Computed tomography (CT) scans and magnetic resonance imaging (MRI) are two types of imaging procedures. They both create detailed images of the internal body structures. While CT scans use X-rays to produce the images, MRIs use magnetic fields and radio waves.
Both CT scans and MRIs are relatively safe procedures. It’s important to talk with your healthcare provider to discuss the benefits and limitations of an MRI or CT scan before undergoing the procedure.
A computed tomography (CT) scan is a diagnostic procedure that uses X-ray imaging to produce two-dimensional images of your body. These images can then be digitally assembled to form a three-dimensional image that may help your healthcare provider better identify basic structures, tumors, or other abnormalities.
How It Works
For a CT scan, you lie on a table that moves through the opening of the scanner, which is a large donut-shaped device. You may need to remain still and hold your breath for a few seconds as the machine takes many X-ray images.
To take the images, the machine’s X-ray beam rotates around you, measuring the amount of radiation absorbed throughout your body. A computer then processes this data into two-dimensional images of your body. It then assembles these images to create a detailed three-dimensional view of your body’s internal organs and tissues.
Your healthcare provider may recommend a CT scan with a contrast agent (dye). They may give you an intravenous (IV) injection, which may cause a warm feeling throughout your body. Your healthcare provider may also give you specific instructions for eating and drinking before a contrast scan.
Uses
CT scans can be helpful in the diagnosis of various conditions, including:
- Bone fractures and injuries
- Heart disease
- Blood clots
- Internal injuries and bleeding
- Cancer
Advantages
CT scan has many advantages, such as:
- It can image bone, tissues, and blood vessels at the same time.
- The procedure is fast, simple, and painless.
- Slight movements during the scan do not hinder the procedure’s results much compared to an MRI.
- Having any implanted device does not prevent you from getting a CT scan.
Limitations
One common limitation of CT scans is that they use ionizing radiation, which may increase the risk of cancer, especially in the case of repeated scans. Other limitations include:
- It’s not suitable during pregnancy, as it can pose a risk to the growing fetus.
- Rarely, some people may experience an allergic reaction to the contrast agent.
- It doesn’t provide detailed images of soft tissues such as nerves, muscles, brain tissue, and others.
Magnetic resonance imaging (MRI) is also a diagnostic imaging procedure. It uses strong magnetic fields and radio waves to create detailed, three-dimensional pictures of the inside of your body. Healthcare providers often recommend an MRI to detect, diagnose, and guide treatment for conditions such as torn ligaments or tumors.
MRIs may also sometimes use a contrast dye that a healthcare provider delivers through a vein in your arm before the test. The contrast helps to make certain areas more clearly visible.
How It Works
To undergo an MRI scan, you lie on a movable table that slides into a large, tunnel-shaped scanner. The healthcare provider who performs the test may place small devices containing coils around the part of your body they’re examining. The coils help receive and send the radio waves.
MRI uses a strong magnetic field that causes the protons (positively charged particles) in your body to align with the field. MRI also uses radio waves. When a radio wave passes through your body, it changes the alignment of the protons. Once the radio wave turns off, the protons return to their original position and release energy.
The MRI scanner detects this energy and sends a signal to a computer, which then produces images based on the amount of energy and how quickly the protons returned to alignment.
Uses
MRI can help provide detailed images of your body’s soft tissues and non-bony areas. It can help to diagnose or evaluate:
- Pelvic or abdominal tumors in organs such as your liver, kidney, pancreas, spleen, and adrenal glands
- Liver disease
- Bowel duct inflammation
- Abnormalities or tumors in your brain, spinal cord, and nerves
- Other symptoms or concerns in your muscles, blood vessels, tissues, and ligaments
Advantages
Healthcare providers can see your brain, nerves, spinal cord, muscles, tendons, and ligaments more clearly with an MRI than with CT scans. MRI is also better at differentiating between types of soft tissues, which can help detect tumors and aneurysms.
MRI can also help diagnose conditions that require more frequent imaging because it does not use radiation.
Limitations
MRI is generally a very safe procedure with almost no risks. However, common limitations of MRI include:
- People with medical implants such as pacemakers or insulin pumps may not be able to undergo an MRI.
- Some people may experience an allergic reaction to the contrast.
- People with claustrophobia may struggle to tolerate being inside the MRI machine.
- The use of contrast dye is usually not appropriate in people who are pregnant.
A few similarities between CT scans and MRIs include:
- They’re non-invasive and provide detailed images of internal organs and tissues
- They’re relatively safe with low risk.
- They help detect conditions with good precision.
- They require you to lie on a table in a machine and may sometimes involve using an injectable contrast dye.
Differences between CT scans and MRIs include:
- Mechanism: CT scans use X-rays to create images, while MRIs use magnetic fields and radio waves.
- Use: CT scans can create detailed images of bone structures and less-detailed images of soft tissues, while MRIs can provide detailed soft tissue images.
- Speed: CT scans are typically fast, taking only a few minutes. MRIs take longer, usually 30-60 minutes.
- Cost and availability: CT scans are less expensive and more readily available compared to MRIs.
- Noise: MRIs produce loud noise that may require special ear protection. CT scans typically do not.
Your healthcare provider may recommend either a CT scan or an MRI based on your condition, symptoms, and medical history. They may recommend CT scans in emergency situations, which require quick evaluation, because these scans require less time and are readily available.
Your healthcare provider may recommend MRIs for conditions requiring detailed images of soft tissues and in cases where frequent and repeated imaging is necessary.
You can talk to your healthcare provider about the benefits and limitations of both procedures to understand which one may be best for you.
CT scans and MRIs are imaging procedures that help healthcare providers look at the internal structures and tissues of your body.
CT scans are generally faster, less expensive, and more widely available compared to MRIs. These differences make CT scans more suitable in emergency cases. On the other hand, MRIs provide detailed images of soft tissues, which CT scans can’t provide.
Consider talking to your healthcare provider about your condition and medical history to understand which procedure is most appropriate for you.
