and there was a sharp decrease in number of control points observed in dynalog files by switching dose rate from 300 MU/min to 600 MU/min. Gamma Analysis of all plans passes the confidence limit of ≥95% with greater number of passing points in 300 MU/min dose rate plans. Conclusion: The dynalog files are compatible tool for software based IMRT QA. It can work perfectly parallel to measurement based QA setup and stand-by procedure for pre and post delivery of treatment plan.

  3. SU-E-T-541: Bolus Effect of Thermoplastic Masks in IMRT and VMAT Head and Neck Treatments

    International Nuclear Information System (INIS)

    Zhen, H; Nedzi, L; Chen, S; Jiang, S; Zhao, B

    2014-01-01

    Purpose: To quantitatively evaluate the bolus effect of thermoplalstic mask on patient skin dose during multi-field IMRT and VMAT treatment. Methods: The clinically approved target contours for five head and neck patients were deformably registered to an anthropomorphic Rando phantom. Two plans: Multifield IMRT plan with 7-9 beams and VMAT plan with 2-4 arcs were created for each patient following same dose constraints. 3mm skin was excluded from PTVs but not constrained during optimization. The prescription dose was 200-220 cGy/fraction. A thermoplastic head and shoulder mask was customized for the Rando phantom. Each plan was delivered to the phantom twice with and without mask. During each delivery, two rectangular strips of EBT3 films (1cm x 6.8cm) were placed across the anterior upper and lower neck near PTVs to measure the surface dose. For consistency films were positioned at same locations for same patient. A total of 8 film strips were obtained for each patient. Film dose was calibrated in the range of 0-400cGy on the day of plan delivery. For dose comparison 3 regions of interests (ROIs) of 1×1 cm 2 were selected at left, right and middle part of each film, resulting in 6 point doses at each plan delivery. Results: The films without mask show relatively uniform dose distribution while those with mask clearly show mesh pattern of mask, usually indicating an increase in skin dose. On average the increase in skin dose over all ROIs with mask was 31.9%(±14.8%) with a range of 11.4%- 58.4%. There is no statistically significant difference (p=0.44) between skin dose increase in VMAT (30.8%±15.3%) and IMRT delivery (33.0%±14.9%). Conclusion: Thermoplastic immobilization masks increase surface dose for HN patient by around 30%. The magnitude is comparable between multi-field IMRT and VMAT. Radiochromic EBT3 film serves as an effective tool to quantify bolus effect

  4. Re-Planning for Compensator-Based IMRT with Original Compensators

    International Nuclear Information System (INIS)

    Zhang, Geoffrey; Feygelman, Vladimir; Stevens, Craig; Li Weiqi; Leuthold, Susan; Springett, Gregory; Hoffe, Sarah

    2011-01-01

    Compared with multileaf collimator (MLC)-based intensity-modulated radiotherapy (IMRT) for moving targets, compensator-based IMRT has advantages such as shorter beam-on time, fewer monitor units with potentially decreased secondary carcinogenesis risk, better optimization-to-deliverable dose conversion, and often better dose conformity. Some of the disadvantages include additional time for the compensators to be built and delivered, as well as extra cost. Patients undergoing treatment of abdominal cancers often experience weight loss. It would be necessary to account for this change in weight with a new plan and a second set of compensators. However, this would result in treatment delays and added costs. We have developed a method to re-plan the patient using the same set of compensators. Because the weight changes seen with the treatment of abdominal cancers are usually relatively small, a new 4D computed tomography (CT) acquired in the treatment position with markers on the original isocenter tattoos can be registered to the original planning scan. The contours of target volumes from the original scans are copied to the new scan after fusion. The original compensator set can be used together with a few field-in-field (FiF) beams defined by the MLC (or beams with cerrobend blocks for accelerators not equipped with a MLC). The weights of the beams with compensators are reduced so that the FiF or blocked beams can be optimized to mirror the original plan and dose distribution. Seven abdominal cancer cases are presented using this technique. The new plan on the new planning CT images usually has the same dosimetric quality as the original. The target coverage and dose uniformity are improved compared with the plan without FiF/block modification. Techniques combining additional FiF or blocked beams with the original compensators optimize the treatment plans when patients lose weight and save time and cost compared with generating plans with a new set of compensators.

  5. Quality assurance device for four-dimensional IMRT or SBRT and respiratory gating using patient-specific intrafraction motion kernels.

    Science.gov (United States)

    Nelms, Benjamin E; Ehler, Eric; Bragg, Henry; Tomé, Wolfgang A

    2007-09-17

    Emerging technologies such as four-dimensional computed tomography (4D CT) and implanted beacons are expected to allow clinicians to accurately model intrafraction motion and to quantitatively estimate internal target volumes (ITVs) for radiation therapy involving moving targets. In the case of intensity-modulated (IMRT) and stereotactic body radiation therapy (SBRT) delivery, clinicians must consider the interplay between the temporal nature of the modulation and the target motion within the ITV. A need exists for a 4D IMRT/SBRT quality assurance (QA) device that can incorporate and analyze customized intrafraction motion as it relates to dose delivery and respiratory gating. We built a 4D IMRT/SBRT prototype device and entered (X, Y, Z)(T) coordinates representing a motion kernel into a software application that 1. transformed the kernel into beam-specific two-dimensional (2D) motion "projections," 2. previewed the motion in real time, and 3. drove a recision X-Y motorized device that had, atop it, a mounted planar IMRT QA measurement device. The detectors that intersected the target in the beam's-eye-view of any single phase of the breathing cycle (a small subset of all the detectors) were defined as "target detectors" to be analyzed for dose uniformity between multiple fractions. Data regarding the use of this device to quantify dose variation fraction-to-fraction resulting from target motion (for several delivery modalities and with and without gating) have been recently published. A combined software and hardware solution for patient-customized 4D IMRT/SBRT QA is an effective tool for assessing IMRT delivery under conditions of intrafraction motion. The 4D IMRT QA device accurately reproduced the projected motion kernels for all beam's-eye-view motion kernels. This device has been proved to, effectively quantify the degradation in dose uniformity resulting from a moving target within a static planning target volume, and, integrate with a commercial

  6. Quality assurance device for four‐dimensional IMRT or SBRT and respiratory gating using patient‐specific intrafraction motion kernels

    Science.gov (United States)

    Ehler, Eric; Bragg, Henry; Tomé, Wolfgang A.

    2007-01-01

    Emerging technologies such as four‐dimensional computed tomography (4D CT) and implanted beacons are expected to allow clinicians to accurately model intrafraction motion and to quantitatively estimate internal target volumes (ITVs) for radiation therapy involving moving targets. In the case of intensity‐modulated (IMRT) and stereotactic body radiation therapy (SBRT) delivery, clinicians must consider the interplay between the temporal nature of the modulation and the target motion within the ITV. A need exists for a 4D IMRT/SBRT quality assurance (QA) device that can incorporate and analyze customized intrafraction motion as it relates to dose delivery and respiratory gating. We built a 4D IMRT/SBRT prototype device and entered (X, Y, Z)(T) coordinates representing a motion kernel into a software application that transformed the kernel into beam‐specific two‐dimensional (2D) motion “projections,”previewed the motion in real time, anddrove a precision X–Y motorized device that had, atop it, a mounted planar IMRT QA measurement device. The detectors that intersected the target in the beam's‐eye‐view of any single phase of the breathing cycle (a small subset of all the detectors) were defined as “target detectors” to be analyzed for dose uniformity between multiple fractions. Data regarding the use of this device to quantify dose variation fraction‐to‐fraction resulting from target motion (for several delivery modalities and with and without gating) have been recently published. A combined software and hardware solution for patient‐customized 4D IMRT/ SBRT QA is an effective tool for assessing IMRT delivery under conditions of intrafraction motion. The 4D IMRT QA device accurately reproduced the projected motion kernels for all beam's‐eye‐view motion kernels. This device has been proved to • effectively quantify the degradation in dose uniformity resulting from a moving target within a static planning target volume, and • integrate

  7. Determination of beam intensity in a single step for IMRT inverse planning

    International Nuclear Information System (INIS)

    Chuang, Keh-Shih; Chen, Tzong-Jer; Kuo, Shan-Chi; Jan, Meei-Ling; Hwang, Ing-Ming; Chen, Sharon; Lin, Ying-Chuan; Wu, Jay

