Yamoah Kosj, Zaorsky Nicholas G, Siglin Joshua, Shi Wenyin, Werner-Wasik Maria, Andrews David W, Dicker Adam P, Bar-Ad Voichita, Liu Haisong
Department of Radiation Oncology, Jefferson Medical College and Kimmel Cancer Center of Thomas Jefferson University, Philadelphia, USA.
Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, USA.
Int J Med Phys Clin Eng Radiat Oncol. 2014 Feb;3(1):1-8. doi: 10.4236/ijmpcero.2014.31001.
To determine the precision of our institution's current immobilization devices for spine SBRT, ultimately leading to recommendations for appropriate planning margins.
We identified 12 patients (25 treatments) with spinal metastasis treated with spine Stereotactic Body Radiation Therapy (SBRT). The Body-FIX system was used as immobilization device for thoracic (T) and lumbar (L) spine lesions. The head and shoulder mask system was used as immobilization device for cervical (C) spine lesions. Initial patient setup used the infrared positioning system with body markers. Stereotactic X-ray imaging was then performed and correction was made if the initial setup error exceeded predetermined institutional tolerances, 1.5 mm for translation and 2° for rotation. Three additional sets of verification X-rays were obtained pre-, mid-, and post-treatment for all treatments.
Intrafraction motion regardless of immobilization technique was found to be 1.28 ± 0.57 mm. The mean and standard deviation of the variances along each direction were as follows: Superior-inferior, 0.56 ± 0.39 mm and 0.77 ± 0.52 mm, ( = 0.25); Anterior-posterior, 0.57 ± 0.43 mm and 1.14 ± 0.61 mm, ( = 0.01); Left-right, 0.48 ± 0.34 mm and 0.74 ± 0.40 mm, ( = 0.09) respectively. There was a significantly greater difference in the average 3D variance of the BodyFIX as compared to the head and shoulder mask immobilization system, 1.04 ± 0.46 mm and 1.71 ± 0.52 mm; ( = 0.003) respectively.
Overall, our institution's image guidance system using stereotactic X-ray imaging verification provides acceptable localization accuracy as previously defined in the literature. We observed a greater intrafraction motion for the head and shoulder mask as compared with the BodyFIX immobilization system, which may be a result of greater C-spine mobility and/or the suboptimal mask immobilization. Thus, better immobilization techniques for C-spine SBRT are needed to reduce setup error and intrafraction motion. We are currently exploring alternative C-spine immobilization techniques to improve set up accuracy and decrease intrafraction motion during treatment.
确定本机构当前用于脊柱立体定向放射治疗（SBRT）的固定装置的精度，最终为合适的计划靶区边缘提出建议。
我们确定了12例接受脊柱立体定向体部放射治疗（SBRT）的脊柱转移瘤患者（25次治疗）。Body-FIX系统用作胸部（T）和腰部（L）脊柱病变的固定装置。头部和肩部面罩系统用作颈椎（C）脊柱病变的固定装置。初始患者摆位使用带有身体标记物的红外定位系统。然后进行立体定向X线成像，如果初始摆位误差超过预定的机构公差（平移1.5mm，旋转2°），则进行校正。所有治疗在治疗前、治疗中和治疗后均额外获取三组验证性X线片。
无论采用何种固定技术，分次治疗期间的运动为1.28±0.57mm。各方向上的方差均值和标准差如下：上下方向，0.56±0.39mm和0.77±0.52mm，（P=0.25）；前后方向，0.57±0.43mm和1.14±0.61mm，（P=0.01）；左右方向，分别为0.48±0.34mm和0.74±0.40mm，（P=0.09）。与头部和肩部面罩固定系统相比，BodyFIX的平均三维方差差异显著更大，分别为1.04±0.46mm和1.71±0.52mm；（P=0.003）。
总体而言，我们机构使用立体定向X线成像验证的图像引导系统提供了如先前文献中所定义的可接受的定位精度。与BodyFIX固定系统相比，我们观察到头部和肩部面罩的分次治疗期间运动更大，这可能是由于颈椎活动度更大和/或面罩固定欠佳所致。因此，需要更好的颈椎SBRT固定技术来减少摆位误差和分次治疗期间的运动。我们目前正在探索替代的颈椎固定技术，以提高摆位精度并减少治疗期间的分次治疗期间运动。
