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Antunes PCG, Siqueira PDTD, Shorto JMB, Yoriyaz H. Heterogeneous physical phantom for I-125 dose measurements and dose-to-medium determination. Brachytherapy 2024; 23:73-84. [PMID: 38016863 DOI: 10.1016/j.brachy.2023.08.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 07/30/2023] [Accepted: 08/30/2023] [Indexed: 11/30/2023]
Abstract
PURPOSE In this paper we present a further step in the implementation of a physical phantom designed to generate sets of "true" independent reference data as requested by TG-186, intending to address and mitigate the scarcity of experimental studies on brachytherapy (BT) validation in heterogeneous media. To achieve this, we incorporated well-known heterogeneous materials into the phantom in order to perform measurements of 125I dose distribution. The work aims to experimentally validate Monte Carlo (MC) calculations based on MBDCA and determine the conversion factors from LiF response to absorbed dose in different media, using cavity theory. METHODS AND MATERIALS The physical phantom was adjusted to incorporate tissue equivalent materials, such as: adipose tissue, bone, breast and lung with varying thickness. MC calculations were performed using MCNP6.2 code to calculate the absorbed dose in the LiF and the dose conversion factors (DCF). RESULTS The proposed heterogeneous phantom associated with the experimental procedure carried out in this work yielded accurate dose data that enabled the conversion of the LiF responses into absorbed dose to medium. The results showed a maximum uncertainty of 6.92 % (k = 1), which may be considered excellent for dosimetry with low-energy BT sources. CONCLUSIONS The presented heterogeneous phantom achieves the required precision in dose evaluations due to its easy reproducibility in the experimental setup. The obtained results support the dose conversion methodology for all evaluated media. The experimental validation of the DCF in different media holds great significance for clinical procedures, as it can be applied to other tissues, including water, which remains a widely utilized reference medium in clinical practice.
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Affiliation(s)
- Paula Cristina Guimarães Antunes
- Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP, Sao Paulo, Brazil; Institute of Physics, University of Sao Paulo, Sao Paulo, Brazil.
| | | | | | - Hélio Yoriyaz
- Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP, Sao Paulo, Brazil
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Antunes PCG, Siqueira PDTD, Shorto JBM, Yoriyaz H. A versatile physical phantom design and construction for I-125 dose measurements and dose-to-medium determination. Brachytherapy 2023; 22:80-92. [PMID: 36396567 DOI: 10.1016/j.brachy.2022.10.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 09/15/2022] [Accepted: 10/09/2022] [Indexed: 11/16/2022]
Abstract
PURPOSE In this paper we present a phantom designed to provide conditions to generate set of "true" independent reference data as requested by TG-186, and mitigating the scarcity of experimental studies on brachytherapy validation. It was used to perform accurate experimental measurements of dose of 125I brachytherapy seeds using LiF dosimeters, with the objective of experimentally validating Monte Carlo (MC) calculations with model-based dose calculation algorithm (MBDCA). In addition, this work intends to evaluate a methodology to convert the experimental values from LiF into dose in the medium. METHODS AND MATERIALS The proposed PMMA physical phantom features cavities to insert a LiF dosimeter and a 125I seed, adjusted in different configurations with variable thickness. Monte Carlo calculations performed with MCNP6.2 code were used to score the absorbed dose in the LiF and the dose conversion parameters. A sensitivity analysis was done to verify the source of possible uncertainties and quantify their impact on the results. RESULTS The proposed phantom and experimental procedure developed in this work provided precise dose data within 5.68% uncertainty (k = 1). The achieved precision made it possible to convert the LiF responses into absorbed dose to medium and to validate the dose conversion factor methodology. CONCLUSIONS The proposed phantom is simple both in design and as in its composition, thus achieving the demanded precision in dose evaluations due to its easy reproducibility of experimental setup. The results derived from the phantom measurements support the dose conversion methodology. The phantom and the experimental procedure developed here can be applied for other materials and radiation sources.
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Affiliation(s)
| | | | | | - Hélio Yoriyaz
- Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP, São Paulo, Brazil
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Monte-Carlo techniques for radiotherapy applications II: equipment and source modelling, dose calculations and radiobiology. JOURNAL OF RADIOTHERAPY IN PRACTICE 2023. [DOI: 10.1017/s1460396923000080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/05/2023]
Abstract
Abstract
Introduction:
This is the second of two papers giving an overview of the use of Monte-Carlo techniques for radiotherapy applications.
Methods:
The first paper gave an introduction and introduced some of the codes that are available to the user wishing to model the different aspects of radiotherapy treatment. It also aims to serve as a useful companion to a curated collection of papers on Monte-Carlo that have been published in this journal.
Results and Conclusions:
This paper focuses on the application of Monte-Carlo to specific problems in radiotherapy. These include radiotherapy and imaging beam production, brachytherapy, phantom and patient dosimetry, detector modelling and track structure calculations for micro-dosimetry, nano-dosimetry and radiobiology.
