Low-Dose Radioactive Iodine Destroys Thyroid Tissue Left after Surgery

Science.gov (United States)

A low dose of radioactive iodine given after surgery for thyroid cancer destroyed (ablated) residual thyroid tissue as effectively as a higher dose, with fewer side effects and less exposure to radiation, according to two randomized controlled trials.

Effect of low-density lateral interfaces on soft-tissue doses

International Nuclear Information System (INIS)

Hunt, Margie A.; Desobry, Gregory E.; Fowble, Barbara; Coia, Lawrence R.

1997-01-01

Purpose: Doses at the interface between tissue and low-density inhomogeneities with the interface positioned perpendicular to the beam direction have been well studied. When the inhomogeneity lies parallel to the beam direction (i.e., a lateral interface), the resulting dose distribution is not as well known. Lateral lung--soft-tissue interfaces are common in many fields used to treat malignancies in the thorax region including tangential breast fields and anteroposterior fields for lung and esophageal cancer. The purpose of this study was to evaluate the dose distribution along lateral interfaces and to determine the implications for treatment. Methods and Materials: A polystyrene and cork slab phantom was irradiated from the side to simulate treatment fields with lateral lung--soft-tissue interfaces. The beam was positioned with the isocenter in polystyrene and the field edge in cork. Cork slabs (0.6-2.5 cm) were used to simulate different thicknesses of lung between the field edge and the target volume. Measurements were made using a parallel plate ionization chamber. With the chamber position held constant, polystyrene slabs were added between the cork and the chamber to study the dose distribution in the interface region. Interface doses were studied as a function of the amount of cork in the field, field size, beam energy (6-18 MV), and depth. Results: Doses in the interface region were lower by as much as 10% compared to doses in a homogeneous phantom. For a given cork width and field size, the magnitude of the underdose increased by several percent as the x-ray energy increased from 6 to 18 MV. The underdose at the interface was 5% for 6 MV and 8% for 18 MV X-rays with a 1-cm cork width. For a 2.5-cm cork width, underdoses of 2.5% and 3% at distances up to 2.5 and 4 mm lateral to the interface were observed for 6- and 18-MV X-rays, respectively. However, doses right at the interface were 1% greater for 6 MV and 3% less for 18 MV than doses in a homogeneous

Present dose limits and their relation to radiosensitivity of different organs and tissues

International Nuclear Information System (INIS)

Anon.

1987-01-01

Dose equivalent limits in relation to dose thresholds are considered for injury of various tissues and organs to evaluate the protection agains non-stochastic irradiation effects by the existing system of dose limitation for radiotherapeutic personnel. Data on tissue radiosensitivity in relation to non-stochastic effects, obtained from radiotherapeutic experience, are presented. Dose threshold values, derived for patients, with a correction in the direction of increase, may be applied to conditions of occupational exposure except for bone marrow, gonads and eye lens, where threshold doses are lower

Photon beam dose distributions for patients with implanted temporary tissue expanders

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Asena, A.; Kairn, T.; Crowe, S. B.; Trapp, J. V.

2015-01-01

This study examines the effects of temporary tissue expanders (TTEs) on the dose distributions of photon beams in breast cancer radiotherapy treatments. EBT2 radiochromic film and ion chamber measurements were taken to quantify the attenuation and backscatter effects of the inhomogeneity. Results illustrate that the internal magnetic port present in a tissue expander causes a dose reduction of approximately 25% in photon tangent fields immediately downstream of the implant. It was also shown that the silicone elastomer shell of the tissue expander reduced the dose to the target volume by as much as 8%. This work demonstrates the importance for an accurately modelled high-density implant in the treatment planning system for post-mastectomy breast cancer patients.

Low dose X -ray effects on catalase activity in animal tissue

Science.gov (United States)

Focea, R.; Nadejde, C.; Creanga, D.; Luchian, T.

2012-12-01

This study was intended to investigate the effect of low-dose X ray-irradiation upon the activity of catalase (CAT) in freshly excised chicken tissues (liver, kidney, brain, muscle). The tissue samples were irradiated with 0.5Gy and 2Gy respectively, in a 6 MV photon beam produced by a clinical linear accelerator (VARIAN CLINAC 2100SC). The dose rate was of 260.88cGy/min. at 100 cm source to sample distance. The catalase level was assayed spectrophotometrically, based on reaction kinetics, using a catalase UV assay kit (SIGMA). Catalase increased activity in various tissue samples exposed to the studied X ray doses (for example with 24 % in the liver cells, pbonds that ensure the specificity of CAT active site) but the resulted balance of the two concurrent processes indicates the cell ability of decomposing the hydrogen peroxide-with benefits for the cell physiology restoration for the chosen low dose radiation.

Dose distribution around ion track in tissue equivalent material

International Nuclear Information System (INIS)

Zhang Wenzhong; Guo Yong; Luo Yisheng

2007-01-01

Objective: To study the energy deposition micro-specialty of ions in body-tissue or tissue equivalent material (TEM). Methods: The water vapor was determined as the tissue equivalent material, based on the analysis to the body-tissue, and Monte Carlo method was used to simulate the behavior of proton in the tissue equivalent material. Some features of the energy deposition micro-specialty of ion in tissue equivalent material were obtained through the analysis to the data from calculation. Results: The ion will give the energy by the way of excitation and ionization in material, then the secondary electrons will be generated in the progress of ionization, these electron will finished ions energy deposition progress. When ions deposited their energy, large amount energy will be in the core of tracks, and secondary electrons will devote its' energy around ion track, the ion dose distribution is then formed in TEM. Conclusions: To know biological effects of radiation , the research to dose distribution of ions is of importance(significance). (authors)

The difference of scoring dose to water or tissues in Monte Carlo dose calculations for low energy brachytherapy photon sources.

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Landry, Guillaume; Reniers, Brigitte; Pignol, Jean-Philippe; Beaulieu, Luc; Verhaegen, Frank

2011-03-01

The goal of this work is to compare D(m,m) (radiation transported in medium; dose scored in medium) and D(w,m) (radiation transported in medium; dose scored in water) obtained from Monte Carlo (MC) simulations for a subset of human tissues of interest in low energy photon brachytherapy. Using low dose rate seeds and an electronic brachytherapy source (EBS), the authors quantify the large cavity theory conversion factors required. The authors also assess whether ap plying large cavity theory utilizing the sources' initial photon spectra and average photon energy induces errors related to spatial spectral variations. First, ideal spherical geometries were investigated, followed by clinical brachytherapy LDR seed implants for breast and prostate cancer patients. Two types of dose calculations are performed with the GEANT4 MC code. (1) For several human tissues, dose profiles are obtained in spherical geometries centered on four types of low energy brachytherapy sources: 125I, 103Pd, and 131Cs seeds, as well as an EBS operating at 50 kV. Ratios of D(w,m) over D(m,m) are evaluated in the 0-6 cm range. In addition to mean tissue composition, compositions corresponding to one standard deviation from the mean are also studied. (2) Four clinical breast (using 103Pd) and prostate (using 125I) brachytherapy seed implants are considered. MC dose calculations are performed based on postimplant CT scans using prostate and breast tissue compositions. PTV D90 values are compared for D(w,m) and D(m,m). (1) Differences (D(w,m)/D(m,m)-1) of -3% to 70% are observed for the investigated tissues. For a given tissue, D(w,m)/D(m,m) is similar for all sources within 4% and does not vary more than 2% with distance due to very moderate spectral shifts. Variations of tissue composition about the assumed mean composition influence the conversion factors up to 38%. (2) The ratio of D90(w,m) over D90(m,m) for clinical implants matches D(w,m)/D(m,m) at 1 cm from the single point sources, Given

Changes in dose with segmentation of breast tissues in Monte Carlo calculations for low-energy brachytherapy

International Nuclear Information System (INIS)

Sutherland, J. G. H.; Thomson, R. M.; Rogers, D. W. O.

2011-01-01

Purpose: To investigate the use of various breast tissue segmentation models in Monte Carlo dose calculations for low-energy brachytherapy. Methods: The EGSnrc user-code BrachyDose is used to perform Monte Carlo simulations of a breast brachytherapy treatment using TheraSeed Pd-103 seeds with various breast tissue segmentation models. Models used include a phantom where voxels are randomly assigned to be gland or adipose (randomly segmented), a phantom where a single tissue of averaged gland and adipose is present (averaged tissue), and a realistically segmented phantom created from previously published numerical phantoms. Radiation transport in averaged tissue while scoring in gland along with other combinations is investigated. The inclusion of calcifications in the breast is also studied in averaged tissue and randomly segmented phantoms. Results: In randomly segmented and averaged tissue phantoms, the photon energy fluence is approximately the same; however, differences occur in the dose volume histograms (DVHs) as a result of scoring in the different tissues (gland and adipose versus averaged tissue), whose mass energy absorption coefficients differ by 30%. A realistically segmented phantom is shown to significantly change the photon energy fluence compared to that in averaged tissue or randomly segmented phantoms. Despite this, resulting DVHs for the entire treatment volume agree reasonably because fluence differences are compensated by dose scoring differences. DVHs for the dose to only the gland voxels in a realistically segmented phantom do not agree with those for dose to gland in an averaged tissue phantom. Calcifications affect photon energy fluence to such a degree that the differences in fluence are not compensated for (as they are in the no calcification case) by dose scoring in averaged tissue phantoms. Conclusions: For low-energy brachytherapy, if photon transport and dose scoring both occur in an averaged tissue, the resulting DVH for the entire

Changes in dose with segmentation of breast tissues in Monte Carlo calculations for low-energy brachytherapy

Energy Technology Data Exchange (ETDEWEB)

Sutherland, J. G. H.; Thomson, R. M.; Rogers, D. W. O. [Carleton Laboratory for Radiotherapy Physics, Department of Physics, Carleton University, Ottawa K1S 5B6 (Canada)

2011-08-15

Purpose: To investigate the use of various breast tissue segmentation models in Monte Carlo dose calculations for low-energy brachytherapy. Methods: The EGSnrc user-code BrachyDose is used to perform Monte Carlo simulations of a breast brachytherapy treatment using TheraSeed Pd-103 seeds with various breast tissue segmentation models. Models used include a phantom where voxels are randomly assigned to be gland or adipose (randomly segmented), a phantom where a single tissue of averaged gland and adipose is present (averaged tissue), and a realistically segmented phantom created from previously published numerical phantoms. Radiation transport in averaged tissue while scoring in gland along with other combinations is investigated. The inclusion of calcifications in the breast is also studied in averaged tissue and randomly segmented phantoms. Results: In randomly segmented and averaged tissue phantoms, the photon energy fluence is approximately the same; however, differences occur in the dose volume histograms (DVHs) as a result of scoring in the different tissues (gland and adipose versus averaged tissue), whose mass energy absorption coefficients differ by 30%. A realistically segmented phantom is shown to significantly change the photon energy fluence compared to that in averaged tissue or randomly segmented phantoms. Despite this, resulting DVHs for the entire treatment volume agree reasonably because fluence differences are compensated by dose scoring differences. DVHs for the dose to only the gland voxels in a realistically segmented phantom do not agree with those for dose to gland in an averaged tissue phantom. Calcifications affect photon energy fluence to such a degree that the differences in fluence are not compensated for (as they are in the no calcification case) by dose scoring in averaged tissue phantoms. Conclusions: For low-energy brachytherapy, if photon transport and dose scoring both occur in an averaged tissue, the resulting DVH for the entire

Comparison of half-dose and full-dose gadolinium MR contrast on the enhancement of bone and soft tissue tumors

Energy Technology Data Exchange (ETDEWEB)

Costelloe, Colleen M. [University of Texas M. D. Anderson Cancer Center, Department of Diagnostic Radiology, Houston, Texas (United States); University of Texas M. D. Anderson Cancer Center, Houston, Texas (United States); Murphy, William A.; Haygood, Tamara M.; Kumar, Rajendra; McEnery, Kevin W.; Madewell, John E. [University of Texas M. D. Anderson Cancer Center, Department of Diagnostic Radiology, Houston, Texas (United States); Stafford, R.J. [University of Texas M. D. Anderson Cancer Center, Department of Imaging Physics, Houston, Texas (United States); Roy, Anjali [Cancer Treatment Centers of America Medical Diagnostic Imaging Group, Arizona (United States); Bassett, Roland L.; Harrell, Robyn K. [University of Texas M. D. Anderson Cancer Center, Department of Biostatistics, Houston, Texas (United States)

2011-03-15

To evaluate the effect of half-dose intravenous gadolinium contrast on the enhancement of bone and soft tissue tumors. This study is HIPAA compliant and informed consent was waived by the institutional review board. An institutional database search was performed over a 1-year period for patients with full- and half-dose MR examinations performed for musculoskeletal oncologic indications. Examination pairs that were identical with regard to field strength and presence or absence of fat saturation were included, resulting in 29 paired examinations. When multiple, the lesion that was best delineated and enhanced well on the first examination in the pair was chosen, yielding 17 bone and 12 soft tissue. Five musculoskeletal radiologists blinded to dosages were asked to assess for a difference in enhancement when comparing the lesion on both examinations and to rate the degree of difference on a three-point scale. They were also asked to identify the examination on which the lesion enhanced less (tallied as low dose). Results were analyzed with the exact binomial test. The readers perceived an enhancement difference in 41% (59/145) of studies (p = 0.03) and the majority were rated as ''mild'' (66%, 39/59). The readers did not accurately identify the low-dose examinations (54% correctly identified, 32/59, p = 0.60). Half-dose gadolinium enhancement of lesions could not be accurately distinguished from full-dose enhancement upon review of the same lesion imaged at both concentrations. (orig.)

Low dose X –ray effects on catalase activity in animal tissue

International Nuclear Information System (INIS)

Focea, R; Nadejde, C; Creanga, D; Luchian, T

2012-01-01

This study was intended to investigate the effect of low-dose X ray-irradiation upon the activity of catalase (CAT) in freshly excised chicken tissues (liver, kidney, brain, muscle). The tissue samples were irradiated with 0.5Gy and 2Gy respectively, in a 6 MV photon beam produced by a clinical linear accelerator (VARIAN CLINAC 2100SC). The dose rate was of 260.88cGy/min. at 100 cm source to sample distance. The catalase level was assayed spectrophotometrically, based on reaction kinetics, using a catalase UV assay kit (SIGMA). Catalase increased activity in various tissue samples exposed to the studied X ray doses (for example with 24 % in the liver cells, p<0.05) suggested the stimulation of the antioxidant enzyme biosynthesis within several hours after exposure at doses of 0.5 Gy and 2 Gy; the putative enzyme inactivation could also occur (due to the injuries on the hydrogen bonds that ensure the specificity of CAT active site) but the resulted balance of the two concurrent processes indicates the cell ability of decomposing the hydrogen peroxide-with benefits for the cell physiology restoration for the chosen low dose radiation.

Determination of dose equivalent with tissue-equivalent proportional counters

International Nuclear Information System (INIS)

Dietze, G.; Schuhmacher, H.; Menzel, H.G.

1989-01-01

Low pressure tissue-equivalent proportional counters (TEPC) are instruments based on the cavity chamber principle and provide spectral information on the energy loss of single charged particles crossing the cavity. Hence such detectors measure absorbed dose or kerma and are able to provide estimates on radiation quality. During recent years TEPC based instruments have been developed for radiation protection applications in photon and neutron fields. This was mainly based on the expectation that the energy dependence of their dose equivalent response is smaller than that of other instruments in use. Recently, such instruments have been investigated by intercomparison measurements in various neutron and photon fields. Although their principles of measurements are more closely related to the definition of dose equivalent quantities than those of other existing dosemeters, there are distinct differences and limitations with respect to the irradiation geometry and the determination of the quality factor. The application of such instruments for measuring ambient dose equivalent is discussed. (author)

Determination of the tissue inhomogeneity correction in high dose rate Brachytherapy for Iridium-192 source

Directory of Open Access Journals (Sweden)

Barlanka Ravikumar

2012-01-01

Full Text Available In Brachytherapy treatment planning, the effects of tissue heterogeneities are commonly neglected due to lack of accurate, general and fast three-dimensional (3D dose-computational algorithms. In performing dose calculations, it is assumed that the tumor and surrounding tissues constitute a uniform, homogeneous medium equivalent to water. In the recent past, three-dimensional computed tomography (3D-CT based treatment planning for Brachytherapy applications has been popularly adopted. However, most of the current commercially available planning systems do not provide the heterogeneity corrections for Brachytherapy dosimetry. In the present study, we have measured and quantified the impact of inhomogeneity caused by different tissues with a 0.015 cc ion chamber. Measurements were carried out in wax phantom which was employed to measure the heterogeneity. Iridium-192 (192 Ir source from high dose rate (HDR Brachytherapy machine was used as the radiation source. The reduction of dose due to tissue inhomogeneity was measured as the ratio of dose measured with different types of inhomogeneity (bone, spleen, liver, muscle and lung to dose measured with homogeneous medium for different distances. It was observed that different tissues attenuate differently, with bone tissue showing maximum attenuation value and lung tissue resulting minimum value and rest of the tissues giving values lying in between those of bone and lung. It was also found that inhomogeneity at short distance is considerably more than that at larger distances.

MCNP Code in Assessment of Variations of Effective Dose with Torso Adipose Tissue Thickness

International Nuclear Information System (INIS)

Massoud, E.

2005-01-01

The effective dose is the unite used in the field of radiation protection. It is a well defined doubly weighted uantity involving both physical and biological variables. Several factors may induce variation in the effective dose in different individuals of similar exposure data. One of these factors is the variation of adipose tissue thickness in different exposed individuals. This study essentially concenrs the assessment of the possible variation in the effective dose due to variation in the thickness of adipose tissue. The study was done using MCNP4b code to perform mathematical model of the human body depending on that given to the reference man developed by International Commission of Radiological Protection (ICRP), and calculate the effective dose with different thicknessess of adipose tissues. The study includes a comprehensive appraisal of the Monte Cario simulation, the Medical Internal Radiation Dose (MIRD) model for the human body, and the various mathematical considerations involved in the radiation dose calculations for the various pertinent parts of the human body. The radiation energies considered were 80 KeV, 300 KeV and I MeV, applying two exposure positions; anteroposterior (AP), postero-anterior (PA) with different adipose tissue thickness. This study is a theoretical approach based on detailed mathematical calculations of great precision that deals with all considerations involved in the mechanisms of radiation energy absorption in biological system depending on the variation in the densities of the particular in biological system depending on the variation in the densities of the particular tissues. The results obtained indicate that maximum decrease in effective dose occures with the lowest energy at 5cm adipose tissues thickeness for both AP and PA exposure positions. The results obtained were compared to similar work previsouly done using MCNP4 b showing very good agreement

Estimate of the absorbed dose in the mouse organs and tissues after tritium administration

International Nuclear Information System (INIS)

Saito, Masahiro

2000-01-01

Chronic and accidental release of tritium from future fusion facilities may cause some extent of hazardous effect to the public health. Various experiments using small animals such as mice have been performed to mimic the dose accumulation due to tritium intake by the human body. An difficulty in such animal experiments using small animals is that it is rather difficult to administer tritium orally and estimate the dose to small organs or tissues. In the course of our study, a simple method to administer THO and T-labeled amino acids orally to the mouse was dictated and dose accumulation in various organs and tissues was determined. The tritium retention in the bone marrow was also determined using the micro-centrifuge method. Throughout our experiment, colony-bred DDY mice were used. The 8-10 week old male mice were orally and intraperitoneally administered THO water or T-amino acids mixture solution. For the purpose of oral administration, a 10 μl aliquot of T-containing saline solution was placed on the tongue of the mice using an automatic micropipette. At various times after tritium administration, the animals were sacrificed and the amount of tritium in various tissues and organs including bone marrow was examined. Dose accumulation pattern after THO intake and T-amino acids was compared between intraperitoneal injection and oral administration. The accumulated dose after oral administration of THO exhibited a tendency to be 10-20% higher than after intraperitoneal injection. The bone marrow dose after oral intake of THO was found to be lower than the doses to urine, blood, liver and testis. In contrast, the blood dose gave a conservative estimate for the dose to the other tissues and organs. (author)

Fractionation in normal tissues: the (α/β)eff concept can account for dose heterogeneity and volume effects.

Science.gov (United States)

Hoffmann, Aswin L; Nahum, Alan E

2013-10-07

The simple Linear-Quadratic (LQ)-based Withers iso-effect formula (WIF) is widely used in external-beam radiotherapy to derive a new tumour dose prescription such that there is normal-tissue (NT) iso-effect when changing the fraction size and/or number. However, as conventionally applied, the WIF is invalid unless the normal-tissue response is solely determined by the tumour dose. We propose a generalized WIF (gWIF) which retains the tumour prescription dose, but replaces the intrinsic fractionation sensitivity measure (α/β) by a new concept, the normal-tissue effective fractionation sensitivity, [Formula: see text], which takes into account both the dose heterogeneity in, and the volume effect of, the late-responding normal-tissue in question. Closed-form analytical expressions for [Formula: see text] ensuring exact normal-tissue iso-effect are derived for: (i) uniform dose, and (ii) arbitrary dose distributions with volume-effect parameter n = 1 from the normal-tissue dose-volume histogram. For arbitrary dose distributions and arbitrary n, a numerical solution for [Formula: see text] exhibits a weak dependence on the number of fractions. As n is increased, [Formula: see text] increases from its intrinsic value at n = 0 (100% serial normal-tissue) to values close to or even exceeding the tumour (α/β) at n = 1 (100% parallel normal-tissue), with the highest values of [Formula: see text] corresponding to the most conformal dose distributions. Applications of this new concept to inverse planning and to highly conformal modalities are discussed, as is the effect of possible deviations from LQ behaviour at large fraction sizes.

Dose determination algorithms for a nearly tissue equivalent multi-element thermoluminescent dosimeter

International Nuclear Information System (INIS)

Moscovitch, M.; Chamberlain, J.; Velbeck, K.J.

1988-01-01

In a continuing effort to develop dosimetric systems that will enable reliable interpretation of dosimeter readings in terms of the absorbed dose or dose-equivalent, a new multi-element TL dosimeter assembly for Beta and Gamma dose monitoring has been designed. The radiation-sensitive volumes are four LiF-TLD elements, each covered by its own unique filter. For media-matching, care has been taken to employ nearly tissue equivalent filters of thicknesses of 1000 mg/cm 2 and 300 mg/cm 2 for deep dose and dose to the lens-of-the-eye measurements respectively. Only one metal filter (Cu) is employed to provide low energy photon discrimination. A Thin TL element (0.09 mm thick) is located behind an open window designed to improve the energy under-response to low energy beta rays and to provide closer estimate of the shallow dose equivalent. The deep and shallow dose equivalents are derived from the correlation of the response of the various TL elements to the above quantities through computations based on previously defined relationships obtained from experimental results. The theoretical formalization for the dose calculation algorithms is described in detail, and provides a useful methodology which can be applied to different tissue-equivalent dosimeter assemblies. Experimental data has been obtained by performing irradiation according to the specifications established by DOELAP, using 27 types of pure and mixed radiation fields including Cs-137 gamma rays, low energy photons down to 20 keV, Sr/Y-90, Uranium, and Tl-204 beta particles

Measurement of californium-252 gamma photons depth dose distribution in tissue equivalent material. Vol. 4

Energy Technology Data Exchange (ETDEWEB)

Fadel, M A; El-Fiki, M A; Eissa, H M; Abdel-Hafez, A; Naguib, S H [National Institute of Standards, Cairo (Egypt)

1996-03-01

Phantom of tissue equivalent material with and without bone was used measuring depth dose distribution of gamma-rays from californium-252 source. The source was positioned at center of perspex walled phantom. Depth dose measurements were recorded for X, Y and Z planes at different distances from source. TLD 700 was used for measuring the dose distribution. Results indicate that implantation of bone in tissue equivalent medium cause changes in the gamma depth dose distribution which varies according to variation in bone geometry. 9 figs.

Radiobiological aspects of continuous low dose-rate irradiation and fractionated high dose-rate irradiation

International Nuclear Information System (INIS)

Turesson, I.

1990-01-01

The biological effects of continuous low dose-rate irradiation and fractionated high dose-rate irradiation in interstitial and intracavitary radiotherapy and total body irradiation are discussed in terms of dose-rate fractionation sensitivity for various tissues. A scaling between dose-rate and fraction size was established for acute and late normal-tissue effects which can serve as a guideline for local treatment in the range of dose rates between 0.02 and 0.005 Gy/min and fraction sizes between 8.5 and 2.5 Gy. This is valid provided cell-cycle progression and proliferation can be ignored. Assuming that the acute and late tissue responses are characterized by α/β values of about 10 and 3 Gy and a mono-exponential repair half-time of about 3 h, the same total doses given with either of the two methods are approximately equivalent. The equivalence for acute and late non-hemopoietic normal tissue damage is 0.02 Gy/min and 8.5 Gy per fraction; 0.01 Gy/min and 5.5 Gy per fraction; and 0.005 Gy/min and 2.5Gy per fraction. A very low dose rate, below 0.005 Gy/min, is thus necessary to simulate high dose-rate radiotherapy with fraction sizes of about 2Gy. The scaling factor is, however, dependent on the repair half-time of the tissue. A review of published data on dose-rate effects for normal tissue response showed a significantly stronger dose-rate dependence for late than for acute effects below 0.02 Gy/min. There was no significant difference in dose-rate dependence between various acute non-hemopoietic effects or between various late effects. The consistent dose-rate dependence, which justifies the use of a general scaling factor between fraction size and dose rate, contrasts with the wide range of values for repair half-time calculated for various normal-tissue effects. This indicates that the model currently used for repair kinetics is not satisfactory. There are also few experimental data in the clinical dose-rate range, below 0.02 Gy/min. It is therefore

Applicability of the tissue stem cell turnover concept on the validity of cumulative dose based radiation risk evaluation

International Nuclear Information System (INIS)

Otsuka, Kensuke; Hamada, Nobuyuki; Iwasaki, Toshiyasu; Yoshida, Kazuo

2011-01-01

The radiation protection system adopts the linear no-threshold model to achieve proper radiation protection for considering cancer risks resulting from radiation exposure. This model uses cumulative dose to a tissue for risk evaluation in which cumulative dose is related to the amount of DNA damage and consequential induction of gene mutation. In this concept, gene mutation accumulates in tissue stem cells, the putative target of carcinogenesis, with total dose given to the tissue. Unlike high-dose-rate exposure, epidemiological studies in high radiation background areas, such as Kerala in India, revealed that cancer risks is not elevated by the dose to the inhabitants, suggesting that there exists some mechanisms to eliminate the damage/mutation in the exposed tissue under extremely low-dose-rate exposure situations. In this report, the dynamics of tissue stem cell turnover is evaluated as a possible mechanism under extremely low-dose-rate exposure situations. To this end, we reviewed recent literatures studying tissue stem cell turnover, and found that great advances in stem cell research have made it possible to trace a fate of stem cells in tissues. Furthermore, turnover of tissue stem cells is found to occur after irradiation, due to competition of stem cells within tissues. This raises a possibility that radiation effects may not accumulate in a tissue depending on the dose-rate and duration of exposure period. (author)

Modification of transmission dose algorithm for irregularly shaped radiation field and tissue deficit

Energy Technology Data Exchange (ETDEWEB)

Yun, Hyong Geon; Shin, Kyo Chul [Dankook Univ., College of Medicine, Seoul (Korea, Republic of); Huh, Soon Nyung; Woo, Hong Gyun; Ha, Sung Whan [Seoul National Univ., College of Medicine, Seoul (Korea, Republic of); Lee, Hyoung Koo [The Catholic Univ., College of Medicine, Seoul (Korea, Republic of)

2002-07-01

Algorithm for estimation of transmission dose was modified for use in partially blocked radiation fields and in cases with tissue deficit. The beam data was measured with flat solid phantom in various conditions of beam block. And an algorithm for correction of transmission dose in cases of partially blocked radiation field was developed from the measured data. The algorithm was tested in some clinical settings with irregular shaped field. Also, another algorithm for correction of transmission dose for tissue deficit was developed by physical reasoning. This algorithm was tested in experimental settings with irregular contours mimicking breast cancer patients by using multiple sheets of solid phantoms. The algorithm for correction of beam block could accurately reflect the effect of beam block, with error within {+-}1.0%, both with square fields and irregularly shaped fields. The correction algorithm for tissue deficit could accurately reflect the effect of tissue deficit with errors within {+-}1.0% in most situations and within {+-}3.0% in experimental settings with irregular contours mimicking breast cancer treatment set-up. Developed algorithms could accurately estimate the transmission dose in most radiation treatment settings including irregularly shaped field and irregularly shaped body contour with tissue deficit in transmission dosimetry.

Modification of transmission dose algorithm for irregularly shaped radiation field and tissue deficit

International Nuclear Information System (INIS)

Yun, Hyong Geon; Shin, Kyo Chul; Huh, Soon Nyung; Woo, Hong Gyun; Ha, Sung Whan; Lee, Hyoung Koo

2002-01-01

Algorithm for estimation of transmission dose was modified for use in partially blocked radiation fields and in cases with tissue deficit. The beam data was measured with flat solid phantom in various conditions of beam block. And an algorithm for correction of transmission dose in cases of partially blocked radiation field was developed from the measured data. The algorithm was tested in some clinical settings with irregular shaped field. Also, another algorithm for correction of transmission dose for tissue deficit was developed by physical reasoning. This algorithm was tested in experimental settings with irregular contours mimicking breast cancer patients by using multiple sheets of solid phantoms. The algorithm for correction of beam block could accurately reflect the effect of beam block, with error within ±1.0%, both with square fields and irregularly shaped fields. The correction algorithm for tissue deficit could accurately reflect the effect of tissue deficit with errors within ±1.0% in most situations and within ±3.0% in experimental settings with irregular contours mimicking breast cancer treatment set-up. Developed algorithms could accurately estimate the transmission dose in most radiation treatment settings including irregularly shaped field and irregularly shaped body contour with tissue deficit in transmission dosimetry

Assessment of radioactive residues arising from radiolabel instability in a multiple dose tissue distribution study in rats

International Nuclear Information System (INIS)

Slatter, J.G.; Sams, J.P.; Easter, J.A.

2003-01-01

Our study objectives were to quantitatively determine the effect of radiolabel instability on terminal phase radioactive tissue residues in a multiple dose tissue distribution study, to quantitatively compare tissue residue artifacts (non drug-related radioactivity) from two chemically-distinct radiolabel locations, and to conduct a definitive multiple dose tissue distribution study using the better of the two radiolabeled compounds. We compared the excretion and tissue distribution in rats of [ 14 C]linezolid, radiolabeled in two different locations, after 7 consecutive once daily [ 14 C] oral doses. The radiolabels were in the acetamide (two carbon) and oxazolidinone (isolated carbon) functional groups. Terminal phase tissue residue and excretion data were compared to data from rats dosed orally with [ 14 C]sodium acetate. Drug-related radioactivity was excreted rapidly over 24 h. After a single dose, the acetamide and oxazolidinone radiolabel sites both gave 3% of dose as exhaled 14 CO 2 . After 7 daily [ 14 C] oral doses, terminal phase radioactive tissue residues were higher from the acetamide radiolabel, relative to the oxazolidinone radiolabel, and were primarily not drug-related. In the definitive tissue distribution study, low concentrations of drug-related radioactivity in skin and thyroid were observed. We conclude that although small amounts of radiolabel instability do not significantly affect single dose tissue radioactivity C max and area under the curve (AUC), artifacts arising from radiolabel instability can prolong the apparent terminal phase half life and complicate study data interpretation. When possible, it is always preferable to use a completely stable radiolabel site. (author)

Assessment of radioactive residues arising from radiolabel instability in a multiple dose tissue distribution study in rats

Energy Technology Data Exchange (ETDEWEB)

Slatter, J.G. [Pharmacia Corp., Peapack, NJ (United States); Sams, J.P.; Easter, J.A. [Pharmacia Corp., Kalamazoo, MI (United States)] [and others

2003-05-01

Our study objectives were to quantitatively determine the effect of radiolabel instability on terminal phase radioactive tissue residues in a multiple dose tissue distribution study, to quantitatively compare tissue residue artifacts (non drug-related radioactivity) from two chemically-distinct radiolabel locations, and to conduct a definitive multiple dose tissue distribution study using the better of the two radiolabeled compounds. We compared the excretion and tissue distribution in rats of [{sup 14}C]linezolid, radiolabeled in two different locations, after 7 consecutive once daily [{sup 14}C] oral doses. The radiolabels were in the acetamide (two carbon) and oxazolidinone (isolated carbon) functional groups. Terminal phase tissue residue and excretion data were compared to data from rats dosed orally with [{sup 14}C]sodium acetate. Drug-related radioactivity was excreted rapidly over 24 h. After a single dose, the acetamide and oxazolidinone radiolabel sites both gave 3% of dose as exhaled {sup 14}CO{sub 2}. After 7 daily [{sup 14}C] oral doses, terminal phase radioactive tissue residues were higher from the acetamide radiolabel, relative to the oxazolidinone radiolabel, and were primarily not drug-related. In the definitive tissue distribution study, low concentrations of drug-related radioactivity in skin and thyroid were observed. We conclude that although small amounts of radiolabel instability do not significantly affect single dose tissue radioactivity C{sub max} and area under the curve (AUC), artifacts arising from radiolabel instability can prolong the apparent terminal phase half life and complicate study data interpretation. When possible, it is always preferable to use a completely stable radiolabel site. (author)

Forward and backscatter dose profile to diagnostic X-rays at gold/tissue interfaces

International Nuclear Information System (INIS)

Rosa, Luiz A.R. da; Seidenbusch, Michael; Regulla, Dieter F.

1997-01-01

The radiological and clinical significance of dose distributions in the vicinity of media interfaces in radiotherapy and the complex nature of these dose distributions have long been recognised. A possible dosimetry method for dose profile assessment near interfaces is the use of the so-called thermally stimulated exoelectron emission (TSEE) dosemeter. In this work the possibility of using Be O/TSEE dosimeters to assess the forward and backscatter dose profile at the interface soft tissue/gold was investigated for diagnostic heavily filtered X-rays spectrum A-60 of ISO Standard A-quality. Dose and range profiles are presented. (author). 14 refs., 3 figs

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

International Nuclear Information System (INIS)

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

2003-01-01

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

Incidence of late rectal bleeding in high-dose conformal radiotherapy of prostate cancer using equivalent uniform dose-based and dose-volume-based normal tissue complication probability models

International Nuclear Information System (INIS)

Soehn, Matthias; Yan Di; Liang Jian; Meldolesi, Elisa; Vargas, Carlos; Alber, Markus

2007-01-01

Purpose: Accurate modeling of rectal complications based on dose-volume histogram (DVH) data are necessary to allow safe dose escalation in radiotherapy of prostate cancer. We applied different equivalent uniform dose (EUD)-based and dose-volume-based normal tissue complication probability (NTCP) models to rectal wall DVHs and follow-up data for 319 prostate cancer patients to identify the dosimetric factors most predictive for Grade ≥ 2 rectal bleeding. Methods and Materials: Data for 319 patients treated at the William Beaumont Hospital with three-dimensional conformal radiotherapy (3D-CRT) under an adaptive radiotherapy protocol were used for this study. The following models were considered: (1) Lyman model and (2) logit-formula with DVH reduced to generalized EUD (3) serial reconstruction unit (RU) model (4) Poisson-EUD model, and (5) mean dose- and (6) cutoff dose-logistic regression model. The parameters and their confidence intervals were determined using maximum likelihood estimation. Results: Of the patients, 51 (16.0%) showed Grade 2 or higher bleeding. As assessed qualitatively and quantitatively, the Lyman- and Logit-EUD, serial RU, and Poisson-EUD model fitted the data very well. Rectal wall mean dose did not correlate to Grade 2 or higher bleeding. For the cutoff dose model, the volume receiving > 73.7 Gy showed most significant correlation to bleeding. However, this model fitted the data more poorly than the EUD-based models. Conclusions: Our study clearly confirms a volume effect for late rectal bleeding. This can be described very well by the EUD-like models, of which the serial RU- and Poisson-EUD model can describe the data with only two parameters. Dose-volume-based cutoff-dose models performed worse

Total dose meter development

International Nuclear Information System (INIS)

Brackenbush, L.W.

1986-09-01

This report describes an alarming ''pocket'' monitor/dosimeter, based on a tissue-equivalent proportional counter, that measure both neutron and gamma dose and determines dose equivalent for the mixed radiation field. This report details the operation of the device and provides information on: the necessity for a device to measure dose equivalent in mixed radiation fields; the mathematical theory required to determine dose equivalent from tissue equivalent proportional; the detailed electronic circuits required; the algorithms required in the microprocessor used to calculate dose equivalent; the features of the instrument; program accomplishments and future plans

Alpha-particle doses to human organs and tissues from internally-deposited 226Ra and 228Ra

International Nuclear Information System (INIS)

Keane, A.T.; Schlenker, R.A.

1981-01-01

Estimation of radiation doses to the soft tissues from internally-deposited 226 Ra and 228 Ra is relevant to an investigation of soft-tissue malignancies in radium-exposed persons being conducted at the Center for Human Radiobiology. Alpha-particle doses in a 50-year period following a single injection of 226 Ra or 228 Ra are presented for 31 soft tissues and organs of the adult human. The dose estimates were derived from the ICRP alkaline earth model fitted to data on retention of 226 Ra in soft tissues and bone, combined with reported ratios of 226 Ra to Ca in soft tissue and bone at natural levels and the distribution of Ca in the tissues of Reference Man (ICRP23). The median of the 31 organ and tissue doses from the α-particles of 226 Ra itself is 0.08 rad per injected μCi. An additional average dose of 0.01 rad per μCi 226 Ra daughter products produced in soft tissue or transferred from bone to soft tissue. Soft-tissue doses from α-particles of the 228 Ra decay series are about six times those from 226 Ra α-particles for equal injected activities of 228 Ra and 226 Ra, with the assumption that 228 Ra daughter products do not transfer from the organ in which they are produced. The 50-year dose to the red marrow of bone from α-particles originating in bone is 0.55 rad per μCi 226 Ra injected and 1.0 rad per μCi 228 Ra injected. For ingestion by dial painters of luminous compound containg 226 Ra or 228 Ra with a daughter-to-parent activity ratio of 0.5, the dose to the mucosal alyer of the lower large intestine from α-particles originating in the gut contents is about 0.1 rad per μCi systemic intake of 226 Ra or 228 Ra

Dose specification for 192Ir high dose rate brachytherapy in terms of dose-to-water-in-medium and dose-to-medium-in-medium

International Nuclear Information System (INIS)

Fonseca, Gabriel Paiva; Yoriyaz, Hélio; Tedgren, Åsa Carlsson; Nilsson, Josef; Persson, Maria; Reniers, Brigitte; Verhaegen, Frank

2015-01-01

Dose calculation in high dose rate brachytherapy with 192 Ir is usually based on the TG-43U1 protocol where all media are considered to be water. Several dose calculation algorithms have been developed that are capable of handling heterogeneities with two possibilities to report dose: dose-to-medium-in-medium (D m,m ) and dose-to-water-in-medium (D w,m ). The relation between D m,m and D w,m for 192 Ir is the main goal of this study, in particular the dependence of D w,m on the dose calculation approach using either large cavity theory (LCT) or small cavity theory (SCT). A head and neck case was selected due to the presence of media with a large range of atomic numbers relevant to tissues and mass densities such as air, soft tissues and bone interfaces. This case was simulated using a Monte Carlo (MC) code to score: D m,m, D w,m (LCT), mean photon energy and photon fluence. D w,m (SCT) was derived from MC simulations using the ratio between the unrestricted collisional stopping power of the actual medium and water. Differences between D m,m and D w,m (SCT or LCT) can be negligible (<1%) for some tissues e.g. muscle and significant for other tissues with differences of up to 14% for bone. Using SCT or LCT approaches leads to differences between D w,m (SCT) and D w,m (LCT) up to 29% for bone and 36% for teeth. The mean photon energy distribution ranges from 222 keV up to 356 keV. However, results obtained using mean photon energies are not equivalent to the ones obtained using the full, local photon spectrum. This work concludes that it is essential that brachytherapy studies clearly report the dose quantity. It further shows that while differences between D m,m and D w,m (SCT) mainly depend on tissue type, differences between D m,m and D w,m (LCT) are, in addition, significantly dependent on the local photon energy fluence spectrum which varies with distance to implanted sources. (paper)

Improved tissue assignment using dual-energy computed tomography in low-dose rate prostate brachytherapy for Monte Carlo dose calculation

Energy Technology Data Exchange (ETDEWEB)

Côté, Nicolas [Département de Physique, Université de Montréal, Pavillon Roger-Gaudry (D-428), 2900 Boulevard Édouard-Montpetit, Montréal, Québec H3T 1J4 (Canada); Bedwani, Stéphane [Département de Radio-Oncologie, Centre Hospitalier de l’Université de Montréal (CHUM), 1560 Rue Sherbrooke Est, Montréal, Québec H2L 4M1 (Canada); Carrier, Jean-François, E-mail: jean-francois.carrier.chum@ssss.gouv.qc.ca [Département de Physique, Université de Montréal, Pavillon Roger-Gaudry (D-428), 2900 Boulevard Édouard-Montpetit, Montréal, Québec H3T 1J4, Canada and Département de Radio-Oncologie, Centre Hospitalier de l’Université de Montréal (CHUM), 1560 Rue Sherbrooke Est, Montréal, Québec H2L 4M1 (Canada)

2016-05-15

Purpose: An improvement in tissue assignment for low-dose rate brachytherapy (LDRB) patients using more accurate Monte Carlo (MC) dose calculation was accomplished with a metallic artifact reduction (MAR) method specific to dual-energy computed tomography (DECT). Methods: The proposed MAR algorithm followed a four-step procedure. The first step involved applying a weighted blend of both DECT scans (I {sub H/L}) to generate a new image (I {sub Mix}). This action minimized Hounsfield unit (HU) variations surrounding the brachytherapy seeds. In the second step, the mean HU of the prostate in I {sub Mix} was calculated and shifted toward the mean HU of the two original DECT images (I {sub H/L}). The third step involved smoothing the newly shifted I {sub Mix} and the two original I {sub H/L}, followed by a subtraction of both, generating an image that represented the metallic artifact (I {sub A,(H/L)}) of reduced noise levels. The final step consisted of subtracting the original I {sub H/L} from the newly generated I {sub A,(H/L)} and obtaining a final image corrected for metallic artifacts. Following the completion of the algorithm, a DECT stoichiometric method was used to extract the relative electronic density (ρ{sub e}) and effective atomic number (Z {sub eff}) at each voxel of the corrected scans. Tissue assignment could then be determined with these two newly acquired physical parameters. Each voxel was assigned the tissue bearing the closest resemblance in terms of ρ{sub e} and Z {sub eff}, comparing with values from the ICRU 42 database. A MC study was then performed to compare the dosimetric impacts of alternative MAR algorithms. Results: An improvement in tissue assignment was observed with the DECT MAR algorithm, compared to the single-energy computed tomography (SECT) approach. In a phantom study, tissue misassignment was found to reach 0.05% of voxels using the DECT approach, compared with 0.40% using the SECT method. Comparison of the DECT and SECT D

Influence of nuclear interactions in body tissues on tumor dose in carbon-ion radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Inaniwa, T., E-mail: taku@nirs.go.jp; Kanematsu, N. [Medical Physics Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-8555 (Japan); Tsuji, H.; Kamada, T. [Hospital, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)

2015-12-15

Purpose: In carbon-ion radiotherapy treatment planning, the planar integrated dose (PID) measured in water is applied to the patient dose calculation with density scaling using the stopping power ratio. Since body tissues are chemically different from water, this dose calculation can be subject to errors, particularly due to differences in inelastic nuclear interactions. In recent studies, the authors proposed and validated a PID correction method for these errors. In the present study, the authors used this correction method to assess the influence of these nuclear interactions in body tissues on tumor dose in various clinical cases. Methods: Using 10–20 cases each of prostate, head and neck (HN), bone and soft tissue (BS), lung, liver, pancreas, and uterine neoplasms, the authors first used treatment plans for carbon-ion radiotherapy without nuclear interaction correction to derive uncorrected dose distributions. The authors then compared these distributions with recalculated distributions using the nuclear interaction correction (corrected dose distributions). Results: Median (25%/75% quartiles) differences between the target mean uncorrected doses and corrected doses were 0.2% (0.1%/0.2%), 0.0% (0.0%/0.0%), −0.3% (−0.4%/−0.2%), −0.1% (−0.2%/−0.1%), −0.1% (−0.2%/0.0%), −0.4% (−0.5%/−0.1%), and −0.3% (−0.4%/0.0%) for the prostate, HN, BS, lung, liver, pancreas, and uterine cases, respectively. The largest difference of −1.6% in target mean and −2.5% at maximum were observed in a uterine case. Conclusions: For most clinical cases, dose calculation errors due to the water nonequivalence of the tissues in nuclear interactions would be marginal compared to intrinsic uncertainties in treatment planning, patient setup, beam delivery, and clinical response. In some extreme cases, however, these errors can be substantial. Accordingly, this correction method should be routinely applied to treatment planning in clinical practice.

Integral dose conservation in radiotherapy

International Nuclear Information System (INIS)

Reese, Adam S.; Das, Shiva K.; Curle, Charles; Marks, Lawrence B.

2009-01-01

Treatment planners frequently modify beam arrangements and use IMRT to improve target dose coverage while satisfying dose constraints on normal tissues. The authors herein analyze the limitations of these strategies and quantitatively assess the extent to which dose can be redistributed within the patient volume. Specifically, the authors hypothesize that (1) the normalized integral dose is constant across concentric shells of normal tissue surrounding the target (normalized to the average integral shell dose), (2) the normalized integral shell dose is constant across plans with different numbers and orientations of beams, and (3) the normalized integral shell dose is constant across plans when reducing the dose to a critical structure. Using the images of seven patients previously irradiated for cancer of brain or prostate cancer and one idealized scenario, competing three-dimensional conformal and IMRT plans were generated using different beam configurations. Within a given plan and for competing plans with a constant mean target dose, the normalized integral doses within concentric ''shells'' of surrounding normal tissue were quantitatively compared. Within each patient, the normalized integral dose to shells of normal tissue surrounding the target was relatively constant (1). Similarly, for each clinical scenario, the normalized integral dose for a given shell was also relatively constant regardless of the number and orientation of beams (2) or degree of sparing of a critical structure (3). 3D and IMRT planning tools can redistribute, rather than eliminate dose to the surrounding normal tissues (intuitively known by planners). More specifically, dose cannot be moved between shells surrounding the target but only within a shell. This implies that there are limitations in the extent to which a critical structure can be spared based on the location and geometry of the critical structure relative to the target.

A new tissue segmentation method to calculate 3D dose in small animal radiation therapy.

Science.gov (United States)

Noblet, C; Delpon, G; Supiot, S; Potiron, V; Paris, F; Chiavassa, S

2018-02-26

In pre-clinical animal experiments, radiation delivery is usually delivered with kV photon beams, in contrast to the MV beams used in clinical irradiation, because of the small size of the animals. At this medium energy range, however, the contribution of the photoelectric effect to absorbed dose is significant. Accurate dose calculation therefore requires a more detailed tissue definition because both density (ρ) and elemental composition (Z eff ) affect the dose distribution. Moreover, when applied to cone beam CT (CBCT) acquisitions, the stoichiometric calibration of HU becomes inefficient as it is designed for highly collimated fan beam CT acquisitions. In this study, we propose an automatic tissue segmentation method of CBCT imaging that assigns both density (ρ) and elemental composition (Z eff ) in small animal dose calculation. The method is based on the relationship found between CBCT number and ρ*Z eff product computed from known materials. Monte Carlo calculations were performed to evaluate the impact of ρZ eff variation on the absorbed dose in tissues. These results led to the creation of a tissue database composed of artificial tissues interpolated from tissue values published by the ICRU. The ρZ eff method was validated by measuring transmitted doses through tissue substitute cylinders and a mouse with EBT3 film. Measurements were compared to the results of the Monte Carlo calculations. The study of the impact of ρZ eff variation over the range of materials, from ρZ eff  = 2 g.cm - 3 (lung) to 27 g.cm - 3 (cortical bone) led to the creation of 125 artificial tissues. For tissue substitute cylinders, the use of ρZ eff method led to maximal and average relative differences between the Monte Carlo results and the EBT3 measurements of 3.6% and 1.6%. Equivalent comparison for the mouse gave maximal and average relative differences of 4.4% and 1.2%, inside the 80% isodose area. Gamma analysis led to a 94.9% success rate in the 10% isodose

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

Science.gov (United States)

Shi, Chengyu; Guo, Bingqi; Cheng, Chih-Yao; Eng, Tony; Papanikolaou, Nikos

2010-09-01

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent™ x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V100 reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as compared to 95

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

Energy Technology Data Exchange (ETDEWEB)

Shi Chengyu; Guo Bingqi; Eng, Tony; Papanikolaou, Nikos [Cancer Therapy and Research Center, University of Texas Health Science Center at San Antonio, TX 78229 (United States); Cheng, Chih-Yao, E-mail: shic@uthscsa.ed [Radiation Oncology Department, Oklahoma University Health Science Center, Oklahoma, OK 73104 (United States)

2010-09-21

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent(TM) x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V{sub 100} reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

International Nuclear Information System (INIS)

Shi Chengyu; Guo Bingqi; Eng, Tony; Papanikolaou, Nikos; Cheng, Chih-Yao

2010-01-01

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent(TM) x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V 100 reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as compared to 95

Dose in water or dose in tissue. Still a theme of debate; Dosis en agua o dosis en tejido-todavia un tema de debate

Energy Technology Data Exchange (ETDEWEB)

Andreo, P.

2015-07-01

It is shown that the method used so Siebers to convert to Dw Dt, or vice versa, is incorrect. Due to the substantial difference between the electron fluence in water and various tissues, an additional correction for creep, several percent for some bone tissues, which is ignored in the method Siebers needed. Correction is necessary even if an environment that clinically adopted dose in tissue due to normalization of TPS because the beams are always calibrated in terms of absorbed dose in water. (Author)

Quantitative radiation dose-response relationships for normal tissues in man - I. Gustatory tissues response during photon and neutron radiotherapy

International Nuclear Information System (INIS)

Mossman, K.L.

1982-01-01

Quantitative radiation dose-response curves for normal gustatory tissue in man were studied. Taste function, expressed as taste loss, was evaluated in 84 patients who were given either photon or neutron radiotherapy for tumors in the head and neck region. Patients were treated to average tumor doses of 6600 cGy (photon) or 2200 cGy intervals for photon patients and 320-cGy intervals for neutron patients during radiotherapy. The dose-response curves for photons and neutrons were analyzed by fitting a four-parameter logistic equation to the data. Photon and neutron curves differed principally in their relative position along the dose axis. Comparison of the dose-response curves were made by determination of RBE. At 320 cGy, the lowest neutron dose at which taste measurements were made, RBE = 5.7. If this RBE is correct, then the therapeutic gain factor may be equal to or less than 1, indicating no biological advantage in using neutrons over photons for this normal tissue. These studies suggest measurements of taste function and evaluation of dose-response relationships may also be useful in quantitatively evaluating the efficacy of chemical modifiers of radiation response such as hypoxic cell radiosensitizers and radioprotectors

Analysis of ethyl acrylate (EA) and acrylic acid (AA) residues from rat tissues following oral ea dosing

International Nuclear Information System (INIS)

Udinsky, J.R.; Frederick, C.B.

1990-01-01

Gavage dosing of rats with EA at high dose levels (100 or 200 mg/kg) has resulted in tumors at the dosing site, forestomach (FST), but no lesions of the glandular stomach (GST) or other remote tissues. Since previous in vitro studies have demonstrated that EA is very rapidly metabolized to AA and glutathione conjugates, EA and AA residues were analyzed 0-24 hr following gavage dosing of non-fasted F-344/N male rats with [1- 14 C]EA in corn oil at 10, 50, and 200 mg/kg. Analysis of total 14 C indicated that the dose solution was primarily in the FST at ≥5 min after dosing, although 14 C was detected in the GST, duodenum, and small intestine (attributed to distension of the FST and leakage from the FST to the GST). HPLC analysis of the gut contents, gut wall, liver, kidneys, lungs, and blood indicated that EA and AA could only be detected at ≥15 min in the FST and GST contents, and in the FST tissue. AA alone was detected in the GST tissue, duodenum tissue and contents, and small intestine tissue and contents. The minimum level of detection was 0.0005% of the dose. The remaining 14 C was primarily attributed to binding to the gut contents or bioincorporation of AA. The detection of EA and AA residues only in the upper gastrointestinal tract following gavage dosing is consistent with rapid detoxification of EA by hydrolysis and conjugation which prevents toxicity at sites remote form the site of dosing

Sensitivity of low energy brachytherapy Monte Carlo dose calculations to uncertainties in human tissue composition

Energy Technology Data Exchange (ETDEWEB)

Landry, Guillaume; Reniers, Brigitte; Murrer, Lars; Lutgens, Ludy; Bloemen-Van Gurp, Esther; Pignol, Jean-Philippe; Keller, Brian; Beaulieu, Luc; Verhaegen, Frank [Department of Radiation Oncology (MAASTRO), GROW-School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht 6201 BN (Netherlands); Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Departement de Radio-Oncologie et Centre de Recherche en Cancerologie, de l' Universite Laval, CHUQ, Pavillon L' Hotel-Dieu de Quebec, Quebec G1R 2J6 (Canada) and Departement de Physique, de Genie Physique et d' Optique, Universite Laval, Quebec G1K 7P4 (Canada); Department of Radiation Oncology (MAASTRO), GROW-School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht 6201 BN (Netherlands) and Medical Physics Unit, McGill University, Montreal General Hospital, Montreal, Quebec H3G 1A4 (Canada)

2010-10-15

Purpose: The objective of this work is to assess the sensitivity of Monte Carlo (MC) dose calculations to uncertainties in human tissue composition for a range of low photon energy brachytherapy sources: {sup 125}I, {sup 103}Pd, {sup 131}Cs, and an electronic brachytherapy source (EBS). The low energy photons emitted by these sources make the dosimetry sensitive to variations in tissue atomic number due to the dominance of the photoelectric effect. This work reports dose to a small mass of water in medium D{sub w,m} as opposed to dose to a small mass of medium in medium D{sub m,m}. Methods: Mean adipose, mammary gland, and breast tissues (as uniform mixture of the aforementioned tissues) are investigated as well as compositions corresponding to one standard deviation from the mean. Prostate mean compositions from three different literature sources are also investigated. Three sets of MC simulations are performed with the GEANT4 code: (1) Dose calculations for idealized TG-43-like spherical geometries using point sources. Radial dose profiles obtained in different media are compared to assess the influence of compositional uncertainties. (2) Dose calculations for four clinical prostate LDR brachytherapy permanent seed implants using {sup 125}I seeds (Model 2301, Best Medical, Springfield, VA). The effect of varying the prostate composition in the planning target volume (PTV) is investigated by comparing PTV D{sub 90} values. (3) Dose calculations for four clinical breast LDR brachytherapy permanent seed implants using {sup 103}Pd seeds (Model 2335, Best Medical). The effects of varying the adipose/gland ratio in the PTV and of varying the elemental composition of adipose and gland within one standard deviation of the assumed mean composition are investigated by comparing PTV D{sub 90} values. For (2) and (3), the influence of using the mass density from CT scans instead of unit mass density is also assessed. Results: Results from simulation (1) show that variations

Dose planning and dose delivery in radiation therapy

International Nuclear Information System (INIS)

Knoeoes, T.

