The Enterprise: Driving Down Dose

Concern for imaging-based patient radiation dose continues its surge. Recent patient radiation overexposure cases in the U.S., multiple studies relating CT scans to higher incidences of cancer and extensive media reporting on radiation exposure have given the issue of radiation exposure during imaging exams an increasingly high profile.

The controversial Archives of Internal Medicine article published last fall estimated there will be “15,000 excess deaths” just from the CT scans done in 2007 (70 million). A just-released Centers for Disease Control and Prevention (CDC) report estimates there’s been a tripling of imaging exams (CT, MR and PET) ordered during visits to physician offices and outpatient departments from 1996-2007. During the same period, exams ordered in the ED have grown fivefold among adults under 65 years of age and quadrupled among adults 65 years of age and over. In 2007, 12 percent of ED visits among patients under the age of 65 and 26 percent of those visits by people over 65 included advanced imaging scans. In 2007, CDC says, there were more than 10,000 CT units in operation at more than 7,600 U.S. hospital and nonhospital sites. We are a country of 300 million people and 70 million CT scans a year. (But remember, there is a lack of consensus amongst the medical and scientific communities about whether radiation exposure from CT scans causes cancer.)

Now, it’s the FDA’s turn. The agency is stepping up its health imaging and radiation exposure oversight responsibilities with a new initiative, launched last month, to reduce unnecessary radiation exposure from CT, nuclear medicine and fluoroscopy studies.

The goal is to support the benefits associated with imaging, while minimizing risks.

FDA wants to adopt two principles of radiation protection: appropriate justification of the radiation procedure and dose optimization during each study. The agency plans to work with vendors to incorporate dose and reporting safeguards into scanner design, train practitioners, establish national dose registries for benchmarking and increase patient awareness of their own exposure.

If you ask MITA (Medical Imaging & Technology Alliance), they’ll tell you vendors have already significantly cut the dose output of imaging systems—by up to 75 percent for many procedures over the past 20 years. And as you’ll see in this month’s cover story, new vendor-based dose reduction techniques are reducing CCTA dose by 25 to 80 percent, very significant indeed. But those techniques must be used properly by trained technologists to achieve these marked dose reductions.

Step one in CT is weighing benefit of the study vs. long term risk. Once deemed necessary, efforts shift to minimizing CT radiation exposure and standardizing dose across facilities. Imaging well is not about showing all possible information, but visualizing in the image only the information necessary to make a diagnosis.