A descriptive and broadly applicable model of therapeutic and stray absorbed dose from 6 to 25 MV photon beams

Schneider, Christopher; Newhauser, Wayne D.; Wilson, Lydia; Schneider, Uwe; Kaderka, Robert; Miljanić, Saveta; Knežević, Željka; Stolarcyzk, Liliana; Durante, Marco; Harrison, R. M.

doi:10.1002/mp.12286

Cited by 14 publications

(33 citation statements)

References 34 publications

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“…We modeled the total absorbed dose from therapeutic and stray photon sources during photon radiotherapy, D T , as the sum of four terms following Schneider et al, namely

D_{normalT} = D_{normalP} + D_{HS} + D_{PS} + D_{normalL}

where D P denotes the primary therapeutic dose, D HS is the dose from head‐scattered photons, D PS is the dose from photons that scattered in the phantom or patient, and D L is the dose from leakage photons. Each term in Eq.…”

Section: Methodsmentioning

confidence: 99%

“…, all configuration data can be quickly measured in most clinics and proprietary information is not used). A complete description of the model’s components and fitting parameters can be found elsewhere …”

Section: Methodsmentioning

confidence: 99%

“…Analytical models, on the other hand, are comparatively simple, fast, and free of statistical fluctuations. There is also promising evidence suggesting they can be dosimetrically accurate in the out‐of‐field region . Further, a recently published analytical model is readily generalizable to different treatment machines and irradiation conditions without the need for proprietary information due to its physics‐based framework .…”

Section: Introductionmentioning

confidence: 99%

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Method to quickly and accurately calculate absorbed dose from therapeutic and stray photon exposures throughout the entire body in individual patients

et al. 2020

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Purpose: Photon radiotherapy techniques typically devote considerable attention to limiting the exposure of healthy tissues outside of the target volume. Numerous studies have shown, however, that commercial treatment planning systems (TPSs) significantly underestimate the absorbed dose outside of the treatment field. The purpose of this study was to test the feasibility of quickly and accurately calculating the total absorbed dose to the whole body from photon radiotherapy in individual patients. Methods: We created an extended TPS by implementing a physics-based analytical model for the absorbed dose from stray photons during photon therapy into a research TPS. We configured and validated the extended TPS using measurements of 6-and 15-MV photon beams in water-box and anthropomorphic phantoms. We characterized the additional computation time required for therapeutic and stray dose calculations in a 44 9 30 9 180 cm 3 water-box phantom. Results: The extended TPS achieved superior dosimetric accuracy compared to the research TPS in both water and anthropomorphic phantoms, especially outside of the primary treatment field. In the anthropomorphic phantom, the extended TPS increased the generalized gamma index passing rate by a factor of 10 and decreased the median dosimetric discrepancy in the out-of-field region by a factor of 26. The extended TPS achieved an average discrepancy <1% in and near the treatment field and <1 mGy/Gy far from the treatment field in the anthropomorphic phantom. Characterization of computation time revealed that on average, the extended TPS only required 7% longer than the research TPS to calculate the total absorbed dose. Conclusions: The results of this work suggest that it is feasible to quickly and accurately calculate whole-body doses inside and outside of the therapeutic treatment field in individual patients on a routine basis using physics-based analytical dose models. This additional capability enables a more personalized approach to minimizing the risk of radiogenic late effects, such as second cancer and cardiac toxicity, as part of the treatment planning process.

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“…We modeled the total absorbed dose from therapeutic and stray photon sources during photon radiotherapy, D T , as the sum of four terms following Schneider et al, namely

D_{normalT} = D_{normalP} + D_{HS} + D_{PS} + D_{normalL}

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Method to quickly and accurately calculate absorbed dose from therapeutic and stray photon exposures throughout the entire body in individual patients

et al. 2020

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“…Measured dose profiles were previously published by Kaderka et al . The measurements utilized in this study were performed on an electron linear accelerator (Elekta SL25, Stockholm, Sweden) equipped with an MLCi2 at Universitätsklinikum (KGU) in Frankfurt, Germany, operated at 6 MV.…”

Section: Methodsmentioning

confidence: 99%

“…The research TPS, CERR, provided the test data for the three‐dimensional evaluations with a 1 × 1 × 1‐cm 3 grid resolution covering the entire imaged patient anatomy (axial distance of 30 cm). Additionally, we created an extended version of CERR that includes dose calculations in the low‐dose region based on the analytical model of Schneider et al . This extended version of CERR provided the reference data for the three‐dimensional evaluations with a 0.10 × 0.10 × 0.25‐cm 3 grid resolution also covering the entire imaged anatomy.…”

Section: Methodsmentioning

confidence: 99%

An objective method to evaluate radiation dose distributions varying by three orders of magnitude

2019

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Purpose: Modern radiotherapy practices typically report the absorbed dose (D) within the 5% relative isodose volume (i.e., the therapeutic dose region) to an accuracy of 3%-5%. Gamma-index analysis, the most commonly used method to evaluate dosimetric accuracy, has low sensitivity to discrepancies that occur outside of this region. The objective of this study was to develop an evaluation method with high sensitivity across dose distributions spanning three orders of magnitude. Methods: We generalized the gamma index to include an additional criterion, the absolute absorbed dose difference, specifically for the low-dose region (i.e., D ≤ 5%). We also proposed a method to objectively select the appropriate magnitudes for relative-dose-difference, absolute-dose-difference, and distance-to-agreement criteria. We demonstrated the generalized gamma-index method by first finding the appropriate generalized gamma-index agreement criteria at an interval of specified passing rates. Next, we used the generalized gamma index to evaluate one-, two-, and three-dimensional absorbed dose distributions in a water-box phantom and voxelized patient geometry. Results: Generalized gamma-index passing rates for one-, two-, and three-dimensional dose distributions were 55.4%, 44.5%, and 8.9%, respectively. Traditional gamma-index passing rates were 100%, 97.8%, and 96.4%, respectively. These results reveal that the generalized method has adequate sensitivity in all regions (i.e., therapeutic and low dose). Additionally, the algorithmic determination of triplets of agreement criteria revealed that they are strong functions of the specified passing rate. Conclusions: The major finding of this work is that the proposed method provides an objective evaluation of the agreement of dose distributions spanning three orders of magnitude. In particular, this generalized method correctly characterized dosimetric agreement in the low-dose region, which was not possible by traditional methods. The proposed algorithmic selection of agreement criteria decreased subjectivity and requirements of user judgment and skill. This method could find utility in a variety of applications including dose-algorithm development and translation.

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Out-of-field organ doses and associated risk of cancer development following radiation therapy with photons

Mazonakis

Damilakis

2021

Physica Medica

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A descriptive and broadly applicable model of therapeutic and stray absorbed dose from 6 to 25 MV photon beams

Cited by 14 publications

References 34 publications

Method to quickly and accurately calculate absorbed dose from therapeutic and stray photon exposures throughout the entire body in individual patients

Method to quickly and accurately calculate absorbed dose from therapeutic and stray photon exposures throughout the entire body in individual patients

An objective method to evaluate radiation dose distributions varying by three orders of magnitude

Out-of-field organ doses and associated risk of cancer development following radiation therapy with photons

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