European Society of Radiology: Could you please give a detailed overview of when and for which diseases you use cardiac imaging? Which modalities are usually used for what?
Christian Loewe: We as radiologists use three types of imaging tools for cardiovascular diseases, cardiac computed tomography (CT), cardiac magnetic resonance (MR), and cardiac hybrid imaging (PET/CT and MR/PET).
The big advantage of cardiac CT is its high resolution, the possibility to use it to view the entire heart at a glance and the quick image acquisition times. The classic indication for using cardiac CT was and still is to rule out coronary artery diseases in patients with low to intermediate pre-test probability. With recent innovations, CT is becoming more and more important, even in patients with higher pre-test probability. This is due to the future possibilities of accurately calculating the relevance of coronary stenosis with CT-derived fractional flow reserve (FFR) estimation and myocardial perfusion. Furthermore, cardiac CT has become the most important tool for planning minimal invasive treatment of structural heart disease, including treating aortic and mitral valvular diseases. Cardiac CT is the first method of choice to manage patients who are suspected of or who suffer from aortic diseases and is also used for anatomical imaging in congenital heart diseases. Last but not least, the CT derived ‘Agatston Score’ is a powerful predictor of the likelihood of an upcoming major coronary event and plays an important role in cardiovascular risk stratification.
MR represents the classical radiological method to image the heart and has been used for more than 30 years, while cardiac CT entered the stage much later. The uniqueness of cardiac MR is the ability to directly visualise damaged myocardial tissue. Consequently, cardiac MR is used for the management of patients with ischaemic heart disease since MR can directly visualise the tissue which is at risk and is able to differentiate this from necrotic tissue. This information is of extreme importance for indicating and planning revascularisation. Cardiac MR is essential not only in ischaemic heart disease, but also in any other myocardial disorders, including for example myocarditis (MR is the one and only method which can be used to directly view acute myocarditis), sarcoidosis, amyloidosis, and many more. The recently introduced possibility of sophisticated myocardial tissue characterisation by means of T1 and T2 mapping has opened yet another door and is currently changing the diagnostic algorithms in many disorders. Another important application of cardiac MR is the assessment of valvular diseases in addition to echocardiography in patients with limited accessibility to echo. MR is able to accurately calculate the flow gradients among the diseased valve and is important to determine treatment. MR is also applied in cardiac tumours and in patients with congenital heart disease, and is one of the essential tests to be performed in suspected arrhythmogenic right ventricular dysplasia.
The new kids on the block in cardiac imaging are represented by hybrid machines, including PET/CT and MR/PET. PET/CT is mainly used in patients with ischaemic heart diseases since this technique offers the combination between morphology of the coronary arteries and stenoses (CT) with function (PET, myocardial perfusion and viability). MR/PET is not yet routinely in use for many cardiac diseases, but it could offer new options in myocardial and tumour characterisation.
ESR: What is the role of the radiologist within the ‘heart team’? How would you describe the cooperation between radiologists, cardiologists, and other physicians?
CL: The role of the radiologist within the ‘heart team’ should not differ that much as compared to the role in other multidisciplinary teams, for example within the breast care centre or within the oncological multidisciplinary groups. The role of the radiologist within the ‘heart team’ should exceed the function as some kind of core facility; we should not focus on producing and sharing nice images. The radiologist’s role within the ‘heart team’ is to advise the clinicians about appropriate selection of appropriate tests, to avoid self-referrals, to take care of optimised and personalised imaging strategies, to report the imaging studies and to actively take part in the heart team meetings. The active involvement of radiologists is crucial to ensure that all the patient’s imaging information is put together at a glance and that the focus is not only on the heart. The evolution of minimally invasive treatment possibilities for so-called structural heart disease improved the cooperation with cardiologists and cardiac surgeons substantially and represents the driving force for the establishment of a heart team including radiologists.
ESR: Radiographers/radiological technologists are also part of the team. When and how do you interact with them?
CL: Radiographers and/or technologists represent an integrated part of our workflow and are an important part of our cardiac imaging team. I am working closely with them to continuously optimise examination protocols with regard to contrast and radiation dose optimisation. Their dedicated knowledge and experience play a fundamental role in this continuous process of protocol individualisation and optimisation. At our institution, basic patient management at cardiac CT and cardiac MR is in the hands of the technicians, they know when to involve a radiologist for heart rate optimisation and/or other decisions. Finally, the technicians do the standardised post processing as well.
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?
CL: I am currently working within a structured Department of Bioimaging and Image-Guided Therapy. This rather huge department is structured into four divisions including general and paediatric radiology, neuro and MSK radiology, nuclear medicine, and last but not least, the division for cardiovascular and interventional radiology, which I have the honour and pleasure to chair. There are twelve staff radiologists and four residents responsible and dedicated to cardiovascular and interventional radiology. Out of them, four staff members (including myself) spend most of their time focused on cardiovascular imaging. For eight hours a day, we are dedicated to cardiovascular CT using a latest generation CT scanner, and we spend six hours a day dedicated to cardiac MR using a state-of-the-art 1.5T scanner. Additionally, one day a week is dedicated to cardiac MR/PET.
Additionally, I am trying to implement cardiac imaging even in an outpatient environment, which is rather challenging due to the lack of proper reimbursement.
ESR: Do you have direct contact with patients and if yes, what is the nature of that contact?
