Influence of photon energy spectra from brachytherapy sources on Monte Carlo simulations of kerma and dose rates in water and air

Rivard, Mark J.; Granero, Domingo; Pérez‐Calatayud, José; Ballester, F.

doi:10.1118/1.3298008

Cited by 72 publications

(76 citation statements)

References 39 publications

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“…Rivard et al examined the sensitivity of such brachytherapy dosimetry parameters as the Λ to the choice of brachytherapy source photon spectrum for 125 I, 103 Pd, and 192 Ir point sources. 23 They observed that the differences in the selected photon spectra did not substantially (< 0.2%) alter kerma or dose deposition as a function of depth, or dosimetry parameters such as Λ. However, differences of about 2% were observed when tracking dose delivery per disintegration, but not in Λ, g(r), or F(r, h).…”

Section: A Radionuclide Source Spectramentioning

confidence: 99%

Supplement 2 for the 2004 update of theAAPMTask Group No. 43 Report: Joint recommendations by theAAPMandGEC‐ESTRO

et al. 2017

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Cs (IsoRay Medical model CS-1 Rev2). Observations are included on the behavior of these dosimetry parameters as a function of radionuclide. Recommendations are presented on the selection of dosimetry parameters, such as from societal reports issuing consensus datasets (e.g., TG-43U1, AAPM Report #229), the joint AAPM/IROC Houston Registry, the GEC-ESTRO website, the Carleton University website, and those included in software releases from vendors of treatment planning systems. Aspects such as timeliness, maintenance, and rigor of these resources are discussed.Links to reference data are provided for radionuclides (radiation spectra and half-lives) and dose scoring materials (compositions and mass densities). The recent literature is examined on photon energy response corrections for thermoluminescent dosimetry of low-energy photon-emitting brachytherapy sources. Depending upon the dosimetry parameters currently used by individual physicists, use of these recommended consensus datasets may result in changes to patient dose calculations. These changes must be carefully evaluated and reviewed with the radiation oncologist prior to their implementation.

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Section: A Radionuclide Source Spectramentioning

confidence: 99%

Supplement 2 for the 2004 update of theAAPMTask Group No. 43 Report: Joint recommendations by theAAPMandGEC‐ESTRO

et al. 2017

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“…49,50,57 Estimates of k = 1 dosimetric uncertainties due to the physics implementation within MC radiation transport algorithms at r = 1 cm are 0.3% and 0.2% for low-and high-energy sources, respectively, and 0.7% and 0.3% at r = 5 cm. 43,47 …”

Section: Ivf Radiation Transport Codementioning

confidence: 99%

“…For low-energy sources, the dosimetric uncertainties at 0.5 and 5 cm are about 0.08% and 0.76%, respectively; with high-energy sources, dosimetric uncertainties are 0.01% and 0.12% for these same distances. 43,47 Further research on a modern assessment of cross-section uncertainties is needed.…”

Section: Ivg Interaction and Scoring Cross Sectionsmentioning

confidence: 99%

“…46 Since nuclear disintegration processes are well understood, there is little uncertainty associated with knowledge of the radiation spectrum from the radioactive materials. A general uncertainty in dose rate per unit source strength at P͑r 0 , 0 ͒ of 0.1% for low-energy sources 43 and 0.5% for high-energy sources 47 may be assumed. However, physical fabrication of brachytherapy sources often involves radiochemistry and other processes to purify the isotopic and elemental composition of the radioactive product.…”

Section: Ivc Source Emissionsmentioning

confidence: 99%

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A dosimetric uncertainty analysis for photon‐emitting brachytherapy sources: Report of AAPM Task Group No. 138 and GEC‐ESTRO

et al. 2011

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This report addresses uncertainties pertaining to brachytherapy single-source dosimetry preceding clinical use. The International Organization for Standardization ͑ISO͒ Guide to the Expression of Uncertainty in Measurement ͑GUM͒ and the National Institute of Standards and Technology ͑NIST͒ Technical Note 1297 are taken as reference standards for uncertainty formalism. Uncertainties in using detectors to measure or utilizing Monte Carlo methods to estimate brachytherapy dose distributions are provided with discussion of the components intrinsic to the overall dosimetric assessment. Uncertainties provided are based on published observations and cited when available. The uncertainty propagation from the primary calibration standard through transfer to the clinic for air-kerma strength is covered first. Uncertainties in each of the brachytherapy dosimetry parameters of the TG-43 formalism are then explored, ending with transfer to the clinic and recommended approaches. Dosimetric uncertainties during treatment delivery are considered briefly but are not included in the detailed analysis. For low-and high-energy brachytherapy sources of low dose rate and high dose rate, a combined dosimetric uncertainty Ͻ5% ͑k =1͒ is estimated, which is consistent with prior literature estimates. Recommendations are provided for clinical medical physicists, dosimetry investigators, and source and treatment planning system manufacturers. These recommendations include the use of the GUM and NIST reports, a requirement of constancy of manufacturer source design, dosimetry investigator guidelines, provision of the lowest uncertainty for patient treatment dosimetry, and the establishment of an action level based on dosimetric uncertainty. These recommendations reflect the guidance of the American Association of Physicists in Medicine ͑AAPM͒ and the Groupe Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology ͑GEC-ESTRO͒ for their members and may also be used as guidance to manufacturers and regulatory agencies in developing good manufacturing practices for sources used in routine clinical treatments.

