Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN, USA.
J Appl Clin Med Phys. 2010 Oct 11;11(4):3388. doi: 10.1120/jacmp.v11i4.3388.
The purpose was to quantify the setup margin for pediatric patients with neuro-blastoma using cone beam CT imaging (CBCT) and ultrasound localization. Ten patients, with a median age of 4.3 years (1.8 to 7.9) underwent daily pretreatment localization CBCT and every other day post-treatment CBCT to calculate interfractional and intrafraction movement. Localization was based on CBCT to treatment planning CT registration in the lumbar spine region. Each subject was treated in the supine position under IV general anesthesia using intensity-modulated radiation therapy. Patients were repositioned based on the daily pretreatment CBCT. Required setup margins based on inter- and intrafraction positioning errors were calculated based on weekly and daily imaging scenarios. Four patients had ultra-sound localization of the kidneys performed before the CBCT. Correlation between daily CBCT and ultrasound was investigated. A lateral, longitudinal and vertical setup margin of 5.4, 5.6, and 5.9 mm is required without daily CBCT. When daily CBCT was incorporated, the setup margin was reduced to 1.5, 2.1, and 1.7 mm. There was no correlation between the suggested ultrasound shifts and the shifts based on the CBCT. Daily localization based on CBCT of the lumbar spine can reduce the required setup margin for neuroblastoma patients, thereby reducing normal tissue exposure for this young patient population. The internal margin needs further investigation before PTV reduction can be made. Ultrasound localization was highly variable and not correlated to CBCT shifts.
目的是使用锥形束 CT 成像（CBCT）和超声定位来量化神经母细胞瘤患儿的治疗前摆位裕度。10 名患者，中位年龄为 4.3 岁（1.8 至 7.9），每天进行预处理定位 CBCT 和每隔一天进行治疗后 CBCT，以计算分次间和分次内运动。定位基于 CBCT 到腰椎区域的治疗计划 CT 配准。每位患者均在 IV 全身麻醉下仰卧位接受调强放疗。根据每日预处理 CBCT 重新定位患者。根据每周和每日成像情况，计算基于分次内和分次间定位误差的所需摆位裕度。有 4 名患者在 CBCT 前进行了肾脏的超声定位。研究了每日 CBCT 和超声之间的相关性。无每日 CBCT 时，侧位、纵向和垂直的摆位裕度分别为 5.4、5.6 和 5.9mm。当纳入每日 CBCT 时，摆位裕度降低至 1.5、2.1 和 1.7mm。提示的超声移位与基于 CBCT 的移位之间没有相关性。基于腰椎 CBCT 的每日定位可以减少神经母细胞瘤患者所需的治疗前摆位裕度，从而减少该年轻患者群体的正常组织暴露。在进行 PTV 缩小之前，还需要进一步研究内部裕度。超声定位的变化性很大，与 CBCT 移位没有相关性。
