Cardiac Positron Emission Tomography Research Articles

Worse outcomes in patients with cardiac sarcoidosis and involvement of the right ventricle in cardiac magnetic resonance

Abstract Background Cardiac sarcoidosis (CS) can manifest with variety of unspecific symptoms. It can mimic all types of cardiomyopathies but most often it resembles dilated cardiomyopathy. Involvement of right ventricle (RV) is rare and may lead to a false diagnosis of arrhythmogenic right ventricular cardiomyopathy and delay of the immunosuppressive therapy. Purpose The aim of this research was to study the characteristics and the outcomes of this peculiar subtype of patients. Methods We analyzed 112 patients diagnosed with CS after elaborate work-up with cardiac magnetic resonance (CMR), FDG PET and endomyocardial biopsy (EMB). All patients underwent follow-up for occurrence of combined endpoint of death, LV assist device implantation or heart transplantation. Patients with evidence of late gadolinium enhancement (LGE) involving RV (RV group) were identified and compared to the rest (DCM group) for baseline clinical characteristics, arhythmic outcomes and combined endpoint. Results Involvement of the RV in CMR was observed in 19 (17%) patients. Patients in the RV group were more frequently male: 84% vs. 57%, P = 0.032. EMB confirmed CS in 63% vs. 19.4% in the DCM group; P= 0.0001. LV ejection fraction in the RV group was comparable to the DCM group: 42±14% vs. 45±14%; P = 0.3. Furthermore, in the RV group the rates of sustained ventricular tachycardia were significantly higher than the DCM: 68% vs. 34%; P = 0.009. Long-term immunosuppressive therapy was started in 74% in RV and in 70% of the DCM group; P=0.77. Despite this, during follow-up, the rate of death, LVAD implantation or heart transplantation was significantly higher in the RV than in the DCM group; 26.3% vs. 7.5%; P = 0.03. In binary logistic analysis, the OR for the combined endpoint was 4.4; 95% CI 1.2-15.7. Conclusions Patients with CS and RV involvement in CMR have worse outcomes as compared to patients presenting as DCM, despite the comparable LV EF and immunosuppressive therapy.

Inflammation and Myocardial Blood Flow in Cardiac Sarcoidosis.

Cardiac involvement in systemic sarcoidosis or isolated cardiac sarcoidosis plays a pivotal role in the clinical manifestation and prognostication. Active-inflammatory cardiac sarcoidosis is associated with a regional impairment of coronary microvascular function that may confer further detrimental effects on myocardial function needing further characterization. Clinical investigations with cardiac positron emission tomography/computed tomography in conjunction with 18F-fluorodeoxyglucose to determine myocardial inflammation and 13N-ammonia to quantify myocardial blood flow (MBF) in patients with known or suspected cardiac sarcoidosis outlined that sarcoidosis-induced myocardial inflammation was associated with adverse effects on corresponding regional coronary microvascular function. Notably, immune-suppressive treatment caused reductions in myocardial inflammation were paralleled by improvements of coronary microvascular dysfunction outlining direct adverse effect of inflammation on coronary arteriolar function. This review summarizes contributions of cardiac PET imaging in the identification and characterization of active-inflammatory cardiac sarcoidosis, its effect on coronary microvascular function, treatment responses, and prognostic implications.

Automatic implantable cardioverter defibrillator (AICD) implantation as secondary prevention of cardiac sarcoidosis-associated ventricular tachycardia

Background: Cardiac sarcoidosis can cause a wide range of symptoms, including shortness of breath, chest pain, oedema, and fatal arrhythmias such as ventricular tachycardia (VT). Because the symptoms can be nonspecific, diagnosing cardiac sarcoidosis can be challenging. Treatment options may include corticosteroids to reduce inflammation, immunosuppressive drugs to prevent further damage, medications to control symptoms, ablation procedures, and defibrillators to prevent cardiac arrest. Case: A 60-year-old woman who has sarcoidosis affecting multiple organs including cardiac sarcoidosis, non-ischemic cardiomyopathy with reduced ejection fraction, and hypertension, was admitted with tachycardia, shortness of breath, and a recently fired automatic implantable cardioverter defibrillator (AICD). Three months prior, the patient was admitted for a syncopal episode and diagnosed with cardiac sarcoidosis through cardiac magnetic resonance imaging (MRI) and positron emission tomography (PET), which demonstrated active inflammation, and an AICD was implanted. During this admission, the patient had an episode of ventricular tachycardia and was treated with amiodarone and lidocaine. The patient received steroids, sacubitril/valsartan, and methotrexate. After 48 hours of observation, the patient was discharged without further events. Conclusion: Cardiac sarcoidosis is a rare but serious disease that can lead to life-threatening cardiac complications such as ventricular tachycardia. Early diagnosis and aggressive management are crucial for improving outcomes and preventing sudden cardiac death. AICD implantation as a secondary prevention in cardiac sarcoidosis might prevent cardiac arrest.

