Assessing medical students’ competence in calculating drug doses
Directory of Open Access Journals (Sweden)
Catherine Harries
2013-09-01
Full Text Available Evidence suggests that healthcare professionals are not optimally able to calculate medicine doses and various strategies have been employed to improve these skills. In this study, the performance of third and fourth year medical students was assessed and the success of various educational interventions investigated. Students were given four types of dosing calculations typical of those required in an emergency setting. Full competence (at the 100% level was defined as correctly answering all four categories of calculation at any one time. Three categories correct meant competence at the 75% level. Interventions comprised an assignment with a model answer for self-assessment in the third year and a small group tutorial in the fourth year. The small groups provided opportunities for peer-assisted learning. A subgroup of 23 students received individual tuition from the lecturer prior to the start of the fourth year. Amongst the 364 eligible students, full competence rose from 23% at the beginning of the third year to 66% by the end of the fourth year. More students succeeded during the fourth than the third year of study. Success of small group tuition was assessed in a sample of 200 students who had formal assessments both before and after the fourth year tuition. Competence at the 75% level improved by 10% in attendees and decreased by 3% in non-attendees, providing evidence of the value of students receiving assistance from more able same-language peers. Good results were achieved with one-on-one tuition where individualised assistance allowed even struggling students to improve.
Ability of medical students to calculate drug doses in children after their paediatric attachment
Directory of Open Access Journals (Sweden)
Oshikoya KA
2008-12-01
Full Text Available Dose calculation errors constitute a significant part of prescribing errors which might have resulted from informal teaching of the topic in medical schools. Objectives: To determine adequacy of knowledge and skills of drug dose calculations in children acquired by medical students during their clinical attachment in paediatrics.Methods: Fifty two 5th year medical students of the Lagos State University College of Medicine (LASUCOM, Ikeja were examined on drug dose calculations from a vial and ampoules of injections, syrup and suspension, and tablet formulation. The examination was with a structured questionnaire mostly in the form of multiple choice questions.Results: Thirty-six (69.2% and 30 (57.7% students were taught drug dose calculation in neonatal posting and during ward rounds/ bed-side teaching, respectively. Less than 50% of the students were able to calculate the correct doses of each of adrenaline, gentamicin, chloroquine and sodium bicarbonate injections required by the patient. Dose calculation was however relatively better with adrenalin when compared with the other injections. The proportion of female students that calculated the correct doses of quinine syrup and cefuroxime suspension were significantly higher than those of their male counterparts (p<0.05 and p<0.01, respectively; Chi-square test. When doses calculated in mg/dose and mL/dose was compared for adrenalin injection and each of quinine syrup and cefuroxime suspension, there were significant differences (adrenaline and quinine, p=0.005; adrenaline and cefuroxime, p=0.003: Fischer’s exact test. Dose calculation errors of similar magnitude to injections, syrup and suspension were also observed with tablet formulation.Conclusions: LASUCOM medical students lacked the basic knowledge of paediatric drug dose calculations but were willing to learn if the topic was formally taught. Drug dose calculations should be given a prominent consideration in the undergraduate medical
Directory of Open Access Journals (Sweden)
Gracieli Prado Elias
2005-06-01
Full Text Available The present study was conducted to evaluate the utilization of Clark's, Salisbury and Penna's rules and the Body Surface Area (BSA formula for calculation of pediatric drug dosage, as well as their reliability and viability in the clinical use. These rules are frequently cited in the literature, but much controversy still exists with regards to their use. The pediatric drug dosage was calculated by utilization of the aforementioned rules and using the drugs Paracetamol, Dipyrone, Diclofenac Potassium, Nimesulide, Amoxicillin and Erythromycin, widely employed in Pediatric Dentistry. Weight and body surface areas were considered of children with ages between 1 and 12 years old as well as the dosage for the adult. The pediatric dosages achieved were compared to the predetermined dosages in mg kg-1 herein-named standard dosages. The results were submitted to the parametric test ANOVA and to the Tukey test (pO presente estudo foi realizado com a finalidade de avaliar as fórmulas de Clark, Salisbury, Área da Superfície Corpórea (ASC e Penna, quanto a sua confiabilidade e viabilidade de uso clínico para o cálculo de doses medicamentosas infantis, uma vez que tais fórmulas são freqüentemente citadas na literatura, mas muita controvérsia ainda existe com relação ao seu uso. As doses infantis foram calculadas utilizando as fórmulas descritas e os medicamentos Paracetamol, Dipirona, Diclofenaco de Potássio, Nimesulida, Amoxicilina e Eritromicina, largamente usados na clínica odontopediátrica. Foram considerados parâmetros como o peso e área da superfície corpórea de crianças com idades entre 1 e 12 anos e a dose para o adulto. As doses obtidas foram comparadas às doses em mg/kg consideradas como padrão de referência para os medicamentos. Os resultados foram submetidos ao teste paramétrico ANOVA e de Tukey (P<0,05. Os antibióticos e o Diclofenaco propiciam utilização aceitável das fórmulas na Odontopediatria, porém para a
Calculational Tool for Skin Contamination Dose Assessment
Hill, R L
2002-01-01
Spreadsheet calculational tool was developed to automate the calculations preformed for dose assessment of skin contamination. This document reports on the design and testing of the spreadsheet calculational tool.
Entrance surface dose according to dose calculation: Head and wrist
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Sung, Ho Jin [Dept. Radiology, Chonnam National University Hospital, Gwangju (Korea, Republic of); Han, Jae Bok; Song, Jong Nam; Choi, Nam Gil [Dept. of Radiological Science, Dongshin University, Naju (Korea, Republic of)
2016-09-15
This study were compared with the direct measurement and indirect dose methods through various dose calculation in head and wrist. And, the modified equation was proposed considering equipment type, setting conditions, tube voltage, inherent filter, added filter and its accompanied back scatter factor. As a result, it decreased the error of the direct measurement than the existing dose calculation. Accordingly, diagnostic radiography patient dose comparison would become easier and radiographic exposure control and evaluation will become more efficient. The study findings are expected to be useful in patients' effective dose rate evaluation and dose reduction.
Basak, Tulay; Yildiz, Dilek
2014-01-01
Objective: The aim of this study was to compare the effectiveness of cooperative learning and traditional learning methods on the development of drug-calculation skills. Design: Final-year nursing students ("n" = 85) undergoing internships during the 2010-2011 academic year at a nursing school constituted the study group of this…
Dose calculations for intakes of ore dust
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O`Brien, R.S
1998-08-01
This report describes a methodology for calculating the committed effective dose for mixtures of radionuclides, such as those which occur in natural radioactive ores and dusts. The formulae are derived from first principles, with the use of reasonable assumptions concerning the nature and behaviour of the radionuclide mixtures. The calculations are complicated because these `ores` contain a range of particle sizes, have different degrees of solubility in blood and other body fluids, and also have different biokinetic clearance characteristics from the organs and tissues in the body. The naturally occurring radionuclides also tend to occur in series, i.e. one is produced by the radioactive decay of another `parent` radionuclide. The formulae derived here can be used, in conjunction with a model such as LUDEP, for calculating total dose resulting from inhalation and/or ingestion of a mixture of radionuclides, and also for deriving annual limits on intake and derived air concentrations for these mixtures. 15 refs., 14 tabs., 3 figs.
Dose-Response Calculator for ArcGIS
Hanser, Steven E.; Aldridge, Cameron L.; Leu, Matthias; Nielsen, Scott E.
2011-01-01
The Dose-Response Calculator for ArcGIS is a tool that extends the Environmental Systems Research Institute (ESRI) ArcGIS 10 Desktop application to aid with the visualization of relationships between two raster GIS datasets. A dose-response curve is a line graph commonly used in medical research to examine the effects of different dosage rates of a drug or chemical (for example, carcinogen) on an outcome of interest (for example, cell mutations) (Russell and others, 1982). Dose-response curves have recently been used in ecological studies to examine the influence of an explanatory dose variable (for example, percentage of habitat cover, distance to disturbance) on a predicted response (for example, survival, probability of occurrence, abundance) (Aldridge and others, 2008). These dose curves have been created by calculating the predicted response value from a statistical model at different levels of the explanatory dose variable while holding values of other explanatory variables constant. Curves (plots) developed using the Dose-Response Calculator overcome the need to hold variables constant by using values extracted from the predicted response surface of a spatially explicit statistical model fit in a GIS, which include the variation of all explanatory variables, to visualize the univariate response to the dose variable. Application of the Dose-Response Calculator can be extended beyond the assessment of statistical model predictions and may be used to visualize the relationship between any two raster GIS datasets (see example in tool instructions). This tool generates tabular data for use in further exploration of dose-response relationships and a graph of the dose-response curve.
DEFF Research Database (Denmark)
Nielsen, Tine B; Wieslander, Elinore; Fogliata, Antonella;
2011-01-01
To investigate differences in calculated doses and normal tissue complication probability (NTCP) values between different dose algorithms.......To investigate differences in calculated doses and normal tissue complication probability (NTCP) values between different dose algorithms....
Phage therapy pharmacology: calculating phage dosing.
Abedon, Stephen
2011-01-01
Phage therapy, which can be described as a phage-mediated biocontrol of bacteria (or, simply, biocontrol), is the application of bacterial viruses-also bacteriophages or phages-to reduce densities of nuisance or pathogenic bacteria. Predictive calculations for phage therapy dosing should be useful toward rational development of therapeutic as well as biocontrol products. Here, I consider the theoretical basis of a number of concepts relevant to phage dosing for phage therapy including minimum inhibitory concentration (but also "inundation threshold"), minimum bactericidal concentration (but also "clearance threshold"), decimal reduction time (D value), time until bacterial eradication, threshold bacterial density necessary to support phage population growth ("proliferation threshold"), and bacterial density supporting half-maximal phage population growth rates (K(B)). I also address the concepts of phage killing titers, multiplicity of infection, and phage peak densities. Though many of the presented ideas are not unique to this chapter, I nonetheless provide variations on derivations and resulting formulae, plus as appropriate discuss relative importance. The overriding goal is to present a variety of calculations that are useful toward phage therapy dosing so that they may be found in one location and presented in a manner that allows facile appreciation, comparison, and implementation. The importance of phage density as a key determinant of the phage potential to eradicate bacterial targets is stressed throughout the chapter.
Aspects of the relationship between drug dose and drug effect.
Peper, Abraham
2009-02-09
It is generally assumed that there exists a well-defined relationship between drug dose and drug effect and that this can be expressed by a dose-response curve. This paper argues that there is no such clear relation and that the dose-response curve provides only limited information about the drug effect. It is demonstrated that tolerance development during the measurement of the dose-response curve may cause major distortion of the curve and it is argued that the curve may only be used to indicate the response to the first administration of a drug, before tolerance has developed. The precise effect of a drug on an individual depends on the dynamic relation between several variables, particularly the level of tolerance, the dose anticipated by the organism and the actual drug dose. Simulations with a previously published mathematical model of drug tolerance demonstrate that the effect of a dose smaller than the dose the organism has developed tolerance to is difficult to predict and may be opposite to the action of the usual dose.
Fast Electron Beam Simulation and Dose Calculation
Trindade, A; Peralta, L; Lopes, M C; Alves, C; Chaves, A
2003-01-01
A flexible multiple source model capable of fast reconstruction of clinical electron beams is presented in this paper. A source model considers multiple virtual sources emulating the effect of accelerator head components. A reference configuration (10 MeV and 10x10 cm2 field size) for a Siemens KD2 linear accelerator was simulated in full detail using GEANT3 Monte Carlo code. Our model allows the reconstruction of other beam energies and field sizes as well as other beam configurations for similar accelerators using only the reference beam data. Electron dose calculations were performed with the reconstructed beams in a water phantom and compared with experimental data. An agreement of 1-2% / 1-2 mm was obtained, equivalent to the accuracy of full Monte Carlo accelerator simulation. The source model reduces accelerator simulation CPU time by a factor of 7500 relative to full Monte Carlo approaches. The developed model was then interfaced with DPM, a fast radiation transport Monte Carlo code for dose calculati...
Aspects of the Relationship Between Drug Dose and Drug Effect
Peper, Abraham
2009-01-01
It is generally assumed that there exists a well-defined relationship between drug dose and drug effect and that this can be expressed by a dose-response curve. This paper argues that there is no such clear relation and that the dose-response curve provides only limited information about the drug effect. It is demonstrated that tolerance development during the measurement of the dose-response curve may cause major distortion of the curve and it is argued that the curve may only be used to ind...
Recommendations for Insulin Dose Calculator Risk Management
2014-01-01
Several studies have shown the usefulness of an automated insulin dose bolus advisor (BA) in achieving improved glycemic control for insulin-using diabetes patients. Although regulatory agencies have approved several BAs over the past decades, these devices are not standardized in their approach to dosage calculation and include many features that may introduce risk to patients. Moreover, there is no single standard of care for diabetes worldwide and no guidance documents for BAs, specifically. Given the emerging and more stringent regulations on software used in medical devices, the approval process is becoming more difficult for manufacturers to navigate, with some manufacturers opting to remove BAs from their products altogether. A comprehensive literature search was performed, including publications discussing: diabetes BA use and benefit, infusion pump safety and regulation, regulatory submissions, novel BAs, and recommendations for regulation and risk management of BAs. Also included were country-specific and international guidance documents for medical device, infusion pump, medical software, and mobile medical application risk management and regulation. No definitive worldwide guidance exists regarding risk management requirements for BAs, specifically. However, local and international guidance documents for medical devices, infusion pumps, and medical device software offer guidance that can be applied to this technology. In addition, risk management exercises that are algorithm-specific can help prepare manufacturers for regulatory submissions. This article discusses key issues relevant to BA use and safety, and recommends risk management activities incorporating current research and guidance. PMID:24876550
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Park, Jong Min; Park, So Yeon; Kim, Jung In; Kim, Jin Ho [Dept. of Radiation Oncology, Seoul National University Hospital, Seoul (Korea, Republic of); Wu, Hong Gyun [Dept. of Radiation Oncology, Seoul National University College of Medicine, Seoul (Korea, Republic of)
2015-10-15
Since those organs are small in volume, dose calculation for those organs seems to be more susceptible to the calculation grid size in the treatment planning system (TPS). Moreover, since they are highly radio-sensitive organs, especially eye lens, they should be considered carefully for radiotherapy. On the other hand, in the treatment of head and neck (H and N) cancer or brain tumor that generally involves radiation exposure to eye lens and optic apparatus, intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT) techniques are frequently used because of the proximity of various radio-sensitive normal organs to the target volumes. Since IMRT and VMAT can deliver prescription dose to target volumes while minimizing dose to nearby organs at risk (OARs) by generating steep dose gradients near the target volumes, high dose gradient sometimes occurs near or at the eye lenses and optic apparatus. In this case, the effect of dose calculation resolution on the accuracy of calculated dose to eye lens and optic apparatus might be significant. Therefore, the effect of dose calculation grid size on the accuracy of calculated doses for each eye lens and optic apparatus was investigated in this study. If an inappropriate calculation resolution was applied for dose calculation of eye lens and optic apparatus, considerable errors can be occurred due to the volume averaging effect in high dose gradient region.
Methods of calculating radiation absorbed dose.
Wegst, A V
1987-01-01
The new tumoricidal radioactive agents being developed will require a careful estimate of radiation absorbed tumor and critical organ dose for each patient. Clinical methods will need to be developed using standard imaging or counting instruments to determine cumulated organ activities with tracer amounts before the therapeutic administration of the material. Standard MIRD dosimetry methods can then be applied.
Calculation of dose conversion factors for thoron decay products
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Ishikawa, Tetsuo [National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555 (Japan); Tokonami, Shinji [National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555 (Japan); Nemeth, Csaba [Pannon University, 10 Egyetem St, 8201 Veszprem (Hungary)
2007-12-15
The dose conversion factors for short-lived thoron decay products were calculated using a dosimetric approach. The calculations were based on a computer program LUDEP, which implements the ICRP 66 respiratory tract model. The dose per equilibrium equivalent concentration for thoron (EETC) was calculated with respect to (1) equivalent dose to each region of the lung tissues (bronchial, bronchiolar and alveolar), (2) weighted equivalent dose to organs other than lung, and (3) effective dose. The calculations indicated that (1) the most exposed region of the lung tissues was the bronchial for the unattached fraction and the bronchiolar for the attached fraction, (2) the effective dose is dominated by the contribution of lung dose, and (3) the effective dose per EETC was about four times larger than the effective dose per equilibrium equivalent concentration for radon (EERC). The calculated dose conversion factors were applied to the comparative dosimetry for some thoron-enhanced areas where the EERC and EETC have been measured. In the case of a spa in Japan, the dose from thoron decay products was larger than the dose from radon decay products.
Calculation of dose conversion factors for thoron decay products.
Ishikawa, Tetsuo; Tokonami, Shinji; Nemeth, Csaba
2007-12-01
The dose conversion factors for short-lived thoron decay products were calculated using a dosimetric approach. The calculations were based on a computer program LUDEP, which implements the ICRP 66 respiratory tract model. The dose per equilibrium equivalent concentration for thoron (EETC) was calculated with respect to (1) equivalent dose to each region of the lung tissues (bronchial, bronchiolar and alveolar), (2) weighted equivalent dose to organs other than lung, and (3) effective dose. The calculations indicated that (1) the most exposed region of the lung tissues was the bronchial for the unattached fraction and the bronchiolar for the attached fraction, (2) the effective dose is dominated by the contribution of lung dose, and (3) the effective dose per EETC was about four times larger than the effective dose per equilibrium equivalent concentration for radon (EERC). The calculated dose conversion factors were applied to the comparative dosimetry for some thoron-enhanced areas where the EERC and EETC have been measured. In the case of a spa in Japan, the dose from thoron decay products was larger than the dose from radon decay products.
MLHD online : manual for the herbicide dose calculation module
PRI,; Kempenaar, C.
2004-01-01
MLHD is short for Minimum Lethal Herbicide Dose. MLHD is a new concept within chemical weed control. It supports effective weed control while herbicide doses are kept at minimum effective levels (minimum lethal doses). This manual describes how to use of the MLHD calculation module for users from ou
Paramedics’ Ability to Perform Drug Calculations
Directory of Open Access Journals (Sweden)
Eastwood, Kathyrn J
2009-11-01
Full Text Available Background: The ability to perform drug calculations accurately is imperative to patient safety. Research into paramedics’ drug calculation abilities was first published in 2000 and for nurses’ abilities the research dates back to the late 1930s. Yet, there have been no studies investigating an undergraduate paramedic student’s ability to perform drug or basic mathematical calculations. The objective of this study was to review the literature and determine the ability of undergraduate and qualified paramedics to perform drug calculations.Methods: A search of the prehospital-related electronic databases was undertaken using the Ovid and EMBASE systems available through the Monash University Library. Databases searched included the Cochrane Central Register of Controlled Trials (CENTRAL, MEDLINE, CINAHL, JSTOR, EMBASE and Google Scholar, from their beginning until the end of August 2009. We reviewed references from articles retrieved.Results: The electronic database search located 1,154 articles for review. Six additional articles were identified from reference lists of retrieved articles. Of these, 59 were considered relevant. After reviewing the 59 articles only three met the inclusion criteria. All articles noted some level of mathematical deficiencies amongst their subjects.Conclusions: This study identified only three articles. Results from these limited studies indicate a significant lack of mathematical proficiency amongst the paramedics sampled. A need exists to identify if undergraduate paramedic students are capable of performing the required drug calculations in a non-clinical setting.[WestJEM. 2009;10:240-243.
Fast dose calculation in magnetic fields with GPUMCD
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Hissoiny, S; Ozell, B [Ecole Polytechnique de Montreal, Departement de genie informatique et genie logiciel, 2500 Chemin de Polytechnique, Montreal, Quebec H3T 1J4 (Canada); Raaijmakers, A J E; Raaymakers, B W [Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht (Netherlands); Despres, P, E-mail: sami.hissoiny@polymtl.ca [Departement de physique, Universite Laval, Quebec (Canada)
2011-08-21
A new hybrid imaging-treatment modality, the MRI-Linac, involves the irradiation of the patient in the presence of a strong magnetic field. This field acts on the charged particles, responsible for depositing dose, through the Lorentz force. These conditions require a dose calculation engine capable of taking into consideration the effect of the magnetic field on the dose distribution during the planning stage. Also in the case of a change in anatomy at the time of treatment, a fast online replanning tool is desirable. It is improbable that analytical solutions such as pencil beam calculations can be efficiently adapted for dose calculations within a magnetic field. Monte Carlo simulations have therefore been used for the computations but the calculation speed is generally too slow to allow online replanning. In this work, GPUMCD, a fast graphics processing unit (GPU)-based Monte Carlo dose calculation platform, was benchmarked with a new feature that allows dose calculations within a magnetic field. As a proof of concept, this new feature is validated against experimental measurements. GPUMCD was found to accurately reproduce experimental dose distributions according to a 2%-2 mm gamma analysis in two cases with large magnetic field-induced dose effects: a depth-dose phantom with an air cavity and a lateral-dose phantom surrounded by air. Furthermore, execution times of less than 15 s were achieved for one beam in a prostate case phantom for a 2% statistical uncertainty while less than 20 s were required for a seven-beam plan. These results indicate that GPUMCD is an interesting candidate, being fast and accurate, for dose calculations for the hybrid MRI-Linac modality.
Dosimetric accuracy of tomotherapy dose calculation in thorax lesions
Directory of Open Access Journals (Sweden)
Mangili Paola
2011-02-01
Full Text Available Abstract Background To analyse limits and capabilities in dose calculation of collapsed-cone-convolution (CCC algorithm implemented in helical tomotherapy (HT treatment planning system for thorax lesions. Methods The agreement between measured and calculated dose was verified both in homogeneous (Cheese Phantom and in a custom-made inhomogeneous phantom. The inhomogeneous phantom was employed to mimic a patient's thorax region with lung density encountered in extreme cases and acrylic inserts of various dimensions and positions inside the lung cavity. For both phantoms, different lung treatment plans (single or multiple metastases and targets in the mediastinum using HT technique were simulated and verified. Point and planar dose measurements, both with radiographic extended-dose-range (EDR2 and radiochromic external-beam-therapy (EBT2 films, were performed. Absolute point dose measurements, dose profile comparisons and quantitative analysis of gamma function distributions were analyzed. Results An excellent agreement between measured and calculated dose distributions was found in homogeneous media, both for point and planar dose measurements. Absolute dose deviations Conclusions Very acceptable accuracy was found for complex lung treatment plans calculated with CCC algorithm implemented in the tomotherapy TPS even in the heterogeneous phantom with very low lung-density.
Methodology of dose calculation for the SRS SAR
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Price, J.B.
1991-07-01
The Savannah River Site (SRS) Safety Analysis Report (SAR) covering K reactor operation assesses a spectrum of design basis accidents. The assessment includes estimation of the dose consequences from the analyzed accidents. This report discusses the methodology used to perform the dose analysis reported in the SAR and also includes the quantified doses. Doses resulting from postulated design basis reactor accidents in Chapter 15 of the SAR are discussed, as well as an accident in which three percent of the fuel melts. Doses are reported for both atmospheric and aqueous releases. The methodology used to calculate doses from these accidents as reported in the SAR is consistent with NRC guidelines and industry standards. The doses from the design basis accidents for the SRS reactors are below the limits set for commercial reactors by the NRC and also meet industry criteria. A summary of doses for various postulated accidents is provided.
Fluence-convolution broad-beam (FCBB) dose calculation.
Lu, Weiguo; Chen, Mingli
2010-12-07
IMRT optimization requires a fast yet relatively accurate algorithm to calculate the iteration dose with small memory demand. In this paper, we present a dose calculation algorithm that approaches these goals. By decomposing the infinitesimal pencil beam (IPB) kernel into the central axis (CAX) component and lateral spread function (LSF) and taking the beam's eye view (BEV), we established a non-voxel and non-beamlet-based dose calculation formula. Both LSF and CAX are determined by a commissioning procedure using the collapsed-cone convolution/superposition (CCCS) method as the standard dose engine. The proposed dose calculation involves a 2D convolution of a fluence map with LSF followed by ray tracing based on the CAX lookup table with radiological distance and divergence correction, resulting in complexity of O(N(3)) both spatially and temporally. This simple algorithm is orders of magnitude faster than the CCCS method. Without pre-calculation of beamlets, its implementation is also orders of magnitude smaller than the conventional voxel-based beamlet-superposition (VBS) approach. We compared the presented algorithm with the CCCS method using simulated and clinical cases. The agreement was generally within 3% for a homogeneous phantom and 5% for heterogeneous and clinical cases. Combined with the 'adaptive full dose correction', the algorithm is well suitable for calculating the iteration dose during IMRT optimization.
[CUDA-based fast dose calculation in radiotherapy].
Wang, Xianliang; Liu, Cao; Hou, Qing
2011-10-01
Dose calculation plays a key role in treatment planning of radiotherapy. Algorithms for dose calculation require high accuracy and computational efficiency. Finite size pencil beam (FSPB) algorithm is a method commonly adopted in the treatment planning system for radiotherapy. However, improvement on its computational efficiency is still desirable for such purpose as real time treatment planning. In this paper, we present an implementation of the FSPB, by which the most time-consuming parts in the algorithm are parallelized and ported on graphic processing unit (GPU). Compared with the FSPB completely running on central processing unit (CPU), the GPU-implemented FSPB can speed up the dose calculation for 25-35 times on a low price GPU (Geforce GT320) and for 55-100 times on a Tesla C1060, indicating that the GPU-implemented FSPB can provide fast enough dose calculations for real-time treatment planning.
Dose Rate Calculations for Rotary Mode Core Sampling Exhauster
Foust, D J
2000-01-01
This document provides the calculated estimated dose rates for three external locations on the Rotary Mode Core Sampling (RMCS) exhauster HEPA filter housing, per the request of Characterization Field Engineering.
DEFF Research Database (Denmark)
Faralli, Adele; Melander, Fredrik; Larsen, Esben Kjær Unmack;
2014-01-01
Polyethylene glycol (PEG)-based hydrogels are widely used for biomedical applications, including matrices for controlled drug release. We present a method for defining drug dosing in screening assays by light-activated cross-linking of PEG-diacrylate hydrogels with embedded drug-loaded liposome...
A decision tool to adjust the prescribed dose after change in the dose calculation algorithm
Directory of Open Access Journals (Sweden)
Abdulhamid Chaikh
2014-12-01
Full Text Available Purpose: This work aims to introduce a method to quantify and assess the differences in monitor unites MUs when changing to new dose calculation software that uses a different algorithm, and to evaluate the need and extent of adjustment of the prescribed dose to maintain the same clinical results. Methods: Doses were calculated using two classical algorithms based on the Pencil Beam Convolution PBC model, using 6 patients presenting lung cancers. For each patient, 3 treatment plans were generated: Plan 1 was calculated using reference algorithm PBC without heterogeneity correction, Plan 2 was calculated using test algorithm with heterogeneity correction, and in plan 3 the dose was recalculated using test algorithm and monitor unites MUs obtained from plan 1 as input. To assess the differences in the calculated MUs, isocenter dose, and spatial dose distributions using a gamma index were compared. Statistical analysis was based on a Wilcoxon signed rank test. Results: The test algorithm in plan 2 calculated significantly less MUs than reference algorithm in plan 1 by on average 5%, (p < 0.001. We also found underestimating dose for target volumes using 3D gamma index analysis. In this example, in order to obtain the same clinical outcomes with the two algorithms the prescribed dose should be adjusted by 5%.Conclusion: This method provides a quantitative evaluation of the differences between two dose calculation algorithms and the consequences on the prescribed dose. It could be used to adjust the prescribed dose when changing calculation software to maintain the same clinical results as obtained with the former software. In particular, the gamma evaluation could be applied to any situation where changes in the dose calculation occur in radiotherapy.
Widder, Joachim; Hollander, Miranda; Ubbels, Jan F.; Bolt, Rene A.; Langendijk, Johannes A.
2010-01-01
Purpose: To define a method of dose prescription employing Monte Carlo (MC) dose calculation in stereotactic body radiotherapy (SBRT) for lung tumours aiming at a dose as low as possible outside of the PTV. Methods and materials: Six typical T1 lung tumours - three small, three large - were construc
Study of dose calculation on breast brachytherapy using prism TPS
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Fendriani, Yoza; Haryanto, Freddy [Nuclear Physics and Biophysics Research Division, FMIPA Institut Teknologi Bandung, Physics Buildings, Jl. Ganesha 10, Bandung 40132 (Indonesia)
2015-09-30
PRISM is one of non-commercial Treatment Planning System (TPS) and is developed at the University of Washington. In Indonesia, many cancer hospitals use expensive commercial TPS. This study aims to investigate Prism TPS which been applied to the dose distribution of brachytherapy by taking into account the effect of source position and inhomogeneities. The results will be applicable for clinical Treatment Planning System. Dose calculation has been implemented for water phantom and CT scan images of breast cancer using point source and line source. This study used point source and line source and divided into two cases. On the first case, Ir-192 seed source is located at the center of treatment volume. On the second case, the source position is gradually changed. The dose calculation of every case performed on a homogeneous and inhomogeneous phantom with dimension 20 × 20 × 20 cm{sup 3}. The inhomogeneous phantom has inhomogeneities volume 2 × 2 × 2 cm{sup 3}. The results of dose calculations using PRISM TPS were compared to literature data. From the calculation of PRISM TPS, dose rates show good agreement with Plato TPS and other study as published by Ramdhani. No deviations greater than ±4% for all case. Dose calculation in inhomogeneous and homogenous cases show similar result. This results indicate that Prism TPS is good in dose calculation of brachytherapy but not sensitive for inhomogeneities. Thus, the dose calculation parameters developed in this study were found to be applicable for clinical treatment planning of brachytherapy.
Superposition dose calculation in lung for 10MV photons.
Hoban, P W; Murray, D C; Metcalfe, P E; Round, W H
1990-06-01
Currently available radiotherapy treatment planning systems employ scatter function models such as ETAR and Batho dSAR for dose calculation. Errors using these models for high energy photon irradiation occur in and beyond lung tissue for small fields. For larger fields, central axis dose is correctly predicted but penumbral broadening in lung is underestimated. The major source of error is the assumption that lateral electronic equilibrium is always established. A superposition algorithm has been developed for 10MV photons which calculates the dose by convolving the TERMA (Total Energy Released per unit MAss by primary photons) with a dose spread array formed using the EGS4 Monte Carlo code. TERMA and dose spread arrays are both generated using a 10 component photon energy spectrum. Dose in inhomogeneous media is calculated using dose spread arrays generated for different density media and by scaling dose spread arrays according to density variations. This method ensures that electronic disequilibrium is modelled in situations where it exists. Superposition results in a lung phantom for a 5 x 5 cm field agree with EGS4 Monte Carlo results to within 2% for p = 0.20 gcm-3 and p = 0.30 gcm-3 lung. Profiles generated by superposition for a 10 x 10 cm field at mid-lung and compared with film measurements show that penumbral broadening in low density material is also correctly predicted.
Calculation of the dose caused by internal radiation
Energy Technology Data Exchange (ETDEWEB)
NONE
2000-07-01
For the purposes of monitoring radiation exposure it is necessary to determine or to estimate the dose caused by both external and internal radiation. When comparing the value of exposure to the dose limits, account must be taken of the total dose incurred from different sources. This guide explains how to calculate the committed effective dose caused by internal radiation and gives the conversion factors required for the calculation. Application of the maximum values for radiation exposure is dealt with in ST guide 7.2, which also sets out the definitions of the quantities and concepts most commonly used in the monitoring of radiation exposure. The monitoring of exposure and recording of doses are dealt with in ST Guides 7.1 and 7.4.
Quantification of Proton Dose Calculation Accuracy in the Lung
Energy Technology Data Exchange (ETDEWEB)
Grassberger, Clemens, E-mail: Grassberger.Clemens@mgh.harvard.edu [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts (United States); Center for Proton Radiotherapy, Paul Scherrer Institute, Villigen (Switzerland); Daartz, Juliane; Dowdell, Stephen; Ruggieri, Thomas; Sharp, Greg; Paganetti, Harald [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts (United States)
2014-06-01
Purpose: To quantify the accuracy of a clinical proton treatment planning system (TPS) as well as Monte Carlo (MC)–based dose calculation through measurements and to assess the clinical impact in a cohort of patients with tumors located in the lung. Methods and Materials: A lung phantom and ion chamber array were used to measure the dose to a plane through a tumor embedded in the lung, and to determine the distal fall-off of the proton beam. Results were compared with TPS and MC calculations. Dose distributions in 19 patients (54 fields total) were simulated using MC and compared to the TPS algorithm. Results: MC increased dose calculation accuracy in lung tissue compared with the TPS and reproduced dose measurements in the target to within ±2%. The average difference between measured and predicted dose in a plane through the center of the target was 5.6% for the TPS and 1.6% for MC. MC recalculations in patients showed a mean dose to the clinical target volume on average 3.4% lower than the TPS, exceeding 5% for small fields. For large tumors, MC also predicted consistently higher V5 and V10 to the normal lung, because of a wider lateral penumbra, which was also observed experimentally. Critical structures located distal to the target could show large deviations, although this effect was highly patient specific. Range measurements showed that MC can reduce range uncertainty by a factor of ∼2: the average (maximum) difference to the measured range was 3.9 mm (7.5 mm) for MC and 7 mm (17 mm) for the TPS in lung tissue. Conclusion: Integration of Monte Carlo dose calculation techniques into the clinic would improve treatment quality in proton therapy for lung cancer by avoiding systematic overestimation of target dose and underestimation of dose to normal lung. In addition, the ability to confidently reduce range margins would benefit all patients by potentially lowering toxicity.
COMPARING MEASURED AND CALCULATED DOSES IN INTERVENTIONAL CARDIOLOGY PROCEDURES.
Oliveira da Silva, M W; Canevaro, L V; Hunt, J; Rodrigues, B B D
2017-03-16
Interventional cardiology requires complex procedures and can result in high doses and dose rates to the patient and medical staff. The many variables that influence the dose to the patient and staff include the beam position and angle, beam size, kVp, filtration, kerma-area product and focus-skin distance. A number of studies using the Monte Carlo method have been undertaken to obtain prospective dose assessments. In this paper, detailed irradiation scenarios were simulated mathematically and the resulting dose estimates were compared with real measurements made previously under very similar irradiation conditions and geometries. The real measurements and the calculated doses were carried out using or simulating an interventional cardiology system with a flat monoplane detector installed in a dedicated room with an Alderson phantom placed on the procedure table. The X-ray spectra, beam angles, focus-skin distance, measured kerma-area product and filtration were simulated, and the real dose measurements and calculated doses were compared. It was shown that the Monte Carlo method was capable of reproducing the real dose measurements within acceptable levels of uncertainty.
Limitations of analytical dose calculations for small field proton radiosurgery
Geng, Changran; Daartz, Juliane; Lam-Tin-Cheung, Kimberley; Bussiere, Marc; Shih, Helen A.; Paganetti, Harald; Schuemann, Jan
2017-01-01
The purpose of the work was to evaluate the dosimetric uncertainties of an analytical dose calculation engine and the impact on treatment plans using small fields in intracranial proton stereotactic radiosurgery (PSRS) for a gantry based double scattering system. 50 patients were evaluated including 10 patients for each of 5 diagnostic indications of: arteriovenous malformation (AVM), acoustic neuroma (AN), meningioma (MGM), metastasis (METS), and pituitary adenoma (PIT). Treatment plans followed standard prescription and optimization procedures for PSRS. We performed comparisons between delivered dose distributions, determined by Monte Carlo (MC) simulations, and those calculated with the analytical dose calculation algorithm (ADC) used in our current treatment planning system in terms of dose volume histogram parameters and beam range distributions. Results show that the difference in the dose to 95% of the target (D95) is within 6% when applying measured field size output corrections for AN, MGM, and PIT. However, for AVM and METS, the differences can be as great as 10% and 12%, respectively. Normalizing the MC dose to the ADC dose based on the dose of voxels in a central area of the target reduces the difference of the D95 to within 6% for all sites. The generally applied margin to cover uncertainties in range (3.5% of the prescribed range + 1 mm) is not sufficient to cover the range uncertainty for ADC in all cases, especially for patients with high tissue heterogeneity. The root mean square of the R90 difference, the difference in the position of distal falloff to 90% of the prescribed dose, is affected by several factors, especially the patient geometry heterogeneity, modulation and field diameter. In conclusion, implementation of Monte Carlo dose calculation techniques into the clinic can reduce the uncertainty of the target dose for proton stereotactic radiosurgery. If MC is not available for treatment planning, using MC dose distributions to
Calculation of surface dose in rotational total skin electron irradiation
Energy Technology Data Exchange (ETDEWEB)
Pla, C.; Heese, R.; Pla, M.; Podgorsak, E.B.
1984-07-01
A single-field rotational total skin electron irradiation technique has recently been developed at the McGill University for treatment of skin malignancies. The dose received by a given surface point during rotation in a uniform large electron field depends on the radius of rotation of the surface point, on the local radius of curvature of the contour in the vicinity of the point of interest, and on the shadows cast by limbs (arms upon trunk or head and neck, and legs upon each other). A method for calculating the surface dose distribution on a patient is presented accounting for the various parameters affecting the dose. A series of measurements were performed with polystyrene and a humanoid phantom, and an excellent agreement between measured and calculated dose distributions was obtained.
Development of a computational methodology for internal dose calculations
Yoriyaz, H
2000-01-01
A new approach for calculating internal dose estimates was developed through the use of a more realistic computational model of the human body and a more precise tool for the radiation transport simulation. The present technique shows the capability to build a patient-specific phantom with tomography data (a voxel-based phantom) for the simulation of radiation transport and energy deposition using Monte Carlo methods such as in the MCNP-4B code. In order to utilize the segmented human anatomy as a computational model for the simulation of radiation transport, an interface program, SCMS, was developed to build the geometric configurations for the phantom through the use of tomographic images. This procedure allows to calculate not only average dose values but also spatial distribution of dose in regions of interest. With the present methodology absorbed fractions for photons and electrons in various organs of the Zubal segmented phantom were calculated and compared to those reported for the mathematical phanto...
Impact of dose calculation algorithm on radiation therapy
Institute of Scientific and Technical Information of China (English)
Wen-Zhou; Chen; Ying; Xiao; Jun; Li
2014-01-01
The quality of radiation therapy depends on the ability to maximize the tumor control probability while minimizing the normal tissue complication probability.Both of these two quantities are directly related to the accuracy of dose distributions calculated by treatment planning systems.The commonly used dose calculation algorithms in the treatment planning systems are reviewed in this work.The accuracy comparisons among these algorithms are illustrated by summarizing the highly cited research papers on this topic.Further,the correlation between the algorithms and tumor control probability/normal tissue complication probability values are manifested by several recent studies from different groups.All the cases demonstrate that dose calculation algorithms play a vital role in radiation therapy.
Russell, Kellie R; Tedgren, Asa K Carlsson; Ahnesjö, Anders
2005-09-01
In brachytherapy, tissue heterogeneities, source shielding, and finite patient/phantom extensions affect both the primary and scatter dose distributions. The primary dose is, due to the short range of secondary electrons, dependent only on the distribution of material located on the ray line between the source and dose deposition site. The scatter dose depends on both the direct irradiation pattern and the distribution of material in a large volume surrounding the point of interest, i.e., a much larger volume must be included in calculations to integrate many small dose contributions. It is therefore of interest to consider different methods for the primary and the scatter dose calculation to improve calculation accuracy with limited computer resources. The algorithms in present clinical use ignore these effects causing systematic dose errors in brachytherapy treatment planning. In this work we review a primary and scatter dose separation formalism (PSS) for brachytherapy source characterization to support separate calculation of the primary and scatter dose contributions. We show how the resulting source characterization data can be used to drive more accurate dose calculations using collapsed cone superposition for scatter dose calculations. Two types of source characterization data paths are used: a direct Monte Carlo simulation in water phantoms with subsequent parameterization of the results, and an alternative data path built on processing of AAPM TG43 formatted data to provide similar parameter sets. The latter path is motivated of the large amounts of data already existing in the TG43 format. We demonstrate the PSS methods using both data paths for a clinical 192Ir source. Results are shown for two geometries: a finite but homogeneous water phantom, and a half-slab consisting of water and air. The dose distributions are compared to results from full Monte Carlo simulations and we show significant improvement in scatter dose calculations when the collapsed
Monte Carlo dose calculation in dental amalgam phantom.
Aziz, Mohd Zahri Abdul; Yusoff, A L; Osman, N D; Abdullah, R; Rabaie, N A; Salikin, M S
2015-01-01
It has become a great challenge in the modern radiation treatment to ensure the accuracy of treatment delivery in electron beam therapy. Tissue inhomogeneity has become one of the factors for accurate dose calculation, and this requires complex algorithm calculation like Monte Carlo (MC). On the other hand, computed tomography (CT) images used in treatment planning system need to be trustful as they are the input in radiotherapy treatment. However, with the presence of metal amalgam in treatment volume, the CT images input showed prominent streak artefact, thus, contributed sources of error. Hence, metal amalgam phantom often creates streak artifacts, which cause an error in the dose calculation. Thus, a streak artifact reduction technique was applied to correct the images, and as a result, better images were observed in terms of structure delineation and density assigning. Furthermore, the amalgam density data were corrected to provide amalgam voxel with accurate density value. As for the errors of dose uncertainties due to metal amalgam, they were reduced from 46% to as low as 2% at d80 (depth of the 80% dose beyond Zmax) using the presented strategies. Considering the number of vital and radiosensitive organs in the head and the neck regions, this correction strategy is suggested in reducing calculation uncertainties through MC calculation.
Monte carlo dose calculation in dental amalgam phantom
Directory of Open Access Journals (Sweden)
Mohd Zahri Abdul Aziz
2015-01-01
Full Text Available It has become a great challenge in the modern radiation treatment to ensure the accuracy of treatment delivery in electron beam therapy. Tissue inhomogeneity has become one of the factors for accurate dose calculation, and this requires complex algorithm calculation like Monte Carlo (MC. On the other hand, computed tomography (CT images used in treatment planning system need to be trustful as they are the input in radiotherapy treatment. However, with the presence of metal amalgam in treatment volume, the CT images input showed prominent streak artefact, thus, contributed sources of error. Hence, metal amalgam phantom often creates streak artifacts, which cause an error in the dose calculation. Thus, a streak artifact reduction technique was applied to correct the images, and as a result, better images were observed in terms of structure delineation and density assigning. Furthermore, the amalgam density data were corrected to provide amalgam voxel with accurate density value. As for the errors of dose uncertainties due to metal amalgam, they were reduced from 46% to as low as 2% at d80 (depth of the 80% dose beyond Zmax using the presented strategies. Considering the number of vital and radiosensitive organs in the head and the neck regions, this correction strategy is suggested in reducing calculation uncertainties through MC calculation.
Benchmarking analytical calculations of proton doses in heterogeneous matter.
Ciangaru, George; Polf, Jerimy C; Bues, Martin; Smith, Alfred R
2005-12-01
A proton dose computational algorithm, performing an analytical superposition of infinitely narrow proton beamlets (ASPB) is introduced. The algorithm uses the standard pencil beam technique of laterally distributing the central axis broad beam doses according to the Moliere scattering theory extended to slablike varying density media. The purpose of this study was to determine the accuracy of our computational tool by comparing it with experimental and Monte Carlo (MC) simulation data as benchmarks. In the tests, parallel wide beams of protons were scattered in water phantoms containing embedded air and bone materials with simple geometrical forms and spatial dimensions of a few centimeters. For homogeneous water and bone phantoms, the proton doses we calculated with the ASPB algorithm were found very comparable to experimental and MC data. For layered bone slab inhomogeneity in water, the comparison between our analytical calculation and the MC simulation showed reasonable agreement, even when the inhomogeneity was placed at the Bragg peak depth. There also was reasonable agreement for the parallelepiped bone block inhomogeneity placed at various depths, except for cases in which the bone was located in the region of the Bragg peak, when discrepancies were as large as more than 10%. When the inhomogeneity was in the form of abutting air-bone slabs, discrepancies of as much as 8% occurred in the lateral dose profiles on the air cavity side of the phantom. Additionally, the analytical depth-dose calculations disagreed with the MC calculations within 3% of the Bragg peak dose, at the entry and midway depths in the phantom. The distal depth-dose 20%-80% fall-off widths and ranges calculated with our algorithm and the MC simulation were generally within 0.1 cm of agreement. The analytical lateral-dose profile calculations showed smaller (by less than 0.1 cm) 20%-80% penumbra widths and shorter fall-off tails than did those calculated by the MC simulations. Overall
Analytical probabilistic proton dose calculation and range uncertainties
Bangert, M.; Hennig, P.; Oelfke, U.
2014-03-01
We introduce the concept of analytical probabilistic modeling (APM) to calculate the mean and the standard deviation of intensity-modulated proton dose distributions under the influence of range uncertainties in closed form. For APM, range uncertainties are modeled with a multivariate Normal distribution p(z) over the radiological depths z. A pencil beam algorithm that parameterizes the proton depth dose d(z) with a weighted superposition of ten Gaussians is used. Hence, the integrals ∫ dz p(z) d(z) and ∫ dz p(z) d(z)2 required for the calculation of the expected value and standard deviation of the dose remain analytically tractable and can be efficiently evaluated. The means μk, widths δk, and weights ωk of the Gaussian components parameterizing the depth dose curves are found with least squares fits for all available proton ranges. We observe less than 0.3% average deviation of the Gaussian parameterizations from the original proton depth dose curves. Consequently, APM yields high accuracy estimates for the expected value and standard deviation of intensity-modulated proton dose distributions for two dimensional test cases. APM can accommodate arbitrary correlation models and account for the different nature of random and systematic errors in fractionated radiation therapy. Beneficial applications of APM in robust planning are feasible.
A simplified analytical random walk model for proton dose calculation
Yao, Weiguang; Merchant, Thomas E.; Farr, Jonathan B.
2016-10-01
We propose an analytical random walk model for proton dose calculation in a laterally homogeneous medium. A formula for the spatial fluence distribution of primary protons is derived. The variance of the spatial distribution is in the form of a distance-squared law of the angular distribution. To improve the accuracy of dose calculation in the Bragg peak region, the energy spectrum of the protons is used. The accuracy is validated against Monte Carlo simulation in water phantoms with either air gaps or a slab of bone inserted. The algorithm accurately reflects the dose dependence on the depth of the bone and can deal with small-field dosimetry. We further applied the algorithm to patients’ cases in the highly heterogeneous head and pelvis sites and used a gamma test to show the reasonable accuracy of the algorithm in these sites. Our algorithm is fast for clinical use.
Chlorpromazine equivalents versus defined daily doses : How to compare antipsychotic drug doses?
Rijcken, CAW; Monster, TBM; Brouwers, JRBJ; de Jong-van den Berg, LTW
2003-01-01
Classic chlorpromazine (CPZ) equivalents can be used to chart relative antipsychotic potencies of antipsychotic drugs. Values of CPZ equivalents per drug are ambiguous in literature. In drug use evaluation studies, antipsychotic doses are frequently compared by use of the defined daily dose (DDD). T
External dose-rate conversion factors for calculation of dose to the public
Energy Technology Data Exchange (ETDEWEB)
1988-07-01
This report presents a tabulation of dose-rate conversion factors for external exposure to photons and electrons emitted by radionuclides in the environment. This report was prepared in conjunction with criteria for limiting dose equivalents to members of the public from operations of the US Department of Energy (DOE). The dose-rate conversion factors are provided for use by the DOE and its contractors in performing calculations of external dose equivalents to members of the public. The dose-rate conversion factors for external exposure to photons and electrons presented in this report are based on a methodology developed at Oak Ridge National Laboratory. However, some adjustments of the previously documented methodology have been made in obtaining the dose-rate conversion factors in this report. 42 refs., 1 fig., 4 tabs.
A convolution-superposition dose calculation engine for GPUs
Energy Technology Data Exchange (ETDEWEB)
Hissoiny, Sami; Ozell, Benoit; Despres, Philippe [Departement de genie informatique et genie logiciel, Ecole polytechnique de Montreal, 2500 Chemin de Polytechnique, Montreal, Quebec H3T 1J4 (Canada); Departement de radio-oncologie, CRCHUM-Centre hospitalier de l' Universite de Montreal, 1560 rue Sherbrooke Est, Montreal, Quebec H2L 4M1 (Canada)
2010-03-15
Purpose: Graphic processing units (GPUs) are increasingly used for scientific applications, where their parallel architecture and unprecedented computing power density can be exploited to accelerate calculations. In this paper, a new GPU implementation of a convolution/superposition (CS) algorithm is presented. Methods: This new GPU implementation has been designed from the ground-up to use the graphics card's strengths and to avoid its weaknesses. The CS GPU algorithm takes into account beam hardening, off-axis softening, kernel tilting, and relies heavily on raytracing through patient imaging data. Implementation details are reported as well as a multi-GPU solution. Results: An overall single-GPU acceleration factor of 908x was achieved when compared to a nonoptimized version of the CS algorithm implemented in PlanUNC in single threaded central processing unit (CPU) mode, resulting in approximatively 2.8 s per beam for a 3D dose computation on a 0.4 cm grid. A comparison to an established commercial system leads to an acceleration factor of approximately 29x or 0.58 versus 16.6 s per beam in single threaded mode. An acceleration factor of 46x has been obtained for the total energy released per mass (TERMA) calculation and a 943x acceleration factor for the CS calculation compared to PlanUNC. Dose distributions also have been obtained for a simple water-lung phantom to verify that the implementation gives accurate results. Conclusions: These results suggest that GPUs are an attractive solution for radiation therapy applications and that careful design, taking the GPU architecture into account, is critical in obtaining significant acceleration factors. These results potentially can have a significant impact on complex dose delivery techniques requiring intensive dose calculations such as intensity-modulated radiation therapy (IMRT) and arc therapy. They also are relevant for adaptive radiation therapy where dose results must be obtained rapidly.
Prenatal radiation exposure. Dose calculation; Praenatale Strahlenexposition. Dosisermittlung
Energy Technology Data Exchange (ETDEWEB)
Scharwaechter, C.; Schwartz, C.A.; Haage, P. [University Hospital Witten/Herdecke, Wuppertal (Germany). Dept. of Diagnostic and Interventional Radiology; Roeser, A. [University Hospital Witten/Herdecke, Wuppertal (Germany). Dept. of Radiotherapy and Radio-Oncology
2015-05-15
The unborn child requires special protection. In this context, the indication for an X-ray examination is to be checked critically. If thereupon radiation of the lower abdomen including the uterus cannot be avoided, the examination should be postponed until the end of pregnancy or alternative examination techniques should be considered. Under certain circumstances, either accidental or in unavoidable cases after a thorough risk assessment, radiation exposure of the unborn may take place. In some of these cases an expert radiation hygiene consultation may be required. This consultation should comprise the expected risks for the unborn while not perturbing the mother or the involved medical staff. For the risk assessment in case of an in-utero X-ray exposition deterministic damages with a defined threshold dose are distinguished from stochastic damages without a definable threshold dose. The occurrence of deterministic damages depends on the dose and the developmental stage of the unborn at the time of radiation. To calculate the risks of an in-utero radiation exposure a three-stage concept is commonly applied. Depending on the amount of radiation, the radiation dose is either estimated, roughly calculated using standard tables or, in critical cases, accurately calculated based on the individual event. The complexity of the calculation thereby increases from stage to stage. An estimation based on stage one is easily feasible whereas calculations based on stages two and especially three are more complex and often necessitate execution by specialists. This article demonstrates in detail the risks for the unborn child pertaining to its developmental phase and explains the three-stage concept as an evaluation scheme. It should be noted, that all risk estimations are subject to considerable uncertainties.
Review of dose-response curves for acute antimigraine drugs
DEFF Research Database (Denmark)
Hougaard, Anders; Tfelt-Hansen, Peer
2015-01-01
INTRODUCTION: Dose-response curves for efficacy and tolerability are the important determinants for the choice of doses of acute migraine drugs. Areas covered: Dose-response curves for the efficacy of seven triptans (5-HT1B/1D receptor agonists), a 5-HT1F receptor agonist (lasmiditan) and four oral...... calcitonin-gene related peptide receptor antagonists (telcagepant, MK-3207, BI 44370 TA and BMS-927711) in placebo-controlled trials were reviewed. In addition, dose-response curves for adverse events (AEs) were reviewed. Expert opinion: For most triptans, the dose-response curve for efficacy is flat......, whereas AEs often increase with increasing doses. The two other groups of drugs also have flat dose-response curves for efficacy. Overall, the triptans still have the most favorable efficacy-tolerability profile. Current acute antimigraine drugs do not fulfill the expectations of the patients, and thus...
Kanematsu, Nobuyuki
2007-01-01
A simple and efficient variant of the pencil-beam algorithm for dose distribution calculation is proposed. Compared to the conventional pencil-beam algorithms, the new algorithm is intrinsically faster due to minimized computation within the convolution integral. Namely, computation for physical interaction is decoupled from the convolution integral and the convolution kernel is approximated by simple grid-to-grid correlation. Implementation to a treatment planning system for carbon-ion radiotherapy has enabled realistic beam blurring with marginal speed decrease from the broad-beam calculation. Evaluation of a modeled proton pencil beam exhibits inaccuracy within its spread at the Bragg peak when the beam incidence is angled to all the dose grid axes, which will be minimized in broad-beam formation and may be acceptable depending on its relative significance to the other sources of errors. The new algorithm will provide balanced accuracy and speed without technical difficulty for high-resolution dose distrib...
Investigation of Nonuniform Dose Voxel Geometry in Monte Carlo Calculations.
Yuan, Jiankui; Chen, Quan; Brindle, James; Zheng, Yiran; Lo, Simon; Sohn, Jason; Wessels, Barry
2015-08-01
The purpose of this work is to investigate the efficacy of using multi-resolution nonuniform dose voxel geometry in Monte Carlo (MC) simulations. An in-house MC code based on the dose planning method MC code was developed in C++ to accommodate the nonuniform dose voxel geometry package since general purpose MC codes use their own coupled geometry packages. We devised the package in a manner that the entire calculation volume was first divided into a coarse mesh and then the coarse mesh was subdivided into nonuniform voxels with variable voxel sizes based on density difference. We name this approach as multi-resolution subdivision (MRS). It generates larger voxels in small density gradient regions and smaller voxels in large density gradient regions. To take into account the large dose gradients due to the beam penumbra, the nonuniform voxels can be further split using ray tracing starting from the beam edges. The accuracy of the implementation of the algorithm was verified by comparing with the data published by Rogers and Mohan. The discrepancy was found to be 1% to 2%, with a maximum of 3% at the interfaces. Two clinical cases were used to investigate the efficacy of nonuniform voxel geometry in the MC code. Applying our MRS approach, we started with the initial voxel size of 5 × 5 × 3 mm(3), which was further divided into smaller voxels. The smallest voxel size was 1.25 × 1.25 × 3 mm(3). We found that the simulation time per history for the nonuniform voxels is about 30% to 40% faster than the uniform fine voxels (1.25 × 1.25 × 3 mm(3)) while maintaining similar accuracy.
Energy Technology Data Exchange (ETDEWEB)
Strenge, D.L.; Peloquin, R.A.
1981-04-01
The computer code HADOC (Hanford Acute Dose Calculations) is described and instructions for its use are presented. The code calculates external dose from air submersion and inhalation doses following acute radionuclide releases. Atmospheric dispersion is calculated using the Hanford model with options to determine maximum conditions. Building wake effects and terrain variation may also be considered. Doses are calculated using dose conversion factor supplied in a data library. Doses are reported for one and fifty year dose commitment periods for the maximum individual and the regional population (within 50 miles). The fractional contribution to dose by radionuclide and exposure mode are also printed if requested.
Tallarida, Ronald J.; Raffa, Robert B.
2010-01-01
In this review we show that the concept of dose equivalence for two drugs, the theoretical basis of the isobologram, has a wider use in the analysis of pharmacological data derived from single and combination drug use. In both its application to drug combination analysis with isoboles and certain other actions, listed below, the determination of doses, or receptor occupancies, that yield equal effects provide useful metrics that can be used to obtain quantitative information on drug actions w...
Emergency Doses (ED) - Revision 3: A calculator code for environmental dose computations
Energy Technology Data Exchange (ETDEWEB)
Rittmann, P.D.
1990-12-01
The calculator program ED (Emergency Doses) was developed from several HP-41CV calculator programs documented in the report Seven Health Physics Calculator Programs for the HP-41CV, RHO-HS-ST-5P (Rittman 1984). The program was developed to enable estimates of offsite impacts more rapidly and reliably than was possible with the software available for emergency response at that time. The ED - Revision 3, documented in this report, revises the inhalation dose model to match that of ICRP 30, and adds the simple estimates for air concentration downwind from a chemical release. In addition, the method for calculating the Pasquill dispersion parameters was revised to match the GENII code within the limitations of a hand-held calculator (e.g., plume rise and building wake effects are not included). The summary report generator for printed output, which had been present in the code from the original version, was eliminated in Revision 3 to make room for the dispersion model, the chemical release portion, and the methods of looping back to an input menu until there is no further no change. This program runs on the Hewlett-Packard programmable calculators known as the HP-41CV and the HP-41CX. The documentation for ED - Revision 3 includes a guide for users, sample problems, detailed verification tests and results, model descriptions, code description (with program listing), and independent peer review. This software is intended to be used by individuals with some training in the use of air transport models. There are some user inputs that require intelligent application of the model to the actual conditions of the accident. The results calculated using ED - Revision 3 are only correct to the extent allowed by the mathematical models. 9 refs., 36 tabs.
Zhao, Weijie; Li, Huiwen; Duan, Lianshan; Liang, Guifang; Zhang, Tongqun; Lu, Yu
2002-06-01
OBJECTIVE To study the pharmacodynamics and pharmacokinetics of domestic fixed-dose of antituberculosis drugs and to evaluate its quality and activity against Mycobacterium tuberculosis both in vitro and in vivo. METHODS The MIC was determined by the tube doubling dilution method, and the effect of the drugs was assessed by half survival time of the mice. A single oral dose of domestic and imported fixed-dose combination of antituberculosis drugs was given to healthy volunteers, and the drug concentration in serum was determined by HPLC. The pharmacokinetic parameters and the relative bioavailability were calculated. RESULTS The MIC of each composition in the compound (INH, RFP, PZA) against Mycobacterium tuberculosis was lower than that of each composition used by single-dose. In a murine tuberculosis model, the antituberculosis activity of this compound drug was superior to that of each agent used alone with the same dose. No significant difference was found as compared to the imported drug, Refater; The major pharmacokinetic parameters of the domestic and the imported drugs, t (1/2), C (max), AUC, and t(max), were not significantly different. Statistical analysis showed the two formulations were bioequivalent. CONCLUSION The three compositions in the combination had synergistic effect, and the domestic and the imported drugs were bioequivalent.
Lee, Boram; Lee, Jungseok; Kang, Sangwon; Cho, Hyelim; Shin, Gwisoon; Lee, Jeong-Woo; Choi, Jonghak
2013-01-01
The objective of this study was to evaluate the patient effective dose and scattered dose from recently developed dental mobile equipment in Korea. The MCNPX 2.6 (Los Alamos National Laboratory, USA) was used in a Monte Carlo simulation to calculate both the effective and scattered doses. The MCNPX code was constructed identically as in the general use of equipment and the effective dose and scattered dose were calculated using the KTMAN-2 digital phantom. The effective dose was calculated as 906 μSv. The equivalent doses per organ were calculated via the MCNPX code, and were 32 174 and 19 μSv in the salivary gland and oesophagus, respectively. The scattered dose of 22.5-32.6 μSv of the tube side at 25 cm from the centre in anterior and posterior planes was measured as 1.4-3 times higher than the detector side of 10.5-16.0 μSv.
Considerations of beta and electron transport in internal dose calculations
Energy Technology Data Exchange (ETDEWEB)
Bolch, W.E.; Poston, J.W. Sr.
1990-12-01
Ionizing radiation has broad uses in modern science and medicine. These uses often require the calculation of energy deposition in the irradiated media and, usually, the medium of interest is the human body. Energy deposition from radioactive sources within the human body and the effects of such deposition are considered in the field of internal dosimetry. In July of 1988, a three-year research project was initiated by the Nuclear Engineering Department at Texas A M University under the sponsorship of the US Department of Energy. The main thrust of the research was to consider, for the first time, the detailed spatial transport of electron and beta particles in the estimation of average organ doses under the Medical Internal Radiation Dose (MIRD) schema. At the present time (December of 1990), research activities are continuing within five areas. Several are new initiatives begun within the second or third year of the current contract period. They include: (1) development of small-scale dosimetry; (2) development of a differential volume phantom; (3) development of a dosimetric bone model; (4) assessment of the new ICRP lung model; and (5) studies into the mechanisms of DNA damage. A progress report is given for each of these tasks within the Comprehensive Report. In each case, preliminary results are very encouraging and plans for further research are detailed within this document.
Drug monitoring and individual dose optimization of antimicrobial drugs : oxazolidinones
Cattaneo, Dario; Alffenaar, Jan-Willem; Neely, Michael
2016-01-01
INTRODUCTION: Oxazolidinones are synthetic antibiotics with bacteriostatic activity against Gram-positive pathogens. Linezolid, the first marketed oxazolidinone, has shown also activity against Mycobaterium tuberculosis, including multidrug-resistant and extensively drug-resistant strains. Recently,
An evaluation of the drug calculation skills of registered nurses.
Fleming, Sandra; Brady, Anne-Marie; Malone, Anne-Marie
2014-01-01
Mathematical skill and proficiency underpin a number of nursing activities, with the most common application being in relation to drug dosage calculation and administration. Medication errors have been identified as the most common type of error affecting patient safety and the most common single preventable cause of adverse events and they can occur as a result of mathematical calculation error and or conceptual error. The purpose of this study was to evaluate the drug calculation skills of registered nurses (n = 124) on commencement of employment. The findings of this study indicate that there are inconsistencies in the amount of pharmacology content and drug calculation skills delivered within nursing curricula. The most frequent type of drug calculation errors are attributed to conceptual errors and participants identified ward based education on drug calculation as a pathway for improving the drug calculation skills of registered nurses. The study recommends that medication education, encompassing mathematical and conceptual drug calculation skills should be identified as a distinct competency in nursing curricula and continuing education programme.
BENCHMARKING UPGRADED HOTSPOT DOSE CALCULATIONS AGAINST MACCS2 RESULTS
Energy Technology Data Exchange (ETDEWEB)
Brotherton, Kevin
2009-04-30
The radiological consequence of interest for a documented safety analysis (DSA) is the centerline Total Effective Dose Equivalent (TEDE) incurred by the Maximally Exposed Offsite Individual (MOI) evaluated at the 95th percentile consequence level. An upgraded version of HotSpot (Version 2.07) has been developed with the capabilities to read site meteorological data and perform the necessary statistical calculations to determine the 95th percentile consequence result. These capabilities should allow HotSpot to join MACCS2 (Version 1.13.1) and GENII (Version 1.485) as radiological consequence toolbox codes in the Department of Energy (DOE) Safety Software Central Registry. Using the same meteorological data file, scenarios involving a one curie release of {sup 239}Pu were modeled in both HotSpot and MACCS2. Several sets of release conditions were modeled, and the results compared. In each case, input parameter specifications for each code were chosen to match one another as much as the codes would allow. The results from the two codes are in excellent agreement. Slight differences observed in results are explained by algorithm differences.
Wieringa, NF; Vos, R; de Graeff, PA
2001-01-01
Registration files of 13 cardiovascular drugs were analysed with respect to the number of double-blind phase-III clinical trials, the use of placebo and active comparator drugs and their dosing schemes. Half of the 146 double-blind trials used active comparator drugs. The majority of files included
Bicalho, Millena Drumond; Soares, Danielly Botelho; Botoni, Fernando Antonio; Reis, Adriano Max Moreira; Martins, Maria Auxiliadora Parreiras
2015-09-09
: Hospitalized patients require the use of a variety of drugs, many of which individually or in combination have the potential to cause kidney damage. The use of potentially nephrotoxic drugs is often unavoidable, and the need for dose adjustment should be evaluated. This study is aimed at assessing concordance in information on drug-induced nephrotoxicity and dose adjustment recommendations by comparing four drug information sources (DRUGDEX(®), UpToDate(®), Medscape(®) and the Brazilian Therapeutic Formulary) using the formulary of a Brazilian public hospital. A total of 218 drugs were investigated. The global Fleiss' kappa coefficient was 0.265 for nephrotoxicity (p < 0.001; CI 95%, 0.211-0.319) and 0.346 for recommendations (p < 0.001; CI 95%, 0.292-0.401), indicating fair concordance among the sources. Anti-infectives and anti-hypertensives were the main drugs cited as nephrotoxic by the different sources. There were no clear definitions for qualitative data or quantitative values for dose adjustments among the four information sources. There was no advice for dosing for a large number of the drugs in the international databases. The National Therapeutic Formulary offered imprecise dose adjustment recommendations for many nephrotoxic drugs. Discrepancies among information sources may have a clinical impact on patient care and contribute to drug-related morbidity and mortality.
Directory of Open Access Journals (Sweden)
Millena Drumond Bicalho
2015-09-01
Full Text Available : Hospitalized patients require the use of a variety of drugs, many of which individually or in combination have the potential to cause kidney damage. The use of potentially nephrotoxic drugs is often unavoidable, and the need for dose adjustment should be evaluated. This study is aimed at assessing concordance in information on drug-induced nephrotoxicity and dose adjustment recommendations by comparing four drug information sources (DRUGDEX®, UpToDate®, Medscape® and the Brazilian Therapeutic Formulary using the formulary of a Brazilian public hospital. A total of 218 drugs were investigated. The global Fleiss’ kappa coefficient was 0.265 for nephrotoxicity (p < 0.001; CI 95%, 0.211–0.319 and 0.346 for recommendations (p < 0.001; CI 95%, 0.292–0.401, indicating fair concordance among the sources. Anti-infectives and anti-hypertensives were the main drugs cited as nephrotoxic by the different sources. There were no clear definitions for qualitative data or quantitative values for dose adjustments among the four information sources. There was no advice for dosing for a large number of the drugs in the international databases. The National Therapeutic Formulary offered imprecise dose adjustment recommendations for many nephrotoxic drugs. Discrepancies among information sources may have a clinical impact on patient care and contribute to drug-related morbidity and mortality.
Kusano, Maggie; Caldwell, Curtis B
2014-07-01
A primary goal of nuclear medicine facility design is to keep public and worker radiation doses As Low As Reasonably Achievable (ALARA). To estimate dose and shielding requirements, one needs to know both the dose equivalent rate constants for soft tissue and barrier transmission factors (TFs) for all radionuclides of interest. Dose equivalent rate constants are most commonly calculated using published air kerma or exposure rate constants, while transmission factors are most commonly calculated using published tenth-value layers (TVLs). Values can be calculated more accurately using the radionuclide's photon emission spectrum and the physical properties of lead, concrete, and/or tissue at these energies. These calculations may be non-trivial due to the polyenergetic nature of the radionuclides used in nuclear medicine. In this paper, the effects of dose equivalent rate constant and transmission factor on nuclear medicine dose and shielding calculations are investigated, and new values based on up-to-date nuclear data and thresholds specific to nuclear medicine are proposed. To facilitate practical use, transmission curves were fitted to the three-parameter Archer equation. Finally, the results of this work were applied to the design of a sample nuclear medicine facility and compared to doses calculated using common methods to investigate the effects of these values on dose estimates and shielding decisions. Dose equivalent rate constants generally agreed well with those derived from the literature with the exception of those from NCRP 124. Depending on the situation, Archer fit TFs could be significantly more accurate than TVL-based TFs. These results were reflected in the sample shielding problem, with unshielded dose estimates agreeing well, with the exception of those based on NCRP 124, and Archer fit TFs providing a more accurate alternative to TVL TFs and a simpler alternative to full spectral-based calculations. The data provided by this paper should assist
Hanford Site Annual Report Radiological Dose Calculation Upgrade Evaluation
Energy Technology Data Exchange (ETDEWEB)
Snyder, Sandra F.
