Department of Radiation Medicine, University of Kentucky, Lexington, Kentucky 40536, USA.
Med Phys. 2013 Sep;40(9):091714. doi: 10.1118/1.4818825.
To assess the hypothesis that the volume of whole brain that receives a certain dose level is primarily dependent on the treated volume rather than on the number, shape, or location of the lesions. This would help a physician validate the suitability of GammaKnife(®) based stereotactic radiosurgery (GKSR) prior to treatment.
Simulation studies were performed to establish the hypothesis for both oblong and spherical shaped lesions of various numbers and sizes. Forty patients who underwent GKSR [mean age of 54 years (range 7-80), mean number of lesions of 2.5 (range 1-6), and mean lesion volume of 4.4 cm(3) (range 0.02-22.2 cm(3))] were also studied retrospectively. Following recommendations of QUANTEC, the volume of brain irradiated by the 12 Gy (VB12) isodose line was measured and a power-law based relation is proposed here for estimating VB12 from the known tumor volume and the prescription dose.
In the simulation study on oblong, spherical, and multiple lesions, the volume of brain irradiated by 50%, 10%, and 1% of maximum dose was found to have linear, linear, and exponentially increasing dependence on the volume of the treated region, respectively. In the retrospective study on 40 GKSR patients, a similar relationship was found to predict the brain dose with a Spearman correlation coefficient >0.9. In both the studies, the volume of brain irradiated by a certain dose level does not have a statistically significant relationship (p ≥ 0.05) with the number, shape, or position of the lesions. The measured VB12 agrees with calculation to within 1.7%.
The results from the simulation and the retrospective clinical studies indicate that the volume of whole brain that receives a certain percentage of the maximum dose is primarily dependent on the treated volume and less on the number, shape, and location of the lesions.
评估这样一种假设，即接收特定剂量水平的整个大脑体积主要取决于治疗体积，而不是病变的数量、形状或位置。这将有助于医生在治疗前验证基于伽玛刀（®）的立体定向放射外科（GKSR）的适用性。
进行了模拟研究，以验证各种数量和大小的长形和球形病变的假设。还回顾性研究了 40 名接受 GKSR 治疗的患者[平均年龄 54 岁（范围 7-80），平均病变数为 2.5（范围 1-6），平均病变体积为 4.4cm³（范围 0.02-22.2cm³）]。根据 QUANTEC 的建议，测量了 12Gy（VB12）等剂量线照射的脑体积，并提出了一种基于幂律的关系，用于根据已知肿瘤体积和处方剂量估计 VB12。
在长形、球形和多个病变的模拟研究中，发现 50%、10%和 1%最大剂量照射的脑体积与治疗区域的体积呈线性、线性和指数增长关系。在 40 名 GKSR 患者的回顾性研究中，发现了类似的关系，可以用 Spearman 相关系数>0.9 预测脑剂量。在这两项研究中，特定剂量水平照射的脑体积与病变的数量、形状或位置均无统计学显著关系（p≥0.05）。测量的 VB12 与计算值相差 1.7%以内。
模拟和回顾性临床研究的结果表明，接收特定百分比最大剂量的整个大脑体积主要取决于治疗体积，而病变的数量、形状和位置的影响较小。