Quantitative Myocardial Perfusion in Liver Transplantation Candidates: Poorly metabolized caffeine inhibition of vasodilatory stress

BackgroundData on cardiac positron emission tomography (PET) in liver transplantation (LT) candidates are limited with no prior study accounting for poorly metabolized caffeine reducing stress perfusion. MethodConsecutive LT candidates (n=114) undergoing cardiac rest/stress PET were instructed to abstain from caffeine for 2 days extended to 5 and 7 days. Due to persistently high prevalence of measurable blood caffeine after 5-day caffeine abstinence, dipyridamole (n=41) initially used was changed to dobutamine (n=73). Associations of absolute flow, coronary flow reserve (CFR), detectable blood caffeine, and Modified End-Stage Liver Disease (MELD) score for liver failure severity were evaluated. Coronary flow data of LT candidates were compared to non-LT control group (n=102 for dipyridamole, n=29 for dobutamine) ResultsPrevalence of patients with detectable blood caffeine was 63.3%, 36.7% and 33.3% after 2-, 5- and 7-day of caffeine abstinence, respectively. MELD score was associated with detectable caffeine (odd ratio 1.18,p<0.001). CFR was higher during dipyridamole stress without-caffeine vs. with-caffeine (2.22±0.80 vs. 1.55±0.37,p=0.048) but lower than dobutamine stress (2.22±0.80 vs. 2.82±1.02,p=0.026). Mediation analysis suggested that the dominant association between CFR and MELD score in dipyridamole group derived from caffeine-impaired CFR and liver failure/caffeine interaction. CFR in LT candidates was lower than non-LT control population in both dipyridamole and dobutamine group. ConclusionsWe demonstrate exceptionally high prevalence of detectable blood caffeine in LT candidates undergoing stress PET myocardial perfusion imaging resulting in reduced CFR with dipyridamole compared to dobutamine. The delayed caffeine clearance in LT candidates makes dobutamine a preferred stress agent in this population.

The role of cardiac PET in diagnosis and prognosis of patients with ischemia with no obstructive coronary arteries (INOCA)

Chest pain, a common symptom in cardiovascular care, often leads to the investigation of obstructive coronary artery disease (CAD). However, many patients experience chest pain without obstructive CAD, termed INOCA (Ischemia with Non-Obstructive Coronary Arteries) or CMD (Coronary Microvascular Dysfunction). INOCA can be attributed to endothelial dysfunction, vascular smooth muscle dysfunction, or both, affecting about 20–30 % of patients with nonobstructive CAD. The diagnostic approach for INOCA includes both invasive and non-invasive methods, with cardiac PET (Positron Emission Tomography) playing a significant role in risk stratification and management. PET evaluates various parameters like myocardial blood flow under stress and rest, myocardial flow reserve, and myocardial ischemia. Such comprehensive assessment is essential in accurately diagnosing and managing INOCA, considering the complexity of this condition.

