Diffusion-weighted MRI in the evaluation of renal lesions:preliminary results

The purpose of this study was to evaluate the capability and the reliability of diffusion-weighted MRI in the evaluation of normal kidney and different renal lesions. 39 patients (10 normal volunteers and 29 patients with known renal lesions) underwent MRI of the kidneys by using a 1.5 T superconducting magnet. Axial fat suppressed turbo spin echo (TSE) T2 and coronal fast field echo (FFE) T1 or TSE T1 weighted images were acquired for each patient. Diffusion-weighted (DW) images were obtained in the axial plane during breath-hold (17 s) with a spin-echo echo planar imaging (SE EPI) single shot sequence (repetition time (TR)52883 ms, echo time (TE)561 ms, flip angle590°), with b value of 500 s mm22. 16 slices were produced with slice thickness of 7 mm and interslice gap of 1 mm. An apparent diffusion coefficient (ADC) map was obtained at each slice position. The ADC was measured in an approximately 1 cm region of interest (ROI) within the normal renal parenchyma, the detected renal lesions and the collecting system if dilated. ADC values in normal renal parenchyma ranged from 1.7261023 mm2 s21 to 2.6561023 mm2 s21, while ADC values in simple cysts (n513) were higher (2.8761023 mm2 s21 to 4.0061023 mm2 s21). In hydronephrotic kidneys (n56) the ADC values of renal pelvis ranged from 3.3961023 mm2 s21 to 4.0061023 mm2 s21. In cases of pyonephrosis (n53) ADC values of the renal pelvis were found to be lower than those of renal pelvis of hydronephrotic kidneys (0.7761023 mm2 s21 to 1.0761023 mm2 s21). Solid benign and malignant renal tumours (n57) showed ADC values ranging between 1.2861023 mm2 s21 and 1.8361023 mm2 s21. In conclusion diffusion-weighted MR imaging of the kidney seems to be a reliable way to differentiate normal renal parenchyma and different renal diseases. Clinical experience with this method is still preliminary and further studies are required.