Servizio di Fisica Sanitaria, Arceispedale S. Maria Nuova, Reggio Emilia 42100, Italy.
Med Phys. 2010 Jan;37(1):377-90. doi: 10.1118/1.3271107.
The electronic portal imaging device (EPID) is a system for checking the patient setup; as a result of its integration with the linear accelerator and software customized for dosimetry, it is increasingly used for verification of the delivery of fixed-field intensity-modulated radiation therapy (IMRT). In order to extend such an approach to intensity-modulated arc therapy (IMAT), the combined use of an EPID system and a portal dose image prediction (PDIP) tool has been investigated.
The dosimetric behavior of an EPID system, mechanically reinforced to maintain its positional stability during the accelerator gantry rotation, has been studied to assess its ability to measure portal dose distributions for IMAT treatment beams. In addition, the PDIP tool of a commercial treatment planning system, commonly used for static IMRT dosimetry, has been validated for simulating the PDIs of IMAT treatment fields. The method has been applied to the delivery verification of 23 treatment fields that were measured in their dual mode of IMRT and IMAT modalities.
The EPID system has proved to be appropriate for measuring the PDIs of IMAT fields; additionally the PDIP tool was able to simulate these accurately. The results are quite similar to those obtained for static IMRT treatment verification, although it was necessary to investigate the dependence of the EPID signal and of the accelerator monitor chamber response on variable dose rate.
Our initial tests indicate that the EPID system, together with the PDIP tool, is a suitable device for the verification of IMAT plan delivery; however, additional tests are necessary to confirm these results.
电子射野影像装置（EPID）是一种用于检查患者摆位的系统；由于其与直线加速器的集成以及针对剂量学定制的软件，它越来越多地用于验证固定野强度调制放射治疗（IMRT）的剂量传递。为了将这种方法扩展到强度调制弧形治疗（IMAT），已经研究了 EPID 系统和门户剂量图像预测（PDIP）工具的联合使用。
对机械加固以在加速器旋转时保持其位置稳定性的 EPID 系统的剂量学行为进行了研究，以评估其测量 IMAT 治疗束门户剂量分布的能力。此外，还验证了商业治疗计划系统的 PDIP 工具，该工具通常用于静态 IMRT 剂量学，以模拟 IMAT 治疗场的 PDIs。该方法已应用于 23 个治疗场的交付验证，这些治疗场以其 IMRT 和 IMAT 模式的双重模式进行了测量。
EPID 系统已被证明适合测量 IMAT 场的 PDIs；此外，PDIP 工具能够准确地模拟这些 PDIs。结果与静态 IMRT 治疗验证获得的结果非常相似，尽管有必要研究 EPID 信号和加速器监测腔响应随剂量率变化的依赖性。
我们的初步测试表明，EPID 系统与 PDIP 工具一起，是验证 IMAT 计划交付的合适设备；然而，需要进行更多的测试来证实这些结果。
