Quantification of lung perfusion blood volume with dual-energy CT: assessment of the severity of acute pulmonary thromboembolism

Dual-Energy Computed Tomography Applications in Lung Cancer

This article examines the intrathoracic applications for dual-energy computed tomography (DECT), focusing on lung cancer. The topics covered include the image data sets, methods for iodine quantification, and clinical applications. The applications of DECT are to differentiate benign and malignant lung nodules, determining the grade of lung cancer and expression of ki-67 expression. Iodine quantification has role in assessment of treatment response in both the primary tumor and nodal metastases.

Advances for Pulmonary Functional Imaging: Dual-Energy Computed Tomography for Pulmonary Functional Imaging

Dual-energy computed tomography (DECT) can improve the differentiation of material by using two different X-ray energy spectra, and may provide new imaging techniques to diagnostic radiology to overcome the limitations of conventional CT in characterizing tissue. Some techniques have used dual-energy imaging, which mainly includes dual-sourced, rapid kVp switching, dual-layer detectors, and split-filter imaging. In iodine images, images of the lung's perfused blood volume (PBV) based on DECT have been applied in patients with pulmonary embolism to obtain both images of the PE occluding the pulmonary artery and the consequent perfusion defects in the lung's parenchyma. PBV images of the lung also have the potential to indicate the severity of PE, including chronic thromboembolic pulmonary hypertension. Virtual monochromatic imaging can improve the accuracy of diagnosing pulmonary vascular diseases by optimizing kiloelectronvolt settings for various purposes. Iodine images also could provide a new approach in the area of thoracic oncology, for example, for the characterization of pulmonary nodules and mediastinal lymph nodes. DECT-based lung ventilation imaging is also available with noble gases with high atomic numbers, such as xenon, which is similar to iodine. A ventilation map of the lung can be used to image various pulmonary diseases such as chronic obstructive pulmonary disease.

Evaluation of CT angiography obstruction score and pulmonary perfusion defect score using the third-generation dual-source CT for pulmonary embolism

AIM

To investigate the application value of computed tomography (CT) angiography (CTA) obstruction score and pulmonary perfusion defect score on the third-generation dual-source CT for pulmonary embolism and the changes of the right ventricular function.

MATERIALS AND METHODS

The clinical data of 52 patients with pulmonary embolism (PE) confirmed using the third-generation dual-source dual-energy CTPA were analysed retrospectively. These patients were divided into the severe group and non-severe group according to their clinical manifestations. The results of CTPA and dual-energy pulmonary perfusion imaging (DEPI) were recorded by two radiologists for index computation. The ratio of the maximum short-axis diameter of the right ventricle (RV) to that of the left ventricle (LV) was also recorded. The correlation analysis between RV/LV and the mean values of CTA obstruction score and perfusion defect score was performed. Correlation analysis and agreement analysis were performed on the data measured by two radiologists, CTA obstruction score, and pulmonary perfusion defect score.

RESULTS

CTA obstruction score and perfusion defect score measured by the two radiologists had good correlation and agreement. CTA obstruction score, perfusion defect score, and RV/LV were significantly lower in the non-severe group than in the severe PE group. RV/LV had a significant positive correlation with CTA obstruction score and perfusion defect score (p<0.05).

CONCLUSION

The third-generation dual-source dual-energy CT plays a positive role in assessing PE severity and RV function and can provide additional information for the clinical management and treatment of PE patients.

Pulmonary perfusion defect volume on dual-energy CT: prognostic marker of adverse events in patients with suspected pulmonary embolism

To assess whether quantification of pulmonary perfusion defects on dual-energy computed tomography (DECT) relates to adverse events beyond clinical parameters and traditional embolus detection in patients with suspected pulmonary embolism (PE). We included consecutive patients who underwent DECT to rule out acute PE in 2018-2020 and recorded incident adverse events, defined as a composite of short-term (< 30 days) in-hospital all-cause mortality or admission to intensive care unit. Relative perfusion defect volume (PDV) was measured on DECT and indexed by total lung volume. PDV was then related to adverse events using logistic regressions adjusting for clinical parameters, clinical PE pre-test probability (Wells score), and visual PE burden on pulmonary angiography (Qanadli score). Among 136 included patients (63 [46%] females; age: 70 ± 14 years), 19/136 (14%) experienced adverse events during a median hospitalization of 7.5 (4-14) days. Overall, 7/19 (37%) events occurred in those without visible emboli but with measurable perfusion defects. An increase of PDV by one standard deviation was associated with over two times higher odds of adverse events (OR = 2.24; 95%CI:1.37-3.65; p = 0.001). This association remained significant after adjusting for the Wells and Qanadli scores (OR = 2.34; 95%CI:1.20-4.60; p = 0.013). PDV significantly increased the combined discriminatory capacity of Wells and Qanadli scores (AUC 0.76 vs. 0.80; p = 0.011 for difference). DECT-derived PDV may represent a prognostic imaging marker with incremental value beyond clinical and traditional imaging findings, improving risk stratification and aiding clinical management in patients with suspected PE.

