Dr. E. Gordon DePuey,
director of nuclear medicine
at St. Luke's-Roosevelt Hospital

New guidelines for low-dose myocardial perfusion in effect

January 06, 2014
by Loren Bonner, DOTmed News Online Editor
Nuclear cardiologists are under immense pressure these days to reduce radiation dose. In reaction to mounting evidence of inappropriate overutilization of myocardial perfusion imaging over the years, the American Society of Nuclear Cardiology has responded with guidelines, which are effective Jan. 1, 2014, to reduce dose. And they offer three specific ways it can be achieved. DOTmed News spoke with Dr. E. Gordon DePuey, director of nuclear medicine at St. Luke's-Roosevelt Hospital in New York City, about these recommendations.

DMN: Why is the field of nuclear medicine, and specifically nuclear cardiology, under pressure to reduce radiation dose?

EGD: The radiation dose that is afforded to patients with a standard myocardial perfusion SPECT scan is relatively high compared to other radiography modalities. With a standard protocol we are affording patients approximately 11 millisieverts of radiation exposure. Also, compared with other nuclear medicine procedures the dose is relatively high. Nevertheless, any harm from this degree of radiation is still very theoretical. Although there have been no hard data to suggest there's an increased risk of cancer due to this degree of radiation, from a theoretical standpoint, there might be a very, very slight increase. The medical community, the public, and the media are well aware of this small, theoretical risk. So specialists in nuclear cardiology, as well as all of nuclear medicine and radiology, are under pressure to decrease radiation dose.

DMN: Tell me about the new 2014 ASNC guidelines that are intended to reduce dose in nuclear cardiology procedures?

EGD: These guidelines have been published by ASNC [The American Society of Nuclear Cardiology]. By 2014, 50 percent of patients undergoing myocardial perfusion imaging should have a radiation dose of less than 9 millisieverts. That is somewhat lower than the 11 millisieverts associated with the most commonly used myocardial perfusion SPECT protocol. Of note, there are other protocols in nuclear cardiology that actually give higher doses than 11 millisieverts. First, the ASNC guidelines try to eliminate — or at least minimize — these other protocols that afford a higher radiation dose. Second, there is a move to perform stress-only imaging, where only the stress part of the test is performed. Generally, you need both the stress and resting parts of the test, but if you chose your patients carefully, and have rigorous technology quality control, you can perform the stress-only part of the study, thereby decreasing patient radiation dose to about half, well below the 9 millisievert guideline. However, to do stress-only imaging well, you really need attenuation correction. Unfortunately only a few nuclear cardiology labs have attenuation correction, so implementation of stress-only imaging is not so easy.

DMN: How else can labs decrease dose, as recommended by ASNC in the new guidelines?

EGD: Another way to decrease dose, besides the stress-only protocol, is by using new, state-of-the-art equipment that is available only recently. These cameras are more sensitive, counting radiation much faster than standard cameras. By using this new equipment, patient radiation dose can easily be decreased to 5 millisieverts, or even less, with excellent quality myocardial perfusion images. But such new equipment is very expensive. Unfortunately, with decreasing reimbursement, not many departments can afford it.

An alternative is to implement low-count density software, now available from all of the nuclear camera vendors and also from UltraSPECT Ltd., which sells software that can be interfaced to old and new cameras from all vendors. Software methods have been developed that provide maintained or even improved image quality despite only one half or even one quarter the counting statistics. Therefore, instead of a patient dose of 11 millisieverts, the dose is only 5-6 millisieverts. This is a less expensive solution, about 20-30 thousand dollars, compared to the purchase of a new camera

DMN: What do you anticipate most labs will do?

EGD: Most people will probably adopt software solutions. In our lab, we use either stress-only testing or, additionally, UltraSPECT software and routinely afford our patients radiation doses of 5-7 millisieverts. So this puts us well within the ASNC guidelines.

One of the latest studies conducted at our lab showed the difference between the level of radiation exposure vs. a lab without any low-dose technique. We compared 257 patients with the use of full-dose protocol, and our 205 patients using a half-dose protocol, using Wide Beam Reconstruction (WBR™) algorithm-based Xpress.Cardiac™ software from UltraSPECT. Evaluation of the results showed an impressively high number, 77 percent of studies performed with the half dose protocol were below 9mSv while in the other site none of the studies were below 9mSv. Most of the latter were in the range of 12-13 mSv.

DMN: How could dose reduction eventually be tied to reimbursement?

EGD: Right now dose reduction is just a guideline, or a recommendation, but ultimately, with value-based imaging and PQRS requirements, reimbursement from the Centers for Medicare and Medicaid Services and other third party carriers will be tied to quality. One of those quality metrics will certainly be patient radiation dose. So as these value-based parameters are implemented, labs will very likely be rewarded for lowering dose and penalized for exceeding recommended dose guidelines.

DMN: What are some of the main challenges for labs in adopting these guidelines?

EGD: Recognition and adaptation of the ASNC dose-reduction guidelines are permeating the field slowly. I'd say only a minority of laboratories have actually implemented any of these dose-reduction strategies. Such implementation takes a long time. We've been talking about dose reduction at ASNC, ACC, SNMMI and RSNA for quite a while. However, when reimbursement becomes tied to value-based imaging, I feel there will be much more rapid and significant progress in following the ASNC guidelines to reduce patient radiation dose.