1991-01-01

A method has been developed for calibration of CT-numbers to volumetric electron density distributions using tissue substitutes of known elemental composition and experimentally determined electron density. This information have been used in a dose calculation method based on photon and electron interaction processes. The method utilizes a convolution integral between the photon fluence matrix and dose distribution kernels. Inhomogeneous media are accounted for using the theorems of Fano and O'Connor for scaling dose distribution kernels in proportion to electron density. For clinical application of a calculated dose plan, a method for prediction of accelerator output have been developed. The methods gives the number of monitor units that has to be given to obtain a certain absorbed dose to a point inside an irregular, inhomogeneous object. The method for verification of dose distributions outlined in this study makes it possible to exclude the treatment related variance contributions, making an objective evaluation of dose calculations with experiments feasible. The methods for electron density determination, dose calculation and prediction of accelerator output discussed in this study will all contribute to an increased accuracy in the mean absorbed dose to the target volume. However, a substantial gain in the accuracy for the spatial absorbed dose distribution will also follow, especially using CT for mapping of electron density together with the dose calculation algorithm. (au)

We can do better than effective dose for estimating or comparing low-dose radiation risks

International Nuclear Information System (INIS)

Brenner, D.J.

2012-01-01

The effective dose concept was designed to compare the generic risks of exposure to different radiation fields. More commonly these days, it is used to estimate or compare radiation-induced cancer risks. For various reasons, effective dose represents flawed science: for instance, the tissue-specific weighting factors used to calculate effective dose are a subjective mix of different endpoints; and the marked and differing age and gender dependencies for different health detriment endpoints are not taken into account. This paper suggests that effective dose could be replaced with a new quantity, ‘effective risk’, which, like effective dose, is a weighted sum of equivalent doses to different tissues. Unlike effective dose, where the tissue-dependent weighting factors are a set of generic, subjective committee-defined numbers, the weighting factors for effective risk are simply evaluated tissue-specific lifetime cancer risks per unit equivalent dose. Effective risk, which has the potential to be age and gender specific if desired, would perform the same comparative role as effective dose, be just as easy to estimate, be less prone to misuse, be more directly understandable, and would be based on solid science. An added major advantage is that it gives the users some feel for the actual numerical values of the radiation risks they are trying to control.

The Contribution of Tissue Level Organization to Genomic Stability Following Low Dose/Low Dose Rate Gamma and Proton Irradiation

Energy Technology Data Exchange (ETDEWEB)

Cheryl G. Burrell, Ph.D.

2012-05-14

The formation of functional tissue units is necessary in maintaining homeostasis within living systems, with individual cells contributing to these functional units through their three-dimensional organization with integrin and adhesion proteins to form a complex extra-cellular matrix (ECM). This is of particular importance in those tissues susceptible to radiation-induced tumor formation, such as epithelial glands. The assembly of epithelial cells of the thyroid is critical to their normal receipt of, and response to, incoming signals. Traditional tissue culture and live animals present significant challenges to radiation exposure and continuous sampling, however, the production of bioreactor-engineered tissues aims to bridge this gap by improve capabilities in continuous sampling from the same functional tissue, thereby increasing the ability to extrapolate changes induced by radiation to animals and humans in vivo. Our study proposes that the level of tissue organization will affect the induction and persistence of low dose radiation-induced genomic instability. Rat thyroid cells, grown in vitro as 3D tissue analogs in bioreactors and as 2D flask grown cultures were exposed to acute low dose (1, 5, 10 and 200 cGy) gamma rays. To assess immediate (6 hours) and delayed (up to 30 days) responses post-irradiation, various biological endpoints were studied including cytogenetic analyses, apoptosis analysis and cell viability/cytotoxicity analyses. Data assessing caspase 3/7 activity levels show that, this activity varies with time post radiation and that, overall, 3D cultures display more genomic instability (as shown by the lower levels of apoptosis over time) when compared to the 2D cultures. Variation in cell viability levels were only observed at the intermediate and late time points post radiation. Extensive analysis of chromosomal aberrations will give further insight on the whether the level of tissue organization influences genomic instability patterns after

Radiation doses to the tissues of rat from tritiated thymidine administered by three different routes

International Nuclear Information System (INIS)

Takeda, Hiroshi; Iwakura, Tetsuo; Mabuchi, Yasuo.

1984-01-01

Biological behaviour of tritiated thymidine were investigated in rat over 120 days after oral, intraperitoneal or intravenous administration and the absorbed doses to different tissues were estimated. The result of present study revealed that the absorbed dose from tritiated thymidine varied with the route of administration. Among the three routes of administration, intraperitoneal injection gave the highest dose to all of the tissues examined. A significant difference due to the route of administration was found in spleen and small intestine, where the doses were, respectively, 3.3 and 4.5 times higher after intraperitoneal injection than after oral ingestion. The difference was substantially dependent on the dose value from non-volatile tritium which would be incorporated into DNA. Present observation suggests that the radiation hazards of tritiated thymidine differ depending on the route of entry into the body. (author)

Research on the dose of the tissues located outside the treatment field when breast cancer was irradiated by linear accelerator

International Nuclear Information System (INIS)

Tu Yu; Zhou Juying; Jiang Dezhi; Qin Songbing

1999-10-01

The purpose of study was to determine the dose of the tissues which located outside the treatment field, when breast cancer was irradiated by 9 MeV electron-beam and 6 MV-X ray after operation. A search for decreasing the dose of the tissues outside the treatment field was made. Clinically relevant treatment fields were simulated on a tissue-equivalent material phantom and subsequently irradiated with 9 MeV electron-beam and 6 MV-X ray. TLD were used to measure absorbed doses. The prescribed dose of breast cancer region was 50.0 Gy, region-lymph-nodes were 60.0 Gy, each exposure dose was 2.0 Gy. In breast cancer region, if only with 9 MeV electron-beam, the dose of the tissues located outside the treatment field were from 29.0 cGy to 295.5 cGy, when shielded with Pb lump, the doses of the tissues outside the treatment field may descended 9.4%-53.6%; if only with 6 MV-X ray, the doses of aforementioned tissues were from 32.0 cGy to 206.7 cGy, when shielded with Pb lump, the doses of the tissues outside the treatment field descended 19.7%-56.6%. In region-lymph-nodes, with 6 MV-X ray, the doses of aforementioned tissues were from 22.5 cGy to 1650.9 cGy, when shielded with Pb lump, the doses of the tissues outside the treatment field descended 19.7-65.6%. If mix-irradiation (9 MeV electron-beam vs. 6 MV-X ray 2:3) was used, the doses outside field would be lower than only used 9 MeV electron-beam or 6 MV-X ray were used

Dose-specific transcriptional responses in thyroid tissue in mice after 131I administration

International Nuclear Information System (INIS)

Rudqvist, Nils; Schüler, Emil; Parris, Toshima Z.; Langen, Britta; Helou, Khalil; Forssell-Aronsson, Eva

2015-01-01

Introduction: In the present investigation, microarray analysis was used to monitor transcriptional activity in thyroids in mice 24 h after 131 I exposure. The aims of this study were to 1) assess the transcriptional patterns associated with 131 I exposure in normal mouse thyroid tissue and 2) propose biomarkers for 131 I exposure of the thyroid. Methods: Adult BALB/c nude mice were i.v. injected with 13, 130 or 260 kBq of 131 I and killed 24 h after injection (absorbed dose to thyroid: 0.85, 8.5, or 17 Gy). Mock-treated mice were used as controls. Total RNA was extracted from thyroids and processed using the Illumina platform. Results: In total, 497, 546, and 90 transcripts were regulated (fold change ≥ 1.5) in the thyroid after 0.85, 8.5, and 17 Gy, respectively. These were involved in several biological functions, e.g. oxygen access, inflammation and immune response, and apoptosis/anti-apoptosis. Approximately 50% of the involved transcripts at each absorbed dose level were dose-specific, and 18 transcripts were commonly detected at all absorbed dose levels. The Agpat9, Plau, Prf1, and S100a8 gene expression displayed a monotone decrease in regulation with absorbed dose, and further studies need to be performed to evaluate if they may be useful as dose-related biomarkers for 131I exposure. Conclusion: Distinct and substantial differences in gene expression and affected biological functions were detected at the different absorbed dose levels. The transcriptional profiles were specific for the different absorbed dose levels. We propose that the Agpat9, Plau, Prf1, and S100a8 genes might be novel potential absorbed dose-related biomarkers to 131 I exposure of thyroid. Advances in knowledge: During the recent years, genomic techniques have been developed; however, they have not been fully utilized in nuclear medicine and radiation biology. We have used RNA microarrays to investigate genome-wide transcriptional regulations in thyroid tissue in mice after low

Gustatory tissue injury in man: radiation dose response relationships and mechanisms of taste loss

International Nuclear Information System (INIS)

Mossman, K.L.

1986-01-01

In this report dose response data for gustatory tissue damage in patients given total radiation doses ranging from 3000 to 6000 cGy are presented. In order to evaluate direct radiation injury to gustatory tissues as a mechanism of taste loss, measurements of damage to specific taste structures in bovine and murine systems following radiation exposure in the clinical range are correlated to taste impairment observed in radiotherapy patients. (author)

Minimising the risk: reducing breast tissue dose in an adolescent female

International Nuclear Information System (INIS)

Thompson, Ann; Toe, Aimee; Ungureanu, Elena; Wolf, M.; Wirth, Andrew

2005-01-01

Breast cancer is amongst the leading radiation-associated, second malignancies that develop in patients after treatment for Hodgkin's disease. This risk is affected by two main factors: 1. The age of the patient at the time of radiotherapy; and 2. The dose received by the breast tissue The adolescent female thus faces an exceptionally high risk, as breast tissue at this age is undergoing rapid developmental growth and small doses of radiation exposure could be carcinogenic. This case report of a fifteen-year-old girl who received radiotherapy for Hodgkin's disease demonstrates how radiation therapists worked together with the radiation oncologists and medical physicists to provide an optimal treatment plan for a high-risk patient. Copyright (2005) Australian Institute of Radiography

Calculation of normal tissue complication probability and dose-volume histogram reduction schemes for tissues with a critical element architecture

International Nuclear Information System (INIS)

Niemierko, Andrzej; Goitein, Michael

1991-01-01

The authors investigate a model of normal tissue complication probability for tissues that may be represented by a critical element architecture. They derive formulas for complication probability that apply to both a partial volume irradiation and to an arbitrary inhomogeneous dose distribution. The dose-volume isoeffect relationship which is a consequence of a critical element architecture is discussed and compared to the empirical power law relationship. A dose-volume histogram reduction scheme for a 'pure' critical element model is derived. In addition, a point-based algorithm which does not require precomputation of a dose-volume histogram is derived. The existing published dose-volume histogram reduction algorithms are analyzed. The authors show that the existing algorithms, developed empirically without an explicit biophysical model, have a close relationship to the critical element model at low levels of complication probability. However, it is also showed that they have aspects which are not compatible with a critical element model and the authors propose a modification to one of them to circumvent its restriction to low complication probabilities. (author). 26 refs.; 7 figs

Dosimetry of {sup 223}Ra-chloride: dose to normal organs and tissues

Energy Technology Data Exchange (ETDEWEB)

Lassmann, Michael [University of Wuerzburg, Department of Nuclear Medicine, Wuerzburg (Germany); Nosske, Dietmar [Federal Office for Radiation Protection (BfS), Department of Radiation and Health, Oberschleissheim (Germany)

2013-02-15

{sup 223}Ra-Chloride (also called Alpharadin {sup registered}) targets bone metastases with short range alpha particles. In recent years several clinical trials have been carried out showing, in particular, the safety and efficacy of palliation of painful bone metastases in patients with castration-resistant prostate cancer using {sup 223}Ra-chloride. The purpose of this work was to provide a comprehensive dosimetric calculation of organ doses after intravenous administration of {sup 223}Ra-chloride according to the present International Commission on Radiological Protection (ICRP) model for radium. Absorbed doses were calculated for 25 organs or tissues. Bone endosteum and red bone marrow show the highest dose coefficients followed by liver, colon and intestines. After a treatment schedule of six intravenous injections with 0.05 MBq/kg of {sup 223}Ra-chloride each, corresponding to 21 MBq for a 70 kg patient, the absorbed alpha dose to the bone endosteal cells is about 16 Gy and the corresponding absorbed dose to the red bone marrow is approximately 1.5 Gy. The comprehensive list of dose coefficients presented in this work will assist in comparing and evaluating organ doses from various therapy modalities used in nuclear medicine and will provide a base for further development of patient-specific dosimetry. (orig.)

Tumor significant dose

International Nuclear Information System (INIS)

Supe, S.J.; Nagalaxmi, K.V.; Meenakshi, L.

1983-01-01

In the practice of radiotherapy, various concepts like NSD, CRE, TDF, and BIR are being used to evaluate the biological effectiveness of the treatment schedules on the normal tissues. This has been accepted as the tolerance of the normal tissue is the limiting factor in the treatment of cancers. At present when various schedules are tried, attention is therefore paid to the biological damage of the normal tissues only and it is expected that the damage to the cancerous tissues would be extensive enough to control the cancer. Attempt is made in the present work to evaluate the concent of tumor significant dose (TSD) which will represent the damage to the cancerous tissue. Strandquist in the analysis of a large number of cases of squamous cell carcinoma found that for the 5 fraction/week treatment, the total dose required to bring about the same damage for the cancerous tissue is proportional to T/sup -0.22/, where T is the overall time over which the dose is delivered. Using this finding the TSD was defined as DxN/sup -p/xT/sup -q/, where D is the total dose, N the number of fractions, T the overall time p and q are the exponents to be suitably chosen. The values of p and q are adjusted such that p+q< or =0.24, and p varies from 0.0 to 0.24 and q varies from 0.0 to 0.22. Cases of cancer of cervix uteri treated between 1978 and 1980 in the V. N. Cancer Centre, Kuppuswamy Naidu Memorial Hospital, Coimbatore, India were analyzed on the basis of these formulations. These data, coupled with the clinical experience, were used for choice of a formula for the TSD. Further, the dose schedules used in the British Institute of Radiology fraction- ation studies were also used to propose that the tumor significant dose is represented by DxN/sup -0.18/xT/sup -0.06/

Accurate tissue area measurements with considerably reduced radiation dose achieved by patient-specific CT scan parameters

DEFF Research Database (Denmark)

Brandberg, J.; Bergelin, E.; Sjostrom, L.

2008-01-01

A low-dose technique was compared with a standard diagnostic technique for measuring areas of adipose and muscle tissue and CT numbers for muscles in a body composition application. The low-dose technique was intended to keep the expected deviation in the measured area of adipose and muscle tissu...

Pocket total dose meter

International Nuclear Information System (INIS)

Brackenbush, L.W.; Endres, G.W.R.

1984-10-01

Laboratory measurements have demonstrated that it is possible to simultaneously measure absorbed dose and dose equivalent using a single tissue equivalent proportional counter. Small, pocket sized instruments are being developed to determine dose equivalent as the worker is exposed to mixed field radiation. This paper describes the electronic circuitry and computer algorithms used to determine dose equivalent in these devices

Establishing the impact of temporary tissue expanders on electron and photon beam dose distributions.

Science.gov (United States)

Asena, A; Kairn, T; Crowe, S B; Trapp, J V

2015-05-01

This study investigates the effects of temporary tissue expanders (TTEs) on the dose distributions in breast cancer radiotherapy treatments under a variety of conditions. Using EBT2 radiochromic film, both electron and photon beam dose distribution measurements were made for different phantoms, and beam geometries. This was done to establish a more comprehensive understanding of the implant's perturbation effects under a wider variety of conditions. The magnetic disk present in a tissue expander causes a dose reduction of approximately 20% in a photon tangent treatment and 56% in electron boost fields immediately downstream of the implant. The effects of the silicon elastomer are also much more apparent in an electron beam than a photon beam. Evidently, each component of the TTE attenuates the radiation beam to different degrees. This study has demonstrated that the accuracy of photon and electron treatments of post-mastectomy patients is influenced by the presence of a tissue expander for various beam orientations. The impact of TTEs on dose distributions establishes the importance of an accurately modelled high-density implant in the treatment planning system for post-mastectomy patients. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Radiation doses to normal tissues during craniospinal irradiation ...

African Journals Online (AJOL)

Mohamed Farouk Mostafa

2011-10-15

Oct 15, 2011 ... not in the center of the brain as this shows lower doses to eyes and lenses. ª 2011 Alexandria .... dose plan function was used to check the dose coverage of the .... maximum dose received by the right and left lens were listed.

Quantitative radiation dose-response relationships for normal tissues in man. II. Response of the salivary glands during radiotherapy

International Nuclear Information System (INIS)

Mossman, K.L.

1983-01-01

A quantitative dose-response curve for salivary gland function in patients during radiotherapy is presented. Salivary-function data used in this study were obtained from four previously published reports. All patients were treated with 60 Co teletherapy to the head and neck using conventional treatment techniques. Salivary dysfunction was determined at specific dose levels by comparing salivary flow rates before therapy with flow rates at specific dose intervals during radiotherapy up to a total dose of 6000 cGy. Fifty percent salivary dysfunction occurred after 1000 cGy and eighty percent dysfunction was observed by the end of the therapy course (6000 cGy). The salivary-function curve was also compared to the previously published dose-response curve for taste function. Comparisons of the two curves indicate that salivary dysfunction precedes taste loss and that the shapes of the dose-response curves are different. A new term, tissue tolerance ratio, defined as the ratio of responses of two tissues given the same radiation dose, was used to make the comparisons between gustatory and salivary gland tissue effects. Measurements of salivary gland function and analysis of dose-response curves may be useful in evaluating chemical modifiers of radiation response

Distribution of chloramphenicol to tissues, plasma and urine in pigs after oral intake of low doses.

Science.gov (United States)

Aspenström-Fagerlund, Bitte; Nordkvist, Erik; Törnkvist, Anna; Wallgren, Per; Hoogenboom, Ron; Berendsen, Bjorn; Granelli, Kristina

2016-09-01

Toxic effects of chloramphenicol in humans caused the ban for its use in food-producing animals in the EU. A minimum required performance level (MRPL) was specified for chloramphenicol at 0.3 μg kg(-1) for various matrices, including urine. In 2012, residues of chloramphenicol were found in pig urine and muscle without signs of illegal use. Regarding its natural occurrence in straw, it was hypothesised that this might be the source, straw being compulsory for use as bedding material for pigs in Sweden. Therefore, we investigated if low daily doses of chloramphenicol (4, 40 and 400 μg/pig) given orally during 14 days could result in residues in pig tissues and urine. A dose-related increase of residues was found in muscle, plasma, kidney and urine (showing the highest levels), but no chloramphenicol was found in the liver. At the lowest dose, residues were below the MRPL in all tissues except in the urine. However, in the middle dose, residues were above the MRPL in all tissues except muscle, and at the highest dose in all matrices. This study proves that exposure of pigs to chloramphenicol in doses occurring naturally in straw could result in residues above the MRPL in plasma, kidney and especially urine.

CALDoseX-a software tool for the assessment of organ and tissue absorbed doses, effective dose and cancer risks in diagnostic radiology

International Nuclear Information System (INIS)

Kramer, R; Khoury, H J; Vieira, J W

2008-01-01

CALDose X is a software tool that provides the possibility of calculating incident air kerma (INAK) and entrance surface air kerma (ESAK), two important quantities used in x-ray diagnosis, based on the output of the x-ray equipment. Additionally, the software uses conversion coefficients (CCs) to assess the absorbed dose to organs and tissues of the human body, the effective dose as well as the patient's cancer risk for radiographic examinations. The CCs, ratios between organ or tissue absorbed doses and measurable quantities, have been calculated with the FAX06 and the MAX06 phantoms for 34 projections of 10 commonly performed x-ray examinations, for 40 combinations of tube potential and filtration ranging from 50 to 120 kVcp and from 2.0 to 5.0 mm aluminum, respectively, for various field positions, for 29 selected organs and tissues and simultaneously for the measurable quantities, INAK, ESAK and kerma area product (KAP). Based on the x-ray irradiation parameters defined by the user, CALDose X shows images of the phantom together with the position of the x-ray beam. By using true to nature voxel phantoms, CALDose X improves earlier software tools, which were mostly based on mathematical MIRD5-type phantoms, by using a less representative human anatomy.

TU-F-18A-03: Improving Tissue Segmentation for Monte Carlo Dose Calculation Using DECT Data

International Nuclear Information System (INIS)

Di, Salvio A; Bedwani, S; Carrier, J

2014-01-01

Purpose: To develop a new segmentation technique using dual energy CT (DECT) to overcome limitations related to segmentation from a standard Hounsfield unit (HU) to electron density (ED) calibration curve. Both methods are compared with a Monte Carlo analysis of dose distribution. Methods: DECT allows a direct calculation of both ED and effective atomic number (EAN) within a given voxel. The EAN is here defined as a function of the total electron cross-section of a medium. These values can be effectively acquired using a calibrated method from scans at two different energies. A prior stoichiometric calibration on a Gammex RMI phantom allows us to find the parameters to calculate EAN and ED within a voxel. Scans from a Siemens SOMATOM Definition Flash dual source system provided the data for our study. A Monte Carlo analysis compares dose distribution simulated by dosxyz-nrc, considering a head phantom defined by both segmentation techniques. Results: Results from depth dose and dose profile calculations show that materials with different atomic compositions but similar EAN present differences of less than 1%. Therefore, it is possible to define a short list of basis materials from which density can be adapted to imitate interaction behavior of any tissue. Comparison of the dose distributions on both segmentations shows a difference of 50% in dose in areas surrounding bone at low energy. Conclusion: The presented segmentation technique allows a more accurate medium definition in each voxel, especially in areas of tissue transition. Since the behavior of human tissues is highly sensitive at low energies, this reduces the errors on calculated dose distribution. This method could be further developed to optimize the tissue characterization based on anatomic site

TU-F-18A-03: Improving Tissue Segmentation for Monte Carlo Dose Calculation Using DECT Data

Energy Technology Data Exchange (ETDEWEB)

Di, Salvio A; Bedwani, S; Carrier, J [CHUM - Notre-Dame, Montreal, QC (Canada)

2014-06-15

Purpose: To develop a new segmentation technique using dual energy CT (DECT) to overcome limitations related to segmentation from a standard Hounsfield unit (HU) to electron density (ED) calibration curve. Both methods are compared with a Monte Carlo analysis of dose distribution. Methods: DECT allows a direct calculation of both ED and effective atomic number (EAN) within a given voxel. The EAN is here defined as a function of the total electron cross-section of a medium. These values can be effectively acquired using a calibrated method from scans at two different energies. A prior stoichiometric calibration on a Gammex RMI phantom allows us to find the parameters to calculate EAN and ED within a voxel. Scans from a Siemens SOMATOM Definition Flash dual source system provided the data for our study. A Monte Carlo analysis compares dose distribution simulated by dosxyz-nrc, considering a head phantom defined by both segmentation techniques. Results: Results from depth dose and dose profile calculations show that materials with different atomic compositions but similar EAN present differences of less than 1%. Therefore, it is possible to define a short list of basis materials from which density can be adapted to imitate interaction behavior of any tissue. Comparison of the dose distributions on both segmentations shows a difference of 50% in dose in areas surrounding bone at low energy. Conclusion: The presented segmentation technique allows a more accurate medium definition in each voxel, especially in areas of tissue transition. Since the behavior of human tissues is highly sensitive at low energies, this reduces the errors on calculated dose distribution. This method could be further developed to optimize the tissue characterization based on anatomic site.

Estimation of the transit dose component in high dose rate brachytherapy

International Nuclear Information System (INIS)

Garcia Romero, A.; Millan Cebrian, E.; Lozano Flores, F.J.; Lope Lope, R.; Canellas Anoz, M.

2001-01-01

Current high dose rate brachytherapy (HDR) treatment planning systems usually calculate dose only from source stopping positions (stationary component), but fails to account for the administered dose when the source is moving (dynamic component or transit dose). Numerical values of this transit dose depends upon the source velocity, implant geometry, source activity and prescribed dose. In some HDR treatments using particular geometry the transit dose cannot be ignored because it increases the dose at the prescriptions points and also could increase potential late tissue complications as predicted by the linear quadratic model. International protocols recommend to verify this parameter. The aim of this paper has been to establish a procedure for the transit dose calculation for the Gammamed 12i equipment at the RT Department in the Clinical University Hospital (Zaragoza-Spain). A numeric algorithm was implemented based on a dynamic point approximation for the moving HDR source and the calculated results for the entrance-exit transit dose was compared with TLD measurements made in some discrete points. (author) [es

Dose of radiation enhancement, using silver nanoparticles in a human tissue equivalent gel dosimeter.

Science.gov (United States)

Hassan, Muhammad; Waheed, Muhammad Mohsin; Anjum, Muhammad Naeem

2016-01-01

To quantify the radiation dose enhancement in a human tissue-equivalent polymer gel impregnated with silver nanoparticles. The case-control study was conducted at the Bahawalpur Institute of Nuclear Medicine and Oncology, Bahawalpur, Pakistan, in January 2014. Silver nanoparticles used in this study were prepared by wet chemical method. Polymer gel was prepared by known quantity of gelatine, methacrylic acid, ascorbic acid, copper sulphate pentahydrate, hydroquinone and water. Different concentrations of silver nanoparticles were added to the gel during its cooling process. The gel was cooled in six plastic vials of 50ml each. Two vials were used as a control sample while four vials were impregnated with silver nanoparticles. After 22 hours, the vials were irradiated with gamma rays by aCobalt-60 unit. Radiation enhancement was assessed by taking magnetic resonance images of the vials. The images were analysed using Image J software. The dose enhancement factor was 24.17% and 40.49% for 5Gy and 10Gy dose respectively. The dose enhancement factor for the gel impregnated with 0.10mM silver nanoparticles was 32.88% and 51.98% for 5Gy and 10Gy dose respectively. The impregnation of a tissue-equivalent gel with silver nanoparticles resulted in dose enhancement and this effect was magnified up to a certain level with the increase in concentration of silver nanoparticles.

MOSFET dosimeter depth-dose measurements in heterogeneous tissue-equivalent phantoms at diagnostic x-ray energies

International Nuclear Information System (INIS)

Jones, A.K.; Pazik, F.D.; Hintenlang, D.E.; Bolch, W.E.

2005-01-01

The objective of the present study was to explore the use of the TN-1002RD metal-oxide-semiconductor field effect transistor (MOSFET) dosimeter for measuring tissue depth dose at diagnostic photon energies in both homogeneous and heterogeneous tissue-equivalent materials. Three cylindrical phantoms were constructed and utilized as a prelude to more complex measurements within tomographic physical phantoms of pediatric patients. Each cylindrical phantom was constructed as a stack of seven 5-cm-diameter and 1-cm-thick discs of materials radiographically representative of either soft tissue (S), bone (B), or lung tissue (L) at diagnostic photon energies. In addition to a homogeneous phantom of soft tissue (SSSSSSS), two heterogeneous phantoms were constructed: SSBBSSS and SBLLBSS. MOSFET dosimeters were then positioned at the interface of each disc, and the phantoms were then irradiated at 66 kVp and 200 mAs. Measured values of absorbed dose at depth were then compared to predicated values of point tissue dose as determined via Monte Carlo radiation transport modeling. At depths exceeding 2 cm, experimental results matched the computed values of dose with high accuracy regardless of the dosimeter orientation (epoxy bubble facing toward or away from the x-ray beam). Discrepancies were noted, however, between measured and calculated point doses near the surface of the phantom (surface to 2 cm depth) when the dosimeters were oriented with the epoxy bubble facing the x-ray beam. These discrepancies were largely eliminated when the dosimeters were placed with the flat side facing the x-ray beam. It is therefore recommended that the MOSFET dosimeters be oriented with their flat sides facing the beam when they are used at shallow depths or on the surface of either phantoms or patients

Revised age-dependent doses to members of the public from intake of radionuclides using the new tissue weighting factors

International Nuclear Information System (INIS)

Jain, S.C.; Gupta, M.M.; Nagaratnam, A.; Reddy, A.R.; Mehta, S.C.

1992-01-01

ICRP 56 gave age-dependent dose coefficients to members of the public from intake of most radiologically significant radionuclides that might be released to the environment due to various human activities. It has computed effective dose equivalent (now called effective dose) from these dose coefficients utilising the tissue weighting factors as given by ICRP 26. The recent ICRP 1990 recommendations have revised the tissue weighting factors based on new information on risk estimates of fatal cancer and hereditary disorders. This change in the tissue weighting factors will subsequently affect the computation of effective dose due to intake of various radio-nuclides considered by ICRP 56. The revised effective doses for ingested as well as inhaled radionuclides have been worked out and compared from corresponding earlier values. No change was found in the case of tritiated water, organically bound tritium and 14 C. For the majority of the radionuclides, the revised effective dose was within ± 20% of the earlier values. Larger variations in effective dose were noted for radionuclides which deposit preferentially in one or two organs. (author)

SU-C-BRC-01: A Monte Carlo Study of Out-Of-Field Doses From Cobalt-60 Teletherapy Units Intended for Historical Correlations of Dose to Normal Tissue

Energy Technology Data Exchange (ETDEWEB)

Petroccia, H [University of Florida, Gainesville, FL (United States); Olguin, E [Gainesville, FL (United States); Culberson, W [University of Wisconsin Madison, Madison, WI (United States); Bednarz, B [University of Wisconsin, Madison, WI (United States); Mendenhall, N [UF Health Proton Therapy Institute, Jacksonville, FL (United States); Bolch, W [University Florida, Gainesville, FL (United States)

2016-06-15

Purpose: Innovations in radiotherapy treatments, such as dynamic IMRT, VMAT, and SBRT/SRS, result in larger proportions of low-dose regions where normal tissues are exposed to low doses levels. Low doses of radiation have been linked to secondary cancers and cardiac toxicities. The AAPM TG Committee No.158 entitled, ‘Measurements and Calculations of Doses outside the Treatment Volume from External-Beam Radiation Therapy’, has been formed to review the dosimetry of non-target and out-of-field exposures using experimental and computational approaches. Studies on historical patients can provide comprehensive information about secondary effects from out-of-field doses when combined with long-term patient follow-up, thus providing significant insight into projecting future outcomes of patients undergoing modern-day treatments. Methods: We present a Monte Carlo model of a Theratron-1000 cobalt-60 teletherapy unit, which historically treated patients at the University of Florida, as a means of determining doses located outside the primary beam. Experimental data for a similar Theratron-1000 was obtained at the University of Wisconsin’s ADCL to benchmark the model for out-of-field dosimetry. An Exradin A12 ion chamber and TLD100 chips were used to measure doses in an extended water phantom to 60 cm outside the primary field at 5 and 10 cm depths. Results: Comparison between simulated and experimental measurements of PDDs and lateral profiles show good agreement for in-field and out-of-field doses. At 10 cm away from the edge of a 6×6, 10×10, and 20×20 cm2 field, relative out-of-field doses were measured in the range of 0.5% to 3% of the dose measured at 5 cm depth along the CAX. Conclusion: Out-of-field doses can be as high as 90 to 180 cGy assuming historical prescription doses of 30 to 60 Gy and should be considered when correlating late effects with normal tissue dose.

Evaluation of dose components for healthy tissue tolerance studies on dogs at the HFR Petten

International Nuclear Information System (INIS)

Watkins, P.; Moss, R.L.; Siefert, A.; Huiskamp, R.; Gavin, P.; Konijnenberg, M.

1993-01-01

Before the start of clinical trails of BNCT on glioma patients at the Petten reactor, certain preconditions must be determined. In particular the tolerance of healthy brain tissue exposed to the epithermal neutron beam requires investigation. In these studies, beagle dogs have been subjected to different levels of irradiation and 10 B, the latter in the form of BSH. To support this work a treatment planning tool is being developed to predict the various dose components within the treatment volume. A Monte Carlo code, MCNP, has been used to simulate the particle transport and to predict the different dose rate distributions. The doses rates generated by MCNP are manipulated with a processing code, TREAT, to give irradiation times, peak dose positions and to display the required data in a graphical format. This paper explains the basic methodology used in the system and a practical case is presented for one of the healthy tissue tolerance dogs. Doses, both physical and RBE weighted, have been produced for pre-treatment planning studies

Dose gradient curve: A new tool for evaluating dose gradient.

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Sung, KiHoon; Choi, Young Eun

2018-01-01

Stereotactic radiotherapy, which delivers an ablative high radiation dose to a target volume for maximum local tumor control, requires a rapid dose fall-off outside the target volume to prevent extensive damage to nearby normal tissue. Currently, there is no tool to comprehensively evaluate the dose gradient near the target volume. We propose the dose gradient curve (DGC) as a new tool to evaluate the quality of a treatment plan with respect to the dose fall-off characteristics. The average distance between two isodose surfaces was represented by the dose gradient index (DGI) estimated by a simple equation using the volume and surface area of isodose levels. The surface area was calculated by mesh generation and surface triangulation. The DGC was defined as a plot of the DGI of each dose interval as a function of the dose. Two types of DGCs, differential and cumulative, were generated. The performance of the DGC was evaluated using stereotactic radiosurgery plans for virtual targets. Over the range of dose distributions, the dose gradient of each dose interval was well-characterized by the DGC in an easily understandable graph format. Significant changes in the DGC were observed reflecting the differences in planning situations and various prescription doses. The DGC is a rational method for visualizing the dose gradient as the average distance between two isodose surfaces; the shorter the distance, the steeper the dose gradient. By combining the DGC with the dose-volume histogram (DVH) in a single plot, the DGC can be utilized to evaluate not only the dose gradient but also the target coverage in routine clinical practice.

Mechanistic simulation of normal-tissue damage in radiotherapy-implications for dose-volume analyses

International Nuclear Information System (INIS)

Rutkowska, Eva; Baker, Colin; Nahum, Alan

2010-01-01

A radiobiologically based 3D model of normal tissue has been developed in which complications are generated when 'irradiated'. The aim is to provide insight into the connection between dose-distribution characteristics, different organ architectures and complication rates beyond that obtainable with simple DVH-based analytical NTCP models. In this model the organ consists of a large number of functional subunits (FSUs), populated by stem cells which are killed according to the LQ model. A complication is triggered if the density of FSUs in any 'critical functioning volume' (CFV) falls below some threshold. The (fractional) CFV determines the organ architecture and can be varied continuously from small (series-like behaviour) to large (parallel-like). A key feature of the model is its ability to account for the spatial dependence of dose distributions. Simulations were carried out to investigate correlations between dose-volume parameters and the incidence of 'complications' using different pseudo-clinical dose distributions. Correlations between dose-volume parameters and outcome depended on characteristics of the dose distributions and on organ architecture. As anticipated, the mean dose and V 20 correlated most strongly with outcome for a parallel organ, and the maximum dose for a serial organ. Interestingly better correlation was obtained between the 3D computer model and the LKB model with dose distributions typical for serial organs than with those typical for parallel organs. This work links the results of dose-volume analyses to dataset characteristics typical for serial and parallel organs and it may help investigators interpret the results from clinical studies.

Calculation of midplane dose for total body irradiation from entrance and exit dose MOSFET measurements.

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Satory, P R

2012-03-01

This work is the development of a MOSFET based surface in vivo dosimetry system for total body irradiation patients treated with bilateral extended SSD beams using PMMA missing tissue compensators adjacent to the patient. An empirical formula to calculate midplane dose from MOSFET measured entrance and exit doses has been derived. The dependency of surface dose on the air-gap between the spoiler and the surface was investigated by suspending a spoiler above a water phantom, and taking percentage depth dose measurements (PDD). Exit and entrances doses were measured with MOSFETs in conjunction with midplane doses measured with an ion chamber. The entrance and exit doses were combined using an exponential attenuation formula to give an estimate of midplane dose and were compared to the midplane ion chamber measurement for a range of phantom thicknesses. Having a maximum PDD at the surface simplifies the prediction of midplane dose, which is achieved by ensuring that the air gap between the compensator and the surface is less than 10 cm. The comparison of estimated midplane dose and measured midplane dose showed no dependence on phantom thickness and an average correction factor of 0.88 was found. If the missing tissue compensators are kept within 10 cm of the patient then MOSFET measurements of entrance and exit dose can predict the midplane dose for the patient.

A review of radiology staff doses and dose monitoring requirements

International Nuclear Information System (INIS)

Martin, C. J.

2009-01-01

Studies of radiation doses received during X-ray procedures by radiology, cardiology and other clinical staff have been reviewed. Data for effective dose (E), and doses to the eyes, thyroid, hands and legs have been analysed. These data have been supplemented with local measurements to determine the most exposed part of the hand for monitoring purposes. There are ranges of 60-100 in doses to individual tissues reported in the literature for similar procedures at different centres. While ranges in the doses per unit dose-area product (DAP) are between 10 and 25, large variations in dose result from differences in the sensitivity of the X-ray equipment, the type of procedure and the operator technique, but protection factors are important in maintaining dose levels as low as possible. The influence of shielding devices is significant for determining the dose to the eyes and thyroid, and the position of the operator, which depends on the procedure, is the most significant factor determining doses to the hands. A second body dosemeter worn at the level of the collar is recommended for operators with high workloads for use in assessment of effective dose and the dose to the eye. It is proposed that the third quartile values from the distributions of dose per unit DAP identified in the review might be employed in predicting the orders of magnitude of doses to the eye, thyroid and hands, based on interventional operator workloads. Such dose estimates could be employed in risk assessments when reviewing protection and monitoring requirements. A dosemeter worn on the little finger of the hand nearest to the X-ray tube is recommended for monitoring the hand. (authors)

Dose equivalent near the bone-soft tissue interface from nuclear fragments produced by high-energy protons

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Shavers, M. R.; Poston, J. W.; Cucinotta, F. A.; Wilson, J. W.

1996-01-01

During manned space missions, high-energy nucleons of cosmic and solar origin collide with atomic nuclei of the human body and produce a broad linear energy transfer spectrum of secondary particles, called target fragments. These nuclear fragments are often more biologically harmful than the direct ionization of the incident nucleon. That these secondary particles increase tissue absorbed dose in regions adjacent to the bone-soft tissue interface was demonstrated in a previous publication. To assess radiological risks to tissue near the bone-soft tissue interface, a computer transport model for nuclear fragments produced by high energy nucleons was used in this study to calculate integral linear energy transfer spectra and dose equivalents resulting from nuclear collisions of 1-GeV protons transversing bone and red bone marrow. In terms of dose equivalent averaged over trabecular bone marrow, target fragments emitted from interactions in both tissues are predicted to be at least as important as the direct ionization of the primary protons-twice as important, if recently recommended radiation weighting factors and "worst-case" geometry are used. The use of conventional dosimetry (absorbed dose weighted by aa linear energy transfer-dependent quality factor) as an appropriate framework for predicting risk from low fluences of high-linear energy transfer target fragments is discussed.

SU-E-T-573: Normal Tissue Dose Effect of Prescription Isodose Level Selection in Lung Stereotactic Body Radiation Therapy

International Nuclear Information System (INIS)

Zhang, Q; Lei, Y; Zheng, D; Zhu, X; Wahl, A; Lin, C; Zhou, S; Zhen, W

2015-01-01

Purpose: To evaluate dose fall-off in normal tissue for lung stereotactic body radiation therapy (SBRT) cases planned with different prescription isodose levels (IDLs), by calculating the dose dropping speed (DDS) in normal tissue on plans computed with both Pencil Beam (PB) and Monte-Carlo (MC) algorithms. Methods: The DDS was calculated on 32 plans for 8 lung SBRT patients. For each patient, 4 dynamic conformal arc plans were individually optimized for prescription isodose levels (IDL) ranging from 60% to 90% of the maximum dose with 10% increments to conformally cover the PTV. Eighty non-overlapping rind structures each of 1mm thickness were created layer by layer from each PTV surface. The average dose in each rind was calculated and fitted with a double exponential function (DEF) of the distance from the PTV surface, which models the steep- and moderate-slope portions of the average dose curve in normal tissue. The parameter characterizing the steep portion of the average dose curve in the DEF quantifies the DDS in the immediate normal tissue receiving high dose. Provided that the prescription dose covers the whole PTV, a greater DDS indicates better normal tissue sparing. The DDS were compared among plans with different prescription IDLs, for plans computed with both PB and MC algorithms. Results: For all patients, the DDS was found to be the lowest for 90% prescription IDL and reached a highest plateau region for 60% or 70% prescription. The trend was the same for both PB and MC plans. Conclusion: Among the range of prescription IDLs accepted by lung SBRT RTOG protocols, prescriptions to 60% and 70% IDLs were found to provide best normal tissue sparing

Study of Different Tissue Density Effects on the Dose Distribution of a 103Pd Brachytherapy Source Model MED3633

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Ali Asghar Mowlavi

2010-09-01

Full Text Available Introduction: Clinical application of encapsulated radioactive brachytherapy sources has a major role in cancer treatment. In the present research, the effects of different tissue densities on the dose distribution of a 103Pd brachytherapy source in a spherical phantom of 50 cm radius have been studied. Material and Methods: As is well known, absorbed dose in tissue depends to its density, but this difference is not clear in measurements. Therefore, we applied the MCNP code to evaluate the effect of density on the dose distribution. 103Pd brachytherapy sources are used to treat prostate, breast and other cancers. Results: Absorbed dose has been calculated and presented around a source placed in the center of the phantom for different tissue densities. Also, we derived anisotropy and radial dose functions and compared our Monte Carlo results with experimental results of Rivard and Li et al. for F(1, θ and g(r in 1.040 g/cm3 tissue. Conclusion: The results of this study show that relative dose variations around the source center are very considerable at different densities, because of the presence of a photoabsorber (Au-Cu alloy in the source core. Dose variation exceeds 80% at the point (Z = 2.4 mm, Y = 0 mm. Computed values of anisotropy and radial dose functions are in good agreement with the experimental results of Rivard and Li et al.

Tolerance doses of cutaneous and mucosal tissues in ring-necked parakeets (Psittacula krameri) for external beam megavoltage radiation.

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Barron, Heather W; Roberts, Royce E; Latimer, Kenneth S; Hernandez-Divers, Stephen; Northrup, Nicole C

2009-03-01

Currently used dosages for external-beam megavoltage radiation therapy in birds have been extrapolated from mammalian patients and often appear to provide inadequate doses of radiation for effective tumor control. To determine the tolerance doses of cutaneous and mucosal tissues of normal birds in order to provide more effective radiation treatment for tumors that have been shown to be radiation responsive in other species, ingluvial mucosa and the skin over the ingluvies of 9 ring-necked parakeets (Psittacula krameri) were irradiated in 4-Gy fractions to a total dose of either 48, 60, or 72 Gy using an isocentric cobalt-60 teletherapy unit. Minimal radiation-induced epidermal changes were present in the high-dose group histologically. Neither dose-related acute nor chronic radiation effects could be detected in any group grossly in cutaneous or mucosal tissue over a 9-month period. Radiation doses of 72 Gy in 4-Gy fractions were well tolerated in the small number of ring-necked parakeets in this initial tolerance dose study.

Dose reconstruction in deforming lung anatomy: Dose grid size effects and clinical implications

International Nuclear Information System (INIS)

Rosu, Mihaela; Chetty, Indrin J.; Balter, James M.; Kessler, Marc L.; McShan, Daniel L.; Ten Haken, Randall K.

2005-01-01

In this study we investigated the accumulation of dose to a deforming anatomy (such as lung) based on voxel tracking and by using time weighting factors derived from a breathing probability distribution function (p.d.f.). A mutual information registration scheme (using thin-plate spline warping) provided a transformation that allows the tracking of points between exhale and inhale treatment planning datasets (and/or intermediate state scans). The dose distributions were computed at the same resolution on each dataset using the Dose Planning Method (DPM) Monte Carlo code. Two accumulation/interpolation approaches were assessed. The first maps exhale dose grid points onto the inhale scan, estimates the doses at the 'tracked' locations by trilinear interpolation and scores the accumulated doses (via the p.d.f.) on the original exhale data set. In the second approach, the 'volume' associated with each exhale dose grid point (exhale dose voxel) is first subdivided into octants, the center of each octant is mapped to locations on the inhale dose grid and doses are estimated by trilinear interpolation. The octant doses are then averaged to form the inhale voxel dose and scored at the original exhale dose grid point location. Differences between the interpolation schemes are voxel size and tissue density dependent, but in general appear primarily only in regions with steep dose gradients (e.g., penumbra). Their magnitude (small regions of few percent differences) is less than the alterations in dose due to positional and shape changes from breathing in the first place. Thus, for sufficiently small dose grid point spacing, and relative to organ motion and deformation, differences due solely to the interpolation are unlikely to result in clinically significant differences to volume-based evaluation metrics such as mean lung dose (MLD) and tumor equivalent uniform dose (gEUD). The overall effects of deformation vary among patients. They depend on the tumor location, field

Up-regulation of calreticulin in mouse liver tissues after long-term irradiation with low-dose-rate gamma rays.

Science.gov (United States)

Yi, Lan; Hu, Nan; Yin, Jie; Sun, Jing; Mu, Hongxiang; Dai, Keren; Ding, Dexin

2017-01-01

The biological effects of low-dose or low-dose-rate ionizing radiation on normal tissues has attracted attention. Based on previous research, we observed the morphology of liver tissues of C57BL/6J mice that received irradiation dose rates increased. Additionally, differential protein expression in liver tissues was analyzed using a proteomics approach. Compared with the matched group in the 2D gel analysis of the irradiated groups, 69 proteins had ≥ 1.5-fold changes in expression. Twenty-three proteins were selected based on ≥2.5-fold change in expression, and 22 of them were meaningful for bioinformatics and protein fingerprinting analysis. These molecules were relevant to cytoskeleton processes, cell metabolism, biological defense, mitochondrial damage, detoxification and tumorigenesis. The results from real-time PCR and western blot (WB) analyses showed that calreticulin (CRT) was up-regulated in the irradiated groups, which indicates that CRT may be relevant to stress reactions when mouse livers are exposed to low-dose irradiation and that low-dose-rate ionizing radiation may pose a cancer risk. The CRT protein can be a potential candidate for low-dose or low-dose-rate ionizing radiation early-warning biomarkers. However, the underlying mechanism requires further investigation.

Study of the equivalent dose distribution in organs and tissues using periapical odontological radiography

International Nuclear Information System (INIS)

Santos, H.F.S.; Cipeli, J.F.; Fortes, M.A.B.; Federico, C.A.

2017-01-01

In this article presents a study of the doses obtained in periapical odontological radiography in main tissues of the head, using thermoluminescent dosemeters of type TLD-700H applied to a anthropomorphic simulator. The results indicate that the skin and salivary glands received the highest doses and the risk of calculated injury was 1.44 x 10 -6 Sv -1 per radiograph

In situ biological dose mapping estimates the radiation burden delivered to 'spared' tissue between synchrotron X-ray microbeam radiotherapy tracks.

Directory of Open Access Journals (Sweden)

Kai Rothkamm

Full Text Available Microbeam radiation therapy (MRT using high doses of synchrotron X-rays can destroy tumours in animal models whilst causing little damage to normal tissues. Determining the spatial distribution of radiation doses delivered during MRT at a microscopic scale is a major challenge. Film and semiconductor dosimetry as well as Monte Carlo methods struggle to provide accurate estimates of dose profiles and peak-to-valley dose ratios at the position of the targeted and traversed tissues whose biological responses determine treatment outcome. The purpose of this study was to utilise γ-H2AX immunostaining as a biodosimetric tool that enables in situ biological dose mapping within an irradiated tissue to provide direct biological evidence for the scale of the radiation burden to 'spared' tissue regions between MRT tracks. Γ-H2AX analysis allowed microbeams to be traced and DNA damage foci to be quantified in valleys between beams following MRT treatment of fibroblast cultures and murine skin where foci yields per unit dose were approximately five-fold lower than in fibroblast cultures. Foci levels in cells located in valleys were compared with calibration curves using known broadbeam synchrotron X-ray doses to generate spatial dose profiles and calculate peak-to-valley dose ratios of 30-40 for cell cultures and approximately 60 for murine skin, consistent with the range obtained with conventional dosimetry methods. This biological dose mapping approach could find several applications both in optimising MRT or other radiotherapeutic treatments and in estimating localised doses following accidental radiation exposure using skin punch biopsies.

Equivalent dose, effective dose and risk assessment from cephalometric radiography to critical organs

International Nuclear Information System (INIS)

Kang, Seong Sook; Cho, Bon Hae; Kim, Hyun Ja

1995-01-01

In head and neck region, the critical organ and tissue doses were determined, and the risks were estimated from lateral, posteroanterial and basilar cephalometric radiography. For each cephalometric radiography, 31 TLDs were placed in selected sites (18 internal and 13 external sites) in a tissue-equivalent phantom and exposed, then read-out in the TLD reader. The following results were obtained; 1. From lateral cephalometric radiography, the highest effective dose recorded was that delivered to the salivary gland (3.6 μSv) and the next highest dose was that received by the bone marrow (3 μSv). 2. From posteroanterial cephalometric radiography, the highest effective dose recorded was that delivered to the salivary gland (2 μSv) and the next highest dose was that received by the bone marrow (1.8 μSv). 3. From basilar cephalometric radiography, the highest effective dose recorded was that delivered to the thyroid gland (31.4 μSv) and the next highest dose was that received by the salivary gland (13.3 μSv). 4. The probabilities of stochastic effect from lateral, posteroanterial and basilar cephalometric radiography were 0.72 X 10 -6 , 0.49 X 10 -6 and 3.51 X 10 -6 , respectively.

A simple method to calculate the influence of dose inhomogeneity and fractionation in normal tissue complication probability evaluation

International Nuclear Information System (INIS)

Begnozzi, L.; Gentile, F.P.; Di Nallo, A.M.; Chiatti, L.; Zicari, C.; Consorti, R.; Benassi, M.

1994-01-01

Since volumetric dose distributions are available with 3-dimensional radiotherapy treatment planning they can be used in statistical evaluation of response to radiation. This report presents a method to calculate the influence of dose inhomogeneity and fractionation in normal tissue complication probability evaluation. The mathematical expression for the calculation of normal tissue complication probability has been derived combining the Lyman model with the histogram reduction method of Kutcher et al. and using the normalized total dose (NTD) instead of the total dose. The fitting of published tolerance data, in case of homogeneous or partial brain irradiation, has been considered. For the same total or partial volume homogeneous irradiation of the brain, curves of normal tissue complication probability have been calculated with fraction size of 1.5 Gy and of 3 Gy instead of 2 Gy, to show the influence of fraction size. The influence of dose distribution inhomogeneity and α/β value has also been simulated: Considering α/β=1.6 Gy or α/β=4.1 Gy for kidney clinical nephritis, the calculated curves of normal tissue complication probability are shown. Combining NTD calculations and histogram reduction techniques, normal tissue complication probability can be estimated taking into account the most relevant contributing factors, including the volume effect. (orig.) [de

Biological effect of pulsed dose rate brachytherapy with stepping sources if short half-times of repair are present in tissues

International Nuclear Information System (INIS)

Fowler, Jack F.; Limbergen, Erik F.M. van

1997-01-01

Purpose: To explore the possible increase of radiation effect in tissues irradiated by pulsed brachytherapy (PDR) for local tissue dose rates between those 'averaged over the whole pulse' and the instantaneous high dose rates close to the dwell positions. Increased effect is more likely for tissues with short half-times of repair of the order of a few minutes, similar to pulse durations. Methods and Materials: Calculations were done assuming the linear quadratic formula for radiation damage, in which only the dose-squared term is subject to exponential repair. The situation with two components of T (1(2)) is addressed. A constant overall time of 140 h and a constant total dose of 70 Gy were assumed throughout, the continuous low dose rate of 0.5 Gy/h (CLDR) providing the unitary standard effects for each PDR condition. Effects of dose rates ranging from 4 Gy/h to 120 Gy/h (HDR at 2 Gy/min) were studied, covering the gap in an earlier publication. Four schedules were examined: doses per pulse of 0.5, 1, 1.5, and 2 Gy given at repetition frequencies of 1, 2, 3, and 4 h, respectively, each with a range of assumed half-times of repair of 4 min to 1.5 h. Results are presented for late-responding tissues, the differences from CLDR being two or three times greater than for early-responding tissues and most tumors. Results: Curves are presented relating the ratio of increased biological effect (proportional to log cell kill) calculated for PDR relative to CLDR. Ratios as high as 1.5 can be found for large doses per pulse (2 Gy) if the half-time of repair in tissues is as short as a few minutes. The major influences on effect are dose per pulse, half-time of repair in tissue, and--when T (1(2)) is short--the instantaneous dose rate. Maximum ratios of PDR/CLDR occur when the dose rate is such that pulse duration is approximately equal to T (1(2)) . As dose rate in the pulse is increased, a plateau of effect is reached, for most T (1(2)) s, above 10 to 20 Gy/h, which is

A trial of radiation dose prescription based on dose-cell survival formula

International Nuclear Information System (INIS)

Allen, E.P.

