Renal arteries: isotropic, high-spatial-resolution, unenhanced MR angiography with three-dimensional radial phase contrast.
OBJECTIVE
To prospectively compare a new three-dimensional (3D) radial phase-contrast magnetic resonance (MR) angiographic method with contrast material-enhanced MR angiography for anatomic assessment of the renal arteries.


METHODS
An institutional review board approved this prospective HIPAA-compliant study. Informed consent was obtained. Twenty-seven subjects (mean age, 52.6 years ± 20.5 [standard deviation]) were imaged with respiratory-gated phase-contrast vastly undersampled isotropic projection reconstruction (VIPR) prior to contrast-enhanced MR angiographic acquisition with a 3.0-T clinical system. The imaging duration for phase-contrast VIPR was 10 minutes and provided magnitude and complex difference ("angiographic") images with 3D volumetric (320 mm) coverage and isotropic high spatial resolution (1.25 mm(3)). Quantitative analysis consisted of comparing vessel diameters between the two techniques. Qualitative assessment included evaluation of the phase-contrast VIPR and contrast-enhanced MR angiographic techniques for artifacts, noise, and image quality. Bland-Altman analysis was used for comparison of quantitative measurements, and the Wilcoxon signed rank test was used for comparison of qualitative scores.


RESULTS
Phase-contrast VIPR images were successfully acquired in all subjects. The vessel diameters measured with phase-contrast VIPR were slightly greater than those measured with contrast-enhanced MR angiography (mean bias = 0.09 mm). Differences in mean artifact, quality scores for the proximal renal arteries, and overall image quality scores between phase-contrast VIPR and contrast-enhanced MR angiographic techniques were not statistically significant (P = .31 and .29, .27 and .39, and .43 and .69 for readers 1 and 2, respectively). The quality scores for the segmental renal arteries were higher for phase-contrast VIPR than for contrast-enhanced MR angiography (P < .05). Although the noise scores were higher with phase-contrast VIPR than with contrast-enhanced MR angiography and were statistically significant (P < .05), the presence of noise did not interfere with the ability to interpret the images.


CONCLUSIONS
Isotropic, high-spatial-resolution, unenhanced MR angiography of the renal arteries is feasible with 3D radial undersampling.
François
Christopher J
CJ
Department of Radiology, Cardiothoracic and MRI Divisions, University of Wisconsin, 600 Highland Ave, Madison, WI 53792-3252, USA. CFrancois@uwhealth.org
Lum
Darren P
DP
Johnson
Kevin M
KM
Landgraf
Benjamin R
BR
Bley
Thorsten A
TA
Reeder
Scott B
SB
Schiebler
Mark L
ML
Grist
Thomas M
TM
Wieben
Oliver
O
D015901:Angiography, Digital Subtraction; D016477:Artifacts; D003287:Contrast Media; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012078:Renal Artery Obstruction / Q000175:diagnosis*; D018709:Statistics, Nonparametric; D013997:Time Factors
D003287:Contrast Media