Long fasting is effective in inhibiting physiological myocardial 18F-FDG uptake and for evaluating active lesions of cardiac sarcoidosis

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.

Machine learning approach using 18F-FDG-PET-radiomic features and the visibility of right ventricle 18F-FDG uptake for predicting clinical events in patients with cardiac sarcoidosis

OBJECTIVES

To investigate the usefulness of machine learning (ML) models using pretreatment 18F-FDG-PET-based radiomic features for predicting adverse clinical events (ACEs) in patients with cardiac sarcoidosis (CS).

MATERIALS AND METHODS

This retrospective study included 47 patients with CS who underwent 18F-FDG-PET/CT scan before treatment. The lesions were assigned to the training (n = 38) and testing (n = 9) cohorts. In total, 49 18F-FDG-PET-based radiomic features and the visibility of right ventricle 18F-FDG uptake were used to predict ACEs using seven different ML algorithms (namely, decision tree, random forest [RF], neural network, k-nearest neighbors, Naïve Bayes, logistic regression, and support vector machine [SVM]) with tenfold cross-validation and the synthetic minority over-sampling technique. The ML models were constructed using the top four features ranked by the decrease in Gini impurity. The AUCs and accuracies were used to compare predictive performances.

RESULTS

Patients who developed ACEs presented with a significantly higher surface area and gray level run length matrix run length non-uniformity (GLRLM_RLNU), and lower neighborhood gray-tone difference matrix_coarseness and sphericity than those without ACEs (each, p < 0.05). In the training cohort, all seven ML algorithms had a good classification performance with AUC values of > 0.80 (range: 0.841-0.944). In the testing cohort, the RF algorithm had the highest AUC and accuracy (88.9% [8/9]) with a similar classification performance between training and testing cohorts (AUC: 0.945 vs 0.889). GLRLM_RLNU was the most important feature of the modeling process of this RF algorithm.

CONCLUSION

ML analyses using 18F-FDG-PET-based radiomic features may be useful for predicting ACEs in patients with CS.

PSMA-targeted radiotheranostics in modern nuclear medicine: then, now, and what of the future?

In 1853, the perception of prostate cancer (PCa) as a rare ailment prevailed, was described by the eminent Londoner surgeon John Adams. Rapidly forward to 2018, the landscape dramatically altered. Currently, men face a one-in-nine lifetime risk of PCa, accentuated by improved diagnostic methods and an ageing population. With more than three million men in the United States alone grappling with this disease, the overall risk of succumbing to stands at one in 39. The intricate clinical and biological diversity of PCa poses serious challenges in terms of imaging, ongoing monitoring, and disease management. In the field of theranostics, diagnostic and therapeutic approaches that harmoniously merge targeted imaging with treatments are integrated. A pivotal player in this arena is radiotheranostics, employing radionuclides for both imaging and therapy, with prostate-specific membrane antigen (PSMA) at the forefront. Clinical milestones have been reached, including FDA- and/or EMA-approved PSMA-targeted radiodiagnostic agents, such as [18F]DCFPyL (PYLARIFY®, Lantheus Holdings), [18F]rhPSMA-7.3 (POSLUMA®, Blue Earth Diagnostics) and [68Ga]Ga-PSMA-11 (Locametz®, Novartis/ ILLUCCIX®, Telix Pharmaceuticals), as well as PSMA-targeted radiotherapeutic agents, such as [177Lu]Lu-PSMA-617 (Pluvicto®, Novartis). Concurrently, ligand-drug and immune therapies designed to target PSMA are being advanced through rigorous preclinical research and clinical trials. This review delves into the annals of PSMA-targeted radiotheranostics, exploring its historical evolution as a signature molecule in PCa management. We scrutinise its clinical ramifications, acknowledge its limitations, and peer into the avenues that need further exploration. In the crucible of scientific inquiry, we aim to illuminate the path toward a future where the enigma of PCa is deciphered and where its menace is met with precise and effective countermeasures. In the following sections, we discuss the intriguing terrain of PCa radiotheranostics through the lens of PSMA, with the fervent hope of advancing our understanding and enhancing clinical practice.

Cardiac Sarcoidosis

Cardiac involvement is a major cause of morbidity and mortality in patients with sarcoidosis. It is important to distinguish between clinical manifest diseases from clinically silent diseases. Advanced cardiac imaging studies are crucial in the diagnostic pathway. In suspected isolated cardiac sarcoidosis, it's key to rule out alternative diagnoses. Therapeutic options can be divided into immunosuppressive agents, guideline-directed medical therapy, antiarrhythmic medications, device/ablation therapy, and heart transplantation.

Prospective Analysis of Immunosuppressive Therapy in Cardiac Sarcoidosis With Fluorodeoxyglucose Myocardial Accumulation: The PRESTIGE Study

BACKGROUND

Fluorodeoxyglucose positron emission tomography (18F-FDG-PET) can noninvasively assess active inflammatory myocardium in patients with cardiac sarcoidosis (CS). Prednisolone (PSL) is the initial drug of choice for active CS; however, its efficacy has not been prospectively evaluated. Moreover, there are no alternative systematic treatment strategies.

OBJECTIVES

The goal of this study was to evaluate the efficacy of methotrexate (MTX) in patients refractory to PSL assessed by using cardiac metabolic activity (CMA) in 18F-FDG-PET.

METHODS

A total of 59 patients with active CS were prospectively enrolled. CMA (standardized uptake value × accumulation area) was used as an indicator of active inflammation, and a 6-month regimen of PSL therapy was introduced, followed by a second FDG scan. Poor responders to PSL therapy (CMA reduction rate <70%) and patients with recurrent CS (CMA reduction rate ≥70% after initial PSL therapy but CMA recurred after an additional 6 months of therapy) were randomly assigned to the MTX or repeat PSL (re-PSL) therapy groups for another 6 months.