1984-01-01

Radiation treatment has been prescribed for 379 basal cell carcinomata on the basis of a selected equivalent single dose derived from the standard multi-target dose-cell survival formula using values of m = 2 and Do = 130 rads for orthovoltage x-rays. The results suggest that the approach provides a flexible and acceptable alternative to prescription by total dose or by Nominal Standard Dose. It is submitted that Total Dose is an inadequate expression of radiobiological effects: that the NSD and related systems are valuable measures of the ability of normal tissues to recover from radiation damage: and that a parallel measure of the degree of tumour depopulation has become necessary to allow further progress in alternative fractionation schedules

Assessment of a new p-Mosfet usable as a dose rate insensitive gamma dose sensor

International Nuclear Information System (INIS)

Vettese, F.; Donichak, C.; Bourgeault, P.

1995-01-01

Dosimetric response of unbiased MOS devices has been assessed at dose rates greater than 2000 cGy/h. Application have been made to a personal dosemeter / dose rate meter to measure the absorbed tissue dose received in the case of acute external irradiation. (D.L.)

Neutrons in active proton therapy. Parameterization of dose and dose equivalent

Energy Technology Data Exchange (ETDEWEB)

Schneider, Uwe; Haelg, Roger A. [Univ. of Zurich (Switzerland). Dept. of Physics; Radiotherapy Hirslanden AG, Aarau (Switzerland); Lomax, Tony [Paul Scherrer Institute, Villigen (Switzerland). Center for Proton Therapy

2017-08-01

One of the essential elements of an epidemiological study to decide if proton therapy may be associated with increased or decreased subsequent malignancies compared to photon therapy is an ability to estimate all doses to non-target tissues, including neutron dose. This work therefore aims to predict for patients using proton pencil beam scanning the spatially localized neutron doses and dose equivalents. The proton pencil beam of Gantry 1 at the Paul Scherrer Institute (PSI) was Monte Carlo simulated using GEANT. Based on the simulated neutron dose and neutron spectra an analytical mechanistic dose model was developed. The pencil beam algorithm used for treatment planning at PSI has been extended using the developed model in order to calculate the neutron component of the delivered dose distribution for each treated patient. The neutron dose was estimated for two patient example cases. The analytical neutron dose model represents the three-dimensional Monte Carlo simulated dose distribution up to 85 cm from the proton pencil beam with a satisfying precision. The root mean square error between Monte Carlo simulation and model is largest for 138 MeV protons and is 19% and 20% for dose and dose equivalent, respectively. The model was successfully integrated into the PSI treatment planning system. In average the neutron dose is increased by 10% or 65% when using 160 MeV or 177 MeV instead of 138 MeV. For the neutron dose equivalent the increase is 8% and 57%. The presented neutron dose calculations allow for estimates of dose that can be used in subsequent epidemiological studies or, should the need arise, to estimate the neutron dose at any point where a subsequent secondary tumour may occur. It was found that the neutron dose to the patient is heavily increased with proton energy.

Dose volume assessment of high dose rate 192IR endobronchial implants

International Nuclear Information System (INIS)

Cheng, B. Saw; Korb, Leroy J.; Pawlicki, Todd; Wu, Andrew

1996-01-01

Purpose: To study the dose distributions of high dose rate (HDR) endobronchial implants using the dose nonuniformity ratio (DNR) and three volumetric irradiation indices. Methods and Materials: Multiple implants were configured by allowing a single HDR 192 Ir source to step through a length of 6 cm along an endobronchial catheter. Dwell times were computed to deliver a dose of 5 Gy to points 1 cm away from the catheter axis. Five sets of source configurations, each with different dwell position spacings from 0.5 to 3.0 cm, were evaluated. Three-dimensional (3D) dose distributions were then generated for each source configuration. Differential and cumulative dose-volume curves were generated to quantify the degree of target volume coverage, dose nonuniformity within the target volume, and irradiation of tissues outside the target volume. Evaluation of the implants were made using the DNR and three volumetric irradiation indices. Results: The observed isodose distributions were not able to satisfy all the dose constraints. The ability to optimally satisfy the dose constraints depended on the choice of dwell position spacing and the specification of the dose constraint points. The DNR and irradiation indices suggest that small dwell position spacing does not result in a more homogeneous dose distribution for the implant. This study supports the existence of a relationship between the dwell position spacing and the distance from the catheter axis to the reference dose or dose constraint points. Better dose homogeneity for an implant can be obtained if the spacing of the dwell positions are about twice the distance from the catheter axis to the reference dose or dose constraint points

SU-E-T-409: Evaluation of Tissue Composition Effect On Dose Distribution in Radiotherapy with 6 MV Photon Beam of a Medical Linac

Energy Technology Data Exchange (ETDEWEB)

Ghorbani, M; Tabatabaei, Z; Noghreiyan, A Vejdani [Mashhad University of Medical Sciences, Mashhad (Iran, Islamic Republic of); Meigooni, A Soleimani [Comprehensive Cancer Center of Nevada, Las Vegas, NV (United States)

2015-06-15

Purpose: The aim of this study is to evaluate soft tissue composition effect on dose distribution for various soft tissues and various depths in radiotherapy with 6 MV photon beam of a medical linac. Methods: A phantom and Siemens Primus linear accelerator were simulated using MCNPX Monte Carlo code. In a homogeneous cubic phantom, six types of soft tissue and three types of tissue-equivalent materials were defined separately. The soft tissues were muscle (skeletal), adipose tissue, blood (whole), breast tissue, soft tissue (9-component) and soft tissue (4-component). The tissue-equivalent materials included: water, A-150 tissue-equivalent plastic and perspex. Photon dose relative to dose in 9-component soft tissue at various depths on the beam’s central axis was determined for the 6 MV photon beam. The relative dose was also calculated and compared for various MCNPX tallies including,F8, F6 and,F4. Results: The results of the relative photon dose in various materials relative to dose in 9-component soft tissue and using different tallies are reported in the form of tabulated data. Minor differences between dose distributions in various soft tissues and tissue-equivalent materials were observed. The results from F6 and F4 were practically the same but different with,F8 tally. Conclusion: Based on the calculations performed, the differences in dose distributions in various soft tissues and tissue-equivalent materials are minor but they could be corrected in radiotherapy calculations to upgrade the accuracy of the dosimetric calculations.

The usefulness of metal markers for CTV-based dose prescription in high-dose-rate interstitial brachytherapy

International Nuclear Information System (INIS)

Yoshida, Ken; Mitomo, Masanori; Nose, Takayuki; Koizumi, Masahiko; Nishiyama, Kinji; Yoshida, Mineo

2002-01-01

We employ a clinical target volume (CTV)-based dose prescription for high-dose-rate (HDR) interstitial brachytherapy. However, it is not easy to define CTV and organs at risk (OAR) from X-ray film or CT scanning. To solve this problem, we have utilized metal markers since October 1999. Moreover, metal markers can help modify dose prescription. By regulating the doses to the metal markers, refining the dose prescription can easily be achieved. In this research, we investigated the usefulness of the metal markers. Between October 1999 and May 2001, 51 patients were implanted with metal markers at Osaka Medical Center for Cancer and Cardiovascular Diseases (OMCC), Osaka National Hospital (ONH) and Sanda City Hospital (SCH). Forty-nine patients (head and neck: 32; pelvis: 11; soft tissue: 3; breast: 3) using metal markers were analyzed. During operation, we implanted 179 metal markers (49 patients) to CTV and 151 markers (26 patients) to OAR. At treatment planning, CTV was reconstructed judging from the metal markers, applicator position and operation records. Generally, we prescribed the tumoricidal dose to an isodose surface that covers CTV. We also planned to limit the doses to OAR lower than certain levels. The maximum normal tissue doses were decided 80%, 150%, 100%, 50% and 200% of the prescribed doses for the rectum, the urethra, the mandible, the skin and the large vessel, respectively. The doses to the metal markers using CTV-based dose prescription were generated. These were compared with the doses theoretically calculated with the Paris system. Treatment results were also investigated. The doses to the 158 metal markers (42 patients) for CTV were higher than ''tumoricidal dose''. In 7 patients, as a result of compromised dose prescription, 9 markers were lower than the tumoricidal dose. The other 12 markers (7%) were excluded from dose evaluation because they were judged as miss-implanted. The doses to the 142 metal markers (24 patients) for OAR were lower

Split-dose recovery in epithelial and vascular-connective tissue of pig skin

International Nuclear Information System (INIS)

Peel, D.M.; Hopewell, J.W.; Simmonds, R.H.; Dodd, P.; Meistrich, M.L.

1984-01-01

In the first 16 weeks after irradiation, two distinct waves of reaction can be observed in pig skin; the first wave (3-9 weeks) represents the expression of damage to the epithelium while the second is indicative of primary damage to the dermis, mediated through vascular injury. Following β-irradiation with a strontium-90 applicator, a severe epithelial reaction was seen with little subsequent dermal effects. X-rays (250 kV) on the other hand, produced a minimal epithelial response at doses which led to the development of dermal necrosis after 10-16 weeks. Comparison of single doses with two equal doses separated by 24 h produced a D 2 -D 1 value of 7.0 Gy at the doses which produced moist desquamation in 50% of fields (ED 50 ) after strontium-90 irradiation. After X-irradiation comparison of ED 50 doses for the later dermal reaction suggested a D 2 -D 1 value of 4.5 Gy. Over this same dose range of X-rays the D 2 -D 1 value for the first wave epithelial reaction was 3.5 Gy. These values of D 2 -D 1 for epithelial and dermal reactions in pig skin were compared with published data and were examined in relation to the theoretical predictions of a linear quadratic model for tissue target cell survival. The results were broadly in keeping with the productions of such a model. (Auth.)

In vivo tissue heterogeneity influence on dose distributhon in high energy radiotheraphy with x ray

International Nuclear Information System (INIS)

Aldred, M.A.

1987-01-01

In vivo effects of tissue heterogeneity of pelvic region on dose distribution are studied. Eight patients under radiotherapy with linear accelerator are analysed. Thermoluminescent dosimeters placed under the skin are used for dose measurements of radiation beams. A comparative evaluation between this study and homogeneneous phantoms is presented. (M.A.C.) [pt

Investigation of real tissue water equivalent path lengths using an efficient dose extinction method

Science.gov (United States)

Zhang, Rongxiao; Baer, Esther; Jee, Kyung-Wook; Sharp, Gregory C.; Flanz, Jay; Lu, Hsiao-Ming

2017-07-01

For proton therapy, an accurate conversion of CT HU to relative stopping power (RSP) is essential. Validation of the conversion based on real tissue samples is more direct than the current practice solely based on tissue substitutes and can potentially address variations over the population. Based on a novel dose extinction method, we measured water equivalent path lengths (WEPL) on animal tissue samples to evaluate the accuracy of CT HU to RSP conversion and potential variations over a population. A broad proton beam delivered a spread out Bragg peak to the samples sandwiched between a water tank and a 2D ion-chamber detector. WEPLs of the samples were determined from the transmission dose profiles measured as a function of the water level in the tank. Tissue substitute inserts and Lucite blocks with known WEPLs were used to validate the accuracy. A large number of real tissue samples were measured. Variations of WEPL over different batches of tissue samples were also investigated. The measured WEPLs were compared with those computed from CT scans with the Stoichiometric calibration method. WEPLs were determined within  ±0.5% percentage deviation (% std/mean) and  ±0.5% error for most of the tissue surrogate inserts and the calibration blocks. For biological tissue samples, percentage deviations were within  ±0.3%. No considerable difference (extinction measurement took around 5 min to produce ~1000 WEPL values to be compared with calculations. This dose extinction system measures WEPL efficiently and accurately, which allows the validation of CT HU to RSP conversions based on the WEPL measured for a large number of samples and real tissues.

Tissue classifications in Monte Carlo simulations of patient dose for photon beam tumor treatments

Science.gov (United States)

Lin, Mu-Han; Chao, Tsi-Chian; Lee, Chung-Chi; Tung-Chieh Chang, Joseph; Tung, Chuan-Jong

2010-07-01

The purpose of this work was to study the calculated dose uncertainties induced by the material classification that determined the interaction cross-sections and the water-to-material stopping-power ratios. Calculations were made for a head- and neck-cancer patient treated with five intensity-modulated radiotherapy fields using 6 MV photon beams. The patient's CT images were reconstructed into two voxelized patient phantoms based on different CT-to-material classification schemes. Comparisons of the depth-dose curve of the anterior-to-posterior field and the dose-volume-histogram of the treatment plan were used to evaluate the dose uncertainties from such schemes. The results indicated that any misassignment of tissue materials could lead to a substantial dose difference, which would affect the treatment outcome. To assure an appropriate material assignment, it is desirable to have different conversion tables for various parts of the body. The assignment of stopping-power ratio should be based on the chemical composition and the density of the material.

Tissue classifications in Monte Carlo simulations of patient dose for photon beam tumor treatments

International Nuclear Information System (INIS)

Lin, Mu-Han; Chao, Tsi-Chian; Lee, Chung-Chi; Tung-Chieh Chang, Joseph; Tung, Chuan-Jong

2010-01-01

The purpose of this work was to study the calculated dose uncertainties induced by the material classification that determined the interaction cross-sections and the water-to-material stopping-power ratios. Calculations were made for a head- and neck-cancer patient treated with five intensity-modulated radiotherapy fields using 6 MV photon beams. The patient's CT images were reconstructed into two voxelized patient phantoms based on different CT-to-material classification schemes. Comparisons of the depth-dose curve of the anterior-to-posterior field and the dose-volume-histogram of the treatment plan were used to evaluate the dose uncertainties from such schemes. The results indicated that any misassignment of tissue materials could lead to a substantial dose difference, which would affect the treatment outcome. To assure an appropriate material assignment, it is desirable to have different conversion tables for various parts of the body. The assignment of stopping-power ratio should be based on the chemical composition and the density of the material.

SU-F-T-46: The Effect of Inter-Seed Attenuation and Tissue Composition in Prostate 125I Brachytherapy Dose Calculations

Energy Technology Data Exchange (ETDEWEB)

Tamura, K; Araki, F; Ohno, T [Kumamoto University, Kumamoto, Kumamoto (Japan)

2016-06-15

Purpose: To investigate the difference of dose distributions with/without the effect of inter-seed attenuation and tissue compositions in prostate {sup 125}I brachytherapy dose calculations, using Monte Carlo simulations of Particle and Heavy Ion Transport code System (PHITS). Methods: The dose distributions in {sup 125}I prostate brachytherapy were calculated using PHITS for non-simultaneous and simultaneous alignments of STM1251 sources in water or prostate phantom for six patients. The PHITS input file was created from DICOM-RT file which includes source coordinates and structures for clinical target volume (CTV) and organs at risk (OARs) of urethra and rectum, using in-house Matlab software. Photon and electron cutoff energies were set to 1 keV and 100 MeV, respectively. The dose distributions were calculated with the kerma approximation and the voxel size of 1 × 1 × 1 mm{sup 3}. The number of incident photon was set to be the statistical uncertainty (1σ) of less than 1%. The effect of inter-seed attenuation and prostate tissue compositions was evaluated from dose volume histograms (DVHs) for each structure, by comparing to results of the AAPM TG-43 dose calculation (without the effect of inter-seed attenuation and prostate tissue compositions). Results: The dose reduction due to the inter-seed attenuation by source capsules was approximately 2% for CTV and OARs compared to those of TG-43. In additions, by considering prostate tissue composition, the D{sub 90} and V{sub 100} of CTV reduced by 6% and 1%, respectively. Conclusion: It needs to consider the dose reduction due to the inter-seed attenuation and tissue composition in prostate {sup 125}I brachytherapy dose calculations.

Effective dose: a radiation protection quantity

CERN Document Server

Menzel, H G

2012-01-01

Modern radiation protection is based on the principles of justification, limitation, and optimisation. Assessment of radiation risks for individuals or groups of individuals is, however, not a primary objective of radiological protection. The implementation of the principles of limitation and optimisation requires an appropriate quantification of radiation exposure. The International Commission on Radiological Protection (ICRP) has introduced effective dose as the principal radiological protection quantity to be used for setting and controlling dose limits for stochastic effects in the regulatory context, and for the practical implementation of the optimisation principle. Effective dose is the tissue weighted sum of radiation weighted organ and tissue doses of a reference person from exposure to external irradiations and internal emitters. The specific normalised values of tissue weighting factors are defined by ICRP for individual tissues, and used as an approximate age- and sex-averaged representation of th...

Response functions for computing absorbed dose to skeletal tissues from neutron irradiation

Science.gov (United States)

Bahadori, Amir A.; Johnson, Perry; Jokisch, Derek W.; Eckerman, Keith F.; Bolch, Wesley E.

2011-11-01

Spongiosa in the adult human skeleton consists of three tissues—active marrow (AM), inactive marrow (IM) and trabecularized mineral bone (TB). AM is considered to be the target tissue for assessment of both long-term leukemia risk and acute marrow toxicity following radiation exposure. The total shallow marrow (TM50), defined as all tissues lying within the first 50 µm of the bone surfaces, is considered to be the radiation target tissue of relevance for radiogenic bone cancer induction. For irradiation by sources external to the body, kerma to homogeneous spongiosa has been used as a surrogate for absorbed dose to both of these tissues, as direct dose calculations are not possible using computational phantoms with homogenized spongiosa. Recent micro-CT imaging of a 40 year old male cadaver has allowed for the accurate modeling of the fine microscopic structure of spongiosa in many regions of the adult skeleton (Hough et al 2011 Phys. Med. Biol. 56 2309-46). This microstructure, along with associated masses and tissue compositions, was used to compute specific absorbed fraction (SAF) values for protons originating in axial and appendicular bone sites (Jokisch et al 2011 Phys. Med. Biol. 56 6857-72). These proton SAFs, bone masses, tissue compositions and proton production cross sections, were subsequently used to construct neutron dose-response functions (DRFs) for both AM and TM50 targets in each bone of the reference adult male. Kerma conditions were assumed for other resultant charged particles. For comparison, AM, TM50 and spongiosa kerma coefficients were also calculated. At low incident neutron energies, AM kerma coefficients for neutrons correlate well with values of the AM DRF, while total marrow (TM) kerma coefficients correlate well with values of the TM50 DRF. At high incident neutron energies, all kerma coefficients and DRFs tend to converge as charged-particle equilibrium is established across the bone site. In the range of 10 eV to 100 Me

Simulation studies of optimum energies for DXA: dependence on tissue type, patient size and dose model

International Nuclear Information System (INIS)

Michael, G. J.; Henderson, C. J.

1999-01-01

Dual-energy x-ray absorptiometry (DXA) is a well established technique for measuring bone mineral density (BMD). However, in recent years DXA is increasingly being used to measure body composition in terms of fat and fat-free mass. DXA scanners must also determine the soft tissue baseline value from soft-tissue-only regions adjacent to bone. The aim of this work is to determine, using computer simulations, the optimum x- ray energies for a number of dose models, different tissues, i.e. bone mineral, average soft tissue, lean soft tissue and fat; and a range of anatomical sites and patient sizes. Three models for patient dose were evaluated total beam energy, entrance exposure and absorbed dose calculated by Monte Carlo modelling. A range of tissue compositions and thicknesses were chosen to cover typical patient variations for the three sites femoral neck, PA spine and lateral spine. In this work, the optimisation of the energies is based on (1) the uncertainty that arises from the quantum statistical nature of the number of x-rays recorded by the detector, and (2) the radiation dose received by the patient. This study has deliberately not considered other parameters such as detector response, electronic noise, x-ray tube heat load etc, because these are technology dependent parameters, not ones that are inherent to the measuring technique. Optimisation of the energies is achieved by minimisation of the product of variance of density measurement and dose which is independent of the absolute intensities of the x-ray beams. The results obtained indicate that if solving for bone density, then E-low in the range 34 to 42 keV, E-high in the range 100 to 200 keV and incident intensity ratio (low energy/high energy) in the range 3 to 10 is a reasonable compromise for the normal range of patient sizes. The choice of energies is complicated by the fact that the DXA unit must also solve for fat and lean soft tissue in soft- tissue-only regions adjacent to the bone. In this

External dose distributions of exposure to natural uranium slab for calibration of beta absorbed dose

International Nuclear Information System (INIS)

Chen Lishu

1987-01-01

The depth dose distributions and uniformity of beta radiation fields from a natural uranium slab in equilibration were measured using a tissue equivalent extrapolation chamber and film dosimeter. The advantages for calibration of enviromental dose instument or survey meter and personal dosimeter, for routine monitoring in terms of directional dose equivalent and superficial individual dose equivalent were summarized. Finally, the values measured agree well with that of theoretical calculation

External dose distributions of exposure to natural uranium slab for calibration of beta absorbed dose

Energy Technology Data Exchange (ETDEWEB)

Lishu, Chen

1987-05-01

The depth dose distributions and uniformity of beta radiation fields from a natural uranium slab in equilibration were measured using a tissue equivalent extrapolation chamber and film dosimeter. The advantages for calibration of enviromental dose instument or survey meter and personal dosimeter, for routine monitoring in terms of directional dose equivalent and superficial individual dose equivalent were summarized. Finally, the values measured agree well with that of theoretical calculation.

Effect of tissue inhomogeneity on dose distribution of point sources of low-energy electrons

International Nuclear Information System (INIS)

Kwok, C.S.; Bialobzyski, P.J.; Yu, S.K.; Prestwich, W.V.

1990-01-01

Perturbation in dose distributions of point sources of low-energy electrons at planar interfaces of cortical bone (CB) and red marrow (RM) was investigated experimentally and by Monte Carlo codes EGS and the TIGER series. Ultrathin LiF thermoluminescent dosimeters were used to measure the dose distributions of point sources of 204 Tl and 147 Pm in RM. When the point sources were at 12 mg/cm 2 from a planar interface of CB and RM equivalent plastics, dose enhancement ratios in RM averaged over the region 0--12 mg/cm 2 from the interface were measured to be 1.08±0.03 (SE) and 1.03±0.03 (SE) for 204 Tl and 147 Pm, respectively. The Monte Carlo codes predicted 1.05±0.02 and 1.01±0.02 for the two nuclides, respectively. However, EGS gave consistently 3% higher dose in the dose scoring region than the TIGER series when point sources of monoenergetic electrons up to 0.75 MeV energy were considered in the homogeneous RM situation or in the CB and RM heterogeneous situation. By means of the TIGER series, it was demonstrated that aluminum, which is normally assumed to be equivalent to CB in radiation dosimetry, leads to an overestimation of backscattering of low-energy electrons in soft tissue at a CB--soft-tissue interface by as much as a factor of 2

Effects of tissue inhomogeneities on dose patterns in cylinders irradiated by negative pion beams

International Nuclear Information System (INIS)

Hamm, R.N.; Wright, H.A.; Turner, J.E.

1975-10-01

Effects of the presence of inhomogeneities in tissue irradiated by negative pion beams are investigated. Soft-tissue targets are considered with embedded regions of bone and cavities of air. The absorbed dose is calculated as a function of position in the targets for parallel and converging beams and for two parallel beams that enter the target from opposite sides. Isodose contours are calculated and displayed in each case. While these studies show expected trends, they indicate that specific calculations are needed for other beam parameters and target geometries. The contributions of neutrons to the dose contours can be seen from several calculations made both with and without neutrons

Active specific immunotherapy using the immune reaction of a low-dose irradiated tumor tissue

International Nuclear Information System (INIS)

Ogawa, Y.; Imanaka, K.; Ashida, C.; Takashima, H.; Imajo, Y.; Kimura, S.

1983-01-01

Active specific immunotherapy using the immune reaction of a low-dose irradiated tumor tissue was studied on the transplanted MM46 tumor of female C3H/He mice after radiotherapy. MM46 tumor cells were inoculated into the right hind paws of mice. On the 5th day, irradiation with the dose irradiated tumor tissue (2000 rad on the fifth day), were injected into the left hind paws of the tumor-bearing mice. Effectiveness of this active specific immunotherapy against tumor was evaluated by the regression of tumor and survival rate of mice. Tumor was markedly regressed and survival rate was significantly increased by the active specific immunitherapy

Characterization of the dose perturbation in tissue by stents as a function of external beam energy

International Nuclear Information System (INIS)

Schell, M.C.; Rosenzweig, D.P.; Weaver, K.A.; Rubin, P.

1997-01-01

Purpose: External beam irradiation of coronary arteries was shown to be detrimental in an animal model for the prevention of neointimal hyperplasia in the presence of stents when orthovoltage x-ray beams are used. This present study investigated the effect of beam energy on the dose distribution in the wall of the artery as a function of energy in the presence of stents in order to ascertain the effect on the dose due to beam energy. Materials and Methods: 250 kVp x-rays and 6-MV x rays were used to irradiate a stent placed in an homogeneous phantom. Radiochromic film densitometry and Monte Carlo calculations were used to measure and to simulate the dose distribution in the proximity of the stent. Result: External beam irradiation was reported to not only fail to prevent neointimal hyperplasia, but actually accentuate the neointimal response to a prompt mechanical injury in the artery. The photoelectric effect, which dominates low-energy x-ray interactions, produces recoil electrons in the stent which enhance the dose surrounding intima. The photoelectrons generated in nickel and iron have an extremely short range in normal tissue, approximately 0.1 mm. Initial estimates of orthovoltage x-ray interactions with the stent indicate a dose enhancement in the orthovoltage range by a factor of 2 to 3 due to the rise in the photoelectric cross section in this energy range depending on the elemental composition of the stent. Film densitometry verifies this dose enhancement. The Monte Carlo calculations yield a dose enhancement and the dose fall off with distance from the stent when irradiated with orthovoltage x-rays. Conversely when the tissue and stent are irradiated with megavoltage x-rays, the dose enhancement in this region is a factor of 1.15 in close proximity to the stent and 1.0 at distances greater than 0.1 mm. 6-MV photon interactions in tissue and iron are predominantly through Compton scattering. The Compton effect is dependent on the electron density in the

The Effects of Low Dose Irradiation on Inflammatory Response Proteins in a 3D Reconstituted Human Skin Tissue Model

Energy Technology Data Exchange (ETDEWEB)

Varnum, Susan M.; Springer, David L.; Chaffee, Mary E.; Lien, Katie A.; Webb-Robertson, Bobbie-Jo M.; Waters, Katrina M.; Sacksteder, Colette A.

2012-12-01

Skin responses to moderate and high doses of ionizing radiation include the induction of DNA repair, apoptosis, and stress response pathways. Additionally, numerous studies indicate that radiation exposure leads to inflammatory responses in skin cells and tissue. However, the inflammatory response of skin tissue to low dose radiation (<10 cGy) is poorly understood. In order to address this, we have utilized a reconstituted human skin tissue model (MatTek EpiDerm FT) and assessed changes in 23 cytokines twenty-four and forty eight hours following treatment of skin with either 3 or 10 cGy low-dose of radiation. Three cytokines, IFN-γ, IL-2, MIP-1α, were significantly altered in response to low dose radiation. In contrast, seven cytokines were significantly altered in response to a high radiation dose of 200 cGy (IL-2, IL-10, IL-13, IFN-γ, MIP-1α, TNF α, and VEGF) or the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (G-CSF, GM-CSF, IL-1α, IL-8, MIP-1α, MIP-1β, RANTES). Additionally, radiation induced inflammation appears to have a distinct cytokine response relative to the non-radiation induced stressor, TPA. Overall, these results indicate that there are subtle changes in the inflammatory protein levels following exposure to low dose radiation and this response is a sub-set of what is seen following a high dose in a human skin tissue model.

Outcome of stroke patients receiving different doses of recombinant tissue plasminogen activator.

Science.gov (United States)

Ong, Cheung-Ter; Wong, Yi-Sin; Wu, Chi-Shun; Su, Yu-Hsiang

2017-01-01

Intravenous recombinant tissue plasminogen activator (tPA) at a dose of 0.9 mg/kg body weight is associated with a high hemorrhagic transformation (HT) rate. Low-dose tPA (0.6 mg/kg) may have a lower hemorrhage rate but the mortality and disability rates at 90 days cannot be confirmed as non-inferior to standard-dose tPA. Whether the doses 0.7 and 0.8 mg/kg have better efficacy and safety needs further investigation. Therefore, this study is to compare the efficacy and safety of each dose of tPA (0.6, 0.7, 0.8, and 0.9 mg/kg body weight) and to investigate the factors affecting early neurological improvement (ENI) and early neurological deterioration (END). For this observational study, data were obtained from 274 patients who received tPA thrombolytic therapy in Chia-Yi Christian Hospital stroke unit. The tPA dose was given at the discretion of each physician. The definition of ENI was a >8 point improvement (compared with baseline) at 24 h following thrombolytic therapy or an improvement in the National Institutes of Health Stroke Score (NIHSS) to 0 or 1 toward the end of tPA infusion. The definition of END was a >4 point increase in NIHSS (compared with baseline) within 24 h of tPA infusion. The primary objective was to investigate whether 0.7 and 0.8 mg/kg of tPA have higher ENI rate, lower END rate, and better outcome at 6 months. Poor outcome was defined as having a modified Rankin Scale of 3 to 6 (range, 0 [no symptoms] to 6 [death]). The secondary objective was to investigate whether low-dose tPA has a lower risk of intracerebral HT than that with standard-dose tPA. We also investigated the factors affecting ENI, END, HT, and 6-month outcome. A total of 274 patients were included during the study period, of whom 260 were followed up for >6 months. There was a trend for the HT rate to increase as the dose increased ( P =0.02). The symptomatic HT rate was not significantly different among the low-dose and standard-dose groups. The ENI and END ( P =0.52) were

Absorbed dose measurement by using tissue equivalent ionization chamber (pair ionization chamber) in the Yayoi reactor

International Nuclear Information System (INIS)

Sasuga, N.; Okamura, K.; Terakado, T.; Mabuchi, Y.; Nakagawa, T.; Sukegawa, Toshio; Aizawa, C.; Saito, I.; Oka, Yoshiaki

1998-01-01

Each dose rate of neutron and gamma ray in the thermal column of the Yayoi reactor, in which an epithermal neutron field will be used for the boron neutron capture therapy, was measured by using a tissue equivalent ionization chamber and a graphite chamber. The tissue equivalent ionization chamber has some response to both neutron and gamma ray, but the graphite chamber has a few response to the neutron, so called pair ionization chamber method. The epithermal neutron fluxes of the thermal column were calculated by ANISN (one dimensional neutron-gamma transport code). A measured value for gamma dose rate by the pair ionization chamber agrees relevantly with a calculated result. For neutron dose rate, however, the measured value was too much small in comparison with the calculated result. The discrepancy between the measured value and the calculated result for neutron dose rate is discussed in detail in the report. (M. Suetake)

High dose rate brachytherapy for the treatment of soft tissue sarcoma of the extremity

International Nuclear Information System (INIS)

Speight, J.L.; Streeter, O.E.; Chawla, S.; Menendez, L.E.

1996-01-01

Purpose: we examined the role of preoperative neoadjuvant chemoradiation and adjuvant high-dose rate brachytherapy on the management of prognostically unfavorable soft tissue sarcomas of the extremities. Our goal was to examine the effect of high dose rate interstitial brachytherapy (HDR IBT) on reducing the risk of local recurrence following limb-sparing resection, as well as shortening treatment duration. Materials and methods: eleven patients, ranging in age from 31 to 73 years old, with soft tissue sarcoma of the extremity were treated at USC/Norris Comprehensive Cancer Center during 1994 and 1995. All patients had biopsy proven soft tissue sarcoma, and all were suitable candidates for limb-sparing surgery. All lesions were greater than 5cm in size and were primarily high grade. Tumor histologies included malignant fibrous histiocytoma (45%), liposarcoma (18%) and leiomyosarcoma, synovial cell sarcoma and spindle cell sarcoma (36%). Sites of tumor origin were the lower extremity (55%), upper extremity (18%) and buttock (9%), 1 patient (9%) had lesions in both the upper and lower extremity. Patients received HDR IBT following combined chemotherapy and external beam irradiation (EBRT) and en bloc resection of the sarcoma. Neoadjuvant chemotherapy consisted of three to four cycles of either Ifosfamide/Mesna with or without Adriamycin, or Mesna, Adriamycin, Ifosfamide and Dacarbazine. One patient received Cis-platin in addition to Ifos/Adr. A minimum of two cycles of chemotherapy were administered prior to EBRT. Additional cycles of chemotherapy were completed concurrently with EBRT but prior to HDR IBT. Preoperative EBRT doses ranging from 40 to 59.4 Gy were given in daily fractions of 180 to 200cGy. Following en bloc resection, HDR IBT was administered using the Omnitron tm 2000 remote afterloading system. Doses ranging from 13 to 30 Gy were delivered to the surgical tumor bed at depths of 0.5mm to 0.75mm from the radioactive source. Results: median follow-up was

Dose-rate effects in external beam radiotherapy redux

International Nuclear Information System (INIS)

Ling, C. Clifton; Gerweck, Leo E.; Zaider, Marco; Yorke, Ellen

2010-01-01

Recent developments in external beam radiotherapy, both in technical advances and in clinical approaches, have prompted renewed discussions on the potential influence of dose-rate on radio-response in certain treatment scenarios. We consider the multiple factors that influence the dose-rate effect, e.g. radical recombination, the kinetics of sublethal damage repair for tumors and normal tissues, the difference in α/β ratio for early and late reacting tissues, and perform a comprehensive literature review. Based on radiobiological considerations and the linear-quadratic (LQ) model we estimate the influence of overall treatment time on radio-response for specific clinical situations. As the influence of dose-rate applies to both the tumor and normal tissues, in oligo-fractionated treatment using large doses per fraction, the influence of delivery prolongation is likely important, with late reacting normal tissues being generally more sensitive to the dose-rate effect than tumors and early reacting tissues. In conventional fractionated treatment using 1.8-2 Gy per fraction and treatment times of 2-10 min, the influence of dose-rate is relatively small. Lastly, the dose-rate effect in external beam radiotherapy is governed by the overall beam-on-time, not by the average linac dose-rate, nor by the instantaneous dose-rate within individual linac pulses which could be as high as 3 x 10 6 MU/min.

Absorbed dose calculation of the energy deposition close to bone, lung and soft tissue interfaces in molecular radiotherapy

International Nuclear Information System (INIS)

Fernandez, M.; Lassman, M.

2015-01-01

Full text of publication follows. Aim: for voxel-based dosimetry in molecular radiotherapy (MRT) based on tabulated voxel S-values these values are usually obtained only for soft tissue. In order to study the changes in the dose deposition patterns at interfaces between different materials we have performed Monte Carlo simulations. Methods: the deposited energy patterns were obtained using the Monte-Carlo radiation code MCNPX v2.7 for Lu 177 (medium-energy) and Y 90 (high-energy). The following interfaces were studied: soft tissue-bone and soft tissue-lungs. For this purpose a volume of soft tissue homogeneously filled with Lu 177 or Y 90 was simulated at the interface to 3 different volumes containing no activity: soft tissue, lungs and bone. The emission was considered to be isotropic. The dimensions were chosen to ensure that the energy deposited by all generated particles was scored. The materials were defined as recommended by ICPR46; the decay schemes of Eckerman and Endo were used. With these data the absorbed dose patterns normalized to the maximum absorbed dose in the source region (soft tissue) were calculated. Results: the absorbed dose fractions in the boundary with soft tissue, bone and lungs are 50%, 47% and 57%, respectively, for Lu 177 and 50%, 47% and 51% for Y 90 . The distances to the interface at which the absorbed fractions are at 0.1% are 1.0, 0.6 and 3.0 mm for Lu 177 and 7.0, 4.0 and 24 mm for Y 90 , for soft tissue, bone and lungs respectively. Conclusions: in MRT, the changes in the absorbed doses at interfaces between soft tissue and bone/lungs need to be considered for isotopes emitting high energy particles. (authors)

Carcinogenesis induced by low-dose radiation

Directory of Open Access Journals (Sweden)

Piotrowski Igor

2017-11-01

Full Text Available Although the effects of high dose radiation on human cells and tissues are relatively well defined, there is no consensus regarding the effects of low and very low radiation doses on the organism. Ionizing radiation has been shown to induce gene mutations and chromosome aberrations which are known to be involved in the process of carcinogenesis. The induction of secondary cancers is a challenging long-term side effect in oncologic patients treated with radiation. Medical sources of radiation like intensity modulated radiotherapy used in cancer treatment and computed tomography used in diagnostics, deliver very low doses of radiation to large volumes of healthy tissue, which might contribute to increased cancer rates in long surviving patients and in the general population. Research shows that because of the phenomena characteristic for low dose radiation the risk of cancer induction from exposure of healthy tissues to low dose radiation can be greater than the risk calculated from linear no-threshold model. Epidemiological data collected from radiation workers and atomic bomb survivors confirms that exposure to low dose radiation can contribute to increased cancer risk and also that the risk might correlate with the age at exposure.

Development of Real-Time Measurement of Effective Dose for High Dose Rate Neutron Fields

International Nuclear Information System (INIS)

Braby, L. A.; Reece, W. D.; Hsu, W. H.

2003-01-01

Studies of the effects of low doses of ionizing radiation require sources of radiation which are well characterized in terms of the dose and the quality of the radiation. One of the best measures of the quality of neutron irradiation is the dose mean lineal energy. At very low dose rates this can be determined by measuring individual energy deposition events, and calculating the dose mean of the event size. However, at the dose rates that are normally required for biology experiments, the individual events can not be separated by radiation detectors. However, the total energy deposited in a specified time interval can be measured. This total energy has a random variation which depends on the size of the individual events, so the dose mean lineal energy can be calculated from the variance of repeated measurements of the energy deposited in a fixed time. We have developed a specialized charge integration circuit for the measurement of the charge produced in a small ion chamber in typical neutron irradiation experiments. We have also developed 4.3 mm diameter ion chambers with both tissue equivalent and carbon walls for the purpose of measuring dose mean lineal energy due to all radiations and due to all radiations except neutrons, respectively. By adjusting the gas pressure in the ion chamber, it can be made to simulate tissue volumes from a few nanometers to a few millimeters in diameter. The charge is integrated for 0.1 seconds, and the resulting pulse height is recorded by a multi channel analyzer. The system has been used in a variety of photon and neutron radiation fields, and measured values of dose and dose mean lineal energy are consistent with values extrapolated from measurements made by other techniques at much lower dose rates. It is expected that this technique will prove to be much more reliable than extrapolations from measurements made at low dose rates because these low dose rate exposures generally do not accurately reproduce the attenuation and

Relative implications of protective responses versus damage induction at low dose and low-dose-rate exposures, using the microdose approach

Energy Technology Data Exchange (ETDEWEB)

Feinendegen, L.E

2003-07-01

In reviewing tissue effects of low-dose radiation (1) absorbed dose to tissue is replaced by the sum of energy deposited with track events in cell-equivalent tissue micromasses, i.e. with microdose hits, in the number of exposed micromasses and (2) induced cell damage and adaptive protection are related to microdose hits in exposed micromasses for a given radiation quality. DNA damage increases with the number of microdose hits. They also can induce adaptive protection, mainly against endogenous DNA damage. This protection involves cellular defenses, DNA repair and damage removal. With increasing numbers of low linear energy transfer (LET) microdose hits in exposed micromasses, adaptive protection first tends to outweigh damage and then (above 200 mGy) fails and largely disappears. These experimental data predict that cancer risk coefficients derived by epidemiology at high-dose irradiation decline at low doses and dose rates when adaptive protection outdoes DNA damage. The dose-risk function should include both linear and non-linear terms at low doses. (author)

Relative implications of protective responses versus damage induction at low dose and low-dose-rate exposures, using the microdose approach

International Nuclear Information System (INIS)

Feinendegen, L.E.

2003-01-01

In reviewing tissue effects of low-dose radiation (1) absorbed dose to tissue is replaced by the sum of energy deposited with track events in cell-equivalent tissue micromasses, i.e. with microdose hits, in the number of exposed micromasses and (2) induced cell damage and adaptive protection are related to microdose hits in exposed micromasses for a given radiation quality. DNA damage increases with the number of microdose hits. They also can induce adaptive protection, mainly against endogenous DNA damage. This protection involves cellular defenses, DNA repair and damage removal. With increasing numbers of low linear energy transfer (LET) microdose hits in exposed micromasses, adaptive protection first tends to outweigh damage and then (above 200 mGy) fails and largely disappears. These experimental data predict that cancer risk coefficients derived by epidemiology at high-dose irradiation decline at low doses and dose rates when adaptive protection outdoes DNA damage. The dose-risk function should include both linear and non-linear terms at low doses. (author)

Technical specification of the NRPB thermoluminescent dosemeter used for the measurement of body dose and skin dose

CERN Document Server

Shaw, K B

1977-01-01

This report specifies the NRPB thermoluminescent dosemeter used for the measurement of radiation dose in tissue at a depth of 700 mg cm sup - sup 2 (body dose) and at a depth of 5-10 mg cm sup - sup 2 (skin dose).

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

Science.gov (United States)

Rosca, Florin

2012-06-01

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

High-dose mode of mortality in Tribolium: A model system for study of radiation injury and repair in non-proliferative tissues

International Nuclear Information System (INIS)

Cheng, Chihing Christina.

1989-01-01

With appropriate doses of ionizing radiation, both the acute, or lethal-midlethal, dose-independent pattern of mortality, and the hyperacute, dose-dependent pattern, were demonstrated within a single insect genus (Tribolium). This demonstration provides resolution of apparently contradictory reports of insect radiation responses in terms of doses required to cause lethality and those based on survival time as a function of dose. A dose-dependent mortality pattern was elicited in adult Tribolium receiving high doses, viz., 300 Gy or greater; its time course was complete in 10 days, before the dose-independent pattern of mortality began. Visual observations of heavily-irradiated Tribolium suggested neural and/or neuromuscular damage, as had been previously proposed by others for lethally-irradiated wasps, flies, and mosquitoes. Results of experiments using fractionated high doses supported the suggestion that the hyperacute or high-dose mode of death is the result of damage to nonproliferative tissues. Relative resistance of a strain to the hyperacute or high-dose mode of death was not correlated with resistance to the midlethal mode, which is believed to be the result of damage to the proliferative cells of the midgut. Using the high-dose mode of death as a model of radiation damage to nonproliferative tissues, the effects of age, and of a moderate priming dose were assessed. Beetles showed age-related increase in sensitivity to the high-dose mode of death, suggesting a decline in capacity to repair radiation damage to postmitotic tissue. This correlated with a decrease (50%) in the amount of repair reflected in the sparing effect of dose-fractionation (SDF) between the age of 1 to 3 months. The age related increase in radiosensitivity was reduced by a moderate priming dose (40 or 65 Gy) given at a young age

Estimates of Health Detriments and Tissue Weighting Factors for Hong Kong Populations from Low Dose, Low Dose Rate and Low LET Ionising Radiation Exposure

International Nuclear Information System (INIS)

Lee, S.K.

1998-01-01

The total health detriments and the tissue weighting factors for the Hong Kong populations from low dose, low dose rate and low LET ionising radiation exposure are obtained according to the methodology recommended in ICRP Publication 60. The probabilities of fatal cancers for the general (ages 0-90) and working (ages 20-64) populations due to lifetime exposure at low dose and low dose rate are 4.9 x 10 -2 Sv -1 and 3.6 x 10 -2 Sv -1 respectively, comparing with the ICRP 60 estimates of 5.0 x 10 -2 Sv -1 and 4.0 x 10 -2 Sv -1 . The corresponding total health detriments for the general and working populations are 6.9 x 10 -2 Sv -1 and 4.9 x 10 -2 Sv -1 respectively comparing with the ICRP 60 estimates of 7.3 x 10 -2 Sv -1 and 5.6 x 10 -2 Sv -1 . Tissue weighting factors for the general population are 0.01 (bone surface and skin), 0.02 (liver, oesophagus and thyroid), 0.04 (bladder and breast), 0.08 (remainder), 0.10 (stomach), 0.11 (bone marrow), 0.15 (colon), 0.19 (lung) and 0.21 (gonads) and for the working population are 0.01 (bone surface and skin), 0.03 (liver, oesophagus and thyroid), 0.04 (breast), 0.06 (remainder), 0.07 (bladder), 0.08 (colon), 0.14 (bone marrow and stomach), 0.16 (lung) and 0.20 (gonads). (author)

The effect of iodine uptake on radiation dose absorbed by patient tissues in contrast enhanced CT imaging. Implications for CT dosimetry

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Perisinakis, Kostas; Damilakis, John [University of Crete, Department of Medical Physics, Medical School, Heraklion, Crete (Greece); University Hospital of Heraklion, Department of Medical Physics, Heraklion, Crete (Greece); Tzedakis, Antonis; Papadakis, Antonios E. [University Hospital of Heraklion, Department of Medical Physics, Heraklion, Crete (Greece); Spanakis, Kostas [University Hospital of Heraklion, Department of Radiology, Heraklion, Crete (Greece); Hatzidakis, Adam [University Hospital of Heraklion, Department of Radiology, Heraklion, Crete (Greece); University of Crete, Department of Radiology, Medical School, Heraklion, Crete (Greece)

2018-01-15

To investigate the effect of iodine uptake on tissue/organ absorbed doses from CT exposure and its implications in CT dosimetry. The contrast-induced CT number increase of several radiosensitive tissues was retrospectively determined in 120 CT examinations involving both non-enhanced and contrast-enhanced CT imaging. CT images of a phantom containing aqueous solutions of varying iodine concentration were obtained. Plots of the CT number increase against iodine concentration were produced. The clinically occurring iodine tissue uptake was quantified by attributing recorded CT number increase to a certain concentration of aqueous iodine solution. Clinically occurring iodine uptake was represented in mathematical anthropomorphic phantoms. Standard 120 kV CT exposures were simulated using Monte Carlo methods and resulting organ doses were derived for non-enhanced and iodine contrast-enhanced CT imaging. The mean iodine uptake range during contrast-enhanced CT imaging was found to be 0.02-0.46% w/w for the investigated tissues, while the maximum value recorded was 0.82% w/w. For the same CT exposure, iodinated tissues were found to receive higher radiation dose than non-iodinated tissues, with dose increase exceeding 100% for tissues with high iodine uptake. Administration of iodinated contrast medium considerably increases radiation dose to tissues from CT exposure. (orig.)

Time- and dose rate-related effects of internal 177Lu exposure on gene expression in mouse kidney tissue

International Nuclear Information System (INIS)

Schüler, Emil; Rudqvist, Nils; Parris, Toshima Z.; Langen, Britta; Spetz, Johan; Helou, Khalil; Forssell-Aronsson, Eva

2014-01-01

Introduction: The kidneys are the dose-limiting organs in some radionuclide therapy regimens. However, the biological impact of internal exposure from radionuclides is still not fully understood. The aim of this study was to examine the effects of dose rate and time after i.v. injection of 177 LuCl 3 on changes in transcriptional patterns in mouse kidney tissue. Methods: To investigate the effect of dose rate, female Balb/c nude mice were i.v. injected with 11, 5.6, 1.6, 0.8, 0.30, and 0 MBq of 177 LuCl 3 , and killed at 3, 6, 24, 48, 168, and 24 hours after injection, respectively. Furthermore, the effect of time after onset of exposure was analysed using mice injected with 0.26, 2.4, and 8.2 MBq of 177 LuCl 3 , and killed at 45, 90, and 140 days after injection. Global transcription patterns of irradiated kidney cortex and medulla were assessed and enriched biological processes were determined from the regulated gene sets using Gene Ontology terms. Results: The average dose rates investigated were 1.6, 0.84, 0.23, 0.11 and 0.028 mGy/min, with an absorbed dose of 0.3 Gy. At 45, 90 and 140 days, the absorbed doses were estimated to 0.3, 3, and 10 Gy. In general, the number of differentially regulated transcripts increased with time after injection, and decreased with absorbed dose for both kidney cortex and medulla. Differentially regulated transcripts were predominantly involved in metabolic and stress response-related processes dependent on dose rate, as well as transcripts associated with metabolic and cellular integrity at later time points. Conclusion: The observed transcriptional response in kidney tissue was diverse due to difference in absorbed dose, dose rate and time after exposure. Nevertheless, several transcripts were significantly regulated in all groups despite differences in exposure parameters, which may indicate potential biomarkers for exposure of kidney tissue

Influence of length of interval between pulses in PDR brachytherapy (PDRBT on value of Biologically Equivalent Dose (BED in healthy tissues

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Tomasz Piotrowski

2010-07-01

Full Text Available Purpose: Different PDR treatment schemas are used in clinical practice, however optimal length of interval between pulses still remains unclear. The aim of this work was to compare value of BED doses measured in surrounded healthy tissues according to different intervals between pulses in PDRBT. Influence of doses optimization on BED values was analyzed.Material and methods: Fifty-one patients treated in Greater Poland Cancer Centre were qualified for calculations.Calculations of doses were made in 51 patients with head and neck cancer, brain tumor, breast cancer, sarcoma, penis cancer and rectal cancer. Doses were calculated with the use of PLATO planning system in chosen critical points in surrounded healthy tissues. For all treatment plans the doses were compared using Biologically Equivalent Dose formula.Three interval lengths (1, 2 and 4 hours between pulses were chosen for calculations. For statistical analysis Friedman ANOVA test and Kendall ratio were used.Results: The median value of BED in chosen critical points in healthy tissues was statistically related to the length of interval between PDR pulses and decreased exponentially with 1 hour interval to 4 hours (Kendall = from 0.48 to 1.0; p = from 0.002 to 0.00001.Conclusions: Prolongation of intervals between pulses in PDR brachytherapy was connected with lower values of BED doses in healthy tissues. It seems that longer intervals between pulses reduced the risk of late complications, but also decreased the tumour control. Furthermore, optimization influenced the increase of doses in healthy tissues.

Consideration of the ICRP 2006 revised tissue weighting factors on age-dependent values of the effective dose for external photons

Science.gov (United States)

Lee, Choonsik; Lee, Choonik; Han, Eun Young; Bolch, Wesley E.

2007-01-01

The effective dose recommended by the International Commission on Radiological Protection (ICRP) is the sum of organ equivalent doses weighted by corresponding tissue weighting factors, wT. ICRP is in the process of revising its 1990 recommendations on the effective dose where new values of organs and tissue weighting factors have been proposed and published in draft form for consultation by the radiological protection community. In its 5 June 2006 draft recommendations, new organs and tissues have been introduced in the effective dose which do not exist within the 1987 Oak Ridge National Laboratory (ORNL) phantom series (e.g., salivary glands). Recently, the investigators at University of Florida have updated the series of ORNL phantoms by implementing new organ models and adopting organ-specific elemental composition and densities. In this study, the effective dose changes caused by the transition from the current recommendation of ICRP Publication 60 to the 2006 draft recommendations were investigated for external photon irradiation across the range of ICRP reference ages (newborn, 1-year, 5-year, 10-year, 15-year and adult) and for six idealized irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), left-lateral (LLAT), right-lateral (RLAT), rotational (ROT) and isotropic (ISO). Organ-absorbed doses were calculated by implementing the revised ORNL phantoms in the Monte Carlo radiation transport code, MCNPX2.5, after which effective doses were calculated under the 1990 and draft 2006 evaluation schemes of the ICRP. Effective doses calculated under the 2006 draft scheme were slightly higher than estimated under ICRP Publication 60 methods for all irradiation geometries exclusive of the AP geometry where an opposite trend was observed. The effective doses of the adult phantom were more greatly affected by the change in tissue weighting factors than that seen within the paediatric members of the phantom series. Additionally, dose conversion

Dosimetric systems of high dose, dose rate and dose uniformity in food and medical products

International Nuclear Information System (INIS)

Vargas, J.; Vivanco, M.; Castro, E.

2014-08-01

implants with a weight of 1393 g the maximum dose rate of 6.5276 kGy /h, the minimum dose rate of 3.5684 kGy /h and the dose uniformity of 1 83 were determined. Then, based on the minimum dose rate irradiation times were calculated for different doses to evaluate in the microbial decontamination of food (3, 5, 8 and 12 kGy) and the sterilization of medical material by radiation (15, 20, 25 and 40 kGy), corroborating the applied doses with routine dosimeters of ethanol chlorobenzene (1-100 kGy) and perspex network 4034 (5-50 kGy). Other routine dosimeters used in different applications according to the doses range are Gafchromic Hd (40-400 Gray) for induced mutation by radiation and the development of new varieties of plants, the sterile insect technique to eradicate pests, quarantine treatment to solve plant health problems. Ambar Perspex 3042 C (3-15 kGy) for microbial decontamination of dried foods, spices, aromatic herbs, medicinal plants, etc. GEX B-3000 (1-140 kGy) and FWT (0.5-200 kGy) for sterilization of medical and pharmaceutical material, cosmetics, biological tissues, etc. The minimum dose rate allowing to calculate the irradiation times to apply the desired dose for the research or industrial processes, taking into account the density and geometry of product. Is notorious the difference in dose uniformity in food (1, 16) and medical material (1, 83) due to the geometry and relative density of the products within the irradiation cylinder. (author)

A simple calculation for the determination of organ or tissue dose from medical x-ray diagnosis for stomach and chest

International Nuclear Information System (INIS)

Nishizawa, Kanae

1984-01-01

A simple calculation method has been developed to determine the organ or tissue doses of patients for typical X-ray diagnoses. The absorbed doses related to radiation-induced stochastic effects were calculated based on the dosimetric parameters experimentally determined and technical parameters for X-ray diagnostic examinations. The present method is principally based on the TRA method for the beam therapy. The dosimetric parameters such as percentage depth-dose curves and isodose curves were measured with ionization chambers in the MixDP phantom. The distance from the incident surface of X-ray beams to the organ or tissue of interest was determined with a mathematical phantom, which was the modified version of the MIRD phantom for the average Japanese adult. The absorbed doses were determined with a simple table look-up method using a computer. The calculated doses were tabulated for various technical parameters of stomach and chest X-ray examinations. The present calculation was applied to the Rando woman phantom to compare with the phantom measurements. The calculated values agree with the experimental doses within 20% discrepancy. It was concluded that the present calculation method can determine organ or tissue doses very simply for various X-ray examinations and that it was valuable for the estimation of population doses and risks from X-ray diagnoses. (author)

Modification of the biologic dose to normal tissue by daily fraction

Energy Technology Data Exchange (ETDEWEB)

Wollin, M; Kagan, A R [Southern California Permanente Medical Group, Los Angeles Calif. (USA). Dep. of Radiation Therapy

1976-12-01

A method to predict normal tissue injury is proposed that includes high daily doses and unusual times successfully by calculating a new value called BIR (Biologic Index of Reaction). BIR and NSD were calculated for various normal tissue reactions. With the aid of statistical correlation techniques it is found that the BIR model is better than the NSD model in predicting radiation myelopathy and vocal edema and as good as NSD IN PREDICTING RIB FRACTURE/ Neither model predicts pericardial effusion. In no case were the results of BIR inferior to those of NSD.

