High spatial resolution contrast-enhanced MR angiography of the supraaortic arteries using the quadrature body coil at 3.0T: A feasibility study

Abstract

To examine whether the the increased signal-to-noise (S/N) available at 3.0T would permit the use of the quadrature body coil for high spatial resolution contrast-enhanced (CE) MR angiography (MRA), and whether the large FOV that was used in our routine 1.5T protocol would also be feasible at 3.0T. In a prospective study, 43 patients and five volunteers were examined on a clinical whole-body 3.0T MR unit (Intera, Philips Medical Systems, Best, The Netherlands) after institutional review board approval and informed consent. Three-dimensional CE MRA (T1 gradient echo-sequence with TR/TE = 5.7/1.93 msec.; acquisition time, 1:54 min.) using randomly segmented central k-space ordering (CENTRA) was acquired with the quadrature body coil, using over a FOV of 350 mm. A high-image matrix of 432x432 yielded a non-zero filled voxel size of 0.81 mm x 0.81 mm x 1.0 mm (0.66 mm(3)). For quantitative analysis, contrast ratios (CR) between vessels (S) and signal in surrounding tissue (ST) were calculated [(S-ST)/(S+ST)]. For qualitative analysis, image quality and presence of artifacts were rated by two radiologists in consensus on a five-point scale (1=excellent to 5=nondiagnostic). Digital subtraction angiography (DSA) served as the standard of reference in patients with vascular disease. In the five volunteers, 1.5T CE MRA using a phased array neurovascular coil was available for intraindividual comparison. 3.0T CE MRA was successfully performed in 48/48 subjects (100%). Mean CR+/- SD were 0.76 (139.30/182.42) and 0.87 (235.18/270.14) at 3.0T and 1.5T respectively . Mean image quality was 3.82+/-0.86. Intraindividual comparison between 1.5T and 3.0T CE MRA in the volunteers revealed no significant difference in image quality (4.2+/-0.74 vs 4.6+/-0.80; p>0.05). Vascular disease was correctly identified in 13/13 patients with DSA correlation. CE MRA of the supraaortic arteries is feasible at 3.0T using a large FOV of 350 mm. The signal gain at 3.0T enables high spatial resolution contrast-enhanced MR angiography by using the built-in quadrature body coil only.

Quality-Evaluation Scheme for Cerebral Time-Resolved 3D Contrast-Enhanced MR Angiography Techniques

“…Diagnostic confidence index grading of images was recommended by most authors 4,11,12,17,21,31,33,35 because an initial appraisal is necessary before a more specific evaluation. The grading provides an immediate estimate of the level of diagnostic accuracy of the images to characterize possible vascular disease.…”

“…11,14,22,28,30,31,33 The type of artifacts, such as aliasing, ringing, movement, or vascular edge, must be specified because it is influenced by the TR-3D-CE-MRA strategy used. 11,35,[37][38][39] Arterial-to-venous separation, assessed with a semiquantitative scale, 5,11,12,30,34 provides a quick evaluation of the practical temporal resolution (ie, the ability of TR-3D-CE-MRA to detect rapid arteriovenous shunt involved in certain vascular malformations). However, our study shows no obvious interest in visually grading maximum arterial or venous SI.…”

“…4,11,12,14,17,21,31,33,35 Grading was as follows: 0, no vascular study possible; 1, vascular study possible but with low diagnostic confidence; 2, vascular study possible with adequate diagnostic confidence; and 3, vascular study possible with high diagnostic confidence.…”

“…4) Arterial-to-venous separation during the arterial phase. 5,12,21,30,34,35 Grading was as follows: 0, poor, Յ2 phases without venous contamination; 1, good, 3 phases without venous contamination; and 2, excellent, Ն4 phases without venous contamination. This parameter reflected the temporal resolution and determined the ability of the TR-3D-CE-MRA to identify the rapid arteriovenous shunt involved in most vascular malformations.…”

“…The region of interest was chosen to cover a large part of the vascular lumen with careful exclusion of voxels containing partial volume and to provide an easily reproducible location. 3,24 We defined arterial and venous SI and arteriovenous contrast with methods excluding noise estimation 3,11,12,24 because of the inhomogeneous distribution of noise throughout the image due to parallel imaging. 36 Arterial and venous SI curves were obtained, and 4 quantitative parameters were plotted (Fig 1): 1) Maximum arterial SI.…”