Comparative assessment of qualitative and quantitative perfusion with dual-energy CT and planar and SPECT-CT V/Q scanning in patients with chronic thromboembolic pulmonary hypertension

Pulmonary emphysema: the assessment of lung perfusion with Dual-Energy CT and pulmonary scintigraphy

AIM

To assess the correlation of quantitative data of pulmonary Perfused Blood Volume (PBV) on Dual-Energy CT (DECT) datasets in patients with moderate - severe Pulmonary Emphysema (PE) with Lung Perfusion Scintigraphy (LPS) as the reference standard. The secondary endpoints are the correlation between the CT densitometric analysis and the visual assessment of parenchymal destruction with PBV.

MATERIALS AND METHODS

Patients with moderate - severe PE candidate to Lung Volumetric Reduction (LVR), with available a pre-procedural LS and a contrast-enhanced DECT were retrospectively included. DECT studies were performed with a 3rd generation Dual-Source CT and the PBV was obtained with a 3-material decomposition algorithm. The CT densitometric analysis was performed with a dedicated commercial software (Pulmo3D). The Goddard Score was used for visual assessment. The perfusion LS were performed after the administration of albumin macroaggregates labeled with 99mTechnetium. The image revision was performed by two radiologists or nuclear medicine physicians blinded, respectively, to LS and DECT data. The statistical analysis was performed with nonparametric tests.

RESULTS

Thirty-one patients (18 males, median age 69 y.o., interquartile range 62-71 y.o.) with moderate - severe PE (Median Goddard Score 14/20 and 31% of emphysematous parenchyma at quantitative CT) candidate to LVR were retrospectively included. The median enhancement on PBV was 17 HU. Significant correlation coefficients were demonstrated between lung PBV and LS, poor in apical regions (Rho = 0.1-0.2) and fair (Rho = 0.3-0.5) in middle and lower regions. No significant correlations were recorded between the CT densitometric analysis, the visual score, and the PBV.

CONCLUSIONS

Lung perfusion with PBV on DECT is feasible in patients with moderate - severe PE candidate to LVR, and has a poor to fair agreement with LPS.

Image quality of lung perfusion with photon-counting-detector CT: comparison with dual-source, dual-energy CT

PURPOSE

To evaluate the quality of lung perfusion imaging obtained with photon-counting-detector CT (PCD-CT) in comparison with dual-source, dual-energy CT (DECT).

METHODS

Seventy-one consecutive patients scanned with PCD-CT were compared to a paired population scanned with dual-energy on a 3rd-generation DS-CT scanner using (a) for DS-CT (Group 1): collimation: 64 × 0.6 × 2 mm; pitch: 0.55; (b) for PCD-CT (Group 2): collimation: 144 × 0.4 mm; pitch: 1.5; single-source acquisition. The injection protocol was similar in both groups with the reconstruction of perfusion images by subtraction of high- and low-energy virtual monoenergetic images.

RESULTS

Compared to Group 1, Group 2 examinations showed: (a) a shorter duration of data acquisition (0.93 ± 0.1 s vs 3.98 ± 0.35 s; p < 0.0001); (b) a significantly lower dose-length-product (172.6 ± 55.14 vs 339.4 ± 75.64 mGy·cm; p < 0.0001); and (c) a higher level of objective noise (p < 0.0001) on mediastinal images. On perfusion images: (a) the mean level of attenuation did not differ (p = 0.05) with less subjective image noise in Group 2 (p = 0.049); (b) the distribution of scores of fissure visualization differed between the 2 groups (p < 0.0001) with a higher proportion of fissures sharply delineated in Group 2 (n = 60; 84.5% vs n = 26; 26.6%); (c) the rating of cardiac motion artifacts differed between the 2 groups (p < 0.0001) with a predominance of examinations rated with mild artifacts in Group 2 (n = 69; 97.2%) while the most Group 1 examinations showed moderate artifacts (n = 52; 73.2%).

CONCLUSION

PCD-CT acquisitions provided similar morphologic image quality and superior perfusion imaging at lower radiation doses.

CLINICAL RELEVANCE STATEMENT

The improvement in the overall quality of perfusion images at lower radiation doses opens the door for wider applications of lung perfusion imaging in clinical practice.

