Validation of fast Monte Carlo dose calculation in small animal radiotherapy with EBT3 radiochromic films

Noblet, Caroline L.; Chiavassa, S.; Smekens, F.; Sarrut, David; Passal, V.; Suhard, Jérôme; Lisbona, A.; Pâris, François; Delpon, G.

doi:10.1088/0031-9155/61/9/3521

Cited by 16 publications

(23 citation statements)

References 28 publications

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“…We are uniquely positioned to explore this problem because of our ability to produce anatomically accurate mouse phantoms with heterogeneous internal structures. Previous related work with small animal irradiations have either been purely computational (30) or made comparisons using simple phantoms (31). This work investigates dose distributions, specifically scattered dose outside the beam target region, from specialized animal irradiators using both a complex physical phantom and an accompanying complex computational phantom to generate new insight into small animal irradiation investigations.…”

Section: Introductionmentioning

confidence: 99%

Scattered Dose Calculations and Measurements in a Life-Like Mouse Phantom

et al. 2017

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Anatomically accurate phantoms are useful tools for radiation dosimetry studies. In this work, we demonstrate the construction of a new generation of life-like mouse phantoms in which the methods have been generalized to be applicable to the fabrication of any small animal. The mouse phantoms, with built-in density inhomogeneity, exhibit different scattering behavior dependent on where the radiation is delivered. Computer models of the mouse phantoms and a small animal irradiation platform were devised in Monte Carlo N-Particle code (MCNP). A baseline test replicating the irradiation system in a computational model shows minimal differences from experimental results from 50 Gy down to 0.1 Gy. We observe excellent agreement between scattered dose measurements and simulation results from X-ray irradiations focused at either the lung or the abdomen within our phantoms. This study demonstrates the utility of our mouse phantoms as measurement tools with the goal of using our phantoms to verify complex computational models.

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Section: Introductionmentioning

confidence: 99%

Scattered Dose Calculations and Measurements in a Life-Like Mouse Phantom

et al. 2017

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“…E.g., Noblet et al used 4% as dose difference to compare Monte Carlo-simulated and film-measured dose distributions. 26 Because the dimensions involved in preclinical radiotherapy are small, distance criteria must be reduced to a smaller scale for comparison in realistic conditions. In this study, we proposed to set DTA to one tenth of the size of the collimator.…”

Section: Discussionmentioning

confidence: 99%

Online dose delivery verification in small animal image‐guided radiotherapy

et al. 2020

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Purpose: To accomplish novel radiation treatment techniques in preclinical radiation research, small animal image-guided radiotherapy systems have been increasingly integrated into preclinical radiation research over the last decade. Although such systems have sophisticated tools (such as conebeam computed tomography-based image guidance, robotic couch, treatment planning system (TPS), and electronic portal imaging devices [EPIDs]). To our knowledge, no established technique can perform independent and online verification of the delivered dose during radiotherapy. In this study, we implement an online EPID dosimetry for each administered SA-IGRT fraction in a rat orthotopic model of prostate cancer. Methods: To verify the accuracy of delivered dose to rat, we compared the two-dimensional (2D) calculated dose distribution by TPS as the planned dose, with online dose distribution estimated using an EPID as the delivered dose. Since image acquisition software was not capable of acquiring integrated images over a long period of time, we used the EPID to estimate dose rate rather than dose. The central axis (CAX) dose rate values at the beam's exit surface were compared. In addition, 2D dose distributions were also compared under different gamma criteria. To verify the accuracy of our EPID dosimetry technique, we measured transit and exit doses with film during animal treatment. In this study, 20-mm cone was used to collimate beam. We previously observed that the EPID response was independent of collimator size for collimator size ≥15-mm, we did not apply for additional correction factor. Results: Comparison of exit CAX dose rate values of TPS-calculated and EPID-estimated showed that the average difference was 3.1%, with a maximum of 9.3%. Results of gamma analysis for 2D comparison indicated an average of 90% passing rate with global gamma criterion of 2 mm/5%. We observed that TPS could not calculate dose accurately in peripheral regions in which the penumbra effect was dominant. Dose rate values estimated by EPID were within 2.1% agreement with film at both the imager plane and the beam's exit surface for 4 randomly selected animals for which film measurement verification was performed. Conclusions: The small animal radiation research platform (SARRP) system's built-in EPID was utilized to estimate dose delivered to rats at kilovoltage energy x-rays. The results of this study suggest that the EPID is an invaluable tool for verifying delivered dose to small animal to help validate conclusions made from preclinical radiation research.

