Radiation Dose and Image Quality of Prospective Triggering With Dual-Source Cardiac Computed Tomography

Prospectively triggered (PT) cardiac computed tomography (CT), whereby radiation is administered only at a predefined phase of the cardiac cycle, has been shown to substantially decrease radiation dose. The aim of our study was to assess the use of this technique in a clinical population using dual-source cardiac CT. Of 312 consecutive patients referred for a dual-source cardiac computed tomographic examination, PT was used in 42 patients for whom, based on physician judgment, it was decided to minimize radiation, whereas retrospective gating was used for 188 patients (coronary artery bypass grafting and pulmonary vein studies were excluded). Kilovolt and milliampere per second were chosen for each patient based on assessment of body habitus and effective radiation dose was calculated. Analysis of nonevaluable vessels was based on clinical readings. For each study, image quality (IQ) was rated on a subjective IQ score and contrast-to-noise and signal-to-noise ratios were calculated. Of the 42 PT examinations (mean age 44.3 years, body mass index 27.8 kg/m2, 62% men), 28 were referred for coronary evaluation, 11 for aortic disease with/without coronaries, and 3 for other reasons (i.e., suspected mass and congenital disease). Average heart rate was 64.5 beats/min. Average radiation dose of all 42 PT scans was 3.2 ± 1.6 vs 13.4 ± 7.8 mSv for the 188 non-PT scans. There was no significant difference in IQ score and contrast-to-noise and signal-to-noise ratios between the 2 groups. Furthermore, the incidence of limited right coronary artery evaluation and of limitations related to right coronary artery motion did not differ between PT and non-PT scans. In conclusion, in selected patients, prospective triggering with dual-source cardiac CT is feasible and results in a dramatic decrease of radiation dose without compromising IQ. Future advances in cardiac CT may further improve this technique, thus allowing for wider use.