KEY POINTS

The speed of data acquisition with PCD-CT accounts for mild motion artifacts. Sharply delineated fissures are depicted on PCD-CT perfusion images. High-quality perfusion imaging was obtained with a 52% dose reduction.

A Novel Dual Energy Computed Tomography Score Correlates With Postoperative Outcomes in Chronic Thromboembolic Pulmonary Hypertension

PURPOSE

To compare dual-energy computed tomography (DECT) based qualitative and quantitative parameters in chronic thromboembolic pulmonary hypertension with various postoperative primary and secondary endpoints.

MATERIALS AND METHODS

This was a retrospective analysis of 64 patients with chronic thromboembolic pulmonary hypertension who underwent DECT. First, a clot score was calculated by assigning the following score: pulmonary trunk-5, each main pulmonary artery-4, each lobar-3, each segmental-2, and subsegmental-1 per lobe; the sum total was then calculated. The perfusion defect (PD) score was calculated by assigning 1 point to each segmental PD. The combined score was calculated by adding clot and PD scores. For quantitative evaluation, we calculated perfused blood volume (PBV) (%) of each lung and the sum of both lungs. Primary endpoints included testing association between combined score and total PBV with change in mean pulmonary arterial pressure ([mPAP], change calculated as preop minus postop values). Secondary endpoints included explorative analysis of the correlation between combined score and PBV with change in preoperative and postoperative pulmonary vascular resistance, change in preoperative 6-minute walk distance (6MWD), and immediate postoperative complications such as reperfusion edema, ECMO placement, stroke, death and mechanical ventilation for more than 48 hours, all within 1 month of surgery.

RESULTS

Higher combined scores were associated with larger decreases in mPAP ( =0.27, P =0.036). On average, the decrease in mPAP (pre mPAP-post mPAP) increased by 2.2 mm Hg (95% CI: -0.6, 5.0) with each 10 unit increase in combined score. The correlation between total PBV and change in mPAP was small and not statistically significant. During an exploratory analysis, higher combined scores were associated with larger increases in 6MWD at 6 months postprocedure ( =0.55, P =0.002).

CONCLUSION

Calculation of DECT-based combined score offers potential in the evaluation of hemodynamic response to surgery. This response can also be objectively quantified.

Evaluation of diagnostic accuracy of dual-energy computed tomography in patients with chronic thromboembolic pulmonary hypertension compared to V/Q-SPECT and pulmonary angiogram

Purpose

The relevance of dual-energy computed tomography (DECT) for the detection of chronic thromboembolic pulmonary hypertension (CTEPH) still lies behind V/Q-SPECT in current clinical guidelines. Therefore, our study aimed to assess the diagnostic accuracy of DECT compared to V/Q-SPECT with invasive pulmonary angiogram (PA) serving as the reference standard.

Methods

A total of 28 patients (mean age 62.1 years ± 10.6SD; 18 women) with clinically suspected CTEPH were retrospectively included. All patients received DECT with the calculation of iodine maps, V/Q-SPECT, and PA. Results of DECT and V/Q-SPECT were compared, and the percent of agreement, concordance (utilizing Cohen's kappa), and accuracy (kappa2) to PA were calculated. Furthermore, radiation doses were analyzed and compared.

Results

In total, 18 patients were diagnosed with CTEPH (mean age 62.4 years ± 11.0SD; 10 women) and 10 patients had other diseases. Compared to PA, accuracy and concordance for DECT were superior to V/Q-SPECT in all patients (88.9% vs. 81.3%; k = 0.764 vs. k = 0.607) and in CTEPH patients (82.4% vs. 70.1%; k = 0.694 vs. k = 0.560). Furthermore, the mean radiation dose was significantly lower for DECT vs. V/Q-SPECT (p = 0.0081).

Conclusion

In our patient cohort, DECT is at least equivalent to V/Q-SPECT in diagnosing CTEPH and has the added advantage of significantly lower radiation doses in combination with simultaneous assessment of lung and heart morphology. Hence, DECT should be the subject of ongoing research, and if our results are further confirmed, it should be implemented in future diagnostic PH algorithms at least on par with V/Q-SPECT.

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.

