A modified projection reconstruction trajectory for reduction of undersampling artifacts

Wang, Wen Tung; Grimm, Roger C.; Riederer, Stephen J.

doi:10.1002/jmri.20248

Cited by 2 publications

(1 citation statement)

References 19 publications

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“…In particular, the difference is obvious for images whose spatial resolution is substantially different from the nominal spatial resolution. Examples of the images include those acquired from trajectories with a smaller sampling coverage in k ‐space, such as the spiral images used in this work whose spatial resolution is about 2 pixels (14), and images obtained from undersampled projection reconstruction (15) data. In these cases, a 2‐pixel separation for tag lines in Wayte and Redpath's method cannot result in resolved tag lines.…”

Section: Discussionmentioning

confidence: 99%

Estimating the spatial resolution of in vivo magnetic resonance images using radiofrequency tagging pulses

Wang

Meyer

2007

Magnetic Resonance in Med

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The spatial resolution of magnetic resonance (MR) images is usually specified by using nominal spatial resolution, the width of the simulated point-spread function (PSF), or measurement from a resolution phantom. The accuracy of these measures is limited because they do not take into account the effects of in vivo image degradation. In this work, tag lines were used to estimate the spatial resolution of in vivo MR images. The idea of using tag lines to measure resolution was originally proposed In magnetic resonance imaging (MRI), the image spatial resolution is often specified by using a nominal spatial resolution or the width of the point-spread function (PSF). The nominal spatial resolution is the pixel size of the image matrix, which is equal to the field of view (FOV) divided by the image matrix dimension. It is a good estimate of the spatial resolution for conventional fully sampled images. However, it does not take into account the effects of partial k-space sampling and image quality degradation factors, including B 0 /B 1 -field inhomogeneity, T 2 blurring, and susceptibility. These effects are common sources of image degradation for rapid MRI sequences. One can also compute a simulated PSF based on the sampling trajectory and thus take partial k-space sampling into account. Since no image degradation is included, the simulated PSF width represents the best image quality achievable by the sampling trajectory. Therefore, when there are minimal effects from the degradation factors, the simulated PSF width is a good estimate of the spatial resolution. Alternatively, the spatial resolution can be measured experimentally by using a resolution phantom. The measurement is a better estimate of the spatial resolution because it includes the effects of image degradation factors. It also provides a quick visual estimate of the spatial resolution. This method, however, may not be able to measure spatially varying resolution. The accuracy of the measurement is limited by the size of small structures available in the resolution phantom, and by how well the phantom is aligned with the slice-select direction. More importantly, the image degradation effects on phantom images are different from those on in vivo images.

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Section: Discussionmentioning

confidence: 99%

Estimating the spatial resolution of in vivo magnetic resonance images using radiofrequency tagging pulses

Wang

Meyer

2007

Magnetic Resonance in Med

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Using Adaptive Imaging Parameters to Improve PEGylated Ultrasmall Iron Oxide Nanoparticles‐Enhanced Magnetic Resonance Angiography

Li,

Shan,

Chen

et al. 2024

Advanced Science

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The PEGylated ultrasmall iron oxide nanoparticles (PUSIONPs) exhibit longer blood residence time and better biodegradability than conventional gadolinium‐based contrast agents (GBCAs), enabling prolonged acquisitions in contrast‐enhanced magnetic resonance angiography (CE‐MRA) applications. The image quality of CE‐MRA is dependent on the contrast agent concentration and the parameters of the pulse sequences. Here, a closed‐form mathematical model is demonstrated and validated to automatically optimize the concentration, echo time (TE), repetition time (TR) and flip angle (FA). The pharmacokinetic studies are performed to estimate the dynamic intravascular concentrations within 12 h postinjection, and the adaptive concentration‐dependent sequence parameters are determined to achieve optimal signal enhancement during a prolonged measurement window. The presented model is tested on phantom and in vivo rat images acquired from a 3T scanner. Imaging results demonstrate excellent agreement between experimental measurements and theoretical predictions, and the adaptive sequence parameters obtain better signal enhancement than the fixed ones. The low‐dose PUSIONPs (0.03 mmol kg−1 and 0.05 mmol kg−1) give a comparable signal intensity to the high‐dose one (0.10 mmol kg−1) within 2 h postinjection. The presented mathematical model provides guidance for the optimization of the concentration and sequence parameters in PUSIONPs‐enhanced MRA, and has great potential for further clinical translation.

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A modified projection reconstruction trajectory for reduction of undersampling artifacts

Cited by 2 publications

References 19 publications

Estimating the spatial resolution of in vivo magnetic resonance images using radiofrequency tagging pulses

Estimating the spatial resolution of in vivo magnetic resonance images using radiofrequency tagging pulses

Using Adaptive Imaging Parameters to Improve PEGylated Ultrasmall Iron Oxide Nanoparticles‐Enhanced Magnetic Resonance Angiography

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