The difference between CT and MRI scans

Computed tomography (CT) and magnetic resonance imaging (MRI) are both used to capture images within your body. CT scans and MRIs both help diagnose cancer and detect or monitor diseases.

Often our patients ask us “What’s the difference between a CT scan and an MRI scan?” so we are going to explain both methods and explain the key differences between them.

The difference between CT and MRI scans

What is the difference between a CT scan and an MRI scan?

The biggest difference between the two methods is that CT scans utilise X-rays to form images of organs, bones and tissues whereas MRI scans use magnetic fields and radiofrequency pulses to generate detailed pictures of internal organs.

Another comparison is that MRIs are known to provide more detailed information about soft tissues and internal organs such as the brain, reproductive system, skeletal system and more. On the other hand, CT scans can be quicker.

CT scans are used when speed is of primary importance. Most emergency departments have a CT scan machine on hand as it is the best option for trauma, strokes or blood and organ injuries.

MRIs are best used when there is a need for a detailed image when a doctor is looking for causes of dementia, neurological diseases, joint problems or cancer. MRI imaging is also the best option for spine and nerve problems.

What are the advantages for each imaging method?

As mentioned above with a CT scan, an image can be created in just a few seconds, so the key benefit is time.  CTs are extremely useful for diagnosing, staging and monitoring cancer. The scans are very beneficial for checking the entire body when looking for metastases.

The MRI excels in showing specific diseases that a CT scan cannot detect.  For example, certain liver cancers cannot be detected on a CT scan and others can be completely invisible. Metastases to the bone and brain can also show up better on an MRI as MRI scans provide a far more detailed image than a CT scan.

How does a CT scan work?

A CT scan is a series of X-ray images taken at different angles. The patient lies on a table that moves through a scanning ring, the data is collected, and a computer is then used to create images from the X-rays.

X-ray images can reveal abnormalities in both bone and soft tissues, such as bone fractures and tumours.

How does an MRI scan work?

The difference between CT and MRI scans


An MRI scan produces thorough images of the body’s soft tissue and bones. The person lies on a table that moves into a round-shaped tube, or in our case, an open MRI scanner for the patient to see around them.

MRIs use magnetic and radiofrequency waves to produce energy. The energy created sends a signal to the computer and the computer uses mathematical formulas to change the signal to an image.


Our open MRI scanner is double the width of a traditional scanner, it has no walls, and produces a lot less noise. It is completely open on both sides which makes it easy for your friend or family member to hold your hand.

While both these scans have their own benefits, it is important to note that your medical history must be checked by a professional that will be able to advise you on the best scan for you. Please call us on 0191 281 2636 and we will be able to give you any extra information that you require.