There is, in general, no closed-form solution to equation 4.1 (although section 14.1.6 introduces two approximate solutions). T 1and T 2contribute independently to the contrast between different tissues. Both relaxation times are determined by the interaction of water or other nuclei with macromolecules in tissues. Likewise, T 2is the characteristic time for decay of coherent magnetization in the transverse plane: the transverse magnetization decays exponentially with time constant T 2to its equilibrium value, M° xy = 0. T 1is the characteristic relaxation time for longitudinal magnetization to align with the magnetic field: following a perturbation such as a 90 ° RF pulse, the longitudinal magnetization typically returns to its equilibrium value, M 0, with a time constant T 1. Where - is the gyromagnetic ratio, H the effective field, M 0 the equilibrium magnetization, and T 1and T 2the relaxation times. There is every reason to believe exciting progress still lies ahead.

For example, Figure 4.1 demonstrates a tremendous improvement in resolution over that period. MRI technology has undergone amazing strides over the last two decades, much of it due to advances from the mathematical sciences and physics.

Finally, this chapter highlights recent technological advances toward real-time monitoring of interventional and therapeutic procedures. Significant attention is given also to two applications for which MRI has unique potential: blood flow imaging and quantification, and functional neuroimaging based on exploiting dynamic changes in the magnetic susceptibility. High-speed imaging pulse sequences, with particular focus on functional imaging, are discussed in this chapter, as are algorithms for image reconstruction both are promising fields of research. For example, the development of suitable high-temperature superconductors (HTSs) and their integration into MRI magnets represents one potentially fruitful area of interaction between solid-state physicists, materials scientists, and the biomedical imaging research community. Among the hardware systems of an MRI device, the magnet, radio-frequency (RF), and gradient systems deserve particular R&D attention. This chapter highlights areas of interest related to magnetic resonance (MR) technology and its applications, particularly applications that involve dynamic magnetic resonance imaging (MRI).

X-ray reader shields mri for mac