EFFECT OF GADOLINIUM ON PHASE-CONTRAST MR-ANGIOGRAPHY OF THE RENAL-ARTERIES

OBJECTIVE. Our aim was to evaluate the effect of gadolinium chelates o n image quality in phase-contrast MR angiography of renal arteries in patients suspected of having renal artery stenosis. MATERIALS AND METH ODS. In 24 patients, axial three-dimensional phase-contrast MR angiogr aphy of the renal arteries was obtained on a 1.5-T MR imaging system b efore and after administration of gadolinium contrast agent. The impro vement in distal renal artery signal-to-noise ratio after enhancement was measured and correlated with patient age, serum creatinine level, clinical estimation of renal artery flow, and the imaging parameter fl ip angle. RESULTS. On average, the distal renal artery signal-to-noise ratio increased 2.2-fold after gadolinium administration (p < .001). The increase was greatest in patients more than 60 years old (3.1-fold ; p < .001) and in patients with serum creatinine levels greater than 3.0 mg/dl (4.3-fold; p < .01). After enhancement, we found an apparent increase in renal artery diameter (3.5 +/- 1.1 mm before enhancement versus 4.8 +/- 1.4 mm after enhancement [mean +/- SD; p < .001]). We b elieve this increase reflects improved visualization of slow blood flo w along the artery wall. Although the visualization of renal arteries was better in most patients after enhancement, two patients had poorer image quality after enhancement because of increased venous signal ob scuring the arteries. CONCLUSION. Gadolinium administration significan tly increases distal renal artery signal-to-noise ratio on three-dimen sional phase-contrast MR angiography in most patients. The signal-to-n oise ratio improvement is greatest in older patients and in patients w ith impaired renal function. However, in some cases, increased venous signal may obscure arteries.