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Assam I, Vijande J, Ballester F, Pérez-Calatayud J, Poppe B, Siebert FA. Evaluation of dosimetric effects of metallic artifact reduction and tissue assignment on Monte Carlo dose calculations for 125 I prostate implants. Med Phys 2022; 49:6195-6208. [PMID: 35925023 DOI: 10.1002/mp.15865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 05/24/2022] [Accepted: 06/25/2022] [Indexed: 11/06/2022] Open
Abstract
PURPOSE Monte Carlo (MC) simulation studies, aimed at evaluating the magnitude of tissue heterogeneity in 125 I prostate permanent seed implant brachytherapy (BT), customarily use clinical post-implant CT images to generate a virtual representation of a realistic patient model (virtual patient model). Metallic artifact reduction (MAR) techniques and tissue assignment schemes (TAS) are implemented on the post-implant CT images to mollify metallic artifacts due to BT seeds and to assign tissue types to the voxels corresponding to the bright seed spots and streaking artifacts, respectively. The objective of this study is to assess the combined influence of MAR and TAS on MC absorbed dose calculations in post-implant CT-based phantoms. The virtual patient models used for 125 I prostate implant MC absorbed dose calculations in this study are derived from the CT images of an external radiotherapy prostate patient without BT seeds and prostatic calcifications, thus averting the need to implement MAR and TAS. METHODS The geometry of the IsoSeed I25.S17plus source is validated by comparing the MC calculated results of the TG-43 parameters for the line source approximation with the TG-43U1S2 consensus data. Four MC absorbed dose calculations are performed in two virtual patient models using the egs_brachy MC code: (1) TG-43-based Dw,w-TG 43 , (2) Dw,w-MBDC that accounts for interseed scattering and attenuation (ISA), (3) Dm,m that examines ISA and tissue heterogeneity by scoring absorbed dose in tissue, and (4) Dw,m that unlike Dm,m scores absorbed dose in water. The MC absorbed doses (1) and (2) are simulated in a TG-43 patient phantom derived by assigning the densities of every voxel to 1.00 g cm-3 (water), whereas MC absorbed doses (3) and (4) are scored in the TG-186 patient phantom generated by mapping the mass density of each voxel to tissue according to a CT calibration curve. The MC absorbed doses calculated in this study are compared with VariSeed v8.0 calculated absorbed doses. To evaluate the dosimetric effect of MAR and TAS, the MC absorbed doses of this work (independent of MAR and TAS) are compared to the MC absorbed doses of different 125 I source models from previous studies that were calculated with different MC codes using post-implant CT-based phantoms generated by implementing MAR and TAS on post-implant CT images. RESULTS The very good agreement of TG-43 parameters of this study and the published consensus data within 3% validates the geometry of the IsoSeed I25.S17plus source. For the clinical studies, the TG-43-based calculations show a D90 overestimation of more than 4% compared to the more realistic MC methods due to ISA and tissue composition. The results of this work generally show few discrepancies with the post-implant CT-based dosimetry studies with respect to the D90 absorbed dose metric parameter. These discrepancies are mainly Type B uncertainties due to the different 125 I source models and MC codes. CONCLUSIONS The implementation of MAR and TAS on post-implant CT images have no dosimetric effect on the 125 I prostate MC absorbed dose calculation in post-implant CT-based phantoms.
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Affiliation(s)
- Isong Assam
- UKSH, Campus Kiel, Clinic of Radiotherapy (Radiooncology), Kiel, Germany
| | - Javier Vijande
- Departamento de Física Atómica, Molecular y Nuclear, Universitat de Valencia (UV), Burjassot, Spain.,Unidad Mixta de Investigación en Radiofísica e Instrumentación Nuclear en Medicina (IRIMED), Instituto de Investigación Sanitaria La Fe (IIS-La Fe), Universitat de Valencia (UV), Valencia, Spain.,Instituto de Física Corpuscular, IFIC (UV-CSIC), Burjassot, Spain
| | - Facundo Ballester
- Departamento de Física Atómica, Molecular y Nuclear, Universitat de Valencia (UV), Burjassot, Spain.,Unidad Mixta de Investigación en Radiofísica e Instrumentación Nuclear en Medicina (IRIMED), Instituto de Investigación Sanitaria La Fe (IIS-La Fe), Universitat de Valencia (UV), Valencia, Spain
| | - José Pérez-Calatayud
- Radiotherapy Department, La Fe Hospital, Valencia, Spain.,Radiotherapy Department, Clinica Benidorm, Alicante, Spain
| | - Björn Poppe
- Center for Radiotherapy and Radiation Oncology - University Center for Medical Radiation Physics, Pius-Hospital, Medical Campus of Carl-von-Ossietzky University of Oldenburg, Oldenburg, Germany
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ARAS S. The Investigation of Tissue Composition Effects on Dose Distributions Using Monte Carlo Method in Permanent Prostate Brachytherapy. CLINICAL AND EXPERIMENTAL HEALTH SCIENCES 2021. [DOI: 10.33808/clinexphealthsci.884245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Vaniqui A, Walters BR, Fonseca GP, Verhaegen F. Dose to water versus dose to medium from cavity theory applied to small animal irradiation with kilovolt x-rays. Phys Med Biol 2019; 64:165001. [PMID: 31252419 DOI: 10.1088/1361-6560/ab2db1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Dose reporting is a matter of concern in the preclinical field as the different dose descriptors dose-to-water-in-medium [Formula: see text] and dose-to-medium-in-medium [Formula: see text] coexist. For kV photons differences between both quantities are expected to be amplified due to photon energy absorption coefficients differences for different media, and could represent a limiting factor for accurate translation of pre-clinical research into clinical trials. The main goal of this study was to analyse the relationship between [Formula: see text] and [Formula: see text] for kV irradiation of small animals, using different flavours of the intermediate cavity theory (ICT). Irradiations of mathematical phantoms and a mouse CT scan, both with different voxel sizes and materials, were investigated. A modified version of the Monte Carlo code DOSXYZnrc was used to derive [Formula: see text] and convert to [Formula: see text] using ICT. Local photon spectra were generated in different regions of the mouse. Depending on energy and cavity size, which we equate to the voxel size, [Formula: see text] ranged from 0.68 to 4.37 times [Formula: see text]. Higher kV energy combined with very small cavity sizes yielded decreased [Formula: see text] in comparison to [Formula: see text]; this behaviour was reversed for larger cavities combined with lower kV energies. Hence, the impact of the cavity dimensions on estimated [Formula: see text] is significant on pre-clinical kV beams. [Formula: see text] and [Formula: see text] in the ex vivo male mouse were found to differ by -29% to 286%. Caution is advised when using the ICT due to a lack of consensus on weighting factor (d-parameter) deriving methods; for the same irradiation conditions, different d-values affected [Formula: see text] up to 20%. Pre-clinically, such divergence between dose descriptors could enable biological damage. The abiding debate over which quantity to favour is foreseen to linger while it is unclear which quantity correlates better with the biological effects of ionizing irradiation: preclinical radiotherapy might represent an ideal platform for measurement-based studies to settle this fundamental question. Finally, dose distribution comparisons require caution and should use the same reporting quantity.