    2003-01-01

    In intensity modulated radiotherapy (IMRT), targets are treated by multiple beams at different orientations each with spatially-modulated beam intensities. This approach spreads the normal tissue dose to a greater volume and produces a higher dose conformation to the target. In general, inverse planning is used for IMRT treatment planning. The inverse planning requires iterative calculation of dose distribution in order to optimize the intensity profile for each beam and is very computation intensive. In this paper, we propose a single-step method utilizing a figure of merit (FoM) to estimate the beam intensities for IMRT treatment planning. The FoM of a ray is defined as the ratio between the delivered tumour dose and normal tissue dose and is a good index for the dose efficacy of the ray. To maximize the beam utility, it is natural to irradiate the tumour with intensity of each ray proportional to the value of the FoM. The nonuniform beam intensity profiles are then fixed and the weights of the beam are determined iteratively in order to yield a uniform tumour dose. In this study, beams are employed at equispaced angles around the patient. Each beam with its field size that just covers the tumour is divided into a fixed number of beamlets. The FoM is calculated for each beamlet and this value is assigned to be the beam intensity. Various weighting factors are incorporated in the FoM computation to accommodate different clinical considerations. Two clinical datasets are used to test the feasibility of the algorithm. The resultant dose-volume histograms of this method are presented and compared to that of conformal therapy. Preliminary results indicate that this method reduces the critical organ doses at a small expense of uniformity in tumour dose distribution. This method estimates the beam intensity in one single step and the computation time is extremely fast and can be finished in less than one minute using a regular PC

  8. Intensity modulated radiotherapy (IMRT) with compensators

    International Nuclear Information System (INIS)

    Salz, H.; Wiezorek, T.; Scheithauer, M.; Kleen, W.; Schwedas, M.; Wendt, T.G.

    2002-01-01

    The irradiation with intensity-modulated fields is possible with static as well as dynamic methods. In our university hospital, the intensity-modulated radiotherapy (IMRT) with compensators was prepared and used for the first time for patient irradiation in July 2001. The compensators consist of a mixture of tin granulate and wax, which is filled in a milled negative mould. The treatment planning is performed with Helax-TMS (MDS Nordion). An additional software is used for editing the modulation matrix ('Modifix'). Before irradiation of the first patient, extensive measurements have been carried out in terms of quality assurance of treatment planning and production of compensators. The results of the verification measurements have shown that IMRT with compensators possesses high spatial and dosimetric exactness. The calculated dose distributions are applied correctly. The accuracy of the calculated monitor units is normally better than 3%; in small volumes, further dosimetric inaccuracies between calculated and measured dose distributions are mostly less than 3%. Therefore, the compensators contribute to the achievement of high-level IMRT even when apparatuses without MLC are used. This paper describes the use of the IMRT with compensators, presents the limits of this technology, and discusses the first practical experiences. (orig.) [de

  9. Evaluation of different set-up error corrections on dose-volume metrics in prostate IMRT using CBCT images

    International Nuclear Information System (INIS)

    Hirose, Yoshinori; Tomita, Tsuneyuki; Kitsuda, Kenji; Notogawa, Takuya; Miki, Katsuhito; Nakamura, Mitsuhiro; Nakamura, Kiyonao; Ishigaki, Takashi

    2014-01-01

    We investigated the effect of different set-up error corrections on dose-volume metrics in intensity-modulated radiotherapy (IMRT) for prostate cancer under different planning target volume (PTV) margin settings using cone-beam computed tomography (CBCT) images. A total of 30 consecutive patients who underwent IMRT for prostate cancer were retrospectively analysed, and 7-14 CBCT datasets were acquired per patient. Interfractional variations in dose-volume metrics were evaluated under six different set-up error corrections, including tattoo, bony anatomy, and four different target matching groups. Set-up errors were incorporated into planning the isocenter position, and dose distributions were recalculated on CBCT images. These processes were repeated under two different PTV margin settings. In the on-line bony anatomy matching groups, systematic error (Σ) was 0.3 mm, 1.4 mm, and 0.3 mm in the left-right, anterior-posterior (AP), and superior-inferior directions, respectively. Σ in three successive off-line target matchings was finally comparable with that in the on-line bony anatomy matching in the AP direction. Although doses to the rectum and bladder wall were reduced for a small PTV margin, averaged reductions in the volume receiving 100% of the prescription dose from planning were within 2.5% under all PTV margin settings for all correction groups, with the exception of the tattoo set-up error correction only (≥ 5.0%). Analysis of variance showed no significant difference between on-line bony anatomy matching and target matching. While variations between the planned and delivered doses were smallest when target matching was applied, the use of bony anatomy matching still ensured the planned doses. (author)

  10. Dosimetry audit for a multi-centre IMRT head and neck trial

    International Nuclear Information System (INIS)

    Clark, Catharine H.; Hansen, Vibeke Nordmark; Chantler, Hannah; Edwards, Craig; James, Hayley V.; Webster, Gareth; Miles, Elizabeth A.; Guerrero Urbano, M. Teresa; Bhide, Shree A.; Bidmead, A. Margaret; Nutting, Christoper M.

    2009-01-01

    Background and purpose: PARSPORT was a multi-centre randomised trial in the UK which compared Intensity-Modulated Radiotherapy (IMRT) and conventional radiotherapy (CRT) for patients with head and neck cancer. The dosimetry audit goals were to verify the plan delivery in participating centres, ascertain what tolerances were suitable for head and neck IMRT trials and develop an IMRT credentialing program. Materials and methods: Centres enrolling patients underwent rigorous quality assurance before joining the trial. Following this each centre was visited for a dosimetry audit, which consisted of treatment planning system tests, fluence verification films, combined field films and dose point measurements. Results: Mean dose point measurements were made at six centres. For the primary planning target volume (PTV) the differences with the planned values for the IMRT and CRT arms were -0.6% (1.8% to -2.4%) and 0.7% (2.0% to -0.9%), respectively. Ninety-four percent of the IMRT fluence films for individual fields passed gamma criterion of 3%/3 mm and 75% of the films for combined fields passed gamma criterion 4%/3 mm (no significant difference between dynamic delivery and step and shoot delivery). Conclusions: This audit suggests that a 3% tolerance could be applied for PTV point doses. For dose distributions tolerances of 3%/3 mm on individual fields and 4%/3 mm for combined fields are proposed for multi-centre head and neck IMRT trials.

  11. Rectal balloon use limits vaginal displacement, rectal dose, and rectal toxicity in patients receiving IMRT for postoperative gynecological malignancies.

    Science.gov (United States)

    Wu, Cheng-Chia; Wuu, Yen-Ruh; Yanagihara, Theodore; Jani, Ashish; Xanthopoulos, Eric P; Tiwari, Akhil; Wright, Jason D; Burke, William M; Hou, June Y; Tergas, Ana I; Deutsch, Israel

    2018-01-01

    Pelvic radiotherapy for gynecologic malignancies traditionally used a 4-field box technique. Later trials have shown the feasibility of using intensity-modulated radiotherapy (IMRT) instead. But vaginal movement between fractions is concerning when using IMRT due to greater conformality of the isodose curves to the target and the resulting possibility of missing the target while the vagina is displaced. In this study, we showed that the use of a rectal balloon during treatment can decrease vaginal displacement, limit rectal dose, and limit acute and late toxicities. Little is known regarding the use of a rectal balloon (RB) in treating patients with IMRT in the posthysterectomy setting. We hypothesize that the use of an RB during treatment can limit rectal dose and acute and long-term toxicities, as well as decrease vaginal cuff displacement between fractions. We performed a retrospective review of patients with gynecological malignancies who received postoperative IMRT with the use of an RB from January 1, 2012 to January 1, 2015. Rectal dose constraint was examined as per Radiation Therapy Oncology Group (RTOG) 1203 and 0418. Daily cone beam computed tomography (CT) was performed, and the average (avg) displacement, avg magnitude, and avg magnitude of vector were calculated. Toxicity was reported according to RTOG acute radiation morbidity scoring criteria. Acute toxicity was defined as less than 90 days from the end of radiation treatment. Late toxicity was defined as at least 90 days after completing radiation. Twenty-eight patients with postoperative IMRT with the use of an RB were examined and 23 treatment plans were reviewed. The avg rectal V40 was 39.3% ± 9.0%. V30 was65.1% ± 10.0%. V50 was 0%. Separate cone beam computed tomography (CBCT) images (n = 663) were reviewed. The avg displacement was as follows: superior 0.4 + 2.99 mm, left 0.23 ± 4.97 mm, and anterior 0.16 ± 5.18 mm. The avg magnitude of displacement was superior

  12. TU-C-17A-09: Multi-Case Knowledge-Based IMRT Treatment Planning in Head and Neck Cancer: Are Six Heads Better Than One?