The diagnostic performance of CT pulmonary angiography in the detection of chronic thromboembolic pulmonary hypertension-systematic review and meta-analysis

OBJECTIVES

To examine the diagnostic performance of CT of the pulmonary artery (CTPA) as a potential first-choice imaging modality in patients with pulmonary arterial hypertension and suspected chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS

A systematic review and meta-analysis were conducted in accordance with the PRISMA reporting checklist. Six scientific databases and registers (PubMed, EMBASE, Scopus, Web of Science, Cochrane, ClinicalTrials.gov ) were searched for studies evaluating the diagnostic performance of CTPA in suspected CTEPH in adult patients. Results were pooled separately for studies based on the evaluation of the pulmonary artery and those that relied solely on changes in parenchymal perfusion.

RESULTS

Ten single-center studies with 734 patients were eligible for pooling of the diagnostic performance of CTPA by evaluation of the pulmonary artery. The pooled sensitivity, specificity, PPV, NPV, accuracy, and diagnostic odds ratio (DOR) estimates for CTPA in the detection of CTEPH were 0.98, 0.99, 0.94, 1.00, 0.96, 0.96, and 292. Evaluation of perfusion changes yielded pooled estimates for sensitivity, specificity, PPV, NPV, accuracy, and DOR of 0.99, 0.84, 0.79, 0.98, 0.89, 0.89, and 98 across four studies with 278 patients. Scintigraphy, SPECT, digital subtraction angiography, right heart catheterization, pulmonary endarterectomy, and international guidelines were used to establish the diagnosis.

CONCLUSION

CTPA has high sensitivity and specificity in the detection of CTEPH when the examination is evaluated by expert radiologists. Evaluation of parenchymal perfusion alone is associated with slightly lower specificity. Further research is needed to determine the diagnostic performance of CTPA in excluding CTEPH in general radiology departments.

KEY POINTS

• CT pulmonary angiography (CTPA) is recommended in the diagnostic workup of chronic thromboembolic pulmonary hypertension (CTEPH). • CTPA has high sensitivity and specificity in the detection of CTEPH when evaluated by an expert radiologist. • Evaluation of changes in parenchymal perfusion alone is associated with slightly lower specificity. • Little is known about the diagnostic performance of CTPA in the detection of CTEPH in general radiology departments.

Dual energy CT based scoring in chronic thromboembolic pulmonary hypertension and correlation with clinical and hemodynamic parameters: a retrospective cross-sectional study

BACKGROUND

We used a dual energy computed tomography (DECT) based scoring system in patients with chronic thromboembolic pulmonary hypertension (CTEPH) and correlated it with functional and hemodynamic parameters.

METHODS

This was a retrospective study on 78 patients with CTEPH who underwent DECT. First, clot burden score was calculated by assigning a following score: pulmonary trunk-5, each main pulmonary artery-4, each lobar-3, each segmental-2, and subsegmental-1 per lobe; sum total was then calculated. Perfusion defect (PD) score was calculated by assigning 1 point to each segmental PD. Combined score was calculated by adding the clot burden and PD score. All three scores were correlated with clinical and hemodynamic parameters that included New York Heart Association (NYHA) functional class, 6-minute walk distance (6MWT) in feet, forced expiratory volume in one second (FEV1), forced vital capacity (FVC), diffusing capacity of the lung for carbon monoxide (DLCO), pulmonary arterial pressure (PAP) [systolic PAP (sPAP), diastolic PAP (dPAP) and mean PAP (mPAP)], pulmonary vascular resistance (PVR), right atrial pressure, cardiac output, and cardiac index.

RESULTS

Clot burden score, PD score, and combined score all positively correlated with sPAP (0.25, 0.34, 0.34), PVR (0.27, 0.30, 0.34), and mPAP (0.28, 0.31, 0.36). There was no statistically significant correlation of clot burden score, PD score and combined score with 6MWT, % predicted 6MWT, FEV1, FEV1%, FVC, FVC%, DLCO% and NYHA functional class.

CONCLUSIONS

DECT based scoring in CTEPH is feasible and correlates positively with sPAP, mPAP and PVR. Combined score has the highest magnitude of correlation.

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.

Pilot study for comparative assessment of dual-energy computed tomography and single-photon emission computed tomography V/Q scanning for lung perfusion evaluation in infants

OBJECTIVE

To evaluate clinical applications of dual-energy computed tomography (DECT) in pediatric-specific lung diseases and compare ventilation and perfusion findings with those from single-photon emission computed tomography (SPECT-CT) V/Q.

