Recently, major developments have occurred involving organized radiology and the public with respect to the topic of radiation. This renewed interest has stemmed from general awareness of the putative effects of dose. A report issued at the National Council of Radiation Protection and Measurements, which met in Arlington, VA in April of 2007, has fueled the discussion. The author of the report, Dr. Fred Mettler, emeritus professor of Nuclear Medicine at the University of New Mexico made the pronouncement that the estimated collective dose the US population receives from diagnostic imaging procedures in 1980 was 0.54 mSv per capita. However, 26 years later, that total has increased to 3.2 mSv per annum per capita, a more than sixfold increase [1].

This report was directed by a National Council of Radiation Protection scientific committee that compiled estimates on radiation exposure of the US population both from background radiation and from medical imaging equipment. Data for this study includes records of imaging modalities that did not make it to the last such comprehensive evaluation in 1987. In that year, CT fluoroscopy, Nuclear Medicine studies like PET and hybrid scans such as PET/CT were not included. The contemporary data was gathered from public and private sources including information from Medicare and the Veteran’s Administration hospitals. The medical radiation sources encompass radiography, CT, dental x-rays, Nuclear Medicine, Radiotherapy, and Interventional Radiology.

The assessment of the committee, as announced by Mettler, was that CT and nuclear medicine studies account for the largest increase in dose with CT, representing 12 % of all procedures but 45 % of collective dose received. Nuclear medicine is responsible for merely 3 % of the total number of medical imaging exams but deposited 23 % of the effective dose. The growth of CT has been greater than 10 % per year and I am sure that it was accelerated in the last 5 years with the advent of multi-detector CT. In comparison, the US population has grown only 1 % per year.

As I have stated before we went from less than five million CT’s in 1980 to more than 60 million in 2006. Similarly, nuclear medicine has grown steadily, about 5 % per year, since the 1980s. In 2005 there were almost 20 million nuclear procedures performed. Cardiac nuclear examinations accounts for 57 % of all nuclear medicine studies and 85 % of the dose derived from them. By the way, most cardiac studies are now done by cardiologists, not radiologists.

The most recent increase in studies under the purview of radiologists and nuclear medicine physicians has been from PET. Whereas over the past 20 years, there has been a steady rise in nuclear imaging studies done by radiologists and nuclear physicians, it has been PET scanning that has shown the marked increase most recently.

Mettler stated that the Chernobyl nuclear power plant accident in 1986 produced a global collective dose of 600,000 per person/sv. Although the estimated collective dose of 930,000 per person/sv in the US population today seems impressive by comparison, it is too early to extrapolate figures to make meaningful predictions. The conclusion of this study was that dose has increased markedly yet physicians do not understand the magnitude of this increase even though the largest collective source of radiation exposure is medical imaging. Nevertheless, imaging remains unregulated, a circumstance perhaps initially to the benefit of radiologists. Yet ultimately, it will most likely induce a health problem which radiologists must now attend to or be blamed for.

In that regard, and in anticipation of the NRCP report, the ACR convened a blue ribbon panel which met for several months and recommended a raft of changes governing the tracking and physician management of radiation exposure. This committee was chaired by Dr. Steve Amis, and consisted of radiologists and physicists. It offered 33 recommendations which were announced to coincide with the revelations announced by the NRCP which I have just referred to.