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21 March 2022

The 3D coronary MR technology has an almost zero percent failure rate

Biomedical Imaging researchers from King’s College London have developed a safe and efficient alternative for imaging the coronary arteries non-invasively (no radiation, no needles), involving a reduced scan time with an almost zero percent failure rate. The technology is currently in use at Guy’s and St Thomas’ NHS Foundation Trust.  

Led by Professor René Botnar, Head of Biomedical Engineering at the School of Biomedical Engineering & Imaging Sciences, the new technology now allows clinicians to not only diagnose the status of the myocardium (ischemia and scarring) but also relate it to the stenosed coronary arteries thereby having more information prior to percutaneous intervention or bypass surgery. 

The new CMRA technology, which was developed between 2012 and 2020 addresses the limitations of x-ray and CT coronary angiography (ionizing radiation, nephrotoxic contrast agents) as it does not require catheterisation; does not require injection of a contrast agent and does not expose patients to harmful ionising radiation. Moreover, the new CMRA technology addresses the limitations of current CMRA protocols which suffered from long and unpredictable scan times.

Sometimes when you see a perfusion deficit, say in a certain part of the muscle, often clinicians are still not sure which coronary artery it is. If you can overlay this information then you have the complete picture.

Professor René Botnar, Head of Biomedical Engineering, School of Biomedical Engineering & Imaging Sciences

Professor Botnar refers to an 87-year-old woman with elevated troponin, indicative of a potential heart attack. With clinicians concerned, it was suggested they undertake an invasive x-ray or CT. Opting against x-ray and due to its invasiveness and against CT due to its sensitivity to heart rate variations or arrhythmias, the team then performed a CMR which showed that there was no infarcted heart tissue. However, if Professor Botnar’s test was run they would have known whether there was an occluded or stenosed coronary artery and consequently whether an intervention was necessary.

Instead of having multiple exams, such as a cardiac MR, CT and an echocardiogram, with this technique we can do a ‘one-stop shop’. We can get a single cardiac MR and we can tell the patients whether they have a coronary artery stenosis and associated perfusion deficit, we can tell them whether they have scar tissue, i.e. an infarction and we can tell them about the pump function of their heart. It is a complete cardiac exam. It saves a lot of time and it is non-invasive.

Professor René Botnar

The new CMRA technology is based on several key developments. The researchers developed a novel motion correction approach that can compensate the complex motion of the heart similar to an autofocus camera while also making the scans faster as no data need to be discarded. To further shorten the scan time, they combined their motion correction technology with a novel image denoising technique resulting in crisp images of the heart.

Now it takes between 3-5 minutes to do a scan whereas previously, with the same resolution it took between 10-25 minutes.

Making the scan time shorter and predictable is a great step forward as it now allows adding this test to any cardiac MR exam and providing a complete assessment of the heart with a single modality in a 45-minute exam. With over 100k cardiac MRs been done annually in the UK.

The researchers are currently collaborating and planning for a multi-centre trial. The plan is to involve 5-8 centres to scan 250 patients, comparing them against CT angiography the current non-invasive reference standard. If the results of that study show that their method is non-inferior to CT, it will allow for a worldwide rollout.

The team is also working on super resolution and deep learning reconstruction methods that have shown to decrease scan time to less than a minute or even a breath hold and which promises to make this technology a quick test that could be used in any patient with heart problems.

“We are confident that this will change the way we examine patients with suspected coronary artery disease.”

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René  Botnar

Chair of Cardiovascular Imaging