Assessment of perfusion pattern and extent of perfusion defect on dual-energy CT angiography: correlations between the causes of pulmonary hypertension and vascular parameters

Dual-energy CT lung perfusion characteristics in pulmonary arterial hypertension (PAH) and pulmonary veno-occlusive disease and/or pulmonary capillary hemangiomatosis (PVOD/PCH): preliminary experience in 63 patients

BACKGROUND

In the stratification of potential causes of PH, current guidelines recommend performing V/Q lung scintigraphy to screen for CTEPH. The recognition of CTEPH is based on the identification of lung segments or sub-segments without perfusion but preserved ventilation. The presence of mismatched perfusion defects has also been described in a small proportion of idiopathic pulmonary arterial hypertension (PAH) and pulmonary veno-occlusive disease and/or pulmonary capillary hemangiomatosis (PVOD/PCH). Dual-energy CT lung perfusion changes have not been specifically investigated in these two entities.

PURPOSE

To compare dual-energy CT (DECT) perfusion characteristics in PAH and PVOD/PCH, with specific interest in PE-type perfusion defects.

MATERIALS AND METHODS

Sixty-three patients with idiopathic or heritable PAH (group A; n = 51) and PVOD/PCH (group B; n = 12) were investigated with DECT angiography with reconstruction of morphologic and perfusion images.

RESULTS

The number of patients with abnormal perfusion did not differ between group A (35/51; 68.6%) and group B (6/12; 50%) (p = 0.31) nor did the mean number of segments with abnormal perfusion per patient (group A: 17.9 ± 4.9; group B: 18.3 ± 4.1; p = 0.91). The most frequent finding was the presence of patchy defects in group A (15/35; 42.9%) and a variable association of perfusion abnormalities in group B (4/6; 66.7%). The median percentage of segments with PE-type defects per patient was significantly higher in group B than in group A (p = 0.041). Two types of PE-type defects were depicted in 8 patients (group A: 5/51; 9.8%; group B: 3/12; 25%), superimposed on PH-related lung abnormalities (7/8) or normal lung (1/8). The iodine concentration was significantly lower in patients with abnormal perfusion (p < 0.001) but did not differ between groups.

CONCLUSION

Perfusion abnormalities did not differ between the two groups at the exception of a higher median percentage of segments with PE-type defects in patients with PVOD/PCH.

KEY POINTS

• Patchy perfusion defect was the most frequent pattern in PAH. • A variable association of perfusion abnormalities was seen in PVOD/PCH. • Lobular and PE-type perfusion defects larger than a sub-segment were depicted in both PAH and PVOD/PCH patients.

Spectral Detector CT-Derived Pulmonary Perfusion Maps and Pulmonary Parenchyma Characteristics for the Semiautomated Classification of Pulmonary Hypertension

Objectives

To evaluate the usefulness of spectral detector CT (SDCT)-derived pulmonary perfusion maps and pulmonary parenchyma characteristics for the semiautomated classification of pulmonary hypertension (PH).

Methods

A total of 162 consecutive patients with right heart catheter (RHC)-proven PH of different aetiologies as defined by the current ESC/ERS guidelines who underwent CT pulmonary angiography (CTPA) on SDCT and 20 patients with an invasive rule-out of PH were included in this retrospective study. Semiautomatic lung segmentation into normal and malperfused areas based on iodine density (ID) as well as automatic, virtual non-contrast-based emphysema quantification were performed. Corresponding volumes, histogram features and the ID SkewnessPerfDef-Emphysema-Index (δ-index) accounting for the ratio of ID distribution in malperfused lung areas and the proportion of emphysematous lung parenchyma were computed and compared between groups.

Results

Patients with PH showed a significantly greater extent of malperfused lung areas as well as stronger and more homogenous perfusion defects. In group 3 and 4 patients, ID skewness revealed a significantly more homogenous ID distribution in perfusion defects than in all other subgroups. The δ-index allowed for further subclassification of subgroups 3 and 4 (p &lt; 0.001), identifying patients with chronic thromboembolic PH (CTEPH, subgroup 4) with high accuracy (AUC: 0.92, 95%-CI, 0.85–0.99).

Conclusion

Abnormal pulmonary perfusion in PH can be detected and quantified by semiautomated SDCT-based pulmonary perfusion maps. ID skewness in malperfused lung areas, and the δ-index allow for a classification of PH subgroups, identifying groups 3 and 4 patients with high accuracy, independent of reader expertise.

Detection of patients with chronic thromboembolic pulmonary hypertension by volumetric iodine quantification in the lung-a case control study

Background

To evaluate whether volumetric iodine quantification of the lung allows for the automatic identification of patients with chronic thromboembolic pulmonary hypertension (CTEPH) and whether the extent of pulmonary malperfusion correlates with invasive hemodynamic parameters.