Comparison of effective doses using tissue-weighting factors in the 1977, 1990, and 2007 recommendations of the ICRP

International Nuclear Information System (INIS)

Matsunaga, Yuta; Kawaguchi, Ai; Suzuki, Shoichi

2013-01-01

The International Commission on Radiological Protection (ICRP) has established recommended tissue-weighting factors. Although there have been international reports on effective doses using the factors listed in the 1977, 1990, and 2007 recommendations of the ICRP, there have been no papers in Japan. The aim of this study was to evaluate effective doses using the tissue-weighting factors listed in each recommendation of the ICRP under 2011 exposure conditions in Japan. We used a human body phantom to estimate patient exposure doses during chest, abdomen, lumbar spine (anteroposterior and lateral), and head radiographs. With thermoluminescence dosimeters placed at various positions on and in the phantom, radiation doses were determined. There was little change in the effective doses to the chest and head from each recommendation. However, the effective doses recommended in 1977 were 0.2 mSv to the abdomen, 0.1 mSv to the lumbar spine anteroposteriorally, and 0.1 mSv to the lumbar spine laterally; these values are lower than those recommended in 1990 and 2007, which were 0.5 mSv to the abdomen, 0.4 mSv to the lumbar spine anteroposteriorally, and 0.6 mSv to the lumbar spine laterally. We could evaluate the effective doses using each recommendation and 2011 exposure conditions in Japan. (author)

Technical Note: Dose effects of 1.5 T transverse magnetic field on tissue interfaces in MRI-guided radiotherapy

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Chen, Xinfeng; Prior, Phil; Chen, Guang-Pei; Schultz, Christopher J.; Li, X. Allen, E-mail: ali@mcw.edu [Department of Radiation Oncology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226 (United States)

2016-08-15

Purpose: The integration of MRI with a linear accelerator (MR-linac) offers great potential for high-precision delivery of radiation therapy (RT). However, the electron deflection resulting from the presence of a transverse magnetic field (TMF) can affect the dose distribution, particularly the electron return effect (ERE) at tissue interfaces. The purpose of the study is to investigate the dose effects of ERE at air-tissue and lung-tissue interfaces during intensity-modulated radiation therapy (IMRT) planning. Methods: IMRT and volumetric modulated arc therapy (VMAT) plans for representative pancreas, lung, breast, and head and neck (HN) cases were generated following commonly used clinical dose volume (DV) criteria. In each case, three types of plans were generated: (1) the original plan generated without a TMF; (2) the reconstructed plan generated by recalculating the original plan with the presence of a TMF of 1.5 T (no optimization); and (3) the optimized plan generated by a full optimization with TMF = 1.5 T. These plans were compared using a variety of DV parameters, including V{sub 100%}, D{sub 95%}, DHI [dose heterogeneity index: (D{sub 20%}–D{sub 80%})/D{sub prescription}], D{sub max}, and D{sub 1cc} in OARs (organs at risk) and tissue interface. All the optimizations and calculations in this work were performed on static data. Results: The dose recalculation under TMF showed the presence of the 1.5 T TMF can slightly reduce V{sub 100%} and D{sub 95%} for PTV, with the differences being less than 4% for all but one lung case studied. The TMF results in considerable increases in D{sub max} and D{sub 1cc} on the skin in all cases, mostly between 10% and 35%. The changes in D{sub max} and D{sub 1cc} on air cavity walls are dependent upon site, geometry, and size, with changes ranging up to 15%. The VMAT plans lead to much smaller dose effects from ERE compared to fixed-beam IMRT in pancreas case. When the TMF is considered in the plan optimization, the

Mixed field dose equivalent measuring instruments

International Nuclear Information System (INIS)

Brackenbush, L.W.; McDonald, J.C.; Endres, G.W.R.; Quam, W.

1985-01-01

In the past, separate instruments have been used to monitor dose equivalent from neutrons and gamma rays. It has been demonstrated that it is now possible to measure simultaneously neutron and gamma dose with a single instrument, the tissue equivalent proportional counter (TEPC). With appropriate algorithms dose equivalent can also be determined from the TEPC. A simple ''pocket rem meter'' for measuring neutron dose equivalent has already been developed. Improved algorithms for determining dose equivalent for mixed fields are presented. (author)

Absorbed dose rate meter for β-ray

International Nuclear Information System (INIS)

Bingo, K.

1977-01-01

The absorbed dose of β-ray depends on the energy of β-rays and the epidermal thickness of tissue in interest. In order to measure the absorbed dose rate at the interested tissue directly, the ratio of counting rate to absorbed dose should be constant independent of β-ray energy. In this purpose, a thin plastic scintillator was used as a detector with a single channel analyzer. The pulse height distribution, obtained using the scintillator whose thickness is less than the range of β-rays, shows a peak at a particular pulse height depending on the thickness of scintillator used. This means an increase of the number of pulses at lower pulse height. The lower level of discrimination and window width of the single channel analyzer are chosen according to the epidermal thickness of the tissue. In the experiment, scintillators of 0.5, 1, 2, 3, 5 and 10 mm thick were tested. It was found that desirable pulse height distribution, to obtain a constant dose sensitivity, could be obtained using the 2 mm thick scintillator. The sensitivity of the absorbed dose rate meter is constant within +-15% for β-ray with maximum energy from 0.4 to 3.5 MeV, when the absorbed dose rate for skin (epidermal thickness 7mg/cm 2 ) is measured. In order to measure the dose rate for a hand (epithermal thickness 40mg/cm 2 ) the lower level of discrimination is changed to be higher and at the same time the window width is also changed. Combining these techniques, one can get an absorbed dose rate meter for the tissue dose of various thickness, which has the constant dose sensitivity within +-15% for β-rays with maximum energy from 0.4 to 3.5 MeV

Prenatal radiation doses from radiopharmaceuticals

International Nuclear Information System (INIS)

Rojo, A.M.; Gomez Parada, I.M.; Di Trano, J.L.

1998-01-01

The radiopharmaceutical administration with diagnostic or therapeutic purpose during pregnancy implies a prenatal radiation dose. The dose assessment and the evaluation of the radiological risks become relevant due to the great radiosensitivity of the fetal tissues in development. This paper is a revision of the available data for estimating fetal doses in the cases of the more frequently used radiopharmaceuticals in nuclear medicine, taking into account recent investigation in placental crossover. The more frequent diagnostic and therapeutic procedures were analyzed according to the radiation doses implied. (author) [es

In vitro and in vivo effects of low dose HTO contamination modulated by dose rate

International Nuclear Information System (INIS)

Petcu, I.; Savu, D.; Moisoi, N.; Koeteles, G.J.

1997-01-01

The experiment performed in vitro intended to examine whether an adaptive response could be elicited on lymphocytes by low-level contamination of whole blood with tritiated water and if the modification of the dose rate has any influence on it. Lymphocytes pre-exposed to 3 HOH (0.2 - 6.6 MBq/ml) and subsequently irradiated with I Gy γ-rays showed micronuclei frequency significantly lower (40% - 45%) than the expected member (sum of the yields induced by 3 HOH and γ-rays separately). The degree of the radioresistance induced by HTO pre-treatments became higher with decreasing dose-rate for a rather similar total adapting dose. In vivo, the aim of the study was to investigate if different dose rates are inducing modulation of the lipid peroxidation level and of the thymidine uptake in different tissues of animals contaminated by HTO ingestion. The total doses varied between 5 and 20 cGy and were delivered as chronic (100 days) or acute contamination (5 days). It was observed that only doses about 20 cGy caused a dose-rate dependent increase of the lipid peroxidation level in the tissues of small intestine, kidney and spleen. Both chronic and acute contamination did produce reduced incorporation of thymidine in the cells of bone marrow. The most effective decrease of thymidine uptake was induced by the acute contamination in the lower dose domain (approx. 5 cGy). Our hypothesis is that in this dose domain the modification of thymidine uptake could be due to changes at the level of membrane transport. (author)

Doses from radioactive methane

International Nuclear Information System (INIS)

Phipps, A.W.; Kendall, G.M.; Fell, T.P.; Harrison, J.D.

1990-01-01

A possible radiation hazard arises from exposure to methane labelled with either a 3 H or a 14 C nuclide. This radioactive methane could be released from a variety of sources, e.g. land burial sites containing radioactive waste. Standard assumptions adopted for vapours would not apply to an inert alkane like methane. This paper discusses mechanisms by which radioactive methane would irradiate tissues and provides estimates of doses. Data on skin thickness and metabolism of methane are discussed with reference to these mechanisms. It is found that doses are dominated by dose from the small fraction of methane which is inhaled and metabolised. This component of dose has been calculated under rather conservative assumptions. (author)

Angular dependence of shallow dose

International Nuclear Information System (INIS)

Alvarez, J.L.

1986-01-01

The theoretical response of a detector is discussed and compared to measurements of shallow dose with tissue and phantom response detectors. A definite energy dependent angular response of dose and measurement was observed which could not be explained by simple trigonometric arguments. The response is back scatter dependent and must be considered in detector design and dose measurements. It is not possible for standard detectors to follow this response

Sparing Healthy Tissue and Increasing Tumor Dose Using Bayesian Modeling of Geometric Uncertainties for Planning Target Volume Personalization

International Nuclear Information System (INIS)

Herschtal, Alan; Te Marvelde, Luc; Mengersen, Kerrie; Foroudi, Farshad; Eade, Thomas; Pham, Daniel; Caine, Hannah; Kron, Tomas

2015-01-01

Objective: To develop a mathematical tool that can update a patient's planning target volume (PTV) partway through a course of radiation therapy to more precisely target the tumor for the remainder of treatment and reduce dose to surrounding healthy tissue. Methods and Materials: Daily on-board imaging was used to collect large datasets of displacements for patients undergoing external beam radiation therapy for solid tumors. Bayesian statistical modeling of these geometric uncertainties was used to optimally trade off between displacement data collected from previously treated patients and the progressively accumulating data from a patient currently partway through treatment, to optimally predict future displacements for that patient. These predictions were used to update the PTV position and margin width for the remainder of treatment, such that the clinical target volume (CTV) was more precisely targeted. Results: Software simulation of dose to CTV and normal tissue for 2 real prostate displacement datasets consisting of 146 and 290 patients treated with a minimum of 30 fractions each showed that re-evaluating the PTV position and margin width after 8 treatment fractions reduced healthy tissue dose by 19% and 17%, respectively, while maintaining CTV dose. Conclusion: Incorporating patient-specific displacement patterns from early in a course of treatment allows PTV adaptation for the remainder of treatment. This substantially reduces the dose to healthy tissues and thus can reduce radiation therapy–induced toxicities, improving patient outcomes

Sparing Healthy Tissue and Increasing Tumor Dose Using Bayesian Modeling of Geometric Uncertainties for Planning Target Volume Personalization

Energy Technology Data Exchange (ETDEWEB)

Herschtal, Alan, E-mail: Alan.Herschtal@petermac.org [Department of Biostatistics and Clinical Trials, Peter MacCallum Cancer Centre, Melbourne (Australia); Faculty of Health, Arts and Design, Swinburne University of Technology, Melbourne (Australia); Te Marvelde, Luc [Department of Biostatistics and Clinical Trials, Peter MacCallum Cancer Centre, Melbourne (Australia); Mengersen, Kerrie [School of Mathematical Sciences, Science and Engineering Faculty, Queensland University of Technology, Brisbane (Australia); Foroudi, Farshad [Department of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne (Australia); The Sir Peter MacCallum Department of Oncology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne (Australia); Eade, Thomas [Northern Sydney Cancer Centre, Radiation Oncology Department, Royal North Shore Hospital, St. Leonards, Sydney (Australia); Northern Clinical School, University of Sydney (Australia); Pham, Daniel [Department of Radiation Therapy, Peter MacCallum Cancer Centre, Melbourne (Australia); Caine, Hannah [Northern Sydney Cancer Centre, Radiation Oncology Department, Royal North Shore Hospital, St. Leonards, Sydney (Australia); Kron, Tomas [The Sir Peter MacCallum Department of Oncology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne (Australia); Department of Physical Sciences, Peter MacCallum Cancer Centre, Melbourne (Australia)

2015-06-01

Objective: To develop a mathematical tool that can update a patient's planning target volume (PTV) partway through a course of radiation therapy to more precisely target the tumor for the remainder of treatment and reduce dose to surrounding healthy tissue. Methods and Materials: Daily on-board imaging was used to collect large datasets of displacements for patients undergoing external beam radiation therapy for solid tumors. Bayesian statistical modeling of these geometric uncertainties was used to optimally trade off between displacement data collected from previously treated patients and the progressively accumulating data from a patient currently partway through treatment, to optimally predict future displacements for that patient. These predictions were used to update the PTV position and margin width for the remainder of treatment, such that the clinical target volume (CTV) was more precisely targeted. Results: Software simulation of dose to CTV and normal tissue for 2 real prostate displacement datasets consisting of 146 and 290 patients treated with a minimum of 30 fractions each showed that re-evaluating the PTV position and margin width after 8 treatment fractions reduced healthy tissue dose by 19% and 17%, respectively, while maintaining CTV dose. Conclusion: Incorporating patient-specific displacement patterns from early in a course of treatment allows PTV adaptation for the remainder of treatment. This substantially reduces the dose to healthy tissues and thus can reduce radiation therapy–induced toxicities, improving patient outcomes.

Dose constraints in paediatric radiotherapy; Contraintes de dose en radiotherapie pediatrique

Energy Technology Data Exchange (ETDEWEB)

Bernier, V. [Groupe de radiotherapie pediatrique SFCE, Centre Alexis-Vautrin, 54 - Nancy (France)

2010-10-15

The author discusses the issue of dose constraints for organs at risk when performing paediatric radiotherapy, and outlines that this issue is only partially resolved by the QUANTEC publication (quantitative estimates of normal tissue effects in the clinic). Then, he presents a guide elaborated by the French group of paediatric radiotherapists. This guide reviews organs at risk, imagery delineation requirements, dose constraints and short-, medium- and long-term consequences of organ irradiation. Short communication

Study of the influence of gold particles on the absorbed dose in soft tissue using polymer gel dosimetry

International Nuclear Information System (INIS)

Afonso, Luciana Caminha

2011-01-01

The presence of high-Z material adjacent to soft tissue, when submitted to irradiation, enhances locally the absorbed dose in these soft tissues. Such effect occurs due to the outscattering of photoelectrons from the high-Z material. Polymer gel dosimeters have been used to investigate this effect. Analytic calculations to estimate the dose enhancement and Monte Carlo simulations have been performed. Samples containing polymer gel (PG) with 0.005 gAu/gPG and pure polymer gel have been irradiated using an X-rays beam produced by 150 kV, filtered with 4 mm Al and 5 mm Cu, which resulted in an approximately 20% higher absorbed dose in the samples with gold in comparison to those with pure polymer gel. The analytic calculations and the Monte Carlo simulation resulted in a dose enhancement factor of approximately 30%. (author)

Dose specification for radiation therapy: dose to water or dose to medium?

International Nuclear Information System (INIS)

Ma, C-M; Li Jinsheng

2011-01-01

The Monte Carlo method enables accurate dose calculation for radiation therapy treatment planning and has been implemented in some commercial treatment planning systems. Unlike conventional dose calculation algorithms that provide patient dose information in terms of dose to water with variable electron density, the Monte Carlo method calculates the energy deposition in different media and expresses dose to a medium. This paper discusses the differences in dose calculated using water with different electron densities and that calculated for different biological media and the clinical issues on dose specification including dose prescription and plan evaluation using dose to water and dose to medium. We will demonstrate that conventional photon dose calculation algorithms compute doses similar to those simulated by Monte Carlo using water with different electron densities, which are close (<4% differences) to doses to media but significantly different (up to 11%) from doses to water converted from doses to media following American Association of Physicists in Medicine (AAPM) Task Group 105 recommendations. Our results suggest that for consistency with previous radiation therapy experience Monte Carlo photon algorithms report dose to medium for radiotherapy dose prescription, treatment plan evaluation and treatment outcome analysis.

Skin dose variation: influence of energy

International Nuclear Information System (INIS)

Cheung, T.; Yu, P.K.N.; Butson, M.J.; Cancer Services, Wollongong, NSW

2004-01-01

Full text: This research aimed to quantitatively evaluate the differences in percentage dose of maximum for 6MV and 18MV x-ray beams within the first lcm of interactions. Thus provide quantitative information regarding the basal, dermal and subcutaneous dose differences achievable with these two types of high-energy x-ray beams. Percentage dose of maximum build up curves are measured for most clinical field sizes using 6MV and 18MV x-ray beams. Calculations are performed to produce quantitative results highlighting the percentage dose of maximum differences delivered to various depths within the skin and subcutaneous tissue region by these two beams Results have shown that basal cell layer doses are not significantly different for 6MV and 18Mv x-ray beams At depths beyond the surface and basal cell layer there is a measurable and significant difference in delivered dose. This variation increases to 20% of maximum and 22% of maximum at Imm and 1cm depths respectively. The percentage variations are larger for smaller field sizes where the photon in phantom component of the delivered dose is the most significant contributor to dose By producing graphs or tables of % dose differences in the build up region we can provide quantitative information to the oncologist for consideration (if skin and subcutaneous tissue doses are of importance) during the beam energy selection process for treatment. Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

Optimal dose-response relationships in voice therapy.

Science.gov (United States)

Roy, Nelson

2012-10-01

Like other areas of speech-language pathology, the behavioural management of voice disorders lacks precision regarding optimal dose-response relationships. In voice therapy, dosing can presumably vary from no measurable effect (i.e., no observable benefit or adverse effect), to ideal dose (maximum benefit with no adverse effects), to doses that produce toxic or harmful effects on voice production. Practicing specific vocal exercises will inevitably increase vocal load. At ideal doses, these exercises may be non-toxic and beneficial, while at intermediate or high doses, the same exercises may actually be toxic or damaging to vocal fold tissues. In pharmacology, toxicity is a critical concept, yet it is rarely considered in voice therapy, with little known regarding "effective" concentrations of specific voice therapies vs "toxic" concentrations. The potential for vocal fold tissue damage related to overdosing on specific vocal exercises has been under-studied. In this commentary, the issue of dosing will be explored within the context of voice therapy, with particular emphasis placed on possible "overdosing".

The link between tissue elasticity and thermal dose in vivo

International Nuclear Information System (INIS)

Sapin-de Brosses, Emilie; Pernot, Mathieu; Tanter, Mickaël

2011-01-01

The objective of this study was to investigate in vivo the relationship between stiffness and thermal dose. For this purpose, shear wave elastography (SWE)—a novel ultrasound-based technique for real-time mapping of the stiffness of biological soft tissues—is performed in temperature-controlled experiments. Experiments were conducted on nine anesthetized rats. Their right leg was put in a thermo-regulated waterbath. The right leg of each animal was heated at one particular temperature between 38 °C and 48.5 °C for 15 min to 3 h. Shear waves were generated in the muscle using the acoustic radiation force induced by a linear ultrasonic probe. The shear wave propagation was imaged in real time by the probe using an ultrafast scanner prototype (10 000 frames s −1 ). The local tissue stiffness was derived from the shear wave speed. Two optical fiber sensors were inserted into the muscle to measure in situ the temperature. Stiffness was found to increase strongly during the experiments. When expressed as a function of the thermal dose, the stiffness curves were found to be the same for all experiments. A thermal dose threshold was found at 202 min for an eightfold stiffness increase. Finally, the time–temperature relationship was established for different stiffness ratios. The slope of the time–temperature relationship based on stiffness measurements was found identical to the one obtained for cell death in the seminal paper on the thermal dose by Sapareto and Dewey in 1984 (Int. J. Radiat. Oncol. Biol. Phys. 10 787–800). The present results highlight the stiffness increase as a good indicator of thermal necrosis. SWE imaging can be used in vivo for necrosis threshold determination in thermal therapy.

Radon Exposure and the Definition of Low Doses-The Problem of Spatial Dose Distribution.

Science.gov (United States)

Madas, Balázs G

2016-07-01

Investigating the health effects of low doses of ionizing radiation is considered to be one of the most important fields in radiological protection research. Although the definition of low dose given by a dose range seems to be clear, it leaves some open questions. For example, the time frame and the target volume in which absorbed dose is measured have to be defined. While dose rate is considered in the current system of radiological protection, the same cancer risk is associated with all exposures, resulting in a given amount of energy absorbed by a single target cell or distributed among all the target cells of a given organ. However, the biological effects and so the health consequences of these extreme exposure scenarios are unlikely to be the same. Due to the heterogeneous deposition of radon progeny within the lungs, heterogeneous radiation exposure becomes a practical issue in radiological protection. While the macroscopic dose is still within the low dose range, local tissue doses on the order of Grays can be reached in the most exposed parts of the bronchial airways. It can be concluded that progress in low dose research needs not only low dose but also high dose experiments where small parts of a biological sample receive doses on the order of Grays, while the average dose over the whole sample remains low. A narrow interpretation of low dose research might exclude investigations with high relevance to radiological protection. Therefore, studies important to radiological protection should be performed in the frame of low dose research even if the applied doses do not fit in the dose range used for the definition of low doses.

Test of tissue-equivalent scintillation detector for dose measurement of megavoltage beams

International Nuclear Information System (INIS)

Geso, M.; Ackerly, T.; Clift, M.A.

2000-01-01

Full text: The measurement of depth doses and profiles for a stereotactic radiotherapy beam presents special problems associated with the small beam size compared to the dosimeter's active detection area. In this work a locally fabricated organic plastic scintillator detector has been used to measure the depth dose and profile of a stereotactic radiotherapy beam. The 6MV beam is 1.25 cm diameter at isocentre, typical of small field stereotactic radiosurgery. The detector is a water/tissue equivalent plastic scintillator that is accompanied by Cerenkov subtraction detector. In this particular application, a negligible amount of Cerenkov light was detected. A photodiode and an electronic circuit is used instead of a photomultiplier for signal amplification. Comparison with data using a diode detector and a small size ionization chamber, indicate that the organic plastic scintillator detector is a valid detector for stereotactic radiosurgery dosimetry. The tissue equivalence of the organic scintillator also holds the promise of accurate dosimetry in the build up region. Depth doses measured using our plastic scintillator agree to within about 1% with those obtained using commercially available silicon diodes. Beam profiles obtained using plastic scintillator presents correct field width to within 0.35 mm, however some artifacts are visible in the profiles. These artifacts are about 5% discrepancy which has been shown not to be a significant factor in stereotactic radiotherapy dosimetry. Copyright (2000) Australasian College of Physical Scientists and Engineers in Medicine

The Study of Tissue Dose Perturbation by Air Cavity with 6MV Photon Beam

International Nuclear Information System (INIS)

Shin, Byung Chul; Yoo, Myung Jin; Moon, Chang Woo; Jeung, Tae Sig; Yum, Ha Yong

1995-01-01

Purpose : To determine the perturbation effect in the tissue downstream from surface layers of lesions located in the air/tumor-tissue interface of larynx using 6MV photon beam. Materials and Methods : Thermoluminescent dosimeters(TLDs). Were embedded at 3 measurement locations in slab no.7 of a humanoid phantom and exposed to forward and backward direction using various field sizes(4 X 4cm 2 - 15 X 15 cm 2 ). Results : At the air/tissue interface, forward dose perturbation factor(FDPF) is about 1.085 with 4 X 4 cm 2 , 1.05 with 7 X 7 cm 2 , 1.048 with 10 X 10 cm 2 , and 1.041 with 15 X 15 cm 2 . Backscatter dose perturbation factor(BDPF) is about 0.99 with 4 X 4 cm 2 , 0.981 with 7 X 7 cm 2 , 0.956 with 10 X 10 cm 2 and 0.97 with 15 X 15 cm 2 . Conclusion : FDPF is greater as field size is smaller. And FDPF is smaller as the distance is further from the air/tissue interface

ESR signal features of 60Co γ-ray irradiated bone tissue and its dose response relationship

International Nuclear Information System (INIS)

Wu Ke; Sun Zunpu; Shi Yuanming

1993-01-01

Electron spin resonance (ESR) technique was used to study the radiation-induced ESR signal features of different paramagnetic species of 60 Co γ-ray irradiated bone tissue. The results showed that the intensity of an ESR signal at that the intensity of an ESR signal at g 2.0022 of human bones exposed to a dose range of 0-50 Gy had linear dose response relationships. The lower limit of detectable dose was about 2 Gy and the detecting error was about 10%. The signal was stable at room temperature during 60 days, and the effect of radiation dose rate of 0.5-8.0 Gy/min could be neglected. This signal was insensitive to microwave power and temperature, which was suitable for rapid and direct detection with ESR technique. These features suggest that human bones could be used for radiation accident dose evaluation by ESR

Effects of low-dose irradiation of X-rays on IUdR incorporation into mouse tissues

International Nuclear Information System (INIS)

Misonoh, J.; Ishii, K.; Yoshida, M.; Okumura, Y.; Kodama, S.

1992-01-01

It is well known that biological responses get smaller when a radiation dose gets lower, and it makes it difficult to detect them with significant differences from background levels. Therefore we know little about biological effects arisen from very low-dose radiation in mammals and mammalian cells. Feinendegen et al. detected a significant reduction of 125 I-UdR uptake in bone marrow cells at doses below 0.01 Gy. Using this extremely sensitive biological response, they also indicated that cells of mice irradiated twice with an interval of 4 hours did not show any reaction after the second irradiation. This meant that cells became radio-resistant after whole-body irradiation with low-doses. This phenomenon, an acquired radio-resistance after low-dose irradiation, is explained as an adaptive response to radiation , which is recently well documented in cytogenic studies. In order to confirm that whether it is common in the cell renewal systems, IUdR incorporation into mouse spleen and the other tissues were studied after whole-body irradiation. (author). 7 refs., 1 fig., 2 tabs

Evaluation of absorbed radiation dose in mammography using Monte Carlo simulation; Avaliacao da dose absorvida em mamografia usando simulacao Monte Carlo

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, Bruno L.; Tomal, Alessandra [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil). Instituto de Fisica Gleb Wataghin

2016-07-01

Mammography is the main tool for breast cancer diagnosis, and it is based on the use of X-rays to obtain images. However, the glandular tissue present within the breast is highly sensitive to ionizing radiation, and therefore requires strict quality control in order to minimize the absorbed dose. The quantification of the absorbed dose in the breast tissue can be done by using Monte Carlo simulation, which allows a detailed study of the deposition of energy in different regions of the breast. Besides, the results obtained from the simulation can be associated with experimental data and provide values of dose interest, such as the dose deposited in glandular tissue. (author)

Response functions for computing absorbed dose to skeletal tissues from photon irradiation-an update

Energy Technology Data Exchange (ETDEWEB)

Johnson, Perry B; Bahadori, Amir A [Nuclear and Radiological Engineering, University of Florida, Gainesville, FL 32611 (United States); Eckerman, Keith F [Life Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Lee, Choonsik [Radiation Epidemiology Branch, National Cancer Institute, Bethesda, MD 20892 (United States); Bolch, Wesley E, E-mail: wbolch@ufl.edu [Nuclear and Radiological/Biomedical Engineering, University of Florida, Gainesville, FL 32611 (United States)

2011-04-21

A comprehensive set of photon fluence-to-dose response functions (DRFs) is presented for two radiosensitive skeletal tissues-active and total shallow marrow-within 15 and 32 bone sites, respectively, of the ICRP reference adult male. The functions were developed using fractional skeletal masses and associated electron-absorbed fractions as reported for the UF hybrid adult male phantom, which in turn is based upon micro-CT images of trabecular spongiosa taken from a 40 year male cadaver. The new DRFs expand upon both the original set of seven functions produced in 1985, and a 2007 update calculated under the assumption of secondary electron escape from spongiosa. In this study, it is assumed that photon irradiation of the skeleton will yield charged particle equilibrium across all spongiosa regions at energies exceeding 200 keV. Kerma coefficients for active marrow, inactive marrow, trabecular bone and spongiosa at higher energies are calculated using the DRF algorithm setting the electron-absorbed fraction for self-irradiation to unity. By comparing kerma coefficients and DRF functions, dose enhancement factors and mass energy-absorption coefficient (MEAC) ratios for active marrow to spongiosa were derived. These MEAC ratios compared well with those provided by the NIST Physical Reference Data Library (mean difference of 0.8%), and the dose enhancement factors for active marrow compared favorably with values calculated in the well-known study published by King and Spiers (1985 Br. J. Radiol. 58 345-56) (mean absolute difference of 1.9 percentage points). Additionally, dose enhancement factors for active marrow were shown to correlate well with the shallow marrow volume fraction (R{sup 2} = 0.91). Dose enhancement factors for the total shallow marrow were also calculated for 32 bone sites representing the first such derivation for this target tissue.

Dose limits to the eye lens

International Nuclear Information System (INIS)

Sion, N.

2016-01-01

Protecting the human body from the effects of ionizing radiation is essential to forestall stochastic effects and require placing limits on the effective dose. Dose limits on specific organs are also necessary to reduce the deterministic effects and tissue reactions. The standard for radiation protection was ISO 15382 (2002) which mainly dealt with beta radiation for nuclear power plant workers. Clearly an update is required to allow for new technology and the proliferative use of radiation in medical practices. There is a need for more explicit radiation monitoring to operators and staff. ICRP118 (International Commission on Radiological Protection), Ref. 1, evolved their recommendations to include eye lens doses as a follow on to their publication 103 and to focus on radiation exposures. It provides updated estimates of 'practical' threshold doses for tissue injury at the level of 1% incidence. This paper discusses the current status and the recommendation for a drastic reduction of the dose limit to the eye lens. (author)

Dose limits to the eye lens

Energy Technology Data Exchange (ETDEWEB)

Sion, N.

2016-09-15

Protecting the human body from the effects of ionizing radiation is essential to forestall stochastic effects and require placing limits on the effective dose. Dose limits on specific organs are also necessary to reduce the deterministic effects and tissue reactions. The standard for radiation protection was ISO 15382 (2002) which mainly dealt with beta radiation for nuclear power plant workers. Clearly an update is required to allow for new technology and the proliferative use of radiation in medical practices. There is a need for more explicit radiation monitoring to operators and staff. ICRP118 (International Commission on Radiological Protection), Ref. 1, evolved their recommendations to include eye lens doses as a follow on to their publication 103 and to focus on radiation exposures. It provides updated estimates of 'practical' threshold doses for tissue injury at the level of 1% incidence. This paper discusses the current status and the recommendation for a drastic reduction of the dose limit to the eye lens. (author)

Collective effective dose equivalent, population doses and risk estimates from occupational exposures in Japan

International Nuclear Information System (INIS)

Maruyama, Takashi; Nishizawa, Kanae; Kumamoto, Yoshikazu; Iwai, Kazuo; Mase, Naomichi.

1993-01-01

Collective dose equivalent and population dose from occupational exposures in Japan, 1988 were estimated on the basis of a nationwide survey. The survey was conducted on annual collective dose equivalents by sex, age group and type of radiation work for about 0.21 million workers except for the workers in nuclear power stations. The data on the workers in nuclear power stations were obtained from the official report of the Japan Nuclear Safety Commission. The total number of workers including nuclear power stations was estimated to be about 0.26 million. Radiation works were subdivided as follows: medical works including dental; non-atomic energy industry; research and education; atomic energy industry and nuclear power station. For the determination of effective dose equivalent and population dose, organ or tissue doses were measured with a phantom experiment. The resultant doses were compared with the doses previously calculated using a chord length technique and with data from ICRP publications. The annual collective effective dose equivalent were estimated to be about 21.94 person·Sv for medical workers, 7.73 person·Sv for industrial workers, 0.75 person·Sv for research and educational workers, 2.48 person·Sv for atomic energy industry and 84.4 person ·Sv for workers in nuclear power station. The population doses were calculated to be about 1.07 Sv for genetically significant dose, 0.89 Sv for leukemia significant dose and 0.42 Sv for malignant significant dose. The population risks were estimated using these population doses. (author)

HDRMC, an accelerated Monte Carlo dose calculator for high dose rate brachytherapy with CT-compatible applicators

Energy Technology Data Exchange (ETDEWEB)

Chibani, Omar, E-mail: omar.chibani@fccc.edu; C-M Ma, Charlie [Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111 (United States)

2014-05-15

Purpose: To present a new accelerated Monte Carlo code for CT-based dose calculations in high dose rate (HDR) brachytherapy. The new code (HDRMC) accounts for both tissue and nontissue heterogeneities (applicator and contrast medium). Methods: HDRMC uses a fast ray-tracing technique and detailed physics algorithms to transport photons through a 3D mesh of voxels representing the patient anatomy with applicator and contrast medium included. A precalculated phase space file for the{sup 192}Ir source is used as source term. HDRM is calibrated to calculated absolute dose for real plans. A postprocessing technique is used to include the exact density and composition of nontissue heterogeneities in the 3D phantom. Dwell positions and angular orientations of the source are reconstructed using data from the treatment planning system (TPS). Structure contours are also imported from the TPS to recalculate dose-volume histograms. Results: HDRMC was first benchmarked against the MCNP5 code for a single source in homogenous water and for a loaded gynecologic applicator in water. The accuracy of the voxel-based applicator model used in HDRMC was also verified by comparing 3D dose distributions and dose-volume parameters obtained using 1-mm{sup 3} versus 2-mm{sup 3} phantom resolutions. HDRMC can calculate the 3D dose distribution for a typical HDR cervix case with 2-mm resolution in 5 min on a single CPU. Examples of heterogeneity effects for two clinical cases (cervix and esophagus) were demonstrated using HDRMC. The neglect of tissue heterogeneity for the esophageal case leads to the overestimate of CTV D90, CTV D100, and spinal cord maximum dose by 3.2%, 3.9%, and 3.6%, respectively. Conclusions: A fast Monte Carlo code for CT-based dose calculations which does not require a prebuilt applicator model is developed for those HDR brachytherapy treatments that use CT-compatible applicators. Tissue and nontissue heterogeneities should be taken into account in modern HDR

Iodine-131 dose dependent gene expression in thyroid cancers and corresponding normal tissues following the Chernobyl accident.

Directory of Open Access Journals (Sweden)

Michael Abend

Full Text Available The strong and consistent relationship between irradiation at a young age and subsequent thyroid cancer provides an excellent model for studying radiation carcinogenesis in humans. We thus evaluated differential gene expression in thyroid tissue in relation to iodine-131 (I-131 doses received from the Chernobyl accident. Sixty three of 104 papillary thyroid cancers diagnosed between 1998 and 2008 in the Ukrainian-American cohort with individual I-131 thyroid dose estimates had paired RNA specimens from fresh frozen tumor (T and normal (N tissue provided by the Chernobyl Tissue Bank and satisfied quality control criteria. We first hybridized 32 randomly allocated RNA specimen pairs (T/N on 64 whole genome microarrays (Agilent, 4×44 K. Associations of differential gene expression (log(2(T/N with dose were assessed using Kruskall-Wallis and trend tests in linear mixed regression models. While none of the genes withstood correction for the false discovery rate, we selected 75 genes with a priori evidence or P kruskall/P trend <0.0005 for validation by qRT-PCR on the remaining 31 RNA specimen pairs (T/N. The qRT-PCR data were analyzed using linear mixed regression models that included radiation dose as a categorical or ordinal variable. Eleven of 75 qRT-PCR assayed genes (ACVR2A, AJAP1, CA12, CDK12, FAM38A, GALNT7, LMO3, MTA1, SLC19A1, SLC43A3, ZNF493 were confirmed to have a statistically significant differential dose-expression relationship. Our study is among the first to provide direct human data on long term differential gene expression in relation to individual I-131 doses and to identify a set of genes potentially important in radiation carcinogenesis.

Radiobiological modelling of dose-gradient effects in low dose rate, high dose rate and pulsed brachytherapy

International Nuclear Information System (INIS)

Armpilia, C; Dale, R G; Sandilos, P; Vlachos, L

2006-01-01

This paper presents a generalization of a previously published methodology which quantified the radiobiological consequences of dose-gradient effects in brachytherapy applications. The methodology uses the linear-quadratic (LQ) formulation to identify an equivalent biologically effective dose (BED eq ) which, if applied uniformly to a specified tissue volume, would produce the same net cell survival as that achieved by a given non-uniform brachytherapy application. Multiplying factors (MFs), which enable the equivalent BED for an enclosed volume to be estimated from the BED calculated at the dose reference surface, have been calculated and tabulated for both spherical and cylindrical geometries. The main types of brachytherapy (high dose rate (HDR), low dose rate (LDR) and pulsed (PB)) have been examined for a range of radiobiological parameters/dimensions. Equivalent BEDs are consistently higher than the BEDs calculated at the reference surface by an amount which depends on the treatment prescription (magnitude of the prescribed dose) at the reference point. MFs are closely related to the numerical BED values, irrespective of how the original BED was attained (e.g., via HDR, LDR or PB). Thus, an average MF can be used for a given prescribed BED as it will be largely independent of the assumed radiobiological parameters (radiosensitivity and α/β) and standardized look-up tables may be applicable to all types of brachytherapy treatment. This analysis opens the way to more systematic approaches for correlating physical and biological effects in several types of brachytherapy and for the improved quantitative assessment and ranking of clinical treatments which involve a brachytherapy component

Radiation doses to normal tissues during craniospinal irradiation ...

African Journals Online (AJOL)

Objective: This dosimetric study is aiming to report the results of the analysis of doses received by target volumes and organs outside the target volumes during the treatment of medulloblastoma patients. And also by comparing the doses reaching the eyes and the lens with the use of different shielding methods.

Dose dependent disposition of gallium-67 in rats

International Nuclear Information System (INIS)

Gautam, S.R.

1982-01-01

Radioactive gallium-67 has been employed as a diagnostic and follow-up agent for cancer therapy. Currently gallium nitrate is undergoing Phase I clinical studies. A million fold increase in the concentration of the carrier gallium citrate over the range of carrier-free gallium-67 (pgm) to 1.0 μg caused no significant alteration in the disposition of gallium-67 in rats.Gallium-67 was eliminated from blood with a biological t1/2 of 4.1 days. A linear tissue binding profile was observed for gallium-67 over this concentration range. A multi-compartment pharmacokinetic model was developed in which all the tissues studied were treated as separate compartments. At 1.0 mg dose level, significant alteration in the disposition of gallium-67 was observed in rats, > 95% of the initial radioactivity was characteristic reappearance of the radioactivity in the blood approximately 4 hours after dosing leading to a ''hump'' in the blood concentration-time profiles. Following the 1.0 mg dose low tissue levels were observed, except for the kidneys, which contained about 8% of the administered dose per gram of the tissue one-half hour after dosing. A non-linear tissue binding profile was observed to be associated with gallium at high doses. It was hypothesized that the rapid loss of gallium-67 from the vascular system following the high doses of gallium citrate was due to the accumulation of the drug in the kidneys where it was eventually eliminated via urine. The kidneys thus would act as a temporary storage site for gallium. It was concluded that the dose-related renal toxicity associated with gallium therapy may be attributed to the kidney's role as a temporary storage site following high doses

Low-Dose Tissue Plasminogen Activator in Acute Ischemic Stroke: A Systematic Review and Meta-Analysis.

Science.gov (United States)

Cheng, Ji-Wei; Zhang, Xiao-Jing; Cheng, Li-Shan; Li, Guo-Yi; Zhang, Li-Jun; Ji, Kang-Xiang; Zhao, Qing; Bai, Yu

2018-02-01

Intravenous thrombolysis using tissue plasminogen activator (tPA) improves significantly the neurologic function in patients with acute ischemic stroke (AIS). However, it brings financial burden to patients and is associated with symptomatic intracranial hemorrhage (SICH). Whether low-dose tPA can effectively reduce SICH and has the same efficacy as standard-dose tPA is still controversial. We searched for English clinical trials published before March, 2017on the comparison of the efficacy and safety between low and standard dose of tPA in the treatment of AIS using MEDLINE, Embase, and Cochrane Library. The modified Rankin scale (mRS) score was used as the primary efficacy outcome. The mRS1 corresponded to 0-1, whereas mRS2 corresponded to 0-2. The SICH and mortality were adopted as primary safety outcomes. Twelve high-quality studies were selected, including 7686 patients (low-dose: 2888, standard-dose: 4798). With no statistical heterogeneity, the fixed effects model was adopted in the analysis. Similarly to standard doses, low-dose tPA improved the mRS scores (mRS1: odds ratio [OR] = .92, 95% confidence interval [CI] .84-1.02; P = .12; mRS2: OR = .97, 95% CI .88-1.08; P = .57). Compared with standard-dose tPA, low-dose tPA reduced the incidence of SICH (by National Institute of Neurological Disorders and Stroke [NINDS] definition: OR = .71, 95% CI .57-0.89; P = .003; by Safe Implementation of Thrombolysis in Stroke Monitoring Study [SITS-MOST] definition: OR = .64, 95% CI .42-0.99; P = .04), while both reduced mortality (OR = .87, 95% CI .74-1.02; P = .08). Low-dose tPA is comparable to standard-dose tPA in improving the neurologic function and reducing mortality in AIS patients. Moreover, low-dose tPA can reduce the incidence of SICH compared with standard-dose tPA. Therefore, low-dose tPA is highly recommended in AIS patients. Copyright © 2018 National Stroke Association. Published by Elsevier Inc. All rights reserved.

SU-F-J-86: Method to Include Tissue Dose Response Effect in Deformable Image Registration

Energy Technology Data Exchange (ETDEWEB)

Zhu, J; Liang, J; Chen, S; Qin, A; Yan, D [Beaumont Health Systeml, Royal Oak, MI (United States)

2016-06-15

Purpose: Organ changes shape and size during radiation treatment due to both mechanical stress and radiation dose response. However, the dose response induced deformation has not been considered in conventional deformable image registration (DIR). A novel DIR approach is proposed to include both tissue elasticity and radiation dose induced organ deformation. Methods: Assuming that organ sub-volume shrinkage was proportional to the radiation dose induced cell killing/absorption, the dose induced organ volume change was simulated applying virtual temperature on each sub-volume. Hence, both stress and heterogeneity temperature induced organ deformation. Thermal stress finite element method with organ surface boundary condition was used to solve deformation. Initial boundary correspondence on organ surface was created from conventional DIR. Boundary condition was updated by an iterative optimization scheme to minimize elastic deformation energy. The registration was validated on a numerical phantom. Treatment dose was constructed applying both the conventional DIR and the proposed method using daily CBCT image obtained from HN treatment. Results: Phantom study showed 2.7% maximal discrepancy with respect to the actual displacement. Compared with conventional DIR, subvolume displacement difference in a right parotid had the mean±SD (Min, Max) to be 1.1±0.9(−0.4∼4.8), −0.1±0.9(−2.9∼2.4) and −0.1±0.9(−3.4∼1.9)mm in RL/PA/SI directions respectively. Mean parotid dose and V30 constructed including the dose response induced shrinkage were 6.3% and 12.0% higher than those from the conventional DIR. Conclusion: Heterogeneous dose distribution in normal organ causes non-uniform sub-volume shrinkage. Sub-volume in high dose region has a larger shrinkage than the one in low dose region, therefore causing more sub-volumes to move into the high dose area during the treatment course. This leads to an unfavorable dose-volume relationship for the normal organ

Direct dose mapping versus energy/mass transfer mapping for 4D dose accumulation: fundamental differences and dosimetric consequences.

Science.gov (United States)

Li, Haisen S; Zhong, Hualiang; Kim, Jinkoo; Glide-Hurst, Carri; Gulam, Misbah; Nurushev, Teamour S; Chetty, Indrin J

2014-01-06

The direct dose mapping (DDM) and energy/mass transfer (EMT) mapping are two essential algorithms for accumulating the dose from different anatomic phases to the reference phase when there is organ motion or tumor/tissue deformation during the delivery of radiation therapy. DDM is based on interpolation of the dose values from one dose grid to another and thus lacks rigor in defining the dose when there are multiple dose values mapped to one dose voxel in the reference phase due to tissue/tumor deformation. On the other hand, EMT counts the total energy and mass transferred to each voxel in the reference phase and calculates the dose by dividing the energy by mass. Therefore it is based on fundamentally sound physics principles. In this study, we implemented the two algorithms and integrated them within the Eclipse treatment planning system. We then compared the clinical dosimetric difference between the two algorithms for ten lung cancer patients receiving stereotactic radiosurgery treatment, by accumulating the delivered dose to the end-of-exhale (EE) phase. Specifically, the respiratory period was divided into ten phases and the dose to each phase was calculated and mapped to the EE phase and then accumulated. The displacement vector field generated by Demons-based registration of the source and reference images was used to transfer the dose and energy. The DDM and EMT algorithms produced noticeably different cumulative dose in the regions with sharp mass density variations and/or high dose gradients. For the planning target volume (PTV) and internal target volume (ITV) minimum dose, the difference was up to 11% and 4% respectively. This suggests that DDM might not be adequate for obtaining an accurate dose distribution of the cumulative plan, instead, EMT should be considered.

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

PURPOSE: Helium ions ((4)He) may supplement current particle beam therapy strategies as they possess advantages in physical dose distribution over protons. To assess potential clinical advantages, a dose calculation module accounting for relative biological effectiveness (RBE) was developed...... published so far. The advantage of (4)He seems to lie in the reduction of dose to surrounding tissue and to OARs. Nevertheless, additional biological experiments and treatment planning studies with larger patient numbers and more tumor indications are necessary to study the possible benefits of helium ion...

Cancer radiotherapy based on femtosecond IR laser-beam filamentation yielding ultra-high dose rates and zero entrance dose.

Science.gov (United States)

Meesat, Ridthee; Belmouaddine, Hakim; Allard, Jean-François; Tanguay-Renaud, Catherine; Lemay, Rosalie; Brastaviceanu, Tiberius; Tremblay, Luc; Paquette, Benoit; Wagner, J Richard; Jay-Gerin, Jean-Paul; Lepage, Martin; Huels, Michael A; Houde, Daniel

2012-09-18

Since the invention of cancer radiotherapy, its primary goal has been to maximize lethal radiation doses to the tumor volume while keeping the dose to surrounding healthy tissues at zero. Sadly, conventional radiation sources (γ or X rays, electrons) used for decades, including multiple or modulated beams, inevitably deposit the majority of their dose in front or behind the tumor, thus damaging healthy tissue and causing secondary cancers years after treatment. Even the most recent pioneering advances in costly proton or carbon ion therapies can not completely avoid dose buildup in front of the tumor volume. Here we show that this ultimate goal of radiotherapy is yet within our reach: Using intense ultra-short infrared laser pulses we can now deposit a very large energy dose at unprecedented microscopic dose rates (up to 10(11) Gy/s) deep inside an adjustable, well-controlled macroscopic volume, without any dose deposit in front or behind the target volume. Our infrared laser pulses produce high density avalanches of low energy electrons via laser filamentation, a phenomenon that results in a spatial energy density and temporal dose rate that both exceed by orders of magnitude any values previously reported even for the most intense clinical radiotherapy systems. Moreover, we show that (i) the type of final damage and its mechanisms in aqueous media, at the molecular and biomolecular level, is comparable to that of conventional ionizing radiation, and (ii) at the tumor tissue level in an animal cancer model, the laser irradiation method shows clear therapeutic benefits.

Calculation of dose distribution in compressible breast tissues using finite element modeling, Monte Carlo simulation and thermoluminescence dosimeters

Science.gov (United States)

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%.

Calculation of dose distribution in compressible breast tissues using finite element modeling, Monte Carlo simulation and thermoluminescence dosimeters

International Nuclear Information System (INIS)

Mohammadyari, Parvin; Faghihi, Reza; Mosleh-Shirazi, Mohammad Amin; Lotfi, Mehrzad; Hematiyan, Mohammad Rahim; Koontz, Craig; Meigooni, Ali S

2015-01-01

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%. (paper)

Converting dose distributions into tumour control probability

International Nuclear Information System (INIS)

Nahum, A.E.

1996-01-01

The endpoints in radiotherapy that are truly of relevance are not dose distributions but the probability of local control, sometimes known as the Tumour Control Probability (TCP) and the Probability of Normal Tissue Complications (NTCP). A model for the estimation of TCP based on simple radiobiological considerations is described. It is shown that incorporation of inter-patient heterogeneity into the radiosensitivity parameter a through s a can result in a clinically realistic slope for the dose-response curve. The model is applied to inhomogeneous target dose distributions in order to demonstrate the relationship between dose uniformity and s a . The consequences of varying clonogenic density are also explored. Finally the model is applied to the target-volume DVHs for patients in a clinical trial of conformal pelvic radiotherapy; the effect of dose inhomogeneities on distributions of TCP are shown as well as the potential benefits of customizing the target dose according to normal-tissue DVHs. (author). 37 refs, 9 figs

Converting dose distributions into tumour control probability

Energy Technology Data Exchange (ETDEWEB)

Nahum, A E [The Royal Marsden Hospital, London (United Kingdom). Joint Dept. of Physics

1996-08-01

The endpoints in radiotherapy that are truly of relevance are not dose distributions but the probability of local control, sometimes known as the Tumour Control Probability (TCP) and the Probability of Normal Tissue Complications (NTCP). A model for the estimation of TCP based on simple radiobiological considerations is described. It is shown that incorporation of inter-patient heterogeneity into the radiosensitivity parameter a through s{sub a} can result in a clinically realistic slope for the dose-response curve. The model is applied to inhomogeneous target dose distributions in order to demonstrate the relationship between dose uniformity and s{sub a}. The consequences of varying clonogenic density are also explored. Finally the model is applied to the target-volume DVHs for patients in a clinical trial of conformal pelvic radiotherapy; the effect of dose inhomogeneities on distributions of TCP are shown as well as the potential benefits of customizing the target dose according to normal-tissue DVHs. (author). 37 refs, 9 figs.

A PC program for estimating organ dose and effective dose values in computed tomography

International Nuclear Information System (INIS)

Kalender, W.A.; Schmidt, B.; Schmidt, M.; Zankl, M.

1999-01-01

Dose values in CT are specified by the manufacturers for all CT systems and operating conditions in phantoms. It is not trivial, however, to derive dose values in patients from this information. Therefore, we have developed a PC-based program which calculates organ dose and effective dose values for arbitrary scan parameters and anatomical ranges. Values for primary radiation are derived from measurements or manufacturer specifications; values for scattered radiation are derived from Monte Carlo calculations tabulated for standard anthropomorphic phantoms. Based on these values, organ doses can be computed by the program for arbitrary scan protocols in conventional and in spiral CT. Effective dose values are also provided, both with ICRP 26 and ICRP 60 tissue-weighting coefficients. Results for several standard CT protocols are presented in tabular form in this paper. In addition, potential for dose reduction is demonstrated, for example, in spiral CT and in quantitative CT. Providing realistic patient dose estimates for arbitrary CT protocols is relevant both for the physician and the patient, and it is particularly useful for educational and training purposes. The program, called WinDose, is now in use at the Erlangen University hospitals (Germany) as an information tool for radiologists and patients. Further extensions are planned. (orig.)

222Rn alpha dose to organs other than lung

International Nuclear Information System (INIS)

Harley, N.H.; Robbins, E.S.

1991-01-01

The alpha dose to cells in tissues or organs other theft the lung has been calculated using the solubility coefficients for 222 Rn measured in human tissue. The annual alpha dose equivalent f rom 222 Rn and decay products in most tissues is a maximum of 30% of the annual average natural background dose equivalent (1 mSv) for external and internally deposited nuclides. The dose to the small population of lymphocytes located in or under the bronchial epithelium is a special case and their annual dose equivalent is essentially the same as that to basal cells in bronchial epithelium (200 mSv) for continuous exposure to 200 Bq M -3 . The significance of this dose is uncertain because the only excess cancer observed in follow up studies of underground miners with high 222 Rn exposure is bronchogenic carcinoma

Pharmacokinetics of sulfamethoxazole and trimethoprim in Pacific white shrimp, Litopenaeus vannamei, after oral administration of single-dose and multiple-dose.

Science.gov (United States)

Ma, Rongrong; Wang, Yuan; Zou, Xiong; Hu, Kun; Sun, Beibei; Fang, Wenhong; Fu, Guihong; Yang, Xianle

2017-06-01

The tissue distribution and depletion of sulfamethoxazole (SMZ) and trimethoprim (TMP) were studied in Pacific white shrimp, Litopenaeus vannamei, after single-dose and multiple-dose oral administration of SMZ-TMP (5:1) via medicated feed. In single-dose oral administration, shrimps were fed once at a dose of 100 mg/kg (drug weight/body weight). In multiple-dose oral administration, shrimps were fed three times a day for three consecutive days at a dose of 100mg/kg. The results showed the kinetic characteristic of SMZ was different from TMP in Pacific white shrimp. In the single-dose administration, the SMZ was widely distributed in the tissues, while TMP was highly concentrated in the hepatopancreas. The t 1/2z values of SMZ were larger and persist longer than TMP in Pacific white shrimp. In the multiple-dose administration, SMZ accumulated well in the tissues, and reached steady state level after successive administrations, while TMP did not. TMP concentration even appeared the downward trend with the increase of drug times. Compared with the single dose, the t 1/2z values of SMZ in hepatopancreas (8.22-11.33h) and muscle (6.53-10.92h) of Pacific white shrimps rose, but the haemolymph dropped (13.76-11.03) in the multiple-dose oral administration. Meanwhile, the corresponding values of TMP also rose in hepatopancreas (4.53-9.65h) and muscle (2.12-2.71h), and declined in haemolymph (7.38-5.25h) following single-dose and multiple-dose oral administration in Pacific white shrimps. In addition, it is worth mentioning that the ratios of SMZ and TMP were unusually larger than the general aim ratio. Copyright © 2017 Elsevier B.V. All rights reserved.

