CT SCAN OF HEART-WHY?

I have a medium high risk LDL cholesterol and an HDL of about 58 plus tryglycerides in the 300 level. . I have well conrolled BP and very good genetic history. Good genetic history and exersize  eat well. My Cardiologist wants me to have a CT scan of my heart. sounds drastic to me. I am 78 years young. he did no other tests at my annual appointment. Is it a new thing that has to be paid for? I am on medicare & am also a doubting Thomas . My husband was a pathologist, but died several years ago with Prostate Ca.  I am somewhat medically literate. DL