COMPARISON OF THE EFFECT OF THREE DIFFERENT DIETARY MODIFICATIONS ON MYOCARDIAL SUPPRESSION IN 18F-FDG PET/CT EVALUATION OF PATIENTS FOR SUSPECTED CARDIAC SARCOIDOSIS

XTR003, a fatty acid metabolism PET tracer: A phase I study to evaluate the safety, biodistribution, radiation dosimetry, and pharmacokinetics in healthy volunteers

PURPOSE

XTR003 is a novel 18F-labeled fatty acid PET tracer to image myocardial fatty acid metabolism that can be potentially used to assess myocardial viability for ischemic heart disease. This Phase I study evaluated its safety, biodistribution, radiation dosimetry, and pharmacokinetics.

METHODS

Ten healthy Chinese volunteers (mean age of 28.4 ± 4.6 years, 3 females) were intravenously injected with XTR003 (296-370 MBq) at rest and monitored for adverse events on the day of injection and follow-up days. Multiple whole-body PET images were acquired within 290 minutes and processed to investigate the biodistribution and radiation dosimetry. Whole blood, plasma, and urine were collected simultaneously for 420 minutes to evaluate the pharmacokinetics with the measurement of radioactivity.

RESULTS

Only two treatment-related adverse events occurred with no severe adverse effects. After tracer injection, XTR003 in the plasma peaked at 2.883 minutes as .0108235% of injected dose per gram (%ID/g) and reduced to the minimum at 30 minutes. The 0-20 minutes whole-body PET images indicated that both heart and liver were two critical organs with the highest percentage of injected dose (%ID) (4.37 ± .66 and 48.76 ± 4.17 %ID). Specifically, XTR003 demonstrated high initial uptake in the heart, with sustained retention for up to 290 minutes (standardized uptake value: 6.50 ± 2.54 at 0-20 minutes and 5.89 ± 2.18 at 270-290 minutes). The whole-body effective radiation dose was 17 μSv/MBq. The cumulative urinary excretion was 9.009%.

CONCLUSIONS

XTR003, as an18F-labeled radiotracer, was safe and well-tolerated. The rapid uptake and prolonged retention of XTR003 in the heart show promise for evaluating myocardial fatty acid metabolism. The Phase II clinical trial to explore the efficacy of XTR003 for detecting myocardial viability should be warranted.

TRAIL REGISTRATION NUMBER

ClinicalTrials.gov Identifier: NCT05136391.

Assessment of Cardiac Sarcoidosis with PET/CT

18F-FDG PET with CT is an important advanced imaging modality used to assess patients with suspected or known cardiac sarcoidosis (CS). 18F-FDG PET is indicated for CS work-up in patients with extra-CS and abnormal screening results for cardiac involvement, patients under 60 y old presenting with unexplained high-grade atrioventricular heart block, and patients with suspected CS and idiopathic ventricular arrhythmias. In patients with established CS, serial 18F-FDG PET can be used to assess response to immunosuppressive therapy and long-term surveillance for reactivation of myocardial inflammation in patients with low-grade or quiescent disease. Patient preparation before 18F-FDG PET scanning is key in ensuring adequate suppression of physiologic myocardial 18F-FDG uptake, to maximize the power of the test to detect pathology. Inadequate dietary preparation can cause diffuse or focal-on-diffuse 18F-FDG uptake in the absence of active inflammation. It is important to assess resting myocardial perfusion, typically with 82Rb cardiac PET. Several different patterns of abnormalities have been reported in patients with CS, including normal myocardial perfusion with focal or patchy 18F-FDG uptake suggesting myocardial inflammation without scarring; the presence of a myocardial perfusion defect with abnormal 18F-FDG uptake suggesting myocardial scarring with inflammation; and the presence of a myocardial perfusion defect without 18F-FDG uptake indicating myocardial scarring without inflammation. Prognostically, the presence of myocardial perfusion defects and abnormal 18F-FDG uptake has been shown to be an independent predictor of death or ventricular arrythmias. A high myocardial SUVmax in the left and right ventricles has been shown to be an independent predictor of adverse clinical outcomes. Although the diagnostic performance of 18F-FDG PET has been studied, the reference standard for CS tended to rely on clinical criteria, which may be less sensitive than 18F-FDG PET at detecting CS. Therefore, the diagnosis of CS should rely on a multidisciplinary team approach involving multimodality advanced imaging, including echocardiography, cardiovascular MR, and 18F-FDG PET.

