Cardiac Positron Emission Tomography Research Articles

Automated cardiovascular risk categorization through AI-driven coronary calcium quantification in cardiac PET acquired attenuation correction CT

BackgroundWe present an automatic method for coronary artery calcium (CAC) quantification and cardiovascular risk categorization in CT attenuation correction (CTAC) scans acquired at rest and stress during cardiac PET/CT. The method segments CAC according to visual assessment rather than the commonly used CT-number threshold. MethodsThe method decomposes an image containing CAC into a synthetic image without CAC and an image showing only CAC. Extensive evaluation was performed in a set of 98 patients, each having rest and stress CTAC scans and a dedicated calcium scoring CT (CSCT). Standard manual calcium scoring in CSCT provided the reference standard. ResultsThe interscan reproducibility of CAC quantification computed as average absolute relative differences between CTAC and CSCT scan pairs was 75% and 85% at rest and stress using the automatic method compared to 121% and 114% using clinical calcium scoring. Agreement between automatic risk assessment in CTAC and clinical risk categorization in CSCT resulted in linearly weighted kappa of 0.65 compared to 0.40 between CTAC and CSCT using clinically used calcium scoring. ConclusionThe increased interscan reproducibility achieved by our method may allow routine cardiovascular risk assessment in CTAC, potentially relieving the need for dedicated CSCT.

Value of PET ECG gating in a cross-validation study of cardiac function assessment by PET/MR imaging

BackgroundThis work investigated the impact of different cardiac gating methods on the assessment of cardiac function by FDG-PET in a cross-validation PET/MR study. Methods and resultsMR- and PET-based left ventricular end-diastolic, end-systolic volumes, and ejection fraction (EDV, ESV, and EF) were delineated in 30 patients with a PET/MR examination. Cardiac PET imaging was performed using three ECG gating methods: fixed number of gates per beat (STD), STD with a beat acceptance window (STD-BR), and fixed gate duration (FW). High MR-PET correlations were found in all the values. ESVs correlated better than EDVs and EFs: Pearson’s r coefficient [0.92, 0.92, 0.92] in ESV vs [0.75, 0.81, 0.80] in EDV and [0.79, 0.91, 0.87] in EF, for each method [STD, STD-BR, FW]. Biases with respect to MRI for all the evaluated PET methods were less than 13% in EDV, 5% in ESV, and 14% in EF, but with wide limits of agreements, in the range (59-68)% in EDV, (65-70)% in ESV, and (49-71)% in EF. STD showed the strongest disagreement, while there were no marked differences between STD-BR and FW. ConclusionBased on these findings, PET- and MR-based cardiac function parameters were highly correlated but in substantial disagreement with variabilities introduced by the selected PET ECG gating method. The most significant differences were associated with the ECG gating method susceptible to highly irregular beats, while similar performance was observed in the methods using uniform adjustment of gates width per beat with the beat acceptance window, and fixed gate width along all the beats. Thus, strict quality controls of R peak detection are needed to minimize its impact on the function assessment.

0488 The Relationship between Myocardial Blood Flow and Diastolic Function in a Clinical Population with Obstructive Sleep Apnea

Abstract Introduction Emerging evidence links abnormal myocardial blood flow reserve (MBFR), a marker of coronary microvascular dysfunction (CMD), and heart failure with preserved ejection fraction (HFpEF). However, the relationship between CMD and diastolic dysfunction (DD) in patients with OSA remains unclear. We analyzed the relationship between OSA, abnormal MBFR and markers of DD in a patient cohort. Methods Using healthcare records, we generated a cross-sectional database of 231 individuals who had sleep testing, echocardiogram(s), and cardiac PET stress test. Abnormal MBFR was defined as the stress-to-rest ratio of myocardial blood flow < 2.0. We created DD score with a point each given to a) left atrial volume index (LAVI) ≥34, b)average E/e’ ratio>14/lateral e’>10/medial e’>7, and in a subgroup of 122 individuals with available data we added c)tricuspid regurgitation jet (TR) velocity > 2.7m/s. Higher scores suggest greater likelihood of DD. Models were adjusted for demographics and cardiometabolic risk factors. Results The mean (SD) age and BMI was 60(11) years and 39.5(8.7) kg/m2; 61% were female. Eighty-four participants had severe OSA (apnea-hypopnea index ≥ 30/hr). Compared to non-severe OSA, severe OSA was associated with 2-fold odds of abnormal MBFR (adjusted OR [aOR) 2.1, 95%CI:1.1–4.0). However, there was no association with abnormal LAVI, abnormal E/e’ (average E/e’>14 vs. < 9), or elevated TR velocity. In the adjusted model, abnormal MBFR was associated with abnormal E/e’ (aOR 4.4 [95% CI: 1.6-11.8]) and elevated TR velocity (aOR: 3.7 [95%CI: 1.3-10.9]). Abnormal MBFR was associated with increase in DD score (range 0–2; aOR per-unit increase = 1.7 [95% CI: 1.0-3.0]. In the subset with data on TR velocity, abnormal MBFR was associated with a three-fold increase in the odds of a unit increase in DD score (range 0–3; aOR 3.3 [95% CI: 1.5,7.4]). The association between abnormal MBFR and DD was present regardless of OSA severity. Severe OSA was not associated with DD. Conclusion Abnormal MBFR/CMD may be implicated in the development of DD and HFpEF in patients with OSA. MBFR assessment may be useful in HFpEF risk stratification in non-severe OSA. Larger studies are required to determine the role of CMD in the development of DD/HFpEF in OSA. Support (if any)

