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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.

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