Updated January 27, 2010

CT Radiation Dose in the News

By:  Michael Lechner RT(R)(MR)CAPPM

Nationally there is quite a bit of media coverage about the dangers of radiation dose when having CT imaging procedures. It is important to know that CT medical radiation overdose incidents are extremely rare and not the norm for CT imaging. University Medical Imaging has always imaged based on the ALARA principle (As Low As Reasonably Achievable).

The ALARA principle assumes that there is no "safe" dose of radiation. Under this assumption, the probability for harmful effects increases with increased radiation dose, no matter how small. Therefore, it is important to keep radiation doses to as low as is reasonably achievable. Specifically relating to radiologic examinations such as CT, it is vital to utilize the least amount of radiation in order to provide the image outcomes required.

There is no concrete radiation dose limit per examination, rather a goal to utilize the least dose to create a diagnostic exam. There are many variables that affect the radiation dose for a procedure. Some of these variables include patient body habitus (size/weight), body part being imaged, coverage area, number of sequences acquired, age and capabilities of the equipment as well as the PM testing and QA schedule frequency of the equipment. Below are key areas that UMI has implemented to help reduce radiation dose.

• UMI has optional ACR accreditation in CT. This process reviews the doses of a selection of CT protocols to confirm that they are below standardized levels.

• UMI performes daily phantom QA testing which is above manufacturer suggested intervals.

• UMI CT scanners are checked every year by independent professional medical physicists who perform dose measurements to confirm that dose exposures remain below permissible levels.

• UMI employs the use of “Featherlight” imaging technology through the use of specialized color coded techniques customized by patient size in order to optimize dose reduction.

• UMI Technologists and Radiologists have pledged to “Image Gently” through review of protocol recommendations, implement adjustments to our practice processes, to respect and listen to suggestion of all members of the imaging team and to communicate openly with all patients.

• UMI has installed new CT system upgrades that will reduce patient radiation dose by 40% on average compared to standard CT imaging performed elsewhere in the community.

Everyone should understand that no x-ray exam gives zero radiation and that any exposure, no matter how small, may slightly increase the risks of cancer. Your doctor has determined that the potential benefits of the scan outweigh the small radiation risks.  Other simple medical procedures, such as injections, administration of common medications, elective surgical procedures all carry some risk. As long as the benefits outweigh the risks, it generally makes sense to do them.  

It's tricky to compare cancer rates between people who have had CT scans with those who haven't. People undergoing scans may have underlying health problems that predispose them to cancer. People receive radiation throughout their lives from various sources, such as cosmic rays, radon in homes, and other natural and man-made sources. The natural incidence is so high that if someone gets cancer, it is most likely that it came from natural causes and not a medical exposure.

Reducing radiation exposure to patients is not something new. It is a principal that UMI has always practiced and takes very seriously. We have an obligation to our patients to provide diagnostic imaging services with the least amount of radiation. With this in mind, UMI has invested in providing safer CT imaging to the general public as we continue to follow the guiding principles of ALARA.

If you have concerns about diagnostic imaging and appropriateness, UMI advises that you have this discussion with your physician.

For more information about CT and radiation dosage you can visit these informational sites:

www.radiologyinfo.org/en/news/target.cfm?ID=387

www.ACR.org/safety

ww.imagegently.org