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Affiliation(s)
- Ana Vaniqui
- Department of Radiation Oncology (MAASTRO), GROW-School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
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Evaluation of BrachyDose Monte Carlo code for HDR brachytherapy: dose comparison against Acuros®BV and TG-43 algorithms. JOURNAL OF RADIOTHERAPY IN PRACTICE 2019. [DOI: 10.1017/s1460396919000220] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractAim:The aim of this study is to investigate the accuracy of dose distributions calculated by the BrachyDose Monte Carlo (MC) code in heterogeneous media for high-dose-rate (HDR) brachytherapy and to evaluate its usability in the clinical brachytherapy treatment planning systems.Materials and methods:For dose comparisons, three different dose calculation algorithms were used in this study. Namely, BrachyDose MC code, Eclipse TG-43 dose calculation tool and Acuros®BV model-based dose calculation algorithm (MBDCA). Dose distributions were obtained using any of the above codes in various scenarios including ‘homogenous water medium scenario’, an ‘extreme case heterogeneous media scenario’ and clinically important ‘a patient with a cervical cancer scenario’. In the ‘extreme case, heterogeneous media scenario’, geometry is a rare combination of unusual high-density and low-density materials and it is chosen to provide a test environment for the propagation of photons in the interface of two materials with different absorption and scattering properties. GammaMed 192Ir Model 12i Source is used as the HDR brachytherapy source in this study. Dose calculations were performed for the cases where there is either a single source or five sources planted into the phantom geometry in all homogenous water phantom and extreme case heterogeneous media scenarios. For the scenario a patient with a cervical cancer, dose calculations were performed in a voxelized rectilinear phantom, which is constructed from a series of computed tomography (CT) slices of a patient, which are obtained from a CT device.Results:In homogeneous water phantom scenario, we observed no statistically significant dose differences among the dose distributions calculated by any of the three algorithms at almost every point in the geometry. In the extreme case heterogeneous media scenario, the dose calculation engines Acuros®BV and BrachyDose are agreed well within statistics in every region of the geometry and even in the points close to the interfaces of low-density and high-density materials. On the other hand, the dose values calculated by these two codes are significantly different from those calculated by the TG-43 algorithm. In the ‘a patient with a cervical cancer scenario’, the calculated D2cc dose difference between Acuros®BV and BrachyDose codes is within 2% in the rectum and 11% for the bladder and sigmoid. There was no meaningful difference in the mean dose values between MBDCAs in the bone structures.Conclusions:In this study, the accurate dose calculation capabilities of the BrachyDose program in HDR brachytherapy were investigated on various scenarios and, as a MC dose calculation tool, its effectiveness in HDR brachytherapy was demonstrated by comparative dose analysis.
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Robert C, Dumas I, Martinetti F, Chargari C, Haie-Meder C, Lefkopoulos D. Nouveaux algorithmes de calcul en curiethérapie pour les traitements par iridium 192. Cancer Radiother 2018; 22:319-325. [DOI: 10.1016/j.canrad.2017.11.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 11/15/2017] [Indexed: 10/16/2022]
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Remy C, Lalonde A, Béliveau-Nadeau D, Carrier JF, Bouchard H. Dosimetric impact of dual-energy CT tissue segmentation for low-energy prostate brachytherapy: a Monte Carlo study. Phys Med Biol 2018; 63:025013. [PMID: 29260727 DOI: 10.1088/1361-6560/aaa30c] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of this study is to evaluate the impact of a novel tissue characterization method using dual-energy over single-energy computed tomography (DECT and SECT) on Monte Carlo (MC) dose calculations for low-dose rate (LDR) prostate brachytherapy performed in a patient like geometry. A virtual patient geometry is created using contours from a real patient pelvis CT scan, where known elemental compositions and varying densities are overwritten in each voxel. A second phantom is made with additional calcifications. Both phantoms are the ground truth with which all results are compared. Simulated CT images are generated from them using attenuation coefficients taken from the XCOM database with a 100 kVp spectrum for SECT and 80 and 140Sn kVp for DECT. Tissue segmentation for Monte Carlo dose calculation is made using a stoichiometric calibration method for the simulated SECT images. For the DECT images, Bayesian eigentissue decomposition is used. A LDR prostate brachytherapy plan is defined with 125I sources and then calculated using the EGSnrc user-code Brachydose for each case. Dose distributions and dose-volume histograms (DVH) are compared to ground truth to assess the accuracy of tissue segmentation. For noiseless images, DECT-based tissue segmentation outperforms the SECT procedure with a root mean square error (RMS) on relative errors on dose distributions respectively of 2.39% versus 7.77%, and provides DVHs closest to the reference DVHs for all tissues. For a medium level of CT noise, Bayesian eigentissue decomposition still performs better on the overall dose calculation as the RMS error is found to be of 7.83% compared to 9.15% for SECT. Both methods give a similar DVH for the prostate while the DECT segmentation remains more accurate for organs at risk and in presence of calcifications, with less than 5% of RMS errors within the calcifications versus up to 154% for SECT. In a patient-like geometry, DECT-based tissue segmentation provides dose distributions with the highest accuracy and the least bias compared to SECT. When imaging noise is considered, benefits of DECT are noticeable if important calcifications are found within the prostate.
