Contrast enhancement and artifact reduction in steady-state magnetic resonance imaging

Magnetic resonance imaging (MRI) is a noninvasive and highly flexible medical imaging technique that yields excellent soft tissue contrast. The past decade has seen significant improvements in the gradient hardware available for MRI, making feasible a class of steady state MRI techniques that were formerly impractical. Fully-refocused, or balanced, steady state free-precession (SSFP) MRI yields high signal-to-noise ratio (SNR) images in very short scan times.; One drawback of balanced SSFP imaging is its high sensitivity to magnetic field inhomogeneity. Severe image artifacts result if the magnetic field variations are too large across the body to be imaged. Several methods have been proposed which combine data from multiple "phase-cycled" SSFP images to eliminate this sensitivity. A statistical analysis framework for studying the SNR characteristics of these methods is described in this dissertation, and an alternate combination method introduced. The new technique yields significantly higher SNR than the other methods while achieving good image artifact reduction.; The past decade has also seen the introduction of several steady-state "catalyzation" methods which, when combined with certain magnetization-preparation techniques, aid in the manipulation of SSFP contrast. This dissertation presents a new application of magnetization-prepared SSFP imaging to CSF-suppressed neurological imaging. Specifically, a fast 2D multi-slice fluid-suppressed SSFP technique is presented, and results are shown from an in vivo study of the human brain. Excellent CSF suppression and good visualization of the brain parenchyma is achieved.; Lastly, this dissertation presents an application of balanced SSFP to peripheral angiography. To accurately depict the vessels of the lower leg, foot, or hand, the typically bright MR signals from lipid (such as bone marrow) and fluid (such as synovial fluid) need to be suppressed. Signal independence of blood flow velocities, good arterial/muscle contrast, and arterial/venous separation are also desirable. A novel magnetization-prepared 3D SSFP technique for fat- and fluid-suppressed peripheral angiography is presented. High SNR flow-independent MR angiograms with excellent blood/muscle contrast and arterial/venous separation are achieved in very short scan times with the new technique.