Improved contrast at 1.5 Tesla using half-Fourier imaging: Application to spin-echo and angiographic imaging

Haacke, E. Mark; Mitchell, James R.; Lee, Doohi

doi:10.1016/0730-725x(90)90216-o

Cited by 30 publications

(5 citation statements)

References 8 publications

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“…Unfortunately, the half-Fourier technique is very susceptible to local phase errors, a problem that is particularly bad near the sinuses and regions of phase variations due to incompletely rephased moving spins. Iterative techniques to reduce these artifacts are being pursued (19).…”

Section: ( B ) Resolutionmentioning

confidence: 99%

Optimizing blood vessel contrast in fast three‐dimensional MRI

Haacke

Masaryk

Wielopolski

et al. 1990

Magnetic Resonance in Med

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Magnetic resonance angiography has matured to the point where clinically useful images can be acquired in half an hour or less. In this paper, the role of 3D imaging techniques is primarily considered. Specifically, the optimal imaging parameters, sequences, and reconstruction techniques are evaluated for moving spins. A variant of FISP known as ROAST with low flip angles, short repeat times, and a thick slab has been found to yield the best 3D survey scan of the cranial vessels with roughly 1 X 1 X 1-mm3 resolution in each of the processed images (slices). For the faster flowing carotids, a sagittal scout with as short a TE as possible is required to avoid spin dephasing. Localization is accomplished in both cases by acquiring thin slab 3D, thin partition, larger flip angle, longer repeat time FLASH sequences. Different choices of dephase/rephase sequences and directions are also reviewed. These choices are discussed from a practical and theoretical perspective. In particular, improvements in contrast and resolution are evaluated using half-Fourier, 512 acquisition, small fields of view and constrained reconstruction for both rephased gradient echo sequences and dephased thin slice long TR spin-echo sequences. A resolution of 0.5-0.75 mm is recommended to obtain sufficient image quality for consistent clinical interpretation of stenoses and vessel abnormalities.

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Section: ( B ) Resolutionmentioning

confidence: 99%

Optimizing blood vessel contrast in fast three‐dimensional MRI

Haacke

Masaryk

Wielopolski

et al. 1990

Magnetic Resonance in Med

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“…Performing super-resolution in the frequency domain: In the frequency domain, super-resolution may be accomplished by frequency extrapolation, i.e., using low frequency information to estimate high frequency behaviour. There are some standard methods to accomplish such extrapolation, e.g., the Papoulis-Gerchberg algorithm [4,12,20,24,25,26] and projection methods [7,8,14,15,18,29]. We are currently investigating the application of these methods to multiple data sets in the frequency domain, a subject that is beyond the scope of this paper.…”

Section: -Case I: Phase Ramp Applied After Filtering/sampling Of Raw mentioning

confidence: 99%

Mathematical Analysis of “Phase Ramping” for Super-Resolution Magnetic Resonance Imaging

Mayer

Vrscay

2006

Lecture Notes in Computer Science

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Super-resolution image processing algorithms are based on the principle that repeated imaging together with information about the acquisition process may be used to enhance spatial resolution. In the usual implementation, a series of low-resolution images shifted by typically subpixel distances are acquired. The pixels of these low-resolution images are then interleaved and modeled as a blurred image of higher resolution and the same field-of-view. A high-resolution image is then obtained using a standard deconvolution algorithm. Although this approach has been applied in magnetic resonance imaging (MRI), some controversy has surfaced regarding the validity and circumstances under which super-resolution may be applicable. We investigate the factors that limit the applicability of super-resolution MRI.

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“…The LF MRI method was combined with a conventional half Fourier image reconstruction algorithm (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) to achieve a further reduction in the required number of signal measurements. This was done by using Eq.…”

Section: Half K-space Lf Mrimentioning

confidence: 99%

Locally focused mri

Cao

Levin

Lian

1995

Magnetic Resonance in Med

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Conventional magnetic resonance images are reconstructed by Fourier transformation and have uniform spatial resolution across the entire field of view (FOV). This paper describes a way of creating MR images that have higher spatial resolution in some areas than in others. High resolution imaging can be confined to just those areas where it is necessary to resolve strong edges without truncation artifact. Such locally focused images can be acquired in less scan time than that required to image the entire FOV with uniformly high resolution. Images are reconstructed from a subset of the usual phase-encoded signals required to create a uniformly well-resolved image. The measured signals are usually nonuniformly scattered in k-space. Functional and interventional imaging may benefit from this technique, which makes it possible to acquire a rapid series of dynamical images that have high resolution in areas of expected change and lower resolution elsewhere. Spectroscopic images may be improved by using high resolution in the neighborhood of sharp edges (e.g., scalp lipids) that might otherwise cause truncation artifacts.

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Improved contrast at 1.5 Tesla using half-Fourier imaging: Application to spin-echo and angiographic imaging

Cited by 30 publications

References 8 publications

Optimizing blood vessel contrast in fast three‐dimensional MRI

Optimizing blood vessel contrast in fast three‐dimensional MRI

Mathematical Analysis of “Phase Ramping” for Super-Resolution Magnetic Resonance Imaging

Locally focused mri

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