Onrad系统宫颈癌放疗兆伏级CT扫描pitch选择对摆位误差的影响

Effect of pitch selection on positioning errors in megavoltage CT scanning of Onradsystem for cervical cancer radiotherapy

目的应用断层径照放疗系统(Onrad系统)进行宫颈癌放疗,研究Onrad系统在兆伏级CT(MVCT)扫描时pitch选择对摆位误差的影响。方法选取2023年10月~2024年1月深圳市人民医院放疗科接受Onrad系统放疗的16例宫颈癌患者,根据患者放疗时MVCT扫描采用pitch的不同,分为两组:Normal组(n=8)与Coarse组(n=8),每日行MVCT扫描,与定位CT图像匹配获取XYZ三维平移误差及绕Y轴滚动误差Roll,记录扫描时长及获得的误差数据并整理分析。结果Normal组与Coarse组各获得摆位误差数据200组,Normal组三维平移误差分别为X=1.80±1.28 mm、Y=2.22±1.43 mm、Z=1.78±1.30 mm,滚动误差为Roll=0.32±0.41°;Coarse组三维平移误差分别为X=1.98±1.18 mm、Y=2.38±1.34 mm、Z=1.96±1.27 mm,滚动误差为Roll=0.31±0.47°;两组摆位误差相比较,平移误差X、Y、Z(P=0.15、0.23、0.17)及滚动误差Roll(P=0.71)的差异无统计学意义。扫描效率方面,pitch选择Normal较Coarse扫描时间明显延长(253.4±9.7 vs 173.3±7.9 s,P<0.001)。结论Onrad系统宫颈癌放疗,行MVCT图像扫描时,pitch选择Normal或Coarse进行位置校准,XYZ三维平移误差及滚动误差Roll均无差异,但pitch选择Coarse扫描效率更高,推荐选用Coarse。

Objective To investigate how pitch choice affects positioning errors during megavoltage computed tomography(MVCT)scanning using the Onrad system,a tomography radial radiotherapy system,for cervical cancer treatment.Methods A total of 16 cervical cancer patients who underwent Onrad system treatment in Department of Radiotherapy Shenzhen People's Hospital from October 2023 to January 2024 were chosen.The patients were split into two groups:Normal group(n=8)and Coarse group(n=8)based on the pitch utilized during MVCT scanning.Every day,an MVCT scan was conducted.By comparing the results with the positioning CT picture,the XYZ three-dimensional translation error and rolling error around the Y axis(Roll)were determined.Both the error data and the scanning time were tracked down and examined.Results In the Normal group and the Coarse group,200 sets of displacement error data in total were collected.The three-dimensional translation errors of Normal group were X=1.80±1.28 mm,Y=2.22±1.43 mm,Z=1.78±1.30 mm,and the rolling error was Roll=0.32±0.41°.The 3D translation errors of Coarse group were X=1.98±1.18 mm,Y=2.38±1.34 mm,Z=1.96±1.27 mm,and rolling error was Roll=0.31±0.47°.For both the rolling error Roll(P=0.71)and the translation errors X,Y,Z(P=0.15,0.23,0.17),there was no discernible difference in the positioning errors between the two groups.When the pitch was set to Normal,the scanning time was substantially greater than when the pitch was set to Coarse in terms of scanning efficiency(253.4±9.7 vs 173.3±7.9 s,P<0.001).Conclusion For position calibration,MVCT images are scanned with Normal and Coarse pitch when the Onrad system is utilized for cervical cancer radiation therapy.The XYZ 3D translation errors and rolling error do not differ.Nevertheless,Coarse pitch selection increased scanning efficiency.There fore,Coarse pitch was advised.