Imaging of upper urinary tract cancer: using conventional MRI and diffusion-weighted MRI with different b values.

BACKGROUND: Diffusion-weighted magnetic resonance imaging (DW-MRI) has been considered to be useful in diagnosing upper urinary tract (UUT) disease; however, the value of DW-MRI with different b values has not been reported. PURPOSE: To evaluate the performance of using conventional MRI alone and in combination with DWI with different b values in diagnosing UUT cancer. MATERIAL AND METHODS: Seventy patients with suspected UUT cancer underwent conventional MRI (T1-weighted and T2-weighted) and DW-MRI (b = 500 and 1500 s/mm(2)) on a 3 T-MRI scanner. The ureteroscopic and histopathologic findings were compared with the imaging findings. The utility of detecting UUT cancer using conventional MRI (set A), combined DW-MRI (b = 500 s/mm(2)) and conventional MRI (set B), and combined DW-MRI (b = 1500 s/mm(2)) and conventional MRI (set C) were independently evaluated by two readers. RESULTS: A total of 32 patients had verified cancer; 23 patients had benign UUT diseases, and 15 had no abnormality. Sets B and C had significantly improved diagnostic accuracy for UUT cancer compared with set A; the specificity in diagnosing UUT cancer was significantly improved when using set C compared with sets A and B. In patients without UUT obstructions, improved sensitivity and accuracy in diagnosis was achieved when using sets B and C compared with set A. CONCLUSION: Using DW-MRI in combination with conventional MRI provides increased diagnostic accuracy and sensitivity in patients without UUT obstruction. The combination of conventional MRI and DW-MRI with a higher b value (1500 s/mm(2)) improved the specificity in diagnosing UUT cancer compared to conventional sequences and DW-MRI with a lower b value (500 s/mm(2)).