Resolution In Slice Direction Research Articles

Time-of-flight MR-angiography with a helical trajectory and slice-super-resolution reconstruction.

To improve 2D noncontrast-enhanced MRA by using a helical time-of-flight (TOF) acquisition technique and a slice-super-resolution reconstruction. The TOF technique is combined with a helical trajectory with golden-angle-based radial projection reordering. A continuous spatial shift in slice direction is realized by adjusting the frequency of the excitation pulse between the individual projections. The limited resolution along the shift direction is improved by a deconvolution with simulated slice profile. The helical TOF (hTOF) was compared in vivo with a conventional 2D and 3D TOF. Results from in vivo experiments on the carotid show that the visual resolution in slice direction can be improved by using hTOF and the slice-super-resolution reconstruction. The vessels appear up to 1.5 times sharper and can be better separated from each other. Compared to 2D TOF images, the stair step artifacts are strongly reduced in reformatted hTOF images, whereas measurement time is decreased by at least 35%. Compared to 3D TOF, the hTOF offers a higher blood-to-background contrast, better visualization of smaller vessels, and reduced measurement time. The hTOF benefits from a 2D acquisition and a 3D reconstruction, which makes it a promising technique for the noncontrast-enhanced imaging of the carotid.

Volumetric black-blood imaging of aortic dissection using T2 prepared inversion recovery

Background Aortic dissection is a life threatening condition, and the commonest presentation of the acute aortic syndrome, occurring in 80-90% of such cases. Identification of intimal tears is important to enable the success of an interventional procedure. MRI allows for black-blood contrast to depict the aortic vessel wall and intimal flap with positive contrast which help delineate tear and intimal anatomy. However, the conventional black-blood approach (double inversion recovery) is limited to single slice imaging with relatively low resolution in slice direction. In this study, we compare the usefulness of two approaches using T2 prepared inversion recovery (T2IR) and T2 prepared phase sensitive inversion recovery (T2PSIR) for volumetric high-resolution black-blood aortic imaging in healthy volunteers including a pilot study to optimize flow-independence.