Eugenio Picano: Radioprotection Not Equal for All Myocardial Perfusion Imaging Tests
The United States will likely adopt the strategies that other countries have already implemented to reduce radiation exposure related to myocardial perfusion imaging, which accounts for a major portion of Americans’ overall radiation burden, predicts Eugenio Picano, MD, PhD.
Picano, who worked in the stress echocardiography field for 25 years, is currently research director at the Institute of Clinical Physiology, Italian National Research Council (Pisa, Italy). He is the co-principal investigator of a study exploring the cardiac and noncardiac effects of long-term radiation exposure in patients and clinicians using a molecular epidemiology approach and of a large-scale study on stress echo’s applications outside of CAD.
TCTMD asked Picano to comment on 2 studies exploring the use of best practices in the United States and elsewhere to reduce radiation exposure from myocardial perfusion imaging (MPI). Those studies showed that US nuclear cardiology labs were less likely to adhere to best practices, resulting in higher radiation doses.
Q: Why is MPI used so much more frequently in the United States than in other countries?
A: The United States was less affected, until very recently, by 3 factors that had a disruptive effect on the practice of cardiac imaging in other countries: perception of radiation risk, social cost, and legal implications of use of medical radiation.
First, the paradox of plenty is a major challenge for contemporary healthcare, and it is now known that more resource use may lead to poorer measures of care. More is not necessarily better and may in fact be worse. If you perform millions of cardiac stress imaging tests per year with MPI, you will have thousands of additional long-term downstream cancers. Small individual risks multiplied by millions of examinations become significant population risks.
At the same time, you pay more for any information that you might get other techniques of similar diagnostic and prognostic accuracy. In healthcare systems with universal access (as in Europe, Australia, Canada, and many countries outside the United States) if you pay for luxury information for some patients you will deny essential services to others, since healthcare money is not unlimited and declining. The cost should be affordable not only for the individual, but also in a societal perspective. Small extra costs multiplied by millions of tests translate into unsustainable social costs.
Lastly, in Europe you have to handle with care the radiation issue also from the legal viewpoint, since the legal framework of the 1997 Euratom law accepts the principle of justification (“if an exposure cannot be justified, it should be prohibited”), the principle of optimization (“according to the ALARA principle, all doses due to medical exposures must be kept As Low As Reasonably Achievable”), and the principle of responsibility (“both the referring physician ordering the test, the prescriber, and the physician performing the test, the practitioner, are responsible for the justification of the test exposing the patient to ionizing radiation”). If you perform clearly inappropriate examinations or appropriate examinations with nonoptimized, too-high radiation dose, you are subject to penalties and fines. Patients are paying increasing attention to this issue because of recent reports with wide media impact that medical low-dose radiation exposures in patients are associated with increased rates of cancer in the irradiated organs years down the line.
These 3 factors will increasingly affect medical practice also in the United States and the consequences in use of cardiac stress imaging can be striking. The United States will follow the path of other countries, equally rich but perhaps more sensitive to environmental, economic, and social issues. In Australia, from 2002 to 2013 the number of services per 100,000 people remained stable for MPI (from 287 to 337, with a peak in 2007) and increased for stress echo—lower cost, radiation free, and no environmental burden—from 181 to 947. This adaptation will be unavoidable also in the United States if the country wants to regain its lead in medicine, now lost in spite of (or because of?) exorbitant healthcare expenditure, according to recent statistics incorporating quality, equity, and efficiency of delivered healthcare.
Q: What can be done to improve adherence to best practices in the United States and elsewhere?
A: A key piece in the puzzle is a better radiological informed consent form: more informative, in plain language, with clear description of risks and doses. Kenneth Arrow, a Nobel Prize winner in economics, showed 50 years ago that buyers have marked disadvantages when they know less about a good than the seller does. At that time, in 1963, his prime example was healthcare. In radiological informed consent, the communication of doses and risks is often based on highly specialized technical language, and often difficult to understand even for practitioners and radiologists. As a result, patients often are unaware of what they are doing in terms of doses and radiation risks. The informed consent form should spell out, in tabular form and possibly with a figure, the specific reference dose. After the examination, the actual delivered dose should be stored in the patient’s and laboratory’s records. The jargon should be translated into an equivalent number of chest radiographs, and equivalent periods of natural background radiation. After the procedure, the patient should be provided with dose information if he/she asks, and this has become a requirement enforced by law in many countries. This simple consent process also will gently force the doctor to learn what he/she already should know, enabling him/her to make more responsible choices.
Q: In terms of stress-only imaging specifically, what are the barriers to using such testing and what can be done to overcome them?
A: One barrier is administrative, and the second is cultural. The administrative barrier was built by policy makers and administrators, who reimburse $137 more for a multiple stress–rest study than for a single stress-only study. To overcome the administrative barrier, the dose given should always be recorded, and the reimbursement should be lower with doses above a certain threshold, and higher for doses below a given threshold. If you do the multiple study when a single stress-only study was indicated, you will not be reimbursed for the useless part of the exam you performed. If you appropriately perform a single stress study, the reimbursement will increase with a radioprotection bonus. The system will become more flexible and require a physician reviewing the stress images, but this is the standard outside of the United States and the patient will benefit with this change.
The cultural barrier is even more important, and was built by cardiologists and imaging specialists themselves. For decades, basic radioprotection issues (such as the dose of common examinations) were absent from monumental cardiology and imaging textbooks. Until recently, it was very difficult to find a single presentation (not to say a structured session) on radiation risks in major cardiology and cardiac imaging meetings. At our own tertiary care referral center, in 2005 most cardiologists and imaging experts ignored the difference between ionizing and nonionizing testing, and the majority of those who knew the difference underestimated by 100 to 500 times the dose of a common cardiac scintigraphy.
Administrators and policy makers should tear down the administrative wall, and cardiologists and imaging specialists the second, higher and thicker wall that we built with our own hands.
Q: What is the take-home message from these 2 studies?
A: These 2 important and timely studies demonstrate that not all MPI tests were created equal from the radioprotection standpoint and you can buy the same diagnostic information at very different radiological costs in different countries, and even in different laboratories of the same country. The findings highlight the need to audit doses in cardiac imaging labs, to track cumulative exposures, and to standardize doses for each technique. This high-priority scientific and clinical need is also propelled by the European radiation protection legislation which was recently updated and now requires monitoring of radiation exposure of patients (Council Directive 2013/59/Euratom). All member states are forced to transpose the Directive into national legislation and to implement its requirements by 2018.
I would end with the final statement of the 2014 European Society of Cardiology position paper on radiation: a smart cardiologist cannot be afraid of the essential and often life-saving use of medical radiation, but must be very scared of radiation unawareness. The actual delivered dose should always be recorded and included in patients’ records. Because of the numerous sources of variability, there is no clear threshold between acceptable and unacceptable exposure for any given examination, but the dose that is not even considered is certainly unacceptable.
- Picano reports no relevant financial conflicts of interest.