Acute Pulmonary Embolism Severity Assessment Evaluated with Dual Energy CT Perfusion Compared to Conventional CT Angiographic Measurements

Abstract

The purpose of the study was to investigate whether Dual Energy CT (DECT) can be used as a diagnostic tool to assess the severity of acute pulmonary embolism (PE) by correlating parenchymal perfusion defect volume, obstruction score and right ventricular-to-left ventricular (RV/LV) diameter ratio using CT angiography (CTA) and DECT perfusion imaging. A total of 43 patients who underwent CTA and DECT perfusion imaging with clinical suspicion of acute PE were retrospectively included in the study. In total, 25 of these patients had acute PE findings on CTA. DECT assessed perfusion defect volume (PDvol) were automatically and semiautomatically quantified. Overall, two CTA methods for risk assessment in patients with acute PE were assessed: the RV/LV diameter ratio and the Modified Miller obstruction score. Automatic PDvol had a weak correlation (r = 0.47, p = 0.02) and semiautomatic PDvol (r = 0.68, p < 0.001) had a moderate correlation to obstruction score in patients with confirmed acute PE, while only semiautomatic PDvol (r = 0.43, p = 0.03) had a weak correlation with the RV/LV diameter ratio. Our data indicate that PDvol assessed by DECT software technique may be a helpful tool to assess the severity of acute PE when compared to obstruction score and RV/LV diameter ratio.

Keywords: Dual Energy CT; Dual Source CT; lung perfusion; pulmonary embolism; pulmonary perfusion.

Figure 1

Flowchart of patient inclusion and exclusion. CTA = CT angiography, PE = Pulmonary embolism.

Figure 2

CT angiography in a patient with acute pulmonary embolism. (a) Partial occluding thrombus in right basal trunk (Modified Miller score = 4); (b) Partial occluding thrombus in the left apical anterior segmental artery (Modified Miller score = 1).

Figure 3

Measurement of right and left ventricle diameter using the axial method on a transverse CT angiography.

Figure 4

Dual-energy CT, Thoracic VCAR application, gemstone spectral imaging (GSI) pulmonary perfusion in a patient with acute pulmonary embolism. (a) Visualization of pulmonary perfusion by colorized iodine overlay. (b) Automatic segmentation showing regions (blue areas) representing relative perfusion deficit. (c) Monochromatic input volume.

Figure 5

Scatterplot of obstruction score and perfusion defect volume (PDvol) (n = 43). Line of best fit is shown with a dotted line. The large red dot in the left corner of the scatterplot represents 18 patients, while the large blue dot in the left corner represents 14 patients. The yellow dots represent patients with identical automatic and semiautomatic PDvol.

Figure 6

Scatterplot of right ventricular-to-left ventricular (RV/LV) diameter ratio and perfusion defect volume (PDvol) (n = 43). Line of best fit is shown with a dotted line. The slightly larger blue and red dots represent 2 or 3 patients, depending on the dot size. The yellow dots represent patients with identical automatic and semiautomatic PDvol.