Health and Fitness

A Brief Comparison of CT Scans and MRI Scans

Patients often find it confusing to differentiate between a CT scan and an MRI scan. To them, they may seem similar and whether you need one or the other doesn’t matter. It is important however to identify key differences of each procedure so that next time you are required to undergo a scan you’ll know exactly what to expect. Here is a comparison of common patient concerns regarding undergoing a CT scan or MRI scan.


The MRI scan is a relatively new procedure with the first commercial MRI machine made available in 1981. Over time, significant advancements have been made to the machine resulting in greater accuracy. The CT scan, on the other hand, was invented a little earlier in 1971 when the very first brain scan was done.

Radiation exposure

This is a major concern for many patients who undergo scans in different areas of the body. CT scans emit minimal radiation doses. This equates to the same amount of radiation exposure an average person gets through daily activities within a period of three to five years. With an MRI scan, however, there is virtually no radiation exposure.


CT scans, like the private CT scans in London clinics, are widely used on emergency patients and are suitable for detecting injuries to bones, taking high-resolution images of the chest, as well as detecting cancer. MRI scans are used to evaluate soft tissues. Some examples include damage to ligaments and tendons, injury to the spinal column, trauma and damage to the brain, as well as abnormal mass or growth.

Comfort level

MRI scans can be challenging for patients with claustrophobia as well as children who have difficulty lying still. Movement can affect the accuracy of images for MRI which is why patients have to lie very still for a certain amount of time. In some instances, when a patient experiences anxiety, sedation may become necessary. This is not the case with CT scans. The scanner is open thus the patient feels more comfortable and less closed in.

Time taken for a complete scan

CT scans are completed in less time than MRI scans. CT scans are normally done within five minutes. With MRI scans, it can take anywhere from 20 to 40 minutes and in some instances much longer.

Contrast agent administration

CT scans use iodinated agents that are non-ionic which have little to no known side effects. In some cases, allergic reactions to this compound may occur but this is also very rare. With MRI scans, on the other hand, there are very few known incidences of allergic reactions to the dye used.

Both of these procedures provide invaluable information for medical practitioners making disease diagnosis more accurate. In general, the need for either of these procedures depends on the body part that will be scanned.

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