Randomized Placebo-Controlled Trial to Evaluate Effects of Eplerenone on Myocardial Perfusion and Function Among Persons With Human Immunodeficiency Virus (HIV)-Results From the MIRACLE HIV Study.

Increased renin angiotensin aldosterone system (RAAS) activity may contribute to excess cardiovascular disease in people with HIV (PWH). We investigated how RAAS blockade may improve myocardial perfusion, injury, and function among well-treated PWH. Forty PWH, on stable ART, without known heart disease were randomized to eplerenone 50 mg PO BID (n = 20) or identical placebo (n = 20) for 12 months. The primary endpoints were (1) myocardial perfusion assessed by coronary flow reserve (CFR) on cardiac PET or stress myocardial blood flow (sMBF) on cardiac MRI or (2) myocardial inflammation by extracellular mass index (ECMi) on cardiac MRI. Beneficial effects on myocardial perfusion were seen for sMBF by cardiac MRI (mean [SD]: 0.09 [0.56] vs -0.53 [0.68] mL/min/g; P = .03) but not CFR by cardiac PET (0.01 [0.64] vs -0.07 [0.48]; P = .72, eplerenone vs placebo). Eplerenone improved parameters of myocardial function on cardiac MRI including left ventricular end diastolic volume (-13 [28] vs 10 [26] mL; P = .03) and global circumferential strain (GCS; median [interquartile range 25th-75th]: -1.3% [-2.9%-1.0%] vs 2.3% [-0.4%-4.1%]; P = .03), eplerenone versus placebo respectively. On cardiac MRI, improvement in sMBF related to improvement in global circumferential strain (ρ = -0.65, P = .057) among those treated with eplerenone. Selecting for those with impaired myocardial perfusion (CFR <2.5 and/or sMBF <1.8), there was a treatment effect of eplerenone versus placebo to improve CFR (0.28 [0.27] vs -0.05 [0.36]; P = .04). Eplerenone prevented a small increase in troponin (0.00 [-0.13-0.00] vs 0.00 [0.00-0.74] ng/L; P = .03) without effects on ECMi (0.9 [-2.3-4.3] vs -0.7 [-2.2--0.1] g/m2; P = .38). CD4+ T-cell count (127 [-38-286] vs -6 [-168-53] cells/μL; P = .02) increased in the eplerenone- versus placebo-treated groups. RAAS blockade with eplerenone benefitted key indices and prevented worsening of myocardial perfusion, injury, and function among PWH with subclinical cardiac disease when compared with placebo. NCT02740179 (https://clinicaltrials.gov/ct2/show/NCT02740179?term=NCT02740179&draw=2&rank=1).

Role of Multimodality Imaging in Transcatheter Structural Interventions.

Cardiac imaging is the backbone for safe and optimal transcatheter structural interventions. Transthoracic echocardiogram is the initial modality to assess valvular disorders, while transesophageal echocardiogram is best to delineate the mechanism of valvular regurgitation, preprocedural assessment for transcatheter edge-to-edge repair, and for intraprocedural guidance. Cardiac computed tomography is the modality of choice for assessing calcifications, maneuvering multiplaner reconstruction of different cardiac structures, preprocedural planning for various transcatheter valve replacement, and assessing for hypoattenuated leaflet thickening and reduced leaflet motion. Cardiac magnetic resonance imaging is best known for most accurate volumetric assessment of valvular regurgitation and chamber size quantification. Cardiac positron emission tomography is the only modality that could assess active infection through using fluorine 18 fluorodeoxyglucose radiotracer.