CL: In my role as cardiac radiologist at the university hospital, I take care of all small children investigated due to congenital heart diseases personally. I am present and in charge during all these examinations and have direct contact with the parents or the children (depending on the age of the patients) and of course with the cardiac surgeons afterwards. As often as possible, I speak with the adult patients prior to the examination and explain the results afterwards. Since I have a lot of administration to be done as well, my staff members communicate with most other patients, explaining indications and signs, administering beta blockers where needed, and explaining the results to the patients and to the referring physicians. One of my staff members (or myself) is present at the daily morning conference at the Department of Cardiology and presents our imaging studies there.
ESR: If you had the means: what would you change in education, training and daily practice in cardiac imaging?
CL: As also described in the following answer, cardiac imaging is not yet fully accepted as a central part of radiology. There are still many colleagues without knowledge and training in cardiac imaging, and they follow the approach that cardiac imaging is reserved for cardiac specialists only. However, considering the number of people suffering from cardiovascular diseases and the fantastic possibilities of modern cardiac imaging methods, these techniques should be provided by almost all radiologists. Cardiac CT should become a normal, daily routine – comparable to a CT scan of the brain or for pulmonary embolism. This is something I would like to change: to train our young residents in cardiac radiology from the very beginning of their residency.
ESR: What are the most recent advances in cardiac imaging and what significance do they have for improving healthcare?
CL: It is very difficult to summarise the ‘most recent advances’ in such a dynamically developing field in modern medicine in a few sentences. One of the most recent and fantastic developments in cardiac imaging is the introduction of functional information into cardiac CT. By introducing CT to the perfusion technique it becomes possible to assess myocardial perfusion by CT. Establishing this technique in the clinical routine could represent a fundamental breakthrough in cardiac diagnosis, since cardiac CT could represent the first imaging modality providing both morphological and functional information within one single examination. A second important innovation includes the ability to calculate the CT-derived fractional flow reserve (FFR). With this technology, the real haemodynamic relevance of coronary stenoses could be estimated. The third really amazing recent development is the possibility to perform extremely low dose CT scans without the need for anaesthesia in newborns or very small children with congenital heart diseases. Concerning MR, the introduction of myocardial tissue characterisation represents a fundamental change in the management of patients suffering from structural heart diseases. Due to the highly accurate estimation of early changes at the level of the myocardium, optimised time points for treatment decisions could be established non-invasively. The potential for risk and outcome prediction by means of MR myocardial tissue characterisation will involve cardiac MR as the key factor for patient management in the very near future.
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?
CL: One very big change is still a work in progress, but it is the big jump into the radiology routine, into the daily radiological business. In the beginning, cardiovascular radiology was something for the ‘cardiac freaks’, it always seemed too complex, too specialised for ‘normal’ radiologists. But this has to change, and the change is ongoing. Cardiovascular diseases are too common and too important to be ‘reserved’ for a few cardiac radiologists; we have to continue to work to implement these examinations within the daily routine to provide a 24/7 service. A cardiac CT has to become something as ‘normal’ as a CT of the brain, and every radiologist should be capable of performing and reporting on it. But there is still some way to go in that direction. Another big chance during the last few years was caused by the implementation of treatment options for so-called structural heart diseases, meaning minimally invasive treatment options for valvular and many other cardiac diseases. The need for planning these modern and innovative procedures linked us radiologists much closer to the cardiologists since they need our tools to perform their own treatments.
ESR: Is artificial intelligence already having an impact on cardiac imaging and how do you see that developing in the future?
CL: Honestly speaking, as in many fields in modern radiology, the focus of the AI development is currently on applications within oncology. Nevertheless, I am sure that AI will play a fundamental role in cardiovascular imaging in the near future, and many initiatives and projects are already on the way or at least preparing for this. Currently, we are not using all the morphological information provided by modern cardiovascular imaging and are focused on the traditional mechanistic approach (like estimating the relevance of a stenosis by measuring the luminal narrowing). We know that modern CT and MR provide much more information, and we need artificial intelligence and deep learning strategies to use this information and to link it with other biomarkers in favour to our patients. I am sure that with these modern techniques and strategies we might be able to early identify patients at risk and to prevent them from suffering from major cardiovascular events. This will be for sure the main attempt of research in the field of cardiovascular imaging within the next decade.
Professor Christian Loewe is a cardiovascular radiologist and Head of the Division of Cardiovascular and Interventional Radiology at the Department of Bioimaging and Image-Guided Therapy at the Medical University of Vienna, Austria. He is highly interested and active in radiological education, exemplified by a couple of functions and activities: He is actively involved with the Austrian Roentgen Society and has been responsible for the Austrian Board examination for many years. Furthermore, he has been a member of the Executive committee of the European Society of Cardiovascular Radiology (ESCR) for the past five years and the Chairman of the Educational Committee and the European Board of Cardiovascular Radiology (EBCR) within the ESCR. He is a member of the Programme Planning Committee of ECR 2018, 2019 and 2020 and he is a member of the Steering Committee of the European School of Radiology. He founded Vienna Heart, a successful teaching initiative to train radiologists in modern cardiac imaging. He is also chairman of the Accreditation Council in Imaging (ACI) responsible for the accreditation of radiological events on behalf of the UEMS. Professor Loewe served as a member of the Editorial Board for European Radiology for ten years, and he served for two periods as Associate Editor for Radiology. He has published more than 100 scientific articles in peer-reviewed journals and gave more than 300 invited lectures so far. His main focus is cardiac imaging, imaging peripheral arteries, diagnosis and the treatment of aortic diseases, as well as minimally invasive treatment of oncological diseases.