基于四维CT探讨腹部加压对周围型肺部肿瘤立体定向放疗靶区位移及外扩边界的影响

目的 基于四维CT(4DCT)探讨腹部加压对周围型肺部肿瘤立体定向放疗(SBRT)靶区位移幅度、靶区体积大小及外扩边界的影响.方法 前瞻性收集拟行SBRT的周围型肺部肿瘤患者,CT模拟定位时依次完成腹部加压3DCT、腹部加压4DCT(4DCTcom)、自由呼吸4DCT(4DCTfree)扫描,并于照射前行腹部加压锥形束...

The effectiveness of abdominal compression in the target movement and external extension boundary of peripheral pulmonary tumors treated with stereotactic radiotherapy based on 4DCT

Objective To investigate the effectiveness of abdominal compression in tumor motion and the target volume,and analyze the suitable margins of planning target volume(PTV)for patients treated with lung-SBRT based on 4DCT.Methods Patients diagnosed with peripheral pulmonary tumor were enrolled.The patients were divided into the whole group,upper-middle-lobe group(group A)and the lower-lobe group(group B).Each patient underwent 3DCT,4DCT with abdominal compression(4DCT_com)and 4DCT with free breath(4DCT_free)scans.The GTVs were delineated and IGTVs on these images.PTV MIP_(5 mm),PTV MIP_(4 mm),PTV MI_(P3 mm)were constructed with a 5,4,3 mm margin in leftright(LR),anterior-posterior(AP)directions and cranial-caudal(CC)directions.Results The median motion vector with compression reduced by 30.92%in whole group,increased by 3.42%in group A and reduced by 18.80%in group B,respectively.And there were no significant differences of TMA LR,TMAAP,TMACC and motion vector by the Wilcoxon test(P>0.05).The median sizes of IGTV MIP_com,IGTV MIP_freeand IGTV10_com,IGTV10free were 4.01,5.36 cm³and 6.59,7.65 cm³,with statistically significant difference(Z=-3.45,-3.14,P<0.01).The median ratio of DI of IGTV CBCT_comin PTV MIP_(5 mm),PTV MIP_(4 mm)and PTV MIP_(3 mm)≥95%was 100%,100%and 83.33%,respectively.Conclusions The patients′respiratory pattern changed with abdominal compression and abdominal compression is useful in reducing the size of IGTV MIP and IGTV10,which could reduce the target volume and protect the normal tissue.Adding a 4 mm margin to IGTV MIPcom based on 4DCT account for respiration in SBRT is a tendency for precise radiotherapy.