RESULTS

Fifty-six patients completed the initial 6-month PSL therapy regimen. Median CMA reduced from 203.3 to 1.0 (P < 0.001), and 47 patients were allocated to the response group, 9 to the poor response group, and 2 to the recurrent group. Accordingly, 11 patients were randomly assigned to the MTX (n = 5) or re-PSL (n = 6) groups. After 6 months, neither group showed a significant reduction in CMA values. MTX was comparable to re-PSL in reducing CMA.

CONCLUSIONS

The 6-month regimen of PSL was a potent therapeutic tool for active CS. When MTX was added to low-dose PSL in patients refractory to the initial PSL therapy, there was no significant difference compared with re-PSL. Further studies are needed to evaluate the therapeutic potential of MTX for active CS, including how MTX works when it is administered in higher doses or for longer periods.

Meta-analysis of the effectiveness of heparin in suppressing physiological myocardial FDG uptake in PET/CT

BACKGROUND

The present meta-analysis aims to investigate the effectiveness of heparin administration in suppressing physiological myocardial 18F-fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET)/computed tomography (CT), as its role in this regard has not been well investigated.

METHODS

PRISMA guidelines were used to interrogate the PubMed, Embase, Cochrane library, Web of Knowledge, and www.clinicaltrail.gov databases from the earliest records to March 2023. The final analysis included five randomized controlled trials (RCTs). Meta-analysis was conducted to compare the effectiveness of unfractionated heparin (UFH) administration versus non-UFH administration, and subgroup analysis based on fixed and variable fasting durations was conducted. Effect sizes were pooled using a random-effects model, and the pooled odds ratios (ORs) were calculated.

RESULTS

Five eligible RCTs with a total of 910 patients (550 with heparin, 360 without heparin) were included. The forest plot analysis initially indicated no significant difference in the suppression of myocardial FDG uptake between the UFH and non-UFH groups (OR 2.279, 95% CI 0.593 to  8.755, p = 0.23), with a high degree of statistical heterogeneity (I2 = 91.16%). Further subgroup analysis showed that the fixed fasting duration group with UFH administration had statistically significant suppression of myocardial FDG uptake (OR 4.452, 95% CI 1.221 to 16.233, p = 0.024), while the varying fasting duration group did not show a significant effect.

CONCLUSIONS

According to the findings of our meta-analysis, we suggest that intravenous administration of UFH can be considered as a supplementary approach to suppress myocardial FDG uptake.

Cardiac Metastasis of Malignant Melanoma Detected by 18F-FDG PET/CT

A 63-year-old man with a history of right plantar malignant melanoma (T3bN0M0, IIb) developed multiple metastases in bilateral lungs 19 months after surgery. Subsequent ¹⁸F-FDG PET/CT revealed multiple pulmonary metastases with intense FDG uptake and detected a hypermetabolic lesion in the lateral wall of the left ventricle, which was considered to be a cardiac metastasis of malignant melanoma. This lesion was later confirmed in the dynamic myocardial perfusion MR. This case demonstrates the effectiveness of ¹⁸F-FDG PET/CT in detecting occult cardiac metastases of malignant melanoma.

Effective suppression of myocardial glucose uptake using predesigned low-carbohydrate boxed meals

BACKGROUND

Dietary preparation protocols are an effective means to suppress physiological myocardial 18F-fluorodeoxyglucose (FDG) uptake. This study aimed to investigate the efficacy of various carbohydrate-restricted diets using predesigned boxed meals.

METHODS

The patients were divided into four groups to undergo different preparatory protocols as follows: a minimum 15-hour fast alone, two meals of high-fat, low-carbohydrate diet (HFLCD), two meals of high-animal-protein, low-carbohydrate diet (HAPLCD), and two meals of high-plant-based-protein, low-carbohydrate diet (HPPLCD). Boxed meals were prepared to meet the required carbohydrate restrictions. Myocardial SUVmax and SUVmean were measured and the suppression rate was analyzed.

RESULTS

The average myocardial SUVmax of fast alone, HFLCD, HAPLCD, and HPPLCD were 8.26 ± 5.85, 2.21 ± 1.50, 2.34 ± 1.88, and 4.10 ± 3.61, respectively, and the suppression rates were 36.6%, 93.3%, 93.3%, and 70%, respectively. The effectiveness of HFLCD, HAPLCD, and HPPLCD was all statistically superior to that of a 15-hour fast alone. SUVmax of HFLCD and HAPLCD showed no significant differences (p = 1), whereas HFLCD and HPPLCD had significant differences (p = .046).

CONCLUSIONS

Using the predesigned boxed meals based on carbohydrate restriction, HFLCD, HAPLCD, and HPPLCD can be administered to patients with different dietary needs while providing a substantial reduction in physiological myocardial FDG uptake.

Sarcoid Heart Disease: Review of Current Knowledge

Sarcoidosis is a granulomatous disease with the potential of multiple organ system involvement and its etiology remains unknown. Cardiac involvement is associated with worse clinical outcome, and has been reported to be 20-30% in white and as high as 58% in Japanese populations with sarcoidosis. Clinical manifestations of cardiac sarcoidosis highly depend on the extent and location of granulomatous inflammation. The most frequent presentations include heart block, tachyarrhythmia, or heart failure. Endomyocardial biopsy is the most specific diagnostic test, but has poor sensitivity due to often patchy involvement. The diagnosis of cardiac sarcoidosis remains challenging due to nonspecific imaging findings. Both 18 F-fluorodeoxyglucose-positron emission tomography (FDG-PET) and cardiac magnetic resonance imaging can be used to evaluate cardiac sarcoidosis, but evaluate different stages of the disease process. FDG-PET detects metabolically active inflammatory cells while cardiac magnetic resonance imaging with late gadolinium enhancement reveals areas of myocardial necrosis and fibrosis. Aggressive therapy of symptomatic cardiac sarcoidosis is often sought due to the high risk of sudden death and/or progression to heart failure. Prednisone 20-40 mg a day is the recommended initial treatment. In refractory or severe cases, higher doses of prednisone, 1-1.5 mg/kg/d (or its equivalent) and addition of a steroid-sparing agent have been utilized. Methotrexate is added most commonly. Long-term improvement has been reported with the use of a combination of weekly methotrexate and prednisone versus prednisone alone. After initiation of treatment, a cardiac FDG-PET scan may be performed 2-3 months later to assess treatment response.