Quantitative analysis of pulmonary perfusion with dual-energy CT angiography: comparison of two quantification methods in patients with pulmonary embolism

The study aimed to evaluate a quantification method of pulmonary perfusion with Dual-Energy CT Angiography (DE-CTA) normalized by lung density in the prediction of outcome in acute pulmonary embolism (PE). In this prospective study with CTA scans acquired with different breathing protocols, two perfusion parameters were calculated: %PBV (relative value of PBV, expressed per unit volume) and PBVm (PBV normalized by lung density, expressed per unit mass). DE-CTA parameters were correlated with simplified pulmonary embolism severity index (sPESI) and with outcome groups, alone and in combinationwith tomographic right-to-left ventricular ratios (RV/LV). PBVm showed significant correlation with sPESI. PBVm presented higher accuracy than %PBV In the prediction of ICU admission or death in patients with PE, with the best performance when combined with RV/LV volumetric ratio.

Evaluating cardiopulmonary function following acute pulmonary embolism

INTRODUCTION

Pulmonary embolism is a common cause of cardiopulmonary mortality and morbidity worldwide. Survivors of acute pulmonary embolism may experience dyspnea, report reduced exercise capacity, or develop overt pulmonary hypertension. Clinicians must be alert for these phenomena and appreciate the modalities and investigations available for evaluation.

AREAS COVERED

In this review, the current understanding of available contemporary imaging and physiologic modalities is discussed, based on available literature and professional society guidelines. The purpose of the review is to provide clinicians with an overview of these modalities, their strengths and disadvantages, and how and when these investigations can support the clinical work-up of patients post-pulmonary embolism.

EXPERT OPINION

Echocardiography is a first test in symptomatic patients post-pulmonary embolism, with ventilation/perfusion scanning vital to determination of whether there is chronic residual emboli. The role of computed tomography and magnetic resonance in assessing the pulmonary arterial tree in post-pulmonary embolism patients is evolving. Functional testing, in particular cardiopulmonary exercise testing, is emerging as an important modality to quantify and determine cause of functional limitation. It is possible that future investigations of the post-pulmonary embolism recovery period will better inform treatment decisions for acute pulmonary embolism patients.

Diagnosis of Chronic Thromboembolic Pulmonary Hypertension Using Quantitative Lung Perfusion Parameters Extracted From Dual-energy Computed Tomography Images

PURPOSE

To evaluate quantified iodine mapping parameters in dual-energy computed tomography in normal patients versus those with chronic thromboembolic pulmonary hypertension (CTEPH) with and without pulmonary thromboembolism.

MATERIALS AND METHODS

Using automatically quantified iodine mapping in dual-energy computed tomography, we evaluated lung relative average enhancement, standard deviation (SD), and the SD/lung relative average enhancement ratio. We compared the values for these parameters in normal patients versus those with CTEPH. We also performed a receiver operating characteristic curve analysis to determine the diagnostic cutoffs for the parameters.

RESULTS

Patients constituted 41 patients (10 male [24.4%] and 31 female [75.6%]; mean age [SD]: 70.0 y [13.3]) with CTEPH and 237 (92 male [38.8%] and 145 female [61.2%]; mean age [SD]: 65.9 y [15.9]) normal patients. We found significant differences in lung relative average enhancement (34.9±6.3 vs. 26.9±6.3; P <0.0001), SD (11.6±1.9 vs. 14.7±3.3; P <0.001), and the SD/lung relative average enhancement ratio (33.7±5.0 vs. 55.7±10.4; P <0.001) between the normal and CTEPH groups, respectively. The ROC analyses demonstrated high discriminatory power (area under the curve=0.99) for using the SD/lung relative average enhancement ratio to differentiate between patients in the normal group and CTEPH group. At a threshold for the area under the curve of 44.2, diagnostic sensitivity, specificity, positive predictive value, and negative predictive value for the ratio were 92.7%, 97.5%, 86.5%, and 98.7%, respectively.

CONCLUSIONS

Patients with CTEPH were well-discriminated from normal patients using the SD/lung relative average enhancement ratio.

Lobar pulmonary perfusion quantification with dual-energy CT angiography: Interlobar variability and relationship with regional clot burden in pulmonary embolism

Purpose

Semi-automated lobar segmentation tools enable an anatomical assessment of regional pulmonary perfusion with Dual-Energy CTA (DE-CTA). We aimed to quantify lobar pulmonary perfusion with DE-CTA, analyze the perfusion distribution among the pulmonary lobes in subjects without cardiopulmonary diseases and assess the correlation between lobar perfusion and regional endoluminal clots in patients with acute pulmonary embolism (PE).

Methods

We evaluated 151 consecutive subjects with suspected PE and without cardiopulmonary comorbidities. DE-CTA derived perfused blood volume (PBV) of each pulmonary lobe was measured applying a semi-automated lobar segmentation technique. In patients with PE, blood clot location was assessed, and CT-based vascular obstruction index of each lobe (CTOI_lobe) was calculated and classified into three groups: CTOI_lobe= 0, low CTOI_lobe (1–50%) and high CTOI_lobe (>50%).

