Hacker F, Bondeson J, Lewis J, Mannarino E, Friesen S, Balboni T, Alexander B, Sher D
Brigham and Women's Hospital, Boston, Massachusetts.
Dana-Farber Cancer Institute, Boston, Massachusetts.
Med Phys. 2012 Jun;39(6Part16):3796. doi: 10.1118/1.4735490.
Quantify initial setup accuracy and intra-fraction motion using stereotactic body frames (SBF) for spine SBRT.
10 patients (11 sites, 31 fractions) treated with spine SBRT using SBF immobilization were evaluated for initial setup accuracy and intra-fraction motion. Either the commercial Elekta SBF or an in-house developed SBF (BHS-SBF) were used. The BHS-SBF uses the same setup/immobilization principle as the Elekta but with increased interior space and couch indexing. Both frames include sidewalls to conform the vac-loc rigidly to the patient's sides. All patients were setup using the Brainlab ExacTrac system which includes IR and stereoscopic kV x-ray based positioning. Patients were initially positioned in the frame using skin tattoos then shifted to treatment isocenter based on IR markers affixed to the frame with known geometry relative to isocenter. kV imaging was acquired and automatic 6-D bony fusion performed. Resulting translations and rotations give the initial setup accuracy. Calculated shifts and rotations were performed using a robotic couch and verification imaging acquired. The imaging/fusion process was repeated multiple times during treatment providing intra-fraction motion data.
Mean initial setup error in the VRT, LNG and LAT directions was 0.1+/-3.0 mm (0.1+/-0.6 deg), 0.5+/-5.2 mm (0.1+/-1.1 deg) and -0.3+/- 3.7 mm (0.4+/-0.8 deg) respectively. Mean 3-D error magnitude was 6.6 mm with a 95% certainty of 11.2 mm. Mean intra-fraction shifts observed in the VRT, LNG and LAT directions were -0.1+/-0.4 mm, -0.1+/-0.4 mm and 0.1+/-0.3 mm respectively. Mean 3-D intra-fraction shift magnitude was 0.6 mm with a 95% certainty of 1.4 mm. No significant difference was observed between the SBFs.
Patient positioning is not sufficiently reproducible with the evaluated SBF to allow non-image guided treatment. However, provided image guidance is used for patient positioning, these frames provide excellent immobilization which is on par with mask based cranial radiosurgery.
使用立体定向体架（SBF）对脊柱立体定向放射治疗（SBRT）的初始设置精度和分次内运动进行量化。
对10例使用SBF固定进行脊柱SBRT治疗的患者（11个部位，31次分次）的初始设置精度和分次内运动进行评估。使用了商业的医科达SBF或内部开发的SBF（BHS-SBF）。BHS-SBF使用与医科达相同的设置/固定原理，但内部空间更大且有治疗床索引功能。两种体架都包括侧壁，以使真空定位垫牢固地贴合患者身体两侧。所有患者均使用Brainlab ExacTrac系统进行设置，该系统包括基于红外和立体千伏X射线的定位。患者最初通过皮肤纹身定位在体架中，然后根据固定在体架上且相对于等中心具有已知几何关系的红外标记物转移到治疗等中心。采集千伏成像并进行自动6维骨融合。由此得到的平移和旋转给出初始设置精度。使用机器人治疗床和采集的验证成像进行计算的移位和旋转。在治疗过程中多次重复成像/融合过程，以提供分次内运动数据。
在垂直（VRT）、左右（LNG）和前后（LAT）方向上的平均初始设置误差分别为0.1±3.0毫米（0.1±0.6度）、0.5±5.2毫米（0.1±1.1度）和-0.3±3.7毫米（0.4±0.8度）。平均三维误差幅度为6.6毫米，95%置信度为11.2毫米。在VRT、LNG和LAT方向上观察到的平均分次内移位分别为-0.1±0.4毫米、-0.1±0.4毫米和0.1±0.3毫米。平均三维分次内移位幅度为0.6毫米，95%置信度为1.4毫米。两种SBF之间未观察到显著差异。
使用评估的SBF进行患者定位的重复性不足以允许非图像引导治疗。然而，如果使用图像引导进行患者定位，这些体架可提供与基于面罩的颅脑放射外科相当的出色固定效果。