Successful treatment of recurrent cardiac sarcoidosis with the combination of corticosteroid and methotrexate monitored by 18F-fluoro-2-deoxyglucose positron emission tomography: case series

Background

The standard treatment for cardiac sarcoidosis (CS) is corticosteroids, including prednisolone (PSL). Previous studies have shown that the addition of methotrexate (MTX) to PSL is effective for steroid-refractory and recurrent cases. ¹⁸F-fluoro-2-deoxyglucose positron emission tomography (FDG-PET) is an essential tool for the diagnosis of CS. However, it is unclear whether FDG-PET is useful for detecting recurrence of CS and monitoring the effectiveness of PSL and MTX combination therapy.

Case summary

We detected CS recurrence during PSL treatment using FDG-PET. Patient 1 was accompanied by increased FDG uptake in other organs, Patient 2 was complicated with a decrease in left ventricular ejection fraction, and Patient 3 showed enlargement of the late gadolinium enhancement area, which was compatible with the recurrence of CS. We successfully monitored the inflammation activity by FDG-PET and treated recurrent CS by increasing the PSL dose and adding MTX to suppress inflammation.

Discussion

FDG-PET is useful for detecting CS recurrence and monitoring the effectiveness of PSL and MTX combination therapy. Serial FDG-PET scans indicated that it might be more difficult to suppress inflammation in recurrent CS than in the initial treatment. The use of FDG-PET is necessary to monitor long-term disease activity.

Various Aspects of Fasting on the Biodistribution of Radiopharmaceuticals

It is demonstrated that fasting can alter the biodistribution of radiopharmaceuticals in nuclear medicine. Various studies have highlighted that fasting is interpreted to be easy for physicians during PET study, fasting is one of the most important factors determining the usefulness of this protocol. It is well documented that fasting can suppress normal ¹⁸F-FDG PET uptake during nuclear cardiology. However, there is no consensus about the usefulness of fasting on radiopharmaceuticals, especially on ¹⁸F-FDG in PET imaging, but special attention should be paid to the setting of the fasting duration. Nevertheless, it does seem we still need extensive clinical studies in the future. The present study aims to review the various aspects of fasting, especially metabolic alteration on radiopharmaceutical biodistribution. In this study, we focused more on the effect of fasting on ¹⁸F-FDG biodistribution, which alters its imaging contrast in cardiology and cancer imaging. Therefore, shifting substrate metabolism from glucose to free fatty acids during fasting can be an alternative approach to suppress physiological myocardial uptake.

Right Atrial Fluorodeoxyglucose Uptake Is a Risk Factor for Stroke and Improves Prediction of Stroke Above the CHA2DS2-VASc Score in Patients With Atrial Fibrillation

Background

Atrial fibrillation (AF) is a common arrhythmia, and its most severe and dreaded complication is stroke. The CHA2DS2-VASc score is currently recommended for stroke risk assessment in AF. We aimed to explore the relationship between atrial FDG uptake and stroke and whether atrial FDG uptake could provide incremental value above the CHA2DS2-VAS score to predict stroke in AF by 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT).

Materials and Methods

From September 2017 to December 2020, we retrospectively enrolled 230 patients (115 with AF and 115 without AF as the non-AF group, matched for the date of PET/CT examination and the basic characteristics of the patient) who underwent 18F-FDG PET/CT due to tumor screening or preoperative staging after prolonged fasting and followed up for at least 12 months from the date of PET/CT examination; the endpoint event is the occurrence of stroke. We visually and quantitatively analyzed 18F-FDG uptake in the right and left atria (RA/LA), right and left atrial appendage (RAA/LAA), right and left ventricle (RV/LV), and collected clinical features. In addition, according to the endpoint event (stroke), the enrolled population was divided into the stroke group and non-stroke group, and relevant clinical features and atrial FDG uptake indicators of the two groups were analyzed. Univariate and multivariate Cox regression analyzes were used to analyze the risk factors of stroke events. The Kaplan–Meier survival curve of atrial FDG uptake was drawn, and the log-rank method was used to compare the differences in the survival curves of the two groups. Receiver operating characteristic (ROC) curves were used to examine the discriminatory power of atrial FDG uptake in predicting stroke and determine whether the addition of atrial FDG uptake improves predictive value beyond the CHA2DS2-VASc score for stroke.

Results

In the AF group, more than half of patients had RA FDG uptake and one-fifth had LA FDG uptake, while one patient had RA FDG uptake and two patients had LA FDG uptake in the non-AF group. In quantitative analysis, the maximum standardized uptake value (SUVmax) of the RA and LA in the AF group was significantly higher than that of the non-AF group (all P &lt; 0.001). We followed up the patients for 28 ± 10 months, and finally, 31 patients had stroke. In the stroke group, atrial fibrillation, RA SUVmax, RAA SUVmax, LAA SUVmax, age ≥ 75 years, and left atrial dilation were significantly higher than those of the non-stroke group (all P &lt; 0.05). Multivariate Cox regression analysis showed that high RA SUVmax (RA SUVmax ≥ 2.62) was an independent risk factor for stroke (HR = 4.264, 95% CI 1.368–13.293, P = 0.012). By using the log-rank test, patients with high RA SUVmax had a significantly higher incidence of stroke compared with patients with low RA SUVmax (P &lt; 0.001). Addition of high RA SUVmax to the CHA2DS2-VASc score could predict stroke more effectively, with a larger AUC 0.790 (P &lt; 0.001).

