Objective To explore the feasibility of using a low-dose contrast agent volume and a low flow rate in dual-layer detector spectral computed tomography (CT) for CT pulmonary angiography (CTPA).

Methods In total, 80 patients clinically diagnosed with pulmonary embolisms were collected for CTPA examination and randomly divided into two groups, comprising 40 cases each. The low-dose group received a contrast agent dose of 15 mL at a flow rate of 2 mL/s, and the images were reconstructed using a 40 keV monochromatic spectrum. The conventional group underwent a small-dose test with a contrast agent dose of 50 mL at a flow rate of 5.0 mL/s. The CT dose index volume (CTDI_vol), dose length product (DLP), CT values, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were recorded and calculated for both groups, and the image quality was subjectively scored.

Results (1) The differences in these indicators between the two groups were statistically significant. The pulmonary artery CT values for the conventional and the low-dose groups were 368.450 HU and 569.050 HU, respectively, with a statistically significant difference between the two groups. There were statistically significant differences in SNR and CNR between the two groups. (2) There was no statistically significant difference in the subjective scoring of image quality between the two groups. (3) The DLP values for the conventional and low-dose groups were 376.500 mGy/cm and 294.500 mGy/cm, respectively; the CTDI_vol values were 11.150 mGy and 8.350 mGy, respectively; and the ED values were 5.271 mSv and 4.123 mSv, respectively, with statistically significant differences between the groups.

Conclusion The scanning protocol with the "low" contrast agent dose and flow rate using dual-layer detector spectral CT for CTPA examinations met the diagnostic requirements while reducing risks such as contrast extravasation and contrast-induced nephropathy.