Results

Among patients without PE (103/151, 68.2%), median lobar PBV was 13.7% (IQR 10.2–18.0%); the right middle lobe presented lower PBV when compared to all the other lobes (p < .001). In patients with PE (48/151, 31.8%), lobar PBV was 12.6% (IQR 9.6–15.7%), 13.7% (IQR 10.1–16.7%) and 6.5% (IQR 5.1–10.2%) in the lobes with CTOI_lobe= 0, low CTOI_lobe and high CTOI_lobe scores, respectively, with a significantly decreased PBV in the lobes with high CTOI_lobe score (p < .001). ROC analysis of lobar PBV for prediction of high CTOI_lobe score revealed AUC of 0.847 (95%CI 0.785–0.908).

Conclusion

Pulmonary perfusion was heterogeneously distributed along the pulmonary lobes in patients without cardiopulmonary diseases. In patients with PE, the lobes with high vascular obstruction score (CTOI_lobe> 50%) presented a decreased lobar perfusion.

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Semi-automated tools enable assessment of lobar perfusion with Dual-Energy CTA.

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The pulmonary perfusion is heterogeneously distributed along the pulmonary lobes.

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Lobar perfusion was decreased only in the lobes with high vascular obstruction index.

Evaluation Of a New Reconstruction Technique for Dual-Energy (DECT) Lung Perfusion: Preliminary Experience In 58 Patients

PURPOSE

To compare dual-energy (DE) lung perfused blood volume generated by subtraction of virtual monoenergetic images (Lung Mono) with images obtained by three-compartment decomposition (Lung PBV).

MATERIAL AND METHODS

The study included 58 patients (28 patients with and 30 patients without PE) with reconstruction of Lung PBV images (i.e., the reference standard) and Lung Mono images. The inter-technique comparison was undertaken at a patient and segment level.

RESULTS

The distribution of scores of subjective image noise (patient level) significantly differed between the two reconstructions (p<0.0001), with mild noise in 58.6% (34/58) of Lung Mono images vs 25.9% (15/58) of Lung PBV images. Detection of perfusion defects (segment level) was concordant in 1104 segments (no defect: n=968; defects present: n=138) and discordant in 2 segments with a PE-related defect only depicted on Lung Mono images. Among the 28 PE patients, the distribution of gradient of attenuation between perfused areas and defects was significantly higher on Lung Mono images compared to Lung PBV (median= 73.5 HU (QI=65.0; Q3=86.0) vs 24.5 HU (22.0; 30.0); p<0.0001). In all patients, fissures were precisely identified in 77.6% of patients (45/58) on Lung Mono images while blurred (30/58; 51.7%) or not detectable (28/58; 48.3%) on Lung PBV images.

CONCLUSION

Lung Mono perfusion imaging allows significant improvement in the overall image quality and improved detectability of PE-type perfusion defects.

Quantitative lung perfusion blood volume using dual energy CT-based effective atomic number (Zeff ) imaging

BACKGROUND

Iodine material images (aka iodine basis images) generated from dual energy computed tomography (DECT) have been used to assess potential perfusion defects in the pulmonary parenchyma. However, iodine material images do not provide the needed absolute quantification of the pulmonary blood pool, as materials with effective atomic numbers (Z_eff ) different from those of basis materials may also contribute to iodine material images, thus confounding the quantification of perfusion defects.

PURPOSE

(i) To demonstrate the limitations of iodine material images in pulmonary perfusion defect quantification and (ii) to develop and validate a new quantitative biomarker using effective atomic numbers derived from DECT images.

METHODS

The quantitative relationship between the perfusion blood volume (PBV) in pulmonary parenchyma and the effective atomic number (Z_eff ) spatial distribution was studied to show that the desired quantitative PBV maps are determined by the spatial maps of Z_eff as PB V Z eff ( x ) = a Z eff β ( x ) + b , where a, b, and β are three constants. Namely, quantitative PB V Z eff is determined by Z_eff images instead of the iodine basis images. Perfusion maps were generated for four human subjects to demonstrate the differences between conventional iodine material image-based PBV (PBV_iodine ) derived from two-material decompositions and the proposed PB V Z eff method.

RESULTS

Among patients with pulmonary emboli, the proposed PB V Z eff maps clearly show the perfusion defects while the PBV_iodine maps do not. Additionally, when there are no perfusion defects present in the derived PBV maps, no pulmonary emboli were diagnosed by an experienced thoracic radiologist.

CONCLUSION

Effective atomic number-based quantitative PBV maps provide the needed sensitive and specific biomarker to quantify pulmonary perfusion defects.

Effect of Balloon Pulmonary Angioplasty on Homogenization of Lung Perfusion Blood Volume by Dual-Energy Computed Tomography in Patients with Chronic Thromboembolic Pulmonary Hypertension

OBJECTIVE

Balloon pulmonary angioplasty (BPA) is used to treat patients with inoperable chronic thromboembolic pulmonary hypertension (CTEPH); the goal is to improve pulmonary perfusion. We aimed to evaluate lung perfusion blood volume (PBV) with haemodynamic and exercise-capacity parameters to assess the efficacy of BPA in the treatment of CTEPH.

METHODS

We retrospectively studied 33 patients over a 6-year period. DECT pulmonary angiography was performed before and after BPA. DECT provided iodine distribution maps; whole-lung and regional PBV images and quantification were generated using post-processing software. A mosaic pattern suggesting perfusion inhomogeneity is typical in CTEPH. Hypothetically, BPA treatment would promote homogenization that would be reflected in the calculated standard deviation.

RESULTS

Lung perfusion images showed decreased heterogeneity after BPA. There was a significant difference before and after BPA in the whole-lung PBV and in the regional standard deviation for pulmonary arterial pressure (R = 0.37, p = 0.032 and R = 0.57, p = 0.006), pulmonary vascular resistance (R = 0.51, p = 0.023 and R = 0.60, p = 0.002), transtricuspid pressure gradient (R = 0.50, p = 0.0028 and R = 0.61, p = 0.0001), brain natriuretic peptide (R = 0.54, p = 0.0012 and R = 0.46, p = 0.0078), and 6-min walking distance (R = 0.59, p = 0.003 and R = 0.26, p = 0.14). The effects were especially pronounced after the first BPA procedure.

CONCLUSION

Decreased lung heterogeneity may suggest BPA efficacy in treating CTEPH. After BPA treatment, improved lung PBV and improved regional standard deviation showed a strong positive correlation with haemodynamic parameters and exercise capacity, which also suggests that BPA is effective in treating CTEPH.

Pulmonary angioplasty: A step further in the continuously changing landscape of chronic thromboembolic pulmonary hypertension management

Chronic thromboembolic pulmonary hypertension (CTEPH) is a potentially fatal and frequently undiagnosed form of pulmonary hypertension (PH), classified within group 4 by the World Health Organization (WHO). It is a type of precapillary PH, which uncommonly develops as a peculiar sequel of acute pulmonary embolism due to the partial resolution of the mechanically obstructing thrombus with a coexisting inflammatory response from pulmonary vessels. CTEPH is one of the potentially treatable forms of PH whose current standard of care is surgical pulmonary endarterectomy. Medical therapy with few drugs in non-operable disease is approved and has shown improvement in patients' hemodynamic condition and functional ability. Recently, balloon pulmonary angioplasty (BPA) has shown promising results as a treatment option for technically inoperable patients, those with unacceptable risk-to-benefit ratio and in a case of residual PH after endarterectomy. Lack of meticulous CTEPH screening programs in post-pulmonary embolism patients leading to underdiagnosis of this condition, complex operability assessment, and diversity in BPA techniques among different institutions are still the issues that need to be addressed. In this paper, we review the recent achievements in the management of non-operable CTEPH, their outcome and safety, based on available data.

Dynamic Chest X-Ray Using a Flat-Panel Detector System: Technique and Applications

Dynamic X-ray (DXR) is a functional imaging technique that uses sequential images obtained by a flat-panel detector (FPD). This article aims to describe the mechanism of DXR and the analysis methods used as well as review the clinical evidence for its use. DXR analyzes dynamic changes on the basis of X-ray translucency and can be used for analysis of diaphragmatic kinetics, ventilation, and lung perfusion. It offers many advantages such as a high temporal resolution and flexibility in body positioning. Many clinical studies have reported the feasibility of DXR and its characteristic findings in pulmonary diseases. DXR may serve as an alternative to pulmonary function tests in patients requiring contact inhibition, including patients with suspected or confirmed coronavirus disease 2019 or other infectious diseases. Thus, DXR has a great potential to play an important role in the clinical setting. Further investigations are needed to utilize DXR more effectively and to establish it as a valuable diagnostic tool.

Morphologic and Functional Dual-Energy CT Parameters in Patients With Chronic Thromboembolic Pulmonary Hypertension and Chronic Thromboembolic Disease

OBJECTIVE. The objective of our study was to compare morphologic and functional dual-energy CT (DECT) parameters in patients with chronic thromboembolic disease (CTED) and chronic thromboembolic pulmonary hypertension (CTEPH). MATERIALS AND METHODS. Using the local CTEPH registry, we identified 28 patients with CTED and 72 patients with CTEPH. On each DECT examination, a clot burden score was calculated by assigning the following scores for chronic changes by location: pulmonary trunk, 5; each main pulmonary artery (MPA), 4; each lobar branch, 3; each segmental branch, 2; and each subsegmental branch, 1. The total clot burden score was calculated by adding the individual scores from both lungs. Functional parameters were assessed using perfused blood volume (PBV) maps and included lung enhancement (in Hounsfield units), percentage of PBV, MPA peak enhancement (in Hounsfield units), maximum enhancement corresponding to 100, and the ratio of MPA peak enhancement to lung enhancement. A perfusion defect (PD) score was calculated by assigning 1 point to each segmental PD. Patients with CTED and patients with CTEPH were matched using propensity score matching to account for potential confounders. RESULTS. After matching, the CTEPH group showed a higher PD score than the CTED group and unilateral disease was more common in the CTED group than in the CTEPH group. In the unmatched sample, patients with CTED showed increased percentages of PBV for both lungs (PBV total) and for the right lung as compared with the CTEPH group (adjusted p = 0.040 and 0.028, respectively); after adjustment for clot burden, the difference between groups was still noted but was not statistically significant. No statistically significant differences were noted in the various functional DECT parameters after propensity score matching. CONCLUSION. Patients with CTED show anatomic and functional changes in the pulmonary vasculature and lung parenchyma similar to those seen in patients with CTEPH. Functional DECT parameters support the observation that CTED is an intermediate clinical phenotype in the population with chronic pulmonary embolism.

CT Pulmonary Angiography for Risk Stratification of Patients with Nonmassive Acute Pulmonary Embolism

Purpose

To investigate the prognostic value of an integrative approach combining clinical variables and the Qanadli CT obstruction index (CTOI) in patients with nonmassive acute pulmonary embolism (PE).

Materials and Methods

This retrospective study included 705 consecutive patients (mean age, 63 years; range, 18-95 years) with proven PE. Clot burden was quantified using the CTOI, which reflects the ratio of fully or partially obstructed pulmonary arteries to normal arteries. Patients were subdivided into two groups according to the presence (group A) or absence (group B) of preexisting cardiopulmonary disease. Thirty-day and 3-month mortality was evaluated. CTOI thresholds of 20% and 40% were used to stratify patients regarding outcome (low, intermediate, and high risk). The predictive value of CTOI was assessed through logistic regression analysis.

Results

Analysis included 690 patients (mean age, 63.3 years ± 18 [standard deviation]) with complete follow-up data: 247 (36%) in group A and 443 (64%) in group B. The mean CTOI was 23% ± 19, 30-day mortality was 9.7%, and 3-month mortality was 11.6%. Three-month mortality was higher in group A than in group B (17.8% and 8.1%, respectively; P = .001). Within group B, CTOI predicted outcome and allowed stratification: significantly higher mortality with CTOI greater than 40% (P < .001) and lower mortality with CTOI less than 20% (P = .05). CTOI did not predict outcome in group A. Age was an independent mortality risk factor (P ≤ .04).

Conclusion

CTOI predicted outcome in this cohort of patients with PE and no cardiopulmonary disease, and it may provide a simple single-examination-based approach for risk stratification in this subset of patients.© RSNA, 2020See also the commentary by Kay and Abbara in this issue.

Dual-energy CT angiography in suspected pulmonary embolism: influence of injection protocols on image quality and perfused blood volume

To compare intravenous contrast material (CM) injection protocols for dual-energy CT pulmonary angiography (CTPA) in patients with suspected acute pulmonary embolism with regard to image quality and pulmonary perfused blood volume (PBV) values. A total of 198 studies performed with four CM injection protocols varying in CM volume and iodine delivery rates (IDR) were retrospectively included: (A) 60 ml at 5 ml/s (IDR = 1.75gI/s), (B) 50 ml at 5 ml/s (IDR = 1.75gI/s), (C) 50 ml at 4 ml/s (IDR = 1.40gI/s), (D) 40 ml at 3 ml/s (IDR = 1.05gI/s). Image quality and PBV values at different resolution settings were compared. Pulmonary arterial tract attenuation was highest for protocol A (397 ± 110 HU; p vs. B = 0.13; vs. C = 0.02; vs. D < 0.001). CTPA image quality of protocol A was rated superior compared to protocols B and D by reader 1 (p = 0.01; < 0.001), and superior to protocols B, C and D by reader 2 (p < 0.001; 0.02; < 0.001). Otherwise, there were no significant differences in CTPA quality ratings. Subjective iodine map ratings did not vary significantly between protocols A, B, and C. Both readers rated protocol D inferior to all other protocols (p < 0.05). PBV values did not vary significantly between protocols A and B at resolution settings of 1, 4 and 10 (p = 0.10; 0.10; 0.09), while otherwise PBV values displayed a decreasing trend from protocol A to D (p < 0.05). Higher CM volume and IDR are associated with superior CTPA and iodine map quality and higher absolute PBV values.

Evaluation of Vascular Parameters in Patients With Pulmonary Thromboembolic Disease Using Dual-energy Computed Tomography

PURPOSE

The purpose of this study was to evaluate patterns of vascular and lung parenchymal enhancement in patients with suspected chronic thromboembolic pulmonary hypertension (CTEPH) and in those with acute pulmonary embolism (PE) and compare those two groups.

MATERIALS AND METHODS

We retrospectively studied 186 thoracic DECT studies referred for evaluation of CTEPH or pulmonary hypertension. A total of 80 of these patients had a negative scan (control group), 13 had acute PE, and 53 had chronic thromboembolic disease (CTED)/CTEPH. Five different DECT-based parameters were evaluated that highlight patterns of vascular kinetics. Specifically, total DECT-based parenchymal attenuation in Hounsfield Unit (HU) (LungHU), percentage of perfused blood volume (PBV), peak enhancement of main pulmonary artery (PApeak in HU), maximum enhancement corresponding to 100 (PAmax), and the ratio of PApeak to LungHU were calculated.

RESULTS

Compared with patients with negative CT, patients with CTED/CTEPH tended to have lower LungHU (median: 27 vs. 38, P<0.001), lower PBV (median: 39 vs. 51, P=0.003), and higher PApeak/LungHU ratio (median: 17 vs. 13, P=0.003). Compared with patients with acute PE, patients with CTED/CTEPH tended to have lower LungHU (median: 27 vs. 39, P=0.006), lower PBV (median: 39 vs. 62, P=0.023), and higher PApeak/LungHU ratio (median: 17 vs. 11, P=0.023). No statistically significant differences were observed between patients with acute PE and those with negative CT.

