MRI of the Abdomen
MRI of the abdomen generally is used to evaluate individual organs, and it is an extremely important tool for radiologists. Most MRI examinations of the abdomen are organ specific, ie, liver, kidney, adrenal gland. CT scanning is more useful in the workup of nonspecific regional complaints, such as "upper abdominal pain" that is not necessarily associated with one organ.
MRI of the Liver
MRI's superior soft tissue contrast makes it excellent at detecting and characterizing diseases of the liver. And whereas CT is sensitive at detecting liver abnormalities, MRI is far superior at further characterizing them. Because the liver is a common organ for metastatic spread of disease (for instance from GI malignancies), it is important to be able to distinguish between benign masses (such as hemangiomas or adenomas) and malignancies. MRI can do this with a high degree of accuracy, and frequently eliminate the need for liver biopsy.
MRI of the Kidneys
As with MRI of the liver, in the kidneys, MRI is frequently used to distinguish between benign lesions (such as cysts) and malignancies. Because fluid and fluid containing lesions such as cysts are common lesions in kidneys, it is important to distinguish them from potential cancers, and MRI can do this quite well. CT scanning is also quite good at this, but sometimes lesions are too small, and the ability to characterize them is diminished on CT scanning. MRI has a better chance of characterizing small kidney lesions because of its superior soft tissue contrast.
MRI of the Adrenals
Because of a phenomenon called "chemical shift" that exists between fat containing substances and water containing substances, MRI is exceptionally suited to differentiate between benign adrenal masses, which are common and called adenomas, and malignancies, which spread frequently to the adrenal glands. With a high degree of accuracy, MRI can tell whether the adrenal glands are involved in the spread of cancer, or contain merely a benign adrenal adenoma.
MRI of the Bowel
Although CT scanning has been the cross-sectional technique historically used in work up of bowel related problems, MRI has been making advances in bowel imaging. This relies on new fast imaging sequences, combined with the soft tissue contrast superiority of MRI. Bowel wall inflammation and thickening is now easily detected on MRI studies called MR enterograms, and can help in evaluating the extent of diseases such as Crohn's disease or ulcerative colitis.