To compare the diagnostic performance of “triple rule out” CT angiography (TRO-CTA) at 100kVp using sinogram affirmed iterative reconstruction (SAFIRE) with TRO-CTA at 120kVp using filtered back projection (FBP) in patients with acute chest pain.

Consecutive non-prepared patients from a single radiological emergency department, referred for acute chest pain evaluation with TRO-CTA, were randomly assigned to two different TRO-CTA protocols. Fifty patients (66% men; mean age, 66.6±19.0 [SD] years [range: 24–97years]) had TRO-CTA at 120kVp with FBP and 97 patients (67% men; mean age, 62.8±17.9 [SD] years [range: 24–93years]) had TRO-CTA at 100kVp with SAFIRE. Two radiologists reviewed the TRO-CTA images for pathologic findings and degree of diagnostic confidence. Image noise, vessel attenuation value, signal-to-noise and contrast-to-noise ratios in five main thoracic arteries were measured for objective and subjective analysis.

A total of 147 patients (98 men, 49 women; mean age, 64.7±18.4 [SD] [range, 24–97years) were included with good diagnostic confidence and equivalent pathological findings between the two TRO-CTA protocols. Objective and subjective analysis were identical between protocols and radiologists, except for vessel attenuation in the ascending aorta (P=0.02) and image noise in the pulmonary trunk (P=0.04). The effective radiation dose decreased significantly by 34% in the low dose TRO-CTA using SAFIRE protocol (5.7±2.7 vs 8.6±6.1mSv; P=4.7×10^–6).

Low dose TRO-CTA protocol using SAFIRE allows a high confidence diagnostic level with the benefit of a 34% radiation dose decrease compared with a standard TRO-CTA protocol using FBP.