The Role of Cardiac PET in Diagnosis and Prognosis of Ischemic Heart Disease: Optimal Modality Across Different Patient Populations.

Despite single-photon emission computerized tomography (SPECT) being the most used nuclear imaging technique for diagnosis of coronary artery disease (CAD), many now consider positron emission tomography (PET) as a superior modality. This review will focus on the advances of cardiac PET in recent years and its advantages compared to SPECT in diagnosis and prognosis of CAD. PET's higher resolution and enhanced diagnostic accuracy, as well as lower radiation exposure, all help explain the rationale for its wider spread and use. PET also allows for measurement of myocardial blood flow (MBF) and myocardial flow reserve (MFR), which aids in several different clinical scenarios, such as diagnosing multivessel disease or identifying non-responders. PET has also been shown to be useful in diagnosing CAD in various specific populations, such as patients with prior COVID-19 infection, cardiac transplant, and other comorbidities.

MP-453090-11 HIBERNATING MYOCARDIUM IS ASSOCIATED WITH A LOWER INCIDENCE OF SUSTAINED VENTRICULAR ARRHYTHMIAS IN PATIENTS WITH ISCHEMIC CARDIOMYOPATHY

Prognostic markers for the prediction of major arrhythmic events (MAE) in patients with ischemic cardiomyopathy (ICM) are scarce. Although myocardial scar is associated with ventricular arrhythmias (VA), the role of hibernating myocardium (HM) is unclear. The aim of this study was to identify prognostic markers for MAE using positron emission tomography (PET) in patients with ICM. In this retrospective single-center study, consecutive patients with ICM confirmed by invasive coronary angiography undergoing both 13N-ammonia (NH3) and 18F-fluorodeoxyglucose (FDG) scan for evaluation of myocardial ischemia and HM were assessed for the occurrence of MAE after PET scan of sudden cardiac death (SCD), survived SCD, VA requiring external or ICD shock, antitachycardia pacing (ATP) or sustained VA during follow-up. PET scan was performed in 254 with ICM and they were followed up for a median of 5.4 years (IQR 3.6-9.8). Mean age was 65.6 years (±10.9), mean ejection fraction was 36.2% (±12.1), 69 patients (27%) had an ICD at baseline, 39 (56.5%) for primary prevention. PET scan revealed myocardial ischemia, scar (=NH3-PET resting perfusion defect) and HM in 94 (37%), 229 (90.2%) and 121 (47.6%) patients, respectively. Mean left ventricular (LV) scar size was 23.5% (±13.5) and mean HM size 8.1% (±7.6). MAE after PET scan occurred in 34 patients (13.4%); 18 patients (7%) suffered SCD, 19 patients had sustained VA, 4 (1.6%) an external, 4 (1.6%) an ICD shock and 12 (4.7%) received ATP. Median time to MAE was 2.5 years (IQR 1-3.9). Scar >10% detected by NH3-PET scan was associated with a higher incidence of MAE (HR 1.24, CI 1.21-9.82, p=0.02) compared to ≤10%. HM >10% detected by FDG-PET scan in patients with scars >10% had lower incidence of MAE (HR 0.89, CI 0.18-0.93, p=0.033) compared to HM ≤10% or scar ≤10%, even after adjusting for LVEF ≤35%. This association remained significant when patients (n=49) revascularized within 90 days of PET scan were censored at the time of revascularization. There was no significant association between MAE and myocardial ischemia (HR 0.84, CI 0.42-1.7, p=0.63), independent of any revascularization. Patients with large and non-viable myocardial scars are at increased risk for MAE. Large (>10% of LV), but viable scars carry similar risk of MAE as smaller (≤10% of LV) scars. The combination of cardiac NH3 and FDG PET scans may serve as a prognostic tool for the prediction of clinically important endpoints such as SCD and sustained VA.