TAI-GAN: A Temporally and Anatomically Informed Generative Adversarial Network for early-to-late frame conversion in dynamic cardiac PET inter-frame motion correction

Inter-frame motion in dynamic cardiac positron emission tomography (PET) using rubidium-82 (82Rb) myocardial perfusion imaging impacts myocardial blood flow (MBF) quantification and the diagnosis accuracy of coronary artery diseases. However, the high cross-frame distribution variation due to rapid tracer kinetics poses a considerable challenge for inter-frame motion correction, especially for early frames where intensity-based image registration techniques often fail. To address this issue, we propose a novel method called Temporally and Anatomically Informed Generative Adversarial Network (TAI-GAN) that utilizes an all-to-one mapping to convert early frames into those with tracer distribution similar to the last reference frame. The TAI-GAN consists of a feature-wise linear modulation layer that encodes channel-wise parameters generated from temporal information and rough cardiac segmentation masks with local shifts that serve as anatomical information. Our proposed method was evaluated on a clinical 82Rb PET dataset, and the results show that our TAI-GAN can produce converted early frames with high image quality, comparable to the real reference frames. After TAI-GAN conversion, the motion estimation accuracy and subsequent myocardial blood flow (MBF) quantification with both conventional and deep learning-based motion correction methods were improved compared to using the original frames. The code is available at https://github.com/gxq1998/TAI-GAN.

Mental stress-induced myocardial ischemia detected by global longitudinal strain and quantitative myocardial contrast echocardiography in women with nonobstructive coronary artery disease

BackgroundThe utility of radionuclide myocardial perfusion imaging including positron emission tomography (PET) for diagnosing mental stress-induced myocardial ischemia (MSIMI) is clinically restricted. This study aims to assess the diagnostic performance of novel echocardiographic techniques, including automated strain and quantitative myocardial contrast echocardiography (MCE) with dedicated software and deep neural network (DNN) model, for MSIMI detection. The secondary objective was to explore the correlation between changes in myocardial blood flow (MBF) and MSIMI. Methods72 female patients aged 18 to 75 with angina and nonobstructive coronary artery disease (ANOCA), and 23 healthy controls were prospectively recruited. Both echocardiography with contrast agent and PET imaging were performed during structured mental stress testing. MSIMI was defined as a summed difference score ≥3 on PET. Echocardiographic parameters including left ventricular global longitudinal strain (LVGLS), β and A×β were obtained, and their trends during mental stress testing were observed. ΔGLS, β reserve and A×β reserve were respectively calculated. Results32 ANOCA patients (44%) and 1 control (4%) were diagnosed with MSIMI (P<0.01). For ANOCA patients with MSIMI, LVGLS, β and A×β declined to varied extent during mental stress testing compared to those without MSIMI and the controls (P<0.05). Bland-Altman plots demonstrated good consistency between β reserve and A×β reserve output by the DNN model and iMCE software. Receiver operating characteristic (ROC) curve analyses showed that ΔGLS, β reserve and A×β reserve demonstrated favorable ability to predict MSIMI, especially the combination of A×β reserve using iMCE analysis and ΔGLS (area under the curve [AUC] 0.94, sensitivity 83%, specificity 97%). ConclusionsNovel technologies in echocardiography exhibit the potential to be a clinical alternative to cardiac PET for effectively detecting MSIMI. Attenuated MBF response during structured mental stress testing was correlated with MSIMI, providing a reasonable explanation for the chest discomfort persisting in ANOCA women.

Noninvasive Monitoring of Early Cardiac Fibrosis in Diabetic Mice by [68Ga]Ga-DOTA-FAPI-04 PET/CT Imaging.

Cardiac fibrosis represents one of the representative pathological characteristics in the diabetic heart. Active fibroblasts play an essential role in the progression of cardiac fibrosis. The technologies for noninvasive monitoring of activated fibroblasts still have to be investigated. The purpose of this study was to evaluate the feasibility of targeted fibroblast activation protein (FAP) molecular imaging in the early evaluation of diabetic cardiac fibrosis using [68Ga]Ga-DOTA-FAPI-04 PET/CT. PET/CT imaging was conducted in db/db mice and db/m mice at weeks 12 and 24. Diabetic heart injury was determined using echocardiography and serum biomarkers. Additionally, the levels of cardiac fibrosis were also assessed. In our study, conventional diagnostic modalities, including echocardiography and serum biomarkers, failed to monitor early-stage cardiac dysfunction and fibrosis in diabetic mice. Conversely, the results of [68Ga]Ga-DOTA-FAPI-04 PET/CT imaging demonstrated that diabetic mice had increased myocardial uptake of radioactive tracers in both early-stage and late-stage diabetes, consistent with the elevated FAP expression and increased cardiac fibrosis level. Notably, cardiac PET signals exhibited significant correlations with left ventricular ejection fractions, the E/A ratio, and the level of serum TGF-β1, PIIINP, and sST2. The results demonstrated the potential of [68Ga]Ga-DOTA-FAPI-04 PET/CT imaging for visualizing activated fibroblasts and detecting early-stage diabetic heart injury and fibrosis noninvasively. They also demonstrated the clinical superiority of [68Ga]Ga-DOTA-FAPI-04 PET/CT imaging over echocardiography and serum biomarkers in the early monitoring of diabetes-related cardiac dysfunction and fibrosis.

