Hi @Moorehealth I was diagnosed with DCIS in April this year. You are lucky that your surgeon lets you do a MRI before the surgery. Mine didn't think it was necessary but I kind of insisted of doing something before my surgery, so, I did a CT scan of the body and bone, which showed nothing. However, after my surgery (I had a double mastectomy), the pathology results showed that I had a micromet in one of the lymph nodes, ended up doing 3 months of chemo after the surgery.
So, everyone diagnosed with DCIS will be different and I guess a MRI may be more accurate than a CT scan. Hope that a surgery is all you need and you can be on the mend very soon. Good luck and all the best <3