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“…This is similar to the observation by Rivard et al, who found that within water the high energy photon contribution caused a more gradual falloff in the radial dose function beyond 11 cm for Pd-103. 41 Our simulations indicated that differences in refractive index during reconstruction within the channel should have minimal effect on the reconstructed signal at the detector surface. However, our measured signal was lower than expected at distances closer than 0.3 cm from the source (see Fig.…”

Section: Discussionmentioning

confidence: 99%

On the feasibility of polyurethane based 3D dosimeters with optical CT for dosimetric verification of low energy photon brachytherapy seeds

et al. 2014

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Purpose:To investigate the feasibility of and challenges yet to be addressed to measure dose from low energy (effective energy <50 keV) brachytherapy sources (Pd-103, Cs-131, and I-125) using polyurethane based 3D dosimeters with optical CT. Methods: The authors' evaluation used the following sources: models 200 (Pd-103), CS-1 Rev2 (Cs-131), and 6711 (I-125). The authors used the Monte Carlo radiation transport code MCNP5, simulations with the ScanSim optical tomography simulation software, and experimental measurements with PRESAGE R dosimeters/optical CT to investigate the following: (1) the water equivalency of conventional (density = 1.065 g/cm 3 ) and deformable (density = 1.02 g/cm 3 ) formulations of polyurethane dosimeters, (2) the scatter conditions necessary to achieve accurate dosimetry for low energy photon seeds, (3) the change in photon energy spectrum within the dosimeter as a function of distance from the source in order to determine potential energy sensitivity effects, (4) the optimal delivered dose to balance optical transmission (per projection) with signal to noise ratio in the reconstructed dose distribution, and (5) the magnitude and characteristics of artifacts due to the presence of a channel in the dosimeter. Monte Carlo simulations were performed using both conventional and deformable dosimeter formulations. For verification, 2.8 Gy at 1 cm was delivered in 92 h using an I-125 source to a PRESAGE R dosimeter with conventional formulation and a central channel with 0.0425 cm radius for source placement. The dose distribution was reconstructed with 0.02 and 0.04 cm 3 voxel size using the Duke midsized optical CT scanner (DMOS). Results: While the conventional formulation overattenuates dose from all three sources compared to water, the current deformable formulation has nearly water equivalent attenuation properties for Cs-131 and I-125, while underattenuating for Pd-103. The energy spectrum of each source is relatively stable within the first 5 cm especially for I-125. The inherent assumption of radial symmetry in the TG43 geometry leads to a linear increase in sample points within the 3D dosimeter as a function of distance away from the source, which partially offsets the decreasing signal. Simulations of dose reconstruction using optical CT showed the feasibility of reconstructing dose out to a radius of 10 cm without saturating projection images using an optimal dose and high dynamic range scanning; the simulations also predicted that reconstruction artifacts at the channel surface due to a small discrepancy in refractive index should be negligible. Agreement of the measured with calculated radial dose function for I-125 was within 5% between 0.3 and 2.5 cm from the source, and the median difference of measured from calculated anisotropy function was within 5% between 0.3 and 2.0 cm from the source. Conclusions: 3D dosimetry using polyurethane dosimeters with optical CT looks to be a promising application to verify dosimetric distributions surrounding low energy brachytherapy sources.

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Influence of photon energy spectra from brachytherapy sources on Monte Carlo simulations of kerma and dose rates in water and air

Abstract: Given the standardization of radionuclide data available from the National Nuclear Data Center (NNDC) and the rigorous infrastructure for performing and maintaining the data set evaluations, NNDC spectra are suggested for brachytherapy simulations in medical physics applications.

Cited by 72 publications

References 39 publications

Supplement 2 for the 2004 update of theAAPMTask Group No. 43 Report: Joint recommendations by theAAPMandGEC‐ESTRO

Supplement 2 for the 2004 update of theAAPMTask Group No. 43 Report: Joint recommendations by theAAPMandGEC‐ESTRO

A dosimetric uncertainty analysis for photon‐emitting brachytherapy sources: Report of AAPM Task Group No. 138 and GEC‐ESTRO

On the feasibility of polyurethane based 3D dosimeters with optical CT for dosimetric verification of low energy photon brachytherapy seeds

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