Prognostic value of myocardial flow reserve vs corrected myocardial flow reserve in patients without obstructive coronary artery disease

BackgroundMyocardial flow reserve (MFR) by positron emission tomography (PET) is a validated measure of cardiovascular risk. Elevated resting rate pressure product (RPP = heart rate x systolic blood pressure) can cause high resting myocardial blood flow (MBF), resulting in reduced MFR despite normal/near-normal peak stress MBF. When resting MBF is high, it is not known if RPP-corrected MFR (MFRcorrected) helps reclassify CV risk. We aimed to study this question in patients without obstructive coronary artery disease (CAD). MethodsWe retrospectively studied patients referred for rest/stress cardiac PET at our center from 2006 to 2020. Patients with abnormal perfusion (summed stress score >3) or prior coronary artery bypass grafting (CABG) were excluded. MFRcorrected was defined as stress MBF/corrected rest MBF where corrected rest MBF = rest MBF x 10,000/RPP. The primary outcome was major cardiovascular events (MACE): cardiovascular death or myocardial infarction. Associations of MFR and MFRcorrected with MACE were assessed using unadjusted and adjusted Cox regression. Results3276 patients were followed for a median of 7 (IQR 3–12) years. 1685 patients (51%) had MFR <2.0, and of those 366 (22%) had an MFR ≥2.0 after RPP correction. MFR <2.0 was associated with an increased absolute risk of MACE (HR 2.24 [1.79–2.81], P < 0.0001). Among patients with MFR <2.0, the risk of MACE was not statistically different between patients with an MFRcorrected ≥2.0 compared with those with MFRcorrected <2.0 (1.9% vs 2.3% MACE/year, HR 0.84 [0.63–1.13], P = 0.26) even after adjustment for confounders (P = 0.66). ConclusionsIn patients without overt obstructive CAD and MFR< 2.0, there was no significant difference in cardiovascular risk between patients with discordant (≥2.0) and concordant (<2) MFR following RPP correction. This suggests that RPP-corrected MFR may not consistently provide accurate risk stratification in patients with normal perfusion and MFR <2.0. Stress MBF and uncorrected MFR should be reported to more reliably convey cardiovascular risk beyond perfusion results.

Myocardial flow reserve recovery in patients with Takotsubo syndrome: Insights from positron emission tomography

BackgroundCoronary microvascular dysfunction (CMD) has been implicated in the pathogenesis of Takotsubo syndrome (TTS). Positron emission tomography (PET) plays a key role in the assessment of CMD through myocardial flow reserve (MFR). However, there is limited information on the temporal progression of MFR and its relationship to coronary artery disease (CAD) in TTS patients. MethodsThis study evaluated patients with TTS who underwent cardiac catheterization and PET within one year of hospitalization. Patients were categorized into acute (≤10 days), subacute (11–30 days), and chronic (≥31 days) stages based on post-onset time of PET assessment. MFR values and prevalence of abnormal MFR (<2.0) were compared between stages. Temporal MFR changes in patients with obstructive CAD (≥70% stenosis by coronary angiography), non-obstructive CAD, and normal coronaries were compared. ResultsOf the 88 patients studied (mean age 70; 96% female), 52 (59%) were in the acute, 17 (19%) in the subacute, and 19 (22%) in the chronic stage. Median MFR in the acute stage was 2.0 (1.5–2.3), with 58% of patients showing abnormal MFR. A significant time-dependent improvement in MFR was observed (P = 0.002), accompanied by a decreased prevalence of abnormal MFR (P = 0.016). While patients with normal coronaries showed significant MFR improvement over time (P = 0.045), patients with obstructive or non-obstructive CAD demonstrated no improvement across three stages (P = 0.346 and 0.174, respectively). ConclusionPET-derived MFR was impaired in TTS patients during the acute phase, with improvement suggesting potential recovery from CMD over time. The concurrent presence of obstructive CAD might impede this recovery process.

