Triple-rule-out dual-source CT angiography of patients with acute chest pain: Dose reduction potential of 100kV scanning.

PURPOSE: To investigate the dose reduction potential of low kV triple-rule-out dual-source CT angiography (TRO-CTA) in non-obese (BMI≤25kg/m(2)) patients with acute chest pain. MATERIALS AND METHODS: Sixty consecutive patients were randomly assigned to two different retrospectively ECG-gated TRO-CTA protocols in this prospective trial: Thirty patients were examined with a 120-kV standard protocol (320 reference mAs with automatic tube current modulation, automatically adapted pitch and ECG-pulsing) and served as the control group (group 1), an otherwise identical 100kV protocol was used in the other thirty patients (group 2) for a radiation dose reduction. Subjective image quality was assessed on a 5 point scale (1: excellent, 5: non-diagnostic) by two blinded observers. Quantitative image analysis assessed vascular attenuation, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in different vascular segments. The effective dose was calculated from the dose length product (DLP) using a conversion coefficient of 0.017mSvmGy(-1)cm(-1). RESULTS: There was no significant difference of age, BMI, heart rate, pitch or scan length between both patient groups. Subjective image quality was rated similar in both groups (group 1: 1.2±0.4, group 2: average score=1.3±0.5). Vessel attenuation was significantly higher in group 2 than in group 1 (ascending aorta: 456±83 HU vs. 370±78 HU, p<0.001; pulmonary artery: 468±118 HU vs. 411±91 HU, p=0.03; left coronary artery: 437±110 HU vs. 348±89 HU, p<0.001), however, there was no significant difference in SNR (13.2±7.6 vs. 14.5±7.5, p=0.49) or CNR (13.8±6.6 vs. 15.9±7.7, p=0.25). The effective radiation dose of the 100kV protocol was significantly lower (9.6±3.2mSv vs. 18.1±9.4mSv, p<0.0001). CONCLUSION: TRO-CTA with 100kV is feasible in non-obese patients and results in diagnostic image quality and significantly reduced radiation dose.