Jeon Seung Hyuck, Kim Jin Ho
Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea.
Radiat Oncol J. 2018 Jun;36(2):122-128. doi: 10.3857/roj.2017.00591. Epub 2018 Jun 29.
To investigate positional uncertainty and its correlation with clinical parameters in spine stereotactic body radiotherapy (SBRT) using thermoplastic mask (TM) immobilization. Materials and.
A total of 21 patients who underwent spine SBRT for cervical or upper thoracic spinal lesions were retrospectively analyzed. All patients were treated with image guidance using cone beam computed tomography (CBCT) and 4 degrees-of-freedom (DoF) positional correction. Initial, pre-treatment, and post-treatment CBCTs were analyzed. Setup error (SE), pre-treatment residual error (preRE), post-treatment residual error (postRE), intrafraction motion before treatment (IM1), and intrafraction motion during treatment (IM2) were determined from 6 DoF manual rigid registration.
The three-dimensional (3D) magnitudes of translational uncertainties (mean ± 2 standard deviation) were 3.7±3.5 mm (SE), 0.9±0.9 mm (preRE), 1.2±1.5 mm (postRE), 1.4±2.4 mm (IM1), and 0.9±1.0 mm (IM2), and average angular differences were 1.1°±1.2° (SE), 0.9°±1.1° (preRE), 0.9°±1.1° (postRE), 0.6°±0.9° (IM1), and 0.5°±0.5° (IM2). The 3D magnitude of SE, preRE, postRE, IM1, and IM2 exceeded 2 mm in 18, 0, 3, 3, and 1 patients, respectively. No association were found between all positional uncertainties and body mass index, pain score, and treatment location (p > 0.05, Mann-Whitney test). There was a tendency of intrafraction motion to increase with overall treatment time; however, the correlation was not statistically significant (p > 0.05, Spearman rank correlation test).
In spine SBRT using TM immobilization, CBCT and 4 DoF alignment correction, a minimum residual translational uncertainty was 2 mm. Shortening overall treatment time and 6 DoF positional correction may further reduce positional uncertainties.
探讨在使用热塑性面罩（TM）固定技术的脊柱立体定向体部放射治疗（SBRT）中，位置不确定性及其与临床参数的相关性。材料与方法：回顾性分析21例因颈椎或上胸椎病变接受脊柱SBRT的患者。所有患者均采用锥形束计算机断层扫描（CBCT）图像引导和四自由度（DoF）位置校正进行治疗。分析初始、治疗前和治疗后的CBCT图像。通过六自由度手动刚性配准确定摆位误差（SE）、治疗前残余误差（preRE）、治疗后残余误差（postRE）、治疗前分次内运动（IM1）和治疗中分次内运动（IM2）。结果：平移不确定性的三维（3D）幅度（均值±2标准差）分别为3.7±3.5mm（SE）、0.9±0.9mm（preRE）、1.2±1.5mm（postRE）、1.4±2.4mm（IM1）和0.9±1.0mm（IM2），平均角度差异分别为1.1°±1.2°（SE）、0.9°±1.1°（preRE）、0.9°±1.1°（postRE）〕、0.6°±0.9°（IM1）和0.5°±0.5°（IM2）。SE、preRE、postRE、IM1和IM2的3D幅度分别在18、0、3、3和1例患者中超过2mm。所有位置不确定性与体重指数、疼痛评分和治疗部位之间均未发现相关性（p>0.05，曼-惠特尼检验）。分次内运动有随总治疗时间增加的趋势；然而，相关性无统计学意义（p>0.05，斯皮尔曼等级相关检验）。结论：在使用TM固定技术、CBCT和四自由度对准校正的脊柱SBRT中，最小残余平移不确定性为2mm。缩短总治疗时间和六自由度位置校正可能进一步降低位置不确定性。
