New Radiation Reduction Standards Proposed for Worldwide Implementation

As a result of an initiative that combines optimizing test protocols, state-of-the art equipment, and high-tech software, two-thirds of the Ottawa Heart Institutes (UOHI; Ottawa, Ontario, Canada) nuclear cardiology patients are currently receiving half the radiation dosage that they would normally get. Radiation reduction techniques have been accomplished across all kinds of radiation-based cardiac imaging--computed tomography (CT), nuclear imaging, and positron emission tomography (PET). The Heart Institute is one of only a one of a couple of centers in Canada with the in-house expertise to assess and clinically apply these latest developments across these technologies.

The American Society for Nuclear Cardiology has challenged the nuclear cardiology community to reduce radiation exposure below 9 millisieverts (mSv) by 2014. The techniques being employed at the Heart Institute regularly reduce exposure to 5 mSv, and frequently much less, putting UOHI well ahead of the game. This figure has not bottomed out, as efforts will continue to minimize radiation wherever possible.

“Our clinicians are taking a much more critical look at who they are testing with radioactive methods and making decisions based upon risk and necessity which will only expose patients to radiation who truly need the test,” said Dr. Benjamin Chow, codirector of cardiac radiology at the University of Ottawa Heart Institute. These responsible practices, along with a judicious use of technology, could revolutionize cardiac imaging in Canada.”

The payback for this effort include reduced radiation dosages for patients, greater flexibility for customizing modalities for patients, and, in some instances, a decreased need placed on radioisotopes. For example, for younger patients, radiation exposure presents greater risks because they have more years in which cancer could develop. So lessening their dosage is a high priority. In the case of older patients whose lives may be threatened by an immediate cardiac problem condition, the advantages would overshadow the small risk of developing cancer later in life.

UOHI also uses a combination of effective applications that facilitate a better diagnosis of cardiovascular problems. The cadmium-zinc-telluride camera system used for nuclear imaging is a significant development and it was implemented by Dr. Glenn Wells, medical physicist in nuclear cardiology. The Heart Institute was one of the first centers in the world with this technology in 2009, and it had a major impact on reducing radiation in perfusion single emission computed tomography (SPECT) scans, the most typical cardiac imaging modality.

The introduction of PET imaging in the late 1990s, which provides much more detailed imagery with much lower levels of injected isotopes, has also had an impact on reducing radiation exposure. The use of these cameras in Canada is still uncommon but increasing.

Software is another critical part of imaging, transforming the scanner data into coherent two- or even three-dimensional (3D) images of what is seen in a patient’s body. The Heart Institute has helped commercial developers evaluate and enhance new, sophisticated software packages for both PET and SPECT scanners that maintain image quality while using less radioactive isotopes.

Radiation has become a concern for both medical professionals and patients; however, frequently people do not realize the considerable advantages of very effective diagnostic imaging modalities that may require very low amounts of medical radiation. “Careful and appropriate selection of the right test for the right patient balancing benefit and risk enables optimal patient care,” said Dr. Terrence Ruddy, director of nuclear cardiology, University of Ottawa Heart Institute.

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