Association of Coronary Calcium Score on Cardiac PET During Pre-Kidney Transplant Assessment with Persistent Hyperparathyroidism: A Retrospective Study.

BACKGROUND Secondary hyperparathyroidism and coronary calcifications are common complications in chronic kidney disease. However, the relation between coronary calcium score (CCS) and persistent hyperparathyroidism (pHPT) after kidney transplantation (KT) remains unknown. MATERIAL AND METHODS This was a single-center retrospective study of KT candidates from January 2017 to May 2020. We collected patients' demographics, cardiovascular (CV) risk factors, and the findings of pre-KT CV imaging. We also collected parathyroid hormone (PTH) values before KT, at 1-6 months, 6-12 months, and 12-24 months after KT. We defined pHPT as PTH ≥25.5 pmol/L after 12 months post-KT. RESULTS A total of 111 KT recipients (KTRs) with a mean age of 50.4 years were included, of which 62.2% were men and 77.5% were living-donor KTRs. Dialysis modality used before KT was peritoneal dialysis in 9.9% and hemodialysis in 82.9%. Dialysis vintage was 3±2.9 years. The prevalence of pHPT was 24.3% (n=27), and the prevalence of severe coronary calcifications (CCS >400 Agatston units) was 19.8% (n=22). PTH values at baseline, 1-6 months, 6-12 months, and 12-24 months were not different among between CCS >400 or CCS <400 groups. However, pHPT after KT was significantly more prevalent in KTRs with severe CCS (37% vs 14.3%, p=0.014). Severe CCS was associated with less improvement of PTH values after KT (r=0.288, p=0.020). Otherwise, the findings of cardiac PET and coronary angiogram were not significantly different between pHPT and non-pHPT patients. CCS >400 was independently associated with pHPT after transplant (aOR=18.8, P=0.012). CONCLUSIONS Severe CCS on pre-KT cardiac assessment is associated with pHPT after KT.

Novel Functional Radiomics for Prediction of Cardiac Positron Emission Tomography Avidity in Lung Cancer Radiotherapy.

Traditional methods of evaluating cardiotoxicity focus on radiation doses to the heart. Functional imaging has the potential to provide improved prediction for cardiotoxicity for patients with lung cancer. Fluorine-18 (18F) fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) imaging is routinely obtained in a standard cancer staging workup. This work aimed to develop a radiomics model predicting clinical cardiac assessment using 18F-FDG PET/CT scans before thoracic radiation therapy. Pretreatment 18F-FDG PET/CT scans from three study populations (N = 100, N = 39, N = 70) were used, comprising two single-institutional protocols and one publicly available data set. A clinician (V.J.) classified the PET/CT scans per clinical cardiac guidelines as no uptake, diffuse uptake, or focal uptake. The heart was delineated, and 210 novel functional radiomics features were selected to classify cardiac FDG uptake patterns. Training data were divided into training (80%)/validation (20%) sets. Feature reduction was performed using the Wilcoxon test, hierarchical clustering, and recursive feature elimination. Ten-fold cross-validation was carried out for training, and the accuracy of the models to predict clinical cardiac assessment was reported. From 202 of 209 scans, cardiac FDG uptake was scored as no uptake (39.6%), diffuse uptake (25.3%), and focal uptake (35.1%), respectively. Sixty-two independent radiomics features were reduced to nine clinically pertinent features. The best model showed 93% predictive accuracy in the training data set and 80% and 92% predictive accuracy in two external validation data sets. This work used an extensive patient data set to develop a functional cardiac radiomic model from standard-of-care 18F-FDG PET/CT scans, showing good predictive accuracy. The radiomics model has the potential to provide an automated method to predict existing cardiac conditions and provide an early functional biomarker to identify patients at risk of developing cardiac complications after radiotherapy.

Supplemental Transmission Aided Attenuation Correction for Quantitative Cardiac PET.

