基于磁共振放疗平台模拟胰腺癌不同配准策略的研究

Simulation of Different Alignment Strategies for Pancreatic Cancer Based on MRI-Guided Radiotherapy Platform

目的:探讨胰腺癌图像引导放射治疗过程中骨性配准、体表配准与靶区配准之间的差异,为胰腺癌精准放疗配准策略提供参考。方法:纳入2021年11月至2023年4月在四川省肿瘤医院医科达Unity磁共振加速器治疗的16例胰腺癌患者,采集放疗前MR图像,将MR图像与计划CT图像融合,分别以骨性标志、患者体表和肿瘤靶区进行配准,获得左右(X轴),头脚(Y轴),前后(Z轴)方向的移床参数,比较骨性配准、体表配准与靶区配准之间的差异,以绝对值表示绝对位移数值,计算两组与靶区配置相对位置的统计学差异。统计位移值的出现频次,验证临床稳定性。结果:16位患者共进行了92个放疗分次治疗。与靶区配准组相比较,骨性配准组在X、Y、Z方向上差值分别(1.12±0.90)mm、(2.01±2.12)mm、(0.10±0.84)mm;体表配准组在X、Y、Z方向上差值分别为(1.64±1.28)mm、(3.48±2.29)mm、(3.94±2.76)mm;仅体表配准组和骨性配准组在X和Z轴的摆位误差差异有统计学意义(P<0.05)。在误差出现频次统计方面,骨性配准策略仅有少量Y轴方向存在大于5 mm的误差,频次为14.13%,而体表配准策略则在X、Y、Z三个方向存在不同频次大于5 mm的误差,其中X轴方向频次为1%,Y轴方向为16.3%,Z轴方向29.35%。结论:在胰腺癌图像引导放疗中,采用骨性配准策略较为可靠,但在头脚方向上位移较大,建议根据具体情况制定个体化治疗策略。

Objective:To investigate the differences among bone alignment,skin surface alignment and tumor alignment for adaptive radiotherapy of pancreatic cancer with a magnetic resonance accelerator,and provide evidence for precision radiotherapy alignment strategies for pancreatic cancer.Methods:From November 2021 to April 2023,16 patients with pancreatic cancer treated with a Unity magnetic resonance accelerator at Sichuan Cancer Hospital were selected.MR images were obtained before each radiotherapy session,and were registered with planned CT images.Alignment was performed in three ways,bone,patient's body surface,and actual tumor.Setup errors in the left-right(X axis),superior-inferior(Y axis)and anterior-posterior(Z axis)directions were obtained.The differences between the two alignment methods and the tumor alignment were compared.The results were expressed in absolute values,and the statistical difference between the two groups and the tumor alignment was calculated.The frequency of displacement values was counted to verify the clinical stability.Results:A total of 92 radiotherapy sessions were performed in 16 patients.The differences in the X,Y and Z directions in the bone alignment group were(1.12±0.90)mm,(2.01±2.12)mm and(0.10±0.84)mm,the differences in the X,Y and Z directions were(1.64±1.28)mm,(3.48±2.29)mm and(3.94±2.76)mm in the skin surface alignment group.Differences between tumor alignment and skin surface alignment were statistically significant in X and Z axes.The frequency of error greater than 5 mm in the Y-axis direction in the bone alignment strategy was 14.13%,while the skin surface alignment strategy had errors greater than 5 mm of different frequency in the X,Y and Z directions(1%in the X direction,16.3%in the Y direction and 29.35%in the Z direction).Conclusion:Bone alignment is more reliable in image-guided radiotherapy for pancreatic cancer.However,it is shown that there are substantial differences in the superior-inferior direction.Therefore,individual treatment strategies should be considered for radiotherapy in pancreatic cancer.