MRI vs. CT

What is magnetic resonance imaging?

Magnetic resonance imaging (MRI) is a form of radiological imaging that uses powerful magnets, radio waves, and a computer to process data and thus create detailed images of the inside of the body. This imaging technique makes it possible to obtain high-quality images of organs, tissues, and structures inside the body without the use of X-rays.

The advantages of MRI include the following:

• Excellent capacity to show detailed images of soft tissues, thus allowing for a thorough insight into organs such as the brain, muscles, ligaments, and internal organs.

• No exposure to X-rays, which is useful for repeated examinations or when pregnant women are being examined.

• The possibility of obtaining images within different sections, which enables a more precise examination of anatomical structures.

What is a CT scanner?

A computed tomography (CT) scanner is a medical device that is used to obtain detailed three-dimensional images of the inside of the body using X-rays and computer data processing. This device provides precise visualization of structures such as bones, organs, and soft tissues, and helps diagnose various medical conditions.

The advantages of CT scanners include the scanning speed, high image quality, the capacity to display tissue and bone density, as well as a wide application in the diagnosis of various medical conditions, such as trauma, tumors, infections, and hemorrhage.

Key differences between CT and MRI imaging

CT and MRI are two different medical procedures used for obtaining detailed images of the inside of the body. They employ different principles and technologies.

Operating principles

A CT scanner uses X-rays to create detailed images of the inside of the body. For imaging purposes, the patient lies on a table that slowly moves through the opening of the CT machine while X-rays rotate around the patient.

MRI uses powerful magnets and radio waves to create images of the inside of the body. Here too, the patient lies on a table, but in this case, inside a large cylindrical magnet.

Capacity of soft tissue differentiation

Magnetic resonance imaging is undoubtedly more accurate in differentiating soft tissues such as the brain, muscles, ligaments, and organs, because it uses magnetic signals that respond to different properties of those tissues.

A multislice scanner can provide very detailed quality images of bone and tissue density, however, it is not as accurate in distinguishing soft tissues.

Radiation exposure

In order to obtain detailed insight into the part of the body being imaged, the CT scanner activates a certain dose of X-rays during its operation. The amount of radiation that is present during the operation of the device is extremely small and cannot affect the patient’s body in one imaging session, but it should not be neglected in case of repeated examinations or in pregnant women.

On the other hand, MRI does not employ X-rays and therefore does not expose the patient to ionizing radiation, making it safer to repeat MRI examinations.

Duration of the examination

CT scans usually last shorter than MRI scans. A CT scan can only take a few minutes, while an MRI scan often takes longer, usually between 15 minutes and an hour, depending on the part of the body being imaged.

Contraindications

CT imaging may be contraindicated in case of allergy to contrast agents or in case of severe kidney disease. If your doctor believes that the application of a contrast agent is necessary for obtaining images of the highest quality, make sure to inform him/her about any allergies and/or chronic diseases you are suffering from so that other solutions may be considered.

MRI can also have its limitations, specifically in patients with implanted metal devices such as pacemakers or metal prostheses. Due to the activation of the magnetic field during the operation of the MRI device, the quality of the image may be compromised if the patient has metal parts implanted in his/her body.

When will your doctor refer you for an MRI and when will he/she refer you for a CT scan?

Deciding when to use MRI and when to use CT for body imaging depends on many factors, including the type of health issue that is troubling the patient, the area of the body to be examined, the patient’s medical history, and other factors. Below is the description of several situations where one procedure has advantages over the other:

• Trauma and emergencies: In emergencies, where rapid diagnosis is critical, CT is often preferred because of its speed. CT can quickly provide detailed images of bones and internal organs, which can aid in the rapid diagnosis and treatment of injuries.

• Problems with bones: For bone imaging, especially fractures, CT is preferred because it provides excellent imaging of bone and tissue density. CT is useful for identifying traumatic bone injuries, degenerative changes, or bone tumors.

• Problems with soft tissues: For the purpose of examining soft tissues such as the brain, muscles, ligaments, or internal organs, MRI is often the best choice. MRI provides more detailed images of soft tissues and allows better differentiation among different types of tissue.

• Brain and spinal cord scans: For brain and spinal cord scans, MRI is the better choice due to its ability to show detailed images of soft tissues, such as the brain, spinal cord, and nerves.

• Imaging of abdominal organs: CT is usually the method of choice when examining abdominal organs such as the liver, kidneys, spleen, or pancreas, because of its ability to quickly scan and provide detailed images of the internal organs.

The decision on which procedure to use depends on the specific needs of the patient and the clinical context, and it is best to make this decision with the participation of a physician who will take into account all the relevant facts.