PO-04-140 ARRHYTHMIA PRESENTATION AND MANAGEMENT IN PATIENTS WITH CLINICALLY DIAGNOSED CARDIAC SARCOIDOSIS

The diagnosis of cardiac sarcoidosis (CS) is often suspected based on clinical features when histologic evidence is lacking. While the arrhythmic characteristics of CS with histologic evidence meeting the 2014 Heart Rhythm Society criteria (definite or probable CS) have been extensively studied, the arrhythmic presentations and outcomes of clinical CS are less known. To compare arrhythmia manifestations, management, and outcomes between clinically diagnosed and definite/probable CS. We retrospectively analyzed a single-center referral cohort of patients with available electrophysiologic data stratified by CS category (definite/probable or clinical). Patients with clinical CS had no histologic evidence of cardiac or extracardiac sarcoidosis (biopsy negative or not performed) and the diagnosis was based on clinical course (unexplained sustained VT, Mobitz II, or complete AV block) and imaging features (patchy uptake on dedicated cardiac positron emission tomography or late gadolinium enhancement on cardiac magnetic resonance imaging). History of arrhythmias at index evaluation, arrhythmia management, and outcomes were comparatively assessed for patients with definite/probable CS compared to those with clinical CS. The cohort included 629 CS patients (median age 57 years, male 67%, NYHA class I-II 78%), including 12% definite, 54% probable, and 34% clinical CS patients. History of ventricular and supraventricular arrhythmias was more common in clinical CS compared to definite/probable CS (Figure). Accordingly, the rate of antiarrhythmic drug use was higher in clinical (33%) than definite/probable CS (22%, p=0.002). Median follow-up after index evaluation at our institution was 3.1y (IQR 4.2y). The number of incident VT/VF events per patient per year was greater in clinical CS than definite/probable CS (Figure). Catheter ablations for ventricular arrhythmia were more frequent in clinical CS (27%) than definite/probable CS (9%, p<0.001). Patients with clinical CS exhibited a more severe arrhythmic phenotype compared to patients with definite/probable CS. These findings have implications for the management and prognosis of CS patients within this common clinical category.

Influence of image reconstruction on quantitative cardiac 15O-water positron emission tomography

BackgroundThe impact on quantitative 15O-water PET/CT of a wide range of different reconstruction settings, including regularized reconstruction by block-sequential regularized expectation maximization (BSREM), was investigated. MethodsTwenty clinical stress scans from patients referred for assessment of myocardial ischemia were included. Patients underwent a 4-min dynamic stress PET scan with 15O-water on a digital PET/CT scanner. Twenty-two reconstructions were generated from each scan and a clinical reconstruction was used as reference. Varied parameters were number of iterations, filter, exclusion of time-of-flight and point-spread function, and regularization parameter with BSREM. Analyses were performed in aQuant utilizing two different methods and resulting regional myocardial blood flow (MBF), perfusable tissue fraction (PTF), and transmural MBF (MBFt) values were evaluated. ResultsAcross the two analyses, correlations toward the reference reconstruction were strong for all parameters (ρ ≥ 0.83). Using automated analysis and the diagnostic threshold of hyperemic MBF at 2.3 mL⋅g−1⋅min−1, diagnosis was unchanged irrespective of reconstruction method in all patients except for one, where only four of the most extreme reconstruction methods resulted in a change of diagnosis. ConclusionThe low sensitivity of MBF values to reconstruction method and, as previously shown, scanner type and PET/CT misalignment, confirms that diagnostic hyperemic MBF cutoff values can be consistently used for 15O-water.

18F-FDG/13N-ammonia cardiac PET findings in ATTR cardiac amyloidosis

18F-flurodeoxyglycose (FDG)/13N-ammonia positron emission tomography/computed tomography (PET/CT) is frequently utilized to evaluate cardiac sarcoidosis (CS) but findings can reflect other forms of myocardial inflammation or altered myocardial metabolic activity. Herein, we present five cases where cardiac PET findings suggested CS, but right ventricular endomyocardial biopsy samples revealed ATTR-type cardiac amyloidosis.

Deep learning for improving PET/CT attenuation correction by elastic registration of anatomical data.

