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With so many diagnostic imaging tests available, patients often ask us to explain the differences between them. We have decided to start with the trusted CT scan and MRI.
As a diagnostic healthcare professional, you often come across several questions on what modality to choose for a certain diagnosis and what the benefits of one modality are over another according to the clinical indications presented.
What is the difference between a CT scan and an MRI?
What are the advantages of CT and MRI?
With a CT scan, we can create an image of almost the entire body, from the head to the lower limbs, in a few seconds. CTs are incredibly useful for diagnosing and staging cancer, checking whether it has come back, and monitoring whether a treatment is working. It’s very effective for surveying the entire body to look for places where the cancer has spread, such as the lungs, liver, or bone. These are called metastases.
Most of the time, CT is the first choice to stage cancer. We can also do special scans, such as CT cardiac scans which combined with a dye contrast injection can identify and quantify possible narrowing or blockage of the main coronary arteries.
MRI is great to show some type of cancers, tumours or lesions that the CT scans can’t show. Some cancers, such as prostate cancer, uterine cancer, and certain liver cancers, are very hard to detect on a CT scan. Also, an MRI provides much more detailed images which can be used to characterize some lesions in much greater detail. Metastases to the bone and brain also show up better on an MRI, as do sports injuries.
Both CT scans and MRIs pose some disadvantages and risks when used. These are based on the type of imaging as well as how the imaging is performed.
CT scan disadvantages and risks include:
MRI disadvantages and risks include:
Choosing between an MRI and CT scan
Your doctor will likely provide a recommendation based on your symptoms and explain whether an MRI or CT scan is more suitable for you. If you need a more detailed image of your soft tissue, ligaments, or organs, your doctor will commonly suggest an MRI.
Such cases include:
Your doctor is likely to recommend a CT scan if you have experienced:
It is important to remember that both CT scans and MRI scans are relatively low risk and both offer important information to help your doctor properly diagnose specific conditions. If your doctor sees something on your CT scan that they are unsure about, they may recommend an MRI for further evaluation. If you are unable to lie still or hold your breath (during some scans), the doctor may suggest that you have a CT scan as an alternative. If you have a cardiac pacemaker or other medical implant contraindicated for an MRI scan, you might have to have a CT scan instead. Rest assured that doctors will always choose your imaging scan based on the principle of whether the benefits of a test outweigh its risks.
If you would like to discuss the topics in this blog, contact our friendly patient services team on 01442 331 900 or fill out our contact form here.
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