Investigation of myocardial extracellular volume fraction in heart failure patients using iodine map with rapid-kV switching dual-energy CT: Segmental comparison with MRI T1 mapping

Pre-procedural imaging with cardiac computed tomography for endo-epicardial ventricular tachycardia ablation

BACKGROUND

Studies evaluating the systematic use of cardiac computer tomography (CCT) for the pre-procedural assessment of myocardial fibrosis are limited and their implementation in the electrophysiology workflow has not been extensively described.

OBJECTIVE

To explore the degree of concordance between cardiac fibrosis evaluated by CCT compared to electroanatomical mapping (EAM) in patients undergoing endo-epicardial ventricular tachycardia (VT) ablation.

METHODS

From November-2017 to December-2021, patients undergoing endo-epicardial VT catheter ablation (CA) with CCT as the only source of pre-procedural scar assessment were prospectively enrolled. After image integration, myocardial fibrosis detected with CCT was compared with low voltage areas identified by endo-epicardial EAM. Post-procedural VT recurrences of this approach were evaluated after at least one-year follow-up.

RESULTS

35 patients (mean age 60.7±13.2 years, 94.2% males) were enrolled. The most common underlying arrhythmic substrate was dilated cardiomyopathy (48.6%). CCT was employed for contraindications to cardiac magnetic resonance, as unstable VTs (31.4%) or non-conditional ICDs (28.8%), but also for patients' and operators' preferences (14.3%-25.7%). Myocardial fibrosis was correctly identified by CCT and EAM, with strong agreement between these two techniques, both overall (Cohen's Kappa for agreement=0.933) and in per-segment analysis (K ranging from 0.796 to 1.0). Ischemic patients showed the best correlation (K=1.000) while myocarditis showed the worst (K=0.750). After a median follow-up of 14 [12-24] months, 1-year freedom from recurrences was achieved in 74.3% patients; overall freedom from recurrences was 60.0%.

CONCLUSIONS

A CCT-based pre-procedural assessment pre-VT ablation is feasible, showing high diagnostic concordance with EAM in detecting myocardial fibrosis.

Prognostic value of measurement of myocardial extracellular volume using dual-energy CT in heart failure with preserved ejection fraction

Diffuse myocardial fibrosis is associated with adverse outcomes in heart failure with preserved ejection fraction (HFpEF). Dual-energy CT (DECT) can noninvasively assess myocardial fibrosis by quantification of extracellular volume (ECV) fraction. This study evaluated the association between ECV measured by DECT and clinical outcomes in patients with HFpEF. 125 hospitalized HFpEF patients were enrolled in this retrospective cohort study. ECV was measured using DECT with late iodine enhancement. The composite endpoint was defined as HFpEF hospitalization and all-cause mortality during the follow-up. During the median follow-up of 10.4 months, 34 patients (27.20%) experienced the composite outcomes, including 5 deaths; and 29 HFpEF hospitalizations. The higher DECT-ECV group had higher rates of composite outcomes than the low ECV group (log-rank X2 = 6.818, P = 0.033). In multivariate Cox regression analysis, the ECV (HR 1.17, 95% CI 1.06-1.30, P = 0.001) and NT-pro BNP (HR 2.83, 95% CI 1.16-6.88, P = 0.022) were independent risk factors for the adverse outcomes. Myocardial ECV measured using DECT was an independent risk factor for adverse outcomes in patients with HFpEF.

Imaging biomarkers in cardiac CT: moving beyond simple coronary anatomical assessment

Cardiac computed tomography angiography (CCTA) is considered the standard non-invasive tool to rule-out obstructive coronary artery disease (CAD). Moreover, several imaging biomarkers have been developed on cardiac-CT imaging to assess global CAD severity and atherosclerotic burden, including coronary calcium scoring, the segment involvement score, segment stenosis score and the Leaman-score. Myocardial perfusion imaging enables the diagnosis of myocardial ischemia and microvascular damage, and the CT-based fractional flow reserve quantification allows to evaluate non-invasively hemodynamic impact of the coronary stenosis. The texture and density of the epicardial and perivascular adipose tissue, the hypodense plaque burden, the radiomic phenotyping of coronary plaques or the fat radiomic profile are novel CT imaging features emerging as biomarkers of inflammation and plaque instability, which may implement the risk stratification strategies. The ability to perform myocardial tissue characterization by extracellular volume fraction and radiomic features appears promising in predicting arrhythmogenic risk and cardiovascular events. New imaging biomarkers are expanding the potential of cardiac CT for phenotyping the individual profile of CAD involvement and opening new frontiers for the practice of more personalized medicine.

Feasibility of spectral CT-derived extracellular volume fraction for differentiating aldosterone-producing from nonfunctioning adrenal nodules

OBJECTIVE

To assess the feasibility of spectral CT-derived extracellular volume (ECV) for differentiating aldosterone-producing nodules (APN) from nonfunctioning adrenal nodules (NFN).

METHODS

Sixty-nine patients with biochemically and histologically confirmed unilateral APN (34) and NFN (35) as well as 23 patients with bilateral APN (19) and NFN (27) confirmed biochemically and by adrenal vein sampling (AVS) were enrolled in this retrospective study from October 2020 to April 2022. All patients underwent contrast-enhanced spectral CT of the adrenal glands with a 10-min delayed phase. The haematocrit level was measured within 2 days of CT. An iodine density map was derived from the delayed CT. The ECV fractions of the APN and NFN were calculated and compared in the test cohort of 69 patients with unilateral adrenal nodules. The optimal cut-off value was determined to evaluate the diagnostic efficacy of the ECV fraction for differentiating APN from NFN in the validation cohort of 23 patients with bilateral adrenal nodules.

