Evaluate the Feasibility of Gd-based Contrast Clearance Differenceto Delineate Subvolume Target in Primary and Metastatic Brain Tumors Radiotherapy- A Prospective Study

Abstract

Background: To evaluate the feasibility ofdelineating subvolume target in brain tumor radiotherapy using gd-based contrast clearance difference.Methods：Twenty-six patients with malignant brain tumor were scanned with MRI. The first and second acquisitions of standard T2-weighted images (T2WI) andT1-weighted images (T1WI) were respectively performed?> at 5 minutes and 60 minutesafter injection of contrast agent. Delayed contrast extravasation MRI(DCEM) computed by Brainlab concludesregions of contrast agent clearance which represent active tumor，andregions of contrast accumulation which represent non-tumor tissues. Based on T2WI images,14 patients were divided into group A and group B, with andwithout liquefaction necrosis, respectively. Then,gross target volume (GTV) was delineated on T1WI images. Based on the GTV, active tumor (GTV tumor) and non-tumorregions(GTV non-tumor) were delineated on T1WI-DCEM fusion images, whileliquefaction necrosis (GTVliquefaction)and non-liquefaction(GTVnon-liquefaction)were delineated on T1-T2WI fusion images. Finally, the differences between different subvolumes were compared by paired t-test.Results：In group A,the mean value of GTVA was 21.38±25.70 cm3, and the GTVnon-liquefaction and GTVliquefaction were 13.65±18.15cm3 and6.30±7.57cm3, respectively. The GTV tumor was 10.40±13.52 cm3 whilethe GTV non-tumor was 9.55±14.57 cm3, The GTVnon-liquefaction increased by an average of 28.2%（P＜0.05）,compared to GTV tumor . While the GTV non-tumor increased by an average of 46.3% (P＜0.05), compared tothe GTVliquefaction.In group B, the mean value of GTVB on enhanced T1WI was4.39±3.75 cm3. The GTV non-tumorreduced by an average of 50.3% (P＜0.05) , compared totheGTV tumor.Conclusion：Comparedto T2WI, the DCEM has advantages in identifyingthe liquefaction areaand could clearly differentiatesubvolume of active tumor from non-liquefaction necrosis.DCEMis meaningful in guiding the delineation of subvolume in primary and metastatic brain tumors.