Kim Jina, Jang Hong Seok, Kim Yeon Sil, Choi Byung Ock, Kang Young-Nam
Department of Biomedicine Health Sciences, The Catholic University of Korea, Seoul 06591, Republic of Korea; Department of Radiation Oncology, Seoul St. Mary's hospital, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea.
Department of Radiation Oncology, Seoul St. Mary's hospital, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea; Advanced Institute for Radiation Fusion Medical Technology, The Catholic University of Korea, Seoul 06591, Republic of Korea.
Med Dosim. 2017;42(3):210-215. doi: 10.1016/j.meddos.2017.04.001. Epub 2017 May 16.
Stereotactic body radiotherapy (SBRT) delivers a highly conformal, hypofractionated radiation dose to a small target with minimal radiation applied to the surrounding areas. Therefore, using the proper treatment planning techniques for SBRT is important. Intensity modulation techniques, such as static intensity-modulated radiation therapy (IMRT), modulated arc therapy (mARC), and helical tomotherapy (HT), are useful for spinal SBRT because of a rapid dose fall-off and spinal cord avoidance. This study compared the planning characteristics for hypofractionated spinal SBRT administered using 3 treatment techniques. The factors evaluated for spinal SBRT planning were dose coverage, cord avoidance, target conformity, homogeneity, and dose spillage. Target coverage was 82.74% ± 3.35%, 80.92% ± 0.81%, and 85.01% ± 7.27% for IMRT, mARC, and HT, respectively. HT was therefore a powerful technique with respect to target coverage. The spinal cord dose for HT (mean, 1763.96 cGy; standard deviation [SD], 164.48) was significantly different from those for mARC (mean, 1991.75 cGy; SD, 248.00) and IMRT (mean, 2053.24 cGy; SD, 164.48). In addition, the partial spinal cord volume at 2000 cGy for HT (mean, 0.12 cc, SD, 0.01) was significantly different from those for IMRT and mARC (0.50 ± 0.10 cc and 0.56 ± 0.25 cc, respectively). The conformity index was 1.30 ± 0.12, 1.08 ± 0.05, and 1.36 ± 0.23 for IMRT, mARC, and HT planning, respectively. mARC showed the highest conformity (p = 0.000). HT used a narrow field fan beam and exhibited remarkable improvement of target coverage and cord dose, offering an important benefit to spinal SBRT. mARC had the highest target conformity and better high- and intermediate-dose spillage than HT and IMRT did, respectively. These planning techniques have different advantages. In the case of spine SBRT, HT should be used for cord avoidance. In some cases, such as for a short treatment duration when the patient is considered to be in a poor general condition, mARC can be used.
立体定向体部放疗（SBRT）可将高度适形的低分割放射剂量精准投送至小靶区，同时对周围区域施加最小剂量的辐射。因此，采用恰当的SBRT治疗计划技术至关重要。强度调制技术，如静态调强放射治疗（IMRT）、调强弧形治疗（mARC）和螺旋断层放疗（HT），由于剂量跌落迅速且能避开脊髓，在脊柱SBRT中很有用。本研究比较了采用3种治疗技术进行低分割脊柱SBRT的计划特征。评估脊柱SBRT计划的因素包括剂量覆盖、脊髓避让、靶区适形性、均匀性和剂量泄漏。IMRT、mARC和HT的靶区覆盖率分别为82.74%±3.35%、80.92%±0.81%和85.01%±7.27%。因此，就靶区覆盖而言，HT是一种强大的技术。HT的脊髓剂量（平均值为1763.96 cGy；标准差[SD]为164.48）与mARC（平均值为1991.75 cGy；SD为248.00）和IMRT（平均值为2053.24 cGy；SD为164.48）的脊髓剂量有显著差异。此外，HT在2000 cGy时的部分脊髓体积（平均值为0.12 cc，SD为0.01）与IMRT和mARC的部分脊髓体积（分别为0.50±0.10 cc和0.56±0.25 cc）有显著差异。IMRT、mARC和HT计划的适形指数分别为1.30±0.12、1.08±0.05和1.36±0.23。mARC显示出最高适形性（p = 0.000）。HT使用窄野扇形束，在靶区覆盖和脊髓剂量方面有显著改善，为脊柱SBRT带来重要益处。mARC具有最高的靶区适形性，且在高剂量和中剂量泄漏方面分别优于HT和IMRT。这些计划技术各有不同优势。在脊柱SBRT中，应使用HT来避让脊髓。在某些情况下，例如当患者一般状况较差且治疗时间较短时，可使用mARC。
