The effectiveness of abdominal compression in the target movement and external extension boundary of peripheral pulmonary tumors treated with stereotactic radiotherapy based on 4DCT / 中华放射医学与防护杂志

ABSTRACT

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 MIP 3 mm were constructed with a 5, 4, 3 mm margin in left-right (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, TMA AP, TMA CC and motion vector by the Wilcoxon test ( P>0.05). The median sizes of IGTV MIP com , IGTV MIP free and IGTV10 com, IGTV10 free were 4.01, 5.36 cm 3and 6.59, 7.65 cm 3, with statistically significant difference ( Z=-3.45, -3.14, P<0.01). The median ratio of DI of IGTV CBCT com in 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 MIP com based on 4DCT account for respiration in SBRT is a tendency for precise radiotherapy.