Cardiovascular Magnetic Resonance (CMR) Scan
These scans enable cardiologists to view detailed images of the inside of the body. An MRI (magnetic resonance imaging) scan is used for imaging most parts of the body, whereas a CMR (cardiovascular magnetic resonance) or Cardiac MRI scan is used specifically to provide an image of the heart structure and blood vessels.
An MRI scan is a sophisticated type of scan that does not use any radiation. The scanner uses a large magnetic tube to align the body’s protons – small particles contained within each hydrogen atom, found in every water molecule – and then uses short bursts of radio waves directed at specific areas of the body. These knock the protons out of alignment, which realign when the radio waves are turned off. This sends out radio signals that are picked up by receivers.
These signals provide the exact location of each proton and help distinguish between the different types of tissue inside the body, because the protons of each type of tissue realign at different speeds and produce a different signal. Computers then produce a detailed image of the body. These CMR images allow doctors to assess cardiac function, scarring of the heart muscle and a lack of blood supply (myocardial ischaemia). CMR is considered the gold standard imaging modality for patients with cardiomyopathy as it allows for better visualisation of the heart and is the only way of detect the scarring of heart muscle that is often seen in these conditions.
During an MRI scan, you will lie flat on a bed which is moved into the scanner. The procedure is operated by a radiographer, to whom you can communicate via an intercom, and typically lasts 45 minutes. Headphones with music or ear plugs are normally provided. Some patients may feel claustrophobic but often simple reassurance is enough to allow the scan to conclude. The Cambridge Heart Clinic has access to an open MRI scanner for those who cannot tolerate a conventional scanner due to claustrophobia.