2010-02-28
Operations at the Hanford Site, Richland, Washington, result in the release of radioactive materials to offsite residents. Site authorities are required to estimate the dose to the maximally exposed offsite resident. Due to the very low levels of exposure at the residence, computer models, rather than environmental samples, are used to estimate exposure, intake, and dose. A DOS-based model has been used in the past (GENII version 1.485). GENII v1.485 has been updated to a Windows®-based software (GENII version 2.08). Use of the updated software will facilitate future dose evaluations, but must be demonstrated to provide results comparable to those of GENII v1.485. This report describes the GENII v1.485 and GENII v2.08 dose exposure, intake, and dose estimates for the maximally exposed offsite resident reported for calendar year 2008. The GENII v2.08 results reflect updates to implemented algorithms. No two environmental models produce the same results, as was again demonstrated in this report. The aggregated dose results from 2008 Hanford Site airborne and surface water exposure scenarios provide comparable dose results. Therefore, the GENII v2.08 software is recommended for future offsite resident dose evaluations.
Komemushi, Atsushi; Tanigawa, Noboru; Kariya, Shuji; Yagi, Rie; Nakatani, Miyuki; Suzuki, Satoshi; Sano, Akira; Ikeda, Koshi; Utsunomiya, Keita; Harima, Yoko; Sawada, Satoshi
2012-01-01
Purpose. To assess differences in dose distribution of a vertebral body injected with bone cement as calculated by radiation treatment planning system (RTPS) and actual dose distribution. Methods. We prepared two water-equivalent phantoms with cement, and the other two phantoms without cement. The bulk density of the bone cement was imported into RTPS to reduce error from high CT values. A dose distribution map for the phantoms with and without cement was calculated using RTPS with clinical setting and with the bulk density importing. Actual dose distribution was measured by the film density. Dose distribution as calculated by RTPS was compared to the dose distribution measured by the film dosimetry. Results. For the phantom with cement, dose distribution was distorted for the areas corresponding to inside the cement and on the ventral side of the cement. However, dose distribution based on film dosimetry was undistorted behind the cement and dose increases were seen inside cement and around the cement. With the equivalent phantom with bone cement, differences were seen between dose distribution calculated by RTPS and that measured by the film dosimetry. Conclusion. The dose distribution of an area containing bone cement calculated using RTPS differs from actual dose distribution.
Monte Carlo PENRADIO software for dose calculation in medical imaging
Adrien, Camille; Lòpez Noriega, Mercedes; Bonniaud, Guillaume; Bordy, Jean-Marc; Le Loirec, Cindy; Poumarede, Bénédicte
2014-06-01
The increase on the collective radiation dose due to the large number of medical imaging exams has led the medical physics community to deeply consider the amount of dose delivered and its associated risks in these exams. For this purpose we have developed a Monte Carlo tool, PENRADIO, based on a modified version of PENELOPE code 2006 release, to obtain an accurate individualized radiation dose in conventional and interventional radiography and in computed tomography (CT). This tool has been validated showing excellent agreement between the measured and simulated organ doses in the case of a hip conventional radiography and a coronography. We expect the same accuracy in further results for other localizations and CT examinations.
Dose calculation and in-phantom measurement in BNCT using response matrix method.
Rahmani, Faezeh; Shahriari, Majid
2011-12-01
In-phantom measurement of physical dose distribution is very important for Boron Neutron Capture Therapy (BNCT) planning validation. If any changes take place in therapeutic neutron beam due to the beam shaping assembly (BSA) change, the dose will be changed so another group of simulations should be carried out for dose calculation. To avoid this time consuming procedure and speed up the dose calculation to help patients not wait for a long time, response matrix method was used. This procedure was performed for neutron beam of the optimized BSA as a reference beam. These calculations were carried out using the MCNPX, Monte Carlo code. The calculated beam parameters were measured for a SNYDER head phantom placed 10 cm away from beam the exit of the BSA. The head phantom can be assumed as a linear system and neutron beam and dose distribution can be assumed as an input and a response of this system (head phantom), respectively. Neutron spectrum energy was digitized into 27 groups. Dose response of each group was calculated. Summation of these dose responses is equal to a total dose of the whole neutron/gamma spectrum. Response matrix is the double dimension matrix (energy/dose) in which each parameter represents a depth-dose resulted from specific energy. If the spectrum is changed, response of each energy group may be differed. By considering response matrix and energy vector, dose response can be calculated. This method was tested for some BSA, and calculations show statistical errors less than 10%.
User Guide for GoldSim Model to Calculate PA/CA Doses and Limits
Energy Technology Data Exchange (ETDEWEB)
Smith, F. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2016-10-31
A model to calculate doses for solid waste disposal at the Savannah River Site (SRS) and corresponding disposal limits has been developed using the GoldSim commercial software. The model implements the dose calculations documented in SRNL-STI-2015-00056, Rev. 0 “Dose Calculation Methodology and Data for Solid Waste Performance Assessment (PA) and Composite Analysis (CA) at the Savannah River Site”.
Radiopharmaceuticals introduction to drug evaluation and dose estimation
Williams, Lawerence E
2010-01-01
Nanoengineering, energized by the desire to find specific targeting agents, is leading to dramatic acceleration in novel drug design. However, in this flurry of activity, some issues may be overlooked. This is especially true in the area of determining dosage and evaluating the effects of multiple agents designed to target more than one site of metastasis. Offering the unique perspective of a medical physicist who has worked directly with cancer patients for over three decades, Radiopharmaceuticals: Introduction to Drug Evaluation and Dose Estimation starts by exploring the recent history and
An alternate method for estimating the dose-response relationships of neuromuscular blocking drugs.
Kopman, A F; Klewicka, M M; Neuman, G G
2000-05-01
Slopes of the dose-response relationships for all available neuromuscular blocking drugs appear to be essentially parallel and to approximate a log-dose/logit value of 4.75. We tested the possibility of estimating both 50% effective dose (ED(50)) and 95% effective dose (ED(95)) values from a single dose-response data point when that slope is postulated. We compared the ED(50) and ED(95) values of rocuronium and succinylcholine calculated by using traditional log-dose/logit regression analysis with the same values obtained by averaging individual estimates of potency as determined by using the Hill equation. After the induction of anesthesia (propofol/alfentanil), tracheal intubation was accomplished without the administration of neuromuscular blocking drugs. Anesthesia was maintained with nitrous oxide and propofol. The evoked electromyographic response to 0.10-Hz single stimuli was continuously recorded. After baseline stabilization, a single IV bolus of succinylcholine (0.08-0.26 mg/kg, n = 50) or rocuronium (0. 13-0.30 mg/kg, n = 40) was administered and the peak effect noted. By using log-dose/logit regression analysis, we calculated ED(50) and ED(95) values for rocuronium of 0.17 and 0.33 mg/kg and 0.14 and 0.27 mg/kg for succinylcholine. When potency was calculated from the Hill equation, the resultant ED(50) and ED(95) values did not differ by more than +/-4% from those obtained by using regression analysis. Averaging of single-dose estimates of neuromuscular potency provides a useful adjunct and reasonable alternative to conventional regression analysis.
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Vianello, Elizabeth A.; Almeida, Carlos E. de [Instituto Nacional do Cancer, Rio de Janeiro, RJ (Brazil); Biaggio, Maria F. de [Universidade do Estado, Rio de Janeiro, RJ (Brazil)
1998-09-01
This paper describes a manual method for dose calculation in brachytherapy of gynecological tumors, which allows the calculation of the doses at any plane or point of clinical interest. This method uses basic principles of vectorial algebra and the simulating orthogonal films taken from the patient with the applicators and dummy sources in place. The results obtained with method were compared with the values calculated with the values calculated with the treatment planning system model Theraplan and the agreement was better than 5% in most cases. The critical points associated with the final accuracy of the proposed method is related to the quality of the image and the appropriate selection of the magnification factors. This method is strongly recommended to the radiation oncology centers where are no treatment planning systems available and the dose calculations are manually done. (author) 10 refs., 5 figs.
A GPU implementation of a track-repeating algorithm for proton radiotherapy dose calculations
Yepes, Pablo P; Taddei, Phillip J
2010-01-01
An essential component in proton radiotherapy is the algorithm to calculate the radiation dose to be delivered to the patient. The most common dose algorithms are fast but they are approximate analytical approaches. However their level of accuracy is not always satisfactory, especially for heterogeneous anatomic areas, like the thorax. Monte Carlo techniques provide superior accuracy, however, they often require large computation resources, which render them impractical for routine clinical use. Track-repeating algorithms, for example the Fast Dose Calculator, have shown promise for achieving the accuracy of Monte Carlo simulations for proton radiotherapy dose calculations in a fraction of the computation time. We report on the implementation of the Fast Dose Calculator for proton radiotherapy on a card equipped with graphics processor units (GPU) rather than a central processing unit architecture. This implementation reproduces the full Monte Carlo and CPU-based track-repeating dose calculations within 2%, w...
A comparison of Monte Carlo dose calculation denoising techniques
El Naqa, I.; Kawrakow, I.; Fippel, M.; Siebers, J. V.; Lindsay, P. E.; Wickerhauser, M. V.; Vicic, M.; Zakarian, K.; Kauffmann, N.; Deasy, J. O.
2005-03-01
Recent studies have demonstrated that Monte Carlo (MC) denoising techniques can reduce MC radiotherapy dose computation time significantly by preferentially eliminating statistical fluctuations ('noise') through smoothing. In this study, we compare new and previously published approaches to MC denoising, including 3D wavelet threshold denoising with sub-band adaptive thresholding, content adaptive mean-median-hybrid (CAMH) filtering, locally adaptive Savitzky-Golay curve-fitting (LASG), anisotropic diffusion (AD) and an iterative reduction of noise (IRON) method formulated as an optimization problem. Several challenging phantom and computed-tomography-based MC dose distributions with varying levels of noise formed the test set. Denoising effectiveness was measured in three ways: by improvements in the mean-square-error (MSE) with respect to a reference (low noise) dose distribution; by the maximum difference from the reference distribution and by the 'Van Dyk' pass/fail criteria of either adequate agreement with the reference image in low-gradient regions (within 2% in our case) or, in high-gradient regions, a distance-to-agreement-within-2% of less than 2 mm. Results varied significantly based on the dose test case: greater reductions in MSE were observed for the relatively smoother phantom-based dose distribution (up to a factor of 16 for the LASG algorithm); smaller reductions were seen for an intensity modulated radiation therapy (IMRT) head and neck case (typically, factors of 2-4). Although several algorithms reduced statistical noise for all test geometries, the LASG method had the best MSE reduction for three of the four test geometries, and performed the best for the Van Dyk criteria. However, the wavelet thresholding method performed better for the head and neck IMRT geometry and also decreased the maximum error more effectively than LASG. In almost all cases, the evaluated methods provided acceleration of MC results towards statistically more accurate
A comparison of Monte Carlo dose calculation denoising techniques
Energy Technology Data Exchange (ETDEWEB)
Naqa, I El [Washington University, St Louis, MO (United States); Kawrakow, I [National Research Council of Canada, Ottawa, Ontario, Canada (Canada); Fippel, M [Univ Tuebingen, Tuebingen (Germany); Siebers, J V [Virginia Commonwealth University, Richmond, VA (United States); Lindsay, P E [Washington University, St Louis, MO (United States); Wickerhauser, M V [Washington University, St Louis, MO (United States); Vicic, M [Washington University, St Louis, MO (United States); Zakarian, K [Washington University, St Louis, MO (United States); Kauffmann, N [Ecole Polytechnique, Palaiseau (France); Deasy, J O [Washington University, St Louis, MO (United States)
2005-03-07
Recent studies have demonstrated that Monte Carlo (MC) denoising techniques can reduce MC radiotherapy dose computation time significantly by preferentially eliminating statistical fluctuations ('noise') through smoothing. In this study, we compare new and previously published approaches to MC denoising, including 3D wavelet threshold denoising with sub-band adaptive thresholding, content adaptive mean-median-hybrid (CAMH) filtering, locally adaptive Savitzky-Golay curve-fitting (LASG), anisotropic diffusion (AD) and an iterative reduction of noise (IRON) method formulated as an optimization problem. Several challenging phantom and computed-tomography-based MC dose distributions with varying levels of noise formed the test set. Denoising effectiveness was measured in three ways: by improvements in the mean-square-error (MSE) with respect to a reference (low noise) dose distribution; by the maximum difference from the reference distribution and by the 'Van Dyk' pass/fail criteria of either adequate agreement with the reference image in low-gradient regions (within 2% in our case) or, in high-gradient regions, a distance-to-agreement-within-2% of less than 2 mm. Results varied significantly based on the dose test case: greater reductions in MSE were observed for the relatively smoother phantom-based dose distribution (up to a factor of 16 for the LASG algorithm); smaller reductions were seen for an intensity modulated radiation therapy (IMRT) head and neck case (typically, factors of 2-4). Although several algorithms reduced statistical noise for all test geometries, the LASG method had the best MSE reduction for three of the four test geometries, and performed the best for the Van Dyk criteria. However, the wavelet thresholding method performed better for the head and neck IMRT geometry and also decreased the maximum error more effectively than LASG. In almost all cases, the evaluated methods provided acceleration of MC results towards
Tedgren, Åsa Carlsson; Carlsson, Gudrun Alm
2013-04-21
Model-based dose calculation algorithms (MBDCAs), recently introduced in treatment planning systems (TPS) for brachytherapy, calculate tissue absorbed doses. In the TPS framework, doses have hereto been reported as dose to water and water may still be preferred as a dose specification medium. Dose to tissue medium Dmed then needs to be converted into dose to water in tissue Dw,med. Methods to calculate absorbed dose to differently sized water compartments/cavities inside tissue, infinitesimal (used for definition of absorbed dose), small, large or intermediate, are reviewed. Burlin theory is applied to estimate photon energies at which cavity sizes in the range 1 nm-10 mm can be considered small or large. Photon and electron energy spectra are calculated at 1 cm distance from the central axis in cylindrical phantoms of bone, muscle and adipose tissue for 20, 50, 300 keV photons and photons from (125)I, (169)Yb and (192)Ir sources; ratios of mass-collision-stopping powers and mass energy absorption coefficients are calculated as applicable to convert Dmed into Dw,med for small and large cavities. Results show that 1-10 nm sized cavities are small at all investigated photon energies; 100 µm cavities are large only at photon energies <20 keV. A choice of an appropriate conversion coefficient Dw, med/Dmed is discussed in terms of the cavity size in relation to the size of important cellular targets. Free radicals from DNA bound water of nanometre dimensions contribute to DNA damage and cell killing and may be the most important water compartment in cells implying use of ratios of mass-collision-stopping powers for converting Dmed into Dw,med.
Energy Technology Data Exchange (ETDEWEB)
Napier, B.A.; Kennedy, W.E. Jr.; Soldat, J.K.
1980-03-01
A computer program, PABLM, was written to facilitate the calculation of internal radiation doses to man from radionuclides in food products and external radiation doses from radionuclides in the environment. This report contains details of mathematical models used and calculational procedures required to run the computer program. Radiation doses from radionuclides in the environment may be calculated from deposition on the soil or plants during an atmospheric or liquid release, or from exposure to residual radionuclides in the environment after the releases have ended. Radioactive decay is considered during the release of radionuclides, after they are deposited on the plants or ground, and during holdup of food after harvest. The radiation dose models consider several exposure pathways. Doses may be calculated for either a maximum-exposed individual or for a population group. The doses calculated are accumulated doses from continuous chronic exposure. A first-year committed dose is calculated as well as an integrated dose for a selected number of years. The equations for calculating internal radiation doses are derived from those given by the International Commission on Radiological Protection (ICRP) for body burdens and MPC's of each radionuclide. The radiation doses from external exposure to contaminated water and soil are calculated using the basic assumption that the contaminated medium is large enough to be considered an infinite volume or plane relative to the range of the emitted radiations. The equations for calculations of the radiation dose from external exposure to shoreline sediments include a correction for the finite width of the contaminated beach.
Kinetics and dose calculations of amikacin in the newborn
DEFF Research Database (Denmark)
Sardemann, H; Colding, H; Hendel, J;
1976-01-01
compartment model. The absorption was evaluated in 8 of the infants after intramuscular injection of 7.5 mg amikacin per kilogram of body weight. The absorption rate, estimated by the tmax, was significantly faster than reported in adults. The total body clearance and apparent volume of distribution were...... weight. The volume of distribution per kilogram was significantly greater than in adults. On the basis of the derived kinetic parameters, a dose schedule is presented. In 5 children there was a reasonable agreement between the measured and predicted serum levels....
Sakamoto, Y
2002-01-01
In the prevention of nuclear disaster, there needs the information on the dose equivalent rate distribution inside and outside the site, and energy spectra. The three dimensional radiation transport calculation code is a useful tool for the site specific detailed analysis with the consideration of facility structures. It is important in the prediction of individual doses in the future countermeasure that the reliability of the evaluation methods of dose equivalent rate distribution and energy spectra by using of Monte Carlo radiation transport calculation code, and the factors which influence the dose equivalent rate distribution outside the site are confirmed. The reliability of radiation transport calculation code and the influence factors of dose equivalent rate distribution were examined through the analyses of critical accident at JCO's uranium processing plant occurred on September 30, 1999. The radiation transport calculations including the burn-up calculations were done by using of the structural info...
Molecular modeling study of chiral drug crystals: lattice energy calculations.
Li, Z J; Ojala, W H; Grant, D J
2001-10-01
The lattice energies of a number of chiral drugs with known crystal structures were calculated using Dreiding II force field. The lattice energies, including van der Waals, Coulombic, and hydrogen-bonding energies, of homochiral and racemic crystals of some ephedrine derivatives and of several other chiral drugs, are compared. The calculated energies are correlated with experimental data to probe the underlying intermolecular forces responsible for the formation of racemic species, racemic conglomerates, or racemic compounds, termed chiral discrimination. Comparison of the calculated energies among ephedrine derivatives reveals that a greater Coulombic energy corresponds to a higher melting temperature, while a greater van der Waals energy corresponds to a larger enthalpy of fusion. For seven pairs of homochiral and racemic compounds, correlation of the differences between the two forms in the calculated energies and experimental enthalpy of fusion suggests that the van der Waals interactions play a key role in the chiral discrimination in the crystalline state. For salts of the chiral drugs, the counter ions diminish chiral discrimination by increasing the Coulombic interactions. This result may explain why salt forms favor the formation of racemic conglomerates, thereby facilitating the resolution of racemates.
Bevelacqua, J J
2011-07-01
Conservatism in the calculation of the effective dose following an airborne release from an accident involving a fuel reprocessing waste tank is examined. Within the regulatory constraints at the Hanford Site, deterministic effective dose calculations are conservative by at least an order of magnitude. Deterministic calculations should be used with caution in reaching decisions associated with required safety systems and mitigation philosophy related to the accidental release of airborne radioactive material to the environment.
Energy Technology Data Exchange (ETDEWEB)
Han, C; Schultheiss, T [City of Hope National Medical Center, Duarte, CA (United States)
2015-06-15
Purpose: In this study, we aim to evaluate the effect of dose grid size on the accuracy of calculated dose for small lesions in intracranial stereotactic radiosurgery (SRS), and to verify dose calculation accuracy with radiochromic film dosimetry. Methods: 15 intracranial lesions from previous SRS patients were retrospectively selected for this study. The planning target volume (PTV) ranged from 0.17 to 2.3 cm{sup 3}. A commercial treatment planning system was used to generate SRS plans using the volumetric modulated arc therapy (VMAT) technique using two arc fields. Two convolution-superposition-based dose calculation algorithms (Anisotropic Analytical Algorithm and Acuros XB algorithm) were used to calculate volume dose distribution with dose grid size ranging from 1 mm to 3 mm with 0.5 mm step size. First, while the plan monitor units (MU) were kept constant, PTV dose variations were analyzed. Second, with 95% of the PTV covered by the prescription dose, variations of the plan MUs as a function of dose grid size were analyzed. Radiochomic films were used to compare the delivered dose and profile with the calculated dose distribution with different dose grid sizes. Results: The dose to the PTV, in terms of the mean dose, maximum, and minimum dose, showed steady decrease with increasing dose grid size using both algorithms. With 95% of the PTV covered by the prescription dose, the total MU increased with increasing dose grid size in most of the plans. Radiochromic film measurements showed better agreement with dose distributions calculated with 1-mm dose grid size. Conclusion: Dose grid size has significant impact on calculated dose distribution in intracranial SRS treatment planning with small target volumes. Using the default dose grid size could lead to under-estimation of delivered dose. A small dose grid size should be used to ensure calculation accuracy and agreement with QA measurements.
Bourguignon, Laurent; Goutelle, Sylvain; Gérard, Cécile; Guillermet, Anne; Burdin de Saint Martin, Julie; Maire, Pascal; Ducher, Michel
2009-01-01
The use of amikacin is difficult because of its toxicity and its pharmacokinetic variability. This variability is almost ignored in adult standard dosage regimens since only the weight is used in the dose calculation. Our objective is to test if the pharmacokinetic of amikacin can be regarded as homogenous, and if the method for calculating the dose according to patients' weight is appropriate. From a cohort of 580 patients, five groups of patients were created by statistical data partitioning. A population pharmacokinetic analysis was performed in each group. The adult population is not homogeneous in term of pharmacokinetics. The doses required to achieve a maximum concentration of 60 mg/L are strongly different (585 to 1507 mg) between groups. The exclusive use of the weight to calculate the dose of amikacine appears inappropriate for 80% of the patients, showing the limits of the formulae for calculating doses of aminoglycosides.
Energy Technology Data Exchange (ETDEWEB)
NONE
2000-07-01
The guide sets out the mathematical definitions and principles involved in the calculation of the equivalent dose and the effective dose, and the instructions concerning the application of the maximum values of these quantities. further, for monitoring the dose caused by internal radiation, the guide defines the limits derived from annual dose limits (the Annual Limit on Intake and the Derived Air Concentration). Finally, the guide defines the operational quantities to be used in estimating the equivalent dose and the effective dose, and also sets out the definitions of some other quantities and concepts to be used in monitoring radiation exposure. The guide does not include the calculation of patient doses carried out for the purposes of quality assurance.
Porous hydroxyapatite tablets as carriers for low-dosed drugs.
Cosijns, A; Vervaet, C; Luyten, J; Mullens, S; Siepmann, F; Van Hoorebeke, L; Masschaele, B; Cnudde, V; Remon, J P
2007-09-01
The present study evaluated an innovative technique for the manufacturing of low-dosed tablets. Tablets containing hydroxyapatite and a pore forming agent (50% (w/w) Avicel PH 200/20, 37.5% and 50% corn starch/37.5% sorbitol) were manufactured by direct compression followed by sintering. The influence of pore forming agent (type and concentration), sinter temperature and sinter time on tablet properties was investigated. Sintering (1250 degrees C) revealed tablets with an acceptable friability (manufactured using a modified gelcasting technique yielding tablets with a median pore size of 60 and 80 microm. Release from these tablets was drastically increased indicating that the permeability of the tablets was influenced by the pore size, shape and connectivity of the porous network. Changing and controlling these parameters made it possible to obtain drug delivery systems providing different drug delivery behaviour.
Nikanjam, Mina; Liu, Sariah; Kurzrock, Razelle
2016-11-01
Combining agents has the potential to attenuate resistance in metastatic cancer. However, knowledge of appropriate starting doses for novel drug combinations in clinical trials and practice is lacking. Analysis of 372 published studies was used to ascertain safe starting doses for doublets involving a cytotoxic and targeted agent. Phase I-III adult oncology clinical trial publications (January 1, 2010 to December 31, 2013) were identified (PubMed). The dose of drug used in each combination was compared to the single agent recommended dose [FDA-approved/recommended phase 2 dose (RP2D)/maximum tolerated dose (MTD)]. Dose percentages were calculated as: (safe dose of drug in combination/dose of drug as single agent at FDA/RP2D/MTD) × 100. Additive dose percentages were the sum of the dose percentage for each drug. A total of 24,326 patients (248 drug combinations) were analyzed. In 38% of studies, both drugs could be administered at 100% of their FDA-approved/RP2D/MTD dose. The lowest safe additive dose percentage was 41% with poly-ADP ribose polymerase (PARP) or histone deacetylase inhibitors as the targeted agents; 82%, in the absence of these agents; and 97%, with an antibody in the combination. If one drug was administered at 100% of the single agent dose, the lowest safe dose percentage for the second drug was 17% (cytotoxic at 100%) or 36% (targeted at 100%) of the FDA-approved/RP2D/MTD dose. The current findings can help inform safe starting doses for novel two-drug combinations (cytotoxic and targeted agents) in the context of clinical trials and practice.
Yamamoto, Hideo; Yoneda, Tarou; Satou, Shuji; Ishikawa, Toru; Hara, Misako
2009-12-20
By input of the actual dose of a drug given into a radiology information system, the system converting with an accounting system into a cost of the drug from the actual dose in the electronic medical record was built. In the drug master, the first unit was set as the cost of the drug, and we set the second unit as the actual dose. The second unit in the radiology information system was received by the accounting system through electronic medical record. In the accounting system, the actual dose was changed into the cost of the drug using the dose of conversion to the first unit. The actual dose was recorded on a radiology information system and electronic medical record. The actual dose was indicated on the accounting system, and the cost for the drug was calculated. About the actual dose of drug, cooperation of the information in a radiology information system and electronic medical record were completed. It was possible to decide the volume of drug from the correct dose of drug at the previous inspection. If it is necessary for the patient to have another treatment of medicine, it is important to know the actual dose of drug given. Moreover, authenticity of electronic medical record based on a statute has also improved.
Monte Carlo calculation of skyshine'' neutron dose from ALS (Advanced Light Source)
Energy Technology Data Exchange (ETDEWEB)
Moin-Vasiri, M.
1990-06-01
This report discusses the following topics on skyshine'' neutron dose from ALS: Sources of radiation; ALS modeling for skyshine calculations; MORSE Monte-Carlo; Implementation of MORSE; Results of skyshine calculations from storage ring; and Comparison of MORSE shielding calculations.
Implementation of spot scanning dose optimization and dose calculation for helium ions in Hyperion
DEFF Research Database (Denmark)
Fuchs, Hermann; Alber, Markus; Schreiner, Thomas
2015-01-01
and integrated into the treatment planning system Hyperion. METHODS: Current knowledge on RBE of (4)He together with linear energy transfer considerations motivated an empirical depth-dependent "zonal" RBE model. In the plateau region, a RBE of 1.0 was assumed, followed by an increasing RBE up to 2...... doses resulted in a γ mean of 0.3, with 3.4% of the values above 1 and γ 1% of 1.5 and better. Treatment plan evaluation showed comparable planning target volume coverage for both particles, with slightly increased coverage for (4)He. Organ at risk (OAR) doses were generally reduced using (4)He, some...
A centralized dose calculation system for radiation therapy.
Xiao, Y; Galvin, J
2000-05-01
Centralization of treatment planning in a radiation therapy department is a realistic strategy to achieve an integrated and quality-controlled planning system, especially for institutions with numerous affiliations. The rapid evolution of computer hardware and software technology makes this a distinct possibility. However, the procedure of three-dimensional treatment planning involves a number of steps, such as: (1) input of patient computed tomography (CT) images and contour information; (2) interactions with local devices such as a film digitizer; and (3) output of beam information to be integrated with the record and verify the system. A full-fledged realization of the web-based centralized three-dimensional treatment planning system will require an extensive commercial development effort. We have developed and incorporated a web-based Timer/Monitor Unit (MU) program as a first step towards the full implementation of a centralized treatment planning system. The software application was developed in JAVA language. It uses the internet server and client technology. With one server that can handle multiple threads, it is a simple process to access the application anywhere on the network with an internet browser. Both the essential data needed for the calculation and the results are stored on the server, which centralizes the maintenance of the software and the storage of patient information.
Tallarida, Ronald J; Raffa, Robert B
2010-08-01
In this review we show that the concept of dose equivalence for two drugs, the theoretical basis of the isobologram, has a wider use in the analysis of pharmacological data derived from single and combination drug use. In both its application to drug combination analysis with isoboles and certain other actions, listed below, the determination of doses, or receptor occupancies, that yield equal effects provide useful metrics that can be used to obtain quantitative information on drug actions without postulating any intimate mechanism of action. These other drug actions discussed here include (1) combinations of agonists that produce opposite effects, (2) analysis of inverted U-shaped dose-effect curves of single agents, (3) analysis on the effect scale as an alternative to isoboles and (4) the use of occupation isoboles to examine competitive antagonism in the dual receptor case. New formulas derived to assess the statistical variance for additive combinations are included, and the more detailed mathematical topics are included in the Appendix.
Validation of Monte Carlo calculated surface doses for megavoltage photon beams.
Abdel-Rahman, Wamied; Seuntjens, Jan P; Verhaegen, Frank; Deblois, François; Podgorsak, Ervin B
2005-01-01
Recent work has shown that there is significant uncertainty in measuring build-up doses in mega-voltage photon beams especially at high energies. In this present investigation we used a phantom-embedded extrapolation chamber (PEEC) made of Solid Water to validate Monte Carlo (MC)-calculated doses in the dose build-up region for 6 and 18 MV x-ray beams. The study showed that the percentage depth ionizations (PDIs) obtained from measurements are higher than the percentage depth doses (PDDs) obtained with Monte Carlo techniques. To validate the MC-calculated PDDs, the design of the PEEC was incorporated into the simulations. While the MC-calculated and measured PDIs in the dose build-up region agree with one another for the 6 MV beam, a non-negligible difference is observed for the 18 MV x-ray beam. A number of experiments and theoretical studies of various possible effects that could be the source of this discrepancy were performed. The contribution of contaminating neutrons and protons to the build-up dose region in the 18 MV x-ray beam is negligible. Moreover, the MC calculations using the XCOM photon cross-section database and the NIST bremsstrahlung differential cross section do not explain the discrepancy between the MC calculations and measurement in the dose build-up region for the 18 MV. A simple incorporation of triplet production events into the MC dose calculation increases the calculated doses in the build-up region but does not fully account for the discrepancy between measurement and calculations for the 18 MV x-ray beam.
Calculation of dose in homogeneous phantoms for partially attenuated photon beams
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El-Khatib, E.; Podgorsak, E.B.; Pla, C.
1988-03-01
Measured and calculated dose distributions under attenuators, which are of smaller cross-sectional dimensions than the radiation field, are presented. The study was performed on a 4-MV linac at a source--surface distance of 120 cm on the beam central axis in a water phantom for several thicknesses and cross sections of lead attenuators. Dose correction factors, which are used to multiply the open beam data to get dose distributions under partial attenuators, depend strongly on attenuator parameters and on depths in phantom. A method to calculate dose correction factors for any combination of attenuator parameters and any phantom depth is presented. The calculated dose distributions under partial attenuators agree well with measured data, which indicates that the method can be applied in clinical situations.
Fellows, Kelly; Rodriguez-Cruz, Vivian; Covelli, Jenna; Droopad, Alyssa; Alexander, Sheril; Ramanathan, Murali
2015-03-01
Lack of adherence is a frequent cause of hospitalizations, but its effects on dosing patterns have not been extensively investigated. The purpose of this work was to critically evaluate a novel pharmacometric model for deriving the relationships of adherence to dosing patterns and the dosing interval distribution. The hybrid, stochastic model combines a Markov chain process with the von Mises distribution. The model was challenged with electronic medication monitoring data from 207 hypertension patients and against 5-year persistence data. The model estimates distributions of dosing runs, drug holidays, and dosing intervals. Drug holidays, which can vary between individuals with the same adherence, were characterized by the patient cooperativity index parameter. The drug holiday and dosing run distributions deviate markedly from normality. The dosing interval distribution exhibits complex patterns of multimodality and can be long-tailed. Dosing patterns are an important but under recognized covariate for explaining within-individual variance in drug concentrations.
A Mass-Conserving 4D XCAT Phantom for Dose Calculation and Accumulation
Williams, Christopher L; Seco, Joao; James, Sara St; Mak, Raymond H; Berbeco, Ross I; Lewis, John H
2013-01-01
The XCAT phantom is a realistic 4D digital torso phantom that is widely used in imaging and therapy research. However, lung mass is not conserved between respiratory phases of the phantom, making detailed dosimetric simulations and dose accumulation unphysical. A framework is developed to correct this issue by enforcing local mass conservation in the XCAT lung. Dose calculations are performed to assess the implications of neglecting mass conservation, and to demonstrate an application of the phantom to calculate the accumulated delivered dose in an irregularly breathing patient. Monte Carlo methods are used to simulate conventional and SBRT treatment delivery. The spatial distribution of the lung dose was qualitatively changed by the use of mass conservation; however the corresponding DVH did not change significantly. Comparison of the delivered dose with 4DCT-based predictions shows similar lung metric results, however dose differences of 10% can be seen in some spatial regions. Using this tool to simulate p...
Influence of polarization and a source model for dose calculation in MRT
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Bartzsch, Stefan, E-mail: s.bartzsch@dkfz.de; Oelfke, Uwe [The Institute of Cancer Research, 15 Cotswold Road, Belmont, Sutton, Surrey SM2 5NG, United Kingdom and Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 280, D-69120 Heidelberg (Germany); Lerch, Michael; Petasecca, Marco [Centre for Medical Radiation Physics, University of Wollongong, Northfields Avenue, Wollongong 2522 (Australia); Bräuer-Krisch, Elke [European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, 38000 Grenoble (France)
2014-04-15
Purpose: Microbeam Radiation Therapy (MRT), an alternative preclinical treatment strategy using spatially modulated synchrotron radiation on a micrometer scale, has the great potential to cure malignant tumors (e.g., brain tumors) while having low side effects on normal tissue. Dose measurement and calculation in MRT is challenging because of the spatial accuracy required and the arising high dose differences. Dose calculation with Monte Carlo simulations is time consuming and their accuracy is still a matter of debate. In particular, the influence of photon polarization has been discussed in the literature. Moreover, it is controversial whether a complete knowledge of phase space trajectories, i.e., the simulation of the machine from the wiggler to the collimator, is necessary in order to accurately calculate the dose. Methods: With Monte Carlo simulations in the Geant4 toolkit, the authors investigate the influence of polarization on the dose distribution and the therapeutically important peak to valley dose ratios (PVDRs). Furthermore, the authors analyze in detail phase space information provided byMartínez-Rovira et al. [“Development and commissioning of a Monte Carlo photon model for the forthcoming clinical trials in microbeam radiation therapy,” Med. Phys. 39(1), 119–131 (2012)] and examine its influence on peak and valley doses. A simple source model is developed using parallel beams and its applicability is shown in a semiadjoint Monte Carlo simulation. Results are compared to measurements and previously published data. Results: Polarization has a significant influence on the scattered dose outside the microbeam field. In the radiation field, however, dose and PVDRs deduced from calculations without polarization and with polarization differ by less than 3%. The authors show that the key consequences from the phase space information for dose calculations are inhomogeneous primary photon flux, partial absorption due to inclined beam incidence outside
SU-E-T-481: In Vivo and Post Mortem Animal Irradiation: Measured Vs. Calculated Doses
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Heintz, P [Univ New Mexico Radiology Dept., Albuquerque, NM (United States); Heintz, B [Texas Oncology, PA, Southlake, TX (United States); Sandoval, D [University of New Mexico, Albuquerque, NM (United States); Weber, W; Melo, D; Guilmette, R [Lovelace Respiratory Research Institute, Albuquerque, NM (United States)
2015-06-15
Purpose: Computerized radiation therapy treatment planning is performed on almost all patients today. However it is seldom used for laboratory irradiations. The first objective is to assess whether modern radiation therapy treatment planning (RTP) systems accurately predict the subject dose by comparing in vivo and decedent dose measurements to calculated doses. The other objective is determine the importance of using a RTP system for laboratory irradiations. Methods: 5 MOSFET radiation dosimeters were placed enterically in each subject (2 sedated Rhesus Macaques) to measure the absorbed dose at 5 levels (carina, lung, heart, liver and rectum) during whole body irradiation. The subjects were treated with large opposed lateral fields and extended distances to cover the entire subject using a Varian 600C linac. CT simulation was performed ante-mortem (AM) and post-mortem (PM). To compare AM and PM doses, calculation points were placed at the location of each dosimeter in the treatment plan. The measured results were compared to the results using Varian Eclipse and Prowess Panther RTP systems. Results: The Varian and Prowess treatment planning system agreed to within in +1.5% for both subjects. However there were significant differences between the measured and calculated doses. For both animals the calculated central axis dose was higher than prescribed by 3–5%. This was caused in part by inaccurate measurement of animal thickness at the time of irradiation. For one subject the doses ranged from 4% to 7% high and the other subject the doses ranged 7% to 14% high when compared to the RTP doses. Conclusions: Our results suggest that using proper CT RTP system can more accurately deliver the prescribed dose to laboratory subjects. It also shows that there is significant dose variation in such subjects when inhomogeneities are not considered in the planning process.
Method for calculating dose when lung tissue lies in the treatment field
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McDonald, S.C.; Keller, B.E.; Rubin, P.
1976-07-01
The absorbed dose in lung and beyond lung as a result of increased lung transmission of x and ..gamma.. irradiation is described. The correction factor used to calculate the absorbed dose is a function of beam energy, field area, lung density, and lung and soft tissue depth. Agreement between measurements and calculations in the Alderson phantom is within 3%. An example of how this technique can be used is described. (AIP)
X-ray tube output based calculation of patient entrance surface dose: validation of the method
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Harju, O.; Toivonen, M.; Tapiovaara, M.; Parviainen, T. [Radiation and Nuclear Safety Authority, Helsinki (Finland)
2003-06-01
X-ray departments need methods to monitor the doses delivered to the patients in order to be able to compare their dose level to established reference levels. For this purpose, patient dose per radiograph is described in terms of the entrance surface dose (ESD) or dose-area product (DAP). The actual measurement is often made by using a DAP-meter or thermoluminescent dosimeters (TLD). The third possibility, the calculation of ESD from the examination technique factors, is likely to be a common method for x-ray departments that do not have the other methods at their disposal or for examinations where the dose may be too low to be measured by the other means (e.g. chest radiography). We have developed a program for the determination of ESD by the calculation method and analysed the accuracy that can be achieved by this indirect method. The program calculates the ESD from the current time product, x-ray tube voltage, beam filtration and focus- to-skin distance (FSD). Additionally, for calibrating the dose calculation method and thereby improving the accuracy of the calculation, the x-ray tube output should be measured for at least one x-ray tube voltage value in each x-ray unit. The aim of the present work is to point out the restrictions of the method and details of its practical application. The first experiences from the use of the method will be summarised. (orig.)
Graves, Yan Jiang; Jia, Xun; Jiang, Steve B
2013-03-21
The γ-index test has been commonly adopted to quantify the degree of agreement between a reference dose distribution and an evaluation dose distribution. Monte Carlo (MC) simulation has been widely used for the radiotherapy dose calculation for both clinical and research purposes. The goal of this work is to investigate both theoretically and experimentally the impact of the MC statistical fluctuation on the γ-index test when the fluctuation exists in the reference, the evaluation, or both dose distributions. To the first order approximation, we theoretically demonstrated in a simplified model that the statistical fluctuation tends to overestimate γ-index values when existing in the reference dose distribution and underestimate γ-index values when existing in the evaluation dose distribution given the original γ-index is relatively large for the statistical fluctuation. Our numerical experiments using realistic clinical photon radiation therapy cases have shown that (1) when performing a γ-index test between an MC reference dose and a non-MC evaluation dose, the average γ-index is overestimated and the gamma passing rate decreases with the increase of the statistical noise level in the reference dose; (2) when performing a γ-index test between a non-MC reference dose and an MC evaluation dose, the average γ-index is underestimated when they are within the clinically relevant range and the gamma passing rate increases with the increase of the statistical noise level in the evaluation dose; (3) when performing a γ-index test between an MC reference dose and an MC evaluation dose, the gamma passing rate is overestimated due to the statistical noise in the evaluation dose and underestimated due to the statistical noise in the reference dose. We conclude that the γ-index test should be used with caution when comparing dose distributions computed with MC simulation.
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Rui-Ru Ji
2009-09-01
Full Text Available The dose response curve is the gold standard for measuring the effect of a drug treatment, but is rarely used in genomic scale transcriptional profiling due to perceived obstacles of cost and analysis. One barrier to examining transcriptional dose responses is that existing methods for microarray data analysis can identify patterns, but provide no quantitative pharmacological information. We developed analytical methods that identify transcripts responsive to dose, calculate classical pharmacological parameters such as the EC50, and enable an in-depth analysis of coordinated dose-dependent treatment effects. The approach was applied to a transcriptional profiling study that evaluated four kinase inhibitors (imatinib, nilotinib, dasatinib and PD0325901 across a six-logarithm dose range, using 12 arrays per compound. The transcript responses proved a powerful means to characterize and compare the compounds: the distribution of EC50 values for the transcriptome was linked to specific targets, dose-dependent effects on cellular processes were identified using automated pathway analysis, and a connection was seen between EC50s in standard cellular assays and transcriptional EC50s. Our approach greatly enriches the information that can be obtained from standard transcriptional profiling technology. Moreover, these methods are automated, robust to non-optimized assays, and could be applied to other sources of quantitative data.
TH-A-19A-09: Towards Sub-Second Proton Dose Calculation On GPU
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Silva, J da [University of Cambridge, Cambridge, Cambridgeshire (United Kingdom)
2014-06-15
Purpose: To achieve sub-second dose calculation for clinically relevant proton therapy treatment plans. Rapid dose calculation is a key component of adaptive radiotherapy, necessary to take advantage of the better dose conformity offered by hadron therapy. Methods: To speed up proton dose calculation, the pencil beam algorithm (PBA; clinical standard) was parallelised and implemented to run on a graphics processing unit (GPU). The implementation constitutes the first PBA to run all steps on GPU, and each part of the algorithm was carefully adapted for efficiency. Monte Carlo (MC) simulations obtained using Fluka of individual beams of energies representative of the clinical range impinging on simple geometries were used to tune the PBA. For benchmarking, a typical skull base case with a spot scanning plan consisting of a total of 8872 spots divided between two beam directions of 49 energy layers each was provided by CNAO (Pavia, Italy). The calculations were carried out on an Nvidia Geforce GTX680 desktop GPU with 1536 cores running at 1006 MHz. Results: The PBA reproduced within ±3% of maximum dose results obtained from MC simulations for a range of pencil beams impinging on a water tank. Additional analysis of more complex slab geometries is currently under way to fine-tune the algorithm. Full calculation of the clinical test case took 0.9 seconds in total, with the majority of the time spent in the kernel superposition step. Conclusion: The PBA lends itself well to implementation on many-core systems such as GPUs. Using the presented implementation and current hardware, sub-second dose calculation for a clinical proton therapy plan was achieved, opening the door for adaptive treatment. The successful parallelisation of all steps of the calculation indicates that further speedups can be expected with new hardware, brightening the prospects for real-time dose calculation. This work was funded by ENTERVISION, European Commission FP7 grant 264552.
Fast Monte Carlo Simulation for Patient-specific CT/CBCT Imaging Dose Calculation
Jia, Xun; Gu, Xuejun; Jiang, Steve B
2011-01-01
Recently, X-ray imaging dose from computed tomography (CT) or cone beam CT (CBCT) scans has become a serious concern. Patient-specific imaging dose calculation has been proposed for the purpose of dose management. While Monte Carlo (MC) dose calculation can be quite accurate for this purpose, it suffers from low computational efficiency. In response to this problem, we have successfully developed a MC dose calculation package, gCTD, on GPU architecture under the NVIDIA CUDA platform for fast and accurate estimation of the x-ray imaging dose received by a patient during a CT or CBCT scan. Techniques have been developed particularly for the GPU architecture to achieve high computational efficiency. Dose calculations using CBCT scanning geometry in a homogeneous water phantom and a heterogeneous Zubal head phantom have shown good agreement between gCTD and EGSnrc, indicating the accuracy of our code. In terms of improved efficiency, it is found that gCTD attains a speed-up of ~400 times in the homogeneous water ...
Wilson, J. W.; Khandelwal, G. S.
1976-01-01
Calculational methods for estimation of dose from external proton exposure of arbitrary convex bodies are briefly reviewed. All the necessary information for the estimation of dose in soft tissue is presented. Special emphasis is placed on retaining the effects of nuclear reaction, especially in relation to the dose equivalent. Computer subroutines to evaluate all of the relevant functions are discussed. Nuclear reaction contributions for standard space radiations are in most cases found to be significant. Many of the existing computer programs for estimating dose in which nuclear reaction effects are neglected can be readily converted to include nuclear reaction effects by use of the subroutines described herein.
FOOD: an interactive code to calculate internal radiation doses from contaminated food products
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Baker, D.A.; Hoenes, G.R.; Soldat, J.K.
1976-01-01
An interactive code, FOOD, has been written in BASIC for the UNIVAC 1108 to facilitate calculation of internal radiation doses to man from radionuclides in food products. In the dose model, vegetation may be contaminated by either air or irrigation water containing radionuclides. The model considers two mechanisms for radionuclide contamination of vegetation: direct deposition on leaves and uptake from soil through the root system. The user may select up to 14 food categories with corresponding consumption rates, growing periods and either irrigation rates or atmospheric deposition rates. These foods include various kinds of produce, grains and animal products. At present, doses may be calculated for the skin, total body and five internal organs from 190 radionuclides. Dose summaries can be displayed at the local terminal. Further details on percent contribution to dose by nuclide and by food type are available from an auxiliary high-speed printer. This output also includes estimated radionuclide concentrations in soil, plants and animal products.
Dose calculation using a numerical method based on Haar wavelets integration
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Belkadhi, K., E-mail: khaled.belkadhi@ult-tunisie.com [Unité de Recherche de Physique Nucléaire et des Hautes Énergies, Faculté des Sciences de Tunis, Université Tunis El-Manar (Tunisia); Manai, K. [Unité de Recherche de Physique Nucléaire et des Hautes Énergies, Faculté des Sciences de Tunis, Université Tunis El-Manar (Tunisia); College of Science and Arts, University of Bisha, Bisha (Saudi Arabia)
2016-03-11
This paper deals with the calculation of the absorbed dose in an irradiation cell of gamma rays. Direct measurement and simulation have shown that they are expensive and time consuming. An alternative to these two operations is numerical methods, a quick and efficient way can furnish an estimation of the absorbed dose by giving an approximation of the photon flux at a specific point of space. To validate the numerical integration method based on the Haar wavelet for absorbed dose estimation, a study with many configurations was performed. The obtained results with the Haar wavelet method showed a very good agreement with the simulation highlighting good efficacy and acceptable accuracy. - Highlights: • A numerical integration method using Haar wavelets is detailed. • Absorbed dose is estimated with Haar wavelets method. • Calculated absorbed dose using Haar wavelets and Monte Carlo simulation using Geant4 are compared.
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Pla, C.; Podgorsak, E.B.; El-Khatib, E.
1988-07-01
Measured and calculated dose profiles under partial attenuators which cover only part of the radiation beam are presented. The study was performed for x-ray beams generated with a 4-MV linear accelerator at a source--surface distance of 120 cm in a water phantom for lead attenuators of arbitrary shape but constant thickness. Dose correction factors, which are used to multiply the open beam data to predict doses under partial attenuators, depend strongly on attenuator parameters, such as its thickness, lateral dimensions, and distance from phantom or patient surface, in addition to depending on depths in the phantom. The dose correction factors are calculated with Clarkson sector integration techniques, and the results, in spite of the simplifying assumptions used in the algorithm, generally agree with measured data to within 3%. The calculational method therefore may be applied to general clinical situations in which partial attenuators are used.
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Klüter, Sebastian, E-mail: sebastian.klueter@med.uni-heidelberg.de; Schubert, Kai; Lissner, Steffen; Sterzing, Florian; Oetzel, Dieter; Debus, Jürgen [Department of Radiation Oncology, Heidelberg University Hospital, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany, and Heidelberg Institute for Radiation Oncology (HIRO), Im Neuenheimer Feld 400, 69120 Heidelberg, Germany, and German Consortium for Translational Cancer Research (DKTK), Im Neuenheimer Feld 400, 69120 Heidelberg (Germany); Schlegel, Wolfgang [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany); Oelfke, Uwe [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany and Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG (United Kingdom); Nill, Simeon [Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG (United Kingdom)
2014-08-15
Purpose: The dosimetric verification of treatment plans in helical tomotherapy usually is carried out via verification measurements. In this study, a method for independent dose calculation of tomotherapy treatment plans is presented, that uses a conventional treatment planning system with a pencil kernel dose calculation algorithm for generation of verification dose distributions based on patient CT data. Methods: A pencil beam algorithm that directly uses measured beam data was configured for dose calculation for a tomotherapy machine. Tomotherapy treatment plans were converted into a format readable by an in-house treatment planning system by assigning each projection to one static treatment field and shifting the calculation isocenter for each field in order to account for the couch movement. The modulation of the fluence for each projection is read out of the delivery sinogram, and with the kernel-based dose calculation, this information can directly be used for dose calculation without the need for decomposition of the sinogram. The sinogram values are only corrected for leaf output and leaf latency. Using the converted treatment plans, dose was recalculated with the independent treatment planning system. Multiple treatment plans ranging from simple static fields to real patient treatment plans were calculated using the new approach and either compared to actual measurements or the 3D dose distribution calculated by the tomotherapy treatment planning system. In addition, dose–volume histograms were calculated for the patient plans. Results: Except for minor deviations at the maximum field size, the pencil beam dose calculation for static beams agreed with measurements in a water tank within 2%/2 mm. A mean deviation to point dose measurements in the cheese phantom of 0.89% ± 0.81% was found for unmodulated helical plans. A mean voxel-based deviation of −0.67% ± 1.11% for all voxels in the respective high dose region (dose values >80%), and a mean local
Patient-specific dose calculations for pediatric CT of the chest, abdomen and pelvis
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Kost, Susan D.; Carver, Diana E.; Stabin, Michael G. [Vanderbilt University, Physics and Astronomy Department, Nashville, TN (United States); Vanderbilt University Medical Center, Department of Radiology and Radiological Sciences, Nashville, TN (United States); Fraser, Nicholas D.; Pickens, David R.; Price, Ronald R.; Hernanz-Schulman, Marta [Vanderbilt University Medical Center, Department of Radiology and Radiological Sciences, Nashville, TN (United States)
2015-11-15
Organ dose is essential for accurate estimates of patient dose from CT. To determine organ doses from a broad range of pediatric patients undergoing diagnostic chest-abdomen-pelvis CT and investigate how these relate to patient size. We used a previously validated Monte Carlo simulation model of a Philips Brilliance 64 multi-detector CT scanner (Philips Healthcare, Best, The Netherlands) to calculate organ doses for 40 pediatric patients (M:F = 21:19; range 0.6-17 years). Organ volumes and positions were determined from the images using standard segmentation techniques. Non-linear regression was performed to determine the relationship between volume CT dose index (CTDI{sub vol})-normalized organ doses and abdominopelvic diameter. We then compared results with values obtained from independent studies. We found that CTDI{sub vol}-normalized organ dose correlated strongly with exponentially decreasing abdominopelvic diameter (R{sup 2} > 0.8 for most organs). A similar relationship was determined for effective dose when normalized by dose-length product (R{sup 2} = 0.95). Our results agreed with previous studies within 12% using similar scan parameters (e.g., bowtie filter size, beam collimation); however results varied up to 25% when compared to studies using different bowtie filters. Our study determined that organ doses can be estimated from measurements of patient size, namely body diameter, and CTDI{sub vol} prior to CT examination. This information provides an improved method for patient dose estimation. (orig.)
Fast pencil beam dose calculation for proton therapy using a double-Gaussian beam model
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Joakim eda Silva
2015-12-01
Full Text Available The highly conformal dose distributions produced by scanned proton pencil beams are more sensitive to motion and anatomical changes than those produced by conventional radiotherapy. The ability to calculate the dose in real time as it is being delivered would enable, for example, online dose monitoring, and is therefore highly desirable. We have previously described an implementation of a pencil beam algorithm running on graphics processing units (GPUs intended specifically for online dose calculation. Here we present an extension to the dose calculation engine employing a double-Gaussian beam model to better account for the low-dose halo. To the best of our knowledge, it is the first such pencil beam algorithm for proton therapy running on a GPU. We employ two different parametrizations for the halo dose, one describing the distribution of secondary particles from nuclear interactions found in the literature and one relying on directly fitting the model to Monte Carlo simulations of pencil beams in water. Despite the large width of the halo contribution, we show how in either case the second Gaussian can be included whilst prolonging the calculation of the investigated plans by no more than 16%, or the calculation of the most time-consuming energy layers by about 25%. Further, the calculation time is relatively unaffected by the parametrization used, which suggests that these results should hold also for different systems. Finally, since the implementation is based on an algorithm employed by a commercial treatment planning system, it is expected that with adequate tuning, it should be able to reproduce the halo dose from a general beam line with sufficient accuracy.
SU-E-I-28: Evaluating the Organ Dose From Computed Tomography Using Monte Carlo Calculations
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Ono, T; Araki, F [Faculty of Life Sciences, Kumamoto University, Kumamoto (Japan)
2014-06-01
Purpose: To evaluate organ doses from computed tomography (CT) using Monte Carlo (MC) calculations. Methods: A Philips Brilliance CT scanner (64 slice) was simulated using the GMctdospp (IMPS, Germany) based on the EGSnrc user code. The X-ray spectra and a bowtie filter for MC simulations were determined to coincide with measurements of half-value layer (HVL) and off-center ratio (OCR) profile in air. The MC dose was calibrated from absorbed dose measurements using a Farmer chamber and a cylindrical water phantom. The dose distribution from CT was calculated using patient CT images and organ doses were evaluated from dose volume histograms. Results: The HVLs of Al at 80, 100, and 120 kV were 6.3, 7.7, and 8.7 mm, respectively. The calculated HVLs agreed with measurements within 0.3%. The calculated and measured OCR profiles agreed within 3%. For adult head scans (CTDIvol) =51.4 mGy), mean doses for brain stem, eye, and eye lens were 23.2, 34.2, and 37.6 mGy, respectively. For pediatric head scans (CTDIvol =35.6 mGy), mean doses for brain stem, eye, and eye lens were 19.3, 24.5, and 26.8 mGy, respectively. For adult chest scans (CTDIvol=19.0 mGy), mean doses for lung, heart, and spinal cord were 21.1, 22.0, and 15.5 mGy, respectively. For adult abdominal scans (CTDIvol=14.4 mGy), the mean doses for kidney, liver, pancreas, spleen, and spinal cord were 17.4, 16.5, 16.8, 16.8, and 13.1 mGy, respectively. For pediatric abdominal scans (CTDIvol=6.76 mGy), mean doses for kidney, liver, pancreas, spleen, and spinal cord were 8.24, 8.90, 8.17, 8.31, and 6.73 mGy, respectively. In head scan, organ doses were considerably different from CTDIvol values. Conclusion: MC dose distributions calculated by using patient CT images are useful to evaluate organ doses absorbed to individual patients.
Estimates of Columbia River radionuclide concentrations: Data for Phase 1 dose calculations
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Richmond, M.C.; Walters, W.H.
1991-05-01
Pacific Northwest Laboratory is conducting the Hanford Environmental Dose Reconstruction Project to estimate the radiation doses people may have received from historical Hanford Site operations. Under the direction of an independent Technical Steering Panel, the project is being conducted in phases. The objective of the first phase is to assess the feasibility of the project-wide technical approach for acquiring data and developing models needed to calculate potential radiation doses. This report summarizes data that were generated for the Phase 1 dose calculations. These included monthly average concentrations of specific radionuclides in Columbia River water and sediments between Priest Rapids Dam and McNary Dam for the years 1964 to 1966. Nine key radionuclides were selected for analysis based on estimation of their contribution to dose. Concentrations of these radionuclides in the river were estimated using existing measurements and hydraulic calculations based on the simplifying assumption that dilution and decay were the primary processes controlling the fate of radionuclides released to the river. Five sub-reaches between Priest Rapids Dam and McNary Dam, corresponding to population centers and tributary confluences, were identified and monthly average radionuclide concentrations were calculated for each sub-reach. The hydraulic calculations were performed to provide radionuclide concentration estimates for time periods and geographic locations where measured data were not available. The validity of the calculation method will be evaluated in Phase 2. 12 refs., 13 figs., 49 tabs.
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Suresh Rana
2013-01-01
Full Text Available Purpose: The purpose of this study is to assess the dosimetric impact of Acuros XB dose calculation algorithm (AXB, in comparisons with Anisotropic Analytical Algorithm (AAA calculations in prostate cancer treatment using RapidArc. Materials and Methods: A computed tomography (CT dataset of low-risk prostate cancer patients treated at Arizona Center for Cancer Care was selected and contoured for prostate, seminal vesicles, and organs at risk (OARs(rectum, bladder, and femur heads. Plans were created for 6 MV photon beam using RapidArc technique in Eclipse treatment planning system. Dose calculations were performed with AAA and AXB for same number of monitor units and identical beam setup. Mean and maximum doses to planning target volume (PTV and OARs were analyzed. Additionally, minimum dose to PTV and V100 was analyzed. Finally, point-dose difference between planar dose distributions of AAA and AXB plans was investigated. Results: The highest dose difference was up to 0.43% (range: 0.05−0.43%, P> 0.05 for PTV and 1.98% (range: 0.22−1.98%, P> 0.05 for OARs with AAA predicting higher dose than AXB. The V100 values of AAA plans (95 % and AXB plans (range: 93.1−97.9 % had an average difference of 0.89±1.47% with no statistical significance (P = 0.25411. The point-dose difference analysis showed that AAA predicted higher dose than AXB at significantly higher percentage (in average 94.15 of total evaluated points. Conclusion: The dosimetric results of this study suggest that the AXB can perform the dose computation comparable to AAA in RapidArc prostate cancer treatment plans that are generated by a partial single-arc technique.
Directory of Open Access Journals (Sweden)
Seyed Mohsen Hosseini Daghigh
2012-03-01
Full Text Available Introduction Interaluminal brachytherapy is one of the important methods of esophageal cancer treatment. The effect of applicator attenuation is not considered in dose calculation method released by AAPM-TG43. In this study, the effect of High-Dose Rate (HDR brachytherapy esophageal applicator on dose distribution was surveyed in HDR brachytherapy. Materials and Methods A cylindrical PMMA phantom was built in order to be inserted by various sizes of esophageal applicators. EDR2 films were placed at 33 mm from Ir-192 source and irradiated with 1.5 Gy after planning using treatment planning system for all applicators. Results The results of film dosimetry in reference point for 6, 8, 10, and 20 mm applicators were 1.54, 1.53, 1.48, and 1.50 Gy, respectively. The difference between practical and treatment planning system results was 0.023 Gy (
Effects of the difference in tube voltage of the CT scanner on dose calculation
Rhee, Dong Joo; Moon, Young Min; Kim, Jung Ki; Jeong, Dong Hyeok
2015-01-01
Computed Tomography (CT) measures the attenuation coefficient of an object and converts the value assigned to each voxel into a CT number. In radiation therapy, CT number, which is directly proportional to the linear attenuation coefficient, is required to be converted to electron density for radiation dose calculation for cancer treatment. However, if various tube voltages were applied to take the patient CT image without applying the specific CT number to electron density conversion curve, the accuracy of dose calculation would be unassured. In this study, changes in CT numbers for different materials due to change in tube voltage were demonstrated and the dose calculation errors in percentage depth dose (PDD) and a clinical case were analyzed. The maximum dose difference in PDD from TPS dose calculation and Monte Carlo simulation were 1.3 % and 1.1 % respectively when applying the same CT number to electron density conversion curve to the 80 kVp and 140 kVp images. In the clinical case, the different CT nu...
SU-E-T-27: A Tool for Routine Quality Assurance of Radiotherapy Dose Calculation Software
Energy Technology Data Exchange (ETDEWEB)
Popple, R; Cardan, R; Duan, J; Wu, X; Shen, S; Brezovich, I [The University of Alabama at Birmingham, Birmingham, AL (United States)
2014-06-01
Purpose: Dose calculation software is thoroughly evaluated when it is commissioned; however, evaluation of periodic software updates is typically limited in scope due to staffing constraints and the need to quickly return the treatment planning system to clinical service. We developed a tool for quickly and comprehensively testing and documenting dose calculation software against measured data. Methods: A tool was developed using MatLab (The MathWorks, Natick, MA) for evaluation of dose calculation algorithms against measured data. Inputs to the tool are measured data, reference DICOM RT PLAN files describing the measurements, and dose calculations in DICOM format. The tool consists of a collection of extensible modules that can perform analysis of point dose, depth dose curves, and profiles using dose difference, distance-to-agreement, and the gamma-index. Each module generates a report subsection that is incorporated into a master template, which is converted to final form in portable document format (PDF). Results: After each change to the treatment planning system, a report can be generated in approximately 90 minutes. The tool has been in use for more than 5 years, spanning 5 versions of the eMC and 4 versions of the AAA. We have detected changes to the algorithms that affected clinical practice once during this period. Conclusion: Our tool provides an efficient method for quality assurance of dose calculation software, providing a complete set of tests for an update. Future work includes the addition of plan level tests, allowing incorporation of, for example, the TG-119 test suite for IMRT, and integration with the treatment planning system via an application programming interface. Integration with the planning system will permit fully-automated testing and reporting at scheduled intervals.
Energy Technology Data Exchange (ETDEWEB)
García-Garduño, O. A., E-mail: oagarciag@innn.edu.mx, E-mail: amanda.garcia.g@gmail.com [Laboratorio de Física Médica, Instituto Nacional de Neurología y Neurocirugía, Mexico City 14269, México and Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Instituto Politécnico Nacional, Legaria 694, México City 11500, México (Mexico); Rodríguez-Ponce, M. [Departamento de Biofísica, Instituto Nacional de Cancerología, Mexico City 14080, México (Mexico); Gamboa-deBuen, I. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico City 04510 (Mexico); Rodríguez-Villafuerte, M. [Instituto de Física, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico City 04510 (Mexico); Galván de la Cruz, O. O. [Laboratorio de Física Médica, Instituto Nacional de Neurología y Neurocirugía, Mexico City 14269, México (Mexico); and others
2014-09-15
Purpose: To assess the impact of the detector used to commission small photon beams on the calculated dose distribution in stereotactic radiosurgery (SRS). Methods: In this study, six types of detectors were used to characterize small photon beams: three diodes [a silicon stereotactic field diode SFD, a silicon diode SRS, and a silicon diode E], an ionization chamber CC01, and two types of radiochromic film models EBT and EBT2. These detectors were used to characterize circular collimated beams that were generated by a Novalis linear accelerator. This study was conducted in two parts. First, the following dosimetric data, which are of particular interest in SRS, were compared for the different detectors: the total scatter factor (TSF), the tissue phantom ratios (TPRs), and the off-axis ratios (OARs). Second, the commissioned data sets were incorporated into the treatment planning system (TPS) to compare the calculated dose distributions and the dose volume histograms (DVHs) that were obtained using the different detectors. Results: The TSFs data measured by all of the detectors were in good agreement with each other within the respective statistical uncertainties: two exceptions, where the data were systematically below those obtained for the other detectors, were the CC01 results for all of the circular collimators and the EBT2 film results for circular collimators with diameters below 10.0 mm. The OAR results obtained for all of the detectors were in excellent agreement for all of the circular collimators. This observation was supported by the gamma-index test. The largest difference in the TPR data was found for the 4.0 mm circular collimator, followed by the 10.0 and 20.0 mm circular collimators. The results for the calculated dose distributions showed that all of the detectors passed the gamma-index test at 100% for the 3 mm/3% criteria. The aforementioned observation was true regardless of the size of the calculation grid for all of the circular collimators
Multi-dose drug dispensing is a challenge across the primary-secondary care interface
DEFF Research Database (Denmark)
Reuther, Lene Orskov; Lysen, Charlotte; Faxholm, Mette
2011-01-01
Multi-dose drug dispensing (MDDD) signifies that the patient's medicine is packed in disposable bags corresponding to the dose that should be taken. The purpose of the present study was to investigate how a hospital MDDD instruction was followed....
The denoising of Monte Carlo dose distributions using convolution superposition calculations
Energy Technology Data Exchange (ETDEWEB)
El Naqa, I [Department of Radiation Oncology, Washington University School of Medicine, St Louis, MO (United States); Cui, J [Department of Radiation Oncology, Washington University School of Medicine, St Louis, MO (United States); Lindsay, P [MD Anderson, Houston, TX (United States); Olivera, G [Tomotherapy Inc., Madison, WI (United States); Deasy, J O [Department of Radiation Oncology, Washington University School of Medicine, St Louis, MO (United States)
2007-09-07
Monte Carlo (MC) dose calculations can be accurate but are also computationally intensive. In contrast, convolution superposition (CS) offers faster and smoother results but by making approximations. We investigated MC denoising techniques, which use available convolution superposition results and new noise filtering methods to guide and accelerate MC calculations. Two main approaches were developed to combine CS information with MC denoising. In the first approach, the denoising result is iteratively updated by adding the denoised residual difference between the result and the MC image. Multi-scale methods were used (wavelets or contourlets) for denoising the residual. The iterations are initialized by the CS data. In the second approach, we used a frequency splitting technique by quadrature filtering to combine low frequency components derived from MC simulations with high frequency components derived from CS components. The rationale is to take the scattering tails as well as dose levels in the high-dose region from the MC calculations, which presumably more accurately incorporates scatter; high-frequency details are taken from CS calculations. 3D Butterworth filters were used to design the quadrature filters. The methods were demonstrated using anonymized clinical lung and head and neck cases. The MC dose distributions were calculated by the open-source dose planning method MC code with varying noise levels. Our results indicate that the frequency-splitting technique for incorporating CS-guided MC denoising is promising in terms of computational efficiency and noise reduction. (note)
NOTE: The denoising of Monte Carlo dose distributions using convolution superposition calculations
El Naqa, I.; Cui, J.; Lindsay, P.; Olivera, G.; Deasy, J. O.
2007-09-01
Monte Carlo (MC) dose calculations can be accurate but are also computationally intensive. In contrast, convolution superposition (CS) offers faster and smoother results but by making approximations. We investigated MC denoising techniques, which use available convolution superposition results and new noise filtering methods to guide and accelerate MC calculations. Two main approaches were developed to combine CS information with MC denoising. In the first approach, the denoising result is iteratively updated by adding the denoised residual difference between the result and the MC image. Multi-scale methods were used (wavelets or contourlets) for denoising the residual. The iterations are initialized by the CS data. In the second approach, we used a frequency splitting technique by quadrature filtering to combine low frequency components derived from MC simulations with high frequency components derived from CS components. The rationale is to take the scattering tails as well as dose levels in the high-dose region from the MC calculations, which presumably more accurately incorporates scatter; high-frequency details are taken from CS calculations. 3D Butterworth filters were used to design the quadrature filters. The methods were demonstrated using anonymized clinical lung and head and neck cases. The MC dose distributions were calculated by the open-source dose planning method MC code with varying noise levels. Our results indicate that the frequency-splitting technique for incorporating CS-guided MC denoising is promising in terms of computational efficiency and noise reduction.
