PACS administrators assess imaging modalities, ionizing radiation levels
SEATTLE –PACS administrators gained insight into the specifics of imaging physics within clinical engineering during the 2008 Society of Imaging Informatics in Medicine (SIIM) pre-conference symposium held Wednesday on education and certification preparation for Imaging Informatics Professionals (IIP).

Ann Scherzinger, PhD, associate professor, University of Colorado School of Medicine, University of Colorado Hospital, instructor in medical physics and IT programs, led attendees through “PACS Clinical Engineering Part 1,” with a focus on assessing imaging modality capabilities and understanding the different equipment’s levels of ionizing radiation.

The objective of the session was to differentiate among all imaging modalities including x-ray, interventional and fluoroscopy, CT, nuclear medicine [gamma and SPECT], PET, PET/CT, MRI and ultrasound. Scherzinger outlined the basic operating principles for each modality, its typical clinical applications, image formats and appearances, data volumes and file sizes, interpretive considerations and typical exam protocols.

The presentation also highlighted which modalities had higher levels of ionizing radiation—namely x-ray, CT, nuclear medicine and PET. MRI and ultrasound were described as “safe modalities,” due to their low energy levels.

“The reason people are concerned about x-ray is that it is a particularly high level of energy and has the ability to ionize tissue,” Scherzinger said. “There are certain protocols and techniques that are pretty well defined now for basic x-ray imaging.”

For example, energy is typically 60-140 kVp for x-ray. There are also exposure parameters associated with x-ray images, it usually depends on the current energy in the tube and the time of exposure, or mAs, she said.

Scherzinger said that CT “gives us much higher resolution, higher contrast imaging technology with the same basic x-ray energies.” She told administrators that many clinicians will request that they set windows with some set levels on CT for density values, which “makes CT unique compared to other modalities.”

Attendees were also instructed on acceptable exposure times to ionizing radiation doses during the presentation. The total yearly background average is about 3.6 mSv—a normal level of exposure typically received by occupational workers, she said. According to the National Council for Radiation Protection (NCRP), the recommended background dose limit acceptable for staff such as PACS administrators, is approximately 1 mSv.