CONCLUSIONS

DECT-based vascular parameters offer the potential to differentiate patients with acute versus chronic PE. These various anatomic and functional vascular DECT-based parameters might be reflective of the state of the underlying vascular bed.

Diagnostic Accuracy of Dual-Energy CT in Detection of Acute Pulmonary Embolism: A Systematic Review and Meta-Analysis

PURPOSE

In this systematic review and meta-analysis, we aimed to investigate the accuracy of dual-energy computed tomography (DECT) in the detection of acute pulmonary embolism (PE).

METHODS

We searched Medline (via PubMed), EBSCO, Web of Science, Scopus, and the Cochrane Library for relevant published studies. We selected studies assessing the accuracy of DECT in the detection of PE. Quality assessment of bias and applicability was conducted using the Quality of Diagnostic Accuracy Studies-2 tool. Meta-analysis was performed to calculate mean estimates of sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR). The summary receiver operating characteristic (sROC) curve was drawn to get the Cochran Q-index and the area under the curve (AUC).

RESULTS

Seven studies were included in our systematic review. Of the 182 patients included, 108 patients had PEs. The pooled analysis showed an overall sensitivity and specificity of 88.9% (95% confidence interval [CI]: 81.4%-94.1%) and 94.6% (95% CI: 86.7%-98.5%), respectively. The pooled PLR was 8.186 (95% CI: 3.726-17.986), while the pooled NLR was 0.159 (95% CI: 0.093-0.270). Cochran-Q was 0.8712, and AUC was 0.935 in the sROC curve.

CONCLUSION

Dual-energy computed tomography shows high sensitivity, specificity, and diagnostic accuracy in the detection of acute PE. The high PLR highlights the high clinical importance of DECT as a prevalence-independent, rule-in test. Studies with a larger sample size with standardized reference tests are still needed to increase the statistical power of the study and support these findings.

Histogram-based comparison between dynamic and static lung perfused blood volume images using dual energy CT

OBJECTIVE

The purpose of this study was to compare the results of a histogram-based analysis of static and dynamic lung perfused blood volume (LPBV) images.

METHODS

Sixty-five patients (mean age: 61.3 years, 36 male) underwent dynamic and static LPBV for evaluation of pulmonary vascular diseases (n = 11), lung carcinoma (n = 27) or pulmonary thromboembolism (PTE: n = 27). Seven sets of dynamic sequential scans were performed at the pulmonary trunk using dual-energy technique before the static LPBV scan. The image of lung parenchyma that showed the greatest mean attenuation in dynamic series was defined as the peak dynamic LPBV image. The differences and correlations in the mean attenuation, image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), histogram skewness and histogram kurtosis were evaluated according to the type of disease in static and dynamic LPBV images.

RESULTS

Static LPBV images showed significantly larger mean attenuation (Rt:24.2, Lt: 24.2), SNR (Rt:2.31, Lt:2.30), and CNR (Rt:2.40, Lt:2.39), and smaller kurtosis values (Rt:1.06, Lt:0.61) values in comparison to dynamic LPBV images (p < 0.001); however, with the exception of kurtosis of the left lung (r = 0.17), these values were well-corrected with that of the dynamic LPBV images in these values (r = 0.4-0.77, p ≤ 0.001) without kurtosis of left lung (r = 0.17) in all patients. The histogram kurtosis of static LPBV image showed a good correlation with that of dynamic LPBV (r = 0.41-0.77, p < 0.05), especially in patients with PTE.

CONCLUSION

In patients with PTE, the static LPBV image valueswere well correlated with the peak dynamic LPBV images which demonstrated pulmonary artery-dominant flow.

Histogram-pattern analysis of the lung perfused blood volume for assessment of pulmonary thromboembolism

PURPOSE

We aimed to evaluate the usefulness of histograms of lung perfused blood volume (HLPBV) based on the presence of pulmonary thromboembolism (PTE) and the pulmonary embolic burden.

METHODS

A total of 168 patients (55 males; mean age, 62.9 years) underwent contrast-enhanced dual-energy computed tomography (DECT) between January 1 2012 and October 31 2014. Initial DECT images were three-dimensionally reconstructed, and the HLPBV patterns were divided into three types, including the symmetric type (131 patients, 78.0%), gradual type (25 patients, 14.9%), and asymmetric type (12 patients, 7.1%).

RESULTS

Acute PTE was diagnosed in all 12 patients with asymmetric type (100%), 19 of the 25 patients with gradual type (76%) and 24 of the 131 patients with symmetric type (18.3%). HLPBV pattern exhibited correlations with the right/left ventricular diameter ratio (r=0.36, P = 0.007) and CT obstruction index (r=0.63, P < 0.001) in patients with PTEs. When the gradual and asymmetric types were regarded as positive for PTE, the specificity, positive predictive value, negative predictive value, and accuracy were 92.9%, 83.8%, 87.6%, and 81.0%, respectively.

CONCLUSION

Histogram-pattern analysis using DECT might be a useful application to diagnose PTE.

Value of Dual-energy Lung Perfusion Imaging Using a Dual-source CT System for the Pulmonary Embolism

Objective

To investigate the diagnostic value of dual-energy lung perfusion imaging (DEPI) using a dual-source CT system for the pulmonary embolism (PE).

