Dual-energy CT pulmonary angiography in patients with suspected pulmonary embolism: value for the detection and quantification of pulmonary venous congestion

Objective:

To evaluate if vascular and pulmonary parenchymal enhancement values in dual-energy (DE) CT pulmonary angiography (CTPA) can suggest the diagnosis of pulmonary congestion.

Methods:

DE-CTPA images of 90 out of 1321 patients negative for pulmonary embolism showed signs of congestive heart failure. We measured DE-derived pulmonary parenchymal [perfused blood volume (PBV)], pulmonary artery (PA) and left atrium (LA) enhancement values in these patients and in 142 control patients. Enhancement values were compared between the populations and correlated with serum values of B-type natriuretic peptide (BNP) and proBNP, where available.

Results:

No significant difference of PBV but significant differences of mean PA and LA enhancement and individual enhancement differences (PA − LA) were found between the populations. PA − LA was higher in patients with elevated BNP and proBNP and was positively correlated with these values. Receiver operating characteristic analysis revealed a moderate discriminatory power of the PA − LA difference for the presence of cardiac biomarker elevations.

Conclusion:

PBV in DE-CTPA is not altered in patients with signs of congestive heart failure. However, differences in enhancement values in the pre- and post-pulmonary vessels were found in comparison with the control population.

Advances in knowledge:

Altered pulmonary vascular haemodynamics in pulmonary venous congestion are not reflected in dual-energy-derived PBV maps. In the diagnosis of left heart failure in patients with chest pain and dyspnoea, density measurements in the pulmonary artery and in the left atrium in CTPA images may be a helpful diagnostic tool.In the diagnostic algorithms for patients with acute dyspnoea, CT pulmonary angiography (CTPA) plays a major role, specifically in cases when pulmonary embolism (PE) is suspected. Whenever no PE can be detected, radiologists face the challenge to detect alternative pathological thoracic findings. An undiagnosed acute or chronic left heart failure with pulmonary congestion can be an alternative cause of acute dyspnoea. Although there are some direct and indirect CT criteria that suggest the diagnosis of congestive heart failure with pulmonary venous hypertension (e.g. dilated pulmonary veins with a blurry appearance of the vessel walls, thickening of the interlobular septal lines, ground-glass opacities/alveolar oedema, pleural effusions and an enlargement of the left atrium and/or ventricle), the diagnosis of left heart failure on the basis of CT findings is often equivocal and rather rater dependent. For suspected left heart failure, chest radiography represents the primary diagnostic tool rather than CT. Still, if CTPA is performed in chest pain workup, an improved, more objective diagnosis of congestive heart failure would be desirable.Dual-energy CTPA (DE-CTPA) can quantify the iodine-related pulmonary beam absorption and thus allow an automated, reader-independent, software-based quantification of the pulmonary content of iodinated contrast material [termed “perfused blood volume” (PBV)].¹ Based on the assumption that an impaired left heart function leads to variances in the pulmonary blood content and in the dynamics of the pulmonary passage of the contrast bolus, we tried to find out if measured absorption values in iodine-enhanced DE-CTPA, that is, DE-based pulmonary PBV values as well as density measurements in the pulmonary trunk and the left atrium, can be helpful in the diagnosis of pulmonary congestion.For this purpose, we retrospectively compared pulmonary parenchymal, pulmonary artery (PA) and left atrium (LA) enhancement values in patients with CT signs of pulmonary congestion with those from patients with no detectable cardiopulmonary pathologies in DE-CTPA and correlated those values with serum levels of established left heart insufficiency markers [cardiac peptides: B-type natriuretic peptide (BNP) and proBNP].