Luo Guozhen, Neimat Joseph S, Cmelak Anthony, Kirschner Austin N, Attia Albert, Morales-Paliza Manuel, Ding George X
Department of Radiation Oncology, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Physics and Astronomy, Vanderbilt University, College of Art and sciences, Nashville, Tennessee.
Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee.
Pract Radiat Oncol. 2017 May-Jun;7(3):e223-e231. doi: 10.1016/j.prro.2016.08.006. Epub 2016 Aug 20.
To report on radiosurgery delivery positioning accuracy in the treatment of tremor patients with frameless image guided radiosurgery using the linear accelerator (LINAC) based ExacTrac system and to describe quality assurance (QA) procedures used.
Between 2010 and 2015, 20 patients underwent radiosurgical thalamotomy targeting the ventral intermediate nucleus for the treatment of severe tremor. The median prescription dose was 140 Gy (range, 120-145 Gy) in a single fraction. The median maximum dose was 156 Gy (range, 136-162 Gy). All treatment planning was performed with the iPlan system using a 4-mm circular cone with multiple arcs. Before each treatment, QA procedures were performed, including the imaging system. As a result of the extremely high dose delivered in a single fraction, a well-defined circular mark developed on the posttreatment magnetic resonance imaging (MRI). Eight of these 20 patients were selected to evaluate treatment localization errors because their circular marks were available in posttreatment MRI. In this study, the localization error is defined as the distance between the center of the intended target and the center of the posttreatment mark.
The mean error of distance was found to be 1.1 mm (range, 0.4-1.5 mm). The mean errors for the left-right, anteroposterior, and superoinferior directions are 0.5 mm, 0.6 mm, and 0.7 mm, respectively.
The result reported in this study includes all tremor patients treated at our institution when their posttreatment MRI data were available for study. It represents a direct confirmation of target positioning accuracy in radiosurgery with a LINAC-based frameless system and its limitations. This level of accuracy is only achievable with an appropriate QA program in place for a LINAC-based frameless radiosurgery system.
报告使用基于直线加速器（LINAC）的ExacTrac系统进行无框架图像引导放射外科治疗震颤患者时放射外科治疗的定位准确性，并描述所采用的质量保证（QA）程序。
2010年至2015年期间，20例患者接受了针对腹中间核的放射外科丘脑切开术以治疗严重震颤。单次分割的中位处方剂量为140 Gy（范围120 - 145 Gy）。中位最大剂量为156 Gy（范围136 - 162 Gy）。所有治疗计划均使用iPlan系统，采用4毫米的圆形准直器和多个弧度进行。每次治疗前，都要进行QA程序，包括成像系统。由于单次分割给予的剂量极高，治疗后的磁共振成像（MRI）上出现了一个清晰的圆形标记。这20例患者中有8例被选来评估治疗定位误差，因为他们治疗后的MRI上有圆形标记。在本研究中，定位误差定义为预期靶点中心与治疗后标记中心之间的距离。
发现距离的平均误差为1.1毫米（范围0.4 - 1.5毫米）。左右、前后和上下方向的平均误差分别为0.5毫米、0.6毫米和0.7毫米。
本研究报告的结果包括了我们机构所有接受治疗且治疗后MRI数据可供研究的震颤患者。它直接证实了基于LINAC的无框架系统在放射外科治疗中的靶点定位准确性及其局限性。只有为基于LINAC的无框架放射外科系统制定适当的QA程序，才能达到这种准确性水平。