Directory of Open Access Journals (Sweden)
Takashi Kadowaki
Full Text Available BACKGROUND: Pragmatic methods for dose optimization are required for the successful basal management in daily clinical practice. To derive a useful formula for calculating recommended glargine doses, we analyzed data from the Add-on Lantus® to Oral Hypoglycemic Agents (ALOHA study, a 24-week observation of Japanese type 2 diabetes patients. METHODOLOGY/PRINCIPAL FINDINGS: The patients who initiated insulin glargine in basal-supported oral therapy (BOT regimen (n = 3506 were analyzed. The correlations between average changes in glargine dose and HbA1c were calculated, and its regression formula was estimated from grouped data categorized by baseline HbA1c levels. Starting doses of the background-subgroup achieving the HbA1c target with a last-observed dose above the average were compared to an assumed optimal starting dose of 0.15 U/kg/day. The difference in regression lines between background-subgroups was examined. A formula for determining the optimal starting and titration doses was thereby derived. The correlation coefficient between changes in dose and HbA1c was -0.9043. The estimated regression line formula was -0.964 × change in HbA1c+2.000. A starting dose of 0.15 U/kg/day was applicable to all background-subgroups except for patients with retinopathy (0.120 U/kg/day and/or with eGFR<60 mL/min/1.73 m(2 (0.114 U/kg/day. Additionally, women (0.135 U/kg/day and patients with sulfonylureas (0.132 U/kg/day received a slightly decreased starting dose. CONCLUSIONS/SIGNIFICANCE: We suggest a simplified and pragmatic dose calculation formula for type 2 diabetes patients starting glargine BOT optimal daily dose at 24 weeks = starting dose (0.15×weight + incremental dose (baseline HbA1c - target HbA1c+2. This formula should be further validated using other samples in a prospective follow-up, especially since several patient groups required lower starting doses.
SU-E-T-202: Impact of Monte Carlo Dose Calculation Algorithm On Prostate SBRT Treatments
Energy Technology Data Exchange (ETDEWEB)
Venencia, C; Garrigo, E; Cardenas, J; Castro Pena, P [Instituto de Radioterapia - Fundacion Marie Curie, Cordoba (Argentina)
2014-06-01
Purpose: The purpose of this work was to quantify the dosimetric impact of using Monte Carlo algorithm on pre calculated SBRT prostate treatment with pencil beam dose calculation algorithm. Methods: A 6MV photon beam produced by a Novalis TX (BrainLAB-Varian) linear accelerator equipped with HDMLC was used. Treatment plans were done using 9 fields with Iplanv4.5 (BrainLAB) and dynamic IMRT modality. Institutional SBRT protocol uses a total dose to the prostate of 40Gy in 5 fractions, every other day. Dose calculation is done by pencil beam (2mm dose resolution), heterogeneity correction and dose volume constraint (UCLA) for PTV D95%=40Gy and D98%>39.2Gy, Rectum V20Gy<50%, V32Gy<20%, V36Gy<10% and V40Gy<5%, Bladder V20Gy<40% and V40Gy<10%, femoral heads V16Gy<5%, penile bulb V25Gy<3cc, urethra and overlap region between PTV and PRV Rectum Dmax<42Gy. 10 SBRT treatments plans were selected and recalculated using Monte Carlo with 2mm spatial resolution and mean variance of 2%. DVH comparisons between plans were done. Results: The average difference between PTV doses constraints were within 2%. However 3 plans have differences higher than 3% which does not meet the D98% criteria (>39.2Gy) and should have been renormalized. Dose volume constraint differences for rectum, bladder, femoral heads and penile bulb were les than 2% and within tolerances. Urethra region and overlapping between PTV and PRV Rectum shows increment of dose in all plans. The average difference for urethra region was 2.1% with a maximum of 7.8% and for the overlapping region 2.5% with a maximum of 8.7%. Conclusion: Monte Carlo dose calculation on dynamic IMRT treatments could affects on plan normalization. Dose increment in critical region of urethra and PTV overlapping region with PTV could have clinical consequences which need to be studied. The use of Monte Carlo dose calculation algorithm is limited because inverse planning dose optimization use only pencil beam.
Monte Carlo dose calculation improvements for low energy electron beams using eMC.
Fix, Michael K; Frei, Daniel; Volken, Werner; Neuenschwander, Hans; Born, Ernst J; Manser, Peter
2010-08-21
The electron Monte Carlo (eMC) dose calculation algorithm in Eclipse (Varian Medical Systems) is based on the macro MC method and is able to predict dose distributions for high energy electron beams with high accuracy. However, there are limitations for low energy electron beams. This work aims to improve the accuracy of the dose calculation using eMC for 4 and 6 MeV electron beams of Varian linear accelerators. Improvements implemented into the eMC include (1) improved determination of the initial electron energy spectrum by increased resolution of mono-energetic depth dose curves used during beam configuration; (2) inclusion of all the scrapers of the applicator in the beam model; (3) reduction of the maximum size of the sphere to be selected within the macro MC transport when the energy of the incident electron is below certain thresholds. The impact of these changes in eMC is investigated by comparing calculated dose distributions for 4 and 6 MeV electron beams at source to surface distance (SSD) of 100 and 110 cm with applicators ranging from 6 x 6 to 25 x 25 cm(2) of a Varian Clinac 2300C/D with the corresponding measurements. Dose differences between calculated and measured absolute depth dose curves are reduced from 6% to less than 1.5% for both energies and all applicators considered at SSD of 100 cm. Using the original eMC implementation, absolute dose profiles at depths of 1 cm, d(max) and R50 in water lead to dose differences of up to 8% for applicators larger than 15 x 15 cm(2) at SSD 100 cm. Those differences are now reduced to less than 2% for all dose profiles investigated when the improved version of eMC is used. At SSD of 110 cm the dose difference for the original eMC version is even more pronounced and can be larger than 10%. Those differences are reduced to within 2% or 2 mm with the improved version of eMC. In this work several enhancements were made in the eMC algorithm leading to significant improvements in the accuracy of the dose
Calculation of depth-dose distribution of intermediate energy heavy-ion beams
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Based on the characteristics of the interactions between intermediate energy heavy-ion beam and target matter, a method to calculate the depth-dose distribution of heavy-ion beams with intermediate energy (10 -100 MeV/u) is presented. By comparing high energy beams where projectile fragmentation is overwhelm ing with lowenergies where energy straggling is the sole factor instead, a crescent energy spread with increasing depth and a simple fragmentation assumption were included for the depth-dose calculation of the intermediate energy beam. Rel ative depth-dose curves of carbon and oxygen ion beams with intermediate energie s were computed according to the method here. Comparisons between the calculated relative doses and measurements are shown. The calculated Bragg curves, especially the upstream and downstream Bragg peaks, agree with the measured data. Differences between the two results appear only around the peak regions because of th e limitations of the calculation and experimental conditions, but the calculated curves generally reproduce the measured data within the experimental errors. Th e reasons for the divergences were analyzed carefully and the magnitudes of the deviations are given.
Zhang, Aizhen; Wen, Ning; Nurushev, Teamour; Burmeister, Jay; Chetty, Indrin J
2013-03-04
A commercial electron Monte Carlo (eMC) dose calculation algorithm has become available in Eclipse treatment planning system. The purpose of this work was to evaluate the eMC algorithm and investigate the clinical implementation of this system. The beam modeling of the eMC algorithm was performed for beam energies of 6, 9, 12, 16, and 20 MeV for a Varian Trilogy and all available applicator sizes in the Eclipse treatment planning system. The accuracy of the eMC algorithm was evaluated in a homogeneous water phantom, solid water phantoms containing lung and bone materials, and an anthropomorphic phantom. In addition, dose calculation accuracy was compared between pencil beam (PB) and eMC algorithms in the same treatment planning system for heterogeneous phantoms. The overall agreement between eMC calculations and measurements was within 3%/2 mm, while the PB algorithm had large errors (up to 25%) in predicting dose distributions in the presence of inhomogeneities such as bone and lung. The clinical implementation of the eMC algorithm was investigated by performing treatment planning for 15 patients with lesions in the head and neck, breast, chest wall, and sternum. The dose distributions were calculated using PB and eMC algorithms with no smoothing and all three levels of 3D Gaussian smoothing for comparison. Based on a routine electron beam therapy prescription method, the number of eMC calculated monitor units (MUs) was found to increase with increased 3D Gaussian smoothing levels. 3D Gaussian smoothing greatly improved the visual usability of dose distributions and produced better target coverage. Differences of calculated MUs and dose distributions between eMC and PB algorithms could be significant when oblique beam incidence, surface irregularities, and heterogeneous tissues were present in the treatment plans. In our patient cases, monitor unit differences of up to 7% were observed between PB and eMC algorithms. Monitor unit calculations were also preformed
Impact of temporal probability in 4D dose calculation for lung tumors.
Rouabhi, Ouided; Ma, Mingyu; Bayouth, John; Xia, Junyi
2015-11-08
The purpose of this study was to evaluate the dosimetric uncertainty in 4D dose calculation using three temporal probability distributions: uniform distribution, sinusoidal distribution, and patient-specific distribution derived from the patient respiratory trace. Temporal probability, defined as the fraction of time a patient spends in each respiratory amplitude, was evaluated in nine lung cancer patients. Four-dimensional computed tomography (4D CT), along with deformable image registration, was used to compute 4D dose incorporating the patient's respiratory motion. First, the dose of each of 10 phase CTs was computed using the same planning parameters as those used in 3D treatment planning based on the breath-hold CT. Next, deformable image registration was used to deform the dose of each phase CT to the breath-hold CT using the deformation map between the phase CT and the breath-hold CT. Finally, the 4D dose was computed by summing the deformed phase doses using their corresponding temporal probabilities. In this study, 4D dose calculated from the patient-specific temporal probability distribution was used as the ground truth. The dosimetric evaluation matrix included: 1) 3D gamma analysis, 2) mean tumor dose (MTD), 3) mean lung dose (MLD), and 4) lung V20. For seven out of nine patients, both uniform and sinusoidal temporal probability dose distributions were found to have an average gamma passing rate > 95% for both the lung and PTV regions. Compared with 4D dose calculated using the patient respiratory trace, doses using uniform and sinusoidal distribution showed a percentage difference on average of -0.1% ± 0.6% and -0.2% ± 0.4% in MTD, -0.2% ± 1.9% and -0.2% ± 1.3% in MLD, 0.09% ± 2.8% and -0.07% ± 1.8% in lung V20, -0.1% ± 2.0% and 0.08% ± 1.34% in lung V10, 0.47% ± 1.8% and 0.19% ± 1.3% in lung V5, respectively. We concluded that four-dimensional dose computed using either a uniform or sinusoidal temporal probability distribution can
Calculation of absorbed doses to water pools in severe accident sequences
Energy Technology Data Exchange (ETDEWEB)
Weber, C.F. [Oak Ridge National Lab., TN (United States)
1991-12-01
A methodology is presented for calculating the radiation dose to a water pool from the decay of uniformly distributed nuclides in that pool. Motivated by the need to accurately model radiolysis reactions of iodine, direct application is made to fission product sources dissolved or suspended in containment sumps or pools during a severe nuclear reactor accident. Two methods of calculating gamma absorption are discussed - one based on point-kernal integration and the other based on Monte Carlo techniques. Using least-squares minimization, the computed results are used to obtain a correlation that relates absorbed dose to source energy and surface-to-volume ratio of the pool. This correlation is applied to most relevant fission product nuclides and used to actually calculate transient sump dose rate in a pressurized-water reactor (PWR) severe accident sequence.
Directory of Open Access Journals (Sweden)
Polednik Martin
2006-11-01
Full Text Available Abstract Background The aim of this study was to compare and to validate different dose calculation algorithms for the use in radiation therapy of small lung lesions and to optimize the treatment planning using accurate dose calculation algorithms. Methods A 9-field conformal treatment plan was generated on an inhomogeneous phantom with lung mimics and a soft tissue equivalent insert, mimicking a lung tumor. The dose distribution was calculated with the Pencil Beam and Collapsed Cone algorithms implemented in Masterplan (Nucletron and the Monte Carlo system XVMC and validated using Gafchromic EBT films. Differences in dose distribution were evaluated. The plans were then optimized by adding segments to the outer shell of the target in order to increase the dose near the interface to the lung. Results The Pencil Beam algorithm overestimated the dose by up to 15% compared to the measurements. Collapsed Cone and Monte Carlo predicted the dose more accurately with a maximum difference of -8% and -3% respectively compared to the film. Plan optimization by adding small segments to the peripheral parts of the target, creating a 2-step fluence modulation, allowed to increase target coverage and homogeneity as compared to the uncorrected 9 field plan. Conclusion The use of forward 2-step fluence modulation in radiotherapy of small lung lesions allows the improvement of tumor coverage and dose homogeneity as compared to non-modulated treatment plans and may thus help to increase the local tumor control probability. While the Collapsed Cone algorithm is closer to measurements than the Pencil Beam algorithm, both algorithms are limited at tissue/lung interfaces, leaving Monte-Carlo the most accurate algorithm for dose prediction.
Institute of Scientific and Technical Information of China (English)
GAO Ci-xiu; XU Shi-xiong; JIANG Yu-ping; TU Jiang-long
2009-01-01
This work aims to investigate the effects of dosing regiments on drug delivery in solid tumors and to validate them with experiments on rats.The lumped parameter models of pharmacokinetics and of drug delivery in tumor were developed to simulate time courses of average drug concentration(Ct)of tumor interstitium in two types of dosing regiments(i.e.,single-shot and triple-shot ones).The two regiments were performed via antitumor drug,hydroxycamptothecin(HCPT),on rats,to measure the drug concentration in the tumor.The simulations of the drug concentration in the tumor of the two dosing regiments were conducted and compared with the experimental data on rats.The coefficients in the models were investigated.It is concluded that the triple-shot method is more effective than that of single-shot injection.The present lumped-parameter model is quantitatively competent for drug delivery in solid tumor.
Dose calculation method with 60-cobalt gamma rays in total body irradiation
Scaff, L A M
2001-01-01
Physical factors associated to total body irradiation using sup 6 sup 0 Co gamma rays beams, were studied in order to develop a calculation method of the dose distribution that could be reproduced in any radiotherapy center with good precision. The method is based on considering total body irradiation as a large and irregular field with heterogeneities. To calculate doses, or doses rates, of each area of interest (head, thorax, thigh, etc.), scattered radiation is determined. It was observed that if dismagnified fields were considered to calculate the scattered radiation, the resulting values could be applied on a projection to the real size to obtain the values for dose rate calculations. In a parallel work it was determined the variation of the dose rate in the air, for the distance of treatment, and for points out of the central axis. This confirm that the use of the inverse square law is not valid. An attenuation curve for a broad beam was also determined in order to allow the use of absorbers. In this wo...
Noblet, C.; Chiavassa, S.; Smekens, F.; Sarrut, D.; Passal, V.; Suhard, J.; Lisbona, A.; Paris, F.; Delpon, G.
2016-05-01
In preclinical studies, the absorbed dose calculation accuracy in small animals is fundamental to reliably investigate and understand observed biological effects. This work investigated the use of the split exponential track length estimator (seTLE), a new kerma based Monte Carlo dose calculation method for preclinical radiotherapy using a small animal precision micro irradiator, the X-RAD 225Cx. Monte Carlo modelling of the irradiator with GATE/GEANT4 was extensively evaluated by comparing measurements and simulations for half-value layer, percent depth dose, off-axis profiles and output factors in water and water-equivalent material for seven circular fields, from 20 mm down to 1 mm in diameter. Simulated and measured dose distributions in cylinders of water obtained for a 360° arc were also compared using dose, distance-to-agreement and gamma-index maps. Simulations and measurements agreed within 3% for all static beam configurations, with uncertainties estimated to 1% for the simulation and 3% for the measurements. Distance-to-agreement accuracy was better to 0.14 mm. For the arc irradiations, gamma-index maps of 2D dose distributions showed that the success rate was higher than 98%, except for the 0.1 cm collimator (92%). Using the seTLE method, MC simulations compute 3D dose distributions within minutes for realistic beam configurations with a clinically acceptable accuracy for beam diameter as small as 1 mm.
[Calculation of the first dose of amikacine: evaluation of the current dosage recommendations].
Jean-Bart, E; Debeurme, G; Ducher, M; Bourguignon, L
2013-01-01
Aminoglycosides, including amikacin, are antibiotics with major interest in the management of sepsis, but with a high potential toxicity. The French national recommendations revised in 2011 recommend a dose of amikacin ranging from 15 to 30 mg/kg. The objective was to assess if such a dose interval allows reaching the efficiency target concentrations of 64 mg/L without exceeding the toxic threshold of 2.5mg/L. From a cohort of 100 patients treated with amikacin, the individual pharmacokinetic parameters were estimated using pharmacokinetic software (MM-USCPACK). Peak and residual concentrations obtained after simulated doses ranging from 15 to 30 mg/kg were estimated and compared with the effective and toxic thresholds. The optimum dose to achieve precisely the efficiency target was calculated for each patient. Patients studied had a mean age of 79 years, mean weight of 58 kg, and mean creatinine clearance of 45 mL/min. The dose of 30 mg/kg allows the achievement of an effective peak in 98.7% of patients, but led to a potentially toxic through for 72.4% of them. The optimal dose was at mean of 1264 mg, significantly different than doses calculated with weight (P<0.0001). A weak correlation was found between weight and the optimal dose. A fixed dose of 30 mg/kg seems to be effective for most patients, but often excessive and leads to a toxic residual to 72% of patients, whereas 15 mg/kg was insufficient for most patients. The low correlation between optimal dose and patient weight shows that weight does not explain fully the interindividual variability.
Applying graphics processor units to Monte Carlo dose calculation in radiation therapy
Directory of Open Access Journals (Sweden)
Bakhtiari M
2010-01-01
Full Text Available We investigate the potential in using of using a graphics processor unit (GPU for Monte-Carlo (MC-based radiation dose calculations. The percent depth dose (PDD of photons in a medium with known absorption and scattering coefficients is computed using a MC simulation running on both a standard CPU and a GPU. We demonstrate that the GPU′s capability for massive parallel processing provides a significant acceleration in the MC calculation, and offers a significant advantage for distributed stochastic simulations on a single computer. Harnessing this potential of GPUs will help in the early adoption of MC for routine planning in a clinical environment.
DEFF Research Database (Denmark)
Christiansen, Rasmus Lübeck; Jensen, Henrik R.; Brink, Carsten
2017-01-01
Background: Current state of the art radiotherapy planning of prostate cancer utilises magnetic resonance (MR) for soft tissue delineation and computed tomography (CT) to provide an electron density map for dose calculation. This dual scan workflow is prone to setup and registration error....... This study evaluates the feasibility of an MR-only workflow and the validity of dose calculation from an MR derived pseudo CT. Material and methods: Thirty prostate cancer patients were CT and MR scanned. Clinical treatment plans were generated on CT using a single 18 MV arc volumetric modulated arc therapy...
Monte Carlo Calculations of Dose to Medium and Dose to Water for Carbon Ion Beams in Various Media
DEFF Research Database (Denmark)
Herrmann, Rochus; Petersen, Jørgen B.B.; Jäkel, Oliver
. The dose to medium (Dm ) may however differ from Dw , due to the different particle spectrum and stopping power found herein. Monte Carlo particle transport codes are capable of directly calculating dose to medium (Dm ), and was for instance recently investigated by Paganetti 2009 for various proton...... treatment plans. Here, we quantisize the effect of dose to water vs. dose to medium for a series of typical target materials found in medical physics. 2 Material and Methods The Monte Carlo code FLUKA [Battistioni et al. 2007] is used to simulate the particle fluence spectrum in a series of target...... the PSTAR, ASTAR stopping power routines available at NIST1 and MSTAR2 provided by H. Paul et al. 3 Results For a pristine carbon ion beam we encountered a maximum deviation between Dw and Dm up to 8% for bone. In addition we investigate spread out Bragg peak configurations which dilutes the effect...
Quantification of confounding factors in MRI-based dose calculations as applied to prostate IMRT
Maspero, Matteo; Seevinck, Peter R.; Schubert, Gerald; Hoesl, Michaela A. U.; van Asselen, Bram; Viergever, Max A.; Lagendijk, Jan J. W.; Meijer, Gert J.; van den Berg, Cornelis A. T.
2017-02-01
Magnetic resonance (MR)-only radiotherapy treatment planning requires pseudo-CT (pCT) images to enable MR-based dose calculations. To verify the accuracy of MR-based dose calculations, institutions interested in introducing MR-only planning will have to compare pCT-based and computer tomography (CT)-based dose calculations. However, interpreting such comparison studies may be challenging, since potential differences arise from a range of confounding factors which are not necessarily specific to MR-only planning. Therefore, the aim of this study is to identify and quantify the contribution of factors confounding dosimetric accuracy estimation in comparison studies between CT and pCT. The following factors were distinguished: set-up and positioning differences between imaging sessions, MR-related geometric inaccuracy, pCT generation, use of specific calibration curves to convert pCT into electron density information, and registration errors. The study comprised fourteen prostate cancer patients who underwent CT/MRI-based treatment planning. To enable pCT generation, a commercial solution (MRCAT, Philips Healthcare, Vantaa, Finland) was adopted. IMRT plans were calculated on CT (gold standard) and pCTs. Dose difference maps in a high dose region (CTV) and in the body volume were evaluated, and the contribution to dose errors of possible confounding factors was individually quantified. We found that the largest confounding factor leading to dose difference was the use of different calibration curves to convert pCT and CT into electron density (0.7%). The second largest factor was the pCT generation which resulted in pCT stratified into a fixed number of tissue classes (0.16%). Inter-scan differences due to patient repositioning, MR-related geometric inaccuracy, and registration errors did not significantly contribute to dose differences (0.01%). The proposed approach successfully identified and quantified the factors confounding accurate MRI-based dose calculation in
Energy Technology Data Exchange (ETDEWEB)
Cristy, M.
1980-01-01
Mathematical phantoms of the human body at various ages are employed with Monte Carlo radiation transport codes for calculation of photon specific absorbed fractions. The author has developed a pediatric phantom series based on the design of the adult phantom, but with explicit equations for each organ so that organ sizes and marrow distributions could be assigned properly. Since the phantoms comprise simple geometric shapes, predictive dose capability is limited when geometry is critical to the calculation. Hence, there is a demand for better phantom design in situations where geometry is critical, such as for external irradiation or for internal emitters with low energy photons. Recent advances in computerized axial tomography (CAT) present the potential for derivation of anatomical information, which is so critical to development of phantoms, and ongoing developmental work on compuer architecture to handle large arrays for Monte Carlo calculations should make complex-geometry dose calculations economically feasible within this decade.
Monte Carlo calculations of the depth-dose distribution in skin contaminated by hot particles
Energy Technology Data Exchange (ETDEWEB)
Patau, J.-P. (Toulouse-3 Univ., 31 (France))
1991-01-01
Accurate computer programs were developed in order to calculate the spatial distribution of absorbed radiation doses in the skin, near high activity particles (''hot particles''). With a view to ascertaining the reliability of the codes the transport of beta particles was simulated in a complex configuration used for dosimetric measurements: spherical {sup 60}Co sources of 10-1000 {mu}m fastened to an aluminium support with a tissue-equivalent adhesive overlaid with 10 {mu}m thick aluminium foil. Behind it an infinite polystyrene medium including an extrapolation chamber was assumed. The exact energy spectrum of beta emission was sampled. Production and transport of secondary knock-on electrons were also simulated. Energy depositions in polystyrene were calculated with a high spatial resolution. Finally, depth-dose distributions were calculated for hot particles placed on the skin. The calculations will be continued for other radionuclides and for a configuration suited to TLD measurements. (author).
SU-E-T-639: Proton Dose Calculation for Irregular Motion Using a Sliding Interface
Energy Technology Data Exchange (ETDEWEB)
Phillips, J; Gueorguiev, G; Grassberger, C; Paganetti, H; Sharp, G [Massachusetts General Hospital, Boston, MA (United States)
2015-06-15
Purpose: While many techniques exist to evaluate dose to regularly moving lung targets, there are few available to calculate dose at tumor positions not present in the 4DCT. We have previously developed a method that extrapolates an existing dose to a new tumor location. In this abstract, we present a novel technique that accounts for relative anatomical shifts at the chest wall interface. We also utilize this procedure to simulate breathing motion functions on a cohort of eleven patients. Amplitudes exceeding the original range of motion were used to evaluate coverage using several aperture and smearing beam settings. Methods: The water-equivalent depth (WED) technique requires an initial dose and CT image at the corresponding tumor position. Each dose volume was converted from its Cartesian geometry into a beam-specific radiological depth space. The sliding chest wall interface was determined by converting the lung contour into this same space. Any dose proximal to the initial boundary of the warped lung contour was held fixed, while the remaining distal dose was moved in the direction of motion along the interface. Results: V95 coverage was computed for each patient using the updated algorithm. Incorporation of the sliding motion yielded large dose differences, with gamma pass rates as low as 69.7% (3mm, 3%) and V95 coverage differences up to 2.0%. Clinical coverage was maintained for most patients with 5 mm excess simulated breathing motion, and up to 10 mm of excess motion was tolerated for a subset of patients and beam settings. Conclusion: We have established a method to determine the maximum allowable excess breathing motion for a given plan on a patient-by-patient basis. By integrating a sliding chest wall interface into our dose calculation technique, we have analyzed the robustness of breathing patterns that differ during treatment from at the time of 4DCT acquisition.
Calculation of organ doses in x-ray examinations of premature babies.
Smans, Kristien; Tapiovaara, Markku; Cannie, Mieke; Struelens, Lara; Vanhavere, Filip; Smet, Marleen; Bosmans, Hilde
2008-02-01
Lung disease represents one of the most life-threatening conditions in prematurely born children. In the evaluation of the neonatal chest, the primary and most important diagnostic study is the chest radiograph. Since prematurely born children are very sensitive to radiation, those radiographs may lead to a significant radiation detriment. Knowledge of the radiation dose is therefore necessary to justify the exposures. To calculate doses in the entire body and in specific organs, computational models of the human anatomy are needed. Using medical imaging techniques, voxel phantoms have been developed to achieve a representation as close as possible to the anatomical properties. In this study two voxel phantoms, representing prematurely born babies, were created from computed tomography- and magnetic resonance images: Phantom 1 (1910 g) and Phantom 2 (590 g). The two voxel phantoms were used in Monte Carlo calculations (MCNPX) to assess organ doses. The results were compared with the commercially available software package PCXMC in which the available mathematical phantoms can be downsized toward the prematurely born baby. The simple phantom-scaling method used in PCXMC seems to be sufficient to calculate doses for organs within the radiation field. However, one should be careful in specifying the irradiation geometry. Doses in organs that are wholly or partially outside the primary radiation field depend critically on the irradiation conditions and the phantom model.
Accuracy of out-of-field dose calculations by a commercial treatment planning system
Energy Technology Data Exchange (ETDEWEB)
Howell, Rebecca M; Scarboro, Sarah B; Kry, S F; Yaldo, Derek Z, E-mail: Rhowell@mdanderson.or [University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, TX 77030 (United States)
2010-12-07
The dosimetric accuracy of treatment planning systems (TPSs) decreases for locations outside the treatment field borders. However, the true accuracy of specific TPSs for locations beyond the treatment field borders is not well documented. Our objective was to quantify the accuracy of out-of-field dose predicted by the commercially available Eclipse version 8.6 TPS (Varian Medical Systems, Palo Alto, CA) for a clinical treatment delivered on a Varian Clinac 2100. We calculated (in the TPS) and determined (with thermoluminescent dosimeters) doses at a total of 238 points of measurement (with distance from the field edge ranging from 3.75 to 11.25 cm). Our comparisons determined that the Eclipse TPS underestimated out-of-field doses by an average of 40% over the range of distances examined. As the distance from the treatment field increased, the TPS underestimated the dose with increasing magnitude--up to 55% at 11.25 cm from the treatment field border. These data confirm that accuracy beyond the treatment border is inadequate, and out-of-field data from TPSs should be used only with a clear understanding of this limitation. Studies that require accurate out-of-field dose should use other dose reconstruction methods, such as direct measurements or Monte Carlo calculations.
Accuracy of out-of-field dose calculations by a commercial treatment planning system
Howell, Rebecca M.; Scarboro, Sarah B.; Kry, S. F.; Yaldo, Derek Z.
2010-12-01
The dosimetric accuracy of treatment planning systems (TPSs) decreases for locations outside the treatment field borders. However, the true accuracy of specific TPSs for locations beyond the treatment field borders is not well documented. Our objective was to quantify the accuracy of out-of-field dose predicted by the commercially available Eclipse version 8.6 TPS (Varian Medical Systems, Palo Alto, CA) for a clinical treatment delivered on a Varian Clinac 2100. We calculated (in the TPS) and determined (with thermoluminescent dosimeters) doses at a total of 238 points of measurement (with distance from the field edge ranging from 3.75 to 11.25 cm). Our comparisons determined that the Eclipse TPS underestimated out-of-field doses by an average of 40% over the range of distances examined. As the distance from the treatment field increased, the TPS underestimated the dose with increasing magnitude--up to 55% at 11.25 cm from the treatment field border. These data confirm that accuracy beyond the treatment border is inadequate, and out-of-field data from TPSs should be used only with a clear understanding of this limitation. Studies that require accurate out-of-field dose should use other dose reconstruction methods, such as direct measurements or Monte Carlo calculations.
Wu, Vincent W C; Tse, Teddy K H; Ho, Cola L M; Yeung, Eric C Y
2013-01-01
Monte Carlo (MC) simulation is currently the most accurate dose calculation algorithm in radiotherapy planning but requires relatively long processing time. Faster model-based algorithms such as the anisotropic analytical algorithm (AAA) by the Eclipse treatment planning system and multigrid superposition (MGS) by the XiO treatment planning system are 2 commonly used algorithms. This study compared AAA and MGS against MC, as the gold standard, on brain, nasopharynx, lung, and prostate cancer patients. Computed tomography of 6 patients of each cancer type was used. The same hypothetical treatment plan using the same machine and treatment prescription was computed for each case by each planning system using their respective dose calculation algorithm. The doses at reference points including (1) soft tissues only, (2) bones only, (3) air cavities only, (4) soft tissue-bone boundary (Soft/Bone), (5) soft tissue-air boundary (Soft/Air), and (6) bone-air boundary (Bone/Air), were measured and compared using the mean absolute percentage error (MAPE), which was a function of the percentage dose deviations from MC. Besides, the computation time of each treatment plan was recorded and compared. The MAPEs of MGS were significantly lower than AAA in all types of cancers (pplans was significantly lower than that of the MGS (palgorithms demonstrated dose deviations of less than 4.0% in most clinical cases and their performance was better in homogeneous tissues than at tissue boundaries. In general, MGS demonstrated relatively smaller dose deviations than AAA but required longer computation time.
Tolerances for the accuracy of photon beam dose calculations of treatment planning systems
Venselaar, J; Welleweerd, H; Mijnheer, B
2001-01-01
Background and purpose: To design a consistent set of criteria for acceptability of photon beam dose calculations of treatment planning systems. The set should be applicable in combination with a test package used for evaluation of a treatment planning system, such as the ones proposed by the AAPM T
Sensitivity of NTCP parameter values against a change of dose calculation algorithm
DEFF Research Database (Denmark)
Brink, Carsten; Berg, Martin; Nielsen, Morten
2007-01-01
predicted for a given treatment will in general depend on the algorithm. The purpose of this work is to test whether the optimal NTCP parameter values change significantly when the dose calculation algorithm is changed. The treatment plans for 17 breast cancer patients have retrospectively been recalculated...
Ulmer, W
2010-01-01
We have developed a model for proton depth dose and lateral distributions based on Monte Carlo calculations (GEANT4) and an integration procedure of the Bethe-Bloch equation (BBE). The model accounts for the transport of primary and secondary protons, the creation of recoil protons and heavy recoil nuclei as well as lateral scattering of these contributions. The buildup, which is experimentally observed in higher energy depth dose curves, is modeled by inclusion of two different origins: 1. Secondary reaction protons with a contribution of ca. 65 % of the buildup (for monoenergetic protons). 2. Landau tails as well as Gaussian type of fluctuations for range straggling effects. All parameters of the model for initially monoenergetic proton beams have been obtained from Monte Carlo calculations or checked by them. Furthermore, there are a few parameters, which can be obtained by fitting the model to measured depth dose curves in order to describe individual characteristics of the beamline - the most important b...
Modulation index for VMAT considering both mechanical and dose calculation uncertainties
Energy Technology Data Exchange (ETDEWEB)
Park, Jong Min; Park, So Yeon; Kim, Jung In [Dept. of Radiation Oncology, Seoul National University Hospital, Seoul (Korea, Republic of); Ye, Sung Joon [Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Seoul National University Graduate School of Convergence Science and Technology, Seoul (Korea, Republic of); Wu, Hong Gyun [Dept. of Radiation Oncology, Seoul National University College of Medicine, Seoul (Korea, Republic of); Kim, Hyoung Nyoun [Graduate School of Information, Yonsei University, Seoul (Korea, Republic of)
2015-10-15
The mechanical uncertainty of multi-leaf collimator (MLC) movements, gantry rotations and beam control systems as well as inaccurate dose calculations of small or irregular fields result in discrepancies between planned dose distributions as intended to be delivered to the patient, and the actual delivery to the patient. In this study, we designed a weighting factor which considers the size and irregularity of field apertures at each control point (CP) by utilizing the thinning algorithm, an image processing technique. After that, we combined this weighting factor with the previously suggested MIt, which considers the mechanical uncertainty of VMAT. In doing so, we attempted to design a modulation index which considers both mechanical and dose calculation uncertainties due to excessive modulation of VMAT plans. The MI{sub c} (f = 0.5) demonstrated considerable power to predict VMAT delivery accuracy showing strong correlations to various measures of VMAT delivery accuracy.
Suitability of point kernel dose calculation techniques in brachytherapy treatment planning
Directory of Open Access Journals (Sweden)
Lakshminarayanan Thilagam
2010-01-01
Full Text Available Brachytherapy treatment planning system (TPS is necessary to estimate the dose to target volume and organ at risk (OAR. TPS is always recommended to account for the effect of tissue, applicator and shielding material heterogeneities exist in applicators. However, most brachytherapy TPS software packages estimate the absorbed dose at a point, taking care of only the contributions of individual sources and the source distribution, neglecting the dose perturbations arising from the applicator design and construction. There are some degrees of uncertainties in dose rate estimations under realistic clinical conditions. In this regard, an attempt is made to explore the suitability of point kernels for brachytherapy dose rate calculations and develop new interactive brachytherapy package, named as BrachyTPS, to suit the clinical conditions. BrachyTPS is an interactive point kernel code package developed to perform independent dose rate calculations by taking into account the effect of these heterogeneities, using two regions build up factors, proposed by Kalos. The primary aim of this study is to validate the developed point kernel code package integrated with treatment planning computational systems against the Monte Carlo (MC results. In the present work, three brachytherapy applicators commonly used in the treatment of uterine cervical carcinoma, namely (i Board of Radiation Isotope and Technology (BRIT low dose rate (LDR applicator and (ii Fletcher Green type LDR applicator (iii Fletcher Williamson high dose rate (HDR applicator, are studied to test the accuracy of the software. Dose rates computed using the developed code are compared with the relevant results of the MC simulations. Further, attempts are also made to study the dose rate distribution around the commercially available shielded vaginal applicator set (Nucletron. The percentage deviations of BrachyTPS computed dose rate values from the MC results are observed to be within plus/minus 5
Individual Dose Calculations with Use of the Revised Techa River Dosimetry System TRDS-2009D
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Degteva, M. O.; Shagina, N. B.; Tolstykh, E. I.; Vorobiova, M. I.; Anspaugh, L. R.; Napier, Bruce A.
2009-10-23
An updated deterministic version of the Techa River Dosimetry System (TRDS-2009D) has been developed to estimate individual doses from external exposure and intake of radionuclides for residents living on the Techa River contaminated as a result of radioactive releases from the Mayak plutonium facility in 1949–1956. The TRDS-2009D is designed as a flexible system that uses, depending on the input data for an individual, various elements of system databases to provide the dosimetric variables requested by the user. Several phases are included in the computation schedule. The first phase includes calculations with use of a common protocol for all cohort members based on village-average-intake functions and external dose rates; individual data on age, gender and history of residence are included in the first phase. This phase results in dose estimates similar to those obtained with system TRDS-2000 used previously to derive risks of health effects in the Techa River Cohort. The second phase includes refinement of individual internal doses for those persons who have had body-burden measurements or exposure parameters specific to the household where he/she lived on the Techa River. The third phase includes summation of individual doses from environmental exposure and from radiological examinations. The results of TRDS-2009D dose calculations have demonstrated for the ETRC members on average a moderate increase in RBM dose estimates (34%) and a minor increase (5%) in estimates of stomach dose. The calculations for the members of the ETROC indicated similar small changes for stomach, but significant increase in RBM doses (400%). Individual-dose assessments performed with use of TRDS-2009D have been provided to epidemiologists for exploratory risk analysis in the ETRC and ETROC. These data provide an opportunity to evaluate the possible impact on radiogenic risk of such factors as confounding exposure (environmental and medical), changes in the Techa River source
GPU-based fast Monte Carlo simulation for radiotherapy dose calculation.
Jia, Xun; Gu, Xuejun; Graves, Yan Jiang; Folkerts, Michael; Jiang, Steve B
2011-11-21
Monte Carlo (MC) simulation is commonly considered to be the most accurate dose calculation method in radiotherapy. However, its efficiency still requires improvement for many routine clinical applications. In this paper, we present our recent progress toward the development of a graphics processing unit (GPU)-based MC dose calculation package, gDPM v2.0. It utilizes the parallel computation ability of a GPU to achieve high efficiency, while maintaining the same particle transport physics as in the original dose planning method (DPM) code and hence the same level of simulation accuracy. In GPU computing, divergence of execution paths between threads can considerably reduce the efficiency. Since photons and electrons undergo different physics and hence attain different execution paths, we use a simulation scheme where photon transport and electron transport are separated to partially relieve the thread divergence issue. A high-performance random number generator and a hardware linear interpolation are also utilized. We have also developed various components to handle the fluence map and linac geometry, so that gDPM can be used to compute dose distributions for realistic IMRT or VMAT treatment plans. Our gDPM package is tested for its accuracy and efficiency in both phantoms and realistic patient cases. In all cases, the average relative uncertainties are less than 1%. A statistical t-test is performed and the dose difference between the CPU and the GPU results is not found to be statistically significant in over 96% of the high dose region and over 97% of the entire region. Speed-up factors of 69.1 ∼ 87.2 have been observed using an NVIDIA Tesla C2050 GPU card against a 2.27 GHz Intel Xeon CPU processor. For realistic IMRT and VMAT plans, MC dose calculation can be completed with less than 1% standard deviation in 36.1 ∼ 39.6 s using gDPM.
Calculation of mean central dose in interstitial brachytherapy using Delaunay triangulation.
Astrahan, M A; Streeter, O E; Jozsef, G
2001-06-01
In 1997 the ICRU published Report 58 "Dose and Volume Specification for Reporting Interstitial Therapy" with the objective of addressing the problem of absorbed dose specification for reporting contemporary interstitial therapy. One of the concepts proposed in that report is "mean central dose." The fundamental goal of the mean central dose (MCD) calculation is to obtain a single, readily reportable and intercomparable value which is representative of dose in regions of the implant "where the dose gradient approximates a plateau." Delaunay triangulation (DT) is a method used in computational geometry to partition the space enclosed by the convex hull of a set of distinct points P into a set of nonoverlapping cells. In the three-dimensional case, each point of P becomes a vertex of a tetrahedron and the result of the DT is a set of tetrahedra. All treatment planning for interstitial brachytherapy inherently requires that the location of the radioactive sources, or dwell positions in the case of HDR, be known or digitized. These source locations may be regarded as a set of points representing the implanted volume. Delaunay triangulation of the source locations creates a set of tetrahedra without manual intervention. The geometric centers of these tetrahedra define a new set of points which lie "in between" the radioactive sources and which are distributed uniformly over the volume of the implant. The arithmetic mean of the dose at these centers is a three dimensional analog of the two-dimensional triangulation and inspection methods proposed for calculating MCD in ICRU 58. We demonstrate that DT can be successfully incorporated into a computerized treatment planning system and used to calculate the MCD.
GPU-based fast Monte Carlo dose calculation for proton therapy.
Jia, Xun; Schümann, Jan; Paganetti, Harald; Jiang, Steve B
2012-12-07
Accurate radiation dose calculation is essential for successful proton radiotherapy. Monte Carlo (MC) simulation is considered to be the most accurate method. However, the long computation time limits it from routine clinical applications. Recently, graphics processing units (GPUs) have been widely used to accelerate computationally intensive tasks in radiotherapy. We have developed a fast MC dose calculation package, gPMC, for proton dose calculation on a GPU. In gPMC, proton transport is modeled by the class II condensed history simulation scheme with a continuous slowing down approximation. Ionization, elastic and inelastic proton nucleus interactions are considered. Energy straggling and multiple scattering are modeled. Secondary electrons are not transported and their energies are locally deposited. After an inelastic nuclear interaction event, a variety of products are generated using an empirical model. Among them, charged nuclear fragments are terminated with energy locally deposited. Secondary protons are stored in a stack and transported after finishing transport of the primary protons, while secondary neutral particles are neglected. gPMC is implemented on the GPU under the CUDA platform. We have validated gPMC using the TOPAS/Geant4 MC code as the gold standard. For various cases including homogeneous and inhomogeneous phantoms as well as a patient case, good agreements between gPMC and TOPAS/Geant4 are observed. The gamma passing rate for the 2%/2 mm criterion is over 98.7% in the region with dose greater than 10% maximum dose in all cases, excluding low-density air regions. With gPMC it takes only 6-22 s to simulate 10 million source protons to achieve ∼1% relative statistical uncertainty, depending on the phantoms and energy. This is an extremely high efficiency compared to the computational time of tens of CPU hours for TOPAS/Geant4. Our fast GPU-based code can thus facilitate the routine use of MC dose calculation in proton therapy.
Calculation of residence times and radiation doses using the standard PC software Excel.
Herzog, H; Zilken, H; Niederbremer, A; Friedrich, W; Müller-Gärtner, H W
1997-12-01
We developed a program which aims to facilitate the calculation of radiation doses to single organs and the whole body. IMEDOSE uses Excel to include calculations, graphical displays, and interactions with the user in a single general-purpose PC software tool. To start the procedure the input data are copied into a spreadsheet. They must represent percentage uptake values of several organs derived from measurements in animals or humans. To extrapolate these data up to seven half-lives of the radionuclide, fitting to one or two exponentional functions is included and can be checked by the user. By means of the approximate time-activity information the cumulated activity or residence times are calculated. Finally these data are combined with the absorbed fraction doses (S-values) given by MIRD pamphlet No. 11 to yield radiation doses, the effective dose equivalent and the effective dose. These results are presented in a final table. Interactions are realized with push-buttons and drop-down menus. Calculations use the Visual Basic tool of Excel. In order to test our program, biodistribution data of fluorine-18 fluorodeoxyglucose were taken from the literature (Meija et al., J Nucl Med 1991; 32:699-706). For a 70-kg adult the resulting radiation doses of all target organs listed in MIRD 11 were different from the ICRP 53 values by 1%+/-18% on the average. When the residence times were introduced into MIRDOSE3 (Stabin, J Nucl Med 1996; 37:538-546) the mean difference between our results and those of MIRDOSE3 was -3%+/-6%. Both outcomes indicate the validity of the present approach.
Neutron spectra and dose equivalents calculated in tissue for high-energy radiation therapy
Energy Technology Data Exchange (ETDEWEB)
Kry, Stephen F.; Howell, Rebecca M.; Salehpour, Mohammad; Followill, David S. [Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States)
2009-04-15
Neutrons are by-products of high-energy radiation therapy and a source of dose to normal tissues. Thus, the presence of neutrons increases a patient's risk of radiation-induced secondary cancer. Although neutrons have been thoroughly studied in air, little research has been focused on neutrons at depths in the patient where radiosensitive structures may exist, resulting in wide variations in neutron dose equivalents between studies. In this study, we characterized properties of neutrons produced during high-energy radiation therapy as a function of their depth in tissue and for different field sizes and different source-to-surface distances (SSD). We used a previously developed Monte Carlo model of an accelerator operated at 18 MV to calculate the neutron fluences, energy spectra, quality factors, and dose equivalents in air and in tissue at depths ranging from 0.1 to 25 cm. In conjunction with the sharply decreasing dose equivalent with increased depth in tissue, the authors found that the neutron energy spectrum changed drastically as a function of depth in tissue. The neutron fluence decreased gradually as the depth increased, while the average neutron energy decreased sharply with increasing depth until a depth of approximately 7.5 cm in tissue, after which it remained nearly constant. There was minimal variation in the quality factor as a function of depth. At a given depth in tissue, the neutron dose equivalent increased slightly with increasing field size and decreasing SSD; however, the percentage depth-dose equivalent curve remained constant outside the primary photon field. Because the neutron dose equivalent, fluence, and energy spectrum changed substantially with depth in tissue, we concluded that when the neutron dose equivalent is being determined at a depth within a patient, the spectrum and quality factor used should be appropriate for depth rather than for in-air conditions. Alternately, an appropriate percent depth-dose equivalent curve
Bagnasco, Annamaria; Galaverna, Lucia; Aleo, Giuseppe; Grugnetti, Anna Maria; Rosa, Francesca; Sasso, Loredana
2016-01-01
In the literature we found many studies that confirmed our concerns about nursing students' poor maths skills that directly impact on their ability to correctly calculate drug dosages with very serious consequences for patient safety. The aim of our study was to explore where students had most difficulty and identify appropriate educational interventions to bridge their mathematical knowledge gaps. This was a quali-quantitative descriptive study that included a sample of 726 undergraduate nursing students. We identified exactly where students had most difficulty and identified appropriate educational interventions to bridge their mathematical knowledge gaps. We found that the undergraduate nursing students mainly had difficulty with basic maths principles. Specific learning interventions are needed to improve their basic maths skills and their dosage calculation skills. For this purpose, we identified safeMedicate and eDose (Authentic World Ltd.), only that they are only available in English. In the near future we hope to set up a partnership to work together on the Italian version of these tools.
Absorbed Dose Calculations Using Mesh-based Human Phantoms And Monte Carlo Methods
Kramer, Richard
2011-08-01
Health risks attributable to the exposure to ionizing radiation are considered to be a function of the absorbed or equivalent dose to radiosensitive organs and tissues. However, as human tissue cannot express itself in terms of equivalent dose, exposure models have to be used to determine the distribution of equivalent dose throughout the human body. An exposure model, be it physical or computational, consists of a representation of the human body, called phantom, plus a method for transporting ionizing radiation through the phantom and measuring or calculating the equivalent dose to organ and tissues of interest. The FASH2 (Female Adult meSH) and the MASH2 (Male Adult meSH) computational phantoms have been developed at the University of Pernambuco in Recife/Brazil based on polygon mesh surfaces using open source software tools and anatomical atlases. Representing standing adults, FASH2 and MASH2 have organ and tissue masses, body height and body mass adjusted to the anatomical data published by the International Commission on Radiological Protection for the reference male and female adult. For the purposes of absorbed dose calculations the phantoms have been coupled to the EGSnrc Monte Carlo code, which can transport photons, electrons and positrons through arbitrary media. This paper reviews the development of the FASH2 and the MASH2 phantoms and presents dosimetric applications for X-ray diagnosis and for prostate brachytherapy.
PCXMC, a Monte Carlo program for calculating patient doses in medical x-ray examinations
Energy Technology Data Exchange (ETDEWEB)
Tapiovaara, M.; Siiskonen, T.
2008-11-15
PCXMC is a Monte Carlo program for calculating patients' organ doses and effective doses in medical x-ray examinations. The organs and tissues considered in the program are: active bone marrow, adrenals, brain, breasts, colon (upper and lower large intestine), extrathoracic airways, gall bladder, heart, kidneys, liver, lungs, lymph nodes, muscle, oesophagus, oral mucosa, ovaries, pancreas, prostate, salivary glands, skeleton, skin, small intestine, spleen, stomach, testicles, thymus, thyroid, urinary bladder and uterus. The program calculates the effective dose with both the present tissue weighting factors of ICRP Publication 103 (2007) and the old tissue weighting factors of ICRP Publication 60 (1991). The anatomical data are based on the mathematical hermaphrodite phantom models of Cristy and Eckerman (1987), which describe patients of six different ages: new-born, 1, 5, 10, 15-year-old and adult patients. Some changes are made to these phantoms in order to make them more realistic for external irradiation conditions and to enable the calculation of the effective dose according to the new ICRP Publication 103 tissue weighting factors. The phantom sizes are adjustable to mimic patients of an arbitrary weight and height. PCXMC allows a free adjustment of the x-ray beam projection and other examination conditions of projection radiography and fluoroscopy
A fourier analysis on the maximum acceptable grid size for discrete proton beam dose calculation.
Li, Haisen S; Romeijn, H Edwin; Dempsey, James F
2006-09-01
We developed an analytical method for determining the maximum acceptable grid size for discrete dose calculation in proton therapy treatment plan optimization, so that the accuracy of the optimized dose distribution is guaranteed in the phase of dose sampling and the superfluous computational work is avoided. The accuracy of dose sampling was judged by the criterion that the continuous dose distribution could be reconstructed from the discrete dose within a 2% error limit. To keep the error caused by the discrete dose sampling under a 2% limit, the dose grid size cannot exceed a maximum acceptable value. The method was based on Fourier analysis and the Shannon-Nyquist sampling theorem as an extension of our previous analysis for photon beam intensity modulated radiation therapy [J. F. Dempsey, H. E. Romeijn, J. G. Li, D. A. Low, and J. R. Palta, Med. Phys. 32, 380-388 (2005)]. The proton beam model used for the analysis was a near monoenergetic (of width about 1% the incident energy) and monodirectional infinitesimal (nonintegrated) pencil beam in water medium. By monodirection, we mean that the proton particles are in the same direction before entering the water medium and the various scattering prior to entrance to water is not taken into account. In intensity modulated proton therapy, the elementary intensity modulation entity for proton therapy is either an infinitesimal or finite sized beamlet. Since a finite sized beamlet is the superposition of infinitesimal pencil beams, the result of the maximum acceptable grid size obtained with infinitesimal pencil beam also applies to finite sized beamlet. The analytic Bragg curve function proposed by Bortfeld [T. Bortfeld, Med. Phys. 24, 2024-2033 (1997)] was employed. The lateral profile was approximated by a depth dependent Gaussian distribution. The model included the spreads of the Bragg peak and the lateral profiles due to multiple Coulomb scattering. The dependence of the maximum acceptable dose grid size on the
Development of CT scanner models for patient organ dose calculations using Monte Carlo methods
Gu, Jianwei
CT scanner models in this dissertation were versatile and accurate tools for estimating dose to different patient phantoms undergoing various CT procedures. The organ doses from kV and MV CBCT were also calculated. This dissertation finally summarizes areas where future research can be performed including MV CBCT further validation and application, dose reporting software and image and dose correlation study.
Patient-specific Monte Carlo dose calculations for 103Pd breast brachytherapy
Miksys, N.; Cygler, J. E.; Caudrelier, J. M.; Thomson, R. M.
2016-04-01
This work retrospectively investigates patient-specific Monte Carlo (MC) dose calculations for 103Pd permanent implant breast brachytherapy, exploring various necessary assumptions for deriving virtual patient models: post-implant CT image metallic artifact reduction (MAR), tissue assignment schemes (TAS), and elemental tissue compositions. Three MAR methods (thresholding, 3D median filter, virtual sinogram) are applied to CT images; resulting images are compared to each other and to uncorrected images. Virtual patient models are then derived by application of different TAS ranging from TG-186 basic recommendations (mixed adipose and gland tissue at uniform literature-derived density) to detailed schemes (segmented adipose and gland with CT-derived densities). For detailed schemes, alternate mass density segmentation thresholds between adipose and gland are considered. Several literature-derived elemental compositions for adipose, gland and skin are compared. MC models derived from uncorrected CT images can yield large errors in dose calculations especially when used with detailed TAS. Differences in MAR method result in large differences in local doses when variations in CT number cause differences in tissue assignment. Between different MAR models (same TAS), PTV {{D}90} and skin {{D}1~\\text{c{{\\text{m}}3}}} each vary by up to 6%. Basic TAS (mixed adipose/gland tissue) generally yield higher dose metrics than detailed segmented schemes: PTV {{D}90} and skin {{D}1~\\text{c{{\\text{m}}3}}} are higher by up to 13% and 9% respectively. Employing alternate adipose, gland and skin elemental compositions can cause variations in PTV {{D}90} of up to 11% and skin {{D}1~\\text{c{{\\text{m}}3}}} of up to 30%. Overall, AAPM TG-43 overestimates dose to the PTV ({{D}90} on average 10% and up to 27%) and underestimates dose to the skin ({{D}1~\\text{c{{\\text{m}}3}}} on average 29% and up to 48%) compared to the various MC models derived using the post-MAR CT images studied
Doucet, R.; Olivares, M.; DeBlois, F.; Podgorsak, E. B.; Kawrakow, I.; Seuntjens, J.
2003-08-01
Calculations of dose distributions in heterogeneous phantoms in clinical electron beams, carried out using the fast voxel Monte Carlo (MC) system XVMC and the conventional MC code EGSnrc, were compared with measurements. Irradiations were performed using the 9 MeV and 15 MeV beams from a Varian Clinac-18 accelerator with a 10 × 10 cm2 applicator and an SSD of 100 cm. Depth doses were measured with thermoluminescent dosimetry techniques (TLD 700) in phantoms consisting of slabs of Solid WaterTM (SW) and bone and slabs of SW and lung tissue-equivalent materials. Lateral profiles in water were measured using an electron diode at different depths behind one and two immersed aluminium rods. The accelerator was modelled using the EGS4/BEAM system and optimized phase-space files were used as input to the EGSnrc and the XVMC calculations. Also, for the XVMC, an experiment-based beam model was used. All measurements were corrected by the EGSnrc-calculated stopping power ratios. Overall, there is excellent agreement between the corrected experimental and the two MC dose distributions. Small remaining discrepancies may be due to the non-equivalence between physical and simulated tissue-equivalent materials and to detector fluence perturbation effect correction factors that were calculated for the 9 MeV beam at selected depths in the heterogeneous phantoms.
Energy Technology Data Exchange (ETDEWEB)
Doucet, R [Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Ave Cedar, Montreal H3G 1A4 (Canada); Olivares, M [Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Ave Cedar, Montreal H3G 1A4 (Canada); DeBlois, F [Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Ave Cedar, Montreal H3G 1A4 (Canada); Podgorsak, E B [Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Ave Cedar, Montreal H3G 1A4 (Canada); Kawrakow, I [National Research Council Canada, Ionizing Radiation Standards Group, Ottawa K1A 0R6, Canada (Canada); Seuntjens, J [Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Ave Cedar, Montreal H3G 1A4 (Canada)
2003-08-07
Calculations of dose distributions in heterogeneous phantoms in clinical electron beams, carried out using the fast voxel Monte Carlo (MC) system XVMC and the conventional MC code EGSnrc, were compared with measurements. Irradiations were performed using the 9 MeV and 15 MeV beams from a Varian Clinac-18 accelerator with a 10 x 10 cm{sup 2} applicator and an SSD of 100 cm. Depth doses were measured with thermoluminescent dosimetry techniques (TLD 700) in phantoms consisting of slabs of Solid Water{sup TM} (SW) and bone and slabs of SW and lung tissue-equivalent materials. Lateral profiles in water were measured using an electron diode at different depths behind one and two immersed aluminium rods. The accelerator was modelled using the EGS4/BEAM system and optimized phase-space files were used as input to the EGSnrc and the XVMC calculations. Also, for the XVMC, an experiment-based beam model was used. All measurements were corrected by the EGSnrc-calculated stopping power ratios. Overall, there is excellent agreement between the corrected experimental and the two MC dose distributions. Small remaining discrepancies may be due to the non-equivalence between physical and simulated tissue-equivalent materials and to detector fluence perturbation effect correction factors that were calculated for the 9 MeV beam at selected depths in the heterogeneous phantoms.
Results of 1 year of clinical experience with independent dose calculation software for VMAT fields
Directory of Open Access Journals (Sweden)
Juan Fernando Mata Colodro
2014-01-01
Full Text Available It is widely accepted that a redundant independent dose calculation (RIDC must be included in any treatment planning verification procedure. Specifically, volumetric modulated arc therapy (VMAT technique implies a comprehensive quality assurance (QA program in which RIDC should be included. In this paper, the results obtained in 1 year of clinical experience are presented. Eclipse from Varian is the treatment planning system (TPS, here in use. RIDC were performed with the commercial software; Diamond ® (PTW which is capable of calculating VMAT fields. Once the plan is clinically accepted, it is exported via Digital Imaging and Communications in Medicine (DICOM to RIDC, together with the body contour, and then a point dose calculation is performed, usually at the isocenter. A total of 459 plans were evaluated. The total average deviation was -0.3 ± 1.8% (one standard deviation (1SD. For higher clearance the plans were grouped by location in: Prostate, pelvis, abdomen, chest, head and neck, brain, stereotactic radiosurgery, lung stereotactic body radiation therapy, and miscellaneous. The highest absolute deviation was -0.8 ± 1.5% corresponding to the prostate. A linear fit between doses calculated by RIDC and by TPS produced a correlation coefficient of 0.9991 and a slope of 1.0023. These results are very close to those obtained in the validation process. This agreement led us to consider this RIDC software as a valuable tool for QA in VMAT plans.
Results of 1 year of clinical experience with independent dose calculation software for VMAT fields.
Colodro, Juan Fernando Mata; Berna, Alfredo Serna; Puchades, Vicente Puchades; Amores, David Ramos; Baños, Miguel Alcaraz
2014-10-01
It is widely accepted that a redundant independent dose calculation (RIDC) must be included in any treatment planning verification procedure. Specifically, volumetric modulated arc therapy (VMAT) technique implies a comprehensive quality assurance (QA) program in which RIDC should be included. In this paper, the results obtained in 1 year of clinical experience are presented. Eclipse from Varian is the treatment planning system (TPS), here in use. RIDC were performed with the commercial software; Diamond(®) (PTW) which is capable of calculating VMAT fields. Once the plan is clinically accepted, it is exported via Digital Imaging and Communications in Medicine (DICOM) to RIDC, together with the body contour, and then a point dose calculation is performed, usually at the isocenter. A total of 459 plans were evaluated. The total average deviation was -0.3 ± 1.8% (one standard deviation (1SD)). For higher clearance the plans were grouped by location in: Prostate, pelvis, abdomen, chest, head and neck, brain, stereotactic radiosurgery, lung stereotactic body radiation therapy, and miscellaneous. The highest absolute deviation was -0.8 ± 1.5% corresponding to the prostate. A linear fit between doses calculated by RIDC and by TPS produced a correlation coefficient of 0.9991 and a slope of 1.0023. These results are very close to those obtained in the validation process. This agreement led us to consider this RIDC software as a valuable tool for QA in VMAT plans.
Modulation index for VMAT considering both mechanical and dose calculation uncertainties
Park, Jong Min; Park, So-Yeon; Kim, Hyoungnyoun
2015-09-01
The aim of this study is to present a modulation index considering both mechanical and dose calculation uncertainties for volumetric modulated arc therapy (VMAT). As a modulation index considering only mechanical uncertainty of VMAT, MIt has been previously suggested. In this study, we developed a weighting factor which represents dose calculation uncertainty based on the aperture shapes of fluence maps at every control point of VMAT plans. In order to calculate the weighting factor, the thinning algorithm of image processing techniques was applied to measure field aperture irregularity. By combining this weighting factor with the previously suggested modulation index, MIt, comprehensive modulation index (MIc) was designed. To evaluate the performance of MIc, gamma passing rates, differences in mechanical parameters between plans and log files and differences in dose-volume parameters between plans and the plans reconstructed from log files were acquired with a total of 52 VMAT plans. Spearman’s correlation coefficients (rs) between the values of MIc and measures of VMAT delivery accuracy were calculated. The rs values of MIc (f = 0.5) to global gamma passing rates with 2%/2 mm, 1%/2 mm and 2%/1 mm were -0.728,-0.847 and -0.617, respectively (p VMAT delivery accuracy showing strong correlations to various measures of VMAT delivery accuracy.
Clouvas, A; Antonopoulos-Domis, M; Silva, J
2000-01-01
The dose rate conversion factors D/sub CF/ (absorbed dose rate in air per unit activity per unit of soil mass, nGy h/sup -1/ per Bq kg/sup -1/) are calculated 1 m above ground for photon emitters of natural radionuclides uniformly distributed in the soil. Three Monte Carlo codes are used: 1) The MCNP code of Los Alamos; 2) The GEANT code of CERN; and 3) a Monte Carlo code developed in the Nuclear Technology Laboratory of the Aristotle University of Thessaloniki. The accuracy of the Monte Carlo results is tested by the comparison of the unscattered flux obtained by the three Monte Carlo codes with an independent straightforward calculation. All codes and particularly the MCNP calculate accurately the absorbed dose rate in air due to the unscattered radiation. For the total radiation (unscattered plus scattered) the D/sub CF/ values calculated from the three codes are in very good agreement between them. The comparison between these results and the results deduced previously by other authors indicates a good ag...
Mizutani, Shohei; Takada, Yoshihisa; Kohno, Ryosuke; Hotta, Kenji; Tansho, Ryohei; Akimoto, Tetsuo
2016-03-01
Full Monte Carlo (FMC) calculation of dose distribution has been recognized to have superior accuracy, compared with the pencil beam algorithm (PBA). However, since the FMC methods require long calculation time, it is difficult to apply them to routine treatment planning at present. In order to improve the situation, a simplified Monte Carlo (SMC) method has been introduced to the dose kernel calculation applicable to dose optimization procedure for the proton pencil beam scanning. We have evaluated accuracy of the SMC calculation by comparing a result of the dose kernel calculation using the SMC method with that using the FMC method in an inhomogeneous phantom. The dose distribution obtained by the SMC method was in good agreement with that obtained by the FMC method. To assess the usefulness of SMC calculation in clinical situations, we have compared results of the dose calculation using the SMC with those using the PBA method for three clinical cases of tumor treatment. The dose distributions calculated with the PBA dose kernels appear to be homogeneous in the planning target volumes (PTVs). In practice, the dose distributions calculated with the SMC dose kernels with the spot weights optimized with the PBA method show largely inhomogeneous dose distributions in the PTVs, while those with the spot weights optimized with the SMC method have moderately homogeneous distributions in the PTVs. Calculation using the SMC method is faster than that using the GEANT4 by three orders of magnitude. In addition, the graphic processing unit (GPU) boosts the calculation speed by 13 times for the treatment planning using the SMC method. Thence, the SMC method will be applicable to routine clinical treatment planning for reproduction of the complex dose distribution more accurately than the PBA method in a reasonably short time by use of the GPU-based calculation engine. PACS number(s): 87.55.Gh.
Directory of Open Access Journals (Sweden)
Hassan Ranjbar
2010-06-01
Full Text Available Introduction: Secondary radiation such as photoelectrons, Auger electrons and characteristic radiations cause a local boost in dose for a tumor when irradiated with an external X-ray beam after being loaded with elements capable of activating the tumor, e.g.; I and Gd. Materials and Methods: In this investigation, the MCNPX code was used for simulation and calculation of dose enhancement factor for a tumor loaded with activating elements. The designed model comprised the X-ray source, phantom (target tissue and loaded tumor with activating agent, detector, interactions modeling and results. The source was defined as monochromatic and plane surface situated at 50 cm (z = 50. Phantom geometry was a 10 × 10 × 10 cm3 cube centered at (0, 0, 0 with a 2.2 × 2.2 × 2.2 cm3 cubic tumor with a center located at 3 cm depth inside the phantom Results: Dose enhancement factor and optimum energy in radiotherapy are evaluated using the photon activation therapy method. Result show that the dose enhancement factor increases with activating concentration in the tumor. The maximum dose enhancement factor for iodine in the tumor occurs for photons in the energy range of 50-60 keV. Dose uniformity is less for lower energy photons within the activated region inside the tumor. Results indicate that the dose enhancement factor varies linearly with the activating concentration agent. Discussion and Conclusion: In this study, the obtained results point out a considerable enhancement in dose in the presence of activating agents in the tumor regions.
The Evaluation of Skin Toxicity during Brain Tumor Irradiation Dose Calculation
Directory of Open Access Journals (Sweden)
Oxana A. Pashkovskaya
2013-12-01
Full Text Available Background: Radiotherapy is the keystone in brain tumor treatment, including posterior fossa tumors, and can achieve better patient health-related quality of life. Radiation exposure can be associated with the risk of skin radiation injuries. Accurate tumor and critical structure delineations and precise dose planning may improve the outcomes and decrease radiation complications. The objective of this study was to compare the influence of the headrest and treatment couch during dose planning, on the dose distributions and skin injury post irradiation. Material and Methods: Treatment planning calculations were performed for 14 brain tumor patients using the volumetric modulated arc therapy (VMAT to study the dose distribution and dose-volume histograms (DVH. We compared the following three cases of general patient contours: patient body contour alone, body contour including the headrest, and body contour with headrest, couch and immobilization mask. The same configuration beams were used in all these cases; general patient contours alone were altered. Results: For dose estimations, the skin was delineated as a 2 mm layer beneath the patient’s body contour. The comparisons showed that the average dose on the skin, among all the patients included in this study, in the case of body contour alone is 3.3 Gy, whereas in the case of body contour with headrest, it is 6.3 Gy and in the case of body contour with headrest, couch and immobilization mask it is 9.4 Gy. Conclusion: For brain tumors, located in the posterior fossa and near the patient’s skin, the skin needed to be included as a critical structure. The skin dose should be considered when evaluating treatment plans, taking into account the bolus effect of the headrest and couch.
DEFF Research Database (Denmark)
Christensen, Erik R.; Kusk, Kresten Ole; Nyholm, Niels
2009-01-01
% inhibition). For illustration, data from closed, freshwater algal assays are analyzed using the green alga Pseudokirchneriella subcapitata with growth rate as the response parameter. Dose-response regressions for four test chemicals (tetraethylammonium bromide, musculamine, benzonitrile, and 4......-4-(trifluoromethyl)phenoxy-phenol) with ranges of representative slopes at 50% response (0.54-2.62) and EC50s (2.20-357 mg/L) were selected. Reference EC50s and EC10s with 95% confidence limits using probit or Weibull models are calculated by nonlinear regression on the whole dataset using a dose - response......We derive equations for the effective concentration giving 10% inhibition (EC10) with 95% confidence limits for probit (log-normal), Weibull, and logistic dose -responsemodels on the basis of experimentally derived median effective concentrations (EC50s) and the curve slope at the central point (50...
A comparison of measured and calculated organ doses from CT examinations
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Calzado, A.; Ruiz Sanz, S.; Melchor, M.; Vano, E. [Universidad Complutense, Madrid (Spain). Facultad de Medicina
1995-12-31
Organ doses from a set of frequent CT examinations have been estimated from measurements in a physical anthropomorphic phantom (Remab system) by using thermoluminescence dosemeters. For the same examination techniques, organ dose coefficients (taken from the literature) obtained by Monte Carlo techniques and using mathematical phantoms. The results arrived at by the two methods are compared, trying to explain the most significant differences and their influence on the estimated values of effective dose. The experimental and calculated outcomes from such simulations are also compared to the mean dosimetric results on patients from a 1991 regional survey of CT practice in the area of Madrid. Some comments about the complementary use of information coming from both methods are made. (Author).
