Feb. 20, 2008 Aiming to promote the best medical imaging practices nationwide and help ensure the health and safety of the millions of people who undergo computed tomography (CT) scans each year in the United States, the American Association of Physicists in Medicine has issued a CT radiation dose management report this month recommending standardized ways of reporting doses and educating users on the latest dose reduction technology.
Targeted at radiologists, medical physicists, and other medical professionals, the report outlines the best ways to measure, manage, and prescribe radiation dosages. It also gives an overview of ways that doctors can optimize modern CT scanners to get the most bang for the buck -- reducing to a bare minimum the amount of radiation to which patients are exposed while still allowing them to benefit from the technique's life-saving ability to image inside the human body.
"The medical applications of CT have grown tremendously in the last decade as the technology had become more and more sophisticated," says Mayo Clinic Medical Physicist Cynthia McCollough, who was chair of the AAPM Task Group that authored the report. "In the era of increasingly personalized medicine, the report provides a roadmap for doctors and medical physicists to tailor the CT radiation dosages to individuals."
CT scans and radiation
The benefits of CT scans are enormous, and the technology has revolutionized medicine in the last generation because it can provide cross-sectional snapshots deep inside someone's body with unprecedented clarity. These images help doctors diagnose unseen illnesses and injuries, and they guide treatment for millions of people a year in the United States.
In the last few years, reports in the medical literature and in the popular press have challenged public perceptions of CT scans by raising questions of risk related to the fact that CT scanners use X rays, which in high doses can damage the DNA inside cells.
However, says McCollough, the benefits of receiving a medically justified CT scan far outweighs the risk associated with the low levels of radiation used. To put this into perspective, the U.S. Food and Drug Administration (FDA) considers the risk of absorbed X rays from CT scans to be very small.
Even so, the FDA recommends avoiding unnecessary exposure to radiation during medical procedures, especially for children. The FDA published a public health notice in 2001, calling for pediatric CT scans to be tailored to the specific needs and smaller sizes of children and only administered when appropriate.
While they are not regulatory bodies, the AAPM and allied organizations like the American College of Radiology (ACR) play important roles in helping to achieve the FDA's goal of keeping the radiation dose as low as reasonably achievable, consistent with the medical need, by making recommendations and providing accreditation of CT scan facilities. This is essential because while the FDA is responsible for regulating CT scanning equipment, it does not actually regulate the CT scans themselves. Oversight of the use of X-ray technology in the United States is regulated by individual states' laws.
The ACR plays an important role in guaranteeing the quality and safety of CT scanning through its voluntary accreditation program. To achieve ACR accreditation, CT facilities must demonstrate both clinical and technical competency, as well as meet requirements for staff training and quality assurance. Only sites with sufficient image quality and appropriate radiation doses can receive ACR accreditation. While the program is voluntary, many insurers require that facilities be accredited in order to qualify for reimbursement.
Similarly, the AAPM contributes to the safety and quality of CT imaging by providing reports like the one just published, which gives the most current standards for CT dose measurement techniques and discusses how facilities can reduce radiation dosages by using new technical features that automatically adjust the radiation exposure according to each patient's size.
The information contained in this report is crucial, says McCollough, because it can help medical practitioners take full advantage of sophisticated CT technology. "Essentially, all modern CT systems can be equipped with automatic exposure control systems. These tools help to ensure that no patient receives more radiation dose than they need. We believe that this report equips users to properly describe and manage CT dose levels."
The report was generated by a committee of medical physicists with special expertise in CT technology and its clinical uses. It can be downloaded from the AAPM website.
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