Assessment of cold sink effect in postulated renal cryoablation by analyzing radiographic ice ball on computed tomography

Abstract

OBJECTIVE: We analyzed CT characteristics of radiographic ice ball according to anatomical location and freezing number in renal cryoablation.

METHODS: 30 patients who underwent percutaneous cryoablation for renal lesions. Computed tomography (CT) was conducted at 9 min during every freezing in order to evaluate a radiographic ice ball. Software was used to reconstruct CT images of the radiographic ice ball perpendicular to cryoprobes. For each radiographic ice ball, two types of radius were measured: (a) lateral radius from epicenter to perirenal direction and (b) medial radius from epicenter to renal sinus direction. Lateral and medial radius or diameters (lateral radius plus medial radius) during the first and second freezing were compared using paired t-test, respectively.

RESULTS: Medial radius of radiographic ice ball was significantly shorter than lateral radius (first freezing, 13.8 vs 17.0 mm, p < 0.001; second freezing, 16.0 vs 19.3 mm, p < 0.001). The diameter during the second freezing was significantly longer than that during the first freezing (35.3 vs 30.8 mm, p < 0.001).

CONCLUSION: In renal cryoablation, evaluating radiographic ice ball helps identify potential postulated cold sink effect in the central portion of kidney. Advances in knowledge: Radiologic information of postulated cold sink effect in the kidney may help secure sufficient safety margins.