Oshika Riki, Moriya Shunsuke, Yamanaka Masashi, Matsumoto Kazuki, Sakae Takeji, Isobe Tomonori
Degree Programs in Comprehensive Human Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan.
Proton Medical Research Center, University of Tsukuba, Ibaraki, Japan.
Int J Part Ther. 2025 Jun 18;17:100755. doi: 10.1016/j.ijpt.2025.100755. eCollection 2025 Sep.
To develop and validate a novel 3-dimensional quality assurance (QA) method using an X-ray computed tomography-based polymer gel dosimeter (XCT-PGD) and an integrated cone-beam computed tomography (CBCT) system, enabling comprehensive verification of spot positions and isocenter accuracy for proton therapy.
A PROBEAT-M1 proton therapy system was used to irradiate an XCT-PGD with spot scanning beams from 4 gantry angles (45°, 180°, 270°, and 315°). Three spot positions, including the isocenter position, were evaluated. Pre- and postirradiation CBCT scans were acquired to determine the spot positions. The accuracy of the proposed method was validated against conventional Winston-Lutz tests and beam delivery log file analysis. Spot positions were analyzed using 3-dimensional visualization of the beam trajectories within the gel dosimeter.
The proposed method demonstrated excellent agreement with conventional techniques. The isocenter position determined using our method was within 0.39 mm that from the Winston-Lutz test. Spot position from our method was within 0.37 mm that from log file analysis. Three-dimensional detection using the gel dosimeter enabled simultaneous verification of multiple spot positions and beam trajectories, providing comprehensive spatial information not available through conventional 2-dimensional methods.
Combining an XCT-PGD with CBCT provides a robust and comprehensive method for 3-dimensional verification of the accuracy of proton therapy delivery. This novel approach offers advantages over conventional QA techniques by enabling simultaneous evaluation of spot positions and isocenter accuracy while minimizing setup uncertainties. The method is particularly suitable for annual QA and commissioning procedures in proton therapy facilities.
开发并验证一种新型的三维质量保证（QA）方法，该方法使用基于X射线计算机断层扫描的聚合物凝胶剂量计（XCT-PGD）和集成的锥形束计算机断层扫描（CBCT）系统，能够全面验证质子治疗的束斑位置和等中心精度。
使用PROBEAT-M1质子治疗系统，从4个机架角度（45°、180°、270°和315°）用束斑扫描束照射XCT-PGD。评估了包括等中心位置在内的三个束斑位置。在照射前和照射后进行CBCT扫描以确定束斑位置。所提出方法的准确性通过传统的温斯顿-卢茨测试和束流传输日志文件分析进行验证。使用凝胶剂量计内束流轨迹的三维可视化分析束斑位置。
所提出的方法与传统技术显示出极好的一致性。使用我们的方法确定的等中心位置与温斯顿-卢茨测试确定的位置相差在0.39毫米以内。我们方法确定的束斑位置与日志文件分析确定的位置相差在0.37毫米以内。使用凝胶剂量计进行的三维检测能够同时验证多个束斑位置和束流轨迹，提供了传统二维方法无法获得的全面空间信息。
将XCT-PGD与CBCT相结合，为质子治疗传输精度的三维验证提供了一种强大而全面的方法。这种新方法通过能够同时评估束斑位置和等中心精度，同时将设置不确定性降至最低，比传统QA技术具有优势。该方法特别适用于质子治疗设施的年度QA和调试程序。