Conclusion

This study found a significant correlation between atrial FDG uptake and AF, especially in RA. Meanwhile, RA FDG uptake is an independent risk factor for stroke, and patients with high RA SUVmax have a significantly higher risk of stroke. Moreover, RA FDG uptake improves prediction of stroke above the CHA2DS2-VASc score in patients with AF.

Underdiagnosis of cardiac sarcoidosis by ECG and echocardiography in cases of extracardiac sarcoidosis

Background

Although screening with 12-lead electrocardiography and transthoracic echocardiography for cardiac involvement has been recommended for patients with biopsy-proven extracardiac sarcoidosis, cardiac sarcoidosis has been reported even in patients with normal electrocardiography and echocardiography findings. We investigated the prevalence and characteristics of these patient cohorts.

Methods

We studied 112 consecutive patients (age, 55±17 years, 64% females) with biopsy-proven extracardiac sarcoidosis who had undergone ¹⁸F-fluorodeoxyglucose positron emission tomography and cardiac magnetic resonance imaging for cardiac sarcoidosis evaluation. The patients were categorised as those showing normal findings both in electrocardiography and transthoracic echocardiography (normal group) and those showing abnormal findings in one or both examinations (abnormal group).

Results

33 (29%) and 79 (71%) patients were categorised into the normal and abnormal groups, respectively, of which 6 (18%) and 43 (54%) patients, respectively, were diagnosed with cardiac sarcoidosis (p<0.01). Of these six patients in the normal group, two with multiple-organ sarcoidosis showed clinical deterioration of cardiac involvement and required steroid therapy; three with small cardiac involvement showed natural remission over follow-up assessments; and one underwent steroid therapy and showed an improvement in the left ventricular ejection fraction to within normal limits.

Conclusions

The prevalence of cardiac sarcoidosis in patients with biopsy-proven extracardiac sarcoidosis and normal electrocardiography and transthoracic echocardiography findings was ∼20%. Electrocardiography and transthoracic echocardiography may not detect cardiac sarcoidosis in patients without conduction and morphological abnormalities. However, some of these patients may subsequently show clinically manifested cardiac sarcoidosis. Physicians should be mindful of this population.

ECG and transthoracic echocardiography may not detect cardiac sarcoidosis in patients without conduction and morphological abnormalities. Some of these patients may subsequently develop clinically manifested cardiac sarcoidosis.https://bit.ly/3qeQuff

Combined Cardiac Fluorodeoxyglucose-Positron Emission Tomography/Magnetic Resonance Imaging Assessment of Myocardial Injury in Patients Who Recently Recovered From COVID-19

IMPORTANCE

Although myocardial injury can occur with acute COVID-19, there is limited understanding of changes with myocardial metabolism in recovered patients.

OBJECTIVE

To examine myocardial metabolic changes early after recovery from COVID-19 using fluorodeoxyglucose-positron emission tomography (PET) and associate these changes to abnormalities in cardiac magnetic resonance imaging (MRI)-based function and tissue characterization measures and inflammatory blood markers.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study took place at a single-center tertiary referral hospital system. A volunteer sample of adult patients within 3 months of a diagnosis of COVID-19 who responded to a mail invitation were recruited for cardiac PET/MRI and blood biomarker evaluation between November 2020 and June 2021.

EXPOSURES

Myocardial inflammation as determined by focal fluorodeoxyglucose (FDG) uptake on PET.

MAIN OUTCOMES AND MEASURES

Demographic characteristics, cardiac and inflammatory blood markers, and fasting combined cardiac 18F-FDG PET/MRI imaging were obtained. All patients with focal FDG uptake at baseline returned for repeated PET/MRI and blood marker assessment 2 months later.

RESULTS

Of 47 included patients, 24 (51%) were female, and the mean (SD) age was 43 (13) years. The mean (SD) interval between COVID-19 diagnosis and PET/MRI was 67 (16) days. Most patients recovered at home during the acute infection (40 [85%]). Eight patients (17%) had focal FDG uptake on PET consistent with myocardial inflammation. Compared with those without FDG uptake, patients with focal FDG uptake had higher regional T2, T1, and extracellular volume (colocalizing with focal FDG uptake), higher prevalence of late gadolinium enhancement (6 of 8 [75%] vs 9 of 39 [23%], P = .009), lower left ventricular ejection fraction (mean [SD], 55% [4%] vs 62% [5%], P < .001), worse global longitudinal and circumferential strain (mean [SD], -16% [2%] vs -17% [2%], P = .02 and -18% [2%] vs -20% [2%], P = .047, respectively), and higher systemic inflammatory blood markers including interleukin 6, interleukin 8, and high-sensitivity C-reactive protein. Among patients with focal FDG uptake, PET/MRI, and inflammatory blood markers resolved or improved at follow-up performed a mean (SD) of 52 (17) days after baseline PET/MRI.

CONCLUSIONS AND RELEVANCE

In this study of patients recently recovered from COVID-19, myocardial inflammation was identified on PET in a small proportion of patients, was associated with cardiac MRI abnormalities and elevated inflammatory blood markers at baseline, and improved at follow-up.

PET Imaging in Cardiac Sarcoidosis: A Narrative Review with Focus on Novel PET Tracers

Sarcoidosis is a multi-system inflammatory disease characterized by the development of inflammation and noncaseating granulomas that can involve nearly every organ system, with a predilection for the pulmonary system. Cardiac involvement of sarcoidosis (CS) occurs in up to 70% of cases, and accounts for a significant share of sarcoid-related mortality. The clinical presentation of CS can range from absence of symptoms to conduction abnormalities, heart failure, arrhythmias, valvular disease, and sudden cardiac death. Given the significant morbidity and mortality associated with CS, timely diagnosis is important. Traditional imaging modalities and histologic evaluation by endomyocardial biopsy often provide a low diagnostic yield. Cardiac positron emission tomography (PET) has emerged as a leading advanced imaging modality for the diagnosis and management of CS. This review article will summarize several aspects of the current use of PET in CS, including indications for use, patient preparation, image acquisition and interpretation, diagnostic and prognostic performance, and evaluation of treatment response. Additionally, this review will discuss novel PET radiotracers currently under study or of potential interest in CS.

