Wednesday, June 1, 2011

Dose Issues Not Only For CT

There is a lot of activity around radiation dose reduction, especially for CT exams. This is partly due to the incidents that got a lot of press in which people were overdosed due to operator errors and negligence. Another important factor is the increase in CT exams, especially in the ER. It used to be that trauma cases would get a couple of X-rays done to look at potential fractures and/or internal damage, however, most ER's now have a resident CT and a body scan is pretty much standard procedure. 

After numerous studies raising safety concerns about the amount of radiation exposure for all these CT scans, vendors are finally taking notice and implementing techniques to reduce radiation exposure. One step being taken is to start registering the dose administered to the patient. This sometimes requires dosimeters in the X-ray chain, as well as reporting mechanisms. The reporting is still very much a work in progress. For some modalities, such as digital mammography, there already is relatively reliable information in the image header, which could be extracted by the PACS and stored. Some systems use the DICOM Modality Performed Procedure Step (MPPS) information as it also (optionally) can contain the dose. This is used in some cardiology applications whereby the cardiology information system records this information. There are drawbacks of the MPPS method as it is design dependent on the images that are created, and, for example, for fluoroscopy exams, there might not be any or only a few images taken. If one would depend on the dose information in the MPPS for those types of exams, the exposure would be severely under reported. 

This is especially true for CT, in which there is often a separate screen archived with the dose information, however, there is no digital representation, which means that the data extraction needs to depend on so-called screen-scraping or optical character recognition to get the actual information. The best way of reporting the dose information would be by using the dose-structured report. As a matter of fact, the Integrating the Healthcare Enterprise or IHE initiative has defined a special profile, called the radiation exposure monitoring or REM profile. This was demonstrated at the recent Radiological Society of North America meeting, however, there is a still a lack of recording and reporting systems, which is causing very slow implementation. 

CT dose reporting is getting most of the attention, however, in my opinion, the over exposure and unnecessary exams using standard X-rays such as DR or CR is underestimated. As an example, my little six-year-old grandson has issues with allergies and congestion, especially during the flu season. He has already had several chest X-rays over the course of his first six years as pediatric physicians like to play it safe and order an X-ray "just in case." There are also no guidelines on how much to reduce the technique factors to maintain reasonable image quality, and still to be able to make a diagnosis. The Image Gently campaign has developed online teaching materials, but to my knowledge, there are no guidelines published yet. In addition, if images are taken, there is also often a lack of shielding, an issue which was reported in the article “X-rays and Unshielded Infants” on Feb. 27, 2011 in the New York Times. 

It might seem strange to hear a message of reduction of X-rays from someone like myself who works in this industry, however, one should realize that 80 percent of the world’s population has no access to X-rays at all. Rather than over utilizing these systems for the privileged 20 percent, it might be better to expand it to those who have no access. This requires the development of low cost digital systems, which are very durable and easy to use. I believe that this can be done, if some of the major vendors would just make this a priority. 

In conclusion, dose registration is still challenging, the IHE REM profile implementation should be a major push. However, registration is just the first step, further development of dose reduction techniques and guidelines by professional organizations are needed as well. 

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