My experience with MRI has been that it's more accurate than ultrasound. My IPMN-MD was resected last July, after a year of surveillance, because, although the IPMN had only grown from 2 cm to 2.1 cm, the duct was dilated more than had previously been observed. Evidence of cancer was found in the resected pancreas tail. I am stage 1b, undergoing chemo now. Doctors speculated that the IPMN may have played a role in the development of cancer. Hope this is somewhat helpful.