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Affiliation(s)
- Charlotte Remy
- Département de Physique, Université de Nantes, 2 Chemin de la Houssinière, 44300 Nantes, France. Département de Physique, Université de Montréal, Pavillon Roger-Gaudry, 2900 Boulevard Édouard-Montpetit, Montréal, Québec H3T 1J4, Canada. Author to whom any correspondence should be addressed
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Wang J, Tanderup K, Cunha A, Damato AL, Cohen GN, Kudchadker RJ, Mourtada F. Magnetic resonance imaging basics for the prostate brachytherapist. Brachytherapy 2017; 16:715-727. [PMID: 28396178 DOI: 10.1016/j.brachy.2017.03.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Revised: 02/23/2017] [Accepted: 03/04/2017] [Indexed: 11/27/2022]
Abstract
Magnetic resonance imaging (MRI) is increasingly being used in radiation therapy, and integration of MRI into brachytherapy in particular is becoming more common. We present here a systematic review of the basic physics and technical aspects of incorporating MRI into prostate brachytherapy. Terminology and MRI system components are reviewed along with typical work flows in prostate high-dose-rate and low-dose-rate brachytherapy. In general, the brachytherapy workflow consists of five key components: diagnosis, implantation, treatment planning (scan + plan), implant verification, and delivery. MRI integration is discussed for diagnosis; treatment planning; and MRI-guided brachytherapy implants, in which MRI is used to guide the physical insertion of the brachytherapy applicator or needles. Considerations and challenges for establishing an MRI brachytherapy program are also discussed.
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Affiliation(s)
- Jihong Wang
- Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX.
| | - Kari Tanderup
- Department of Oncology, Aarhus University Hospital, Aarhus, Denmark
| | - Adam Cunha
- Department of Radiation Oncology, University of California-San Francisco, CA
| | - Antonio L Damato
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY
| | - Gil'ad N Cohen
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY
| | - Rajat J Kudchadker
- Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX
| | - Firas Mourtada
- Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX; Department of Radiation Oncology, Helen F. Graham Cancer Center, Newark, DE; Department of Radiation Oncology, Bodine Cancer Center, Thomas Jefferson University, Philadelphia, PA.
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Large-scale Retrospective Monte Carlo Dosimetric Study for Permanent Implant Prostate Brachytherapy. Int J Radiat Oncol Biol Phys 2017; 97:606-615. [DOI: 10.1016/j.ijrobp.2016.11.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 10/22/2016] [Accepted: 11/16/2016] [Indexed: 01/24/2023]
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Rivard MJ. A directional 103Pd brachytherapy device: Dosimetric characterization and practical aspects for clinical use. Brachytherapy 2016; 16:421-432. [PMID: 28039011 DOI: 10.1016/j.brachy.2016.11.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 11/10/2016] [Accepted: 11/29/2016] [Indexed: 02/08/2023]
Abstract
PURPOSE A brachytherapy (BT) device has been developed with shielding to provide directional BT for preferentially irradiating malignancies while sparing healthy tissues. The CivaSheet is a flexible low-dose-rate BT device containing CivaDots with 103Pd shielded by a thin Au disk. This is the first report of a clinical dosimetric characterization of the CivaSheet device. METHODS AND MATERIALS Radiation dose distributions near a CivaDot were estimated using the MCNP6 radiation transport code. CivaSheet arrays were also modeled to evaluate the dose superposition principle for treatment planning. The resultant data were commissioned in a treatment planning system (TPS) (VariSeed 9.0), and the accuracy of the dose superposition principle was evaluated for summing individual elements comprising a planar CivaSheet. RESULTS The dose-rate constant (0.579 cGy/h/U) was lower than for 103Pd seeds due to Au L-shell x-rays increasing the air-kerma strength. Radial dose function values at 0.1, 0.5, 2, 5, and 10 cm were 1.884, 1.344, 0.558, 0.088, and 0.0046, respectively. The two-dimensional anisotropy function exhibited dramatic reduction between the forward (0°) and rearward (180°) directions by a factor of 276 at r = 0.1 cm, 24 at r = 1 cm, and 5.3 at r = 10 cm. This effect diminished due to increasingly scattered radiation. The largest gradient in the two-dimensional anisotropy function was in contact with the device at 92° due to the Au disk shielding. TPS commissioning and dose superposition accuracies were typically within 2%. CONCLUSIONS Simulations of the CivaDot yielded comprehensive dosimetry parameters that were entered into a TPS and deemed acceptable for clinical use. Dosimetry measurements of the CivaSheet are also of interest to the BT community.
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Affiliation(s)
- Mark J Rivard
- Department of Radiation Oncology, Tufts University School of Medicine, Boston, MA.
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Giménez-Alventosa V, Antunes PCG, Vijande J, Ballester F, Pérez-Calatayud J, Andreo P. Collision-kerma conversion between dose-to-tissue and dose-to-water by photon energy-fluence corrections in low-energy brachytherapy. Phys Med Biol 2016; 62:146-164. [PMID: 27991455 DOI: 10.1088/1361-6560/aa4f6a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The AAPM TG-43 brachytherapy dosimetry formalism, introduced in 1995, has become a standard for brachytherapy dosimetry worldwide; it implicitly assumes that charged-particle equilibrium (CPE) exists for the determination of absorbed dose to water at different locations, except in the vicinity of the source capsule. Subsequent dosimetry developments, based on Monte Carlo calculations or analytical solutions of transport equations, do not rely on the CPE assumption and determine directly the dose to different tissues. At the time of relating dose to tissue and dose to water, or vice versa, it is usually assumed that the photon fluence in water and in tissues are practically identical, so that the absorbed dose in the two media can be related by their ratio of mass energy-absorption coefficients. In this work, an efficient way to correlate absorbed dose to water and absorbed dose to tissue in brachytherapy calculations at clinically relevant distances for low-energy photon emitting seeds is proposed. A correction is introduced that is based on the ratio of the water-to-tissue photon energy-fluences. State-of-the art Monte Carlo calculations are used to score photon fluence differential in energy in water and in various human tissues (muscle, adipose and bone), which in all cases include a realistic modelling of low-energy brachytherapy sources in order to benchmark the formalism proposed. The energy-fluence based corrections given in this work are able to correlate absorbed dose to tissue and absorbed dose to water with an accuracy better than 0.5% in the most critical cases (e.g. bone tissue).
