Image Wisely, a joint initiative of ACR, RSNA, ASRT and AAPM,
provides information to the medical community to promote safety in medical imaging.
William W. Mayo-Smith, MD, Brigham and Women's Hospital, Boston, MA
Updated September 2016 | Download PDF
Computed tomography (CT) scanners have become markedly more complex over the past three decades, with a myriad of new options for performing CT examinations. Technical developments in the past have focused on helical technology, increased speed of gantry rotation, increasing number of detector rows, and increasing tube outputs to maintain adequate signal-to-noise ratios. These advances have resulted in our ability to image faster, capture rapidly moving structures such as the heart, and improve both temporal and spatial resolution. However, achieving these goals may also result in increased radiation exposure for our patients.
Currently many new strategies and technologies are being developed to address concerns over CT radiation exposure. Network radiology exam databases and software to load outside examinations into regional PACs have been developed to prevent unnecessary duplication of CT exams. Decision support to determine appropriateness of the exam before ordering are assuring appropriate CT exams are being performed. Home-grown and commercial software solutions have been developed to track radiation exposure by machine, CT protocol, geographic location, and patient, which is important to document processes and have data to promote quality improvement. The ACR Dose Index Registry has been developed to determine national Diagnostic Reference Levels.
CT vendors have developed multiple technical options to reduce the dose from CT exams. These include but are not limited to: X-ray beam filtration, X-ray beam collimation, tube current modulation, peak kilovoltage optimization, improved detector efficiency, and noise-reduction reconstruction algorithms. Other strategies to reduce dose occur at the ordering stage when referring doctors and patients are made aware of duplicate exams and referring doctors are educated about alternative exams with lower dose or no radiation. A third area with potential to reduce radiation dose involves specific CT protocol development to maximize diagnostic yield while tailoring dose to the appropriate indication and patient size. All of these attempts to reduce dose adhere to the “As Low As Reasonably Achievable” (ALARA) principle.
The first steps are to be sure the examination is JUSTIFIED:
If the exam is clinically indicated, be sure it is OPTIMIZED to tailor the CT dose:
At the dictation level, consider the following:
At the protocol development and quality improvement levels, consider the following:
In addition, there are a number of websites which list specific protocols for various types of CT scanners and manufacturers. Some examples include: