Complex cystic renal masses: comparison of cyst complexity and Bosniak classification between 1.5 T and 3 T MRI

To retrospectively compare perceived complexity and Bosniak cyst classification of cystic renal lesions between 1.5 T and 3 T MRI.

33 cystic renal lesions in 26 patients that underwent contrast-enhanced MRI at both 1.5 T and 3 T within a 12 month span were included. Two radiologists (R1, R2) independently assessed lesions, unaware of field strength, in terms of number of septations, septal thickening, mural thickening, presence of mural nodule, and Bosniak cyst category. Scores were compared between field strengths for each lesion.

R1 observed increases in septal number, septal thickening, mural thickening, and presence of mural nodule at 3T in 8, 7, 4, and 2 lesions, and at 1.5 T in 3, 3, 2, and 0 lesions, respectively; R2 observed increases in septal number, septal thickening, mural thickening, and presence of mural nodule at 3T in 3, 4, 3, and 0 lesions, and at 1.5 T in 2, 0, 0, and 0 lesions, respectively. R1 provided higher Bosniak category at 3T in 9 cases and at 1.5 T in 4 cases; R2 provided higher Bosniak category at 3T in 4 cases and at 1.5 T in 0 cases. Higher scores at 3T than 1.5 T were associated with differences in advised clinical management in 7/9 cases for R1 and 4/4 cases for R2.

There was an overall tendency for both readers to upgrade cyst complexity and Bosniak cyst category at 3T than 1.5 T, which impacted advised management. Thus, we suggest that serial MRI evaluation of cystic renal lesions be performed at constant field strength.