METHODS

All patients at our institution who underwent exams using both techniques within a 3-month period were included in this study. Two readers independently described findings for DECT, and two other readers independently analyzed the SPECT-CT V/Q scan data. All findings were compared between readers and disagreements were reassessed and resolved by consensus. Inter-modality agreements are described throughout this study.

RESULTS

Eight patients were included for evaluation. The median age for DECT scanning was 3.5 months (IQR = 2). Five of these patients were scanned for both DECT and SPECT-CT V/Q studies the same day, and three had a time gap of 7, 65, and 94 days between studies. The most common indications were chronic lung disease (5/8; 63%) and pulmonary hypertension (6/8; 75%). DECT and SPECT-CT V/Q identified perfusion abnormalities in concordant lobes in most patients (7/8; 88%). In one case, atelectasis limited DECT perfusion assessment. Three patients ultimately underwent lobectomy with corresponding perfusion abnormalities identified by all reviewers on both DECT and SPECT-CT V/Q in all resected lobes.

CONCLUSION

DECT is a feasible technique that could be considered as an alternative for SPECT-CT V/Q for lung perfusion evaluation in infants.

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.

A Feasibility Study on Using Single-Photon Emission Computed Tomography Pulmonary Perfusion/Ventilation Imaging for the Diagnosis of Chronic Thromboembolic Pulmonary Hypertension and Patient Risk Assessment

Objective

The study is designed to evaluate the diagnostic ability of single-photon emission computed tomography (SPECT) pulmonary ventilation/perfusion (V/Q) imaging in patients with chronic thromboembolic pulmonary hypertension (CTEPH) and investigate its feasibility in assessing patient risk.

Methods

A total of 83 patients suspected of having CTEPH who received V/Q tomography were retrospectively analyzed. The consistency between SPECT V/Q imaging and pulmonary angiography was compared to investigate the correlation between the percentage of pulmonary perfusion defect score (PPDs%) and the hemodynamic indices. Patients were grouped according to the pulmonary arterial hypertension risk stratification, and the V/Q imaging results were compared between different groups.

Results

For the 1494 pulmonary segments of the 83 patients, the sensitivity, specificity, and accuracy of identifying pulmonary segments with defects using V/Q imaging was 87.05%, 82.78% (668/807), and 84.74% (1266/1494), respectively. The average PPDs% (58.8 ± 12.6%) was positively correlated with the mean pulmonary arterial pressure (mPAP), pulmonary vascular resistance (PVR), and right ventricular pressure (RVP; r =0.316, 0.318, and 0.432, respectively; P < 0.05) and negatively correlated with the six-minute walk distance (6MWD; r = −0.309; P < 0.05). There were 37 patients in the low-risk group and 46 in the medium-high-risk group. The number of pulmonary segments with perfusion defects (NPSPDs) and PPDs% were higher in the medium-high risk than in the low-risk group (t = −6.721, −5.032; P < 0.05). In the low- and medium-high-risk groups, the cut-off values for the NPSPDs (7.2 ± 2.1 and 10.2 ± 2.0) and PPDs% (51.9 ± 11.1% and 64.3 ± 11.1%,) were 8.5 and 61.25%, respectively.

Conclusion

SPECT V/Q imaging achieved an accurate diagnosis of CTEPH. The semi-quantitative analysis index (PPDs%) was correlated with the hemodynamic indices and 6MWD. SPECT V/Q could be used for the preoperative risk assessment of patients with CTEPH.

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 (Zeff ) 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 (Zeff ) spatial distribution was studied to show that the desired quantitative PBV maps are determined by the spatial maps of Zeff 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 Zeff 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 (PBViodine ) 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 PBViodine 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.

Dual-Energy Computed Tomography Compared to Lung Perfusion Scintigraphy to Assess Pulmonary Perfusion in Patients Screened for Endoscopic Lung Volume Reduction

BACKGROUND

Endoscopic lung volume reduction (ELVR) using one-way endobronchial valves is a technique to reduce hyperinflation in patients with severe emphysema by inducing collapse of a severely destroyed pulmonary lobe. Patient selection is mainly based on evaluation of emphysema severity on high-resolution computed tomography and evaluation of lung perfusion with perfusion scintigraphy. Dual-energy contrast-enhanced CT scans may be useful for perfusion assessment in emphysema but has not been compared against perfusion scintigraphy.

