Wiant D, Bourland J D
Department of Radiation Oncology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
Technol Cancer Res Treat. 2009 Aug;8(4):265-70. doi: 10.1177/153303460900800403.
The Leksell Gamma Knife (GK) is capable of targeting intracranial lesions with a high degree of accuracy. A headframe is rigidly attached to the patient's skull to establish a stereotactic coordinate system and provide a means for precisely positioning the patient in stereotactic space. After stereotactic target localization and radiosurgical treatment planning the skull and headframe are then moved with sub-millimeter precision to bring a target volume to the radiological focus of the GK unit. However, for GK models 4C and earlier, the treatable intracranial volume may be limited by collisions between the skull/headframe and the GK collimator helmet, or by mechanical travel limits of the skull/headframe within the collimator helmet. Both of these treatment-limiting conditions can be found only after the headframe has been placed on the patient. If the volume of interest cannot be treated with the initial headframe placement, additional headframe placements or a different course of treatment are needed. We have developed a software package that allows for simulated headframe placement and collision checks using pre-treatment day image sets, in order to minimize the need for multiple headframe placements. We performed a small validation experiment with an anthropomorphic head phantom to evaluate the software's capabilities for predicting a clinically useable headframe position. We also used the software in an IRB-approved retrospective review for twenty-five GK image sets for a group of patients that could not be treated with the initial headframe placement, to determine if the software tool could locate an optimized headframe position to enable GK radiosurgery of all identified targets with a single headframe placement. We found that four of the cases could have been completed with a single optimized headframe placement and twenty-four of the cases could not be treated with any single headframe placement.
Leksell伽玛刀（GK）能够高精度地靶向颅内病变。一个头架被牢固地固定在患者的颅骨上，以建立立体定向坐标系，并提供一种在立体定向空间中精确放置患者的方法。在立体定向靶点定位和放射外科治疗计划完成后，颅骨和头架随后以亚毫米级的精度移动，将目标体积带到GK装置的放射焦点处。然而，对于4C型及更早的GK型号，可治疗的颅内体积可能会受到颅骨/头架与GK准直器头盔之间的碰撞限制，或者受到颅骨/头架在准直器头盔内的机械行程限制。这两种限制治疗的情况只有在头架放置在患者身上后才能发现。如果感兴趣的体积在初始头架放置时无法治疗，则需要额外的头架放置或不同的治疗方案。我们开发了一个软件包，该软件包允许使用治疗前一天的图像集进行模拟头架放置和碰撞检查，以尽量减少多次头架放置的需求。我们使用一个拟人化头部模型进行了一个小型验证实验，以评估该软件预测临床可用头架位置的能力。我们还在一项经机构审查委员会（IRB）批准的回顾性研究中，将该软件用于一组因初始头架放置无法治疗的25个GK图像集，以确定该软件工具是否能够找到一个优化的头架位置，从而通过单次头架放置实现对所有已识别靶点的GK放射外科治疗。我们发现，其中4例可以通过单次优化头架放置完成，而24例无法通过任何单次头架放置进行治疗。