    International Nuclear Information System (INIS)

    Grzetic, S; Lutzky, C; Das, S; Lo, J

    2014-01-01

    Purpose: HNC IMRT treatment planning is a challenging process that relies heavily on the planner’s experience. Previously, we used the single, best match from a library of manually planned cases to semi-automatically generate IMRT plans for a new patient. The current multi-case Knowledge Based Radiation Therapy (MC-KBRT) study utilized different matching cases for each of six individual organs-at-risk (OARs), then combined those six cases to create the new treatment plan. Methods: From a database of 103 patient plans created by experienced planners, MC-KBRT plans were created for 40 (17 unilateral and 23 bilateral) HNC “query” patients. For each case, 2D beam’s-eye-view images were used to find similar geometric “match” patients separately for each of 6 OARs. Dose distributions for each OAR from the 6 matching cases were combined and then warped to suit the query case’s geometry. The dose-volume constraints were used to create the new query treatment plan without the need for human decision-making throughout the IMRT optimization. The optimized MC-KBRT plans were compared against the clinically approved plans and Version 1 (original KBRT) using the dose metrics: mean, median, and maximum (brainstem and cord+5mm) doses. Results: Compared to Version 1, MC-KBRT had no significant reduction of the dose to any of the OARs in either unilateral/bilateral cases. Compared to the manually-planned unilateral cases, there was significant reduction of the oral cavity mean/median dose (>2Gy) at the expense of the contralateral parotid. Compared to the manually-planned bilateral cases, reduction of dose was significant in the ipsilateral parotid, larynx, and oral cavity (>3Gy mean/median) while maintaining PTV coverage. Conclusion: MC-KBRT planning in head and neck cancer generates IMRT plans with equivalent dose sparing to manually created plans. MC-KBRT using multiple case matches does not show significant dose reduction compared to using a single match case with

  13. Is it beneficial to selectively boost high-risk tumor subvolumes? A comparison of selectively boosting high-risk tumor subvolumes versus homogeneous dose escalation of the entire tumor based on equivalent EUD plans

    International Nuclear Information System (INIS)

    Kim, Yusung; To me, Wolfgang A.

    2008-01-01

    Purpose. To quantify and compare expected local tumor control and expected normal tissue toxicities between selective boosting IMRT and homogeneous dose escalation IMRT for the case of prostate cancer. Methods. Four different selective boosting scenarios and three different high-risk tumor subvolume geometries were designed to compare selective boosting and homogeneous dose escalation IMRT plans delivering the same equivalent uniform dose (EUD) to the entire PTV. For each scenario, differences in tumor control probability between both boosting strategies were calculated for the high-risk tumor subvolume and remaining low-risk PTV, and were visualized using voxel based iso-TCP maps. Differences in expected rectal and bladder complications were quantified using radiobiological indices (generalized EUD (gEUD) and normal tissue complication probability (NTCP)) as well as %-volumes. Results. For all investigated scenarios and high-risk tumor subvolume geometries, selective boosting IMRT improves expected TCP compared to homogeneous dose escalation IMRT, especially when lack of control of the high-risk tumor subvolume could be the cause for tumor recurrence. Employing, selective boosting IMRT significant increases in expected TCP can be achieved for the high-risk tumor subvolumes. The three conventional selective boosting IMRT strategies, employing physical dose objectives, did not show significant improvement in rectal and bladder sparing as compared to their counterpart homogeneous dose escalation plans. However, risk-adaptive optimization, utilizing radiobiological objective functions, resulted in reduction in NTCP for the rectum when compared to its corresponding homogeneous dose escalation plan. Conclusions. Selective boosting is a more effective method than homogeneous dose escalation for achieving optimal treatment outcomes. Furthermore, risk-adaptive optimization increases the therapeutic ratio as compared to conventional selective boosting IMRT

  14. Comparison of whole-field simultaneous integrated boost VMAT and IMRT in the treatment of nasopharyngeal cancer

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Xiance; Yi, Jinling; Zhou, Yongqiang; Yan, Huawei; Han, Ce; Xie, Congying, E-mail: billy07@wzhospital.cn

    2013-01-01

    To study the feasibility of using volumetric-modulated arc therapy (VMAT) to deliver whole-field simultaneous integrated boost (WF-SIB) to treat patients with nasopharyngeal cancer (NPC). WF-SIB intensity-modulated radiotherapy (IMRT) plans, one-arc WF-SIB VMAT plans, and two-arc WF-SIB VMAT plans were generated with identical objective functions for 8 patients with NPC of various stages. Isodose distributions and dose-volume histograms were evaluated. Dosimetric and biological quality indices of clinical target volume (CTV) and organs at risk (OARs) were calculated to study the optimization capability of these 3 modalities in the treatment of patients with NPC. The optimization time, delivery time, required monitor units (MUs), and delivery accuracy were also compared to investigate the feasibility of these 3 modalities. There was no significant difference (p = 0.92) in target coverage (TC) between WF-SIB IMRT (99.00 ± 0.79) and two-arc WF-SIB VMAT (97.98 ± 1.29). However, both had higher TC than one-arc VMAT plans (89.92 ± 6.32, p < 0.01). IMRT demonstrated the best protection of the spinal cord, whereas two-arc VMAT showed the minimum D{sub max} to OARs. No other significant differences were observed among these 3 modalities on CTV coverage and OAR sparing. The delivery and MU efficiency of one-arc and two-arc WF-SIB VMAT were greatly improved compared with WF-SIB IMRT. The optimization time of one-arc and two-arc WF-SIB VMAT plans were 5 and 10 times greater than that of WF-SIB IMRT, respectively. The delivery accuracy of WF-SIB VMAT was not affected by the increased freedom. For patients with NPC, one-arc WF-SIB VMAT might not be able to achieve sufficient TC, whereas two-arc WF-SIB VMAT was able to achieve reasonable TC. No significant advantage on OAR protection was demonstrated by VMAT compared with IMRT. WF-SIB VMAT has significantly shorter delivery times, but WF-SIB IMRT may still be the first treatment choice for patients with NPC.

  15. A non-voxel-based broad-beam (NVBB) framework for IMRT treatment planning.

    Science.gov (United States)

    Lu, Weiguo

    2010-12-07

    We present a novel framework that enables very large scale intensity-modulated radiation therapy (IMRT) planning in limited computation resources with improvements in cost, plan quality and planning throughput. Current IMRT optimization uses a voxel-based beamlet superposition (VBS) framework that requires pre-calculation and storage of a large amount of beamlet data, resulting in large temporal and spatial complexity. We developed a non-voxel-based broad-beam (NVBB) framework for IMRT capable of direct treatment parameter optimization (DTPO). In this framework, both objective function and derivative are evaluated based on the continuous viewpoint, abandoning 'voxel' and 'beamlet' representations. Thus pre-calculation and storage of beamlets are no longer needed. The NVBB framework has linear complexities (O(N(3))) in both space and time. The low memory, full computation and data parallelization nature of the framework render its efficient implementation on the graphic processing unit (GPU). We implemented the NVBB framework and incorporated it with the TomoTherapy treatment planning system (TPS). The new TPS runs on a single workstation with one GPU card (NVBB-GPU). Extensive verification/validation tests were performed in house and via third parties. Benchmarks on dose accuracy, plan quality and throughput were compared with the commercial TomoTherapy TPS that is based on the VBS framework and uses a computer cluster with 14 nodes (VBS-cluster). For all tests, the dose accuracy of these two TPSs is comparable (within 1%). Plan qualities were comparable with no clinically significant difference for most cases except that superior target uniformity was seen in the NVBB-GPU for some cases. However, the planning time using the NVBB-GPU was reduced many folds over the VBS-cluster. In conclusion, we developed a novel NVBB framework for IMRT optimization. The continuous viewpoint and DTPO nature of the algorithm eliminate the need for beamlets and lead to better plan

  16. A non-voxel-based broad-beam (NVBB) framework for IMRT treatment planning

    Energy Technology Data Exchange (ETDEWEB)

    Lu Weiguo, E-mail: wlu@tomotherapy.co [TomoTherapy Inc., 1240 Deming Way, Madison, WI 53717 (United States)

