University of Minnesota, Minneapolis, Minnesota 55455, USA.
Med Phys. 2010 Jan;37(1):244-8. doi: 10.1118/1.3271582.
Cone beam CT is increasingly being used for daily patient positioning verification during radiation therapy treatments. The daily use of CBCT could lead to accumulated patient doses higher than the older technique of weekly portal imaging. There have been several studies focusing on measurement or calculation of the patient dose from CBCT recently.
This study investigates the feasibility of configuring a kV x-ray source in a commercial treatment planning system to calculate the dose to patient resulting from an IGRT procedure. The method proposed in this article can be used to calculate dose from CBCT imaging procedure and include that in the patient treatment plans.
The kilovoltage beam generated by the CBCT imager has been modeled using the planning system. The modeled profiles agree with the measured ones to within 5%. The modeled beam was used to calculate dose to phantom in the pelvic region and the calculations were compared to TLD measurements. The agreement between calculated and measured doses ranges from 0% to 19% in soft tissue with larger variations observed near and within the bone.
The modeling of the beam produces reasonable results and the dose calculation comparisons indicate the potential for computing kilovoltage CBCT doses using a treatment planning system. Further improvements in the dose calculation algorithm are necessary, especially for dose calculations in and near the bone.
锥形束 CT 越来越多地用于放射治疗过程中的日常患者定位验证。与每周进行的端口成像的旧技术相比，每日使用 CBCT 可能会导致累积的患者剂量更高。最近有几项研究专注于测量或计算 CBCT 的患者剂量。
本研究探讨了在商业治疗计划系统中配置千伏 X 射线源以计算来自 IGRT 程序的患者剂量的可行性。本文提出的方法可用于计算 CBCT 成像程序的剂量，并将其包含在患者治疗计划中。
使用该计划系统对 CBCT 成像仪产生的千伏光束进行了建模。模型化的轮廓与测量值相差在 5%以内。使用模拟光束计算盆腔区域中的模体剂量，并将计算结果与 TLD 测量值进行比较。在软组织中，计算剂量与测量剂量的差异在 0%到 19%之间，在骨骼附近和内部观察到更大的变化。
光束的建模产生了合理的结果，剂量计算比较表明使用治疗计划系统计算千伏 CBCT 剂量具有潜力。需要进一步改进剂量计算算法，特别是在骨骼内和附近的剂量计算。