RESULTS

The ECV fractions of the APN (11.17 ± 4.57%) were significantly lower (p < 0.001) than that of the NFN (24.79 ± 6.01%) in the test cohort. At cut-off ECV value of 17.16%, the optimal area under the receiver operating characteristic curve was 0.974 (95% confidence interval: 0.942-1) with 91.4% sensitivity, 93.9% specificity, and 92.8% accuracy in the test cohort and 89.5% sensitivity, 96.3% specificity, and 93.5% accuracy in the validation cohort for differentiating APN from NFN.

CONCLUSION

The spectral CT-derived ECV fraction can differentiate APN from NFN with high diagnostic performance.

CLINICAL RELEVANCE STATEMENT

Spectral CT-derived extracellular volume fraction could accurately differentiate between adrenal aldosterone-producing nodules and nonfunctioning nodules. It might serve as a noninvasive alternative to adrenal vein sampling in primary aldosteronism patients with bilateral adrenal nodules.

KEY POINTS

• Conventional CT cannot differentiate aldosterone-producing adrenal nodules from nonfunctioning nodules. • Extracellular volume of adrenal aldosterone-producing nodules was significantly lower than that of nonfunctioning nodules and normal adrenal glands. It can accurately differentiate between aldosterone-producing and nonfunctioning adrenal nodules. • Extracellular volume may be a novel, noninvasive biomarker alternative to adrenal vein sampling for determining the functional status of bilateral adrenal nodules in patients with primary aldosteronism.

Prediction of pancreatic fibrosis by dual-energy CT-derived extracellular volume fraction: Comparison with MRI

OBJECTIVES

To investigate the correlation between dual-energy CT (DECT) and MRI measurements of the extracellular volume fraction (ECV) and to assess the accuracy of both methods in predicting pancreatic fibrosis (PF).

METHODS

We retrospectively analyzed 43 patients who underwent pancreatectomy and preoperative pancreatic DECT and MRI between November 2018 and May 2022. The ECV was calculated using the T1 relaxation time (for MR-ECV) or absolute enhancement (for DECT-ECV) at equilibrium phase (180 s after contrast injection in our study). Pearson coefficient and Bland-Altman analysis were used to compare the correlation between the two ECVs, Spearman correlations were used to investigate the association between imaging parameters and PF, Receiver operating characteristic (ROC) curves were used to assess the diagnostic performance of the ECVs for advanced fibrosis (F2-F3), and multivariate logistic regression analysis was used to examine the relationship between PF and imaging parameters.

RESULTS

There was a strong correlation between DECT- and MR-derived ECVs (r = 0.948; p < 0.001). The two ECVs were positively correlated with PF (DECT: r = 0.647, p < 0.001; MR: r = 0.614, p < 0.001), and the mean values were 0.34 ± 0.08 (range: 0.22-0.62) and 0.35 ± 0.09 (range: 0.24-0.66), respectively. The area under the operating characteristic curve (AUC) for subjects with advanced fibrosis diagnosed by ECV was 0.86 for DECT-ECV and 0.87 for MR-ECV. Multivariate logistic regression analysis showed that the DECT-ECV was an independent predictor of PF.

CONCLUSIONS

The ECV could be an effective predictor of histological fibrosis, and DECT is equivalent to MRI for characterizing pancreatic ECV changes.

CT for the evaluation of myocardial extracellular volume with MRI as reference: a systematic review and meta-analysis

OBJECTIVE

Myocardial extracellular volume (ECV) fraction is an important imaging biomarker in clinical decision-making. CT-ECV is a potential alternative to MRI for ECV quantification. We conducted a meta-analysis to comprehensively assess the reliability of CT for ECV quantification with MRI as a reference.

METHODS

We systematically searched PubMed, EMBASE, and the Cochrane Library for relevant articles published since the establishment of the database in July 2022. The articles comparing CT-ECV with MRI as a reference were included. Meta-analytic methods were applied to determine the pooled weighted bias, limits of agreement (LOA), and correlation coefficient (r) between CT-ECV and MRI-ECV.

RESULTS

Seventeen studies with a total of 459 patients and 2231 myocardial segments were included. The pooled mean difference (MD), LOA, and r for ECV quantification at the per-patient level was (0.07%; 95% LOA: - 0.42 to 0.55%) and 0.89 (95% CI: 0.86-0.91), respectively, while on the per-segment level was (0.44%; 95% LOA: 0.16-0.72%) and 0.84 (95% CI: 0.82-0.85), respectively. The pooled r from studies with the ECViodine method for ECV quantification was significantly higher compared to those with the ECVsub method (0.94 (95% CI: 0.91-0.96) vs. 0.84 (95% CI: 0.80-0.88), respectively, p = 0.03). The pooled r from septal segments was significantly higher than those from non-septal segments (0.88 (95% CI: 0.86-0.90) vs. 0.76 (95% CI: 0.71-0.90), respectively, p = 0.009).

CONCLUSION

CT showed a good agreement and excellent correlation with MRI for ECV quantification and is a potentially attractive alternative to MRI.

CLINICAL RELEVANCE STATEMENT

The myocardial extracellular volume fraction can be acquired using a CT scan, which is not only a viable alternative to myocardial extracellular volume fraction derived from MRI but is also less time-consuming and costly for patients.

KEY POINTS

• Noninvasive CT-ECV is a viable alternative to MRI-ECV for ECV quantification. • CT-ECV using the ECViodine method showed more accurate myocardial ECV quantification than ECVsub. • Septal myocardial segments showed lower measurement variability than non-septal segments for the ECV quantification.

Microvascular Myocardial Ischemia in Patients With Diabetes Without Obstructive Coronary Stenosis and Its Association With Angina

OBJECTIVE

To investigate the incidence of microvascular myocardial ischemia in diabetic patients without obstructive coronary artery disease (CAD) and its relationship with angina.

