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目的探讨体质指数(BMI)对肺癌图像引导放射治疗(IGRT)中摆位误差的影响,为临床治疗提供依据。方法选取2015年1月至6月行IGRT的肺癌患者32例。根据患者BMI值分为体重过低组(A组5例:BMI<18.5)、体重正常组(B组12例:18.5≤BMI<24)、超重组(C组8例:24≤BMI<28)和肥胖组(D组7例:BMI≥28)。使用千伏级锥形CT采集32例肺癌患者每周治疗前的锥形束CT(CBCT)图像,分别采用骨性配准和灰度配准,比较不同配准方式和不同BMI的摆位差异。结果共获取256幅CBCT图像。A、B、C、D组患者在x、y、z三维方向上骨性配准的摆位误差分别为(-0.34±0.20,0.33±0.17,0.25±0.22)、(-0.28±0.19,0.29±0.14,0.18±0.21)、(-0.67±0.22,0.31±0.17,0.61±0.25)、(-0.75±0.19,0.38±0.11,0.68±0.25)和灰度配准的摆位误差分别为(-0.25±0.22,0.31±0.17,0.21±0.21)、(-0.25±0.18,0.28±0.14,0.19±0.22)、(-0.67±0.17,0.30±0.16,0.56±0.23)、(-0.72±0.22,0.36±0.12,0.63±0.21)。随患者BMI的递升(A组→B组→C组→D组),在两种配准方式、三维方向上的摆位误差均呈递增(除B组骨性标准前后方向外),以D组(肥胖组)摆位误差最高,差异有统计学意义(P均<0.01)。不同BMI患者采用灰度配准在三维方向上的误差值部分小于采用骨性配准。结论采用相同配准框和图像质量下,肺癌患者IGRT中建议优先采用灰度配准。患者BMI越大,摆位差异越明显,对于肥胖患者的摆位要注意误差影响。
Objective To investigate the effect of body mass index (BMI) on the setup error in image guided radiotherapy (IGRT) of lung cancer and provide the basis for clinical treatment. Methods Thirty-two patients with lung cancer undergoing IGRT from January 2015 to June 2015 were selected. According to the patients’ BMI, the patients were divided into 5 groups (5 cases in group A: BMI <18.5), normal weight group (12 cases in group B: 18.5≤BMI <24), 8 cases in group C ) And obesity group (7 cases in group D: BMI≥28). Conical beam CT (CBCT) images of 32 patients with lung cancer before treatment were collected by using kilovoltage cone CT. Bone registration and grayscale registration were used respectively to compare the differences of registration between different registration methods and different BMI . Results A total of 256 CBCT images were obtained. The set-up errors of bony registration in the three-dimensional directions of x, y and z were (-0.34 ± 0.20,0.33 ± 0.17,0.25 ± 0.22), (-0.28 ± 0.19,0.29, ± 0.14,0.18 ± 0.21), (-0.67 ± 0.22,0.31 ± 0.17,0.61 ± 0.25), (-0.75 ± 0.19,0.38 ± 0.11,0.68 ± 0.25), and the grayscale registration were (- (-0.25 ± 0.18,0.28 ± 0.14,0.19 ± 0.22), (-0.67 ± 0.17,0.30 ± 0.16,0.56 ± 0.23), (-0.72 ± 0.22,0.36 ± 0.22,0.31 ± 0.17,0.21 ± 0.21) ± 0.12, 0.63 ± 0.21). With the increase of BMI in patients (Group A → Group B → Group C → Group D), the setup errors in three-dimensional directions increased with the increase of BMI (except for B group before and after bony criteria) Group (obesity group) placed the highest error, the difference was statistically significant (P all <0.01). Different BMI patients using grayscale registration in the three-dimensional direction of the error value is less than the use of bone registration. Conclusions With the same registration frame and image quality, gray-scale registration is preferred in IGRT for lung cancer patients. The greater the patient BMI, the more obvious differences in positioning, positioning for obese patients should pay attention to the error.