用于测量千伏锥形束计算机断层摄影剂量的闪烁塑料光纤装置的评估。

Evaluation of a Scintillating Plastic Optical Fiber Device for Measuring kV-Cone Beam Computed Tomography Dose.

机构信息

INSERM Unité U1296 Radiations: Défense, Santé Environnement, 69008 Lyon, France.

Fibermetrix, 7 Allée de l'Europe, 67960 Entzheim, France.

出版信息

Sensors (Basel). 2023 Sep 9;23(18):7778. doi: 10.3390/s23187778.

DOI:10.3390/s23187778

PMID:37765835

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC10536616/

Abstract

BACKGROUND

Justification of imaging procedures such as cone beam computed tomography (CBCT) in radiotherapy makes no doubt. However, the CBCT composite dose is rarely reported or optimized, even though the repeated CBCT cumulative dose can be up to 3% of the prescription dose. This study aimed to evaluate the performance and utility of a new plastic scintillating optical fiber dosimeter for CBCT dosimetric quality assurance (QA) applications before a potential application in patient composite CBCT dosimetry.

METHODS

The dosimeter, made of 1 mm diameter plastic fiber, was installed under a linear accelerator treatment table and linked to photodetectors. The fiber impact on the fluence and dose delivered was respectively assessed with an electronic portal imaging device (EPID) and EBT3 Gafchromic film. The presence of artifacts was visually evaluated on kV images. The dosimeter performances were determined for various acquisition parameters by comparison with ionization chamber values.

RESULTS

The maximum impact of the fiber on the fluence measured by the EPID was -1.2% for the 6 MV flattening filter-free beam. However, the fiber did not alter the film dose profile when measured for all the beams tested. The fiber was not visible at energies ≥ 80 kV and was merely visible on the CBCT images. When the rate of images per second or mA was changed, the maximum relative difference between the device and the ionization chamber CTDIs was <5%. Changing collimation led to a -7.2% maximum relative difference with an absolute dose difference that was insignificant (-0.3 mGy). Changing kV was associated with a -8.7% maximum relative difference, as published in the literature.

CONCLUSIONS

The dosimeter may be a promising device for CBCT recurrent dosimetry quality control or dose optimization. According to these results, further developments are in progress in order to adapt the solution to the measurement of patient composite CBCT doses.

摘要

背景

锥形束 CT（CBCT）等影像学检查在放射治疗中的应用是有充分依据的。然而，CBCT 复合剂量很少被报告或优化，尽管重复 CBCT 累积剂量可能达到处方剂量的 3%。本研究旨在评估新型塑料闪烁光纤剂量计在患者复合 CBCT 剂量测量中的潜在应用之前，用于 CBCT 剂量学质量保证（QA）应用的性能和实用性。

方法

该剂量计由 1 毫米直径的塑料光纤制成，安装在直线加速器治疗台上，并与光电探测器相连。通过电子射野影像装置（EPID）和 EBT3 Gafchromic 胶片分别评估光纤对注量和剂量的影响。通过千伏图像评估伪影的存在。通过与电离室值比较，确定了各种采集参数下的剂量计性能。

结果

对于 6 MV 无均整器射束，光纤对 EPID 测量的注量的最大影响为-1.2%。然而，当测量所有测试的射束时，光纤不会改变胶片剂量分布。当能量≥80 kV 时，光纤不可见，仅在 CBCT 图像上可见。当每秒图像或毫安数改变时，设备与电离室 CTID 的最大相对差异<5%。准直变化导致最大相对差异为-7.2%，绝对剂量差异无意义（-0.3 mGy）。改变千伏时，最大相对差异为-8.7%，与文献报道一致。