For PET/CT, the CT transmission data are used to correct the PET emission data for attenuation. However, subject motion between the consecutive scans can cause problems for the PET reconstruction. A method to match the CT to the PET would reduce resulting artifacts in the reconstructed images. This work presents a deep learning technique for inter-modality, elastic registration of PET/CT images for improving PET attenuation correction (AC). The feasibility of the technique is demonstrated for two applications: general whole-body (WB) imaging and cardiac myocardial perfusion imaging (MPI), with a specific focus on respiratory and gross voluntary motion. A convolutional neural network (CNN) was developed and trained for the registration task, comprising two distinct modules: a feature extractor and a displacement vector field (DVF) regressor. It took as input a non-attenuation-corrected PET/CT image pair and returned the relative DVF between them-it was trained in a supervised fashion using simulated inter-image motion. The 3D motion fields produced by the network were used to resample the CT image volumes, elastically warping them to spatially match the corresponding PET distributions. Performance of the algorithm was evaluated in different independent sets of WB clinical subject data: for recovering deliberate misregistrations imposed in motion-free PET/CT pairs and for improving reconstruction artifacts in cases with actual subject motion. The efficacy of this technique is also demonstrated for improving PET AC in cardiac MPI applications. A single registration network was found to be capable of handling a variety of PET tracers. It demonstrated state-of-the-art performance in the PET/CT registration task and was able to significantly reduce the effects of simulated motion imposed in motion-free, clinical data. Registering the CT to the PET distribution was also found to reduce various types of AC artifacts in the reconstructed PET images of subjects with actual motion. In particular, liver uniformity was improved in the subjects with significant observable respiratory motion. For MPI, the proposed approach yielded advantages for correcting artifacts in myocardial activity quantification and potentially for reducing the rate of the associated diagnostic errors. This study demonstrated the feasibility of using deep learning for registering the anatomical image to improve AC in clinical PET/CT reconstruction. Most notably, this improved common respiratory artifacts occurring near the lung/liver border, misalignment artifacts due to gross voluntary motion, and quantification errors in cardiac PET imaging.

Second-Line Myocardial Perfusion Imaging to Detect Obstructive Stenosis: Head-to-Head Comparison of CMR and PET

BackgroundGuidelines recommend verification of myocardial ischemia by selective second-line myocardial perfusion imaging (MPI) following a coronary computed tomography angiography (CTA) with suspected obstructive coronary artery disease (CAD). Head-to-head data on the diagnostic performance of different MPI modalities in this setting are sparse. ObjectivesThe authors sought to compare, head-to-head, the diagnostic performance of selective MPI by 3.0-T cardiac magnetic resonance (CMR) and 82rubidium positron emission tomography (RbPET) in patients with suspected obstructive stenosis at coronary CTA using invasive coronary angiography (ICA) with fractional flow reserve (FFR) as reference. MethodsConsecutive patients (n = 1,732, mean age: 59.1 ± 9.5 years, 57.2% men) referred for coronary CTA with symptoms suggestive of obstructive CAD were included. Patients with suspected stenosis were referred for both CMR and RbPET and subsequently ICA. Obstructive CAD was defined as FFR ≤0.80 or >90% diameter stenosis by visual assessment. ResultsIn total, 445 patients had suspected stenosis on coronary CTA. Of these, 372 patients completed both CMR, RbPET and subsequent ICA with FFR. Hemodynamically obstructive CAD was identified in 164 of 372 (44.1%) patients. Sensitivities for CMR and RbPET were 59% (95% CI: 51%-67%) and 64% (95% CI: 56%-71%); P = 0.21, respectively, and specificities 84% (95% CI: 78%-89%) and 89% (95% CI: 84%-93%]); P = 0.08, respectively. Overall accuracy was higher for RbPET compared with CMR (73% vs 78%; P = 0.03). ConclusionsIn patients with suspected obstructive stenosis at coronary CTA, CMR, and RbPET show similar and moderate sensitivities but high specificities compared with ICA with FFR. This patient group represents a diagnostic challenge with frequent mismatch between advanced MPI tests and invasive measurements. (Danish Study of Non-Invasive Diagnostic Testing in Coronary Artery Disease 2 [Dan-NICAD 2]; NCT03481712)

Quantifying Myocardial Blood Flow and Resistance Using 4D-Flow Cardiac Magnetic Resonance Imaging.

Ischaemia with nonobstructive coronary arteries is most commonly caused by coronary microvascular dysfunction but remains difficult to diagnose without invasive testing. Myocardial blood flow (MBF) can be quantified noninvasively on stress perfusion cardiac magnetic resonance (CMR) or positron emission tomography but neither is routinely used in clinical practice due to practical and technical constraints. Quantification of coronary sinus (CS) flow may represent a simpler method for CMR MBF quantification. 4D flow CMR offers comprehensive intracardiac and transvalvular flow quantification. However, it is feasibility to quantify MBF remains unknown. Patients with acute myocardial infarction (MI) and healthy volunteers underwent CMR. The CS contours were traced from the 2-chamber view. A reformatted phase contrast plane was generated through the CS, and flow was quantified using 4D flow CMR over the cardiac cycle and normalised for myocardial mass. MBF and resistance (MyoR) was determined in ten healthy volunteers, ten patients with myocardial infarction (MI) without microvascular obstruction (MVO), and ten with known MVO. MBF was quantified in all 30 subjects. MBF was highest in healthy controls (123.8 ± 48.4 mL/min), significantly lower in those with MI (85.7 ± 30.5 mL/min), and even lower in those with MI and MVO (67.9 ± 29.2 mL/min/) (P < 0.01 for both differences). Compared with healthy controls, MyoR was higher in those with MI and even higher in those with MI and MVO (0.79 (±0.35) versus 1.10 (±0.50) versus 1.50 (±0.69), P=0.02). MBF and MyoR can be quantified from 4D flow CMR. Resting MBF was reduced in patients with MI and MVO.

