Myocardial Late Iodine Enhancement and Extracellular Volume Quantification with Dual-Layer Spectral Detector Dual-Energy Cardiac CT

Efficacy of Computed Tomography-Based Evaluation of Myocardial Extracellular Volume Combined With Red Flags for Early Screening of Concealed Cardiac Amyloidosis in Patients With Atrial Fibrillation

BACKGROUND

The prevalence of transthyretin amyloid cardiomyopathy (ATTR-CM) in atrial fibrillation (AF) patients remains unclear. We explored the efficacy of computed tomography-based myocardial extracellular volume (CT-ECV) combined with red flags for the early screening of concealed ATTR-CM in AF patients undergoing catheter ablation.Methods and Results: Patients referred for AF ablation at Oita University Hospital were prescreened using the red-flag signs defined by echocardiographic or electrocardiographic findings, medical history, symptoms, and blood biochemical findings. Myocardial CT-ECV was quantified in red flag-positive patients using routine pre-AF ablation planning cardiac CT with the addition of delayed-phase cardiac CT scans. Patients with high (>35%) ECV were evaluated using technetium pyrophosphate (99 mTc-PYP) scintigraphy. A cardiac biopsy was performed during the planned AF ablation procedure if 99 mTc-PYP scintigraphy was positive. Between June 2022 and June 2023, 342 patients were referred for AF ablation. Sixty-seven (19.6%) patients had at least one of the red-flag signs. Myocardial CT-ECV was evaluated in 57 patients because of contraindications to contrast media, revealing that 16 patients had high CT-ECV. Of these, 6 patients showed a positive 99 mTc-PYP study, and 6 patients were subsequently diagnosed with wild-type ATTR-CM via cardiac biopsy and genetic testing.

CONCLUSIONS

CT-ECV combined with red flags could contribute to the systematic early screening of concealed ATTR-CM in AF patients undergoing catheter ablation.

Cardiac computed tomography with late contrast enhancement: A review

Cardiac computed tomography (CCT) has assumed an increasingly significant role in the evaluation of coronary artery disease (CAD) during the past few decades, whereas cardiovascular magnetic resonance (CMR) remains the gold standard for myocardial tissue characterization. The discovery of late myocardial enhancement following intravenous contrast administration dates back to the 1970s with ex-vivo CT animal investigations; nevertheless, the clinical application of this phenomenon for cardiac tissue characterization became prevalent for CMR imaging far earlier than for CCT imaging. Recently the technical advances in CT scanners have made it possible to take advantage of late contrast enhancement (LCE) for tissue characterization in CCT exams. Moreover, the introduction of extracellular volume calculation (ECV) on cardiac CT images combined with the possibility of evaluating cardiac function in the same exam is making CCT imaging a multiparametric technique more and more similar to CMR. The aim of our review is to provide a comprehensive overview on the role of CCT with LCE in the evaluation of a wide range of cardiac conditions.

Feasibility of the Threshold-Based Quantification of Myocardial Fibrosis on Cardiac CT as a Prognostic Marker in Nonischemic Dilated Cardiomyopathy

OBJECTIVE

This study investigated the feasibility and prognostic relevance of threshold-based quantification of myocardial delayed enhancement (MDE) on CT in patients with nonischemic dilated cardiomyopathy (NIDCM).

MATERIALS AND METHODS

Forty-three patients with NIDCM (59.3 ± 17.1 years; 21 male) were included in the study and underwent cardiac CT and MRI. MDE was quantified manually and with a threshold-based quantification method using cutoffs of 2, 3, and 4 standard deviations (SDs) on three sets of CT images (100 kVp, 120 kVp, and 70 keV). Interobserver agreement in MDE quantification was assessed using the intraclass correlation coefficient (ICC). Agreement between CT and MRI was evaluated using the Bland-Altman method and the concordance correlation coefficient (CCC). Patients were followed up for the subsequent occurrence of the primary composite outcome, including cardiac death, heart transplantation, heart failure hospitalization, or appropriate use of an implantable cardioverter-defibrillator. The Kaplan-Meier method was used to estimate event-free survival according to MDE levels.

RESULTS

Late gadolinium enhancement (LGE) was observed in 29 patients (67%, 29/43), and the mean LGE found with the 5-SD threshold was 4.1% ± 3.6%. The 4-SD threshold on 70-keV CT showed excellent interobserver agreement (ICC = 0.810) and the highest concordance with MRI (CCC = 0.803). This method also yielded the smallest bias with the narrowest range of 95% limits of agreement compared to MRI (bias, -0.119%; 95% limits of agreement, -4.216% to 3.978%). During a median follow-up of 1625 days (interquartile range, 712-1430 days), 10 patients (23%, 10/43) experienced the primary composite outcome. Event-free survival significantly differed between risk subgroups divided by the optimal MDE cutoff of 4.3% (log-rank P = 0.005).

CONCLUSION

The 4-SD threshold on 70-keV monochromatic CT yielded results comparable to those of MRI for quantifying MDE as a marker of myocardial fibrosis, which showed prognostic value in patients with NIDCM.

