With the improved survival of children with brain tumors, understanding the late effects of the treatment has become critical. This study explores the effects of RT on vascular structure using a combined MRA-SWI sequence at 7T and a new method for arterial segmentation and quantification. Normalized arterial volume was significantly reduced with increasing RT treatment volume, number of CMBs, and at follow-up. CMBs were located closer to veins than arteries and were larger when further away. Our findings demonstrate the feasibility of our approach for quantifying subtle vascular changes in arterial structure and CMB properties due to RT.