Peripheral magnetic resonance angiography (MRA) is limited by the need to cover a large field of view using a limited amount of contrast material. The """"""""bolus chase"""""""" technique images several stations following a single slow injection. Recent reports indicate that this technique provides limited spatial resolution due to the limited time available at each station. Optimal acquisition timing is difficult due to potential variations in contrast arrival times within the same field of view. Finally, venous contamination is common in the lower extremities. We are developing novel high resolution, sparsely sampled projection acquisitions. Combining volume coverage, spatial resolution and speed into a single quality measure, these time-resolved sequences perform 4-13 times better than our previously reported Cartesian, time-resolved technique (3D TRICKS). These sequences will be optimized for peripheral angiography. Time-resolved information eliminates timing considerations below the abdominal station while reducing sensitivity to filling delays between vessels. We propose to use extended scanning times and intra-vascular contrast material to increase SNR. This will require vein suppression that will be based on the spatial and temporal correlation of voxels relative to reference arterial and venous regions of interest. Extended time-resolved imaging following separate injections at several imaging stations can simultaneously increase coverage, spatial resolution and SNR. The sequences and vein suppression method will be optimized in Specific Aim I using simulations, phantoms and pigs.
In Specific Aim 2, the ability to image delayed vessel filling and to suppress veins in a pig model using an intra-vascular agent, MS-325, will be validated using DSA.
In Specific Aim 3, volunteers and patients will be imaged at one station with full doses of conventional contrast. Tl will be measured to develop injections that mimic the Tl from 1/3 dose MS-325. Intra-operative X-ray angiography will be used for validation of the patient MRA studies The proposed techniques have similar potential in other areas of MRA.
| Mistretta, C A; Wieben, O; Velikina, J et al. (2006) Highly constrained backprojection for time-resolved MRI. Magn Reson Med 55:30-40 |
| Unal, Orhan; Li, Junwei; Cheng, Weiguo et al. (2006) MR-visible coatings for endovascular device visualization. J Magn Reson Imaging 23:763-9 |
| Carroll, Timothy J; Rowley, Howard A; Haughton, Victor M (2003) Automatic calculation of the arterial input function for cerebral perfusion imaging with MR imaging. Radiology 227:593-600 |