Quantitative PET attenuation correction (AC) for cardiac PET/CT and PET/MR is a challenging problem. We propose and evaluate an AC approach that uses coincidences from a relatively weak and physically fixed sparse external source, in combination with that from the patient, to reconstruct μ -maps based on physics principles alone. The low 30 cm3 volume of the source makes it easy to fill and place, and the method does not use prior image data or attenuation map assumptions. Our supplemental transmission aided maximum likelihood reconstruction of attenuation and activity (sTX-MLAA) algorithm contains an attenuation map update that maximizes the likelihood of terms representing coincidences originating from tracer in the patient and a weighted expression of counts segmented from the external source alone. Both external source and patient scatter and randoms are fully corrected. We evaluated performance of sTX-MLAA compared to reference standard CT-based AC with FDG PET/CT phantom studies; including modeling a patient with myocardial inflammation. Through an ROI analysis we measured ≤ 5 % bias in activity concentrations for PET images generated with sTX-MLAA and a TX source strength ≥ 12.7 MBq, relative to CT-AC. PET background variability (from noise and sparse sampling) was substantially reduced with sTX-MLAA compared to using counts segmented from the transmission source alone for AC. Results suggest that sTX-MLAA will enable quantitative PET during cardiac PET/CT and PET/MR of human patients.

Ventricular arrhythmia inducibility in porcine infarct model after stereotactic body radiation therapy

BackgroundVentricular arrhythmia (VA) is the primary mechanism of sudden death in patients with structural heart disease. Cardiac stereotactic body radiation therapy (SBRT) delivered to the scar in the left ventricle significantly reduces the burden of VA. ObjectiveThe goal of this study was to investigate the impact of SBRT on scar morphology and VA inducibility in a porcine infarct model. MethodsMyocardial infarction (MI) was created in 10 Yorkshire pigs involving the left anterior descending artery territory. Cardiac positron emission tomography and computed tomography were performed for targeted SBRT. Alternative pigs received SBRT at 25 Gy in a single fraction. The terminal experiment included endocardial mapping, programmed ventricular stimulation, and tissue harvesting. ResultsOf the 10 pigs infarcted, 2 died prematurely after MI and 8 (4 MI and 4 MI+SBRT) survived. Mean time from MI to SBRT was 48 ± 12 days, and mean time from SBRT to harvest was 32 ± 12 days. Scar was localized on intracardiac mapping in all pigs, and the scar was denser in the MI+SBRT compared with the MI-only group (33% ± 20% vs 14% ± 11%; P = .07). All 4 MI pigs had inducible VA during programmed stimulation, whereas only 1 of 4 pigs had inducible VA in the MI+SBRT arm (100% vs 25%; P = .07). No myocardial fibrosis was seen in the remote areas in either group. ConclusionSBRT reduced VA inducibility in pigs with scarring after MI. Endocardial mapping revealed denser scar in pigs receiving SBRT compared with those that did not, suggesting that SBRT suppresses VA inducibility through better scar homogenization.

Kinetic analysis of cardiac dynamic 18F-Florbetapir PET in healthy volunteers and amyloidosis patients: A pilot study

ObjectivesThis study aimed to explore the potential of full dynamic PET kinetic analysis in assessing amyloid binding and perfusion in the cardiac region using 18F-Florbetapir PET, establishing a quantitative approach in the clinical assessment of cardiac amyloidosis disease. Materials & methodsThe distribution volume ratios (DVRs) and the relative transport rate constant (R1), were estimated by a pseudo-simplified reference tissue model (pSRTM2) and pseudo-Logan plot (pLogan plot) with kidney reference for the region of interest-based and voxel-wise-based analyses. The parametric images generated using the pSRTM2 and linear regression with spatially constrained (LRSC) algorithm were then evaluated. Semi-quantitative analyses include standardized uptake value ratios at the early phase (SUVREP, 0.5–5 min) and late phase (SUVRLP, 50–60 min) were also calculated. ResultsTen participants [7 healthy controls (HC) and 3 cardiac amyloidosis (CA) subjects] underwent a 60-min dynamic 18F-Florbetapir PET scan. The DVRs estimated from pSRTM2 and Logan plot were significantly increased (HC vs CA; DVRpSRTM2: 0.95 ± 0.11 vs 2.77 ± 0.42, t’(2.13) = 7.39, P = 0.015; DVRLogan: 0.80 ± 0.12 vs 2.90 ± 0.55, t’(2.08) = 6.56, P = 0.020), and R1 were remarkably decreased in CA groups, as compared to HCs (HC vs CA; 1.08 ± 0.37 vs 0.56 ± 0.10, t’(7.63) = 3.38, P = 0.010). The SUVREP and SUVRLP were highly correlated to R1 (r = 0.97, P < 0.001) and DVR(r = 0.99, P < 0.001), respectively. The DVRs in the total myocardium region increased slightly as the size of FWHM increased and became stable at a Gaussian filter ≥6 mm. The secular equilibrium of SUVR was reached at around 50-min p.i. time. ConclusionThe DVR and R1 estimated from cardiac dynamic 18F-Florbetapir PET using pSRTM with kidney pseudo-reference tissue are suggested to quantify cardiac amyloid deposition and relative perfusion, respectively, in amyloidosis patients and healthy controls. We recommend a dual-phase scan: 0.5–5 min and 50–60 min p.i. as the appropriate time window for clinically assessing cardiac amyloidosis and perfusion measurements using 18F-Florbetapir PET.