Low-Dose and Standard-Dose Unenhanced Helical Computed Tomography for the Assessment of Acute Renal Colic: Prospective Comparative Study

Energy Technology Data Exchange (ETDEWEB)

Kim, Bong Soo; Hwang, Im Kyung; Choi, Yo Won; Namkung, Sook; Kim, Heung Cheol; Hwang, Woo Cheol; Choi, Kuk Myung; Park, Ji Kang; Han, Tae Il; Kang, Weechang [Cheju National Univ. College of Medicine, Jeju (Korea, Republic of). Dept. of Diagnostic Radiology

2005-11-01

Purpose: To compare the efficacy of low-dose and standard-dose computed tomography (CT) for the diagnosis of ureteral stones. Material and Methods: Unenhanced helical CT was performed with both a standard dose (260 mAs, pitch 1.5) and a low dose (50 mAs, pitch 1.5) in 121 patients suspected of having acute renal colic. The two studies were prospectively and independently interpreted for the presence and location of ureteral stones, abnormalities unrelated to stone disease, identification of secondary signs, i.e. hydronephrosis and perinephric stranding, and tissue rim sign. The standard-dose CT images were interpreted by one reviewer and the low-dose CT images independently by two reviewers unaware of the standard-dose CT findings. The findings of the standard and low-dose CT scans were compared with the exact McNemar test. Interobserver agreements were assessed with kappa analysis. The effective radiation doses resulting from two different protocols were calculated by means of commercially available software to which the Monte-Carlo phantom model was given. Results: The sensitivity, specificity, and accuracy of standard-dose CT for detecting ureteral stones were 99%, 93%, and 98%, respectively, whereas for the two reviewers the sensitivity of low-dose CT was 93% and 95%, specificity 86%, and accuracy 92% and 94%. We found no significant differences between standard-dose and low-dose CT in the sensitivity and specificity for diagnosing ureter stones ( P >0.05 for both). However, the sensitivity of low-dose CT for detection of 19 stones less than or equal to 2 mm in diameter was 79% and 68%, respectively, for the two reviewers. Low-dose CT was comparable to standard-dose CT in visualizing hydronephrosis and the tissue rim sign. Perinephric stranding was far less clear on low-dose CT. Low-dose CT had the same diagnostic performance as standard-dose CT in diagnosing alternative diseases. Interobserver agreement between the two low-dose CT reviewers in the diagnosis of

Influence of Ultra-Low-Dose and Iterative Reconstructions on the Visualization of Orbital Soft Tissues on Maxillofacial CT.

Science.gov (United States)

Widmann, G; Juranek, D; Waldenberger, F; Schullian, P; Dennhardt, A; Hoermann, R; Steurer, M; Gassner, E-M; Puelacher, W

2017-08-01

Dose reduction on CT scans for surgical planning and postoperative evaluation of midface and orbital fractures is an important concern. The purpose of this study was to evaluate the variability of various low-dose and iterative reconstruction techniques on the visualization of orbital soft tissues. Contrast-to-noise ratios of the optic nerve and inferior rectus muscle and subjective scores of a human cadaver were calculated from CT with a reference dose protocol (CT dose index volume = 36.69 mGy) and a subsequent series of low-dose protocols (LDPs I-4: CT dose index volume = 4.18, 2.64, 0.99, and 0.53 mGy) with filtered back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR)-50, ASIR-100, and model-based iterative reconstruction. The Dunn Multiple Comparison Test was used to compare each combination of protocols (α = .05). Compared with the reference dose protocol with FBP, the following statistically significant differences in contrast-to-noise ratios were shown (all, P ≤ .012) for the following: 1) optic nerve: LDP-I with FBP; LDP-II with FBP and ASIR-50; LDP-III with FBP, ASIR-50, and ASIR-100; and LDP-IV with FBP, ASIR-50, and ASIR-100; and 2) inferior rectus muscle: LDP-II with FBP, LDP-III with FBP and ASIR-50, and LDP-IV with FBP, ASIR-50, and ASIR-100. Model-based iterative reconstruction showed the best contrast-to-noise ratio in all images and provided similar subjective scores for LDP-II. ASIR-50 had no remarkable effect, and ASIR-100, a small effect on subjective scores. Compared with a reference dose protocol with FBP, model-based iterative reconstruction may show similar diagnostic visibility of orbital soft tissues at a CT dose index volume of 2.64 mGy. Low-dose technology and iterative reconstruction technology may redefine current reference dose levels in maxillofacial CT. © 2017 by American Journal of Neuroradiology.

Prediction of midline dose from entrance ad exit dose using OSLD measurements for total irradiation

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Choi, Chang Heon; Park, Jong Min; Park, So Yeon; Chun, Min Soo; Han, Ji Hye; Cho, Jin Dong; Kim, Jung In [Dept. of Radiation Oncology, Seoul National University Hospital, Seoul (Korea, Republic of)

2017-06-15

This study aims to predict the midline dose based on the entrance and exit doses from optically stimulated luminescence detector (OSLD) measurements for total body irradiation (TBI). For TBI treatment, beam data sets were measured for 6 MV and 15 MV beams. To evaluate the tissue lateral effect of various thicknesses, the midline dose and peak dose were measured using a solid water phantom (SWP) and ion chamber. The entrance and exit doses were measured using OSLDs. OSLDs were attached onto the central beam axis at the entrance and exit surfaces of the phantom. The predicted midline dose was evaluated as the sum of the entrance and exit doses by OSLD measurement. The ratio of the entrance dose to the exit dose was evaluated at various thicknesses. The ratio of the peak dose to the midline dose was 1.12 for a 30 cm thick SWP at both energies. When the patient thickness is greater than 30 cm, the 15 MV should be used to ensure dose homogeneity. The ratio of the entrance dose to the exit dose was less than 1.0 for thicknesses of less than 30 cm and 40 cm at 6 MV and 15 MV, respectively. Therefore, the predicted midline dose can be underestimated for thinner body. At 15 MV, the ratios were approximately 1.06 for a thickness of 50 cm. In cases where adult patients are treated with the 15 MV photon beam, it is possible for the predicted midline dose to be overestimated for parts of the body with a thickness of 50 cm or greater. The predicted midline dose and OSLD-measured midline dose depend on the phantom thickness. For in-vivo dosimetry of TBI, the measurement dose should be corrected in order to accurately predict the midline dose.

Dose tracking and dose auditing in a comprehensive computed tomography dose-reduction program.

Science.gov (United States)

Duong, Phuong-Anh; Little, Brent P

2014-08-01

Implementation of a comprehensive computed tomography (CT) radiation dose-reduction program is a complex undertaking, requiring an assessment of baseline doses, an understanding of dose-saving techniques, and an ongoing appraisal of results. We describe the role of dose tracking in planning and executing a dose-reduction program and discuss the use of the American College of Radiology CT Dose Index Registry at our institution. We review the basics of dose-related CT scan parameters, the components of the dose report, and the dose-reduction techniques, showing how an understanding of each technique is important in effective auditing of "outlier" doses identified by dose tracking. Copyright © 2014 Elsevier Inc. All rights reserved.

Fetal absorbed doses by radiopharmaceutical administration

International Nuclear Information System (INIS)

Rojo, Ana M; Gomez Parada, Ines M.; Di Trano, Jose L.

2000-01-01

The radiopharmaceutical administration with diagnostic or therapeutic purpose during pregnancy implies a prenatal radiation dose. The dose assessment and the evaluation of the radiological risks become relevant due to the great radiosensitivity of the fetal tissues in development. This paper is a revision of the available data for estimating fetal doses in the cases of the more frequently used radiopharmaceuticals in nuclear medicine, taking into account recent investigation in placental crossover. The more frequent diagnostic and therapeutic procedures were analyzed according to the radiation doses implied. (author)

Radiation doses and risks from internal emitters

International Nuclear Information System (INIS)

Harrison, John; Day, Philip

2008-01-01

This review updates material prepared for the UK Government Committee Examining Radiation Risks from Internal Emitters (CERRIE) and also refers to the new recommendations of the International Commission on Radiological Protection (ICRP) and other recent developments. Two conclusions from CERRIE were that ICRP should clarify and elaborate its advice on the use of its dose quantities, equivalent and effective dose, and that more attention should be paid to uncertainties in dose and risk estimates and their implications. The new ICRP recommendations provide explanations of the calculation and intended purpose of the protection quantities, but further advice on their use would be helpful. The new recommendations refer to the importance of understanding uncertainties in estimates of dose and risk, although methods for doing this are not suggested. Dose coefficients (Sv per Bq intake) for the inhalation or ingestion of radionuclides are published as reference values without uncertainty. The primary purpose of equivalent and effective dose is to enable the summation of doses from different radionuclides and from external sources for comparison with dose limits, constraints and reference levels that relate to stochastic risks of whole-body radiation exposure. Doses are calculated using defined biokinetic and dosimetric models, including reference anatomical data for the organs and tissues of the human body. Radiation weighting factors are used to adjust for the different effectiveness of different radiation types, per unit absorbed dose (Gy), in causing stochastic effects at low doses and dose rates. Tissue weighting factors are used to take account of the contribution of individual organs and tissues to overall detriment from cancer and hereditary effects, providing a simple set of rounded values chosen on the basis of age- and sex-averaged values of relative detriment. While the definition of absorbed dose has the scientific rigour required of a basic physical quantity

Microdosimetric approach for lung dose assessments

International Nuclear Information System (INIS)

Hofmann, W.; Steinhausler, F.; Pohl, E.; Bernroider, G.

1980-01-01

In the macroscopic region the term ''organ dose'' is related to an uniform energy deposition within a homogeneous biological target. Considering the lung, inhaled radioactive nuclides, however, show a significant non-uniform distribution pattern throughout the respiratory tract. For the calculation of deposition and clearance of inhaled alpha-emitting radionuclides within different regions of this organ, a detailed compartment model, based on the Weibel model A was developed. Since biological effects (e.g. lung cancer initiation) are primarily caused at the cellular level, the interaction of alpha particles with different types of cells of the lung tissue was studied. The basic approach is to superimpose alpha particle tracks on magnified images of randomly selected tissue slices, simulating alpha emitting sources. Particle tracks are generated by means of a specially developed computer program and used as input data for an on-line electronic image analyzer (Quantimet-720). Using adaptive pattern recognition methods the different cells in the lung tissue can be identified and their distribution within the whole organ determined. This microdosimetric method is applied to soluble radon decay products as well as to insoluble, highly localized, plutonium particles. For a defined microdistribution of alpha emitters, the resulting dose, integrated over all cellular dose values, is compared to the compartmental doses of the ICRP lung model. Furthermore this methodology is also applicable to other organs and tissues of the human body for dose calculations in practical health physics. (author)

Assessments for high dose radionuclide therapy treatment planning

International Nuclear Information System (INIS)

Fisher, D.R.

2003-01-01

Advances in the biotechnology of cell specific targeting of cancer and the increased number of clinical trials involving treatment of cancer patients with radiolabelled antibodies, peptides, and similar delivery vehicles have led to an increase in the number of high dose radionuclide therapy procedures. Optimised radionuclide therapy for cancer treatment is based on the concept of absorbed dose to the dose limiting normal organ or tissue. The limiting normal tissue is often the red marrow, but it may sometimes be the lungs, liver, intestinal tract, or kidneys. Appropriate treatment planning requires assessment of radiation dose to several internal organs and tissues, and usually involves biodistribution studies in the patient using a tracer amount of radionuclide bound to the targeting agent and imaged at sequential timepoints using a planar gamma camera. Time-activity curves are developed from the imaging data for the major organ tissues of concern, for the whole body and sometimes for selected tumours. Patient specific factors often require that dose estimates be customised for each patient. In the United States, the Food and Drug Administration regulates the experimental use of investigational new drugs and requires 'reasonable calculation of radiation absorbed dose to the whole body and to critical organs' using the methods prescribed by the Medical Internal Radiation Dose (MIRD) Committee of the Society of Nuclear Medicine. Review of high dose studies shows that some are conducted with minimal dosimetry, that the marrow dose is difficult to establish and is subject to large uncertainties. Despite the general availability of software, internal dosimetry methods often seem to be inconsistent from one clinical centre to another. (author)

Determination of Absorbed Dose in Large 60-Co Fields Radiotherapy

International Nuclear Information System (INIS)

Hrsak, H.

2003-01-01

Radiation in radiotherapy has selective impact on ill and healthy tissue. During the therapy the healthy tissue receives certain amount of dose. Therefore dose calculations in outer radiotherapy must be accurate because too high doses produce damage in healthy tissue and too low doses cannot ensure efficient treatment of cancer cells. A requirement on accuracy in the dose calculations has lead to improvement of detectors, and development of absolute and relative dosimetry. Determination of the dose distribution with use of computer is based on data provided by the relative dosimetry. This paper compares the percentage depth doses in cubic water phantoms of various dimensions with percentage depth doses calculated with use of Mayneord factor from the experimental depth doses measured in water phantom of large dimension. Depth doses in water phantoms were calculated by the model of empirical dosimetrical functions. The calculations were based on the assumption that large 6 0C o photon field exceeds the phantom's limits. The experimental basis for dose calculations by the model of empirical dosimetrical functions were exposure doses measured in air and dose reduction factors because of finite phantom dimensions. Calculations were performed by fortran 90 software. It was found that the deviation of dosimetric model was small in comparison to the experimental data. (author)

Determination of Radiation Absorbed Dose to Primary Liver Tumors and Normal Liver Tissue Using Post Radioembolization 90Y PET

Directory of Open Access Journals (Sweden)

Shyam Mohan Srinivas

2014-10-01

Full Text Available Background: Radioembolization with Yttrium-90 (90Y microspheres is becoming a more widely used transcatheter treatment for unresectable hepatocellular carcinoma (HCC. Using post-treatment 90Y PET/CT scans,the distribution of microspheres within the liver can be determined and quantitatively assessesed . We studied the radiation dose of 90Y delivered to liver and treated tumors.Methods: This retrospective study of 56 patients with HCC, including analysis of 98 liver tumors, measured and correlated the dose of radiation delivered to liver tumors and normal liver tissue using glass microspheres (TheraSpheres® to the frequency of complications with mRECIST. 90Y PET/CT and triphasic liver CT scans were used to contour treated tumor and normal liver regions and determine their respective activity concentrations. An absorbed dose factor was used to convert the measured activity concentration (Bq/mL to an absorbed dose (Gy.Results: The 98 studied tumors received a mean dose of 169 Gy (mode 90-120 Gy;range 0-570 Gy. Tumor response by mRECIST criteria was performed for 48 tumors that had follow up scans. There were 21 responders (mean dose 215 Gy and 27 nonresponders (mean dose 167 Gy. The association between mean tumor absorbed dose and response suggests a trend but did not reach statistical significance (p=0.099. Normal liver tissue received a mean dose of 67 Gy (mode 60-70 Gy; range 10-120 Gy. There was a statistically significant association between absorbed dose to normal liver and the presence of two or more severe complications (p=0.036.Conclusion: Our cohort of patients showed a possible dose response trend for the tumors. Collateral dose to normal liver is nontrivial and can have clinical implications. These methods help us understand whether patient adverse events, treatment success, or treatment failure can be attributed to the dose which the tumor or normal liver received.

The efficacy of hyperbaric oxygen in modifying the response of tissue to irradiation in doses of 200-400 rad per fraction

International Nuclear Information System (INIS)

Suit, D.D.; Orsi, L.

1975-01-01

The efficacy of respiration of O 2 at 30 psi in modifying the response of normal and tumour tissue to irradiation administered at 200 to 400 rad per fraction to anaesthetized mice has been evaluated. End-points have been delay in growth and TCD 50 for an early generation iso-transplant of a C 3 H mouse mammary carcinoma, and the acute reaction of skin of the C 3 H/Sed mouse. Results showed that the ratios of dose (air)/dose (O 2 30 psi) to elicit these end points were in the range 1.2 to 1.4. In earlier work using the same end points but doses per fraction 430 to 2100 rad, the ratios were 1.6 to 1.8. That is, for these tissue responses, respiration of O 2 at 30 psi increases the response of both normal and tumour tissue to all radiation doses tested. It is of greater effectiveness when combined with large doses per fraction, eg. greater than 430 rad. (author)

Biological effect of Pulsed Dose Rate brachytherapy with stepping sources

International Nuclear Information System (INIS)

Limbergen, Erik F.M. van; Fowler, Jack F.

1996-01-01

Purpose: To explore the possible increase of radiation effect in tissues irradiated by pulsed brachytherapy (PDR), for local tissue dose-rates between those 'averaged over the whole pulse' and the instantaneous high dose rates close to the dwell positions. An earlier publication (Fowler and Mount 1992) had shown that, for dose rates (averaged for the duration of the pulse) up to 3 Gy/h, little change of isoeffect doses from continuous low dose rate (CLDR) are expected, unless larger doses per fraction than 1 Gy are used, and especially if components of very rapid repair are present with half-times of less than about 0.5 hours. However, local and transient dose rates close to stepping sources can be up to several Gy per minute. Methods: Calculations were done assuming the linear quadratic formula for radiation damage, in which only the dose-squared term is subject to repair, at a constant exponential rate. The formula developed by Dale for fractionated low-dose-rate radiotherapy was used. A constant overall time of 140 hours and constant total dose of 70 Gy were assumed throughout, the continuous low dose-rate of 0.5 Gy/h (CLDR) providing the unitary standard effects for each PDR condition. Effects of dose-rates ranging from 4 Gy/h to 120 Gy/h (HDR at 2 Gy/min) were studied, and T (1(2)) from 4 minutes to 1.5 hours. Results: Curves are presented relating the ratio of increased biological effect (proportional to log cell kill) calculated for PDR relative to CLDR. Ratios as high as 1.5 can be found for large doses per pulse (> 1 Gy) at high instantaneous dose-rates if T (1(2)) in tissues is as short as a few minutes. The major influences on effect are dose per pulse, half-time of repair in the tissue, and - when T (1(2)) is short - the instantaneous dose-rate. Maximum ratios of PDR/CLDR effect occur when the dose-rate is such that pulse duration is approximately equal to T (1(2)) of repair. Results are presented for late-responding tissues, the differences from CLDR

Does the fluence map editing in electronic tissue compensator improve dose homogeneity in bilateral field plan of head and neck patients?

Directory of Open Access Journals (Sweden)

Kinhikar Rajesh

2008-01-01

Full Text Available The purpose of this study was to evaluate the effect of fluence map editing in electronic tissue compensator (ETC on the dose homogeneity for head and neck cancer patients. Treatment planning using 6-MV X-rays and bilateral field arrangement employing ETC was carried out on the computed tomography (CT datasets of 20 patients with head and neck cancer. All the patients were planned in Varian Eclipse three-dimensional treatment planning system (3DTPS with dynamic multileaf collimator (DMLC. The treatment plans, with and without fluence editing, was compared and the effect of pre-editing and post-editing the fluence maps in the treatment field was evaluated. The skin dose was measured with thermoluminescent dosimeters (TLDs and was compared with the skin dose estimated by TPS. The mean percentage volume of the tissue receiving at least 107% of the prescription dose was 5.4 (range 1.5-10; SD 2.4. Post-editing fluence map showed that the mean percentage volume of the tissue receiving at least 107% of the prescription dose was 0.47 (range 0.1-0.9; SD 0.3. The mean skin dose measured with TLD was found to be 74% (range 71-80% of the prescribed dose while the TPS showed the mean skin dose as 85% (range 80-90%. The TPS overestimated the skin dose by 11%. Fluence map editing thus proved to be a potential tool for improving dose homogeneity in head and neck cancer patients planned with ETC, thus reducing the hot spots in the treatment region as well. The treatment with ETC is feasible with DMLC and does not take any additional time for setup or delivery. The method used to edit the fluence maps is simple and time efficient. Manual control over a plan is essential to create the best treatment plan possible.

Tumor sterilization dose and radiation induced change of the brain tissue in radiotherapy of brain tumors

International Nuclear Information System (INIS)

Yoshii, Yoshihiko; Maki, Yutaka; Takano, Shingo

1987-01-01

Ninety-seven patients with brain tumors (38 gliomas, 26 brain metastases, 18 sellar tumors, 15 others) were treated by cobalt gamma ray or proton radiotherapy. In this study, normal brain injury due to radiation was analysed in terms of time-dose-fractionation (TDF), nominal standard dose (NSD) by the Ellis formula and NeuNSD by a modification in which the N exponent was -0.44 and the T exponent was -0.06. Their calculated doses were analysed in relationship to the normal brain radiation induced change (RIC) and the tumor sterilization dose. All brain tumors with an exception of many patients with brain metastases were received a surgical extirpation subtotally or partially prior to radiotherapy. And all patients with glioma and brain metastasis received also immuno-chemotherapy in the usual manner during radiotherapy. The calculated dose expressed by NeuNSD and TDF showed a significant relationship between a therapeutic dose and a postradiation time in terms of the appearance of RIC. It was suggested that RIC was caused by a dose over 800 in NeuNSD and a dose over 70 in TDF. Furthermore, it was suggested that an aged patient and a patient who had the vulnerable brain tissue to radiation exposure in the irradiated field had the high risk of RIC. On the other hand, our results suggested that the tumor sterilization dose should be over 1,536 NeuNSD and the irradiated method should be further considered in addition to the radiobiological concepts for various brain tumors. (author)

Radiation absorbed doses in cephalography

International Nuclear Information System (INIS)

Eliasson, S.; Julin, P.; Richter, S.; Stenstroem, B.

1984-01-01

Radiation absorbed doses to different organs in the head and neck region in lateral (LAT) and postero-anterior (PA) cephalography were investigated. The doses were measured by thermoluminescence dosimeters (TLD) on a tissue equivalent phantom head. Lanthanide screens in speed group 4 were used at 90 and 85 k Vp. A near-focus aluminium dodger was used and the radiation beam was collimated strictly to the face. The maximum entrance dose from LAT was 0.25 mGy and 0.42 mGy from a PA exposure. The doses to the salivary glands ranged between 0.2 and 0.02 mGy at LAT and between 0.15 and 0.04 mGy at PA exposures. The average thyroid gland dose without any shielding was 0.11 mGy (LAT) and 0.06 mGy (PA). When a dodger was used the dose was reduced to 0.07 mGy (LAT). If the thyroid gland was sheilded off, the dose was further reduced to 0.01 mGy and if the thyroid region was collimated out of the primary radiation field the dose was reduced to only 0.005 mGy. (authors)

Carcinogenesis in mice after low doses and dose rates

International Nuclear Information System (INIS)

Ullrich, R.L.

1979-01-01

The results from the experimental systems reported here indicate that the dose-response curves for tumor induction in various tissues cannot be described by a single model. Furthermore, although the understanding of the mechanisms involved in different systems is incomplete, it is clear that very different mechanisms for induction are involved. For some tumors the mechanism of carcinogenesis may be mainly a result of direct effects on the target cell, perhaps involving one or more mutations. While induction may occur, in many instances, through such direct effects, the eventual expression of the tumor can be influenced by a variety of host factors including endocrine status, competence of the immune system, and kinetics of target and interacting cell populations. In other tumors, indirect effects may play a major role in the initiation or expression of tumors. Some of the hormone-modulated tumors would fall into this class. Despite the complexities of the experimental systems and the lack of understanding of the types of mechanisms involved, in nearly every example the tumorigenic effectiveness per rad of low-LET radiation tends to decrease with decreasing dose rate. For some tumor types the differences may be small or may appear only with very low dose rates, while for others the dose-rate effects may be large

TU-D-209-06: Head and Neck Tissue Dose From X-Ray Scatter to Physicians Performing Cardiovascular Procedures

Energy Technology Data Exchange (ETDEWEB)

Fetterly, K; Schueler, B; Grams, M [Mayo Clinic, Rochester, MN (United States); Sturchio, G [Mayo Clinic, Jacksonville, FL (United States)

2016-06-15

Purpose: The purpose of this work was to characterize the spatial distribution of scatter radiation to the head and neck of a physician performing an x-ray interventional procedure and assess brain, eye lens, and carotid artery dose. Methods: Radiographic x-ray beams were tuned to match the peak energy (56 to 106 keV) and HVL (3.5 to 6.5 mm Al) of x-ray scatter originating from a patient during a fluoroscopic procedure. The radiographic beam was directed upon a Rando phantom from an inferior-left location to mimic a typical patient-operator geometric relationship. A lead-equivalent protective garment was secured to the phantom. Direct exposure Gafchromic film (XRQA2) was placed between the transverse plane layers of the head and neck region of the phantom and exposed with 4 scatter-equivalent radiographic beams. A 3×3 cm{sup 2} film placed at the left collar of the phantom was used to monitor incident dose in the position of a radiation monitoring badge. The films were converted to 2D dose distribution maps using FilmQA Pro software and an Epson 11000-XL scanner. The 2D dose distributions maps were normalized by the left collar dose and the percent of left collar dose (%LCD) was calculated for select tissues. Results: The dose maps had high dynamic range (10{sub 4}) and spatial detail. Considering all transverse planes and 4 scatter beam qualities, the median %LCD values were: whole brain 8.5%, left brain 13%, right brain 5.4%, left eye lens 67%, right eye lens 25%, left carotid artery 72%, and right carotid artery 28%. Conclusion: Scatter radiation dose to an operator can be simulated using a tuned radiographic beam and used to expose a phantom and Gafchromic film, thereby creating detailed 2D dose distribution maps. This work facilitates individualized estimation of dose to select head and neck tissues based on an operator’s radiation monitoring badge value.

Effects of low doses of ionizing radiation; Effets des faibles doses de rayonnements ionisants

Energy Technology Data Exchange (ETDEWEB)

Masse, R. [Office de Protection contre les Rayonnements Ionisants, 78 - le Vesinet (France)

2006-07-01

Several groups of human have been irradiated by accidental or medical exposure, if no gene defect has been associated to these exposures, some radioinduced cancers interesting several organs are observed among persons exposed over 100 to 200 mSv delivered at high dose rate. Numerous steps are now identified between the initial energy deposit in tissue and the aberrations of cell that lead to tumors but the sequence of events and the specific character of some of them are the subject of controversy. The stake of this controversy is the risk assessment. From the hypothesis called linear relationship without threshold is developed an approach that leads to predict cancers at any tiny dose without real scientific foundation. The nature and the intensity of biological effects depend on the quantity of energy absorbed in tissue and the modality of its distribution in space and time. The probability to reach a target (a gene) associated to the cancerating of tissue is directly proportional to the dose without any other threshold than the quantity of energy necessary to the effect, its probability of effect can be a more complex function and depends on the quality of the damage produced as well as the ability of the cell to repair the damage. These two parameters are influenced by the concentration of initial injuries in the target so by the quality of radiation and by the dose rate. The mechanisms of defence explain the low efficiency of radiation as carcinogen and then the linearity of effects in the area of low doses is certainly the least defensible scientific hypothesis for the prediction of the risks. (N.C.)

Radiobiological Determination of Dose Escalation and Normal Tissue Toxicity in Definitive Chemoradiation Therapy for Esophageal Cancer

Energy Technology Data Exchange (ETDEWEB)

Warren, Samantha, E-mail: Samantha.warren@oncology.ox.ac.uk [Department of Oncology, Gray Institute of Radiation Oncology and Biology, University of Oxford, Oxford (United Kingdom); Partridge, Mike [Department of Oncology, Gray Institute of Radiation Oncology and Biology, University of Oxford, Oxford (United Kingdom); Carrington, Rhys [Velindre Cancer Centre, Velindre Hospital, Cardiff (United Kingdom); Hurt, Chris [Wales Cancer Trials Unit, School of Medicine, Heath Park, Cardiff (United Kingdom); Crosby, Thomas [Velindre Cancer Centre, Velindre Hospital, Cardiff (United Kingdom); Hawkins, Maria A. [Department of Oncology, Gray Institute of Radiation Oncology and Biology, University of Oxford, Oxford (United Kingdom)

2014-10-01

Purpose: This study investigated the trade-off in tumor coverage and organ-at-risk sparing when applying dose escalation for concurrent chemoradiation therapy (CRT) of mid-esophageal cancer, using radiobiological modeling to estimate local control and normal tissue toxicity. Methods and Materials: Twenty-one patients with mid-esophageal cancer were selected from the SCOPE1 database (International Standard Randomised Controlled Trials number 47718479), with a mean planning target volume (PTV) of 327 cm{sup 3}. A boost volume, PTV2 (GTV + 0.5 cm margin), was created. Radiobiological modeling of tumor control probability (TCP) estimated the dose required for a clinically significant (+20%) increase in local control as 62.5 Gy/25 fractions. A RapidArc (RA) plan with a simultaneously integrated boost (SIB) to PTV2 (RA{sub 62.5}) was compared to a standard dose plan of 50 Gy/25 fractions (RA{sub 50}). Dose-volume metrics and estimates of normal tissue complication probability (NTCP) for heart and lungs were compared. Results: Clinically acceptable dose escalation was feasible for 16 of 21 patients, with significant gains (>18%) in tumor control from 38.2% (RA{sub 50}) to 56.3% (RA{sub 62.5}), and only a small increase in predicted toxicity: median heart NTCP 4.4% (RA{sub 50}) versus 5.6% (RA{sub 62.5}) P<.001 and median lung NTCP 6.5% (RA{sub 50}) versus 7.5% (RA{sub 62.5}) P<.001. Conclusions: Dose escalation to the GTV to improve local control is possible when overlap between PTV and organ-at-risk (<8% heart volume and <2.5% lung volume overlap for this study) generates only negligible increase in lung or heart toxicity. These predictions from radiobiological modeling should be tested in future clinical trials.

Mammalian Tissue Response to Low Dose Ionizing Radiation: The Role of Oxidative Metabolism and Intercellular Communication

Energy Technology Data Exchange (ETDEWEB)

Azzam, Edouard I

2013-01-16

The objective of the project was to elucidate the mechanisms underlying the biological effects of low dose/low dose rate ionizing radiation in organs/tissues of irradiated mice that differ in their susceptibility to ionizing radiation, and in human cells grown under conditions that mimic the natural in vivo environment. The focus was on the effects of sparsely ionizing cesium-137 gamma rays and the role of oxidative metabolism and intercellular communication in these effects. Four Specific Aims were proposed. The integrated outcome of the experiments performed to investigate these aims has been significant towards developing a scientific basis to more accurately estimate human health risks from exposures to low doses ionizing radiation. By understanding the biochemical and molecular changes induced by low dose radiation, several novel markers associated with mitochondrial functions were identified, which has opened new avenues to investigate metabolic processes that may be affected by such exposure. In particular, a sensitive biomarker that is differentially modulated by low and high dose gamma rays was discovered.

Calculation of dose distribution for 252Cf fission neutron source in tissue equivalent phantoms using Monte Carlo method

International Nuclear Information System (INIS)

Ji Gang; Guo Yong; Luo Yisheng; Zhang Wenzhong

2001-01-01

Objective: To provide useful parameters for neutron radiotherapy, the author presents results of a Monte Carlo simulation study investigating the dosimetric characteristics of linear 252 Cf fission neutron sources. Methods: A 252 Cf fission source and tissue equivalent phantom were modeled. The dose of neutron and gamma radiations were calculated using Monte Carlo Code. Results: The dose of neutron and gamma at several positions for 252 Cf in the phantom made of equivalent materials to water, blood, muscle, skin, bone and lung were calculated. Conclusion: The results by Monte Carlo methods were compared with the data by measurement and references. According to the calculation, the method using water phantom to simulate local tissues such as muscle, blood and skin is reasonable for the calculation and measurements of dose distribution for 252 Cf

Incase of Same Region Treatment by using a Tomotherapy and a Linear Accelerator Absorbed Dose Evaluation of Normal Tissues and a Tumor

International Nuclear Information System (INIS)

Cheon, Geum Seong; Kim, Chang Uk; Kim, Hoi Nam; Heo, Gyeong Hun; Song, Jin Ho; Hong, Joo Yeong; Jeong, Jae Yong

2010-01-01

Treating same region with different modalities there is a limit to evaluate the total absorbed dose of normal tissues. The reason is that it does not support to communication each modalities yet. In this article, it evaluates absorbed dose of the patients who had been treated same region by a tomotherapy and a linear accelerator. After reconstructing anatomic structure with a anthropomorphic phantom, administrate 45 Gy to a tumor in linac plan system as well as prescribe 15 Gy in tomotherapy plan system for make an ideal treatment plan. After the plan which made by tomoplan system transfers to the oncentra plan system for reproduce plan under the same condition and realize total treatment plan with summation 45 Gy linac treatment plan. To evaluate the absorbed dose of two different modalities, do a comparative study both a simple summation dose values and integration dose values. Then compare and analyze absorbed dose of normal tissues and a tumor with the patients who had been exposured radiation by above two different modalities. The result of compared data, in case of minimum dose, there are big different dose values in spleen (12.4%). On the other hand, in case of the maximum dose, it reports big different in a small bowel (10.2%) and a cord (5.8%) in head and neck cancer patients, there presents that oral (20.3%), right lens (7.7%) in minimum dose value. About maximum dose, it represents that spinal (22.5), brain stem (12%), optic chiasm (8.9%), Rt lens (11.5%), mandible (8.1%), pituitary gland (6.2%). In case of Rt abdominal cancer patients, there represents big different minimum dose as Lt kidney (20.3%), stomach (8.1%) about pelvic cancer patients, it reports there are big different in minimum dose as a bladder (15.2%) as well as big different value in maximum dose as a small bowel (5.6%), a bladder (5.5%) in addition, making treatment plan it is able us to get. In case of comparing both simple summation absorbed dose and integration absorbed dose, the

Dose Calculation Accuracy of the Monte Carlo Algorithm for CyberKnife Compared with Other Commercially Available Dose Calculation Algorithms

International Nuclear Information System (INIS)

Sharma, Subhash; Ott, Joseph; Williams, Jamone; Dickow, Danny

2011-01-01

Monte Carlo dose calculation algorithms have the potential for greater accuracy than traditional model-based algorithms. This enhanced accuracy is particularly evident in regions of lateral scatter disequilibrium, which can develop during treatments incorporating small field sizes and low-density tissue. A heterogeneous slab phantom was used to evaluate the accuracy of several commercially available dose calculation algorithms, including Monte Carlo dose calculation for CyberKnife, Analytical Anisotropic Algorithm and Pencil Beam convolution for the Eclipse planning system, and convolution-superposition for the Xio planning system. The phantom accommodated slabs of varying density; comparisons between planned and measured dose distributions were accomplished with radiochromic film. The Monte Carlo algorithm provided the most accurate comparison between planned and measured dose distributions. In each phantom irradiation, the Monte Carlo predictions resulted in gamma analysis comparisons >97%, using acceptance criteria of 3% dose and 3-mm distance to agreement. In general, the gamma analysis comparisons for the other algorithms were <95%. The Monte Carlo dose calculation algorithm for CyberKnife provides more accurate dose distribution calculations in regions of lateral electron disequilibrium than commercially available model-based algorithms. This is primarily because of the ability of Monte Carlo algorithms to implicitly account for tissue heterogeneities, density scaling functions; and/or effective depth correction factors are not required.

Computational assessment of effective dose and patient specific doses for kilovoltage stereotactic radiosurgery of wet age-related macular degeneration

Science.gov (United States)

Hanlon, Justin Mitchell

Age-related macular degeneration (AMD) is a leading cause of vision loss and a major health problem for people over the age of 50 in industrialized nations. The current standard of care, ranibizumab, is used to help slow and in some cases stabilize the process of AMD, but requires frequent invasive injections into the eye. Interest continues for stereotactic radiosurgery (SRS), an option that provides a non-invasive treatment for the wet form of AMD, through the development of the IRay(TM) (Oraya Therapeutics, Inc., Newark, CA). The goal of this modality is to destroy choroidal neovascularization beneath the pigment epithelium via delivery of three 100 kVp photon beams entering through the sclera and overlapping on the macula delivering up to 24 Gy of therapeutic dose over a span of approximately 5 minutes. The divergent x-ray beams targeting the fovea are robotically positioned and the eye is gently immobilized by a suction-enabled contact lens. Device development requires assessment of patient effective dose, reference patient mean absorbed doses to radiosensitive tissues, and patient specific doses to the lens and optic nerve. A series of head phantoms, including both reference and patient specific, was derived from CT data and employed in conjunction with the MCNPX 2.5.0 radiation transport code to simulate treatment and evaluate absorbed doses to potential tissues-at-risk. The reference phantoms were used to evaluate effective dose and mean absorbed doses to several radiosensitive tissues. The optic nerve was modeled with changeable positions based on individual patient variability seen in a review of head CT scans gathered. Patient specific phantoms were used to determine the effect of varying anatomy and gaze. The results showed that absorbed doses to the non-targeted tissues were below the threshold levels for serious complications; specifically the development of radiogenic cataracts and radiation induced optic neuropathy (RON). The effective dose

Bone and marrow dose modeling

International Nuclear Information System (INIS)

Stabin, Michael G.

2004-01-01

Nuclear medicine therapy is being used increasingly in the treatment of cancer (thyroid, leukemia/lymphoma with RIT, primary and secondary bone malignancies, and neuroblastomas). In all cases it is marrow toxicity that limits the amount of treatment that can be administered safely. Marrow dose calculations are more difficult than for many major organs because of the intricate association of bone and soft tissue elements. In RIT, there appears to be no consensus on how to calculate that dose accurately, or of individual patients ability to tolerate planned therapy. Available dose models are designed after an idealized average, healthy individual. Patient-specific methods are applied in evaluation of biokinetic data, and need to be developed for treatment of the physical data (dose conversion factors) as well: age, prior patient therapy, disease status. Contributors to marrow dose: electrons and photons

Dose rate constants for new dose quantities

International Nuclear Information System (INIS)

Tschurlovits, M.; Daverda, G.; Leitner, A.

1992-01-01

Conceptual changes and new quantities made is necessary to reassess dose rate quantities. Calculations of the dose rate constant were done for air kerma, ambient dose equivalent and directional dose equivalent. The number of radionuclides is more than 200. The threshold energy is selected as 20 keV for the dose equivalent constants. The dose rate constant for the photon equivalent dose as used mainly in German speaking countries as a temporary quantity is also included. (Author)

Tissue decomposition from dual energy CT data for MC based dose calculation in particle therapy

Energy Technology Data Exchange (ETDEWEB)

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

Absorbed dose optimization in the microplanar beam radiotherapy

International Nuclear Information System (INIS)

Company, F.Z.; Jaric, J.; Allen, B.J.

1996-01-01

Full text: Recent advances in synchrotron generated X-ray beams with high fluence rate, small divergence and sharply defined microbeam margins permit investigation of the application of an array of closely spaced, parallel or converging microbeams for radiotherapy. The proposed technique takes advantage of the repair mechanism hypothesis of capillary endothelial cells between alternate microbeam zones, which regenerates the lethally irradiated capillaries. Unlike a pencil beam, more accurate dose calculation, beam width and spacing are essential to minimise radiation damage to normal tissue cells outside the target. The absorbed dose between microbeam zones should be kept below the threshold for irreversible radiation damage. Thus the peak-to-valley ratio for the dose distribution should be optimized. The absorbed dose profile depends on the energy of the incident beam and the composition and density of the medium. Using Monte Carlo computations, the radial absorbed dose of single 24 x 24 μm 2 cross-section X-ray beams of different energies in a tissue/lung/tissue phantom was investigated. The results indicated that at 100 keV, closely spaced square cross-sectional microbeams can be applied to the lung. A bundle of parallel 24 μm-wide planar microbeams spaced at 200 μm intervals provides much more irradiation coverage of tissue than is provided by a bundle of parallel, square cross-sectional microbeam, although the former is associated with much smaller Peak (maximum absorbed dose on the beam axis) -to-Valley ( minimum interbeam absorbed dose ) ratios than the latter. In this study the lateral and depth dose of single and multiple microplanar beams with beam dimensions of width 24 μm and 48 μm and height 2-20 cm with energy of 100 keV in a tissue/lung/tissue phantom are investigated. The EGS4 Monte Carlo code is used to calculate dose profiles at different depths and bundles of beams (2 x 2 cm 2 to 20 x 20 cm 2 square cross section) with a 150 μm 200 μm and

SU-F-J-45: Sparing Normal Tissue with Ultra-High Dose Rate in Radiation Therapy

Energy Technology Data Exchange (ETDEWEB)

Feng, Y [DCH Reg. Medical Center, Tuscaloosa, AL (United States)

2016-06-15

Purpose: To spare normal tissue by reducing the location uncertainty of a moving target, we proposed an ultra-high dose rate system and evaluated. Methods: High energy electrons generated with a linear accelerator were injected into a storage ring to be accumulated. The number of the electrons in the ring was determined based on the prescribed radiation dose. The dose was delivered within a millisecond, when an online imaging system found that the target was in the position that was consistent with that in a treatment plan. In such a short time period, the displacement of the target was negligible. The margin added to the clinical target volume (CTV) could be reduced that was evaluated by comparing of volumes between CTV and ITV in 14 cases of lung stereotactic body radiation therapy (SBRT) treatments. A design of the ultra-high dose rate system was evaluated based clinical needs and the recent developments of low energy (a few MeV) electron storage ring. Results: This design of ultra-high dose rate system was feasible based on the techniques currently available. The reduction of a target volume was significant by reducing the margin that accounted the motion of the target. ∼50% volume reduction of the internal target volume (ITV) could be achieved in lung SBRT treatments. Conclusion: With this innovation of ultra-high dose rate system, the margin of target is able to be significantly reduced. It will reduce treatment time of gating and allow precisely specified gating window to improve the accuracy of dose delivering.

Toward an organ based dose prescription method for the improved accuracy of murine dose in orthovoltage x-ray irradiators

International Nuclear Information System (INIS)

Belley, Matthew D.; Wang, Chu; Nguyen, Giao; Gunasingha, Rathnayaka; Chao, Nelson J.; Chen, Benny J.; Dewhirst, Mark W.; Yoshizumi, Terry T.

2014-01-01

Purpose: Accurate dosimetry is essential when irradiating mice to ensure that functional and molecular endpoints are well understood for the radiation dose delivered. Conventional methods of prescribing dose in mice involve the use of a single dose rate measurement and assume a uniform average dose throughout all organs of the entire mouse. Here, the authors report the individual average organ dose values for the irradiation of a 12, 23, and 33 g mouse on a 320 kVp x-ray irradiator and calculate the resulting error from using conventional dose prescription methods. Methods: Organ doses were simulated in the Geant4 application for tomographic emission toolkit using the MOBY mouse whole-body phantom. Dosimetry was performed for three beams utilizing filters A (1.65 mm Al), B (2.0 mm Al), and C (0.1 mm Cu + 2.5 mm Al), respectively. In addition, simulated x-ray spectra were validated with physical half-value layer measurements. Results: Average doses in soft-tissue organs were found to vary by as much as 23%–32% depending on the filter. Compared to filters A and B, filter C provided the hardest beam and had the lowest variation in soft-tissue average organ doses across all mouse sizes, with a difference of 23% for the median mouse size of 23 g. Conclusions: This work suggests a new dose prescription method in small animal dosimetry: it presents a departure from the conventional approach of assigninga single dose value for irradiation of mice to a more comprehensive approach of characterizing individual organ doses to minimize the error and uncertainty. In human radiation therapy, clinical treatment planning establishes the target dose as well as the dose distribution, however, this has generally not been done in small animal research. These results suggest that organ dose errors will be minimized by calibrating the dose rates for all filters, and using different dose rates for different organs

Parotid gland mean dose as a xerostomia predictor in low-dose domains.

Science.gov (United States)

Gabryś, Hubert Szymon; Buettner, Florian; Sterzing, Florian; Hauswald, Henrik; Bangert, Mark

2017-09-01

Xerostomia is a common side effect of radiotherapy resulting from excessive irradiation of salivary glands. Typically, xerostomia is modeled by the mean dose-response characteristic of parotid glands and prevented by mean dose constraints to either contralateral or both parotid glands. The aim of this study was to investigate whether normal tissue complication probability (NTCP) models based on the mean radiation dose to parotid glands are suitable for the prediction of xerostomia in a highly conformal low-dose regime of modern intensity-modulated radiotherapy (IMRT) techniques. We present a retrospective analysis of 153 head and neck cancer patients treated with radiotherapy. The Lyman Kutcher Burman (LKB) model was used to evaluate predictive power of the parotid gland mean dose with respect to xerostomia at 6 and 12 months after the treatment. The predictive performance of the model was evaluated by receiver operating characteristic (ROC) curves and precision-recall (PR) curves. Average mean doses to ipsilateral and contralateral parotid glands were 25.4 Gy and 18.7 Gy, respectively. QUANTEC constraints were met in 74% of patients. Mild to severe (G1+) xerostomia prevalence at both 6 and 12 months was 67%. Moderate to severe (G2+) xerostomia prevalence at 6 and 12 months was 20% and 15%, respectively. G1 + xerostomia was predicted reasonably well with area under the ROC curve ranging from 0.69 to 0.76. The LKB model failed to provide reliable G2 + xerostomia predictions at both time points. Reduction of the mean dose to parotid glands below QUANTEC guidelines resulted in low G2 + xerostomia rates. In this dose domain, the mean dose models predicted G1 + xerostomia fairly well, however, failed to recognize patients at risk of G2 + xerostomia. There is a need for the development of more flexible models able to capture complexity of dose response in this dose regime.

High-Dose-Rate Endobronchial Brachytherapy for Recurrent Airway Obstruction From Hyperplastic Granulation Tissue

International Nuclear Information System (INIS)

Tendulkar, Rahul D.; Fleming, Peter A.; Reddy, Chandana A.; Gildea, Thomas R.; Machuzak, Michael; Mehta, Atul C.

2008-01-01

Purpose: Benign endobronchial granulation tissue causes airway obstruction in up to 20% of patients after lung transplantation or stent placement. High-dose-rate endobronchial brachytherapy (HDR-EB) has been successful in some cases refractory to standard bronchoscopic interventions. Methods and Materials: Between September 2004 and May 2005, 8 patients with refractory benign airway obstruction were treated with HDR-EB, using one to two fractions of Ir-192 prescribed to 7.1 Gy at a radius of 1 cm. Charts were retrospectively reviewed to evaluate subjective clinical response, forced expiratory volume in 1 second (FEV 1 ), and frequency of therapeutic bronchoscopies over 6-month periods before and after HDR-EB. Results: The median follow-up was 14.6 months, and median survival was 10.5 months. The mean number of bronchoscopic interventions improved from 3.1 procedures in the 6-month pretreatment period to 1.8 after HDR-EB. Mean FEV 1 improved from 36% predicted to 46% predicted. Six patients had a good-to-excellent subjective early response, but only one maintained this response beyond 6 months, and this was the only patient treated with HDR-EB within 24 h from the most recent bronchoscopic intervention. Five patients have expired from causes related to their chronic pulmonary disease, including one from hemoptysis resulting from a bronchoarterial fistula. Conclusion: High-dose-rate-EB may be an effective treatment for select patients with refractory hyperplastic granulation tissue causing recurrent airway stenosis. Performing HDR-EB within 24-48 h after excision of obstructive granulation tissue could further improve outcomes. Careful patient selection is important to maximize therapeutic benefit and minimize toxicity. The optimal patient population, dose, and timing of HDR-EB should be investigated prospectively

Assessment of doses caused by electrons in thin layers of tissue-equivalent materials, using MCNP.

Science.gov (United States)

Heide, Bernd

2013-10-01

Absorbed doses caused by electron irradiation were calculated with Monte Carlo N-Particle transport code (MCNP) for thin layers of tissue-equivalent materials. The layers were so thin that the calculation of energy deposition was on the border of the scope of MCNP. Therefore, in this article application of three different methods of calculation of energy deposition is discussed. This was done by means of two scenarios: in the first one, electrons were emitted from the centre of a sphere of water and also recorded in that sphere; and in the second, an irradiation with the PTB Secondary Standard BSS2 was modelled, where electrons were emitted from an (90)Sr/(90)Y area source and recorded inside a cuboid phantom made of tissue-equivalent material. The speed and accuracy of the different methods were of interest. While a significant difference in accuracy was visible for one method in the first scenario, the difference in accuracy of the three methods was insignificant for the second one. Considerable differences in speed were found for both scenarios. In order to demonstrate the need for calculating the dose in thin small zones, a third scenario was constructed and simulated as well. The third scenario was nearly equal to the second one, but a pike of lead was assumed to be inside the phantom in addition. A dose enhancement (caused by the pike of lead) of ∼113 % was recorded for a thin hollow cylinder at a depth of 0.007 cm, which the basal-skin layer is referred to in particular. Dose enhancements between 68 and 88 % were found for a slab with a radius of 0.09 cm for all depths. All dose enhancements were hardly noticeable for a slab with a cross-sectional area of 1 cm(2), which is usually applied to operational radiation protection.

Biology of dose rate in brachytherapy

International Nuclear Information System (INIS)

Brenner, David J.

1995-01-01

Purpose: This course is designed for practitioners and beginners in brachytherapy. The aim is to review biological principles underlying brachytherapy, to understand why current treatment regimes are the way they are, and to discuss what the future may hold in store. Brachytherapy has a long history. It was suggested as long ago as 1903 by Alexander Graham Bell, and the optimal application of this technique has been a subject of debate ever since. 'Brachy' means 'short', and the essential features of conventional brachytherapy are: positioning of the source a short distance from, or in, the tumor, allowing good dose distributions; short overall treatment times, to counter tumor repopulation; low dose rate, enabling a good therapeutic advantage between tumor control and damage to late-responding tissue. The advantages of good dose distributions speak for themselves; in some situations, as we shall see, computer-based dose optimization can be used to improve them still further. The advantages of short overall times stem from the fact that accelerated repopulation of the tumor typically begins a few weeks after the start of a radiation treatment. If all the radiation can be crammed in before that time, the risks of tumor repopulation can be considerably reduced. In fact even external-beam radiotherapy is moving in this direction, with the use of highly accelerated protocols. The advantages of low dose rate stem from the differential response to fractionation of early- and late-responding tissues. Essentially, lowering the dose rate spares late-responding tissue more than it does early-responding tissue such as tumors. We shall also discuss some recent innovations in the context of the general principles that have been outlined. For example, High dose rate brachytherapy, particularly for the uterine cervix: Does it work? If so, when and why? Use of Ir-192 sources, with a half life of 70 days: Should corrections be made for changing biological effectiveness as the dose

Effects of dose, species, and dosing vehicle on the disposition of methacrylonitrile (MAN) in male rats

International Nuclear Information System (INIS)

Sanchez, I.M.; Ghanayem, B.I.

1991-01-01

MAN is structurally similar to known carcinogen acrylontrile (AN), with nitriles having similar industrial uses. Current studies were designed to investigate the biological fate of 2- 14 C-MAN in rats. After gavage administration of 115, 11.5 or 1.15 mg MAN/kg in water, F344 male rats were placed in glass metabolism cages and urine, expired air and feces were collected. Rats were sacrificed at various times and concentration of MAN-derived radioactivity in tissues was determined. MAN was rapidly absorbed from the GI tract and distributed to all major tissues. Sixty-70% of the low and medium doses were exhaled as 14 CO 2 in 72 hr compared to 25% of the highest dose. While 40% of the highest dose was expired as organic volatiles in 72 hr, only 9-12% of the low and accounted for 20-30% of all doses within 72 hr after dosing. Comparison of MAN disposition in Sprague-Dawley (SD) and F344 rats at 115 mg/kg revealed that SD rats excreted a greater % of the dose as 14 CO 2 and in the urine than did F344 rats. Administration of 115 mg MAN/kg to SD male rats in safflower oil resulted in increased elimination of MAN-derived radioactivity as CO 2 , volatiles, and in the urine over that observed when administered in water. These results suggest that: (1) saturation of MAN metabolism occurs at high doses: (2) MAN metabolism and disposition differ with the strain of rats studied; (3) MAN disposition may vary with the dosing vehicle used; and (4) MAN metabolism and disposition is apparently different from that reported on AN

Risk assessment from heterogeneous energy deposition in tissue, the problem of effects from low doses of ionizing radiation

International Nuclear Information System (INIS)

Feinendegen, L.E.; Booz, J.

1992-01-01

Low doses of ionizing radiation from external or internal sources cause heterogeneous distribution of energy deposition events in the exposed biological system. With the cell being the individual element of the tissue system, the fraction of cells hit, the dose received by the hit, and the biological response of the cell to the dose received eventually determine the effect in tissue. The hit cell may experience detriment, such as change in its DNA leading to a malignant transformation, or it may derive benefit in terms of an adaptive response such as a temporary improvement of DNA repair or temporary prevention of effects from intracellular radicals through enhanced radical detoxification. These responses are protective also to toxic substances that are generated during normal metabolism. Within a multicellular system the probability of detriment must be weighed against the probability of benefit through adaptive responses with protection against various toxic agents including those produced by normal metabolism. Because irradiation can principally induce both, detriment and adaptive responses, one type of affected cells may not be simply summed up at the expense of cells with other types of effects, in assessing risk to tissue. An inventory of various types of effects in the blood-forming system of mammals, even with large ranges of uncertainty, uncovers the possibility of benefit to the system from exposure to low doses of low-LET radiation. This experimental approach may complement epidemiological data on individuals exposed to low doses of ionizing radiation and may lead to a more rational appraisal of risk

Angular dependence of depth doses in a tissue slab irradiated with monoenergetic photons

International Nuclear Information System (INIS)

Till, E.; Zankl, M.; Drexler, G.

1995-12-01

This report presents dose equivalents from external photon irradiation, normalised to air kerma free in air, on the central axis of a cuboid slab of ICRU tissue for various depths, photon energies and angles of beam incidence. The data were calculated by a Monte Carlo method using an idealised planar parallel source of monoenergetic photons. The data presented here aim at facilitating the calibration of individual dosimeters; they provide also an estimate of the quantity 'personal dose equivalent' defined by the ICRU. A detailed evaluation of the dependence of the calculated conversion coefficients on depth in the slab, photon energy and angle of incidence is given. A comparison with published measured an calculated values of angular dependence factors is made. (orig.)

[Evaluation of Organ Dose Estimation from Indices of CT Dose Using Dose Index Registry].

Science.gov (United States)

Iriuchijima, Akiko; Fukushima, Yasuhiro; Ogura, Akio

Direct measurement of each patient organ dose from computed tomography (CT) is not possible. Most methods to estimate patient organ dose is using Monte Carlo simulation with dedicated software. However, dedicated software is too expensive for small scale hospitals. Not every hospital can estimate organ dose with dedicated software. The purpose of this study was to evaluate the simple method of organ dose estimation using some common indices of CT dose. The Monte Carlo simulation software Radimetrics (Bayer) was used for calculating organ dose and analysis relationship between indices of CT dose and organ dose. Multidetector CT scanners were compared with those from two manufactures (LightSpeed VCT, GE Healthcare; SOMATOM Definition Flash, Siemens Healthcare). Using stored patient data from Radimetrics, the relationships between indices of CT dose and organ dose were indicated as each formula for estimating organ dose. The accuracy of estimation method of organ dose was compared with the results of Monte Carlo simulation using the Bland-Altman plots. In the results, SSDE was the feasible index for estimation organ dose in almost organs because it reflected each patient size. The differences of organ dose between estimation and simulation were within 23%. In conclusion, our estimation method of organ dose using indices of CT dose is convenient for clinical with accuracy.

