光学表面成像引导热塑模固定盆腔肿瘤放射治疗的临床可行性研究

Clinical feasibility of optical surface imaging system in guiding thermoplastic body film to fix radiotherapy of pelvic tumors

目的探讨光学表面成像(optical surface imaging,OSI)系统用于引导热塑模固定盆腔肿瘤放射治疗摆位的临床可行性。方法选取2019年1月—5月用热塑模固定盆腔肿瘤的患者20例,首次治疗的患者摆位后进行锥形束CT(cone beam CT,CBCT)验证并纠正摆位误差,用OSI采集患者图像信息作为后期治疗摆位时的参考影像。后期治疗先以传统三点式标记摆位、OSI记录摆位误差数据,CBCT扫描纠正误差后再以OSI监测。以CBCT扫描结果为标准,计算三点式摆位、OSI摆位的系统误差(Σ)、随机误差(σ)与外扩边界。CBCT扫描的结果定义为三点式摆位误差。结果 OSI在左右、头脚、前后方向的系统误差分别为0.14、0.37、0.14 cm,随机误差分别为0.20、0.57、0.23 cm,相应的外扩边界为0.49、1.32、0.51 cm。三点式摆位在左右、头脚、前后方向的系统误差分别为0.13、0.39、0.12 cm,随机误差分别为0.15、0.43、0.13 cm,相应的外扩边界分别为0.43、1.28、0.39 cm。如果以0.8 cm外扩边界进行靶区覆盖率统计,三点式摆位与OSI摆位在左右、头脚及前后方向所占比例分别为100.00%、80.65%、100.00%和100.00%、95.48%、99.35%。经Pearson法分析OSI与CBCT摆位误差相关性,两者在左右、头脚方向呈弱相关(P<0.05),其余方向均无统计学相关(P>0.05)。结论相比传统三点式摆位,OSI并不能提高热塑模固定盆腔肿瘤放射治疗的摆位精度;OSI获取的是热塑模的影像,热塑模与患者实际靶区位置存在较大差异,应在临床运用中改进其使用方法。

Objective To investigate the clinical feasibility of optical surface imaging(OSI) system in guiding thermoplastic body film to fix radiotherapy of pelvic tumors. Methods From January to May in 2019, 20 pelvic tumor patients fixed with thermoplastic films were selected. After the first treatment, cone beam CT(CBCT) was performed to verify and correct the setup errors. OSI was used to collect the patient’s image information as the reference image for the later treatment setup. The later treatment was performed by traditional three-point setup, and OSI was used to record the setup data and monitor the treatment. CBCT scan results were taken as the standard, to calculate the system error(Σ), random error(σ) and margin of three-point and OSI setup. The result of CBCT scan was defined as three-point setup error. Results In lateral-medial, superior-inferior, and anterior-posterior directions, the OSI system errors were0.14, 0.37, and 0.14 cm, respectively, the random errors were 0.20, 0.57, and 0.23 cm, respectively, and the corresponding margins were 0.49, 1.32, and 0.51 cm, respectively;the three-point setup system errors were 0.13, 0.39, and 0.12 cm,respectively, the random errors were 0.15, 0.43, and 0.13 cm, respectively, and the corresponding margins were 0.43, 1.28,and 0.39 cm, respectively. If the target coverage rate was counted at the 0.8 cm outward margin, the proportions of the three-point setup in lateral-medial, superior-inferior and anterior-posterior were 100.00%, 80.65%, and 100.00%,respectively, and those of the OSI setup were 100.00%, 95.48%, and 99.35%, respectively. Pearson analysis showed that the weakly correlation of lateral-medial, superior-inferior directions had statistical significance(P<0.05), and there was no statistical significance in the other directions(P>0.05). Conclusions Compared with the traditional three-point setup,OSI cannot improve the setup precision of thermoplastic body film fixation in pelvic tumor radiotherapy. OSI acquired the image of thermoplastic phantom, which is quite different from the actual target location of the patient. OSI application method should be improved in clinical application.