Among the facets of Magnetic Resonance Imaging which enhance its potential for detection and diagnosis of diseases in the body is its ability to measure and image blood flow. Current flow MRI techniques include signal amplitude dependent measures which monitor signal gain or loss due to flow perpendicular to the imaging plane, or phase dependent measure which rely on phase shifts of proton signals due to motion through magnetic field gradients. Neither amplitude dependent nor simple phase display techniques are well suited for imaging complicated small vessel flow patterns characteristic of some neovascular tumors. However, this condition of many small intertwined vessels having multi-directional flow coexisting within individual voxels is the target of the proposed technique referred to as """"""""flow enhanced MRI"""""""". This approach strives to produce images in which static tissues are suppressed to intensity levels of non-signal area while enhancing regions of flow. Furthermore, this approach is tailored to treat forward and reverse flow equivalently, and does not require a high degree of flow phase shift coherence as does phase display methods. The overall objective of this work is to develop and evaluate flow enhanced imaging on an experimental scanner for its eventual application on a whole body system to study abnormal flow patterns in neovascular tumors such as those found in the breast. In addition to continued refinement of the theoretical description of flow, the objective will be sought through a series of phantom studies in which flow complexity is increased from continuous flow through large tubes to pulsatile flow through an entanglement of sub-pixel caliber tubes. Modifications to conventional imaging gradients are proposed to suppress undesired flow induced phase shifts to optimize performance of the flow imaging techniques. Limited animal studies are proposed to evauate flow phase and flow enhanced imaging methods, and compare to real-time Doppler flow imaging. The VX2 tumor implanted in the rear flanks of rabbits will be imaged in the study since it mimicks hypervascular flow patterns of human breast lesions.
| Zaoui, P; Hakim, R M (1993) Natural killer-cell function in hemodialysis patients: effect of the dialysis membrane. Kidney Int 43:1298-305 |
| Chenevert, T L; Fechner, K P; Gelblum, D Y (1989) Improvements in MR angiography using phase-corrected data sets. Magn Reson Med 10:38-49 |
