Application of 50-keV virtual monochromatic imaging combined with a personalized contrast agent protocol in computed tomography pulmonary angiography: a randomized controlled trial.

BACKGROUND: Computed tomography pulmonary angiography (CTPA) is the preferred imaging modality for the diagnosis of pulmonary embolism (PE). Conventional fixed contrast agent protocols are associated with high contrast volume and severe superior vena cava (SVC) artifacts. This study aimed to evaluate the value of 50-keV virtual monochromatic imaging (VMI) combined with a body weight-adjusted personalized contrast agent protocol in reducing contrast load and optimizing image quality in CTPA. METHODS: A total of 76 patients undergoing CTPA were randomly allocated to the control group (Group A; n=38) or the experimental group (Group B; n=38). Since this was a small-sample exploratory study on imaging technology, it was not registered on any official platform. Both groups were scanned with a tube voltage of 120-kVp and automatic tube current modulation. Patients in group A received a fixed contrast protocol (flow rate 4.0 mL/s; volume 40 mL) with 120-kVp reconstruction. Meanwhile, patients in Group B were subjected to a body weight-adjusted protocol with weights of 40-60 kg, 60-80 kg, and 80-100 kg, having a flow rate and volume of 2.3 mL/s and 13 mL, 2.6 mL/s and 15 mL, and 2.9 mL/s and 17 mL, respectively. For all weights, 50-keV VMI reconstruction was conducted. Objective and subjective image quality was compared between the groups. RESULTS: All images were diagnostically acceptable. Group B had a significantly lower contrast dose (15.1±0.64 mL; 62.25% reduction) and flow rate (2.55±0.18 mL/s; 36.25% reduction) (both P values <0.05). Group B also demonstrated significantly higher computed tomography (CT) values in the right pulmonary artery [406.3±112.9 vs. 345.9±102.6 Hounsfield units (HU)], right upper lobe pulmonary artery (398.3±109.3 vs. 366.7±116.1 HU), and right lower lobe pulmonary artery (441.1±111.7 vs. 357.2±120.6 HU), as well as improved signal-to-noise ratio (SNR) in the right pulmonary artery (18.01±5.70 vs. 14.33±5.23), right upper lobe pulmonary artery (17.67±5.55 vs. 15.17±5.78), and right lower lobe pulmonary artery (19.55±5.66 vs. 14.81±6.10). Similar improvements were observed in contrast-to-noise ratio (CNR) values for the corresponding regions. No significant difference was observed in pulmonary artery visualization scores between the two groups (P>0.05), but Group B had higher SVC artifact scores and a lower number of artifacts (P<0.05). CONCLUSIONS: In CTPA examination, 50-keV VMI combined with a personalized contrast agent protocol can improve image quality while substantially reducing both the contrast dose and injection flow rate.