Hybrid cardiovascular imaging. A clinical consensus statement of the european association of nuclear medicine (EANM) and the european association of cardiovascular imaging (EACVI) of the ESC

Hybrid imaging consists of a combination of two or more imaging modalities, which equally contribute to image information. To date, hybrid cardiovascular imaging can be performed by either merging images acquired on different scanners, or with truly hybrid PET/CT and PET/MR scanners. The European Association of Nuclear Medicine (EANM), and the European Association of Cardiovascular Imaging (EACVI) of the European Society of Cardiology (ESC) aim to review clinical situations that may benefit from the use of hybrid cardiac imaging and provide advice on acquisition protocols providing the most relevant information to reach diagnosis in various clinical situations.

Can FDG PET Serve as a Clinically Relevant Tool for Detecting Active Non-sarcoidotic Myocarditis?

The diagnostic work-up for myocarditis largely depends on non-invasive imaging because of the low yield of endomyocardial biopsy. In addition, differentiation among possible impressions is essential because of its non-specific clinical presentations. This ambiguity has led to the predominant use of cardiac magnetic resonance imaging techniques in the management of myocarditis, particularly during the global pandemic. Despite the unique ability of F-18 fluorodeoxyglucose positron emission tomography to visualize and quantify active myocardial inflammation, which has been well established in cardiac sarcoidosis, its diagnostic contribution in non-sarcoidotic myocarditis remains uncertain. This article reviews the current evidence on the non-invasive imaging diagnosis of non-sarcoidotic myocarditis and discusses the potential role of F-18 fluorodeoxyglucose positron emission tomography as a clinically relevant imaging tool.

Heparin does not improve myocardial glucose metabolism suppression in [18 F]FDG PET/CT in patients with low β-hydroxybutyrate level

BACKGROUND

Inadequate myocardial glucose metabolism suppression (GMS) can hamper interpretation of cardiac [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET/CT). Use of β-hydroxybutyrate (BHB) measurement before [18F]FDG injection has been proposed for predicting adequate GMS. However, limited information is available on BHB measurement in guiding preparations for [18F]FDG-PET/CT. The purpose of this study was to evaluate if point-of-care measured BHB is useful in guiding heparin premedication for cardiac [18F]FDG-PET/CT.

RESULTS

155 patients (82 male) had followed a high-fat, low-carbohydrate diet and fasted for at least twelve hours. For the first 63 patients, BHB was measured, but it was not used to guide premedication. For the subsequent 92 patients, heparin 50 IU/kg was injected intravenously 15-20 min before [18F]FDG injection if the BHB level was low (< 0.35 mmol/l). Cardiac [18F]FDG uptake pattern was evaluated visually and [18F]FDG uptake in the myocardium and blood pool were measured. Median BHB level was 0.4 (range 0.1-5.8) mmol/l. Eighty-eight patients (57%) reached a BHB level higher than 0.35 mmol/l. 112 patients (72%) had adequate GMS. In the high BHB group, 74 patients (84%) had adequate GMS, whereas of those with low BHB, only 38 (57%) had adequate GMS (p < 0.001). In the low BHB group, the prevalence of inadequate GMS was comparable in patients with and without heparin (44% vs. 42%, p = 0.875).

CONCLUSIONS

While high BHB predicts adequate GMS, unfractionated heparin does not improve GMS in patients with low BHB.

