Can capsules be seen on an ultrasound? Will they show up on an MRI? Is an MRI necessary to locate capsules?

I had my saline implants of 14 years removed 2/2/16 due to diagnosis of lupus, Lymes, infertility, and homozygous MTHFR C677T. My surgeon decided not to remove them because they were "thin and translucent". My surgeon's response was that I needed to wait 6 weeks for proper healing before a second surgery and should have an u/s done to confirm that they hadn't been fully dissolved. The capsules were not visible in the 11/22/16 u/s. My surgeon has now ordering an MRI to locate the capsules.