Cardiac positron emission tomography in prediction of the clinical course of chronic thromboembolic pulmonary hypertension: prospective cohort study

INTRODUCTION: During the development of CTEPH maladaptive mechanisms in the right ventricle are accompanied by disturbances in myocardial energy metabolism and perfusion. These changes can be assessed visually and quantitatively using the molecular imaging method — PET with [18F]-FDG and [13N]-NH3.OBJECTIVE: Using cardiac PET/CT investigate the relationship between perfusion and metabolism of the right ventricular myocardium and the results of other instrumental examination methods in patients with CTEPH of different severity, as well as to calculate the threshold PET values to determine the group of patients with an unfavorable clinical course of the disease.MATERIALS AND METHODS: The study included 36 patients with a verified diagnosis of CTEPH, who were examined using a standard diagnostic protocol. Patients underwent cardiac PET/CT examinations with two radiopharmaceuticals: with [18F]-FDG to study the metabolism of the ventricular myocardium and with [13N]-NH3 to assess cardiac perfusion. For each radiopharmaceutical semi-quantitative accumulation indices (SUV) and the ratio of the levels of radiopharmaceutical uptake in the right and left ventricles (SUV RV/SUV LV) were obtained. Statistics: Shapiro-Wilk test, Student’s t-test, and Mann-Whitney U-test, Pearson correlation analysis, linear regression analysis, ROC analysis.RESULTS: The level of [18F]-FDG accumulation in the right ventricular myocardium is higher in patients with a high functional class of PH than in groups I, II (p&lt;0.01). All indicators of SUV RV/SUV LV for [18F]-FDG demonstrate a direct linear relation-ship with the level of mean PAP (r=0.691, p&lt;0.0001), PVR (r=0.715, p&lt;0.0001), right ventricular size (r=0.658, p&lt;0.0001), PASP (r=0.581, p&lt;0.001) and inverse linear relationship with the functional parameters of the right ventricle CI (r=–0.555, p=0.001), CO (r=–0.488, p=0.005), TAPSE (r=–0.552, p&lt;0.001), TAVS (r=–0.537, p&lt;0.001), and SvO2 (r=–0.666, p&lt;0.0001). A correlation was found between the accumulation of [13N]-NH3 and the main hemodynamic parameters used to assess the severity of the disease (СI, SvO2). The threshold values of [18F]-FDG and [13N]-NH3 accumulation indices have been obtained, which with high sensitivity (69.2–83.3%), specificity (68.4–94.7%) and diagnostic accuracy (0.73–0.83) make it possible to identify patients with a low cardiac index and an unfavorable prognosis.DISCUSSION: The obtained results confirm the presence of glucose hypermetabolism in right ventricular cardiomyocytes in the development of pulmonary hypertension and the association of these metabolic changes with the severity of PH. A significant correlation was demonstrated between the accumulation of both radiopharmaceuticals in the heart and the results of other examination methods characterizing the severity of disease and the prognosis of patients with CTEPH. Using a non-invasive PET/CT procedure, threshold values of PET parameters were obtained, which in the future can be used to identify patients with an unfavorable clinical prognosis.CONCLUSION: Cardiac PET/CT with [18F]-FDG and [13N]-NH3 is a promising non-invasive imaging technique that can be used to study metabolic and perfusion changes in the right ventricular myocardium in CTEPH, as well as to identify patients with a high risk of adverse events.