    2010-12-07

    We present a novel framework that enables very large scale intensity-modulated radiation therapy (IMRT) planning in limited computation resources with improvements in cost, plan quality and planning throughput. Current IMRT optimization uses a voxel-based beamlet superposition (VBS) framework that requires pre-calculation and storage of a large amount of beamlet data, resulting in large temporal and spatial complexity. We developed a non-voxel-based broad-beam (NVBB) framework for IMRT capable of direct treatment parameter optimization (DTPO). In this framework, both objective function and derivative are evaluated based on the continuous viewpoint, abandoning 'voxel' and 'beamlet' representations. Thus pre-calculation and storage of beamlets are no longer needed. The NVBB framework has linear complexities (O(N{sup 3})) in both space and time. The low memory, full computation and data parallelization nature of the framework render its efficient implementation on the graphic processing unit (GPU). We implemented the NVBB framework and incorporated it with the TomoTherapy treatment planning system (TPS). The new TPS runs on a single workstation with one GPU card (NVBB-GPU). Extensive verification/validation tests were performed in house and via third parties. Benchmarks on dose accuracy, plan quality and throughput were compared with the commercial TomoTherapy TPS that is based on the VBS framework and uses a computer cluster with 14 nodes (VBS-cluster). For all tests, the dose accuracy of these two TPSs is comparable (within 1%). Plan qualities were comparable with no clinically significant difference for most cases except that superior target uniformity was seen in the NVBB-GPU for some cases. However, the planning time using the NVBB-GPU was reduced many folds over the VBS-cluster. In conclusion, we developed a novel NVBB framework for IMRT optimization. The continuous viewpoint and DTPO nature of the algorithm eliminate the need for beamlets

  17. Use of a realistic breathing lung phantom to evaluate dose delivery errors

    International Nuclear Information System (INIS)

    Court, Laurence E.; Seco, Joao; Lu Xingqi; Ebe, Kazuyu; Mayo, Charles; Ionascu, Dan; Winey, Brian; Giakoumakis, Nikos; Aristophanous, Michalis; Berbeco, Ross; Rottman, Joerg; Bogdanov, Madeleine; Schofield, Deborah; Lingos, Tania

    2010-01-01

    Purpose: To compare the effect of respiration-induced motion on delivered dose (the interplay effect) for different treatment techniques under realistic clinical conditions. Methods: A flexible resin tumor model was created using rapid prototyping techniques based on a computed tomography (CT) image of an actual tumor. Twenty micro-MOSFETs were inserted into the tumor model and the tumor model was inserted into an anthropomorphic breathing phantom. Phantom motion was programed using the motion trajectory of an actual patient. A four-dimensional CT image was obtained and several treatment plans were created using different treatment techniques and planning systems: Conformal (Eclipse), step-and-shoot intensity-modulated radiation therapy (IMRT) (Pinnacle), step-and-shoot IMRT (XiO), dynamic IMRT (Eclipse), complex dynamic IMRT (Eclipse), hybrid IMRT [60% conformal, 40% dynamic IMRT (Eclipse)], volume-modulated arc therapy (VMAT) [single-arc (Eclipse)], VMAT [double-arc (Eclipse)], and complex VMAT (Eclipse). The complex plans were created by artificially pushing the optimizer to give complex multileaf collimator sequences. Each IMRT field was irradiated five times and each VMAT field was irradiated ten times, with each irradiation starting at a random point in the respiratory cycle. The effect of fractionation was calculated by randomly summing the measured doses. The maximum deviation for each measurement point per fraction and the probability that 95% of the model tumor had dose deviations less than 2% and 5% were calculated as a function of the number of fractions. Tumor control probabilities for each treatment plan were calculated and compared. Results: After five fractions, measured dose deviations were less than 2% for more than 95% of measurement points within the tumor model for all plans, except the complex dynamic IMRT, step-and-shoot IMRT (XiO), complex VMAT, and single-arc VMAT plans. Reducing the dose rate of the complex IMRT plans from 600 to 200 MU

  18. Use of a realistic breathing lung phantom to evaluate dose delivery errors

    Energy Technology Data Exchange (ETDEWEB)

    Court, Laurence E.; Seco, Joao; Lu Xingqi; Ebe, Kazuyu; Mayo, Charles; Ionascu, Dan; Winey, Brian; Giakoumakis, Nikos; Aristophanous, Michalis; Berbeco, Ross; Rottman, Joerg; Bogdanov, Madeleine; Schofield, Deborah; Lingos, Tania [Dana-Farber Cancer Institute and Brigham and Women' s Hospital, Harvard Medical School, Boston, Massachusetts 02115 (United States); Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114 (United States); Beth-Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02130 (United States); JA Jouetsu Hospital, Jouetsu 355-0063 (Japan); University of Massachusetts Memorial Medical Center, Worcester, Massachusetts 01655 (United States); William Beaumont Hospital, Royal Oak, Michigan 48073 (United States); Dana-Farber Cancer Institute and Brigham and Women' s Hospital, Harvard Medical School, Boston, Massachusetts 02115 (United States) and Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114 (United States); Dana-Farber Cancer Institute and Brigham and Women' s Hospital, Harvard Medical School, Boston, Massachusetts 02115 (United States)

    2010-11-15

    Purpose: To compare the effect of respiration-induced motion on delivered dose (the interplay effect) for different treatment techniques under realistic clinical conditions. Methods: A flexible resin tumor model was created using rapid prototyping techniques based on a computed tomography (CT) image of an actual tumor. Twenty micro-MOSFETs were inserted into the tumor model and the tumor model was inserted into an anthropomorphic breathing phantom. Phantom motion was programed using the motion trajectory of an actual patient. A four-dimensional CT image was obtained and several treatment plans were created using different treatment techniques and planning systems: Conformal (Eclipse), step-and-shoot intensity-modulated radiation therapy (IMRT) (Pinnacle), step-and-shoot IMRT (XiO), dynamic IMRT (Eclipse), complex dynamic IMRT (Eclipse), hybrid IMRT [60% conformal, 40% dynamic IMRT (Eclipse)], volume-modulated arc therapy (VMAT) [single-arc (Eclipse)], VMAT [double-arc (Eclipse)], and complex VMAT (Eclipse). The complex plans were created by artificially pushing the optimizer to give complex multileaf collimator sequences. Each IMRT field was irradiated five times and each VMAT field was irradiated ten times, with each irradiation starting at a random point in the respiratory cycle. The effect of fractionation was calculated by randomly summing the measured doses. The maximum deviation for each measurement point per fraction and the probability that 95% of the model tumor had dose deviations less than 2% and 5% were calculated as a function of the number of fractions. Tumor control probabilities for each treatment plan were calculated and compared. Results: After five fractions, measured dose deviations were less than 2% for more than 95% of measurement points within the tumor model for all plans, except the complex dynamic IMRT, step-and-shoot IMRT (XiO), complex VMAT, and single-arc VMAT plans. Reducing the dose rate of the complex IMRT plans from 600 to 200 MU

  19. A comprehensive analysis of the IMRT dose delivery process using statistical process control (SPC)

    Energy Technology Data Exchange (ETDEWEB)

    Gerard, Karine; Grandhaye, Jean-Pierre; Marchesi, Vincent; Kafrouni, Hanna; Husson, Francois; Aletti, Pierre [Research Center for Automatic Control (CRAN), Nancy University, CNRS, 54516 Vandoeuvre-les-Nancy (France); Department of Medical Physics, Alexis Vautrin Cancer Center, 54511 Vandoeuvre-les-Nancy Cedex (France) and DOSIsoft SA, 94230 Cachan (France); Research Laboratory for Innovative Processes (ERPI), Nancy University, EA 3767, 5400 Nancy Cedex (France); Department of Medical Physics, Alexis Vautrin Cancer Center, 54511 Vandoeuvre-les-Nancy Cedex (France); DOSIsoft SA, 94230 Cachan (France); Research Center for Automatic Control (CRAN), Nancy University, CNRS, 54516 Vandoeuvre-les-Nancy, France and Department of Medical Physics, Alexis Vautrin Cancer Center, 54511 Vandoeuvre-les-Nancy Cedex (France)

    2009-04-15

    The aim of this study is to introduce tools to improve the security of each IMRT patient treatment by determining action levels for the dose delivery process. To achieve this, the patient-specific quality control results performed with an ionization chamber--and which characterize the dose delivery process--have been retrospectively analyzed using a method borrowed from industry: Statistical process control (SPC). The latter consisted in fulfilling four principal well-structured steps. The authors first quantified the short term variability of ionization chamber measurements regarding the clinical tolerances used in the cancer center ({+-}4% of deviation between the calculated and measured doses) by calculating a control process capability (C{sub pc}) index. The C{sub pc} index was found superior to 4, which implies that the observed variability of the dose delivery process is not biased by the short term variability of the measurement. Then, the authors demonstrated using a normality test that the quality control results could be approximated by a normal distribution with two parameters (mean and standard deviation). Finally, the authors used two complementary tools--control charts and performance indices--to thoroughly analyze the IMRT dose delivery process. Control charts aim at monitoring the process over time using statistical control limits to distinguish random (natural) variations from significant changes in the process, whereas performance indices aim at quantifying the ability of the process to produce data that are within the clinical tolerances, at a precise moment. The authors retrospectively showed that the analysis of three selected control charts (individual value, moving-range, and EWMA control charts) allowed efficient drift detection of the dose delivery process for prostate and head-and-neck treatments before the quality controls were outside the clinical tolerances. Therefore, when analyzed in real time, during quality controls, they should