Best Practices for Imaging Cardiac Device-Related Infections and Endocarditis: A JACC: Cardiovascular Imaging Expert Panel Statement

The diagnosis of cardiac device infection and, more importantly, accurate localization of the infection site, such as defibrillator pocket, pacemaker lead, along the peripheral driveline or central portion of the left ventricular assist device, prosthetic valve ring abscesses, and perivalvular extensions, remain clinically challenging. Although transthoracic and transesophageal echocardiography are the first-line imaging tests in suspected endocarditis and for assessing hemodynamic complications, recent studies suggest that cardiac computed tomography (CT) or CT angiography and functional imaging with ¹⁸F-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) with CT (FDG PET/CT) may have an incremental role in technically limited or inconclusive cases on echocardiography. One of the key benefits of FDG PET/CT is in its detection of inflammatory cells early in the infection process, before morphological damages ensue. However, there are many unanswered questions in the literature. In this document, we provide consensus on best practices among the various imaging studies, which includes the detection of cardiac device infection, differentiation of infection from inflammation, image-guided patient management, and detailed recommendations on patient preparation, image acquisition, processing, interpretation, and standardized reporting.

18F-FDG PET/CT in Infective Endocarditis: Indications and Approaches for Standardization

Purpose of Review

Additional imaging modalities, such as FDG-PET/CT, have been included into the workup for patients with suspected infective endocarditis, according to major international guidelines published in 2015. The purpose of this review is to give an overview of FDG-PET/CT indications and standardized approaches in the setting of suspected infective endocarditis.

Recent Findings

There are two main indications for performing FDG-PET/CT in patients with suspected infective endocarditis: (i) detecting intracardiac infections and (ii) detection of (clinically silent) disseminated infectious disease. The diagnostic performance of FDG-PET/CT for intracardiac lesions depends on the presence of native valves, prosthetic valves, or implanted cardiac devices, with a sensitivity that is poor for native valve endocarditis and cardiac device-related lead infections, but much better for prosthetic valve endocarditis and cardiac device-related pocket infections. Specificity is high for all these indications. The detection of disseminated disease may also help establish the diagnosis and/or impact patient management.

Summary

Based on current evidence, FDG-PET/CT should be considered for detection of disseminated disease in suspected endocarditis. Absence of intracardiac lesions on FDG-PET/CT cannot rule out native valve endocarditis, but positive findings strongly support the diagnosis. For prosthetic valve endocarditis, standard use of FDG-PET/CT is recommended because of its high sensitivity and specificity. For implanted cardiac devices, FDG-PET/CT is also recommended, but should be evaluated with careful attention to clinical context, because its sensitivity is high for pocket infections, but low for lead infections. In patients with prosthetic valves with or without additional aortic prosthesis, combination with CTA should be considered. Optimal timing of FDG-PET/CT is important, both during clinical workup and technically (i.e., post tracer injection). In addition, procedural standardization is key and encompasses patient preparation, scan acquisition, reconstruction, subsequent analysis, and clinical interpretation. The recommendations discussed here will hopefully contribute to improved standardization and enhanced performance of FDG-PET/CT in the clinical management of patients with suspected infective endocarditis.

The rate of myocardial perfusion recovery after steroid therapy and its implication for cardiac events in cardiac sarcoidosis and primarily preserved left ventricular ejection fraction

BACKGROUND

Sarcoidosis is a multisystemic disorder of unknown cause characterized by immune granuloma formation in the involved organs. Few studies have reported on the myocardial perfusion changes by immunosuppression therapy in cardiac sarcoidosis (CS). Additionally, the relationship between myocardial perfusion changes and prognosis is unknown. Therefore, this study aimed to clarify myocardial perfusion recovery after steroid therapy and its prognostic value for major adverse cardiac events (MACE) in patients with CS.

METHODS AND RESULTS

Thirty-eight consecutive patients with CS {median age, 63 [interquartile range (IQR) 51-68] years; 10 men} underwent both 18F-fluorodeoxyglucose positron emission tomography/computed tomography (CT) and electrocardiography-gated single-photon emission CT (SPECT) pre- and post-steroid therapy. Patients with improved or preserved myocardial perfusion after post-therapy were defined as the recovery group and those with worsened myocardial perfusion as the non-recovery group. Twenty-six patients (68%) were categorized as the recovery group. MACE occurred in eight patients. The Kaplan-Meier curves revealed a significantly higher rate of MACE in the non-recovery group (17.4%/y vs 2.9%/y, P = 0.007).

CONCLUSIONS

Myocardial perfusion was recovered by steroid therapy in 61% and preserved in 8% of patients. Myocardial perfusion recovery after steroid therapy was significantly associated with a low incidence of MACE.

Myocardial Glucose Metabolism Is Increased in Newly Diagnosed Lung Adenocarcinoma

BACKGROUND

Cardiac metabolism alterations may be involved in abnormalities of cancer patients' cardiovascular system. This study aimed to explore whether left ventricular myocardial glucose metabolism is altered and its related factors in newly diagnosed patients with lung adenocarcinoma (LAD) who underwent fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT).

