Radiation Therapy Services, Peter MacCallum Cancer Centre, Victoria, Australia.
Int J Radiat Oncol Biol Phys. 2010 Jul 15;77(4):1248-56. doi: 10.1016/j.ijrobp.2009.09.050.
To compare volumetric in-room computed tomography (CT) and kilovoltage (kV) cone-beam CT (CBCT) to planar imaging with respect to their ability to localize fiducial markers (FMs) for radiotherapy of prostate cancer.
Image guidance options from two linear accelerators were compared in terms of identifying the center of gravity (COG) of FMs from the isocenter: a Siemens Primatom, where the couch is rotated 180 degrees from the treatment isocenter to the in-room CT vs. electronic portal imaging (EPI); and a Varian OBI system, where kV CBCT, EPI, and planar kV radiographs were compared. In all, 387 image pairs (CBCT = 133; CT = 254) from 18 patients were analyzed. A clinical tolerance of 3 mm was predefined as the acceptable threshold for agreement.
COG location on in-room CT and EPI was in agreement 96.9%, 85.8%, and 89.0% of the time in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) directions, respectively, vs. 99.2%, 91.7%, and 93.2% for the CBCT and EPI analysis. The CBCT vs. kV radiographs were in agreement 100% (LR), 85.4% (SI), and 88.5% (AP), and EPI vs. kV radiographs were in agreement 100% (LR), 94.6% (SI), and 91.5% (AP) of the time.
Identification of FMs on volumetric or planar images was found to be not equivalent (+/-3 mm) using either linear accelerator. Intrafraction prostate motion, interpretation of FM location, and spatial properties of images are contributing factors. Although in-room CT has superior image quality, the process of realigning the treatment couch to acquire a CT introduces an error, highlighting the benefits of a single isocentric system.
比较容积式机房 CT（kV 锥形束 CT（CBCT）与平面成像在前列腺癌放疗中定位基准标记物（FM）的能力。
从两台直线加速器的图像引导选项方面进行比较，从等中心识别 FM 的重心（COG）：Siemens Primatom 治疗等中心将治疗床旋转 180 度到机房 CT 与电子门控成像（EPI）；Varian OBI 系统比较 kV CBCT、EPI 和平面 kV 射线照相。共分析了 18 例患者的 387 对图像（CBCT=133；CT=254）。临床可接受的 3mm 误差作为一致性的可接受阈值。
在左右（LR）、上下（SI）和前后（AP）方向，COG 位置在机房 CT 和 EPI 上的一致性分别为 96.9%、85.8%和 89.0%，而 CBCT 和 EPI 分析的一致性分别为 99.2%、91.7%和 93.2%。CBCT 与 kV 射线照相的一致性为 100%（LR）、85.4%（SI）和 88.5%（AP），EPI 与 kV 射线照相的一致性为 100%（LR）、94.6%（SI）和 91.5%（AP）。
使用任何一种直线加速器，都发现容积式或平面图像上 FM 的识别（±3mm）并不等效。分次内前列腺运动、FM 位置的解释和图像的空间特性是影响因素。虽然机房 CT 具有较好的图像质量，但重新调整治疗床以获取 CT 会引入误差，突出了单等中心系统的优势。
