Modified Elliptical Centric View Orders for Improved Real-Time MRA

DESCRIPTION (provided by applicant): The overall purpose of this grant application is to further draw on the extensive developments made in contrast-enhanced MR angiography (CE-MRA) during the previous funding cycle and push the field to even higher levels. The last several years have seen multiple developments in CE-MRA, and we believe that the work of our own group has contributed materially to this. Specific developments include: (i) demonstration of a signal enhancement effect when 2D parallel acquisition is applied to elliptical centric CE-MRA; (ii) demonstration of improved vessel sharpness in accelerated CE-MRA; (iii) development of the Cartesian Acquisition with Projection-Reconstruction-like sampling (CAPR) pulse sequence for time-resolved CE-MRA; (iv) routine demonstration of acceleration factors exceeding 10 in CE-MRA; (v) development of modular coil arrays for accelerated CE-MRA; (v) demonstration that CAPR provides high fidelity in the portrayal of dynamic phenomena; and (vi) routine demonstration of high quality time-resolved 3D CE-MR angiograms of the brain and calves. Specific aims to be studied are: 1. High Quality Comprehensive Neurovascular Exam. In an extension of the work performed during Years 20- 23 we will generate high quality images of the vasculature of the aortic arch, carotid arteries, intracranial arteries, and the draining veins of he brain in one comprehensive exam. The traditional test bolus used to assess timing in a 2D slice will be replaced with a low dose (1-2 ml) 3D time-resolved CE-MRA sequence. This will be followed by normal dose (18 ml) acquisition in which multi-element, modular RF coil arrays will allow 2D accelerated acquisition, providing high spatial resolution data sets for all territories. . High Resolution CAPR of the Upper Extremities and Abdomen. Parallel acquisition techniques previously developed for MR angiography of the brain and calves will be adapted to other anatomic regions. For each region the modular coil array elements will be matched to the specific field-of-view (FOV) and desired spatial resolution. For the hands the FOV is typically asymmetric (L/R vs. A/P), suggesting that elements having different sizes be used as for the calves. For the abdomen the increased FOV calls for larger coil elements. 3. Combined Angiographic and Perfusion MR Imaging. Analysis of the signal levels in brain parenchyma from CAPR CE-MRA studies of the brain has shown that first-pass parenchymal blush is detectable, suggesting the potential for providing perfusion information from the angiographic data set. However, this can be limited by a frame time which is still marginally too long and SNR which is marginally too small. To address this we will adapt the basic CAPR sequence for improved temporal resolution using 2D SENSE acceleration factors of ten-fold and higher. To retain SNR, particularly within the parenchymal signal, we will apply recently developed compressive sensing methods. 1