Trial on Radiation Dose Reduction for CT Angiography

Study Questions:

Recent advances in image reconstruction techniques have enabled reduction in computed tomography (CT) radiation exposures while maintaining apparent image quality. How does coronary CT angiography (CTA) imaging compare to standard techniques for low radiation dose?


The PROTECTION V study investigators conducted a 400-subject randomized controlled trial across eight trial sites using CT scanners from all major CT vendors. One-half of the subjects were randomized (n = 202) to a 30% reduction in X-ray tube current with iterative reconstruction (IR) to maintain image quality. The remaining patients (n = 198) had standard coronary CTA. The primary endpoint was diagnostic image quality, as assessed by a blinded core laboratory. Secondary endpoints included radiation exposure, vessel blurring, and downstream testing.


There were no differences in image quality scores between standard and iteratively reconstructed images (p for noninferiority < 0.016). Radiation exposure in the low tube current/IR group was approximately 30% lower than in the standard group (2.2 mSv vs. 3.1 mSv, p < 0.0001), although both groups had very low exposures. Low tube current/IR did not result in any change in clinical use of downstream testing such as stress echo, stress nuclear perfusion imaging, or stress cardiac magnetic resonance imaging.


Further reductions in coronary CTA radiation exposures can be achieved by reducing tube current and utilizing widely available IR techniques to preserve image quality.


This study adds to the literature demonstrating rapid and continuing reduction in CTA techniques. IR techniques are continuing to advance and may enable even larger radiation dose reductions in the future. Unfortunately, while these IR techniques are widely available from all major vendors for both CT and nuclear imaging, many centers have not purchased these upgrades due to lack of incremental reimbursement. This study supports incorporation of IR and reduction of X-ray tube current into standard practice and imaging guidelines. The primary limitation of this study is the lack of assessment of effects on diagnostic accuracy.

Clinical Topics: Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Interventions and Imaging, Angiography, Computed Tomography, Magnetic Resonance Imaging, Nuclear Imaging

Keywords: Angiography, Diagnostic Imaging, Image Processing, Computer-Assisted, Magnetic Resonance Imaging, Perfusion Imaging, Quality Improvement, Radiation Dosage, Tomography, X-Ray Computed, Tomography Scanners, X-Ray Computed, X-Rays

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