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CT vs. MRI: What Is The Difference?

CT vs. MRI: What Is The Difference?

Two of the most well-known imaging exams are CT Scans and MRIs. Both are used to capture detailed images of organs, bones, and other tissues. The biggest difference between the two is that MRIs (magnetic resonance imaging) use radio waves and CT (computed tomography) scans use X-rays.

While both are relatively low risk, there are advantages and disadvantages to each, and how doctors choose which option is best depends on the circumstances that may make one a better option over the other.

CT Scan

CT scans work much like an X-ray, only in greater detail. During the scan, the patient lies on a table that moves through a narrow scanning ring, which is taking a series of images from different angles. These images that are collected can be assembled to form three-dimensional images. These images are used to detect abnormalities in both bone and soft tissues, joint problems, tumors, cancer, heart disease, evidence of internal bleeding, or blood clots. A contrast dye may also be used for better clarity on the resulting images.

Advantages Of A CT Scan

With a CT scan, we can create an image of almost the entire body, from the neck to the thighs, in a few seconds. CTs are incredibly useful for diagnosing cancer patients, checking whether it has come back, and monitoring whether a treatment is working. CT scans are more widely used than MRIs and are typically less expensive.

Disadvantages Of A CT Scan

Because CTs use ionizing radiation, they could damage DNA and may very slightly raise the risk of developing cancer. CT risks also include harm to unborn babies and a potential reaction to the use of dyes.


MRI also creates detailed pictures of areas inside the body, but it uses radio waves and a powerful magnet to generate the pictures. During an MRI, the patient lies within a tube-like machine that produces a strong magnetic field to create its images, which are processed and stored in a computer. Similar to a CT Scan, these pictures can show the difference between normal and diseased tissue.

Advantages Of An MRI

An MRI is highly adept at capturing images that help doctors determine if there are abnormal tissues within the body. MRIs are thought to be superior in regards to the detail of the images, but where MRI really excels is showing certain diseases that a CT scan cannot detect. Some cancers, such as prostate cancer, uterine cancer, and certain liver cancers, are pretty much invisible or very hard to detect on a CT scan. Metastases to the bone and brain also show up better on an MRI. MRIs also do not use ionizing radiation, so there is no issue of raising cancer risk.

Disadvantages Of An MRI

MRIs take much longer to complete than a CT. They require the patient to lie still within a closed space for about 20 to 40 minutes. This can affect some people with claustrophobia, and the procedure is very noisy. Earplugs are given but it can still be an uncomfortable procedure for some. Possible risks include reactions to metals due to magnets and increase in body temperature during long MRIs.

How Do Doctors Decide Which Option Is Best?

Your doctor will give you a recommendation based on your symptoms whether you should get an MRI or CT scan. If you need a general image of an area like your internal organs, or have a fracture or head trauma, a CT scan will commonly be recommended. Doctors may use CT scans first for most people, unless something such as a tumor is much better seen on an MRI. But they can go back and forth as needed. If they see something on a CT scan they’re unsure about, an MRI may be recommended for further evaluation. If someone has several MRIs and is unable to lie still or hold their breath to get a good image, a CT may be suggested as an alternative. Every patient and circumstance is different and choices are guided by the principle of whether the benefits of a test outweigh its risks which is what medical imaging is all about.  

Townsen Memorial Hospital’s Imaging Centers make Townsen Memorial Hospital Houston’s premier, one-stop shop. From CT to MRI, we offer a wide variety of services operated by skilled medical professionals to provide patients with the best in imaging and patient care. We not only have technological advancements, but we also have a medical team that is always going to put you first. 

Townsen Memorial Hospital Is Here For You

At Townsen Memorial, safe, effective, and affordable care is our top priority. Therefore, we strive to provide the best patient experience across all Townsen Memorial affiliated sites. The high-quality care starts at our Emergency Room and carries on through our Imaging Centers, Surgery Centers, and up through our Townsen Memorial Hospital. Our medical sites are located in Houston, TX, and the surrounding areas, to provide the best care to patients in and around Harris County. To learn more, visit our website or call 1-877-494-9487.

Health Tips, MRI, CT Scan