A practical biphasic contrast media injection protocol strongly enhances the aorta and pulmonary artery simultaneously using a single CT angiography scan

Cheng-Chih Hsieh, An-Bang Zeng, Chia-Hung Chen, Zong-Yi Jhou, Chih-Hsin Wang, Ya-Ling Yang, Feng-Chuan Hsieh, Jing-Kai Lin, Ju-Yen Yeh, Chun-Chao Huang, Cheng-Chih Hsieh, An-Bang Zeng, Chia-Hung Chen, Zong-Yi Jhou, Chih-Hsin Wang, Ya-Ling Yang, Feng-Chuan Hsieh, Jing-Kai Lin, Ju-Yen Yeh, Chun-Chao Huang

Abstract

Background: Enhancement profiles of the pulmonary artery (PA) and aorta differ when using computed tomography (CT) angiography. Our aim was to determine the optimal CT protocol for a one-time CT scan that assesses both blood vessels.

Methods: We prospectively enrolled 101 cases of CT angiography in patients with suspected pulmonary embolism or aortic dissection from our center between 2018 and 2020. We also retrospectively collected the data of 40 patients who underwent traditional two-time CT scans between 2015 and 2018. Patients were divided into four groups: test bolus (TB) I, TB II, bolus-tracking (BT) I, and BT II. The enhancement of the PA and aorta, and the radiation doses used in the four groups were collected. Those who underwent two-time scans were classified into the traditional PA or aorta scan groups. Data were compared between the BT and traditional groups.

Results: The aortic enhancement was highest in BT II (294.78 ± 64.48 HU) followed BT I (285.18 ± 64.99 HU), TB II (186.58 ± 57.53 HU), and TB I (173.62 ± 69.70 HU). The radiation dose used was lowest in BT I (11.85 ± 5.55 mSv) and BT II (9.07 ± 3.44 mSv) compared with that used in the traditional groups (20.07 ± 7.78 mSv) and accounted for half of the traditional group (45.17-59.02%). The aortic enhancement was also highest in BT II (294.78 ± 64.48 HU) followed by BT I (285.18 ± 64.99 HU) when compared with that in the traditional aorta scan group (234.95 ± 94.18 HU).

Conclusion: Our CT protocol with a BT technique allows for a lower radiation dose and better image quality of the PA and aorta than those obtained using traditional CT scans.

Trial registration: NCT04832633, retrospectively registered in April 2021 to the clinical trial registry.

Keywords: Aortic dissection; Computed tomography angiography; Contrast media; Pulmonary embolism.

Conflict of interest statement

The authors declare that they have no competing interests.

© 2021. The Author(s).

Figures

Fig. 1
Fig. 1
The details of the contrast medium injections and CT scan protocols of the four experimental groups. TB: test bolus; BT: bolus-tracking; A: peak enhancement time of the aorta on prediagnostic scan; P: peak enhancement time of the pulmonary artery on prediagnostic scan; PA: pulmonary artery; ROI: region of interest
Fig. 2
Fig. 2
Black: high density of contrast medium. White: low density of contrast medium. Time point 1 is before contrast medium injections; therefore, all the vascular structures are white. Time point 2 is about the midway of the two contrast injection phases and the first slowly injected contrast media, shown in gray color, arrive the pulmonary artery and at the same time, the second fast injected contrast media, shown in black color, arrive the superior vena cava. There is very low contrast media in the aorta at this time point. Time point 3 is the start point of the diagnostic scan. At this time point, the first slowly injected contrast media, shown in gray color, arrive the aorta and at the same time, the second fast injected contrast media, shown in black color, arrive the pulmonary artery

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