The effect of dose, dose rate, route of administration, and species on tissue and blood levels of benzene metabolites

International Nuclear Information System (INIS)

Henderson, R.F.; Sabourin, P.J.; Bechtold, W.E.; Griffith, W.C.; Medinsky, M.A.; Birnbaum, L.S.; Lucier, G.W.

1989-01-01

Studies were completed in F344/N rats and B6C3F 1 mice to determine the effect of dose, dose rate, route of administration, and rodent species on formation of total and individual benzene metabolites. Oral doses of 50 mg/kg or higher saturated the capacity for benzene metabolism in both rats and mice, resulting in an increased proportion of the administered dose being exhaled as benzene. The saturating air concentration for benzene metabolism during 6-hr exposures was between 130 and 900 ppm. At the highest exposure concentration, rats exhaled approximately half of the internal dose retained at the end of the 6-hr exposure as benzene; mice exhaled only 15% as benzene. Mice were able to convert more of the inhaled benzene to metabolites than were rats. In addition, mice metabolized more of the benzene by pathways leading to the putative toxic metabolites, benzoquinone and muconaldehyde, than did rats. In both rats and mice, the effect of increasing dose, administered orally or by inhalation, was to increase the proportion of the total metabolites that were the products of detoxification pathways relative to the products of pathways leading to putative toxic metabolites. This indicates low-affinity, high-capacity pathways for detoxification and high-affinity, low-capacity pathways leading to putative toxic metabolites. If the results of rodent studied performed at high doses were used to assess the health risk at low-dose exposures to benzene, the toxicity of benzene would be underestimated

Reduction of dose enhancement from backscattered radiation at tissue-metal interfaces irradiated with 6MeV electrons

International Nuclear Information System (INIS)

Steel, B.

1996-01-01

Due to Electron Back Scatter (EBS), electron irradiation of tissue having under lying lead shielding results in an increase in dose to the tissue on the entrance side of the lead. In these situations dose increases as high as 80% have been reported in the literature. Saunders (British Journal of Radiology, 47, 467-470) noted that dose enhancement is dependent on atomic number of the under lying material approximately as Z 0.5 , and it increases at lower incident electron energies. In our clinic we use 2mm of lead shielding to protect under lying normal tissue when 6MeV electrons are used to treat lips and ears. The object of this study was to find the thinnest combination of materials to reduce the total dose to an acceptable level, with the provisos that; the patient does not come into contact with the lead or other metals, the finished shield could comfortabley be placed between the patient's lip and teeth, and that the materials are sufficietly malleable to work into custom shields. Various combinations of dental wax and aluminium were trialed. That which proved to give the best compromise between reduction of EBS and total shielding thickness was, 1mm of aluminim on the beam side of the lead with 1mm of dental wax to completely enclose the shield. In practice the manufactured shields are approximately 6 mm thick, and are usually not uncomfortable for the patient. (author)

Physics and quality assurance for brachytherapy - Part II: Low dose rate and pulsed dose rate

International Nuclear Information System (INIS)

Williamson, Jeffrey F.

1997-01-01

Purpose: A number of recent developments have revitalized brachytherapy including remote afterloading, implant optimization, increasing use of 3D imaging, and advances in dose specification and basic dosimetry. However, the core physical principles underlying the classical methods of dose calculation and arrangement of multiple sources remain unchanged. The purpose of this course is to review these principles and their applications to low dose-rate interstitial and intracavitary brachytherapy. Emphasis will be placed upon the classical implant systems along with classical and modern methods of dose specification. The level of presentation is designed for radiation oncology residents and beginning clinical physicists. A. Basic Principles (1) Radium-substitute vs. low-energy sealed sources (2) Dose calculation principles (3) The mysteries of source strength specification revealed: mgRaEq, mCi and air-kerma strength B. Interstitial Brachytherapy (1) Target volume, implanted volume, dose specification in implants and implant optimization criteria (2) Classical implant systems: Manchester Quimby and Paris a) Application of the Manchester system to modern brachytherapy b) Comparison of classical systems (3) Permanent interstitial implants a) Photon energy and half life b) Dose specification and pre-operative planning (4) The alphabet soup of dose specification: MCD (mean central dose), minimum dose, MPD (matched peripheral dose), MPD' (minimum peripheral dose) and DVH (dose-volume histogram) quality indices C. Intracavitary Brachytherapy for Carcinoma of the Cervix (1) Basic principles a) Manchester System: historical foundation of U.S. practice patterns b) Principles of applicator design (2) Dose specification and treatment prescription a) mg-hrs, reference points, ICRU Report 38 reference volume -- Point A dose vs mg-hrs and IRAK (Integrated Reference Air Kerma) -- Tissue volume treated vs mg-hrs and IRAK b) Practical methods of treatment specification and prescription

Physics and quality assurance for brachytherapy - Part II: Low dose rate and pulsed dose rate

International Nuclear Information System (INIS)

Williamson, Jeffrey F.

1996-01-01

Purpose: A number of recent developments have revitalized brachytherapy including remote afterloading, implant optimization, increasing use of 3D imaging, and advances in dose specification and basic dosimetry. However, the core physical principles underlying the classical methods of dose calculation and arrangement of multiple sources remain unchanged. The purpose of this course is to review these principles and their applications to low dose-rate interstitial and intracavitary brachytherapy. Emphasis will be placed upon the classical implant systems along with classical and modern methods of dose specification. The level of presentation is designed for radiation oncology residents and beginning clinical physicists. A. Basic Principles (1) Radium-substitute vs. low-energy sealed sources (2) Dose calculation principles (3) The mysteries of source strength specification revealed: mgRaEq, mCi and air-kerma strength B. Interstitial Brachytherapy (1) Target volume, implanted volume, dose specification in implants and implant optimization criteria (2) Classical implant systems: Manchester Quimby and Paris a) Application of the Manchester system to modern brachytherapy b) Comparison of classical systems (3) Permanent interstitial implants a) Photon energy and half life b) Dose specification and pre-operative planning (4) The alphabet soup of dose specification: MCD (mean central dose), minimum dose, MPD (matched peripheral dose), MPD' (minimum peripheral dose) and DVH (dose-volume histogram) quality indices C. Intracavitary Brachytherapy for Carcinoma of the Cervix (1) Basic principles a) Manchester System: historical foundation of U.S. practice patterns b) Principles of applicator design (2) Dose specification and treatment prescription a) mg-hrs, reference points, ICRU Report 38 reference volume --Point A dose vs mg-hrs and IRAK (Integrated Reference Air Kerma) --Tissue volume treated vs mg-hrs and IRAK b) Practical methods of treatment specification and prescription

On the radiation dose to lung tissues from radon daughters

International Nuclear Information System (INIS)

Wise, K.N.

1980-04-01

The work of Harley and Pasternak on calculating dose conversion factors for radon daughters is re-examined. It is found that their estimates of the deposit of radon daughters on the lung airways are too low and the factor for converting from equilibrium activity of radon daughters on the airways to dose to basal cells is too high; these are re-calculated. However, it is shown that inter-subject variability of the depth of the basal cells leads to considerable uncertainty in the individual dose. Finally average dose conversion factors are re-calculated for atmospheres which may be charactersitic of underground mines; the dose conversion factors range from 8 mGy/WLM to 40 mGy/WLM as calculated from the Weibel lung model and from 3 mGy/WLM to 17 mGy/WLM as calculated from the Landahl lung model

SU-F-T-51: Investigating the Effect of Eye Size and Eccentricity On Normal Tissue Doses From Eye Plaque Brachytherapy

Energy Technology Data Exchange (ETDEWEB)

Polsdofer, E; Crilly, R [Oregon Health & Science University Portland, OR (United States)

2016-06-15

Purpose: This study investigates the effect of eye size and eccentricity on doses to critical tissues by simulating doses in the Plaque Simulator (v. 6.3.1) software. Present OHSU plaque brachytherapy treatment focuses on delivering radiation to the tumor measured with ocular ultrasound plus a small margin and assumes the orbit has the dimensions of a “standard eye.” Accurately modeling the dimensions of the orbit requires a high resolution ocular CT. This study quantifies how standard differences in equatorial diameters and eccentricity affect calculated doses to critical structures in order to query the justification of the additional CT scan to the treatment planning process. Methods: Tumors of 10 mm × 10 mm × 5 mm were modeled at the 12:00:00 hour with a latitude of 45 degrees. Right eyes were modeled at a number of equatorial diameters from 17.5 to 28 mm for each of the standard non-notched COMS plaques with silastic inserts. The COMS plaques were fully loaded with uniform activity, centered on the tumor, and prescribed to a common tumor dose (85 Gy/100 hours). Variations in the calculated doses to normal structures were examined to see if the changes were significant. Results: The calculated dose to normal structures show a marked dependence on eye geometry. This is exemplified by fovea dose which more than doubled in the smaller eyes and nearly halved in the larger model. Additional significant dependence was found in plaque size on the calculated dose in spite of all plaques giving the same dose to the prescription point. Conclusion: The variation in dose with eye dimension fully justifies the addition of a high resolution ocular CT to the planning technique. Additional attention must be made to plaque size beyond simply covering the tumor when considering normal tissue dose.

Calculation of dose for β point and sphere sources in soft tissue

International Nuclear Information System (INIS)

Sun Fuyin; Yuan Shuyu; Tan Jian

1999-01-01

Objective: To compare the results of the distribution of dose rate calculated by three typical methods for point source and sphere source of β nuclide. Methods: Calculating and comparing the distributions of dose rate from 32 P β point and sphere sources in soft tissue calculated by the three methods published in references, [1]. [2] and [3], respectively. Results: For the point source of 3.7 x 10 7 Bq (1mCi), the variations of the calculation results of the three formulas are within 10% if r≤0.35 g/cm 2 , r being the distance from source, and larger than 10% if r > 0.35 g/cm 2 . For the sphere source whose volume is 50 μl and activity is 3.7 x 10 7 Bq(1 mCi), the variations are within 10% if z≤0.15 g/cm 2 , z being the distance from the surface of the sphere source to a point outside the sphere. Conclusion: The agreement of the distributions of the dose rate calculated by the three methods mentioned above for point and sphere β source are good if the distances from point source or the surface of sphere source to the points observed are small, and poor if they are large

Normal tissue complication probabilities: dependence on choice of biological model and dose-volume histogram reduction scheme

International Nuclear Information System (INIS)

Moiseenko, Vitali; Battista, Jerry; Van Dyk, Jake

2000-01-01

Purpose: To evaluate the impact of dose-volume histogram (DVH) reduction schemes and models of normal tissue complication probability (NTCP) on ranking of radiation treatment plans. Methods and Materials: Data for liver complications in humans and for spinal cord in rats were used to derive input parameters of four different NTCP models. DVH reduction was performed using two schemes: 'effective volume' and 'preferred Lyman'. DVHs for competing treatment plans were derived from a sample DVH by varying dose uniformity in a high dose region so that the obtained cumulative DVHs intersected. Treatment plans were ranked according to the calculated NTCP values. Results: Whenever the preferred Lyman scheme was used to reduce the DVH, competing plans were indistinguishable as long as the mean dose was constant. The effective volume DVH reduction scheme did allow us to distinguish between these competing treatment plans. However, plan ranking depended on the radiobiological model used and its input parameters. Conclusions: Dose escalation will be a significant part of radiation treatment planning using new technologies, such as 3-D conformal radiotherapy and tomotherapy. Such dose escalation will depend on how the dose distributions in organs at risk are interpreted in terms of expected complication probabilities. The present study indicates considerable variability in predicted NTCP values because of the methods used for DVH reduction and radiobiological models and their input parameters. Animal studies and collection of standardized clinical data are needed to ascertain the effects of non-uniform dose distributions and to test the validity of the models currently in use

Considerations on absorbed dose estimates based on different β-dose point kernels in internal dosimetry

International Nuclear Information System (INIS)

Uchida, Isao; Yamada, Yasuhiko; Yamashita, Takashi; Okigaki, Shigeyasu; Oyamada, Hiyoshimaru; Ito, Akira.

1995-01-01

In radiotherapy with radiopharmaceuticals, more accurate estimates of the three-dimensional (3-D) distribution of absorbed dose is important in specifying the activity to be administered to patients to deliver a prescribed absorbed dose to target volumes without exceeding the toxicity limit of normal tissues in the body. A calculation algorithm for the purpose has already been developed by the authors. An accurate 3-D distribution of absorbed dose based on the algorithm is given by convolution of the 3-D dose matrix for a unit cubic voxel containing unit cumulated activity, which is obtained by transforming a dose point kernel into a 3-D cubic dose matrix, with the 3-D cumulated activity distribution given by the same voxel size. However, beta-dose point kernels affecting accurate estimates of the 3-D absorbed dose distribution have been different among the investigators. The purpose of this study is to elucidate how different beta-dose point kernels in water influence on the estimates of the absorbed dose distribution due to the dose point kernel convolution method by the authors. Computer simulations were performed using the MIRD thyroid and lung phantoms under assumption of uniform activity distribution of 32 P. Using beta-dose point kernels derived from Monte Carlo simulations (EGS-4 or ACCEPT computer code), the differences among their point kernels gave little differences for the mean and maximum absorbed dose estimates for the MIRD phantoms used. In the estimates of mean and maximum absorbed doses calculated using different cubic voxel sizes (4x4x4 mm and 8x8x8 mm) for the MIRD thyroid phantom, the maximum absorbed doses for the 4x4x4 mm-voxel were estimated approximately 7% greater than the cases of the 8x8x8 mm-voxel. They were found in every beta-dose point kernel used in this study. On the other hand, the percentage difference of the mean absorbed doses in the both voxel sizes for each beta-dose point kernel was less than approximately 0.6%. (author)

Dose De-escalation of Intrapleural Tissue Plasminogen Activator Therapy for Pleural Infection. The Alteplase Dose Assessment for Pleural Infection Therapy Project.

Science.gov (United States)

Popowicz, Natalia; Bintcliffe, Oliver; De Fonseka, Duneesha; Blyth, Kevin G; Smith, Nicola A; Piccolo, Francesco; Martin, Geoffrey; Wong, Donny; Edey, Anthony; Maskell, Nick; Lee, Y C Gary

2017-06-01

Intrapleural therapy with a combination of tissue plasminogen activator (tPA) 10 mg and DNase 5 mg administered twice daily has been shown in randomized and open-label studies to successfully manage over 90% of patients with pleural infection without surgery. Potential bleeding risks associated with intrapleural tPA and its costs remain important concerns. The aim of the ongoing Alteplase Dose Assessment for Pleural infection Therapy (ADAPT) project is to investigate the efficacy and safety of dose de-escalation for intrapleural tPA. The first of several planned studies is presented here. To evaluate the efficacy and safety of a reduced starting dose regimen of 5 mg of tPA with 5 mg of DNase administered intrapleurally for pleural infection. Consecutive patients with pleural infection at four participating centers in Australia, the United Kingdom, and New Zealand were included in this observational, open-label study. Treatment was initiated with tPA 5 mg and DNase 5 mg twice daily. Subsequent dose escalation was permitted at the discretion of the attending physician. Data relating to treatment success, radiological and systemic inflammatory changes (blood C-reactive protein), volume of fluid drained, length of hospital stay, and treatment complications were extracted retrospectively from the medical records. We evaluated 61 patients (41 males; age, 57 ± 16 yr). Most patients (n = 58 [93.4%]) were successfully treated without requiring surgery for pleural infection. Treatment success was corroborated by clearance of pleural opacities visualized by chest radiography (from 42% [interquartile range, 22-58] to 16% [8-31] of hemithorax; P < 0.001), increase in pleural fluid drainage (from 175 ml in the 24 h preceding treatment to 2,025 ml [interquartile range, 1,247-2,984] over 72 h of therapy; P <  0.05) and a reduction in blood C-reactive protein (P < 0.05). Seven patients (11.5%) had dose escalation of tPA to 10 mg. Three patients underwent

Deuterons at energies of 10 MeV to 1 TeV: Conversion coefficients for fluence-to-absorbed dose, equivalent dose, effective dose and gray equivalent, calculated using Monte Carlo radiation transport code MCNPX 2.7.C

International Nuclear Information System (INIS)

Copeland, K.; Parker, D. E.; Friedberg, W.

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 TM 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. (authors)

Evaluation of concave dose distributions created using an inverse planning system

International Nuclear Information System (INIS)

Hunt, Margie A.; Hsiung, C.-Y.; Spirou, Spirodon V.; Chui, C.-S.; Amols, Howard I.; Ling, Clifton C.

2002-01-01

Purpose: To evaluate and develop optimum inverse treatment planning strategies for the treatment of concave targets adjacent to normal tissue structures. Methods and Materials: Optimized dose distributions were designed using an idealized geometry consisting of a cylindrical phantom with a concave kidney-shaped target (PTV) and cylindrical normal tissues (NT) placed 5-13 mm from the target. Targets with radii of curvature from 1 to 2.75 cm were paired with normal tissues with radii between 0.5 and 2.25 cm. The target was constrained to a prescription dose of 100% and minimum and maximum doses of 95% and 105% with relative penalties of 25. Maximum dose constraint parameters for the NT varied from 10% to 70% with penalties from 10 to 1000. Plans were evaluated using the PTV uniformity index (PTV D max /PTV D 95 ) and maximum normal tissue doses (NT D max /PTV D 95 ). Results: In nearly all situations, the achievable PTV uniformity index and the maximum NT dose exceeded the corresponding constraints. This was particularly true for small PTV-NT separations (5-8 mm) or strict NT dose constraints (10%-30%), where the achievable doses differed from the requested by 30% or more. The same constraint parameters applied to different PTV-NT separations yielded different dose distributions. For most geometries, a range of constraints could be identified that would lead to acceptable plans. The optimization results were fairly independent of beam energy and radius of curvature, but improved as the number of beams increased, particularly for small PTV-NT separations or strict dose constraints. Conclusion: Optimized dose distributions are strongly affected by both the constraint parameters and target-normal tissue geometry. Standard site-specific constraint templates can serve as a starting point for optimization, but the final constraints must be determined iteratively for individual patients. A strategy whereby NT constraints and penalties are modified until the highest

Doses from radiation exposure

International Nuclear Information System (INIS)

Menzel, H-G.; Harrison, J.D.

2012-01-01

Practical implementation of the International Commission on Radiological Protection’s (ICRP) system of protection requires the availability of appropriate methods and data. The work of Committee 2 is concerned with the development of reference data and methods for the assessment of internal and external radiation exposure of workers and members of the public. This involves the development of reference biokinetic and dosimetric models, reference anatomical models of the human body, and reference anatomical and physiological data. Following ICRP’s 2007 Recommendations, Committee 2 has focused on the provision of new reference dose coefficients for external and internal exposure. As well as specifying changes to the radiation and tissue weighting factors used in the calculation of protection quantities, the 2007 Recommendations introduced the use of reference anatomical phantoms based on medical imaging data, requiring explicit sex averaging of male and female organ-equivalent doses in the calculation of effective dose. In preparation for the calculation of new dose coefficients, Committee 2 and its task groups have provided updated nuclear decay data (ICRP Publication 107) and adult reference computational phantoms (ICRP Publication 110). New dose coefficients for external exposures of workers are complete (ICRP Publication 116), and work is in progress on a series of reports on internal dose coefficients to workers from inhaled and ingested radionuclides. Reference phantoms for children will also be provided and used in the calculation of dose coefficients for public exposures. Committee 2 also has task groups on exposures to radiation in space and on the use of effective dose.

Methods of bone marrow dose calculation

International Nuclear Information System (INIS)

Taboaco, R.C.

1982-02-01

Several methods of bone marrow dose calculation for photon irradiation were analised. After a critical analysis, the author proposes the adoption, by the Instituto de Radioprotecao e Dosimetria/CNEN, of Rosenstein's method for dose calculations in Radiodiagnostic examinations and Kramer's method in case of occupational irradiation. It was verified by Eckerman and Simpson that for monoenergetic gamma emitters uniformly distributed within the bone mineral of the skeleton the dose in the bone surface can be several times higher than dose in skeleton. In this way, is also proposed the Calculation of tissue-air ratios for bone surfaces in some irradiation geometries and photon energies to be included in the Rosenstein's method for organ dose calculation in Radiodiagnostic examinations. (Author) [pt

Advanced Computational Approaches for Characterizing Stochastic Cellular Responses to Low Dose, Low Dose Rate Exposures

Energy Technology Data Exchange (ETDEWEB)

Scott, Bobby, R., Ph.D.

2003-06-27

applications of NEOTRANS2, indicate that nonlinear threshold-type, dose-response relationships for excess stochastic effects (problematic nonlethal mutations, neoplastic transformation) should be expected after exposure to low linear energy transfer (LET) gamma rays or gamma rays in combination with high-LET alpha radiation. Similar thresholds are expected for low-dose-rate low-LET beta irradiation. We attribute the thresholds to low-dose, low-LET radiation induced protection against spontaneous mutations and neoplastic transformations. The protection is presumed mainly to involve selective elimination of problematic cells via apoptosis. Low-dose, low-LET radiation is presumed to trigger wide-area cell signaling, which in turn leads to problematic bystander cells (e.g., mutants, neoplastically transformed cells) selectively undergoing apoptosis. Thus, this protective bystander effect leads to selective elimination of problematic cells (a tissue cleansing process in vivo). However, this protective bystander effects is a different process from low-dose stimulation of the immune system. Low-dose, low-LET radiation stimulation of the immune system may explain why thresholds for inducing excess cancer appear much larger (possibly more than 100-fold larger) than thresholds for inducing excess mutations and neoplastic transformations, when the dose rate is low. For ionizing radiation, the current risk assessment paradigm is such that the relative risk (RR) is always ¡Ý 1, no matter how small the dose. Our research results indicate that for low-dose or low-dose-rate, low-LET irradiation, RR < 1 may be more the rule than the exception. Directly tied to the current RR paradigm are the billion-dollar cleanup costs for radionuclide-contaminated DOE sites. Our research results suggest that continued use of the current RR paradigm for which RR ¡Ý 1 could cause more harm than benefit to society (e.g., by spreading unwarranted fear about phantom excess risks associated with low-dose low

Mechanisms underlying cellular responses of cells from haemopoietic tissue to low dose/low LET radiation

Energy Technology Data Exchange (ETDEWEB)

Munira A Kadhim

2010-03-05

To accurately define the risks associated with human exposure to relevant environmental doses of low LET ionizing radiation, it is necessary to completely understand the biological effects at very low doses (i.e., less than 0.1 Gy), including the lowest possible dose, that of a single electron track traversal. At such low doses, a range of studies have shown responses in biological systems which are not related to the direct interaction of radiation tracks with DNA. The role of these “non-targeted” responses in critical tissues is poorly understood and little is known regarding the underlying mechanisms. Although critical for dosimetry and risk assessment, the role of individual genetic susceptibility in radiation risk is not satisfactorily defined at present. The aim of the proposed grant is to critically evaluate radiation-induced genomic instability and bystander responses in key stem cell populations from haemopoietic tissue. Using stem cells from two mouse strains (CBA/H and C57BL/6J) known to differ in their susceptibility to radiation effects, we plan to carefully dissect the role of genetic predisposition on two non-targeted radiation responses in these models; the bystander effect and genomic instability, which we believe are closely related. We will specifically focus on the effects of low doses of low LET radiation, down to doses approaching a single electron traversal. Using conventional X-ray and γ-ray sources, novel dish separation and targeted irradiation approaches, we will be able to assess the role of genetic variation under various bystander conditions at doses down to a few electron tracks. Irradiations will be carried out using facilities in routine operation for bystander targeted studies. Mechanistic studies of instability and the bystander response in different cell lineages will focus initially on the role of cytokines which have been shown to be involved in bystander signaling and the initiation of instability. These studies also aim

Oesteosarcomagenic doses of radium (224Ra) and infectious endogenous retroviruses enhance proliferation and osteogenic differentiation of skeletal tissue dofferentiating in vitro

International Nuclear Information System (INIS)

Schmidt, J.; Heermeier, K.; Linzner, U.; Luz, A.; Silbermann, M.; Livne, E.; Erfle, V.

1994-01-01

Cartilage tissue from embryonic mice which undergoes osteogenic differentiation during in vitro cultivation was used to study the effect of osteosarcomagenic doses of α-irradiation and bone-tumor-inducing retroviruses on proliferation and phenotypic differentiation of skeletal cells in a defined tissue culture model. Irradiated mandibular condyles showed dose-dependent enhancement of cell proliferation at day 7 of the culture and increased osteogenic differentiation at day 14. Maximal effects were found with 7.4 Bq/ml of 224 Ra-labeled medium. Doses of 740 and 7400 Bq/ml of 224 Ra-labeled medium induced increasing cell death. Retrovirus infection enhanced osteogenic differentiation and extended the viability of irradiated cells. After transplantation none of the treated tissues developed tumors in syngeneic mice. (orig.)

Relative effect of dose-rate values and fractionation on late responding tissues and tumours

International Nuclear Information System (INIS)

Malgieri, F.

1995-01-01

There are currently available different facilities for radiotherapy also with regard to the dose-rate values (in the ranges LDR - MDR - HDR), sometimes used alternatively or subsequently for the same tumour. We have set up a 'unitary' L-Q model, based on Liversage's and Dale's works, that explicitly include also the dose-rate value and a correction factor of the β parameter depending on the sublethal damage repair time constant, on the length of time of each irradiation and on the time interval between following irradiation for to realize the effect of the incomplete repair when the time interval is short as, for example, in the PLDR. This 'unitary' L-Q model is, of course, usable in the same way both for external beam therapy and for curietherapy and make possible to compute and compare, for each kind of tumour and normal tissue, the relative effect of the different available modality of radiotherapy also with regard to the dose-rate. We show and discuss the resulting relationships of the ratio BED 'late'/BED tumour changing the time-dose parameters and the values of the biological characteristic parameters T p , α/β and μ, for defined size of tumour control and different value of the doserate

Calculated dose factors for the radiosensitive tissues in bone irradiated by surface-deposited radionuclides

International Nuclear Information System (INIS)

Spiers, F.W.; Whitwell, J.R.; Beddoe, A.H.

1978-01-01

The method of calculating dose factors for the haemopoietic marrow and endosteal tissues in human trabecular bone, used by Whitwell and Spiers for volume-seeking radionuclides, has been developed for the case of radionuclides which are deposited as very thin layers on bone surfaces. The Monte Carlo method is again used, but modifications to the computer program are made to allow for a surface rather than a volume source of particle emission. The principal change is the introduction of a surface-orientation factor which is shown to have a value of approximately 2, varying slightly with bone structure. Results are given for β-emitting radionuclides ranging from 171 Tm(anti Esub(β) = 0.025 MeV) to 90 Y(anti Esub(β) = 0.93 MeV), and also for the α-emitter 239 Pu. It is shown that where the particle ranges are short compared with the dimensions of the bone structures the dose factors for the surface seekers are much greater than those for the volume seekers. For long range particles the dose factors for surface- and volume-seeking radionuclides converge. Comparisons are given relating the dose factors calculated in this paper on the basis of measured bone structures to those of other workers based on single plane geometry. (author)

Bone-and-muscle-equivalent solid chemical dose meters for photon and electron doses above one kilorad

International Nuclear Information System (INIS)

McLaughlin, W.L.; Rosenstein, M.; Levine, H.

1975-01-01

Conventional solid dose meters, such as plastic films, powders, emulsions, glasses, ceramics and gels, have a response to ionizing photons and electrons that varies markedly over a broad spectrum when compared with the absorption characteristics of biological tissues. New radiochromic dyed plastic dose meters have been developed with X- and gamma ray and electron energy absorption cross-sections (calculated) and radiation energy responses (experimental) corresponding approximately to those for human muscle and bone, for a spectrum from a few keV to at least 10 MeV. Three-dimensional solid dose meters useful over the absorbed dose range of 10 3 to 10 6 rad are formed by thermosetting a selected combination of monomers containing the radiochromic dye in solution. Thin-film dose meters for the dose range 10 5 to 10 7 rad are formed by casting on optically flat surfaces strippable layers of special combinations of polymers and dyes in solution. The response of these systems to X- and gamma rays and electrons has been studied over various radiation spectra, dose-rates and temperatures during irradiation. (author)

Experience of micromultileaf collimator linear accelerator based single fraction stereotactic radiosurgery: Tumor dose inhomogeneity, conformity, and dose fall off

Energy Technology Data Exchange (ETDEWEB)

Hong, Linda X.; Garg, Madhur; Lasala, Patrick; Kim, Mimi; Mah, Dennis; Chen, Chin-Cheng; Yaparpalvi, Ravindra; Mynampati, Dinesh; Kuo, Hsiang-Chi; Guha, Chandan; Kalnicki, Shalom [Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, New York 10461 (United States); Department of Neurosurgery, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, New York 10461 (United States); Department of Epidemiology and Population Health, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, New York 10461 (United States); Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, New York 10461 (United States)

2011-03-15

Purpose: Sharp dose fall off outside a tumor is essential for high dose single fraction stereotactic radiosurgery (SRS) plans. This study explores the relationship among tumor dose inhomogeneity, conformity, and dose fall off in normal tissues for micromultileaf collimator (mMLC) linear accelerator (LINAC) based cranial SRS plans. Methods: Between January 2007 and July 2009, 65 patients with single cranial lesions were treated with LINAC-based SRS. Among them, tumors had maximum diameters {<=}20 mm: 31; between 20 and 30 mm: 21; and >30 mm: 13. All patients were treated with 6 MV photons on a Trilogy linear accelerator (Varian Medical Systems, Palo Alto, CA) with a tertiary m3 high-resolution mMLC (Brainlab, Feldkirchen, Germany), using either noncoplanar conformal fixed fields or dynamic conformal arcs. The authors also created retrospective study plans with identical beam arrangement as the treated plan but with different tumor dose inhomogeneity by varying the beam margins around the planning target volume (PTV). All retrospective study plans were normalized so that the minimum PTV dose was the prescription dose (PD). Isocenter dose, mean PTV dose, RTOG conformity index (CI), RTOG homogeneity index (HI), dose gradient index R{sub 50}-R{sub 100} (defined as the difference between equivalent sphere radius of 50% isodose volume and prescription isodose volume), and normal tissue volume (as a ratio to PTV volume) receiving 50% prescription dose (NTV{sub 50}) were calculated. Results: HI was inversely related to the beam margins around the PTV. CI had a ''V'' shaped relationship with HI, reaching a minimum when HI was approximately 1.3. Isocenter dose and mean PTV dose (as percentage of PD) increased linearly with HI. R{sub 50}-R{sub 100} and NTV{sub 50} initially declined with HI and then reached a plateau when HI was approximately 1.3. These trends also held when tumors were grouped according to their maximum diameters. The smallest tumor group

Prediction of standard-dose brain PET image by using MRI and low-dose brain [{sup 18}F]FDG PET images

Energy Technology Data Exchange (ETDEWEB)

Kang, Jiayin [School of Electronics Engineering, Huaihai Institute of Technology, Lianyungang, Jiangsu 222005, China and IDEA Laboratory, Department of Radiology and BRIC, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 (United States); Gao, Yaozong [IDEA Laboratory, Department of Radiology and BRIC, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 and Department of Computer Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 (United States); Shi, Feng [IDEA Laboratory, Department of Radiology and BRIC, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 (United States); Lalush, David S. [Joint UNC-NCSU Department of Biomedical Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Lin, Weili [MRI Laboratory, Department of Radiology and BRIC, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 (United States); Shen, Dinggang, E-mail: dgshen@med.unc.edu [IDEA Laboratory, Department of Radiology and BRIC, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 and Department of Brain and Cognitive Engineering, Korea University, Seoul 136-713 (Korea, Republic of)

2015-09-15

Purpose: Positron emission tomography (PET) is a nuclear medical imaging technology that produces 3D images reflecting tissue metabolic activity in human body. PET has been widely used in various clinical applications, such as in diagnosis of brain disorders. High-quality PET images play an essential role in diagnosing brain diseases/disorders. In practice, in order to obtain high-quality PET images, a standard-dose radionuclide (tracer) needs to be used and injected into a living body. As a result, it will inevitably increase the patient’s exposure to radiation. One solution to solve this problem is predicting standard-dose PET images using low-dose PET images. As yet, no previous studies with this approach have been reported. Accordingly, in this paper, the authors propose a regression forest based framework for predicting a standard-dose brain [{sup 18}F]FDG PET image by using a low-dose brain [{sup 18}F]FDG PET image and its corresponding magnetic resonance imaging (MRI) image. Methods: The authors employ a regression forest for predicting the standard-dose brain [{sup 18}F]FDG PET image by low-dose brain [{sup 18}F]FDG PET and MRI images. Specifically, the proposed method consists of two main steps. First, based on the segmented brain tissues (i.e., cerebrospinal fluid, gray matter, and white matter) in the MRI image, the authors extract features for each patch in the brain image from both low-dose PET and MRI images to build tissue-specific models that can be used to initially predict standard-dose brain [{sup 18}F]FDG PET images. Second, an iterative refinement strategy, via estimating the predicted image difference, is used to further improve the prediction accuracy. Results: The authors evaluated their algorithm on a brain dataset, consisting of 11 subjects with MRI, low-dose PET, and standard-dose PET images, using leave-one-out cross-validations. The proposed algorithm gives promising results with well-estimated standard-dose brain [{sup 18}F]FDG PET

Prediction of standard-dose brain PET image by using MRI and low-dose brain ["1"8F]FDG PET images

International Nuclear Information System (INIS)

Kang, Jiayin; Gao, Yaozong; Shi, Feng; Lalush, David S.; Lin, Weili; Shen, Dinggang

2015-01-01

Purpose: Positron emission tomography (PET) is a nuclear medical imaging technology that produces 3D images reflecting tissue metabolic activity in human body. PET has been widely used in various clinical applications, such as in diagnosis of brain disorders. High-quality PET images play an essential role in diagnosing brain diseases/disorders. In practice, in order to obtain high-quality PET images, a standard-dose radionuclide (tracer) needs to be used and injected into a living body. As a result, it will inevitably increase the patient’s exposure to radiation. One solution to solve this problem is predicting standard-dose PET images using low-dose PET images. As yet, no previous studies with this approach have been reported. Accordingly, in this paper, the authors propose a regression forest based framework for predicting a standard-dose brain ["1"8F]FDG PET image by using a low-dose brain ["1"8F]FDG PET image and its corresponding magnetic resonance imaging (MRI) image. Methods: The authors employ a regression forest for predicting the standard-dose brain ["1"8F]FDG PET image by low-dose brain ["1"8F]FDG PET and MRI images. Specifically, the proposed method consists of two main steps. First, based on the segmented brain tissues (i.e., cerebrospinal fluid, gray matter, and white matter) in the MRI image, the authors extract features for each patch in the brain image from both low-dose PET and MRI images to build tissue-specific models that can be used to initially predict standard-dose brain ["1"8F]FDG PET images. Second, an iterative refinement strategy, via estimating the predicted image difference, is used to further improve the prediction accuracy. Results: The authors evaluated their algorithm on a brain dataset, consisting of 11 subjects with MRI, low-dose PET, and standard-dose PET images, using leave-one-out cross-validations. The proposed algorithm gives promising results with well-estimated standard-dose brain ["1"8F]FDG PET image and substantially

Influence of dose, dose rate, and radiation quality on radiation carcinogenesis and life shortening in RFM and BALB/C mice

International Nuclear Information System (INIS)

Ullrich, R.L.; Storer, J.B.

1978-01-01

The effects produced by 137 Cs gamma rays delivered at a high (45 rads/min) or intermediate (8.2 rads/day) dose rate and the effect of fission neutrons at a high (25 rads/min) and low (1 rad/day) rate in a population of nearly 30,000 RFM and 11,000 BALB/c mice have been studied. Gamma ray doses ranged from 10 to 400 rads with the RFM's and from 50-400 rads with the BALB/c's, while neutron doses ranged from 5 to 200 rads with both strains. The present paper will present an overview of these data and the general findings while subsequent publications will present detailed analyses of each aspect. A variety of neoplasms were sensitive to induction after radiation exposure, including tumors of both reticular tissue origin (leukemia, lymphoma, etc.) and solid tumors. For the RFM, thymic lymphomas were the dominant reticular tissue neoplasm while the majority of solid tumors were either lung adenomas or fit into the broad category of endocrine related tumors, including ovarian, pituitary, harderian, and uterine tumors. The BALB/c was much less sensitive to induction of reticular tissue neoplasms. The tumors that were most sensitive to induction included malignant lung carcinomas, mammary adenocarcinomas and ovarian tumors. In general for both life shortening and tumor induction after gamma ray exposures, when the low to intermediate dose range was sufficiently defined, linearity could be rejected and a dose squared or linear-dose squared relationship adequately fit the data. For neutron exposures, on the other hand, linear relationships were the general finding. The RBE for neutrons varied with tumor type and total dose level. For gamma ray irradiation, the intermediate dose rate resulted in a decreased effectiveness in all cases, while for neutron exposures the dose rate relationships were more complex

Assessment of dose inhomogeneity at target level by in vivo dosimetry

International Nuclear Information System (INIS)

Leunens, G.; Verstraete, J.; Dutreix, A.; Schueren, E. van der

1992-01-01

Inhomogeneity of dose delivered to the target volume due to irregular body surface and tissue densities remains in many cases unknown, since dose distribution is calculated for most radiation treatments in only one transverse section and assuming the patient to be water equivalent. In this study transmission and target absorbed dose homogeneity is assessed for 11 head-and-neck cancer treatments by in vivo measurements with silicon diodes. Besides the dose to specification point, the dose delivered to 2-4 off-axis points in midline sagittal plane is estimated from entrance and exit dose measurements. Simultaneously made portal films allow to identify anatomical structures passed by the beam before reaching exit diode. Mean deviation from expected transmission is -6.8% for bone, +6% for air cavities and -2.5% for soft tissue. At midplane, mean deviations from expected target dose are respectively -3.5%, +2.3% and -1.9%. Deviations from prescribed dose are larger than 5% in 12/39 target points. Accuracy requirements in target dose delivery of plus or minus 5%, as proposed by ICRU, cannot be fulfilled in 7/11 patients and is mostly due to irregular body contour and tissue densities. as only a limited number of points are considered, inhomogeneity in dose delivered throughout whole irradiated volume is underestimated, as is illustrated from exit dose profiles obtained from portal image. Besides its tremendous value as a quality assurance procedure, in vivo dose measurements are shown to be a valid method for assessing dose delivered to irradiated tissues when dose computations are assumed to be inaccurate or even impossible in current practice. (author). 21 refs., 8 figs., 1 tab

Dose sculpting with generalized equivalent uniform dose

International Nuclear Information System (INIS)

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

2005-01-01

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

Dose Distributions of an 192Ir Brachytherapy Source in Different Media

Directory of Open Access Journals (Sweden)

C. H. Wu

2014-01-01

Full Text Available This study used MCNPX code to investigate the brachytherapy 192Ir dose distributions in water, bone, and lung tissue and performed radiophotoluminescent glass dosimeter measurements to verify the obtained MCNPX results. The results showed that the dose-rate constant, radial dose function, and anisotropy function in water were highly consistent with data in the literature. However, the lung dose near the source would be overestimated by up to 12%, if the lung tissue is assumed to be water, and, hence, if a tumor is located in the lung, the tumor dose will be overestimated, if the material density is not taken into consideration. In contrast, the lung dose far from the source would be underestimated by up to 30%. Radial dose functions were found to depend not only on the phantom size but also on the material density. The phantom size affects the radial dose function in bone more than those in the other tissues. On the other hand, the anisotropy function in lung tissue was not dependent on the radial distance. Our simulation results could represent valid clinical reference data and be used to improve the accuracy of the doses delivered during brachytherapy applied to patients with lung cancer.

Computer aided display of multiple soft tissue anatomical surfaces for simultaneous structural and area-dose appreciation in 3D-radiationtherapy planning. 115

International Nuclear Information System (INIS)

Moore, C.J.; Mott, D.J.; Wilkinson, J.M.

1987-01-01

For radiotherapy applications a 3D display that includes soft tissues is required but the presentation of all anatomical structures is often unnecessary and is potentially confusing. A tumour volume and a small number of critical organs, usually embedded within other soft tissue anatomy, are likely to be all that can be clearly displayed when presented in a 3D format. The inclusion of dose data (in the form of isodose lines or surfaces) adds to the complication of any 3D display. A solution to this problem is to incorporate the presentation of dose distribution into the technique used to provide the illusion of 3D. This illusion can be provided by either depth cueing or by the hypothetical illumination of spatially defined object surfaces. The dose distribution from irradiation fields or, in the case of brachytherapy from radioactive sources, can be regarded as a source of illumination for tumour and critical organs. The intensity of illumination at any point on a tissue surface represents the dose at that point. Such an approach also allows the variation of dose over a given surface (and by extension, over the corresponding volume) to be quantified using histogram techniques. This may be of value in analysing and comparing techniques in which vulnerable tissue surfaces are irradiated. The planning of intracavitary treatments for cervical cancer is one application which might benefit from the display approach described above. Here the variation of dose over the mucosal surfaces of the bladder and the rectum is of particular interest, since dose related morbidity has often been reported following these treatments. 7 refs.; 8 figs

IGRT of the breast : doses to contralateral breast, heart and other untargeted tissues

International Nuclear Information System (INIS)

Taylor, M.L.; Lye, J.E.; Franich, R.D.

2011-01-01

Full text: Radiotherapy has an important role to play in locoregional therapy after surgery, particularly in reducing the likelihood of local recurrence. While there is no doubt about the benefit of adjuvant radiotherapy, concerns have been raised about radiation induced secondary cancers in the contralateral breast, lung and-if the left breast is treated-damage to the heart. We recently showed that Monte Carlo methods may be the most appropriate means for determination of such out-of-field doses to healthy tissues at intermediate distances from the primary field (J Med Phys 36 (20 I I) 59-71). A detailed, dosimetrically-matched Monte Carlo model of a Varian 21iX linear accelerator with mounted Varian G242 KV cone-beam computed tomography (CBCT) unit was constructed based on comprehensive manufacturer specifications. Patient CT scans were converted to voxelised phantoms and real treatment plans were replicated in silico. Doses to out of- field healthy structures (such as breast, heart and lung) were evaluated and risks of radiocarcinogenesis and cardiotoxicity estimated. It is possible to vary kV imager blade openings to influence out-of-field doses and associated risks.

Fetal doses from plutonium-239 and polonium-210

International Nuclear Information System (INIS)

Harrison, J.D.; Morgan, A.; Stather, J.W.

1992-01-01

The transfer of 239 Pu and 210 Po from the maternal circulation to the developing embryo and fetus was studied in rodents. The highest concentrations of both isotopes were measured in the yolk sac. In utero doses to haemopoietic tissue have been calculated taking account of transfer to the blastocyst/egg cylinder, yolk sac, liver and bone marrow. From animal data, the concentration ratios relative to maternal liver for these tissues were taken to be 0.1, 2, 0.01 and o.02, respectively for 239 Pu; and 1, 2, 0.1 and 0.1, respectively, for 210 Po. These concentration ratios were applied to periods of human gestation of 0-2.5 weeks, 2.5-6 weeks, 6-12 weeks and 12-38 weeks, and used to calculate fetal tissue doses for chronic maternal intake by ingestion of 1 kBq 239 Pu or 2 kBq 210 Po in the year of pregnancy (1 ALI for a member of the public). On this basis, the total in utero dose to haemopoietic tissue was about 1 μSv from 239 Pu and 60 μSv from 210 Po compared with red bone marrow doses to the mother in the year of 19 μSv from 239 Pu and 160 μSv from 210 Po. The yolk sac and bone marrow dominated in utero doses from both nuclides. For 239 Pu, because of its long half life, an important consideration was activity present in the offspring at birth and committed dose equivalents to red bone marrow in the child and mother. The total dose to haemopoietic tissue in the offspring to age 70 years, including in utero doses, was calculated as 13 μSv compared with a maternal dose to red bone marrow of 1400 μSv. For both isotopes the risk of leukaemia in the year of pregnancy was estimated to be of the same order for mother and fetus. For 239 Pu, the overall risk to 70 years of age was two orders of magnitude higher for the mother than her offspring. For 239 Pu, an acute intake of 1 kBq by ingestion during the period of yolk sac haemopoiesis would result in the highest in utero dose, estimated at about 20 μSv. However, activity at birth would be lower and the overall

Late effects of low-dose ionizing radiation on man

International Nuclear Information System (INIS)

Brilliant, M.D.; Vorob'ev, A.I.; Gogin, E.E.

1987-01-01

One of the most important problems, being stated before the medicine by the accident, which took place in Chernobyl in 1986- the problem of the so-called ionizing radiation low dose effect on a man's organism, is considered because a lot of people were subjected to low dose action. The concept of low doses of radiaion action and specificity of its immediate action in comparison with high dose action is considered. One of the most important poit while studying low dose action is the necessity to develop a system including all irradiated people and dosimetry, and espicially to study frequencies and periods of tumor appearance in different irradiated tissues. The results obtained when examining people who survived the atomic explosion in Japan and on the Marshall islands are analyzed. They testify to the fact that radiation affets more tissues than the clinical picture about the acute radiation sickness tells, and that tumors developing in them many years after radiation action tell about radiosensitivity in some tissues

Stereotactic intracranial radiotherapy: Dose prescription

International Nuclear Information System (INIS)

Schlienger, M.; Lartigau, E.; Nataf, F.; Mornex, F.; Latorzeff, I.; Lisbona, A.; Mahe, M.

2012-01-01

The aim of this article was the study of the successive steps permitting the prescription of dose in stereotactic intracranial radiotherapy, which includes radiosurgery and fractionated stereotactic radiotherapy. The successive steps studied are: the choice of stereotactic intracranial radiotherapy among the therapeutic options, based on curative or palliative treatment intent, then the selection of lesions according to size/volume, pathological type and their number permitting the choice between radiosurgery or fractionated stereotactic radiotherapy, which have the same methodological basis. Clinical experience has determined the level of dose to treat the lesions and limit the irradiation of healthy adjacent tissues and organs at risk structures. The last step is the optimization of the different parameters to obtain a safe compromise between the lesion dose and healthy adjacent structures. Study of dose-volume histograms, coverage indices and 3D imaging permit the optimization of irradiation. For lesions close to or included in a critical area, the prescribed dose is planned using the inverse planing method. Implementation of the successively described steps is mandatory to insure the prescription of an optimized dose. The whole procedure is based on the delineation of the lesion and adjacent healthy tissues. There are sometimes difficulties to assess the delineation and the volume of the target, however improvement of local control rates and reduction of secondary effects are the proof that the totality of the successive procedures are progressively improved. In practice, stereotactic intracranial radiotherapy is a continually improved treatment method, which constantly benefits from improvements in the choice of indications, imaging, techniques of irradiation, planing/optimization methodology and irradiation technique and from data collected from prolonged follow-up. (authors)

From personnel dose to personal dose

International Nuclear Information System (INIS)

Hoefert, M.; Raffnsoe, R.C.; Tuyn, J.W.N.; Wittekind, D.

1985-01-01

From following the development of personnel doses at CERN over the past six years it has become evident that work in areas of induced radioactivity is the principal cause of exposure. The results of photon dose measurements free-in-air and around a phantom are presented and discussed in the light of new quantities in individual monitoring. The importance of these results, with respect to the practical situation, is discussed and the problem of phantom size is mentioned. Finally, the results of dose measurements in the phantom are presented, since such information is important in cases where it becomes necessary to transform personnel doses into personal doses. (author)

Effects of proton radiation dose, dose rate and dose fractionation on hematopoietic cells in mice

International Nuclear Information System (INIS)

Ware, J.H.; Rusek, A.; Sanzari, J.; Avery, S.; Sayers, C.; Krigsfeld, G.; Nuth, M.; Wan, X.S.; Kennedy, A.R.

2010-01-01

The present study evaluated the acute effects of radiation dose, dose rate and fractionation as well as the energy of protons in hematopoietic cells of irradiated mice. The mice were irradiated with a single dose of 51.24 MeV protons at a dose of 2 Gy and a dose rate of 0.05-0.07 Gy/min or 1 GeV protons at doses of 0.1, 0.2, 0.5, 1, 1.5 and 2 Gy delivered in a single dose at dose rates of 0.05 or 0.5 Gy/min or in five daily dose fractions at a dose rate of 0.05 Gy/min. Sham-irradiated animals were used as controls. The results demonstrate a dose-dependent loss of white blood cells (WBCs) and lymphocytes by up to 61% and 72%, respectively, in mice irradiated with protons at doses up to 2 Gy. The results also demonstrate that the dose rate, fractionation pattern and energy of the proton radiation did not have significant effects on WBC and lymphocyte counts in the irradiated animals. These results suggest that the acute effects of proton radiation on WBC and lymphocyte counts are determined mainly by the radiation dose, with very little contribution from the dose rate (over the range of dose rates evaluated), fractionation and energy of the protons.

Effects of proton radiation dose, dose rate and dose fractionation on hematopoietic cells in mice.

Science.gov (United States)

Ware, J H; Sanzari, J; Avery, S; Sayers, C; Krigsfeld, G; Nuth, M; Wan, X S; Rusek, A; Kennedy, A R

2010-09-01

The present study evaluated the acute effects of radiation dose, dose rate and fractionation as well as the energy of protons in hematopoietic cells of irradiated mice. The mice were irradiated with a single dose of 51.24 MeV protons at a dose of 2 Gy and a dose rate of 0.05-0.07 Gy/min or 1 GeV protons at doses of 0.1, 0.2, 0.5, 1, 1.5 and 2 Gy delivered in a single dose at dose rates of 0.05 or 0.5 Gy/min or in five daily dose fractions at a dose rate of 0.05 Gy/min. Sham-irradiated animals were used as controls. The results demonstrate a dose-dependent loss of white blood cells (WBCs) and lymphocytes by up to 61% and 72%, respectively, in mice irradiated with protons at doses up to 2 Gy. The results also demonstrate that the dose rate, fractionation pattern and energy of the proton radiation did not have significant effects on WBC and lymphocyte counts in the irradiated animals. These results suggest that the acute effects of proton radiation on WBC and lymphocyte counts are determined mainly by the radiation dose, with very little contribution from the dose rate (over the range of dose rates evaluated), fractionation and energy of the protons.

Derivation of dose conversion factors for tritium

Energy Technology Data Exchange (ETDEWEB)

Killough, G. G.

1982-03-01

For a given intake mode (ingestion, inhalation, absorption through the skin), a dose conversion factor (DCF) is the committed dose equivalent to a specified organ of an individual per unit intake of a radionuclide. One also may consider the effective dose commitment per unit intake, which is a weighted average of organ-specific DCFs, with weights proportional to risks associated with stochastic radiation-induced fatal health effects, as defined by Publication 26 of the International Commission on Radiological Protection (ICRP). This report derives and tabulates organ-specific dose conversion factors and the effective dose commitment per unit intake of tritium. These factors are based on a steady-state model of hydrogen in the tissues of ICRP's Reference Man (ICRP Publication 23) and equilibrium of specific activities between body water and other tissues. The results differ by 27 to 33% from the estimate on which ICRP Publication 30 recommendations are based. The report also examines a dynamic model of tritium retention in body water, mineral bone, and two compartments representing organically-bound hydrogen. This model is compared with data from human subjects who were observed for extended periods. The manner of combining the dose conversion factors with measured or model-predicted levels of contamination in man's exposure media (air, drinking water, soil moisture) to estimate dose rate to an individual is briefly discussed.

Derivation of dose conversion factors for tritium

International Nuclear Information System (INIS)

Killough, G.G.

1982-03-01

For a given intake mode (ingestion, inhalation, absorption through the skin), a dose conversion factor (DCF) is the committed dose equivalent to a specified organ of an individual per unit intake of a radionuclide. One also may consider the effective dose commitment per unit intake, which is a weighted average of organ-specific DCFs, with weights proportional to risks associated with stochastic radiation-induced fatal health effects, as defined by Publication 26 of the International Commission on Radiological Protection (ICRP). This report derives and tabulates organ-specific dose conversion factors and the effective dose commitment per unit intake of tritium. These factors are based on a steady-state model of hydrogen in the tissues of ICRP's Reference Man (ICRP Publication 23) and equilibrium of specific activities between body water and other tissues. The results differ by 27 to 33% from the estimate on which ICRP Publication 30 recommendations are based. The report also examines a dynamic model of tritium retention in body water, mineral bone, and two compartments representing organically-bound hydrogen. This model is compared with data from human subjects who were observed for extended periods. The manner of combining the dose conversion factors with measured or model-predicted levels of contamination in man's exposure media (air, drinking water, soil moisture) to estimate dose rate to an individual is briefly discussed

Absorbed doses profiles vs Synovia tissue depth for the Y-90 and P-32 used in radiosynoviortesis treatment

International Nuclear Information System (INIS)

Torres B, M.B.; Ayra P, F.E.; Garcia R, E.; Cornejo D, N.; Yoriyaz, H.

2006-01-01

The radiosynoviortesis treatment has been used during more of 40 years as an alternative to the chemical and surgical synovectomy to alleviate the pain and to reduce the inflammation in suffered patients of rheumatic arthropathies, haemophilic arthropathies and other articulation disorders. It consists on the injection of radioactive isotopes inside a synovial cavity. For to evaluate the dosimetry of the radiosynoviortesis treatment is of great interest to know the absorbed dose in the volume of the target (synovia). The precise calculation of the absorbed dose in the inflamed synovia it is difficult, for numerous reasons, since the same one will depend on the thickness of the synovial membrane, the size of the articular space, the structure of the synovial membrane, the distribution in the articulation, the nature of the articular liquid, etc. Also the presence of the bone and the articular cartilage, components also of the articulation, it even complicated more the calculations. The method used to evaluate the dosimetry in radioactive synovectomy is known as the Monte Carlo method. The objective of our work consists on estimating with the Monte Carlo code MCNP4B the absorbed dose of the Y-90 and the P-32 in the depth of the synovial tissue. The results are presented as absorbed dose for injected millicurie (Gy/mCi) versus depth of synovial tissue. The simulation one carries out keeping in mind several synovia areas, of 50 cm 2 to 250 cm 2 keeping in mind three states of progression of the illness. Those obtained values of absorbed dose using the MCNP4B code will allow to introduce in our country an optimized method of dose prescription to the patient, to treat the rheumatic arthritis in medium and big articulations using the Y-90 and the P-32, eliminating the fixed doses and fixed radionuclides for each articulation like it happens in many clinics of Europe, as well as the empiric doses. (Author)

Estimation of lung tissue doses following exposure to low-LET radiation in the Canadian study of cancer following multiple fluoroscopies

International Nuclear Information System (INIS)

Howe, G.R.; Yaffe, M.

