CT Scan or MRI before surgery after diagnosis of colon cancer?

[nervoustoday]

My mom is in her eighties and was just diagnosed with colon cancer. Her gastroenterologist recommended a CT Scan with po and IV contrast.  
Is the radiation from the CT Scan dangerous for an elderly woman and should she have an MRI instead?

In addition, should she wait until she sees a surgeon for any scan or should she go before she sees a surgeon?

[nervoustoday]

Thank you so much for your prompt reply.   My mom has spoken to a friend whose husband had a MRI ordered by his surgeon, however my mom's gastroenterologist told her that the CT Scan would give more pertinent information as it scans deeper into the bowel.  She's scared of the contrast that she has to drink, and I'm assuming the IV contrast means that there's something that's injected intravenously, too.  I've also read that the radiation from a CT Scan is less than that from a normal X-ray?  Is this correct?

The main question is which is the most common and thorough test (especially for elderly women) when someone is diagnosed with colon cancer?  Is it an MRI or the CT Scan?  Both her gastroenterologist and her internist have recommended a CT Scan

[Jaybay]

Neither a CT scan or MRI will be dangerous for your mom.  I suspect her doctor wants the scan prior to surgery to serve as a roadmap for any other lesions that may be in there.  You don't want your surgeon going in "blind".  If he knows exactly where to go, the surgery will go faster and be a more productive operation.