Impaired insulin-stimulated myocardial glucose metabolic rate is associated with reduced estimated myocardial energetic efficiency in subjects with different degrees of glucose tolerance

BackgroundAlterations in myocardial mechano-energetic efficiency (MEEi), which represents the capability of the left ventricles to convert the chemical energy obtained by oxidative metabolism into mechanical work, have been associated with cardiovascular disease. Although whole-body insulin resistance has been related to impaired myocardial MEEi, it is unknown the relationship between cardiac insulin resistance and MEEi. Aim of this study was to evaluate the relationship between insulin-stimulated myocardial glucose metabolic rate (MrGlu) and myocardial MEEi in subjects having different degrees of glucose tolerance.MethodsWe evaluated insulin-stimulated myocardial MrGlu using cardiac dynamic positron emission tomography (PET) with 18F-Fluorodeoxyglucose (18F-FDG) combined with euglycemic-hyperinsulinemic clamp, and myocardial MEEi in 57 individuals without history of coronary heart disease having different degrees of glucose tolerance. The subjects were stratified into tertiles according to their myocardial MrGlu values.ResultsAfter adjusting for age, gender and BMI, subjects in I tertile showed a decrease in myocardial MEEi (0.31 ± 0.05 vs 0.42 ± 0.14 ml/s*g, P = 0.02), and an increase in myocardial oxygen consumption (MVO2) (10,153 ± 1375 vs 7816 ± 1229 mmHg*bpm, P < 0.0001) as compared with subjects in III tertile. Univariate correlations showed that insulin-stimulated myocardial MrGlu was positively correlated with MEEi and whole-body glucose disposal, and negatively correlated with waist circumference, fasting plasma glucose, HbA1c and MVO2. In a multivariate regression analysis running a model including several CV risk factors, the only variable that remained significantly associated with MEEi was myocardial MrGlu (β 0.346; P = 0.01).ConclusionsThese data suggest that an impairment in insulin-stimulated myocardial glucose metabolism is an independent contributor of depressed myocardial MEEi in subjects without history of CHD.

Primary Cardiac Burkitt’s Lymphoma- A Deadlock

Burkitt’s lymphoma is a high-grade, extremely aggressive form of B-cell non Hodgkin lymphoma with a very fast replication time (tumour doubling time of around 25 hours). The three forms of Burkitt’s lymphoma are documented which include endemic, sporadic, and immunodeficiency associated. It is enormously rare with less than 30 cases reported till date. Primary cardiac lymphoma is a rare cardiac neoplasm. The most common type is diffuse large B-cell lymphoma. Diagnosis is usually late and with poor prognosis. Primary cardiac lymphoma is more common in immunodeficient patients. This is a case of primary cardiac Burkitt’s lymphoma which was diagnosed in a 58-year-old immunocompetent male. The patient’s two-dimensional echocardiography and plain Computed Tomography (CT) scan of the chest revealed presence of massive pericardial effusion with mild to moderate bilateral pleural effusion. Cardiac Positron Emission Tomography (PET) CT revealed a soft tissue mass at atrioventricular groove which indicated either pericardial lymphoma or inflammatory serositis. The patient was opted for surgery, but the mass was noted involving the free wall of right ventricle including the diaphragmatic surface which extended onto atrioventricular groove and base of right atrial appendage. Thus, a decision to not proceed further with surgical repair was made. The histopathological and cytogenetic findings confirmed the presence of Burkitt's lymphoma. Later, it was discovered that the patient died within one month of diagnosis.

Clinical Utilization of Multimodality Imaging for Myocarditis and Cardiac Sarcoidosis

Myocarditis is defined as inflammation of the myocardium according to clinical, histological, biochemical, immunohistochemical, or imaging findings. Inflammation can be categorized histologically by cell type or pattern, and many causes have been implicated, including infectious, most commonly viral, systemic autoimmune diseases, vaccine-associated processes, environmental factors, toxins, and hypersensitivity to drugs. Sarcoid myocarditis is increasingly recognized as an important cause of cardiomyopathy and has important diagnostic, prognostic, and therapeutic implications in patients with systemic sarcoidosis. The clinical presentation of myocarditis may include an asymptomatic, subacute, acute, fulminant, or chronic course and may have focal or diffuse involvement of the myocardium depending on the cause and time point of the disease. For most causes of myocarditis except sarcoidosis, myocardial biopsy is the gold standard but is limited due to risk, cost, availability, and variable sensitivity. Diagnostic criteria have been established for both myocarditis and cardiac sarcoidosis and include clinical and imaging findings particularly the use of cardiac magnetic resonance and positron emission tomography. Beyond diagnosis, imaging findings may also provide prognostic value. This case-based review focuses on the current state of multimodality imaging for the diagnosis and management of myocarditis and cardiac sarcoidosis, highlighting multimodality imaging approaches with practical clinical vignettes, with a discussion of knowledge gaps and future directions.

