Objective: To optimize enhancement of pulmonary arteries and facilitate diagnosis of pulmonary embolism (PE), modern computed tomography angiography (CTA) contains a contrast bolus tracking system. We explored the diagnostic accuracy of the time-intensity curves given by this automated system to identify right ventricular dysfunction (RVD) in acute PE.
Methods: 114 CTAs with a diagnosis of PE were reviewed. RVD was defined as right-to-left ventricular diameter ratio of 1 or greater. Four parameters on time-intensity curves were identified. Parameters between CTAs with and those without RVD were compared with the Wilcoxon rank-sum test. The ability of the four parameters to discriminate patients with RVD was explored by compiling the area under the operating curves (AUC).
Results: The time needed by the contrast media to reach the pulmonary artery [8 seconds (IQR: 7-9) versus 7 seconds (IQR: 6-8), p<0.01], the time needed to reach 40 Hounsfield units (HU) [11 seconds (IQR: 8.5-14) versus 9.5 seconds (IQR: 8-10.5), p<0.01], and the contrast intensity reached after 10 seconds [19 HU (IQR: 4-67) versus 53 HU (IQR: 32-80), p<0.05] were all statistically different between CTA with and CTA without RVD. Those three parameters changed gradually across severity categories of RVD (p<0.05 for trend). Their AUC to identify RVD ranged from 0.63 to 0.66. The slope of contrast intensity over time was not informative: [31 HU/s (IQR: 20-57) in CTA with, compared to 36 HU/s (IQR: 22.5-53) in CTA without RVD, p = 0.60].
Conclusion: Several parameters of the time-intensity curve obtained by the bolus tracking system are associated with RVD assessed on CTA images. Of those, the time needed to reach a predefined threshold seems to be the easiest to obtain in any CTA without additional processing time or contrast injection. However, the performance of those parameters is globally low.