Imaging of Cardiac Sarcoidosis: An Update and Future Aspects

Cardiac sarcoidosis (CS), an increasingly recognized disease of unknown etiology, is associated with significant morbidity and mortality. Given the limited diagnostic yield of traditional endomyocardial biopsy (EMB), there is increasing reliance on multimodality cardiovascular imaging in the diagnosis and management of CS, with EMB being largely supplanted by the use of 18F-fluorodeoxyglucose (FDG-PET) and cardiac magnetic resonance imaging (CMR). This article aims to provide a comprehensive review of imaging modalities currently utilized in the screening, diagnosis, and monitoring of CS, while highlighting the latest developments in each area.

Diagnosis and Management of Cardiac Sarcoidosis: A Scientific Statement From the American Heart Association

Cardiac sarcoidosis is an infiltrative cardiomyopathy that results from granulomatous inflammation of the myocardium and may present with high-grade conduction disease, ventricular arrhythmias, and right or left ventricular dysfunction. Over the past several decades, the prevalence of cardiac sarcoidosis has increased. Definitive histological confirmation is often not possible, so clinicians frequently face uncertainty about the accuracy of diagnosis. Hence, the likelihood of cardiac sarcoidosis should be thought of as a continuum (definite, highly probable, probable, possible, low probability, unlikely) rather than in a binary fashion. Treatment should be initiated in individuals with clinical manifestations and active inflammation in a tiered approach, with corticosteroids as first-line treatment. The lack of randomized clinical trials in cardiac sarcoidosis has led to treatment decisions based on cohort studies and consensus opinions, with substantial variation observed across centers. This scientific statement is intended to guide clinical practice and to facilitate management conformity by providing a framework for the diagnosis and management of cardiac sarcoidosis.

The active papillary muscle sign in 18F-FDG PET/CT cardiac sarcoidosis exams and its relationship with myocardial suppression

OBJECTIVE

Papillary muscle (PM) activity may demonstrate true active cardiac sarcoidosis (CS) or mimic CS in 18FDG-PET/CT if adequate myocardial suppression (MS) is not achieved. We aim to examine whether PM uptake can be used as a marker of failed MS and measure the rate of PM activity presence in active CS with different dietary preparations.

MATERIALS AND METHODS

We retrospectively reviewed PET/CTs obtained with three different dietary preparations. Diet-A: 24-h ketogenic diet with overnight fasting (n = 94); Diet-B: 18-h fasting (n = 44); and Diet-C: 72-h daytime ketogenic diet with 3-day overnight fasting (n = 98). Each case was evaluated regarding CS diagnosis (negative, positive, and indeterminant) and presence of PM activity. MaxSUV was measured from bloodpool, liver, and the most suppressed normal myocardium. Linear mixed-effects models were used to compare these factors between those with PM activity and those without.

RESULTS

PM activity was markedly lower in the Diet-C group compared with others: Diet-C: 6 (6.1%), Diet-A: 36 (38.3%), and Diet-B: 26 (59.1%) (p < 0.001). MyocardiumMaxSUV was higher, and MyocardiummaxSUV/BloodpoolmaxSUV, MyocardiummaxSUV/LivermaxSUV ratios were significantly higher in the cases with PM activity (p < 0.001). Among cases that used Diet-C and had PM activity, 66.7% were positive and 16.7% were indeterminate. If Diet-A or Diet-B was used, those with PM activity had a higher proportion of indeterminate cases (Diet-A: 61.1%, Diet-B: 61.5%) than positive cases (Diet-A: 36.1%, Diet-B: 38.5%).

CONCLUSION

Lack of PM activity can be a sign of appropriate MS. PM activity is less common with a specific dietary preparation (72-h daytime ketogenic diet with 3-day overnight fasting), and if it is present with this particular preparation, the likelihood that the case being true active CS might be higher than the other traditional dietary preparations.

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

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.

Myocardial glucose suppression may interfere with the detection of inflammatory cells with FDG-PET as suggested in a canine model of myocardial infarction

BACKGROUND

After myocardial infarction, fibrosis and an ongoing dysregulated inflammatory response have been shown to lead to adverse cardiac remodeling. FDG PET is an imaging modality sensitive to inflammation as long as suppression protocols are observed while gadolinium enhanced MRI can be used to determine extracellular volume (ECV), a measure of fibrosis. In patients, glucose suppression is achieved variously through a high fat diet, fasting and injection of heparin. To emulate this process in canines, a heparin injection and lipid infusion are used, leading to similar fatty acids in the blood. The aim of this study was to examine the effect of glucose suppression on the uptake of FDG in the infarcted myocardial tissue and also on the determination of ECV in both the infarcted tissue and in the myocardium remote to the zone of infarction during a long constant infusion of FDG and Gd-DTPA.