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Affiliation(s)
- Vicent Giménez-Alventosa
- Department of Atomic, Molecular, and Nuclear Physics, University of Valencia, E46100 Burjassot, Spain
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Branco ISL, Antunes PCG, Fonseca GP, Yoriyaz H. Monte Carlo studies on water and LiF cavity properties for dose-reporting quantities when using x-ray and brachytherapy sources. Phys Med Biol 2016; 61:8890-8907. [DOI: 10.1088/1361-6560/61/24/8890] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Braad PEN, Andersen T, Hansen SB, Høilund-Carlsen PF. Strategies for CT tissue segmentation for Monte Carlo calculations in nuclear medicine dosimetry. Med Phys 2016; 43:6507. [DOI: 10.1118/1.4967267] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Lalonde A, Bouchard H. A general method to derive tissue parameters for Monte Carlo dose calculation with multi-energy CT. Phys Med Biol 2016; 61:8044-8069. [DOI: 10.1088/0031-9155/61/22/8044] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Kron T, Lehmann J, Greer PB. Dosimetry of ionising radiation in modern radiation oncology. Phys Med Biol 2016; 61:R167-205. [DOI: 10.1088/0031-9155/61/14/r167] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Miksys N, Cygler JE, Caudrelier JM, Thomson RM. Patient-specific Monte Carlo dose calculations for (103)Pd breast brachytherapy. Phys Med Biol 2016; 61:2705-29. [PMID: 26976478 DOI: 10.1088/0031-9155/61/7/2705] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This work retrospectively investigates patient-specific Monte Carlo (MC) dose calculations for (103)Pd permanent implant breast brachytherapy, exploring various necessary assumptions for deriving virtual patient models: post-implant CT image metallic artifact reduction (MAR), tissue assignment schemes (TAS), and elemental tissue compositions. Three MAR methods (thresholding, 3D median filter, virtual sinogram) are applied to CT images; resulting images are compared to each other and to uncorrected images. Virtual patient models are then derived by application of different TAS ranging from TG-186 basic recommendations (mixed adipose and gland tissue at uniform literature-derived density) to detailed schemes (segmented adipose and gland with CT-derived densities). For detailed schemes, alternate mass density segmentation thresholds between adipose and gland are considered. Several literature-derived elemental compositions for adipose, gland and skin are compared. MC models derived from uncorrected CT images can yield large errors in dose calculations especially when used with detailed TAS. Differences in MAR method result in large differences in local doses when variations in CT number cause differences in tissue assignment. Between different MAR models (same TAS), PTV [Formula: see text] and skin [Formula: see text] each vary by up to 6%. Basic TAS (mixed adipose/gland tissue) generally yield higher dose metrics than detailed segmented schemes: PTV [Formula: see text] and skin [Formula: see text] are higher by up to 13% and 9% respectively. Employing alternate adipose, gland and skin elemental compositions can cause variations in PTV [Formula: see text] of up to 11% and skin [Formula: see text] of up to 30%. Overall, AAPM TG-43 overestimates dose to the PTV ([Formula: see text] on average 10% and up to 27%) and underestimates dose to the skin ([Formula: see text] on average 29% and up to 48%) compared to the various MC models derived using the post-MAR CT images studied herein. The considerable differences between TG-43 and MC models underline the importance of patient-specific MC dose calculations for permanent implant breast brachytherapy. Further, the sensitivity of these MC dose calculations due to necessary assumptions illustrates the importance of developing a consensus modelling approach.
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Affiliation(s)
- N Miksys
- Department of Physics, Carleton Laboratory for Radiotherapy Physics, Carleton University, Ottawa, ON, Canada
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Hueso-González F, Vijande J, Ballester F, Perez-Calatayud J, Siebert FA. A simple analytical method for heterogeneity corrections in low dose rate prostate brachytherapy. Phys Med Biol 2015; 60:5455-69. [PMID: 26118956 DOI: 10.1088/0031-9155/60/14/5455] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In low energy brachytherapy, the presence of tissue heterogeneities contributes significantly to the discrepancies observed between treatment plan and delivered dose. In this work, we present a simplified analytical dose calculation algorithm for heterogeneous tissue. We compare it with Monte Carlo computations and assess its suitability for integration in clinical treatment planning systems. The algorithm, named as RayStretch, is based on the classic equivalent path length method and TG-43 reference data. Analytical and Monte Carlo dose calculations using Penelope2008 are compared for a benchmark case: a prostate patient with calcifications. The results show a remarkable agreement between simulation and algorithm, the latter having, in addition, a high calculation speed. The proposed analytical model is compatible with clinical real-time treatment planning systems based on TG-43 consensus datasets for improving dose calculation and treatment quality in heterogeneous tissue. Moreover, the algorithm is applicable for any type of heterogeneities.