Optimization of Intraventricular Radioactive Concentration for 13N ammonia PET with Time-of-Flight Scanner: Simplified Phantom Study with Noise Equivalent Count Rate Analysis.

Background: Myocardial blood flow quantification (MBF) is one of the distinctive features for cardiac positron emission tomography. The MBF calculation is mostly obtained by estimating the input function from the time activity curve in dynamic scan. However, there is a substantial risk of count-loss because the high radioactivity pass through the left ventricular (LV) cavity within a short period. We aimed to determine the optimal intraventricular activity using the noise equivalent count rate (NECR) analysis with simplified phantom model. Methods: Positron emission tomography computed tomography scanner with LYSO crystal and time of flight was used for phantom study. 150 MBq/mL of 13N was filled in 10 mL of syringe, placed in neck phantom to imitate end-systolic small LV. 3D list-mode acquisition was repeatedly performed along radioactive decay. Net true and random count rate were calculated and compared to the theoretical activity in the syringe. NECR curve analysis was used to determine the optimal radioactive concentration. Result: The attenuation curves showed good correlation to the theoretical activity between 20 to 370, and 370 to 740 MBq (r2=1.0 ± 0.0001, p<0.0001; r2=0.99 ± 0.0001, p<0.0001 for 20 to 370, and 370 to 740, respectively), while did not over 740 MBq (p=0.62). NECR analysis revealed that the peak rate was at 2.9 Mcps, there at the true counts were significantly suppressed. The optimal radioactive concentration was determined as 36 MBq/mL. Conclusion: Simulative analysis for high-dose of 13N using the phantom imitating small LV confirmed that the risk of count-loss was increased. The result can be useful information in assessing the feasibility of MBF quantification in clinical routine.

TAI-GAN: Temporally and Anatomically Informed GAN for Early-to-Late Frame Conversion in Dynamic Cardiac PET Motion Correction.

The rapid tracer kinetics of rubidium-82 (82Rb) and high variation of cross-frame distribution in dynamic cardiac positron emission tomography (PET) raise significant challenges for inter-frame motion correction, particularly for the early frames where conventional intensity-based image registration techniques are not applicable. Alternatively, a promising approach utilizes generative methods to handle the tracer distribution changes to assist existing registration methods. To improve frame-wise registration and parametric quantification, we propose a Temporally and Anatomically Informed Generative Adversarial Network (TAI-GAN) to transform the early frames into the late reference frame using an all-to-one mapping. Specifically, a feature-wise linear modulation layer encodes channel-wise parameters generated from temporal tracer kinetics information, and rough cardiac segmentations with local shifts serve as the anatomical information. We validated our proposed method on a clinical 82Rb PET dataset and found that our TAI-GAN can produce converted early frames with high image quality, comparable to the real reference frames. After TAI-GAN conversion, motion estimation accuracy and clinical myocardial blood flow (MBF) quantification were improved compared to using the original frames. Our code is published at https://github.com/gxq1998/TAI-GAN.

A highly predictive cardiac positron emission tomography (PET) risk score for 90-day and one-year major adverse cardiac events and revascularization

BackgroundWith the increase in cardiac PET/CT availability and utilization, the development of a PET/CT-based major adverse cardiovascular events, including death, myocardial infarction (MI), and revascularization (MACE-Revasc) risk assessment score is needed. Here we develop a highly predictive PET/CT-based risk score for 90-day and one-year MACE-Revasc. Methods and results11,552 patients had a PET/CT from 2015 to 2017 and were studied for the training and development set. PET/CT from 2018 was used to validate the derived scores (n = 5049). Patients were on average 65 years old, half were male, and a quarter had a prior MI or revascularization. Baseline characteristics and PET/CT results were used to derive the MACE-Revasc risk models, resulting in models with 5 and 8 weighted factors. The PET/CT 90-day MACE-Revasc risk score trended toward outperforming ischemic burden alone [P = .07 with an area under the curve (AUC) 0.85 vs 0.83]. The PET/CT one-year MACE-Revasc score was better than the use of ischemic burden alone (P < .0001, AUC 0.80 vs 0.76). Both PET/CT MACE-Revasc risk scores outperformed risk prediction by cardiologists. ConclusionThe derived PET/CT 90-day and one-year MACE-Revasc risk scores were highly predictive and outperformed ischemic burden and cardiologist assessment. These scores are easy to calculate, lending to straightforward clinical implementation and should be further tested for clinical usefulness.