CAT Scans vs MRIs. What Only a CAT Scan Can Reveal


CAT scans and MRIs are two commonly used medical imaging techniques that can provide detailed views inside the human body. CAT scans, also known as computed tomography (CT) scans, use X-rays and computer processing to create cross-sectional images of the body. MRIs, or magnetic resonance imaging scans, utilize powerful magnetic fields and radio waves to produce detailed pictures of organs and tissues.

While there is some overlap in what CAT scans and MRIs can detect, there are key differences in what each type of scan specializes in seeing. CAT scans provide clearer images of bones, blood vessels, and tumors. MRIs excel at imaging soft tissues, organs, and detecting certain health conditions. This article will go into more detail on the strengths and differences between CAT scans and MRIs.

Overview of CAT Scans

A CAT scan, also known as a CT or computed tomography scan, is a medical imaging procedure that uses x-rays and computer technology to produce cross-sectional images of the body (Verywell Health, 2023). The CAT scan works by rotating an x-ray beam around the body and taking multiple images from different angles. A computer then processes this data to create 2D and 3D images that provide more detail than a regular x-ray.

The main uses of CAT scans are looking at bones, blood vessels, soft tissues like organs, and detecting tumors or other abnormalities (Verywell Health, 2023). Unlike regular x-rays which just show dense structures like bone, the CAT scan allows doctors to see greater detail in both hard and soft tissue. The level of detail in CAT scan images allows doctors to more accurately identify and diagnose medical conditions.

Overall, CAT scans are a vital medical imaging tool that provide a non-invasive way for doctors to get a closer look inside the body, beyond what regular x-rays can offer (Uofl Health, 2023). The scans have become an essential part of diagnosis and monitoring for many medical conditions.

Overview of MRIs

A magnetic resonance imaging (MRI) scan is a medical imaging technique that uses a strong magnetic field and radio waves to create detailed images of the organs and tissues within the body (Healthdirect, 2021). Unlike X-rays and CT scans, an MRI does not use ionizing radiation. Instead, MRI scanners use powerful magnets which produce a strong magnetic field that aligns the protons of hydrogen atoms in the body. When radio waves are then pulsed through the magnetic field, the protons are excited, and when the radio waves are turned off, the protons relax. This relaxation process produces signals that are detected by the scanner and translated into highly detailed images (Medicalnewstoday, 2022).

MRIs create more detailed images of soft tissues compared to CT scans and X-rays, making them especially useful for examining organs, tumors, joints, cartilage, ligaments, and tendons. Doctors frequently use MRI scans to diagnose and monitor conditions affecting the brain and spinal cord, heart and blood vessels, bones and joints, breasts, reproductive organs, bladder, liver, gallbladder, adrenal glands, and more.

Overall, MRIs provide a non-invasive way to capture high resolution images of internal body structures without the use of ionizing radiation. Their excellent soft tissue contrast allows radiologists to clearly see organs, tumors, and other tissues.

Bones and Joints

CAT scans are typically better than MRIs for imaging bones and joints. This is because CT scans utilize X-rays, which are very good at differentiating dense structures like bone. The X-rays easily pass through soft tissues but get blocked or absorbed by denser material like bone 1. This allows the CT scanner to create clear, detailed images of the bones. MRIs on the other hand use strong magnetic fields and radio waves. These radio waves have difficulty penetrating bone, which means the images of bones and joints are not as sharp compared to CT scans. Doctors often prefer CT scans over MRIs when evaluating bones, joints, and fractures since the CT provides superior detail of these dense structures.

Some examples where CT excels over MRI for imaging bones and joints include:

  • Detecting small fractures or bone trauma
  • Evaluating arthritis and joint abnormalities
  • Identifying bony lesions related to cancer
  • Assessing spinal fractures and disc herniations
  • Evaluating bone integrity and mineral density

In summary, CAT scans provide clearer images of bones and joints than MRIs due to their use of X-rays. Doctors typically order CT scans when specifically evaluating the skeletal system.

Blood Vessels

One key advantage of CAT scans over MRIs when it comes to circulatory issues is the ability to better visualize calcification in blood vessels. CT scans utilize X-rays and are able to detect calcium deposits in the coronary arteries and aorta, which can be an indicator for blockages or plaque buildup. This allows doctors to assess heart disease risk and look for signs of atherosclerosis (Cardiac CT & MRI).

CT angiography (CTA) is a specific type of CAT scan that looks at the blood vessels and can create 3D images of the vascular system. CTA is considered more sensitive than MRI for detecting stenosis and blockages in arteries (Nikolaou, 2011). The high resolution of CT scans provides detailed views of blood vessel anatomy and circulation that can help identify aneurysms, leaks, clots, plaque buildup and other vascular problems that may not be as visible on an MRI.