RESULTS

Extracellular volume was affected neither by suppression nor the length of the constant infusion in remote and infarcted tissue. Metabolic rate of glucose in infarcted tissue decreased during and after suppression of glucose uptake by lipid infusion and heparin injection. An increase in fibrosis and inflammatory cells was found in the center of the infarct as compared to remote tissue.

CONCLUSION

The decrease in the metabolic rate of glucose in the infarcted tissue suggests that inflammatory cells may be affected by glucose suppression through heparin injection and lipid infusion.

Positron Emission Tomography in Heart Failure: From Pathophysiology to Clinical Application

Imaging modalities are increasingly being used to evaluate the underlying pathophysiology of heart failure. Positron emission tomography (PET) is a non-invasive imaging technique that uses radioactive tracers to visualize and measure biological processes in vivo. PET imaging of the heart uses different radiopharmaceuticals to provide information on myocardial metabolism, perfusion, inflammation, fibrosis, and sympathetic nervous system activity, which are all important contributors to the development and progression of heart failure. This narrative review provides an overview of the use of PET imaging in heart failure, highlighting the different PET tracers and modalities, and discussing fields of present and future clinical application.

Pathophysiological Gaps, Diagnostic Challenges, and Uncertainties in Cardiac Sarcoidosis

Cardiac sarcoidosis can mimic any cardiomyopathy in different stages. Noncaseating granulomatous inflammation can be missed, because of the nonhomogeneous distribution in the heart. The current diagnostic criteria show discrepancies and are partly nonspecific and insensitive. Besides the diagnostic pitfalls, there are controversies in the understanding of the causes, genetic and environmental background, and the natural evolution of the disease. Here, we review the current pathophysiological aspects and gaps that are relevant for future cardiac sarcoidosis diagnostics and research.

Emerging PET Tracers in Cardiac Molecular Imaging

¹⁸F-fluorodeoxyglucose (FDG) and ¹⁸F-sodium fluoride (NaF) represent emerging PET tracers used to assess atherosclerosis-related inflammation and molecular calcification, respectively. By localizing to sites with high glucose utilization, FDG has been used to assess myocardial viability for decades, and its role in evaluating cardiac sarcoidosis has come to represent a major application. In addition to determining late-stage changes such as loss of perfusion or viability, by targeting mechanisms present in atherosclerosis, PET-based techniques have the ability to characterize atherogenesis in the early stages to guide intervention. Although it was once thought that FDG would be a reliable indicator of ongoing plaque formation, micro-calcification as portrayed by NaF-PET/CT appears to be a superior method of monitoring disease progression. PET imaging with NaF has the additional advantage of being able to determine abnormal uptake due to coronary artery disease, which is obscured by physiologic myocardial activity on FDG-PET/CT. In this review, we discuss the evolving roles of FDG, NaF, and other PET tracers in cardiac molecular imaging.

The utility of beta-hydroxybutyrate in detecting myocardial glucose uptake suppression in patients undergoing inflammatory [18F]-FDG PET studies

PURPOSE

We evaluated whether serum beta-hydroxybutyrate (BHB) can identify adequate suppression of the left ventricle (LV) among patients undergoing [18F]-fluorodeoxyglucose positron emission tomography ([18F]-FDG PET) for cardiac inflammatory/infectious studies.

METHODS

Consecutive patients who underwent [18F]-FDG PET imaging were included. Serum BHB levels were measured in all patients on the day of imaging prior to injecting [18F]-FDG. Myocardial [18F]-FDG suppression was defined if [18F]-FDG uptake in the walls of myocardium, measured using standardized uptake values (SUV), was lower than the blood pool. The optimal threshold of BHB to identify myocardial suppression was based on receiver operating characteristics (ROC) in a random 30% sample of the study population (derivation cohort) and tested in the remaining 70% of sample (validation cohort).

