European Society of Radiology: Could you please give a detailed overview of when and for which diseases you use cardiac imaging?
John Hoe: We mainly use cardiac imaging to assess chronic ischaemic heart disease e.g. angina, atypical chest pain, post-infarct, and pre and post coronary artery bypass graft (CABG) or percutaneous coronary intervention (PCI).
The most commonly used modalities are cardiac computed tomography (CT), magnetic resonance (MR) or single-photon emission computed tomography (SPECT) and PET/CT, using rubidium as a tracer.
ESR: Which modalities are usually used for what purpose?
JH: Calcium scoring-risk stratification is used in patients with low, intermediate or high risk of coronary artery disease (CAD).
Cardiac CT is used mainly in radiofrequency ablation (RFA) and transcatheter aortic valve replacement (TAVR) planning and suspected CAD – both stable and chronic.
Cardiac MR is mostly used to assess cardiomyopathies and post-infarct assessment for planning revascularisation. It’s also used to image congenital heart disease, intracardiac shunts and some valve diseases.
We do not perform stress testing for ischaemic heart disease because we don’t have the time or resources to do so; instead we use stress echocardiography, CT or SPECT/PET/CT. SPECT/PET/CT is mainly used in ischaemia imaging, to assess the extent of ischaemia.
ESR: What is the role of the radiologist within the ‘heart team’? How would you describe the cooperation between radiologists, cardiologists, and other physicians?
JH: Cooperation is generally quite good, depending on the location of the scanners. In my centre, we operate the scanners, interpret the scans and do the reports. We have a good interaction with the cardiologists, both interventional and non-interventional, especially regarding scan findings, results and clinical implications. We also use WhatsApp to send key images to referring physicians.
In my country, heart teams of public hospitals operate their own CT scanners, and therefore completely exclude the radiologists, unless CMR is needed, since these scanners are located in the radiology department.
At the National Heart Centre, cooperation between radiologists and cardiologists runs smoothly; radiologists operate the scanner although it is located in the cardiology centre. In private centres and private hospitals, it depends. CT scanners are usually located in the radiology department, but depending on the training of the radiologists – most have not received any subspecialty training –, reporting control often falls on to the cardiologists, who then exclude the radiologists from the process. Cardiologists charge their own fees to patients for the reporting. Radiologists’ reporting fees tend to be half of what cardiologists charge.
ESR: Radiographers/radiological technologists are also part of the team. When and how do you interact with them?
JH: We interact all the time with imaging technologists to protocol cases and discuss which type of post-processing is needed. Being a private hospital, we do not have adequate physicians to perform post-processing and are therefore dependent on radiographers to post-process and create images, including 3D volume-rendered images filmed at correct catheter angles, curved planar reconstructed images (CPRs), multiplanar reconstructed images (MPRs), calcium subtraction, plaque assessment and quantification.
Producing nice images, which are annotated with the lesion, is an important marketing tool. Most cardiology-run sites do not produce images, as they are usually self-referral sites. In CMR, radiographers also calculate left ventricular ejection fraction (LVEF), right ventricular ejection fraction (RVEF), volume calculations and flow data.
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?
JH: I work in a tertiary care private hospital. Radiologists and nuclear physicians operate CT and MR scanners. The radiology department staff administers echocardiography lab, but cardiologists are in charge of reporting and echo performance, including stress studies. As mentioned above, cardiologists charge their own fees for these services.
ESR: Do you have direct contact with patients and if yes, what is the nature of that contact?
JH: We sometimes do. We work close to the CT and MR scanners, and we often talk to patients if they have any questions before and after the examination. Most patient routine management is done by nurses, who also insert IV lines, and radiographers, who need to instruct and practise the procedure with the patients beforehand to ensure good quality studies.
ESR: If you had the means: what would you change in education, training and daily practice in cardiac imaging?
JH: I would ensure cardiac imaging is taught as a subspecialty, separately from thoracic imaging (chest and pulmonary), since it requires multi-modality imaging. This would include familiarity with echo, cath lab procedures, as well as cardiac CT, CMR and nuclear cardiology. Radiologists need to be able to communicate with cardiologists using the correct terminology and to become familiar with the procedures that cardiologists perform. Too many radiologists do not bother to learn the correct terminology or anatomy, and this leads to lack of respect from the cardiologists, due to our limited knowledge of their specialty and how it is practised.
I would also mandate that all radiologists practising cardiac imaging get certified, and receive proper certification from a recognised body, college or cardiac imaging society, such as the Society for Cardiovascular MR and the Society for Cardiovascular CT.
The cardiologists get certification and use this qualification to argue that they are more qualified to operate imaging scanners. As a result, we are gradually losing control over CT and MR in large hospitals in our country.
Radiologists, for some reason, do not see the need to get a certificate or paper qualification for cardiac imaging, possibly because subspecialists like neuroradiologists or musculoskeletal radiologists do not have their own certificate. However, as more and more neurosurgeons and neurologists perform interventional neuroradiology procedures, I also foresee the need for certification for other subspecialty radiologists, to avoid losing control of angio labs to orthopaedic surgeons, neurologists and neurosurgeons.
ESR: What are the most recent advances in cardiac imaging and what significance do they have for improving healthcare?
JH: In cardiac CT, development of software to assess functional significance of coronary artery stenosis (CT-FFR) is a likely game changer. Currently, its use is limited to a single commercial site in the US, as far as I know. Most CT scanner vendors develop their own software or licence the software from this one company. Once the software is validated and shown to be viable for daily use on all commercial scanners, it will reduce the number of diagnostic invasive cath procedures, improve patient safety and reduce costs.
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?
JH: There has been a significant reduction in radiation exposure associated with cardiac CT scanning over the last ten years. This was led entirely by the cardiologists, who demanded that the vendors reduce radiation exposure.
Radiologists are only concerned about image quality and have never been concerned about reducing doses in daily routine. Luckily, some of the dose reduction technological advances have been translated into daily practice in body CT imaging etc., but again, the radiologists are not at the forefront of trying to reduce dose when using CT scanners. We are still too concerned with not missing a lesion and demanding perfect images at the cost of higher radiation doses. The difference in radiation doses for body imaging compared to cardiac CT can be up to 3–4 times higher, and is often due to scanning protocols prescribed by radiologists.
ESR: Is artificial intelligence already having an impact on cardiac imaging and how do you see that developing in the future?
JH: Artificial intelligence has not impacted our daily practice yet, but I anticipate that in the near future it will become a tool for daily use in some aspects of cardiac imaging.
Dr. John Hoe is a consultant radiologist at Medi-Rad Associates Ltd, Mt. Elizabeth Hospital in Singapore. He is a past president (2013–2015) and founding member of the Asian Society of Cardiac Imaging (ASCI). Dr. Hoe has been involved in cardiac CT since 2003 and notably organised the annual CT coronary angiography teaching course previously held in Singapore, Australia (Sydney), Thailand, Taiwan and Hong Kong. He was also president of the 2nd ASCI Congress, which was held in April 2008. His main research interest is coronary CT angiography, and he was one of the principal investigators in the first international multicentre study on 64MSCT and more recently CorE320 MSCT multicentre trial on CT myocardial perfusion. Dr. Hoe has been course director of the advanced CT training course for cardiac MSCT users held at the CT Centre of Mt. Elizabeth Hospital since 2004. He also holds certification of the Fellow of the Society of Cardiovascular Computed Tomography (FSCCT).