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“…Gamma analysis was also performed to compare the calculated and measured dose distributions, for which the typical clinical criteria are 3% dose difference and 3 mm distance to agreement (DTA) . In previous studies, these criteria have been adapted for small animal radiotherapy to 4% and 0.3 mm to account for the approximate order of magnitude difference in imaging resolution . Thus, 4%/0.3 mm criteria were used for analysis in this study.…”

Section: Methodsmentioning

confidence: 99%

“…59 In previous studies, these criteria have been adapted for small animal radiotherapy to 4% and 0.3 mm to account for the approximate order of magnitude difference in imaging resolution. 60,61 Thus, 4%/0.3 mm criteria were used for analysis in this study.…”

Section: F Dosimetric Testingmentioning

confidence: 99%

A sparse orthogonal collimator for small animal intensity‐modulated radiation therapy. Part II: hardware development and commissioning

et al. 2019

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Purpose A dose‐modulation device for small animal radiotherapy is required to use clinically analogous treatment techniques, which will likely increase the translatability of preclinical research results. Because the clinically used multileaf collimator (MLC) is impractical for miniaturization, we have developed a simpler, better‐suited sparse orthogonal collimator (SOC) for delivering small animal intensity‐modulated radiation therapy (IMRT) using a rectangular aperture optimization (RAO) treatment planning system. Methods The SOC system was modeled in computer‐aided design software and fabricated with machined tungsten leaves and three‐dimensional (3D) printed leaf housing. A graphical user interface was developed for controlling and calibrating the SOC leaves, which are driven by Arduino‐controlled stepper motors. A Winston‐Lutz test was performed to assess mechanical alignment, and abutting field and grid dose patterns were created to analyze intra‐ and intercalibration leaf positioning error. Leaf transmission and penumbra were measured over the full range of gantry angles and leaf positions, respectively. Three SOC test plans were delivered, and film measurements were compared to the intended dose distributions. The differences in maximum, mean, and minimum, as well as pixelwise absolute dose differences, were compared for each structure, and a gamma analysis was performed for the target structures using criteria of 4% dose difference and 0.3 mm distance to agreement. Results The Winston‐Lutz test revealed maximum directional offsets between the SOC and primary collimator axes of 0.53 mm at 0° and 0.68 mm over the full 360°. Upper and lower abutting field patterns had maximum dose deviations of 18.8 ± 3.1% and 15.5 ± 2.9%, respectively, and grid patterns showed intra‐ and intercalibration repeatability of 93% and 91%, respectively. Extremely low midleaf (0.15 ± 0.05%) and interleaf (0.27 ± 0.22%) transmission was measured, with no significant rotational variation. The average penumbra was ~0.8 mm for all leaves at field center, with a range of 0.17 mm for all leaf positions. A highly concave test plan was delivered with a ~ 95% gamma analysis pass rate, and a realistic mouse phantom liver irradiation plan achieved a pass rate of ~98%. A highly complex dose distribution was also created with 551 SOC apertures averaging 2.4 mm in size. Conclusions A sparse orthogonal collimator was developed and commissioned, with promising preliminary dosimetry results. The SOC design, with its limited moving components and high dose‐modulation resolution, is ideal for delivering high‐quality small animal IMRT with our RAO‐based treatment planning system.

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Validation of fast Monte Carlo dose calculation in small animal radiotherapy with EBT3 radiochromic films

Cited by 16 publications

References 28 publications

Scattered Dose Calculations and Measurements in a Life-Like Mouse Phantom

Scattered Dose Calculations and Measurements in a Life-Like Mouse Phantom

Online dose delivery verification in small animal image‐guided radiotherapy

A sparse orthogonal collimator for small animal intensity‐modulated radiation therapy. Part II: hardware development and commissioning

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