MRIs tend to be better than CAT scans for getting detailed images of internal organs, especially the soft tissues. MRIs utilize powerful magnetic fields and radio waves to generate images, allowing radiologists to see very fine details of organs and distinguish between soft tissues. This makes MRIs ideal for getting clear views inside organs like the brain, spinal cord, liver, kidneys, pancreas, etc. The soft tissue contrast is superior with MRI compared to CAT scans.

MRIs can capture multiple planes and angles during the scan, providing a 3D construct of organs. This allows for better visualization and diagnosis of subtle abnormalities. Specific protocols can be tailored for scanning different organs. For example, unique contrasts can enhance certain structures in the brain or abdomen. Overall, MRIs excel at providing high resolution, detailed images of soft tissues and organs that CAT scans cannot match.

Soft Tissue

MRIs are able to provide better contrast and detail for viewing soft tissues in the body compared to CAT scans. This is because MRI utilizes powerful magnetic fields and radio waves to generate images, allowing it to distinguish between different types of soft tissue much more clearly. Some examples where MRI excels over CAT for imaging soft tissues include the brain, muscles, ligaments, tendons, and the spinal cord (Healthline).

Since CAT scans use X-rays, they are unable to differentiate between soft tissues as precisely. The X-rays pass through soft tissue and are absorbed in different degrees based on density, resulting in less contrast between soft tissues. While CAT scans can still view soft tissues, the images are not nearly as detailed as MRI for this purpose. MRI is the preferred choice for brain tumors, disc disease, and injuries to knee ligaments or the rotator cuff (Hopkins Medicine).


One of the key advantages of CAT scans is their ability to detect tumors in the body. However, MRI scans excel at finding tumors as well, especially those located in soft tissues.

MRIs use magnets and radio waves to generate detailed images, providing high contrast between normal and abnormal soft tissues. This makes MRI ideal for detecting tumors in organs like the brain, spinal cord, liver, breasts, and other soft tissue areas.

MRI has been shown to find smaller tumors than CT scans in cases of liver, prostate, bladder, and colorectal cancers. MRIs can also help distinguish between benign and malignant soft tissue tumors better than CAT scans in most cases.

Additionally, MRIs aid in evaluating the full extent of tumors, showing involvement of local structures and metastasis more clearly. The detailed images produced by MRI avoid the tissue superimposition seen in CT scans, making the size and spread of tumors more evident.

In summary, when it comes to detecting tumors, especially those located in soft tissues, MRI is considered superior to CAT scans in most circumstances.

Radiation Exposure

One of the main differences between CAT scans and MRIs is that CAT scans expose patients to radiation, while MRIs use magnets and radio waves so there is no radiation exposure. source

CAT scans (also known as CT scans) work by rotating an X-ray beam around the body and taking multiple images that are processed by a computer into cross-sectional views. The ionizing radiation from the X-ray beam has the potential to damage cells and cause cancer. While the amount of radiation in one CAT scan is not extremely high, the effects are cumulative if a person gets multiple scans. This is especially concerning for children whose bodies are still developing.

MRIs create detailed images using strong magnetic fields and radio frequency pulses, so there is no ionizing radiation involved. This makes MRIs a safer choice when frequent scans are required for ongoing health monitoring. However, MRIs have limited availability and take longer to perform than CAT scans. There are also safety issues with MRIs for people who have metal implants or fragments in their body.

When determining which type of scan is most appropriate, doctors must balance the need for clear diagnostic images with limiting radiation exposure as much as possible. CAT scans are often used for emergency cases, while MRIs may be preferred for children and non-urgent situations where radiation risks outweigh the benefits of a quicker scan. The best option depends on each patient’s specific health status and scan requirements.


In summary, there are several key differences in what CAT scans and MRIs can detect in the human body:

CAT scans are better than MRIs at seeing bones, detecting fractures, and examining joints. The high resolution of CAT scans provides detailed images of the skeleton and any bone abnormalities.

MRIs are superior to CAT scans at detecting problems in soft tissues such as ligaments, tendons, and spinal cord abnormalities. The high contrast of MRIs allows them to differentiate between various soft tissue structures.

For imaging blood vessels, MRIs have significant advantages over CAT scans. MRIs can image blood vessels without needing contrast dye. CAT scans require contrast dye to visualize blood vessels.

MRIs provide better visualization of abdominal and pelvic organs than CAT scans. MRIs show more detail in organs like the liver, kidneys, pancreas, and reproductive organs.

Overall, CAT scans are ideal for examining bones and blood vessels while MRIs excel at imaging soft tissues and abdominal organs. Knowing the strengths of each imaging technique helps doctors select the most appropriate scan for a patient’s condition.

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