METHODS

From our 18F-FDG PET/CT imaging database, 171 patients with newly diagnosed LAD and 43 nononcologic subjects with matched age and sex were retrospectively analyzed. The included patients underwent conventional 18F-FDG PET/CT imaging with a >12-h fasting before 18F-FDG administration. The standardized uptake values (SUVs) of the left ventricular (LV) myocardium, arterial wall, epicardial adipose tissue (EAT), spleen, and bone marrow were separately measured. Laboratory parameters and echocardiographic results were collected as well. LAD patients were divided into 2 groups based on the 95th percentile of LV maximal SUV (SUVmax) obtained from the 43 nononcologic subjects. Univariate analysis and multiple logistic regression analysis were used to identify significant factors.

RESULTS

Higher LV SUVmax was found (3.8 [2.4, 7.7] vs. 3.0 [2.0, 5.4], p = 0.052) in LAD than that in nononcologic patients, whereas no significant differences of 18F-FDG uptake were found in the arterial wall, EAT, spleen, or bone marrow between LAD patients and controls. The maximum diameter (Dmax) of the LAD lesion, SUVmax of spleen, and SUVmax of EAT were related to LV SUVmax in LAD.

CONCLUSIONS

Myocardial glucose metabolism is increased in patients with newly diagnosed LAD. Dmax of LAD lesion, spleen activity, and EAT activity contribute to the increased LV activity in LAD.

Effect of fasting duration on myocardial fluorodeoxyglucose uptake in diabetic and nondiabetic patients

OBJECTIVE

To detect cardiac hypermetabolic lesions using fluorodeoxyglucose (FDG) with PET/computed tomography (PET/CT), the efficiency of long fasting and temperature condition for lowering physiological myocardial FDG uptake is controversial and may be confounded by other factors. We thus aimed to investigate the impact of fasting duration and ambient temperature on myocardial uptake in diabetic and nondiabetic patients.

METHODS

FDG PET/CT scans (n = 666) were reviewed and the myocardial uptake was visually graded on a four-point scale and quantified using standardized uptake value (SUV). The associations between myocardial uptake and fasting duration, diabetes status, ambient temperature parameters, age, gender, and BMI were evaluated.

RESULTS

Intraobserver [κ = 0.94; intraclass correlation coefficient (ICC) = 0.99] and interobserver (κ = 0.91; ICC = 0.99) reliabilities of both visual and SUV measurements were all excellent. Fasting duration and diabetes status were found to be significantly associated with myocardial FDG uptake, but the ambient temperature parameters and other factor were not. Patients with intense (Grade 4) myocardial uptake had a shorter fasting duration (P = 0.011). The SUVmax of myocardium was significantly higher in nondiabetic than diabetic patients (P < 0.001). Fasting duration ≥ 12 h in diabetic and ≥16 h in nondiabetic patients was associated with low prevalence of Grade 4 uptake (4.2%, P = 0.016; 2.3%, P = 0.028).

CONCLUSION

Fasting for long enough durations but not ambient temperature was associated with decreased physiological myocardial FDG uptake. A fasting duration of more than 12 h for diabetic, 16 h for nondiabetic patients is a simple and valuable recommendation.

Value of Patlak Ki images from 18F-FDG-PET/CT for evaluation of the relationships between disease activity and clinical events in cardiac sarcoidosis

The association between ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) myocardial uptake and clinical presentations in cardiac sarcoidosis (CS) has not yet been clarified. The Patlak slope, Ki, which represents the rate of ¹⁸F-FDG uptake is a quantitative index of ¹⁸F-FDG metabolism. This study aims to investigate the usefulness of standardized uptake value (SUV) and Patlak Ki images (Ki images) extracted from dynamic ¹⁸F-FDG-PET/CT for evaluating the risk of clinical events (CEs) in CS. The SUV and Ki myocardial images were generated from 30 dynamic ¹⁸F-FDG-PET/CT scans of 21 CS patients. The SUV and Ki images both were rated as positive in 19 scans and negative in 11 scans with the same incidence of CEs which were significantly higher in positive than negative scans [cardiac dysfunction: 78.9% (15/19) vs. 27.2% (3/11); arrhythmic events: 65.5% (10/19) vs. 0% (0/11)]. In 19 positive scans, the three Ki parameters (Ki max, Ki mean and Ki volume) were significantly higher in scans for patients with arrhythmic events than in those without. Logistic regression analysis showed that the Ki volume alone was significantly associated with the risk of arrhythmic events. Our study suggests that Ki images may add value to SUV images for evaluating the risk of CEs in CS patients.

Associations of physiologic myocardial 18F-FDG uptake with fasting duration, HbA1c, and regular exercise

OBJECTIVE

The variability of physiologic ¹⁸F-FDG uptake in the myocardium has hampered the accurate evaluation of cardiac glucose metabolism. We investigated the effects of multiple factors, including fasting duration and physical activity, on the physiologic uptake of ¹⁸F-FDG by the myocardium in healthy participants.

METHODS

A total of 446 participants (predominantly male, 91%) in a health screening program were included in this retrospective study. For the visual analysis of myocardial ¹⁸F-FDG uptake, the participants were categorized into three groups according to qualitative visual scales (QVS). For the quantitative analysis, the maximum SUV of the left ventricular myocardium was measured.

RESULTS

Significant differences were observed in fasting duration (p < 0.001), SUV_max (p < 0.001), aspartate aminotransferase (AST) (p < 0.001), alanine aminotransferase (ALT) (p < 0.001), gamma-glutamyl transpeptidase (γ-GTP) (p = 0.001), and uric acid (p = 0.015) among the QVS groups. Participants who regularly exercised with vigorous activity (p = 0.032) and HbA1c > 6% (p = 0.005) showed significant association with myocardial FDG uptake in the Chi-squared test. The median value of fasting duration decreased significantly as the QVS of the myocardium increased. Twenty-nine of the 31 participants (93.5%) who fasted for 21.5 h or more showed a suppressed FDG uptake (mean SUV_max = 2.1). In multivariate logistic regression analysis, fasting duration (OR = 0.74, 95% CI 0.69-0.80, p < 0.001), HbA1c > 6% (OR = 0.29, 95% CI: 0.12 - 0.66, p = 0.004), uric acid (OR = 0.82, 95% CI 0.68-1.00, p = 0.049) and regular exercise with vigorous activity (OR = 1.75, 95% CI 1.13-2.70, p = 0.012) were significant factors for physiologic myocardial FDG uptake.