  20. A comprehensive analysis of the IMRT dose delivery process using statistical process control (SPC).

    Science.gov (United States)

    Gérard, Karine; Grandhaye, Jean-Pierre; Marchesi, Vincent; Kafrouni, Hanna; Husson, François; Aletti, Pierre

    2009-04-01

    The aim of this study is to introduce tools to improve the security of each IMRT patient treatment by determining action levels for the dose delivery process. To achieve this, the patient-specific quality control results performed with an ionization chamber--and which characterize the dose delivery process--have been retrospectively analyzed using a method borrowed from industry: Statistical process control (SPC). The latter consisted in fulfilling four principal well-structured steps. The authors first quantified the short-term variability of ionization chamber measurements regarding the clinical tolerances used in the cancer center (+/- 4% of deviation between the calculated and measured doses) by calculating a control process capability (C(pc)) index. The C(pc) index was found superior to 4, which implies that the observed variability of the dose delivery process is not biased by the short-term variability of the measurement. Then, the authors demonstrated using a normality test that the quality control results could be approximated by a normal distribution with two parameters (mean and standard deviation). Finally, the authors used two complementary tools--control charts and performance indices--to thoroughly analyze the IMRT dose delivery process. Control charts aim at monitoring the process over time using statistical control limits to distinguish random (natural) variations from significant changes in the process, whereas performance indices aim at quantifying the ability of the process to produce data that are within the clinical tolerances, at a precise moment. The authors retrospectively showed that the analysis of three selected control charts (individual value, moving-range, and EWMA control charts) allowed efficient drift detection of the dose delivery process for prostate and head-and-neck treatments before the quality controls were outside the clinical tolerances. Therefore, when analyzed in real time, during quality controls, they should improve the

  1. Use of plan quality degradation to evaluate tradeoffs in delivery efficiency and clinical plan metrics arising from IMRT optimizer and sequencer compromises

    Science.gov (United States)

    Wilkie, Joel R.; Matuszak, Martha M.; Feng, Mary; Moran, Jean M.; Fraass, Benedick A.

    2013-01-01

    Purpose: Plan degradation resulting from compromises made to enhance delivery efficiency is an important consideration for intensity modulated radiation therapy (IMRT) treatment plans. IMRT optimization and/or multileaf collimator (MLC) sequencing schemes can be modified to generate more efficient treatment delivery, but the effect those modifications have on plan quality is often difficult to quantify. In this work, the authors present a method for quantitative assessment of overall plan quality degradation due to tradeoffs between delivery efficiency and treatment plan quality, illustrated using comparisons between plans developed allowing different numbers of intensity levels in IMRT optimization and/or MLC sequencing for static segmental MLC IMRT plans. Methods: A plan quality degradation method to evaluate delivery efficiency and plan quality tradeoffs was developed and used to assess planning for 14 prostate and 12 head and neck patients treated with static IMRT. Plan quality was evaluated using a physician's predetermined “quality degradation” factors for relevant clinical plan metrics associated with the plan optimization strategy. Delivery efficiency and plan quality were assessed for a range of optimization and sequencing limitations. The “optimal” (baseline) plan for each case was derived using a clinical cost function with an unlimited number of intensity levels. These plans were sequenced with a clinical MLC leaf sequencer which uses >100 segments, assuring delivered intensities to be within 1% of the optimized intensity pattern. Each patient's optimal plan was also sequenced limiting the number of intensity levels (20, 10, and 5), and then separately optimized with these same numbers of intensity levels. Delivery time was measured for all plans, and direct evaluation of the tradeoffs between delivery time and plan degradation was performed. Results: When considering tradeoffs, the optimal number of intensity levels depends on the treatment

  2. The effect of respiratory cycle and radiation beam-on timing on the dose distribution of free-breathing breast treatment using dynamic IMRT

    International Nuclear Information System (INIS)

    Ding Chuxiong; Li Xiang; Huq, M. Saiful; Saw, Cheng B.; Heron, Dwight E.; Yue, Ning J.

    2007-01-01

    In breast cancer treatment, intensity-modulated radiation therapy (IMRT) can be utilized to deliver more homogeneous dose to target tissues to minimize the cosmetic impact. We have investigated the effect of the respiratory cycle and radiation beam-on timing on the dose distribution in free-breathing dynamic breast IMRT treatment. Six patients with early stage cancer of the left breast were included in this study. A helical computed tomography (CT) scan was acquired for treatment planning. A four-dimensional computed tomography (4D CT) scan was obtained right after the helical CT scan with little or no setup uncertainty to simulate patient respiratory motion. After optimizing based on the helical CT scan, the sliding-window dynamic multileaf collimator (DMLC) leaf sequence was segmented into multiple sections that corresponded to various respiratory phases per respiratory cycle and radiation beam-on timing. The segmented DMLC leaf sections were grouped according to respiratory phases and superimposed over the radiation fields of corresponding 4D CT image set. Dose calculation was then performed for each phase of the 4D CT scan. The total dose distribution was computed by accumulating the contribution of dose from each phase to every voxel in the region of interest. This was tracked by a deformable registration program throughout all of the respiratory phases of the 4D CT scan. A dose heterogeneity index, defined as the ratio between (D 20 -D 80 ) and the prescription dose, was introduced to numerically illustrate the impact of respiratory motion on the dose distribution of treatment volume. A respiratory cycle range of 4-8 s and randomly distributed beam-on timing were assigned to simulate the patient respiratory motion during the free-breathing treatment. The results showed that the respiratory cycle period and radiation beam-on timing presented limited impact on the target dose coverage and slightly increased the target dose heterogeneity. This motion impact

  3. Pareto navigation-algorithmic foundation of interactive multi-criteria IMRT planning

    International Nuclear Information System (INIS)

    Monz, M; Kuefer, K H; Bortfeld, T R; Thieke, C

    2008-01-01

    Inherently, IMRT treatment planning involves compromising between different planning goals. Multi-criteria IMRT planning directly addresses this compromising and thus makes it more systematic. Usually, several plans are computed from which the planner selects the most promising following a certain procedure. Applying Pareto navigation for this selection step simultaneously increases the variety of planning options and eases the identification of the most promising plan. Pareto navigation is an interactive multi-criteria optimization method that consists of the two navigation mechanisms 'selection' and 'restriction'. The former allows the formulation of wishes whereas the latter allows the exclusion of unwanted plans. They are realized as optimization problems on the so-called plan bundle-a set constructed from pre-computed plans. They can be approximately reformulated so that their solution time is a small fraction of a second. Thus, the user can be provided with immediate feedback regarding his or her decisions. Pareto navigation was implemented in the MIRA navigator software and allows real-time manipulation of the current plan and the set of considered plans. The changes are triggered by simple mouse operations on the so-called navigation star and lead to real-time updates of the navigation star and the dose visualizations. Since any Pareto-optimal plan in the plan bundle can be found with just a few navigation operations the MIRA navigator allows a fast and directed plan determination. Besides, the concept allows for a refinement of the plan bundle, thus offering a middle course between single plan computation and multi-criteria optimization. Pareto navigation offers so far unmatched real-time interactions, ease of use and plan variety, setting it apart from the multi-criteria IMRT planning methods proposed so far

  4. Pareto navigation: algorithmic foundation of interactive multi-criteria IMRT planning.

    Science.gov (United States)

    Monz, M; Küfer, K H; Bortfeld, T R; Thieke, C

    2008-02-21

    Inherently, IMRT treatment planning involves compromising between different planning goals. Multi-criteria IMRT planning directly addresses this compromising and thus makes it more systematic. Usually, several plans are computed from which the planner selects the most promising following a certain procedure. Applying Pareto navigation for this selection step simultaneously increases the variety of planning options and eases the identification of the most promising plan. Pareto navigation is an interactive multi-criteria optimization method that consists of the two navigation mechanisms 'selection' and 'restriction'. The former allows the formulation of wishes whereas the latter allows the exclusion of unwanted plans. They are realized as optimization problems on the so-called plan bundle -- a set constructed from pre-computed plans. They can be approximately reformulated so that their solution time is a small fraction of a second. Thus, the user can be provided with immediate feedback regarding his or her decisions. Pareto navigation was implemented in the MIRA navigator software and allows real-time manipulation of the current plan and the set of considered plans. The changes are triggered by simple mouse operations on the so-called navigation star and lead to real-time updates of the navigation star and the dose visualizations. Since any Pareto-optimal plan in the plan bundle can be found with just a few navigation operations the MIRA navigator allows a fast and directed plan determination. Besides, the concept allows for a refinement of the plan bundle, thus offering a middle course between single plan computation and multi-criteria optimization. Pareto navigation offers so far unmatched real-time interactions, ease of use and plan variety, setting it apart from the multi-criteria IMRT planning methods proposed so far.

