Gadolinium-enhanced 3D MR angiography of renal artery stenosis: a pilot comparison of maximum intensity projection, multiplanar reformatting, and 3D volume-rendering postprocessing algorithms.
OBJECTIVE
The authors compared diagnostic accuracy of maximum intensity projection (MIP), multiplanar reformatting (MPR), and three-dimensional (3D) volume rendering (VR) in the evaluation of gadolinium-enhanced 3D magnetic resonance (MR) angiography of the renal arteries. They hypothesized that VR is as accurate as or more accurate than MIP and MPR at depicting renal artery stenosis.


METHODS
The study group comprised 28 consecutive patients who underwent gadolinium-enhanced 3D MR angiography of the renal arteries. Studies were postprocessed to display images in MIP, MPR, and VR formats. Digital subtraction angiography (DSA), when performed (nine of 28 patients), was the standard for comparison. For each main renal artery, an estimate of percentage stenosis was made for any stenoses detected by three independent radiologists. For calculation of sensitivity, specificity, and accuracy, MR angiographic stenosis estimates were categorized as mild (0%-39%), moderate (40%-69%), or severe (> or = 70%). DSA stenosis estimates of 70% or greater were considered hemodynamically significant.


RESULTS
Analysis of variance demonstrated MIP estimates of stenosis were statistically greater than VR estimates in two readers and greater than MPR estimates in all readers for all patients. MIP images also showed the largest mean difference from DSA stenosis estimates for all three readers. For both VR and MPR, mean differences between MR angiographic stenoses estimates and DSA estimates reached significance for only one reader, whereas, for MIP versus DSA, mean differences reached significance for all three readers. Although not statistically significant compared with DSA, accuracies of VR (87%) and MPR (89%) were greater than that of MIP (81%).


CONCLUSIONS
In this pilot study, MIP was the least accurate of the three image display algorithms tested. VR and MPR yielded similar values for each method of comparison.
Baskaran
Visveshwar
V
Department of Radiology, Northwestern University, Northwestern Memorial Hospital, Chicago, IL 60611, USA.
Pereles
F Scott
FS
Nemcek
Albert A
AA
Carr
James C
JC
Miller
Frank H
FH
Ly
John
J
Krupinski
Elizabeth
E
Finn
J Paul
JP
D000328:Adult; D000368:Aged; D000465:Algorithms; D000704:Analysis of Variance; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement; D021621:Imaging, Three-Dimensional; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D012078:Renal Artery Obstruction / Q000175:diagnosis*; D012680:Sensitivity and Specificity
D003287:Contrast Media; D019786:Gadolinium DTPA