1992-02-01

Lung tissue doses from exposure to external low-LET radiation have been estimated for each year between 1930 and 1960 for 92,707 tuberculosis patients first treated in Canadian institutions between 1930 and 1952. Many of these patients received multiple chest fluoroscopies together with treatment by artificial pneumothorax, and thus accumulated doses up to 15.7 grays. The estimated doses have been used in a statistical analysis of lung cancer mortality between 1950 and 1987 occurring among 64,698 patients known to be alive at the start of 1950, and followed by linkage to the Canadian national mortality data base. There were substantial variations in the total cumulative lung tissue dose received by the cohort, with 2,490 individuals having doses in excess of 1.7 grays. A total of 1,156 lung cancer deaths was observed in the cohort, and these have been used to estimate relative risks. The most appropriate risk model appears to be a simple linear relative risk function, with an excess relative risk coefficient of 0.089 for an absorbed dose of 1 gray. This contrasts with estimates of relative risk based on the atomic bomb survivors study, for which the excess relative risk coefficient for males 20 years after the first exposure is estimated to be 0.64. The difference is statistically significant. It is postulated that fractionation and dose rate effectiveness factors may account for some of the discrepancy. (Modified author abstract) (14 refs., 20 tabs.)

Review of time-dose effects in radiation therapy

International Nuclear Information System (INIS)

Peschel, R.E.; Fischer, J.J.

1980-01-01

A historical review of conventional fractionation offers little confidence that such treatment is optimal for all tumors. Thus manipulation of time-dose schedules may provide a relatively inexpensive yet potentially useful technique for improving therapeutic results in radiation therapy. Consideration of basic radiobiological principles and animal model data illustrates the complex and heterogeneous nature of normal tissue and tumor response to time-dose effects and supports the hypothesis that better time-dose prescriptions can be found in clinical practice. The number of possible time-dose prescriptions is very large, and a review of the clinical trials using nonconventional fractionation demonstrates that the sampled portion of the total three-dimensional space of time, fraction number, and dose has been very small. Only carefully designed clinical trials can establish the therapeutic advantage of a new treatment schedule, and methods for selecting the most promising schedules are discussed. The use of simple data reduction formulas for time-dose effects should be discarded since they ignore the very complexity and heterogeneity of tissues and tumors which may form the basis of improved clinical results

On uncertainties in definition of dose equivalent

International Nuclear Information System (INIS)

Oda, Keiji

1995-01-01

The author has entertained always the doubt that in a neutron field, if the measured value of the absorbed dose with a tissue equivalent ionization chamber is 1.02±0.01 mGy, may the dose equivalent be taken as 10.2±0.1 mSv. Should it be 10.2 or 11, but the author considers it is 10 or 20. Even if effort is exerted for the precision measurement of absorbed dose, if the coefficient being multiplied to it is not precise, it is meaningless. [Absorbed dose] x [Radiation quality fctor] = [Dose equivalent] seems peculiar. How accurately can dose equivalent be evaluated ? The descriptions related to uncertainties in the publications of ICRU and ICRP are introduced, which are related to radiation quality factor, the accuracy of measuring dose equivalent and so on. Dose equivalent shows the criterion for the degree of risk, or it is considered only as a controlling quantity. The description in the ICRU report 1973 related to dose equivalent and its unit is cited. It was concluded that dose equivalent can be considered only as the absorbed dose being multiplied by a dimensionless factor. The author presented the questions. (K.I.)

Dose evaluation of narrow-beam

International Nuclear Information System (INIS)

Goto, Shinichi

1999-01-01

Reliability of the dose from the narrow photon beam becomes more important since the single high-dose rate radiosurgery becoming popular. The dose evaluation for the optimal dose is difficult due to absence of lateral electronic equilibrium. Data necessary for treatment regimen are TMR (tissue maximum ratio), OCR (off center ratio) and S c,p (total scatter factor). The narrow-beam was 10 MV X-ray from Varian Clinac 2100C equipped with cylindrical Fischer collimator CBI system. Detection was performed by Kodak XV-2 film, a PTW natural diamond detector M60003, Scanditronics silicon detector EDD-5 or Fujitec micro-chamber FDC-9.4C. Phantoms were the water equivalent one (PTW, RW3), water one (PTW, MP3 system) and Wellhofer WP600 system. Factors above were actually measured to reveal that in the dose evaluation of narrow photon beam, TMR should be measured by micro-chamber, OCR, by film, and S c,p , by the two. The use of diamond detector was recommended for more precise measurement and evaluation of the dose. The importance of water phantom in the radiosurgery system was also shown. (K.H.)

Accuracy of internal dose calculations with special consideration of radiopharmaceutical biokinetics

International Nuclear Information System (INIS)

Roedler, H.D.

1981-01-01

The individual steps of internal dose calculation, including the models and data used, as well as error considerations, are analysed following a short synopsis on the formalism of absorbed dose calculation. The mean dose in a target tissue depends on the administered activity, the residence time of the activity in the source tissues and the mean absorbed dose in the target tissue per transformation in a source tissue. Usually, a standard dosage is applied in radionuclide studies except in children. Actually administered and nomial activities generally differ by less than 10%. For the purpose of internal dose calculation, the biokinetics of a radiopharmaceutical are reflected in the residence times for the individual source tissues. The methods and the evaluation of measurements of biodistribution and retention data are discussed. The extrapolation of animal data to man is treated in some detail, including a survey of the methods used, as well as an attempt for validating these methods. None of these seem to yield more convincing results than the direct transfer of the residence times from animal to man, at least for the two radiopharmaceuticals discussed. The minimum period of measurement to derive residence times for the purpose of dose calculation has been determined as about one physical half-time. Some problems of the dose per transformation to a phantom are presented, including the age- or size-dependence of the internal dose. Organ doses to the phantom, calculated from different apparently reliable sets of biokinetic data, are generally compatible within a factor of 2 to 3, and somatically effective doses are generally compatible within a factor of less than 2

Monte Carlo Method in the calculate of conversion coefficients for dose in children's organs and tissues subjected to dentistric radiography

International Nuclear Information System (INIS)

Loureiro, E.C.M.; Khoury, H.; Lima, F.R.A.

1998-01-01

The increasing utilization of oral X-rays, specially in youngsters and children, prompts the assessment of equivalent doses in their organs and tissues. With this purpose, Monte Carlo code was adopted to simulate an X-ray source irradiating phantoms of the MIRD-5 type with different ages (10, 15 and 40 years old) to calculate the conversion coefficients which transform the exposure at skin to equivalent doses at several organs and tissues of interest. In order to check the computer program, simulations were performed for adult patients using the original code (ADAM,FOR developed by GSF Germany) and the adapted program (MCDRO,PAS). Good agreement between results obtained by both programs was observed. Applications to incisive, canine and molar teeth were simulated. The conversion factors were calculated for the following organs and tissues: thyroid, active bone marrow (head and whole body), bone (facial skeleton, cranium and whole body), skin (head and whole body) and crystalline. Based on the obtained results, it follows that the younger the patient and the langer the field area, the higher the doses in assessed organs and tissues

I-125 seed dose estimates in heterogeneous phantom

International Nuclear Information System (INIS)

Branco, Isabela S.L.; Antunes, Paula C.G.; Cavalieri, Tassio A.; Moura, Eduardo S.; Zeituni, Carlos A.; Yoriyaz, Helio

2015-01-01

Brachytherapy plays an important role in the healing process involving tumors in a variety of diseases. Several studies are currently conducted to examine the heterogeneity effects of different tissues and organs in brachytherapy clinical situations and a great effort has been made to incorporate new methodologies to estimate doses with greater accuracy. The objective of this study is to contribute to the assessment of heterogeneous effects on dose due to I-125 brachytherapy source in the presence of different materials with different densities and chemical compositions. The study was performed in heterogeneous phantoms using materials that simulate human tissues. Among these is quoted: breast, fat, muscle, lungs (exhaled and inhaled) and bones with different densities. Monte Carlo simulations for dose calculation in these phantoms were held and subsequently validated. The model 6711 I-125 seed was considered because it is widely used as a brachytherapy permanent implant and the one used in clinics and hospitals in Brazil. Thermoluminescent dosimeters TLD-700 (LiF: Mg, Ti) were simulated for dose assess. Several tissue configurations and positioning of I-125 sources were studied by simulations for future dose measurements. The methodology of this study so far shall be suitable for accurate dosimetric evaluation for different types of brachytherapy treatments, contributing to brachytherapy planning systems complementation allowing a better assessment of the dose actually delivered to the patient. (author)

I-125 seed dose estimates in heterogeneous phantom

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Branco, Isabela S.L.; Antunes, Paula C.G.; Cavalieri, Tassio A.; Moura, Eduardo S.; Zeituni, Carlos A.; Yoriyaz, Helio, E-mail: isabela.slbranco@gmail.com [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2015-07-01

Brachytherapy plays an important role in the healing process involving tumors in a variety of diseases. Several studies are currently conducted to examine the heterogeneity effects of different tissues and organs in brachytherapy clinical situations and a great effort has been made to incorporate new methodologies to estimate doses with greater accuracy. The objective of this study is to contribute to the assessment of heterogeneous effects on dose due to I-125 brachytherapy source in the presence of different materials with different densities and chemical compositions. The study was performed in heterogeneous phantoms using materials that simulate human tissues. Among these is quoted: breast, fat, muscle, lungs (exhaled and inhaled) and bones with different densities. Monte Carlo simulations for dose calculation in these phantoms were held and subsequently validated. The model 6711 I-125 seed was considered because it is widely used as a brachytherapy permanent implant and the one used in clinics and hospitals in Brazil. Thermoluminescent dosimeters TLD-700 (LiF: Mg, Ti) were simulated for dose assess. Several tissue configurations and positioning of I-125 sources were studied by simulations for future dose measurements. The methodology of this study so far shall be suitable for accurate dosimetric evaluation for different types of brachytherapy treatments, contributing to brachytherapy planning systems complementation allowing a better assessment of the dose actually delivered to the patient. (author)

TU-H-207A-08: Estimating Radiation Dose From Low-Dose Lung Cancer Screening CT Exams Using Tube Current Modulation

International Nuclear Information System (INIS)

Hardy, A; Bostani, M; McMillan, K; Zankl, M; Cagnon, C; McNitt-Gray, M

2016-01-01

Purpose: The purpose of this work is to estimate effective and lung doses from a low-dose lung cancer screening CT protocol using Tube Current Modulation (TCM) across patient models of different sizes. Methods: Monte Carlo simulation methods were used to estimate effective and lung doses from a low-dose lung cancer screening protocol for a 64-slice CT (Sensation 64, Siemens Healthcare) that used TCM. Scanning parameters were from the AAPM protocols. Ten GSF voxelized patient models were used and had all radiosensitive organs identified to facilitate estimating both organ and effective doses. Predicted TCM schemes for each patient model were generated using a validated method wherein tissue attenuation characteristics and scanner limitations were used to determine the TCM output as a function of table position and source angle. The water equivalent diameter (WED) was determined by estimating the attenuation at the center of the scan volume for each patient model. Monte Carlo simulations were performed using the unique TCM scheme for each patient model. Lung doses were tallied and effective doses were estimated using ICRP 103 tissue weighting factors. Effective and lung dose values were normalized by scanspecific 32 cm CTDIvol values based upon the average tube current across the entire simulated scan. Absolute and normalized doses were reported as a function of WED for each patient. Results: For all ten patients modeled, the effective dose using TCM protocols was below 1.5 mSv. Smaller sized patient models experienced lower absolute doses compared to larger sized patients. Normalized effective and lung doses showed some dependence on patient size (R2 = 0.77 and 0.78, respectively). Conclusion: Effective doses for a low-dose lung screening protocol using TCM were below 1.5 mSv for all patient models used in this study. Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical

TU-H-207A-08: Estimating Radiation Dose From Low-Dose Lung Cancer Screening CT Exams Using Tube Current Modulation

Energy Technology Data Exchange (ETDEWEB)

Hardy, A; Bostani, M [University of California, Los Angeles, Los Angeles, CA (United States); McMillan, K [Mayo Clinic, Rochester, MN (United States); Zankl, M [Helmholtz Zentrum Munchen, Neuherberg (Germany); Cagnon, C [UCLA Medical Center, Los Angeles, CA (United States); McNitt-Gray, M [UCLA School of Medicine, Los Angeles, CA (United States)

2016-06-15

Purpose: The purpose of this work is to estimate effective and lung doses from a low-dose lung cancer screening CT protocol using Tube Current Modulation (TCM) across patient models of different sizes. Methods: Monte Carlo simulation methods were used to estimate effective and lung doses from a low-dose lung cancer screening protocol for a 64-slice CT (Sensation 64, Siemens Healthcare) that used TCM. Scanning parameters were from the AAPM protocols. Ten GSF voxelized patient models were used and had all radiosensitive organs identified to facilitate estimating both organ and effective doses. Predicted TCM schemes for each patient model were generated using a validated method wherein tissue attenuation characteristics and scanner limitations were used to determine the TCM output as a function of table position and source angle. The water equivalent diameter (WED) was determined by estimating the attenuation at the center of the scan volume for each patient model. Monte Carlo simulations were performed using the unique TCM scheme for each patient model. Lung doses were tallied and effective doses were estimated using ICRP 103 tissue weighting factors. Effective and lung dose values were normalized by scanspecific 32 cm CTDIvol values based upon the average tube current across the entire simulated scan. Absolute and normalized doses were reported as a function of WED for each patient. Results: For all ten patients modeled, the effective dose using TCM protocols was below 1.5 mSv. Smaller sized patient models experienced lower absolute doses compared to larger sized patients. Normalized effective and lung doses showed some dependence on patient size (R2 = 0.77 and 0.78, respectively). Conclusion: Effective doses for a low-dose lung screening protocol using TCM were below 1.5 mSv for all patient models used in this study. Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical

Importance of scatter compensation algorithm in heterogeneous tissue for the radiation dose calculation of small lung nodules. A clinical study

International Nuclear Information System (INIS)

Baba, Yuji; Murakami, Ryuji; Mizukami, Naohisa; Morishita, Shoji; Yamashita, Yasuyuki; Araki, Fujio; Moribe, Nobuyuki; Hirata, Yukinori

2004-01-01

The purpose of this study was to compare radiation doses of small lung nodules calculated with beam scattering compensation and those without compensation in heterogeneous tissues. Computed tomography (CT) data of 34 small (1-2 cm: 12 nodules, 2-3 cm 11 nodules, 3-4 cm 11 nodules) lung nodules were used in the radiation dose measurements. Radiation planning for lung nodule was performed with a commercially available unit using two different radiation dose calculation methods: the superposition method (with scatter compensation in heterogeneous tissues), and the Clarkson method (without scatter compensation in heterogeneous tissues). The energy of the linac photon used in this study was 10 MV and 4 MV. Monitor unit (MU) to deliver 10 Gy at the center of the radiation field (center of the nodule) calculated with the two methods were compared. In 1-2 cm nodules, MU calculated by Clarkson method (MUc) was 90.0±1.1% (4 MV photon) and 80.5±2.7% (10 MV photon) compared to MU calculated by superposion method (MUs), in 2-3 cm nodules, MUc was 92.9±1.1% (4 MV photon) and 86.6±2.8% (10 MV photon) compared to MUs, and in 3-4 cm nodules, MUc was 90.5±2.0% (4 MV photon) and 90.1±1.7% (10 MV photon) compared to MUs. In 1-2 cm nodules, MU calculated without lung compensation (MUn) was 120.6±8.3% (4 MV photon) and 95.1±4.1% (10 MV photon) compared to MU calculated by superposion method (MUs), in 2-3 cm nodules, MUc was 120.3±11.5% (4 MV photon) and 100.5±4.6% (10 MV photon) compared to MUs, and in 3-4 cm nodules, MUc was 105.3±9.0% (4 MV photon) and 103.4±4.9% (10 MV photon) compared to MUs. The MU calculated without lung compensation was not significantly different from the MU calculated by superposition method in 2-3 cm nodules. We found that the conventional dose calculation algorithm without scatter compensation in heterogeneous tissues substantially overestimated the radiation dose of small nodules in the lung field. In the calculation of dose distribution of small

GSK1265744 pharmacokinetics in plasma and tissue after single-dose long-acting injectable administration in healthy subjects.

Science.gov (United States)

Spreen, William; Ford, Susan L; Chen, Shuguang; Wilfret, David; Margolis, David; Gould, Elizabeth; Piscitelli, Stephen

2014-12-15

GSK1265744 (744) is an HIV-1 integrase inhibitor in clinical development as a long-acting (LA) injectable formulation. This study evaluated plasma and tissue pharmacokinetics after single-dose administration of 744 LA administered by intramuscular (IM) or subcutaneous injections. This was a phase I, open-label, 9-cohort, parallel study of 744 in healthy subjects. 744 was administered as a 200 mg/mL nanosuspension at doses of 100-800 mg IM and 100-400 mg subcutaneous. Eight (6 active and 2 placebo) male and female subjects participated in each of the first 7 cohorts. All 8 subjects, 4 males and 4 females, received active 744 LA in cohorts 8 and 9 and underwent rectal and cervicovaginal tissue sampling, respectively. Plasma pharmacokinetic sampling was performed for a minimum of 12 weeks or until 744 concentrations were ≤0.1 μg/mL. Rectal and cervicovaginal tissue biopsies were performed at weeks 2 and 8 (cohort 8) and weeks 4 and 12 (cohort 9). 744 LA was generally safe and well tolerated after single injections. A majority of subjects reported injection site reactions, all graded as mild in intensity. Plasma concentration-time profiles were prolonged with measureable concentrations up to 52 weeks after dosing. 744 LA 800 mg IM achieved mean concentrations above protein adjusted-IC90 for approximately 16 weeks. Rectal and cervicovaginal tissue concentrations ranged from injection has potential application as a monthly or less frequent HIV treatment or prevention agent.

Dose effect on the uptake and accumulation of hydroxytyrosol and its metabolites in target tissues in rats.

Science.gov (United States)

López de las Hazas, Maria-Carmen; Rubió, Laura; Kotronoulas, Aristotelis; de la Torre, Rafael; Solà, Rosa; Motilva, Maria-José

2015-07-01

Hydroxytyrosol (HT) is the most prominent phenolic compound of virgin olive oil and due to its scientifically validated biological activities it is entering to the market as a potentially useful supplement for cardiovascular disease prevention. The aim of the present study was to investigate the relationship between the HT dose intake and its tissue uptake in rats, and thus, providing complementary information in relation to the target-dose relationship. Rats were given a refined olive oil enriched with HT at different doses (1, 10, and 100 mg/kg) and they were sacrificed after 5 h to ensure the cell tissue uptake of HT and its metabolites. Plasma samples and different organs as liver, kidney, heart and brain were obtained, and HT metabolites were analyzed by UPLC-MS/MS. The results showed that HT and its metabolites could be accumulated in a dose-dependent manner basically in the liver, kidney, and brain and were detected in these tissues even at nutritionally relevant human doses. The detection of free HT in liver and kidney was noteworthy. To date, this appears to be the only biologically active form, and thus, it provides relevant information for optimizing the potential applications of HT to prevent certain hepatic and renal diseases. In recent years, HT and its derivatives have led to a great interest from the virgin olive oil producers and manufacturers of nutraceutical supplements. The increasing interest in HT is mainly due to the European Food Safety Agency (EFSA) Panel on Dietetic Products, Nutrition, and Allergies (NDA) scientific opinion that established a cause-and-effect relationship between the consumption of olive oil polyphenols and protection of LDL particles from oxidative damage . Based on this positive opinion, the health claim "Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress" was included in the list of health claims , being the only authorized health claim in the European Union regarding polyphenols

Doses to organs and tissues from concomitant imaging in radiotherapy: a suggested framework for clinical justification.

Science.gov (United States)

Harrison, R M

2008-12-01

The increasing use of imaging for localization and verification in radiotherapy has raised issues concerning the justifiable doses to critical organs and tissues from concomitant exposures, particularly when extensive image-guided radiotherapy is indicated. Doses at positions remote from the target volume include components from high-energy leakage and scatter, as well as from concomitant imaging. In this paper, simulated prostate, breast and larynx treatments are used to compare doses from both high-energy and concomitant exposures as a function of distance from the target volume. It is suggested that the fraction, R, of the total dose at any point within the patient that is attributable to concomitant exposures may be a useful aid in their justification. R is small within the target volume and at large distances from it. However, there is a critical region immediately adjacent to the planning target volume where the dose from concomitant imaging combines with leakage and scatter to give values of R that approach 0.5 in the examples given here. This is noteworthy because the regions just outside the target volume will receive total doses in the order of 1 Gy, where commensurately high risk factors may not be substantially reduced because of cell kill. Other studies have identified these regions as sites of second cancers. The justification of an imaging regimen might therefore usefully take into account the maximum value of R encountered from the combination of imaging and radiotherapy for particular treatment sites.

Tritons at energies of 10 MeV to 1 TeV: Conversion coefficients for fluence-to-absorbed dose, equivalent dose, effective dose, and gray equivalent, calculated using Monte Carlo radiation transport code MCNPX 2.7.C

International Nuclear Information System (INIS)

Copeland, K.; Parker, D. E.; Friedberg, W.

2010-01-01

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 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 TM 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. Published by Oxford Univ. Press on behalf of the US Government 2010. (authors)

Helions at energies of 10 MeV to 1 TeV: Conversion coefficients for fluence-to-absorbed dose, equivalent dose, effective dose and gray equivalent, calculated using Monte Carlo radiation transport code MCNPX 2.7.C

International Nuclear Information System (INIS)

Copeland, K.; Parker, D. E.; Friedberg, W.

2010-01-01

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 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 TM 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. Published by Oxford Univ. Press on behalf of the U.S. Government 2010. (authors)

Dose distribution in head and neck during dental x-ray procedures

International Nuclear Information System (INIS)

Mason, E.W.; Goepp, R.A.

1978-01-01

Previous studies, notably by Franklin (Angle Ortho., 43:53-64, 1973), have shown significant exposures during cephalometric dental procedures and ways in which these exposures can be reduced. Skin dose over thyroid tissue has been measured by Alcox (J. Am. Dent. Assoc., 88:568-579, 1974), and others. This study is an expansion of thyroid dose measurements by Block, Goepp, and Mason (Angle Ortho., 47:17-24, 1977). The internal dose distribution in the head and neck area due to cephalometric and panoramic dental x-ray procedures is shown along with the dependence of orbit and thyroid dose on patient positioning. Higher doses can be delivered to deep tissue by panoramic machines since tissue at the axis of rotation is exposed during the entire procedure. (author)

Dose rates from a C-14 source using extrapolation chamber and MC calculations

International Nuclear Information System (INIS)

Borg, J.

1996-05-01

The extrapolation chamber technique and the Monte Carlo (MC) calculation technique based on the EGS4 system have been studied for application for determination of dose rates in a low-energy β radiation field e.g., that from a 14 C source. The extrapolation chamber measurement method is the basic method for determination of dose rates in β radiation fields. Applying a number of correction factors and the stopping power ratio, tissue to air, the measured dose rate in an air volume surrounded by tissue equivalent material is converted into dose to tissue. Various details of the extrapolation chamber measurement method and evaluation procedure have been studied and further developed, and a complete procedure for the experimental determination of dose rates from a 14 C source is presented. A number of correction factors and other parameters used in the evaluation procedure for the measured data have been obtained by MC calculations. The whole extrapolation chamber measurement procedure was simulated using the MC method. The measured dose rates showed an increasing deviation from the MC calculated dose rates as the absorber thickness increased. This indicates that the EGS4 code may have some limitations for transport of very low-energy electrons. i.e., electrons with estimated energies less than 10 - 20 keV. MC calculations of dose to tissue were performed using two models: a cylindrical tissue phantom and a computer model of the extrapolation chamber. The dose to tissue in the extrapolation chamber model showed an additional buildup dose compared to the dose in the tissue model. (au) 10 tabs., 11 ills., 18 refs

Evaluation of the dose received in the tissues of the neck during quantification of iodine in the thyroid by X-ray fluorescence spectrometry

Science.gov (United States)

Portararo, Antonio; Licour, Caroline; Gerardy, Isabelle; Pozuelo Navarro, Fausto

2018-04-01

The determination of the iodine content in the thyroid is of great interest for many investigations of this gland. The conventional scintigraphic method, using radionuclides, is efficient but delivers a significant dose to the patient. The X-ray fluorescence spectrometry could give information about the iodine content in the thyroid. The measured signal is obtained after stimulation of the stable iodine contained in the gland by X-rays. The advantage of this technique is the complete absence of radioactive isotope injected into the patient body. By applying this, a decrease in effective dose to the patient should be obtained. In this work, the study of the dose received by a thyroid phantom (surrounded by the different tissues of the neck) was performed. The phantom is made of PLA. The dose is measured in optimised conditions defined for the analytical technique. A total head-neck phantom was also used in order to consider the absorbed dose in each different tissues and organs as spinal cord or eyes. Thermo-luminescence dosimeters were chosen for their small size, their sensitivity and the easy positioning on the surface of the phantom but also inside of it to evaluate dose to internal organs. Those LiF 100 dosimeters have been calibrated within the X-ray beam also used for the analysis of iodine. The repeatability and reproducibility of the method has been evaluated. The influence of parameters as concentration of iodine in the thyroid, distance between the X-ray generator and the neck, thickness of the tissues surrounding the thyroid, has been investigated in terms of modifying parameters of the dose received by different tissues situated in the neck and the head.

Patient dose in image guided radiotherapy: Monte Carlo study of the CBCT dose contribution

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Salvatore Leotta

2018-02-01

Full Text Available Image Guided RadioTherapy (IGRT is a technique whose diffusion is growing thanks to the well-recognized gain in accuracy of dose delivery. However, multiple Cone Beam Computed Tomography (CBCT scans add dose to patients, and its contribution has to be assessed and minimized. Aim of our work was to evaluate, through Monte Carlo simulations, organ doses in IGRT due to CBCT and therapeutic MV irradiation in head-neck, thorax and pelvis districts. We developed a Monte Carlo simulation in GAMOS (Geant4-based Architecture for Medicine-Oriented Simulations, reproducing an Elekta Synergy medical linac operating at 6 and 10 MV photon energy, and we set up a scalable anthropomorphic model. After a validation by comparison with the experimental quality indexes, we evaluated the average doses to all organs and tissues belonging to the model for the three cases of irradiated district. Scattered radiation in therapy is larger than that diffused by CBCT by one to two orders of magnitude.

Dose/volume–response relations for rectal morbidity using planned and simulated motion-inclusive dose distributions

International Nuclear Information System (INIS)

Thor, Maria; Apte, Aditya; Deasy, Joseph O.; Karlsdóttir, Àsa; Moiseenko, Vitali; Liu, Mitchell; Muren, Ludvig Paul

2013-01-01

Background and purpose: Many dose-limiting normal tissues in radiotherapy (RT) display considerable internal motion between fractions over a course of treatment, potentially reducing the appropriateness of using planned dose distributions to predict morbidity. Accounting explicitly for rectal motion could improve the predictive power of modelling rectal morbidity. To test this, we simulated the effect of motion in two cohorts. Materials and methods: The included patients (232 and 159 cases) received RT for prostate cancer to 70 and 74 Gy. Motion-inclusive dose distributions were introduced as simulations of random or systematic motion to the planned dose distributions. Six rectal morbidity endpoints were analysed. A probit model using the QUANTEC recommended parameters was also applied to the cohorts. Results: The differences in associations using the planned over the motion-inclusive dose distributions were modest. Statistically significant associations were obtained with four of the endpoints, mainly at high doses (55–70 Gy), using both the planned and the motion-inclusive dose distributions, primarily when simulating random motion. The strongest associations were observed for GI toxicity and rectal bleeding (Rs = 0.12–0.21; Rs = 0.11–0.20). Applying the probit model, significant associations were found for tenesmus and rectal bleeding (Rs = 0.13, p = 0.02). Conclusion: Equally strong associations with rectal morbidity were observed at high doses (>55 Gy), for the planned and the simulated dose distributions including in particular random rectal motion. Future studies should explore patient-specific descriptions of rectal motion to achieve improved predictive power

SU-E-T-92: Achieving Desirable Lung Doses in Total Body Irradiation Based On in Vivo Dosimetry and Custom Tissue Compensation

International Nuclear Information System (INIS)

Cui, G; Shiu, A; Zhou, S; Cui, J; Ballas, L

2015-01-01

Purpose: To achieve desirable lung doses in total body irradiation (TBI) based on in vivo dosimetry and custom tissue compensation. Methods: The 15 MV photon beam of a Varian TrueBeam STx linac was used for TBI. Patients were positioned in the lateral decubitus position for AP/PA treatment delivery. Dose was calculated using the midpoint of the separation distance across the patient’s umbilicus. Patients received 200 cGy twice daily for 3 days. The dose rate at the patient’s midplane was approximately 10 cGy/min. Cerrobend blocks with a 5-HVL thickness were used for the primary lung shielding. A custom styrofoam holder for rice-flour filled bags was created based on the lung block cutouts. This was used to provide further lung shielding based on in vivo dose measurements. Lucite plates and rice-flour bags were placed in the head, neck, chest, and lower extremity regions during the treatment to compensate for the beam off-axis output variations. Two patients were included in the study. Patients 1 and 2 received a craniospinal treatment (1080 cGy) and a mediastinum treatment (2520 cGy), respectively, before the TBI. During the TBI nanoDot dosimeters were placed on the patient skin in the forehead, neck, umbilicus, and lung regions for dose monitoring. The doses were readout immediately after the treatment. Based on the readings, fine tuning of the thickness of the rice-flour filled bags was exploited to achieve the desirable lung doses. Results: For both patients the mean lung doses, which took into consideration all treatments, were controlled within 900 +/−10% cGy, as desired. Doses to the forehead, neck, and umbilicus were achieved within +/−10% of the prescribed dose (1200 cGy). Conclusion: A reliable and robust method was developed to achieve desirable lung doses and uniform body dose in TBI based on in vivo dosimetry and custom tissue compensator

SU-E-T-92: Achieving Desirable Lung Doses in Total Body Irradiation Based On in Vivo Dosimetry and Custom Tissue Compensation

Energy Technology Data Exchange (ETDEWEB)

Cui, G; Shiu, A; Zhou, S; Cui, J; Ballas, L [Univ Southern California, Los Angeles, CA (United States)

2015-06-15

Purpose: To achieve desirable lung doses in total body irradiation (TBI) based on in vivo dosimetry and custom tissue compensation. Methods: The 15 MV photon beam of a Varian TrueBeam STx linac was used for TBI. Patients were positioned in the lateral decubitus position for AP/PA treatment delivery. Dose was calculated using the midpoint of the separation distance across the patient’s umbilicus. Patients received 200 cGy twice daily for 3 days. The dose rate at the patient’s midplane was approximately 10 cGy/min. Cerrobend blocks with a 5-HVL thickness were used for the primary lung shielding. A custom styrofoam holder for rice-flour filled bags was created based on the lung block cutouts. This was used to provide further lung shielding based on in vivo dose measurements. Lucite plates and rice-flour bags were placed in the head, neck, chest, and lower extremity regions during the treatment to compensate for the beam off-axis output variations. Two patients were included in the study. Patients 1 and 2 received a craniospinal treatment (1080 cGy) and a mediastinum treatment (2520 cGy), respectively, before the TBI. During the TBI nanoDot dosimeters were placed on the patient skin in the forehead, neck, umbilicus, and lung regions for dose monitoring. The doses were readout immediately after the treatment. Based on the readings, fine tuning of the thickness of the rice-flour filled bags was exploited to achieve the desirable lung doses. Results: For both patients the mean lung doses, which took into consideration all treatments, were controlled within 900 +/−10% cGy, as desired. Doses to the forehead, neck, and umbilicus were achieved within +/−10% of the prescribed dose (1200 cGy). Conclusion: A reliable and robust method was developed to achieve desirable lung doses and uniform body dose in TBI based on in vivo dosimetry and custom tissue compensator.

Experimental study on active specific immunotherapy utilizing the immune reaction of low-dose irradiated tumor tissue

International Nuclear Information System (INIS)

Imanaka, Kazufumi; Tanaka, Koji; Sasai, Keisuke

1984-01-01

We have already reported the effectiveness of active specific immunotherapy based on the immune reaction of low-dose irradiated tumor tissue. In the present study, three kinds of immunotherapeutic methods subdivided by used cells were performed in order to compare each effectiveness. C3H/He mice bearing MM 46 tumor transplanted in the right hind paws received local irradiation with the dose of 3,000 rad on the 6th day, and the above-mentioned three methods, using tumor cells, lymphocytes, and tumor cells combining lymphocytes which were all separated from the topical tumor tissue exposed to 2,000 rad, were applied respectively on the 14 th day. The most effective data were obtained from two groups treated by the immunotherapy with tumor cells combining lymphocytes, which virtually caused the longest survival and best tumor growth control. (author)

The influence of dose per fraction on repair kinetics

International Nuclear Information System (INIS)

Rojas, A.; Joiner, M.C.

1989-01-01

The use of multiple fractions per day (MFD) in radiotherapy requires information about the rate of repair of radiation injury. It is important to know the minimum interval between fractions necessary for maximum sparing of normal tissue damage, whether rate of repair is dependent on the size of dose per fraction and if it is different in early and late responding tissues and in tumours. To address these questions, the rate of repair between radiation dose fractions was measured in mouse skin (acute damage), mouse kidney (late damage) and a mouse tumour (carcinoma NT). Skin and kidney measurements were made using multiple split doses of X-rays, followed by a neutron top-up. For skin, faster recovery was obtained with 4.4 Gy fractions (t1/2 = 3.46 ± 0.88 h). In contrast kidney showed slower recovery at a low dose per fraction of 2 Gy (t1/2 = 1.69 ± 0.39 h) than at a higher dose of 7 Gy per fraction (t1/2 = 0.92 ± 0.1h). These data show that repair rate is dependent on the size of dose per fraction, but not in a simple way. T1/2 values now available for many different tissues generally lie in the range of 1-2h, and are not correlated with proliferation status or early versus late response to treatment. At the doses used currently in clinical MFD treatments, these data indicate that damage in almost all normal tissues would increase if interfraction intervals less than 6 h were used. The t1/2 for CaNT (0.31 ± 0.15 h) is less than for any normal tissue. This underlines that the excess morbidity resulting from interfraction intervals < 6 h will not be paralleled by an increased effect in tumours. (author). 25 refs.; 7 figs

Distributions of neutron and gamma doses in phantom under a mixed field

International Nuclear Information System (INIS)

Beraud-Sudreau, E.

1982-06-01

A calculation program, based on Monte Carlo method, allowed to estimate the absorbed doses relatives to the reactor primary radiation, in a water cubic phantom and in cylindrical phantoms modelized from tissue compositions. This calculation is a theoretical approach of gamma and neutron dose gradient study in an animal phantom. PIN junction dosimetric characteristics have been studied experimentally. Air and water phantom radiation doses measured by PIN junction and lithium 7 fluoride, in reactor field have been compared to doses given by dosimetry classical techniques as tissue equivalent plastic and aluminium ionization chambers. Dosimeter responses have been employed to evaluate neutron and gamma doses in plastinaut (tissue equivalent plastic) and animal (piglet). Dose repartition in the piglet bone medulla has been also determined. This work has been completed by comparisons with Doerschell, Dousset and Brown results and by neutron dose calculations; the dose distribution related to lineic energy transfer in Auxier phantom has been also calculated [fr

Inhomogeneous dose escalation increases expected local control for NSCLC patients with lymph node involvement without increased mean lung dose

DEFF Research Database (Denmark)

Nielsen, Tine B; Hansen, Olfred; Schytte, Tine

2014-01-01

in mediastinum, and the thorax wall. The dose was escalated using a TCP model implemented into the planning system. The difference in TCP values between the homogeneous and inhomogeneous plans were evaluated using two different TCP models. RESULTS: Dose escalation was possible for all patients. TCP values based...... to the mediastinum were observed: 2.5 Gy for aorta, 4.4 Gy for the connective tissue, 1.6 Gy for the heart, and 2.6 Gy for trachea + bronchi. CONCLUSION: Increased target doses and TCP values using inhomogeneous dose distributions could be achieved for all patients, regardless of lymph node involvement, tumour stage...

Patient dose and risk in mammography

International Nuclear Information System (INIS)

Law, J.

1991-01-01

Patient dose in mammography is estimated by two methods compared and giving agreement. A mean tissue dose of about 1 mGy per film is found for a breast of 4.5 cm compressed thickness. Variables affecting dose are then considered quantitatively, including compressed breast thickness, tube potential, grids, magnification and beam collimation. The variables having the greatest effect are breast thickness and magnification. The dose estimates are combined with existing data on breast cancer induction to predict the risk of carcinogenesis in a breast screening programme. For example, in a screening centre performing 15 000 examinations per year, only one induced cancer is predicted in about 7 years of screening under average UK conditions of age and breast thickness. (author)

Therapeutic dose from a pyroelectric electron accelerator.

Science.gov (United States)

Fullem, T Z; Fazel, K C; Geuther, J A; Danon, Y

2009-11-01

Simple heating of pyroelectric crystals has been used as the basis for compact sources of X rays, electrons, ions and neutrons. We report on the evaluation of the feasibility of using a portable pyroelectric electron accelerator to deliver a therapeutic dose to tissue. Such a device could be mass produced as a handheld, battery-powered instrument. Experiments were conducted with several crystal sizes in which the crystal was heated inside a vacuum chamber and the emitted electrons were allowed to penetrate a thin beryllium window into the surrounding air. A Faraday cup was used to count the number of electrons that exited the window. The energy of these electrons was determined by measuring the energy spectrum of the X rays that resulted from the electron interactions with the Faraday cup. Based on these measurements, the dose that this source could deliver to tissue was calculated using Monte Carlo calculations. It was found that 10(13) electrons with a peak energy of the order of 100 keV were emitted from the beryllium window and could deliver a dose of 1664 Gy to a 2-cm-diameter, 110-microm-deep region of tissue located 1.5 cm from the window with air between the window and the tissue. This dose level is high enough to consider this technology for medical applications in which shallow energy deposition is beneficial.

Radiation dose assessment in nuclear medicine

International Nuclear Information System (INIS)

Stabin, M.G.

2002-01-01

In any application involving the use of ionizing radiation in humans, risks and benefits must be properly evaluated and balanced. Radionuclides are used in nuclear medicine in a variety of diagnostic and therapeutic procedures. Recently, interest has grown in therapeutic agents for a number of applications in nuclear medicine, particularly in the treatment of hematologic and non-hematologic malignancies. This has heightened interest in the need for radiation dose calculations and challenged the scientific community to develop more patient-specific and relevant dose models. Consideration of radiation dose in such studies is central to efforts to maximize dose to tumor while sparing normal tissues. In many applications, a significant absorbed dose may be received by some radiosensitive organs, particularly the active marrow. This talk will review the methods and models used in internal dosimetry in nuclear medicine, and discuss some current trends and challenges in this field

Breast internal dose measurements in a physical thoracic phantom

Energy Technology Data Exchange (ETDEWEB)

Silva, S.D.; Oliveira, M.A.; Castro, A.L.S.; Dias, H.G.; Nogueira, L.B.; Campos, T.P.R., E-mail: sadonatosilva@hotmail.com [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Nuclear; Hospital das Clinicas de Uberlandia, MG (Brazil). Departamento de Oncologia; Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Anatomia e Departamento de Imagem

2017-10-01

Radiotherapy is a cancer treatment intended to deposit the entire prescribed dose homogeneously into a target volume in order to eliminate the tumor and to spare the surrounding healthy tissues. This paper aimed to provide a dosimetric comparison between the treatment planning system (TPS) ECLIPSE from Varian Medical Systems and the internal dosimetric measurements in a breast phantom. The methodology consisted in performing a 3D conformal radiotherapy planning with two tangential opposite parallel fields applied to the synthetic breast in a thoracic phantom. The irradiation was reproduced in the Varian Linear accelerator, model SL - 20 Precise, 6 MV energy. EBT2 Radiochromic films, placed into the glandular equivalent tissue of the breast, were used to measure the spatial dose distribution. The absorbed dose was compared to those values predicted by the treatment planning system; besides, the dosimetric uncertainties were analyzed. The modal absorbed dose was in agreement with the prescribed value of 180 cGy, although few high dose points between 180 and 220 cGy were detected. The findings suggested a non-uniform dose distribution in the glandular tissue of the synthetic breast, similar to those found in the TPS, associated with the irregular anatomic breast shape and presence of inhomogeneities next to the thoracic wall generated by the low lung density. (author)

DIANE, a simulation code for the interaction of neutrons with living tissues. Application to low doses of fast neutrons on human tumoral cells

International Nuclear Information System (INIS)

Nenot, M.L.

2003-07-01

Our work deals with the irradiation of cells and living tissues by 14 MeV neutrons at very low doses (a few 10 -2 Gy). Such experiments require an accurate knowledge of the values of neutron dose rates and fluences at the level of cell cultures. We have performed measurements of fluence rates through an activation method applied to gold and copper foils. The fluence rate is deduced from the gamma rays emitted by the irradiated foils. Neutron doses and dose rates have been measured through varied methods: PIN diodes, ionization tissue equivalent chambers, and Geiger-Mueller counters. We have designed the DIANE code to simulate the impact of energetic neutrons on cells. This code can be used with isolated cells or macroscopic tissues, it takes into account the roles of the ionisation electrons produced by recoil nuclei entering the cell. This point is all the more important since recent works have highlighted the impact of very low energy electrons on DNA. (A.C.)

Determination of electron depth-dose curves for water, ICRU tissue, and PMMA and their application to radiation protection dosimetry

International Nuclear Information System (INIS)

Grosswendt, B.

1994-01-01

For monoenergetic electrons in the energy range between 60 keV and 10 MeV, normally incident on water, 4-element ICRU tissue and PMMA phantoms, depth-dose curves have been calculated using the Monte Carlo method. The phantoms' shape was that of a rectangular solid with a square front face of 30 cm x 30 cm and a thickness of 15 cm; it corresponds to that recommended by the ICRU for use in the procedure of calibrating radiation protection dosemeters. The depth-dose curves have been used to determine practical ranges, half-value depths, electron fluence to maximum absorbed dose conversion factors, and conversion factors between electron fluence and absorbed dose at depths d corresponding to 0.007 g.cm -2 , 0.3 g.cm -2 , and 1.0 g.cm -2 . The latter data can be used as fluence to dose equivalent conversion factors for extended parallel electron beams. (Author)

Patient radiation dose in conventional and xerographic cephalography

International Nuclear Information System (INIS)

Copley, R.L.; Glaze, S.A.; Bushong, S.C.; West, D.C.

1979-01-01

A comparison of the radiation doses for xeroradiographic and conventional film screen cephalography was made. Alderson tissue-equivalent phantoms were used for patient simulation. An optimum technique in terms of patient dose and image quality indicated that the dose for the Xerox process ranged from five to eleven times greater than that for the conventional process for entrance and exit exposures, respectively. This dose, however, falls within an acceptable range for other dental and medical radiation doses. It is recommended that conventional cephalography be used for routine purposes and that xeroradiography be reserved for situations requiring the increased image quality that the process affords

Comparison between linear quadratic and early time dose models

International Nuclear Information System (INIS)

Chougule, A.A.; Supe, S.J.

1993-01-01

During the 70s, much interest was focused on fractionation in radiotherapy with the aim of improving tumor control rate without producing unacceptable normal tissue damage. To compare the radiobiological effectiveness of various fractionation schedules, empirical formulae such as Nominal Standard Dose, Time Dose Factor, Cumulative Radiation Effect and Tumour Significant Dose, were introduced and were used despite many shortcomings. It has been claimed that a recent linear quadratic model is able to predict the radiobiological responses of tumours as well as normal tissues more accurately. We compared Time Dose Factor and Tumour Significant Dose models with the linear quadratic model for tumour regression in patients with carcinomas of the cervix. It was observed that the prediction of tumour regression estimated by the Tumour Significant Dose and Time Dose factor concepts varied by 1.6% from that of the linear quadratic model prediction. In view of the lack of knowledge of the precise values of the parameters of the linear quadratic model, it should be applied with caution. One can continue to use the Time Dose Factor concept which has been in use for more than a decade as its results are within ±2% as compared to that predicted by the linear quadratic model. (author). 11 refs., 3 figs., 4 tabs

Dose prescription in boron neutron capture therapy

International Nuclear Information System (INIS)

Gupta, N.M.S.; Gahbauer, R.A.; Blue, T.E.; Wambersie, A.

1994-01-01

The purpose of this paper is to address some aspects of the many considerations that need to go into a dose prescription in boron neutron capture therapy (BNCT) for brain tumors; and to describe some methods to incorporate knowledge from animal studies and other experiments into the process of dose prescription. Previously, an algorithm to estimate the normal tissue tolerance to mixed high and low linear energy transfer radiations in BNCT was proposed. The authors have developed mathematical formulations and computational methods to represent this algorithm. Generalized models to fit the central axis dose rate components for an epithermal neutron field were also developed. These formulations and beam fitting models were programmed into spreadsheets to simulate two treatment techniques which are expected to be used in BNCT: a two-field bilateral scheme and a single-field treatment scheme. Parameters in these spreadsheets can be varied to represent the fractionation scheme used, the 10 B microdistribution in normal tissue, and the ratio of 10 B in tumor to normal tissue. Most of these factors have to be determined for a given neutron field and 10 B compound combination from large animal studies. The spreadsheets have been programmed to integrate all of the treatment-related information and calculate the location along the central axis where the normal tissue tolerance is exceeded first. This information is then used to compute the maximum treatment time allowable and the maximum tumor dose that may be delivered for a given BNCT treatment. The effect of different treatment variables on the treatment time and tumor dose has been shown to be very significant. It has also been shown that the location of D max shifts significantly, depending on some of the treatment variables-mainly the fractionation scheme used. These results further emphasize the fact that dose prescription in BNCT is very complicated and nonintuitive. 11 refs., 6 figs., 3 tabs

Occupational radiation doses during interventional procedures

International Nuclear Information System (INIS)

Nuraeni, N; Hiswara, E; Kartikasari, D; Waris, A; Haryanto, F

2016-01-01

Digital subtraction angiography (DSA) is a type of fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. The use of DSA procedures has been increased quite significantly in the Radiology departments in various cities in Indonesia. Various reports showed that both patients and medical staff received a noticeable radiation dose during the course of this procedure. A study had been carried out to measure these doses among interventionalist, nurse and radiographer. The results show that the interventionalist and the nurse, who stood quite close to the X-ray beams compared with the radiographer, received radiation higher than the others. The results also showed that the radiation dose received by medical staff were var depending upon the duration and their position against the X-ray beams. Compared tothe dose limits, however, the radiation dose received by all these three medical staff were still lower than the limits. (paper)

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

Science.gov (United States)

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

2017-11-01

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

An examination of resveratrol's mechanisms of action in human tissue: impact of a single dose in vivo and dose responses in skeletal muscle ex vivo.

Directory of Open Access Journals (Sweden)

Cameron B Williams

Full Text Available The current study tested the hypothesis that a single, moderate dose of RSV would activate the AMPK/SIRT1 axis in human skeletal muscle and adipose tissue. Additionally, the effects of RSV on mitochondrial respiration in PmFBs were examined. Eight sedentary men (23.8±2.4 yrs; BMI: 32.7±7.1 reported to the lab on two occasions where they were provided a meal supplemented with 300 mg of RSV or a placebo. Blood samples, and a muscle biopsy were obtained in the fasted state and again, with the addition of an adipose tissue biopsy, two hours post-prandial. The effect of RSV on mitochondrial respiration was examined in PmFBs taken from muscle biopsies from an additional eight men (23.4±5.4 yrs; BMI: 24.4±2.8. No effect of RSV was observed on nuclear SIRT1 activity, acetylation of p53, or phosphorylation of AMPK, ACC or PKA in either skeletal muscle or adipose tissue. A decrease in post absorptive insulin levels was accompanied by elevated skeletal muscle phosphorylation of p38 MAPK, but no change in either skeletal muscle or adipose tissue insulin signalling. Mitochondrial respiration in PmFBs was rapidly inhibited by RSV at 100-300 uM depending on the substrate examined. These results question the efficacy of a single dose of RSV at altering skeletal muscle and adipose tissue AMPK/SIRT1 activity in humans and suggest that RSV mechanisms of action in humans may be associated with altered cellular energetics resulting from impaired mitochondrial ATP production.

Thorium-232 in human tissues: Metabolic parameters and radiation doses

International Nuclear Information System (INIS)

Stehney, A.F.

1994-01-01

Higher than environmental levels of 232 Th have been found in autopsy samples of lungs and other organs from four former employees of a Th refinery. Working periods of the subjects ranged from 3 to 24 years, and times from end of work to death ranged from 6 to 31 years. Concentrations of 232 Th in these samples and in tissues from two cases of non-occupational exposure were examined for compatibility with dosimetric models in Publication 30 of the International Commission on Radiological Protection (ICPP 1979a). The concentrations of 232 Th in the lungs of the Th workers relative to the concentrations in bone or liver were much higher than calculated from the model for class Y aerosols of Th and the exposure histories of the subjects, and concentrations in the pulmonary lymph nodes were much lower than calculated for three of the Th workers and both non-occupational cases. Least-squares fits to the measured concentrations showed that the biological half-times of Th in liver, spleen, and kidneys are similar to the half-time in bone instead of the factor of 10 less suggested in Publication 30, and the fractions translocated from body fluids were found to be about 0.03, 0.02, and 0.005, respectively, when the fraction to bone was held at the suggested value of 0.7. Fitted values of the respiratory parameters differed significantly between cases and the differences were ascribable to aerosol differences. Average inhalation rates calculated for individual Th workers ranged from 50 to 110 Bq 232 Th y -1 , and dose equivalents as high as 9.3 Sv to the lungs, 2.0 Sv to bone surfaces, and 1.1 Sv effective dose equivalent were calculated from the inhalation rates and fitted values of the metabolic parameters. The radiation doses were about the same when calculated from parameter values fitted with an assumed translocation fraction of 0.2 from body fluids to bone instead of 0.7

Low-dose dental CT

International Nuclear Information System (INIS)

Rustemeyer, P.; Eich, H.T.; John-Mikolajewski, V.; Mueller, R.D.

1999-01-01

Purpose: The intention of this study was to reduce patient dose during dental CT in the planning for osseointegrated implants. Methods and Materials: Dental CTs were performed with a spiral CT (Somatom Plus 4, Siemens) and a dental software package. Use of the usual dental CT technique (120 kVp; 165 mA, 1 s rotation time, 165 mAs; pitch factor 1) was compared with a new protocol (120 kVp; 50 mA; 0.7 s rotation time; 35 mAs; pitch factor 2) which delivered the best image quality at the lowest possible radiation dose, as tested in a preceding study. Image quality was analysed using a human anatomic head preparation. Four radiologists analysed the images independently. A Wilcoxon rank pair-test was used for statistic evaluation. The doses to the thyroid gland, the active bone marrow, the salivary glands, and the eye lens were determined in a tissue-equivalent phantom (Alderson-Rando Phantom) with lithium fluoride thermoluminescent dosimeters at the appropriate locations. Results: By mAs reduction from 165 to 35 and using a pitch factor of 2, the radiation dose could be reduced by a factor of nine (max.) (e.g., the bone marrow dose could be reduced from 23.6 mSv to 2.9 mSv, eye lens from 0.5 mSv to 0.3 mSv, thyroid gland from 2.5 mSv to 0.5 mSv, parotid glands from 2.3 mSv to 0.4 mSv). The dose reduction did not lead to an actual loss of image quality or diagnostic information. Conclusion: A considerable dose reduction without loss of diagnostic information is achievable in dental CT. Dosereducing examination protocols like the one presented may further expand the use of preoperative dental CT. (orig.) [de

Development of virtual patient models for permanent implant brachytherapy Monte Carlo dose calculations: interdependence of CT image artifact mitigation and tissue assignment.

Science.gov (United States)

Miksys, N; Xu, C; Beaulieu, L; Thomson, R M

2015-08-07

This work investigates and compares CT image metallic artifact reduction (MAR) methods and tissue assignment schemes (TAS) for the development of virtual patient models for permanent implant brachytherapy Monte Carlo (MC) dose calculations. Four MAR techniques are investigated to mitigate seed artifacts from post-implant CT images of a homogeneous phantom and eight prostate patients: a raw sinogram approach using the original CT scanner data and three methods (simple threshold replacement (STR), 3D median filter, and virtual sinogram) requiring only the reconstructed CT image. Virtual patient models are developed using six TAS ranging from the AAPM-ESTRO-ABG TG-186 basic approach of assigning uniform density tissues (resulting in a model not dependent on MAR) to more complex models assigning prostate, calcification, and mixtures of prostate and calcification using CT-derived densities. The EGSnrc user-code BrachyDose is employed to calculate dose distributions. All four MAR methods eliminate bright seed spot artifacts, and the image-based methods provide comparable mitigation of artifacts compared with the raw sinogram approach. However, each MAR technique has limitations: STR is unable to mitigate low CT number artifacts, the median filter blurs the image which challenges the preservation of tissue heterogeneities, and both sinogram approaches introduce new streaks. Large local dose differences are generally due to differences in voxel tissue-type rather than mass density. The largest differences in target dose metrics (D90, V100, V150), over 50% lower compared to the other models, are when uncorrected CT images are used with TAS that consider calcifications. Metrics found using models which include calcifications are generally a few percent lower than prostate-only models. Generally, metrics from any MAR method and any TAS which considers calcifications agree within 6%. Overall, the studied MAR methods and TAS show promise for further retrospective MC dose

Dose reduction to normal tissues as compared to the gross tumor by using intensity modulated radiotherapy in thoracic malignancies

Directory of Open Access Journals (Sweden)

Bhalla NK

2006-08-01

Full Text Available Abstract Background and purpose Intensity modulated radiotherapy (IMRT is a powerful tool, which might go a long way in reducing radiation doses to critical structures and thereby reduce long term morbidities. The purpose of this paper is to evaluate the impact of IMRT in reducing the dose to the critical normal tissues while maintaining the desired dose to the volume of interest for thoracic malignancies. Materials and methods During the period January 2002 to March 2004, 12 patients of various sites of malignancies in the thoracic region were treated using physical intensity modulator based IMRT. Plans of these patients treated with IMRT were analyzed using dose volume histograms. Results An average dose reduction of the mean values by 73% to the heart, 69% to the right lung and 74% to the left lung, with respect to the GTV could be achieved with IMRT. The 2 year disease free survival was 59% and 2 year overall survival was 59%. The average number of IMRT fields used was 6. Conclusion IMRT with inverse planning enabled us to achieve desired dose distribution, due to its ability to provide sharp dose gradients at the junction of tumor and the adjacent critical organs.