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Fogliata, Antonella; Nicolini, Giorgia; Clivio, Alessandro; Vanetti, Eugenio; Cozzi, Luca [Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona (Switzerland); Mancosu, Pietro, E-mail: afc@iosi.ch [Istituto Clinico Humanitas, Radio-Oncology Department, Milan-Rozzano (Italy)
2011-03-21
A new algorithm, Acuros (registered) XB Advanced Dose Calculation, has been introduced by Varian Medical Systems in the Eclipse planning system for photon dose calculation in external radiotherapy. Acuros XB is based on the solution of the linear Boltzmann transport equation (LBTE). The LBTE describes the macroscopic behaviour of radiation particles as they travel through and interact with matter. The implementation of Acuros XB in Eclipse has not been assessed; therefore, it is necessary to perform these pre-clinical validation tests to determine its accuracy. This paper summarizes the results of comparisons of Acuros XB calculations against measurements and calculations performed with a previously validated dose calculation algorithm, the Anisotropic Analytical Algorithm (AAA). The tasks addressed in this paper are limited to the fundamental characterization of Acuros XB in water for simple geometries. Validation was carried out for four different beams: 6 and 15 MV beams from a Varian Clinac 2100 iX, and 6 and 10 MV 'flattening filter free' (FFF) beams from a TrueBeam linear accelerator. The TrueBeam FFF are new beams recently introduced in clinical practice on general purpose linear accelerators and have not been previously reported on. Results indicate that Acuros XB accurately reproduces measured and calculated (with AAA) data and only small deviations were observed for all the investigated quantities. In general, the overall degree of accuracy for Acuros XB in simple geometries can be stated to be within 1% for open beams and within 2% for mechanical wedges. The basic validation of the Acuros XB algorithm was therefore considered satisfactory for both conventional photon beams as well as for FFF beams of new generation linacs such as the Varian TrueBeam.
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Tajaldeen, A [RMIT university, Docklands, Vic (Australia); Ramachandran, P [Peter MacCallum Cancer Centre, Bendigo (Australia); Geso, M [RMIT University, Bundoora, Melbourne (Australia)
2015-06-15
Purpose: The purpose of this study was to investigate and quantify the variation in dose distributions in small field lung cancer radiotherapy using seven different dose calculation algorithms. Methods: The study was performed in 21 lung cancer patients who underwent Stereotactic Ablative Body Radiotherapy (SABR). Two different methods (i) Same dose coverage to the target volume (named as same dose method) (ii) Same monitor units in all algorithms (named as same monitor units) were used for studying the performance of seven different dose calculation algorithms in XiO and Eclipse treatment planning systems. The seven dose calculation algorithms include Superposition, Fast superposition, Fast Fourier Transform ( FFT) Convolution, Clarkson, Anisotropic Analytic Algorithm (AAA), Acurous XB and pencil beam (PB) algorithms. Prior to this, a phantom study was performed to assess the accuracy of these algorithms. Superposition algorithm was used as a reference algorithm in this study. The treatment plans were compared using different dosimetric parameters including conformity, heterogeneity and dose fall off index. In addition to this, the dose to critical structures like lungs, heart, oesophagus and spinal cord were also studied. Statistical analysis was performed using Prism software. Results: The mean±stdev with conformity index for Superposition, Fast superposition, Clarkson and FFT convolution algorithms were 1.29±0.13, 1.31±0.16, 2.2±0.7 and 2.17±0.59 respectively whereas for AAA, pencil beam and Acurous XB were 1.4±0.27, 1.66±0.27 and 1.35±0.24 respectively. Conclusion: Our study showed significant variations among the seven different algorithms. Superposition and AcurosXB algorithms showed similar values for most of the dosimetric parameters. Clarkson, FFT convolution and pencil beam algorithms showed large differences as compared to superposition algorithms. Based on our study, we recommend Superposition and AcurosXB algorithms as the first choice of
GPU-based Monte Carlo radiotherapy dose calculation using phase-space sources
Townson, Reid W.; Jia, Xun; Tian, Zhen; Jiang Graves, Yan; Zavgorodni, Sergei; Jiang, Steve B.
2013-06-01
A novel phase-space source implementation has been designed for graphics processing unit (GPU)-based Monte Carlo dose calculation engines. Short of full simulation of the linac head, using a phase-space source is the most accurate method to model a clinical radiation beam in dose calculations. However, in GPU-based Monte Carlo dose calculations where the computation efficiency is very high, the time required to read and process a large phase-space file becomes comparable to the particle transport time. Moreover, due to the parallelized nature of GPU hardware, it is essential to simultaneously transport particles of the same type and similar energies but separated spatially to yield a high efficiency. We present three methods for phase-space implementation that have been integrated into the most recent version of the GPU-based Monte Carlo radiotherapy dose calculation package gDPM v3.0. The first method is to sequentially read particles from a patient-dependent phase-space and sort them on-the-fly based on particle type and energy. The second method supplements this with a simple secondary collimator model and fluence map implementation so that patient-independent phase-space sources can be used. Finally, as the third method (called the phase-space-let, or PSL, method) we introduce a novel source implementation utilizing pre-processed patient-independent phase-spaces that are sorted by particle type, energy and position. Position bins located outside a rectangular region of interest enclosing the treatment field are ignored, substantially decreasing simulation time with little effect on the final dose distribution. The three methods were validated in absolute dose against BEAMnrc/DOSXYZnrc and compared using gamma-index tests (2%/2 mm above the 10% isodose). It was found that the PSL method has the optimal balance between accuracy and efficiency and thus is used as the default method in gDPM v3.0. Using the PSL method, open fields of 4 × 4, 10 × 10 and 30 × 30 cm
GPU-based Monte Carlo radiotherapy dose calculation using phase-space sources.
Townson, Reid W; Jia, Xun; Tian, Zhen; Graves, Yan Jiang; Zavgorodni, Sergei; Jiang, Steve B
2013-06-21
A novel phase-space source implementation has been designed for graphics processing unit (GPU)-based Monte Carlo dose calculation engines. Short of full simulation of the linac head, using a phase-space source is the most accurate method to model a clinical radiation beam in dose calculations. However, in GPU-based Monte Carlo dose calculations where the computation efficiency is very high, the time required to read and process a large phase-space file becomes comparable to the particle transport time. Moreover, due to the parallelized nature of GPU hardware, it is essential to simultaneously transport particles of the same type and similar energies but separated spatially to yield a high efficiency. We present three methods for phase-space implementation that have been integrated into the most recent version of the GPU-based Monte Carlo radiotherapy dose calculation package gDPM v3.0. The first method is to sequentially read particles from a patient-dependent phase-space and sort them on-the-fly based on particle type and energy. The second method supplements this with a simple secondary collimator model and fluence map implementation so that patient-independent phase-space sources can be used. Finally, as the third method (called the phase-space-let, or PSL, method) we introduce a novel source implementation utilizing pre-processed patient-independent phase-spaces that are sorted by particle type, energy and position. Position bins located outside a rectangular region of interest enclosing the treatment field are ignored, substantially decreasing simulation time with little effect on the final dose distribution. The three methods were validated in absolute dose against BEAMnrc/DOSXYZnrc and compared using gamma-index tests (2%/2 mm above the 10% isodose). It was found that the PSL method has the optimal balance between accuracy and efficiency and thus is used as the default method in gDPM v3.0. Using the PSL method, open fields of 4 × 4, 10 × 10 and 30 × 30 cm
The calculation of radial dose from heavy ions: predictions of biological action cross sections
Katz, Robert; Cucinotta, Francis A.; Zhang, C. X.
1996-02-01
The track structure model of heavy ion cross sections was developed by Katz and co-workers in the 1960s. In this model the action cross section is evaluated by mapping the dose-response of a detector to γ rays (modeled from biological target theory) onto the radial dose distribution from δ rays about the path of the ion. This is taken to yield the radial distribution of probability for a "hit" (an interaction leading to an observable end-point). Radial integration of the probability yields the cross section. When different response from ions of different Z having the same stopping power is observed this model may be indicated. Since the 1960s there have been several developments in the computation of the radial dose distribution, in the measurement of these distributions, and in new radiobiological data against which to test the model. The earliest model, by Butts and Katz, made use of simplified δ ray distribution functions, of simplified electron range-energy relations, and neglected angular distributions. Nevertheless it made possible the calculation of cross sections for the inactivation of enzymes and viruses, and allowed extension to tracks in nuclear emulsions and other detectors and to biological cells. It set the pattern for models of observable effects in the matter through which the ion passed. Here we outline subsequent calculations of radial dose which make use of improved knowledge of the electron emission spectrum, the electron range-energy relation, the angular distribution, and some considerations of molecular excitation, of particular interest both close to the path of the ion and the outer limits of electron penetration. These are applied to the modeling of action cross sections for the inactivation of several strains of E-coli and B. subtilis spores where extensive measurements in the "thin-down" region have been made with heavy ion beams. Such calculations serve to test the radial dose calculations at the outer limit of electron penetration
Deterministic Partial Differential Equation Model for Dose Calculation in Electron Radiotherapy
Duclous, Roland; Frank, Martin
2009-01-01
Treatment with high energy ionizing radiation is one of the main methods in modern cancer therapy that is in clinical use. During the last decades, two main approaches to dose calculation were used, Monte Carlo simulations and semi-empirical models based on Fermi-Eyges theory. A third way to dose calculation has only recently attracted attention in the medical physics community. This approach is based on the deterministic kinetic equations of radiative transfer. Starting from these, we derive a macroscopic partial differential equation model for electron transport in tissue. This model involves an angular closure in the phase space. It is exact for the free-streaming and the isotropic regime. We solve it numerically by a newly developed HLLC scheme based on [BerCharDub], that exactly preserves key properties of the analytical solution on the discrete level. Several numerical results for test cases from the medical physics literature are presented.
GPU-based fast Monte Carlo simulation for radiotherapy dose calculation
Jia, Xun; Graves, Yan Jiang; Folkerts, Michael; Jiang, Steve B
2011-01-01
Monte Carlo (MC) simulation is commonly considered to be the most accurate dose calculation method in radiotherapy. However, its efficiency still requires improvement for many routine clinical applications. In this paper, we present our recent progress towards the development a GPU-based MC dose calculation package, gDPM v2.0. It utilizes the parallel computation ability of a GPU to achieve high efficiency, while maintaining the same particle transport physics as in the original DPM code and hence the same level of simulation accuracy. In GPU computing, divergence of execution paths between threads can considerably reduce the efficiency. Since photons and electrons undergo different physics and hence attain different execution paths, we use a simulation scheme where photon transport and electron transport are separated to partially relieve the thread divergence issue. High performance random number generator and hardware linear interpolation are also utilized. We have also developed various components to hand...
Methodology for calculation of radiation doses in the environs from nuclear fuel cycle facilities
Energy Technology Data Exchange (ETDEWEB)
Soldat, J.K.
1976-08-01
Comparison of the impacts of various nuclear fuel cycle alternatives includes the evaluation of the radiological impacts. To evaluate the radiological impacts of fuel cycle alternatives, exposure to man must first be identified. The pathways of consequence by which man can be exposed to radiation from a nuclear facility are listed and are grouped into those associated with gaseous effluents, those associated with liquid effluents, and those involving exposure to direct radiation from the facility or from transportation of radioactive materials to or from the facility. Calculations for each pathway were made for those selected organs which could potentially receive the highest radiation dose. Some of the programs developed for calculating radiation doses from radionuclides in the environment are described. (CH)
Calculation of conversion factors for effective dose for various interventional radiology procedures
Energy Technology Data Exchange (ETDEWEB)
Compagnone, Gaetano; Giampalma, Emanuela; Domenichelli, Sara; Renzulli, Matteo; Golfieri, Rita [Medical Physics Department, S. Orsola-Malpighi University Hospital, Via Massarenti 9, 40138 Bologna (Italy); Radiology Department, S. Orsola-Malpighi University Hospital, Via Massarenti 9, 40138 Bologna (Italy); Medical Physics Department, S. Orsola-Malpighi University Hospital, Via Massarenti 9, 40138 Bologna (Italy); Radiology Department, S. Orsola-Malpighi University Hospital, Via Massarenti 9, 40138 Bologna (Italy)
2012-05-15
Purpose: To provide dose-area-product (DAP) to effective dose (E) conversion factors for complete interventional procedures, based on in-the-field clinical measurements of DAP values and using tabulated E/DAP conversion factors for single projections available from the literature. Methods: Nine types of interventional procedures were performed on 84 patients with two angiographic systems. Different calibration curves (with and without patient table attenuation) were calculated for each DAP meter. Clinical and dosimetric parameters were recorded in-the-field for each projection and for all patients, and a conversion factor linking DAP and effective doses was derived for each complete procedure making use of published, Monte Carlo calculated conversion factors for single static projections. Results: Fluoroscopy time and DAP values for the lowest-dose procedure (biliary drainage) were approximately 3-fold and 13-fold lower, respectively, than those for the highest-dose examination (transjugular intrahepatic portosystemic shunt, TIPS). Median E/DAP conversion factors from 0.12 (abdominal percutaneous transluminal angioplasty) to 0.25 (Nephrostomy) mSvGy{sup -1} cm{sup -2} were obtained and good correlations between E and DAP were found for all procedures, with R{sup 2} coefficients ranging from 0.80 (abdominal angiography) to 0.99 (biliary stent insertion, Nephrostomy and TIPS). The DAP values obtained in this study showed general consistency with the values provided in the literature and median E values ranged from 4.0 mSv (biliary drainage) to 49.6 mSv (TIPS). Conclusions: Values of E/DAP conversion factors were derived for each procedure from a comprehensive analysis of projection and dosimetric data: they could provide a good evaluation for the stochastic effects. These results can be obtained by means of a close cooperation between different interventional professionals involved in patient care and dose optimization.
Methodology for calculation of doses to man and implementation in Pandora
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Avila, Rodolfo [Facilia AB, Bromma (Sweden); Bergstroem, Ulla [Swepro Project Management AB, Solna (Sweden)
2006-07-15
This report describes methods and data for calculation of doses to man to be used in safety assessments of repositories for nuclear fuel. The methods are based on the latest recommendations from the ICRP; the EU and the national radiation protection authorities. Equations are given for calculation of doses from ingestion of contaminated water and food, inhalation of contaminated air and external exposure from radionuclides in the ground. With the exception of the exposure from food ingestion, the equations are the same used in previous safety assessments. A general equation is suggested for estimation of the exposure from food ingestion, in which the annual demand of carbon is used instead of the annual ingestion of different food-stuffs, which was earlier applied. The report contains tables with recommended values for physiological characteristics such as water intake, food intake and inhalation rates, based on information summarised in an Appendix. Furthermore, tables are given with recommended age dependent dose conversion factors for ingestion and inhalation for a number of nuclides of interest for safety assessments. The most recently published dose conversion factors for external exposure from contaminated ground are also given. An overview of the implementation of the methodology in Pandora, which is the tool that SKB and Posiva currently use for biosphere modelling, is also provided. The work presented in the report is a result from a joint project commissioned by SKB and Posiva.
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Gomes B, W. O., E-mail: wilsonottobatista@gmail.com [Instituto Federal da Bahia, Rua Emidio dos Santos s/n, Barbalho 40301-015, Salvador de Bahia (Brazil)
2016-10-15
This study aimed to develop a geometry of irradiation applicable to the software PCXMC and the consequent calculation of effective dose in applications of the Computed Tomography Cone Beam (CBCT). We evaluated two different CBCT equipment s for dental applications: Care stream Cs 9000 3-dimensional tomograph; i-CAT and GENDEX GXCB-500. Initially characterize each protocol measuring the surface kerma input and the product kerma air-area, P{sub KA}, with solid state detectors RADCAL and PTW transmission chamber. Then we introduce the technical parameters of each preset protocols and geometric conditions in the PCXMC software to obtain the values of effective dose. The calculated effective dose is within the range of 9.0 to 15.7 μSv for 3-dimensional computer 9000 Cs; within the range 44.5 to 89 μSv for GXCB-500 equipment and in the range of 62-111 μSv for equipment Classical i-CAT. These values were compared with results obtained dosimetry using TLD implanted in anthropomorphic phantom and are considered consistent. Os effective dose results are very sensitive to the geometry of radiation (beam position in mathematical phantom). This factor translates to a factor of fragility software usage. But it is very useful to get quick answers to regarding process optimization tool conclusions protocols. We conclude that use software PCXMC Monte Carlo simulation is useful assessment protocols for CBCT tests in dental applications. (Author)
Yang, Bo; Qiu, Rui; Li, JunLi; Lu, Wei; Wu, Zhen; Li, Chunyan
2017-02-01
When a strong laser beam irradiates a solid target, a hot plasma is produced and high-energy electrons are usually generated (the so-called "hot electrons"). These energetic electrons subsequently generate hard X-rays in the solid target through the Bremsstrahlung process. To date, only limited studies have been conducted on this laser-induced radiological protection issue. In this study, extensive literature reviews on the physics and properties of hot electrons have been conducted. On the basis of these information, the photon dose generated by the interaction between hot electrons and a solid target was simulated with the Monte Carlo code FLUKA. With some reasonable assumptions, the calculated dose can be regarded as the upper boundary of the experimental results over the laser intensity ranging from 1019 to 1021 W/cm2. Furthermore, an equation to estimate the photon dose generated from ultraintense laser-solid interactions based on the normalized laser intensity is derived. The shielding effects of common materials including concrete and lead were also studied for the laser-driven X-ray source. The dose transmission curves and tenth-value layers (TVLs) in concrete and lead were calculated through Monte Carlo simulations. These results could be used to perform a preliminary and fast radiation safety assessment for the X-rays generated from ultraintense laser-solid interactions.
Directory of Open Access Journals (Sweden)
Karlsson Mikael
2010-06-01
Full Text Available Abstract Background Because of superior soft tissue contrast, the use of magnetic resonance imaging (MRI as a complement to computed tomography (CT in the target definition procedure for radiotherapy is increasing. To keep the workflow simple and cost effective and to reduce patient dose, it is natural to strive for a treatment planning procedure based entirely on MRI. In the present study, we investigate the dose calculation accuracy for different treatment regions when using bulk density assignments on MRI data and compare it to treatment planning that uses CT data. Methods MR and CT data were collected retrospectively for 40 patients with prostate, lung, head and neck, or brain cancers. Comparisons were made between calculations on CT data with and without inhomogeneity corrections and on MRI or CT data with bulk density assignments. The bulk densities were assigned using manual segmentation of tissue, bone, lung, and air cavities. Results The deviations between calculations on CT data with inhomogeneity correction and on bulk density assigned MR data were small. The maximum difference in the number of monitor units required to reach the prescribed dose was 1.6%. This result also includes effects of possible geometrical distortions. Conclusions The dose calculation accuracy at the investigated treatment sites is not significantly compromised when using MRI data when adequate bulk density assignments are made. With respect to treatment planning, MRI can replace CT in all steps of the treatment workflow, reducing the radiation exposure to the patient, removing any systematic registration errors that may occur when combining MR and CT, and decreasing time and cost for the extra CT investigation.
Knöös, Tommy; Wieslander, Elinore; Cozzi, Luca; Brink, Carsten; Fogliata, Antonella; Albers, Dirk; Nyström, Håkan; Lassen, Søren
2006-11-21
A study of the performance of five commercial radiotherapy treatment planning systems (TPSs) for common treatment sites regarding their ability to model heterogeneities and scattered photons has been performed. The comparison was based on CT information for prostate, head and neck, breast and lung cancer cases. The TPSs were installed locally at different institutions and commissioned for clinical use based on local procedures. For the evaluation, beam qualities as identical as possible were used: low energy (6 MV) and high energy (15 or 18 MV) x-rays. All relevant anatomical structures were outlined and simple treatment plans were set up. Images, structures and plans were exported, anonymized and distributed to the participating institutions using the DICOM protocol. The plans were then re-calculated locally and exported back for evaluation. The TPSs cover dose calculation techniques from correction-based equivalent path length algorithms to model-based algorithms. These were divided into two groups based on how changes in electron transport are accounted for ((a) not considered and (b) considered). Increasing the complexity from the relatively homogeneous pelvic region to the very inhomogeneous lung region resulted in less accurate dose distributions. Improvements in the calculated dose have been shown when models consider volume scatter and changes in electron transport, especially when the extension of the irradiated volume was limited and when low densities were present in or adjacent to the fields. A Monte Carlo calculated algorithm input data set and a benchmark set for a virtual linear accelerator have been produced which have facilitated the analysis and interpretation of the results. The more sophisticated models in the type b group exhibit changes in both absorbed dose and its distribution which are congruent with the simulations performed by Monte Carlo-based virtual accelerator.
DRUG-RESISTANCE, SUPPORTIVE CARE AND DOSE INTENSITY
DEVRIES, EGE; HAMILTON, TC; LIND, M; DAUPLAT, J; NEIJT, JP; OZOLS, RF
1993-01-01
Background: Both intrinsic and acquired drug resistance occur in ovarian cancer. Much work on in vivo or in vitro, obtained drug resistance has been done and this knowledge is presently being converted into clinical studies. Materials and methods: The review focuses on the detoxifying system, MDR (m
Mathematical Based Calculation of Drug Penetration Depth in Solid Tumors
Directory of Open Access Journals (Sweden)
Hamidreza Namazi
2016-01-01
Full Text Available Cancer is a class of diseases characterized by out-of-control cells’ growth which affect cells and make them damaged. Many treatment options for cancer exist. Chemotherapy as an important treatment option is the use of drugs to treat cancer. The anticancer drug travels to the tumor and then diffuses in it through capillaries. The diffusion of drugs in the solid tumor is limited by penetration depth which is different in case of different drugs and cancers. The computation of this depth is important as it helps physicians to investigate about treatment of infected tissue. Although many efforts have been made on studying and measuring drug penetration depth, less works have been done on computing this length from a mathematical point of view. In this paper, first we propose phase lagging model for diffusion of drug in the tumor. Then, using this model on one side and considering the classic diffusion on the other side, we compute the drug penetration depth in the solid tumor. This computed value of drug penetration depth is corroborated by comparison with the values measured by experiments.
GPU-based ultra fast dose calculation using a finite pencil beam model
Gu, Xuejun; Men, Chunhua; Pan, Hubert; Majumdar, Amitava; Jiang, Steve B
2009-01-01
Online adaptive radiation therapy (ART) is an attractive concept that promises the ability to deliver an optimal treatment in response to the inter-fraction variability in patient anatomy. However, it has yet to be realized due to technical limitations. Fast dose deposit coefficient calculation is a critical component of the online planning process that is required for plan optimization of intensity modulated radiation therapy (IMRT). Computer graphics processing units (GPUs) are well-suited to provide the requisite fast performance for the data-parallel nature of dose calculation. In this work, we develop a dose calculation engine based on a finite-size pencil beam (FSPB) algorithm and a GPU parallel computing framework. The developed framework can accommodate any FSPB model. We test our implementation on a case of a water phantom and a case of a prostate cancer patient with varying beamlet and voxel sizes. All testing scenarios achieved speedup ranging from 200~400 times when using a NVIDIA Tesla C1060 card...
Energy Technology Data Exchange (ETDEWEB)
Albright, N; Bergstrom, P M; Daly, T P; Descalle, M; Garrett, D; House, R K; Knapp, D K; May, S; Patterson, R W; Siantar, C L; Verhey, L; Walling, R S; Welczorek, D
1999-07-01
PEREGRINE is a 3D Monte Carlo dose calculation system designed to serve as a dose calculation engine for clinical radiation therapy treatment planning systems. Taking advantage of recent advances in low-cost computer hardware, modern multiprocessor architectures and optimized Monte Carlo transport algorithms, PEREGRINE performs mm-resolution Monte Carlo calculations in times that are reasonable for clinical use. PEREGRINE has been developed to simulate radiation therapy for several source types, including photons, electrons, neutrons and protons, for both teletherapy and brachytherapy. However the work described in this paper is limited to linear accelerator-based megavoltage photon therapy. Here we assess the accuracy, reliability, and added value of 3D Monte Carlo transport for photon therapy treatment planning. Comparisons with clinical measurements in homogeneous and heterogeneous phantoms demonstrate PEREGRINE's accuracy. Studies with variable tissue composition demonstrate the importance of material assignment on the overall dose distribution. Detailed analysis of Monte Carlo results provides new information for radiation research by expanding the set of observables.
Energy Technology Data Exchange (ETDEWEB)
Camplin, W C; Brownless, G P; Round, G D; Winpenny, K; Hunt, G J [Centre for Environment, Fisheries and Aquaculture Science, CEFAS Laboratory, Lowestoft (United Kingdom)
2002-12-01
A new method for estimating radiation doses to UK critical groups is proposed for discussion. Amongst others, the Food Standards Agency (FSA) and the Scottish Environment Protection Agency (SEPA) undertake surveillance of UK food and the environment as a check on the effect of discharges of radioactive wastes. Discharges in gaseous and liquid form are made under authorisation by the Environment Agency and SEPA under powers in the Radioactive Substance Act. Results of surveillance by the FSA and SEPA are published in the Radioactivity in Food and the Environment (RIFE) report series. In these reports, doses to critical groups are normally estimated separately for gaseous and liquid discharge pathways. Simple summation of these doses would tend to overestimate doses actually received. Three different methods of combining the effects of both types of discharge in an integrated assessment are considered and ranked according to their ease of application, transparency, scientific rigour and presentational issues. A single integrated assessment method is then chosen for further study. Doses are calculated for surveillance data for the calendar year 2000 and compared with those from the existing RIFE method.
Dose distribution calculation for in-vivo X-ray fluorescence scanning
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Figueroa, R. G. [Universidad de la Frontera, Departamento de Ciencias Fisicas, Av. Francisco Salazar 1145, Temuco 4811230, Araucania (Chile); Lozano, E. [Instituto Nacional del Cancer, Unidad de Fisica Medica, Av. Profesor Zanartu 1010, Santiago (Chile); Valente, M., E-mail: figueror@ufro.cl [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Av. Ravadavia 1917, C1033AAJ, Buenos Aires (Argentina)
2013-08-01
In-vivo X-ray fluorescence constitutes a useful and accurate technique, worldwide established for constituent elementary distribution assessment. Actually, concentration distributions of arbitrary user-selected elements can be achieved along sample surface with the aim of identifying and simultaneously quantifying every constituent element. The method is based on the use of a collimated X-ray beam reaching the sample. However, one common drawback for considering the application of this technique for routine clinical examinations was the lack of information about associated dose delivery. This work presents a complete study of the dose distribution resulting from an in-vivo X-ray fluorescence scanning for quantifying biohazard materials on human hands. Absorbed dose has been estimated by means of dosimetric models specifically developed to this aim. In addition, complete dose distributions have been obtained by means of full radiation transport calculations in based on stochastic Monte Carlo techniques. A dedicated subroutine has been developed using the Penelope 2008 main code also integrated with dedicated programs -Mat Lab supported- for 3 dimensional dose distribution visualization. The obtained results show very good agreement between approximate analytical models and full descriptions by means of Monte Carlo simulations. (Author)
Energy Technology Data Exchange (ETDEWEB)
Strange, D. L.; Bander, T. J.
1981-04-01
The MILDOS Computer Code estimates impacts from radioactive emissions from uranium milling facilities. These impacts are presented as dose commitments to individuals and the regional population within an 80 km radius of the facility. Only airborne releases of radioactive materials are considered: releases to surface water and to groundwater are not addressed in MILDOS. This code is multi-purposed and can be used to evaluate population doses for NEPA assessments, maximum individual doses for predictive 40 CFR 190 compliance evaluations, or maximum offsite air concentrations for predictive evaluations of 10 CFR 20 compliance. Emissions of radioactive materials from fixed point source locations and from area sources are modeled using a sector-averaged Gaussian plume dispersion model, which utilizes user-provided wind frequency data. Mechanisms such as deposition of particulates, resuspension. radioactive decay and ingrowth of daughter radionuclides are included in the transport model. Annual average air concentrations are computed, from which subsequent impacts to humans through various pathways are computed. Ground surface concentrations are estimated from deposition buildup and ingrowth of radioactive daughters. The surface concentrations are modified by radioactive decay, weathering and other environmental processes. The MILDOS Computer Code allows the user to vary the emission sources as a step function of time by adjustinq the emission rates. which includes shutting them off completely. Thus the results of a computer run can be made to reflect changing processes throughout the facility's operational lifetime. The pathways considered for individual dose commitments and for population impacts are: • Inhalation • External exposure from ground concentrations • External exposure from cloud immersion • Ingestioo of vegetables • Ingestion of meat • Ingestion of milk • Dose commitments are calculated using dose conversion factors, which are ultimately based
Zuppa, Athena F
2012-01-01
Multifaceted factors need to be considered when prescribing renal replacement therapy (RRT) and dosing of drugs in pediatric patients with kidney disease. RRTs in pediatrics such as intermittent hemodialysis, continuous venovenous hemofiltration, continuous venovenous hemodialysis, and continuous venovenous hemodiafiltration affect solute and drug clearance. Drug properties such as molecular weight, molecular charge, volume of distribution, and protein binding affect drug clearance. RRT prescription parameters such as blood flow rate, ultrafiltration rate, membrane size, and pore size can also influence drug clearance. Furthermore, the pediatric patient presents additional concerns because of developmental factors in children that affect both pharmacokinetics of drugs.
vantVeld, AA
1997-01-01
Accuracy in dose and position, defined as complementary criteria, was determined for blocked photon field calculations with a pencil beam based treatment planning system. The concept of field accuracy has been defined as a combination of deviations in dose and position. Absolute dose deviations were
Patient-dependent beam-modifier physics in Monte Carlo photon dose calculations.
Schach von Wittenau, A E; Bergstrom, P M; Cox, L J
2000-05-01
Model pencil-beam on slab calculations are used as well as a series of detailed calculations of photon and electron output from commercial accelerators to quantify level(s) of physics required for the Monte Carlo transport of photons and electrons in treatment-dependent beam modifiers, such as jaws, wedges, blocks, and multileaf collimators, in photon teletherapy dose calculations. The physics approximations investigated comprise (1) not tracking particles below a given kinetic energy, (2) continuing to track particles, but performing simplified collision physics, particularly in handling secondary particle production, and (3) not tracking particles in specific spatial regions. Figures-of-merit needed to estimate the effects of these approximations are developed, and these estimates are compared with full-physics Monte Carlo calculations of the contribution of the collimating jaws to the on-axis depth-dose curve in a water phantom. These figures of merit are next used to evaluate various approximations used in coupled photon/electron physics in beam modifiers. Approximations for tracking electrons in air are then evaluated. It is found that knowledge of the materials used for beam modifiers, of the energies of the photon beams used, as well as of the length scales typically found in photon teletherapy plans, allows a number of simplifying approximations to be made in the Monte Carlo transport of secondary particles from the accelerator head and beam modifiers to the isocenter plane.
Diego Azcona, Juan; Barbés, Benigno; Wang, Lilie; Burguete, Javier
2016-01-01
This paper presents a method to obtain the pencil-beam kernels that characterize a megavoltage photon beam generated in a flattening filter free (FFF) linear accelerator (linac) by deconvolution from experimental measurements at different depths. The formalism is applied to perform independent dose calculations in modulated fields. In our previous work a formalism was developed for ideal flat fluences exiting the linac’s head. That framework could not deal with spatially varying energy fluences, so any deviation from the ideal flat fluence was treated as a perturbation. The present work addresses the necessity of implementing an exact analysis where any spatially varying fluence can be used such as those encountered in FFF beams. A major improvement introduced here is to handle the actual fluence in the deconvolution procedure. We studied the uncertainties associated to the kernel derivation with this method. Several Kodak EDR2 radiographic films were irradiated with a 10 MV FFF photon beam from two linacs from different vendors, at the depths of 5, 10, 15, and 20cm in polystyrene (RW3 water-equivalent phantom, PTW Freiburg, Germany). The irradiation field was a 50mm diameter circular field, collimated with a lead block. The 3D kernel for a FFF beam was obtained by deconvolution using the Hankel transform. A correction on the low dose part of the kernel was performed to reproduce accurately the experimental output factors. Error uncertainty in the kernel derivation procedure was estimated to be within 0.2%. Eighteen modulated fields used clinically in different treatment localizations were irradiated at four measurement depths (total of fifty-four film measurements). Comparison through the gamma-index to their corresponding calculated absolute dose distributions showed a number of passing points (3%, 3mm) mostly above 99%. This new procedure is more reliable and robust than the previous one. Its ability to perform accurate independent dose calculations was
Towards real-time photon Monte Carlo dose calculation in the cloud.
Ziegenhein, Peter; Kozin, Igor; Kamerling, Cornelis Philippus; Oelfke, Uwe
2017-01-31
Near real-time application of Monte Carlo (MC) dose calculation in clinic and research is hindered by long computational runtimes of established software. Currently, fast MC software solutions are available utilising accelerators such as GPUs or clusters of central processing units (CPU)-based system. Both platforms are expensive in terms of purchase costs and maintenance and, in case of the GPU, provide only limited scalability. In this work we propose a cloud-based MC solution, which offers high scalability of accurate photon dose calculations. The MC simulations run on a private virtual supercomputer that forms in the cloud. Computational resources can be provisioned dynamically at low costs without upfront investment in expensive hardware. A client-server software solution has been developed which controls the simulations and efficiently transports data to and from the cloud. The client application integrates seamlessly into a Treatment Planning System (TPS). It runs the MC simulation workflow automatically and securely exchanges simulation data with the server side application that controls the virtual supercomputer. The Advanced Encryption Standard (AES) was used to add an addition security layer which encrypts and decrypts patient data on-the-fly at the processor register level. We could show that our cloud-based MC framework enables near real-time dose computation. It delivers excellent linear scaling for high-resolution datasets with absolute runtimes of 1.1 to 10.9 seconds for simulating a clinical prostate and liver case up to 1\\% statistical uncertainty. The computation times include the data transportation processes with the cloud as well as process scheduling and synchronisation overhead. Cloud based MC simulations offer a fast, affordable and easily accessible alternative for near real-time accurate dose calculations to currently used GPU or cluster solutions.
Mayer, Lawrence D; Harasym, Troy O; Tardi, Paul G; Harasym, Natashia L; Shew, Clifford R; Johnstone, Sharon A; Ramsay, Euan C; Bally, Marcel B; Janoff, Andrew S
2006-07-01
Anticancer drug combinations can act synergistically or antagonistically against tumor cells in vitro depending on the ratios of the individual agents comprising the combination. The importance of drug ratios in vivo, however, has heretofore not been investigated, and combination chemotherapy treatment regimens continue to be developed based on the maximum tolerated dose of the individual agents. We systematically examined three different drug combinations representing a range of anticancer drug classes with distinct molecular mechanisms (irinotecan/floxuridine, cytarabine/daunorubicin, and cisplatin/daunorubicin) for drug ratio-dependent synergy. In each case, synergistic interactions were observed in vitro at certain drug/drug molar ratio ranges (1:1, 5:1, and 10:1, respectively), whereas other ratios were additive or antagonistic. We were able to maintain fixed drug ratios in plasma of mice for 24 hours after i.v. injection for all three combinations by controlling and overcoming the inherent dissimilar pharmacokinetics of individual drugs through encapsulation in liposomal carrier systems. The liposomes not only maintained drug ratios in the plasma after injection, but also delivered the formulated drug ratio directly to tumor tissue. In vivo maintenance of drug ratios shown to be synergistic in vitro provided increased efficacy in preclinical tumor models, whereas attenuated antitumor activity was observed when antagonistic drug ratios were maintained. Fixing synergistic drug ratios in pharmaceutical carriers provides an avenue by which anticancer drug combinations can be optimized prospectively for maximum therapeutic activity during preclinical development and differs from current practice in which dosing regimens are developed empirically in late-stage clinical trials based on tolerability.
Comparison of CT number calibration techniques for CBCT-based dose calculation
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Dunlop, Alex [The Royal Marsden NHS Foundation Trust, Joint Department of Physics, Institute of Cancer Research, London (United Kingdom); The Royal Marsden Hospital, Sutton, Surrey, Downs Road (United Kingdom); McQuaid, Dualta; Nill, Simeon; Hansen, Vibeke N.; Oelfke, Uwe [The Royal Marsden NHS Foundation Trust, Joint Department of Physics, Institute of Cancer Research, London (United Kingdom); Murray, Julia; Bhide, Shreerang; Harrington, Kevin [The Royal Marsden Hospital, Sutton, Surrey, Downs Road (United Kingdom); The Institute of Cancer Research, London (United Kingdom); Poludniowski, Gavin [Karolinska University Hospital, Department of Medical Physics, Stockholm (Sweden); Nutting, Christopher [The Institute of Cancer Research, London (United Kingdom); Newbold, Kate [The Royal Marsden Hospital, Sutton, Surrey, Downs Road (United Kingdom)
2015-12-15
The aim of this work was to compare and validate various computed tomography (CT) number calibration techniques with respect to cone beam CT (CBCT) dose calculation accuracy. CBCT dose calculation accuracy was assessed for pelvic, lung, and head and neck (H and N) treatment sites for two approaches: (1) physics-based scatter correction methods (CBCT{sub r}); (2) density override approaches including assigning water density to the entire CBCT (W), assignment of either water or bone density (WB), and assignment of either water or lung density (WL). Methods for CBCT density assignment within a commercially available treatment planning system (RS{sub auto}), where CBCT voxels are binned into six density levels, were assessed and validated. Dose-difference maps and dose-volume statistics were used to compare the CBCT dose distributions with the ground truth of a planning CT acquired the same day as the CBCT. For pelvic cases, all CTN calibration methods resulted in average dose-volume deviations below 1.5 %. RS{sub auto} provided larger than average errors for pelvic treatments for patients with large amounts of adipose tissue. For H and N cases, all CTN calibration methods resulted in average dose-volume differences below 1.0 % with CBCT{sub r} (0.5 %) and RS{sub auto} (0.6 %) performing best. For lung cases, WL and RS{sub auto} methods generated dose distributions most similar to the ground truth. The RS{sub auto} density override approach is an attractive option for CTN adjustments for a variety of anatomical sites. RS{sub auto} methods were validated, resulting in dose calculations that were consistent with those calculated on diagnostic-quality CT images, for CBCT images acquired of the lung, for patients receiving pelvic RT in cases without excess adipose tissue, and for H and N cases. (orig.) [German] Ziel dieser Arbeit ist der Vergleich und die Validierung mehrerer CT-Kalibrierungsmethoden zur Dosisberechnung auf der Grundlage von Kegelstrahlcomputertomographie
SU-F-BRD-06: Robust Dose Calculation in Intensity Modulated Proton Therapy
Energy Technology Data Exchange (ETDEWEB)
Brosch, R [ASU, Tempe, AZ (United States); Liu, W [Mayo Clinic Arizona, Phoenix, AZ (United States)
2015-06-15
Purpose: Commissioning data for intensity modulated proton therapy (IMPT) must be post-processed by fits to ad-hoc functions to derive the dose calculation kernel parameters in a treatment planning system (TPS). Whether from experimental measurement or Monte Carlo simulation, the limited and noisy nature of such data makes this task very challenging. We present a method to improve the modeling of the lateral dose distribution of clinical energy proton beams in water to commission an in-house IMPT dose calculation engine. Methods: A linear sum of three Gaussian distribution functions was fitted to the lateral dose data in logarithmic scale. Starting values of fitting solutions were determined from the Generalized Highland Approximation. We exhaustively optimized the combinations of data weights with upper bounds of the fitting solutions to minimize confidence intervals of the fitting solutions while maintaining the coefficient of determination (R{sup 2}). Results: Across all energies, average confidence bounds improved 72.88% [Max: 88.28%, Min: 55.05%] for small angle coulomb scattering, 114.25% [409.13%, 66.72%,] for nuclear scattering, and 68.66% [141.09%, 33.27%] for large angle coulomb scattering, while the coefficients of determination of the fits (R{sup 2}) remained comparable. On average R {sup 2} only changed 0.18% and were very close to 1 (approx. 0.999). Wilcoxon signed rank tests comparing unweighted/unbounded fits with weighted/bounded fits averaged 0.0146 (Max: 0.177, Min: 7.05×10−{sup 7}) for small angle Coulomb, 0.0903 (0.945, 7.05×10−{sup 7}) for nuclear, and 0.254 (0.871, 1.86×10−{sup 6}) for large angle Coulomb scattering. This allows rejection of the null hypothesis for small angle Coulomb scattering at the 0.015 level and nuclear interaction at the 0.1 level. Conclusion: Optimal weights assigned to IMPT lateral dose data minimized fitting to stochastic noise in the tail region. Optimizing the upper bounds of fitting parameters improved
A deterministic partial differential equation model for dose calculation in electron radiotherapy
Energy Technology Data Exchange (ETDEWEB)
Duclous, R; Dubroca, B [CELIA and IMB Laboratories, Bordeaux University, 33405 Talence (France); Frank, M, E-mail: duclous@celia.u-bordeaux1.f, E-mail: dubroca@celia.u-bordeaux1.f, E-mail: frank@mathcces.rwth-aachen.d [Department of Mathematics and Center for Computational Engineering Science, RWTH Aachen University, Schinkelstr. 2, 52062 Aachen (Germany)
2010-07-07
High-energy ionizing radiation is a prominent modality for the treatment of many cancers. The approaches to electron dose calculation can be categorized into semi-empirical models (e.g. Fermi-Eyges, convolution-superposition) and probabilistic methods (e.g. Monte Carlo). A third approach to dose calculation has only recently attracted attention in the medical physics community. This approach is based on the deterministic kinetic equations of radiative transfer. We derive a macroscopic partial differential equation model for electron transport in tissue. This model involves an angular closure in the phase space. It is exact for the free streaming and the isotropic regime. We solve it numerically by a newly developed HLLC scheme based on Berthon et al (2007 J. Sci. Comput. 31 347-89) that exactly preserves the key properties of the analytical solution on the discrete level. We discuss several test cases taken from the medical physics literature. A test case with an academic Henyey-Greenstein scattering kernel is considered. We compare our model to a benchmark discrete ordinate solution. A simplified model of electron interactions with tissue is employed to compute the dose of an electron beam in a water phantom, and a case of irradiation of the vertebral column. Here our model is compared to the PENELOPE Monte Carlo code. In the academic example, the fluences computed with the new model and a benchmark result differ by less than 1%. The depths at half maximum differ by less than 0.6%. In the two comparisons with Monte Carlo, our model gives qualitatively reasonable dose distributions. Due to the crude interaction model, these so far do not have the accuracy needed in clinical practice. However, the new model has a computational cost that is less than one-tenth of the cost of a Monte Carlo simulation. In addition, simulations can be set up in a similar way as a Monte Carlo simulation. If more detailed effects such as coupled electron-photon transport, bremsstrahlung
A deterministic partial differential equation model for dose calculation in electron radiotherapy
Duclous, R.; Dubroca, B.; Frank, M.
2010-07-01
High-energy ionizing radiation is a prominent modality for the treatment of many cancers. The approaches to electron dose calculation can be categorized into semi-empirical models (e.g. Fermi-Eyges, convolution-superposition) and probabilistic methods (e.g. Monte Carlo). A third approach to dose calculation has only recently attracted attention in the medical physics community. This approach is based on the deterministic kinetic equations of radiative transfer. We derive a macroscopic partial differential equation model for electron transport in tissue. This model involves an angular closure in the phase space. It is exact for the free streaming and the isotropic regime. We solve it numerically by a newly developed HLLC scheme based on Berthon et al (2007 J. Sci. Comput. 31 347-89) that exactly preserves the key properties of the analytical solution on the discrete level. We discuss several test cases taken from the medical physics literature. A test case with an academic Henyey-Greenstein scattering kernel is considered. We compare our model to a benchmark discrete ordinate solution. A simplified model of electron interactions with tissue is employed to compute the dose of an electron beam in a water phantom, and a case of irradiation of the vertebral column. Here our model is compared to the PENELOPE Monte Carlo code. In the academic example, the fluences computed with the new model and a benchmark result differ by less than 1%. The depths at half maximum differ by less than 0.6%. In the two comparisons with Monte Carlo, our model gives qualitatively reasonable dose distributions. Due to the crude interaction model, these so far do not have the accuracy needed in clinical practice. However, the new model has a computational cost that is less than one-tenth of the cost of a Monte Carlo simulation. In addition, simulations can be set up in a similar way as a Monte Carlo simulation. If more detailed effects such as coupled electron-photon transport, bremsstrahlung
Mathematical knowledge and drug dosage calculation: Necessary clinical skills for the nurse
Directory of Open Access Journals (Sweden)
Athanasakis Efstratios
2013-01-01
Full Text Available When nurses perform their tasks, they manage situations where maths knowledge is required. Such a situation is the calculation of medication dosage. Aim: The literature review of papers relevant with the mathematical knowledge and drug calculation skills of nurses and nursing students. Material-Method: A search of published research and review articles from January 1989 until March 2012, has been conducted in Pubmed database. The search terms used were: nurses, mathematics skills, numeracy skills and medication dosology calculation skills. Results: Literature review showed that many studies focus in the mathematical knowledge and drug dosage calculation competency of nursing students. Results from these studies revealed that nursing students had poor mathematical knowledge and drug dosage calculation skills. In contrast with students, professional nurses are more likely to have sufficient skills in drug calculations. Apart from the papers analyzing calculation skills' assessment, several studies examined educational interventions in the context of calculation skills enhancement. Accuracy and proficiency in the dosage calculation of medications is a preventive factor of errors made at medication preparation and administration. Conclusion: Mathematical knowledge and drug dosage calculation abilities are interrelated concepts and essential clinical skills for the nurse. The fact that nursing students do not have adequate skills for calculating medications' dosage, might be an issue that schools of nursing education should focus in. Further research of the drug dosage calculation skills is considered essential.
Directory of Open Access Journals (Sweden)
Yoon-Dong Park
2016-08-01
Full Text Available Cryptococcus neoformans is a pathogenic fungus that is responsible for up to half a million cases of meningitis globally, especially in immunocompromised individuals. Common fungistatic drugs, such as fluconazole, are less toxic for patients but have low efficacy for initial therapy of the disease. Effective therapy against the disease is provided by the fungicidal drug amphotericin B; however, due to its high toxicity and the difficulty in administering its intravenous formulation, it is imperative to find new therapies targeting the fungus. The antiparasitic drug bithionol has been recently identified as having potent fungicidal activity. In this study, we used a combined gene dosing and drug affinity responsive target stability (GD-DARTS screen as well as protein modeling to identify a common drug binding site of bithionol within multiple NAD-dependent dehydrogenase drug targets. This combination genetic and proteomic method thus provides a powerful method for identifying novel fungicidal drug targets for further development.
Wignall, Jessica A.; Shapiro, Andrew J.; Wright, Fred A.; Woodruff, Tracey J.; Chiu, Weihsueh A.; Guyton, Kathryn Z.
2014-01-01
Background: Benchmark dose (BMD) modeling computes the dose associated with a prespecified response level. While offering advantages over traditional points of departure (PODs), such as no-observed-adverse-effect-levels (NOAELs), BMD methods have lacked consistency and transparency in application, interpretation, and reporting in human health assessments of chemicals. Objectives: We aimed to apply a standardized process for conducting BMD modeling to reduce inconsistencies in model fitting and selection. Methods: We evaluated 880 dose–response data sets for 352 environmental chemicals with existing human health assessments. We calculated benchmark doses and their lower limits [10% extra risk, or change in the mean equal to 1 SD (BMD/L10/1SD)] for each chemical in a standardized way with prespecified criteria for model fit acceptance. We identified study design features associated with acceptable model fits. Results: We derived values for 255 (72%) of the chemicals. Batch-calculated BMD/L10/1SD values were significantly and highly correlated (R2 of 0.95 and 0.83, respectively, n = 42) with PODs previously used in human health assessments, with values similar to reported NOAELs. Specifically, the median ratio of BMDs10/1SD:NOAELs was 1.96, and the median ratio of BMDLs10/1SD:NOAELs was 0.89. We also observed a significant trend of increasing model viability with increasing number of dose groups. Conclusions: BMD/L10/1SD values can be calculated in a standardized way for use in health assessments on a large number of chemicals and critical effects. This facilitates the exploration of health effects across multiple studies of a given chemical or, when chemicals need to be compared, providing greater transparency and efficiency than current approaches. Citation: Wignall JA, Shapiro AJ, Wright FA, Woodruff TJ, Chiu WA, Guyton KZ, Rusyn I. 2014. Standardizing benchmark dose calculations to improve science-based decisions in human health assessments. Environ Health
Dependence of pentobarbital kinetics upon the dose of the drug and its pharmacodynamic effects.
Kozlowski, K H; Szaykowski, A; Danysz, A
1977-01-01
Pentobarbital (PB), at dose range of 20--50 mg/kg, displays in rabbits non-linear, dose-dependent kinetics. Pharmacokinetics parameters of drug elimination depend largely upon the dose, while the distribution phase is dose-independent. The rate of disappearance of PB from the central compartment (plasma) decreases with the increase of the dose. The analysis of pharmacodynamic parameters has shown that this dose-dependent retardation of PB elimination is probably caused by an impairment of metabolic processes, resulting from disturbance of the circulatory system. A close correlation has been found between the hypotensive effect of PB and the elimination constant, k13, and also between the hypotensive effect and beta.Vd(extrap), a coefficient proportional to the rate of metabolism of PB [23, 29]. The results indicate the necessity of considering the changes in the functional state of the organism, related to the action of a drug, in pharmacokinetic studies.
Treatment of early AIDS dementia in intravenous drug users : High versus low dose peptide T
Kosten, TR; Rosen, MI; McMahon, TL; Bridge, TP; OMalley, SS; Pearsall, R; OConnor, PG
1997-01-01
This placebo-controlled, double blind, cross-over study tested the efficacy of two different doses of Peptide T in the treatment of nine intravenous drug users with early AIDS dementia who were also receiving methadone and AZT. Subjects received Peptide T doses of either 15 or 1.5 mg daily for four
Influence of metallic dental implants and metal artefacts on dose calculation accuracy
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Maerz, Manuel; Koelbl, Oliver; Dobler, Barbara [Regensburg University Medical Center, Department of Radiotherapy, Regensburg (Germany)
2014-10-31
Metallic dental implants cause severe streaking artefacts in computed tomography (CT) data, which inhibit the correct representation of shape and density of the metal and the surrounding tissue. The aim of this study was to investigate the impact of dental implants on the accuracy of dose calculations in radiation therapy planning and the benefit of metal artefact reduction (MAR). A second aim was to determine the treatment technique which is less sensitive to the presence of metallic implants in terms of dose calculation accuracy. Phantoms consisting of homogeneous water equivalent material surrounding dental implants were designed. Artefact-containing CT data were corrected using the correct density information. Intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans were calculated on corrected and uncorrected CT data and compared to 2-dimensional dose measurements using GafChromic trademark EBT2 films. For all plans the accuracy of dose calculations is significantly higher if performed on corrected CT data (p = 0.015). The agreement of calculated and measured dose distributions is significantly higher for VMAT than for IMRT plans for calculations on uncorrected CT data (p = 0.011) as well as on corrected CT data (p = 0.029). For IMRT and VMAT the application of metal artefact reduction significantly increases the agreement of dose calculations with film measurements. VMAT was found to provide the highest accuracy on corrected as well as on uncorrected CT data. VMAT is therefore preferable over IMRT for patients with metallic implants, if plan quality is comparable for the two techniques. (orig.) [German] Zahnimplantate aus Metall verursachen in Computertomographiedaten (CT) streifenfoermige Artefakte. Diese verhindern eine korrekte Zuordnung von Form und Dichteeigenschaften des Metalls und des umgebenden Gewebes. Ziel dieser Studie war es, den Einfluss von Zahnimplantaten auf die Genauigkeit der Dosisberechnung in der
Radial dose distributions from protons of therapeutic energies calculated with Geant4-DNA
Wang, He; Vassiliev, Oleg N.
2014-07-01
Models based on the amorphous track structure approximation have been successful in predicting the biological effects of heavy charged particles. Development of such models remains an active area of research that includes applications to hadrontherapy. In such models, the radial distribution of the dose deposited by delta electrons and directly by the particle is the main characteristic of track structure. We calculated these distributions with Geant4-DNA Monte Carlo code for protons in the energy range from 10 to 100 MeV. These results were approximated by a simple formula that combines the well-known inverse square distance dependence with two factors that eliminate the divergence of the radial dose integral at both small and large distances. A clear physical interpretation is given to the asymptotic behaviour of the radial dose distribution resulting from these two factors. The proposed formula agrees with the Monte Carlo data within 10% for radial distances of up to 10 μm, which corresponds to a dose range covering over eight orders of magnitude. Differences between our results and those of previously published analytical models are discussed.
Photonuclear dose calculations for high-energy photon beams from Siemens and Varian linacs.
Chibani, Omar; Ma, Chang-Ming Charlie
2003-08-01
The dose from photon-induced nuclear particles (neutrons, protons, and alpha particles) generated by high-energy photon beams from medical linacs is investigated. Monte Carlo calculations using the MCNPX code are performed for three different photon beams from two different machines: Siemens 18 MV, Varian 15 MV, and Varian 18 MV. The linac head components are simulated in detail. The dose distributions from photons, neutrons, protons, and alpha particles are calculated in a tissue-equivalent phantom. Neutrons are generated in both the linac head and the phantom. This study includes (a) field size effects, (b) off-axis dose profiles, (c) neutron contribution from the linac head, (d) dose contribution from capture gamma rays, (e) phantom heterogeneity effects, and (f) effects of primary electron energy shift. Results are presented in terms of absolute dose distributions and also in terms of DER (dose equivalent ratio). The DER is the maximum dose from the particle (neutron, proton, or alpha) divided by the maximum photon dose, multiplied by the particle quality factor and the modulation scaling factor. The total DER including neutrons, protons, and alphas is about 0.66 cSv/Gy for the Siemens 18 MV beam (10 cm x 10 cm). The neutron DER decreases with decreasing field size while the proton (or alpha) DER does not vary significantly except for the 1 cm x 1 cm field. Both Varian beams (15 and 18 MV) produce more neutrons, protons, and alphas particles than the Siemens 18 MV beam. This is mainly due to their higher primary electron energies: 15 and 18.3 MeV, respectively, vs 14 MeV for the Siemens 18 MV beam. For all beams, neutrons contribute more than 75% of the total DER, except for the 1 cm x 1 cm field (approximately 50%). The total DER is 1.52 and 2.86 cSv/Gy for the 15 and 18 MV Varian beams (10 cm x 10 cm), respectively. Media with relatively high-Z elements like bone may increase the dose from heavy charged particles by a factor 4. The total DER is sensitive to
Lung Dose Calculation With SPECT/CT for {sup 90}Yittrium Radioembolization of Liver Cancer
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Yu, Naichang, E-mail: yun@ccf.org [Department of Radiation Oncology, Cleveland Clinic, Cleveland, OH (United States); Srinivas, Shaym M.; DiFilippo, Frank P.; Shrikanthan, Sankaran [Department of Nuclear Medicine, Cleveland Clinic, Cleveland, OH (United States); Levitin, Abraham; McLennan, Gordon; Spain, James [Department of Interventional Radiology, Cleveland Clinic, Cleveland, OH (United States); Xia, Ping; Wilkinson, Allan [Department of Radiation Oncology, Cleveland Clinic, Cleveland, OH (United States)
2013-03-01
Purpose: To propose a new method to estimate lung mean dose (LMD) using technetium-99m labeled macroaggregated albumin ({sup 99m}Tc-MAA) single photon emission CT (SPECT)/CT for {sup 90}Yttrium radioembolization of liver tumors and to compare the LMD estimated using SPECT/CT with clinical estimates of LMD using planar gamma scintigraphy (PS). Methods and Materials: Images of 71 patients who had SPECT/CT and PS images of {sup 99m}Tc-MAA acquired before TheraSphere radioembolization of liver cancer were analyzed retrospectively. LMD was calculated from the PS-based lung shunt assuming a lung mass of 1 kg and 50 Gy per GBq of injected activity shunted to the lung. For the SPECT/CT-based estimate, the LMD was calculated with the activity concentration and lung volume derived from SPECT/CT. The effect of attenuation correction and the patient's breathing on the calculated LMD was studied with the SPECT/CT. With these effects correctly taken into account in a more rigorous fashion, we compared the LMD calculated with SPECT/CT with the LMD calculated with PS. Results: The mean dose to the central region of the lung leads to a more accurate estimate of LMD. Inclusion of the lung region around the diaphragm in the calculation leads to an overestimate of LMD due to the misregistration of the liver activity to the lung from the patient's breathing. LMD calculated based on PS is a poor predictor of the actual LMD. For the subpopulation with large lung shunt, the mean overestimation from the PS method for the lung shunt was 170%. Conclusions: A new method of calculating the LMD for TheraSphere and SIR-Spheres radioembolization of liver cancer based on {sup 99m}Tc-MAA SPECT/CT is presented. The new method provides a more accurate estimate of radiation risk to the lungs. For patients with a large lung shunt calculated from PS, a recalculation of LMD based on SPECT/CT is recommended.
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Westerly, David C. [Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, Colorado 80045 (United States); Mo Xiaohu; DeLuca, Paul M. Jr. [Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53705 (United States); Tome, Wolfgang A. [Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53705 and Institute of Onco-Physics, Albert Einstein College of Medicine and Division of Medical Physics, Department of Radiation Oncology, Montefiore Medical Center, Bronx, New York 10461 (United States); Mackie, Thomas R. [Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53705 and Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53792 (United States)
2013-06-15
Purpose: Pencil beam algorithms are commonly used for proton therapy dose calculations. Szymanowski and Oelfke ['Two-dimensional pencil beam scaling: An improved proton dose algorithm for heterogeneous media,' Phys. Med. Biol. 47, 3313-3330 (2002)] developed a two-dimensional (2D) scaling algorithm which accurately models the radial pencil beam width as a function of depth in heterogeneous slab geometries using a scaled expression for the radial kernel width in water as a function of depth and kinetic energy. However, an assumption made in the derivation of the technique limits its range of validity to cases where the input expression for the radial kernel width in water is derived from a local scattering power model. The goal of this work is to derive a generalized form of 2D pencil beam scaling that is independent of the scattering power model and appropriate for use with any expression for the radial kernel width in water as a function of depth. Methods: Using Fermi-Eyges transport theory, the authors derive an expression for the radial pencil beam width in heterogeneous slab geometries which is independent of the proton scattering power and related quantities. The authors then perform test calculations in homogeneous and heterogeneous slab phantoms using both the original 2D scaling model and the new model with expressions for the radial kernel width in water computed from both local and nonlocal scattering power models, as well as a nonlocal parameterization of Moliere scattering theory. In addition to kernel width calculations, dose calculations are also performed for a narrow Gaussian proton beam. Results: Pencil beam width calculations indicate that both 2D scaling formalisms perform well when the radial kernel width in water is derived from a local scattering power model. Computing the radial kernel width from a nonlocal scattering model results in the local 2D scaling formula under-predicting the pencil beam width by as much as 1.4 mm (21%) at
Takahashi, F; Endo, A
2007-01-01
A system utilising radiation transport codes has been developed to derive accurate dose distributions in a human body for radiological accidents. A suitable model is quite essential for a numerical analysis. Therefore, two tools were developed to setup a 'problem-dependent' input file, defining a radiation source and an exposed person to simulate the radiation transport in an accident with the Monte Carlo calculation codes-MCNP and MCNPX. Necessary resources are defined by a dialogue method with a generally used personal computer for both the tools. The tools prepare human body and source models described in the input file format of the employed Monte Carlo codes. The tools were validated for dose assessment in comparison with a past criticality accident and a hypothesized exposure.
Calculation of fluence and absorbed dose in head tissues due to different photon energies.
Azorín, C; Vega-Carrillo, H R; Rivera, T; Azorín, J
2014-01-01
Calculations of fluence and absorbed dose in head tissues due to different photon energies were carried out using the MCNPX code, to simulate two models of a patient's head: one spherical and another more realistic ellipsoidal. Both head models had concentric shells to describe the scalp skin, the cranium and the brain. The tumor was located at the center of the head and it was a 1 cm-radius sphere. The MCNPX code was run for different energies. Results showed that the fluence decreases as the photons pass through the different head tissues. It can be observed that, although the fluence into the tumor is different for both head models, absorbed dose is the same.
Effects of CT based Voxel Phantoms on Dose Distribution Calculated with Monte Carlo Method
Institute of Scientific and Technical Information of China (English)
Chen Chaobin; Huang Qunying; Wu Yican
2005-01-01
A few CT-based voxel phantoms were produced to investigate the sensitivity of Monte Carlo simulations of X-ray beam and electron beam to the proportions of elements and the mass densities of the materials used to express the patient's anatomical structure. The human body can be well outlined by air, lung, adipose, muscle, soft bone and hard bone to calculate the dose distribution with Monte Carlo method. The effects of the calibration curves established by using various CT scanners are not clinically significant based on our investigation. The deviation from the values of cumulative dose volume histogram derived from CT-based voxel phantoms is less than 1% for the given target.
A BrachyPhantom for verification of dose calculation of HDR brachytherapy planning system
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Austerlitz, C. [Clinica Diana Campos, Recife, PE 52020-030 (Brazil); Campos, C. A. T. [Pontifícia Universidade Católica do Rio de Janeiro, RJ 22451-900 (Brazil)
2013-11-15
Purpose: To develop a calibration phantom for {sup 192}Ir high dose rate (HDR) brachytherapy units that renders possible the direct measurement of absorbed dose to water and verification of treatment planning system.Methods: A phantom, herein designated BrachyPhantom, consists of a Solid Water™ 8-cm high cylinder with a diameter of 14 cm cavity in its axis that allows the positioning of an A1SL ionization chamber with its reference measuring point at the midheight of the cylinder's axis. Inside the BrachyPhantom, at a 3-cm radial distance from the chamber's reference measuring point, there is a circular channel connected to a cylindrical-guide cavity that allows the insertion of a 6-French flexible plastic catheter from the BrachyPhantom surface. The PENELOPE Monte Carlo code was used to calculate a factor, P{sub sw}{sup lw}, to correct the reading of the ionization chamber to a full scatter condition in liquid water. The verification of dose calculation of a HDR brachytherapy treatment planning system was performed by inserting a catheter with a dummy source in the phantom channel and scanning it with a CT. The CT scan was then transferred to the HDR computer program in which a multiple treatment plan was programmed to deliver a total dose of 150 cGy to the ionization chamber. The instrument reading was then converted to absorbed dose to water using the N{sub gas} formalism and the P{sub sw}{sup lw} factor. Likewise, the absorbed dose to water was calculated using the source strength, S{sub k}, values provided by 15 institutions visited in this work.Results: A value of 1.020 (0.09%, k= 2) was found for P{sub sw}{sup lw}. The expanded uncertainty in the absorbed dose assessed with the BrachyPhantom was found to be 2.12% (k= 1). To an associated S{sub k} of 27.8 cGy m{sup 2} h{sup −1}, the total irradiation time to deliver 150 cGy to the ionization chamber point of reference was 161.0 s. The deviation between the absorbed doses to water assessed with
Student nurses need more than maths to improve their drug calculating skills.
Wright, Kerri
2007-05-01
Nurses need to be able to calculate accurate drug calculations in order to safely administer drugs to their patients (NMC, 2002). Studies have shown however that nurses do not always have the necessary skills to calculate accurate drug dosages and are potentially administering incorrect dosages of drugs to their patients (Hutton, M. 1998. Nursing Mathematics: the importance of application. Nursing Standard 13(11), 35-38; Kapborg, I. 1994. Calculation and administration of drug dosage by Swedish nurses, Student Nurses and Physicians. International Journal for Quality in Health Care 6(4), 389-395; O'Shea, E. 1999. Factors contributing to medication errors: a literature review. Journal of Advanced Nursing 8, 496-504; Wilson, A. 2003. Nurses maths: researching a practical approach. Nursing Standard 17(47), 33-36). The literature indicates that in order to improve drug calculations strategies need to focus on both the mathematical skills and conceptual skills of student nurses so they can interpret clinical data into drug calculations to be solved. A study was undertaken to investigate the effectiveness of implementing several strategies which focussed on developing the mathematical and conceptual skills of student nurses to improve their drug calculation skills. The study found that implementing a range of strategies which addressed these two developmental areas significantly improved the drug calculation skills of nurses. The study also indicates that a range of strategies has the potential ensuring that the skills taught are retained by the student nurses. Although the strategies significantly improved the drug calculation skills of student nurses, the fact that only 2 students were able to achieve 100% in their drug calculation test indicates a need for further research into this area.
Poster — Thur Eve — 14: Improving Tissue Segmentation for Monte Carlo Dose Calculation using DECT
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Di Salvio, A.; Bedwani, S.; Carrier, J-F. [Centre hospitalier de l' Université de Montréal (Canada); Bouchard, H. [National Physics Laboratory, Teddington (United Kingdom)
2014-08-15
Purpose: To improve Monte Carlo dose calculation accuracy through a new tissue segmentation technique with dual energy CT (DECT). Methods: Electron density (ED) and effective atomic number (EAN) can be extracted directly from DECT data with a stoichiometric calibration method. Images are acquired with Monte Carlo CT projections using the user code egs-cbct and reconstructed using an FDK backprojection algorithm. Calibration is performed using projections of a numerical RMI phantom. A weighted parameter algorithm then uses both EAN and ED to assign materials to voxels from DECT simulated images. This new method is compared to a standard tissue characterization from single energy CT (SECT) data using a segmented calibrated Hounsfield unit (HU) to ED curve. Both methods are compared to the reference numerical head phantom. Monte Carlo simulations on uniform phantoms of different tissues using dosxyz-nrc show discrepancies in depth-dose distributions. Results: Both SECT and DECT segmentation methods show similar performance assigning soft tissues. Performance is however improved with DECT in regions with higher density, such as bones, where it assigns materials correctly 8% more often than segmentation with SECT, considering the same set of tissues and simulated clinical CT images, i.e. including noise and reconstruction artifacts. Furthermore, Monte Carlo results indicate that kV photon beam depth-dose distributions can double between two tissues of density higher than muscle. Conclusions: A direct acquisition of ED and the added information of EAN with DECT data improves tissue segmentation and increases the accuracy of Monte Carlo dose calculation in kV photon beams.
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Carver, Robert L.; Hogstrom, Kenneth R. [Mary Bird Perkins Cancer Center, 4950 Essen Lane, Baton Rouge, Louisiana 70809 (United States); Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Chu, Connel; Fields, Robert S. [Mary Bird Perkins Cancer Center, 4950 Essen Lane, Baton Rouge, Louisiana 70809 (United States); Sprunger, Conrad P. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)
2013-07-15
Purpose: The purpose of this study was to document the improved accuracy of the pencil beam redefinition algorithm (PBRA) compared to the pencil beam algorithm (PBA) for bolus electron conformal therapy using cylindrical patient phantoms based on patient computed tomography (CT) scans of retromolar trigone and nose cancer.Methods: PBRA and PBA electron dose calculations were compared with measured dose in retromolar trigone and nose phantoms both with and without bolus. For the bolus treatment plans, a radiation oncologist outlined a planning target volume (PTV) on the central axis slice of the CT scan for each phantom. A bolus was designed using the planning.decimal{sup Registered-Sign} (p.d) software (.decimal, Inc., Sanford, FL) to conform the 90% dose line to the distal surface of the PTV. Dose measurements were taken with thermoluminescent dosimeters placed into predrilled holes. The Pinnacle{sup 3} (Philips Healthcare, Andover, MD) treatment planning system was used to calculate PBA dose distributions. The PBRA dose distributions were calculated with an in-house C++ program. In order to accurately account for the phantom materials a table correlating CT number to relative electron stopping and scattering powers was compiled and used for both PBA and PBRA dose calculations. Accuracy was determined by comparing differences in measured and calculated dose, as well as distance to agreement for each measurement point.Results: The measured doses had an average precision of 0.9%. For the retromolar trigone phantom, the PBRA dose calculations had an average {+-}1{sigma} dose difference (calculated - measured) of -0.65%{+-} 1.62% without the bolus and -0.20%{+-} 1.54% with the bolus. The PBA dose calculation had an average dose difference of 0.19%{+-} 3.27% without the bolus and -0.05%{+-} 3.14% with the bolus. For the nose phantom, the PBRA dose calculations had an average dose difference of 0.50%{+-} 3.06% without bolus and -0.18%{+-} 1.22% with the bolus. The PBA
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Scherpelz, R. I.; Borst, F. J.; Hoenes, G. R.