Imaging of Cardiac Fibrosis: An Update, From the AJR Special Series on Imaging of Fibrosis

Myocardial fibrosis (MF) is defined as excessive production and deposition of extra-cellular matrix proteins that result in pathologic myocardial remodeling. Three types of MF have been identified: replacement fibrosis from tissue necrosis, reactive fibrosis from myocardial stress, and infiltrative interstitial fibrosis from progressive deposition of nondegradable material such as amyloid. Although echocardiography, nuclear medicine, and CT play important roles in the assessment of MF, MRI is pivotal in the evaluation of MF, with the late gadolinium enhancement (LGE) technique used as a primary end point. The LGE technique focuses on the pattern and distribution of gadolinium accumulation in the myocardium and assists in the diagnosis and establishment of the cause of both ischemic and nonischemic cardiomyopathy. LGE MRI also aids prognostication and risk stratification. In addition, LGE MRI is used to guide the management of patients considered for ablation for arrhythmias. Parametric mapping techniques, including T1 mapping and extracellular volume measurement, allow detection and quantification of diffuse fibrosis, which may not be detected by LGE MRI. These techniques also allow monitoring of disease progression and therapy response. This review provides an update on the imaging of MF, including prognostication and risk stratification tools, electrophysiologic considerations, and disease monitoring.

Clinical characteristics of patients with high extracellular volume fraction evaluated by cardiac computed tomography for coronary artery evaluation

Aims

This study aims to evaluate the distribution of extracellular volume fraction detected via computed tomography, clinical characteristics of high extracellular volume fraction detected via computed tomography, and the rate of incidental detection of cardiac amyloidosis in patients undergoing cardiac computed tomography for coronary artery evaluation.

Methods and results

This study included 874 consecutive patients (mean age, 74.4 ± 7.1 years; men, 65%), comprising men aged ≥60 years and women aged ≥70 years, who had undergone cardiac computed tomography between January 2020 and September 2022. The mean extracellular volume fraction detected via computed tomography was 29.7 ± 5.2%, and 108 patients (12.4%) had an extracellular volume fraction detected via computed tomography of ≥35%. Older age (75.9 ± 8.2 years vs. 74.2 ± 6.9 years; P = 0.042), male sex (75.9% vs. 63.0%; P = 0.007), impaired left ventricular ejection fraction, increased high-sensitivity cardiac troponin T and B-type natriuretic peptide levels, and increased left ventricular thickness showed significant associations with an extracellular volume fraction detected via computed tomography of ≥35%. Cardiac amyloidosis was diagnosed incidentally in 15 patients based on an increase in extracellular volume fraction detected via computed tomography. The prevalence of cardiac amyloidosis was 1.7% (15/874) and 14.3% (15/105) in the entire study population and in patients with an extracellular volume fraction detected via computed tomography of ≥35%, respectively. An increase in the extracellular volume fraction detected via computed tomography was suggestive of cardiac amyloidosis.

Conclusion

Elevated extracellular volume fraction detected via computed tomography, associated with elevated cardiac biomarker levels and myocardial structural changes, may lead to the incidental diagnosis of cardiac amyloidosis.

Spectral Photon-Counting Computed Tomography: Technical Principles and Applications in the Assessment of Cardiovascular Diseases

Spectral Photon-Counting Computed Tomography (SPCCT) represents a groundbreaking advancement in X-ray imaging technology. The core innovation of SPCCT lies in its photon-counting detectors, which can count the exact number of incoming x-ray photons and individually measure their energy. The first part of this review summarizes the key elements of SPCCT technology, such as energy binning, energy weighting, and material decomposition. Its energy-discriminating ability represents the key to the increase in the contrast between different tissues, the elimination of the electronic noise, and the correction of beam-hardening artifacts. Material decomposition provides valuable insights into specific elements' composition, concentration, and distribution. The capability of SPCCT to operate in three or more energy regimes allows for the differentiation of several contrast agents, facilitating quantitative assessments of elements with specific energy thresholds within the diagnostic energy range. The second part of this review provides a brief overview of the applications of SPCCT in the assessment of various cardiovascular disease processes. SPCCT can support the study of myocardial blood perfusion and enable enhanced tissue characterization and the identification of contrast agents, in a manner that was previously unattainable.

Spectral performance evaluation of a second-generation spectral detector CT

PURPOSE

The aim of this study was to characterize a second-generation wide-detector dual-layer spectral computed tomography (CT) system for material quantification accuracy, acquisition parameter and patient size dependencies, and tissue characterization capabilities.

METHODS

A phantom with multiple tissue-mimicking and material-specific inserts was scanned with a dual-layer spectral detector CT using different tube voltages, collimation widths, radiation dose levels, and size configurations. Accuracy of iodine density maps and virtual monoenergetic images (MonoE) were investigated. Additionally, differences between conventional and MonoE 70 keV images were calculated to evaluate acquisition parameter and patient size dependencies. To demonstrate material quantification and differentiation, liver-mimicking inserts with adipose and iron were analyzed with a two-base decomposition utilizing MonoE 50 and 150 keV, and root mean square error (RMSE) for adipose and iron content was reported.