Radiotherapy Dose Fractionation under Parameter Uncertainty

International Nuclear Information System (INIS)

Davison, Matt; Kim, Daero; Keller, Harald

2011-01-01

In radiotherapy, radiation is directed to damage a tumor while avoiding surrounding healthy tissue. Tradeoffs ensue because dose cannot be exactly shaped to the tumor. It is particularly important to ensure that sensitive biological structures near the tumor are not damaged more than a certain amount. Biological tissue is known to have a nonlinear response to incident radiation. The linear quadratic dose response model, which requires the specification of two clinically and experimentally observed response coefficients, is commonly used to model this effect. This model yields an optimization problem giving two different types of optimal dose sequences (fractionation schedules). Which fractionation schedule is preferred depends on the response coefficients. These coefficients are uncertainly known and may differ from patient to patient. Because of this not only the expected outcomes but also the uncertainty around these outcomes are important, and it might not be prudent to select the strategy with the best expected outcome.

Dose conversion coefficients for high-energy photons, electrons, neutrons and protons

CERN Document Server

Sakamoto, Y; Sato, O; Tanaka, S I; Tsuda, S; Yamaguchi, Y; Yoshizawa, N

2003-01-01

In the International Commission on Radiological Protection (ICRP) 1990 Recommendations, radiation weighting factors were introduced in the place of quality factors, the tissue weighting factors were revised, and effective doses and equivalent doses of each tissues and organs were defined as the protection quantities. Dose conversion coefficients for photons, electrons and neutrons based on new ICRP recommendations were cited in the ICRP Publication 74, but the energy ranges of theses data were limited and there are no data for high energy radiations produced in accelerator facilities. For the purpose of designing the high intensity proton accelerator facilities at JAERI, the dose evaluation code system of high energy radiations based on the HERMES code was developed and the dose conversion coefficients of effective dose were evaluated for photons, neutrons and protons up to 10 GeV, and electrons up to 100 GeV. The dose conversion coefficients of effective dose equivalent were also evaluated using quality fact...

Monte Carlo dose calculation of microbeam in a lung phantom

International Nuclear Information System (INIS)

Company, F.Z.; Mino, C.; Mino, F.

1998-01-01

Full text: Recent advances in synchrotron generated X-ray beams with high fluence rate permit investigation of the application of an array of closely spaced, parallel or converging microplanar beams in radiotherapy. The proposed techniques takes advantage of the hypothesised repair mechanism of capillary cells between alternate microbeam zones, which regenerates the lethally irradiated endothelial cells. The lateral and depth doses of 100 keV microplanar beams are investigated for different beam dimensions and spacings in a tissue, lung and tissue/lung/tissue phantom. The EGS4 Monte Carlo code is used to calculate dose profiles at different depth and bundles of beams (up to 20x20cm square cross section). The maximum dose on the beam axis (peak) and the minimum interbeam dose (valley) are compared at different depths, bundles, heights, widths and beam spacings. Relatively high peak to valley ratios are observed in the lung region, suggesting an ideal environment for microbeam radiotherapy. For a single field, the ratio at the tissue/lung interface will set the maximum dose to the target volume. However, in clinical application, several fields would be involved allowing much greater doses to be applied for the elimination of cancer cells. We conclude therefore that multifield microbeam therapy has the potential to achieve useful therapeutic ratios for the treatment of lung cancer

Review of techniques and detectors used in instruments for field measurement of beta doses and dose rates

International Nuclear Information System (INIS)

Jones, A.R.

1983-01-01

Generally, field measurements are required to assess the hazard from #betta#-rays before personnel are allowed to occupy a working space or perform a task. Occasionally, the measurements are required for an assessment after a #betta#-ray exposure is suspected to have occurred. Until recently the dose or dose rate have been the quantities of interest but there is now felt to be a need to characterize the energies and directions of the #betta#-rays as well. The purpose of #betta#-dosimetry is the assessment of hazard to superficial tissues (within approx. 10 mm of the surface) and that these tissues may also be exposed simultaneously to other ionizing radiations. The #betta#-dosimetry technique must take account of this. With these uses of field instruments in mind the following detectors, and associated techniques will be discussed in terms of the measurement principles, advantages and limitations: thin-walled ion chambers (sometimes in combination with thick-walled ones or with covers thick enough to prevent penetration of #betta#-particles); thin scintillators, nearly tissue equivalent, to provide a detector analogous to skin; scintillators, thick enough to absorb all the energy of the #betta#-particles (circuitry is required to count pulses according to size to permit calculation of dose or dose rate); silicon diodes with thin detection layers operated as photocurrent generators; silicon diodes, reversed biassed, with pulses counted according to size; and simple pulse counters (e.g., GM counters or silicon diodes with thin windows)

Dose and dose rate monitor

International Nuclear Information System (INIS)

Novakova, O.; Ryba, J.; Slezak, V.; Svobodova, B.; Viererbl, L.

1984-10-01

The methods are discussea of measuring dose rate or dose using a scintillation counte. A plastic scintillator based on polystyrene with PBD and POPOP activators and coated with ZnS(Ag) was chosen for the projected monitor. The scintillators were cylindrical and spherical in shape and of different sizes; black polypropylene tubes were chosen as the best case for the probs. For the counter with different plastic scintillators, the statistical error 2σ for natural background was determined. For determining the suitable thickness of the ZnS(Ag) layer the energy dependence of the counter was measured. Radioisotopes 137 Cs, 241 Am and 109 Cd were chosen as radiation sources. The best suited ZnS(Ag) thickness was found to be 0.5 μm. Experiments were carried out to determine the directional dependence of the detector response and the signal to noise ratio. The temperature dependence of the detector response and its compensation were studied, as were the time stability and fatigue manifestations of the photomultiplier. The design of a laboratory prototype of a dose rate and dose monitor is described. Block diagrams are given of the various functional parts of the instrument. The designed instrument is easiiy portable, battery powered, measures dose rates from natural background in the range of five orders, i.e., 10 -2 to 10 3 nGy/s, and allows to determine a dose of up to 10 mGy. Accouracy of measurement in the energy range of 50 keV to 1 MeV is better than +-20%. (E.S.)

Effective dose calculation in CT using high sensitivity TLDs

International Nuclear Information System (INIS)

Brady, Z.; Johnston, P.N.

2010-01-01

Full text: To determine the effective dose for common paediatric CT examinations using thermoluminescence dosimetry (TLD) mea surements. High sensitivity TLD chips (LiF:Mg,Cu,P, TLD-IOOH, Thermo Fisher Scientific, Waltham, MA) were calibrated on a linac at an energy of 6 MY. A calibration was also performed on a superricial X-ray unit at a kilovoltage energy to validate the megavoltage cali bration for the purpose of measuring doses in the diagnostic energy range. The dose variation across large organs was assessed and a methodology for TLD placement in a 10 year old anthropomorphic phantom developed. Effective dose was calculated from the TLD measured absorbed doses for typical CT examinations after correcting for the TLD energy response and taking into account differences in the mass energy absorption coefficients for different tissues and organs. Results Using new tissue weighting factors recommended in ICRP Publication 103, the effective dose for a CT brain examination on a 10 year old was 1.6 millisieverts (mSv), 4.9 mSv for a CT chest exa ination and 4.7 mSv for a CT abdomen/pelvis examination. These values are lower for the CT brain examination, higher for the CT chest examination and approximately the same for the CT abdomen/ pelvis examination when compared with effective doses calculated using ICRP Publication 60 tissue weighting factors. Conclusions High sensitivity TLDs calibrated with a radiotherapy linac are useful for measuring dose in the diagnostic energy range and overcome limitations of output reproducibility and uniformity asso ciated with traditional TLD calibration on CT scanners or beam quality matched diagnostic X-ray units.

Studies of absorbed dose determinations and spatial dose distributions for high energy proton beams

International Nuclear Information System (INIS)

Hiraoka, Takeshi

1982-01-01

Absolute dose determinations were made with three types of ionization chamber and a Faraday cup. Methane based tissue equivalent (TE) gas, nitrogen, carbon dioxide, air were used as an ionizing gas with flow rate of 10 ml per minute. Measurements were made at the entrance position of unmodulated beams and for a beam of a spread out Bragg peak at a depth of 17.3 mm in water. For both positions, the mean value of dose determined by the ionization chambers was 0.993 +- 0.014 cGy for which the value of TE gas was taken as unity. The agreement between the doses estimated by the ionization chambers and the Faraday cup was within 5%. Total uncertainty estimated in the ionization chamber and the Faraday cup determinations is 6 and 4%, respectively. Common sources of error in calculating the dose from ionization chamber measurements are depend on the factors of ion recombination, W value, and mass stopping power ratio. These factors were studied by both experimentally and theoretically. The observed values for the factors show a good agreement to the predicted one. Proton beam dosimetry intercomparison between Japan and the United States was held. Good agreement was obtained with standard deviation of 1.6%. The value of the TE calorimeter is close to the mean value of all. In the proton spot scanning system, lateral dose distributions at any depth for one spot beam can be simulated by the Gaussian distribution. From the Gaussian distributions and the central axis depth doses for one spot beam, it is easy to calculate isodose distributions in the desired field by superposition of dose distribution for one spot beam. Calculated and observed isodose curves were agreed within 1 mm at any dose levels. (J.P.N.)

Low-dose computed tomographic imaging in orbital trauma

Energy Technology Data Exchange (ETDEWEB)

Jackson, A.; Whitehouse, R.W. (Manchester Univ. (United Kingdom). Dept. of Diagnostic Radiology)

1993-08-01

The authors review findings in 75 computed tomographic (CT) examinations of 66 patients with orbital trauma who were imaged using a low-radiation-dose CT technique. Imaging was performed using a dynamic scan mode and exposure factors of 120 kVp and 80 mAs resulting in a skin dose of 11 mGy with an effective dose-equivalent of 0.22 mSv. Image quality was diagnostic in all cases and excellent in 73 examinations. Soft-tissue abnormalities within the orbit including muscle adhesions were well demonstrated both on primary axial and reconstructed multiplanar images. The benefits of multiplanar reconstructions are stressed and the contribution of soft-tissue injuries to symptomatic diplopia examined. (author).

Determination of organ doses and effective doses in radiooncology

International Nuclear Information System (INIS)

Roth, J.; Martinez, A.E.

2007-01-01

Background and Purpose: With an increasing chance of success in radiooncology, it is necessary to estimate the risk from radiation scatter to areas outside the target volume. The cancer risk from a radiation treatment can be estimated from the organ doses, allowing a somewhat limited effective dose to be estimated and compared. Material and Methods: The doses of the radiation-sensitive organs outside the target volume can be estimated with the aid of the PC program PERIDOSE developed by van der Giessen. The effective doses are determined according to the concept of ICRP, whereby the target volume and the associated organs related to it are not taken into consideration. Results: Organ doses outside the target volume are generally < 1% of the dose in the target volume. In some cases, however, they can be as high as 3%. The effective doses during radiotherapy are between 60 and 900 mSv, depending upon the specific target volume, the applied treatment technique, and the given dose in the ICRU point. Conclusion: For the estimation of the radiation risk, organ doses in radiooncology can be calculated with the aid of the PC program PERIDOSE. While evaluating the radiation risk after ICRP, for the calculation of the effective dose, the advanced age of many patients has to be considered to prevent that, e.g., the high gonad doses do not overestimate the effective dose. (orig.)

Indication-related dosing for magnetic resonance contrast media

International Nuclear Information System (INIS)

Yuh, W.T.C.; Parker, J.R.; Carvlin, M.J.

1997-01-01

This presentation reviews the issue of contrast media dosing and imaging protocols for the optimal MR imaging detection and characterization of pathology. The cumulative clinical experience gained in performing contrast-enhanced MR examinations with gadolinium chelates indicates that a dose of 0.1 mmol/kg body weight provides safe and effective enhancement of most CNS pathology. Doses lower than 0.1 mmol/kg have been shown to be inadequate for delineating all but selected types of CNS pathology, such as masses with a high lesion to background ratio on post-contrast images (acoustic neuromas) or lesions located in areas in which the normal tissue very rapidly takes up contrast agent (e. g. microadenomas in the pituitary gland). Recent clinical studies have suggested a role for high dose gadolinium administration (up to 0.3 mmol/kg) for the optimal detection and delineation of cerebral metastases or other small or poorly enhancing lesions. Differences in the histopathologic characteristics (capillary permeability, vascularity, location, size) of specific diseased tissues may require varying doses or even a different contrast agent to be used for optimal imaging results. As new MR contrast agents and new scanning techniques are introduced, the specific diagnostic question posed will likely determine the choice of pulse sequence, contrast agent and dose used. (orig.)

Spatial accuracy of 3D reconstructed radioluminographs of serial tissue sections and resultant absorbed dose estimates

Energy Technology Data Exchange (ETDEWEB)

Petrie, I.A.; Flynn, A.A.; Pedley, R.B.; Green, A.J.; El-Emir, E.; Dearling, J.L.J.; Boxer, G.M.; Boden, R.; Begent, R.H.J. [Cancer Research UK Targeting and Imaging Group, Department of Oncology, Royal Free and University College Medical School, Royal Free Campus, London (United Kingdom)

2002-10-21

Many agents using tumour-associated characteristics are deposited heterogeneously within tumour tissue. Consequently, tumour heterogeneity should be addressed when obtaining information on tumour biology or relating absorbed radiation dose to biological effect. We present a technique that enables radioluminographs of serial tumour sections to be reconstructed using automated computerized techniques, resulting in a three-dimensional map of the dose-rate distribution of a radiolabelled antibody. The purpose of this study is to assess the reconstruction accuracy. Furthermore, we estimate the potential error resulting from registration misalignment, for a range of beta-emitting radionuclides. We compare the actual dose-rate distribution with that obtained from the same activity distribution but with manually defined translational and rotational shifts. As expected, the error produced with the short-range {sup 14}C is much larger than that for the longer range {sup 90}Y; similarly values for the medium range {sup 131}I are between the two. Thus, the impact of registration inaccuracies is greater for short-range sources. (author)

Organ-specific external dose coefficients and protective apron transmission factors for historical dose reconstruction for medical personnel.

Science.gov (United States)

Simon, Steven L

2011-07-01

While radiation absorbed dose (Gy) to the skin or other organs is sometimes estimated for patients from diagnostic radiologic examinations or therapeutic procedures, rarely is occupationally-received radiation absorbed dose to individual organs/tissues estimated for medical personnel; e.g., radiologic technologists or radiologists. Generally, for medical personnel, equivalent or effective radiation doses are estimated for compliance purposes. In the very few cases when organ doses to medical personnel are reconstructed, the data is usually for the purpose of epidemiologic studies; e.g., a study of historical doses and risks to a cohort of about 110,000 radiologic technologists presently underway at the U.S. National Cancer Institute. While ICRP and ICRU have published organ-specific external dose conversion coefficients (DCCs) (i.e., absorbed dose to organs and tissues per unit air kerma and dose equivalent per unit air kerma), those factors have been published primarily for mono-energetic photons at selected energies. This presents two related problems for historical dose reconstruction, both of which are addressed here. It is necessary to derive conversion factor values for (1) continuous distributions of energy typical of diagnostic medical x-rays (bremsstrahlung radiation), and (2) energies of particular radioisotopes used in medical procedures, neither of which are presented in published tables. For derivation of DCCs for bremsstrahlung radiation, combinations of x-ray tube potentials and filtrations were derived for different time periods based on a review of relevant literature. Three peak tube potentials (70 kV, 80 kV, and 90 kV) with four different amounts of beam filtration were determined to be applicable for historic dose reconstruction. The probabilities of these machine settings were assigned to each of the four time periods (earlier than 1949, 1949-1954, 1955-1968, and after 1968). Continuous functions were fit to each set of discrete values of the

In search of the relevant lung dose

International Nuclear Information System (INIS)

Fisher, D.R.

1982-12-01

Researchers have traditionally been inconsistent in their methods of determining and reporting dose to the lung from inhaled radionuclides - a situation which has led to difficulties in later comparing results and deriving dose-response relationships. The dose quantities which at present are most generally assumed to be related to risk of stochastic radiation effects (such as lung cancer) are (1) mean dose equivalent to the bronchial epithelium basal cell layer for radon daughters, and (2) mean dose equivalent to the whole lung (including tracheobronchial lymph nodes) for all other radionuclides. The average radiation dose is calculated by assuming that the energy is homogeneously impared to the entire tissue mass. However, the actual dose received by a cell which becomes transformed or tumorigenic is likely to be very much different than the smear dose to the entire organ. This realization has led to further study of stochastic energy deposition processes in single cells or cell nuclei from internal emitters. The end product of the stochastic approach to dosimetry, sometimes called microdosimetry, is a probability density in specific energy. For alpha-emitting radionuclides in the lung, a concept that may be more important than dose is the probability that a cell is hit by an alpha particle

Is it sensible to “deform” dose? 3D experimental validation of dose-warping

International Nuclear Information System (INIS)

Yeo, U. J.; Taylor, M. L.; Supple, J. R.; Smith, R. L.; Dunn, L.; Kron, T.; Franich, R. D.

2012-01-01

Purpose: Strategies for dose accumulation in deforming anatomy are of interest in radiotherapy. Algorithms exist for the deformation of dose based on patient image sets, though these are sometimes contentious because not all such image calculations are constrained by physical laws. While tumor and organ motion has been a key area of study for a considerable amount of time, deformation is of increasing interest. In this work, we demonstrate a full 3D experimental validation of results from a range of dose deformation algorithms available in the public domain. Methods: We recently developed the first tissue-equivalent, full 3D deformable dosimetric phantom—“DEFGEL.” To assess the accuracy of dose-warping based on deformable image registration (DIR), we have measured doses in undeformed and deformed states of the DEFGEL dosimeter and compared these to planned doses and warped doses. In this way we have directly evaluated the accuracy of dose-warping calculations for 11 different algorithms. We have done this for a range of stereotactic irradiation schemes and types and magnitudes of deformation. Results: The original Horn and Schunck algorithm is shown to be the best performing of the 11 algorithms trialled. Comparing measured and dose-warped calculations for this method, it is found that for a 10 × 10 mm 2 square field, γ 3%/3mm = 99.9%; for a 20 × 20 mm 2 cross-shaped field, γ 3%/3mm = 99.1%; and for a multiple dynamic arc (0.413 cm 3 PTV) treatment adapted from a patient treatment plan, γ 3%/3mm = 95%. In each case, the agreement is comparable to—but consistently ∼1% less than—comparison between measured and calculated (planned) dose distributions in the absence of deformation. The magnitude of the deformation, as measured by the largest displacement experienced by any voxel in the volume, has the greatest influence on the accuracy of the warped dose distribution. Considering the square field case, the smallest deformation (∼9 mm) yields

Absorbed and effective dose from periapical radiography by portable intraoral x-ray machine

International Nuclear Information System (INIS)

Cho, Jeong Yeon; Han, Won Jeong; Kim, Eun Kyung

2007-01-01

The purpose of this study was to measure the absorbed dose and to calculate the effective dose for periapical radiography done by portable intraoral x-ray machines. 14 full mouth, upper posterior and lower posterior periapical radiographs were taken by wall-type 1 and portable type 3 intraoral x-ray machines. Thermoluminescent dosemeters were placed at 23 sites at the layers of the tissue-equivalent ART woman phantom for dosimetry. Average tissue absorbed dose and radiation weighted dose were calculated for each major anatomical site. Effective dose was calculated using 2005 ICRP tissue weighted factors. On 14 full mouth periapical radiographs, the effective dose for wall-type x-ray machine was 30 Sv; for portable x-ray machines were 30 Sv, 22 Sv, 36 Sv. On upper posterior radiograph, the effective dose for wall-type x-ray machine was 4 Sv; for portable x-ray machines doses were 4 Sv, 3 Sv, 5 Sv. On lower posterior radiograph, the effective dose for wall type x-ray machine was 5 Sv; for portable x-ray machines doses were 4 Sv, 4 Sv, 5 Sv. Effective doses for periapical radiographs performed by portable intraoral x-ray machines were similar to doses for periapical radiographs taken by wall type intraoral x-ray machines

Correlation between CT numbers and tissue parameters needed for Monte Carlo simulations of clinical dose distributions

Science.gov (United States)

Schneider, Wilfried; Bortfeld, Thomas; Schlegel, Wolfgang

2000-02-01

We describe a new method to convert CT numbers into mass density and elemental weights of tissues required as input for dose calculations with Monte Carlo codes such as EGS4. As a first step, we calculate the CT numbers for 71 human tissues. To reduce the effort for the necessary fits of the CT numbers to mass density and elemental weights, we establish four sections on the CT number scale, each confined by selected tissues. Within each section, the mass density and elemental weights of the selected tissues are interpolated. For this purpose, functional relationships between the CT number and each of the tissue parameters, valid for media which are composed of only two components in varying proportions, are derived. Compared with conventional data fits, no loss of accuracy is accepted when using the interpolation functions. Assuming plausible values for the deviations of calculated and measured CT numbers, the mass density can be determined with an accuracy better than 0.04 g cm-3 . The weights of phosphorus and calcium can be determined with maximum uncertainties of 1 or 2.3 percentage points (pp) respectively. Similar values can be achieved for hydrogen (0.8 pp) and nitrogen (3 pp). For carbon and oxygen weights, errors up to 14 pp can occur. The influence of the elemental weights on the results of Monte Carlo dose calculations is investigated and discussed.

Evaluation of the effect of change in the radiosensitive tissue weights listed in the ICRP in estimate of effective dose

Energy Technology Data Exchange (ETDEWEB)

Vieira, Jose W.; Leal Neto, Viriato; Lopes Filho, Ferdinand J.; Lima Filho, Jose M.; Santana, Ivan E., E-mail: jose.wilson@recife.ifpe.edu.br [Instituto Federal de Educacao, Ciencia e Tecnologia de Pernambuco, (IFPE), Recife, PE (Brazil); Andrade, Pedro H.A.; Cabral, Manuela O.M. [Universidade Federal de Pernambuco (DEN/UFPE), Recife, PE (Brazil). Departamento de Energia Nuclear; Lima, Vanildo J.M. [Universidade Federal de Pernambuco (DA/UFPE), Recife, PE (Brazil). Departamento de Anatomia; Lima, Fernando R.A., E-mail: falima@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN/CNEN-NE), Recife, PE (Brazil)

2015-07-01

For photons and electrons, the effective dose by gender is a weighted sum of the absorbed doses in radiosensitive organs and tissue of the human body. Effective dose is estimated using Exposure Computational Models (ECM) of both genders for the same age group. The FSTA and MSTA ECMs were developed by researchers from DEN/UFPE and consist of voxel phantoms representing adults coupled to EGSnrc Monte Carlo Code, which, in the folder designed for users of EGS, codes were added to simulate some radioactive sources. The reports 60 and 103 of the ICRP provide the factors that weigh the radiosensitivity of organs and tissues (W{sub T}) required to estimate the effective dose. The two lists were placed in the FSTA and MSTA to simulate radiodiagnostic examination in different regions of the body (cranium, abdomen and thorax). The dosimetric data produced allowed an analysis of the effect of the change in the w{sub T} from the report 60 to the 103. The highest mean percent relative error, 64.3%, occurred in the results for the cranium due to the increase of the w{sub T} for most of the organs and tissues in the head and trunk in the updated list. In this case, it can be concluded that the values of the effective dose with the wT of the ICRP 60 were underestimated. Other types of simulators of radioactive sources can be used in investigating this problem and other variables related to the phantom can be considered for that proposes a W{sub T}'s list specific for the Brazilian population or recommend unrestricted use the ICRP data. (author)

Evaluation of the effect of change in the radiosensitive tissue weights listed in the ICRP in estimate of effective dose

International Nuclear Information System (INIS)

Vieira, Jose W.; Leal Neto, Viriato; Lopes Filho, Ferdinand J.; Lima Filho, Jose M.; Santana, Ivan E.; Andrade, Pedro H.A.; Cabral, Manuela O.M.

2015-01-01

For photons and electrons, the effective dose by gender is a weighted sum of the absorbed doses in radiosensitive organs and tissue of the human body. Effective dose is estimated using Exposure Computational Models (ECM) of both genders for the same age group. The FSTA and MSTA ECMs were developed by researchers from DEN/UFPE and consist of voxel phantoms representing adults coupled to EGSnrc Monte Carlo Code, which, in the folder designed for users of EGS, codes were added to simulate some radioactive sources. The reports 60 and 103 of the ICRP provide the factors that weigh the radiosensitivity of organs and tissues (W T ) required to estimate the effective dose. The two lists were placed in the FSTA and MSTA to simulate radiodiagnostic examination in different regions of the body (cranium, abdomen and thorax). The dosimetric data produced allowed an analysis of the effect of the change in the w T from the report 60 to the 103. The highest mean percent relative error, 64.3%, occurred in the results for the cranium due to the increase of the w T for most of the organs and tissues in the head and trunk in the updated list. In this case, it can be concluded that the values of the effective dose with the wT of the ICRP 60 were underestimated. Other types of simulators of radioactive sources can be used in investigating this problem and other variables related to the phantom can be considered for that proposes a W T 's list specific for the Brazilian population or recommend unrestricted use the ICRP data. (author)

SU-G-BRC-08: Evaluation of Dose Mass Histogram as a More Representative Dose Description Method Than Dose Volume Histogram in Lung Cancer Patients

Energy Technology Data Exchange (ETDEWEB)

Liu, J; Eldib, A; Ma, C [Fox Chase Cancer Center, Philadelphia, PA (United States); Lin, M [The University of Texas Southwestern Medical Ctr, Dallas, TX (United States); Li, J [Cyber Medical Inc, Xian, Shaanxi (China); Mora, G [Universidade de Lisboa, Codex, Lisboa (Portugal)

2016-06-15

Purpose: Dose-volume-histogram (DVH) is widely used for plan evaluation in radiation treatment. The concept of dose-mass-histogram (DMH) is expected to provide a more representative description as it accounts for heterogeneity in tissue density. This study is intended to assess the difference between DVH and DMH for evaluating treatment planning quality. Methods: 12 lung cancer treatment plans were exported from the treatment planning system. DVHs for the planning target volume (PTV), the normal lung and other structures of interest were calculated. DMHs were calculated in a similar way as DVHs expect that the voxel density converted from the CT number was used in tallying the dose histogram bins. The equivalent uniform dose (EUD) was calculated based on voxel volume and mass, respectively. The normal tissue complication probability (NTCP) in relation to the EUD was calculated for the normal lung to provide quantitative comparison of DVHs and DMHs for evaluating the radiobiological effect. Results: Large differences were observed between DVHs and DMHs for lungs and PTVs. For PTVs with dense tumor cores, DMHs are higher than DVHs due to larger mass weighing in the high dose conformal core regions. For the normal lungs, DMHs can either be higher or lower than DVHs depending on the target location within the lung. When the target is close to the lower lung, DMHs show higher values than DVHs because the lower lung has higher density than the central portion or the upper lung. DMHs are lower than DVHs for targets in the upper lung. The calculated NTCPs showed a large range of difference between DVHs and DMHs. Conclusion: The heterogeneity of lung can be well considered using DMH for evaluating target coverage and normal lung pneumonitis. Further studies are warranted to quantify the benefits of DMH over DVH for plan quality evaluation.

Dose-response relationship with radiotherapy: an evidence?

International Nuclear Information System (INIS)

Chauvet, B.; Rauglaudre, G. de; Mineur, L.; Alfonsi, M.; Reboul, F.

2003-01-01

The dose-response relationship is a fundamental basis of radiobiology. Despite many clinical data, difficulties remain to demonstrate a relation between dose and local control: relative role of treatment associated with radiation therapy (surgery, chemotherapy, hormonal therapy), tumor heterogeneity, few prospective randomized studies, uncertainty of local control assessment. Three different situations are discussed: tumors with high local control probabilities for which dose effect is demonstrated by randomized studies (breast cancer) or sound retrospective data (soft tissues sarcomas), tumors with intermediate local control probabilities for which dose effect seems to be important according to retrospective studies and ongoing or published phase III trials (prostate cancer), tumors with low local control probabilities for which dose effect appears to be modest beyond standard doses, and inferior to the benefit of concurrent chemotherapy (lung and oesophageal cancer). For head and neck tumors, the dose-response relationship has been explored through hyperfractionation and accelerated radiation therapy and a dose effect has been demonstrated but must be compared to the benefit of concurrent chemotherapy. Last but not least, the development of conformal radiotherapy allow the exploration of the dose response relationship for tumors such as hepatocellular carcinomas traditionally excluded from the field of conventional radiation therapy. In conclusion, the dose-response relationship remains a sound basis of radiation therapy for many tumors and is a parameter to take into account for further randomized studies. (author)

Natural radiation dose to Gammarus from Hudson river

International Nuclear Information System (INIS)

Paschoa, A.S.; Wrenn, M.E.; Eisenbud, M.

1979-01-01

The purpose of this investigation is to evaluate the natural radiation dose rate to whole body and components of the Gammarus species, a zooplankton which occurs in the Hudson River among other places, and to compare the results with the upper limits of dose rates from man-made sources. The alpha dose rates to the exoskeleton and soft tissues are about 10 times the average alpha dose rate to the whole body, assuming uniform distribution of 226 Ra. The natural alpha radiation dose rate to Gammarus represents only about 5% of the total natural dose to the organism, i.e., 492 mrad/yr. The external dose rate due to 40 K, 238 U plus daughters and 232 Th plus daughters accumulated in the sediments comprise 91% of that total natural dose rate, the remaining percentage being due to natural internal beta emitters and cosmic radiation. Man-made sources can cause an external dose rate up to 224 mrad/yr, which comprises roughly 1/3 of the total dose rate (up to 716 mrad/yr; natural plus man-made) to the Gammarus of Hudson River in front of Indian Point Nuclear Power Station. However, in terms of dose-equivalent the natural sources of radiation would contribute more than 75% of the total dose to Gammarus

Monte Carlo calculations of lung dose in ORNL phantom for boron neutron capture therapy

International Nuclear Information System (INIS)

Krstic, D.; Markovic, V.M.; Jovanovic, Z.; Milenkovic, B.; Nikezic, D.; Atanackovic, J.

2014-01-01

Monte Carlo simulations were performed to evaluate dose for possible treatment of cancers by boron neutron capture therapy (BNCT). The computational model of male Oak Ridge National Laboratory (ORNL) phantom was used to simulate tumours in the lung. Calculations have been performed by means of the MCNP5/X code. In this simulation, two opposite neutron beams were considered, in order to obtain uniform neutron flux distribution inside the lung. The obtained results indicate that the lung cancer could be treated by BNCT under the assumptions of calculations. The difference in evaluated dose in cancer and normal lung tissue suggests that BNCT could be applied for the treatment of cancers. The difference in exposure of cancer and healthy tissue can be observed, so the healthy tissue can be spared from damage. An absorbed dose ratio of metastatic tissue-to-the healthy tissue was ∼5. Absorbed dose to all other organs was low when compared with the lung dose. Absorbed dose depth distribution shows that BNC therapy can be very useful in the treatments for tumour. The ratio of the tumour absorbed dose and irradiated healthy tissue absorbed dose was also ∼5. It was seen that an elliptical neutron field was better irradiation choice. (authors)

Radiation Doses to Members of the U.S. Population from Ubiquitous Radionuclides in the Body: Part 2, Methods and Dose Calculations

International Nuclear Information System (INIS)

Watson, David J.; Strom, Daniel J.

2011-01-01

This paper is part two of a three-part series investigating annual effective doses to residents of the United States from intakes of ubiquitous radionuclides, including radionuclides occurring naturally, radionuclides whose concentrations are technologically enhanced, and anthropogenic radionuclides. This series of papers explicitly excludes intakes from inhaling 222Rn, 220Rn, and their short-lived decay products; it also excludes intakes of radionuclides in occupational and medical settings. Part one reviewed, summarized, characterized, and grouped all published and some unpublished data for U.S. residents on ubiquitous radionuclide concentrations in tissues and organs. Assumptions about equilibrium with long-lived parents are made for the 28 other radionuclides in these series lacking data. This paper describes the methods developed to group the collected data into source regions described in the Radiation Dose Assessment Resource (RADAR) dosimetric methodology. Methods for converting the various units of data published over 50 years into a standard form are developed and described. Often, meaningful values of uncertainty of measurements were not published so that variability in data sets is confounded with measurement uncertainty. A description of the methods developed to estimate variability is included in this paper. The data described in part one are grouped by gender and age to match the RADAR dosimetric phantoms. Within these phantoms, concentration values are grouped into source tissue regions by radionuclide, and they are imputed for source regions lacking tissue data. Radionuclide concentrations are then imputed for other phantoms source regions with missing concentration values, and the uncertainties of the imputed values are increased. The content concentrations of hollow organs are calculated, and activities are apportioned to the bone source regions using assumptions about each radionuclide's bone-seeking behavior. The data sets are then ready to be

In vivo study on influence of the heterogeneity of tissues in the dose distribution in high energy X ray therapy

International Nuclear Information System (INIS)

Aldred, M.A.

1987-01-01

Several authors investigated the effect of the heterogeneity of tissue in the dose distribution in a radiation-therapy. Practically all of them carried out ''in vitro'' measurements using a solid body immersed in a water phantom, in order to simulate the inhomogeneity, such as bone, air cavity, etc. In the present work, ''in vivo'' measurements were performed utilizing thermoluminescent dosimeters, whose appropriateness and convenience are well known. Eight patients at Instituto de Radioterapia Oswaldo Cruz were selected, that were under irradiation treatments in their pelvic region. The ratio between body entry radiation dose and the corresponding exit dose, when compared to the same ratio for a homogeneous phantom, gives the influence of the heterogeneity of the tissue the radiation crosses. The results found in those eight patients have shown that ''in vivo'' measurements present a ratio about 8% smaller that in homogeneous phantom case. (author) [pt

Dose Calculation Evolution for Internal Organ Irradiation in Humans

International Nuclear Information System (INIS)

Jimenez V, Reina A.

2007-01-01

The International Commission of Radiation Units (ICRU) has established through the years, a discrimination system regarding the security levels on the prescription and administration of doses in radiation treatments (Radiotherapy, Brach therapy, Nuclear Medicine). The first level is concerned with the prescription and posterior assurance of dose administration to a point of interest (POI), commonly located at the geometrical center of the region to be treated. In this, the effects of radiation around that POI, is not a priority. The second level refers to the dose specifications in a particular plane inside the patient, mostly the middle plane of the lesion. The dose is calculated to all the structures in that plane regardless if they are tumor or healthy tissue. In this case, the dose is not represented by a point value, but by level curves called 'isodoses' as in a topographic map, so you can assure the level of doses to this particular plane, but it also leave with no information about how this values go thru adjacent planes. This is why the third level is referred to the volumetrical description of doses so these isodoses construct now a volume (named 'cloud') that give us better assurance about tissue irradiation around the volume of the lesion and its margin (sub clinical spread or microscopic illness). This work shows how this evolution has resulted, not only in healthy tissue protection improvement but in a rise of tumor control, quality of life, better treatment tolerance and minimum permanent secuelae

Patient absorbed radiation doses estimation related to irradiation anatomy; Estimativa de dose absorvida pelo paciente relacionada a anatomia irradiada

Energy Technology Data Exchange (ETDEWEB)

Soares, Flavio Augusto Penna; Soares, Amanda Anastacio; Kahl, Gabrielly Gomes, E-mail: prof.flavio@gmail.com, E-mail: amanda-a-soares@hotmail.com, E-mail: gabriellygkahl@gmail.com [Instituto Federal de Eduacao, Ciencia e Tecnologia de Santa Catarina (IFSC), Florianopolis, SC (Brazil)

2014-07-01

Developed a direct equation to estimate the absorbed dose to the patient in x-ray examinations, using electric, geometric parameters and filtering combined with data from irradiated anatomy. To determine the absorbed dose for each examination, the entrance skin dose (ESD) is adjusted to the thickness of the patient's specific anatomy. ESD is calculated from the estimated KERMA greatness in the air. Beer-Lambert equations derived from power data mass absorption coefficients obtained from the NIST / USA, were developed for each tissue: bone, muscle, fat and skin. Skin thickness was set at 2 mm and the bone was estimated in the central ray of the site, in the anteroposterior view. Because they are similar in density and attenuation coefficients, muscle and fat are treated as a single tissue. For evaluation of the full equations, we chose three different anatomies: chest, hand and thigh. Although complex in its shape, the equations simplify direct determination of absorbed dose from the characteristics of the equipment and patient. The input data is inserted at a single time and total absorbed dose (mGy) is calculated instantly. The average error, when compared with available data, is less than 5% in any combination of device data and exams. In calculating the dose for an exam and patient, the operator can choose the variables that will deposit less radiation to the patient through the prior analysis of each combination of variables, using the ALARA principle in routine diagnostic radiology sector.

The interpretation of animal data in the calculation of doses from new radiolabeled compounds

International Nuclear Information System (INIS)

Naylor, G.P.L.; Ellender, M.; Harrison, J.D.

1992-01-01

At NRPB, dose calculations are performed for pharmaceutical companies wishing to obtain approval for human volunteer experiments. Animal data from one or more species are used to estimate the radiation doses to humans that would result from the administration of novel radiolabeled compounds. The calculations themselves are straightforward, but the animal data can be interpreted in different ways, leading to variations in the calculated dose. Doses to the gut compartments usually dominate the committed effective dose equivalent, but retention in other tissues may be important for some compounds. Long-term retention components in tissues can affect doses considerably, and the binding of many radiopharmaceuticals to melanin means that doses to the eye are particularly important. The effect of these considerations on calculating doses are considered, as well as the effect of changes in risk estimates and tissue weighting factors

Dosimetric and radiobiological comparison of volumetric modulated arc therapy, high-dose rate brachytherapy, and low-dose rate permanent seeds implant for localized prostate cancer

Energy Technology Data Exchange (ETDEWEB)

Yang, Ruijie, E-mail: ruijyang@yahoo.com; Zhao, Nan; Liao, Anyan; Wang, Hao; Qu, Ang

2016-10-01

To investigate the dosimetric and radiobiological differences among volumetric modulated arc therapy (VMAT), high-dose rate (HDR) brachytherapy, and low-dose rate (LDR) permanent seeds implant for localized prostate cancer. A total of 10 patients with localized prostate cancer were selected for this study. VMAT, HDR brachytherapy, and LDR permanent seeds implant plans were created for each patient. For VMAT, planning target volume (PTV) was defined as the clinical target volume plus a margin of 5 mm. Rectum, bladder, urethra, and femoral heads were considered as organs at risk. A 78 Gy in 39 fractions were prescribed for PTV. For HDR and LDR plans, the dose prescription was D{sub 90} of 34 Gy in 8.5 Gy per fraction, and 145 Gy to clinical target volume, respectively. The dose and dose volume parameters were evaluated for target, organs at risk, and normal tissue. Physical dose was converted to dose based on 2-Gy fractions (equivalent dose in 2 Gy per fraction, EQD{sub 2}) for comparison of 3 techniques. HDR and LDR significantly reduced the dose to rectum and bladder compared with VMAT. The D{sub mean} (EQD{sub 2}) of rectum decreased 22.36 Gy in HDR and 17.01 Gy in LDR from 30.24 Gy in VMAT, respectively. The D{sub mean} (EQD{sub 2}) of bladder decreased 6.91 Gy in HDR and 2.53 Gy in LDR from 13.46 Gy in VMAT. For the femoral heads and normal tissue, the mean doses were also significantly reduced in both HDR and LDR compared with VMAT. For the urethra, the mean dose (EQD{sub 2}) was 80.26, 70.23, and 104.91 Gy in VMAT, HDR, and LDR brachytherapy, respectively. For localized prostate cancer, both HDR and LDR brachytherapy were clearly superior in the sparing of rectum, bladder, femoral heads, and normal tissue compared with VMAT. HDR provided the advantage in sparing of urethra compared with VMAT and LDR.

Dosimetric and radiobiological comparison of volumetric modulated arc therapy, high-dose rate brachytherapy, and low-dose rate permanent seeds implant for localized prostate cancer

International Nuclear Information System (INIS)

Yang, Ruijie; Zhao, Nan; Liao, Anyan; Wang, Hao; Qu, Ang

2016-01-01

To investigate the dosimetric and radiobiological differences among volumetric modulated arc therapy (VMAT), high-dose rate (HDR) brachytherapy, and low-dose rate (LDR) permanent seeds implant for localized prostate cancer. A total of 10 patients with localized prostate cancer were selected for this study. VMAT, HDR brachytherapy, and LDR permanent seeds implant plans were created for each patient. For VMAT, planning target volume (PTV) was defined as the clinical target volume plus a margin of 5 mm. Rectum, bladder, urethra, and femoral heads were considered as organs at risk. A 78 Gy in 39 fractions were prescribed for PTV. For HDR and LDR plans, the dose prescription was D 90 of 34 Gy in 8.5 Gy per fraction, and 145 Gy to clinical target volume, respectively. The dose and dose volume parameters were evaluated for target, organs at risk, and normal tissue. Physical dose was converted to dose based on 2-Gy fractions (equivalent dose in 2 Gy per fraction, EQD 2 ) for comparison of 3 techniques. HDR and LDR significantly reduced the dose to rectum and bladder compared with VMAT. The D mean (EQD 2 ) of rectum decreased 22.36 Gy in HDR and 17.01 Gy in LDR from 30.24 Gy in VMAT, respectively. The D mean (EQD 2 ) of bladder decreased 6.91 Gy in HDR and 2.53 Gy in LDR from 13.46 Gy in VMAT. For the femoral heads and normal tissue, the mean doses were also significantly reduced in both HDR and LDR compared with VMAT. For the urethra, the mean dose (EQD 2 ) was 80.26, 70.23, and 104.91 Gy in VMAT, HDR, and LDR brachytherapy, respectively. For localized prostate cancer, both HDR and LDR brachytherapy were clearly superior in the sparing of rectum, bladder, femoral heads, and normal tissue compared with VMAT. HDR provided the advantage in sparing of urethra compared with VMAT and LDR.

Phantom measurements and computed estimates of breast dose with radiotherapy for Hodgkin's lymphoma: dose reduction with the use of the involved field

International Nuclear Information System (INIS)

Wirth, A.; Kron, T.; Sorell, G.; Cramb, J.; Wittwer, H.; Sullivan, K.

2008-01-01

Full text: The risk of breast cancer following radiotherapy for Hodgkin's lymphoma appears to be dose related. In this study we compared breast dose in an anthropomorphic phantom for conventional 'mantle'; upper mediastinal/bilateral neck (minimantle) and unilateral neck fields, and evaluated the accuracy of computer planned dose estimates for out-of-field doses. For each field, computer-planned breast dose (CPD) estimates were compared with thermolu-minescence dosimetry measurements in five locations within 'breast tissue'. CPD were also compared with ion chamber measurements in a slab phantom. Measured dose and CPD were within 20% of each other up to approximately 10 cm from the field edge. Beyond 10 cm, the CPD underestimated dose by a factor of 2 or more. The minimantle reduced the breast dose by a factor of approximately 10 compared with the mantle treatment. Treating the neck field lowered the breast dose by a further 50% or more. Modern involved-field radiotherapy for lymphoma substantially reduces breast dose compared with mantle fields. Computer dosimetery underestimated dose at larger distances from the field. This needs to be considered if computer dosimetery is used to estimate breast dose and, by extrapolation, breast cancer risk.

Effective dose for patient in multimode panoramic radiography

International Nuclear Information System (INIS)

Yasaki, Shiro; Daibo, Motoji

1999-01-01

In recent years, multimode panoramic radiography has had various functions, such as the auto exposure function, auto focus function (auto function), TMJ radiography and tomogram radiography functions. The purpose of this study was to estimate the effective dose for patients in each mode of the new multimode panoramic radiography (J. MORITA MFG. CORP. Dental Panorama X-ray Apparatus: Veraview Scope X 600). The absorbed doses in important organs involved in the causation of stochastic effects were measured by a thermoluminescent dosimeter using RANDO phantom. The effective doses were calculated using modified tissue weighting factors recommended by the International Commission on Radiological Protection (ICRP) in 1999. The mean field size over skin in typical panoramic and tomographic examinations was about 3% and 0.4% of the total body surface area of 15000 cm 2 . Assuming that the incidence of skin cancer is proportional to the area of skin exposed to ionizing radiation, the tissue weighting factor of skin can be estimated to be about 0.0003 and 0.00004. The estimate in effective dose was lower (5.3 μSv) in the panoramic auto function mode (an average exposure condition of 69 kV 7 mA) than that (6.5-13.8 μSv) in the linear tomogram modes. Since the linear tomogram mode requires a scout view, such as standard panoramic radiography, the dose in the linear tomogram mode becomes higher than other modes. A percentage of gonad doses in effective doses was negligible. (author)

Evaluation of the dose uniformity for double-plane high dose rate interstitial breast implants with the use of dose reference points and dose non-uniformity ratio

International Nuclear Information System (INIS)

MAjor, T.; Polgar, C.; Somogyi, A.; Nemeth, G.

2000-01-01

This study investigated the influence of dwell time optimizations on dose uniformity characterized by dose values in dose points and dose non-uniformity ratio (DNR) and analyzed which implant parameters have influence on the DNR. Double-plane breast implants with catheters arranged in triangular pattern were used for the calculations. At a typical breast implant, dose values in dose reference points inside the target volume and volumes enclosed by given isodose surfaces were calculated and compared for non-optimized and optimized implants. The same 6-cm treatment length was used for the comparisons. Using different optimizations plots of dose non-uniformity ratio as a function of catheter separation, source step size, number of catheters, length of active sections were drawn and the minimum DNR values were determined. Optimization resulted in less variation in dose values over dose points through the whole volume and in the central plane only compared to the non-optimized case. At implant configurations consisting of seven catheters with 15-mm separation, 5-mm source step size and various active lengths adapted according to the type of optimization, the no optimization, geometrical (volume mode) and dose point (on dose points and geometry) optimization resulted in similar treatment volumes, but an increased high dose volume was observed due to the optimization. The dose non-uniformity ratio always had the minimum at average dose over dose normalization points, defined in the midpoints between the catheters through the implant volume. The minimum value of DNR depended on catheter separation, source step size, active length and number of catheters. The optimization had only a small influence on DNR. In addition to the reference points in the central plane only, dose points positioned in the whole implant volume can be used for evaluating the dose uniformity of interstitial implants. The dose optimization increases not only the dose uniformity within the implant but

A model for dose estimation in therapy of liver with intraarterial microspheres

International Nuclear Information System (INIS)

Zavgorodni, S.F.

1996-01-01

Therapy with intraarterial microspheres is a technique which involves incorporation of radioisotope-labelled microspheres into a capillary bed of tumour and normal tissue. Beta-emitters such as 90 Y and 166 Ho are used for this purpose. This technique provides tumour to normal tissue (TNT) dose ratios in the range of 2-10 and demonstrates significant clinical benefit, which could potentially be increased with more accurate dose predictions and delivery. However, dose calculations in this modality face the difficulties associated with nonuniform and inhomogeneous activity distribution. Most of the dose calculations used clinically do not account for the nonuniformity and assume uniform activity distribution. This paper is devoted to the development of a model which would allow more accurate prediction of dose distributions from microspheres. The model calculates dose assuming that microspheres are aggregated into randomly distributed clusters, and using precomputed dose kernels for the clusters. The dose kernel due to a microsphere cluster was found by numerical integration of a point source dose kernel over the volume of the cluster. It is shown that a random distribution of clusters produces an intercluster distance distribution which agrees well with the one measured by Pillai et al in liver. Dose volume histograms (DVHs) predicted by the model agree closely with the results of Roberson et al for normal tissue and tumour. Dose distributions for different concentrations and types of radioisotope, as well as for tumours of different radii, have been calculated to demonstrate the model's possible applications. (author)

Classification of radiation effects for dose limitation purposes: history, current situation and future prospects

Science.gov (United States)

Hamada, Nobuyuki; Fujimichi, Yuki

2014-01-01

Radiation exposure causes cancer and non-cancer health effects, each of which differs greatly in the shape of the dose–response curve, latency, persistency, recurrence, curability, fatality and impact on quality of life. In recent decades, for dose limitation purposes, the International Commission on Radiological Protection has divided such diverse effects into tissue reactions (formerly termed non-stochastic and deterministic effects) and stochastic effects. On the one hand, effective dose limits aim to reduce the risks of stochastic effects (cancer/heritable effects) and are based on the detriment-adjusted nominal risk coefficients, assuming a linear-non-threshold dose response and a dose and dose rate effectiveness factor of 2. On the other hand, equivalent dose limits aim to avoid tissue reactions (vision-impairing cataracts and cosmetically unacceptable non-cancer skin changes) and are based on a threshold dose. However, the boundary between these two categories is becoming vague. Thus, we review the changes in radiation effect classification, dose limitation concepts, and the definition of detriment and threshold. Then, the current situation is overviewed focusing on (i) stochastic effects with a threshold, (ii) tissue reactions without a threshold, (iii) target organs/tissues for circulatory disease, (iv) dose levels for limitation of cancer risks vs prevention of non-life-threatening tissue reactions vs prevention of life-threatening tissue reactions, (v) mortality or incidence of thyroid cancer, and (vi) the detriment for tissue reactions. For future discussion, one approach is suggested that classifies radiation effects according to whether effects are life threatening, and radiobiological research needs are also briefly discussed. PMID:24794798

A new definition for acoustic dose

International Nuclear Information System (INIS)

Duck, F A

2011-01-01

This paper discusses a recent proposal for definitions of acoustic dose and acoustic dose-rate. Acoustic dose is defined as the energy deposited by absorption of an acoustic wave per unit mass of the medium supporting the wave. Its time-derivative, acoustic dose-rate, Q m , in W kg -1 is central to the prediction of both rate of temperature rise and radiation force. These quantities have spatial and temporal dependency, depending on the local field parameters (acoustic pressure, particle velocity, intensity) and local material properties (absorption coefficient, α a , and mass density, ρ 0 ). Spatial and/or temporal averaging can be applied where appropriate. For plane-wave monochromatic conditions in a homogeneous medium, Q m =2α a I/ρ 0 , (I is the time-averaged intensity), a simple expression which may also incorporate frequency dependencies of energy deposition. Acoustic dose and acoustic does-rate are exact analogues for Specific Absorption and Specific Absorption Rate (SAR), quantities central to radiofrequency (RF) and microwave dosimetry. Acoustic dosimetry in the presence of tissue/gas interfaces remains a considerable challenge.

Analytical evaluation of dose measurement of critical accident at SILENE (Contract research)

CERN Document Server

Nakamura, T; Tonoike, K

2003-01-01

Institute for Radioprotection and Nuclear Safety (IRSN) and the OECD Nuclear Energy Agency (NEA) jointly organized SILENE Accident Dosimetry Intercomparison Exercise to intercompare the dose measurement systems of participating countries. Each participating country carried out dose measurements in the same irradiation field, and the measurement results were mutually compared. The participated in the exercise to measure the doses of gamma rays and neutron from SILENE by using thermoluminescence dosimeters (TLD's) and an alanine dosimeter. In this examination, the derived evaluation formulae for obtaining a tissue-absorbed dose from measured value (ambient dose equivalent) of TLD for neutron. We reported the tissue-absorbed dose computed using this evaluation formula to OECD/NEA. TLD's for neutron were irradiated in the TRACY facility to verify the evaluation formulae. The results of TLD's were compared with the calculations of MCNP and measurements with alanine dose meter. We found that the ratio of the dose b...

Dose modeling in ultraviolet phototherapy

International Nuclear Information System (INIS)

Grimes, David Robert; Robbins, Chris; O'Hare, Neil John

2010-01-01

Purpose: Ultraviolet phototherapy is widely used in the treatment of numerous skin conditions. This treatment is well established and largely beneficial to patients on both physical and psychological levels; however, overexposure to ultraviolet radiation (UVR) can have detrimental effects, such as erythemal responses and ocular damage in addition to the potentially carcinogenic nature of UVR. For these reasons, it is essential to control and quantify the radiation dose incident upon the patient to ensure that it is both biologically effective and has the minimal possible impact on the surrounding unaffected tissue. Methods: To date, there has been little work on dose modeling, and the output of artificial UVR sources is an area where research has been recommended. This work characterizes these sources by formalizing an approach from first principles and experimentally examining this model. Results: An implementation of a line source model is found to give impressive accuracy and quantifies the output radiation well. Conclusions: This method could potentially serve as a basis for a full computational dose model for quantifying patient dose.

Low-dose effects of hormones and endocrine disruptors.

Science.gov (United States)

Vandenberg, Laura N

2014-01-01

Endogenous hormones have effects on tissue morphology, cell physiology, and behaviors at low doses. In fact, hormones are known to circulate in the part-per-trillion and part-per-billion concentrations, making them highly effective and potent signaling molecules. Many endocrine-disrupting chemicals (EDCs) mimic hormones, yet there is strong debate over whether these chemicals can also have effects at low doses. In the 1990s, scientists proposed the "low-dose hypothesis," which postulated that EDCs affect humans and animals at environmentally relevant doses. This chapter focuses on data that support and refute the low-dose hypothesis. A case study examining the highly controversial example of bisphenol A and its low-dose effects on the prostate is examined through the lens of endocrinology. Finally, the chapter concludes with a discussion of factors that can influence the ability of a study to detect and interpret low-dose effects appropriately. © 2014 Elsevier Inc. All rights reserved.

A Method for Correcting IMRT Optimizer Heterogeneity Dose Calculations

International Nuclear Information System (INIS)

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

2010-01-01

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

The crooked shall be made straight: dose response relationships for carcinogenesis