Difference between CT and MRI


You may have ever had a health problem. During treatment, you may have needed a study such as a CT scan or an MRI. And when you had either of these, you were simply following the doctor’s orders. This is without knowing exactly what the study you were having was about. Or without knowing the difference between a CAT scan and an MRI.

It is always advisable to follow the instructions of a health professional. However, you should know the type of study you are having. And what the function of each one is. In this post we will detail what you should know about CT scans and MRIs.

computador del tac

Although both studies are based on obtaining internal images of the patients, here we explain how each one works.

What is a CT scan?

CT stands for computed tomography. This study works with X-rays. The body will be exposed to X-rays from different planes. The images obtained from the X-rays will be processed by a computer. The function of the computer is to unify the information obtained and form with it a three-dimensional image of the tissues and bones inside the patient.


When is CT used?

The use of CT or MRI depends on which part of the body you wish to visualize. CT is ideal for visualizing bone tissue, so it is usually recommended if there are fractures. It is also recommended if you wish to observe infections in organs such as the lungs, injuries in the chest cavity, tumors or anomalies in the spine, among others.

What is an MRI?

The MRI also seeks to obtain images of the inside of a patient’s body. Its name is due to the fact that a “resonator” is used to perform this study. Through magnetism and sound waves, images of tissues are obtained. MRIs are usually more accurate in distinguishing organs.

Resonancia magnética

When is an MRI used?

The magnetic resonance is more used to observe soft tissues. For example, if a study of the knee is desired, an MRI is recommended. This is because what you want to observe in the knee is the ligaments. In the case of a stroke, in order to observe the brain, an MRI is also recommended. Because there are structures in the brain that may not appear on the CT, but may appear on the MRI. In general, the MRI is very useful for detecting even cancerous tumors.

Observación de la resonancia

Time to perform each study

The CT scan is a study that is performed quite quickly. At most, it will take you fifteen minutes to get a CT scan. The MRI, on the other hand, takes a little longer. The study can take up to an hour.


If the patient has any metal prosthesis in his body, he should not have an MRI. As we have already mentioned, the MRI works with magnetic fields. This could cause a metal prosthesis to move out of place. The patient should also not wear any metal item at the time of the study. This is because the images could be damaged.

imagen de tac

Although not all CT scans are performed by contrast, it is important to mention that these are contraindicated for some patients. When a CT is performed by contrast, patients are usually injected with iodine. This can be very dangerous if the patient becomes allergic to this substance. Or if the patient’s kidneys cannot process the iodine well.

CT and MRI Equipment

In both cases, the patient will be inserted into a cylindrical device. Usually, the machine to perform the tomography is open. The patient should not move while the study is being performed, since this can affect the taking of the images.

tac dentro del túnel

Now you know the differences between a CT scan and an MRI. However, it is important that you wait to consult your doctor before having one of these studies. Don’t worry, I’m sure a good specialist will recommend what’s best for your health and well-being.

Tell us if you have ever had an experience where you needed to have one of these studies. Did they explain to you why you would have a CT or MRI scan? Did they explain to you what they wanted to see on the images?

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