Tomé Wolfgang A, Meeks Sanford L, Orton Nigel P, Bouchet Lionel G, Bova Francis J
Department of Human Oncology, University of Wisconsin Medical School, Madison 53792, USA.
Med Phys. 2002 Aug;29(8):1781-8. doi: 10.1118/1.1494835.
Recently, there has been proliferation of image-guided positioning systems for high-precision radiation therapy, with little attention given to quality assurance procedures for such systems. To ensure accurate treatment delivery, errors in the imaging, localization, and treatment delivery processes must be systematically analyzed. This paper details acceptance tests for an optically guided three-dimensional (3D) ultrasound system used for patient localization. While all tests were performed using the same commercial system, the general philosophy and procedures are applicable to all systems utilizing image guidance. Determination of absolute localization accuracy requires a consistent stereotactic, or three-dimensional, coordinate system in the treatment planning system and the treatment vault. We established such a coordinate system using optical guidance. The accuracy of this system for localization of spherical targets imbedded in a phantom at depths ranging from 3 to 13 cm was determined to be (average +/- standard deviation) AP = 0.2 +/- 0.7 mm, Lat = 0.9 +/- 0.6 mm, Ax = 0.6 +/- 1.0 mm. In order to test the ability of the optically guided 3D ultrasound localization system to determine the magnitude of an internal organ shift with respect to the treatment isocenter, a phantom that closely mimics the typical human male pelvic anatomy was used. A CT scan of the phantom was acquired, and the regions of interest were contoured. With the phantom on the treatment couch, optical guidance was used to determine the positions of each organ to within imaging uncertainty, and to align the phantom so the plan and treatment machine coordinates coincided. To simulate a clinical misalignment of the treatment target, the phantom was then shifted by different precise offsets, and an experimenter blind to the offsets used ultrasound guidance to determine the magnitude of the shifts. On average, the magnitude of the shifts could be determined to within 1.0 mm along each axis.
最近，用于高精度放射治疗的图像引导定位系统大量涌现，但对这类系统的质量保证程序却很少关注。为确保精确的治疗实施，必须系统地分析成像、定位和治疗实施过程中的误差。本文详细介绍了用于患者定位的光学引导三维（3D）超声系统的验收测试。虽然所有测试均使用同一商业系统进行，但总体理念和程序适用于所有利用图像引导的系统。确定绝对定位精度需要在治疗计划系统和治疗室中建立一致的立体定向或三维坐标系。我们利用光学引导建立了这样一个坐标系。该系统对嵌入深度在3至13厘米范围内体模中的球形靶标的定位精度确定为（平均值±标准差）前后方向（AP）=0.2±0.7毫米，左右方向（Lat）=0.9±0.6毫米，轴向（Ax）=0.6±1.0毫米。为测试光学引导3D超声定位系统确定内部器官相对于治疗等中心位移大小的能力，使用了一个紧密模拟典型男性盆腔解剖结构的体模。获取了该体模的CT扫描图像，并勾勒出感兴趣区域。将体模置于治疗床上，利用光学引导确定每个器官的位置，使其在成像不确定度范围内，并对齐体模，使计划和治疗机器坐标系重合。为模拟治疗靶标的临床错位，然后将体模以不同的精确偏移量进行移动，一位对偏移量不知情的实验者使用超声引导来确定位移的大小。平均而言，沿每个轴的位移大小可确定在1.0毫米以内。
