Locally focused 3D coronary imaging using volume-selective RF excitation

Yang, Guang; Burger, Peter; Gatehouse, Peter; Firmin, David N.

doi:10.1002/(sici)1522-2594(199901)41:1<171::aid-mrm24>3.0.co;2-5

Cited by 22 publications

(18 citation statements)

References 8 publications

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“…Enormous strides have been made in understanding the key problems involved, and although clear clinical utility has already been demonstrated with the definition of coronary anomalies, much is still left to do to bring MRCA into the clinical arena of coronary artery stenosis assessment; however, with the continuing developments in magnet, coil, and software technology, combined with new innovative imaging approaches [70] and improved contrast agents, there is optimism that CMR will succeed in the future. …”

Section: Resultsmentioning

confidence: 99%

Magnetic resonance of coronary arteries

Bunce¹,

Pennell²

2001

European Radiology

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Section: Resultsmentioning

confidence: 99%

Magnetic resonance of coronary arteries

Bunce¹,

Pennell²

2001

European Radiology

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“…Rectilinear excitation trajectories are the de facto standard for 2D tip-down RF excitation [12][13][14]17], but were excluded since we intend to refocus the resulting transverse magnetization within short echo spacings, conflicting with the occurrence of the excitation's "moment of zero phase precession" near the midpoint of these trajectories. The RF excitation was thus necessarily based on a self-refocused spiral echo-planar trajectory [22], and an associated linear RF design [23] was aimed toward minimizing the RF excitation duration (to reduce offresonance blurring) while yielding a suffciently high-quality profile.…”

Section: A 2d Rf Inner Volume Hpfse Sequence Designmentioning

confidence: 99%

Strategies for inner volume 3D fast spin echo magnetic resonance imaging using nonselective refocusing radio frequency pulsesa)

2005

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Fast Spin Echo (FSE) trains elicited by non-selective "hard" refocusing radio frequency (RF) pulses have been proposed as a means to enable application of FSE methods for high resolution 3D magnetic resonance imaging (MRI). Hard-pulse FSE (HPFSE) trains offer short (3-4 ms) echo spacings, but are unfortunately limited to imaging the entire sample within the coil sensitivity thus requiring lengthy imaging times, consequently limiting clinical application. In this work we formulate and analyze two general purpose combinations of 3D HPFSE with Inner Volume (IV) MR imaging to circumvent this limitation. The first method employs a 2D selective RF excitation followed by the HPFSE train, and focuses on required properties of the spatial excitation profile with respect to limiting RF pulse duration in the 5-6 ms range. The second method employs two orthogonally selective 1D RF excitations (a 90 x°-180 y° pair) to generate an echo from magnetization within the volume defined by their intersection. Subsequent echoes are formed via the HPFSE train, placing the focus of the method on (a) avoiding spurious echoes that may arise from transverse magnetization located outside the slab intersection when it is unavoidably affected by the non-selective refocusing pulses, and (b) avoiding signal losses due to the necessarily different spacing (in time) of the RF pulse applications. The performance of each method is experimentally measured using Carr-PurcellMeiboom-Gill (CPMG) multi-echo imaging, enabling examination of the magnetization evolution throughout the echo train. The methods as implemented achieve 95% to 97% outer volume signal suppression, and higher suppression appears to be well within reach, by further refinement of the selective RF excitations. Example images of the human brain and spine are presented with each technique. We conclude that the SNR effciency of volume imaging in conjunction with the short echo spacing afforded by hard pulse trains enable high resolution 3D HPFSE MRI of a small fieldof-view (FOV) with minimal aliasing artifact.

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“…Swallowing motion artifacts have been addressed by utilization of navigators monitoring the position of the epiglottis (10,13) and the application of segmented gradient echo techniques has enabled time-efficient 3D imaging of the carotid and aortic arteries (9 -11). 2D excitation pulses have been applied in various fields for restricting the field-of-view (FOV) to a confined region-of-interest (ROI) (14,15).In this contribution the application of local excitation by means of 2D excitation pulses using variable-density spiral trajectories (16,17) in combination with diffusion-preparation for blood signal nulling and segmented steady-state gradient echo acquisition for time-efficient 3D data acquisition was investigated. The 2D excitation pulse was optimized regarding duration to avoid excessive prolongation of the excitation pulse and thus short duration.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Local excitation black blood imaging at 3T: Application to the carotid artery wall

Bornstedt

Bernhardt

Hombach

et al. 2008

Magnetic Resonance in Med

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A novel approach for imaging large sections of the carotid artery wall at isotropic spatial resolution is presented. Local excitation by means of 2D excitation pulses was combined with a diffusion-prepared segmented steady-state black-blood gradient echo technique enabling the assessment of the carotid arterial wall over a range of up to 15 cm. The carotid arteries of five healthy volunteers were imaged with the proposed technique. Signal-to-noise ratio (SNR), wall-lumen contrast-tonoise ratio (CNR), and vessel dimensions were assessed and compared to conventional excitation techniques. In all experiments black-blood contrast could be realized over the covered carotid arteries with similar SNR and CNR as the conventional technique covering the region of the bulbus only. The well-established understanding of atherosclerosis as an important risk factor for the development of acute ischemic events like ischemic stroke has stimulated increasing interest in noninvasive assessment of the structure, composition, and burden of plaque depositions in the carotid artery wall. Over the last decade MRI has proven to contribute substantially to the noninvasive assessment and characterization of atherosclerotic plaque, especially in the aorta and the carotid arteries (1-3).Most commonly, vessel wall imaging has been achieved by combining a double-inversion recovery black-blood preparation (4) with 2D data acquisition by means of multi spin-echo (MSE) techniques (1-3). Without compromising spatial resolution due to severe T 2 apodization, this technique allows for the acquisition of a single slice in the minute time range, while providing excellent lumen-wall contrast and enabling differently weighted images including T 2 (T 2 W), proton density (PDW) and, limited by the required inversion recovery time for blood signal nulling and heart rate, T 1 weighting (T 1 W). The extension of this technique to 3D coverage of large sections of the artery of interest has been limited by the resulting long acquisition times, often causing image-distorting motion artifacts (5) due to swallowing, arterial pulsation, breathing, and suboptimal blood suppression (6,7) due to incomplete exchange of the blood in the entire volume. Improvement of blood suppression has been obtained by utilizing phasesensitive reconstruction techniques (8) and diffusion-prepared techniques (9,10,12), all relying rather on the motion of the blood than on complete blood exchange between preparation and readout. Swallowing motion artifacts have been addressed by utilization of navigators monitoring the position of the epiglottis (10,13) and the application of segmented gradient echo techniques has enabled time-efficient 3D imaging of the carotid and aortic arteries (9 -11). 2D excitation pulses have been applied in various fields for restricting the field-of-view (FOV) to a confined region-of-interest (ROI) (14,15).In this contribution the application of local excitation by means of 2D excitation pulses using variable-density spiral trajectories (16,17) in combination ...

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Locally focused 3D coronary imaging using volume-selective RF excitation

Cited by 22 publications

References 8 publications

Magnetic resonance of coronary arteries

Magnetic resonance of coronary arteries

Strategies for inner volume 3D fast spin echo magnetic resonance imaging using nonselective refocusing radio frequency pulsesa)

Local excitation black blood imaging at 3T: Application to the carotid artery wall

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