  5. Superior sulcus non-small cell lung carcinoma: A comparison of IMRT and 3D-RT dosimetry.

    Science.gov (United States)

    Truntzer, Pierre; Antoni, Delphine; Santelmo, Nicola; Schumacher, Catherine; Falcoz, Pierre-Emmanuel; Quoix, Elisabeth; Massard, Gilbert; Noël, Georges

    2016-01-01

    A dosimetric study comparing intensity modulated radiotherapy (IMRT) by TomoTherapy to conformational 3D radiotherapy (3D-RT) in patients with superior sulcus non-small cell lung cancer (NSCLC). IMRT became the main technique in modern radiotherapy. However it was not currently used for lung cancers. Because of the need to increase the dose to control lung cancers but because of the critical organs surrounding the tumors, the gains obtainable with IMRT is not still demonstrated. A dosimetric comparison of the planned target and organs at risk parameters between IMRT and 3D-RT in eight patients who received preoperative or curative intent irradiation. In the patients who received at least 66 Gy, the mean V95% was significantly better with IMRT than 3D-RT (p = 0.043). IMRT delivered a lower D2% compared to 3D-RT (p = 0.043). The IH was significantly better with IMRT (p = 0.043). The lung V 5 Gy and V 13 Gy were significantly higher in IMRT than 3D-RT (p = 0.043), while the maximal dose (D max) to the spinal cord was significantly lower in IMRT (p = 0.043). The brachial plexus D max was significantly lower in IMRT than 3D-RT (p = 0.048). For patients treated with 46 Gy, no significant differences were found. Our study showed that IMRT is relevant for SS-NSCLC. In patients treated with a curative dose, it led to a reduction of the exposure of critical organs, allowing a better dose distribution in the tumor. For the patients treated with a preoperative schedule, our results provide a basis for future controlled trials to improve the histological complete response by increasing the radiation dose.

  6. SU-F-T-440: The Feasibility Research of Checking Cervical Cancer IMRT Pre- Treatment Dose Verification by Automated Treatment Planning Verification System

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X; Yin, Y; Lin, X [Shandong Cancer Hospital and Institute, China, Jinan, Shandong (China)

    2016-06-15

    Purpose: To assess the preliminary feasibility of automated treatment planning verification system in cervical cancer IMRT pre-treatment dose verification. Methods: The study selected randomly clinical IMRT treatment planning data for twenty patients with cervical cancer, all IMRT plans were divided into 7 fields to meet the dosimetric goals using a commercial treatment planning system(PianncleVersion 9.2and the EclipseVersion 13.5). The plans were exported to the Mobius 3D (M3D)server percentage differences of volume of a region of interest (ROI) and dose calculation of target region and organ at risk were evaluated, in order to validate the accuracy automated treatment planning verification system. Results: The difference of volume for Pinnacle to M3D was less than results for Eclipse to M3D in ROI, the biggest difference was 0.22± 0.69%, 3.5±1.89% for Pinnacle and Eclipse respectively. M3D showed slightly better agreement in dose of target and organ at risk compared with TPS. But after recalculating plans by M3D, dose difference for Pinnacle was less than Eclipse on average, results were within 3%. Conclusion: The method of utilizing the automated treatment planning system to validate the accuracy of plans is convenientbut the scope of differences still need more clinical patient cases to determine. At present, it should be used as a secondary check tool to improve safety in the clinical treatment planning.

  7. Implementation of random set-up errors in Monte Carlo calculated dynamic IMRT treatment plans

    International Nuclear Information System (INIS)

    Stapleton, S; Zavgorodni, S; Popescu, I A; Beckham, W A

    2005-01-01

    The fluence-convolution method for incorporating random set-up errors (RSE) into the Monte Carlo treatment planning dose calculations was previously proposed by Beckham et al, and it was validated for open field radiotherapy treatments. This study confirms the applicability of the fluence-convolution method for dynamic intensity modulated radiotherapy (IMRT) dose calculations and evaluates the impact of set-up uncertainties on a clinical IMRT dose distribution. BEAMnrc and DOSXYZnrc codes were used for Monte Carlo calculations. A sliding window IMRT delivery was simulated using a dynamic multi-leaf collimator (DMLC) transport model developed by Keall et al. The dose distributions were benchmarked for dynamic IMRT fields using extended dose range (EDR) film, accumulating the dose from 16 subsequent fractions shifted randomly. Agreement of calculated and measured relative dose values was well within statistical uncertainty. A clinical seven field sliding window IMRT head and neck treatment was then simulated and the effects of random set-up errors (standard deviation of 2 mm) were evaluated. The dose-volume histograms calculated in the PTV with and without corrections for RSE showed only small differences indicating a reduction of the volume of high dose region due to set-up errors. As well, it showed that adequate coverage of the PTV was maintained when RSE was incorporated. Slice-by-slice comparison of the dose distributions revealed differences of up to 5.6%. The incorporation of set-up errors altered the position of the hot spot in the plan. This work demonstrated validity of implementation of the fluence-convolution method to dynamic IMRT Monte Carlo dose calculations. It also showed that accounting for the set-up errors could be essential for correct identification of the value and position of the hot spot

  8. Implementation of random set-up errors in Monte Carlo calculated dynamic IMRT treatment plans

    Science.gov (United States)

    Stapleton, S.; Zavgorodni, S.; Popescu, I. A.; Beckham, W. A.

    2005-02-01

    The fluence-convolution method for incorporating random set-up errors (RSE) into the Monte Carlo treatment planning dose calculations was previously proposed by Beckham et al, and it was validated for open field radiotherapy treatments. This study confirms the applicability of the fluence-convolution method for dynamic intensity modulated radiotherapy (IMRT) dose calculations and evaluates the impact of set-up uncertainties on a clinical IMRT dose distribution. BEAMnrc and DOSXYZnrc codes were used for Monte Carlo calculations. A sliding window IMRT delivery was simulated using a dynamic multi-leaf collimator (DMLC) transport model developed by Keall et al. The dose distributions were benchmarked for dynamic IMRT fields using extended dose range (EDR) film, accumulating the dose from 16 subsequent fractions shifted randomly. Agreement of calculated and measured relative dose values was well within statistical uncertainty. A clinical seven field sliding window IMRT head and neck treatment was then simulated and the effects of random set-up errors (standard deviation of 2 mm) were evaluated. The dose-volume histograms calculated in the PTV with and without corrections for RSE showed only small differences indicating a reduction of the volume of high dose region due to set-up errors. As well, it showed that adequate coverage of the PTV was maintained when RSE was incorporated. Slice-by-slice comparison of the dose distributions revealed differences of up to 5.6%. The incorporation of set-up errors altered the position of the hot spot in the plan. This work demonstrated validity of implementation of the fluence-convolution method to dynamic IMRT Monte Carlo dose calculations. It also showed that accounting for the set-up errors could be essential for correct identification of the value and position of the hot spot.

  9. Real-time beam monitoring for error detection in IMRT plans and impact on dose-volume histograms. A multi-center study

    Energy Technology Data Exchange (ETDEWEB)

    Marrazzo, Livia; Arilli, Chiara; Casati, Marta [Careggi University Hospital, Medical Physic Unit, Florence (Italy); Pasler, Marlies [Lake Constance Radiation Oncology Center, Singen-Friedrichshafen (Germany); Kusters, Martijn; Canters, Richard [Radboud University Medical Center, Department of Radiation Oncology, Nijmegen (Netherlands); Fedeli, Luca; Calusi, Silvia [University of Florence, Department of Experimental and Clinical Biomedical Sciences ' ' Mario Serio' ' , Florence (Italy); Talamonti, Cinzia; Pallotta, Stefania [Careggi University Hospital, Medical Physic Unit, Florence (Italy); University of Florence, Department of Experimental and Clinical Biomedical Sciences ' ' Mario Serio' ' , Florence (Italy); Simontacchi, Gabriele [Careggi University Hospital, Radiation Oncology Unit, Florence (Italy); Livi, Lorenzo [University of Florence, Department of Experimental and Clinical Biomedical Sciences ' ' Mario Serio' ' , Florence (Italy); Careggi University Hospital, Radiation Oncology Unit, Florence (Italy)

