MPH Blog

What Is the Difference Between a CT Scan and an MRI?

CT scans (computerized tomography) and MRIs (magnetic resonance imaging) are both common imaging services offered by hospitals. They both employ large machinery and require no movement on the part of the patient. In fact, they are both similar in that they produce “sliced” imagery of the body, providing a close look at structures and abnormalities. Despite these similarities, they are extremely different in the way they work and in the service they provide to doctors and patients.

Computerized (Axial) Tomography

CT scans work through a rotating x-ray camera in a donut-shaped machine. These create high-contrast images of body structures, such as skeletal structures, blood vessels, and the gastrointestinal tract. They can also be used to look at cysts or tumors because tumors tend to be a far different structure type than surrounding tissue. Contrast can be improved through a contrasting agent, a harmless chemical injected into the patient that is processed and flushed out within days.

These images can be used to “stage” a cancer, a term that describes measuring and classifying how far a cancer has progressed. CT scans can also be used to help surgeons guide needles during procedures that require very precise placement of needles or injections. One major difference between CT scans and MRIs is that CT scans take between 30-60 minutes to prepare, but only a few minutes to execute.

Magnetic Resonance Imaging

MRIs work by placing the patient in a magnetic field and bombarding them with radio waves that return images based on their frequencies. Different frequencies indicate different types of tissue and density, distinguishing between chemicals with different atomic numbers. MRIs are incredibly detailed looks at the body, and they can be used to find abnormalities in the spine, brain, and in various body regions.

They can also find much subtler abnormalities than CT scans because MRIs are capable of receiving a range of radio frequencies, whereas x-rays are much more limited in the levels of contrast they pick up. MRIs are usually better suited to exploring soft tissue than CT scans. The major drawback for MRIs, however, is that they often require the patient to lie still for up to an hour, whereas CT scans are much more patient-friendly with regard to time.

If you have more questions about the tests you may undergo and why, ask your physician. Taking ownership of your own treatment will allow you to better understand why you are going through certain tests, as well as understand what your doctor is looking for.

This article contains general information about medical conditions and treatments. The information is not advice and should not be treated as such. The information is not intended to replace the advice or diagnosis of a physician.

If you have any specific questions about any medical matter you should consult your doctor or other professional healthcare provider.