Both MRI and CT are diagnostic exams used to thoroughly image a selected area of the human body. Similarly, both MRI and CT require the use of a large machine, and each method relies upon computer technology to reconstruct a cross-sectional image of the body. Aside from these very fundamental similarities, there are many inherent differences between MRI and CT scans.

Magnetic Resonance Imaging (MRI)
Compared to CT, MRI technology is still in its infancy. Developed in the mid 1980's, MRI technology utilizes radio frequency waves and very powerful magnets. After applying a very strong, localized electromagnetic field, the MRI scanner emits a series of radio pulses into the body, exciting the hydrogen protons found in the body's soft tissue. Upon measuring the relaxation times of these hydrogen protons, the MRI scanner employs sophisticated computer technology to interpret the protons' behavior and recreates a 3-dimensional image of the body. Since hydrogen is the most abundant element in the body, MRI technology is capable of producing amazingly clear images of organs and soft tissue. MRI is able to detect disease or injury in muscle structure along ligaments, and is used to assist in the visualization of tumors. The ability to visualize soft tissue and the vascular system make MRI and outstanding tool for imaging brain and spinal cord abnormalities. MRI is non-invasive, although certain studies may require the use of an intravenous contrast agent. MRI does not involve any ionizing radiation, and aside from a persistent thumping noise, patients will experience no discomfort or side effects.

Computerized Tomography (CT or CAT scan)
Developed in the 1970's CT technology utilizes a highly sensitive X-ray beam that is focused on a specific part of the body. Upon passing through the body, the beam hits a detector, which relays this information into a computer. The computer analyzes the information based upon tissue density, and feeds it into a cathode ray tube. Like MRI, a cross-sectional representation (like slices of bread) of the body is produced. Bone shows up white, gases and liquids black, and tissue as varying shades of gray, depending on density. Generally, CT provides much better visualization of bone detail than MRI. CT scans provide excellent information on anatomical features and tissue density (this allows for the detection of tumors, and sometimes the ability to distinguish between malignant and benign tumors). CT scans can also detect calcium deposits, cysts, and abscesses. They are often used in place of ultrasound for obese patients because fat deposits often hinder ultrasonic waves. CT scanning does carry with it the risks associated with X-ray exposure, although it is significantly less than that from ordinary X-rays.

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