Magnetic Resonance Imaging (Textbook Chapter)

By Felix Lugauer and Jens Wetzl


Discovered in 1977, magnetic resonance imaging (MRI) has become an increasingly popular imaging tool requiring no ionizing radiation, while producing high-quality, diagnostic images with excellent soft-tissue detail. MRI acquires images by producing a strong external magnetic field and radiofrequency (RF) pulses, while using the body's natural magnetic properties.

Hydrogen nuclei are used in MRI due to their abundance within the body and strong magnetism. When placed in a strong external magnetic field, hydrogen's magnetic field aligns and processes at a specific rate. Introducing an RF source at the same rate will cause resonance, increasing the hydrogen energy state. The release of this energy can then be measured by MRI coils. Pulse sequences apply RF pulses at predetermined intervals in order to take advantage of properties in various tissues and create diagnostic images with optimal visual contrast. Varying the timing and strength of these RF pulses creates a range of imaging options to enhance the radiologist's ability to make an appropriate diagnosis. 

In this chapter, we'll examine the basic fundamentals of MRI, understand how image contrast can be manipulated by pulse sequences, and discover advanced imaging techniques such as cardiac, functional, and 3-dimensional (3D) MR imaging. Advances in MRI continue to improve image quality, techniques, and patient experience, allowing for faster acquisition time and enhanced spatial resolution.

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