    2018-03-15

    This study aimed to test the sensitivity of a transmission detector for online dose monitoring of intensity-modulated radiation therapy (IMRT) for detecting small delivery errors. Furthermore, the correlation of changes in detector output induced by small delivery errors with other metrics commonly employed to quantify the deviations between calculated and delivered dose distributions was investigated. Transmission detector measurements were performed at three institutions. Seven types of errors were induced in nine clinical step-and-shoot (S and S) IMRT plans by modifying the number of monitor units (MU) and introducing small deviations in leaf positions. Signal reproducibility was investigated for short- and long-term stability. Calculated dose distributions were compared in terms of γ passing rates and dose-volume histogram (DVH) metrics (e.g., D{sub mean}, D{sub x%}, V{sub x%}). The correlation between detector signal variations, γ passing rates, and DVH parameters was investigated. Both short- and long-term reproducibility was within 1%. Dose variations down to 1 MU (∇signal 1.1 ± 0.4%) as well as changes in field size and positions down to 1 mm (∇signal 2.6 ± 1.0%) were detected, thus indicating high error-detection sensitivity. A moderate correlation of detector signal was observed with γ passing rates (R{sup 2} = 0.57-0.70), while a good correlation was observed with DVH metrics (R{sup 2} = 0.75-0.98). The detector is capable of detecting small delivery errors in MU and leaf positions, and is thus a highly sensitive dose monitoring device for S and S IMRT for clinical practice. The results of this study indicate a good correlation of detector signal with DVH metrics; therefore, clinical action levels can be defined based on the presented data. (orig.) [German] In dieser Arbeit wurde die Sensitivitaet bezueglich der Fehlererkennung eines Transmissionsdetektors fuer die Online-Dosisueberwachung von intensitaetsmodulierter Strahlentherapie (IMRT

  10. Experimental IMRT breast dosimetry in a thorax phantom

    International Nuclear Information System (INIS)

    Pimenta, Elsa B.; Campos, Tarcisio P.R.; Nogueira, Luciana B.; Lima, Andre C.S.

    2017-01-01

    Radiation therapy (RT) is an essential therapeutic method. RT is often used as adjuvant therapy in the treatment of breast cancer. The dose-volume restrictions of the organs at risk limit the prescribed dose to the target volume and biological and clinical effects may influence the final treatment outcome. The breast RT provides large risks to the adjacent organs and consequently the recommended dosimetry to the prescribed dose volume (PTV) is 50 Gy, lower than the most prescribed dose in other treatments (70-85 Gy). Such values implies in less tumor control compared to other sites. The present research proposal aimed to measure absorbed dose in a thorax phantom with synthetic breasts provided by an Intensity-Modulate Radiation Therapy (IMRT) protocol in a RT center. On the methodology, IMRT protocol was selected following recommendations from the Radiation Therapy Oncology Group (RTOG). Radiochromic films and a thorax simulator were prepared by the Ionizing Radiation Research Group (NRI). Dosimeters were calibrated on a selected linear accelerator (LINAC). The comparison of the dosimetry from treatment planning system (TPS), Xio (Elekta) and from experimental data was performed. The spatial distribution of the breast internal dose and in the adjacent organs was depicted by the experimental data. In the film's calibration, the quadratic polynomial fit presented a satisfactory coefficient. Two-dimensional dose profiles were obtained in the breast suggesting that films can supply details and information that TPS does not provide. At the phantom's dosimetry, the internal mean doses taken at the synthetic breast presented usual values above the prescribed dose, besides overall values were within the dosimetric MSKCC criterion. The non full reproduction of the build-up region in the films had occurred due to the asymmetrical positioning of the films in the inner breast, in addition to their non constant distance from the skin. The hot regions were present may be due to

  11. Dosimetric comparison of RapidArc with fixed gantry dynamic IMRT for loco-regionally advanced nasopharyngeal carcinoma

    International Nuclear Information System (INIS)

    Wu Hao; Han Shukui; Sun Yan; Jiang Fan

    2010-01-01

    Objective: To compare the dosimetric difference of RapidArc and fixed gantry angle dynamic IMRT (dIMRT) for loco-regionally advanced nasopharyngeal carcinoma. Methods: Ten previously treated patients with loco-regionally advanced nasopharyngeal carcinoma were replanned with RapidArc and dIMRT, respectively. The prescription dose was GTV 70 Gy/33 f and PTV 60 Gy/33 f. All plans met the requirement: 95% of PTV was covered by 60 Gy. Dose-volume histogram data, isodose distribution, monitor units, and treatment time were compared. Results: Dose distribution has no significant difference between the two techniques. RapidArc reduced the dose of the brainstem, mandible, and other normal tissues compared with dIMRT. Mean monitor units were 589.5 and 1381.0 for RapidArc and dIMRT (reduced by 57% relatively). Mean treatment time was 2.33 min and 7.82 min for RapidArc and dIMRT (reduced by 70% relatively). Conclusions: Compared with dIMRT, RapidArc achieves equal target coverage and OAR sparing while using fewer monitor units and less time during radiotherapy for patient with loco-regionally advanced nasopharyngeal carcinoma. (authors)

  12. Automatically-generated rectal dose constraints in intensity-modulated radiation therapy for prostate cancer

    Science.gov (United States)

    Hwang, Taejin; Kim, Yong Nam; Kim, Soo Kon; Kang, Sei-Kwon; Cheong, Kwang-Ho; Park, Soah; Yoon, Jai-Woong; Han, Taejin; Kim, Haeyoung; Lee, Meyeon; Kim, Kyoung-Joo; Bae, Hoonsik; Suh, Tae-Suk

    2015-06-01

    The dose constraint during prostate intensity-modulated radiation therapy (IMRT) optimization should be patient-specific for better rectum sparing. The aims of this study are to suggest a novel method for automatically generating a patient-specific dose constraint by using an experience-based dose volume histogram (DVH) of the rectum and to evaluate the potential of such a dose constraint qualitatively. The normal tissue complication probabilities (NTCPs) of the rectum with respect to V %ratio in our study were divided into three groups, where V %ratio was defined as the percent ratio of the rectal volume overlapping the planning target volume (PTV) to the rectal volume: (1) the rectal NTCPs in the previous study (clinical data), (2) those statistically generated by using the standard normal distribution (calculated data), and (3) those generated by combining the calculated data and the clinical data (mixed data). In the calculated data, a random number whose mean value was on the fitted curve described in the clinical data and whose standard deviation was 1% was generated by using the `randn' function in the MATLAB program and was used. For each group, we validated whether the probability density function (PDF) of the rectal NTCP could be automatically generated with the density estimation method by using a Gaussian kernel. The results revealed that the rectal NTCP probability increased in proportion to V %ratio , that the predictive rectal NTCP was patient-specific, and that the starting point of IMRT optimization for the given patient might be different. The PDF of the rectal NTCP was obtained automatically for each group except that the smoothness of the probability distribution increased with increasing number of data and with increasing window width. We showed that during the prostate IMRT optimization, the patient-specific dose constraints could be automatically generated and that our method could reduce the IMRT optimization time as well as maintain the

  13. IMRT treatment planning based on prioritizing prescription goals

    International Nuclear Information System (INIS)

    Wilkens, Jan J; Alaly, James R; Zakarian, Konstantin; Thorstad, Wade L; Deasy, Joseph O

    2007-01-01

    Determining the 'best' optimization parameters in IMRT planning is typically a time-consuming trial-and-error process with no unambiguous termination point. Recently we and others proposed a goal-programming approach which better captures the desired prioritization of dosimetric goals. Here, individual prescription goals are addressed stepwise in their order of priority. In the first step, only the highest order goals are considered (target coverage and dose-limiting normal structures). In subsequent steps, the achievements of the previous steps are turned into hard constraints and lower priority goals are optimized, in turn, subject to higher priority constraints. So-called 'slip' factors were introduced to allow for slight, clinically acceptable violations of the constraints. Focusing on head and neck cases, we present several examples for this planning technique. The main advantages of the new optimization method are (i) its ability to generate plans that meet the clinical goals, as well as possible, without tuning any weighting factors or dose-volume constraints, and (ii) the ability to conveniently include more terms such as fluence map smoothness. Lower level goals can be optimized to the achievable limit without compromising higher order goals. The prioritized prescription-goal planning method allows for a more intuitive and human-time-efficient way of dealing with conflicting goals compared to the conventional trial-and-error method of varying weighting factors and dose-volume constraints

  14. Integral dose delivered to normal brain with conventional intensity-modulated radiotherapy (IMRT) and helical tomotherapy IMRT during partial brain radiotherapy for high-grade gliomas with and without selective sparing of the hippocampus, limbic circuit and neural stem cell compartment

    International Nuclear Information System (INIS)

    Marsh, James C.; Ziel, Ellis G; Diaz, Aidnag Z; Turian, Julius V; Wendt, Julie A.; Gobole, Rohit