RESULTS

A total of 256 images from 220 patients were included. Patients with sufficient LV suppression had significantly higher BHB levels compared to those with non-suppressed myocardium (median (IQR) BHB 0.6 (0.3-0.8) vs. 0.2 (0.2-0.3) mmol/l, p < 0.001, respectively). BHB level ≥ 0.335 mmol/l had a sensitivity of 84.90% and a specificity of 92.60% to identify adequate LV suppression in the validation cohort. All patients (100%) with BHB ≥ 0.41 mmol/l had adequate myocardial suppression compared to 29.63% of patients with BHB ≤ 0.20 mmol/l.

CONCLUSION

Serum BHB level can be used at the point of care to identify sufficient LV suppression in patients undergoing [18F]-FDG PET cardiac inflammatory/infectious studies. Central illustration (image to the right) shows representative cases of patient images and BHB and, in the image to the left, shows the sensitivity and specificity to identify left myocardial suppression using BHB in validation group.

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.

The detection of infectious endocarditis may be enhanced by a repeat FDG-PET while maintaining patients on a ketogenic diet

BACKGROUND

This study aims to determine whether the suppression of myocardial FDG uptake and detection of infectious endocarditis (IE) may be enhanced when FDG-PET is repeated on the next day while maintaining patients on a ketogenic diet in the interim.

METHODS

Seventeen patients with definite IE underwent FDG-PET investigations both after a conventional metabolic preparation (> 12-hour fast after a low-carbohydrate evening meal) and a subsequent 12-hour extension of the low-carbohydrate diet followed by an additional > 12-hour fast.

RESULTS

Plasma biomarkers showed increased ketogenic metabolism between the two FDG-PET scans. A myocardial FDG uptake persisted on the 1st PET in 9 patients (53%) for whom myocardial FDG uptake decreased significantly on the 2nd PET (SUVmax: 6.05 ± 3.25 vs 4.32 ± 3.47, P = 0.021), resulting in an enhancement in the diagnostic confidence of IE in 6 cases. These enhancements were not documented in the 8 patients exhibiting a total suppression of myocardial FDG uptake on the 1st PET.

CONCLUSIONS

Better suppression of myocardial uptake and enhanced detection of IE may be achieved when an FDG-PET, showing an incomplete suppression of the myocardial FDG uptake, is repeated as soon as the next day, while maintaining patients on a ketogenic diet in the interim.

The role of PET in the management of sarcoidosis

PURPOSE OF REVIEW

PET has emerged as method to determine the location and extent of disease activity in sarcoidosis. As most clinicians do not routinely utilize PET in the management of sarcoidosis, an understanding of the imaging technique is needed to comprehend the impact that PET abnormalities have on diagnosis, prognosis, and treatment.

RECENT FINDINGS

Although PET can detect inflammation because of sarcoidosis throughout the body, it is most often utilized for the diagnosis of cardiac sarcoidosis for which it may provide information about prognosis and adverse events. Whenever PET is combined with cardiac magnetic resonance (CMR), clinicians may be able to increase the diagnostic yield of imaging. Furthermore, PET abnormalities have the potential to be utilized in the reduction or augmentation of therapy based on an individual's response to treatment. Although various biomarkers are used to monitor disease activity in sarcoidosis, an established and reproducible relationship between PET and biomarkers does not exist.

SUMMARY

PET has the potential to improve the diagnosis of sarcoidosis and alter treatment decisions but prospective trials are needed to define the role of PET while also standardizing the performance and interpretation of the imaging modality.

