Mikami Mari, Yoshida Ken, Takenaka Tadashi, Yamazaki Hideya, Kotsuma Tadayuki, Yoshida Mineo, Aramoto Kazumasa, Yamada Shigetoshi, Ban Chiaki, Tanaka Eiichi, Honda Kazuya
Department of Radiology, National Hospital Organization Osaka National Hospital, Osaka, Japan.
Brachytherapy. 2011 Jul-Aug;10(4):318-24. doi: 10.1016/j.brachy.2010.11.006. Epub 2011 Jan 14.
We investigated daily needle applicator displacement during high-dose-rate interstitial brachytherapy.
Ten patients with previously untreated uterine cervical cancer received 30Gy in five fractions during 3 days of high-dose-rate interstitial brachytherapy combined with external beam radiotherapy using our unique ambulatory technique. To analyze displacement, we obtained daily computed tomography (CT) images for 147 flexible needle applicators at 21 and 45h after implantation. The distance was defined as the length between the center of gravity of titanium markers and the needle applicator tips along the daily CT axis. We adapted dwell positions of the treatment source to cover clinical target volume with a 15-mm cranial margin.
The median displacement was 1mm (range, -6 to 12mm) at 21h and 2mm (range, -9 to 14mm) at 45h, respectively. Statistically significant caudal displacement was observed only between the displacement at 0 and 21h (p<0.0001), and not between the displacement at 21 and 45h (p=0.1). In cases with displacement of 3mm or more, we changed dwell positions to correct the treatment plan. We corrected 45 applicators (31%) at 21h and 67 (46%) at 45h.
We investigated needle applicator displacement in our ambulatory technique using daily CT examination and considered that a 15-mm cranial margin was sufficient to cover clinical target volume.
我们研究了高剂量率组织间近距离放射治疗期间每日施源器的位移情况。
10例未经治疗的子宫颈癌患者在3天的高剂量率组织间近距离放射治疗联合外照射放疗过程中，采用我们独特的门诊技术分5次接受30Gy照射。为分析位移情况，我们在植入后21小时和45小时获取了147个柔性施源器的每日计算机断层扫描（CT）图像。位移距离定义为钛标记物重心与施源器尖端沿每日CT轴的长度。我们调整了治疗源的驻留位置，以在临床靶区上方留出15毫米的边缘来覆盖临床靶体积。
21小时时的中位位移为1毫米（范围为-6至12毫米），45小时时为2毫米（范围为-9至14毫米）。仅在0小时和21小时的位移之间观察到有统计学意义的尾端位移（p<0.0001），而在21小时和45小时的位移之间未观察到（p=0.1）。对于位移3毫米或更大的情况，我们改变驻留位置以校正治疗计划。我们在21小时校正了45个施源器（31%），在45小时校正了67个（46%）。
我们通过每日CT检查研究了门诊技术中施源器的位移情况，并认为15毫米的颅侧边缘足以覆盖临床靶体积。
