Achieving Very-Low-Dose Radiation Exposure in Cardiac Computed Tomography, Single-Photon Emission Computed Tomography, and Positron Emission Tomography

Cardiac imaging with CT, SPECT, and PET has recently reached new standards in terms of radiation dose reduction. Recent multicenter trials and studies when using the newer scanner technology have reported mean effective doses <10 mSv; however, this is not available in all centers. Mean effective doses from several clinical studies have shown the potential of the newest technology to be associated with radiation below the average annual dose from naturally occurring sources of radiation. Advances in instrumentation in CT, coupled with iterative reconstruction software, have shown the feasibility of sub-mSv radiation dose for coronary CTA. For coronary CTA, optimal heart rate control with beta-blockade is important for both achieving optimal image quality and use of scan parameters that reduce radiation dose, as allowed by patient-based criteria. Recently introduced automated exposure control software can help imaging maintain diagnostic image quality while reducing radiation dose to the patient. Advances in new SPECT instrumentation allow routine stress-rest MPI imaging with low radiation doses. For cardiac SPECT, stress-only protocols can be used to reduce the radiation dose and the overall test time and are increasingly used. With the new systems, stress-only SPECT MPI may be performed with doses as low as 1 mSv. PET perfusion imaging can be performed with very low doses, particularly on new 3D scanners. Radiation dose reduction is associated with the potential benefit of lowered cumulative cancer risk to the patient. However, if sufficient image quality is not maintained for confident diagnostic interpretation,15 such radiation dose-reduction strategies can decrease the diagnostic accuracy and may lead to increased downstream testing. Therefore, a balanced approach that applies the newest technology reasonably, achieving radiation dose reduction but assuring sufficient image quality, is the most desirable. Finally, technological advances that are at the same time cost-saving, diagnostically accurate, and with low associated radiation exposure are likely to be favored by the current healthcare environment. Introduction of the technologies as discussed above and development of new balanced imaging protocols and reconstruction and postprocessing software for cardiac CT, SPECT, and PET have the potential to address these demands. © 2014 American Heart Association, Inc.