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目的观察体质量指数(body mass index,BMI)对图像引导放射治疗(image guided radiotherapy,IGRT)宫颈癌患者摆位误差的影响,探讨IGRT宫颈癌患者的最佳体位。方法收集IGRT宫颈癌患者30例,按BMI分为2组:BMI≥24 kg/m~2组,9例;BMI<24 kg/m2组,21例。锥形束CT扫描,俯卧位68次,仰卧位73次,CT图像进行灰度自动配准计算出X、Y、Z轴方向的校正前摆位误差,分析宫颈癌患者IGRT最佳治疗体位,并根据扩边公式2.5Σ+0.7δ计算出最佳体位扩边值。结果未考虑BMI的情况下,俯卧与仰卧位摆位误差均无统计学差异(P>0.05);BMI<24 kg/m2组,仰卧位与俯卧位在X、Y轴摆位误差无统计学差异(P>0.05),而在Z轴上仰卧位误差为(-0.112±0.041)cm,俯卧位误差为(0.028±0.024)cm,二者有统计学差异(t=-3.186,P=0.002),俯卧位扩边值0.668、1.206、0.335 cm;BMI≥24 kg/m2组,仰卧位与俯卧位在X、Y轴摆位误差无统计学差异(P>0.05),在Z轴仰卧位摆位误差为(0.061±0.045)cm,俯卧位摆位误差为(-0.26±0.031)cm,二者有统计学差异(t=5.832,P<0.001),仰卧位扩边值0.313、1.663、0.501 cm。结论 BMI<24 kg/m2组,俯卧位Z轴方向误差显著小于仰卧位,BMI≥24 kg/m2组,仰卧位的Z轴方向误差显著小于俯卧位,2组在X、Y轴方向的摆位误差无统计学差异。
Objective To observe the effect of body mass index (BMI) on setting error of cervical cancer patients with image guided radiotherapy (IGRT) and to investigate the best position of IGRT patients. Methods Thirty patients with IGRT cervical cancer were divided into two groups according to BMI: BMI≥24 kg / m ~ 2, 9 cases; BMI <24 kg / m2 group, 21 cases. Cone beam CT scan, prone position 68 times, supine position 73 times, automatic grayscale CT image registration to calculate the X, Y, Z axis direction of the pre-correction error, analysis of cervical cancer patients IGRT optimal treatment position, And according to the expansion formula 2.5Σ + 0.7δ to calculate the best posture expansion value. Results There was no significant difference in the placement error between prone and supine position without BMI (P> 0.05). The BMI <24 kg / m2 group had no statistical difference between the supine position and the prone position (P> 0.05). The error of supine position on the Z axis was (-0.112 ± 0.041) cm and that on the prone position was (0.028 ± 0.024) cm (t = -3.186, P = 0.002 ). In the prone position, the expanding values were 0.668, 1.206 and 0.335 cm, respectively. There was no significant difference between the supine position and the prone position in the BMI≥24 kg / m2 group (P> 0.05) The error of positioning was (0.061 ± 0.045) cm, and the error of positioning in prone position was (-0.26 ± 0.031) cm, the difference was statistically significant (t = 5.832, 0.501 cm. Conclusions The errors in the Z axis of prone position are significantly less than those in supine position and BMI ≥ 24 kg / m2 for BMI <24 kg / m2 group. The errors of Z axis in supine position are significantly less than those in prone position. Bit error no significant difference.