RESULTS

Measured inserts exhibited quantitative accuracy across a wide range of MonoE levels. MonoE 70 keV images demonstrated reduced dependence compared to conventional images for phantom size (1 vs. 27 HU) and acquisition parameters, particularly tube voltage (4 vs. 37 HU). Iodine density quantification was successful with errors ranging from -0.58 to 0.44 mg/mL. Similarly, inserts with different amounts of adipose and iron were differentiated, and the small deviation in values within inserts corresponded to a RMSE of 3.49 ± 1.76% and 1.67 ± 0.84 mg/mL for adipose and iron content, respectively.

CONCLUSION

The second-generation dual-layer CT enables acquisition of quantitatively accurate spectral data without compromises from differences in patient size and acquisition parameters.

Assessment of Myocardial Viability in Chronic Myocardial Infarction Using the Dual-Energy Computed Tomography Myocardial Extracellular Volume Fractionation Technique: A Case Report

Assessment of myocardial viability in patients with myocardial infarction is critical to identify residual ischemic tissue in areas of reduced function and to determine the need for revascularization. We present the case of an 80-year-old man with chest pain and a history of hypertension. Initial evaluation revealed abnormal electrocardiogram findings, and subsequent studies suggested chronic anteroseptal myocardial infarction with reduced cardiac function. Dual-energy cardiac computed tomography was performed to evaluate the coronary arteries and myocardium. Late iodine enhancement images obtained by dual-energy computed tomography showed mixed plaques and severe proximal left anterior descending artery stenosis. Conventional late iodine enhancement imaging was inconclusive, prompting extracellular volume fraction analysis using iodine density imaging. Extracellular volume fraction assessment indicated viable anterior myocardium, leading to successful coronary revascularization. Follow-up demonstrated improved wall motion and ejection fraction. Our study highlights the utility of late iodine enhancement with dual-energy computed tomography in assessing myocardial viability as a noninvasive alternative to magnetic resonance imaging, particularly in patients with contraindications to magnetic resonance imaging. This approach aids in treatment planning, evaluation of efficacy and determination of prognosis in cases of ischemic heart disease.

Advances in Multi-Modality Imaging in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is characterized by abnormal growth of the myocardium with myofilament disarray and myocardial hyper-contractility, leading to left ventricular hypertrophy and fibrosis. Where culprit genes are identified, they typically relate to cardiomyocyte sarcomere structure and function. Multi-modality imaging plays a crucial role in the diagnosis, monitoring, and risk stratification of HCM, as well as in screening those at risk. Following the recent publication of the first European Society of Cardiology (ESC) cardiomyopathy guidelines, we build on previous reviews and explore the roles of electrocardiography, echocardiography, cardiac magnetic resonance (CMR), cardiac computed tomography (CT), and nuclear imaging. We examine each modality's strengths along with their limitations in turn, and discuss how they can be used in isolation, or in combination, to facilitate a personalized approach to patient care, as well as providing key information and robust safety and efficacy evidence within new areas of research.

Myocardial extracellular volume quantification in cardiac amyloidosis: a comparative study between cardiac computed tomography and magnetic resonance imaging

OBJECTIVES

Myocardial extracellular volume (ECV) on computed tomography (CT), an alternative to cardiac magnetic resonance (CMR), has significant practical clinical advantages. However, the consistency between ECVs quantified via CT and CMR in cardiac amyloidosis (CA) has not been investigated sufficiently. Therefore, the current study investigated the application of CT-ECV in CA with CMR-ECV as the reference standard.

METHODS

We retrospectively evaluated 31 patients with CA who underwent cardiac CT and CMR. Pearson correlation analysis was performed to investigate correlations between CT-ECV and CMR-ECV at each segment. Further, correlations between ECV and clinical parameters were assessed.

RESULTS

There were no significant differences in the mean global ECVs between CT scan and CMR (51.3% ± 10.2% vs 50.0% ± 10.5%). CT-ECV was correlated with CMR-ECV at the septal (r = 0.88), lateral (r = 0.80), inferior (r = 0.79), anterior (r = 0.77) segments, and global (r = 0.87). In both CT and CMR, the ECV had a weak to strong correlation with high-sensitivity cardiac troponin T level, a moderate correlation with global longitudinal strain, and an inverse correlation with left ventricular ejection fraction. Further, the septal ECV and global ECV had a slightly higher correlation with the clinical parameters.

CONCLUSIONS

Cardiac CT can quantify myocardial ECV and yield results comparable to CMR in patients with CA. Moreover, a significant correlation between CT-ECV and clinical parameters was observed. Thus, CT-ECV can be an imaging biomarker and alternative to CMR-ECV.

CLINICAL RELEVANCE STATEMENT

Cardiac CT can quantify myocardial ECV and yield results comparable to CMR in patients with CA, and CT-ECV can be used clinically as an imaging biomarker and alternative to CMR-ECV.

