| Magnetic resonance imaging (MRI) is a potent medical imaging modality that effectively depicts the morphology and function of biological tissues. Due to its excellent soft-tissue contrast, MRI is particularly useful in the diagnosis and therapeutic assessment of many diseases, and has found wide clinical use in areas such as neurological or cardiovascular imaging. Furthermore, a variety of applications ranging from cellular imaging to the guidance of interventional procedures can benefit from the noninvasive nature of this imaging modality.;In the past, the applicability of MRI has been hindered by the relatively long scan (i.e., imaging) times. The recent developments in MR hardware have produced fast, high-power magnetic field gradients. As a result, there has been growing interest in steady-state pulse sequences that can take full advantage of the speed and power of these gradients. In particular, rapid MRI has been performed with the balanced steady-state free-precession (SSFP) method, which yields the highest signal per scan time among all steady-state pulse sequences. Unfortunately, SSFP imaging has an unconventional T2/T1-weighted contrast and demonstrates greater sensitivity to system imperfections compared to other steady-state techniques. Various problems related to tissue contrast and image artifacts need to be addressed before this method can be used effectively.;Novel acquisition and reconstruction strategies are proposed for manipulating the contrast of SSFP sequences as well as reducing their sensitivity to system imperfections. Putting all these elements together, artifact-free SSFP imaging with application-specific contrast is demonstrated for various applications such as high-resolution peripheral angiography in humans and fast positive-contrast cellular MRI in animals. Improved reliability and contrast-generation capability of the SSFP technique opens the door to exciting applications for rapid MRI, including neurological, musculoskeletal, angiographic, and cancer imaging as well as cell tracking, and interventional guidance. |