AIMS

The aim of the study was to compare perfusion distribution assessed with dual-energy contrast-enhanced computed tomography and perfusion scintigraphy.

MATERIAL AND METHODS

Forty consecutive patients with severe emphysema, who were screened for ELVR, were included. Perfusion was assessed with 99mTc perfusion scintigraphy and using the iodine map calculated from the dual-energy contrast-enhanced CT scans. Perfusion distribution was calculated as usually for the upper, middle, and lower thirds of both lungs with the planar technique and the iodine overlay.

RESULTS

Perfusion distribution between the right and left lung showed good correlation (r = 0.8). The limits of agreement of the mean absolute difference in percentage perfusion per region of interest were 0.75-5.6%. The upper lobes showed more severe perfusion reduction than the lower lobes. Mean difference in measured pulmonary perfusion ranged from -2.8% to 2.3%. Lower limit of agreement ranged from -8.9% to 4.6% and upper limit was 3.3-10.0%.

CONCLUSION

Quantification of perfusion distribution using planar 99mTc perfusion scintigraphy and iodine overlays calculated from dual-energy contrast-enhanced CTs correlates well with acceptable variability.

ERS statement on chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare complication of acute pulmonary embolism, either symptomatic or not. The occlusion of proximal pulmonary arteries by fibrotic intravascular material, in combination with a secondary microvasculopathy of vessels <500 µm, leads to increased pulmonary vascular resistance and progressive right heart failure. The mechanism responsible for the transformation of red clots into fibrotic material remnants has not yet been elucidated. In patients with pulmonary hypertension, the diagnosis is suspected when a ventilation/perfusion lung scan shows mismatched perfusion defects, and confirmed by right heart catheterisation and vascular imaging. Today, in addition to lifelong anticoagulation, treatment modalities include surgery, angioplasty and medical treatment according to the localisation and characteristics of the lesions.This statement outlines a review of the literature and current practice concerning diagnosis and management of CTEPH. It covers the definitions, diagnosis, epidemiology, follow-up after acute pulmonary embolism, pathophysiology, treatment by pulmonary endarterectomy, balloon pulmonary angioplasty, drugs and their combination, rehabilitation and new lines of research in CTEPH.It represents the first collaboration of the European Respiratory Society, the International CTEPH Association and the European Reference Network-Lung in the pulmonary hypertension domain. The statement summarises current knowledge, but does not make formal recommendations for clinical practice.

Pulmonary Functional Imaging: Part 2-State-of-the-Art Clinical Applications and Opportunities for Improved Patient Care

Pulmonary functional imaging may be defined as the regional quantification of lung function by using primarily CT, MRI, and nuclear medicine techniques. The distribution of pulmonary physiologic parameters, including ventilation, perfusion, gas exchange, and biomechanics, can be noninvasively mapped and measured throughout the lungs. This information is not accessible by using conventional pulmonary function tests, which measure total lung function without viewing the regional distribution. The latter is important because of the heterogeneous distribution of virtually all lung disorders. Moreover, techniques such as hyperpolarized xenon 129 and helium 3 MRI can probe lung physiologic structure and microstructure at the level of the alveolar-air and alveolar-red blood cell interface, which is well beyond the spatial resolution of other clinical methods. The opportunities, challenges, and current stage of clinical deployment of pulmonary functional imaging are reviewed, including applications to chronic obstructive pulmonary disease, asthma, interstitial lung disease, pulmonary embolism, and pulmonary hypertension. Among the challenges to the deployment of pulmonary functional imaging in routine clinical practice are the need for further validation, establishment of normal values, standardization of imaging acquisition and analysis, and evidence of patient outcomes benefit. When these challenges are addressed, it is anticipated that pulmonary functional imaging will have an expanding role in the evaluation and management of patients with lung disease.

Chronic thromboembolic pulmonary hypertension: evaluation of V/Q SPECT/CT and V/Q Quotient SPECT findings with postoperative results of pulmonary endarterectomy

OBJECTIVES

We aimed to perform a comparison between V/Q single-photon emission computed tomography/computed tomography (SPECT/CT) and V/Q Quotient single-photon emission computerized tomography (SPECT) in the detection of chronic thromboembolic pulmonary hypertension (CTEPH) and in depicting the extent of the disease on per-segment basis in patients with CTEPH.