KEY POINTS

• A significant correlation was found between CT myocardial extracellular volume and cardiac MR myocardial extracellular volume in patients with cardiac amyloidosis. • In CT and cardiac MR, the myocardial extracellular volume correlated well with high-sensitivity cardiac troponin T level, global longitudinal strain, and left ventricular ejection fraction. • CT myocardial extracellular volume can be an imaging biomarker and alternative to cardiac MR myocardial extracellular volume.

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.

Extracellular volume fraction as a potential predictor to differentiate lung cancer from benign lung lesions with dual-layer detector spectral CT

Background

Extracellular volume (ECV) fraction has been used in cardiovascular diseases, pancreatic fibrosis, and hepatic fibrosis. The diagnostic value of ECV for focal lung lesions remains to be explored. The aim of this study was to evaluate the feasibility of ECV derived from a dual-layer detector computed tomography (DLCT) to differentiate lung cancer (LC) from benign lung lesions (BLLs).

Methods

Retrospectively, 128 consecutive patients with pathologically confirmed LC (n=86) or BLLs (n=42) were included. Conventional computed tomography (CT) characteristics and spectral CT parameters were assessed. All patients' hematocrits were measured to correct contrast volume distributions in blood while calculating ECV. After performing logistic regression analysis, a conventional CT-based model (Model A), DLCT-based model (Model B), combined diagnostic models (Model C), and an ECV-based model (Model D) were developed. The diagnostic effectiveness of each model was examined using the receiver operating characteristic (ROC) curve and their corresponding 95% confidence intervals (CIs). The area under the curve (AUC) of each model was compared using the DeLong test.

Results

Certain conventional CT features (such as lesion size, lobulation, spiculation, pleural indentation, and enlarged lymph nodes) differed significantly between the LC and BLL groups (all P<0.05). Statistical differences were found in the following DLCT parameters (all P<0.05): effective atomic number (Zeff) (non-enhancement), electron density (ED) (non-enhancement), ECV, iodine concentration (IC), and normalized iodine concentration (NIC). Models A, B, C, and D had AUCs of 0.801 [95% confidence interval (CI): 0.721-0.866], 0.805 (95% CI: 0.726-0.870), 0.925 (95% CI: 0.865-0.964), and 0.754 (95% CI: 0.671-0.826), respectively. The AUC of Model D (ECV) showed no significant difference from that of Models A and B (DeLong test, P>0.05).

Conclusions

The ECV derived from DLCT may be a potential new method to differentiate LC from BLLs, broadening the scope of ECV in clinical research.

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.

Cardiac CT in CRT as a Singular Imaging Modality for Diagnosis and Patient-Tailored Management

Between 30-40% of patients with cardiac resynchronization therapy (CRT) do not show an improvement in left ventricular (LV) function. It is generally known that patient selection, LV lead implantation location, and device timing optimization are the three main factors that determine CRT response. Research has shown that image-guided CRT placement, which takes into account both anatomical and functional cardiac properties, positively affects the CRT response rate. In current clinical practice, a multimodality imaging approach comprised of echocardiography, cardiac magnetic resonance imaging, or nuclear medicine imaging is used to capture these features. However, with cardiac computed tomography (CT), one has an all-in-one acquisition method for both patient selection and the division of a patient-tailored, image-guided CRT placement strategy. This review discusses the applicability of CT in CRT patient identification, selection, and guided placement, offering insights into potential advancements in optimizing CRT outcomes.

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).

Characterizing the Heart and the Myocardium With Photon-Counting CT

ABSTRACT

Noninvasive cardiac imaging has rapidly evolved during the last decade owing to improvements in computed tomography (CT)-based technologies, among which we highlight the recent introduction of the first clinical photon-counting detector CT (PCD-CT) system. Multiple advantages of PCD-CT have been demonstrated, including increased spatial resolution, decreased electronic noise, and reduced radiation exposure, which may further improve diagnostics and may potentially impact existing management pathways. The benefits that can be obtained from the initial experiences with PCD-CT are promising. The implementation of this technology in cardiovascular imaging allows for the quantification of coronary calcium, myocardial extracellular volume, myocardial radiomics features, epicardial and pericoronary adipose tissue, and the qualitative assessment of coronary plaques and stents. This review aims to discuss these major applications of PCD-CT with a focus on cardiac and myocardial characterization.

Multimodality Cardiac Imaging in COVID

Infection with SARS-CoV-2, the virus that causes COVID, is associated with numerous potential secondary complications. Global efforts have been dedicated to understanding the myriad potential cardiovascular sequelae which may occur during acute infection, convalescence, or recovery. Because patients often present with nonspecific symptoms and laboratory findings, cardiac imaging has emerged as an important tool for the discrimination of pulmonary and cardiovascular complications of this disease. The clinician investigating a potential COVID-related complication must account not only for the relative utility of various cardiac imaging modalities but also for the risk of infectious exposure to staff and other patients. Extraordinary clinical and scholarly efforts have brought the international medical community closer to a consensus on the appropriate indications for diagnostic cardiac imaging during this protracted pandemic. In this review, we summarize the existing literature and reference major societal guidelines to provide an overview of the indications and utility of echocardiography, nuclear imaging, cardiac computed tomography, and cardiac magnetic resonance imaging for the diagnosis of cardiovascular complications of COVID.

