Quadrature coil design for high-resolution carotid artery imaging scores better than a dual phased-array coil design with the same volume coverage (original) (raw)

An improved quadrature or phased-array coil for MR cardiac imaging

Magnetic Resonance in Medicine, 1995

A tailored receive-only coil for cardiac imaging has been designed. The coil consists of two overlapping coil elements and can be used either as a quadrature surface coil or as a phased-array coil. Through phantom experiments and images of the heart, the authors have shown that the improved cardiac coil provided a signal-to-noise ratio 1.6 times higher than a conventional quadrature spine coil, 1.4 times higher than that of a single coil (having the same shape and total dimension), and three times higher than the body coil at the depth of the posterior wall of the heart. The authors have also shown that the cardiac coil improved image quality everywhere in the heart. This coil will enhance routine clinical cardiac studies as well as other examinations such as myocardial perfusion, wall motion, and coronary artery imaging.

A phased array coil for human cardiac imaging

Magnetic Resonance in Medicine, 1995

A prototype cardiac phased array receiver coil was constructed that comprised a cylindrical array and a separate planar array. Both arrays had two coil loops with the same coil dimensions. Data acquisition with the cylindrical array placed on the human chest, and the planar array placed under the back, yielded an overall enhancement of the signal-to-noise ratio (SNR) over the entire heart by a factor of 1.1-2.85 over a commercially available flexible coil and a commercially available fourloop planar phased array coil. This improvement in SNR can be exploited in cardiac imaging to increase the spatial resolution and reduce the image acquisition time.

Comparison of four MR carotid surface coils at 3T

PLOS ONE, 2019

Background The quality of carotid wall MRI can benefit substantially from a dedicated RF coil that is tailored towards the human neck geometry and optimized for image signal-to-noise ratio (SNR), parallel imaging performance and RF penetration depth and coverage. In last decades, several of such dedicated carotid coils were introduced. However, a comparison of the more successful designs is still lacking. Objective To perform a head-to-head comparison over four dedicated MR carotid surface coils with 4, 6, 8 and 30 coil elements, respectively. Material and methods Ten volunteers were scanned on a 3T scanner. For each subject, multiple black-blood carotid vessel wall images were measured using the four coils with different parallel imaging settings. The performance of the coils was evaluated and compared in terms of image coverage, penetration depth and noise correlations between elements. Vessel wall of a common carotid section was delineated manually. Subsequently, images were assessed based on vessel wall morphology and image quality parameters. The morphological parameters consisted of the vessel wall area, thickness, and normalized wall index (wall area/total vessel area). Image quality parameters consisted of vessel wall SNR, wall-lumen contrast-tonoise ratio (CNR), the vessel g-factor, and CNR index ((wall-lumen signal) / (wall+lumen signal)). Repeated measures analysis of variance (rmANOVA) was applied for each parameter for the averaged 10 slices for all volunteers to assess effect of coil and SENSE factor. If the rmANOVA was significant, post-hoc comparisons were conducted. Results No significant coil effect were found for vessel wall morphological parameters. SENSE acceleration affected some morphological parameters for 6-and 8-channel coils, but had no

Construction and Characterisation of MRI Coils for Vessel Wall Imaging at 7 Tesla

Atherosclerotic plaques in the bifurcation of the carotid artery vessels can pose a significant stroke risk from stenosis, thrombosis and emboli, or plaque rupture. However, the possibility of the latter depends on the structure of the plaque and its stability. So far, the assessment of such depositions, and the evaluation of the risk they pose, is not satisfactory with 3 Tesla black blood imaging. It is expected that the SNR increase at 7 Tesla, together with an appropriate and patient-safe RF coil, will result in higher resolution images that would help in better assessing the composition of atherosclerotic plaques in vessel walls. A custom-built neck array was designed and constructed, with the aim of investigating the benefits of the higher field strength using DANTE-prepared black blood imaging.

What is the optimum phased array coil design for cardiac and torso magnetic resonance?

Magnetic Resonance in Medicine, 1997

To determine the optimum configuration of a phased array MR coil system for human cardiac applications, the sensitivity of 10 flexible array designs operating under ideal conditions was calculated at 13 points circling the myocardium of a model torso whose geometry was determined from healthy volunteers. The array geometries that were evaluated included continuous strips of 2,4,6, and 10 circular coils of diameter equal to half the torso thickness wrapped laterally around the torso, 2 pairs of coils located on the left side of the chest and back, clusters of 3 coils in 2 orientations, clusters of 4 and 6 coils, and a hybrid cross of 6 coils. The 4-, 0-, and 10-coil strip arrays out-performed the other designs for a given number of coils, yielding average theoretical sensitivity improvements of 45%, 53%, and 55% relative to a single flexible coil positioned at the point closest to the anterior myocardium, compared with about 30% for 4-and 6-coil clusters and the 2-pair geometry (P < 0.02). A flexible 4-coil strip array was constructed for a clinical 1.5 T scanner with 15-cm diameter circular surface coils on flexible circuit board. The signal-to-noise ratio (SNR) of this coil at the 13 cardiac locations was measured in 15 normal volunteers and compared with the SNR measured in images acquired with standard commercial MR coils: a body coil, a flexible torso array, a general purpose flexible coil, and, in 4 subjects, a dual array coil. In the prone orientation, the average myocardial SNR improvement of the 4-coil strip array was 650% relative to the whole body coil, compared with 310440% for the other commercial coils (P < 0.0000J). The twofold advantage over the commercial coils persisted in supine studies (P < 0.00005, n = 5). Thus, flexible circumferential phased arrays of strips of surface coils of diameter comparable with the depth of the heart generally out-perform many other standard geometries for a given number of coils, and can yield dramatically improved SNR over coils available for general use in the torso. the maximum SNR for a volume element (voxel) at a depth d is realized when the circular surface coil radius, a, is adjusted such that a = d/ VF, and the coil is

Modified birdcage coils for targeted imaging

Magnetic Resonance Imaging, 1995

The design of a radiofrequency coil of U-shaped geometry, specifically intended to image individual knuckle joints of the hand, has been investigated. The coil geometry is that of a "split and opened" birdcage coil. The optimum leg positions for such a U-shaped coil have been theoretically predicted using a novel technique that considers both the signal-to-noise ratio and the homogeneity of the field-of-view. Two particular coils of this type have been constructed, each optimum for a different size of image space and assuming a different source of image noise (sampledominated or coil-dominated). The experimentally determined radiofrequency fields produced by the coils correspond well to theory. Either coil can be used to obtain good-quality, high-resolution (130 pm x 130 pm in-plane) images in vivo of the first, second, or fifth metacarpophalangeal joints of the hand, sites of particular interest in the study of arthritis.

Phased array coil for implementing parallel MRI in intravascular imaging: A feasibility study

Concepts in Magnetic Resonance Part A, 2014

The use of intravascular MRI imaging of vessels will provide high quality images for improved diagnosis and treatment. An intravascular MR receive coil provides high SNR because of proximity to the tissue but respiratory and cardiovascular motion may affect the quality of acquired images. Parallel MRI provides a framework to reduce the scan time using multiple coils. This article presents a novel design of a Phased Array MR receive coil for intravascular imaging which can implement Parallel MRI. Cartesian and Radial GRAPPA are used as the main reconstruction algorithms. We demonstrate that Moving Segment Radial GRAPPA provides good image reconstruction with minimum artifacts when data is under-sampled by a factor of 16.