Biomedical subjects

G T Luk-Pat

Publications and source records attributed to G T Luk-Pat.

2 recordsLinked to original sources

PubMed2001

Reducing off-resonance distortion by echo-time interpolation.

Off-resonant spins, produced by chemical shift, tissue-susceptibility differences, or main-field inhomogeneity, can cause blurring or shifts, severely compromising the diagnostic value of magnetic resonance images. To mitigate these off-resonance effects, the authors propose a technique whereby two images are acquired at different echo times (TEs) and interpolated to produce a single image with dramatically-reduced blurring. The phase difference of these two images is not used to produce a field map; instead, the weighted complex-valued average of the two images is used to produce a single image. Previously-described methods reconstruct a set of preliminary images, each at a different off-resonant frequency, and then assemble these into one final image, choosing the best off-resonant frequency for each voxel. Compared to these methods, the proposed technique requires the same or less processing time and is much less sensitive to errors in the field map. This technique was applied to centric-ordered EPI but it can be applied to any imaging trajectory, including one-shot EPI, spiral imaging, projection-reconstruction imaging, and 2D GRASE. Magn Reson Med 45:269-276, 2001.

Humans↗

PubMed1999

High-resolution three-dimensional in vivo imaging of atherosclerotic plaque.

The internal structure of atherosclerotic-plaque lesions may be a useful predictor of which lesions will rupture and cause sudden events such as heart attack or stroke. With lipid and flow suppression, we obtained high-resolution, three-dimensional (3D) images of atherosclerotic plaque in vivo that show the cap thickness and core size of the lesions. 3D GRASE was used because it provides flexible T(2) contrast and good resistance to off-resonance artifacts. While 2D RARE has similar properties, its resolution in the slice-select direction, which is important because of the irregular geometry of atherosclerotic lesions, is limited by achievable slice-excitation profiles. Also, 2D imaging generally achieves lower SNR than 3D imaging because, for SNR purposes, 3D image data is averaged over all the slices of a corresponding multislice 2D dataset. Although 3D RARE has many of the advantages of 3D GRASE, it requires a longer scan time because it uses more refocusing pulses to acquire the same amount of data. Finally, cardiac gating is an important part of our imaging sequence, but can make the imaging time quite long. To obtain reasonable scan times, a 2D excitation pulse was used to restrict the field of view. Magn Reson Med 42:762-771, 1999.

Aorta, Thoracic↗