Jason Mendes

Rigid-body motion correction with self-navigation MRI.

The use of phase correlation to detect rigid‐body translational motion is reviewed and applied to individual echotrains in turbo‐spin‐echo data acquisition. It is shown that when the same echotrain is acquired twice, the subsampled correlation provides an array of delta‐functions, from which the motion that occurred between the acquisitions of the two echotrains can be measured. It is shown further that a similar correlation can be found between two sets of equally spaced measurements that are adjacent in k‐space. By measuring the motion between all adjacent pairs of k‐space subgroups, the complete motion history of a subject can be determined and the motion artifacts in the image can be corrected. Some of the limiting factors in using this technique are investigated with turbo‐spin‐echo head and hand images. Magn Reson Med, 2009.

Reduced blood flow artifact in intraplaque hemorrhage imaging using CineMPRAGE.

Magnetization prepared rapid acquisition gradient echo (3D MPRAGE) has been shown to be a sensitive method to image carotid intraplaque hemorrhage. As the MPRAGE sequence used to identify potential intraplaque hemorrhage does not utilize cardiac gating, it is difficult to optimize the inversion times due to the dynamic nature of flowing blood. As a result, a best fit inversion time is often determined experimentally and then used for in vivo clinical examination. This results in compromised blood suppression and occasional hemorrhage mimicking flow artifacts. We demonstrate that a retrospective cardiac correlated reconstruction can be applied to the conventional MPRAGE sequence (CineMPRAGE) to more accurately identify blood signal. This CineMPRAGE reconstruction uses the data from a standard nongated MPRAGE sequence to generate a full sequence of cardiac correlated images throughout the cardiac cycle and, therefore, provides a dynamic view of the carotid artery and a better ability to discern blood signal from potential intraplaque hemorrhage. In our preliminary study of 35 patients, signal from potential hemorrhage was constant over the cardiac cycle, whereas any signal from blood flow artifact was observed as an oscillating signal over the cardiac cycle. Magn Reson Med, 2013.

Three‐dimensional dynamic contrast enhanced imaging of the carotid artery with direct arterial input function measurement

Kinetic analysis using dynamic contrast enhanced MRI to assess neovascularization of carotid plaque requires images with high spatial and temporal resolution. This work demonstrates a new three‐dimensional (3D) dynamic contrast enhanced imaging sequence, which directly measures the arterial input function with high temporal resolution yet maintains the high spatial resolution required to identify areas of increased adventitial neovascularity.

Highly accelerated cardiac cine phase-contrast MRI using an undersampled radial acquisition and temporally constrained reconstruction

To evaluate a method to enable single‐slice or multiple‐slice cine phase contrast (cine‐PC) acquisition during a single breath‐hold using a highly sparsified radial acquisition ordering and temporally constrained image reconstruction with a spatially varying temporal constraint.

CINE turbo spin echo imaging

High‐resolution turbo spin echo (TSE) images have demonstrated important details of carotid artery morphology; however, it is evident that pulsatile blood and wall motion related to the cardiac cycle are still significant sources of image degradation. Although ECG gating can reduce artifacts due to cardiac‐induced pulsations, gating is rarely used because it lengthens the acquisition time and can cause image degradation due to nonconstant repetition time. This work introduces a relatively simple method of converting a conventional TSE acquisition into a retrospectively ECG‐correlated cineTSE sequence. The cineTSE sequence generates a full sequence of ECG‐correlated images at each slice location throughout the cardiac cycle in the same scan time that is conventionally used by standard TSE sequences to produce a single image at each slice location. The cineTSE images exhibit reduced pulsatile artifacts associated with a gated sequence but without the increased scan time or associated nonconstant repetition time effects. Magn Reson Med, 2011.

Free-breathing black-blood CINE fast-spin echo imaging for measuring abdominal aortic wall distensibility: A feasibility study

The paper reports a free-breathing black-blood CINE fast-spin echo (FSE) technique for measuring abdominal aortic wall motion. The free-breathing CINE FSE includes the following MR techniques: (1) variable-density sampling with fast iterative reconstruction; (2) inner-volume imaging; and (3) a blood-suppression preparation pulse. The proposed technique was evaluated in eight healthy subjects. The inner-volume imaging significantly reduced the intraluminal artifacts of respiratory motion (p  =  0.015). The quantitative measurements were a diameter of 16.3  ±  2.8 mm and wall distensibility of 2.0  ±  0.4 mm (12.5  ±  3.4%) and 0.7  ±  0.3 mm (4.1  ±  1.0%) for the anterior and posterior walls, respectively. The cyclic cross-sectional distensibility was 35  ±  15% greater in the systolic phase than in the diastolic phase. In conclusion, we developed a feasible CINE FSE method to measure the motion of the abdominal aortic wall, which will enable clinical scientists to study the elasticity of the abdominal aorta.

3D Dynamic Contrast Enhanced Imaging of the Carotid Artery with Direct Arterial Input Function Measurement

Kinetic analysis using dynamic contrast enhanced MRI to assess neovascularization of carotid plaque requires images with high spatial and temporal resolution. This work demonstrates a new three‐dimensional (3D) dynamic contrast enhanced imaging sequence, which directly measures the arterial input function with high temporal resolution yet maintains the high spatial resolution required to identify areas of increased adventitial neovascularity.

Three-dimensional dynamic contrast enhanced imaging of the carotid artery with direct arterial input function measurement: 3D Carotid DCE

Kinetic analysis using dynamic contrast enhanced MRI to assess neovascularization of carotid plaque requires images with high spatial and temporal resolution. This work demonstrates a new three‐dimensional (3D) dynamic contrast enhanced imaging sequence, which directly measures the arterial input function with high temporal resolution yet maintains the high spatial resolution required to identify areas of increased adventitial neovascularity.