Methods

50 patients in high acute PE prevalence were enrolled to accept the DEPI (lung perfusion image and CTA image of pulmonary artery acquired through the Dual Energy software) and emergent DSA angiography (golden diagnostic criterion).

Results

Patients using CT had significantly reduced examination duration and dosage of contrast agent than those using DSA examination, (P < 0.05). In total, 260 pulmonary arteries and 1020 pulmonary segments were examined through CTA, in which embolisms were identified in 50 lobes of lung, 108 pulmonary segments and 82 sub-segments. Reduction or lack of perfusion was identified through DEPI in 48 lobes of lung (concordance rate of 96.0%), 103 pulmonary segments (concordance rate of 95.4%) and 78 subsegments (concordance rate of 95.1%). The comparison of embolism quantity and morphological characteristics of pulmonary artery between CTA images and DEPI images showed no statistically significant difference.

Conclusion

Better application value can be achieved in the diagnosis of pulmonary embolism by dual-energy lung perfusion imaging using a dual-source CT system.

Clinical Significance of Late Phase of Lung Perfusion Blood Volume (Lung Perfusion Blood Volume) Quantified by Dual-Energy Computed Tomography in Patients With Pulmonary Thromboembolism

PURPOSE

Using dual-energy computed tomography (DECT), we quantified the lung perfusion blood volume (PBV) in the late phase, which may reflect both the pulmonary artery and systemic collateral flow. We then investigated the clinical significance of late-phase lung PBV values.

MATERIALS AND METHODS

We retrospectively studied 206 patients (266 scans) who underwent early-phase and late-phase DECT. The patients were divided into 2 groups depending on whether or not they had pulmonary thromboembolism (PTE) (n=94 and 112). Patients with PTE were further divided into 2 subgroups, depending on whether they had acute PTE or chronic PTE (n=66 and 28). Pulmonary artery enhancement (PAenh) was measured on DECT. We then calculated the [lung PBV/PAenh] ratio in all patients during both the early and late phases for adjustment of timing.

RESULTS

The [late-phase lung PBV/PAenh] ratio was 0.092±0.029 in the group with PTE and 0.108±0.030 in the group without PTE, showing a significant difference between the 2 groups (P<0.0001). The [early-phase lung PBV values/PAenh]/[late-phase lung PBV values/PAenh] ratio was 0.68±0.19 and 0.84±0.20, respectively, also showing a significant difference between the 2 groups (P<0.0001). Finally, the [early-phase lung PBV/PAenh]/[late-phase lung PBV/PAenh] ratio was 0.71±0.19 in patients with acute PTE and 0.56±0.16 in patients with chronic PTE, and there was a significant difference between these 2 subgroups (P=0.0004).

CONCLUSIONS

It may be useful to determine late-phase lung PBV values in patients with PTE, because this parameter may reflect the systemic collateral flow, which is increased in chronic PTE.

Short-Term Subcutaneous Fondaparinux and Oral Edoxaban for Acute Venous Thromboembolism

BACKGROUND

No studies have compared treatment efficacy between subcutaneous (SC) fondaparinux and oral edoxaban, which are categorized as factor Xa inhibitors, for venous thromboembolism (VTE) in the acute phase, and only a limited number of imaging-based quantitative studies have evaluated treatment.Methods and Results:In this open-label, randomized study, 50 patients with acute non-massive pulmonary embolism (PE) and/or deep-vein thrombosis (DVT) were assigned to fondaparinux or edoxaban groups. Lower-limb venous ultrasonography (US), and chest computed tomography (CT) were compared before and 7 days after treatment. Thrombus volume in DVT was calculated using quantitative ultrasound thrombosis (QUT) score on US. For evaluation of PE thrombus volume, lung perfused blood volume (PBV) on CT was calculated. The measurements before and after treatment, respectively, were as follows: QUT score: fondaparinux, 8.1±7.3 to 4.1±4.5; edoxaban, 7.7±6.3 to 4.4±4.3, both significant decreases (P=0.001, P<0.001, respectively); lung PBV: fondaparinux, 32.0±7.8 to 32.1±8.2 HU; edoxaban, 34.2±8.6 to 38.5±11.8 HU (P=0.732, P=0.426, respectively). On subjective CT-based evaluation, all pulmonary artery-related filling defects decreased/disappeared after treatment in both groups (P=NS).

CONCLUSIONS

Both SC fondaparinux and oral edoxaban are effective in acute VTE. Effects on thrombus regression on imaging-based quantitative measurement did not differ between the 2 drugs.

Attenuation-based kV pair selection in dual source dual energy computed tomography angiography of the chest: impact on radiation dose and image quality

OBJECTIVES

The purpose of this study was to evaluate the impact of attenuation-based kilovoltage (kV) pair selection in dual source dual energy (DSDE)-pulmonary embolism (PE) protocol examinations on radiation dose savings and image quality.

METHODS

A prospective study was carried out on 118 patients with suspected PE. In patients in whom attenuation-based kV pair selection selected the 80/140Sn kV pair, the pre-scan 100/140Sn CTDIvol (computed tomography dose index volume) values were compared with the pre-scan 80/140Sn CTDIvol values. Subjective and objective image quality parameters were assessed.

