My Husb. Has A Bicuspid Aortic Valve With Stenosis And

My husb. has a bicuspid aortic valve with stenosis and ascending aortic aneurysm. His cardiologist recommended his son get an MRI since it has been shown to be familial. He went to a Fam. Prac. MD who was clueless and hesitant to order screening. Does it have to be MRI or could he have US or CAT?