Optimization of Spatial Resolution for Peripheral
Magnetic Resonance Angiography
1
An Tang, Guy Cloutier, Eric Therasse, Gilles Beaudoin, Salah D. Qanadli, Marie-France Giroux, Nicolas Boussion
Jacques A. de Guise, Vincent L. Oliva, Gilles Soulez
Rationale and Objectives. To determine optimum spatial resolution when imaging peripheral arteries with magnetic reso-
nance angiography (MRA).
Materials and Methods. Eight vessel diameters ranging from 1.0 to 8.0 mm were simulated in a vascular phantom. A
total of 40 three-dimensional flash MRA sequences were acquired with incremental variations of fields of view, matrix
size, and slice thickness. The accurately known eight diameters were combined pairwise to generate 22 “exact” degrees of
stenosis ranging from 42% to 87%. Then, the diameters were measured in the MRA images by three independent observ-
ers and with quantitative angiography (QA) software and used to compute the degrees of stenosis corresponding to the 22
“exact” ones. The accuracy and reproducibility of vessel diameter measurements and stenosis calculations were assessed
for vessel size ranging from 6 to 8 mm (iliac artery), 4 to 5 mm (femoro-popliteal arteries), and 1 to 3 mm (infrapopliteal
arteries). Maximum pixel dimension and slice thickness to obtain a mean error in stenosis evaluation of less than 10%
were determined by linear regression analysis.
Results. Mean errors on stenosis quantification were 8.8% 6.3% for 6- to 8-mm vessels, 15.5% 8.2% for 4- to 5-mm
vessels, and 18.9% 7.5% for 1- to 3-mm vessels. Mean errors on stenosis calculation were 12.3% 8.2% for observ-
ers and 11.4% 15.1% for QA software (P = .0342). To evaluate stenosis with a mean error of less than 10%, maxi-
mum pixel surface, the pixel size in the phase direction, and the slice thickness should be less than 1.56 mm
2
, 1.34 mm,
1.70 mm, respectively (voxel size 2.65 mm
3
) for 6- to 8-mm vessels; 1.31 mm
2
, 1.10 mm, 1.34 mm (voxel size 1.76
mm
3
), for 4- to 5-mm vessels; and 1.17 mm
2
, 0.90 mm, 0.9 mm (voxel size 1.05 mm
3
) for 1- to 3-mm vessels.
Conclusion. Higher spatial resolution than currently used should be selected for imaging peripheral vessels.
Key Words. Magnetic resonance angiography; peripheral arteries; experimental studies.
©
AUR, 2007
Magnetic resonance angiography (MRA) has gained wide-
spread clinical acceptance for imaging the aorta and its
major branches (1–4). Technical advances in contrast-
enhanced bolus chase three-dimensional (3D)-MRA with
fast-gradient echo-recalled sequences, moving table, and
time-resolved imaging have improved diagnostic accuracy
(5–11).
However, suboptimal correlations with Digital subtrac-
tion angiography (DSA) have often been reported because
of limited spatial resolution and frequent venous contami-
nation observed with the sequence used for bolus-chasing
MRA (12,13). For infrapopliteal vessels, better results
have been obtained when the examination was performed
in two steps: a first injection combined with high-resolu-
Acad Radiol 2007; 14:54 – 61
1
From the Department of Radiology (A.T., E.T., G.B., M.-F.G., V.L.O., G.S.),
the Laboratory of Biorheology and Medical Ultrasonics-Research Center
(G.C., N.B.), and Laboratory of Orthopedic Imaging-Research Center
(J.D.G.), Centre Hospitalier de l’Université de Montréal (CHUM)-Hôpital
Notre-Dame, Montreal, Quebec, Canada; and the Department of Radiology,
Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland (S.D.Q.).
Received March 6, 2006; accepted October 13, 2006. Supported by grants
from the Canadian Institutes of Health Research (G.C., G.S.; #MOP-53244)
and Valorisation-Recherche Québec (group grant #2200-094), and by a Na-
tional scientist award (G.C.) and clinical research scholarship awards from
Fonds de la recherche en santé du Québec (G.C., G.S.). Address corre-
spondence to: G.S. e-mail: gilles.soulez.chum@ssss.gouv.qc.ca
©
AUR, 2007
doi:10.1016/j.acra.2006.10.007
54