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Invest Radiol. 2006 Apr;41(4):391-9.

High spatial-resolution CE-MRA of the carotid circulation with parallel imaging: comparison of image quality between 2 different acceleration factors at 3.0 Tesla.

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Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, 90095, USA.



We sought to evaluate and compare the image quality and vessel delineation of the carotid arteries with high spatial-resolution contrast-enhanced MRA (CE-MRA) at 3.0 T using integrated parallel acquisition (iPAT) with acceleration factors of 2 and 4.


Using an 8-channel neurovascular array coil, we performed prospective high-spatial resolution CE-MRA at 3.0 T of the head and neck on 24 patients (11 men, 13 women, ages 37-89) with suspected arterio-occlusive disease who were assigned randomly to 2 groups. Twelve patients (group A) were examined with a 3D-GRE sequence using iPAT with acceleration factor of 2. For the next 12 patients (group B) a near-identical sequence with an acceleration factor of 4 was applied. Higher iPAT factors were used to increase the spatial-resolution while keeping scan time unchanged. Two volunteers were scanned by both protocols. Phantom measurements were performed to assess the signal-to-noise ratio (SNR). The presence of artifact, noise, image quality of the arterial segments, and the presence and degree of arterial stenosis were evaluated independently by 2 radiologists. Statistical analysis of data was performed by using Wilcoxon rank sum test and 2-sample Student t test (P < 0.05 was indicative a statistically significant difference). The interobserver variability was tested by kappa coefficient.


SNR values were significantly lower when iPAT with acceleration factor of 4 was used (P < 0.001). There was no significant difference between 2 groups in regards to image noise (P = 0.67) and artifact (P = 0.8). Both readers visualized the majority of carotid circulation with good image quality in both groups. For smaller intracranial arteries, such as the second-division of anterior and middle cerebral artery, anterior communicating artery, and superior cerebellar artery, the image quality and vessel delineation was significantly better at an iPAT factor of 4 (P < 0.01). The overall interobserver agreement for both the vessel depiction, and detection of arterial stenoses was higher in group B compared with group A.


Use of parallel acquisition techniques with a high acceleration factor (iPAT-4) results in superior depiction of small intracranial arterial segments. Imaging at higher magnetic field strength, in addition to the use of an optimized 8-channel array coil, provides sufficient SNR to support faster parallel acquisition protocols, leading to improved spatial-resolution. More extensive clinical studies are warranted to establish the range of applications and confirm the accuracy of the technique.

[Indexed for MEDLINE]

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