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What’s the difference between a CT scan and an MRI scan?

To help make a diagnosis or monitor the effectiveness of treatment, your consultant may order a CT scan or MRI scan which will produce detailed images of the inside of the body for analysis. Whether the consultant chooses an MRI scan or a CT scan will depend on the issue or issues they’re investigating, the area to be scanned, patient history and many other factors.

The differences between CT and MRI aren’t immediately obvious (especially if you’ve never needed one before) and this article intends to highlight the main differences so you’re more informed about the care you’re receiving and you can properly prepare.

Let’s first start by considering each of the imaging techniques individually and then take a look at how they differ. 

CT Scan

A CT scan (computed tomography scanner) uses radiation to produce cross-section images with the help of computer processing. CT images are more detailed than standard x-ray images and can show organs, soft tissue and bone which can help diagnose and monitor various conditions.  

A patient being prepared for their CT scan by a radiographer

MRI Scan

An MRI scan (magnetic resonance imaging) images the water molecules in the body through the use of an extremely strong magnetic field and produces a very detailed image. An MRI scan can be used to image almost any part of the body and can help with diagnosing and treating many conditions.

A patient being prepared and positioned for their MRI scan by a radiology department assistant

MRI might be used if you have a neurological condition, unexplained dizziness, tingling or numbing sensations on the body, headaches, vision problems, issues with your central nervous system and more.

What are the differences?

The main difference between CT and MRI is the technology used to scan the patient. MRI relies on strong magnets whereas CT scans use radiation, which some people find worrying.

  • CT scans are usually much quicker than MRI scans. A typical CT scan may last 5 – 10 minutes whereas an MRI can be 30 minutes or more.
  • MRI offers clearer imaging of soft tissue structures and is often preferred for the diagnosis of neurological conditions and spinal or CNS problems.
  • A CT scan is less noisy than an MRI scan.
  • An MRI is preferred for pregnant people due to the radiation of a CT scan.
  • If a CT scan is inconclusive, patients will often need an MRI scan which will produce more detail.
  • For MRI scans, Queen Square Imaging Centre is the preferred choice of many consultants due to the quality of the scanners and the advanced imaging techniques on offer.

    Peter Sutton

    Mr Peter Sutton

    Operations Manager, QS Enterprises Ltd.