1980-12-01
WRAITH is a FORTRAN computer code which calculates the doses received by a standard man exposed to an accidental release of radioactive material. The movement of the released material through the atmosphere is calculated using a bivariate straight-line Gaussian distribution model, with Pasquill values for standard deviations. The quantity of material in the released cloud is modified during its transit time to account for radioactive decay and daughter production. External doses due to exposure to the cloud can be calculated using a semi-infinite cloud approximation. In situations where the semi-infinite cloud approximation is not a good one, the external dose can be calculated by a "finite plume" three-dimensional point-kernel numerical integration technique. Internal doses due to acute inhalation are cal.culated using the ICRP Task Group Lung Model and a four-segmented gastro-intestinal tract model. Translocation of the material between body compartments and retention in the body compartments are calculated using multiple exponential retention functions. Internal doses to each organ are calculated as sums of cross-organ doses, with each target organ irradiated by radioactive material in a number of source organs. All doses are calculated in rads, with separate values determined for high-LET and low-LET radiation.
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Maerz, Manuel; Mittermair, Pia; Koelbl, Oliver; Dobler, Barbara [Regensburg University Medical Center, Department of Radiotherapy, Regensburg (Germany); Krauss, Andreas [Siemens Healthcare GmbH, Forchheim (Germany)
2016-06-15
Metallic dental implants cause severe streaking artifacts in computed tomography (CT) data, which affect the accuracy of dose calculations in radiation therapy. The aim of this study was to investigate the benefit of the metal artifact reduction algorithm iterative metal artifact reduction (iMAR) in terms of correct representation of Hounsfield units (HU) and dose calculation accuracy. Heterogeneous phantoms consisting of different types of tissue equivalent material surrounding metallic dental implants were designed. Artifact-containing CT data of the phantoms were corrected using iMAR. Corrected and uncorrected CT data were compared to synthetic CT data to evaluate accuracy of HU reproduction. Intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans were calculated in Oncentra v4.3 on corrected and uncorrected CT data and compared to Gafchromic trademark EBT3 films to assess accuracy of dose calculation. The use of iMAR increased the accuracy of HU reproduction. The average deviation of HU decreased from 1006 HU to 408 HU in areas including metal and from 283 HU to 33 HU in tissue areas excluding metal. Dose calculation accuracy could be significantly improved for all phantoms and plans: The mean passing rate for gamma evaluation with 3 % dose tolerance and 3 mm distance to agreement increased from 90.6 % to 96.2 % if artifacts were corrected by iMAR. The application of iMAR allows metal artifacts to be removed to a great extent which leads to a significant increase in dose calculation accuracy. (orig.) [German] Metallische Implantate verursachen streifenfoermige Artefakte in CT-Bildern, welche die Dosisberechnung beeinflussen. In dieser Studie soll der Nutzen des iterativen Metall-Artefakt-Reduktions-Algorithmus iMAR hinsichtlich der Wiedergabetreue von Hounsfield-Werten (HU) und der Genauigkeit von Dosisberechnungen untersucht werden. Es wurden heterogene Phantome aus verschiedenen Arten gewebeaequivalenten Materials mit
Investigation of the usability of conebeam CT data sets for dose calculation
Directory of Open Access Journals (Sweden)
Wilbert Jürgen
2008-12-01
Full Text Available Abstract Background To investigate the feasibility and accuracy of dose calculation in cone beam CT (CBCT data sets. Methods Kilovoltage CBCT images were acquired with the Elekta XVI system, CT studies generated with a conventional multi-slice CT scanner (Siemens Somatom Sensation Open served as reference images. Material specific volumes of interest (VOI were defined for commercial CT Phantoms (CATPhan® and Gammex RMI® and CT values were evaluated in CT and CBCT images. For CBCT imaging, the influence of image acquisition parameters such as tube voltage, with or without filter (F1 or F0 and collimation on the CT values was investigated. CBCT images of 33 patients (pelvis n = 11, thorax n = 11, head n = 11 were compared with corresponding planning CT studies. Dose distributions for three different treatment plans were calculated in CT and CBCT images and differences were evaluated. Four different correction strategies to match CT values (HU and density (D in CBCT images were analysed: standard CT HU-D table without adjustment for CBCT; phantom based HU-D tables; patient group based HU-D tables (pelvis, thorax, head; and patient specific HU-D tables. Results CT values in the CBCT images of the CATPhan® were highly variable depending on the image acquisition parameters: a mean difference of 564 HU ± 377 HU was calculated between CT values determined from the planning CT and CBCT images. Hence, two protocols were selected for CBCT imaging in the further part of the study and HU-D tables were always specific for these protocols (pelvis and thorax with M20F1 filter, 120 kV; head S10F0 no filter, 100 kV. For dose calculation in real patient CBCT images, the largest differences between CT and CBCT were observed for the standard CT HU-D table: differences were 8.0% ± 5.7%, 10.9% ± 6.8% and 14.5% ± 10.4% respectively for pelvis, thorax and head patients using clinical treatment plans. The use of patient and group based HU-D tables resulted in
Biological shielding assessment and dose rate calculation for a neutron inspection portal
Donzella, A.; Bonomi, G.; Giroletti, E.; Zenoni, A.
2012-04-01
With reference to the prototype of neutron inspection portal built and successfully tested in the Rijeka seaport (Croatia) within the EURITRACK (EURopean Illicit Trafficking Countermeasures Kit) project, an assessment of the biological shielding in different set-up configurations of a future portal has been calculated with MCNP Monte Carlo code in the frame of the Eritr@C (European Riposte against Illicit TR@ffiCking) project. In the configurations analyzed the compliance with the dose limits for workers and the population stated by the European legislation is provided by appropriate shielding of the neutron sources and by the delimitation of a controlled area.
Yepes, Pablo; Randeniya, Sharmalee; Taddei, Phillip J; Newhauser, Wayne D
2009-01-07
The Monte Carlo method is used to provide accurate dose estimates in proton radiation therapy research. While it is more accurate than commonly used analytical dose calculations, it is computationally intense. The aim of this work was to characterize for a clinical setup the fast dose calculator (FDC), a Monte Carlo track-repeating algorithm based on GEANT4. FDC was developed to increase computation speed without diminishing dosimetric accuracy. The algorithm used a database of proton trajectories in water to calculate the dose of protons in heterogeneous media. The extrapolation from water to 41 materials was achieved by scaling the proton range and the scattering angles. The scaling parameters were obtained by comparing GEANT4 dose distributions with those calculated with FDC for homogeneous phantoms. The FDC algorithm was tested by comparing dose distributions in a voxelized prostate cancer patient as calculated with well-known Monte Carlo codes (GEANT4 and MCNPX). The track-repeating approach reduced the CPU time required for a complete dose calculation in a voxelized patient anatomy by more than two orders of magnitude, while on average reproducing the results from the Monte Carlo predictions within 2% in terms of dose and within 1 mm in terms of distance.
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Fotina, Irina; Kragl, Gabriele; Kroupa, Bernhard; Trausmuth, Robert; Georg, Dietmar [Medical Univ. Vienna (Austria). Division of Medical Radiation Physics, Dept. of Radiotherapy
2011-07-15
Comparison of the dosimetric accuracy of the enhanced collapsed cone (eCC) algorithm with the commercially available Monte Carlo (MC) dose calculation for complex treatment techniques. A total of 8 intensity-modulated radiotherapy (IMRT) and 2 stereotactic body radiotherapy (SBRT) lung cases were calculated with eCC and MC algorithms with the treatment planning systems (TPS) Oncentra MasterPlan 3.2 (Nucletron) and Monaco 2.01 (Elekta/CMS). Fluence optimization as well as sequencing of IMRT plans was primarily performed using Monaco. Dose prediction errors were calculated using MC as reference. The dose-volume histrogram (DVH) analysis was complemented with 2D and 3D gamma evaluation. Both algorithms were compared to measurements using the Delta4 system (Scandidos). Recalculated with eCC IMRT plans resulted in lower planned target volume (PTV) coverage, as well as in lower organs-at-risk (OAR) doses up to 8%. Small deviations between MC and eCC in PTV dose (1-2%) were detected for IMRT cases, while larger deviations were observed for SBRT (up to 5%). Conformity indices of both calculations were similar; however, the homogeneity of the eCC calculated plans was slightly better. Delta4 measurements confirmed high dosimetric accuracy of both TPS. Mean dose prediction errors < 3% for PTV suggest that both algorithms enable highly accurate dose calculations under clinical conditions. However, users should be aware of slightly underestimated OAR doses using the eCC algorithm. (orig.)
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Animesh
2005-01-01
Full Text Available The complexity of interactions and the nature of the approximations made in the formulation of the algorithm require that the user be familiar with the limitations of various models. As computer power keeps growing, calculation algorithms are tending more towards physically based models. The nature and quantity of the data required varies according to the model which may be either measurement based models or physical based models. Multiple dose calculation algorithm support found in XiO Treatment Planning System can be used to advantage when choice is to be made between speed and accuracy. Thus XiO allows end users generate plans accurately and quickly to optimize the delivery of radiation therapy.
A model of the circulating blood for use in radiation dose calculations
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Hui, T.E.; Poston, J.W. Sr.
1987-01-01
Over the last few years there has been a significant increase in the use of radionuclides in leukocyte, platelet, and erythrocyte imaging procedures. Radiopharmaceutical used in these procedures are confined primarily to the blood, have short half-lives, and irradiate the body as they move through the circulatory system. There is a need for a model, to describe the circulatory system in an adult human, which can be used to provide radiation absorbed dose estimates for these procedures. A simplified model has been designed assuming a static circulatory system and including major organs of the body. The model has been incorporated into the MIRD phantom and calculations have been completed for a number of exposure situations and radionuclides of clinical importance. The model will be discussed in detail and results of calculations using this model will be presented.
A model of the circulating blood for use in radiation dose calculations
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Hui, T.E.; Poston, J.W. Sr.
1987-12-31
Over the last few years there has been a significant increase in the use of radionuclides in leukocyte, platelet, and erythrocyte imaging procedures. Radiopharmaceutical used in these procedures are confined primarily to the blood, have short half-lives, and irradiate the body as they move through the circulatory system. There is a need for a model, to describe the circulatory system in an adult human, which can be used to provide radiation absorbed dose estimates for these procedures. A simplified model has been designed assuming a static circulatory system and including major organs of the body. The model has been incorporated into the MIRD phantom and calculations have been completed for a number of exposure situations and radionuclides of clinical importance. The model will be discussed in detail and results of calculations using this model will be presented.
CALCULATION STUDIES OF SPATIAL DISTRIBUTION OF THE ABSORBED DOSE RATE FOR VARIOUS SEEDS
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N. A. Nerozin
2015-01-01
Full Text Available Purpose. Conducting computational studies of dosimetric characteristics of microsources with the radionuclide I‑125, pilot production of which is established in the research and production complex of isotope and radiopharmaceuticals, JSC “State Scientific Centre of the Russian Federation — Institute for Physics and Power Engineering named after A. I. Leypunsky” (SSC RF IPPE. Sources of production IPPE are similar to the model 6711 of the company Nicomed Amersham, dosimetric characteristics of which are standardized in accordance with the TG43 AAPM formalism.Materials and methods. Microsourse «SEED No. 6711» (model of the company Nicomed Amersham is hermetically sealed in a titanium capsule silver rod covered with a thin layer of radioactive I‑125. The half-life of iodine‑125 is 59,43 days. In the process of decay of I‑125 is converted into the Te‑125.Calculation of parameters of microsources and their comparison with the standard model 6711 is carried out with use of the computer code MCNP.Results. The method of calculation of the basic dosimetric characteristics of the microsourse SSC RF-IPPE in accordance with the TG43 formalism is developed. A comparative analysis of experimental data and calculated results by MCNP code, which allowed to identify possible reasons for differences, is performed. The estimated dose characteristics and recommended standard data for dose characteristics of micro «SEED No. 6711» are compared.Conclusions. There are two possible reasons for the differences between experimental and calculated results. The first one may be the roughness of the surface of a silver rod or diffusion of radioactive iodine in silver. The second reason might be the difference of the cross sections of the characteristic radiation of silver used in MCNP code. In the comparison of calculated dose characteristics and recommended standard the role of the application activity is very important. In compliance with the standard
Uncertainties in Monte Carlo-based absorbed dose calculations for an experimental benchmark.
Renner, F; Wulff, J; Kapsch, R-P; Zink, K
2015-10-01
There is a need to verify the accuracy of general purpose Monte Carlo codes like EGSnrc, which are commonly employed for investigations of dosimetric problems in radiation therapy. A number of experimental benchmarks have been published to compare calculated values of absorbed dose to experimentally determined values. However, there is a lack of absolute benchmarks, i.e. benchmarks without involved normalization which may cause some quantities to be cancelled. Therefore, at the Physikalisch-Technische Bundesanstalt a benchmark experiment was performed, which aimed at the absolute verification of radiation transport calculations for dosimetry in radiation therapy. A thimble-type ionization chamber in a solid phantom was irradiated by high-energy bremsstrahlung and the mean absorbed dose in the sensitive volume was measured per incident electron of the target. The characteristics of the accelerator and experimental setup were precisely determined and the results of a corresponding Monte Carlo simulation with EGSnrc are presented within this study. For a meaningful comparison, an analysis of the uncertainty of the Monte Carlo simulation is necessary. In this study uncertainties with regard to the simulation geometry, the radiation source, transport options of the Monte Carlo code and specific interaction cross sections are investigated, applying the general methodology of the Guide to the expression of uncertainty in measurement. Besides studying the general influence of changes in transport options of the EGSnrc code, uncertainties are analyzed by estimating the sensitivity coefficients of various input quantities in a first step. Secondly, standard uncertainties are assigned to each quantity which are known from the experiment, e.g. uncertainties for geometric dimensions. Data for more fundamental quantities such as photon cross sections and the I-value of electron stopping powers are taken from literature. The significant uncertainty contributions are identified as
Petillion, Saskia; Swinnen, Ans; Defraene, Gilles; Verhoeven, Karolien; Weltens, Caroline; Van den Heuvel, Frank
2014-07-08
The comparison of the pencil beam dose calculation algorithm with modified Batho heterogeneity correction (PBC-MB) and the analytical anisotropic algorithm (AAA) and the mutual comparison of advanced dose calculation algorithms used in breast radiotherapy have focused on the differences between the physical dose distributions. Studies on the radiobiological impact of the algorithm (both on the tumor control and the moderate breast fibrosis prediction) are lacking. We, therefore, investigated the radiobiological impact of the dose calculation algorithm in whole breast radiotherapy. The clinical dose distributions of 30 breast cancer patients, calculated with PBC-MB, were recalculated with fixed monitor units using more advanced algorithms: AAA and Acuros XB. For the latter, both dose reporting modes were used (i.e., dose-to-medium and dose-to-water). Next, the tumor control probability (TCP) and the normal tissue complication probability (NTCP) of each dose distribution were calculated with the Poisson model and with the relative seriality model, respectively. The endpoint for the NTCP calculation was moderate breast fibrosis five years post treatment. The differences were checked for significance with the paired t-test. The more advanced algorithms predicted a significantly lower TCP and NTCP of moderate breast fibrosis then found during the corresponding clinical follow-up study based on PBC calculations. The differences varied between 1% and 2.1% for the TCP and between 2.9% and 5.5% for the NTCP of moderate breast fibrosis. The significant differences were eliminated by determination of algorithm-specific model parameters using least square fitting. Application of the new parameters on a second group of 30 breast cancer patients proved their appropriateness. In this study, we assessed the impact of the dose calculation algorithms used in whole breast radiotherapy on the parameters of the radiobiological models. The radiobiological impact was eliminated by
Critical groups vs. representative person: dose calculations due to predicted releases from USEXA
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Ferreira, N.L.D., E-mail: nelson.luiz@ctmsp.mar.mil.br [Centro Tecnologico da Marinha (CTM/SP), Sao Paulo, SP (Brazil); Rochedo, E.R.R., E-mail: elainerochedo@gmail.com [Instituto de Radiprotecao e Dosimetria (lRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Mazzilli, B.P., E-mail: mazzilli@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)
2013-07-01
The critical group cf Centro Experimental Aramar (CEA) site was previously defined based 00 the effluents releases to the environment resulting from the facilities already operational at CEA. In this work, effective doses are calculated to members of the critical group considering the predicted potential uranium releases from the Uranium Hexafluoride Production Plant (USEXA). Basically, this work studies the behavior of the resulting doses related to the type of habit data used in the analysis and two distinct situations are considered: (a) the utilization of average values obtained from official institutions (IBGE, IEA-SP, CNEN, IAEA) and from the literature; and (b) the utilization of the 95{sup tb} percentile of the values derived from distributions fit to the obtained habit data. The first option corresponds to the way that data was used for the definition of the critical group of CEA done in former assessments, while the second one corresponds to the use of data in deterministic assessments, as recommended by ICRP to estimate doses to the so--called 'representative person' . (author)
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Grassberger, C; Daartz, J; Dowdell, S; Ruggieri, T; Sharp, G; Paganetti, H [Massachusetts General Hospital and Harvard Medical School, Boston, MA (United States)
2014-06-15
Purpose: Evaluate Monte Carlo (MC) dose calculation and the prediction of the treatment planning system (TPS) in a lung phantom and compare them in a cohort of 20 lung patients treated with protons. Methods: A 2-dimensional array of ionization chambers was used to evaluate the dose across the target in a lung phantom. 20 lung cancer patients on clinical trials were re-simulated using a validated Monte Carlo toolkit (TOPAS) and compared to the TPS. Results: MC increases dose calculation accuracy in lung compared to the clinical TPS significantly and predicts the dose to the target in the phantom within ±2%: the average difference between measured and predicted dose in a plane through the center of the target is 5.6% for the TPS and 1.6% for MC. MC recalculations in patients show a mean dose to the clinical target volume on average 3.4% lower than the TPS, exceeding 5% for small fields. The lower dose correlates significantly with aperture size and the distance of the tumor to the chest wall (Spearman's p=0.0002/0.004). For large tumors MC also predicts consistently higher V{sub 5} and V{sub 10} to the normal lung, due to a wider lateral penumbra, which was also observed experimentally. Critical structures located distal to the target can show large deviations, though this effect is very patient-specific. Conclusion: Advanced dose calculation techniques, such as MC, would improve treatment quality in proton therapy for lung cancer by avoiding systematic overestimation of target dose and underestimation of dose to normal lung. This would increase the accuracy of the relationships between dose and effect, concerning tumor control as well as normal tissue toxicity. As the role of proton therapy in the treatment of lung cancer continues to be evaluated in clinical trials, this is of ever-increasing importance. This work was supported by National Cancer Institute Grant R01CA111590.
GPU-based Monte Carlo radiotherapy dose calculation using phase-space sources
Townson, Reid; Tian, Zhen; Graves, Yan Jiang; Zavgorodni, Sergei; Jiang, Steve B
2013-01-01
A novel phase-space source implementation has been designed for GPU-based Monte Carlo dose calculation engines. Due to the parallelized nature of GPU hardware, it is essential to simultaneously transport particles of the same type and similar energies but separated spatially to yield a high efficiency. We present three methods for phase-space implementation that have been integrated into the most recent version of the GPU-based Monte Carlo radiotherapy dose calculation package gDPM v3.0. The first method is to sequentially read particles from a patient-dependent phase-space and sort them on-the-fly based on particle type and energy. The second method supplements this with a simple secondary collimator model and fluence map implementation so that patient-independent phase-space sources can be used. Finally, as the third method (called the phase-space-let, or PSL, method) we introduce a novel strategy to pre-process patient-independent phase-spaces and bin particles by type, energy and position. Position bins l...
GMC: a GPU implementation of a Monte Carlo dose calculation based on Geant4.
Jahnke, Lennart; Fleckenstein, Jens; Wenz, Frederik; Hesser, Jürgen
2012-03-07
We present a GPU implementation called GMC (GPU Monte Carlo) of the low energy (CUDA programming interface. The classes for electron and photon interactions as well as a new parallel particle transport engine were implemented. The way a particle is processed is not in a history by history manner but rather by an interaction by interaction method. Every history is divided into steps that are then calculated in parallel by different kernels. The geometry package is currently limited to voxelized geometries. A modified parallel Mersenne twister was used to generate random numbers and a random number repetition method on the GPU was introduced. All phantom results showed a very good agreement between GPU and CPU simulation with gamma indices of >97.5% for a 2%/2 mm gamma criteria. The mean acceleration on one GTX 580 for all cases compared to Geant4 on one CPU core was 4860. The mean number of histories per millisecond on the GPU for all cases was 658 leading to a total simulation time for one intensity-modulated radiation therapy dose distribution of 349 s. In conclusion, Geant4-based Monte Carlo dose calculations were significantly accelerated on the GPU.
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Jingyu Zhang
2016-01-01
Full Text Available In water-cooled reactor, the dominant radioactive source term under normal operation is activated corrosion products (ACPs, which have an important impact on reactor inspection and maintenance. A three-node transport model of ACPs was introduced into the new version of ACPs source term code CATE in this paper, which makes CATE capable of theoretically simulating the variation and the distribution of ACPs in a water-cooled reactor and suitable for more operating conditions. For code testing, MIT PWR coolant chemistry loop was simulated, and the calculation results from CATE are close to the experimental results from MIT, which means CATE is available and credible on ACPs analysis of water-cooled reactor. Then ACPs in the blanket cooling loop of water-cooled fusion reactor ITER under construction were analyzed using CATE and the results showed that the major contributors are the short-life nuclides, especially Mn-56. At last a point kernel integration code ARShield was coupled with CATE, and the dose rate around ITER blanket cooling loop was calculated. Results showed that after shutting down the reactor only for 8 days, the dose rate decreased nearly one order of magnitude, which was caused by the rapid decay of the short-life ACPs.
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Herraiz Lblanca, M. D.; Diaz Romero, F.; Casares Magaz, O.; Garrido Breton, C.; Catalan Acosta, A.; Hernandez Armas, J.
2013-07-01
This paper proposes a method that allows you to calculate the effective dose in any interventional radiology procedure using an anthropomorphic mannequin Alderson RANDO and dosimeters TLD 100 chip. This method has been applied to an angio Radiology procedure: the biliary drainage. The objectives that have been proposed are: to) put together a method that, on an experimental basis, allows to know dosis en organs to calculate effective dose in complex procedures and b) apply the method to the calculation of the effective dose of biliary drainage. (Author)
A GPU-based Monte Carlo dose calculation code for photon transport in a voxel phantom
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Bellezzo, M.; Do Nascimento, E.; Yoriyaz, H., E-mail: mbellezzo@gmail.br [Instituto de Pesquisas Energeticas e Nucleares / CNEN, Av. Lineu Prestes 2242, Cidade Universitaria, 05508-000 Sao Paulo (Brazil)
2014-08-15
As the most accurate method to estimate absorbed dose in radiotherapy, Monte Carlo method has been widely used in radiotherapy treatment planning. Nevertheless, its efficiency can be improved for clinical routine applications. In this paper, we present the CUBMC code, a GPU-based Mc photon transport algorithm for dose calculation under the Compute Unified Device Architecture platform. The simulation of physical events is based on the algorithm used in Penelope, and the cross section table used is the one generated by the Material routine, als present in Penelope code. Photons are transported in voxel-based geometries with different compositions. To demonstrate the capabilities of the algorithm developed in the present work four 128 x 128 x 128 voxel phantoms have been considered. One of them is composed by a homogeneous water-based media, the second is composed by bone, the third is composed by lung and the fourth is composed by a heterogeneous bone and vacuum geometry. Simulations were done considering a 6 MeV monoenergetic photon point source. There are two distinct approaches that were used for transport simulation. The first of them forces the photon to stop at every voxel frontier, the second one is the Woodcock method, where the photon stop in the frontier will be considered depending on the material changing across the photon travel line. Dose calculations using these methods are compared for validation with Penelope and MCNP5 codes. Speed-up factors are compared using a NVidia GTX 560-Ti GPU card against a 2.27 GHz Intel Xeon CPU processor. (Author)
Luszczki, Jarogniew J
2007-04-01
The objective of this study was to characterize the anticonvulsant and acute adverse-effect potentials of topiramate (TPM) and gabapentin (GBP)-two second-generation antiepileptic drugs administered alone and in combination in the maximal electroshock (MES)-induced seizures and chimney test in mice. The anticonvulsant and acute adverse effects of the combination of TPM with GBP at the fixed ratio of 1:1 were determined using the type I isobolographic analysis for nonparallel dose-response relationship curves (DRRCs). To ascertain any pharmacokinetic contribution to the observed interaction between TPM and GBP, total brain concentrations of both drugs were determined. The isobolographic analysis of interaction for TPM and GBP, whose DRRCs were not parallel in both MES and chimney tests, was accompanied with a presentation of all required calculations allowing the determination of lower and upper lines of additivity. The isobolographic analysis revealed that TPM combined with GBP at the fixed-ratio combination of 1:1 interacted supraadditively (synergistically) in terms of suppression of MES-induced seizures, and simultaneously, the combination produced additive interaction with respect to motor coordination impairment (adverse effects) in the chimney test. The evaluation of pharmacokinetic characteristics of interaction for the combination of TPM with GBP revealed that neither TPM nor GBP affected their total brain concentrations in experimental animals, and thus, the observed interaction in the MES test was pharmacodynamic in nature. In conclusion, the combination of TPM with GBP, because of supraadditivity in the MES test and additivity in terms of motor coordination impairment in the chimney test as well as lack of pharmacokinetic interactions between drugs, fulfilled the criterion of a favorable combination, worthy of recommendation in further clinical practice.
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Abdulhamid Chaikh
2015-12-01
Full Text Available Purpose: the objective of this study is to validate a procedure based on a statistical method to assess the agreement and the correlation between measured and calculated dose in the process of quality assurance (QA for Intensity-Modulated Radiation Therapy (IMRT.Patients and methods: 10 patients including 56 fields for head and neck cancer treatment were analyzed. For each patient, one treatment plan was generated using Eclipse TPS®. To compare the calculated dose with measured dose a CT-scan of solid water slabs (30 × 30 × 15 cm3 was used. The measurements were done for absolute dose by a pinpoint ionization chamber and 2D dose distributions using electronic portal imaging device dosimetry. Six criteria levels were applied for each case (3%, 3 mm, (4%, 3 mm, (5%, 3 mm, (4%, 4 mm, (5%, 4 mm and (5%, 5 mm. The normality of the data and the variance homogeneity were tested using Shapiro-Wilks test and Levene’s test, respectively. Wilcoxon signed-rank paired test was used to calculate p-value. Bland-Altman method was used to calculate the limit of agreement between calculated and measured doses and to draw a scatter plot. The correlation between calculated and measured doses was assessed using Spearman’s rank test.Results: The statistical tests indicate that the data do not fulfill normal distribution, p < 0.001 and had a homogenous variance, p = 0.85. The upper and lower limit of agreements for absolute dose measurements were 6.44% and -6.40%, respectively. Wilcoxon test indicated a significance difference between calculated and measured dose with ionization chamber, p = 0.01. Spearman’s test indicated a strong correlation between calculated and absolute measured dose, ρ = 0.99. Therefore, there is a lack of correlation between dose difference for absolute dose measurements and gamma passing rates for 2D dose measurements.Conclusion: the statistical tests showed that the common acceptance criteria’s using gamma evaluation are not able
Element-specific and constant parameters used for dose calculations in SR-Site
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Norden, Sara (Svensk Kaernbraenslehantering AB (Sweden)); Avila, Rodolfo; De la Cruz, Idalmis; Stenberg, Kristofer; Grolander, Sara (Facilia AB (Sweden))
2010-12-15
The report presents Best Estimate (BE) values and Probability Distribution Functions (PDFs) of Concentration Ratios (CR) for different types of terrestrial and aquatic biota and distribution coefficients (K{sub d}) for organic and inorganic deposits, as well as for suspended matter in freshwater and marine ecosystems. The BE values have been used in deterministic simulations for derivation of Landscape Dose Factors (LDF) applied for dose assessments in SR-Site. The PDFs have been used in probabilistic simulations for uncertainty and sensitivity analysis of the LDFs. The derivation of LDFs for SR-Site is described in /Avila et al. 2010/. The CR and K{sub d} values have been derived using both site-specific data measured at Laxemar and Forsmark during the site investigation program and literature data. These two data sources have been combined using Bayesian updating methods, which are described in detail in an Appendix, along with the input data used in the statistical analyses and the results obtained. The report also describes a kinetic-allometric model that was applied for deriving values of CR for terrestrial herbivores in cases when site and literature data for an element were missing. In addition, the report presents values for a number of other parameters used in the SR-Site Radionuclide Model for the biosphere: radionuclide decay-ingrowth data, elemental diffusivities, fractions of element content released during decomposition processes, ingestion of food, water and soil by cattle, elements retention fraction on plant surfaces during irrigation. The report also presents parameter values used in calculation of doses to a reference man: dose coefficients for inhalation, ingestion and external exposure, inhalation rates, ingestion rates of food and water
Weng, Zuquan; Wang, Kejian; Li, Haibo; Shi, Qiang
2015-07-10
It was recently suggested that daily dose, liver metabolism and lipophilicity were associated with an oral drug's potential to cause hepatotoxicity, but this has not been widely accepted. A likely reason is that published data lack comprehensiveness, as they were based on only about one third of all FDA approved single-active-ingredient oral prescription drugs. Here the 975 oral drugs used worldwide which have a Defined Daily Dose (DDD) designated in the World Health Organization's Anatomical Therapeutic Chemical classification system and whose hADRs potential and metabolism data are available in the Micromedex Drugdex® compendium were studied, with their lipophilicity calculated by the partition coefficient LogP. Of the 975 drugs examined, 49% (478) have the potential to induce at least one type of hepatic adverse drug reactions (hADRs) such as fatal hepatotoxicity, acute liver failure, significant ALT/AST elevation, hepatitis, and jaundice. By single factor analysis, a higher DDD (≥100 mg) was found to be associated with all types of hADRs, and extensive liver metabolism (≥50%) was associated with a subset of hADRs including fatal hADRs, hepatitis and jaundice, while LogP showed no relation to any types of hADRs. Contrary to previous reports, none of the combination, neither DDD and liver metabolism, nor DDD and LogP, was found to be more predictive of hADRs than using DDD or liver metabolism alone. These data provide convincing evidence that a higher daily dose and extensive liver metabolism, but not lipophilicity, are independent but not synergistic risk factors for oral drugs to induce hepatotoxicity.
Fix, Michael K.; Cygler, Joanna; Frei, Daniel; Volken, Werner; Neuenschwander, Hans; Born, Ernst J.; Manser, Peter
2013-05-01
The electron Monte Carlo (eMC) dose calculation algorithm available in the Eclipse treatment planning system (Varian Medical Systems) is based on the macro MC method and uses a beam model applicable to Varian linear accelerators. This leads to limitations in accuracy if eMC is applied to non-Varian machines. In this work eMC is generalized to also allow accurate dose calculations for electron beams from Elekta and Siemens accelerators. First, changes made in the previous study to use eMC for low electron beam energies of Varian accelerators are applied. Then, a generalized beam model is developed using a main electron source and a main photon source representing electrons and photons from the scattering foil, respectively, an edge source of electrons, a transmission source of photons and a line source of electrons and photons representing the particles from the scrapers or inserts and head scatter radiation. Regarding the macro MC dose calculation algorithm, the transport code of the secondary particles is improved. The macro MC dose calculations are validated with corresponding dose calculations using EGSnrc in homogeneous and inhomogeneous phantoms. The validation of the generalized eMC is carried out by comparing calculated and measured dose distributions in water for Varian, Elekta and Siemens machines for a variety of beam energies, applicator sizes and SSDs. The comparisons are performed in units of cGy per MU. Overall, a general agreement between calculated and measured dose distributions for all machine types and all combinations of parameters investigated is found to be within 2% or 2 mm. The results of the dose comparisons suggest that the generalized eMC is now suitable to calculate dose distributions for Varian, Elekta and Siemens linear accelerators with sufficient accuracy in the range of the investigated combinations of beam energies, applicator sizes and SSDs.
Fix, Michael K; Cygler, Joanna; Frei, Daniel; Volken, Werner; Neuenschwander, Hans; Born, Ernst J; Manser, Peter
2013-05-07
The electron Monte Carlo (eMC) dose calculation algorithm available in the Eclipse treatment planning system (Varian Medical Systems) is based on the macro MC method and uses a beam model applicable to Varian linear accelerators. This leads to limitations in accuracy if eMC is applied to non-Varian machines. In this work eMC is generalized to also allow accurate dose calculations for electron beams from Elekta and Siemens accelerators. First, changes made in the previous study to use eMC for low electron beam energies of Varian accelerators are applied. Then, a generalized beam model is developed using a main electron source and a main photon source representing electrons and photons from the scattering foil, respectively, an edge source of electrons, a transmission source of photons and a line source of electrons and photons representing the particles from the scrapers or inserts and head scatter radiation. Regarding the macro MC dose calculation algorithm, the transport code of the secondary particles is improved. The macro MC dose calculations are validated with corresponding dose calculations using EGSnrc in homogeneous and inhomogeneous phantoms. The validation of the generalized eMC is carried out by comparing calculated and measured dose distributions in water for Varian, Elekta and Siemens machines for a variety of beam energies, applicator sizes and SSDs. The comparisons are performed in units of cGy per MU. Overall, a general agreement between calculated and measured dose distributions for all machine types and all combinations of parameters investigated is found to be within 2% or 2 mm. The results of the dose comparisons suggest that the generalized eMC is now suitable to calculate dose distributions for Varian, Elekta and Siemens linear accelerators with sufficient accuracy in the range of the investigated combinations of beam energies, applicator sizes and SSDs.
Krstic, D; Nikezic, D
2009-10-01
In this paper the effective dose in the age-dependent ORNL phantoms series, due to naturally occurring radionuclides in building materials, was calculated. The absorbed doses for various organs or human tissues have been calculated. The MCNP-4B computer code was used for this purpose. The effective dose was calculated according to ICRP Publication 74. The obtained values of dose conversion factors for a standard room are: 1.033, 0.752 and 0.0538 nSv h-1 per Bq kg-1 for elements of the U and Th decay series and for the K isotope, respectively. The values of effective dose agreed generally with those found in the literature, although the values estimated here for elements of the U series were higher in some cases.
Mitrikas, V G
2015-01-01
Monitoring of the radiation loading on cosmonauts requires calculation of absorbed dose dynamics with regard to the stay of cosmonauts in specific compartments of the space vehicle that differ in shielding properties and lack means of radiation measurement. The paper discusses different aspects of calculation modeling of radiation effects on human body organs and tissues and reviews the effective dose estimates for cosmonauts working in one or another compartment over the previous period of the International space station operation. It was demonstrated that doses measured by a real or personal dosimeters can be used to calculate effective dose values. Correct estimation of accumulated effective dose can be ensured by consideration for time course of the space radiation quality factor.
Lessons Learned: Dose Selection of Small Molecule-Targeted Oncology Drugs.
Bullock, Julie M; Rahman, Atiqur; Liu, Qi
2016-06-01
Evaluation of dose plays a critical role in a successful oncology development program. Typically for oncology agents, the first-in-man phase I dose-escalation trials are conducted to determine a maximum tolerated dose (MTD). This MTD is taken forward into subsequent trials to establish the safety and efficacy of the drug product. Although this approach was appropriate historically for cytotoxics, the application of MTD as the recommend phase II dose has been problematic for the newer small molecule-targeted oncology agents. Promising alternative approaches using dose and exposure exploration, including lessons learned from recent targeted oncology agent development and approvals, are summarized and discussed. Clin Cancer Res; 22(11); 2630-8. ©2016 AACR SEE ALL ARTICLES IN THIS CCR FOCUS SECTION, "NEW APPROACHES FOR OPTIMIZING DOSING OF ANTICANCER AGENTS".
Directory of Open Access Journals (Sweden)
Brian C. Palmer
2016-12-01
Full Text Available Transdermal drug delivery systems have been around for decades, and current technologies (e.g., patches, ointments, and creams enhance the skin permeation of low molecular weight, lipophilic drugs that are efficacious at low doses. The objective of current transdermal drug delivery research is to discover ways to enhance skin penetration of larger, hydrophilic drugs and macromolecules for disease treatment and vaccination. Nanocarriers made of lipids, metals, or polymers have been successfully used to increase penetration of drugs or vaccines, control drug release, and target drugs to specific areas of skin in vivo. While more research is needed to identify the safety of nanocarriers, this technology has the potential to expand the use of transdermal routes of administration to a wide array of therapeutics. Here, we review the current state of nanoparticle skin delivery systems with special emphasis on targeting skin diseases.
Walters, Robert; Summers, Geoffrey P.; Warmer. Keffreu J/; Messenger, Scott; Lorentzen, Justin R.; Morton, Thomas; Taylor, Stephen J.; Evans, Hugh; Heynderickx, Daniel; Lei, Fan
2007-01-01
This paper presents a method for using the SPENVIS on-line computational suite to implement the displacement damage dose (D(sub d)) methodology for calculating end-of-life (EOL) solar cell performance for a specific space mission. This paper builds on our previous work that has validated the D(sub d) methodology against both measured space data [1,2] and calculations performed using the equivalent fluence methodology developed by NASA JPL [3]. For several years, the space solar community has considered general implementation of the D(sub d) method, but no computer program exists to enable this implementation. In a collaborative effort, NRL, NASA and OAI have produced the Solar Array Verification and Analysis Tool (SAVANT) under NASA funding, but this program has not progressed beyond the beta-stage [4]. The SPENVIS suite with the Multi Layered Shielding Simulation Software (MULASSIS) contains all of the necessary components to implement the Dd methodology in a format complementary to that of SAVANT [5]. NRL is currently working with ESA and BIRA to include the Dd method of solar cell EOL calculations as an integral part of SPENVIS. This paper describes how this can be accomplished.
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Soldat, J.K.
1989-10-01
This report compares the results of the calculation of potential radiation doses to the public by two different environmental dosimetric systems for the years 1983 through 1987. Both systems project the environmental movement of radionuclides released with effluents from Hanford operations; their concentrations in air, water, and foods; the intake of radionuclides by ingestion and inhalation; and, finally, the potential radiation doses from radionuclides deposited in the body and from external sources. The first system, in use for the past decade at Hanford, calculates radiation doses in terms of 50-year cumulative dose equivalents to body organs and to the whole body, based on the methodology defined in ICRP Publication 2. This system uses a suite of three computer codes: PABLM, DACRIN, and KRONIC. In the new system, 50-year committed doses are calculated in accordance with the recommendations of the ICRP Publications 26 and 30, which were adopted by the US Department of Energy (DOE) in 1985. This new system calculates dose equivalent (DE) to individual organs and effective dose equivalent (EDE). The EDE is a risk-weighted DE that is designed to be an indicator of the potential health effects arising from the radiation dose. 16 refs., 1 fig., 38 tabs.
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Sampson, Andrew; Le Yi; Williamson, Jeffrey F. [Department of Radiation Oncology, Virginia Commonwealth University, Richmond, Virginia 23298 (United States)
2012-02-15
Purpose: To demonstrate potential of correlated sampling Monte Carlo (CMC) simulation to improve the calculation efficiency for permanent seed brachytherapy (PSB) implants without loss of accuracy. Methods: CMC was implemented within an in-house MC code family (PTRAN) and used to compute 3D dose distributions for two patient cases: a clinical PSB postimplant prostate CT imaging study and a simulated post lumpectomy breast PSB implant planned on a screening dedicated breast cone-beam CT patient exam. CMC tallies the dose difference, {Delta}D, between highly correlated histories in homogeneous and heterogeneous geometries. The heterogeneous geometry histories were derived from photon collisions sampled in a geometrically identical but purely homogeneous medium geometry, by altering their particle weights to correct for bias. The prostate case consisted of 78 Model-6711 {sup 125}I seeds. The breast case consisted of 87 Model-200 {sup 103}Pd seeds embedded around a simulated lumpectomy cavity. Systematic and random errors in CMC were unfolded using low-uncertainty uncorrelated MC (UMC) as the benchmark. CMC efficiency gains, relative to UMC, were computed for all voxels, and the mean was classified in regions that received minimum doses greater than 20%, 50%, and 90% of D{sub 90}, as well as for various anatomical regions. Results: Systematic errors in CMC relative to UMC were less than 0.6% for 99% of the voxels and 0.04% for 100% of the voxels for the prostate and breast cases, respectively. For a 1 x 1 x 1 mm{sup 3} dose grid, efficiency gains were realized in all structures with 38.1- and 59.8-fold average gains within the prostate and breast clinical target volumes (CTVs), respectively. Greater than 99% of the voxels within the prostate and breast CTVs experienced an efficiency gain. Additionally, it was shown that efficiency losses were confined to low dose regions while the largest gains were located where little difference exists between the homogeneous and
Drug Dose Adjustment in Dialysis Patients Admitted in Clinics Other Than Internal Medicine.
Solak, Yalcin; Biyik, Zeynep; Gaipov, Abduzhappar; Kayrak, Mehmet; Ciray, Hilal; Cizmecioglu, Ahmet; Tonbul, Halil Zeki; Turk, Suleyman
2016-01-01
Many drugs that are administered during hospitalization are metabolized or excreted through kidneys, consequently require dosage adjustment. We aimed to investigate inappropriate prescription of drugs requiring renal dose adjustment (RDA) in various surgical and medical inpatient clinics. We retrospectively determined dialysis patients hospitalized between January 2007 and December 2010. Inpatient clinics, including cardiology, pulmonary medicine, neurology, infectious diseases (medical clinics) and cardiovascular surgery, orthopedics, general surgery, obstetrics and gynecology, and neurosurgery (surgical clinics), were screened via electronic database. Total and RDA medications were determined. RDA drugs correctly adjusted to creatinine clearance were labeled as RDA-A (appropriate), otherwise as RDA-I (inappropriate). Renal doses of RDA medications were based on the "American College of Physicians Drug Prescribing in Renal Failure, fifth Edition." Two hundred seventeen hospitalization records of 172 dialysis patients (92 men and 80 women) were included in the analysis. Mean age of patients was 59.4 ± 14.6 years, and the mean hospitalization duration was 8.5 ± 7.8 days. In total, 247 (84.3%, percentage in drugs requiring dose adjustment) and 175 (46.2%) drugs have been inadequately dosed in surgical and medical clinics, respectively. The percentage of patients to whom at least 1 RDA-I drug was ordered was 92% and 91.4% for surgical and medical clinics, respectively (P > 0.05). Nephrology consultation numbers were 8 (7.1%) in surgical and 32 (30.4%) in medical clinics. The most common RDA-I drugs were aspirin and famotidine. A significant portion of RDA drugs was ordered inappropriately both in surgical and medical clinics. Nephrology consultation rate was very low. Measures to increase physician awareness are required to improve results.
Directory of Open Access Journals (Sweden)
E. A. Drozd
2014-01-01
Full Text Available The basis of methodical approach for calculation of the individualized internal doses is the con-firmed original scientific hypothesis that every group of individuals which are homogeneous on demographic characteristics (gender and age, on a curve of dose distribution that is constructed according to the data of individual measurements of Cs137 in the human body (WB measurements, has the determined location, thus, that is constant in time, i.e. percentiles of dose distribution corresponding to the average internal dose of every age group of men and women on a curve of dose distribution occupy the certain, steady in time, location. Keywords: individualized internal dose, percentile of dose distribution, stability.
Concept for calculating dose rates from activated groundwater at accelerator sites
Prolingheuer, N; Vanderborght, J; Schlögl, B; Nabbi, R; Moormann, R
Licensing of particle accelerators requires the proof that the groundwater outside of the site will not be significantly contaminated by activation products formed below accelerator and target. In order to reduce the effort for this proof, a site independent simplified but conservative method is under development. The conventional approach for calculation of activation of soil and groundwater is shortly described on example of a site close to Forschungszentrum Juelich, Germany. Additionally an updated overview of a data library for partition coefficients for relevant nuclides transported in the aquifer at the site is presented. The approximate model for transport of nuclides with ground water including exemplary results on nuclide concentrations outside of the site boundary and of resulting effective doses is described. Further applications and developments are finally outlined.
Calculating tumor trajectory and dose-of-the-day using cone-beam CT projections
Jones, Bernard L; Miften, Moyed
2015-01-01
Purpose: Cone-beam CT (CBCT) projection images provide anatomical data in real-time over several respiratory cycles, forming a comprehensive picture of tumor movement. We developed and validated a method which uses these projections to determine the trajectory of and dose to highly mobile tumors during each fraction of treatment. Methods: CBCT images of a respiration phantom were acquired, the trajectory of which mimicked a lung tumor with high amplitude (up to 2.5 cm) and hysteresis. A template-matching algorithm was used to identify the location of a steel BB in each CBCT projection, and a Gaussian probability density function for the absolute BB position was calculated which best fit the observed trajectory of the BB in the imager geometry. Two modifications of the trajectory reconstruction were investigated: first, using respiratory phase information to refine the trajectory estimation (Phase), and second, using the Monte Carlo (MC) method to sample the estimated Gaussian tumor position distribution. Resu...
Calculation of Doses Due to Accidentally Released Plutonium From An LMFBR
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Fish, B.R.
2001-08-07
Experimental data and analytical models that should be considered in assessing the transport properties of plutonium aerosols following a hypothetical reactor accident have been examined. Behaviors of released airborne materials within the reactor containment systems, as well as in the atmosphere near the reactor site boundaries, have been semiquantitatively predicted from experimental data and analytical models. The fundamental chemistry of plutonium as it may be applied in biological systems has been used to prepare models related to the intake and metabolism of plutonium dioxide, the fuel material of interest. Attempts have been made to calculate the possible doses from plutonium aerosols for a typical analyzed release in order to evaluate the magnitude of the internal exposure hazards that might exist in the vicinity of the reactor after a hypothetical LMFBR (Liquid-Metal Fast Breeder Reactor) accident. Intake of plutonium (using data for {sup 239}Pu as an example) and its distribution in the body were treated parametrically without regard to the details of transport pathways in the environment. To the extent possible, dose-response data and models have been reviewed, and an assessment of their adequacy has been made so that recommended or preferred practices could be developed.
Lens of the eye dose calculation for neuro-interventional procedures and CBCT scans of the head
Xiong, Zhenyu; Vijayan, Sarath; Rana, Vijay; Jain, Amit; Rudin, Stephen; Bednarek, Daniel R.
2016-03-01
The aim of this work is to develop a method to calculate lens dose for fluoroscopically-guided neuro-interventional procedures and for CBCT scans of the head. EGSnrc Monte Carlo software is used to determine the dose to the lens of the eye for the projection geometry and exposure parameters used in these procedures. This information is provided by a digital CAN bus on the Toshiba Infinix C-Arm system which is saved in a log file by the real-time skin-dose tracking system (DTS) we previously developed. The x-ray beam spectra on this machine were simulated using BEAMnrc. These spectra were compared to those determined by SpekCalc and validated through measured percent-depth-dose (PDD) curves and half-value-layer (HVL) measurements. We simulated CBCT procedures in DOSXYZnrc for a CTDI head phantom and compared the surface dose distribution with that measured with Gafchromic film, and also for an SK150 head phantom and compared the lens dose with that measured with an ionization chamber. Both methods demonstrated good agreement. Organ dose calculated for a simulated neuro-interventional-procedure using DOSXYZnrc with the Zubal CT voxel phantom agreed within 10% with that calculated by PCXMC code for most organs. To calculate the lens dose in a neuro-interventional procedure, we developed a library of normalized lens dose values for different projection angles and kVp's. The total lens dose is then calculated by summing the values over all beam projections and can be included on the DTS report at the end of the procedure.
Zamani, M.; Kasesaz, Y.; Khalafi, H.; Pooya, S. M. Hosseini
Boron Neutron Capture Therapy (BNCT) is used for treatment of many diseases, including brain tumors, in many medical centers. In this method, a target area (e.g., head of patient) is irradiated by some optimized and suitable neutron fields such as research nuclear reactors. Aiming at protection of healthy tissues which are located in the vicinity of irradiated tissue, and based on the ALARA principle, it is required to prevent unnecessary exposure of these vital organs. In this study, by using numerical simulation method (MCNP4C Code), the absorbed dose in target tissue and the equiavalent dose in different sensitive tissues of a patiant treated by BNCT, are calculated. For this purpose, we have used the parameters of MIRD Standard Phantom. Equiavelent dose in 11 sensitive organs, located in the vicinity of target, and total equivalent dose in whole body, have been calculated. The results show that the absorbed dose in tumor and normal tissue of brain equal to 30.35 Gy and 0.19 Gy, respectively. Also, total equivalent dose in 11 sensitive organs, other than tumor and normal tissue of brain, is equal to 14 mGy. The maximum equivalent doses in organs, other than brain and tumor, appear to the tissues of lungs and thyroid and are equal to 7.35 mSv and 3.00 mSv, respectively.
Molecular docking, spectroscopic studies and quantum calculations on nootropic drug.
Uma Maheswari, J; Muthu, S; Sundius, Tom
2014-04-05
A systematic vibrational spectroscopic assignment and analysis of piracetam [(2-oxo-1-pyrrolidineacetamide)] have been carried out using FT-IR and FT-Raman spectral data. The vibrational analysis was aided by an electronic structure calculation based on the hybrid density functional method B3LYP using a 6-311G++(d,p) basis set. Molecular equilibrium geometries, electronic energies, IR and Raman intensities, and harmonic vibrational frequencies have been computed. The assignments are based on the experimental IR and Raman spectra, and a complete assignment of the observed spectra has been proposed. The UV-visible spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies and the maximum absorption wavelengths λmax were determined by the time-dependent DFT (TD-DFT) method. The geometrical parameters, vibrational frequencies and absorption wavelengths were compared with the experimental data. The complete vibrational assignments are performed on the basis of the potential energy distributions (PED) of the vibrational modes in terms of natural internal coordinates. The simulated FT-IR, FT-Raman, and UV spectra of the title compound have been constructed. Molecular docking studies have been carried out in the active site of piracetam by using Argus Lab. In addition, the potential energy surface, HOMO and LUMO energies, first-order hyperpolarizability and the molecular electrostatic potential have been computed.
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Xiong, Z; Vijayan, S; Rana, V; Rudin, S; Bednarek, D [Toshiba Stroke and Vascular Research Center, University at Buffalo, Buffalo, NY (United States)
2015-06-15
Purpose: A system was developed that automatically calculates the organ and effective dose for individual fluoroscopically-guided procedures using a log of the clinical exposure parameters. Methods: We have previously developed a dose tracking system (DTS) to provide a real-time color-coded 3D- mapping of skin dose. This software produces a log file of all geometry and exposure parameters for every x-ray pulse during a procedure. The data in the log files is input into PCXMC, a Monte Carlo program that calculates organ and effective dose for projections and exposure parameters set by the user. We developed a MATLAB program to read data from the log files produced by the DTS and to automatically generate the definition files in the format used by PCXMC. The processing is done at the end of a procedure after all exposures are completed. Since there are thousands of exposure pulses with various parameters for fluoroscopy, DA and DSA and at various projections, the data for exposures with similar parameters is grouped prior to entry into PCXMC to reduce the number of Monte Carlo calculations that need to be performed. Results: The software developed automatically transfers data from the DTS log file to PCXMC and runs the program for each grouping of exposure pulses. When the dose from all exposure events are calculated, the doses for each organ and all effective doses are summed to obtain procedure totals. For a complicated interventional procedure, the calculations can be completed on a PC without manual intervention in less than 30 minutes depending on the level of data grouping. Conclusion: This system allows organ dose to be calculated for individual procedures for every patient without tedious calculations or data entry so that estimates of stochastic risk can be obtained in addition to the deterministic risk estimate provided by the DTS. Partial support from NIH grant R01EB002873 and Toshiba Medical Systems Corp.
Li, Heng; Liu, Wei; Park, Peter; Matney, Jason; Liao, Zhongxing; Chang, Joe; Zhang, Xiaodong; Li, Yupeng; Zhu, Ronald X
2014-09-08
The objective of this study was to evaluate and understand the systematic error between the planned three-dimensional (3D) dose and the delivered dose to patient in scanning beam proton therapy for lung tumors. Single-field and multifield optimized scanning beam proton therapy plans were generated for ten patients with stage II-III lung cancer with a mix of tumor motion and size. 3D doses in CT datasets for different respiratory phases and the time-weighted average CT, as well as the four-dimensional (4D) doses were computed for both plans. The 3D and 4D dose differences for the targets and different organs at risk were compared using dose-volume histogram (DVH) and voxel-based techniques, and correlated with the extent of tumor motion. The gross tumor volume (GTV) dose was maintained in all 3D and 4D doses, using the internal GTV override technique. The DVH and voxel-based techniques are highly correlated. The mean dose error and the standard deviation of dose error for all target volumes were both less than 1.5% for all but one patient. However, the point dose difference between the 3D and 4D doses was up to 6% for the GTV and greater than 10% for the clinical and planning target volumes. Changes in the 4D and 3D doses were not correlated with tumor motion. The planning technique (single-field or multifield optimized) did not affect the observed systematic error. In conclusion, the dose error in 3D dose calculation varies from patient to patient and does not correlate with lung tumor motion. Therefore, patient-specific evaluation of the 4D dose is important for scanning beam proton therapy for lung tumors.
SU-E-T-465: Dose Calculation Method for Dynamic Tumor Tracking Using a Gimbal-Mounted Linac
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Sugimoto, S; Inoue, T; Kurokawa, C; Usui, K; Sasai, K [Juntendo University, Bunkyo, Tokyo, JP (Japan); Utsunomiya, S [Niigata University, Niigata, Nigata, JP (Japan); Ebe, K [Joetsu General Hospital, Joetsu, Niigata, JP (Japan)
2014-06-01
Purpose: Dynamic tumor tracking using the gimbal-mounted linac (Vero4DRT, Mitsubishi Heavy Industries, Ltd., Japan) has been available when respiratory motion is significant. The irradiation accuracy of the dynamic tumor tracking has been reported to be excellent. In addition to the irradiation accuracy, a fast and accurate dose calculation algorithm is needed to validate the dose distribution in the presence of respiratory motion because the multiple phases of it have to be considered. A modification of dose calculation algorithm is necessary for the gimbal-mounted linac due to the degrees of freedom of gimbal swing. The dose calculation algorithm for the gimbal motion was implemented using the linear transformation between coordinate systems. Methods: The linear transformation matrices between the coordinate systems with and without gimbal swings were constructed using the combination of translation and rotation matrices. The coordinate system where the radiation source is at the origin and the beam axis along the z axis was adopted. The transformation can be divided into the translation from the radiation source to the gimbal rotation center, the two rotations around the center relating to the gimbal swings, and the translation from the gimbal center to the radiation source. After operating the transformation matrix to the phantom or patient image, the dose calculation can be performed as the no gimbal swing. The algorithm was implemented in the treatment planning system, PlanUNC (University of North Carolina, NC). The convolution/superposition algorithm was used. The dose calculations with and without gimbal swings were performed for the 3 × 3 cm{sup 2} field with the grid size of 5 mm. Results: The calculation time was about 3 minutes per beam. No significant additional time due to the gimbal swing was observed. Conclusions: The dose calculation algorithm for the finite gimbal swing was implemented. The calculation time was moderate.
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Ehrbar, Stefanie; Lang, Stephanie; Stieb, Sonja; Riesterer, Oliver; Stark, Luisa Sabrina; Guckenberger, Matthias; Kloeck, Stephan [University Hospital Zuerich (Switzerland). Dept. of Radiation Oncology
2016-05-01
Purpose: Respiratory motion is a non-negligible source of uncertainty in radiotherapy. A common approach is to delineate the target volume in all respiratory phases (ITV) and to calculate a treatment plan using the average reconstruction of the four-dimensional computed tomography (4DCT) scans. In this study the extent of the interplay effect caused by interaction between dynamic dose delivery and respiratory tumor motion, as well as other motion effects were investigated. These effects are often ignored when the ITV concept is used. Methods and Materials: Nine previously treated patients with in ten abdominal or thoracic cancer lesions (3 liver, 3 adrenal glands and 4 lung lesions) were selected for this planning study. For all patients, phase-sorted respiration-correlated 4DCT scans were taken, and volumetric modulated arc therapy (VMAT) treatments were planned using the ITV concept. Margins from ITV to planning target volume (PTV) of 3-10 mm were used. Plans were optimized and dose distributions were calculated on the average reconstruction of the 4DCT. 4D dose distributions were calculated to evaluate motion effects, caused by the interference of dynamic treatment delivery with respiratory tumor motion and inhomogeneously planned target dose. These calculations were performed on the phase-sorted CT series with a respiration-correlated assignment of the treatment plan's monitor units (MU) to the respiration phases of the 4DCT. The 4D dose was accumulated with rigid as well as deformable registrations of the CT series and compared to the original 3D dose distribution. Maximum, minimum and mean doses to ITV and PTV, and maximum or mean doses to organs at risk (OAR), were compared after rigid accumulation. The dose variation in the gross tumor volume (GTV) was compared after deformable registration. Results: Using rigid registrations, variations in the investigated dose parameters between 3D and 4D dose calculations were found to be within -2.1% to 1.4% for
Comparison of measured and calculated dose rates near nuclear medicine patients.
Yi, Y; Stabin, M G; McKaskle, M H; Shone, M D; Johnson, A B
2013-08-01
Widely used release criteria for patients receiving radiopharmaceuticals (NUREG-1556, Vol. 9, Rev.1, Appendix U) are known to be overly conservative. The authors measured external exposure rates near patients treated with I, Tc, and F and compared the measurements to calculated values using point and line source models. The external exposure dose rates for 231, 11, and 52 patients scanned or treated with I, Tc, and F, respectively, were measured at 0.3 m and 1.0 m shortly after radiopharmaceutical administration. Calculated values were always higher than measured values and suggested the application of "self-shielding factors," as suggested by Siegel et al. in 2002. The self-shielding factors of point and line source models for I at 1 m were 0.60 ± 0.16 and 0.73 ± 0.20, respectively. For Tc patients, the self-shielding factors for point and line source models were 0.44 ± 0.19 and 0.55 ± 0.23, and the values were 0.50 ± 0.09 and 0.60 ± 0.12, respectively, for F (all FDG) patients. Treating patients as unshielded point sources of radiation is clearly inappropriate. In reality, they are volume sources, but treatment of their exposures using a line source model with appropriate self-shielding factors produces a more realistic, but still conservative, approach for managing patient release.
Park, S H; Lee, J K; Lee, C
2008-01-01
In this study, organ-absorbed doses and effective doses to patient during interventional radiological procedures were estimated using tomographic phantom, Korean Typical Man-2 (KTMAN-2). Four projections of cardiac catheterisation were simulated for dose calculation by Monte Carlo technique. The parameters of X-ray source and exposure conditions were obtained from literature data. Particle transport was simulated using general purposed Monte Carlo code, MCNPX 2.5.0. Organ-absorbed doses and effective doses were normalised to dose area product (DAP). The effective doses per DAP were between 0.1 and 0.5 mSv Gy(-1) per cm2. The results were compared with those derived from adult stylised phantom. KTMAN-2 received up to 105% higher effective doses than stylised phantom. The dose differences were mainly caused by more realistic internal topology of KTMAN-2 compared to stylised phantom that are closely positioned organs near the heart and shift of abdominal organs to the thoracic region due to supine position. The results of this study showed that tomographic phantoms are more suitable for dose assessment of supine patients undergoing the interventional radiology. The results derived from KTMAN-2 were the first radiation dose data based on non-Caucasian individuals for interventional procedures.
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Penfold, S; Miller, A [University of Adelaide, Adelaide, SA (Australia)
2015-06-15
Purpose: Stoichiometric calibration of Hounsfield Units (HUs) for conversion to proton relative stopping powers (RStPs) is vital for accurate dose calculation in proton therapy. However proton dose distributions are not only dependent on RStP, but also on relative scattering power (RScP) of patient tissues. RScP is approximated from material density but a stoichiometric calibration of HU-density tables is commonly neglected. The purpose of this work was to quantify the difference in calculated dose of a commercial TPS when using HU-density tables based on tissue substitute materials and stoichiometric calibrated ICRU tissues. Methods: Two HU-density calibration tables were generated based on scans of the CIRS electron density phantom. The first table was based directly on measured HU and manufacturer quoted density of tissue substitute materials. The second was based on the same CT scan of the CIRS phantom followed by a stoichiometric calibration of ICRU44 tissue materials. The research version of Pinnacle{sup 3} proton therapy was used to compute dose in a patient CT data set utilizing both HU-density tables. Results: The two HU-density tables showed significant differences for bone tissues; the difference increasing with increasing HU. Differences in density calibration table translated to a difference in calculated RScP of −2.5% for ICRU skeletal muscle and 9.2% for ICRU femur. Dose-volume histogram analysis of a parallel opposed proton therapy prostate plan showed that the difference in calculated dose was negligible when using the two different HU-density calibration tables. Conclusion: The impact of HU-density calibration technique on proton therapy dose calculation was assessed. While differences were found in the calculated RScP of bony tissues, the difference in dose distribution for realistic treatment scenarios was found to be insignificant.
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Zankl, M. [GSF - Forschungszentrum fuer Umwelt und Gesundheit Neuherberg GmbH, Oberschleissheim (Germany). Inst. fuer Strahlenschutz; Drexler, G. [GSF - Forschungszentrum fuer Umwelt und Gesundheit Neuherberg GmbH, Oberschleissheim (Germany). Inst. fuer Strahlenschutz; Petoussi-Henss, N. [GSF - Forschungszentrum fuer Umwelt und Gesundheit Neuherberg GmbH, Oberschleissheim (Germany). Inst. fuer Strahlenschutz; Saito, K. [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan)
1997-03-01
This report presents a tabulation of organ and tissue equivalent dose as well as effective dose conversion coefficients, normalised to air kerma free in air, for occupational exposures and environmental exposures of the public to external photon radiation. For occupational exposures, whole-body irradiation with idealised geometries, i.e. broad parallel beams and fully isotropic radiation incidence, is considered. The directions of incidence for the parallel beams are anterior-posterior, posterior-anterior, left lateral, right lateral and a full 360 rotation around the body`s longitudinal axis. The influence of beam divergence on the body doses is also considered as well as the dependence of effective dose on the angle of radiation incidence. Regarding exposure of the public to environmental sources, three source geometries are considered: exposure from a radioactive cloud, from ground contamination and from the natural radionuclides distributed homogeneously in the ground. The precise angular and energy distributions of the gamma rays incident on the human body were taken into account. The organ dose conversion coefficients given in this catalogue were calculated using a Monte Carlo code simulating the photon transport in mathematical models of an adult male and an adult female, respectively. Conversion coefficients are given for the equivalent dose of 23 organs and tissues as well as for effective dose and the equivalent dose of the so-called `remainder`. The organ equivalent dose conversion coefficients are given separately for the adult male and female models and - as arithmetic mean of the conversion coefficients of both - for an average adult. Fitted data of the coefficients are presented in tables; the primary raw data as resulting from the Monte Carlo calculation are shown in figures together with the fitted data. (orig.)
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Cassell, K.J. (Saint Luke' s Hospital, Guildford (UK))
1983-02-01
A method, developed from the Quantisation Method, of calculating dose-rate distributions around uniformly and non-uniformly loaded brachytherapy sources is described. It allows accurate and straightforward corrections for oblique filtration and self-absorption to be made. Using this method, dose-rate distributions have been calculated for sources of radium 226, gold 198, iridium 192, caesium 137 and cobalt 60, all of which show very good agreement with existing measured and calculated data. This method is now the basis of the Interstitial and Intracavitary Dosimetry (IID) program on the General Electric RT/PLAN computerised treatment planning system.
Using Six Sigma to improve once daily gentamicin dosing and therapeutic drug monitoring performance.
LENUS (Irish Health Repository)
Egan, Sean
2012-08-07
BACKGROUND: Safe, effective therapy with the antimicrobial gentamicin requires good practice in dose selection and monitoring of serum levels. Suboptimal therapy occurs with breakdown in the process of drug dosing, serum blood sampling, laboratory processing and level interpretation. Unintentional underdosing may result. This improvement effort aimed to optimise this process in an academic teaching hospital using Six Sigma process improvement methodology. METHODS: A multidisciplinary project team was formed. Process measures considered critical to quality were defined, and baseline practice was examined through process mapping and audit. Root cause analysis informed improvement measures. These included a new dosing and monitoring schedule, and standardised assay sampling and drug administration timing which maximised local capabilities. Three iterations of the improvement cycle were conducted over a 24-month period. RESULTS: The attainment of serum level sampling in the required time window improved by 85% (p≤0.0001). A 66% improvement in accuracy of dosing was observed (p≤0.0001). Unnecessary dose omission while awaiting level results and inadvertent disruption to therapy due to dosing and monitoring process breakdown were eliminated. Average daily dose administered increased from 3.39 mg\\/kg to 4.78 mg\\/kg\\/day. CONCLUSIONS: Using Six Sigma methodology enhanced gentamicin usage process performance. Local process related factors may adversely affect adherence to practice guidelines for gentamicin, a drug which is complex to use. It is vital to adapt dosing guidance and monitoring requirements so that they are capable of being implemented in the clinical environment as a matter of routine. Improvement may be achieved through a structured localised approach with multidisciplinary stakeholder involvement.
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Li, JS; Fan, J; Ma, C-M [Fox Chase Cancer Center, Philadelphia, PA (United States)
2015-06-15
Purpose: To improve the treatment efficiency and capabilities for full-body treatment, a robotic radiosurgery system has equipped with a multileaf collimator (MLC) to extend its accuracy and precision to radiation therapy. To model the MLC and include it in the Monte Carlo patient dose calculation is the goal of this work. Methods: The radiation source and the MLC were carefully modeled to consider the effects of the source size, collimator scattering, leaf transmission and leaf end shape. A source model was built based on the output factors, percentage depth dose curves and lateral dose profiles measured in a water phantom. MLC leaf shape, leaf end design and leaf tilt for minimizing the interleaf leakage and their effects on beam fluence and energy spectrum were all considered in the calculation. Transmission/leakage was added to the fluence based on the transmission factors of the leaf and the leaf end. The transmitted photon energy was tuned to consider the beam hardening effects. The calculated results with the Monte Carlo implementation was compared with measurements in homogeneous water phantom and inhomogeneous phantoms with slab lung or bone material for 4 square fields and 9 irregularly shaped fields. Results: The calculated output factors are compared with the measured ones and the difference is within 1% for different field sizes. The calculated dose distributions in the phantoms show good agreement with measurements using diode detector and films. The dose difference is within 2% inside the field and the distance to agreement is within 2mm in the penumbra region. The gamma passing rate is more than 95% with 2%/2mm criteria for all the test cases. Conclusion: Implementation of Monte Carlo dose calculation for a MLC equipped robotic radiosurgery system is completed successfully. The accuracy of Monte Carlo dose calculation with MLC is clinically acceptable. This work was supported by Accuray Inc.