METHODS

Between January 2015 and November 2019, a total of 412 patients with pulmonary hypertension secondary to CTEPH at the preoperative assessment underwent pulmonary endarterectomy (PEA), of whom 92 consecutive patients with their V/Q SPECT/CT scans have been performed in our institution prior to PEA were included in this study. Histopathological findings and post-PEA fully resected surgical specimens were used as the reference standard.

RESULTS

On a per-patient basis analysis, V/Q SPECT/CT and V/Q Quotient SPECT both revealed CTEPH in the same 85 of the 92 patients (κ = 1) with a detection rate of 92.4%. In six of these patients, chronic thromboembolic disease could not be reported on both of these two methods due to extensive 'matched' V/Q defects. On a per-segment basis analysis, V/Q SPECT/CT and V/Q Quotient SPECT showed a sensitivity of 75.8 and 73.1%, respectively. Correlation analysis results showed a significant correlation (κ = 0.933) between these two methods on a per-segment basis analysis.

CONCLUSION

In the light of histopathological findings and post-PEA surgical specimen examinations, the results of the present study indicated that both V/Q SPECT/CT and V/Q Quotient SPECT showed relatively high efficacy for the detection of CTEPH on per-patient and per-segment bases with an excellent agreement.

Balloon Pulmonary Angioplasty: State of the Art

Balloon pulmonary angioplasty (BPA) is a novel technique for the treatment of chronic thromboembolic pulmonary hypertension. While cardiologists need no introduction to the concept of balloon angioplasty, BPA has its own particular challenges. This article aims to provide the reader with an overview of BPA, starting with an introduction to chronic thromboembolic disease (CTED), the standard management of chronic thromboembolic pulmonary hypertension (CTEPH), technical challenges faced when performing BPA and the evidence base supporting its use. The second part of the article will focus on the future of BPA, in particular the areas where research is required to establish an evidence base to justify the role of BPA in CTEPH and CTED treatment.

Correlation Between Perfusion Abnormalities Extent in Ventilation/Perfusion SPECT/CT with Hemodynamic Parameters in Patients with Chronic Thromboembolic Pulmonary Hypertension

Objectives

Chronic thromboembolic pulmonary hypertension (CTEPH) is a type of pulmonary hypertension with persistent pulmonary vascular obstruction and exercise intolerance, which may benefit from pulmonary endarterectomy (PEA). Ventilation/perfusion (V/Q) scan is the preferred screening test of CTEPH, which can be used to assess the anatomical extent of the disease. This study aimed to analyze the correlation between the extent of mismatched Q defects in V/Q single photon emission computed tomography/computed tomography (SPECT/CT) with preoperative clinical and hemodynamic parameters in patients with CTEPH.

Methods

A total of 102 patients with CTEPH prior to PEA having V/Q SPECT/CT scans were retrospectively reviewed. Age, gender, New York Heart Association classification, intraoperative right-sided heart catheterization (mPAP and PVR), and 6-minute walk test (6MWT) findings were obtained from clinical records of patients.

Results

Linear regression analysis showed a significant but weak correlation between the preoperative mPAP and PVR with the extent of mismatched Q defects in V/Q SPECT/CT (rs=0.09474 with p=0.0016 and rs=0.045 with p=0.045, respectively). No significant correlation was found between 6MWT and extent of mismatched Q defects in V/Q SPECT/CT (p>0.05).

Conclusion

A quantitative assessment of Q defects on V/Q SPECT/CT might provide information about hemodynamic parameters in patients with CTEPH.

Imaging of pulmonary hypertension in adults: a position paper from the Fleischner Society

Pulmonary hypertension (PH) is defined by a mean pulmonary artery pressure greater than 20 mmHg and classified into five different groups sharing similar pathophysiologic mechanisms, haemodynamic characteristics, and therapeutic management. Radiologists play a key role in the multidisciplinary assessment and management of PH. A working group was formed from within the Fleischner Society based on expertise in the imaging and/or management of patients with PH, as well as experience with methodologies of systematic reviews. The working group identified key questions focusing on the utility of CT, MRI, and nuclear medicine in the evaluation of PH: a) Is noninvasive imaging capable of identifying PH? b) What is the role of imaging in establishing the cause of PH? c) How does imaging determine the severity and complications of PH? d) How should imaging be used to assess chronic thromboembolic PH before treatment? e) Should imaging be performed after treatment of PH? This systematic review and position paper highlights the key role of imaging in the recognition, work-up, treatment planning, and follow-up of PH.

