Evolutionary magnetic resonance appearance of renal cell carcinoma after percutaneous cryoablation.

Objective: To determine the evolutionary MRI appearance of renal cell carcinoma (RCC) following cryoablation. Methods: For this institution review board-approved study, we recruited patients with biopsy-proven RCC and treated them with percutaneous cryoablation between November 2009 and October 2014. Two radiologists retrospectively reviewed the pre-procedural and follow-up MRI. The findings included tumour sizes, signal intensities on T-1 weighted imaging (T1WI), T-2 weighted imaging (T2WI), diffusion-weighted imaging, apparent diffusion coefficient (ADC) map and contrast enhancement patterns. The ADC values of the tumours before and after treatment were measured. Results: A total of 26 patients were enrolled. The ablated tumours exhibited predominantly high signals on T1WI at 1-9-month follow-up (47.1% strong hyperintense at 3 months) and subsequently returned to being isointense. In T2WI, the signals of the ablated tumours were highly variable during the first 3 months and became strikingly hypointense after 6 months (58.3% strong hypointense at 6 months). Diffusion restriction was prominent during the first 3 months (lowest ADC: 0.62 +/- 0.29x10(-3)mm(2) s(-1) at 1month). Contrast enhancement persisted up to 6 months after the procedure. The residual enhancement gradually increased in the dynamic scan and was most prominent in the delay phase. Conclusion: The MRI of the cryoablated renal tumour follows a typical evolutionary pattern. Advances in knowledge: Familiarity of practitioners with the normal post-cryoablation change of RCC on MRI can enable the early detection and prevention of tumour recurrence.