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In this study a semi-automated and observer-independent algorithm for quantifying post-stenotic signal loss (PSL) in 3D phase-contrast (PC) magnetic resonance angiography (MRA) of patients with renal artery stenosis is presented. This algorithm was developed on MRA datasets of stenotic phantoms, which were included in a flow circuit with stationary flows. The length and the severity of the PSL (incorporating both length and degree of PSL) in the maximum intensity projections (MIPs) of MRA datasets were proposed for quantifying stenoses. The algorithm was tested in renal arteries of ten patients with renal artery stenosis and seven healthy volunteers. Digital subtraction angiography (DSA) was performed in the patients and served as the gold standard. Stenosis severity showed better correlation with the severity of the PSL than with the length, both for in vitro as in vivo. Spearman correlation coefficients (rS) showed statistically significant correlations between the severity of the PSL and parameters determined by DSA, i.e. percent diameter stenosis (rS = 0.90). The length of the PSL showed no correlation with the diameter stenosis (rS = 0.37).

In this study, a scanning protocol was developed to image the arterial bed of the pelvis and both legs along their entire length in patients with peripheral arterial disease, using standard hard- and software. Three adjacent stations are acquired consecutively, with some small overlap; per station; one Gadolinium contrast bolus is administered. The scanning protocol was optimized in an in vitro phantom study. The optimal flip angle was found to be 50 degrees. Also, the optimal scan delay was chosen to be equal to the arrival time of the contrast bolus thereby minimizing artifacts. Three contrast bolus injections showed sufficient enhancement of the vessels after image subtraction. Finally, stenosis quantification by manual caliper was performed by five observers in the MRA images and correlated with the percent diameter reduction determined by quantitative angiography from corresponding X-ray images. The results of the MRA measurements were reproducible and intra- and inter-observer variabilities were statistically non-significant (p = 0.54 and p = 0.12, respectively). Stenosis quantification performed by four observers showed a good correlation with the X-ray derived values (rp > 0.90, p < 0.02); the results from one observer were not significantly correlated. Five patients with proven peripheral disease were investigated with this new MRA scanning protocol. The images were of good quality which allowed adequate clinical evaluation; the original diagnoses obtained from X-ray examinations, were confirmed with MRA. In conclusion, peripheral arterial disease can be evaluated adequately with this MR scanning protocol.