RESULTS

Attenuation-based kV pair selection switched to the 80/140Sn kV pair ("switched" cohort) in 63 out of 118 patients (53%). The mean 100/140Sn pre-scan CTDIvol was 8.8 mGy, while the mean 80/140Sn pre-scan CTDIvol was 7.5 mGy. The average estimated dose reduction for the "switched" cohort was 1.3 mGy (95% CI 1.2, 1.4; p < 0.001), representing a 15% reduction in dose. After adjusting for patient weight, mean attenuation was significantly higher in the "switched" vs. "non-switched" cohorts in all five pulmonary arteries and in all lobes on iodine maps.

CONCLUSIONS

This study demonstrates that attenuation-based kV pair selection in DSDE examination is feasible and can offer radiation dose reduction without compromising image quality.

KEY POINTS

• Attenuation-based kV pair selection in dual energy examination is feasible. • It can offer radiation dose reduction to approximately 50% of patients. • Approximate 15% reduction in radiation dose was achieved using this technique. • The image quality is not compromised by use of attenuation-based kV pair selection.

The role of dual-energy computed tomography in the assessment of pulmonary function

The assessment of pulmonary function, including ventilation and perfusion status, is important in addition to the evaluation of structural changes of the lung parenchyma in various pulmonary diseases. The dual-energy computed tomography (DECT) technique can provide the pulmonary functional information and high resolution anatomic information simultaneously. The application of DECT for the evaluation of pulmonary function has been investigated in various pulmonary diseases, such as pulmonary embolism, asthma and chronic obstructive lung disease and so on. In this review article, we will present principles and technical aspects of DECT, along with clinical applications for the assessment pulmonary function in various lung diseases.

Detection of pulmonary fat embolism with dual-energy CT: an experimental study in rabbits

OBJECTIVES

To evaluate the use of dual-energy CT imaging of the lung perfused blood volume (PBV) for the detection of pulmonary fat embolism (PFE).

METHODS

Dual-energy CT was performed in 24 rabbits before and 1 hour, 1 day, 4 days and 7 days after artificial induction of PFE via the right ear vein. CT pulmonary angiography (CTPA) and lung PBV images were evaluated by two radiologists, who recorded the presence, number, and location of PFE on a per-lobe basis. Sensitivity, specificity, and accuracy of CTPA and lung PBV for detecting PFE were calculated using histopathological evaluation as the reference standard.

RESULTS

A total of 144 lung lobes in 24 rabbits were evaluated and 70 fat emboli were detected on histopathological analysis. The overall sensitivity, specificity and accuracy were 25.4 %, 98.6 %, and 62.5 % for CTPA, and 82.6 %, 76.0 %, and 79.2 % for lung PBV. Higher sensitivity (p < 0.001) and accuracy (p < 0.01), but lower specificity (p < 0.001), were found for lung PBV compared with CTPA. Dual-energy CT can detect PFE earlier than CTPA (all p < 0.01).

CONCLUSION

Dual-energy CT provided higher sensitivity and accuracy in the detection of PFE as well as earlier detection compared with conventional CTPA in this animal model study.

KEY POINTS

• Fat embolism occurs commonly in patients with traumatic bone injury. • Dual-energy CT improves diagnostic performance for pulmonary fat embolism detection. • Dual-energy CT can detect pulmonary fat embolism earlier than CTPA.

Factors affecting the lung perfused blood volume in patients with intrapulmonary clots after anti-coagulation therapy

OBJECTIVES

Factors affecting the improvement in the lung perfused blood volume (LPBV) were evaluated based on the presence of intrapulmonary clots (IPCs) after anti-coagulation therapy using 64-slice dual-energy CT.

MATERIALS AND METHODS

96 patients exhibiting venous thromboembolism underwent initial and repeated LPBV examinations between December 2008 and July 2014. Fifteen patients were excluded due to pulmonary comorbidities, and a total of 81 patients were included in this study. Acute pulmonary embolism (PE) was diagnosed in 46 of the patients (56.7%). LPBV images were three-dimensionally reconstructed with two threshold ranges: 1-120 HU (V120) and 1-5 HU (V5), and the relative value of V5 per V120 expressed as %V5. These values were subsequently compared with indicators of the severity of PE, such as the D-dimer level, heart rate and CT measurements. This study was approved by the local ethics committee.

RESULTS

In patients with IPCs, the D-dimer, V5 and %V5values were significantly larger (p≤0.01) in the initial LPBV, although these differences disappeared in subsequent LPBV after treatment. The right ventricular (RV) diameter, RV/left ventricular (RV/LV) diameter ratio and %V5 values were also significantly reduced, whereas the V5 value did not significantly decrease (p=0.07), but V120 value significantly increased (p<0.001) after treatment. However, in patients with IPCs the change rate in %V5 [(subsequent-initial)/initial %V5] showed a better correlation with that in V5 (r=0.94, p<0.001) rate than that in V120 (r=0.19, p=0.19) after treatment.

CONCLUSIONS

Increased whole lung perfusion (V120) and a decreased low perfusion volume (V5) affect the improvement in the %V5 values after treatment.