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Affiliation(s)
- Fernando Hueso-González
- Department of Atomic, Molecular and Nuclear Physics, University of Valencia, Dr. Moliner 50, E-46100 Burjassot, Spain
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Fonseca GP, Tedgren ÅC, Reniers B, Nilsson J, Persson M, Yoriyaz H, Verhaegen F. Dose specification for192Ir high dose rate brachytherapy in terms of dose-to-water-in-medium and dose-to-medium-in-medium. Phys Med Biol 2015; 60:4565-79. [DOI: 10.1088/0031-9155/60/11/4565] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Hiatt JR, Davis SD, Rivard MJ. A revised dosimetric characterization of the model S700 electronic brachytherapy source containing an anode-centering plastic insert and other components not included in the 2006 model. Med Phys 2015; 42:2764-76. [DOI: 10.1118/1.4919280] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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Collins Fekete CA, Plamondon M, Martin AG, Vigneault É, Verhaegen F, Beaulieu L. Calcifications in low-dose rate prostate seed brachytherapy treatment: post-planning dosimetry and predictive factors. Radiother Oncol 2015; 114:339-44. [PMID: 25702862 DOI: 10.1016/j.radonc.2015.01.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 01/21/2015] [Accepted: 01/28/2015] [Indexed: 10/24/2022]
Abstract
BACKGROUND AND PURPOSE The brachytherapy dose algorithm of the American Association of Physicists in Medicine Task Group (TG) Report 43 overrides all tissue materials with water. In reality, dose discrepancies will occur around tissue calcifications. This study investigates these perturbations in low dose rate prostate brachytherapy dosimetry. MATERIALS AND METHODS 43 cancer patients with prostatic calcifications are identified. Geant4 Monte Carlo (MC) simulations are made with materials assigned based on TG186 recommendations. Five dose calculation scenarios are presented: MC in water (MCW), MCW with calcifications, (MCCA), MCCA with seeds (MCCASEED) and full tissue definition and seeds with dose to medium in medium (FMC) and dose to water in medium (FMC-Dw,m). RESULTS The mean FMC prostate D90 (V100) difference relative to TG43 is -6.4% (range [-1.8, -14.1]) (-2.6% [-0.3, -6.7]). For MCCA we obtained -3.9% [-1.0, -8.7] (-1.5% [-0.2, -4.1]). The mean urethra D10 difference is -4.5% [-1.3, -9.9] for FMC, -2.4% [-0.7, -5.1] with MCCA. FMC-Dw,m D90 has a -0.45% smaller dose difference than FMC on average. The calcification/prostate volume ratio is a good predictor of dose perturbation (R(2)=0.75). CONCLUSION Based on these results, calcifications alter the dose coverage and may have severe dose perturbation that requires recalculation.
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Affiliation(s)
- Charles-Antoine Collins Fekete
- Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec, Canada; Département de radio-oncologie et CRCHU de Québec, CHU de Québec, Québec, Canada.
| | - Mathieu Plamondon
- Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec, Canada.
| | - André-Guy Martin
- Département de radio-oncologie et CRCHU de Québec, CHU de Québec, Québec, Canada.
| | - Éric Vigneault
- Département de radio-oncologie et CRCHU de Québec, CHU de Québec, Québec, Canada.
| | - Frank Verhaegen
- Department of Radiation Oncology (MAASTRO), GROW - School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands; Medical Physics Unit, McGill University Health Centre and Department of Oncology, McGill University, Montréal, Québec, Canada.
| | - Luc Beaulieu
- Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec, Canada; Département de radio-oncologie et CRCHU de Québec, CHU de Québec, Québec, Canada.
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Verhaegen F, van Hoof S, Granton PV, Trani D. A review of treatment planning for precision image-guided photon beam pre-clinical animal radiation studies. Z Med Phys 2014; 24:323-34. [DOI: 10.1016/j.zemedi.2014.02.004] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Revised: 02/14/2014] [Accepted: 02/17/2014] [Indexed: 12/31/2022]
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Investigation of interseed attenuation and tissue composition effects in 125I seed implant prostate brachytherapy. Brachytherapy 2014; 13:603-10. [DOI: 10.1016/j.brachy.2014.04.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 03/03/2014] [Accepted: 04/11/2014] [Indexed: 11/24/2022]
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Collins Fekete CA, Plamondon M, Martin AG, Vigneault É, Verhaegen F, Beaulieu L. Quantifying the effect of seed orientation in postplanning dosimetry of low-dose-rate prostate brachytherapy. Med Phys 2014; 41:101704. [DOI: 10.1118/1.4895012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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Chiu-Tsao ST, Napoli JJ, Davis SD, Hanley J, Rivard MJ. Dosimetry for 131Cs and 125I seeds in solid water phantom using radiochromic EBT film. Appl Radiat Isot 2014; 92:102-14. [PMID: 25038559 DOI: 10.1016/j.apradiso.2014.06.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 06/23/2014] [Indexed: 12/31/2022]
Abstract
PURPOSE To measure the 2D dose distributions with submillimeter resolution for (131)Cs (model CS-1 Rev2) and (125)I (model 6711) seeds in a Solid Water phantom using radiochromic EBT film for radial distances from 0.06cm to 5cm. To determine the TG-43 dosimetry parameters in water by applying Solid Water to liquid water correction factors generated from Monte Carlo simulations. METHODS Each film piece was positioned horizontally above and in close contact with a (131)Cs or (125)I seed oriented horizontally in a machined groove at the center of a Solid Water phantom, one film at a time. A total of 74 and 50 films were exposed to the (131)Cs and (125)I seeds, respectively. Different film sizes were utilized to gather data in different distance ranges. The exposure time varied according to the seed air-kerma strength and film size in order to deliver doses in the range covered by the film calibration curve. Small films were exposed for shorter times to assess the near field, while larger films were exposed for longer times in order to assess the far field. For calibration, films were exposed to either 40kV (M40) or 50kV (M50) x-rays in air at 100.0cm SSD with doses ranging from 0.2Gy to 40Gy. All experimental, calibration and background films were scanned at a 0.02cmpixel resolution using a CCD camera-based microdensitometer with a green light source. Data acquisition and scanner uniformity correction were achieved with Microd3 software. Data analysis was performed using ImageJ, FV, IDL and Excel software packages. 2D dose distributions were based on the calibration curve established for 50kV x-rays. The Solid Water to liquid water medium correction was calculated using the MCNP5 Monte Carlo code. Subsequently, the TG-43 dosimetry parameters in liquid water medium were determined. RESULTS Values for the dose-rate constants using EBT film were 1.069±0.036 and 0.923±0.031cGyU(-1)h(-1) for (131)Cs and (125)I seed, respectively. The corresponding values determined using the Monte Carlo method were 1.053±0.014 and 0.924±0.016cGyU(-1)h(-1) for (131)Cs and (125)I seed, respectively. The radial dose functions obtained with EBT film measurements and Monte Carlo simulations were plotted for radial distances up to 5cm, and agreed within the uncertainty of the two methods. The 2D anisotropy functions obtained with both methods also agreed within their uncertainties. CONCLUSION EBT film dosimetry in a Solid Water phantom is a viable method for measuring (131)Cs (model CS-1 Rev2) and (125)I (model 6711) brachytherapy seed dose distributions with submillimeter resolution. With the Solid Water to liquid water correction factors generated from Monte Carlo simulations, the measured TG-43 dosimetry parameters in liquid water for these two seed models were found to be in good agreement with those in the literature.
