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 T1 weighted imaging (T1WI), T2 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 ± 0.29 × 10(-3) mm(2) s(-1) at 1 month). 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.