MATERIALS AND METHODS

Diabetic patients and an intermediate-to-high pretest probability of CAD were prospectively enrolled. Non-diabetic patients but with an intermediate-to-high pretest probability of CAD were retrospectively included as controls. The patients underwent dynamic computed tomography-myocardial perfusion imaging (CT-MPI) and coronary computed tomography angiography (CCTA) to quantify coronary stenosis, myocardial blood flow (MBF), and extracellular volume (ECV). The proportion of patients with microvascular myocardial ischemia, defined as any myocardial segment with a mean MBF ≤ of 100 mL/min/100 mL, in patients without obstructive CAD (Coronary Artery Disease-Reporting and Data System [CAD-RADS] grade 0-2 on CCTA) was determined. Various quantitative parameters of the patients with and without diabetes without obstructive CAD were compared. Multivariable analysis was used to determine the association between microvascular myocardial ischemia and angina symptoms in diabetic patients without obstructive CAD.

RESULTS

One hundred and fifty-two diabetic patients (mean age: 59.7 ± 10.7; 77 males) and 266 non-diabetic patients (62.0 ± 12.3; 167 males) were enrolled; CCTA revealed 113 and 155 patients without obstructive CAD, respectively. For patients without obstructive CAD, the mean global MBF was significantly lower for those with diabetes than for those without (152.8 mL/min/100 mL vs. 170.4 mL/min/100 mL, P < 0.001). The mean ECV was significantly higher for diabetic patients (27.2% vs. 25.8%, P = 0.009). Among the patients without obstructive CAD, the incidence of microvascular myocardial ischemia (36.3% [41/113] vs. 10.3% [16/155], P < 0.001) and interstitial fibrosis (69.9% [79/113] vs. 33.3% [8/24], P = 0.001) were significantly higher in diabetic patients than in the controls. The presence of microvascular myocardial ischemia was independently associated with angina symptoms (adjusted odds ratio = 3.439, P = 0.037) in diabetic patients but without obstructive CAD.

CONCLUSION

Dynamic CT-MPI + CCTA revealed a high incidence of microvascular myocardial ischemia in diabetic patients without obstructive CAD. Microvascular myocardial ischemia is strongly associated with angina.

The role of CT in arrhythmia management-treatment planning and post-procedural imaging surveillance

Several interventional treatment options exist in patients with atrial and ventricular arrhythmia. Cardiac CT is routinely performed prior to occlusion of the left atrial appendage, pulmonary vein isolation, and cardiac device implantation. Besides the evaluation of coronary artery disease, cardiac CT provides isotropic, high-resolution CT images of the cardiac anatomy with the possibility of multiplanar reformations and three-dimensional reconstructions which are helpful to guide interventional treatment. In addition, cardiac CT is increasingly used to rapidly evaluate periprocedural complications and for the routine post-procedural imaging surveillance in patients after interventions. This review article will discuss current applications of pre- and post-interventional CT imaging in patients with arrhythmia.

Dual-Energy Computed Tomography in Cardiac Imaging

Dual-energy computed tomography (DECT) acquires images using two energy spectra and offers a variation of reconstruction techniques for improved cardiac imaging. Virtual monoenergetic images decrease artifacts improving coronary plaque and stent visualization. Further, contrast attenuation is increased allowing significant reduction of contrast dose. Virtual non-contrast reconstructions enable coronary artery calcium scoring from contrast-enhanced scans. DECT provides advanced plaque imaging with detailed analysis of plaque components, indicating plaque stability. Extracellular volume assessment using DECT offers noninvasive detection of myocardial fibrosis. This review aims to outline the current cardiac applications of DECT, summarize recent literature, and discuss their findings.

Cardiac Computed Tomography for Quantification of Myocardial Extracellular Volume Fraction: A Systematic Review and Meta-Analysis

BACKGROUND

Extracellular volume (ECV) is a quantitative measure of extracellular compartment expansion, and an increase in ECV is a marker of myocardial fibrosis. Although cardiac magnetic resonance (CMR) is considered the standard imaging tool for ECV quantification, cardiac computed tomography (CT) has also been used for ECV assessment.

OBJECTIVES

The aim of this meta-analysis was to evaluate the correlation and agreement in the quantification of myocardial ECV by CT and CMR.

METHODS

PubMed and Web of Science were searched for relevant publications reporting on the use of CT for ECV quantification compared with CMR as the reference standard. The authors employed a meta-analysis using the restricted maximum-likelihood estimator with a random-effects method to estimate summary correlation and mean difference. A subgroup analysis was performed to compare the correlation and mean differences between single-energy CT (SECT) and dual-energy CT (DECT) techniques for the ECV quantification.

RESULTS

Of 435 papers, 13 studies comprising 383 patients were identified. The mean age range was 57.3 to 82 years, and 65% of patients were male. Overall, there was an excellent correlation between CT-derived ECV and CMR-derived ECV (mean: 0.90 [95% CI: 0.86-0.95]). The pooled mean difference between CT and CMR was 0.96% (95% CI: 0.14%-1.78%). Seven studies reported correlation values using SECT, and 4 studies reported those using DECT. The pooled correlation from studies utilizing DECT for ECV quantification was significantly higher compared with those with SECT (mean: 0.94 [95% CI: 0.91-0.98] vs 0.87 [95% CI: 0.80-0.94], respectively; P = 0.01). There was no significant difference in pooled mean differences between SECT vs DECT (P = 0.85).

CONCLUSIONS

CT-derived ECV showed an excellent correlation and mean difference of <1% with CMR-derived ECV. However, the overall quality of the included studies was low, and larger, prospective studies are needed to examine the accuracy and diagnostic and prognostic utility of CT-derived ECV.

