Optimization of spatial resolution for peripheral magnetic resonance angiography.
OBJECTIVE
To determine optimum spatial resolution when imaging peripheral arteries with magnetic resonance angiography (MRA).


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 observers 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 observers and 11.4% +/- 15.1% for QA software (P = .0342). To evaluate stenosis with a mean error of less than 10%, maximum pixel surface, the pixel size in the phase direction, and the slice thickness should be less than 1.56 mm2, 1.34 mm, 1.70 mm, respectively (voxel size 2.65 mm3) for 6- to 8-mm vessels; 1.31 mm2, 1.10 mm, 1.34 mm (voxel size 1.76 mm3), for 4- to 5-mm vessels; and 1.17 mm2, 0.90 mm, 0.9 mm (voxel size 1.05 mm3) for 1- to 3-mm vessels.


CONCLUSIONS
Higher spatial resolution than currently used should be selected for imaging peripheral vessels.
Tang
An
A
Department of Radiology, Centre Hospitalier de l'Université de Montréal (CHUM)-Hôpital Notre-Dame, Montreal, Quebec, Canada.
Cloutier
Guy
G
Therasse
Eric
E
Beaudoin
Gilles
G
Qanadli
Salah D
SD
Giroux
Marie-France
MF
Boussion
Nicolas
N
de Guise
Jacques A
JA
Oliva
Vincent L
VL
Soulez
Gilles
G
D003251:Constriction, Pathologic; D018810:Magnetic Resonance Angiography / Q000379:methods*; D016491:Peripheral Vascular Diseases / Q000175:diagnosis; D019047:Phantoms, Imaging; D012984:Software