CONCLUSIONS

Reduced physiologic ¹⁸F-FDG uptake of the myocardium was associated with longer fasting duration, higher level of HbA1c, and less frequency of regular exercise with vigorous activity. For the preparation of cardiac ¹⁸F-FDG PET, inclusion of longer fasting duration (more than 18 h) might be necessary for the adequate suppression of physiologic ¹⁸F-FDG myocardial uptake.

Patient Preparation and Patient-related Challenges with FDG-PET/CT in Infectious and Inflammatory Disease

Several factors that influence physiologic 18F-fluorodeoxyglucose (FDG) uptake and general FDG distribution may affect PET/CT imaging in infection and inflammation. The general impact of hyperglycemia on the diagnostic performance of FDG-PET/CT is probably less in infection/inflammation than in malignancy. Patient preparation may reduce physiologic FDG uptake, but recommendations are less established than in malignancy. Local implementation of various patient preparatory measures should reflect the specific patient population and indications. This article outlines some of the challenges with physiologic FDG distribution, focusing on infectious and inflammatory diseases, and potential countermeasures and patient preparation to limit physiologic uptake before scan.

Excellent suppression of physiological myocardial FDG activity in patients with cardiac sarcoidosis

INTRODUCTION

Suppression of physiological myocardial FDG activity is vital in patients undergoing PET/CT for assessment of known or suspected cardiac sarcoidosis. This study aims to evaluate the efficacy of physiological myocardial FDG suppression following a protocol change to a 24-h high fat very low carbohydrate (HFVLC) diet and prolonged fast.

METHODS

A retrospective review of patients undergoing FDG PET/CT for the evaluation of cardiac sarcoidosis was performed. Prior to June-2018, patients were prepared with a single very high-fat low carbohydrate meal followed by a 12-18 h fast (group 1). After June-2018, a protocol change was initiated with patients prepared with a HFVLC diet for 24-h followed by a 12-18 h fast (group 2). Focal myocardial activity was classified as positive, absent activity as negative and diffuse/focal on diffuse activity as indeterminate.

RESULTS

A total of 94 FDG PET/CT scans were included with 46 scans in group 1 and 48 scans in group 2. Studies were classified as positive, negative or indeterminate in 25 (54%), 7 (15%) and 14 (30%) scans in group 1 and in 13 (27%), 33 (69%) and 2 (4%) scans in group 2, respectively. In scans classified as negative, myocardial FDG activity was less than mediastinal blood pool activity in 5/7 (71%) scans in group 1 and 33/33 (100%) scans in group 2.

CONCLUSION

Excellent myocardial FDG suppression can be achieved using a 24-h HFVLC diet and prolonged fast, resulting in a very low indeterminate scan rate in patients with known or suspected cardiac sarcoidosis.

Characterization of a highly effective preparation for suppression of myocardial glucose utilization

BACKGROUND

With appropriate protocols, F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) can visualize myocardial inflammation. Optimal protocols and normative myocardial FDG uptake values are not well-established.

METHODS

We evaluated 111 patients referred for inflammation cardiac FDG PET/CT. Patients followed a low-carbohydrate, high-fat diet for 36 hours before imaging and received unfractionated heparin. Glucose and fatty acid metabolism biomarkers were obtained. Mean blood pool and maximum myocardial uptake (SUVmean, SUVmax) were measured, avoiding areas of abnormal FDG uptake or spillover.

RESULTS

Adequate suppression of myocardial FDG uptake occurred in 95% of patients (n = 106). Myocardial SUVmax was significantly below background blood pool SUVmean: septal myocardial to blood pool ratio 0.75 (95% CI 0.73-0.77; P < 0.001); lateral myocardial to blood pool ratio 0.70 (95% CI 0.68-0.72; P < 0.001). Glucose, insulin, and C-peptide correlated to blood pool SUVmean (Spearman rs = 0.39, P < 0.01; rs = 0.40, P < 0.01; rs = 0.35, P < 0.01) and myocardial SUVmax (Spearman rs = 0.31, P < 0.01; rs = 0.31, P < 0.01; rs = 0.26, P < 0.01). Fatty acid metabolism biomarkers did not correlate to myocardial SUVmax.

CONCLUSIONS

Patients following intensive metabolic preparation have myocardial FDG SUVmax below background SUVmean. Biomarkers of glucose metabolism modestly correlate to FDG uptake.

Global quantification of pulmonary artery atherosclerosis using 18F-sodium fluoride PET/CT in at-risk subjects

The goal of this study was to assess pulmonary artery calcification in healthy controls and subjects with suspicion of stable angina pectoris through the usage of quantitative ¹⁸F-sodium fluoride positron emission tomography/computed tomography (NaF-PET/CT). We hypothesized that these 'at-risk subjects' would demonstrate increase pulmonary artery NaF uptake compared to healthy controls. Retrospectively, 15 healthy controls were compared to 15 at-risk subjects, all of whom underwent full-body NaF-PET/CT scans. The healthy controls and at-risk patients were all randomly sampled from larger datasets. The two sampled groups were male-dominated and similar in age. The global mean standard uptake value (SUVmean), the max standard uptake value (SUVmax), and the mean target-to-background ratio (TBRmean) were acquired through mapping of regions of interest (ROI's) around the pulmonary artery of the subjects. A two-tailed Mann-Whitney U test was used to determine the significance of difference between the two groups. For global SUVmean (0.79 compared to 0.58), global TBRmean (1.15 compared to 0.93), and global SUVmax (1.78 compared to 1.60), the NaF uptake was significantly higher in the at-risk patients compared to the controls (all P<0.05). NaF-PET/CT is a suitable imaging modality for quantification of molecular calcification in the pulmonary artery. Additionally, the connection between atherosclerosis and the risk factor of angina pectoris is further reinforced. We believe that future studies are needed to validate our proof-of-concept, and better confirm the clinical future of NaF-PET/CT as a tracer of atherosclerotic plaques.