Myocardial extracellular volume quantification with computed tomography-current status and future outlook

Non-invasive quantification of the extracellular volume (ECV) is a method for the evaluation of focal and diffuse myocardial fibrosis, potentially obviating the need for invasive endomyocardial biopsy. While ECV quantification with cardiac magnetic resonance imaging (ECVMRI) is already an established method, ECV quantification with CT (ECVCT) is an attractive alternative to ECVMRI, similarly using the properties of extracellular contrast media for ECV calculation. In contrast to ECVMRI, ECVCT provides a more widely available, cheaper and faster tool for ECV quantification and allows for ECV calculation also in patients with contraindications for MRI. Many studies have already shown a high correlation between ECVCT and ECVMRI and accumulating evidence suggests a prognostic value of ECVCT quantification in various cardiovascular diseases. Adding a late enhancement scan (for dual energy acquisitions) or a non-enhanced and late enhancement scan (for single-energy acquisitions) to a conventional coronary CT angiography scan improves risk stratification, requiring only minor adaptations of the contrast media and data acquisition protocols and adding only little radiation dose to the entire scan.Critical relevance statementThis article summarizes the technical principles of myocardial extracellular volume (ECV) quantification with CT, reviews the literature comparing ECVCT with ECVMRI and histopathology, and reviews the prognostic value of myocardial ECV quantification for various cardiovascular disease.Key points• Non-invasive quantification of myocardial fibrosis can be performed with CT.• Myocardial ECV quantification with CT is an alternative in patients non-eligible for MRI.• Myocardial ECV quantification with CT strongly correlates with ECV quantification using MRI.• Myocardial ECV quantification provides incremental prognostic information for various pathologies affecting the heart (e.g., cardiac amyloidosis).

Quantification of extracellular volume with cardiac computed tomography in patients with dilated cardiomyopathy

BACKGROUND

Cardiac computed tomography (CCT) was recently validated to measure extracellular volume (ECV) in the setting of cardiac amyloidosis, showing good agreement with cardiovascular magnetic resonance (CMR). However, no evidence is available with a whole-heart single source, single energy CT scanner in the clinical context of newly diagnosed left ventricular dysfunction. Therefore, the aim of this study was to test the diagnostic accuracy of ECVCCT in patients with a recent diagnosis of dilated cardiomyopathy, having ECVCMR as the reference technique.

METHODS

39 consecutive patients with newly diagnosed dilated cardiomyopathy (LVEF <50%) scheduled for clinically indicated CMR were prospectively enrolled. Myocardial segment evaluability assessment with each technique, agreement between ECVCMR and ECVCCT, regression analysis, Bland-Altman analysis and interclass correlation coefficient (ICC) were performed.

RESULTS

Mean age of enrolled patients was 62 ​± ​11 years, and mean LVEF at CMR was 35.4 ​± ​10.7%. Overall radiation exposure for ECV estimation was 2.1 ​± ​1.1 ​mSv. Out of 624 myocardial segments available for analysis, 624 (100%) segments were assessable by CCT while 608 (97.4%) were evaluable at CMR. ECVCCT demonstrated slightly lower values compared to ECVCMR (all segments, 31.8 ​± ​6.5% vs 33.9 ​± ​8.0%, p ​< ​0.001). At regression analysis, strong correlations were described (all segments, r ​= ​0.819, 95% CI: 0.791 to 0.844). On Bland-Altman analysis, bias between ECVCMR and ECVCCT for global analysis was 2.1 (95% CI: -6.8 to 11.1). ICC analysis showed both high intra-observer and inter-observer agreement for ECVCCT calculation (0.986, 95%CI: 0.983 to 0.988 and 0.966, 95%CI: 0.960 to 0.971, respectively).

CONCLUSIONS

ECV estimation with a whole-heart single source, single energy CT scanner is feasible and accurate. Integration of ECV measurement in a comprehensive CCT evaluation of patients with newly diagnosed dilated cardiomyopathy can be performed with a small increase in overall radiation exposure.

Coronary Computed Tomography Angiography: Beyond Obstructive Coronary Artery Disease

Nowadays, coronary computed tomography angiography (CCTA) has a role of paramount importance in the diagnostic algorithm of ischemic heart disease (IHD), both in stable coronary artery disease (CAD) and acute chest pain. Alongside the quantification of obstructive coronary artery disease, the recent technologic developments in CCTA provide additional relevant information that can be considered as "novel markers" for risk stratification in different settings, including ischemic heart disease, atrial fibrillation, and myocardial inflammation. These markers include: (i) epicardial adipose tissue (EAT), associated with plaque development and the occurrence of arrhythmias; (ii) late iodine enhancement (LIE), which allows the identification of myocardial fibrosis; and (iii) plaque characterization, which provides data about plaque vulnerability. In the precision medicine era, these emerging markers should be integrated into CCTA evaluation to allow for the bespoke interventional and pharmacological management of each patient.

Dual-Energy CT of the Heart: A Review

Dual-energy computed tomography (DECT) represents an emerging imaging technique which consists of the acquisition of two separate datasets utilizing two different X-ray spectra energies. Several cardiac DECT applications have been assessed, such as virtual monoenergetic images, virtual non-contrast reconstructions, and iodine myocardial perfusion maps, which are demonstrated to improve diagnostic accuracy and image quality while reducing both radiation and contrast media administration. This review will summarize the technical basis of DECT and review the principal cardiac applications currently adopted in clinical practice, exploring possible future applications.

Dual energy CT in musculoskeletal applications beyond crystal imaging: bone marrow maps and metal artifact reduction

Dual energy CT (DECT) is becoming increasingly popular and valuable in the domain of musculoskeletal imaging. Gout maps and crystal detection have been predominant indications for about a decade. Other important indications of bone marrow maps and metal artifact reduction are also frequent with added advantages of detection and characterization of bone marrow lesions similar to MR imaging and diagnosis of hardware related complications, respectively. This article discusses technical considerations and physics of DECT imaging and its role in musculoskeletal indications apart from crystal imaging with respective case examples and review of the related literature. DECT pitfalls in these domains are also highlighted and the reader can gain knowledge of above concepts for prudent use of DECT in their musculoskeletal and general practices.

