Takeda Atsuya, Kunieda Etsuo, Sanuki Naoko, Ohashi Toshio, Oku Yohei, Sudo Yasunobu, Iwashita Hideo, Ooka Yoshikazu, Aoki Yosuke, Shigematsu Naoyuki, Kubo Atsushi
Department of Radiology, Ofuna Chuo Hospital, Kanagawa, Japan.
Int J Radiat Oncol Biol Phys. 2009 Jun 1;74(2):363-9. doi: 10.1016/j.ijrobp.2008.08.012.
We have used dynamic conformal multiple arc therapy (DCMAT) for stereotactic body radiotherapy (SBRT) since 2001. We investigated the consistency of DCMAT for SBRT using dose-volume histogram analysis.
A total of 50 patients with peripheral lung tumors underwent SBRT. The median tumor diameter was 2.4 cm (range, 0.9-5.9). Treatment planning was performed using a superposition algorithm. The prescribed 50 Gy dose was divided into five fractions. The prescribed dose was defined as 80% of the maximal dose in the planning target volume (PTV), and the leaf margins were modified to ensure the PTV was included in the 80% isodose surface. The dose-volume histogram analysis was used to assess the PTV and normal lung volume.
The median dose covering 95% of the PTV was 50.27 Gy (range, 46.14-52.67), essentially consistent with the prescribed dose. The median homogeneity and conformity index was 1.41 (range, 1.31-1.53) and 1.73 (range, 1.41-2.21), respectively. The median volume of lung receiving > or =20 Gy (V(20)) was 4.2% (range, 1.4-10.2%). A linear correlation was found between the tumor diameter and V(20), and an even stronger correlation was found between the PTV/(normal lung volume) and V(20). The estimated V(20) was 7.1% (range, 3.9-10.4%) for a 5-cm-diameter tumor, assumed to be the maximal size limitation for SBRT.
SBRT with DCMAT achieved high conformity and delivered adequate doses within the PTV. The median dose covering 95% of the PTV was consistent with the prescribed dose. V(20) can be estimated using the tumor diameter and normal lung volume. DCMAT was thus both a feasible and a reproducible method of SBRT delivery.
自2001年以来，我们一直使用动态适形多弧治疗（DCMAT）进行立体定向体部放射治疗（SBRT）。我们使用剂量体积直方图分析研究了DCMAT用于SBRT的一致性。
共有50例周围型肺肿瘤患者接受了SBRT。肿瘤中位直径为2.4 cm（范围0.9 - 5.9）。使用叠加算法进行治疗计划。规定的50 Gy剂量分为五等份。规定剂量定义为计划靶体积（PTV）中最大剂量的80%，并调整叶片边缘以确保PTV包含在80%等剂量面内。使用剂量体积直方图分析评估PTV和正常肺体积。
覆盖95% PTV的中位剂量为50.27 Gy（范围46.14 - 52.67），与规定剂量基本一致。中位均匀性指数和适形指数分别为1.41（范围1.31 - 1.53）和1.73（范围1.41 - 2.21）。接受≥20 Gy照射的肺中位体积（V(20)）为4.2%（范围1.4 - 10.2%）。发现肿瘤直径与V(20)之间存在线性相关性，并且PTV/（正常肺体积）与V(20)之间存在更强的相关性。对于直径为5 cm的肿瘤（假定为SBRT的最大尺寸限制），估计的V(20)为7.1%（范围3.9 - 10.4%）。
采用DCMAT的SBRT实现了高度适形，并在PTV内给予了足够的剂量。覆盖95% PTV的中位剂量与规定剂量一致。可使用肿瘤直径和正常肺体积估计V(20)。因此，DCMAT是一种可行且可重复的SBRT实施方法。
