European Society of Radiology: Could you please give a detailed overview of when and for which diseases you use cardiac imaging?
Alain Nchimi: We use cardiac imaging when the clinical assessment of the patient has failed to provide a definitive answer regarding his condition and needs for treatment. The clinical assessment is often coupled with electrocardiography (ECG) and echocardiography and establishes a differential that other imaging techniques have to sort out when applicable. The common diseases requiring cardiac imaging alter the shape, the function or the structure of the heart, including ischaemic heart disease (failure to provide sufficient blood to the myocardium), heart valve diseases, congenital heart diseases, cardiomyopathies, masses, pericardial diseases etc.
ESR: Which modalities are usually used for what?
AN: Heart imaging includes invasive techniques performed by cardiologists in the catheter labs that are nowadays rarely performed on the first line. The non-invasive techniques include echocardiography (often performed by cardiologists), computed tomography (CT) and magnetic resonance imaging (MRI) that are performed by radiologists or cardiologists (or both), varying from facility to facility, and nuclear imaging.
Ultrasound is the first-line imaging technique in most cardiovascular diseases.
CT is establishing itself as the imaging flagship for coronary and congenital disease imaging. CT is also helpful for heart valve diseases and provides the unique ability to score tissue calcification, which is an important prognostic tool in cardiovascular diseases. CT is also largely used for pre-treatment planning, due to its excellent spatial resolution.
MRI and CT have overlapping characteristics, which means that MRI may be used when CT is not available and vice versa. However, MRI is the standard in terms of tissue characterisation. As such, MRI applies for cardiomyopathies that demand a comprehensive assessment of the myocardial tissue composition. MRI is also the best imaging modality for myocardial function analysis, which is the mainstay of all cardiac diseases. Lastly, MRI has unmatched abilities to evaluate the haemodynamic significance of cardiovascular diseases (e.g. heart valve diseases, ischaemic heart disease, congenital heart disease …) through flow analysis, and stress tests. Nuclear medicine imaging encompasses a broad range of tracers and imaging techniques that have the ability to evaluate myocardial function and metabolism, as well as stress tests for ischaemic heart diseases.
ESR: What is the role of the radiologist within the ‘heart team’? How would you describe the cooperation between radiologists, cardiologists, and other physicians?
AN: Cardiac imaging techniques are often complementary, but may be redundant. In addition, cardiac diseases are in most cases associated with other conditions that may prevent the use of one or several imaging techniques. The choice of the most appropriate imaging technique regarding a specific clinical concern belongs to the radiologist within the heart team, in addition to both the interpretation and the discussion of its relevant findings. In most institutions, the cooperation between physicians in the heart team is excellent towards personalised patient care. However, not all institutions have developed the concept of a heart team, and in some heart teams, there is no radiologist, despite international recommendations. Reasons for this include absence of involvement or availability of board-certified cardiovascular radiologists or the fact that there may be a competition between radiologists and other specialists with an interest in cardiac imaging.
ESR: Radiographers/radiological technologists are also part of the team. When and how do you interact with them?
AN: The interaction with the radiographers is mandatory to run a successful clinic in cardiovascular imaging. They should have a deep knowledge of imaging technique and disease-specific imaging and post-processing protocols. In most institutions including mine (see next question), they manage the patient from arrival to the end of the procedure. In most cases, they are the only contact with the patient. In addition, they may be requested to process the image after acquisition. As such, they interact with the responsible physician before and after each procedure.
ESR: Please describe your regular working environment (hospital, private practice). Does cardiac imaging take up all, most, or only part of your regular work schedule? How many radiologists are dedicated to cardiac imaging in your team?
AN: I currently work in university general hospitals and a private facility with a public mission. All have up-to-date US, CT, MRI and nuclear imaging equipment and well-trained radiographers. I’m the only radiologist dedicated to cardiac imaging, however, there are other specialists (cardiologists) in cardiac imaging. Only a part (approximately half) of my working time is dedicated to cardiac imaging.
ESR: Do you have direct contact with patients and if yes, what is the nature of that contact?
AN: Patient contact with the radiologists are granted only upon request (please see the question on the role of the radiologist). In general, the clinical information relevant to imaging is provided via the request form or the heart team meeting.
ESR: If you had the means: what would you change in education, training and daily practice in cardiac imaging?