Multimodality imaging in the diagnostic management of concomitant aortic stenosis and transthyretin-related wild-type cardiac amyloidosis

Severe aortic stenosis (AS) is the most common valvular heart disease with a prevalence rate of more than 4% in 75-year-old people or older. Similarly, cardiac amyloidosis (CA), especially "wild-type transthyretin" (wTTR), has shown a prevalence rate ranging from 22% to 25% in people older than 80 years. The detection of the concomitant presence of CA and AS is challenging primarily because of the similar type of changes in the left ventricle caused by AS and CA, which share some morphological characteristics. The aim of this review is to identify the imaging triggers in order to recognize occult wtATTR-CA in patients with AS, clarifying the crucial step of the diagnostic process. Multimodality imaging methods such as echocardiography, cardiac magnetic resonance, cardiac computed tomography, and DPD scintigraphy will be analyzed as part of the available diagnostic workup to identify wtATTR-CA early in patients with AS.

Extracellular volume fraction determined by dual-layer spectral detector CT: Possible role in predicting the efficacy of preoperative neoadjuvant chemotherapy in pancreatic ductal adenocarcinoma

PURPOSE

To clarify the relationship between extracellular volume (ECV) measured by dual-energy CT (DECT) and efficacy of preoperative neoadjuvant chemotherapy (NAC) in patients with pancreatic ductal adenocarcinoma (PDAC), as compared with single-energy CT (SECT).

METHODS

We enrolled 67 patients with PDAC who underwent dynamic contrast-enhanced CT with a dual-energy CT system prior to NAC. Attenuation values were measured on unenhanced and the equilibrium-phase 120-kVp equivalent CT images for PDAC and the aorta. ΔHU-tumor, ΔHU-tumor/ΔHU-aorta, and SECT-ECV were calculated. Iodine densities of the tumor and aorta were measured in the equilibrium phase, and DECT-ECV of the tumor was calculated. Response to NAC was evaluated and the correlation between imaging parameters and response to NAC was statistically assessed.

RESULTS

Tumor DECT-ECVs were significantly lower in the response group (n = 7) than in the non-response group (n = 60), with most significant difference (p = 0.0104). DECT-ECV showed highest diagnostic value with an Az value of 0.798. When using the optimal cut off value of DECT-ECV (<26.0 %), sensitivity, specificity, accuracy, positive predictive value, and negative value for predicting response group were 71.4 %, 85.0 %, 83.6 %, 35.7 % and 96.2 %, respectively.

CONCLUSION

PDAC with lower DECT-ECV can potentially show better response to NAC. DECT-ECV might be a useful biomarker for predicting response to NAC in patients with PDAC.

Towards Automated Brain Aneurysm Detection in TOF-MRA: Open Data, Weak Labels, and Anatomical Knowledge

Brain aneurysm detection in Time-Of-Flight Magnetic Resonance Angiography (TOF-MRA) has undergone drastic improvements with the advent of Deep Learning (DL). However, performances of supervised DL models heavily rely on the quantity of labeled samples, which are extremely costly to obtain. Here, we present a DL model for aneurysm detection that overcomes the issue with "weak" labels: oversized annotations which are considerably faster to create. Our weak labels resulted to be four times faster to generate than their voxel-wise counterparts. In addition, our model leverages prior anatomical knowledge by focusing only on plausible locations for aneurysm occurrence. We first train and evaluate our model through cross-validation on an in-house TOF-MRA dataset comprising 284 subjects (170 females / 127 healthy controls / 157 patients with 198 aneurysms). On this dataset, our best model achieved a sensitivity of 83%, with False Positive (FP) rate of 0.8 per patient. To assess model generalizability, we then participated in a challenge for aneurysm detection with TOF-MRA data (93 patients, 20 controls, 125 aneurysms). On the public challenge, sensitivity was 68% (FP rate = 2.5), ranking 4th/18 on the open leaderboard. We found no significant difference in sensitivity between aneurysm risk-of-rupture groups (p = 0.75), locations (p = 0.72), or sizes (p = 0.15). Data, code and model weights are released under permissive licenses. We demonstrate that weak labels and anatomical knowledge can alleviate the necessity for prohibitively expensive voxel-wise annotations.

