Department of Radiology, Shiga Medical Center for Children, Moriyama City, Shiga,
J Appl Clin Med Phys. 2010 Aug 30;11(4):3162. doi: 10.1120/jacmp.v11i4.3162.
Kilovoltage cone beam computed tomography (CBCT) imaging may be useful in verifying patient position in stereotactic radiosurgery (SRS). To evaluate its efficacy, we investigated isocenter differences in the radiation beam and CBCT with respect to the achievable setup of a conventional frame-based SRS system. A verification phantom constructed from two plastic boards and Gafchromic-EBT film (4 × 4 cm²) pricked with a pin, was scanned by simulation CT. An isocenter at the tip of pin was planned in the treatment planning system and positioned using stereotactic coordinates. Star-shot irradiation was performed to evaluate the difference between the radiation isocenter and the target (pinhole). CBCT rotation of 200° with a micro multileaf collimator (m3) was performed and measured the isocenter difference between CBCT and the target (tip of pin) by comparing relative coordinates. Data acquisition was performed 13 times on different days and differences were analyzed by calculating mean and standard deviation. The mean difference between the radiation beam and the target (pinhole) and between radiation beam and CBCT isocenter, were 0.6 ± 0.2 mm and 0.8 ± 0.1 mm, respectively. The setup accuracy of conventional stereotactic coordinates and the isocenter accuracy of CBCT complied with AAPM Report No. 54.
千伏锥形束 CT（CBCT）成像可用于验证立体定向放射外科（SRS）中的患者位置。为了评估其效果，我们研究了辐射束和 CBCT 的等中心差异，以及传统基于框架的 SRS 系统的可实现设置。使用模拟 CT 扫描了由两块塑料板和带有针的 Gafchromic-EBT 胶片（4×4cm²）构建的验证体模。在治疗计划系统中计划针尖处的等中心，并使用立体定向坐标定位。进行星状照射，以评估辐射等中心与目标（针孔）之间的差异。进行了 200°的 CBCT 旋转，并使用微多叶准直器（m3）进行了测量，通过比较相对坐标，测量了 CBCT 和目标（针尖端）之间的等中心差异。在不同的日子进行了 13 次数据采集，并通过计算平均值和标准差来分析差异。辐射束和目标（针孔）之间以及辐射束和 CBCT 等中心之间的平均差异分别为 0.6±0.2mm 和 0.8±0.1mm。传统立体定向坐标的设置精度和 CBCT 等中心的精度符合 AAPM 报告 No.54。