Methods

Retrospective data base search identified 30 consecutive patients with CTEPH who underwent CT pulmonary angiography (CTPA) on a spectral-detector CT scanner. Thirty consecutive patients who underwent an identical CT examination for evaluation of suspected acute pulmonary embolism and had no signs of pulmonary embolism or PH, served as control cohort. Lungs were automatically segmented for all patients and normal and malperfused volumes were segmented based on iodine density thresholds. Results were compared between groups. For correlation analysis between the extent of malperfused volume and mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR) 3 patients were excluded because of a time span of more than 30 days between CTPA and right heart catheterization.

Results

Patients with CTEPH had a higher percentage of malperfused lung compared to controls (43.25%±24.72% vs. 21.82%±20.72%; P=0.001) and showed reduced mean iodine density in malperfused and normal-perfused lung areas, as well as in the vessel volume. Controls showed a left-tailed distribution of iodine density in malperfused lung areas while patients with CTEPH had a more symmetrical distribution (Skew: -0.382±0.435 vs. -0.010±0.396; P=0.004). Patients with CTEPH showed a significant correlation between the percentage of malperfused lung volume and the PVR (r=0.57, P=0.001).

Conclusions

Volumetric iodine quantification helps to identify patients with CTEPH by showing increased areas of malperfusion. The extent of malperfusion might provide a measurement for disease severity in patients with CTEPH.

Prognostic Value of Dual-Energy CT-Based Iodine Quantification versus Conventional CT in Acute Pulmonary Embolism: A Propensity-Match Analysis

Objective

The present study aimed to investigate whether quantitative dual-energy computed tomography (DECT) parameters offer an incremental risk stratification benefit over the CT ventricular diameter ratio in patients with acute pulmonary embolism (PE) by using propensity score analysis.

Materials and Methods

This study was conducted on 480 patients with acute PE who underwent CT pulmonary angiography (CTPA) or DECT pulmonary angiography (DE CT-PA). This propensity-matched study population included 240 patients with acute PE each in the CTPA and DECT groups. Altogether, 260 (54.1%) patients were men, and the mean age was 64.9 years (64.9 ± 13.5 years). The primary endpoint was all-cause death within 30 days. The Cox proportional hazards regression model was used to identify associations between CT parameters and outcomes and to identify potential predictors. Concordance (C) statistics were used to compare the prognoses between the two groups.

Results

In both CTPA and DECT groups, right to left ventricle diameter ratio ≥ 1 was associated with an increased risk of all-cause death within 30 days (hazard ratio: 3.707, p < 0.001 and 5.573, p < 0.001, respectively). However, C-statistics showed no statistically significant difference between the CTPA and DECT groups for predicting death within 30 days (C-statistics: 0.759 vs. 0.819, p = 0.117).

Conclusion

Quantitative measurement of lung perfusion defect volume by DECT had no added benefit over CT ventricular diameter ratio for predicting all-cause death within 30 days.

Diagnosis of pulmonary hypertension using spectral-detector CT

OBJECTIVES

To evaluate the value of spectral-detector CT (SDCT) in the diagnosis of chronic thromboembolic pulmonary hypertension (CTEPH), its differentiation against other etiologies of pulmonary hypertension (PH) and in the prediction of disease severity.

MATERIALS AND METHODS

60 patients with suspected PH underwent SDCT. Additional diagnostic tests in accordance with the ESC guidelines including right heart catherization and VQ-SPECT were performed. After full diagnostic work-up patients were classified as: 21 precapillary PH, 5 postcapillary PH, 6 combined pre- and postcapillary PH, 19 CTEPH, 9 no PH. SDCT examinations were analyzed by two blinded readers deciding on the diagnosis of CTEPH and scoring the extent of perfusion abnormalities on iodine density images. An additional reading was performed using conventional CTPA images only.

RESULTS

With access to SDCT data, both readers reached a sensitivity of 100% for the diagnosis of CTEPH with a specificity of 95.1% and 87.8%. On analysis of conventional CTPA images alone, specificity and diagnostic confidence decreased for both readers (Specificity 90.2 and 85.3%) while sensitivity dropped for the less experienced reader only (Sensitivity 78.9%). Patients with PH showed significantly more perfusion abnormalities than patients without PH (16.6 ± 8.4 vs. 9.5 ± 8.9 p < 0.001) and the extent of perfusion abnormalities correlated with the mean pulmonary artery pressure (r = 0.37 p = 0.008).

CONCLUSIONS

SDCT offers confident identification of patients with CTEPH and enables a comprehensive analysis of pulmonary vasculature, pulmonary perfusion and the lung parenchyma in a single examination for patients with suspected PH.

