The long term objective of this project continues to be the development of methods which permit MR data acquisition during continuous motion of the patient table for contrast-enhanced MR angiographic studies of the peripheral vasculature. This will allow diagnostic quality imaging of the vasculature from the abdomen and pelvis to the feet to allow diagnosis and characterization of peripheral vascular disease. Imaging during continuous table motion permits high efficiency in the use of scan time and of the contrast dose. Because a given axial level is imaged within the moving field-of-view for only a limited time, typically 20 sec or less, it is critical to allow improvements in spatial resolution for a given acquisition time. To this end, acceleration techniques demonstrated in Years 01-04 in one dimension will be extended to the two lateral dimensions. Another major aim of the study is to image the contrast dose transit in real time, automatically track its position, and use this information to automatically adjust the table velocity. The grant application includes the following specific aims: 1. High Resolution CE-MRA of a Fixed FOV Using 2D Acceleration Techniques. In preparation for imaging during continuous table motion, techniques will first be developed for performing highly accelerated acquisitions during no table motion within a targeted 16 sec. The elliptical centric view order will be combined with 2D homodyne, 2D SENSE, and time-resolved view-shared acquisition for 1 mm isotropic resolution. 2. Parallel Acquisition Techniques Applied During Continuous Table Motion. The accelerated acquisition methods of Aim #1 will be adapted to continuously moving table imaging. Reconstruction algorithms will be developed which account for gradient warping, 2D SENSE-homodyne, and variable FOV acquisition. Coils will be developed which allow efficient 15x accelerated 2D parallel acquisition over an extended FOV. 3. Patient-Specific Acquisition for Continuously Moving Table Peripheral MRA. Methods will be developed to detect the leading edge of the contrast bolus as it moves along the peripheral vasculature and then to use this information to alter the patient table motion in real time. This will be tested initially in phantoms and then using a test bolus. The final technique will be one in which an extended-FOV, high spatial resolution, arterial phase peripheral angiogram is formed by automatically tracking the full contrast bolus with no need for a test bolus.
Peripheral vascular disease is a major problem in the population of the United States, and it is important to image and diagnosis this condition in an easy, accurate, reliable, safe manner which not only accounts for patient-to-patient differences in anatomy and blood flow but also accommodates the long field of view which ex- tends from the abdomen to the feet. This project is relevant to this problem, as the goal is to develop a method which allows high spatial resolution MR imaging of the extended vasculature by using a moving patient table uniquely tuned to the transit of intravenous contrast material within each patient.
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