Excretory MR Urography Using Breathhold Three-dimensional FISP: Comparison with MR Urography Using HASTE Technique

Song, Won Kue; Lee, Jeong Min; Jin, Kong Young; Hwang, Ho Keung; Han, Young Min; Ym, Seong Hee

Abstract

PURPOSE: To compare the usefulness of gadolinium-enhanced excretory MR urography using breath-hold three-dimensional fast imaging with steady state precession (3-D FISP) with conventional MR urography using the half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence in the evaluation of obstructive uropathy.
MATERIALS AND METHODS
Twenty-three patients in whom ultrasonography (US) and/or intravenous urography(IVU) revealed signs of urinary obstruction were enrolled in this study. Fifteen were men and eight were women, and their mean age was 54 (range, 21 -80) years. All MR images were obtained using a 1.5-T MR unit. MR urography using the HASTE technique (MRU) and gadolinium-enhanced excretory MR urography using the 3D-FISP technique were performed, and in all cases, reconstructions involved maximum intensity projection. For contrast-enhanced MR urography (CEMRU), images were obtained 3, 5, 20, and 30 minutes after the administration of intravenous contrast media, and for selected cases, additional images were obtained until 24 hours after contrast media injection. For qualitative analysis, two experienced radiologists compared CEMRU and MRU in terms of their diagnostic value as regards the level and cause of urinary obstruction, and morphologic accuracy. In addition, signal to noise ratio (SNR) and contrast to noise ratio (CNR) of the urinary tract at each anatomic level were quantitatively analysed.
RESULTS
Quantitative analysis showed that in terms of SNR and CNR of the urinary tract at the level of the mid and distal ureter, CEMRU using 3-D FISP was better than MRU using HASTE (p<0.05). Qualitative analysis indicated that for the depiction of the whole length of normal ureter, and detection of the level of obstruction, anatomic anomalies and intrinsic tumors, 3-D FISP was superior to HASTE. There was, however, no difference between these two modalities in the diagnosis of ureteral stone and the degree of hydronephrosis. In addition, 3-D FISP was better than HASTE for the assessment of filling defect, but the difference was not statistically significant.
CONCLUSION
Breath hold 3-D FISP is a very valuable tool in the evaluation of obstructive uropathy. It not only depicts very clearly the anatomy of the urinary tract system, but also provides qualitative information on renal function. We believe that CEMRU using 3-D FISP is a valuable diagnostic approach which can be added to those already available for the workup of obstructive uropathy.