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

Abstract

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.

Image-based data mining applies to data collected from children

“…2 ). We selected these levels to span the noise and uncertainty levels representative of out-of-field dose calculations from Monte Carlo simulations [40] to analytical algorithms [41] , [42] . The three test-volume side lengths were = 0.5 cm, 2.0 cm, and 6.0 cm ( Fig.…”

“…2 ). We selected these relative magnitudes to span from stray-dose magnitudes [41] to clinically acceptable therapeutic dose deviations [43] .

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Development of clinical application program for radiotherapy induced cancer risk calculation using Monte Carlo engine in volumetric-modulated arc therapy

“…The most commonly used methods to analyze the effects of secondary cancers involve the utilization of human phantoms to measure secondary doses using devices such as the thermo-luminescent dosimeter (TLD) and radio-photoluminescent glass dosimeter (RPLD), and the calculation of doses using commercialized treatment planning system (TPS) [ 4 , 8 , 18 – 20 ]. Recently, studies have also been conducted to calculate scattered radiation for in-field and out-field, which has a significant impact on SCR using physics-based analysis algorithms [ 21 – 24 ]. Nevertheless, the existing evaluation methods have limitations.…”

A Publicly Available Dataset of Out-of-Field Dose Profiles of a 6 MV Linear Accelerator

“…Methods of estimating out-of-field doses include consulting simple reference data in the literature [6,[9][10][11], Monte Carlo simulations [12][13][14], and increasingly refined analytical models [15][16][17][18]. These models may need to consider the physical geometry of clinical linacs, including jaws, primary collimator, MLC leaves and carriage, and the arrangement of additional head shielding.…”