Imaging of Pulmonary Hypertension in Adults: A Position Paper from the Fleischner Society

Pulmonary hypertension (PH) is defined by a mean pulmonary artery pressure greater than 20 mm Hg and classified into five different groups sharing similar pathophysiologic mechanisms, hemodynamic characteristics, and therapeutic management. Radiologists play a key role in the multidisciplinary assessment and management of PH. A working group was formed from within the Fleischner Society based on expertise in the imaging and/or management of patients with PH, as well as experience with methodologies of systematic reviews. The working group identified key questions focusing on the utility of CT, MRI, and nuclear medicine in the evaluation of PH: (a) Is noninvasive imaging capable of identifying PH? (b) What is the role of imaging in establishing the cause of PH? (c) How does imaging determine the severity and complications of PH? (d) How should imaging be used to assess chronic thromboembolic PH before treatment? (e) Should imaging be performed after treatment of PH? This systematic review and position paper highlights the key role of imaging in the recognition, work-up, treatment planning, and follow-up of PH. This article is a simultaneous joint publication in Radiology and European Respiratory Journal. The articles are identical except for stylistic changes in keeping with each journal's style. Either version may be used in citing this article. © 2021 RSNA and the European Respiratory Society. Online supplemental material is available for this article.

From Early Morphometrics to Machine Learning-What Future for Cardiovascular Imaging of the Pulmonary Circulation?

Imaging plays a cardinal role in the diagnosis and management of diseases of the pulmonary circulation. Behind the picture itself, every digital image contains a wealth of quantitative data, which are hardly analysed in current routine clinical practice and this is now being transformed by radiomics. Mathematical analyses of these data using novel techniques, such as vascular morphometry (including vascular tortuosity and vascular volumes), blood flow imaging (including quantitative lung perfusion and computational flow dynamics), and artificial intelligence, are opening a window on the complex pathophysiology and structure-function relationships of pulmonary vascular diseases. They have the potential to make dramatic alterations to how clinicians investigate the pulmonary circulation, with the consequences of more rapid diagnosis and a reduction in the need for invasive procedures in the future. Applied to multimodality imaging, they can provide new information to improve disease characterization and increase diagnostic accuracy. These new technologies may be used as sophisticated biomarkers for risk prediction modelling of prognosis and for optimising the long-term management of pulmonary circulatory diseases. These innovative techniques will require evaluation in clinical trials and may in themselves serve as successful surrogate end points in trials in the years to come.

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.

Acute pulmonary embolism multimodality imaging prior to endovascular therapy

The manuscript discusses the application of CT pulmonary angiography, ventilation–perfusion scan, and magnetic resonance angiography to detect acute pulmonary embolism and to plan endovascular therapy. CT pulmonary angiography offers high accuracy, speed of acquisition, and widespread availability when applied to acute pulmonary embolism detection. This imaging modality also aids the planning of endovascular therapy by visualizing the number and distribution of emboli, determining ideal intra-procedural catheter position for treatment, and signs of right heart strain. Ventilation–perfusion scan and magnetic resonance angiography with and without contrast enhancement can also aid in the detection and pre-procedural planning of endovascular therapy in patients who are not candidates for CT pulmonary angiography.

Head-to-head comparison of lung perfusion with dual-energy CT and SPECT-CT

PURPOSE

To compare the quantitative and qualitative lung perfusion data acquired with dual energy CT (DECT) to that acquired with a large field-of-view cadmium-zinc-telluride camera single-photon emission CT coupled to a CT system (SPECT-CT).

MATERIALS AND METHODS

A total of 53 patients who underwent both dual-layer DECT angiography and perfusion SPECT-CT for pulmonary hypertension or pre-operative lobar resection surgery were retrospectively included. There were 30 men and 23 women with a mean age of 65.4±17.5 (SD)years (range: 18-88years). Relative lobar perfusion was calculated by dividing the amount (of radiotracer or iodinated contrast agent) per lobe by the total amount in both lungs. Linear regression, Bland-Altman analysis, and Pearson's correlation coefficient were also calculated. Kappa test was used to test agreements in morphology and severity of perfusion defects assessed on SPECT-CT and on DECT iodine maps with a one-month interval. Wilcoxon rank sum test was used to compare the sharpness of perfusion defects and radiation dose among modalities.