Measurement of myocardial extracellular volume using cardiac dual-energy computed tomography in patients with ischaemic cardiomyopathy: a comparison of different methods

To clarify the consistency and efficiency of four methods for myocardial extracellular volume (ECV) measurement (manual method using dual-energy iodine [manual ECViodine], manual method using subtraction [manual ECVsub], automatic ECViodine, automatic ECVsub) in patients with ischaemic cardiomyopathy. Fifty patients with ischaemic cardiomyopathy who underwent coronary computed tomography angiography (CCTA) following dual-energy computed tomography (CT) with late iodine enhancement (LIE-DECT) were included. LIE with ischaemic patterns representing scarring could be detected using iodine maps in all patients. The global and remote ECVs of non-scarred myocardium were measured using four methods (manual ECViodine, automatic ECViodine, manual ECVsub, and automatic ECVsub). The consistency and time cost of the four methods were analysed. There were no significant differences in the mean global ECVs or remote ECVs among the four methods (p > 0.05). ECViodine resulted in a lower Bland-Altman limit of agreement than that of ECVsub for both global and remote measurements. Intraclass correlation coefficients of the automatic and manual ECViodine measurements demonstrated better concordance (0.804 and 0.859, respectively) than those of automatic and manual ECVsub (0.607 and 0.669, respectively) for both global and remote measurements. The measurement time for automatic ECV was less than that for manual ECV for both global and remote ECV measurements (all p < 0.001). ECV measurement using dual-energy iodine yielded good concordance, and the automatic method has the advantages of being simple and convenient, which can become a useful tool for quantification of myocardial fibrosis.

Extracellular Volume Quantification With Cardiac Late Enhancement Scanning Using Dual-Source Photon-Counting Detector CT

OBJECTIVES

The aim of this study was to evaluate the feasibility and accuracy of cardiac late enhancement (LE) scanning for extracellular volume (ECV) quantification with dual-source photon-counting detector computed tomography (PCD-CT).

MATERIALS AND METHODS

In this institutional review board-approved study, 30 patients (mean age, 79 years; 12 women; mean body mass index, 28 kg/m2) with severe aortic stenosis undergoing PCD-CT as part of their preprocedural workup for transcatheter aortic valve replacement were included. The scan protocol consisted of a nonenhanced calcium-scoring scan, coronary CT angiography (CTA) followed by CTA of the thoracoabdominal aorta, and a low-dose LE scan 5 minutes after the administration of 100 mL contrast media (all scans electrocardiogram-gated). Virtual monoenergetic (65 keV) and dual-energy (DE) iodine images were reconstructed from the LE scan. Extracellular volume was calculated using the iodine ratios of myocardium and blood-pool of the LE scan, and additionally based on single-energy (SE) subtraction of the nonenhanced scan from the LE scan. Three-dimensional analysis was performed automatically for the whole-heart myocardial volume by matching a heart model generated from the respective coronary CTA data. Bland-Altman and correlation analysis were used to compare the ECV values determined by both methods.

RESULTS

The median dose length product for the LE scan was 84 mGy·cm (interquartile range, 69; 125 mGy·cm). Extracellular volume quantification was feasible in all patients. The median ECV value was 30.5% (interquartile range, 28.4%-33.6%). Two focal ECV elevations matched known prior myocardial infarction. The DE- and SE-based ECV quantification correlated well (r = 0.87, P < 0.001). Bland-Altman analysis showed small mean errors between DE- and SE-based ECV quantification (0.9%; 95% confidence interval, 0.1%-1.6%) with narrow limits of agreement (-3.3% to 5.0%).

CONCLUSIONS

Dual-source PCD-CT enables accurate ECV quantification using an LE cardiac DE scan at low radiation dose. Extracellular volume calculation from iodine ratios of the LE scan obviates the need for acquisition of a true nonenhanced scan and is not affected by potential misregistration between 2 separate scans.

Myocardial extracellular volume quantification by cardiac CT in pulmonary hypertension: Comparison with cardiac MRI

PURPOSE

Myocardial extracellular volume (ECV) measured by cardiac magnetic resonance imaging (MRI) has been suggested as a marker of disease severity in pulmonary hypertension (PH). However, consistency between ECVs quantified by computed tomography (CT) and MRI has not been sufficiently investigated in (PH). We investigated the utility of CT-ECV in PH, using MRI-ECV as a reference standard.

METHOD

We evaluated 20 patients with known or suspected PH who underwent dual-energy CT, cardiac MRI, and right heart catheterization. We used Pearson correlation analysis to investigate correlations between CT-ECV and MRI-ECV. We also assessed correlations between ECV and mean pulmonary artery pressure (mPAP).

RESULTS

CT-ECV showed a very strong correlation with MRI-ECV at the anterior (r = 0.83) and posterior right ventricular insertion points (RVIPs) (r = 0.84). CT-ECV and MRI-ECV were strongly correlated in the septum and left ventricular free wall (r = 0.79-0.73) but weakly correlated in the right ventricular free wall (r = 0.26). CT-ECV showed a strong correlation with mPAP in the anterior RVIP (r = 0.64) and a moderate correlation in the posterior RVIP and septum (r = 0.50-0.42). Compared with CT-ECV, MRI-ECV had a higher correlation with mPAP; however, the difference was not significant (anterior RVIP, r = 0.72 [MRI-ECV] vs. 0.64 [CT-ECV], p = 0.663; posterior RVIP, r = 0.67 vs. 0.50, p = 0.446).

CONCLUSION

Dual-energy CT can quantify myocardial ECV and yield results comparable to those obtained using cardiac MRI. CT-ECV in the anterior RVIP could be a noninvasive surrogate marker of disease severity in PH.

Case Report: Dual-Energy Computed Tomography of Cardiac Changes in IgG4-Related Disease

Background

Dual-energy computed tomography (DECT) is used in coronary plaque characterization, myocardial perfusion imaging, and pulmonary embolism diagnosis; however, there is no relevant research on DECT in IgG4-related diseases (IgG4-RD) involving the coronary artery. We are the first to report DECT findings of cardiac morphology and function in IgG4-RD.