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Affiliation(s)
| | - John J Napoli
- John Theurer Cancer Center at Hackensack University Medical Center, Hackensack, NJ 07601, USA
| | - Stephen D Davis
- Medical Physics, McGill University Health Centre, Montreal, QC, Canada H3G 1A4
| | - Joseph Hanley
- Princeton Radiation Oncology Center, Monroe, NJ 08831, USA
| | - Mark J Rivard
- Department of Radiation Oncology, Tufts University School of Medicine, Boston, MA 02111, USA
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Dose enhancement by various nanoparticles in prostate brachytherapy. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2013; 36:431-40. [DOI: 10.1007/s13246-013-0231-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 11/18/2013] [Indexed: 10/26/2022]
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Tedgren ÅC, Carlsson GA. Specification of absorbed dose to water using model-based dose calculation algorithms for treatment planning in brachytherapy. Phys Med Biol 2013; 58:2561-79. [PMID: 23528349 DOI: 10.1088/0031-9155/58/8/2561] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Model-based dose calculation algorithms (MBDCAs), recently introduced in treatment planning systems (TPS) for brachytherapy, calculate tissue absorbed doses. In the TPS framework, doses have hereto been reported as dose to water and water may still be preferred as a dose specification medium. Dose to tissue medium Dmed then needs to be converted into dose to water in tissue Dw,med. Methods to calculate absorbed dose to differently sized water compartments/cavities inside tissue, infinitesimal (used for definition of absorbed dose), small, large or intermediate, are reviewed. Burlin theory is applied to estimate photon energies at which cavity sizes in the range 1 nm-10 mm can be considered small or large. Photon and electron energy spectra are calculated at 1 cm distance from the central axis in cylindrical phantoms of bone, muscle and adipose tissue for 20, 50, 300 keV photons and photons from (125)I, (169)Yb and (192)Ir sources; ratios of mass-collision-stopping powers and mass energy absorption coefficients are calculated as applicable to convert Dmed into Dw,med for small and large cavities. Results show that 1-10 nm sized cavities are small at all investigated photon energies; 100 µm cavities are large only at photon energies <20 keV. A choice of an appropriate conversion coefficient Dw, med/Dmed is discussed in terms of the cavity size in relation to the size of important cellular targets. Free radicals from DNA bound water of nanometre dimensions contribute to DNA damage and cell killing and may be the most important water compartment in cells implying use of ratios of mass-collision-stopping powers for converting Dmed into Dw,med.
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Affiliation(s)
- Åsa Carlsson Tedgren
- Radiation Physics, Department of Medical and Health Sciences, Linköping University and Center of Medical Image Science and Visualization, SE-581 85 Linköping, Sweden.
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Beaulieu L, Carlsson Tedgren A, Carrier JF, Davis SD, Mourtada F, Rivard MJ, Thomson RM, Verhaegen F, Wareing TA, Williamson JF. Report of the Task Group 186 on model-based dose calculation methods in brachytherapy beyond the TG-43 formalism: Current status and recommendations for clinical implementation. Med Phys 2012; 39:6208-36. [PMID: 23039658 DOI: 10.1118/1.4747264] [Citation(s) in RCA: 345] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Luc Beaulieu
- Département de Radio-Oncologie, Centre hospitalier universitaire de Québec, Québec, Québec G1R 2J6, Canada.
