A simulation study of ionizing radiation acoustic imaging (iRAI) as a real-time dosimetric technique for ultra-high dose rate radiotherapy (UHDR-RT).
A simulation study of ionizing radiation acoustic imaging (iRAI) as a real-time dosimetric technique for ultra-high dose rate radiotherapy (UHDR-RT).
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DOI：
10.1002/mp.15188
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发表时间：
2021-10
期刊：
影响因子：
3.8
通讯作者：
El Naqa I
中科院分区：
文献类型：
--
作者：
Ba Sunbul NH;Zhang W;Oraiqat I;Litzenberg DW;Lam KL;Cuneo K;Moran JM;Carson PL;Wang X;Clarke SD;Matuszak MM;Pozzi SA;El Naqa I
基于电子的超高剂量率放射治疗（UHDR-RT），也称为Flash-RT，与常规放射治疗（CONV-RT）相比，通过增加正常组织的保留，已显示出改善治疗指数的能力。然而，UHDR-RT中极高的剂量率提高了对精确实时剂量测定工具的需求。本工作旨在通过模拟研究证明电离辐射声成像（iRAI）新兴技术的潜力，并研究其作为UHDR-RT的有前途的相对体内剂量测定工具的特性。组织等效物被模拟用于理想的超声换能器。使用EGSnrc（BEAMnrc\DOSXYZnrc）Monte Carlo（MC）代码模拟1x 1 cm 2射野的体模中的全3D剂量分布。使用Gafchromic薄膜的剂量实验测量验证了相对剂量学模拟。利用介质依赖剂量-压力关系，将空间剂量分布转换为初始压力源空间分布。然后使用基于MATLAB的工具箱k-Wave对声波通过体模的传播进行建模，并执行基于时间反演（TR）的成像重建。各种直线加速器（直线加速器）的操作参数，包括直线加速器的脉冲持续时间和脉冲重复率（频率）的影响，以及进行了研究。Monte Carlo剂量模拟结果与胶片测量结果一致，特别是在中心射束区域高达80%的剂量，中心轮廓区域的相对误差约为5%，剂量深度百分比的局部相对误差<6%。辐射束的基于IRAI的FWHM相对于束入口处的MC模拟束FWHM在约3 mm内。真实的时间压力信号变化与剂量变化一致，证明了iRAI预测射束位置的能力。IRAI通过其响应的3D模拟进行了测试，其响应基于线性加速器操作参数的时间变化，基于每个脉冲的剂量，正如理论上从压力-剂量比例所预期的那样。通过2D模拟获得的压力信号幅度与每个脉冲的剂量成比例。瞬时压力信号幅度随着直线加速器脉冲持续时间的增加而减小，如从压力波生成方程预测的，使得直线加速器脉冲越短，信号越高并且iRAI的时间（空间）分辨率越好。通过直线加速器脉冲反卷积校正了较长直线加速器脉冲持续时间对3D构建的iRAI图像的空间分辨率的影响。这种校正提高了1%/1 mm伽马测试标准的通过率，在压力构建和剂量测定射束特性之间，高达98%。开发了一个完整的模拟工作流程，用于测试iRAI作为UHDR-RT放射治疗的有前途的相对剂量学工具的有效性。IRAI通过剂量信号线性显示了3D剂量分布的优势，因此有可能成为深度剂量测量和射束定位的有用剂量计，因此有可能用于UHDR-RT中的体内剂量测定。
Electron-based ultra-high dose rate radiation therapy (UHDR-RT), also known as Flash-RT, has shown the ability to improve the therapeutic index in comparison to conventional radiotherapy (CONV-RT) through increased sparing of normal tissue. However, the extremely high-dose rates in UHDR-RT have raised the need for accurate real-time dosimetry tools. This work aims to demonstrate the potential of the emerging technology of Ionized Radiation Acoustic Imaging (iRAI) through simulation studies and investigate its characteristics as a promising relative in vivo dosimetric tool for UHDR-RT. The detection of induced acoustic waves following a single UHDR pulse of a modified 6 MeV 21EX Varian Clinac in a uniform porcine gelatin phantom that is brain-tissue equivalent was simulated for an ideal ultrasound transducer. The full 3D dose distributions in the phantom for a 1x1 cm2 field were simulated using EGSnrc (BEAMnrc\DOSXYZnrc) Monte Carlo (MC) codes. The relative dosimetry simulations were verified with dose experimental measurements using Gafchromic films. The spatial dose distribution was converted into an initial pressure source spatial distribution using the medium dependent dose-pressure relation. The MATLAB based toolbox k-Wave was then used to model the propagation of acoustic waves through the phantom and perform time-reversal (TR) based imaging reconstruction. The effect of the various linear accelerator (linac) operating parameters, including linac pulse duration and pulse repetition rate (frequency), were investigated as well. The Monte Carlo dose simulation results agreed with the film measurement results, specifically at the central beam region up to 80% dose within approximately 5% relative error for the central profile region and a local relative error of < 6 % for percentage dose depth. IRAI-based FWHM of the radiation beam was within approximately 3 mm relative to the MC simulated beam FWHM at the beam entrance. The real time pressure signal change agreed with the dose changes proving the capability of the iRAI for predicting the beam position. IRAI was tested through 3D simulations of its response to be based on the temporal changes in the linac operating parameters on a dose per pulse basis as expected theoretically from the pressure-dose proportionality. The pressure signal amplitude obtained through 2D simulations was proportional to the dose per pulse. The instantaneous pressure signal amplitude decreases as the linac pulse duration increases, as predicted from the pressure wave generation equations, such that the shorter the linac pulse the higher the signal and the better the temporal (spatial) resolutions of iRAI. The effect of the longer linac pulse duration on the spatial resolution of the 3D constructed iRAI images was corrected for through linac pulse deconvolution. This correction has improved the passing rate of the 1%/1mm gamma test criteria, between the pressure-constructed and dosimetric beam characteristic, to as high as 98%. A full simulation workflow was developed for testing the effectiveness of iRAI as a promising relative dosimetry tool for UHDR-RT radiation therapy. IRAI has shown the advantage of 3D dose mapping through the dose signal linearity and hence has the potential to be a useful dosimeter at depth dose measurement and beam localization and hence potentially for in vivo dosimetry in UHDR-RT.
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影响因子：
5.7
作者：
Lohse, Ines;Lang, Stephanie;Zaugg, Kathrin
通讯作者：
Zaugg, Kathrin
影响因子：
5.7
作者：
Montay-Gruel, Pierre;Bouchet, Audrey;Vozenin, Marie-Catherine
通讯作者：
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影响因子：
5.7
作者：
Montay-Gruel, Pierre;Petersson, Kristoffer;Vozenin, Marie-Catherine
通讯作者：
Vozenin, Marie-Catherine
DOI：
10.1109/tuffc.2020.2983732
发表时间：
2020-08-01
影响因子：
3.6
作者：
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通讯作者：
Xiang, Liangzhong
影响因子：
5.7
作者：
Simmons, Danielle A.;Lartey, Frederick M.;Loo, Billy W., Jr.
通讯作者：
Loo, Billy W., Jr.