Patient Findings

Multimodality cardiovascular imaging from a 63-year-old male patient, who presented with IgG4-related pancreatitis, was analyzed. An iodine map and spectral curves were obtained from the DECT, which can help to distinguish between non-calcified plaques and IgG4 lesions of the coronary artery, noninvasive FFR_CT (fractional flow reserve derived from coronary computed tomography angiography) and ECV (extracellular volume fraction) demonstrated myocardial ischemia and myocardial fibrosis, respectively.

Conclusion

The DECT can detect coronary artery tumor-like lesions caused by IgG4-RD and simultaneously assess the morphological, functional, and histological characteristics of the myocardium. This may help to guide individualized and timely treatment and avoid potentially life-threatening complications.

Clinical applications of cardiac computed tomography: a consensus paper of the European Association of Cardiovascular Imaging-part II

Cardiac computed tomography (CT) was initially developed as a non-invasive diagnostic tool to detect and quantify coronary stenosis. Thanks to the rapid technological development, cardiac CT has become a comprehensive imaging modality which offers anatomical and functional information to guide patient management. This is the second of two complementary documents endorsed by the European Association of Cardiovascular Imaging aiming to give updated indications on the appropriate use of cardiac CT in different clinical scenarios. In this article, emerging CT technologies and biomarkers, such as CT-derived fractional flow reserve, perfusion imaging, and pericoronary adipose tissue attenuation, are described. In addition, the role of cardiac CT in the evaluation of atherosclerotic plaque, cardiomyopathies, structural heart disease, and congenital heart disease is revised.

Quantitative analysis of late iodine enhancement using dual-layer spectral detector computed tomography: comparison with magnetic resonance imaging

BACKGROUND

To evaluate the segmental myocardial extracellular volume (ECV) fraction and to define a threshold ECV value that can be used to distinguish positive late gadolinium enhancement (LGE) segments from negative myocardial segments using dual-layer spectral detector computed tomography (SDCT), with magnetic resonance imaging (MRI) as a reference.

METHODS

Fifty-six subjects with cardiac disease or suspected cardiac disease, underwent both late iodine enhancement on CT (CT-LIE) scanning and late gadolinium enhancement on MRI (MRI-LGE) scanning. Each procedure occurred within a week of the other. Global and segmental ECVs of the left ventricle were measured by CT and MRI images. According to the location and pattern of delayed enhancement on MRI image, myocardial segments were classified into 3 groups: ischemic LGE segments (group 1), nonischemic LGE segments (group 2) and negative LGE segments (group 3). The correlation and agreement between CT-ECV and MRI-ECV were compared on a per-segment basis. Receiver operating characteristic (ROC) curve analysis was performed to establish a threshold for LIE detection.

RESULTS

Among the 56 patients, 896 segments were analyzed, and of these, 73 segments were in group 1, 229 segments were in group 2, and 594 segments were in group 3. In segmental analysis, CT-ECV in group 3 (27.0%; 24.9-28.9%) was significantly lower than that in group 1 (33.2%; 30.7-36.3%) and group 2 (34.9%; 32.3-39.8%; all P<0.001). Good correlations were seen between CT-ECV and MRI-ECV for all groups (group 1: r=0.920; group 2: r=0.936; group 3: r=0.799; all P<0.001). Bland-Altman analysis between CT-ECV and MRI-ECV showed a small bias in all 3 groups (group 1: -2.1%, 95% limits of agreement -11.3-7.1%; group 2: -0.6%, 95% limits of agreement -13.1-11.9%; group 3: 1.0%, 95% limits of agreement -12.7-14.7%). CT-ECV could differentiate between LGE-positive and LGE-negative segments with 83.1% sensitivity and 93.3% specificity at a cutoff of 31%.

CONCLUSIONS

ECV values derived from CT imaging showed good correlation and agreement with MR imaging findings, and CT-ECV provided high diagnostic accuracy for discriminating between LGE-positive and LGE-negative segments. Thus, cardiac CT imaging might be a suitable noninvasive imaging technique for myocardial ECV quantification.

Myocardial Late Contrast Enhancement CT in Troponin-Positive Acute Chest Pain Syndrome

Background Acute chest pain with mild troponin rise and inconclusive diagnosis after clinical evaluation represents a diagnostic challenge. Triple-rule-out (TRO) CT may exclude coronary artery disease (CAD), as well as acute aortic syndrome and pulmonary embolism, but cannot help identify other causes of myocardial injury. Purpose To investigate the diagnostic value of a comprehensive CT protocol including both an angiographic and a late contrast enhancement (LCE) scan in participants with troponin-positive acute chest pain. Materials and Methods In this prospective study, consecutive patients with troponin-positive acute chest pain or anginal equivalent and inconclusive diagnosis after clinical evaluation (symptoms, markers, electrocardiography, and echocardiography) who underwent TRO CT between June 2018 and September 2020 were enrolled. TRO CT was performed to evaluate the presence of obstructive CAD (stenosis ≥50%), acute aortic syndrome, and pulmonary embolism. If the findings on the TRO CT scan were negative, an LCE CT scan was acquired after 10 minutes to assess the presence and pattern of scar and quantify the myocardial extracellular volume fraction. CT-based diagnoses were compared with diagnoses obtained with reference standard methods, including invasive coronary angiography, cardiac MRI, and endomyocardial biopsy. Results Eighty-four patients (median age, 69 years [interquartile range, 50-77 years]; 45 men) were enrolled. TRO CT helped identify obstructive CAD in 35 participants (42%), acute aortic syndrome in one (1.2%), and pulmonary embolism in six (7.1%). LCE CT scans were acquired in the remaining 42 participants. The following diagnoses were reached with use of LCE CT: myocarditis (22 of 42 participants [52%]), takotsubo cardiomyopathy (four of 42 [10%]), amyloidosis (three of 42 [7.1%]), myocardial infarction with nonobstructed coronary arteries (three of 42 [7.1%]), dilated cardiomyopathy (two of 42 [4.8%]), and negative or inconclusive findings (eight of 42 [19%]). The addition of LCE CT improved the diagnostic rate of TRO CT from 42 of 84 participants (50% [95% CI: 38.9, 61.1]) to 76 of 84 (90% [95% CI: 82.1, 95.8]) (P < .001). Conclusion A CT protocol including triple-rule-out and late contrast enhancement CT scans improved diagnostic rate in participants presenting with acute chest pain syndrome. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Nagpal and Bluemke in this issue.

