Department of Neurosurgery and Neuro-oncology, CHU Lille, F-59000, Lille, France.
U1189-ONCO-THAI-Image Assisted Laser Therapy for Oncology, Univ. Lille, Inserm, CHU Lille, F-59000, Lille, France.
Acta Neurochir (Wien). 2020 Sep;162(9):2203-2210. doi: 10.1007/s00701-020-04458-8. Epub 2020 Jun 18.
The Gamma Knife planning software (TMR 10, Elekta Instruments, AB, Sweden) affords two ways of defining the skull volume, the "historical" one using manual measurements (still perform in some centers) and the new one using image-based skull contours. Our objective was to assess the potential variation of the dose delivery calculation using consecutively in the same patients the two above-mentioned techniques.
We included in this self-case-control study, 50 patients, treated with GKRS between July 2016 and January 2017 in Lausanne University Hospital, Switzerland, distributed among four groups: convexity targets (n = 18), deep-seated targets (n = 13), vestibular schwannomas (n = 11), and trigeminal neuralgias (n = 8). Each planning was performed consecutively with the 2 skull definition techniques. For each treatment, we recorded the beam-on time (min), target volume coverage (%), prescription isodose volume (cm), and maximal dose (Gy) to the nearest organ at risk if relevant, according to each of the 2 skull definition techniques. The image-based contours were performed using CT scan segmentation, based upon a standardized windowing for all patients.
The median difference in beam-on time between manual measures and image-based contouring was + 0.45 min (IQR; 0.2-0.6) and was statistically significant (p < 0.0001), corresponding to an increase of 1.28% beam-on time per treatment, when using image-based contouring. The target location was not associated with beam-on time variation (p = 0.15). Regarding target volume coverage (p = 0.13), prescription isodose volume (p = 0.2), and maximal dose to organs at risk (p = 0.85), no statistical difference was reported between the two skull contour definition techniques.
The beam-on time significantly increased using image-based contouring, resulting in an increase of the total dose delivery per treatment with the new TMR 10 algorithm. Other dosimetric parameters did not differ significantly. This raises the question of other potential impacts. One is potential dose modulation that should be performed as an adjustment to new techniques developments. The second is how this changes the biologically equivalent dose per case, as related to an increased beam on time, delivered dose, etc., and how this potentially changes the radiobiological effects of GKRS in an individual patient.
伽玛刀计划软件（TMR10，Elekta Instruments，AB，瑞典）提供了两种定义颅骨体积的方法，一种是使用手动测量的“历史”方法（一些中心仍在使用），另一种是使用基于图像的颅骨轮廓的新方法。我们的目的是评估在同一患者中连续使用上述两种技术时，剂量计算的潜在变化。
我们将这项自身对照研究纳入了 50 名 2016 年 7 月至 2017 年 1 月期间在瑞士洛桑大学医院接受伽玛刀放射外科治疗的患者，根据治疗部位将患者分为四组：凸面靶区（n=18）、深部靶区（n=13）、前庭神经鞘瘤（n=11）和三叉神经痛（n=8）。每个计划都是使用 2 种颅骨定义技术连续进行的。对于每种治疗，我们记录了每个治疗的照射时间（分钟）、靶区覆盖率（%）、处方等剂量体积（cm）和如果相关的最近的危及器官的最大剂量（Gy），根据每个颅骨定义技术。图像轮廓是使用 CT 扫描分割来完成的，所有患者的窗口均基于标准化。
手动测量与图像轮廓之间的中位照射时间差为+0.45 分钟（IQR；0.2-0.6），具有统计学意义（p<0.0001），当使用图像轮廓时，每次治疗的照射时间增加了 1.28%。靶区位置与照射时间变化无关（p=0.15）。关于靶区覆盖率（p=0.13）、处方等剂量体积（p=0.2）和危及器官的最大剂量（p=0.85），两种颅骨轮廓定义技术之间没有报告统计学差异。
使用基于图像的轮廓会显著增加照射时间，从而导致新 TMR10 算法下每个治疗的总剂量输送增加。其他剂量参数没有显著差异。这引发了其他潜在影响的问题。一种是潜在的剂量调制，应作为新技术发展的调整。另一个是这如何改变每个病例的生物等效剂量，因为照射时间增加、输送剂量等，以及这如何潜在改变个体患者的伽玛刀放射外科的放射生物学效应。
