Optimised analysis of the right ventricle

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Transesophageal echocardiogram (TOE) is a key imaging approach routinely used to guide the minimally-invasive treatment of many forms of heart disease.

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Hypertrophic cardiomyopathy (HCM) is a condition where the heart muscle becomes thickened. This condition affects about one in 500 people.

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The aim of the project is to develop a commercially available 3D ultrasound technique for accurate measurement

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John Simpson, Alberto Gomez , Graeme Penney, Reza Razavi and Kuberan Pushparajah
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The aim of the project is to develop a commercially available 3D ultrasound technique for accurate measurement of the size and function of the right ventricle of the heart based on ultrasound (echocardiographic) assessment. The right ventricle is the lower chamber of the heart which pumps blood to the lungs. Such assessment is important for several large groups of patients with congenital heart disease, a form of heart disease which means the patient is born with structural problems in the heart. Some examples include patients with hypoplastic left heart (HLHS) and repaired tetralogy of Fallot. Accurate measurement of the size and function of the right ventricle of the heart informs clinical decision-making and can help identify the disease severity.

Magnetic Resonance Imaging (MRI) is a medical imaging technique that uses strong magnetic fields to obtain images inside a patient in real time. MRI is the current ‘gold standard’ or best available imaging method but is expensive compared to other approaches such as ultrasound, requires anaesthesia in younger patients and is not suitable in patients with metallic medical device implants. Echocardiography is an excellent non-invasive bedside test which is cheaper and requires no sedation for young patients. However current echocardiographic techniques do not agree well with MRI and produce lower values of the right ventricular size. One contributing factor to this lack of agreement is that a single 3D echocardiographic “volume” does not take into account the entire right ventricle. Researchers at King’s College London (KCL) with colleagues from Evelina Children’s Hospital have published on techniques to combine multiple 3D volumes together to provide a better more optimised image of the whole of the right ventricle. While a method has been proven to be possible it has not yet been possible to integrate it into the clinical workflow. The aim of this project funded through the NIHR Cardiovascular Healthcare Technology Co-operative (HTC) is to:

The above three steps will lead to a more accurate measurement of right ventricle volumes and help to improve healthcare in children and young adults.

Over the past few years we have developed a new technique to fuse multiple 3D ultrasound images into a single, high quality image. For example the picture on the right shows six ultrasound images taken from different viewing angles and fused into a single high quality image. The resulting single image is more suitable for volume analysis and has the potential to give more accurate volume measurements than any of the individual standard images.

The previous images can be acquired in any patient using standard ultrasound systems in less than ten minutes, without any harm to the patient and with minimum discomfort.

The right ventricle is identified and outlined (segmented) from the high quality image and then, using advanced image processing techniques, the motion of the right ventricular chamber is estimated from image data. This motion is then used to segment the right ventricle (identification and outlining) for all cardiac phases. An example of the resulting ventricular motion can be observed in video on the right where the outlined right ventricle is superimposed to the image data of the beating heart.

Last, the segmented right ventricle is used as input to a new software package, currently under development, which analyses the volume of the right ventricle throughout the cardiac cycle and gives the cardiologists accurate measurements of the right ventricle.

The work in progress includes the application of this software to 3D echocardiographic datasets where we have MRI images for comparison and accuracy assessment.

The ultimate aim remains to provide a means of accurate assessment of right ventricular volume and function in an outpatient setting using a fully automated commercialised software with the collaboration of industry partners. This will allow us to develop a tool that can be used routinely in clinical practice.