Dual-Energy Heart CT: Beyond Better Angiography-Review

Heart CT has undergone substantial development from the use of calcium scores performed on electron beam CT to modern 256+-row CT scanners. The latest big step in its evolution was the invention of dual-energy scanners with much greater capabilities than just performing better ECG-gated angio-CT. In this review, we present the unique features of dual-energy CT in heart diagnostics.

Synthetic Extracellular Volume Fraction Derived Using Virtual Unenhanced Attenuation of Blood on Dual-Energy Contrast-Enhanced Cardiac CT in Nonischemic Cardiomyopathy

Background: Current methods for calculating myocardial extracellular volume fraction (ECV) require blood sampling to obtain serum hematocrit. Synthetic hematocrit and thus synthetic ECV may be derived using unenhanced attenuation of blood. By use of virtual unenhanced (VUE) attenuation of blood, contrast-enhanced dual-energy CT (DECT) may allow synthetic ECV calculations without unenhanced acquisition. Objective: To compare synthetic ECV using synthetic hematocrit derived from VUE images versus conventional ECV using serum hematocrit, both obtained by contrast-enhanced DECT, using MRI-derived ECV as reference. Methods: This retrospective study included 51 patients (26 men, 25 women; mean age 59.9 ± 15.6 years) with nonischemic cardiomyopathy who, as part of an earlier prospective investigation, underwent equilibrium-phase contrast-enhanced cardiac DECT and cardiac MRI, with serum hematocrit measured within 6 hours of both tests. A separate retrospective sample of 198 patients who underwent same-day contrast-enhanced thoracic DECT for suspected pulmonary embolism and serum hematocrit measurement was identified to derive a synthetic hematocrit formula using VUE attenuation of blood by linear regression analysis. In the primary sample, two radiologists independently used DECT iodine maps to obtain conventional ECV using serum hematocrit and synthetic ECV using synthetic hematocrit based on the independently derived formula. Concordance correlation coefficient (CCC) was computed between conventional ECV and synthetic ECV from DECT. Conventional ECV and synthetic ECV from DECT were compared with MRI-derived ECV in Bland-Altman analyses. Results: The linear regression formula for synthetic hematocrit in the independent sample was: synthetic hematocrit = 0.85 x (VUE attenuation of blood) - 5.40. In the primary sample, conventional ECV and synthetic ECV from DECT showed excellent agreement (CCC = 0.95). Bland-Altman analysis showed small bias of -0.44% with 95% limits of agreement from -5.10% to 4.22% between MRI-derived ECV and conventional ECV from DECT, and small bias of -0.78% with 95% limits of agreement from -5.25% to 3.69% between MRI-derived ECV and synthetic ECV from DECT. Conclusion: Synthetic ECV and conventional ECV from DECT show excellent agreement and comparable association with ECV from cardiac MRI. Clinical Impact: Synthetic hematocrit from VUE attenuation of blood may allow myocardial tissue characterization on DECT without inconvenience of blood sampling.

The Potential Role of Cardiac CT in the Evaluation of Patients With Known or Suspected Cardiomyopathy: From Traditional Indications to Novel Clinical Applications

After 15 years from its advent in the clinical field, coronary computed tomography (CCTA) is now widely considered as the best first-step test in patients with low-to-moderate pre-test probability of coronary artery disease. Technological innovation was of pivotal importance for the extensive clinical and scientific interest in CCTA. Recently, the advent of last generation wide-coverage CT scans paved the way for new clinical applications of this technique beyond coronary arteries anatomy evaluation. More precisely, both biventricular volume and systolic function quantification and myocardial fibrosis identification appeared to be feasible with last generation CT. In the present review we would focus on potential applications of cardiac computed tomography (CCT), beyond CCTA, for a comprehensive assessment patients with newly diagnosed cardiomyopathy, from technical requirements to novel clinical applications.

Prognostic Impact of Myocardial Extracellular Volume Fraction Assessment Using Dual-Energy Computed Tomography in Patients Treated With Aortic Valve Replacement for Severe Aortic Stenosis

Background Myocardial extracellular volume fraction (ECV), measured by cardiac magnetic resonance imaging, is a useful prognostic marker for patients who have undergone aortic valve replacement (AVR) for aortic stenosis. However, the prognostic significance of ECV measurements based on computed tomography (CT) is unclear. This study evaluated the association between ECV measured with dual-energy CT and clinical outcomes in patients with aortic stenosis who underwent transcatheter or surgical AVR. Methods and Results We retrospectively enrolled 95 consecutive patients (age, 84.0±5.0 years; 75% women) with severe aortic stenosis who underwent preprocedural CT for transcatheter AVR planning. ECV was measured using iodine density images obtained by delayed enhancement dual-energy CT. The primary end point was a composite outcome of all-cause death and hospitalization for heart failure after AVR. The mean ECV measured with CT was 28.1±3.8%. During a median follow-up of 2.6 years, 22 composite outcomes were observed, including 15 all-cause deaths and 11 hospitalizations for heart failure. In Kaplan-Meier analysis, the high ECV group (≥27.8% [median value]) had significantly higher rates of composite outcomes than the low ECV group (<27.8%) (log-rank test, P=0.012). ECV was the only independent predictor of adverse outcomes on multivariable Cox regression analysis (hazards ratio, 1.25; 95% CI, 1.10‒1.41; P<0.001). Conclusions Myocardial ECV measured with dual-energy CT in patients who underwent aortic valve intervention was an independent predictor of adverse outcomes after AVR.