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Cunliffe, Alexandra R.; Armato, Samuel G.; White, Bradley; Justusson, Julia [Department of Radiology, The University of Chicago, 5841 South Maryland Avenue, Chicago, Illinois 60637 (United States); Contee, Clay; Malik, Renuka; Al-Hallaq, Hania A., E-mail: hal-hallaq@radonc.uchicago.edu [Department of Radiation and Cellular Oncology, The University of Chicago, 5841 South Maryland Avenue, Chicago, Illinois 60637 (United States)
2015-01-15
Purpose: To characterize the effects of deformable image registration of serial computed tomography (CT) scans on the radiation dose calculated from a treatment planning scan. Methods: Eighteen patients who received curative doses (≥60 Gy, 2 Gy/fraction) of photon radiation therapy for lung cancer treatment were retrospectively identified. For each patient, a diagnostic-quality pretherapy (4–75 days) CT scan and a treatment planning scan with an associated dose map were collected. To establish correspondence between scan pairs, a researcher manually identified anatomically corresponding landmark point pairs between the two scans. Pretherapy scans then were coregistered with planning scans (and associated dose maps) using the demons deformable registration algorithm and two variants of the Fraunhofer MEVIS algorithm (“Fast” and “EMPIRE10”). Landmark points in each pretherapy scan were automatically mapped to the planning scan using the displacement vector field output from each of the three algorithms. The Euclidean distance between manually and automatically mapped landmark points (d{sub E}) and the absolute difference in planned dose (|ΔD|) were calculated. Using regression modeling, |ΔD| was modeled as a function of d{sub E}, dose (D), dose standard deviation (SD{sub dose}) in an eight-pixel neighborhood, and the registration algorithm used. Results: Over 1400 landmark point pairs were identified, with 58–93 (median: 84) points identified per patient. Average |ΔD| across patients was 3.5 Gy (range: 0.9–10.6 Gy). Registration accuracy was highest using the Fraunhofer MEVIS EMPIRE10 algorithm, with an average d{sub E} across patients of 5.2 mm (compared with >7 mm for the other two algorithms). Consequently, average |ΔD| was also lowest using the Fraunhofer MEVIS EMPIRE10 algorithm. |ΔD| increased significantly as a function of d{sub E} (0.42 Gy/mm), D (0.05 Gy/Gy), SD{sub dose} (1.4 Gy/Gy), and the algorithm used (≤1 Gy). Conclusions: An
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Ballester, Facundo, E-mail: Facundo.Ballester@uv.es [Department of Atomic, Molecular and Nuclear Physics, University of Valencia, Burjassot 46100 (Spain); Carlsson Tedgren, Åsa [Department of Medical and Health Sciences (IMH), Radiation Physics, Faculty of Health Sciences, Linköping University, Linköping SE-581 85, Sweden and Department of Medical Physics, Karolinska University Hospital, Stockholm SE-171 76 (Sweden); Granero, Domingo [Department of Radiation Physics, ERESA, Hospital General Universitario, Valencia E-46014 (Spain); Haworth, Annette [Department of Physical Sciences, Peter MacCallum Cancer Centre and Royal Melbourne Institute of Technology, Melbourne, Victoria 3000 (Australia); Mourtada, Firas [Department of Radiation Oncology, Helen F. Graham Cancer Center, Christiana Care Health System, Newark, Delaware 19713 (United States); Fonseca, Gabriel Paiva [Instituto de Pesquisas Energéticas e Nucleares – IPEN-CNEN/SP, São Paulo 05508-000, Brazil and Department of Radiation Oncology (MAASTRO), GROW, School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht 6201 BN (Netherlands); Zourari, Kyveli; Papagiannis, Panagiotis [Medical Physics Laboratory, Medical School, University of Athens, 75 MikrasAsias, Athens 115 27 (Greece); Rivard, Mark J. [Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts 02111 (United States); Siebert, Frank-André [Clinic of Radiotherapy, University Hospital of Schleswig-Holstein, Campus Kiel, Kiel 24105 (Germany); Sloboda, Ron S. [Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta T6G 1Z2, Canada and Department of Oncology, University of Alberta, Edmonton, Alberta T6G 2R3 (Canada); and others
2015-06-15
Purpose: In order to facilitate a smooth transition for brachytherapy dose calculations from the American Association of Physicists in Medicine (AAPM) Task Group No. 43 (TG-43) formalism to model-based dose calculation algorithms (MBDCAs), treatment planning systems (TPSs) using a MBDCA require a set of well-defined test case plans characterized by Monte Carlo (MC) methods. This also permits direct dose comparison to TG-43 reference data. Such test case plans should be made available for use in the software commissioning process performed by clinical end users. To this end, a hypothetical, generic high-dose rate (HDR) {sup 192}Ir source and a virtual water phantom were designed, which can be imported into a TPS. Methods: A hypothetical, generic HDR {sup 192}Ir source was designed based on commercially available sources as well as a virtual, cubic water phantom that can be imported into any TPS in DICOM format. The dose distribution of the generic {sup 192}Ir source when placed at the center of the cubic phantom, and away from the center under altered scatter conditions, was evaluated using two commercial MBDCAs [Oncentra{sup ®} Brachy with advanced collapsed-cone engine (ACE) and BrachyVision ACUROS{sup TM}]. Dose comparisons were performed using state-of-the-art MC codes for radiation transport, including ALGEBRA, BrachyDose, GEANT4, MCNP5, MCNP6, and PENELOPE2008. The methodologies adhered to recommendations in the AAPM TG-229 report on high-energy brachytherapy source dosimetry. TG-43 dosimetry parameters, an along-away dose-rate table, and primary and scatter separated (PSS) data were obtained. The virtual water phantom of (201){sup 3} voxels (1 mm sides) was used to evaluate the calculated dose distributions. Two test case plans involving a single position of the generic HDR {sup 192}Ir source in this phantom were prepared: (i) source centered in the phantom and (ii) source displaced 7 cm laterally from the center. Datasets were independently produced by
Wit, D. de; Erp, N. van; Hartigh, J. den; Wolterbeek, R..; Hollander-van Deursen, M. den; Labots, M.; Guchelaar, H.J.; Verheul, H.M.; Gelderblom, H.
2015-01-01
BACKGROUND: Patients treated with the standard dose of pazopanib show a large interpatient variability in drug exposure defined as the area under the plasma concentration-time curve (AUC0-24h). The primary objective of this study was to evaluate the feasibility of pharmacokinetics (PK)-guided indivi
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NONE
2005-11-15
This Regulation refers to the requirements of the Regulation CNEN-NN.3.01. 'Basic Act of Radiological Protection', as expressed in the section 5.9, and its application to the effective dose calculation for individual occupationally exposed. from the internal and external individual monitoring data
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Castro, Robson C. de; Silva, Ademir X. da; Crispim, Verginia R. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia. Programa de Engenharia Nuclear]. E-mail: rcastro@con.ufrj.br; Facure, Alessandro; Falcao, Rossana C. [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil)]. E-mail: afsoares@cnen.gov.br; Lima, Marco A.F. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Dept. de Biologia Geral. Lab. de Radiobiologia e Radiometria]. E-mail: egbakel@vm.uff.br
2005-07-01
Radiotherapy with photon and electron beams still represents the most technique to control and treat tumour diseases. To increase the treatment efficiency of this technique is linked to the increase of beam energy, resulting in fast neutrons in the radiotherapic beams that contribute with an undesired dose to the patient. In this work has been calculated, using the MCNP4B computer code radiation of transport and an mathematical anthropomorphic phantom, the equivalent doses in organs originated from generated photoneutrons from heads of linear accelerators of medical use, that operates in the 15 MV, 18 MV, 20 MV and 25 MV. The calculated values for the equivalent doses in organs established by the 74 publication of ICRP has show variations between 0.11 mSv.n Gy{sup -1} and 7.03 mSv.n Gy{sup -1}, for the accelerator that uses 18 MV therapic beams, showing good agreement with existing values in the literature. (author)
Directory of Open Access Journals (Sweden)
Saganuwan Alhaji Saganuwan
2016-06-01
Full Text Available One million people throughout the world are bitten yearly by poisonous snakes. Of this, one-tenth died and three-tenth suffer some forms of disabilities. In view of this, anti-snake venoms are currently being developed against viper and colubrid snake venoms using mice. Therefore, a new algorithm for calculation of median lethal dose (LD50 and effective dose fifty (ED50 was developed for Micrarus fulvius venom and antivenom respectively. This paper compared the formula of effective dose fifty (ED50 developed by Spearman and Karber with ideal median lethal dose (IMLD50 formula developed by Saganuwan with a view to bringing out their difference and similarity in calculation of ED50 that could be used to develop a new median lethal dose formula for calculation of Micrarus fulvius venom in mice. The findings revealed that ED50 value (477 mg/kg from Spearman and Karber’s formula (ED50=logED50=logX100-logFDn(Σt-n/2 is comparatively similar with ideal median lethal dose value (428.75 mg/kg from Saganuwan’s formula (MLD50 + MSD50/2. The new LD50 formula (LD50=ED503×Wm×10-4 yielded value (0.29 mg/kg of comparative significance with reported value (0.32 mg/kg. When ED50 is equal to 2LD50, the denominator of ED503 becomes 2. In conclusion, the new formula would yield low doses of snake anti-venoms with reduced possibility of hypersensitivity reaction.
[Dose response curve of paclitaxel measured by histoculture drug response assay].
Yoshimasu, Tatsuya; Oura, Shoji; Hirai, Issei; Kokawa, Yozo; Okamura, Yoshitaka; Furukawa, Tomoko
2005-04-01
Dose response curves of paclitaxel were measured by histoculture drug response assay (HDRA) in 11 lung cancer patients. Inhibition rates of paclitaxel at several concentrations were measured and fitted to the sigmoid dose response curve, using non-linear least square analysis, with fitting equation y=A (1-1/(1+exp (b (x-log (ED50)). Parameters A, b, and ED50 were 88.3+/-6.0 (80.0-100.0) %, 9.57+/-4.32 (2.25-15.0), and 26.8+/-8.1 (15.0-41.0) microg/ml, respectively. The parameter b was lower in well-differentiated tumors compared with moderately and poorly-differentiated tumors. Dose response curves of paclitaxel could be measured by HDRA in lung cancer. This method provides us more information for drug sensitivity than the usual HDRA method. This may lead to the improved accuracy of HDRA.
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Habib, B.; Poumarede, B.; Tola, F.; Barthe, J. [CEA, LIST, Dept Technol Capteur et Signal, F-91191 Gif Sur Yvette, (France)
2010-07-01
The aim of the present study is to demonstrate the potential of accelerated dose calculations, using the fast Monte Carlo (MC) code referred to as PENFAST, rather than the conventional MC code PENELOPE, without losing accuracy in the computed dose. For this purpose, experimental measurements of dose distributions in homogeneous and inhomogeneous phantoms were compared with simulated results using both PENELOPE and PENFAST. The simulations and experiments were performed using a Saturne 43 linac operated at 12 MV (photons), and at 18 MeV (electrons). Pre-calculated phase space files (PSFs) were used as input data to both the PENELOPE and PENFAST dose simulations. Since depth-dose and dose profile comparisons between simulations and measurements in water were found to be in good agreement (within {+-} 1% to 1 mm), the PSF calculation is considered to have been validated. In addition, measured dose distributions were compared to simulated results in a set of clinically relevant, inhomogeneous phantoms, consisting of lung and bone heterogeneities in a water tank. In general, the PENFAST results agree to within a 1% to 1 mm difference with those produced by PENELOPE, and to within a 2% to 2 mm difference with measured values. Our study thus provides a pre-clinical validation of the PENFAST code. It also demonstrates that PENFAST provides accurate results for both photon and electron beams, equivalent to those obtained with PENELOPE. CPU time comparisons between both MC codes show that PENFAST is generally about 9-21 times faster than PENELOPE. (authors)
Yasuda, Kie; Miyoshi, Yoko; Tachibana, Makiko; Namba, Noriyuki; Miki, Kazunori; Nakata, Yukiko; Takano, Toru; Ozono, Keiichi
2017-01-01
Abstract. Graves’ disease (GD) accounts for a large proportion of pediatric hyperthyroidism, and the first-line treatment is antithyroid drug (ATD) therapy. Methimazole (MMI) is effective in most patients but is associated with significant adverse events (AEs). We reviewed the medical records of GD patients (n = 56) with onset age of <15 yr and investigated the relationship between MMI dose and AEs. The study population comprised 11 male and 45 female patients and the median age at diagnosis was 11 yr. All patients were initially treated with ATDs. Among the 52 patients initially treated with MMI, 20 received a low dose, and 32 received a high dose of MMI (< 0.7 vs ≥ 0.7 mg/kg/day, respectively). AEs occurred in 20% of the patients in the low-dose MMI group, and in 50% patients in the high-dose MMI group (p = 0.031). A greater variety of AEs was observed in the high-dose group. Neutropenia and rash were observed in both groups. With treatment transition to low-dose MMI according to the Japanese Society for Pediatric Endocrinology guidelines, we expect a decrease in the incidence of AEs in future. However, we should be careful as neutropenia and rash can occur independently of the MMI dose.
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Fogliata, Antonella [Oncology Inst. of Southern Switzerland, Medical Physics Unit, Bellinzona (Switzerland)], e-mail: Antonella.Fogliata-Cozzi@eoc.ch; Scorsetti, Marta; Navarria, Piera [IRCCS Instituto Clinico Humanitas, Radiation Oncology, Rozzano, Milan (Italy)] [and others
2013-04-15
Background: To appraise the potential of volumetric modulated arc therapy (VMAT, RapidArc) and proton beams to simultaneously achieve target coverage and enhanced sparing of bone tissue in the treatment of soft-tissue sarcoma with adequate target coverage. Material and methods: Ten patients presenting with soft-tissue sarcoma of the leg were collected for the study. Dose was prescribed to 66.5 Gy in 25 fractions to the planning target volume (PTV) while significant maximum dose to the bone was constrained to 50 Gy. Plans were optimised according to the RapidArc technique with 6 MV photon beams or for intensity modulated protons. RapidArc photon plans were computed with: 1) AAA; 2) Acuros XB as dose to medium; and 3) Acuros XB as dose to water. Results: All plans acceptably met the criteria of target coverage (V{sub 95%} >90-95%) and bone sparing (D{sub 1cm}{sup 3} <50 Gy). Significantly higher PTV dose homogeneity was found for proton plans. Near-to-maximum dose to bone was similar for RapidArc and protons, while volume receiving medium/low dose levels was minimised with protons. Similar results were obtained for the remaining normal tissue. Dose distributions calculated with the dose to water option resulted 5% higher than corresponding ones computed as dose to medium. Conclusion: High plan quality was demonstrated for both VMAT and proton techniques when applied to soft-tissue sarcoma.
Volumic activities measurements and equivalent doses calculation of indoor 222Rn in Morocco
Directory of Open Access Journals (Sweden)
Abdelmajid Choukri
2015-09-01
Full Text Available Purpose: As a way of prevention, we have measured the volumic activities of indoor 222Rn and we have calculated the corresponding effective dose in some dwellings and enclosed areas in Morocco. Seasonal variation of Radon activities and Relationships between variation of these activities and some parameters such height, depth and type of construction were also established in this work.Methods: The passive time-integrated method of using a solid state nuclear track detector (LR-115 type II was employed. These films, cut in pieces of 3.4 ´ 2.5 cm2, were placed in detector holders and enclosed in heat-scaled polyethylene bags.Results: The measured volumic activities of radon vary in houses, between 31 and 136 Bq/m3 (0.55 and 2.39 mSv/year with an average value of 80 Bq/m3 (1.41 mSv/year. In enclosed work area, they vary between 60 Bq/m3 (0.38 mSv/year in an ordinary area to 1884 Bq/m3 (11.9 mSv/year at not airy underground level of 12 m. the relatively higher volumic activities of 222Rn in houses were measured in Youssoufia and khouribga towns situated in regions rich in phosphate deposits. Measurements at the geophysical observatory of Berchid show that the volumic activity of radon increases with depth, this is most probably due to decreased ventilation. Conclusion: The obtained results show that the effective dose calculated for indoor dwellings are comparable to those obtained in other regions in the word. The risks related to the volumic activities of indoor radon could be avoided by simple precautions such the continuous ventilation. The reached high value of above 1884 Bq/m3 don't present any risk for workers health in the geophysical observatory of Berchid because workers spend only a few minutes by day in the cellar to control and reregister data.
McGinnity, D F; Collington, J; Austin, R P; Riley, R J
2007-06-01
In this article approaches to predict human pharmacokinetics (PK) are discussed and the capability of the exemplified methodologies to estimate individual PK parameters and therapeutic dose for a set of marketed oral drugs has been assessed. For a set of 63 drugs where the minimum efficacious concentration (MEC) and human PK were known, the clinical dose was shown to be well predicted or in some cases over-estimated using a simple one-compartment oral PK model. For a subset of these drugs, in vitro potency against the primary human targets was gathered, and compared to the observed MEC. When corrected for plasma protein binding, the MEC of the majority of compounds was GFR. For approximately 90% of compounds studied, the predicted CL using in vitro-in vivo (IVIV) extrapolation together with a CL(renal) estimate, where appropriate, was within 2-fold of that observed clinically. Encouragingly volume of distribution at steady state (V(ss)) estimated in preclinical species (rat and dog) when corrected for plasma protein binding, predicted human V(ss) successfully on the majority of occasions--73% of compounds within 2-fold. In this laboratory, absorption estimated from oral rat PK studies was lower than the observed human absorption for most drugs, even when solubility and permeability appeared not to be limiting. Preliminary data indicate absorption in the dog may be more representative of human for compounds absorbed via the transcellular pathway. Using predicted PK and MEC values estimated from in vitro potency assays there was a good correlation between predicted and observed dose. This analysis suggests that for oral therapies, human PK parameters and clinical dose can be estimated from a consideration of data obtained from in vitro screens using human derived material and in vivo animal studies. The benefits and limitations of this holistic approach to PK and dose prediction within the drug discovery process are exemplified and discussed.
Pan, Yuxi; Qiu, Rui; Gao, Linfeng; Ge, Chaoyong; Zheng, Junzheng; Xie, Wenzhang; Li, Junli
2014-09-21
With the rapidly growing number of CT examinations, the consequential radiation risk has aroused more and more attention. The average dose in each organ during CT scans can only be obtained by using Monte Carlo simulation with computational phantoms. Since children tend to have higher radiation sensitivity than adults, the radiation dose of pediatric CT examinations requires special attention and needs to be assessed accurately. So far, studies on organ doses from CT exposures for pediatric patients are still limited. In this work, a 1-year-old computational phantom was constructed. The body contour was obtained from the CT images of a 1-year-old physical phantom and the internal organs were deformed from an existing Chinese reference adult phantom. To ensure the organ locations in the 1-year-old computational phantom were consistent with those of the physical phantom, the organ locations in 1-year-old computational phantom were manually adjusted one by one, and the organ masses were adjusted to the corresponding Chinese reference values. Moreover, a CT scanner model was developed using the Monte Carlo technique and the 1-year-old computational phantom was applied to estimate organ doses derived from simulated CT exposures. As a result, a database including doses to 36 organs and tissues from 47 single axial scans was built. It has been verified by calculation that doses of axial scans are close to those of helical scans; therefore, this database could be applied to helical scans as well. Organ doses were calculated using the database and compared with those obtained from the measurements made in the physical phantom for helical scans. The differences between simulation and measurement were less than 25% for all organs. The result shows that the 1-year-old phantom developed in this work can be used to calculate organ doses in CT exposures, and the dose database provides a method for the estimation of 1-year-old patient doses in a variety of CT examinations.
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Pettengill, H.L. [USDOE, Washington, DC (United States); Soldat, J.K.; Swinth, K.L. [Pacific Northwest Lab., Richland, WA (United States)
1994-06-01
Most Manhattan District (MD) and Atomic Energy Commission (AEC) sites began environmental monitoring programs in the earliest years of their operation. The results were used to establish trends and to monitor for effluent releases that might be otherwise undetected. Very few data concerning radiation doses to the public in the vicinity of the sites were generated prior to 1960. Authoritative guidelines for controlling doses to the public were issued by national and international bodies beginning in the 1950s. In 1957, the Hanford Site began calculating and reporting maximum potential radiation doses to the public from several environmental pathways of exposure. Shortly thereafter, most AEC sites began programs aimed at either determining public doses, or ensuring that the doses were below the regulatory limits. Calculations of radiation doses to Maximally Exposed Individuals (MEI) at the Hanford Site have been recently completed by the Hanford Environmental Dose Reconstruction (HEDR) project. Collective doses for the public at Hanford were generated for this paper by utilizing the data developed by HEDR and approximate demographic data.
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Ribeiro, Rosane M.; Santos, Denison de S.; Queiroz Filho, Pedro P. de; Mauricio, CLaudia L.P.; Silva, Livia K. da; Pessanha, Paula R., E-mail: rosanemribeiro@oi.com.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)
2014-07-01
Fluence to dose equivalent conversion coefficients provide the basis for the calculation of area and personal monitors. Recently, the ICRP has started a revision of these coefficients, including new Monte Carlo codes for benchmarking. So far, little information is available about neutron transport below 10 MeV in tissue-equivalent (TE) material performed with Monte Carlo GEANT4 code. The objective of this work is to calculate neutron fluence to personal dose equivalent conversion coefficients, H{sub p} (10)/Φ, with GEANT4 code. The incidence of monoenergetic neutrons was simulated as an expanded and aligned field, with energies ranging between thermal neutrons to 10 MeV on the ICRU slab of dimension 30 x 30 x 15 cm{sup 3}, composed of 76.2% of oxygen, 10.1% of hydrogen, 11.1% of carbon and 2.6% of nitrogen. For all incident energy, a cylindrical sensitive volume is placed at a depth of 10 mm, in the largest surface of the slab (30 x 30 cm{sup 2}). Physic process are included for neutrons, photons and charged particles, and calculations are made for neutrons and secondary particles which reach the sensitive volume. Results obtained are thus compared with values published in ICRP 74. Neutron fluence in the sensitive volume was calculated for benchmarking. The Monte Carlo GEANT4 code was found to be appropriate to calculate neutron doses at energies below 10 MeV correctly. (author)
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Horowitz, Y.S. [Ben Gurion Univ. of the Negev, Beersheva (Israel); Hirning, C.R. [Ontario Hydro, Whitby (Canada); Yuen, P.; Wong, P. [Chalk River Labs., Ontario (Canada)
1994-10-01
Monte Carlo calculations have been carried out for monoenergetic electrons from 0.1 to 4 MeV irradiating LiF chips in both perpendicular and isotropic geometry. This enabled the calculation of skin dose correction factors (beta factors) for typical beta energy spectra as measured with a beta-ray spectrometer at CANDU nuclear generating stations. The correction factors were estimated by averaging the depth dose distributions for the monoenergetic electrons over the experimentally measured beta-ray spectra. The calculations illustrate the large uncertainty in beta factors arising from the unknown angular distribution of the beta-ray radiation field and uncertainties in the shape of the beta-ray spectra below 500 keV. 28 refs., 8 figs., 2 tabs.
Chiang, Po-Chang; South, Sarah A; Wene, Steve P
2011-01-01
In drug discovery, time and resource constraints necessitate increasingly early decision making to accelerate or stop preclinical programs. Early discovery drug candidates may be potent inhibitors of new targets, but all too often exhibit poor pharmaceutical or pharmacokinetic properties that limit the in vivo exposure. Low solubility of a drug candidate often leads to poor oral bioavailability and poor dose linearity. This issue is more significant for efficacy and target safety studies where high drug exposures are desired. When solubility issues are confronted, enabling formulations are often required to improve the exposure. However, this approach often requires a substantial and lengthy investment to develop the formulation. Previously, we introduced a gastrointestinal (GI) transit time-based novel oral tandem dosing strategy that enhanced in vivo exposures in rats. In this study, a refined time interval versus dose theory was tested. The resulting in vivo exposures based on altering frequency and doses were compared, and significant impacts were found.
Directory of Open Access Journals (Sweden)
Po-Chang Chiang
2011-01-01
Full Text Available In drug discovery, time and resource constraints necessitate increasingly early decision making to accelerate or stop preclinical programs. Early discovery drug candidates may be potent inhibitors of new targets, but all too often exhibit poor pharmaceutical or pharmacokinetic properties that limit the in vivo exposure. Low solubility of a drug candidate often leads to poor oral bioavailability and poor dose linearity. This issue is more significant for efficacy and target safety studies where high drug exposures are desired. When solubility issues are confronted, enabling formulations are often required to improve the exposure. However, this approach often requires a substantial and lengthy investment to develop the formulation. Previously, we introduced a gastrointestinal (GI transit time-based novel oral tandem dosing strategy that enhanced in vivo exposures in rats. In this study, a refined time interval versus dose theory was tested. The resulting in vivo exposures based on altering frequency and doses were compared, and significant impacts were found.
A Monte Carlo model for out-of-field dose calculation from high-energy photon therapy.
Kry, Stephen F; Titt, Uwe; Followill, David; Pönisch, Falk; Vassiliev, Oleg N; White, R Allen; Stovall, Marilyn; Salehpour, Mohammad
2007-09-01
As cancer therapy becomes more efficacious and patients survive longer, the potential for late effects increases, including effects induced by radiation dose delivered away from the treatment site. This out-of-field radiation is of particular concern with high-energy radiotherapy, as neutrons are produced in the accelerator head. We recently developed an accurate Monte Carlo model of a Varian 2100 accelerator using MCNPX for calculating the dose away from the treatment field resulting from low-energy therapy. In this study, we expanded and validated our Monte Carlo model for high-energy (18 MV) photon therapy, including both photons and neutrons. Simulated out-of-field photon doses were compared with measurements made with thermoluminescent dosimeters in an acrylic phantom up to 55 cm from the central axis. Simulated neutron fluences and energy spectra were compared with measurements using moderated gold foil activation in moderators and data from the literature. The average local difference between the calculated and measured photon dose was 17%, including doses as low as 0.01% of the central axis dose. The out-of-field photon dose varied substantially with field size and distance from the edge of the field but varied little with depth in the phantom, except at depths shallower than 3 cm, where the dose sharply increased. On average, the difference between the simulated and measured neutron fluences was 19% and good agreement was observed with the neutron spectra. The neutron dose equivalent varied little with field size or distance from the central axis but decreased with depth in the phantom. Neutrons were the dominant component of the out-of-field dose equivalent for shallow depths and large distances from the edge of the treatment field. This Monte Carlo model is useful to both physicists and clinicians when evaluating out-of-field doses and associated potential risks.
Low-dose aspirin or other nonsteroidal anti-inflammatory drug use and prostate cancer risk
DEFF Research Database (Denmark)
Skriver, Charlotte; Dehlendorff, Christian; Borre, Michael
2016-01-01
PURPOSE: Increasing evidence suggests that aspirin use may protect against prostate cancer. In a nationwide case-control study, using Danish high-quality registry data, we evaluated the association between the use of low-dose aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs......) and the risk of prostate cancer. METHODS: We identified 35,600 patients (cases) with histologically verified prostate cancer during 2000-2012. Cases were matched to 177,992 population controls on age and residence by risk-set sampling. Aspirin and nonaspirin NSAID exposure was defined by type, estimated dose......, duration, and consistency of use. We used conditional logistic regression to estimate odds ratios (ORs), with 95 % confidence intervals (CIs), for prostate cancer associated with low-dose aspirin (75-150 mg) or nonaspirin NSAID use, adjusted for potential confounders. RESULTS: Use of low-dose aspirin...
GPUMCD: a new GPU-oriented Monte Carlo dose calculation platform
Hissoiny, Sami; Ozell, Benoît; Després, Philippe
2011-01-01
Purpose: Monte Carlo methods are considered the gold standard for dosimetric computations in radiotherapy. Their execution time is however still an obstacle to the routine use of Monte Carlo packages in a clinical setting. To address this problem, a completely new, and designed from the ground up for the GPU, Monte Carlo dose calculation package for voxelized geometries is proposed: GPUMCD. Method : GPUMCD implements a coupled photon-electron Monte Carlo simulation for energies in the range 0.01 MeV to 20 MeV. An analogue simulation of photon interactions is used and a Class II condensed history method has been implemented for the simulation of electrons. A new GPU random number generator, some divergence reduction methods as well as other optimization strategies are also described. GPUMCD was run on a NVIDIA GTX480 while single threaded implementations of EGSnrc and DPM were run on an Intel Core i7 860. Results : Dosimetric results obtained with GPUMCD were compared to EGSnrc. In all but one test case, 98% o...
OSCAAR calculations for the Hanford dose reconstruction scenario of BIOMASS Theme 2
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Homma, Toshimitsu; Tomita, Kenichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Inoue, Yoshihisa [Visible Information Center Inc., Tokai, Ibaraki (Japan)
2000-10-01
This report presents the results obtained from the application of the accident consequence assessment code, called OSCAAR, developed in Japan Atomic Energy Research Institute to the Hanford dose reconstruction scenario of BIOMASS Theme 2 organized by International Atomic Energy Agency. The scenario relates to an inadvertent release of {sup 131}I to atmosphere from the Hanford Purex Chemical Separations Plant on 2-5 September 1963. This exercise was used to test the atmospheric dispersion and deposition models and food chain transport models for {sup 131}I in OSCAAR with actual measurements and to identify the most important sources of uncertainty with respect both to the part of the assessment and to the overall assessment. The OSCAAR food chain model performed relatively well, while the atmospheric dispersion and deposition calculations made using wind data at the release height and wind fields by simple interpolation of the surrounding surface wind data indicated limited capabilities. The Monte Carlo based uncertainty and sensitivity method linked with OSCAAR successfully demonstrated its usefulness in the scenario. The method presented here also allowed the determination of the parameters that have the most important impact in accident consequence assessments. (author)
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Khazaee, M [shahid beheshti university, Tehran, Tehran (Iran, Islamic Republic of); Asl, A Kamali [Shahid Beheshti University, Tehran, Iran., Tehran, Tehran (Iran, Islamic Republic of); Geramifar, P [Shariati Hospital, Tehran, Iran., Tehran, Tehran (Iran, Islamic Republic of)
2015-06-15
Purpose: the objective of this study was to assess utilizing water dose point kernel (DPK)instead of tissue dose point kernels in convolution algorithms.to the best of our knowledge, in providing 3D distribution of absorbed dose from a 3D distribution of the activity, the human body is considered equivalent to water. as a Result tissue variations are not considered in patient specific dosimetry. Methods: In this study Gate v7.0 was used to calculate tissue dose point kernel. the beta emitter radionuclides which have taken into consideration in this simulation include Y-90, Lu-177 and P-32 which are commonly used in nuclear medicine. the comparison has been performed for dose point kernels of adipose, bone, breast, heart, intestine, kidney, liver, lung and spleen versus water dose point kernel. Results: In order to validate the simulation the Result of 90Y DPK in water were compared with published results of Papadimitroulas et al (Med. Phys., 2012). The results represented that the mean differences between water DPK and other soft tissues DPKs range between 0.6 % and 1.96% for 90Y, except for lung and bone, where the observed discrepancies are 6.3% and 12.19% respectively. The range of DPK difference for 32P is between 1.74% for breast and 18.85% for bone. For 177Lu, the highest difference belongs to bone which is equal to 16.91%. For other soft tissues the least discrepancy is observed in kidney with 1.68%. Conclusion: In all tissues except for lung and bone, the results of GATE for dose point kernel were comparable to water dose point kernel which demonstrates the appropriateness of applying water dose point kernel instead of soft tissues in the field of nuclear medicine.
Exploring Drug Dosing Regimens In Vitro Using Real-Time 3D Spheroid Tumor Growth Assays.
Lal-Nag, Madhu; McGee, Lauren; Titus, Steven A; Brimacombe, Kyle; Michael, Sam; Sittampalam, Gurusingham; Ferrer, Marc
2017-03-01
Two-dimensional monolayer cell proliferation assays for cancer drug discovery have made the implementation of large-scale screens feasible but only seem to reflect a simplified view that oncogenes or tumor suppressor genes are the genetic drivers of cancer cell proliferation. However, there is now increased evidence that the cellular and physiological context in which these oncogenic events occur play a key role in how they drive tumor growth in vivo and, therefore, in how tumors respond to drug treatments. In vitro 3D spheroid tumor models are being developed to better mimic the physiology of tumors in vivo, in an attempt to improve the predictability and efficiency of drug discovery for the treatment of cancer. Here we describe the establishment of a real-time 3D spheroid growth, 384-well screening assay. The cells used in this study constitutively expressed green fluorescent protein (GFP), which enabled the real-time monitoring of spheroid formation and the effect of chemotherapeutic agents on spheroid size at different time points of sphere growth and drug treatment. This real-time 3D spheroid assay platform represents a first step toward the replication in vitro of drug dosing regimens being investigated in vivo. We hope that further development of this assay platform will allow the investigation of drug dosing regimens, efficacy, and resistance before preclinical and clinical studies.
Tissue decomposition from dual energy CT data for MC based dose calculation in particle therapy
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Hünemohr, Nora, E-mail: n.huenemohr@dkfz.de; Greilich, Steffen [Medical Physics in Radiation Oncology, German Cancer Research Center, 69120 Heidelberg (Germany); Paganetti, Harald; Seco, Joao [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States); Jäkel, Oliver [Medical Physics in Radiation Oncology, German Cancer Research Center, 69120 Heidelberg, Germany and Department of Radiation Oncology and Radiation Therapy, University Hospital of Heidelberg, 69120 Heidelberg (Germany)
2014-06-15
Purpose: The authors describe a novel method of predicting mass density and elemental mass fractions of tissues from dual energy CT (DECT) data for Monte Carlo (MC) based dose planning. Methods: The relative electron density ϱ{sub e} and effective atomic number Z{sub eff} are calculated for 71 tabulated tissue compositions. For MC simulations, the mass density is derived via one linear fit in the ϱ{sub e} that covers the entire range of tissue compositions (except lung tissue). Elemental mass fractions are predicted from the ϱ{sub e} and the Z{sub eff} in combination. Since particle therapy dose planning and verification is especially sensitive to accurate material assignment, differences to the ground truth are further analyzed for mass density, I-value predictions, and stopping power ratios (SPR) for ions. Dose studies with monoenergetic proton and carbon ions in 12 tissues which showed the largest differences of single energy CT (SECT) to DECT are presented with respect to range uncertainties. The standard approach (SECT) and the new DECT approach are compared to reference Bragg peak positions. Results: Mean deviations to ground truth in mass density predictions could be reduced for soft tissue from (0.5±0.6)% (SECT) to (0.2±0.2)% with the DECT method. Maximum SPR deviations could be reduced significantly for soft tissue from 3.1% (SECT) to 0.7% (DECT) and for bone tissue from 0.8% to 0.1%. MeanI-value deviations could be reduced for soft tissue from (1.1±1.4%, SECT) to (0.4±0.3%) with the presented method. Predictions of elemental composition were improved for every element. Mean and maximum deviations from ground truth of all elemental mass fractions could be reduced by at least a half with DECT compared to SECT (except soft tissue hydrogen and nitrogen where the reduction was slightly smaller). The carbon and oxygen mass fraction predictions profit especially from the DECT information. Dose studies showed that most of the 12 selected tissues would
Alejnikov, V E; Krylov, A R
2002-01-01
Calculation data of neutron effective dose behind concrete shielding with thickness up to 3 meters is presented. The calculations have been performed by the Monte Carlo and phenomenological methods for monoenergetic neutrons with energy from 5 to 100 MeV as well as for neutron spectra produced by protons with energies of 30 and 72 MeV in thick targets. Comparison between calculations of neutron effective dose behind shielding using phenomenological approach and those by the Monte Carlo method normally shows agreement to within a factor of better than two, i.e. estimation of shielding thickness by those methods shall not exceed one half value layer of neutron effective dose attenuation in shielding. It amounts from 10 to 30 cm of concrete shielding for neutron energies and thickness of shields under consideration
Drug and light dose responses to focal photodynamic therapy of single blood vessels in vivo
Khurana, Mamta; Moriyama, Eduardo H.; Mariampillai, Adrian; Samkoe, Kimberley; Cramb, David; Wilson, Brian C.
2009-11-01
As part of an ongoing program to develop two-photon (2-γ) photodynamic therapy (PDT) for treatment of wet-form age-related macular degeneration (AMD) and other vascular pathologies, we have evaluated the reciprocity of drug-light doses in focal-PDT. We targeted individual arteries in a murine window chamber model, using primarily the clinical photosensitizer Visudyne/liposomal-verteporfin. Shortly after administration of the photosensitizer, a small region including an arteriole was selected and irradiated with varying light doses. Targeted and nearby vessels were observed for a maximum of 17 to 25 h to assess vascular shutdown, tapering, and dye leakage/occlusion. For a given end-point metric, there was reciprocity between the drug and light doses, i.e., the response correlated with the drug-light product (DLP). These results provide the first quantification of photosensitizer and light dose relationships for localized irradiation of a single blood vessel and are compared to the DLP required for vessel closure between 1-γ and 2-γ activation, between focal and broad-beam irradiation, and between verteporfin and a porphyrin dimer with high 2-γ cross section. Demonstration of reciprocity over a wide range of DLP is important for further development of focal PDT treatments, such as the targeting of feeder vessels in 2-γ PDT of AMD.
An OpenCL-based Monte Carlo dose calculation engine (oclMC) for coupled photon-electron transport
Tian, Zhen; Folkerts, Michael; Qin, Nan; Jiang, Steve B; Jia, Xun
2015-01-01
Monte Carlo (MC) method has been recognized the most accurate dose calculation method for radiotherapy. However, its extremely long computation time impedes clinical applications. Recently, a lot of efforts have been made to realize fast MC dose calculation on GPUs. Nonetheless, most of the GPU-based MC dose engines were developed in NVidia CUDA environment. This limits the code portability to other platforms, hindering the introduction of GPU-based MC simulations to clinical practice. The objective of this paper is to develop a fast cross-platform MC dose engine oclMC using OpenCL environment for external beam photon and electron radiotherapy in MeV energy range. Coupled photon-electron MC simulation was implemented with analogue simulations for photon transports and a Class II condensed history scheme for electron transports. To test the accuracy and efficiency of our dose engine oclMC, we compared dose calculation results of oclMC and gDPM, our previously developed GPU-based MC code, for a 15 MeV electron ...
Energy Technology Data Exchange (ETDEWEB)
Adrada, A; Miller, E; Tello, Z; Medina, L; Garrigo, E; Venencia, C [Instituto de Radioterapia - Fundacion Marie Curie, Cordoba (Argentina)
2014-06-01
Purpose: The purpose of this work was to develop and validate an open source independent MU dose calculation software for S and S IMRT based in the algorithm proposed by Kung et.al. Methods: Treatment plans were done using Iplan v4.5 BrainLAB TPS and S and S IMRT modality. A 6MV photon beam produced by a Primus linear accelerator equipped with an Optifocus MLC was used. TPS dose calculation algorithms were pencil beam and Monte Carlo. 230 IMRT treatments plans were selected for the study. The software was written under MALTLAB environment. Treatment plans were imported by the software using RTP format. Field fluences were reconstructed adding all segments.The algorithm implemented in the software calculates the dose at a reference point as the sum of primary and scatter dose. The primary dose is obtained by masking the fluence map with a circle of radius 1cm. The scatter dose is obtained through a shaped ring mask around the previous circle with a thickness of 0.5cm; the rings are increased one after another with constant thickness until cover the entire map of influence. The dosimetric parameters Sc, Sp and TPR vary depending on radio, the transmission effect of the MLC, inverse square law and dose profile are used for the calculation. Results: The average difference between measured and independent calculated dose was 0.4% ± 2.2% [−6.8%, 6.4%]. For 91% of the studied plans the difference was less than 3%. The difference between the measured and TPS dose with pencilbeam algorithm was 2.6% ± 1.41% [−2.0%, 5.6%] and Monte Carlo algorithm was 0.4% ± 1.5% [−4.9%, 3.7%]. The differences obtained are comparable to that obtained with the ionization chamber and TPS. Conclusion: The developed software is suitable for use in S and S IMRT dose calculation. This application is open and can be downloading under request.
Energy Technology Data Exchange (ETDEWEB)
Rusin, Tiago; Rebello, Wilson F.; Vellozo, Sergio O.; Gomes, Renato G., E-mail: tiagorusin@ime.eb.b, E-mail: rebello@ime.eb.b, E-mail: vellozo@cbpf.b, E-mail: renatoguedes@ime.eb.b [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Nuclear; Vital, Helio C., E-mail: vital@ctex.eb.b [Centro Tecnologico do Exercito (CTEx), Rio de Janeiro, RJ (Brazil); Silva, Ademir X., E-mail: ademir@con.ufrj.b [Universidade Federal do Rio de Janeiro (PEN/COPPE/UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-Graduacao de Engenharia. Programa de Engenharia Nuclear
2011-07-01
A cavity-type cesium-137 research irradiating facility at CTEx has been modeled by using the Monte Carlo code MCNPX. The irradiator has been daily used in experiments to optimize the use of ionizing radiation for conservation of many kinds of food and to improve materials properties. In order to correlate the effects of the treatment, average doses have been calculated for each irradiated sample, accounting for the measured dose rate distribution in the irradiating chambers. However that approach is only approximate, being subject to significant systematic errors due to the heterogeneous internal structure of most samples that can lead to large anisotropy in attenuation and Compton scattering properties across the media. Thus this work is aimed at further investigating such uncertainties by calculating the dose rate distribution inside the items treated such that a more accurate and representative estimate of the total absorbed dose can be determined for later use in the effects-versus-dose correlation curves. Samples of different simplified geometries and densities (spheres, cylinders, and parallelepipeds), have been modeled to evaluate internal dose rate distributions within the volume of the samples and the overall effect on the average dose. (author)
Accuracy of the phase space evolution dose calculation model for clinical 25 MeV electron beams
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Korevaar, Erik W. [Daniel den Hoed Cancer Center, University Hospital Rotterdam, PO Box 5201, 3008 AE Rotterdam (Netherlands). E-mail: korevaar at kfih.azr.nl; Akhiat, Abdelhafid; Heijmen, Ben J.M. [Daniel den Hoed Cancer Center, University Hospital Rotterdam, PO Box 5201, 3008 AE Rotterdam (Netherlands); Huizenga, Henk [Joint Center for Radiation Oncology Arnhem-Nijmegen, University Medical Center Nijmegen, PO Box 9101, 6500 HB Nijmegen (Netherlands)
2000-10-01
The phase space evolution (PSE) model is a dose calculation model for electron beams in radiation oncology developed with the aim of a higher accuracy than the commonly used pencil beam (PB) models and with shorter calculation times than needed for Monte Carlo (MC) calculations. In this paper the accuracy of the PSE model has been investigated for 25 MeV electron beams of a MM50 racetrack microtron (Scanditronix Medical AB, Sweden) and compared with the results of a PB model. Measurements have been performed for tests like non-standard SSD, irregularly shaped fields, oblique incidence and in phantoms with heterogeneities of air, bone and lung. MC calculations have been performed as well, to reveal possible errors in the measurements and/or possible inaccuracies in the interaction data used for the bone and lung substitute materials. Results show a good agreement between PSE calculated dose distributions and measurements. For all points the differences - in absolute dose - were generally well within 3% and 3 mm. However, the PSE model was found to be less accurate in large regions of low-density material and errors of up to 6% were found for the lung phantom. Results of the PB model show larger deviations, with differences of up to 6% and 6 mm and of up to 10% for the lung phantom; at shortened SSDs the dose was overestimated by up to 6%. The agreement between MC calculations and measurement was good. For the bone and the lung phantom maximum deviations of 4% and 3% were found, caused by uncertainties about the actual interaction data. In conclusion, using the phase space evolution model, absolute 3D dose distributions of 25 MeV electron beams can be calculated with sufficient accuracy in most cases. The accuracy is significantly better than for a pencil beam model. In regions of lung tissue, a Monte Carlo model yields more accurate results than the current implementation of the PSE model. (author)
Accuracy of the phase space evolution dose calculation model for clinical 25 MeV electron beams
Korevaar, Erik W.; Akhiat, Abdelhafid; Heijmen, Ben J. M.; Huizenga, Henk
2000-10-01
The phase space evolution (PSE) model is a dose calculation model for electron beams in radiation oncology developed with the aim of a higher accuracy than the commonly used pencil beam (PB) models and with shorter calculation times than needed for Monte Carlo (MC) calculations. In this paper the accuracy of the PSE model has been investigated for 25 MeV electron beams of a MM50 racetrack microtron (Scanditronix Medical AB, Sweden) and compared with the results of a PB model. Measurements have been performed for tests like non-standard SSD, irregularly shaped fields, oblique incidence and in phantoms with heterogeneities of air, bone and lung. MC calculations have been performed as well, to reveal possible errors in the measurements and/or possible inaccuracies in the interaction data used for the bone and lung substitute materials. Results show a good agreement between PSE calculated dose distributions and measurements. For all points the differences - in absolute dose - were generally well within 3% and 3 mm. However, the PSE model was found to be less accurate in large regions of low-density material and errors of up to 6% were found for the lung phantom. Results of the PB model show larger deviations, with differences of up to 6% and 6 mm and of up to 10% for the lung phantom; at shortened SSDs the dose was overestimated by up to 6%. The agreement between MC calculations and measurement was good. For the bone and the lung phantom maximum deviations of 4% and 3% were found, caused by uncertainties about the actual interaction data. In conclusion, using the phase space evolution model, absolute 3D dose distributions of 25 MeV electron beams can be calculated with sufficient accuracy in most cases. The accuracy is significantly better than for a pencil beam model. In regions of lung tissue, a Monte Carlo model yields more accurate results than the current implementation of the PSE model.
Drug-induced interstitial pneumonitis due to low-dose lenalidomide.
Kunimasa, Kei; Ueda, Tomoaki; Arita, Machiko; Maeda, Takeshi; Hotta, Machiko; Ishida, Tadashi
2012-01-01
Lenalidomide is a second-generation immunomodulatory drug that has been approved to treat relapsed or refractory multiple myeloma. Here, we describe a patient who was treated with a low dose of lenalidomide (5 mg/day on days 1-21 of a 28-day cycle) because the standard dose of bortezomib was too toxic and adverse events persisted. However, he developed fever, dyspnea, hypoxia and pulmonary infiltrates. The results of an extensive workup for other causes including infections were negative and the final diagnosis was lenalidomide-induced interstitial pneumonitis. This is the first case report of lenalidomide-induced pneumonitis in a Japanese patient.
Barros de Andrade E Sousa, Lisa C; Kühn, Clemens; Tyc, Katarzyna M; Klipp, Edda
2015-01-01
The fungus Candida albicans is the most common causative agent of human fungal infections and better drugs or drug combination strategies are urgently needed. Here, we present an agent-based model of the interplay of C. albicans with the host immune system and with the microflora of the host. We took into account the morphological change of C. albicans from the yeast to hyphae form and its dynamics during infection. The model allowed us to follow the dynamics of fungal growth and morphology, of the immune cells and of microflora in different perturbing situations. We specifically focused on the consequences of microflora reduction following antibiotic treatment. Using the agent-based model, different drug types have been tested for their effectiveness, namely drugs that inhibit cell division and drugs that constrain the yeast-to-hyphae transition. Applied individually, the division drug turned out to successfully decrease hyphae while the transition drug leads to a burst in hyphae after the end of the treatment. To evaluate the effect of different drug combinations, doses, and schedules, we introduced a measure for the return to a healthy state, the infection score. Using this measure, we found that the addition of a transition drug to a division drug treatment can improve the treatment reliability while minimizing treatment duration and drug dosage. In this work we present a theoretical study. Although our model has not been calibrated to quantitative experimental data, the technique of computationally identifying synergistic treatment combinations in an agent based model exemplifies the importance of computational techniques in translational research.
Directory of Open Access Journals (Sweden)
Lisa Corina Barros de Andrade e Sousa1
2016-01-01
Full Text Available The fungus Candida albicans is the most common causative agent of human fungal infections and better drugs or drug combination strategies are urgently needed. Here, we present an agent-based model of the interplay of C. albicans with the host immune system and with the microflora of the host. We took into account the morphological change of C. albicans from the yeast to hyphae form and its dynamics during infection. The model allowed us to follow the dynamics of fungal growth and morphology, of the immune cells and of microflora in different perturbing situations. We specifically focused on the consequences of microflora reduction following antibiotic treatment. Using the agent-based model, different drug types have been tested for their effectiveness, namely drugs that inhibit cell division and drugs that constrain the yeast-to-hyphae transition. Applied individually, the division drug turned out to successfully decrease hyphae while the transition drug leads to a burst in hyphae after the end of the treatment. To evaluate the effect of different drug combinations, doses, and schedules, we introduced a measure for the return to a healthy state, the infection score. Using this measure, we found that the addition of a transition drug to a division drug treatment can improve the treatment reliability while minimizing treatment duration and drug dosage. In this work we present a theoretical study. Although our model has not been calibrated to quantitative experimental data, the technique of computationally identifying synergistic treatment combinations in an agent based model exemplifies the importance of computational techniques in translational research.
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Azcona, J [Department of Radiation Physics, Clinica Universidad de Navarra (Spain); Burguete, J [Universidad de Navarra, Pamplona, Navarra (Spain)
2014-06-01
Purpose: To obtain the pencil beam kernels that characterize a megavoltage photon beam generated in a FFF linac by experimental measurements, and to apply them for dose calculation in modulated fields. Methods: Several Kodak EDR2 radiographic films were irradiated with a 10 MV FFF photon beam from a Varian True Beam (Varian Medical Systems, Palo Alto, CA) linac, at the depths of 5, 10, 15, and 20cm in polystyrene (RW3 water equivalent phantom, PTW Freiburg, Germany). The irradiation field was a 50 mm diameter circular field, collimated with a lead block. Measured dose leads to the kernel characterization, assuming that the energy fluence exiting the linac head and further collimated is originated on a point source. The three-dimensional kernel was obtained by deconvolution at each depth using the Hankel transform. A correction on the low dose part of the kernel was performed to reproduce accurately the experimental output factors. The kernels were used to calculate modulated dose distributions in six modulated fields and compared through the gamma index to their absolute dose measured by film in the RW3 phantom. Results: The resulting kernels properly characterize the global beam penumbra. The output factor-based correction was carried out adding the amount of signal necessary to reproduce the experimental output factor in steps of 2mm, starting at a radius of 4mm. There the kernel signal was in all cases below 10% of its maximum value. With this correction, the number of points that pass the gamma index criteria (3%, 3mm) in the modulated fields for all cases are at least 99.6% of the total number of points. Conclusion: A system for independent dose calculations in modulated fields from FFF beams has been developed. Pencil beam kernels were obtained and their ability to accurately calculate dose in homogeneous media was demonstrated.
DeSilva, Mary Bachman; Hamer, Davidson H.; Keyi, Xu; Wilson, Ira B.; Sabin, Lora
2016-01-01
Adherence to antiretroviral medications is usually expressed in terms of the proportion of doses taken. However, the timing of doses taken may also be an important dimension to overall adherence. Little is known about whether patients who mistime doses are also more likely to skip doses. Using data from the completed Adherence for Life randomized controlled trial, we created visual and statistical models to capture and analyze dose timing data collected longitudinally with electronic drug monitors (EDM). From scatter plots depicting dose time versus calendar date, we identified dominant patterns of dose taking and calculated key features [slope of line over calendar date; residual mean standard error (RMSE)]. Each was assessed for its ability to categorize subjects with ‘suboptimal’ (<95 % of doses taken) using area under the receiver operating characteristic (AROC) curve analysis. Sixty eight subjects contributed EDM data, with ~300 to 400 observations/subject. While regression line slopes did not predict ‘sub-optimal’ adherence (AROC 0.51, 95 % CI 0.26–0.75), the variability in dose timing (RMSE) was strongly predictive (AROC 0.79, 95 % CI 0.62–0.97). Compared with the lowest quartile of RMSE (minimal dose time variability), each successive quartile roughly doubled the odds of ‘sub-optimal’ adherence (OR 2.1, 95 % CI 1.3–3.4). Patterns of dose timing and mistiming are strongly related to overall adherence behavior. Notably, individuals who skip doses are more likely to mistime doses, with the degree of risk positively correlated with the extent of dose timing variability. PMID:25893658
SU-E-T-397: Include Organ Deformation Into Dose Calculation of Prostate Brachytherapy
Energy Technology Data Exchange (ETDEWEB)
Shao, Y; Shen, D; Chen, R; Wang, A; Lian, J [University of North Carolina, Chapel Hill, NC (United States)
2014-06-01
Purpose: Prostate brachytherapy is an important curative treatment for patients with localized prostate cancer. In brachytherapy, rectal balloon is generally needed to adjust for unfavorable prostate position for seed placement. However, rectal balloon causes prostate deformation, which is not accounted for in dosimetric planning. Therefore, it is possible that brachytherapy dosimetry deviates significantly from initial plan when prostate returns to its non-deformed state (after procedure). The goal of this study is to develop a method to include prostate deformation into the treatment planning of brachytherapy dosimetry. Methods: We prospectively collected ultrasound images of prostate pre- and post- rectal balloon inflation from thirty five consecutive patients undergoing I-125 brachytherapy. Based on the cylinder coordinate systems, we learned the initial coordinate transformation parameters between the manual segmentations of both deformed and non-deformed prostates of each patient in training set. With the nearest-neighbor interpolation, we searched the best transformation between two coordinate systems to maximum the mutual information of deformed and non-deformed images. We then mapped the implanted seeds of five selected patients from the deformed prostate into non-deformed prostate. The seed position is marked on original pre-inflation US image and it is imported into VariSeed software for dose calculation. Results: The accuracy of image registration is 87.5% as quantified by Dice Index. The prostate coverage V100% dropped from 96.5±0.5% of prostate deformed plan to 91.9±2.6% (p<0.05) of non-deformed plan. The rectum V100% decreased from 0.44±0.26 cc to 0.10±0.18 cc (p<0.05). The dosimetry of the urethra showed mild change but not significant: V150% changed from 0.05±0.10 cc to 0.14±0.15 cc (p>0.05) and D1% changed from 212.9±37.3 Gy to 248.4±42.8 Gy (p>0.05). Conclusion: We have developed a deformable image registration method that allows
Hyperparasitaemia and low dosing are an important source of anti-malarial drug resistance
Directory of Open Access Journals (Sweden)
Lee Sue J
2009-11-01
Full Text Available Abstract Background Preventing the emergence of anti-malarial drug resistance is critical for the success of current malaria elimination efforts. Prevention strategies have focused predominantly on qualitative factors, such as choice of drugs, use of combinations and deployment of multiple first-line treatments. The importance of anti-malarial treatment dosing has been underappreciated. Treatment recommendations are often for the lowest doses that produce "satisfactory" results. Methods The probability of de-novo resistant malaria parasites surviving and transmitting depends on the relationship between their degree of resistance and the blood concentration profiles of the anti-malarial drug to which they are exposed. The conditions required for the in-vivo selection of de-novo emergent resistant malaria parasites were examined and relative probabilities assessed. Results Recrudescence is essential for the transmission of de-novo resistance. For rapidly eliminated anti-malarials high-grade resistance can arise from a single drug exposure, but low-grade resistance can arise only from repeated inadequate treatments. Resistance to artemisinins is, therefore, unlikely to emerge with single drug exposures. Hyperparasitaemic patients are an important source of de-novo anti-malarial drug resistance. Their parasite populations are larger, their control of the infection insufficient, and their rates of recrudescence following anti-malarial treatment are high. As use of substandard drugs, poor adherence, unusual pharmacokinetics, and inadequate immune responses are host characteristics, likely to pertain to each recurrence of infection, a small subgroup of patients provides the particular circumstances conducive to de-novo resistance selection and transmission. Conclusion Current dosing recommendations provide a resistance selection opportunity in those patients with low drug levels and high parasite burdens (often children or pregnant women. Patients with
Copeland, Kyle; Parker, Donald E; Friedberg, Wallace
2011-01-01
Conversion coefficients were calculated for fluence-to-absorbed dose, fluence-to-equivalent dose, fluence-to-effective dose and fluence-to-gray equivalent for isotropic exposure of an adult female and an adult male to deuterons ((2)H(+)) in the energy range 10 MeV-1 TeV (0.01-1000 GeV). Coefficients were calculated using the Monte Carlo transport code MCNPX 2.7.C and BodyBuilder™ 1.3 anthropomorphic phantoms. Phantoms were modified to allow calculation of the effective dose to a Reference Person using tissues and tissue weighting factors from 1990 and 2007 recommendations of the International Commission on Radiological Protection (ICRP) and gray equivalent to selected tissues as recommended by the National Council on Radiation Protection and Measurements. Coefficients for the equivalent and effective dose incorporated a radiation weighting factor of 2. At 15 of 19 energies for which coefficients for the effective dose were calculated, coefficients based on ICRP 1990 and 2007 recommendations differed by <3%. The greatest difference, 47%, occurred at 30 MeV.
A GPU OpenCL based cross-platform Monte Carlo dose calculation engine (goMC)
Tian, Zhen; Shi, Feng; Folkerts, Michael; Qin, Nan; Jiang, Steve B.; Jia, Xun
2015-09-01
Monte Carlo (MC) simulation has been recognized as the most accurate dose calculation method for radiotherapy. However, the extremely long computation time impedes its clinical application. Recently, a lot of effort has been made to realize fast MC dose calculation on graphic processing units (GPUs). However, most of the GPU-based MC dose engines have been developed under NVidia’s CUDA environment. This limits the code portability to other platforms, hindering the introduction of GPU-based MC simulations to clinical practice. The objective of this paper is to develop a GPU OpenCL based cross-platform MC dose engine named goMC with coupled photon-electron simulation for external photon and electron radiotherapy in the MeV energy range. Compared to our previously developed GPU-based MC code named gDPM (Jia et al 2012 Phys. Med. Biol. 57 7783-97), goMC has two major differences. First, it was developed under the OpenCL environment for high code portability and hence could be run not only on different GPU cards but also on CPU platforms. Second, we adopted the electron transport model used in EGSnrc MC package and PENELOPE’s random hinge method in our new dose engine, instead of the dose planning method employed in gDPM. Dose distributions were calculated for a 15 MeV electron beam and a 6 MV photon beam in a homogenous water phantom, a water-bone-lung-water slab phantom and a half-slab phantom. Satisfactory agreement between the two MC dose engines goMC and gDPM was observed in all cases. The average dose differences in the regions that received a dose higher than 10% of the maximum dose were 0.48-0.53% for the electron beam cases and 0.15-0.17% for the photon beam cases. In terms of efficiency, goMC was ~4-16% slower than gDPM when running on the same NVidia TITAN card for all the cases we tested, due to both the different electron transport models and the different development environments. The code portability of our new dose engine goMC was validated by
Kitamura, Atsushi; Okura, Takashi; Higuchi, Kei; Deguchi, Yoshiharu
2016-02-01
Brain microdialysis is a powerful tool to estimate brain-to-plasma unbound concentration ratio at the steady state (Kp,uu) of compounds by direct measurement of the unbound concentration in brain interstitial fluid. Here, we evaluated a method to estimate Kp,uu values of multiple organic-cationic drugs simultaneously, by means of brain microdialysis combined with cocktail dosing. Five cationic drugs (diphenhydramine, memantine, oxycodone, pyrilamine, and tramadol), substrates of the proton-coupled organic cation antiport system, were selected as model drugs, and compared under single-dosing and cocktail-dosing conditions. We selected doses of the drugs at which no significant drug-drug interaction occurs at the proton-coupled organic cation antiport system in the blood-brain barrier (BBB). This was confirmed by uptake studies in hCMEC/D3 cells, an in vitro BBB model. The Kp,uu values after cocktail administration were in the range of 1.8-5.2, and were in good agreement with those after single administration. These results suggest that the microdialysis method with cocktail dosing is suitable to estimate Kp,uu values of several cationic drugs simultaneously, if there is no drug-drug interaction during BBB transport. The method could be useful for evaluating drug candidates with high Kp,uu values at an early stage in the development of central nervous system-acting drugs.
Gifford, Kent A; Price, Michael J; Horton, John L; Wareing, Todd A; Mourtada, Firas
2008-06-01
The goal of this work was to calculate the dose distribution around a high dose-rate 192Ir brachytherapy source using a multi-group discrete ordinates code and then to compare the results with a Monte Carlo calculated dose distribution. The unstructured tetrahedral mesh discrete ordinates code Attila version 6.1.1 was used to calculate the photon kerma rate distribution in water around the Nucletron microSelectron mHDRv2 source. MCNPX 2.5.c was used to compute the Monte Carlo water photon kerma rate distribution. Two hundred million histories were simulated, resulting in standard errors of the mean of less than 3% overall. The number of energy groups, S(n) (angular order), P(n) (scattering order), and mesh elements were varied in addition to the method of analytic ray tracing to assess their effects on the deterministic solution. Water photon kerma rate matrices were exported from both codes into an in-house data analysis software. This software quantified the percent dose difference distribution, the number of points within +/- 3% and +/- 5%, and the mean percent difference between the two codes. The data demonstrated that a 5 energy-group cross-section set calculated results to within 0.5% of a 15 group cross-section set. S12 was sufficient to resolve the solution in angle. P2 expansion of the scattering cross-section was necessary to compute accurate distributions. A computational mesh with 55 064 tetrahedral elements in a 30 cm diameter phantom resolved the solution spatially. An efficiency factor of 110 with the above parameters was realized in comparison to MC methods. The Attila code provided an accurate and efficient solution of the Boltzmann transport equation for the mHDRv2 source.
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Pereira, Wagner de S.; Py Junior, Delcy de A., E-mail: wspereira@inb.gov.b, E-mail: delcy@inb.gov.b [Industrias Nucleares do Brasil (UTM/INB), Pocos de Caldas, MG (Brazil). Unidade de Tratamento de Minerios; Universidade Federal Fluminense (LARARA/UFF), Niteroi, RJ (Brazil). Lab. de Radiobiologia e Radiometria; Kelecom, Alphonse [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Programa de Pos-Graduacao em Ciencia Ambiental
2011-10-26
This paper evaluates the recommendations of ICRP which has as objective the environmental radioprotection. It was analysed the recommendations 26, 60, 91, 103 and 108 of the ICRP. The ICRP-103 defined the concept of animal and plant of reference (APR) to be used in the RAP based on the calculation of absorbed dose based on APR concept. This last view allows to build a legal framework of environmental protection with a etic, moral and scientific visualization, more defensible than the anthropomorphic concept
Copeland, Kyle; Parker, Donald E; Friedberg, Wallace
2010-12-01
Conversion coefficients were calculated for fluence-to-absorbed dose, fluence-to-equivalent dose, fluence-to-effective dose and fluence-to-gray equivalent for isotropic exposure of an adult female and an adult male to tritons ((3)H(+)) in the energy range of 10 MeV to 1 TeV (0.01-1000 GeV). Coefficients were calculated using Monte Carlo transport code MCNPX 2.7.C and BodyBuilder™ 1.3 anthropomorphic phantoms. Phantoms were modified to allow calculation of effective dose to a Reference Person using tissues and tissue weighting factors from 1990 and 2007 recommendations of the International Commission on Radiological Protection (ICRP) and calculation of gray equivalent to selected tissues as recommended by the National Council on Radiation Protection and Measurements. At 15 of the 19 energies for which coefficients for effective dose were calculated, coefficients based on ICRP 2007 and 1990 recommendations differed by less than 3%. The greatest difference, 43%, occurred at 30 MeV.
Wang, Jing; Toloczko, Mychailo B.; Bailey, Nathan; Garner, Frank A.; Gigax, Jonathan; Shao, Lin
2016-11-01
In radiation effects on materials utilizing self-ion irradiations, it is necessary to calculate the local displacement damage level and ion injection profile because of the short distance that self-ions travel in a material and because of the strong variation of displacement rate with depth in a specimen. The most frequently used tool for this is the software package called Stopping and Range of Ions in Matter (SRIM). A SRIM-calculated depth-dependent dose level is usually determined under the implicit assumption that the target does not undergo any significant changes in volume during the process, in particular SRIM ignores the effect of sputtering, injected ions, and void swelling on the redistribution of the dose and injected ion profiles. This approach become increasingly invalid as the ion fluence reaches ever higher levels, especially for low energy ion irradiations. The original surface is not maintained due to sputter-induced erosion, while within the irradiated region of the specimen, injected ions are adding material, and if void swelling is occurring, it is creating empty space. An iterative mathematical treatment of SRIM outputs to produce corrected dose and injected ion profiles based on these phenomenon and without regard to diffusion is presented along with examples of differences between SRIM-calculated values and corrected values over a range of typical ion energies. The intent is to provide the reader with a convenient tool for more accurately calculating dose and injected ion profiles for heavy-ion irradiations.
Takahashi, F; Shigemori, Y; Seki, A
2009-01-01
A system has been developed to assess radiation dose distribution inside the body of exposed persons in a radiological accident by utilising radiation transport calculation codes-MCNP and MCNPX. The system consists mainly of two parts, pre-processor and post-processor of the radiation transport calculation. Programs for the pre-processor are used to set up a 'problem-dependent' input file, which defines the accident condition and dosimetric quantities to be estimated. The program developed for the post-processor part can effectively indicate dose information based upon the output file of the code. All of the programs in the dosimetry system can be executed with a generally used personal computer and accurately give the dose profile to an exposed person in a radiological accident without complicated procedures. An experiment using a physical phantom was carried out to verify the availability of the dosimetry system with the developed programs in a gamma ray irradiation field.
Arai, Kazuhiro; Kadoya, Noriyuki; Kato, Takahiro; Endo, Hiromitsu; Komori, Shinya; Abe, Yoshitomo; Nakamura, Tatsuya; Wada, Hitoshi; Kikuchi, Yasuhiro; Takai, Yoshihiro; Jingu, Keiichi
2017-01-01
The aim of this study was to confirm On-Board Imager cone-beam computed tomography (CBCT) using the histogram-matching algorithm as a useful method for proton dose calculation. We studied one head and neck phantom, one pelvic phantom, and ten patients with head and neck cancer treated using intensity-modulated radiation therapy (IMRT) and proton beam therapy. We modified Hounsfield unit (HU) values of CBCT and generated two modified CBCTs (mCBCT-RR, mCBCT-DIR) using the histogram-matching algorithm: modified CBCT with rigid registration (mCBCT-RR) and that with deformable image registration (mCBCT-DIR). Rigid and deformable image registration were applied to match the CBCT to planning CT. To evaluate the accuracy of the proton dose calculation, we compared dose differences in the dosimetric parameters (D2% and D98%) for clinical target volume (CTV) and planning target volume (PTV). We also evaluated the accuracy of the dosimetric parameters (Dmean and D2%) for some organs at risk, and compared the proton ranges (PR) between planning CT (reference) and CBCT or mCBCTs, and the gamma passing rates of CBCT and mCBCTs. For patients, the average dose and PR differences of mCBCTs were smaller than those of CBCT. Additionally, the average gamma passing rates of mCBCTs were larger than those of CBCT (e.g., 94.1±3.5% in mCBCT-DIR vs. 87.8±7.4% in CBCT). We evaluated the accuracy of the proton dose calculation in CBCT and mCBCTs for two phantoms and ten patients. Our results showed that HU modification using the histogram-matching algorithm could improve the accuracy of the proton dose calculation.
