Abstract: Objective: To investigate the clinical feasibility of a dual-flow pre-bolus contrast protocol for triple rule-out computed tomography angiography (TRO-CTA) in patients with acute chest pain, in terms of image quality and radiation dose safety, under the “double-low” concept: low tube voltage of 70/80 kV combined with ultra-low contrast volume. Methods: Clinical data from 300 patients with acute chest pain who underwent TRO-CTA between January 2022 and December 2023 were retrospectively analyzed. Based on the actual contrast injection protocols recorded during the examinations, the patients were divided into conventional (n=150, single-phase high-flow-rate injection) and dual-flow (n=150, dual-flow pre-bolus injection method) groups. All included cases were assigned and recorded as 70 kV or 80 kV using an automatic tube voltage selection system. Objective evaluation: CT and standard deviation (SD) values were measured in the pulmonary artery, aorta, superior vena cava (SVC), and coronary arteries to calculate the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). For Coronary Computed Tomography Angiography (CCTA) objective enhancement grading, the CT values of the left main and large branches were defined as excellent (351–450 HU), good (300–350 HU), moderate (200–299 HU), or poor (< 200 HU), and the aortic root SD values were graded as excellent (< 20 HU), good (20–30 HU), fair (31–40 HU), or poor (> 40 HU). Subjective evaluation: A 5-point Likert scale was used for the blinded scoring of the diagnostic acceptability of the CCTA, Computed Tomography Pulmonary Angiography(CTPA), and aortic CTA images. Radiation dose evaluation: The volume CT dose index (CTDI_vol) and dose-length product (DLP) were recorded, and the effective dose (ED) was calculated. The independent samples t-test and Mann-Whitney U test were used for statistical analysis. Results: There were no significant differences in baseline characteristics between the two groups. The CTDI_vol, DLP, and ED values were low in both groups (ED: 1.74±0.30 vs. 1.77±0.32 mSv in the conventional and dual-flow groups, respectively), with no significant difference between the groups. The pure contrast volume in the dual-flow pre-bolus group was reduced by 53.33% compared to the conventional group (35.00±2.10 mL vs. 75.00±4.50 mL, P < 0.001). Regarding objective evaluation, the CT values of all target vessels in the dual-flow pre-bolus group satisfied diagnostic requirements, and high-density artifacts in the SVC were significantly reduced (CT value: 220.40±45.60 HU vs. 850.50±150.20 HU, P < 0.001). In the dual-flow group, the mean coronary CT value was 320.60±35.40 HU, the aortic root image noise (SD) was 24.20±4.10 HU, and the coronary SNR and CNR were significantly higher than those in the conventional group. Regarding subjective scoring, the 5-point Likert scores for CCTA (4.55±0.55 vs. 3.65±0.75, P<0.001) and CTPA (4.60±0.50 vs. 3.80±0.80, P < 0.001) in the dual-flow pre-bolus group were significantly higher than those in the conventional group. Conclusion: In 70/80 kV low tube voltage TRO-CTA, the dual-flow pre-bolus protocol provided diagnostic image quality for CTPA, CCTA, and aortic CTA at a pure contrast volume of approximately 35.00 mL and an ED of approximately 1.75 mSv. Furthermore, it significantly reduced the SVC high-density artifacts, demonstrating clinical application value.