Illustrative review of cardiac amyloidosis by multimodality imaging

Cardiac involvement in amyloidosis is characterized by the extracellular deposition of misfolded proteins in the heart with the pathognomonic histological property of green birefringence when viewed under cross-polarized light after staining with Congo red. Although considered a rare disease, recent data suggest that cardiac amyloidosis is underappreciated as a cause of common cardiac diseases or syndromes. The prognosis for transthyretin (TTR) amyloidosis (ATTR) amyloidosis is better than that for amyloid light-chain amyloidosis; however, it is not as good as for other etiologies heart failure. Although there is no proven therapy for patients with ATTR cardiomyopathy (ATTR-CM), tafamidis meglumine, a TTR stabilizer, a study in 2018 found it was associated with reductions in all-cause mortality and cardiovascular-related hospitalizations, as well as with a reduction in the decline in functional capacity and quality of life compared with a placebo for patients with ATTR-CM. As a result of these findings, tafamidis meglumine is currently the only drug approved for patients with both wild-type and variant ATTR-CM, and should be considered for patients whose survival can be reasonably expected. In addition, recent advances in cardiac imaging, diagnostic strategies, and therapies have improved so that interest has been growing in the diagnosis of ATTR-CM by means of non-invasive imaging modalities as a potential means for better management of patients with ATTR-CM. This article reviews the efficacy of non-invasive imaging, especially echocardiography, cardiac magnetic imaging, and ^99mTc-pyrophosphate scintigraphy for diagnosis of cardiac amyloidosis.

Multimodality imaging in cardiac amyloidosis: State-of-the-art review

Amyloidosis is a systemic disease, characterized by deposition of amyloid fibrils in various organs, including the heart. For the diagnosis of cardiac amyloidosis (CA) it is required a high level of clinical suspicion and in the presence of clinical, laboratorial, and electrocardiographic red flags, a comprehensive multimodality imaging evaluation is warranted, including echocardiography, magnetic resonance, scintigraphy, and computed tomography, that will confirm diagnosis and define the CA subtype, which is of the utmost importance to plan a treatment strategy. We will review the use of multimodality imaging in the evaluation of CA, including the latest applications, and a practical flow-chart will sum-up this evidence.

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.

Deep Learning-based Post Hoc CT Denoising for Myocardial Delayed Enhancement

Background To improve myocardial delayed enhancement (MDE) CT, a deep learning (DL)-based post hoc denoising method supervised with averaged MDE CT data was developed. Purpose To assess the image quality of denoised MDE CT images and evaluate their diagnostic performance by using late gadolinium enhancement (LGE) MRI as a reference. Materials and methods MDE CT data obtained by averaging three acquisitions with a single breath hold 5 minutes after the contrast material injection in patients from July 2020 to October 2021 were retrospectively reviewed. Preaveraged images obtained in 100 patients as inputs and averaged images as ground truths were used to supervise a residual dense network (RDN). The original single-shot image, standard averaged image, RDN-denoised original (DL_original) image, and RDN-denoised averaged (DL_ave) image of holdout cases were compared. In 40 patients, the CT value and image noise in the left ventricular cavity and myocardium were assessed. The segmental presence of MDE in the remaining 40 patients who underwent reference LGE MRI was evaluated. The sensitivity, specificity, and accuracy of each type of CT image and the improvement in accuracy achieved with the RDN were assessed using odds ratios (ORs) estimated with the generalized estimation equation. Results Overall, 180 patients (median age, 66 years [IQR, 53-74 years]; 107 men) were included. The RDN reduced image noise to 28% of the original level while maintaining equivalence in the CT values (P < .001 for all). The sensitivity, specificity, and accuracy of the original images were 77.9%, 84.4%, and 82.3%, of the averaged images were 89.7%, 87.9%, and 88.5%, of the DL_original images were 93.1%, 87.5%, and 89.3%, and of the DL_ave images were 95.1%, 93.1%, and 93.8%, respectively. DL_original images showed improved accuracy compared with the original images (OR, 1.8 [95% CI: 1.2, 2.9]; P = .011) and DL_ave images showed improved accuracy compared with the averaged images (OR, 2.0 [95% CI: 1.2, 3.5]; P = .009). Conclusion The proposed denoising network supervised with averaged CT images reduced image noise and improved the diagnostic performance for myocardial delayed enhancement CT. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Vannier and Wang in this issue.

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.

Effect of image quality on myocardial extracellular volume quantification using cardiac computed tomography: a phantom study

BACKGROUND

The image quality directly affects the accuracy of computed tomography (CT) extracellular volume (ECV) quantification.

PURPOSE

To investigate the effects of image quality and acquisition protocol on the accuracy of ECV quantification.

MATERIAL AND METHODS

One-volume scans were performed on a 320-row multidetector CT volume scanner using a multi-energy CT phantom. To simulate the blood pool and myocardium, solid rods representing blood and soft tissue were used in precontrast CT. Moreover, the solid rods including different iodine concentrations were used in postcontrast CT. The tube voltage was set at 120 kVp, and the tube current was changed from 750 mA (100% dose) to 190 mA (25% dose). All images underwent full- and half-scan reconstructions based on model-based iterative reconstruction. The ECV was calculated from the CT numbers between pre- and postcontrast.