PET-determined myocardial perfusion and flow in coronary artery disease characterization

Positron emission tomography (PET) myocardial perfusion imaging in conjunction with tracer-kinetic modeling enables the concurrent assessment of myocardial perfusion and regional myocardial blood flow (MBF) of the left ventricle in absolute terms in milliliters per gram per minute (mL/g/min). The non-invasive quantification of MBF during pharmacologically induced hyperemia, at rest, and corresponding myocardial flow reserve (MFR) opens a new avenue for the identification and characterization of classical or endogen type of coronary microvascular dysfunction (CMD) as functional substrate for microvascular angina in patients with non-obstructive coronary artery disease (CAD) and/or no CAD at all. Further, PET-MBF quantification expands the scope of conventional myocardial perfusion imaging from the identification of advanced, and flow-limiting, epicardial CAD to early stages of atherosclerosis and/or CMD. Adding MBF assessment to myocardial perfusion may also reliably unravel diffuse ischemia owing to significant left main stenosis and/or multivessel CAD, confirmed by peak stress transient ischemic cavity dilation of the left ventricle during maximal vasomotor stress on gated PET images. Owing to high spatial and contrast resolution in conjunction with photon-attenuation free myocardial perfusion PET images, PET is preferentially used for CAD in advanced obesity and women with pronounced breast habitus. With increasing clinical use of cardiac PET perfusion and MBF assessment, individualized, and image-guided cardiovascular treatment decisions in CAD patients is likely to ensue, while its translation into improved cardiovascular outcome remains to be investigated.

Determination of viable myocardium through delayed enhancement cardiac magnetic resonance imaging combined with 18F-FDG PET myocardial perfusion/metabolic imaging before CABG.

Study aims to investigate the consistency of delayed enhancement cardiac magnetic resonance imaging (DE-CMR) and 18F-FDG PET myocardial imaging in evaluating myocardial viability before CABG. The study analyzed data from 100 patients who were examined with DE-CMR, PET imaging, and echocardiography before and after CABG. All subjects were followed up for 6-12 month post- CABG. DE-CMR and PET imaging have high consistency (90.1%; Kappa value = 0.71, p < 0.01) in determining myocardial viability. The degree of delayed enhancement was negatively correlated with the improvement in myocardial contractile function in this segment after revascularization (P < 0.001). The ratio of scarred myocardial segments and total DE score was significantly lower in the improvement group than non-improvement group. Multivariate regression identified that hibernating myocardium (OR = 1.229, 95%CI: 1.053-1.433, p = 0.009) was influencing factor of LVEF improvement after CABG. Both imaging techniques are consistent in evaluating myocardial viability. Detecting the number of hibernating myocardium by PET is also important to predict the left heart function improvement after CABG.

