ABSTRACT
This chapter presents an overview of some of the pulse sequences used to generate MR images, discussing their advantages and disadvantages for MR microscopy. It is dedicated to image contrast generation, with particular focus on diffusion weighted imaging. Compressed sensing is a signal processing technique introduced by Donoho in 2006. The most commoex periment, ndersampling schemes, either Cartesian or non-Cartesian, consist of variable density random trajectories based on a probability density function. The relaxivity depends on the physicochemical properties of the contrast agent but also on external factors such as the external magnetic field and the temperature. Hybrid pulse sequences use both spin echoes and gradient echoes, the most popular one being the echo planar imaging (EPI) technique, introduced by Mansfield and co-workers. Besides the three basic types of contrast discussed in the previous section, MR images can be sensitized to other physical processes such as molecular diffusion, perfusion, oxygenation level, etc.
