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Unexpected Heating of MR-compatible Cyroablation Probes Using a Conventional 1.5T MR Scanner.

Cryoablation therapy is frequently used for ablation of tumors in many organs in the body and palliative musculoskeletal therapy. Typically cryoablation is performed using CT or ultrasound guidance. Recently more of these procedures have been performed using MRI guidance. FDA-approved MR-compatible cryoprobes consist of hollow needles that pass cooled fluids that freeze tissue. Using two freeze-thaw cycles to at least −40°C, ice crystals are formed within cells and blood flow is interrupted leading to cell rupture, ischemia, and cell death. Many of these devices appear to have been developed for low field MRI prior to the development of high temporal and spatial resolution pulse sequences. Anecdotally, we had observed nerve stimulation and heating during animal studies using an FDA-approved system at 1.5T. In this study, we sought to determine whether heating of the cryoprobe in a clinically approved 1.5T MRI scanner may occur, which could be of concern during MR-guided tissue ablation.