Standardized ketogenic dietary preparation for metabolic PET imaging in suspected and known cardiac sarcoidosis

Abstract Aims A major limitation of cardiac positron emission tomography (PET) with F18-fluorodeoxyglucose (F18-FDG) for the evaluation of cardiac sarcoidosis (CS) is associated with physiologic myocardial glucose uptake. The optimal dietary protocol to suppress physiologic myocardial F18-FDG uptake is not well-established. We aimed to evaluate the diagnostic performance of a novel dietary preparation using a ketone-based infant formula. Methods and results Between 2018 and 2021, consecutive studies using a ketogenic dietary preparation were identified (n = 198). The rate of non-diagnostic studies due to failure to suppress myocardial glucose was 7.1% (n = 14) with a similar incidence in diabetics (n = 6, 8.1%). Among studies reported to have no inflammation (n = 137), 130 studies (66%) had mean myocardial standardized uptake value (SUV) less than or equal to mean blood pool SUV. Conclusion Patient preparation with a ketone-based infant formula resulted in low rate of inappropriate myocardial glucose suppression in patients undergoing F18-FDG cardiac PET to evaluate CS.

Quantitative and qualitative comparison of Rubidium-82 and Oxygen-15 water cardiac PET

BackgroundDifferences in tracer characteristics may influence the interpretation of positron emission tomography myocardial perfusion imaging (MPI). We compare the reading of MPIs with a low-extraction retention tracer (82Rb) and a high-extraction non-retention tracer (15O-water) in a selected cohort of patients with known coronary artery disease (CAD). MethodsThirty-nine patients with known CAD referred to 82Rb MPI due to angina underwent rest and stress imaging with both tracers and experienced MPI readers provided blinded consensus reads of all studies. In addition, a comparison of regional and global quantitative measures of perfusion was performed. ResultsThe results showed 74 % agreement in the reading of 82Rb and 15O-water MPI for regional reversible ischemia and global disease, and 82 % agreement for regional irreversible ischemia. The 15O-water MPI identified more cases of global disease (n = 12 (15O-water) vs n = 4 (82Rb), p = 0.03), whereas differences in reversible ischemia (n = 22 vs n = 16, p = 0.11) and, irreversible ischemia (n = 8 vs n = 11, p = 0.45) were not significant. The correlation between myocardial blood flow measured using the two tracers was similar to previous studies (R2 = 0.78) with wide limits of agreement (−0.93 to 0.84 ml/g/min). ConclusionsAgreement between consensus readings of 82Rb and 15O-water MPI was good in patients with known CAD. In this limited size study, no significant differences in the identification of reversible and irreversible ischemia found, whereas 15O-water MPI had a higher positive rate for suspected global disease.

Cardiac noradrenergic deficiency revealed by 18F-dopamine positron emission tomography identifies preclinical central Lewy body diseases.

In Lewy body diseases (LBDs) Parkinson disease (PD), and dementia with Lewy bodies (DLB), by the time parkinsonism or cognitive dysfunction manifests clinically, substantial neurodegeneration has already occurred. Biomarkers are needed to identify central LBDs in a preclinical phase, when neurorescue strategies might forestall symptomatic disease. This phase may involve catecholamine deficiency in the autonomic nervous system. We analyzed data from the prospective, observational, long-term PDRisk study to assess the predictive value of low versus normal cardiac 18F-dopamine positron emission tomography (PET), an index of myocardial content of the sympathetic neurotransmitter norepinephrine, in at-risk individuals. Participants self-reported risk factor information (genetics, olfactory dysfunction, dream enactment behavior, and orthostatic intolerance or hypotension) at a protocol-specific website. Thirty-four with 3 or more confirmed risk factors underwent serial cardiac 18F-dopamine PET at 1.5-year intervals for up to 7.5 years or until PD was diagnosed. Nine participants had low initial myocardial 18F-dopamine-derived radioactivity (<6,000 nCi-kg/cc-mCi) and 25 had normal radioactivity. At 7 years of follow-up, 8 of 9 with low initial radioactivity and 1 of 11 with normal radioactivity were diagnosed with a central LBD (LBD+) (P = 0.0009 by Fisher's exact test). Conversely, all 9 LBD+ participants had low 18F-dopamine-derived radioactivity before or at the time of diagnosis of a central LBD, whereas among 25 participants without a central LBD only 1 (4%) had persistently low radioactivity (P < 0.0001 by Fisher's exact test). Cardiac 18F-dopamine PET highly efficiently distinguishes at-risk individuals who are diagnosed subsequently with a central LBD from those who are not. gov NCT00775853. Division of Intramural Research, NIH, NINDS.