Biliary stones and biliary gas both produce signal void
on MR; however, nondependent positioning suggests biliary gas.
However, a distinct flow-related signal void
usually indicates a spinal AVF.
At delayed CEMRI, previously unreported characteristic and reproducible findings of signal void
on post-contrast subtraction images ("black hole") correlates with an area of coagulation necrosis at the cryoablation site and a surrounding uniform thin rim enhancement ("cryohalo") corresponds to a zone of inflammation at the cryoablation margin.