Baltz Garrett C, Briere Tina, Luo Dershan, Howell Rebecca M, Krafft Shane, Han Eun Young
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
J Appl Clin Med Phys. 2020 Sep;21(9):6-15. doi: 10.1002/acm2.12956. Epub 2020 Jun 30.
Frameless Gamma Knife stereotactic radiosurgery (SRS) uses a moldable headrest with a thermoplastic mask for patient immobilization. An efficacious headrest is time consuming and difficult to fabricate due to the expertise required to mold the headrest within machine geometrical limitations. The purpose of this study was to design and validate a three-dimensional (3D)-printed headrest for frameless Gamma Knife SRS that can overcome these difficulties.
A headrest 3D model designed to fit within the frameless adapter was 3D printed. Dosimetric properties of the 3D-printed headrest and a standard-of-care moldable headrest were compared by delivering a Gamma Knife treatment to an anthropomorphic head phantom fitted with an ionization chamber and radiochromic film. Ionization measurements were compared to assess headrest attenuation and a gamma index was calculated to compare the film dose distributions. A volunteer study was conducted to assess the immobilization efficacy of the 3D-printed headrest compared to the moldable headrest. Five volunteers had their head motion tracked by a surface tracking system while immobilized in each headrest for 20 min. The recorded motion data were used to calculate the average volunteer movement and a paired t-test was performed.
The ionization chamber readings were within 0.55% for the 3D-printed and moldable headrests, and the calculated gamma index showed 98.6% of points within dose difference of 2% and 2 mm distance to agreement for the film measurement. These results demonstrate that the headrests were dosimetrically equivalent within the experimental uncertainties. Average motion (±standard deviation) of the volunteers while immobilized was 1.41 ± 0.43 mm and 1.36 ± 0.51 mm for the 3D-printed and moldable headrests, respectively. The average observed volunteer motion between headrests was not statistically different, based on a P-value of 0.466.
We designed and validated a 3D-printed headrest for immobilizing patients undergoing frameless Gamma Knife SRS.
无框架伽玛刀立体定向放射外科手术（SRS）使用带有热塑性面罩的可塑形头枕来固定患者。由于需要在机器几何限制内对头枕进行塑形的专业知识，一个有效的头枕制作耗时且困难。本研究的目的是设计并验证一种用于无框架伽玛刀SRS的三维（3D）打印头枕，以克服这些困难。
设计了一个适合无框架适配器的头枕3D模型并进行3D打印。通过对配备电离室和放射变色胶片的人体头部模型进行伽玛刀治疗，比较3D打印头枕和标准护理可塑形头枕的剂量学特性。比较电离测量以评估头枕衰减，并计算伽玛指数以比较胶片剂量分布。进行了一项志愿者研究，以评估3D打印头枕与可塑形头枕相比的固定效果。五名志愿者在分别固定于每个头枕中20分钟时，通过表面跟踪系统跟踪其头部运动。记录的运动数据用于计算志愿者的平均运动，并进行配对t检验。
3D打印头枕和可塑形头枕的电离室读数在0.55%以内，计算出的伽玛指数显示，在胶片测量中，98.6%的点在剂量差异2%和距离一致性2毫米范围内。这些结果表明，在实验不确定性范围内，头枕在剂量学上是等效的。3D打印头枕和可塑形头枕固定时志愿者的平均运动（±标准差）分别为1.41±0.43毫米和1.36±0.51毫米。基于P值0.466，头枕之间观察到的志愿者平均运动在统计学上没有差异。
我们设计并验证了一种用于固定接受无框架伽玛刀SRS治疗患者的3D打印头枕。