Preliminary study: myocardial T1 relaxation time in patients with ischemic findings and normal findings on coronary angiography

OBJECTIVE

The aim of this study is to evaluate the myocardium structure in patients with chest pain who were determined to have moderate and/or high risk for cardiac ischemic heart disease (IHD) but who had normal findings on conventional coronary angiography by using native cardiac magnetic resonance imaging (CMRI) T1 mapping and comparing with healthy volunteers.

METHODS

A total of 50 patients and 30 healthy volunteers who underwent CMRI were included in our prospective study. Patients whose clinical findings were compatible with stable angina pectoris, with moderate and/or high risk for IHD, but whose conventional coronary angiography was normal, were our patient group. Native T1 values were measured for 17 myocardial segments (segmented based on American Heart Association recommendations) by two radiologists independently. The data obtained were statistically compared with the sample t-test.

RESULTS

Myocardial native T1 values were found to be significantly prolonged in the patient group compared with the control group (p<0.05). Inter-observer reliability for native T1 value measurements of groups was high for both patient and control groups (α = 0.92 for the patient group and 0.96 for the control group).

CONCLUSION

Findings suggestive of ischemia were detected by T1 mapping in the myocardium of our patients. For this reason, it is recommended that this patient group should be included in early diagnosis and close follow-up assessments for IHD.

Cardiac computed tomography in the contemporary evaluation of infective endocarditis

Increasing data have accumulated on the role of Cardiac Computed Tomography (CCT) in infective endocarditis (IE) with high accuracy for large vegetations, perivalvular complications and for exclusion of coronary artery disease to avoid invasive angiography. CCT can further help to clarify the etiology of infective prosthetic valve dysfunction (e.g. malposition, abscess, leak, vegetation or mass). Structural interventions have increased the relevance of CCT in valvular heart disease and have amplified its use. CCT may be ideally integrated into a multimodality approach that incorporates a central role of transesophageal echocardiography (TEE) with 18-FDG PET and/or cardiac magnetic resonance in individually selected cases, guided by the Heart Team. The coronavirus-19 (COVID-19) pandemic has resulted in renewed attention to CCT as a safe alternative or adjunct to TEE in selected patients. This review article provides a comprehensive, contemporary review on CCT in IE to include scan optimization, characteristics of common IE findings on CCT, published data on the diagnostic accuracy of CCT, multimodality imaging comparison, limitations and future technical advancements.

Myocardial extracellular volume fraction analysis in doxorubicin-induced beagle models: comparison of dual-energy CT with equilibrium contrast-enhanced single-energy CT

Background

Dual-energy CT (DECT) permits the simultaneous operation of two different kV levels, providing a potential method toward the assessment of diffuse myocardial fibrosis. The purpose of this study was to determine the accuracy of DECT for evaluation of the myocardial extracellular volume (ECV) fraction in comparison with single-energy CT (SECT).

Methods

Myocardial ECV was quantified in fifteen dogs using DECT and dynamic equilibrium SECT before and after doxorubicin administration. Cardiac magnetic resonance imaging (CMRI) was used to assess myocardial function. The histological collagen volume fraction (CVF) was calculated as the gold standard. The Bland-Altman analysis was performed to compare the agreement between DECT-ECV and SECT-ECV. The association among ECV values derived from DECT and SECT, CVF, and left ventricular ejection fraction (LVEF) were determined by correlation analysis. The variations of these values were evaluated using repeated ANOVA.

Results

The DECT- and SECT-ECV were increased with the elongation of modeling time (pre-modeling vs. 16-week models vs. 24-week models: DECT-ECV 24.1%±1.1%, 35.1%±1.3% and 37.6%±1.4%; SECT-ECV 22.9%±0.8%, 33.6%±1.2% and 36.3%±1.0%; n=30 in per-subject analysis, all P<0.05). Both ECV values of DECT and SECT correlated well with the histological CVF results (R=0.935 and 0.952 for the DECT-ECV and SECT-ECV; all P<0.001; n=13). Bland-Altman plots showed no significant differences between DECT- and SECT-ECV.

Conclusions

DECT-ECV correlated well with both SECT-ECV and histology, showing the feasibility of DECT in evaluating doxorubicin-induced diffuse myocardial interstitial fibrosis.

Dual Energy Differential Phase Contrast CT (DE-DPC-CT) Imaging

When more than two elemental materials are present in a given object, material quantification may not be robust and accurate when the routine two-material decomposition scheme in current dual energy CT imaging is employed. In this work, we present an innovative scheme to accomplish accurate three-material decomposition with measurements from a dual energy differential phase contrast CT (DE-DPC-CT) acquisition. A DE-DPC-CT system was constructed using a grating interferometer and a photon counting CT imaging system with two energy bins. The DE-DPC-CT system can simultaneously measure both the imaginary and the real part of the complex refractive index to enable a three-material decomposition. Physical phantom with 21 material inserts were constructed and measured using DE-DPC-CT system. Results demonstrated excellent accuracy in elemental material quantification. For example, relative root-mean-square errors of 4.5% for calcium and 5.2% for iodine were achieved using the proposed three-material decomposition scheme. Biological tissues with iodine inserts were used to demonstrate the potential utility of the proposed spectral CT imaging method. Experimental results showed that the proposed method correctly differentiates the bony structure, iodine, and the soft tissue in the biological specimen samples. A triple spectra CT scan was also performed to benchmark the performance of the DE-DPC-CT scan. Results demonstrated that the material decomposition from the DE-DPC-CT has a much lower quantification noise than that from the triple spectra CT scan.