13 Apr, 2022
Diagnostic imaging allows medical professionals to see exactly what is going on inside your body, and helps them gain valuable information when compiling a diagnosis and treatment plan.
There are several different types of diagnostic scans, all with their own benefits. The different methods we offer (e.g. CT, MRI, Ultrasound) are complementary to each other, and no one type of scan is better than another. Our consultant radiologists, who are specialists in medical imaging, will guide you towards the best scan for your needs from a medical perspective.
However, before you go ahead and book your scan, you might be wondering what the differences are between MRI and CT scans, and which option could best for you. This guide will help you to understand the main features, benefits and risks of each scan type.
🩺 When you book your scan with us, a dedicated clinician will assess your booking and medical history to make sure you receive the correct scan for your requirements.
MRI stands for magnetic resonance imaging, and uses strong magnets and a radiofrequency current to generate images of the inside of your body. It is best suited to scanning the soft tissues of the body, such as tendons and ligaments, the spinal cord, and blood vessels, as well as internal organs, bones and joints.
MRI scans look for abnormalities, inflammation, disease and tumours, and a special type of MRI called Magnetic Resonance Angioplasty (MRA) can be used to assess the health of blood vessels.
An MRI scanner is shaped like a cylinder, with a flat motorised bed that moves the patient into the scanning machine. Open MRI scanners are available, which have magnets above and below the patient, rather than all around them, which can help alleviate feelings of claustrophobia.
📌 Learn more about MRI technology, processes and uses in our complete guide to MRI scans
CT stands for computerised tomography, and uses a large X-ray machine to capture images of the inside of the body. Modern multidetector CT scans can compile a series of 2D images into 3D images, while standard X-ray scans only produce 2D images.
A CT scanner is shaped like a doughnut, with an X-ray source on one side, and detectors on the other. It also has a flat bed, which moves through the scanner.
The X-ray beam circles around you during the scan, and the detectors capture the strength of the rays which have passed through your body. Different bodily tissues allow varying levels of X-rays to pass through them, and the scanning machine uses this variation to compile an image.
Iodine-based contrast materials may be required for vascular enhancement, to image the vessels of the body, and to delineate differences between the tissues.
CT scans are most commonly used for body imaging, including the brain, neck, chest, abdomen and pelvis. Indications can include suspected cancer, suspected or confirmed stroke, clots to the pulmonary artery (pulmonary embolism), and aortic aneurysm. CT scanning is a major modality used to assess trauma of the spine and body in general.
📌 For further information about MRI scans and claustrophobia, visit our guide.
An MRI scan does not normally include any prior preparation, other than removing metal objects such as jewellery, hearing aids or belts. You might be asked to change into a hospital gown, depending on the type of scan you’re having and the clothes you wear to your appointment. You will not usually be asked to refrain from eating, drinking or taking medications prior to your scan.
For a CT scan, you might be required to fast (not eat or drink) for a couple of hours before the scan appointment. You will also be asked to remove any metal objects, not due to a magnetic field, but because they may affect the quality of the images obtained. As with an MRI scan, it might be necessary to change into a hospital gown for a CT procedure.
A key difference between an MRI scan and a CT scan is the radiation involved for CT, whereas MRI does not use any radiation. This means CT scans are more heavily regulated, and can only be carried out where it is deemed medically justifiable. Medical justifications include:
Our expert clinical team assess every CT scan booking we receive, and speak to every prospective patient for a 1-1 pre-scan consultation to understand their medical requirements. Using their expertise, they will refer you for the appropriate scan (CT, MRI or ultrasound) depending on your clinical need and indication.
📌 Next Steps:
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