RESULTS

The mean ECV with full- and half-scan reconstructions at the central portion was 0.275 at 100% scan dose to 0.271 at 25% scan dose and 0.276 at 100% scan dose to 0.269 at 25% scan dose. Compared with that in the 100% scan dose, the variation in each ECV increased with decreasing radiation dose. The ECV at the center of the image along the z-axis had lower variation than that at outer portion of the images. On the reconstruction algorithm, there was no statistical difference in ECVs with full- and half-scan reconstructions.

CONCLUSION

For stable ECV quantifications, excessive radiation dose reduction may be inappropriate, and it is better to consider the variations in ECV values depending on the slice location.

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.

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.

Diagnostic Performance of Extracellular Volume Quantified by Dual-Layer Dual-Energy CT for Detection of Acute Myocarditis

Background: Myocardial extracellular volume (ECV) is a marker of the myocarditis inflammation burden and can be used for acute myocarditis diagnosis. Dual-energy computed tomography (DECT) enables its quantification with high concordance with cardiac magnetic resonance (CMR). Purpose: To investigate the diagnostic performance of myocardial ECV quantified on a cardiac dual-layer DECT in a population of patients with suspected myocarditis, in comparison to CMR. Methods: 78 patients were included in this retrospective monocenter study, 60 were diagnosed with acute myocarditis and 18 patients were considered as a control population, based on the 2009 Lake and Louise criteria. All subjects underwent a cardiac DECT in acute phase consisted in an arterial phase followed by a late iodine enhancement phase at 10 min after injection (1.2 mL/kg, iodinated contrast agent). ECV was calculated using the hematocrit level measured the day of DECT examinations. Non-parametric analyses have been used to test the differences between groups and the correlations between the variables. A ROC curve has been used to identify the optimal ECV cut-off discriminating value allowing the detection of acute myocarditis cases. A p value < 0.05 has been considered as significant. Results: The mean ECV was significantly higher (p < 0.001) for the myocarditis group compared to the control (34.18 ± 0.43 vs. 30.04 ± 0.53%). A cut-off value of ECV = 31.60% (ROC AUC = 0.835, p < 0.001) allows to discriminate the myocarditis with a sensitivity of 80% and a specificity of 78% (positive predictive value = 92.3%, negative predictive value = 53.8% and accuracy = 79.5%). Conclusion: Myocardial ECV enabled by DECT allows to diagnose the acute myocarditis with a cut-off at 31.60% for a sensitivity of 80% and specificity of 78%.

Liver fibrosis assessment with multiphasic dual-energy CT: diagnostic performance of iodine uptake parameters

OBJECTIVES

To evaluate the ability of iodine uptake parameters from hepatic multiphasic CT to predict liver fibrosis, and compare absolute contrast enhancement (ΔHU) with dual-energy iodine density (ID) methods.

METHODS

One hundred seventeen patients with pathologically proven liver fibrosis who underwent dual-energy CT during portal-venous phase (PVP) and 3-min delayed phase (DP) between January 2017 and Octotber 2019 were retrospectively included. Two radiologists measured the hepatic and blood-pool iodine uptake using ΔHU and ID methods; extracellular volume fraction (ECV) and the iodine washout rate (IWR) calculated with both methods were compared between different fibrosis stages (F0-1 vs. F2-4, F0-2 vs. F3-4, or F0-3 vs. F4). The inter-observer reproducibility (intraclass correlation coefficients [ICCs]) for ECV and IWR was compared between the ΔHU and ID methods. The areas under the receiver operating characteristic curves (AUCs) to predict liver fibrosis severity were calculated for serum and imaging fibrosis markers. To identify independent predictors, multivariable logistic regression analysis was performed, and combined performance was assessed for the ΔHU and ID models.

RESULTS

Patients with F ≥ 2 (n = 70), F ≥ 3 (n = 51), and F4 (n = 29) had higher ECV and lower IWR than those with F ≤ 1, F ≤ 2, and F ≤ 3, respectively (all p < 0.001). ICCs were higher in the ID method than in the ΔHU method (ECV: p = 0.045; IWR: p < 0.001). The AUC ranges of ECV_ΔHU, ECV_ID, IWR_ΔHU, and IWR_ID for predicting liver fibrosis severity were 0.65-0.71, 0.67-0.73, 0.76-0.81, and 0.81-0.85, respectively. IWR and fibrosis-4 index were independent predictors, with combined AUCs of 0.82-0.87 for the ΔHU model and 0.86-0.89 for the ID model.

CONCLUSIONS

IWR more accurately predicted liver fibrosis than ECV in routine multiphasic CT. The dual-energy ID method yielded higher inter-observer reproducibility and predictive values than the single-energy ΔHU method.

KEY POINTS

• The IWR calculated from hepatic iodine uptake during PVP and 3-min DP predicted liver fibrosis (AUC, 0.76-0.85), while the ECV had a relatively limited predictive value (ACU, 0.65-0.73). • Compared with the conventional ΔHU method, the dual-energy ID method provided superior inter-observer reproducibility for measurement of ECV (p = 0.046) and IWR (p < 0.001). • The IWR and FIB-4 served as independent predictors of liver fibrosis; their combination yielded the high diagnostic performance particularly when using the ID method (combined AUCs of 0.86-0.89).

