最大误差图像配准方法对肝癌患者摆位误差及外扩边界的影响

Effects of Maximum Error Image Registration Method on Setup Errors and Extended Boundary of Patients with Liver Cancer

目的利用锥形束CT(CBCT)技术,通过靶区内最大误差图像配准方法,对热塑体膜联合发泡胶固定的肝癌患者进行分次间摆位误差分析研究,确定放射治疗计划临床靶区(CTV)至计划靶区(PTV)的外扩边界,为实现精准治疗提供依据。方法选取2019年10月至2020年3月于医院行放射治疗的肝癌患者30例作为研究对象,均取仰卧位,采用热塑体膜联合发泡胶和Klarity一体板固定。每位患者第1次放射治疗前行CBCT扫描,后续治疗期间每周行1次CBCT扫描,将每次获取的CBCT图像与计划CT图像进行自动+手动配准,得出校正前的摆位误差数据,并在此数据基础上通过靶区内最大误差图像配准方法得出最大误差值,并通过此值计算外扩边界。结果30例患者共扫描150次,左右(LR)、头脚(SI)和前后(AP)方向的摆位误差分别为(0.014±0.287)cm、(0.048±0.363)cm和(0.028±0.229)cm。根据摆位扩边公式,外扩边界=2.5Σ+0.7σ,推算出CTV至PTV的LR、SI和AP方向上的外扩边界分别为0.643、0.771、0.488 cm。结论利用CBCT技术,通过靶区内最大误差图像配准方法,可计算出CTV至PTV的外扩边界,在无图像引导情况下估计适当的外扩边界可为肝癌患者的放射治疗提供参考,以实现精准治疗。

Objective The setup errors of different times of patients with liver cancer fixed by thermoplastic body film combined with styrofoam were analyzed and studied through cone beam CT(CBCT) technology and maximum error image registration method within the target area, and the extended boundary from clinical target volume(CTV) to planned target volume(PTV) of radiotherapy plans were determined, thus providing a basis for clinical accurate treatment. Methods 30 patients with liver cancer who received radiotherapy in the hospital from October 2019 to March 2020 were selected. They were all placed in the supine position and fixed with thermoplastic body film combined with styrofoam and Klarity integrated board. Each patient underwent a CBCT scan before radiotherapy for the first time, and CBCT scans were performed once a week during subsequent treatments. The CBCT images acquired each time were registered with the planned CT images automatically and manually to obtain the setup errors before correction. And then the maximum error was obtained based on the setup errors through maximum error image registration method within the target area, and further the extended boundary was calculated. Results A total of 150 scans were implemented for 30 patients and the setup errors in the left and right(LR), head and foot(SI), and anteroposterior(AP) directions were(0.014±0.287)cm,(0.048±0.363)cm, and(0.028±0.229)cm, respectively. According to Van Herk’s formula, that is, extended boundary equals to 2.5∑+0.7σ, the extended boundaries in LR, SI and AP directions from CTV to PTV were 0.643, 0.771 and 0.488 cm. Conclusion The extended boundary could be calculated through CBCT technology and maximum error image registration method within the target area, providing references for estimating proper extended boundary without image-guided in the radiotherapy of patients with liver cancer to realize accurate treatment.