Advantages
MRI provides information that differs from other imaging modalities. Its major technological advantage is that it can characterize and discriminate among tissues using their physical and biochemical properties (water, iron, fat, and extravascular blood and its breakdown products). Blood flow, cerebrospinal fluid flow, and contraction and relaxation of organs, both physiologic and pathologic, can be evaluated. Because calcium emits no signal on spin echo images, tissues surrounded by bone, such as the contents of the posterior fossa and the spine, can be imaged, and beam hardening artifacts are avoided. MRI produces sectional images of equivalent resolution in any projection without moving the patient. The ability to obtain images in multiple planes adds to its versatility and diagnostic utility and offers special advantages for radiation and/or surgical treatment planning. Excellent delineation of anatomic structures results from inherent high levels of contrast resolution.
MRI acquisitions can be programmed to encode for various physiological phenomena including velocity of moving tissue or blood, diffusion of water (useful in detecting stroke)
MR image acquisition does not use ionizing radiation.
Because it requires little patient preparation and is noninvasive, patient acceptability is high.
MRI contrast agents are very well tolerated and are much less likely than x-ray contrast agents to cause allergic reactions or alter kidney function.
Disadvantages
Because of the small bore of the magnet, some patients experience claustrophobia and have difficulty in cooperating during the study. Some obese patients cannot be examined.
Some patients, particularly acutely ill patients, cannot cooperate and movement artifacts may result.
Patient throughput is slow compared with other imaging modalities.
Patients with pacemakers and certain ferromagnetic appliances cannot be studied.
MRI units require careful siting and shielding.
Greater technological expertise is required for utilization of MRI than for most other imaging modalities.
MRI equipment is expensive to purchase, maintain, and operate.