RESULTS

Strong correlations for relative lobar perfusion using linear regression analysis and Pearson's correlation coefficient (r=0.93) were found. Bland-Altman analysis revealed a -0.10 bias, with limits of agreement between [-6.01; 5.81]. With respect to SPECT- CT as standard of reference, the sensitivity, specificity, PPV, NPV, accuracy for lobar perfusion defects were 89.4% (95% 
CI: 82.6-93.4%), 96.5% (95% CI: 92.1-98.5%), 95.6% (95% CI: 
90.9-97.8%), 91.4% (95% CI: 85.6-94.9%) and 93.0% (95% CI: 
87.6-96.1%) respectively. High level of agreement was found for morphology and severity of perfusion defects between modalities (Kappa=0.84 and 0.86 respectively) and on DECT images among readers (Kappa=0.94 and 0.89 respectively). A significantly sharper delineation of perfusion defects was found on DECT images (P<0.0001) using a significantly lower equivalent dose of 4.1±2.3 (SD) mSv (range: 1.9-11.85mSv) compared to an equivalent dose of 5.3±1.1 (SD) mSv (range: 2.8-7.3mSv) for SPECT-CT, corresponding to a 21.2% dose reduction (P=0.0004).

CONCLUSION

DECT imaging shows strong quantitative correlations and qualitative agreements with SPECT-CT for the evaluation of lung perfusion.

Surgical and Percutaneous Interventions for Chronic Thromboembolic Pulmonary Hypertension

The treatment of chronic thromboembolic pulmonary hypertension has expanded considerably. The ability to endarterectomize chronic thromboembolic material, the availability of pulmonary hypertension medical therapy to treat inoperable chronic thromboembolic pulmonary hypertension and/or residual pulmonary hypertension, and the rebirth of pulmonary balloon angioplasty have changed the management landscape. Patient selection requires a multidisciplinary evaluation at an experienced center. What is inoperable chronic thromboembolic pulmonary hypertension to one group may be operable chronic thromboembolic pulmonary hypertension to another. The ultimate challenge then becomes which intervention provides the optimal long-term outcome for any individual patient.

Utility of Iodine Density Perfusion Maps From Dual-Energy Spectral Detector CT in Evaluating Cardiothoracic Conditions: A Primer for the Radiologist

OBJECTIVE. The purpose of this article is to outline the utility of iodine density maps for evaluating cardiothoracic disease and abnormalities. Multiple studies have shown that the variety of images generated from dual-energy spectral detector CT (SDCT) improve identification of cardiothoracic conditions. CONCLUSION. Understanding the technique of SDCT and being familiar with the features of different cardiothoracic conditions on iodine density map images help the radiologist make a better diagnosis.

CTPA, DECT, MRI, V/Q Scan, and SPECT/CT V/Q for the noninvasive diagnosis of chronic thromboembolic pulmonary hypertension: A protocol for systemic review and network meta-analysis of diagnostic test accuracy

BACKGROUND

To determine the diagnostic accuracy of techniques with chronic thromboembolic pulmonary hypertension (CTEPH) patients via a protocol for systemic review and network meta-analysis.

METHODS

We will search PubMed, EMBASE, Web of Science, and Google Scholar from inception to October 1, 2018. The reference lists of the retrieved articles are also consulted. Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) will be used to assess the risk of bias in each study. The direct meta-analyses, network meta-analyses, and ranking of competing diagnostic tests will be used by STATA 12.0 and WINBUGS 1.4. Heterogeneity and inconsistency are assessed.

RESULTS

This study is ongoing, will be submitted to a peer-reviewed journal publication once completed.

CONCLUSION

This study will provide a comprehensive evidence summary of diagnostic test accuracy in detecting the CTEPH, and can help patients and clinicians to select appropriate or best diagnostic test.

ETHICS AND COMMUNICATION

No ethical approval and patient consent are required, because it is based on published researches.

PROSPERO REGISTRATION NUMBER

CRD42019121279.