Buffa, F M; Nahum, A E
2000-10-01
The aim of this work is to investigate the influence of the statistical fluctuations of Monte Carlo (MC) dose distributions on the dose volume histograms (DVHs) and radiobiological models, in particular the Poisson model for tumour control probability (tcp). The MC matrix is characterized by a mean dose in each scoring voxel, d, and a statistical error on the mean dose, sigma(d); whilst the quantities d and sigma(d) depend on many statistical and physical parameters, here we consider only their dependence on the phantom voxel size and the number of histories from the radiation source. Dose distributions from high-energy photon beams have been analysed. It has been found that the DVH broadens when increasing the statistical noise of the dose distribution, and the tcp calculation systematically underestimates the real tumour control value, defined here as the value of tumour control when the statistical error of the dose distribution tends to zero. When increasing the number of energy deposition events, either by increasing the voxel dimensions or increasing the number of histories from the source, the DVH broadening decreases and tcp converges to the 'correct' value. It is shown that the underestimation of the tcp due to the noise in the dose distribution depends on the degree of heterogeneity of the radiobiological parameters over the population; in particular this error decreases with increasing the biological heterogeneity, whereas it becomes significant in the hypothesis of a radiosensitivity assay for single patients, or for subgroups of patients. It has been found, for example, that when the voxel dimension is changed from a cube with sides of 0.5 cm to a cube with sides of 0.25 cm (with a fixed number of histories of 10(8) from the source), the systematic error in the tcp calculation is about 75% in the homogeneous hypothesis, and it decreases to a minimum value of about 15% in a case of high radiobiological heterogeneity. The possibility of using the error
Kartashov, D A; Shurshakov, V A
2012-01-01
The article presents a new procedure of calculating the shielding functions for irregular objects formed from a set of nonintersecting (adjacent) triangles covering completely the surface of each object. Calculated and experimentally derived distributions of space ionizing radiation doses in the spherical tissue-equivalent phantom (experiment MATRYOSHKA-R) inside the International space station were in good agreement in the mass of phantom depths with allowance for measurement error (-10%). The procedure can be applied in modeling radiation loads on cosmonauts, calculating effectiveness of secondary protection in spacecraft, and design review of radiation protection for future space exploration missions.
Sharma, Manish K.; Alajo, Ayodeji B.
2016-08-01
Any source of ionizing radiations could lead to considerable dose acquisition to individuals in a nuclear facility. Evacuation may be required when elevated levels of radiation is detected within a facility. In this situation, individuals are more likely to take the closest exit. This may not be the most expedient decision as it may lead to higher dose acquisition. The strategy followed in preventing large dose acquisitions should be predicated on the path that offers least dose acquisition. In this work, the neutron generator facility at Missouri University of Science and Technology was analyzed. The Monte Carlo N-Particle (MCNP) radiation transport code was used to model the entire floor of the generator's building. The simulated dose rates in the hallways were used to estimate the integrated doses for different paths leading to exits. It was shown that shortest path did not always lead to minimum dose acquisition and the approach was successful in predicting the expedient path as opposed to the approach of taking the nearest exit.
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Sharma, Manish K.; Alajo, Ayodeji B., E-mail: alajoa@mst.edu
2016-08-11
Any source of ionizing radiations could lead to considerable dose acquisition to individuals in a nuclear facility. Evacuation may be required when elevated levels of radiation is detected within a facility. In this situation, individuals are more likely to take the closest exit. This may not be the most expedient decision as it may lead to higher dose acquisition. The strategy followed in preventing large dose acquisitions should be predicated on the path that offers least dose acquisition. In this work, the neutron generator facility at Missouri University of Science and Technology was analyzed. The Monte Carlo N-Particle (MCNP) radiation transport code was used to model the entire floor of the generator's building. The simulated dose rates in the hallways were used to estimate the integrated doses for different paths leading to exits. It was shown that shortest path did not always lead to minimum dose acquisition and the approach was successful in predicting the expedient path as opposed to the approach of taking the nearest exit.
Practical Aspects of Drug Calculations. Mathematics Education Centre. Report No. 24.
Sullivan, Peter; Clarkson, P., Ed.
Concern has been expressed in recent years about the accuracy of medication administered by nurses in Papua New Guinean hospitals. Attention has been focused on the calculation of the drug dosages. This paper discusses the processes involved in the administration of medication, and reports on a study to evaluate the competence of student nurses at…
Application of PK/PD Modeling in Veterinary Field: Dose Optimization and Drug Resistance Prediction
Directory of Open Access Journals (Sweden)
Ijaz Ahmad
2016-01-01
Full Text Available Among veterinary drugs, antibiotics are frequently used. The true mean of antibiotic treatment is to administer dose of drug that will have enough high possibility of attaining the preferred curative effect, with adequately low chance of concentration associated toxicity. Rising of antibacterial resistance and lack of novel antibiotic is a global crisis; therefore there is an urgent need to overcome this problem. Inappropriate antibiotic selection, group treatment, and suboptimal dosing are mostly responsible for the mentioned problem. One approach to minimizing the antibacterial resistance is to optimize the dosage regimen. PK/PD model is important realm to be used for that purpose from several years. PK/PD model describes the relationship between drug potency, microorganism exposed to drug, and the effect observed. Proper use of the most modern PK/PD modeling approaches in veterinary medicine can optimize the dosage for patient, which in turn reduce toxicity and reduce the emergence of resistance. The aim of this review is to look at the existing state and application of PK/PD in veterinary medicine based on in vitro, in vivo, healthy, and disease model.
DITTY - a computer program for calculating population dose integrated over ten thousand years
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Napier, B.A.; Peloquin, R.A.; Strenge, D.L.
1986-03-01
The computer program DITTY (Dose Integrated Over Ten Thousand Years) was developed to determine the collective dose from long term nuclear waste disposal sites resulting from the ground-water pathways. DITTY estimates the time integral of collective dose over a ten-thousand-year period for time-variant radionuclide releases to surface waters, wells, or the atmosphere. This document includes the following information on DITTY: a description of the mathematical models, program designs, data file requirements, input preparation, output interpretations, sample problems, and program-generated diagnostic messages.
Copeland, Kyle; Parker, Donald E; Friedberg, Wallace
2010-12-01
Conversion coefficients were calculated for fluence-to-absorbed dose, fluence-to-equivalent dose, fluence-to-effective dose and fluence-to-gray equivalent, for isotropic exposure of an adult male and an adult female to helions ((3)He(2+)) in the energy range of 10 MeV to 1 TeV (0.01-1000 GeV). Calculations were performed using Monte Carlo transport code MCNPX 2.7.C and BodyBuilder™ 1.3 anthropomorphic phantoms modified to allow calculation of effective dose using tissues and tissue weighting factors from either the 1990 or 2007 recommendations of the International Commission on Radiological Protection (ICRP), and gray equivalent to selected tissues as recommended by the National Council on Radiation Protection and Measurements. At 15 of the 19 energies for which coefficients for effective dose were calculated, coefficients based on ICRP 2007 and 1990 recommendations differed by less than 2%. The greatest difference, 62%, occurred at 100 MeV.
Calculation of effective dose in whole body in dependence of angle of collimator for photon fields
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Fuenzalida, M. [Universidad de la Frontera, Temuco (Chile). Programa de Magister en Fisica Medica; Varon, C.; Piriz, G.; Banguero, Y.; Lozano, E.; Mancilla, C., E-mail: fisicamedica@incancer.c [Instituto Nacional del Cancer, Santiago (Chile). Unidad de Fisica Medica
2011-07-01
The objective of this work is to obtain quantifiable data of whole body effective dose for photons fields of 6 MV and 18 MV in function of the collimator angle of a Varian Clinac 21EX lineal accelerator. It has been made a variety of studies which investigate the form to reduce the dose in whole body with photons fields, specially over the potential risks and the influence of the collimator angle, as performed Stanthakis et al. [1] with the Monte Carlo method. As a result of this work, the values of whole body effective doses are higher with a 0 deg collimator than with a 90 deg collimator, and as the field size increases, the effective doses difference in whole body, between 0 deg and 90 deg collimator angle, for both energies, becomes smaller. (author)
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Kim, Min Joo; Lee, Seu Ran; Suh, Tae Suk [Dept. of Biomedical Engineering, The Catholic University of Korea, Bucheon (Korea, Republic of)
2011-11-15
Modern radiation therapy techniques, such as Image-guided radiation therapy (IGRT), Adaptive radiation therapy (ART) has become a routine clinical practice on linear accelerators for the increase the tumor dose conformity and improvement of normal tissue sparing at the same time. For these highly developed techniques, megavoltage cone beam computed tomography (MVCBCT) system produce volumetric images at just one rotation of the x-ray beam source and detector on the bottom of conventional linear accelerator for real-time application of patient condition into treatment planning. MV CBCT image scan be directly registered to a reference CT data set which is usually kilo-voltage fan-beam computed tomography (kVFBCT) on treatment planning system and the registered image scan be used to adjust patient set-up error. However, to use MV CBCT images in radiotherapy, reliable electron density (ED) distribution are required. Patients scattering, beam hardening and softening effect caused by different energy application between kVCT, MV CBCT can cause cupping artifacts in MV CBCT images and distortion of Houns field Unit (HU) to ED conversion. The goal of this study, for reliable application of MV CBCT images into dose calculation, MV CBCT images was modified to correct distortion of HU to ED using the relationship of HU and ED from kV FBCT and MV CBCT images. The HU-density conversion was performed on MV CBCT image set using Dose difference map was showing in Figure 1. Finally, percentage differences above 3% were reduced depending on applying density calibration method. As a result, total error co uld be reduced to under 3%. The present study demonstrates that dose calculation accuracy using MV CBCT image set can be improved my applying HU-density conversion method. The dose calculation and comparison of dose distribution from MV CBCT image set with/without HU-density conversion method was performed. An advantage of this study compared to other approaches is that HU
Goswami, C Pankaj; Cheng, L; Alexander, P S; Singal, A; Li, L
2015-02-01
Gene expression data before and after treatment with an individual drug and the IC20 of dose-response data were utilized to predict two drugs' interaction effects on a diffuse large B-cell lymphoma (DLBCL) cancer cell. A novel drug interaction scoring algorithm was developed to account for either synergistic or antagonistic effects between drug combinations. Different core gene selection schemes were investigated, which included the whole gene set, the drug-sensitive gene set, the drug-sensitive minus drug-resistant gene set, and the known drug target gene set. The prediction scores were compared with the observed drug interaction data at 6, 12, and 24 hours with a probability concordance (PC) index. The test result shows the concordance between observed and predicted drug interaction ranking reaches a PC index of 0.605. The scoring reliability and efficiency was further confirmed in five drug interaction studies published in the GEO database.
Farah, J.; Martinetti, F.; Sayah, R.; Lacoste, V.; Donadille, L.; Trompier, F.; Nauraye, C.; De Marzi, L.; Vabre, I.; Delacroix, S.; Hérault, J.; Clairand, I.
2014-06-01
Monte Carlo calculations are increasingly used to assess stray radiation dose to healthy organs of proton therapy patients and estimate the risk of secondary cancer. Among the secondary particles, neutrons are of primary concern due to their high relative biological effectiveness. The validation of Monte Carlo simulations for out-of-field neutron doses remains however a major challenge to the community. Therefore this work focused on developing a global experimental approach to test the reliability of the MCNPX models of two proton therapy installations operating at 75 and 178 MeV for ocular and intracranial tumor treatments, respectively. The method consists of comparing Monte Carlo calculations against experimental measurements of: (a) neutron spectrometry inside the treatment room, (b) neutron ambient dose equivalent at several points within the treatment room, (c) secondary organ-specific neutron doses inside the Rando-Alderson anthropomorphic phantom. Results have proven that Monte Carlo models correctly reproduce secondary neutrons within the two proton therapy treatment rooms. Sensitive differences between experimental measurements and simulations were nonetheless observed especially with the highest beam energy. The study demonstrated the need for improved measurement tools, especially at the high neutron energy range, and more accurate physical models and cross sections within the Monte Carlo code to correctly assess secondary neutron doses in proton therapy applications.
Copeland, Kyle
2015-07-01
The superposition approximation was commonly employed in atmospheric nuclear transport modeling until recent years and is incorporated into flight dose calculation codes such as CARI-6 and EPCARD. The useful altitude range for this approximation is investigated using Monte Carlo transport techniques. CARI-7A simulates atmospheric radiation transport of elements H-Fe using a database of precalculated galactic cosmic radiation showers calculated with MCNPX 2.7.0 and is employed here to investigate the influence of the superposition approximation on effective dose rates, relative to full nuclear transport of galactic cosmic ray primary ions. Superposition is found to produce results less than 10% different from nuclear transport at current commercial and business aviation altitudes while underestimating dose rates at higher altitudes. The underestimate sometimes exceeds 20% at approximately 23 km and exceeds 40% at 50 km. Thus, programs employing this approximation should not be used to estimate doses or dose rates for high-altitude portions of the commercial space and near-space manned flights that are expected to begin soon.
Farah, J; Martinetti, F; Sayah, R; Lacoste, V; Donadille, L; Trompier, F; Nauraye, C; De Marzi, L; Vabre, I; Delacroix, S; Hérault, J; Clairand, I
2014-06-07
Monte Carlo calculations are increasingly used to assess stray radiation dose to healthy organs of proton therapy patients and estimate the risk of secondary cancer. Among the secondary particles, neutrons are of primary concern due to their high relative biological effectiveness. The validation of Monte Carlo simulations for out-of-field neutron doses remains however a major challenge to the community. Therefore this work focused on developing a global experimental approach to test the reliability of the MCNPX models of two proton therapy installations operating at 75 and 178 MeV for ocular and intracranial tumor treatments, respectively. The method consists of comparing Monte Carlo calculations against experimental measurements of: (a) neutron spectrometry inside the treatment room, (b) neutron ambient dose equivalent at several points within the treatment room, (c) secondary organ-specific neutron doses inside the Rando-Alderson anthropomorphic phantom. Results have proven that Monte Carlo models correctly reproduce secondary neutrons within the two proton therapy treatment rooms. Sensitive differences between experimental measurements and simulations were nonetheless observed especially with the highest beam energy. The study demonstrated the need for improved measurement tools, especially at the high neutron energy range, and more accurate physical models and cross sections within the Monte Carlo code to correctly assess secondary neutron doses in proton therapy applications.
Gu, Xuejun; Li, Jinsheng; Jia, Xun; Jiang, Steve B
2011-01-01
Targeting at developing an accurate and efficient dose calculation engine for online adaptive radiotherapy, we have implemented a finite size pencil beam (FSPB) algorithm with a 3D-density correction method on GPU. This new GPU-based dose engine is built on our previously published ultrafast FSPB computational framework [Gu et al. Phys. Med. Biol. 54 6287-97, 2009]. Dosimetric evaluations against MCSIM Monte Carlo dose calculations are conducted on 10 IMRT treatment plans with heterogeneous treatment regions (5 head-and-neck cases and 5 lung cases). For head and neck cases, when cavities exist near the target, the improvement with the 3D-density correction over the conventional FSPB algorithm is significant. However, when there are high-density dental filling materials in beam paths, the improvement is small and the accuracy of the new algorithm is still unsatisfactory. On the other hand, significant improvement of dose calculation accuracy is observed in all lung cases. Especially when the target is in the m...
Nedaie, Hassan Ali; Darestani, Hoda; Banaee, Nooshin; Shagholi, Negin; Mohammadi, Kheirollah; Shahvar, Arjang; Bayat, Esmaeel
2014-01-01
High-energy linacs produce secondary particles such as neutrons (photoneutron production). The neutrons have the important role during treatment with high energy photons in terms of protection and dose escalation. In this work, neutron dose equivalents of 18 MV Varian and Elekta accelerators are measured by thermoluminescent dosimeter (TLD) 600 and TLD700 detectors and compared with the Monte Carlo calculations. For neutron and photon dose discrimination, first TLDs were calibrated separately by gamma and neutron doses. Gamma calibration was carried out in two procedures; by standard 60Co source and by 18 MV linac photon beam. For neutron calibration by (241)Am-Be source, irradiations were performed in several different time intervals. The Varian and Elekta linac heads and the phantom were simulated by the MCNPX code (v. 2.5). Neutron dose equivalent was calculated in the central axis, on the phantom surface and depths of 1, 2, 3.3, 4, 5, and 6 cm. The maximum photoneutron dose equivalents which calculated by the MCNPX code were 7.06 and 2.37 mSv.Gy(-1) for Varian and Elekta accelerators, respectively, in comparison with 50 and 44 mSv.Gy(-1) achieved by TLDs. All the results showed more photoneutron production in Varian accelerator compared to Elekta. According to the results, it seems that TLD600 and TLD700 pairs are not suitable dosimeters for neutron dosimetry inside the linac field due to high photon flux, while MCNPX code is an appropriate alternative for studying photoneutron production.
Perceived compliance with AZT dosing among a sample of African-American drug users.
Williams, M; Bowen, A; Ross, M; Freeman, R; Elwood, W
2000-01-01
The purpose of this report was to present findings from a pilot study conducted to explore the associations between sociodemographic, drug use, and health belief factors and perceived compliance with zidovudine (AZT) among African-American drug users. Data were collected in Washington, DC, USA from individuals who were African-American; were recent or current drug injectors or crack smokers; were HIV-seropositive, and were receiving treatment for HIV infection. Participants were recruited through local organizations that provide services to HIV-infected persons. Participants were interviewed using a questionnaire that solicited sociodemographic, lifetime and current drug use, current sexual behaviours, health status, HIV and drug treatment history, and health belief data. Analyses were limited to individuals currently using an illicit substance and who had received AZT during their medical treatment. Parametric (Pearson's r) and nonparametric (Spearman's rho) statistics were used to assess correlations between perceived compliance with AZT dosing and independent variables. As the study was intended to be both descriptive and exploratory, the level of statistical significance was set at 0.10, rather than the customary 0.05. Antiretroviral medications recognized and recalled by participants are presented. The most commonly recalled medication was AZT. Slightly less than one-third of participants reported being completely compliant with an AZT regimen. Perceived compliance was found to be negatively associated with 5 variables: age, homelessness, number of injections in the previous 30 days, trading sex for drugs, and the perception that AIDS is no longer a serious disease since the development of new antiretroviral medications. Intensity of feelings of joy, fear, and the belief that taking more anti-HIV medications would result in better health were found to be positively correlated. Bivariate associations between perceived compliance and sociodemographic, drug use
Elbuken, Gulsah; Tanriverdi, Fatih; Karaca, Zuleyha; Kula, Mustafa; Gokahmetoglu, Selma; Unluhizarci, Kursad; Kelestimur, Fahrettin
2015-03-01
Salivary cortisol (SC) has been increasingly used as a surrogate biomarker of free cortisol (FC) for the assessment of hypothalamo-pituitary-adrenal (HPA) axis, but there are not enough data regarding its use during ACTH stimulation tests. Therefore, we aimed to determine the responses of SC, calculated free cortisol (cFC) and free cortisol index (FCI) to ACTH stimulation tests in healthy adults. Forty-four healthy volunteers (24 men and 20 women) were included in the study. Low-dose (1 µg) and standard-dose (250 µg) ACTH stimulation tests were performed on two consecutive days. Basal and stimulated total cortisol (TC) and cortisol-binding globulin (CBG) levels and SC levels were measured during both doses of ACTH stimulation tests. cFC (by Coolens' equation) and FCI levels were calculated from simultaneously measured TC and CBG levels. The minimum SC, cFC, FCI levels after low-dose ACTH stimulation test were 0.21, 0.33, 16.06 µg/dL, and after standard-dose ACTH were 0.85, 0.46, 26.11 µg/dL, respectively, in healthy individuals who all had TC responses higher than 20 µg/dL. Peak CBG levels after both doses of ACTH stimulation tests were found to be higher in women than in men. So, by its effect, peak cFC and FCI levels were found to be lower in female than in male group. Neither TC nor SC levels were affected by gender. cFC and FCI levels depend on CBG levels and they are affected by gender. Cut-off levels for SC, cFC, FCI levels after both low- and standard-dose ACTH stimulation are presented. Studies including patients with adrenal insufficiency would be helpful to see the diagnostic value of these suggested cut-off levels.
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Thiyagarajan, Rajesh; Vikraman, S; Karrthick, KP; Ramu, M; Sambasivaselli, R; Senniandavar, V; Kataria, Tejinder [Medanta The Medicity, Gurgaon, Haryana (India); Nambiraj, N Arunai; Sigamani, Ashokkumar [VIT University, Vellore, Tamil Nadu (India); Subbarao, Bargavan [Elekta India, Chennai, Tamil Nadu (India)
2015-06-15
Purpose: To evaluate the impact of dose calculation algorithm on the dose distribution of biologically optimized Volumatric Modulated Arc Therapy (VMAT) plans for Esophgeal cancer. Methods: Eighteen retrospectively treated patients with carcinoma esophagus were studied. VMAT plans were optimized using biological objectives in Monaco (5.0) TPS for 6MV photon beam (Elekta Infinity). These plans were calculated for final dose using Monte Carlo (MC), Collapsed Cone Convolution (CCC) & Pencil Beam Convolution (PBC) algorithms from Monaco and Oncentra Masterplan TPS. A dose grid of 2mm was used for all algorithms and 1% per plan uncertainty maintained for MC calculation. MC based calculations were considered as the reference for CCC & PBC. Dose volume histogram (DVH) indices (D95, D98, D50 etc) of Target (PTV) and critical structures were compared to study the impact of all three algorithms. Results: Beam models were consistent with measured data. The mean difference observed in reference with MC calculation for D98, D95, D50 & D2 of PTV were 0.37%, −0.21%, 1.51% & 1.18% respectively for CCC and 3.28%, 2.75%, 3.61% & 3.08% for PBC. Heart D25 mean difference was 4.94% & 11.21% for CCC and PBC respectively. Lung Dmean mean difference was 1.5% (CCC) and 4.1% (PBC). Spinal cord D2 mean difference was 2.35% (CCC) and 3.98% (PBC). Similar differences were observed for liver and kidneys. The overall mean difference found for target and critical structures was 0.71±1.52%, 2.71±3.10% for CCC and 3.18±1.55%, 6.61±5.1% for PBC respectively. Conclusion: We observed a significant overestimate of dose distribution by CCC and PBC as compared to MC. The dose prediction of CCC is closer (<3%) to MC than that of PBC. This can be attributed to poor performance of CCC and PBC in inhomogeneous regions around esophagus. CCC can be considered as an alternate in the absence of MC algorithm.
Internal Dose Calculations with the New Biokinetic Models of the ICRP
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Silverman, I.; Shamai, Y.; Schlesinger, T.; Biran, T
1999-07-01
During the past decade, the ICRP made major revisions in its recommendations regarding protection from ionising radiation and advised the use of new models for estimating doses due to intake of radionuclides. A new Internal Dosimetry code (InDose) is presented which employs all the new biokinetic models together with the new respiratory tract (RT) model and the gastrointestinal tract (GI) model. The code makes use of a generalised form of these new biokinetic models which enables the use of any of them. The code has been used to assess intakes and doses for the 3rd European Intercomparison Exercise on Internal Dose Assessment. A detailed study of one of the test cases of this exercise is presented. Our code using the new plutonium biokinetic model and LUDEP gave similar results. InDose, however, provides a way to insert consistent changes in the models in orderto make estimations under non-standard conditions. The new biokinetic model has been found to give better agreement with measured data than the old (ICRP 30) model. (author)
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Ramounet-le Gall, B.; Fritsch, P.; Abram, M.C.; Rateau, G.; Grillon, G.; Guillet, K. [Lab. de Radiotoxicologie, CEA/DSV/DRR/SRCA, Bruyeres le Chatel (France); Baude, S. [Lab. de Mesures Specifiques Gaz, CEA/DAM/DASE/SRCE, Bruyeres le Chatel (France); Berard, P. [Cabinet du Conseiller medical du CEA, CEA/DEN/DPS/LABM Saclay, Gif sur Yvette (France); Ansoborlo, E. [CEA/DEN/DRCP/CETAMA, Bagnols sur Ceze (France); Delforge, J. [Lab. de Radiotoxicologie, CEA/DSV/DRR/SRCA, Bruyeres le Chatel (France)
2002-07-01
A review on specific parameter measurements to calculate doses per unit of incorporation according to recommendations of the International Commission of Radiological Protection has been performed for inhaled actinide oxides. Alpha activity distribution of the particles can be obtained by autoradiography analysis using aerosol sampling filters at the work places. This allows us to characterize granulometric parameters of 'pure' actinide oxides, but complementary analysis by scanning electron microscopy is needed for complex aerosols. Dissolution parameters with their standard deviation are obtained after rat inhalation exposure, taking into account both mechanical lung clearance and actinide transfer to the blood estimated from bone retention. In vitro experiments suggest that the slow dissolution rate might decrease as a function of time following exposure. Dose calculation software packages have been developed to take into account granulometry and dissolution parameters as well as specific physiological parameters of exposed individuals. In the case of poorly soluble actinide oxides, granulometry and physiology appear as the main parameters controlling dose value, whereas dissolution only alters dose distribution. Validation of these software packages are in progress. (author)
Chiang, Po-Chang; South, Sarah A; Foster, Kimberly A; Daniels, J Scott; Wene, Steve P; Albin, Lesley A; Thompson, David C
2010-07-01
Time and resource constraints necessitate increasingly early decision making to accelerate or stop preclinical drug discovery programs. Early discovery drug candidates may be potent inhibitors of new targets, but all too often exhibit poor pharmaceutical and pharmacokinetic properties that limit the in vivo exposure. Low solubility of a drug candidate often leads to poor oral bioavailability and poor dose linearity that creates an issue for efficacy and target safety studies, where high drug exposures are desired. When solubility issues are encountered, enabling formulations are often used to improve the exposure. However, this approach often requires a substantial and lengthy investment to develop the formulation. In our study, two drug candidates with poor aqueous solubility were dosed in rats as simple suspension formulations using a novel tandem dosing strategy, which employs dosing orally in 2.5 h increments up to three times to simulate an oral infusion by avoiding saturation of absorption associated with bolus dosing. These compounds were also dosed using the same suspension formulations and a standard dosing strategy. The resulting in vivo exposures were compared. It was found that this novel tandem dosing strategy significantly improved the in vivo exposures.
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Nakata, Manabu; Okada, Takashi; Komai, Yoshinori; Nohara, Hiroki [Kyoto Univ. (Japan). Hospital
1996-08-01
Modern linear accelerators have four independent jaws and multileaf collimators (MLC) of 1 cm width at the isocenter. Asymmetric fields defined by such independent jaws and irregular multileaf collimated fields can be used to match adjacent fields or to spare the spinal cord in external photon beam radiotherapy. We have developed a new approximate algorithm for depth dose calculations at the collimator rotation axis. The program is based on Clarkson`s principle, and uses a more accurate modification of Day`s method for asymmetric fields. Using this method, tissue-maximum ratios (TMR) and field factors of ten kinds of asymmetric fields and ten different irregular multileaf collimated fields were calculated and compared with the measured data for 6 MV and 15 MV photon beams. The dose accuracy with the general A/Pe method was about 3%, however, with the new modified Day`s method, accuracy was within 1.7% for TMR and 1.2% for field factors. The calculated TMR and field factors were found to be in good agreement with measurements for both the 6 MV and 15 MV photon beams. (author)
Prostate dose calculations for permanent implants using the MCNPX code and the Voxels phantom MAX
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Reis Junior, Juraci Passos dos; Silva, Ademir Xavier da, E-mail: jjunior@con.ufrj.b, E-mail: Ademir@con.ufrj.b [Coordenacao dos Programas de Pos-Graduacao de Engenharia (COPPE/UFRJ), RJ (Brazil). Programa de Engenharia Nuclear; Facure, Alessandro N.S., E-mail: facure@cnen.gov.b [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil)
2010-07-01
This paper presents the modeling of 80, 88 and 100 of {sup 125}I seeds, punctual and volumetric inserted into the phantom spherical volume representing the prostate and prostate phantom voxels MAX. Starting values of minimum and maximum activity, 0.27 mCi and 0.38 mCi, respectively, were simulated in the Monte Carlo code MCNPX in order to determine whether the final dose, according to the integration of the equation of decay at time t = 0 to t = {infinity} corresponds to the default value set by the AAPM 64 which is 144 Gy. The results showed that consider sources results in doses exceeding the percentage discrepancy of the default value of 200%, while volumetric consider sources result in doses close to 144 Gy. (author)
Efficient calculation of local dose distribution for response modelling in proton and ion beams
Greilich, S; Kiderlen, M; Andersen, C E; Bassler, N
2013-01-01
We present an algorithm for fast and accurate computation of the local dose distribution in MeV beams of protons, carbon ions or other heavy-charged particles. It uses compound Poisson-process modelling of track interaction and succesive convolutions for fast computation. It can handle mixed particle fields over a wide range of fluences. Since the local dose distribution is the essential part of several approaches to model detector efficiency or cellular response it has potential use in ion-beam dosimetry and radiotherapy.
DEFF Research Database (Denmark)
Greilich, Steffen; Hahn, Ute; Kiderlen, Markus;
2014-01-01
We present an algorithm for fast and accurate computation of the local dose distribution in MeV beams of protons, carbon ions or other heavy charged particles. It uses compound Poisson modeling of track interaction and successive convolutions for fast computation. It can handle arbitrary complex ...... mixed particle fields over a wide range of fluences. Since the local dose distribution is the essential part of several approaches to model detector efficiency and cellular response it has potential use in ion-beam dosimetry, radiotherapy, and radiobiology....
Wood, T J; Moore, C S; Saunderson, J R; Beavis, A W
2015-03-01
The use of cone beam CT in common radiotherapy treatments is increasing with the growth of image guided radiotherapy. Whilst the benefits that this technology offers are clear, such as improved patient positioning prior to treatment, it is always important to consider the implications of such intensive imaging regimes on the patient, especially when considering the fundamental radiation protection requirements for justification and optimisation.The purpose of this study was to develop a technique that uses readily available dose calculation software (PCXMC 2.0) to estimate the organ and effective doses that result from these types of examination in prostate treatments on the Varian OBI system. It has been shown that by separating these types of examinations into 28 different projections, with a range of x-ray beam qualities, it is possible to reproduce the complex geometry that is used on these imaging systems in PCXMC i.e. asymmetric radiation field with a half bowtie filter rotating 360° around the patient.This new technique has been validated with thermo-luminescent dosimeter measurements in the Rando anthropomorphic phantom, and has been shown to give excellent agreement with this established method (R(2) = 0.995). This technique will prove to be valuable to radiotherapy departments that are looking to optimise their CBCT imaging protocols as it allows a rapid evaluation of the impact of any changes on patient dose. It also serves to further highlight the levels of dose that these types of patient are subject to when having daily CBCT scans as part of the treatment, which further reinforces the need for optimisation of both patient dose and image quality on these systems.
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Eckerman, K.F. [Oak Ridge National Lab., TN (United States)
1999-01-01
Committee 2 of the International Commission on Radiological Protection (ICRP) has had efforts underway to provide the radiation protection community with age-dependent dose coefficients, i.e.g, the dose per unit intake. The Task Group on Dose Calculations, chaired by the author, is responsible for the computation of these coefficients. The Task Group, formed in 1974 to produce ICRP Publication 30, is now international in its membership and its work load has been distributed among the institutions represented on the task group. This paper discusses: (1) recent advances in biokinetic modeling; (2) the recent changes in the dosimetric methodology; (3) the novel computational problems with some of the ICRP quantities; and (4) quality assurance issues which the Task Group has encountered. Potential future developments of the dosimetric framework which might strengthen the relationships with the emerging understanding of radiation risk will also be discussed.
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Zhang, Y; Zhang, J; Hu, Q; Tie, J; Wu, H [Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Radiotherapy, Peking University Cancer Hospital ' Institute, Beijing (China); Deng, J [Department of Therapeutic Radiology, Yale University, New Haven, CT (United States)
2014-06-01
Purpose: To investigate the possibility of applying optimized scanning protocols for pediatric CT simulation by quantifying the dosimetric inaccuracy introduced by using a fixed HU to density conversion. Methods: The images of a CIRS electron density reference phantom (Model 062) were acquired by a Siemens CT simulator (Sensation Open) using the following settings of tube voltage and beam current: 120 kV/190mA (the reference protocol used to calibrate CT for our treatment planning system (TPS)); Fixed 190mA combined with all available kV: 80, 100, and 140; fixed 120 kV and various current from 37 to 444 mA (scanner extremes) with interval of 30 mA. To avoid the HU uncertainty of point sampling in the various inserts of known electron densities, the mean CT numbers of the central cylindrical volume were calculated using DICOMan software. The doses per 100 MU to the reference point (SAD=100cm, Depth=10cm, Field=10X10cm, 6MV photon beam) in a virtual cubic phantom (30X30X30cm) were calculated using Eclipse TPS (calculation model: AcurosXB-11031) by assigning the CT numbers to HU of typical materials acquired by various protocols. Results: For the inserts of densities less than muscle, CT number fluctuations of all protocols were within the tolerance of 10 HU as accepted by AAPM-TG66. For more condensed materials, fixed kV yielded stable HU with any mA combination where largest disparities were found in 1750mg/cc insert: HU{sub reference}=1801(106.6cGy), HU{sub minimum}=1799 (106.6cGy, error{sub dose}=0.00%), HU{sub maximum}=1815 (106.8cGy, error{sub dose}=0.19%). Yet greater disagreements were observed with increasing density when kV was modified: HU{sub minimum}=1646 (104.5cGy, error{sub dose}=- 1.97%), HU{sub maximum}=2487 (116.4cGy, error{sub dose}=9.19%) in 1750mg/cc insert. Conclusion: Without affecting treatment dose calculation, personalized mA optimization of CT simulator can be conducted by fixing kV for a better cost-effectiveness of imaging dose and quality
DEFF Research Database (Denmark)
Espensen, Charlotte Alfast; Jensen, Peter Koch; Fog, Lotte Stubkjær
2017-01-01
BACKGROUND/AIMS: To present a new method to determine dose depth and the distance from the concave side of the plaque to the tumour base in patients with uveal melanoma treated with ruthenium-106 based on ultrasonic mirror image. METHODS: We used the mirror image associated with ultrasound during...
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Faught, A [UT MD Anderson Cancer Center, Houston, TX (United States); University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, TX (United States); Davidson, S [University of Texas Medical Branch of Galveston, Galveston, TX (United States); Kry, S; Ibbott, G; Followill, D [UT MD Anderson Cancer Center, Houston, TX (United States); Fontenot, J [Mary Bird Perkins Cancer Center, Baton Rouge, LA (United States); Etzel, C [Consortium of Rheumatology Researchers of North America (CORRONA), Inc., Southborough, MA (United States)
2014-06-01
Purpose: To develop a comprehensive end-to-end test for Varian's TrueBeam linear accelerator for head and neck IMRT using a custom phantom designed to utilize multiple dosimetry devices. Purpose: To commission a multiple-source Monte Carlo model of Elekta linear accelerator beams of nominal energies 6MV and 10MV. Methods: A three source, Monte Carlo model of Elekta 6 and 10MV therapeutic x-ray beams was developed. Energy spectra of two photon sources corresponding to primary photons created in the target and scattered photons originating in the linear accelerator head were determined by an optimization process that fit the relative fluence of 0.25 MeV energy bins to the product of Fatigue-Life and Fermi functions to match calculated percent depth dose (PDD) data with that measured in a water tank for a 10x10cm2 field. Off-axis effects were modeled by a 3rd degree polynomial used to describe the off-axis half-value layer as a function of off-axis angle and fitting the off-axis fluence to a piecewise linear function to match calculated dose profiles with measured dose profiles for a 40×40cm2 field. The model was validated by comparing calculated PDDs and dose profiles for field sizes ranging from 3×3cm2 to 30×30cm2 to those obtained from measurements. A benchmarking study compared calculated data to measurements for IMRT plans delivered to anthropomorphic phantoms. Results: Along the central axis of the beam 99.6% and 99.7% of all data passed the 2%/2mm gamma criterion for 6 and 10MV models, respectively. Dose profiles at depths of dmax, through 25cm agreed with measured data for 99.4% and 99.6% of data tested for 6 and 10MV models, respectively. A comparison of calculated dose to film measurement in a head and neck phantom showed an average of 85.3% and 90.5% of pixels passing a 3%/2mm gamma criterion for 6 and 10MV models respectively. Conclusion: A Monte Carlo multiple-source model for Elekta 6 and 10MV therapeutic x-ray beams has been developed as a
Directory of Open Access Journals (Sweden)
Ghavami Seyed Mostafa
2016-01-01
Full Text Available Using the nano-scaled radionuclides in the radionuclide therapy significantly reduces the particles trapping in the organs vessels and avoids thrombosis formations. Additionally, uniform distribution in the target organ may be another benefit of the nanoradionuclides in the radionuclide therapy. Monte Carlo simulation was conducted to model a mathematical humanoid phantom and the liver cells of the simulated phantom were filled with the 90Y nanospheres. Healthy organs doses, fatal and nonfatal risks of the surrounding organs were estimated. The estimations and calculations were made in four different distribution patterns of the radionuclide seeds. Maximum doses and risks estimated for the surrounding organs were obtained in the high edge concentrated distribution model of the liver including the nanoradionuclides. For the dose equivalent, effective dose, fatal and non-fatal risks, the values obtained as 7.51E-03 Sv/Bq, 3.01E-01 Sv/Bq, and 9.16E-01 cases/104 persons for the bladder, colon, and kidney of the modeled phantom, respectively. The mentioned values were the maximum values among the studied modeled distributions. Maximum values of Normal Tissue Complication Probability for the healthy organs calculated as 5.9-8.9 %. Result of using nanoparticles of the 90Y provides promising dosimetric properties in MC simulation results considering non-toxicity reports for the radionuclide.
The MARS15-based FermiCORD Code System for Calculation of the Accelerator-Induced Residual Dose
Energy Technology Data Exchange (ETDEWEB)
Grebe, A.; Leveling, A.; Lu, T.; Mokhov, N.; Pronskikh, V.
2016-09-01
The FermiCORD code system, a set of codes based on MARS15 that calculates the accelerator-induced residual doses at experimental facilities of arbitrary configurations, has been developed. FermiCORD is written in C++ as an add-on to Fortran-based MARS15. The FermiCORD algorithm consists of two stages: 1) simulation of residual doses on contact with the surfaces surrounding the studied location and of radionuclide inventories in the structures surrounding those locations using MARS15, and 2) simulation of the emission of the nuclear decay gamma-quanta by the residuals in the activated structures and scoring the prompt doses of these gamma-quanta at arbitrary distances from those structures. The FermiCORD code system has been benchmarked against similar algorithms based on other code systems and showed a good agreement. The code system has been applied for calculation of the residual dose of the target station for the Mu2e experiment and the results have been compared to approximate dosimetric approaches.
The MARS15-based FermiCORD code system for calculation of the accelerator-induced residual dose
Grebe, A; Lu, T; Mokhov, N; Pronskikh, V
2016-01-01
The FermiCORD code system, a set of codes based on MARS15 that calculates the accelerator-induced residual doses at experimental facilities of arbitrary configurations, has been developed. FermiCORD is written in C++ as an add-on to Fortran-based MARS15. The FermiCORD algorithm consists of two stages: 1) simulation of residual doses on contact with the surfaces surrounding the studied location and of radionuclide inventories in the structures surrounding those locations using MARS15, and 2) simulation of the emission of the nuclear decay gamma-quanta by the residuals in the activated structures and scoring the prompt doses of these gamma-quanta at arbitrary distances from those structures. The FermiCORD code system has been benchmarked against similar algorithms based on other code systems and showed a good agreement. The code system has been applied for calculation of the residual dose of the target station for the Mu2e experiment and the results have been compared to approximate dosimetric approaches.
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Zucca Aparicio, D.; Perez Moreno, J. M.; Fernandez Leton, P.; Garcia Ruiz-Zorrilla, J.; Pinto Monedero, M.; Marti Asensjo, J.; Alonso Iracheta, L.
2015-07-01
Treatment of lung injury SBRT requires great dosimetric accuracy, the increasing clinical importance of dose calculation heterogeneities introducing algorithms that adequately model the transport of particles narrow beams in media of low density, as with Monte Carlo calculation. (Author)
Dose calculations using MARS for Bremsstrahlung beam stops and collimators in APS beamline stations.
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Dooling, J.; Accelerator Systems Division (APS)
2010-11-01
The Monte Carlo radiation transport code MARS is used to model the generation of gas bremsstrahlung (GB) radiation from 7-GeV electrons which scatter from residual gas atoms in undulator straight sections within the Advanced Photon Source (APS) storage ring. Additionally, MARS is employed to model the interactions of the GB radiation with components along the x-ray beamlines and then determine the expected radiation dose-rates that result. In this manner, MARS can be used to assess the adequacy of existing shielding or the specifications for new shielding when required. The GB radiation generated in the 'thin-target' of an ID straight section will consist only of photons in a 1/E-distribution up to the full energy of the stored electron beam. Using this analytical model, the predicted GB power for a typical APS 15.38-m insertion device (ID) straight section is 4.59 x 10{sup -7} W/nTorr/mA, assuming a background gas composed of air (Z{sub eff} = 7.31) at room temperature (293K). The total GB power provides a useful benchmark for comparisons between analytical and numerical approaches. We find good agreement between MARS and analytical estimates for total GB power. The extended straight section 'target' creates a radial profile of GB, which is highly peaked centered on the electron beam. The GB distribution reflects the size of the electron beam that creates the radiation. Optimizing the performance of MARS in terms of CPU time per incident trajectory requires the use of a relatively short, high-density gas target (air); in this report, the target density is {rho}L = 2.89 x 10{sup -2} g/cm{sup 2} over a length of 24 cm. MARS results are compared with the contact dose levels reported in TB-20, which used EGS4 for radiation transport simulations. Maximum dose-rates in 1 cc of tissue phantom form the initial basis for comparison. MARS and EGS4 results are approximately the same for maximum 1-cc dose-rates and attenuation in the photon
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Wang, Jing; Toloczko, Mychailo B.; Bailey, Nathan; Garner, Frank A.; Gigax, Jonathan; Shao, Lin
2016-11-01
In radiation effects on materials utilizing self-ion irradiations, it is necessary to calculate the local displacement damage level and ion injection profile because of the short distance that self-ions travel in a material and because of the strong variation of displacement rate with depth in a specimen. The most frequently used tool for this is the software package called Stopping and Range of Ions in Matter (SRIM). A SRIM-calculated depth-dependent dose level is usually determined under the implicit assumption that the target does not undergo any significant changes in volume during the process, in particular SRIM ignores the effect of sputtering, injected ions, and void swelling on the redistribution of the dose and injected atom profiles. This approach become increasingly invalid as the ion fluence reaches ever higher levels, especially for low energy ion irradiations. The original surface is not maintained due to sputter-induced erosion, while within the irradiated region of the specimen, injected ions are adding material, and if void swelling is occurring, it is creating empty space. An iterative mathematical treatment of SRIM outputs to produce corrected dose and injected atom profiles is presented along with examples differences between SRIM-calculated values and corrected values over a range of typical ion energies.
Dambach, Donna M; Simpson, Natalie E; Jones, Thomas W; Brennan, Richard J; Pazdur, Richard; Palmby, Todd R
2016-06-01
Multidisciplinary approaches that incorporate nonclinical pharmacologic and toxicologic characterization of small-molecule oncology drugs into clinical development programs may facilitate improved benefit-risk profiles and clinical toxicity management in patients. The performance of the current nonclinical safety-testing scheme was discussed, highlighting current strengths and areas for improvement. While current nonclinical testing appears to predict the clinical outcome where the prevalence of specific adverse effects are high, nonclinical testing becomes less reliable for predicting clinical adverse effects that occur infrequently, as with some kinase inhibitors. Although adverse effects associated with kinase inhibitors can often be predicted on the basis of target biology, drugs can be promiscuous and inhibit targets with poorly defined function and associated risks. Improvements in adverse effect databases and better characterization of the biologic activities of drug targets may enable better use of computational modeling approaches in predicting adverse effects with kinase inhibitors. Assessing safety of a lead candidate in parallel with other drug properties enables incorporation of a molecule's best features during chemical design, eliminates the worst molecules early, and permits timely investigation/characterization of toxicity mechanisms for identified liabilities. A safety lead optimization and candidate identification strategy that reduces intrinsic toxicity and metabolic risk and enhances selectivity can deliver selective kinase inhibitors that demonstrate on-target adverse effects identified nonclinically. Integrating clinical and nonclinical data during drug development can facilitate better identification and management of oncology drugs. Follow-up nonclinical studies may be used to better understand the risks in a given patient population and minimize or manage these risks more appropriately. Clin Cancer Res; 22(11); 2618-22. ©2016 AACR SEE ALL
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Cardan, R [UAB University of Alabama, Birmingham, Birmingham, AL (United States); Faught, A [MD Anderson Cancer Center, Houston, TX (United States); Huang, M; Benhabib, S [University of Alabama at Birmingham, Birmingham, AL (United States); Brezovich, I; Popple, R [University of Alabama Birmingham, Birmingham, AL (United States); Followill, D [UT MD Anderson Cancer Center, Houston, TX (United States)
2014-06-01
Purpose: Determine the dose calculation accuracy of a preconfigured Mobius server for use in secondary checks of a treatment planning system. Methods: 10 plans were created for irradiation on two of the IROC (formerly RPC) accreditation phantoms: 4 for the head and neck phantom and 6 for the lung phantom. The plans each were created using one of four different photon energies (6FFF, 10 FFF, 6X, and 15X) and were varied in treatment type including VMAT, step and shoot IMRT, dynamic MLC IMRT (DMLC), and conformal RT (CRT). The TLDs in the phantoms were contoured, and each plan was sent for calculation to Mobius software (Mobius Medical Systems, Houston, TX) with a default configuration. Each plan was then irradiated on the planned phantom 3 times to create an average reading across 56 TLDs. These readings were then compared against the corresponding Mobius calculation at each TLD location. Results: The mean difference (MD) normalized to the plan prescription dose between each TLD and Mobius calculation for all measurements was 0.5 ± 3.3%, with a maximum difference of 8.4%. The MD was 0.6 ± 3.8%, − 2.0 ± 1.9%, 1.7 ± 3.7%, and 1.9 ± 1.2% across the 6FFF, 10FFF, 6X and 15X energies respectively. The MD was −1.2 ± 2.3% for lung plans and 1.8 ± 3.5% for head/neck plans. Across treatment types, the MD ranged from − 1.8 ± 1.7% for CRT to 4.3 ± 2.4 % for DMLC. Conclusion: Out of the box and preconfigured, Mobius provides accurate dose calculations with respect to beam energy, treatment type, and treatment site.
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Wang, L; Fourkal, E; Hayes, S; Jin, L; Ma, C [Fox Chase Cancer Center, Philadelphia, PA (United States)
2014-06-01
Purpose: To study the dosimetric difference resulted in using the pencil beam algorithm instead of Monte Carlo (MC) methods for tumors adjacent to the skull. Methods: We retrospectively calculated the dosimetric differences between RT and MC algorithms for brain tumors treated with CyberKnife located adjacent to the skull for 18 patients (total of 27 tumors). The median tumor sizes was 0.53-cc (range 0.018-cc to 26.2-cc). The absolute mean distance from the tumor to the skull was 2.11 mm (range - 17.0 mm to 9.2 mm). The dosimetric variables examined include the mean, maximum, and minimum doses to the target, the target coverage (TC) and conformality index. The MC calculation used the same MUs as the RT dose calculation without further normalization and 1% statistical uncertainty. The differences were analyzed by tumor size and distance from the skull. Results: The TC was generally reduced with the MC calculation (24 out of 27 cases). The average difference in TC between RT and MC was 3.3% (range 0.0% to 23.5%). When the TC was deemed unacceptable, the plans were re-normalized in order to increase the TC to 99%. This resulted in a 6.9% maximum change in the prescription isodose line. The maximum changes in the mean, maximum, and minimum doses were 5.4 %, 7.7%, and 8.4%, respectively, before re-normalization. When the TC was analyzed with regards to target size, it was found that the worst coverage occurred with the smaller targets (0.018-cc). When the TC was analyzed with regards to the distance to the skull, there was no correlation between proximity to the skull and TC between the RT and MC plans. Conclusions: For smaller targets (< 4.0-cc), MC should be used to re-evaluate the dose coverage after RT is used for the initial dose calculation in order to ensure target coverage.
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Petrizzi, L.; Batistoni, P.; Migliori, S. [Associazione EURATOM ENEA sulla Fusione, Frascati (Roma) (Italy); Chen, Y.; Fischer, U.; Pereslavtsev, P. [Association FZK-EURATOM Forschungszentrum Karlsruhe (Germany); Loughlin, M. [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire, OX (United Kingdom); Secco, A. [Nice Srl Via Serra 33 Camerano Casasco AT (Italy)
2003-07-01
In deuterium-deuterium (D-D) and deuterium-tritium (D-T) fusion plasmas neutrons are produced causing activation of JET machine components. For safe operation and maintenance it is important to be able to predict the induced activation and the resulting shut down dose rates. This requires a suitable system of codes which is capable of simulating both the neutron induced material activation during operation and the decay gamma radiation transport after shut-down in the proper 3-D geometry. Two methodologies to calculate the dose rate in fusion devices have been developed recently and applied to fusion machines, both using the MCNP Monte Carlo code. FZK has developed a more classical approach, the rigorous 2-step (R2S) system in which MCNP is coupled to the FISPACT inventory code with an automated routing. ENEA, in collaboration with the ITER Team, has developed an alternative approach, the direct 1 step method (D1S). Neutron and decay gamma transport are handled in one single MCNP run, using an ad hoc cross section library. The intention was to tightly couple the neutron induced production of a radio-isotope and the emission of its decay gammas for an accurate spatial distribution and a reliable calculated statistical error. The two methods have been used by the two Associations to calculate the dose rate in five positions of JET machine, two inside the vacuum chamber and three outside, at cooling times between 1 second and 1 year after shutdown. The same MCNP model and irradiation conditions have been assumed. The exercise has been proposed and financed in the frame of the Fusion Technological Program of the JET machine. The scope is to supply the designers with the most reliable tool and data to calculate the dose rate on fusion machines. Results showed that there is a good agreement: the differences range between 5-35%. The next step to be considered in 2003 will be an exercise in which the comparison will be done with dose-rate data from JET taken during and
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Endo, Akira; Yamaguchi, Yasuhiro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Tamura, Tsutomu
1999-07-01
Nuclear decay data used for dose calculations were compiled for 162 nuclides with half-lives greater than or equal to 10 min that are not listed in ICRP Publication 38 (Publ. 38) and their 28 daughter nuclides. Additional 14 nuclides that are considered to be important in fusion reactor facilities were also included. The data were compiled using decay data sets of the Evaluated Nuclear Structure Data File (ENSDF), the latest version in August 1997. Investigations of the data sets were performed to check their consistency by referring to recent literature and NUBASE, the database for nuclear and decay properties of nuclides, and by using the utility programs of ENSDF. Possible revisions of the data sets were made for their format and syntax errors, level schemes, normalization records, and so on. The revised data sets were processed by EDISTR in order to calculate the energies and intensities of {alpha} particles, {beta} particles, {gamma} rays including annihilation photons, internal conversion electrons, X rays, and Auger electrons emitted in nuclear transformations of the radionuclides. For spontaneously fissioning nuclides, the average energies and intensities of neutrons, fission fragments, prompt {gamma} rays, delayed {gamma} rays, and {beta} particles were also calculated. The compiled data were presented in two types of format; Publ. 38 and NUCDECAY formats. This report provides the decay data in the Publ. 38 format along with decay scheme drawings. The data will be widely used for internal and external dose calculations in radiation protection. (author)
DEFF Research Database (Denmark)
Tomson, Torbjörn; Battino, Dina; Bonizzoni, Erminio
2011-01-01
Prenatal exposure to antiepileptic drugs is associated with a greater risk of major congenital malformations, but there is inadequate information on the comparative teratogenicity of individual antiepileptic drugs and the association with dose. We aimed to establish the risks of major congenital ...
Energy Technology Data Exchange (ETDEWEB)
Park, Y; Winey, B; Sharp, G [Massachusetts General Hospital, Boston, MA (United States)
2014-06-01
Purpose: To demonstrate feasibility of proton dose calculation on scattercorrected CBCT images for the purpose of adaptive proton therapy. Methods: Two CBCT image sets were acquired from a prostate cancer patient and a thorax phantom using an on-board imaging system of an Elekta infinity linear accelerator. 2-D scatter maps were estimated using a previously introduced CT-based technique, and were subtracted from each raw projection image. A CBCT image set was then reconstructed with an open source reconstruction toolkit (RTK). Conversion from the CBCT number to HU was performed by soft tissue-based shifting with reference to the plan CT. Passively scattered proton plans were simulated on the plan CT and corrected/uncorrected CBCT images using the XiO treatment planning system. For quantitative evaluation, water equivalent path length (WEPL) was compared in those treatment plans. Results: The scatter correction method significantly improved image quality and HU accuracy in the prostate case where large scatter artifacts were obvious. However, the correction technique showed limited effects on the thorax case that was associated with fewer scatter artifacts. Mean absolute WEPL errors from the plans with the uncorrected and corrected images were 1.3 mm and 5.1 mm in the thorax case and 13.5 mm and 3.1 mm in the prostate case. The prostate plan dose distribution of the corrected image demonstrated better agreement with the reference one than that of the uncorrected image. Conclusion: A priori CT-based CBCT scatter correction can reduce the proton dose calculation error when large scatter artifacts are involved. If scatter artifacts are low, an uncorrected CBCT image is also promising for proton dose calculation when it is calibrated with the soft-tissue based shifting.
Sotiropoulou, Maria; Florou, Heleny; Manolopoulou, Metaxia
2016-06-01
In the present study, the radioactivity levels to which terrestrial non-human biota were exposed are examined. Organisms (grass and herbivore mammals) and abiotic components (soil) were collected during the period of 2010 to 2014 from grasslands where sheep and goats were free-range grazing. Natural background radionuclides ((226)Ra, (228)Ra, (228)Th) and artificial radionuclides ((137)Cs, (134)Cs, (131)I) were detected in the collected samples using gamma spectrometry. The actual measured activity concentrations and site-specific data of the studied organisms were imported in ERICA Assessment Tool (version 1.2.0) in order to provide an insight of the radiological dose rates. The highest activity concentrations were detected in samples collected from Lesvos island and the lowest in samples collected from Attiki and Etoloakarnania prefectures. The highest contribution to the total dose rate was clearly derived from the internal exposure and is closely related to the exposure to alpha emitters of natural background ((226)Ra and (228)Th). The Fukushima-derived traces of (137)Cs, (134)Cs, and (131)I, along with the residual (137)Cs, resulted in quite low contribution to the total dose rate. The obtained results may strengthen the adaptation of software tools to a wider range of ecosystems and may be proved useful in further research regarding the possible impact of protracted low level ionizing radiation on non-human biota. This kind of studies may contribute to the effective incorporation of dosimetry tools in the development of integrated environmental and radiological impact assessment policies.
Energy Technology Data Exchange (ETDEWEB)
Baldacci, F.; Delaire, F.; Letang, J.M.; Sarrut, D.; Smekens, F.; Freud, N. [Lyon-1 Univ. - CREATIS, CNRS UMR5220, Inserm U1044, INSA-Lyon, Centre Leon Berard (France); Mittone, A.; Coan, P. [LMU Munich (Germany). Dept. of Physics; LMU Munich (Germany). Faculty of Medicine; Bravin, A.; Ferrero, C. [European Synchrotron Radiation Facility, Grenoble (France); Gasilov, S. [LMU Munich (Germany). Dept. of Physics
2015-05-01
The track length estimator (TLE) method, an 'on-the-fly' fluence tally in Monte Carlo (MC) simulations, recently implemented in GATE 6.2, is known as a powerful tool to accelerate dose calculations in the domain of low-energy X-ray irradiations using the kerma approximation. Overall efficiency gains of the TLE with respect to analogous MC were reported in the literature for regions of interest in various applications (photon beam radiation therapy, X-ray imaging). The behaviour of the TLE method in terms of statistical properties, dose deposition patterns, and computational efficiency compared to analogous MC simulations was investigated. The statistical properties of the dose deposition were first assessed. Derivations of the variance reduction factor of TLE versus analogous MC were carried out, starting from the expression of the dose estimate variance in the TLE and analogous MC schemes. Two test cases were chosen to benchmark the TLE performance in comparison with analogous MC: (i) a small animal irradiation under stereotactic synchrotron radiation therapy conditions and (ii) the irradiation of a human pelvis during a cone beam computed tomography acquisition. Dose distribution patterns and efficiency gain maps were analysed. The efficiency gain exhibits strong variations within a given irradiation case, depending on the geometrical (voxel size, ballistics) and physical (material and beam properties) parameters on the voxel scale. Typical values lie between 10 and 103, with lower levels in dense regions (bone) outside the irradiated channels (scattered dose only), and higher levels in soft tissues directly exposed to the beams.
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Simmer, Gregor
2012-04-11
Due to secondary cosmic radiation (SCR), pilots and flight attendants receive elevated effective doses at flight altitudes. For this reason, since 2003 aircrew members are considered as occupationally exposed, in Germany. This work deals with the calculation of dose conversion coefficients (DCC) for protons, neutrons, electrons, positrons, photons and myons, which are crucial for estimation of effective dose from SCR. For the first time, calculations were performed combining Geant4 - a Monte Carlo code developed at CERN - with the voxel phantoms for the reference female and male published in 2008 by ICRP and ICRU. Furthermore, measurements of neutron fluence spectra - which contribute the major part to the effective dose of SCR - were carried out at the Environmental Research Station Schneefernerhaus (UFS) located at 2650 m above sea level nearby the Zugspitze mountain, Germany. These measured neutron spectra, and additionally available calculated spectra, were then folded with the DCC calculated in this work, and effective dose rates for different heights were calculated.
Anti-Allergic Drugs Tranilast and Ketotifen Dose-Dependently Exert Mast Cell-Stabilizing Properties
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Asuka Baba
2016-01-01
Full Text Available Background: Anti-allergic drugs, such as tranilast and ketotifen, inhibit the release of chemokines from mast cells. However, we know little about their direct effects on the exocytotic process of mast cells. Since exocytosis in mast cells can be monitored electrophysiologically by changes in the whole-cell membrane capacitance (Cm, the absence of such changes by these drugs indicates their mast cell-stabilizing properties. Methods: Employing the standard patch-clamp whole-cell recording technique in rat peritoneal mast cells, we examined the effects of tranilast and ketotifen on the Cm during exocytosis. Using confocal imaging of a water-soluble fluorescent dye, lucifer yellow, we also examined their effects on the deformation of the plasma membrane. Results: Relatively lower concentrations of tranilast (100, 250 µM and ketotifen (1, 10 µM did not significantly affect the GTP-γ-S-induced increase in the Cm. However, higher concentrations of tranilast (500 µM, 1 mM and ketotifen (50, 100 µM almost totally suppressed the increase in the Cm, and washed out the trapping of the dye on the surface of the mast cells. Compared to tranilast, ketotifen required much lower doses to similarly inhibit the degranulation of mast cells or the increase in the Cm. Conclusions: This study provides electrophysiological evidence for the first time that tranilast and ketotifen dose-dependently inhibit the process of exocytosis, and that ketotifen is more potent than tranilast in stabilizing mast cells. The mast cell-stabilizing properties of these drugs may be attributed to their ability to counteract the plasma membrane deformation in degranulating mast cells.
Dose estimation and shielding calculation for X-ray hazard at high intensity laser facilities
Qiu, Rui; Zhang, Hui; Yang, Bo; James, C. Liu; Sayed, H. Rokni; Michael, B. Woods; Li, Jun-Li
2014-12-01
An ionizing radiation hazard produced from the interaction between high intensity lasers and solid targets has been observed. Laser-plasma interactions create “hot” electrons, which generate bremsstrahlung X-rays when they interact with ions in the target. However, up to now only limited studies have been conducted on this laser-induced radiological protection issue. In this paper, the physical process and characteristics of the interaction between high intensity lasers and solid targets are analyzed. The parameters of the radiation sources are discussed, including the energy conversion efficiency from laser to hot electrons, hot electron energy spectrum and electron temperature, and the bremsstrahlung X-ray energy spectrum produced by hot electrons. Based on this information, the X-ray dose generated with high-Z targets for laser intensities between 1014 and 1020 W/cm2 is estimated. The shielding effects of common shielding items such as the glass view port, aluminum chamber wall and concrete wall are also studied using the FLUKA Monte Carlo code. This study provides a reference for the dose estimation and the shielding design of high intensity laser facilities.
Energy Technology Data Exchange (ETDEWEB)
Jin, L; Eldib, A; Li, J; Price, R; Ma, C [Fox Chase Cancer Center, Philadelphia, PA (United States)
2015-06-15
Purpose: Uneven nose surfaces and air cavities underneath and the use of bolus present complexity and dose uncertainty when using a single electron energy beam to plan treatments of nose skin with a pencil beam-based planning system. This work demonstrates more accurate dose calculation and more optimal planning using energy and intensity modulated electron radiotherapy (MERT) delivered with a pMLC. Methods: An in-house developed Monte Carlo (MC)-based dose calculation/optimization planning system was employed for treatment planning. Phase space data (6, 9, 12 and 15 MeV) were used as an input source for MC dose calculations for the linac. To reduce the scatter-caused penumbra, a short SSD (61 cm) was used. Our previous work demonstrates good agreement in percentage depth dose and off-axis dose between calculations and film measurement for various field sizes. A MERT plan was generated for treating the nose skin using a patient geometry and a dose volume histogram (DVH) was obtained. The work also shows the comparison of 2D dose distributions between a clinically used conventional single electron energy plan and the MERT plan. Results: The MERT plan resulted in improved target dose coverage as compared to the conventional plan, which demonstrated a target dose deficit at the field edge. The conventional plan showed higher dose normal tissue irradiation underneath the nose skin while the MERT plan resulted in improved conformity and thus reduces normal tissue dose. Conclusion: This preliminary work illustrates that MC-based MERT planning is a promising technique in treating nose skin, not only providing more accurate dose calculation, but also offering an improved target dose coverage and conformity. In addition, this technique may eliminate the necessity of bolus, which often produces dose delivery uncertainty due to the air gaps that may exist between the bolus and skin.
中子剂量测量及估算方法%The measurement and calculation method for neutron dose
Institute of Scientific and Technical Information of China (English)
向剑; 戴光复; 苑淑渝; 丁艳秋; 张良安
2008-01-01
Company with the development of science,the neutron is used more and more widely,for example,neutron therapy cancer,neutron logging,neutron photograph and so on.The most wide application on medical treatment with neutron is boron neutron capture therapy.But it also brings some problems when it is in use.When the operator perform with the neutron,it may receive neutron irradiation.So the measurement and calculation for neutron dose become important.At home the research of neutron dose need to be advanced research.So the measurement and calculation method of neutron dose are conformed and summarized in this article for advance research.%随着科技的发展,中子在许多行业得到越来越广泛的应用,在医疗上应用最广泛的是硼中子俘获治疗.但在使用中子辐射的过程中,操作人员可能会受到中子辐射,因此中子剂量的测量和估算问题也就变得重要起来.目前,国内关于中子剂量的研究在有些方面还不是很深人,因此对中子剂量的测量和估算方法进行了归纳和阐述.
Mohammadyari, Parvin; Faghihi, Reza; Mosleh-Shirazi, Mohammad Amin; Lotfi, Mehrzad; Rahim Hematiyan, Mohammad; Koontz, Craig; Meigooni, Ali S.
2015-12-01
Compression is a technique to immobilize the target or improve the dose distribution within the treatment volume during different irradiation techniques such as AccuBoost® brachytherapy. However, there is no systematic method for determination of dose distribution for uncompressed tissue after irradiation under compression. In this study, the mechanical behavior of breast tissue between compressed and uncompressed states was investigated. With that, a novel method was developed to determine the dose distribution in uncompressed tissue after irradiation of compressed breast tissue. Dosimetry was performed using two different methods, namely, Monte Carlo simulations using the MCNP5 code and measurements using thermoluminescent dosimeters (TLD). The displacement of the breast elements was simulated using a finite element model and calculated using ABAQUS software. From these results, the 3D dose distribution in uncompressed tissue was determined. The geometry of the model was constructed from magnetic resonance images of six different women volunteers. The mechanical properties were modeled by using the Mooney-Rivlin hyperelastic material model. Experimental dosimetry was performed by placing the TLD chips into the polyvinyl alcohol breast equivalent phantom. The results determined that the nodal displacements, due to the gravitational force and the 60 Newton compression forces (with 43% contraction in the loading direction and 37% expansion in the orthogonal direction) were determined. Finally, a comparison of the experimental data and the simulated data showed agreement within 11.5% ± 5.9%.
Directory of Open Access Journals (Sweden)
Reda Sonia M.
2006-01-01
Full Text Available Radiation dose distributions in various parts of the body are of importance in radiotherapy. Also, the percent depth dose at different body depths is an important parameter in radiation therapy applications. Monte Carlo simulation techniques are the most accurate methods for such purposes. Monte Carlo computer calculations of photon spectra and the dose ratios at surfaces and in some internal organs of a human equivalent phantom were performed. In the present paper, dose distributions in different organs during bladder radiotherapy by 6 MeV X-rays were measured using thermoluminescence dosimetry placed at different points in the human-phantom. The phantom was irradiated in exactly the same manner as in actual bladder radiotherapy. Four treatment fields were considered to maximize the dose at the center of the target and minimize it at non-target healthy organs. All experimental setup information was fed to the MCNP-4b code to calculate dose distributions at selected points inside the proposed phantom. Percent depth dose distribution was performed. Also, the absorbed dose as ratios relative to the original beam in the surrounding organs was calculated by MCNP-4b and measured by thermoluminescence dosimetry. Both measured and calculated data were compared. Results indicate good agreement between calculated and measured data inside the phantom. Comparison between MCNP-4b calculations and measurements of depth dose distribution indicated good agreement between both.
Ali, Imad; Algan, Ozer; Thompson, Spencer; Sindhwani, Puneet; Herman, Terence; Cheng, Chih-Yao; Ahmad, Salahuddin
2009-09-01
This work investigates variation in the volume of the prostate measured at different stages through the prostate brachytherapy procedure for 30 patients treated with I-125 radioactive seeds. The implanted seeds were localized on post-implantation ultrasound (US) images and the effect of prostate enlargement due to edema on dose coverage for 15 patients was studied. The volume of the prostate was measured at four stages as follows: (a) 2-3 weeks prior to implantation using US imaging, (b) then at the start of the intra-operative prostate brachytherapy procedure on the day of the implant, (c) immediately post-implantation using US imaging in the operating room and (d) finally by CT imaging at nearly 4 weeks post-implantation. Comparative prostate volume studies were performed using US imaging stepper and twister modes. For the purpose of this study, the implanted seeds were localized successfully on post-implant ultrasound twister images, retrospectively. The plans using post-implant US imaging were compared with intra-operative plans on US and plans created on CT images. The prostate volume increases about 10 cm3 on average due to edema induced by needle insertion and seed loading during implantation. The visibility of the implanted seeds on US twister images acquired post-implantation is as good as those on CT images and can be localized and used for dose calculation. The dose coverage represented by parameters such as D90 (dose covering 90% of the volume) and V100 (volume covered by 100% dose) is poorer on plans performed on post-implantation twister US studies than on the intra-operative live plan or the CT scan performed 4 weeks post-operatively. For example, the mean D90 difference on post-implantation US is lower by more than 15% than that on pre-implantation US. The volume enlargement of the prostate due to edema induced by needle insertion and seed placement has a significant effect on the quality of dosimetric coverage in brachytherapy prostate seed
Directory of Open Access Journals (Sweden)
Mohite P.B.