    2013-01-01

    We compared integral dose with uninvolved brain (ID brain ) during partial brain radiotherapy (PBRT) for high-grade glioma patients using helical tomotherapy (HT) and seven field traditional inverse-planned intensity-modulated radiotherapy (IMRT) with and without selective sparing (SPA) of contralateral hippocampus, neural stem cell compartment (NSC) and limbic circuit. We prepared four PBRT treatment plans for four patients with high-grade gliomas (60Gy in 30 fractions delivered to planning treatment volume (PTV60Gy)). For all plans, a structure denoted 'uninvolved brain' was created, which included all brain tissue not part of PTV or standard (STD) organs at risk (OAR). No dosimetric constraints were included for uninvolved brain. Selective SPA plans were prepared with IMRT and HT; contralateral hippocampus, NSC and limbic circuit were contoured; and dosimetric constraints were entered for these structures without compromising dose to PTV or STD OAR. We compared V100 and D95 for PTV46Gy and PTV60Gy, and ID brain for all plans. There were no significant differences in V100 and D95 for PTV46Gy and PTV60Gy. ID brain was lower in traditional IMRT versus HT plans for STD and SPA plans (mean ID brain 23.64Gy vs. 28Gy and 18.7Gy vs. 24.5Gy, respectively) and in SPA versus STD plans both with IMRT and HT (18.7Gy vs. 23.64Gy and 24.5Gy vs. 28Gy, respectively). n the setting of PBRT for high-grade gliomas, IMRT reduces ID brain compared with HT with or without selective SPA of contralateral hippocampus, limbic circuit and NSC, and the use of selective SPA reduces ID brain compared with STD PBRT delivered with either traditional IMRT or HT.

  15. A comparison of physically and radiobiologically based optimization for IMRT

    International Nuclear Information System (INIS)

    Jones, Lois; Hoban, Peter

    2002-01-01

    Many optimization techniques for intensity modulated radiotherapy have now been developed. The majority of these techniques including all the commercial systems that are available are based on physical dose methods of assessment. Some techniques have also been based on radiobiological models. None of the radiobiological optimization techniques however have assessed the clinically realistic situation of considering both tumor and normal cells within the target volume. This study considers a ratio-based fluence optimizing technique to compare a dose-based optimization method described previously and two biologically based models. The biologically based methods use the values of equivalent uniform dose calculated for the tumor cells and integral biological effective dose for normal cells. The first biologically based method includes only tumor cells in the target volume while the second considers both tumor and normal cells in the target volume. All three methods achieve good conformation to the target volume. The biologically based optimization without the normal tissue in the target volume shows a high dose region in the center of the target volume while this is reduced when the normal tissues are also considered in the target volume. This effect occurs because the normal tissues in the target volume require the optimization to reduce the dose and therefore limit the maximum dose to that volume

  16. The effect of concomitant chemotherapy on parotid gland function following head and neck IMRT

    International Nuclear Information System (INIS)

    Miah, Aisha B.; Gulliford, Sarah L.; Bhide, Shreerang A.; Zaidi, Shane H.; Newbold, Kate L.; Harrington, Kevin J.; Nutting, Christopher M.

    2013-01-01

    Purpose: To determine whether concomitant chemotherapy increases the incidence of high grade xerostomia following parotid-sparing intensity-modulated radiotherapy (IMRT) in patients with locally advanced head and neck squamous cell cancer. Materials and methods: The incidence of high grade (⩾G2) acute (CTCAEv3.0) and late (LENTSOMA and RTOG) xerostomia was compared between patients treated with either IMRT or concomitant chemo-IMRT (c-IMRT) in 2 prospective studies. Parotid gland mean tolerance doses (D 50 ) were reported using non-linear logistic regression analysis. Results: Thirty-six patients received IMRT alone and 60 patients received c-IMRT. Patients received 65 Gy in 30 daily fractions to the primary site and involved nodal groups and 54 Gy in 30 fractions to elective nodal groups, mean doses to the parotid glands were comparable. Concomitant cisplatin 100 mg/m 2 was administered on days 1 and 29 of IMRT. The incidence of ⩾G2 subjective xerostomia was similar in both groups; acute-64.7% (IMRT) versus 60.3% (c-IMRT), p = 0.83; late-43% (IMRT) versus 34% (c-IMRT), p = 0.51. Recovery of parotid salivary flow at 1 year was higher with IMRT (64% vs 50%), but not statistically significant (p = 0.15). D 50 for absence of parotid saliva flow at 1 year was 23.2 Gy (95% CI: 17.7–28.7) for IMRT and 21.1 Gy (11.8–30.3) for c-IMRT. Conclusion: Concomitant c-IMRT does not increase the incidence of acute or late xerostomia relative to IMRT alone

  17. The effect of concomitant chemotherapy on parotid gland function following head and neck IMRT.

    Science.gov (United States)

    Miah, Aisha B; Gulliford, Sarah L; Bhide, Shreerang A; Zaidi, Shane H; Newbold, Kate L; Harrington, Kevin J; Nutting, Christopher M

    2013-03-01

    To determine whether concomitant chemotherapy increases the incidence of high grade xerostomia following parotid-sparing intensity-modulated radiotherapy (IMRT) in patients with locally advanced head and neck squamous cell cancer. The incidence of high grade (≥G2) acute (CTCAEv3.0) and late (LENTSOMA and RTOG) xerostomia was compared between patients treated with either IMRT or concomitant chemo-IMRT (c-IMRT) in 2 prospective studies. Parotid gland mean tolerance doses (D₅₀) were reported using non-linear logistic regression analysis. Thirty-six patients received IMRT alone and 60 patients received c-IMRT. Patients received 65 Gy in 30 daily fractions to the primary site and involved nodal groups and 54 Gy in 30 fractions to elective nodal groups, mean doses to the parotid glands were comparable. Concomitant cisplatin 100mg/m(2) was administered on days 1 and 29 of IMRT. The incidence of ≥G2 subjective xerostomia was similar in both groups; acute-64.7% (IMRT) versus 60.3% (c-IMRT), p=0.83; late-43% (IMRT) versus 34% (c-IMRT), p=0.51. Recovery of parotid salivary flow at 1 year was higher with IMRT (64% vs 50%), but not statistically significant (p=0.15). D₅₀ for absence of parotid saliva flow at 1 year was 23.2 Gy (95% CI: 17.7-28.7) for IMRT and 21.1 Gy (11.8-30.3) for c-IMRT. Concomitant c-IMRT does not increase the incidence of acute or late xerostomia relative to IMRT alone. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  18. Toward optimizing patient-specific IMRT QA techniques in the accurate detection of dosimetrically acceptable and unacceptable patient plans.

    Science.gov (United States)

    McKenzie, Elizabeth M; Balter, Peter A; Stingo, Francesco C; Jones, Jimmy; Followill, David S; Kry, Stephen F

    2014-12-01

    The authors investigated the performance of several patient-specific intensity-modulated radiation therapy (IMRT) quality assurance (QA) dosimeters in terms of their ability to correctly identify dosimetrically acceptable and unacceptable IMRT patient plans, as determined by an in-house-designed multiple ion chamber phantom used as the gold standard. A further goal was to examine optimal threshold criteria that were consistent and based on the same criteria among the various dosimeters. The authors used receiver operating characteristic (ROC) curves to determine the sensitivity and specificity of (1) a 2D diode array undergoing anterior irradiation with field-by-field evaluation, (2) a 2D diode array undergoing anterior irradiation with composite evaluation, (3) a 2D diode array using planned irradiation angles with composite evaluation, (4) a helical diode array, (5) radiographic film, and (6) an ion chamber. This was done with a variety of evaluation criteria for a set of 15 dosimetrically unacceptable and 9 acceptable clinical IMRT patient plans, where acceptability was defined on the basis of multiple ion chamber measurements using independent ion chambers and a phantom. The area under the curve (AUC) on the ROC curves was used to compare dosimeter performance across all thresholds. Optimal threshold values were obtained from the ROC curves while incorporating considerations for cost and prevalence of unacceptable plans. Using common clinical acceptance thresholds, most devices performed very poorly in terms of identifying unacceptable plans. Grouping the detector performance based on AUC showed two significantly different groups. The ion chamber, radiographic film, helical diode array, and anterior-delivered composite 2D diode array were in the better-performing group, whereas the anterior-delivered field-by-field and planned gantry angle delivery using the 2D diode array performed less well. Additionally, based on the AUCs, there was no significant difference

  19. A case study of IMRT planning (Plan B) subsequent to a previously treated IMRT plan (Plan A)

    International Nuclear Information System (INIS)

    2Department of Radiation Oncology, Fraser Valley Centre, BC Cancer Agency, Surrey, British Columb