Extensive Biventricular Cardiac Sarcoidosis Detected on FDG PET/CT Using a 72-Hour Ketogenic Diet Preparation Protocol

ABSTRACT

A 49-year-old man had right bundle-branch block, with decreased left ventricle ejection fraction of 43%. Cardiac MRI demonstrated abnormal multifocal delayed gadolinium enhancement involving both ventricles. Cardiac sarcoidosis was further confirmed at cardiac biopsy. Dedicated FDG PET/CT with 72-hour ketogenic diet preparation to suppress physiological myocardial uptake of FDG was performed for disease evaluation. PET/CT revealed multifocal abnormal uptake in both ventricles concordant with cardiac MRI findings, in addition to hypermetabolic lymphadenopathy. Six months later, posttreatment PET/CT with the same 72-hour ketogenic diet preparation showed good response with resolution of active inflammation.

What cardiologists should know about cardiac sarcoidosis in 2022?

PURPOSE OF REVIEW

Cardiac sarcoidosis (CS) is a potentially fatal condition when unrecognized or not treated adequately. The purpose of this review is to provide new strategies to increase clinical recognition of CS and to present an updated overview of the immunosuppressive treatments using most recent data published in the last 18 months.

RECENT FINDINGS

CS is an increasingly recognized pathology, and its diagnostic is made 20 times more often in the last two decades. Recent studies have shown that imaging alone usually lacks specificity to distinguish CS from other inflammatory cardiomyopathies. However, imaging can be used to increase significantly diagnostic yield of extracardiac and cardiac biopsy. Recent reviews have also demonstrated that nearly 25% of patients will be refractory to standard treatment with prednisone and that combined treatment with a corticosteroid-sparing agent is often necessary for a period that remains undetermined.

SUMMARY

CS is a complex pathology that should always require a biopsy attempt to have a histological proven diagnosis before starting immunosuppressive therapy consisting of corticosteroids with or without a corticosteroid-sparing agent.

Clinical Presentation and Treatment of High-Risk Sarcoidosis

Sarcoidosis is a multisystem disease of unknown cause with heterogeneous clinical manifestations and variable course. Spontaneous remissions occur in some patients, whereas others have progressive disease impacting survival, organ function, and quality of life. Four high-risk sarcoidosis phenotypes associated with chronic inflammation have recently been identified as high-priority areas for research. These include treatment-refractory pulmonary disease, cardiac sarcoidosis, neurosarcoidosis, and multiorgan sarcoidosis. Significant gaps currently exist in the understanding of these high-risk manifestations of sarcoidosis, including their natural history, diagnostic criteria, biomarkers, and the treatment strategy, such as the ideal agent, optimal dose, and treatment duration. The use of registries with well-phenotyped patients is a critical first step to study high-risk sarcoidosis manifestations systematically. We review the diagnostic and treatment approach to high-risk sarcoidosis manifestations. Appropriately identifying these disease subgroups will help enroll well-phenotyped patients in sarcoidosis registries and clinical trials, a necessary step to narrow existing gaps in understanding of this enigmatic disease.

What Is the Optimal Method on Myocardial Suppression in FDG PET/CT Evaluation of Cardiac Sarcoidosis?

ABSTRACT

Based on the recent publications, including large cohort retrospective study and prospective clinical trial data, we are commenting on the optimal methods on myocardial suppression in FDG PET/CT evaluation of patients with suspected cardiac sarcoidosis.

Normal Variants and Pitfalls in Cardiac PET/CT

Positron emission tomography and/or computed tomography (PET/CT) MPI is a powerful imaging modality for the assessment of cardiovascular diseases. It offers several advantages over single-photon emission computed tomography (SPECT) MPI including robust attenuation correction and absolute quantification of radiotracer activity. PET MPI has a large evidence base and is the only clinical tool to evaluate coronary microvascular dysfunction. In addition, the clinical use and evidence base for 2-deoxy-2-[¹⁸F]fluoro-D-g1ucose (¹⁸F-FDG) cardiac PET imaging for inflammation and metabolism imaging is rising exponentially. In order to gain from the advances of this sophisticated quantitative technique, a high-quality scan is critical. It is important for readers to recognize a poor-quality scan, identify artifacts contributing to the poor image quality, and understand how to correct them prior to reporting the results. In this review, we will discuss some normal variants and pitfalls in cardiac PET/CT radionuclide MPI, myocardial viability, and inflammation imaging.