AN: It is mandatory that the information to the general public and the education to future physicians is updated and provided in the most neutral way. The level of awareness for cardiac imaging capacities and the indications for imaging in cardiovascular diseases strongly varies among patients and other uninvolved physicians. This implies information about cardiac imaging on a regular basis in media and social media, as well as within hospital facilities. The involvement of cardiac radiologists in academic teaching programmes is also mandatory.
ESR: What are the most recent advances in cardiac imaging and what significance do they have for improving healthcare?
AN: Imaging in general is subject to a continuous technological improvement. Cardiac imaging does not escape this trend. The improvement impacts both hard- and software. The CT scanners are scanning faster with lower ionising radiation doses resulting in similar or better image quality than they could previously provide. This is possible because of new detector and detector arrangement technologies, higher computer speed and new image reconstruction algorithms. New hardware technologies also enable CT imaging stress test and improved tissue characterisation. Regarding MRI, the field strengths and the coils channels of clinical scanners are both increasing resolution, resulting in improved image quality. New image acquisition schemes now allow evaluation of the relaxation properties (T1, T2 and T2*) on a voxel basis, which is a major step forward in terms of tissue characterisation.
Newer detection systems are also being implemented on positron emission tomography (PET) scanners to improve spatial resolution.
Software engineering is probably the most active field of research and day-to-day clinical improvement of cardiac imaging. It allows delivering information from images, such as modelisation and fluid-structure simulation on CT images to provide functional information regarding blood flow limitation, or wall stress and blood flow vortices on 4D MRI flow contrast images.
Lastly, there has been progress in pharmacological stressors and contrast agents that improve the accuracy of cardiac imaging stress tests for ischaemic heart disease.
ESR: In what ways has the specialty changed since you started? And where do you see the most important developments in the next ten years?
AN: The specialty has nearly grown from zero since I was a young radiologist. Ultrasound and nuclear imaging were almost the only modalities for non-invasive cardiac imaging two decades ago. Invasive cardiac imaging was performed in almost all patients with cardiovascular diseases, often with no diagnostic yield. Nowadays, CT and MRI have become routine and standard procedures and help to provide better patient care with fewer side-effects and morbidity from diagnostic procedures. These two techniques will take up a larger part in the diagnosis of cardiac diseases in the future, due to their fast progress. Nevertheless, the future of cardiac imaging lies in an integrative approach combining multimodality imaging with clinical and biological inputs. This approach will allow not only diagnosing cardiovascular disease but choosing the appropriate treatment and effectively preventing the complications from subclinical disease, via deep learning and big data analysis.
ESR: Is artificial intelligence already having an impact on cardiac imaging and how do you see that developing in the future?
AN: Most of the current impact of artificial intelligence available in clinical settings addresses image acquisition and standardisation procedures. Aid to the diagnosis and prognosis of cardiovascular diseases will probably come soon as a disruptive evolution for both patients and physicians.
Dr. Alain Nchimi earned his medical degree and completed a master degree in medical imaging at the University of Liège, Belgium. In 2015 he obtained a PhD from the same University. He acquired a diversified professional experience in cardiac radiology, successively at Great Ormond Street Hospital for Sick Children in London and at the Centre Hospitalier Chrétien in Liège, the University Hospital of Liège and currently at the Centre Hospitalier in Luxembourg and as external consultant for both the University Hospital Saint-Luc and the University Hospital Queen Fabiola for Children in Brussels. He is a member of the Belgian Society of Radiology chairing the Section of non-invasive Cardio-Vascular Imaging, the European Society of Cardiovascular Radiology and is a member of the scientific committee. He is also a member of the European Society of Radiology and the European Society of Thoracic Imaging, as well as the European Association of Cardiovascular Imaging and the European Society of Cardiology. Dr. Nchimi is committed to research in non-invasive cardiac radiology, working as a senior consultant in the GIGA cardiovascular disease research unit of the University of Liège. Since 2015 he is Associated Professor of Medical Imaging at the Free University of Brussels. He has given over 200 national and international lectures, authored over 10 book chapters and 70 original articles. He is a well-known expert in non-invasive cardiac imaging, serving as reviewer for prominent international journals such as Radiology, AJR, British Journal of Radiology, European Radiology, Circulation, The International Journal of Cardio-Vascular Imaging, Acta Cardiologica, European Heart Journal and European Heart Journal Cardiovascular Imaging. He is the current editor-in-chief of the Journal of the Belgian Society of Radiology.