Value of lung perfusion scintigraphy in patients with idiopathic pulmonary arterial hypertension: a patchy pattern to consider

The ventilation/perfusion lung scan is recommended to exclude chronic thromboembolic pulmonary hypertension in the diagnostic algorithm of pulmonary hypertension, but its role in pulmonary arterial hypertension (PAH) has not been well explored. We characterized the lung perfusion pattern assessed by lung perfusion scintigraphy in idiopathic PAH (IPAH) patients and evaluate the potential prognostic significance of the patchy pattern perfusion defect. A total of 318 patients with IPAH confirmed by right heart catheterization who performed lung perfusion scintigraphy were included. On lung perfusion scintigraphy, 134 patients had normal lung perfusion and 184 patients showed patchy perfusion defects. In comparison to patients with normal lung perfusion, patients with patchy perfusion defects experienced significantly higher mean pulmonary arterial pressure (58.0 ± 15.4 mmHg vs. 54.1 ± 16.2 mmHg, P = 0.027) and total pulmonary resistance (1192.6 ± 533.7 dyn·s·cm⁻⁵ vs. 1067.2 ± 549.3 dyn·s·cm⁻⁵, P = 0.042). During a median follow-up period of 884.0 days, 53 patients reached the primary endpoint of all-cause mortality. On univariate Cox analysis, the patchy pattern of perfusion defect was significantly associated with the all-cause mortality (hazard ratio [HR] = 2.47, 95% confidence interval [CI] = 1.32–4.63, P = 0.005). Patients with patchy perfusion defects had a worse outcome (log-rank = 8.605, P = 0.003). On multivariate analysis, the patchy pattern remained as a significant independent predictor of the endpoint (HR = 2.30, 95% CI = 1.22–4.31, P = 0.010). IPAH patients presented with heterogeneity in lung perfusion and the patchy pattern of lung perfusion defect commonly existed. Patients with patchy pattern identified by lung perfusion scintigraphy were associated with more severe disease and worse outcome.

Assessment of regional emphysema, air-trapping and Xenon-ventilation using dual-energy computed tomography in chronic obstructive pulmonary disease patients

OBJECTIVES

To compare the parenchymal attenuation change between inspiration/expiration CTs with dynamic ventilation change between xenon wash-in (WI) inspiration and wash-out (WO) expiration CTs.

METHODS

52 prospectively enrolled COPD patients underwent xenon ventilation dual-energy CT during WI and WO periods and pulmonary function tests (PFTs). The parenchymal attenuation parameters (emphysema index (EI), gas-trapping index (GTI) and air-trapping index (ATI)) and xenon ventilation parameters (xenon in WI (Xe-WI), xenon in WO (Xe-WO) and xenon dynamic (Xe-Dyna)) of whole lung and three divided areas (emphysema, hyperinflation and normal) were calculated on virtual non-contrast images and ventilation images. Pearson correlation, linear regression analysis and one-way ANOVA were performed.

RESULTS

EI, GTI and ATI showed a significant correlation with Xe-WI, Xe-WO and Xe-Dyna (EI R = -.744, -.562, -.737; GTI R = -.621, -.442, -.629; ATI R = -.600, -.421, -.610, respectively, p < 0.01). All CT parameters showed significant correlation with PFTs except forced vital capacity (FVC). There was a significant difference in GTI, ATI and Xe-Dyna in each lung area (p < 0.01).

CONCLUSIONS

The parenchymal attenuation change between inspiration/expiration CTs and xenon dynamic change between xenon WI- and WO-CTs correlate significantly. There are alterations in the dynamics of xenon ventilation between areas of emphysema.

KEY POINTS

• The xenon ventilation change correlates with the parenchymal attenuation change. • The xenon ventilation change shows the difference between three lung areas. • The combination of attenuation and xenon can predict more accurate PFTs.

Lung perfusion characteristics in pulmonary arterial hypertension (PAH) and peripheral forms of chronic thromboembolic pulmonary hypertension (pCTEPH): Dual-energy CT experience in 31 patients

PURPOSE

To compare lung perfusion in PAH and pCTEPH on dual-energy CT (DECT) examinations.

MATERIALS AND METHODS

Thirty-one patients with PAH (group 1; n = 19) and pCTEPH (group 2; n = 12) underwent a dual-energy chest CTA with reconstruction of diagnostic and perfusion images. Perfusion alterations were analysed at a segmental level. V/Q scintigraphy was available in 22 patients (group 1: 13/19; group 2: 9/12).

RESULTS

CT perfusion was abnormal in 52.6 % of group 1 patients and in 100 % of group 2 patients (p = 0.0051). The patterns of perfusion alteration significantly differed between the two groups (p < 0.0001): (1) in group 1, 96.6 % of segments with abnormal perfusion showed patchy defects; (2) in group 2, the most frequent abnormalities consisted of patchy (58.5 %) and PE-type (37.5 %) defects. Paired comparison of CT perfusion and scintigraphy showed concordant findings in 76.9 % of group 1 (10/13) and 100 % of group 2 (9/9) patients, with a predominant or an exclusive patchy pattern in group 1 and a mixed pattern of abnormalities in group 2.

CONCLUSION

Lung perfusion alterations at DECT are less frequent and more homogeneous in PAH than in pCTEPH, with a high level of concordant findings with V/Q scintigraphy.

KEY POINTS

• Depiction of chronic pulmonary embolism exclusively located on peripheral arteries is difficult. • The main differential diagnosis of pCTEPH is PAH. • The pattern of DECT perfusion changes can help differentiate PAH and pCETPH. • In PAH, almost all segments with abnormal perfusion showed patchy defects. • In pCTEPH, patchy and PE-type defects were the most frequent abnormalities.