光学表面成像在胸部肿瘤放射治疗中的实用性研究

Clinical applicability of optical surface imaging system in thorax tumor radiation therapy

目的评估光学表面成像(OSI)系统在胸部肿瘤放射治疗中纠正摆位误差的临床价值。方法选择2015年2月至10月四川大学华西医院胸部肿瘤放射治疗病人11例(113例次放射治疗),其中男性8例(89例次有效照射),女性3例(24例次有效照射);年龄46~77岁,平均年龄59岁。原发性肺癌6例,转移性肺癌3例,食管癌2例。均采用仰卧位热塑体膜固定,双手抱肘交叉放于前额。病人首次治疗前行锥形束CT(CBCT)扫描纠正摆位误差后,用OSI系统获取体表图像作为参考图像。从第二次治疗开始以参考图像为准用OSI系统进行预摆位,然后行CBCT扫描验证。记录两个系统每次扫描配准得出的误差数据并进行分析。结果 CBCT配准的分次间摆位误差平移方向x(左右)、y(头脚)、z(前后)和旋转方向rx(PIT)、ry(ROL)、rz(ROT)的结果分别为(-0.83±3.15)mm、(-1.40±3.89)mm、(0.71±2.08)mm和(0.29±0.76)°、(0.36±0.81)°、(0.10±1.00)°;OSI系统配准的分次间摆位误差分别为(0.01±1.34)mm、(-0.12±1.26)mm、(-0.26±1.19)mm和(-0.14±0.57)°、(0.10±0.60)°、(-0.25±0.69)°。两系统相减得出的平移方向x(左右)、y(头脚)、z(前后)和旋转方向rx(PIT)、ry(ROL)、rz(ROT)的结果分别为(-0.85±3.42)mm、(-1.29±3.80)mm、(0.98±2.38)mm和(0.42±0.98)°、(0.26±1.16)°、(0.36±1.24)°(P<0.05)。x、y、z三个方向上的平移误差相减后的标准差分别为3.42 mm、3.80 mm、2.38 mm。两套系统在旋转上的差异很小,标准差近1°。Catalyst^(TM)系统c-motion检测到的分次内误差,放射治疗过程中平移方向x、y、z方向分别为(-0.17±1.25)mm、(0.47±1.42)mm、(-0.17±1.96)mm,旋转方向rx、ry、rz分别为(-0.04±0.51)°、(0.13±0.42)°、(-0.19±0.76)°,各个方向最大偏离值(DEV)为(2.54±1.10)mm。结论 OSI系统与CBCT系统在探测与纠正胸部肿瘤放疗摆位误差上具有一定的差异性。OSI系统可以实时监测放疗分次内误差,由于胸部放射治疗摆位误差受多种因素影响,OSI系统与CBCT系统相结合的综合使用策略还需进一步研究。

Objective To evaluate the clinical applicability of the optical surface imaging（OSI） system in thorax tumor radiation therapy. Methods From February to October in 2015, 11 patients（ll3 radiation therapy fractions） with thorax tumor radiation therapy were enrolled, which included 8 males（89 radiation therapy fractions） and 3 females（24 radiation therapy fractions）, aged 46 - 77 years old with mean age of 59 years old. Among 11 patients, 6 were primary lung cancer, 3 were metastatic lung can- cer and 2 were esophageal cancer. All of them were fixed with heat plastic in supine position, and hands crossed with elbows on forehead. Before the first treatment, the cone beam computed tomography（CBCT） scan was given and corrected the displace- ment error, then OSI system was used to acquire body surface image as the reference image. From the second time, corrected the set-up error with the reference image of OSI system, then CBCT scan was given, and the set-up error data of each scan in 2 systems were recorded and analyzed. Results The results of translational error in CBCT registration x（left and right）, y（head and foot）, z（front and back）, and rotation directions rx（PIT）, ty（ROL）, and rz（ROT） was （- 0.83 ± 3.15） mm, （- 1.40 ± 3.89） mm, （0.71 ±2.08） mm and （0.29 ± 0.76）°, （0.36 ± 0.81）°, （0.10 ± 1.00）°, respectively; OSI was （0.01 ± 1.34） mm, （- 0.12 ±1.26） mm, （- 0.26 ± 1.19） mm and （- 0.14 ± 0.57）°, （0.10 ± 0.60）°, （- 0.25 ± 0.69）°, respectively. Subtraction two system, the result was （- 0.85 ± 3.42） mm, （- 1.29 ± 3.80） mm, （0.98 ± 2.38） mm, （0.42 ± 0.98）°, （0.26 ± 1.16）°and （0.36 ± 1.24）°, respectively（P 〈 0.05）. The standard deviations after subtraction translation errors in x, y and z was 3.42 mm, 3.80 mm and 2.38 ram, respec- tively. The rotation difference between 2 systems was small, and the standard deviation about 1. At x, y and z of translational process in radiotherapy, the intra-fractional error detected by c-motion of CatalystTM system was （- 0.17 ± 1.25） mm, （0.47 ± 1.42） mm and （- 0.17 ± 1.96） mm, respectively, and （- 0.04 ± 0.51）°, （0.13 ± 0.42）°, （- 0.19 ± 0.76）° for rx, ry and rz rota- tions, and maximum deviation value was （2.54 ± 1.10） mm in each direction. Conclusion It is demonstrated that OSI system and CBCT system showed certain differences in detection and correction of chest tumor radiation therapy set-up error, and OSI system could monitor the intra-fractional error in real-time. As the set-up error of chest radiotherapy is affected by many factors, the comorehensive utilization strategy of OSI system and CBCT system needs to be further studied.