Acute Myocarditis Associated with Acute Myocardial Infarction

Concomitant acute myocarditis and acute coronary thrombosis is a rare presentation of acute chest pain in the emergency department, although the association between acute infections with a variety of pathogens and an increased risk of myocardial infarction has been reported. A case of acute myocardial infarction associated with acute myocarditis caused by coronavirus 229E in a middle-aged man without risk factors for coronary artery disease is described here. Coronary CT angiography with late enhancement protocol revealed areas of myocarditis and infarction, and cardiac MRI and coronary angiography were then performed. © RSNA, 2021.

Noninvasive assessment of liver fibrosis by dual-layer spectral detector CT

PURPOSE

To elucidate the diagnostic ability of liver fibrosis using (1) liver parenchymal iodine density on equilibrium computed tomographic imaging and (2) extracellular volume (ECV) measured by dual-layer spectral detector CT.

METHODS

From April 2018 to June 2019, 68 patients [mean age, 62 years; 39 males, 29 females] underwent dynamic contrast-enhanced CT by a dual-layer spectral detector CT system before liver transplantation or liver resection. The iodine densities of liver parenchyma (I _liver) and aorta (I _aorta) were independently measured by two radiologists at the equilibrium phase. The iodine-density ratio (I-ratio) (I _liver/ I _aorta) and the CT-ECV were calculated. Spearman's rank correlation coefficient was used to analyze the relationship between the I-ratio or the CT-ECV and the fibrosis stage. A receiver operating characteristic (ROC) curve analysis was performed to determine the accuracy of the I-ratio and the CT-ECV for discriminating fibrosis stages.

RESULTS

For both readers, the I-ratio and the CT-ECV increased significantly as the fibrosis stage advanced (I-ratio: rho = 0.380 and 0.443, p < 0.01; CT-ECV: rho = 0.423 and 0.469, p < 0.01). The CT-ECV showed better diagnostic accuracy for staging fibrosis, and the area under the ROC curve values for discriminating F4 stage were 0.884 and 0.925. The two readers' cutoff values of the CT-ECV for diagnosing fibrosis as F4 were 26.2 % and 29.3 %, with 95.0 % and 90.0 % sensitivity and 72.9 % and 85.4 % specificity, respectively.

CONCLUSION

The liver parenchymal iodine density on the equilibrium phase and the CT-ECV can be useful for predicting a high stage of liver fibrosis.

Right Ventricular Extracellular Volume with Dual-Layer Spectral Detector CT: Value in Chronic Thromboembolic Pulmonary Hypertension

Background Right ventricular (RV) extracellular volumes (ECVs), as a surrogate for histologic fibrosis, have not been sufficiently investigated. Purpose To evaluate and compare RV and left ventricular (LV) ECVs obtained with dual-layer spectral detector CT (DLCT) in chronic thromboembolic pulmonary hypertension (CTEPH) and investigate the clinical importance of RV ECV. Materials and Methods Retrospective analysis was performed on data from 31 patients with CTEPH (17 were not treated with pulmonary endarterectomy [PEA] or balloon pulmonary angioplasty [BPA] and 14 were) and eight control subjects who underwent myocardial delayed enhancement (MDE) DLCT from January 2019 to June 2020. The ECVs in the RV and LV walls were calculated by using iodine density as derived from spectral data pertaining to MDE. Statistical analyses were performed with one-way repeated analysis of variance with the Tukey post hoc test or the Kruskal-Wallis test with the Steel-Dwass test and linear regression analysis. Results The PEA- and BPA-naive group showed significantly higher ECVs than the PEA- or BPA-treated group and control group in the septum (28.2% ± 2.9 vs 24.3% ± 3.6, P = .005), anterior right ventricular insertion point (RVIP) (32.9% ± 4.6 vs 25.3% ± 3.6, P < .001), posterior RVIP (35.2% ± 5.2 vs 27.3% ± 4.2, P < .001), mean RVIP (34.0% ± 4.2 vs 26.3% ± 3.4, P < .001), RV free wall (29.5% ± 3.3 vs 25.9% ± 4.1, P = .036), and mean RV wall (29.1% ± 3.0 vs 26.1% ± 3.1, P = .029). There were no significant differences between the PEA- or BPA-treated group and control subjects in these segments (septum, P = .93; anterior RVIP, P = .38; posterior RVIP, P = .52; mean RVIP, P = .36; RV free wall, P = .97; and mean RV, P = .33). There were significant correlations between ECV and mean pulmonary artery pressure (PAP) or brain natriuretic peptide (BNP) in the mean RVIP (mean PAP: R = 0.66, P < .001; BNP: R = 0.44, P = .014) and the mean RV (mean PAP: R = 0.49, P = .005; BNP: R = 0.44, P = .013). Conclusion Right ventricular and right ventricular insertion point extracellular volumes could be noninvasive surrogate markers of disease severity and reverse tissue remodeling in chronic thromboembolic pulmonary hypertension. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Sandfort and Bluemke in this issue.

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.