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Reniers B, Landry G, Eichner R, Hallil A, Verhaegen F. In vivo dosimetry for gynaecological brachytherapy using a novel position sensitive radiation detector: feasibility study. Med Phys 2012; 39:1925-35. [PMID: 22482614 DOI: 10.1118/1.3693049] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE In gynecological radiotherapy with high dose rate (HDR)(192)Ir brachytherapy, the treatment complexity has increased due to improved optimization techniques and dose constraints. As a consequence, it has become more important to verify the dose delivery to the target and also to the organs at risk (e.g., the bladder). In vivo dosimetry, where dosimeters are placed in or on the patient, is one way of verifying the dose but until recently this was hampered by motion of the radiation detectors with respect to the source. The authors present a novel dosimetry method using a position sensitive radiation detector. METHODS The prototype RADPOS system (Best Medical Canada) consists of a metal oxide field effect transistor (MOSFET) dosimeter coupled to a position-sensor, which deduces its 3D position in a magnetic field. To assess the feasibility of in vivo dosimetry based on the RADPOS system, different characteristics of the detector need to be investigated. Using a PMMA phantom, the positioning accuracy of the RADPOS system was quantified by comparing position readouts with the known position of the detector along the x and y-axes. RADPOS dose measurements were performed at various distances from a Nucletron(192)Ir source in a PMMA phantom to evaluate the energy dependence of the MOSFET. A sensitivity analysis was performed by calculating the dose after varying (1) the position of the RADPOS detector to simulate organ motion and (2) the position of the first dwell position to simulate errors in delivery. The authors also performed an uncertainty analysis to determine the action level (AL) that should be used during in vivo dosimetry. RESULTS Positioning accuracy is found to be within 1 mm in the 1-10 cm range from the origin along the x-axis (away from the transmitter), meeting the requirements for in vivo dosimetry. Similar results are obtained for the other axes. The ALs are chosen to take into account the total uncertainty on the measurements. As a consequence for in vivo dosimetry, it is determined that the RADPOS sensor, if placed, for example, in the bladder Foley balloon, would detect a 2 mm motion of the bladder, at a 5% chance of a false positive, with an AL limit of 9% of the dose delivered. The authors found that source position errors, caused by, e.g., a wrong first dwell position, are more difficult to detect; indeed, with our single RADPOS detector, positioned in the bladder, dwell position errors below 5 mm and resulting in a dose error within 10%, could be detected in the tandem but not in the colpostats. A possible solution to improve error detection is to use multiple MOSFETs to obtain multiple dose values. CONCLUSIONS In this study, the authors proposed a dosimetry procedure, based on the novel RADPOS system, to accurately determine the position of the radiation dosimeter with respect to the applicator. The authors found that it is possible to monitor the delivered dose in a point and compare it to the predetermined dose. This allows in principle the detection of problems such as bladder motion/filling or source mispositioning. Further clinical investigation is warranted.
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Affiliation(s)
- B Reniers
- Department of Radiation Oncology, Maastricht University Medical Center, Maastricht, The Netherlands.
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White SA, Landry G, van Gils F, Verhaegen F, Reniers B. Influence of trace elements in human tissue in low-energy photon brachytherapy dosimetry. Phys Med Biol 2012; 57:3585-96. [DOI: 10.1088/0031-9155/57/11/3585] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Safigholi H, Faghihi R, Jashni SK, Meigooni AS. Characteristics of miniature electronic brachytherapy x-ray sources based on TG-43U1 formalism using Monte Carlo simulation techniques. Med Phys 2012; 39:1971-9. [DOI: 10.1118/1.3693046] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Afsharpour H, Reniers B, Landry G, Pignol JP, Keller BM, Verhaegen F, Beaulieu L. Consequences of dose heterogeneity on the biological efficiency of ¹⁰³Pd permanent breast seed implants. Phys Med Biol 2012; 57:809-23. [PMID: 22252246 DOI: 10.1088/0031-9155/57/3/809] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Brachytherapy is associated with highly heterogeneous spatial dose distributions. This heterogeneity is usually ignored when estimating the biological effective dose (BED). In addition, the heterogeneities of the medium including the tissue heterogeneity (TH) and the interseed attenuation (ISA) are also contributing to the heterogeneity of the dose distribution, but they are both ignored in Task Group 43 (TG43)-based protocols. This study investigates the effect of dose heterogeneity, TH and ISA on metrics that are commonly used to quantify biological efficiency in brachytherapy. The special case of 29 breast cancer patients treated with permanent (103)Pd seed implant is considered here. BED is compared to equivalent uniform BED (EUBED) capable of considering the spatial heterogeneity of the dose distribution. The effects of TH and ISA on biological efficiency of treatments are taken into account by comparing TG43 with Monte Carlo (MC) dose calculations for each patient. The effect of clonogenic repopulation is also considered. The analysis is performed for different sets of (α/β, α) ratios of (2, 0.3), (4, 0.27) and (10, 0.3) [Gy, Gy(-1)] covering the whole range of reported α/β values in the literature. BED is sometimes larger and sometimes smaller than EUBED(TG43) indicating that the effect of the dose heterogeneity is not similar among patients. The effect of the dose heterogeneity can be characterized by using the D(99) dose metric. For each set of the radiobiological parameters considered, a D(99) threshold is found over which dose heterogeneity will cause an overestimation of the biological efficiencies while the inverse happens for smaller D(99) values. EUBED(MC) is always larger than EUBED(TG43) indicating that by neglecting TH and ISA in TG43-based dosimetry algorithms, the biological efficiencies may be underestimated by about 10 Gy. Overall, by going from BED to the more accurate EUBED(MC) there is a gain of about 9.6 to 13 Gy on the biological efficiency. The efficiency gain is about 10.8 to 14 Gy when the repopulation is considered. Dose heterogeneity does not have a constant impact on the biological efficiencies and may under- or overestimate the efficacy in different patients. However, the combined effect of neglecting dose heterogeneity, TH and ISA results in underestimation of the biological efficiencies in permanent breast seed implants.
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Affiliation(s)
- Hossein Afsharpour
- Département de Radio-Oncologie et Centre de recherche en cancérologie de l'Université Laval, Centre Hospitalier Universitaire de Québec, 11 Côte du Palais, Québec, QC G1R 2J6, Canada
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Afsharpour H, Landry G, Reniers B, Pignol JP, Beaulieu L, Verhaegen F. Tissue modeling schemes in low energy breast brachytherapy. Phys Med Biol 2011; 56:7045-60. [DOI: 10.1088/0031-9155/56/22/004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Landry G, Granton PV, Reniers B, Öllers MC, Beaulieu L, Wildberger JE, Verhaegen F. Simulation study on potential accuracy gains from dual energy CT tissue segmentation for low-energy brachytherapy Monte Carlo dose calculations. Phys Med Biol 2011; 56:6257-78. [DOI: 10.1088/0031-9155/56/19/007] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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