2012-06-01
Full Text Available Purpose: Lamivudine is cytosine and zidovudine is cytidine and is used as an antiretroviral agents. Both drugs are available in tablet dosage forms with a dose of 150 mg for LAM and 300 mg ZID respectively. Method: The method employed is based on first order derivative spectroscopy. Wavelengths 279 nm and 300 nm were selected for the estimation of the Lamovudine and Zidovudine respectively by taking the first order derivative spectra. The conc. of both drugs was determined by proposed method. The results of analysis have been validated statistically and by recovery studies as per ICH guidelines. Result: Both the drugs obey Beer’s law in the concentration range 10-50 μg mL-1,for LAM and ZID; with regression 0.9998 and 0.9999, intercept – 0.0677 and – 0.0043 and slope 0.0457 and 0.0391 for LAM and ZID, respectively.The accuracy and reproducibility results are close to 100% with 2% RSD. Conclusion: A simple, accurate, precise, sensitive and economical procedures for simultaneous estimation of Lamovudine and Zidovudine in tablet dosage form have been developed.
Inoue, R; Hiraga, F; Kiyanagi, Y
2014-06-01
An accelerator based BNCT has been desired because of its therapeutic convenience. However, optimal design of a neutron moderator system is still one of the issues. Therefore, detailed studies on materials consisting of the moderator system are necessary to obtain the optimal condition. In this study, the epithermal neutron flux and the RBE dose have been calculated as the indicators to look for optimal materials for the filter and the moderator. As a result, it was found that a combination of MgF2 moderator with Fe filter gave best performance, and the moderator system gave a dose ratio greater than 3 and an epithermal neutron flux over 1.0×10(9)cm(-2)s(-1).
Mairani, A; Valente, M; Battistoni, G; Botta, F; Pedroli, G; Ferrari, A; Cremonesi, M; Di Dia, A; Ferrari, M; Fasso, A
2011-01-01
Purpose: The calculation of patient-specific dose distribution can be achieved by Monte Carlo simulations or by analytical methods. In this study, FLUKA Monte Carlo code has been considered for use in nuclear medicine dosimetry. Up to now, FLUKA has mainly been dedicated to other fields, namely high energy physics, radiation protection, and hadrontherapy. When first employing a Monte Carlo code for nuclear medicine dosimetry, its results concerning electron transport at energies typical of nuclear medicine applications need to be verified. This is commonly achieved by means of calculation of a representative parameter and comparison with reference data. Dose point kernel (DPK), quantifying the energy deposition all around a point isotropic source, is often the one. Methods: FLUKA DPKS have been calculated in both water and compact bone for monoenergetic electrons (10-3 MeV) and for beta emitting isotopes commonly used for therapy ((89)Sr, (90)Y, (131)I, (153)Sm, (177)Lu, (186)Re, and (188)Re). Point isotropic...
A general method to derive tissue parameters for Monte Carlo dose calculation with multi-energy CT.
Lalonde, Arthur; Bouchard, Hugo
2016-11-21
To develop a general method for human tissue characterization with dual- and multi-energy CT and evaluate its performance in determining elemental compositions and quantities relevant to radiotherapy Monte Carlo dose calculation. Ideal materials to describe human tissue are obtained applying principal component analysis on elemental weight and density data available in literature. The theory is adapted to elemental composition for solving tissue information from CT data. A novel stoichiometric calibration method is integrated to the technique to make it suitable for a clinical environment. The performance of the method is compared with two techniques known in literature using theoretical CT data. In determining elemental weights with dual-energy CT, the method is shown to be systematically superior to the water-lipid-protein material decomposition and comparable to the parameterization technique. In determining proton stopping powers and energy absorption coefficients with dual-energy CT, the method generally shows better accuracy and unbiased results. The generality of the method is demonstrated simulating multi-energy CT data to show the potential to extract more information with multiple energies. The method proposed in this paper shows good performance to determine elemental compositions from dual-energy CT data and physical quantities relevant to radiotherapy dose calculation. The method is particularly suitable for Monte Carlo calculations and shows promise in using more than two energies to characterize human tissue with CT.
A general method to derive tissue parameters for Monte Carlo dose calculation with multi-energy CT
Lalonde, Arthur; Bouchard, Hugo
2016-11-01
To develop a general method for human tissue characterization with dual- and multi-energy CT and evaluate its performance in determining elemental compositions and quantities relevant to radiotherapy Monte Carlo dose calculation. Ideal materials to describe human tissue are obtained applying principal component analysis on elemental weight and density data available in literature. The theory is adapted to elemental composition for solving tissue information from CT data. A novel stoichiometric calibration method is integrated to the technique to make it suitable for a clinical environment. The performance of the method is compared with two techniques known in literature using theoretical CT data. In determining elemental weights with dual-energy CT, the method is shown to be systematically superior to the water-lipid-protein material decomposition and comparable to the parameterization technique. In determining proton stopping powers and energy absorption coefficients with dual-energy CT, the method generally shows better accuracy and unbiased results. The generality of the method is demonstrated simulating multi-energy CT data to show the potential to extract more information with multiple energies. The method proposed in this paper shows good performance to determine elemental compositions from dual-energy CT data and physical quantities relevant to radiotherapy dose calculation. The method is particularly suitable for Monte Carlo calculations and shows promise in using more than two energies to characterize human tissue with CT.
Inaniwa, T.; Kanematsu, N.; Sato, S.; Kohno, R.
2016-01-01
In treatment planning for proton radiotherapy, the dose measured in water is applied to the patient dose calculation with density scaling by stopping power ratio {ρ\\text{S}} . Since the body tissues are chemically different from water, this approximation may cause dose calculation errors, especially due to differences in nuclear interactions. We proposed and validated an algorithm for correcting these errors. The dose in water is decomposed into three constituents according to the physical interactions of protons in water: the dose from primary protons continuously slowing down by electromagnetic interactions, the dose from protons scattered by elastic and/or inelastic interactions, and the dose resulting from nonelastic interactions. The proportions of the three dose constituents differ between body tissues and water. We determine correction factors for the proportion of dose constituents with Monte Carlo simulations in various standard body tissues, and formulated them as functions of their {ρ\\text{S}} for patient dose calculation. The influence of nuclear interactions on dose was assessed by comparing the Monte Carlo simulated dose and the uncorrected dose in common phantom materials. The influence around the Bragg peak amounted to -6% for polytetrafluoroethylene and 0.3% for polyethylene. The validity of the correction method was confirmed by comparing the simulated and corrected doses in the materials. The deviation was below 0.8% for all materials. The accuracy of the correction factors derived with Monte Carlo simulations was separately verified through irradiation experiments with a 235 MeV proton beam using common phantom materials. The corrected doses agreed with the measurements within 0.4% for all materials except graphite. The influence on tumor dose was assessed in a prostate case. The dose reduction in the tumor was below 0.5%. Our results verify that this algorithm is practical and accurate for proton radiotherapy treatment planning, and
Rivard, Mark J; Beaulieu, Luc; Mourtada, Firas
2010-06-01
The current standard for brachytherapy dose calculations is based on the AAPM TG-43 formalism. Simplifications used in the TG-43 formalism have been challenged by many publications over the past decade. With the continuous increase in computing power, approaches based on fundamental physics processes or physics models such as the linear-Boltzmann transport equation are now applicable in a clinical setting. Thus, model-based dose calculation algorithms (MBDCAs) have been introduced to address TG-43 limitations for brachytherapy. The MBDCA approach results in a paradigm shift, which will require a concerted effort to integrate them properly into the radiation therapy community. MBDCA will improve treatment planning relative to the implementation of the traditional TG-43 formalism by accounting for individualized, patient-specific radiation scatter conditions, and the radiological effect of material heterogeneities differing from water. A snapshot of the current status of MBDCA and AAPM Task Group reports related to the subject of QA recommendations for brachytherapy treatment planning is presented. Some simplified Monte Carlo simulation results are also presented to delineate the effects MBDCA are called to account for and facilitate the discussion on suggestions for (i) new QA standards to augment current societal recommendations, (ii) consideration of dose specification such as dose to medium in medium, collisional kerma to medium in medium, or collisional kerma to water in medium, and (iii) infrastructure needed to uniformly introduce these new algorithms. Suggestions in this Vision 20/20 article may serve as a basis for developing future standards to be recommended by professional societies such as the AAPM, ESTRO, and ABS toward providing consistent clinical implementation throughout the brachytherapy community and rigorous quality management of MBDCA-based treatment planning systems.
2010-07-01
... extension for a human drug, antibiotic drug or human biological product. 1.775 Section 1.775 Patents... drug or human biological product is eligible for extension, the term shall be extended by the time as... term of the patent for a human drug, antibiotic drug or human biological product will be extended...
Directory of Open Access Journals (Sweden)
M.A. Zayed
2017-03-01
Full Text Available Naproxen (C14H14O3 is a non-steroidal anti-inflammatory drug (NSAID. It is important to investigate its structure to know the active groups and weak bonds responsible for medical activity. In the present study, naproxen was investigated by mass spectrometry (MS, thermal analysis (TA measurements (TG/DTG and DTA and confirmed by semi empirical molecular orbital (MO calculation, using PM3 procedure. These calculations included, bond length, bond order, bond strain, partial charge distribution, ionization energy and heat of formation (ΔHf. The mass spectra and thermal analysis fragmentation pathways were proposed and compared to select the most suitable scheme representing the correct fragmentation pathway of the drug in both techniques. The PM3 procedure reveals that the primary cleavage site of the charged molecule is the rupture of the COOH group (lowest bond order and high strain which followed by CH3 loss of the methoxy group. Thermal analysis of the neutral drug reveals a high response to the temperature variation with very fast rate. It decomposed in several sequential steps in the temperature range 80–400 °C. These mass losses appear as two endothermic and one exothermic peaks which required energy values of 255.42, 10.67 and 371.49 J g−1 respectively. The initial thermal ruptures are similar to that obtained by mass spectral fragmentation (COOH rupture. It was followed by the loss of the methyl group and finally by ethylene loss. Therefore, comparison between MS and TA helps in selection of the proper pathway representing its fragmentation. This comparison is successfully confirmed by MO-calculation.
Preliminary Calculations of Shutdown Dose Rate for the CTS Diagnostics System
DEFF Research Database (Denmark)
Klinkby, Esben Bryndt; Nonbøl, Erik; Lauritzen, Bent
2015-01-01
DTU and IST 2 are partners in the design of a collective Thomson Scattering (CTS) diagnostics for ITER through a contract with F4E. The CTS diagnostic utilizes probing radiation of ~60 GHz emitted into the plasma and, using a mirror, collects the scattered radiation by an array of receivers. Having...... a direct and unshielded view to the plasma, the first mirror will be subject to significant radiation and among the first tasks in the CTS design, is to determine whether the mirror will need active cooling. At present the CTS is in the conceptual design phase and the related neutronics calculations focus...
Brons, S; Elsässer, T; Ferrari, A; Gadioli, E; Mairani, A; Parodi, K; Sala, P; Scholz, M; Sommerer, F
2010-01-01
Monte Carlo codes are rapidly spreading among hadron therapy community due to their sophisticated nuclear/electromagnetic models which allow an improved description of the complex mixed radiation field produced by nuclear reactions in therapeutic irradiation. In this contribution results obtained with the Monte Carlo code FLUKA are presented focusing on the production of secondary fragments in carbon ion interaction with water and on CT-based calculations of absorbed and biological effective dose for typical clinical situations. The results of the simulations are compared with the available experimental data and with the predictions of the GSI analytical treatment planning code TRiP.
Energy Technology Data Exchange (ETDEWEB)
Savolainen, S. [Helsinki Univ. (Finland). Dept. of Physics; Kairemo, K. [Helsinki Univ. (Finland). Dept. of Clinical Chemistry; Liewendahl, K. [Helsinki Univ. Central Hospital (Finland). Dept. of Isotopes; Rannikko, S. [Finnish Centre for Radiation and Nuclear Safety, Helsinki (Finland)
1995-10-01
In radioimmunotherapy (RIT) monoclonal antibodies to cancer-associated antigens can be utilized for the transport of therapeutic radioisotopes to cancer cells. Intravenous administration of radiolabelled antibody is a potentially curative form of therapy in hematological amignancies as circulating antibodies have easy access to tumour sites. Intravenous RIT is less effective in the treatment of solid tumours because of the low fractional uptake of the injected dose, particularly in the central parts of tumours. In solid tumours more promising results have been achieved by local RIT applications. The choice of radiation - {alpha}, {beta} or {gamma} - will depend of the characteristics of the tumour. The importance of radiation delivered by Auger electrons has been largely underestimated in the past, but recent research has resulted in a remarkable reassessment of this issue significantly influencing the selection of radioisotopes for RIT. Research is now being focused on the therapeutic aspects of different isotopes and microdosimetric problems. There are now good prospects of RIT becoming an important form of cancer treatment before year 2000. (orig.) (78 refs., 3 figs., 1 tab.).
OSCAAR calculations for the Iput dose reconstruction scenario of BIOMASS theme 2
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Homma, Toshimitsu; Matsunaga, Takeshi [Department of Reactor Safety Research, Nuclear Safety Research Center, Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan)
2001-01-01
This report presents the results obtained from the application of the accident consequence assessment code, called OSCAAR, developed in Japan Atomic Energy Research Institute to the Iput dose reconstruction scenario of BIOMASS Theme 2 organized by International Atomic Energy Agency. The Iput Scenario deals with {sup 137}Cs contamination of the catchment basin and agricultural area in the Bryansk Region of Russia, which was heavily contaminated after the Chernobyl accident. This exercise was used to test the chronic exposure pathway models in OSCAAR with actual measurements and to identify the most important sources of uncertainly with respect to each part of the assessment. The OSCAAR chronic exposure pathway models almost successfully reconstructed the whole 10-year time course of {sup 137}Cs activity concentrations in most requested types of agricultural products and natural foodstuffs. Modeling of {sup 137}Cs downward migration in soils is, however, still incomplete and more detail modeling of the changes of cesium bioavailability with time is needed for long term predictions of the contamination of food. (author)
Copeland, Kyle; Parker, Donald E; Friedberg, Wallace
2010-03-01
Conversion coefficients have been calculated for fluence-to-absorbed dose, fluence-to-effective dose and fluence-to-gray equivalent for isotropic exposure of an adult male and an adult female to (56)Fe(26+) in the energy range of 10 MeV to 1 TeV (0.01-1000 GeV). The coefficients were calculated using Monte Carlo transport code MCNPX 2.7.A and BodyBuilder 1.3 anthropomorphic phantoms modified to allow calculation of effective dose using tissues and tissue weighting factors from either the 1990 or 2007 recommendations of the International Commission on Radiological Protection (ICRP) and gray equivalent to selected tissues as recommended by the National Council on Radiation Protection and Measurements. Calculations using ICRP 2007 recommendations result in fluence-to-effective dose conversion coefficients that are almost identical at most energies to those calculated using ICRP 1990 recommendations.
O'Gorman, Jennifer R; O'Leary, Orla; Finner, Natalie; Quinn, Anne; O'Gorman, Clodagh S
2015-01-01
The aim of this study was to assess the carbohydrate and insulin knowledge of the staff at Children's Ark at the University Hospital, Limerick. Carbohydrate counting and insulin dose calculations based on carbohydrates and blood sugars are integral to intensive insulin management of type 1 diabetes mellitus (T1DM). The PedCarbQuiz, a validated questionnaire, was modified, and applied to the staff on our general paediatrics ward. 48/70 eligible staff responded (rate 68 %). Overall knowledge was good: 75.5 % was the average score for correctly identifying foods containing carbohydrate. However, poor scores were obtained for calculating multiple items and meal values (average score 29 %), and exact values of insulin required (average score 38 %). These results highlight the need for re-education among staff on a general paediatrics ward, to empower ward staff to contribute effectively to the education and management of patients with T1DM.
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Dalzell, M.T.J. [Sylvia Fedoruk Canadian Centre for Nuclear Innovation, Saskatoon, Saskatchewan (Canada)
2016-06-15
Concerns arising from misunderstandings about radiation are often cited as a main reason for public antipathy towards nuclear development and impede decision-making by governments and individuals. A lack of information about everyday sources of radiation exposure that is accessible, relatable and factual contributes to the problem. As part of its efforts to be a fact-based source of information on nuclear issues, the Sylvia Fedoruk Canadian Centre for Nuclear Innovation has developed an on-line Canadian Radiation Dose Calculator as a tool to provide context about common sources of radiation. This paper discusses the development of the calculator and describes how the Fedoruk Centre is using it and other tools to support public engagement on nuclear topics. (author)
Van Hoogdalem, E J; Terpstra, I J; Krauwinkel, W J; Volkers-Kamermans, N J; Baven, A L; Verschoor, J S
1996-05-01
Josamycin is a macrolide antibiotic with considerable intra- and interindividual variability in kinetics. In the present study bioequivalence of an intact and dispersed josamycin Solutab tablet, containing 1,000 mg of josamycin in the form of josamycin propionate ester, was tested versus a Josacine 1,000 mg reference sachet. The design of this bioequivalence study was adapted to the drug's pharmacokinetic variability, comprising testing in steady-state, testing the reference in replicate, and maintaining a widened bioequivalence margin. The study was performed in a group of 24 male and 12 female healthy subjects, according to a 3-treatment 4-period crossover design. Blood sampling for establishing josamycin propionate and josamycin base serum level profiles were collected during the 12 h dosing interval on day 4. Steady-state serum levels were reached on day 4. With the reference sachet mean peak levels of 1.02 micrograms/ml and 0.36 microgram/ml were observed for parent drug and metabolite, respectively, reached at peak times of 1.5 h and 1.8 h. Comparable profiles were observed with the intact and dispersed Solutab tablets, both tending towards higher serum levels than the sachet. In terms of josamycin propionate levels as well as josamycin base levels, the intact and dispersed Solutab tablet was bioequivalent with the referent sachet within the preset 0.70-1.43 margins. Variability in josamycin kinetics proved to be substantial, maximum differences in peak levels and AUC values being about 10-fold between individuals, and 3-fold within individuals. Retrospectively, the multiple dosing regimen appeared not to result in a clear reduction of intrasubject variability.
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Endo, Akira; Yamaguchi, Yasuhiro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
2001-03-01
New nuclear decay data used for dose calculation have been compiled for 817 radionuclides that are listed in ICRP Publication 38 (Publ. 38) and for 6 additional isomers. The decay data were prepared using decay data sets from the Evaluated Nuclear Structure Data File (ENSDF), the latest version in August 1997. Basic nuclear properties in the decay data sets that are particularly important for calculating energies and intensities of emissions were examined and updated by referring to NUBASE, the database for nuclear and decay properties of nuclides. The reviewed and updated data were half-life, decay mode and its branching ratio, spin and parity of the ground and isomeric states, excitation energy of isomers, and Q value. In addition, possible revisions of partial and incomplete decay data sets were done for their format and syntax errors, level schemes, normalization records, and so on. After that, the decay data sets were processed by EDISTR in order to compute the energies and intensities of {alpha} particles, {beta} particles, {gamma} rays, internal conversion electrons, X rays, and Auger electrons emitted in nuclear transformation. For spontaneously fissioning nuclides, the average energies and intensities of neutrons, fission fragments, prompt {gamma} rays, delayed {gamma} rays, and {beta} particles were also calculated. The compiled data were prepared in two different types of format: Publ. 38 and NUCDECAY formats. Comparison of the compiled decay data with those in Publ. 38 was also presented. The decay data will be widely used for internal and external dose calculations in radiation protection and will be beneficial to a future revision of ICRP Publ. 38. (author)
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Jin, L; Wang, L; Li, J; Luo, W; Feigenberg, S J; Ma, C-M [Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA 19111 (United States)
2007-07-21
This work investigated the selection of beam margins in lung-cancer stereotactic body radiotherapy (SBRT) with 6 MV photon beams. Monte Carlo dose calculations were used to systematically and quantitatively study the dosimetric effects of beam margins for different lung densities (0.1, 0.15, 0.25, 0.35 and 0.5 g cm{sup -3}), planning target volumes (PTVs) (14.4, 22.1 and 55.3 cm{sup 3}) and numbers of beam angles (three, six and seven) in lung-cancer SBRT in order to search for optimal beam margins for various clinical situations. First, a large number of treatment plans were generated in a commercial treatment planning system, and then recalculated using Monte Carlo simulations. All the plans were normalized to ensure that 95% of the PTV at least receives the prescription dose and compared quantitatively. Based on these plans, the relationships between the beam margin and quantities such as the lung toxicity (quantified by V{sub 20}, the percentage volume of the two lungs receiving at least 20 Gy) and the maximum target (PTV) dose were established for different PTVs and lung densities. The impact of the number of beam angles on the relationship between V{sub 20} and the beam margin was assessed. Quantitative information about optimal beam margins for lung-cancer SBRT was obtained for clinical applications.
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Park, Justin C.; Li, Jonathan G.; Arhjoul, Lahcen; Yan, Guanghua; Lu, Bo; Fan, Qiyong; Liu, Chihray, E-mail: liucr@ufl.edu [Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610-0385 (United States)
2015-04-15
Purpose: The use of sophisticated dose calculation procedure in modern radiation therapy treatment planning is inevitable in order to account for complex treatment fields created by multileaf collimators (MLCs). As a consequence, independent volumetric dose verification is time consuming, which affects the efficiency of clinical workflow. In this study, the authors present an efficient adaptive beamlet-based finite-size pencil beam (AB-FSPB) dose calculation algorithm that minimizes the computational procedure while preserving the accuracy. Methods: The computational time of finite-size pencil beam (FSPB) algorithm is proportional to the number of infinitesimal and identical beamlets that constitute an arbitrary field shape. In AB-FSPB, dose distribution from each beamlet is mathematically modeled such that the sizes of beamlets to represent an arbitrary field shape no longer need to be infinitesimal nor identical. As a result, it is possible to represent an arbitrary field shape with combinations of different sized and minimal number of beamlets. In addition, the authors included the model parameters to consider MLC for its rounded edge and transmission. Results: Root mean square error (RMSE) between treatment planning system and conventional FSPB on a 10 × 10 cm{sup 2} square field using 10 × 10, 2.5 × 2.5, and 0.5 × 0.5 cm{sup 2} beamlet sizes were 4.90%, 3.19%, and 2.87%, respectively, compared with RMSE of 1.10%, 1.11%, and 1.14% for AB-FSPB. This finding holds true for a larger square field size of 25 × 25 cm{sup 2}, where RMSE for 25 × 25, 2.5 × 2.5, and 0.5 × 0.5 cm{sup 2} beamlet sizes were 5.41%, 4.76%, and 3.54% in FSPB, respectively, compared with RMSE of 0.86%, 0.83%, and 0.88% for AB-FSPB. It was found that AB-FSPB could successfully account for the MLC transmissions without major discrepancy. The algorithm was also graphical processing unit (GPU) compatible to maximize its computational speed. For an intensity modulated radiation therapy (
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Schach von Wittenau, A.E.; Cox, L.J.; Bergstrom, P.M. Jr.; Hornstein, S.M. [Lawrence Livermore National Lab., CA (United States); Mohan, R.; Libby, B.; Wu, Q. [Medical Coll. of Virginia, Richmond, VA (United States); Lovelock, D.M.J. [Memorial Sloan-Kettering Cancer Center, New York, NY (United States)
1997-03-01
The goal of the PEREGRINE Monte Carlo Dose Calculation Project is to deliver a Monte Carlo package that is both accurate and sufficiently fast for routine clinical use. One of the operational requirements for photon-treatment plans is a fast, accurate method of describing the photon phase-space distribution at the surface of the patient. The open-field case is computationally the most tractable; we know, a priori, for a given machine and energy, the locations and compositions of the relevant accelerator components (i.e., target, primary collimator, flattening filter, and monitor chamber). Therefore, we can precalculate and store the expected photon distributions. For any open-field treatment plan, we then evaluate these existing photon phase-space distributions at the patient`s surface, and pass the obtained photons to the dose calculation routines within PEREGRINE. We neglect any effect of the intervening air column, including attenuation of the photons and production of contaminant electrons. In principle, for treatment plans requiring jaws, blocks, and wedges, we could precalculate and store photon phase-space distributions for various combinations of field sizes and wedges. This has the disadvantage that we would have to anticipate those combinations and that subsequently PEREGRINE would not be able to treat other plans. Therefore, PEREGRINE tracks photons through the patient-dependent beam modifiers. The geometric and physics methods used to do this are described here. 4 refs., 8 figs.
DEFF Research Database (Denmark)
Aarup, Lasse Rye; Nahum, Alan E; Zacharatou, Christina
2009-01-01
and tumour have unit density). The lung tissue was assigned five densities (rho(lung)): 0.01, 0.1, 0.2, 0.4 and 1g/cm(3). Four-field treatment plans were calculated with 6- and 18 MV narrow beams for each value of rho(lung). We considered the Pencil Beam Convolution (PBC(Ecl)) and the Analytical Anisotropic...... Algorithm (AAA(Ecl)) from Varian Eclipse and the Pencil Beam Convolution (PBC(OMP)) and the Collapsed Cone Convolution (CCC(OMP)) algorithms from Oncentra MasterPlan. RESULTS: When changing rho(lung) from 0.4 to 0.1g/cm(3), the MC median target dose decreased from 89.2% to 74.9% for 6 MV and from 83...... Treatment Planning System (TPS) algorithms and one Monte Carlo (MC) system (EGSnrc). We compared the performance of the algorithms in calculating the target dose for different degrees of lung inflation. The phantoms had a cubic 'body' and 'lung' and a central 2-cm diameter spherical 'tumour' (the body...
A dynamic extraversion model. The brain's response to a single dose of a stimulant drug.
Amigó, Salvador; Caselles, Antonio; Micó, Joan C
2008-05-01
The aim of this paper is to present a mathematical dynamic modelling of the effect a stimulant drug has on different people which, at the same time, can be a useful tool for future brain studies. To this end, a dynamic model of the evolution of extraversion (considering its tonic and phasic aspects) has been constructed taking into account the unique personality trait theory and the general modelling methodology. This model consists of a delayed differential equation which, on one hand, considers that the active stimulus, a consequence of a single intake, is not constant; on the other hand, it contemplates that the state variable representing the phasic extraversion also represents the brain activation. The derivative of this state variable is calculated as the sum of the homeostatic control flow, the excitatory effect flow and the inhibitor effect flow. The solutions of this equation relate the tonic activation of an individual (that characterizes his or her personality) with his or her phasic activation level, whose evolution over time describes the organism's response to a single drug intake. These solutions quantitatively reproduce the predictions of current personality theories and anticipate vulnerability to drug misuse and addiction development.
A dose of ruthlessness: interpersonal moral judgment is hardened by the anti-anxiety drug lorazepam.
Perkins, Adam M; Leonard, Ania M; Weaver, Kristin; Dalton, Jeffrey A; Mehta, Mitul A; Kumari, Veena; Williams, Steven C R; Ettinger, Ulrich
2013-08-01
Neuroimaging data suggest that emotional brain systems are more strongly engaged by moral dilemmas in which innocent people are directly harmed than by dilemmas in which harm is remotely inflicted. In order to test the possibility that this emotional engagement involves anxiety, we investigated the effects of 1 mg and 2 mg of the anti-anxiety drug lorazepam on the response choices of 40 healthy volunteers (20 male) in moral-personal, moral-impersonal, and nonmoral dilemmas. We found that lorazepam caused a dose-dependent increase in participants' willingness to endorse responses that directly harm other humans in moral-personal dilemmas but did not significantly affect response choices in moral-impersonal dilemmas or nonmoral dilemmas. Within the set of moral-personal dilemmas that we administered, lorazepam increased the willingness to harm others in dilemmas where harm was inflicted for selfish reasons (dubbed low-conflict dilemmas) as well as responses to dilemmas where others were harmed for utilitarian reasons (i.e., for the greater good, dubbed high-conflict dilemmas). This suggests that anxiety exerts a general inhibitory effect on harmful acts toward other humans regardless of whether the motivation for those harmful acts is selfish or utilitarian. Lorazepam is also a sedative drug, but we found that lorazepam slowed decision times equally in all 3 dilemma types. This finding implies that its specific capacity to increase ruthlessness in moral-personal dilemmas was not a confound caused by sedation.
Patel, Sarsvatkumar; Bansal, Arvind Kumar
2011-01-17
The aim of the study was to develop, compare and validate predictive model for mechanical property of binary systems. The mechanical properties of binary mixtures of ibuprofen (IBN) a poorly compressible high dose drug, were studied in presence of different excipients. The tensile strength of tablets of individual components viz. IBN, microcrystalline cellulose (MCC), and dicalcium phosphate dihydrate (DCP) and binary mixtures of IBN with excipients was measured at various relative densities. Prediction of the mechanical property of binary mixtures, from that of single components, was attempted using Ryshkewitch-Duckworth (R-D) and Percolation theory, by assuming a linear mixing rule or a power law mixing rule. The models were compared, and the best model was proposed based on the distribution of residuals and the Akaike's information criterion. Good predictions were obtained with the power law combined with linear mixing rule, using R-D and Percolation models. The results indicated that the proposed model can well predict the mechanical properties of binary system containing predominantly poorly compressible drug candidate. The predictions of these models and conclusions can be systematically generalized to other pharmaceutical powders.
Park, Jun-Bom; Kang, Chin-Yang; Kang, Wie-Soo; Choi, Han-Gon; Han, Hyo-Kyung; Lee, Beom-Jin
2013-12-31
The content uniformity of low dose drugs in dosage forms is very important for quality assurance. The aim of this study was to prepare uniformly and homogeneously distributed dosage forms of very low-dose drugs using twin screw hot-melt extrusion (HME) and to investigate the distribution of drugs using instrumental analyses. For the feasibility of HME method, a very low amount of coumarin-6, a fluorescent dye, was used to visualize distribution images using confocal laser scanning microscope (CLSM). Limaprost, tamsulosin and glimepiride were then used as low-dose model drugs to study the applicability of HME for content uniformity and distribution behaviors. Hydrophilic thermosensitive polymers with low melting point, such as Poloxamer188 and polyethylene glycol (PEG) 6000, were chosen as carriers. The melt extrusion was carried out around 50°C, at which both carriers were easily dissolved but model drugs remained in solid form. The physicochemical properties of the hot-melt extrudates, including differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FT-IR), were measured. Content uniformity of the drugs was also checked by HPLC. CLSM imaging showed that model drugs were well distributed throughout the hot-melt extrudate, giving better content uniformity with low batch-to-batch variations compared with simple physical mixtures. DSC, PXRD and FT-IR data showed that there was no interaction or interference between model drugs and thermosensitive polymers. The current HME methods could be used to prepare uniformly distributed and reproducible solid dosage forms containing very low dose drugs for further pharmaceutical applications.
Vincke, Helmut H
2003-01-01
The CERN Neutrino beam to Gran Sasso (CNGS) project and the Large Hadron Collider (LHC) will receive 450 GeV/c protons extracted from the Super Proton Synchrotron (SPS). In the tunnels leading to the CNGS target and the LHC accelerator there is a 150 m straight section where a beam dump (TED) can be moved into the beam chamber, intercepting the proton beam. After the TED, the beam is routed into either the 700m slowly curving TT41 tunnel (CNGS) or the TI8 tunnel consisting of a 400 m straight section followed by a curved 1.5 km long tunnel (LHC). The curved tunnels have a radius of approximately 1 km. During tests a proton beam of 1.2 multiplied by 10**1**3 s**- **1 could be sent to the dump. The question posed was how close to the TED could access be allowed during dumping operations. Initial simulations using the FLUKA Monte-Carlo transport program were optimised assuming that the high-energy muon contribution dominates. Discrepancies with an analytically based calculation led to a revision of this optimisa...
Vijayan, Sarath; Rana, Vijay K; Rudin, Stephen; Bednarek, Daniel R
2015-03-18
The skin dose tracking system (DTS) that we developed provides a color-coded illustration of the cumulative skin dose distribution on a 3D graphic of the patient during fluoroscopic procedures for immediate feedback to the interventionist. To improve the accuracy of dose calculation, we now have incorporated two additional important corrections (1) for the holder used to immobilize the head in neuro-interventions and (2) for the built-in compensation filters used for beam equalization. Both devices have been modeled in the DTS software so that beam intensity corrections can be made. The head-holder is modeled as two concentric hemi-cylindrical surfaces such that the path length between those surfaces can be determined for rays to individual points on the skin surface. The head-holder on the imaging system we used was measured to attenuate the primary x-rays by 10 to 20% for normal incidence, and up to 40% at non-normal incidence. In addition, three compensation filters of different shape are built into the collimator apparatus and were measured to have attenuation factors ranging from 58% to 99%, depending on kVp and beam filtration. These filters can translate and rotate in the beam and their motion is tracked by the DTS using the digital signal from the imaging system. When it is determined that a ray to a given point on the skin passes through the compensation filter, the appropriate attenuation correction is applied. These corrections have been successfully incorporated in the DTS software to provide a more accurate determination of skin dose.
Vijayan, Sarath; Rana, Vijay K.; Rudin, Stephen; Bednarek, Daniel R.
2015-01-01
The skin dose tracking system (DTS) that we developed provides a color-coded illustration of the cumulative skin dose distribution on a 3D graphic of the patient during fluoroscopic procedures for immediate feedback to the interventionist. To improve the accuracy of dose calculation, we now have incorporated two additional important corrections (1) for the holder used to immobilize the head in neuro-interventions and (2) for the built-in compensation filters used for beam equalization. Both devices have been modeled in the DTS software so that beam intensity corrections can be made. The head-holder is modeled as two concentric hemi-cylindrical surfaces such that the path length between those surfaces can be determined for rays to individual points on the skin surface. The head-holder on the imaging system we used was measured to attenuate the primary x-rays by 10 to 20% for normal incidence, and up to 40% at non-normal incidence. In addition, three compensation filters of different shape are built into the collimator apparatus and were measured to have attenuation factors ranging from 58% to 99%, depending on kVp and beam filtration. These filters can translate and rotate in the beam and their motion is tracked by the DTS using the digital signal from the imaging system. When it is determined that a ray to a given point on the skin passes through the compensation filter, the appropriate attenuation correction is applied. These corrections have been successfully incorporated in the DTS software to provide a more accurate determination of skin dose. PMID:26819488
Vijayan, Sarath; Rana, Vijay K.; Rudin, Stephen; Bednarek, Daniel R.
2015-03-01
The skin dose tracking system (DTS) that we developed provides a color-coded illustration of the cumulative skin dose distribution on a 3D graphic of the patient during fluoroscopic procedures for immediate feedback to the interventionist. To improve the accuracy of dose calculation, we now have incorporated two additional important corrections (1) for the holder used to immobilize the head in neuro-interventions and (2) for the built-in compensation filters used for beam equalization. Both devices have been modeled in the DTS software so that beam intensity corrections can be made. The head-holder is modeled as two concentric hemi-cylindrical surfaces such that the path length between those surfaces can be determined for rays to individual points on the skin surface. The head-holder on the imaging system we used was measured to attenuate the primary x-rays by 10 to 20% for normal incidence, and up to 40% at non-normal incidence. In addition, three compensation filters of different shape are built into the collimator apparatus and were measured to have attenuation factors ranging from 58% to 99%, depending on kVp and beam filtration. These filters can translate and rotate in the beam and their motion is tracked by the DTS using the digital signal from the imaging system. When it is determined that a ray to a given point on the skin passes through the compensation filter, the appropriate attenuation correction is applied. These corrections have been successfully incorporated in the DTS software to provide a more accurate determination of skin dose.
Copeland, Kyle; Parker, Donald E; Friedberg, Wallace
2010-03-01
Conversion coefficients have been calculated for fluence to absorbed dose, fluence to effective dose and fluence to gray equivalent, for isotropic exposure to alpha particles in the energy range of 10 MeV to 1 TeV (0.01-1000 GeV). The coefficients were calculated using Monte Carlo transport code MCNPX 2.7.A and BodyBuilder 1.3 anthropomorphic phantoms modified to allow calculation of effective dose to a Reference Person using tissues and tissue weighting factors from 1990 and 2007 recommendations of the International Commission on Radiological Protection (ICRP) and gray equivalent to selected tissues as recommended by the National Council on Radiation Protection and Measurements. Coefficients for effective dose are within 30 % of those calculated using ICRP 1990 recommendations.
Eriksson, Robert; Werge, Thomas; Jensen, Lars Juhl; Brunak, Søren
2014-01-01
Background Data collected for medical, filing and administrative purposes in electronic patient records (EPRs) represent a rich source of individualised clinical data, which has great potential for improved detection of patients experiencing adverse drug reactions (ADRs), across all approved drugs and across all indication areas. Objectives The aim of this study was to take advantage of techniques for temporal data mining of EPRs in order to detect ADRs in a patient- and dose-specific manner....
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Schloemer, Luc Laurent Alexander
2014-12-17
The compliance with the dose rate limits for transport and storage casks (TLB) for spent nuclear fuel from pressurised water reactors can be proved by calculation. This includes the determination of the radioactive sources and the shielding-capability of the cask. In this thesis the entire computational chain, which extends from the determination of the source terms to the final Monte-Carlo-transport-calculation is analysed and the arising uncertainties are quantified not only by benchmarks but also by variational calculi. The background of these analyses is that the comparison with measured dose rates at different TLBs shows an overestimation by the values calculated. Regarding the studies performed, the overestimation can be mainly explained by the detector characteristics for the measurement of the neutron dose rate and additionally in case of the gamma dose rates by the energy group structure, which the calculation is based on. It turns out that the consideration of the uncertainties occurring along the computational chain can lead to even greater overestimation. Concerning the dose rate calculation at cask loadings with spent uranium fuel assemblies an uncertainty of (({sup +21}{sub -28}) ±2) % (rel.) for the total gamma dose rate and of ({sup +28±23}{sub -55±4}) % (rel.) for the total neutron dose rate are estimated. For mixed-loadings with spent uranium and MOX fuel assemblies an uncertainty of ({sup +24±3}{sub -27±2}) % (rel.) for the total gamma dose rate and of ({sup +28±23}{sub -55±4}) % (rel.) for the total neutron dose rate are quantified. The results show that the computational chain has not to be modified, because the calculations performed lead to conservative dose rate predictions, even if high uncertainties at neutron dose rate measurements arise. Thus at first the uncertainties of the neutron dose rate measurement have to be decreased to enable a reduction of the overestimation of the calculated dose rate afterwards. In the present thesis
Kelly, T H; Foltin, R W; Emurian, C S; Fischman, M W
1993-09-01
The time courses of the effects of acute doses of amphetamine (5 and 10 mg/70 kg), alcohol (0.3 and 0.6 g/kg), diazepam (5 and 10 mg/70 kg), and marijuana (2.0% and 3.5% delta 9-THC) on performance engendered by each of four computerized behavioral tasks were evaluated in six human subjects. These performance-based tasks have potential commercial utility for drug-use detection in the workplace. Alcohol and marijuana effects were reliably detected for up to three hours following dose administration with most procedures. Amphetamine and diazepam effects were also detected, but the dose effects and time courses were variable. The profile of behavioral effects varied across drugs, suggesting that performance-based testing procedures might be useful in discriminating which drug was administered and the time course of the drug's effects. Results indicate that repeated measurement with performance-based drug detection procedures can provide immediate indications of performance impairment in a cost-effective and noninvasive manner and, as such, would be a useful supplement to biological sample testing for drug-use detection.
SU-E-T-252: Developing a Pencil Beam Dose Calculation Algorithm for CyberKnife System
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Liang, B [Image processing center, Beihang University, Beijing (China); Duke University Medical Center, Durham, NC (United States); Liu, B; Zhou, F [Image processing center, Beihang University, Beijing (China); Xu, S [Chinese PLA General Hospital, Beijing (China); Wu, Q [Duke University Medical Center, Durham, NC (United States)
2015-06-15
Purpose: Currently there are two dose calculation algorithms available in the Cyberknife planning system: ray-tracing and Monte Carlo, which is either not accurate or time-consuming for irregular field shaped by the MLC that was recently introduced. The purpose of this study is to develop a fast and accurate pencil beam dose calculation algorithm which can handle irregular field. Methods: A pencil beam dose calculation algorithm widely used in Linac system is modified. The algorithm models both primary (short range) and scatter (long range) components with a single input parameter: TPR{sub 20}/{sub 10}. The TPR{sub 20}/{sub 20}/{sub 10} value was first estimated to derive an initial set of pencil beam model parameters (PBMP). The agreement between predicted and measured TPRs for all cones were evaluated using the root mean square of the difference (RMSTPR), which was then minimized by adjusting PBMPs. PBMPs are further tuned to minimize OCR RMS (RMSocr) by focusing at the outfield region. Finally, an arbitrary intensity profile is optimized by minimizing RMSocr difference at infield region. To test model validity, the PBMPs were obtained by fitting to only a subset of cones (4) and applied to all cones (12) for evaluation. Results: With RMS values normalized to the dmax and all cones combined, the average RMSTPR at build-up and descending region is 2.3% and 0.4%, respectively. The RMSocr at infield, penumbra and outfield region is 1.5%, 7.8% and 0.6%, respectively. Average DTA in penumbra region is 0.5mm. There is no trend found in TPR or OCR agreement among cones or depths. Conclusion: We have developed a pencil beam algorithm for Cyberknife system. The prediction agrees well with commissioning data. Only a subset of measurements is needed to derive the model. Further improvements are needed for TPR buildup region and OCR penumbra. Experimental validations on MLC shaped irregular field needs to be performed. This work was partially supported by the National
Calculs de doses générées par les rayonnements ionisants principes physiques et codes de calcul
Vivier, Alain
2016-01-01
Cet ouvrage et les codes associés s’adressent aux utilisateurs de sources de rayonnements ionisants : techniciens, ingénieurs de sécurité, personnes compétentes en radioprotection, mais aussi médecins, chercheurs, concepteurs, décideurs… Les contraintes croissantes liées à la radioprotection rendent indispensables l’utilisation de codes de calcul permettant d’évaluer les débits de doses générées par ces sources et la façon dont on peut s’en protéger au mieux. De nombreux codes existent, dont certains restent des références incontournables, mais ils sont relativement complexes à mettre en oeuvre et restent en général réservés aux bureaux d’études. En outre, ces codes sont souvent des « boîtes noires » qui ne permettent pas de comprendre la physique sous-jacente. L’objectif de cet ouvrage est double : - Exposer les principes physiques permettant de comprendre les phénomènes à l’oeuvre lorsque la matière est irradiée par des rayonnements ionisants. Il devient al...
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Valdes, Gilmer, E-mail: gilmer.valdes@uphs.upenn.edu [Department of Radiation Oncology, Perelman Center for Advanced Medicine, University of Pennsylvania, Philadelphia, PA (United States); Robinson, Clifford [Department of Radiation Oncology, Siteman Cancer Center, Washington University in St. Louis, St. Louis, MO (United States); Lee, Percy [Department of Radiation Oncology, David Geffen School of Medicine, UCLA, Los Angeles, CA (United States); Morel, Delphine [Department of Biomedical Engineering, AIX Marseille 2 University, Marseille (France); Department of Medical Physics, Joseph Fourier University, Grenoble (France); Low, Daniel; Iwamoto, Keisuke S.; Lamb, James M. [Department of Radiation Oncology, David Geffen School of Medicine, UCLA, Los Angeles, CA (United States)
2015-04-01
Four-dimensional (4D) dose calculations for lung cancer radiotherapy have been technically feasible for a number of years but have not become standard clinical practice. The purpose of this study was to determine if clinically significant differences in tumor control probability (TCP) exist between 3D and 4D dose calculations so as to inform the decision whether 4D dose calculations should be used routinely for treatment planning. Radiotherapy plans for Stage I-II lung cancer were created for 8 patients. Clinically acceptable treatment plans were created with dose calculated on the end-exhale 4D computed tomography (CT) phase using a Monte Carlo algorithm. Dose was then projected onto the remaining 9 phases of 4D-CT using the Monte Carlo algorithm and accumulated onto the end-exhale phase using commercially available deformable registration software. The resulting dose-volume histograms (DVH) of the gross tumor volume (GTV), planning tumor volume (PTV), and PTV{sub setup} were compared according to target coverage and dose. The PTV{sub setup} was defined as a volume including the GTV and a margin for setup uncertainties but not for respiratory motion. TCPs resulting from these DVHs were estimated using a wide range of alphas, betas, and tumor cell densities. Differences of up to 5 Gy were observed between 3D and 4D calculations for a PTV with highly irregular shape. When the TCP was calculated using the resulting DVHs for fractionation schedules typically used in stereotactic body radiation therapy (SBRT), the TCP differed at most by 5% between 4D and 3D cases, and in most cases, it was by less than 1%. We conclude that 4D dose calculations are not necessary for most cases treated with SBRT, but they might be valuable for irregularly shaped target volumes. If 4D calculations are used, 4D DVHs should be evaluated on volumes that include margin for setup uncertainty but not respiratory motion.
Directory of Open Access Journals (Sweden)
Mini S Jacob
2011-01-01
Full Text Available Background: Single dose of Nevirapine to prevent mother to child transmission of HIV is the commonest preventive regimen in resource-limited countries. Objectives: The objective of this study was to detect drug-resistant virus after single dose of Nevirapine (sdNVP provided to delivering HIV seropositive (HIV+ve women and to evaluate the time taken for its decay. Results: Of the 36 consenting HIV+ve pregnant women enrolled into the study, the mean hemoglobin and total lymphocyte counts were 10.8 g/dl and 1843 cells/mm 3 , respectively. Mean CD4 counts in 64% of women was 363 cells/mm 3 and mean viral load for 16/36 women was 28,143 copies/ml of plasma. Nevirapine-resistance mutations were detected in 28% of women at delivery; using OLA (Oligonucleotide Ligation Assay. K103N mutations were seen in 19.4% of women while the Y181C mutation was seen in 5%. Both the mutations were detected in 2.7% of women. Sequential blood samples collected at delivery, 7-10 days, 6 weeks, 4 months, 6 months and one year postpartum showed that 81% of K103N mutations and 66.7% of Y181C mutations were detected at 6 weeks postpartum . Wild-type virus had replaced the mutants by one year postpartum in all women except one. Conclusion : These observations are relevant for future treatment with antiretroviral therapy in these women for their HIV disease.
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Garcez, R.W.D.; Lopes, J.M.; Silva, A.X., E-mail: marqueslopez@yahoo.com.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/PEN/UFRJ), Rio de Janeiro, RJ (Brazil). Centro de Tecnologia; Domingues, A.M. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Instituto de Fisica; Lima, M.A.F. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Instituto de Biologia
2014-07-01
A method based on gamma spectroscopy and on the use of voxel phantoms to calculate dose due to ingestion of {sup 40}K contained in bean samples are presented in this work. To quantify the activity of radionuclide, HPGe detector was used and the data entered in the input file of MCNP code. The highest value of equivalent dose was 7.83 μSv.y{sup -1} in the stomach for white beans, whose activity 452.4 Bq.Kg{sup -1} was the highest of the five analyzed. The tool proved to be appropriate when you want to calculate the dose in organs due to ingestion of food. (author)
Kazemi, M.; Afarideh, H.; Riazi, Z.
2015-11-01
The aim of this research work is to use a better parallel software structure to improve the performance of the Monte Carlo Geant4 code in proton treatment planning. The hadron therapy simulation is rewritten to parallelize the shared memory multiprocessor systems by using the Message-Passing Interface (MPI). The speedup performance of the code has been studied by using two MPI-compliant libraries including Open MPI and the MPICH2, separately. Despite the speedup, the results are almost linear for both the Open MPI and MPICH2; the latter was chosen because of its better characteristics and lower computation time. The Geant4 parameters, including the step limiter and the set cut, have been analyzed to minimize the simulation time as much as possible. For a reasonable compromise between the spatial dose distribution and the calculation time, the improvement in time reduction coefficient reaches about 157.
Bednarz, Bryan; Xu, X George
2009-02-21
There is a serious and growing concern about the increased risk of radiation-induced second cancers and late tissue injuries associated with radiation treatment. To better understand and to more accurately quantify non-target organ doses due to scatter and leakage radiation from medical accelerators, a detailed Monte Carlo model of the medical linear accelerator is needed. This paper describes the development and validation of a detailed accelerator model of the Varian Clinac operating at 6 and 18 MV beam energies. Over 100 accelerator components have been defined and integrated using the Monte Carlo code MCNPX. A series of in-field and out-of-field dose validation studies were performed. In-field dose distributions calculated using the accelerator models were tuned to match measurement data that are considered the de facto 'gold standard' for the Varian Clinac accelerator provided by the manufacturer. Field sizes of 4 cm x 4 cm, 10 cm x 10 cm, 20 cm x 20 cm and 40 cm x 40 cm were considered. The local difference between calculated and measured dose on the percent depth dose curve was less than 2% for all locations. The local difference between calculated and measured dose on the dose profile curve was less than 2% in the plateau region and less than 2 mm in the penumbra region for all locations. Out-of-field dose profiles were calculated and compared to measurement data for both beam energies for field sizes of 4 cm x 4 cm, 10 cm x 10 cm and 20 cm x 20 cm. For all field sizes considered in this study, the average local difference between calculated and measured dose for the 6 and 18 MV beams was 14 and 16%, respectively. In addition, a method for determining neutron contamination in the 18 MV operating model was validated by comparing calculated in-air neutron fluence with reported calculations and measurements. The average difference between calculated and measured neutron fluence was 20%. As one of the most detailed accelerator models for both in-field and out
SU-E-T-496: A Study of Two Commercial Dose Calculation Algorithms in Low Density Phantom
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Lim, S; Lovelock, D; Yorke, E; Kuo, L; LoSasso, T [Memorial Sloan- Kettering Cancer Center, NY, NY (United States)
2014-06-01
Purpose: Some lung cancer patients have very low lung density due to comorbidities. We investigate calculation accuracy of Eclipse AAA and Acuros(AXB) using a phantom that simulates this situation. Methods: A 2.5 x 5.0 x 5 cm (long) solid water inhomogeneity positioned 10 cm deep in a Balsa lung phantom (density 0.099 gm/cc) was irradiated with an off-center field such that the central axis was parallel to one side of the inhomogeneity. Radiochromic films were placed at 2.5cm(S1) and 5cm(S2) depths. After CT scanning, Hounsfield Units(HU) were converted to electron(ρe) and mass(ρm) density using in-house(IH) and vendor-supplied(V) calibration curves. IH electron densities were generated using a commercial electron density phantom. The phantom was exposed to 6 MV 3x3 and 20x20 fields. Dose distributions were calculated using the AAA and AXB algorithms. Results: The HU of BW is -910±40 which translates to ρe of 0.088±0.050(IH) and 0.090±0.050(V), and ρm of 0.101±0.045(IH) and 0.103±0.039(V). Both ρe(V) and ρm(V) are higher than ρe(IH) and ρm(IH) respectively by 1.4-5.3% and 0.5-12.3%. The average calculated dose inside the solid water ‘tumor’ are within 3.7% and 2.4% of measurements for both calibrations and field sizes using AAA and AXB. Within 10mm outside the ‘tumor’, AAA on average underestimates by 18.3% and 17.0% respectively for 3x3 using IH and V. AXB underestimates by 5.9%(S1)-6.6%(S2) and 13.1%(S1)-16.0%(S2) respectively using IH and V. For 20x20, AAA and AXB underestimate by 2.8%(S1)-4.4%(S2) and 0.3%(S1)-1.4%(S2) respectively with either calibration. Conclusion: The difference in the HU calibration between V and IH is not of clinical significance in normal field sizes. In the low density region of small fields, the calculations from both algorithms differ significantly from measurements. This may be attributed to the insufficient lateral electron transport modeled by two algorithms resulting in the over-estimation in penumbra
Behrens, R
2013-07-01
In this work, conversion coefficients from electron fluence to absorbed dose to the eye lens were calculated using Monte Carlo simulations based on a detailed stylised eye model and a very simple but whole body phantom. These data supersede and complement data published earlier based on the simulation of only a single stylised eye. The new data differ from the old ones by not more than 3, 4, 7 and 16 % for angles of radiation incidence of α=0°, 15°, 30° and 45°, respectively, due to the inclusion of the whole body phantom. The data presented in the present work also complement those of a recent report of the International Commission on Radiological Protection (ICRP) (ICRP Publication 116), where conversion coefficients from electron fluence to absorbed dose to the lens of the eye are shown for solely 0°, 180° and isotropic radiation incidence (but for a much broader range of energies). In this article, values are provided for angles of incidence of 0° up to 180° in steps of 15° and for rotational geometry; no systematic deviation was observed from the values given in ICRP Publication 116 for 0° (based on the application of a bare eye) and 180° (based on the application of a voxel whole body phantom). Data are given for monoenergetic electrons from 0.1 up to 10 MeV and for a broad parallel beam geometry in vacuum.
Dose-response effects of lycopene on selected drug-metabolizing and antioxidant enzymes in the rat
DEFF Research Database (Denmark)
Breinholt, V.; Lauridsen, S. T.; Daneshvar, B.
2000-01-01
The administration of lycopene to female rats at doses ranging from 0.001 to 0.1 g/kg b.w, per day for 2 weeks was found to alter the drug-metabolizing capacity and antioxidant status of the exposed animals. An investigation of four cytochrome P450-dependent enzymes revealed that benzyloxyresoruf...
van Maarseveen, Erik M; Sprij, Arwen; Touw, Daniel J
2016-01-01
BACKGROUND Current gentamicin dosing algorithms in adult populations target a high peak concentration (Cmax) assuring efficacy and a drug-free period (concentration 8 mg·L and estimated trough concentrations 8 mg·L with a Cmin value
van Maarseveen, Erik M.; Sprij, Arwen; Touw, Daniel J.
2016-01-01
Background:Current gentamicin dosing algorithms in adult populations target a high peak concentration (C-max) assuring efficacy and a drug-free period (concentration 8 mgL(-1) and estimated trough concentrations 8 mgL(-1) with a C-min value
Indian Academy of Sciences (India)
R MORSY
2016-09-01
This study was designed to develop innovative degradable hydroxyapatite (HAp)-based systems working as potential carriers for low-dose drugs. The HAp-based systems combine three components: HAp, sodium silicate and citric acid (HSC), which together could exhibit optimal characteristics as drug carriers. Both synthetic HAp (s-HAp) and extracted biological HAp (b-HAp) were used as sources of HAp due to their optimal biological properties and adsorption capacity. The s-HAp powder was prepared by co-precipitation method, while the b-HAp powder was extracted from bovine bone. Aqueous drug solutions of the atenolol, antihypertensive drug, were used as a model drug to investigate the drug release behaviour from HSC composites. The properties of s-HAP, b-HAp powders and HSC composite tablets were characterized by conventional methods. The results revealed that both s-HAp and b-HAp are pure powders and exhibited agglomerated microstructures with grain sizes less than 100 $\\mu$m. The HSC composite tablets exhibited a dense structure, excellent compressive strength and excellent in-vitro release behaviour of atenolol. The results indicated that HAp powders and their composite tablets can be promised as economic raw materials and carriers for low-dose drugs.
Preskorn, Sheldon H
2010-05-01
This column continues the discussion of outliers on the dose-response curve begun in earlier columns. It focuses on therapeutic drug monitoring (TDM) as an underutilized tool in psychiatry to minimize this problem. The scientific rationale for dose adjustment based on TDM is presented and its efficiency is contrasted with dose adjustment based on clinical assessment of response. In current practice, the use of TDM with psychiatric drugs is generally restricted to drugs with narrow therapeutic windows or drugs imported into psychiatry from neurology where TDM is more commonly used. Examples of each of these types of drugs are cited.
DEFF Research Database (Denmark)
Eriksson, Robert; Werge, Thomas; Jensen, Lars Juhl
2014-01-01
all indication areas.The aim of this study was to take advantage of techniques for temporal data mining of EPRs in order to detect ADRs in a patient- and dose-specific manner.We used a psychiatric hospital’s EPR system to investigate undesired drug effects. Within one workflow the method identified...... patient-specific adverse events (AEs) and links these to specific drugs and dosages in a temporal manner, based on integration of text mining results and structured data. The structured data contained precise information on drug identity, dosage and strength.When applying the method to the 3,394 patients......Data collected for medical, filing and administrative purposes in electronic patient records (EPRs) represent a rich source of individualised clinical data, which has great potential for improved detection of patients experiencing adverse drug reactions (ADRs), across all approved drugs and across...
Institute of Scientific and Technical Information of China (English)
Sayaka Nakashima; Shinichi Ota; Shin Arai; Kiyoko Yoshino; Mie Inao; Keiko Ishikawa; Nobuaki Nakayama; Yukinori Imai; Sumiko Nagoshi; Satoshi Mochida
2009-01-01
AIM: To investigate the usefulness of anti-ulcer drugs for the prevention and treatment of low-dose aspirininduced peptic ulcer. METHODS: Upper gastrointestinal endoscopy was performed in 68 patients receiving daily low-dose aspirin (81 or 100 mg/day). The endoscopic findings were classified according to the Lanza score, and the scores were compared between groups categorized according to the concomitant use of anti-ulcer drugs and the types of drugs used. In another study, 31 hemorrhagic peptic ulcer patients who had been receiving low-dose aspirin were enrolled. The patients were randomly classified into the proton pump inhibitor (PPI)-treated group and the H2 receptor antagonist (H2RA)-treated group. The administration of low-dose aspirin was continued concomitantly, and endoscopic examinations were performed 8 wk later. ``RESULTS: The Lanza scores (mean ± SD) of the gastro-mucosal lesions were 1.0 ± 1.9 and 1.9 ± 2.3 in 8 and 16 patients receiving prevention therapy with a PPI and an H2RA, respectively. Both scores were significantly smaller than the scores in 34 patients who were not receiving prevention therapy (4.7 ± 1.0) and in 10 patients receiving cytoprotective anti-ulcer drugs (4.3 ± 1.6). In the prospective study, 18 and 13 patients received a PPI and an H2RA, respectively. Endoscopic examinations revealed that the tissue in the region of the gastro-mucosal lesions had reverted to normal in all patients in the PPI-treated group and in 12 patients (92%) in the H2RA-treated group; no significant differences were observed between the groups. CONCLUSION: H2RA therapy was effective for both the prevention and treatment of low-dose aspirininduced peptic ulcer, similar to the effects of PPIs, while cytoprotective anti-ulcer drugs were ineffective in preventing ulceration.
Mikell, Justin; Cheenu Kappadath, S; Wareing, Todd; Erwin, William D; Titt, Uwe; Mourtada, Firas
2016-06-21
To evaluate the 3D Grid-based Boltzmann Solver (GBBS) code ATTILA (®) for coupled electron and photon transport in the nuclear medicine energy regime for electron (beta, Auger and internal conversion electrons) and photon (gamma, x-ray) sources. Codes rewritten based on ATTILA are used clinically for both high-energy photon teletherapy and (192)Ir sealed source brachytherapy; little information exists for using the GBBS to calculate voxel-level absorbed doses in nuclear medicine. We compared DOSXYZnrc Monte Carlo (MC) with published voxel-S-values to establish MC as truth. GBBS was investigated for mono-energetic 1.0, 0.1, and 0.01 MeV electron and photon sources as well as (131)I and (90)Y radionuclides. We investigated convergence of GBBS by analyzing different meshes ([Formula: see text]), energy group structures ([Formula: see text]) for each radionuclide component, angular quadrature orders ([Formula: see text], and scattering order expansions ([Formula: see text]-[Formula: see text]); higher indices imply finer discretization. We compared GBBS to MC in (1) voxel-S-value geometry for soft tissue, lung, and bone, and (2) a source at the interface between combinations of lung, soft tissue, and bone. Excluding Auger and conversion electrons, MC agreed within ≈5% of published source voxel absorbed doses. For the finest discretization, most GBBS absorbed doses in the source voxel changed by less than 1% compared to the next finest discretization along each phase space variable indicating sufficient convergence. For the finest discretization, agreement with MC in the source voxel ranged from -3% to -20% with larger differences at lower energies (-3% for 1 MeV electron in lung to -20% for 0.01 MeV photon in bone); similar agreement was found for the interface geometries. Differences between GBBS and MC in the source voxel for (90)Y and (131)I were -6%. The GBBS ATTILA was benchmarked against MC in the nuclear medicine regime. GBBS can be a
Mikell, Justin; Cheenu Kappadath, S.; Wareing, Todd; Erwin, William D.; Titt, Uwe; Mourtada, Firas
2016-06-01
To evaluate the 3D Grid-based Boltzmann Solver (GBBS) code ATTILA ® for coupled electron and photon transport in the nuclear medicine energy regime for electron (beta, Auger and internal conversion electrons) and photon (gamma, x-ray) sources. Codes rewritten based on ATTILA are used clinically for both high-energy photon teletherapy and 192Ir sealed source brachytherapy; little information exists for using the GBBS to calculate voxel-level absorbed doses in nuclear medicine. We compared DOSXYZnrc Monte Carlo (MC) with published voxel-S-values to establish MC as truth. GBBS was investigated for mono-energetic 1.0, 0.1, and 0.01 MeV electron and photon sources as well as 131I and 90Y radionuclides. We investigated convergence of GBBS by analyzing different meshes ({{M}0},{{M}1},{{M}2} ), energy group structures ({{E}0},{{E}1},{{E}2} ) for each radionuclide component, angular quadrature orders (≤ft. {{S}4},{{S}8},{{S}16}\\right) , and scattering order expansions ({{P}0} -{{P}6} ); higher indices imply finer discretization. We compared GBBS to MC in (1) voxel-S-value geometry for soft tissue, lung, and bone, and (2) a source at the interface between combinations of lung, soft tissue, and bone. Excluding Auger and conversion electrons, MC agreed within ≈5% of published source voxel absorbed doses. For the finest discretization, most GBBS absorbed doses in the source voxel changed by less than 1% compared to the next finest discretization along each phase space variable indicating sufficient convergence. For the finest discretization, agreement with MC in the source voxel ranged from -3% to -20% with larger differences at lower energies (-3% for 1 MeV electron in lung to -20% for 0.01 MeV photon in bone); similar agreement was found for the interface geometries. Differences between GBBS and MC in the source voxel for 90Y and 131I were -6%. The GBBS ATTILA was benchmarked against MC in the nuclear medicine regime. GBBS can be a viable
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Salvado, M.; Hernandez-Giron, I.; Morant, J. J.; Casanova, R.; Lopez, M.; Calzada, A.
2011-07-01
The optimization of the dose given in radiology scans, one of the three fundamental principles of radiation protection implies sufficiently precise knowledge of the dose distribution in organs with weighting factor for the calculation of effective dose in patients.
Sun, Baozhou; Rangaraj, Dharanipathy; Boddu, Sunita; Goddu, Murty; Yang, Deshan; Palaniswaamy, Geethpriya; Yaddanapudi, Sridhar; Wooten, Omar; Mutic, Sasa
2012-09-06
Experimental methods are commonly used for patient-specific IMRT delivery verification. There are a variety of IMRT QA techniques which have been proposed and clinically used with a common understanding that not one single method can detect all possible errors. The aim of this work was to compare the efficiency and effectiveness of independent dose calculation followed by machine log file analysis to conventional measurement-based methods in detecting errors in IMRT delivery. Sixteen IMRT treatment plans (5 head-and-neck, 3 rectum, 3 breast, and 5 prostate plans) created with a commercial treatment planning system (TPS) were recalculated on a QA phantom. All treatment plans underwent ion chamber (IC) and 2D diode array measurements. The same set of plans was also recomputed with another commercial treatment planning system and the two sets of calculations were compared. The deviations between dosimetric measurements and independent dose calculation were evaluated. The comparisons included evaluations of DVHs and point doses calculated by the two TPS systems. Machine log files were captured during pretreatment composite point dose measurements and analyzed to verify data transfer and performance of the delivery machine. Average deviation between IC measurements and point dose calculations with the two TPSs for head-and-neck plans were 1.2 ± 1.3% and 1.4 ± 1.6%, respectively. For 2D diode array measurements, the mean gamma value with 3% dose difference and 3 mm distance-to-agreement was within 1.5% for 13 of 16 plans. The mean 3D dose differences calculated from two TPSs were within 3% for head-and-neck cases and within 2% for other plans. The machine log file analysis showed that the gantry angle, jaw position, collimator angle, and MUs were consistent as planned, and maximal MLC position error was less than 0.5 mm. The independent dose calculation followed by the machine log analysis takes an average 47 ± 6 minutes, while the experimental approach (using IC and
Estrada, J
1994-01-01
Direct measurement of the absolved dose to lung tissue from inhalation of radon and its progeny is not possible and must be calculated using dosimetric models, taking into consideration the several parameters upon which the dose calculation depends. To asses the dose due to inhalation of radon and its progeny, it is necessary to estimate the cumulative exposure. Historically, this has been done using WLM values estimated with measurements of radon concentration in air. The radon concentration in air varies significantly, however, in space with time, and the exposed individual is also constantly moving around. This makes it almost impossible to obtain a precise estimate of an individual's inhalation exposure. This work describes a pilot study to calculate lung dose from the deposition of radon progeny, via estimates of cumulative exposure derived from in vivo measurements of sup 2 sup 1 sup 0 Pb, in subjects exposed to above-average radon and its progeny concentrations in their home environments. The measureme...
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Silvia Vogl
Full Text Available Currently, genotyping of patients for polymorphic enzymes responsible for metabolic elimination is considered a possibility to adjust drug dose levels. For a patient to profit from this procedure, the interindividual differences in drug metabolism within one genotype should be smaller than those between different genotypes. We studied a large cohort of healthy young adults (283 subjects, correlating their CYP2C9 genotype to a simple phenotyping metric, using flurbiprofen as probe drug. Genotyping was conducted for CYP2C9*1, *2, *3. The urinary metabolic ratio MR (concentration of CYP2C9-dependent metabolite divided by concentration of flurbiprofen determined two hours after flurbiprofen (8.75 mg administration served as phenotyping metric. Linear statistical models correlating genotype and phenotype provided highly significant allele-specific MR estimates of 0.596 for the wild type allele CYP2C9*1, 0.405 for CYP2C9*2 (68 % of wild type, and 0.113 for CYP2C9*3 (19 % of wild type. If these estimates were used for flurbiprofen dose adjustment, taking 100 % for genotype *1/*1, an average reduction to 84 %, 60 %, 68 %, 43 %, and 19 % would result for genotype *1/*2, *1/*3, *2/*2, *2/*3, and *3/*3, respectively. Due to the large individual variation within genotypes with coefficients of variation ≥ 20 % and supposing the normal distribution, one in three individuals would be out of the average optimum dose by more than 20 %, one in 20 would be 40 % off. Whether this problem also applies to other CYPs and other drugs has to be investigated case by case. Our data for the given example, however, puts the benefit of individual drug dosing to question, if it is exclusively based on genotype.
Vogl, Silvia; Lutz, Roman W; Schönfelder, Gilbert; Lutz, Werner K
2015-01-01
Currently, genotyping of patients for polymorphic enzymes responsible for metabolic elimination is considered a possibility to adjust drug dose levels. For a patient to profit from this procedure, the interindividual differences in drug metabolism within one genotype should be smaller than those between different genotypes. We studied a large cohort of healthy young adults (283 subjects), correlating their CYP2C9 genotype to a simple phenotyping metric, using flurbiprofen as probe drug. Genotyping was conducted for CYP2C9*1, *2, *3. The urinary metabolic ratio MR (concentration of CYP2C9-dependent metabolite divided by concentration of flurbiprofen) dete