图像引导技术对不同体型宫颈癌摆位误差的研究

目的探讨用图像引导放射治疗技术对不同体型宫颈癌摆位误差的影响,以期对临床MPTV外扩值提供依据。方法选取宫颈癌20例,按照体质指数（BMI）分为两个不同体型,在治疗前行锥形束CT扫描1次,在线校正摆位误差后,再行锥形束CT扫描1次,记录并分析校正前后的摆位误差数值的变化,根据公式MPTV=2.5∑±0.7δ来计算CTV到PTV的边界。结果正常体型患者与肥胖体型患者在X轴（左右方向）、Y轴（头脚方向）、Z轴（腹背方向）的摆位误差在校正前分别为：（2.45±0.72）mm、（2.73±0.81）mm、（2.23±0.85）mm与（2.67±0.76）mm、（3.14±0.98）mm、（2.65±0.74）mm,其中Y轴和Z轴摆位误差具有统计学意义（P〈0.05）;校正后在X轴、Y轴、Z轴的摆位误差分别为：（0.96±0.33）mm、（0.91±0.32）mm、（0.89±0.29）与（1.02±0.36）mm、（0.96±0.31）mm、（0.92±0.37）mm,三维方向比较无统计学意义（P〉0.05）。两组体型患者误差校正前后三维方向的摆位误差,有显著统计学意义（P〈0.01）。正常体型和肥胖体型患者在摆位误差校正前X轴、Y轴、Z轴的MPTV值分别为4.7 mm、5.4 mm、4.9 mm和5.7 mm、7.4 mm、6.2 mm,误差校正后X轴、Y轴、Z轴的MPTV值分别为2.4 mm、2.5 mm、2.3 mm和2.6 mm、2.5 mm、2.5 mm。结论肥胖体型患者的摆位误差大,临床在勾画MPTV值时应考虑患者体型;应用CBCT图像引导技术在摆位误差校正后,患者体型对MPTV值的影响不大。

Study on effects of image guided techniques on setup error of cervical cancer in different body types

Objective To explore the effects of image-guided radiotherapy techniques on setup error of cervical cancer in different body types, in order to provide basis for expansion value of clinical MPTV. Methods Twenty patients with cervical cancer were selected and divided into different body shapes according to the body mass index（BMI）. Cone beam CT scan was performed once before treatment and once after online correction of setup error. And the changes of the setup errors before and after the correction were recorded and analyzed. Formula MPTV=was used to calculated the boundary from CTV to PTV. Results Setup errors of normal shaped patients and obese patients in X axis（left and right direction）, Y axis（head and feet direction） and Z axis（back and belly direction） before correction were：（2.45±0.72） mm,（2.73±0.81） mm,（2.23±0.85） mm and（2.67±0.76） mm,（3.14±0.98） mm and（2.65±0.74） mm respectively. Among them,setup errors in Y axis and Z axis showed statistical significance（P〈0.05）; After correction, the corresponding setup errors were：（0.96±0.33） mm,（0.91±0.32） mm,（0.89±0.29） mm and（1.02±0.36） mm,（0.96±0.31） mm and（0.92±0.37）mm. Setup errors in the three directions showed no statistical significance（P〉0.05）. Setup errors along the three directions before and after correction in the two groups of patients showed significant statistical significances（ P〈 0.01）.MPTV values of setup errors along X axis, Y axis and Z axis in normal shaped people and obese patients were 4.7 mm,5.4 mm, 4.9 mm and 5.7 mm, 7.4mm and 6.2mm before correction and 2.4 mm, 2.5 mm, 2.3mm and 2.6 mm, 2.5 mm and 2.5 mm after correction. Conclusion The setup error of obese patients is larger. Drawing MPTV in clinical needs to consider the patient＇s body shape; after application of CBCT image guided technology in setup error correction, it shows that the patient＇s body shape has little impact on MPTV value.