Objective and subjective image quality with prospectively gated versus ECG-controlled tube current modulation using 256-slice computed tomographic angiography

ABSTRACT

Introduction: Radiation exposure is one of the major limitations of computed tomographic coronary angiography [CTA]. The purpose of this study was to compare the objective and subjective image quality and radiation dose using prospective ECG gating [PGA] versus ECG-controlled tube current modulation [ECTCM] scanning techniques. A prospective, single-center study was performed at Prince Sultan Cardiac Centre, Qassim, Saudi Arabia. A total of 104 patients with low-to- intermediate probability of coronary artery disease [CAD] underwent CTA with either PGA or ECTCM acquisition. PGA was performed during the study period and compared with the last 50 CTAs previously done using ECTCM. A 4-point scale was used to assess the image quality subjectively. Objective image quality was assessed using image signal, noise, and signal-to-noise ratio [SNR].Patient's Baseline characteristics were not different between the two scanning protocols. The 4-point score of subjective image quality showed no significant differences between the PGA and ECTCM scans [2.9 +/- 0.7, 2.96 +/- 0.7, respectively; p = 0.87]. The objective image quality showed significantly higher noise and lower SNR with PGA compared with ECTCM [31 +/- 9, 27 +/- 9, respectively; p < 0.001 for noise] and [15 +/- 5, 17 +/- 7, respectively; p < 0.001 for SNR], with no statistical difference in the image signal [434 +/- 123, 425 +/- 103 HU, respectively, p = 0.7]. Radiation exposure was significantly lower with PGA than with ECTCM. The dose-length product [DLP] for PGA was 334 +/- 130 mGy, compared with 822 +/- 286 mGy for the ECTCM. This corresponds to a 59% reduction in radiation exposure [p < 0.0001]. Conclusions: Although prospective ECG-triggered axial scanning increased image noise, it maintained subjective image quality and was associated with a 59% reduction in radiation exposure when compared with ECTCM