CT Scan vs. MRI

Computed tomography (CT) scans and magnetic resonance imaging (MRI) scans are imaging healthcare providers use to produce detailed images of internal anatomy. CT scans are quick and widely available. Providers use them to evaluate many conditions. MRI scans, though they're slower and less widespread, can provide better soft tissue detail than CT scans can.

This article will discuss the differences between CT and MRI scans.

MRIs

Healthcare providers use MRI scans to view detailed images inside the head, abdomen, legs, or joints. MRI scans use a strong magnetic field and radiofrequency energy instead of ionizing radiation like an X-ray or CT scan.

Healthcare providers often use MRIs when they want a closer look at the soft tissues. In some cases, they may perform the MRI with a special dye known as contrast to better define normal and abnormal tissues.

Uses

MRI scans help providers take images of non-bony areas or soft tissues of the body. An MRI scan is best suited to examine the following areas:

• Abdomen
• Brain
• Muscles, ligaments, and tendons
• Pelvis
• Spinal cord or nerves
  

In general, MRI is better than CT at distinguishing between different types of soft (non-bony) tissue. For example, a provider might order an MRI scan to diagnose a knee or shoulder injury because these tests show ligaments, tendons, and muscles more clearly.

MRI scans can also differentiate between the gray and white matter of the brain, which allows healthcare providers to diagnose aneurysms and tumors. Additionally, a specialized MRI scan, called a functional MRI, allows the healthcare provider to identify which brain areas consume more oxygen during different mental functions.

Advantages

Because MRI scans do not use ionizing radiation, healthcare providers often use these if a person requires frequent imaging to support a diagnosis. This is particularly important in the imaging of certain radiation-sensitive people, such as children or pregnant people.

MRI scans tend to produce better images with non-bony structures, and providers often use them to evaluate:

• Joints
• Spine
• Brain
• Heart
  

Risks

MRI scans do create a strong magnetic field that can create safety risks, so it is crucial to inform your healthcare provider if you have any metal in your body, including the following:

• Pacemakers
• Vagus nerve stimulators
• An implanted cardiac defibrillator
• Insulin pumps
• Cochlear implants
• Deep brain stimulators

MRI scans make a loud noise, so your provider will offer hearing protection, such as earplugs. MRI scans take longer than CT scans, sometimes up to an hour, and require absolute stillness to create the detailed images the healthcare provider needs.

Many MRI scans are narrow tubes, so people affected by claustrophobia (a fear of enclosed spaces) or with a specific waist circumference may not fit into the tube and are not candidates for an MRI scan. Finally, MRI scans are more expensive than CT scans or X-rays.

CT Scans

CT scans use ionizing radiation to take a continuous picture of various body areas. Healthcare providers use CT scans to get a closer look inside the head, skeletal system, and internal organs and to identify the following:

• Injuries
• Blood system disease
• Infectious or inflammatory processes
• Internal bleeding

CT scans are typically faster than MRI scans, with most examinations lasting a few minutes.

Uses

CT scans are versatile, and their uses include the diagnosis of the following:

• Circulatory system diseases (coronary artery disease, blood vessel aneurysms, or blood clots)
• Kidney and bladder stones
• Abscesses within different body areas
• Inflammatory diseases (ulcerative colitis or sinusitis)
• Injuries to bones or spine
• Internal injuries from trauma
• Cancer screening and diagnosis

Advantages

CT scans are widely available. They are considered better than MRI scans at imaging bones. CT scans also provide faster results than MRI scans and have less potential to cause claustrophobia.

Risks

Because CT scans use ionizing radiation, there is a low risk of increasing cancer risk. Still, often, healthcare providers will not use repetitive CT scans if comparable alternatives are available.

Even though the amount of ionizing radiation is low, CT scans are used sparingly in certain populations, such as pregnant people and children. In some cases, measures can be taken to reduce the risk of radiation exposure in these populations, such as shielding.

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

MRI scans allow for better viewing of soft tissues, fat, water, and muscle. They also differentiate between gray and white matter in the brain.

CT scans are optimal for viewing bones, such as the spine, and veins to look for clots or aneurysms. Additional differences between CT scans and MRI scans include:

• CT scans produce images faster, are less expensive, and do not cause claustrophobia. However, they utilize low levels of ionizing radiation, which can slightly increase cancer risk.
• MRI scans do not use ionizing radiation but instead leverage a strong magnetic field with radiofrequency current, so there is no impact on cancer risk. However, MRI scans tend to be more expensive, take longer to obtain images, and due to the small size of their tubes, can cause claustrophobia.

What Is Better: CT Scan or MRI?

CT and MRI scans provide excellent anatomic imaging. The underlying reason for the scan determines which is more appropriate. CT scans are better at imaging bones and blood vessels and are frequently taken to assess traumatic injuries. MRI scans provide better soft tissue contrast and help providers distinguish between fat, water, muscle, and other soft tissues.

Summary

CT and MRI scans are two types of radiologic imaging that offer a more detailed view of internal anatomy than X-rays can. CT scans take less time than MRI scans and produce high-quality images of bones and vasculature. MRI scans are optimal at providing detail within the soft tissue and help providers differentiate between gray and white matter in the brain. Each comes with its own set of benefits and risks.