A 1-week extension of a ketogenic diet provides a further decrease in myocardial 18F-FDG uptake and a high detectability of myocarditis with FDG-PET

BACKGROUND

Short periods of fasting and/or low-carbohydrate diet have been proven beneficial for decreasing the myocardial uptake of 18F-fluorodeoxyglucose (18F-FDG) and enhancing the detection of inflammatory heart diseases by 18F-FDG positron emission tomography (PET). This study aimed at determining whether this benefit is increased when a low-carbohydrate ketogenic diet is prolonged up to 7 days.

METHODS

Wistar rats underwent serial 18F-FDG-PET imaging after an 18-hour fasting period and after 2, 4 and 7 days of a ketogenic diet (3% carbohydrate) and they were compared to rats submitted to the same protocol but with normal diet (44% carbohydrate). The 18F-FDG-PET/ketogenic protocol was also applied in rats with immune myocarditis (injection of porcine cardiac myosin).

RESULTS

The 7-day ketogenic diet was associated with (1) a sustained increase in circulating ketone bodies at an equivalent level to that reached after 18-hour fasting, (2) a gradual decrease in 18F-FDG uptake within normal myocardium reaching a lower level compared to fasting at the 7th day (myocardium-to-blood ratios: 1.68 ± 1.02 vs 3.25 ± 1.40, P < .05) and (3) a high 18F-FDG-PET detectability of myocarditis areas.

CONCLUSION

One-week extension of a ketogenic diet provides a further decrease in the 18F-FDG uptake of normal myocardium and a high detectability of inflammatory areas.

Suppression of myocardial glucose metabolism in FDG PET/CT: impact of dose variation in heparin bolus pre-administration

INTRODUCTION

Adequate suppression of physiologic myocardial glucose uptake is important to ensure the interpretability and diagnostic reliability of [¹⁸F]fluorodeoxyglucose (FDG) PET/CT studies performed in the context of cardiac inflammation and infection. This study describes our experience with 4 preparatory protocols used in our institution.

METHODS

FDG PET/CT scans were performed according to 4 preparatory protocols (716 scans total), i.e. 6-h fast (group 1), low-carbohydrate diet plus 12-h fast (group 2), low-carbohydrate diet plus 12-h fast plus intravenous heparin pre-administration (15 IU/kg) (group 3), and low-carbohydrate diet plus 12-h fast plus intravenous heparin pre-administration (50 IU/kg) (group 4). Consecutive scans were retrospectively included from time frames during which the particular protocol was used. FDG uptake in normal myocardium was scored on a scale ranging from 0 (uptake less than that in the left ventricular blood pool) to 4 (diffuse uptake greater than that in the liver). Complete suppression was defined as uptake less than or equal to the blood pool (scores 0-1).

RESULTS

Complete suppression was accomplished in 27% in group 1, 68% in group 2, 69% in group 3 and 81% in group 4. Complete suppression was significantly lower in group 1 compared with all other groups (P < 0.0001 for all comparisons) and significantly higher in group 4 compared with group 2 (P = 0.005) and group 3 (P = 0.007). Groups 2 and 3 did not differ significantly (P = 0.92).

CONCLUSION

A total of 50 IU/kg single-dose heparin administration before FDG PET/CT in addition to a low-carbohydrate diet and prolonged fast significantly outperformed protocols with no or lower dose (15 IU/kg) heparin in completely suppressing myocardial glucose metabolism.

Myocardial Positron Emission Tomography for Evaluation of Cardiac Sarcoidosis: Specialized Protocols for Better Diagnosis

Sarcoidosis is a multisystemic granulomatous disease of unknown etiology with various clinical presentations depending on the organs involved. Since cardiac sarcoidosis (CS) portends a higher risk of morbidity and mortality, early diagnosis and aggressive medical treatment are essential to improve the prognosis. ¹⁸F-Fluorodeoxyglucose (FDG) positron emission tomography (PET) has emerged as an important tool with practical advantages in assessing disease activity and monitoring the treatment response in patients with CS. While it has high sensitivity, it also has great variability in specificity, probably due to normal physiologic myocardial FDG uptake, which interferes with the evaluation and follow-up of CS using FDG-PET. This review details the technical aspects of FDG-PET imaging for evaluating and diagnosing CS, assessing disease activity, and monitoring therapeutic response.

The role of positron emission tomography in the assessment of cardiac sarcoidosis

The myocardium and the cardiovascular system are often involved in patients with sarcoidosis. As therapy should be started as early as possible to avoid complications such as left ventricular dysfunction, a prompt and reliable diagnosis by means of non-invasive tests would be highly warranted. Among other techniques, 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has emerged as a high sensitive tool to detect sites of inflammation before morphological changes are visible to conventional imaging techniques. We therefore aim at summarizing the most relevant findings in the literature on the use of 18F-fluorodeoxyglucose PET in the diagnostic workup of cardiac sarcoidosis and to underline future perspectives.

Volume-based glucose metabolic analysis of FDG PET/CT: The optimum threshold and conditions to suppress physiological myocardial uptake

OBJECTIVE

FDG PET/CT plays a significant role in the diagnosis of inflammatory heart diseases and cardiac tumors. We attempted to determine the optimal FDG uptake threshold for volume-based analyses and to evaluate the relationship between the myocardial physiological uptake volume in FDG PET and several clinical factors.

METHODS

A total of 190 patients were retrospectively analyzed. The cardiac metabolic volume (CMV) was defined as a volume within the boundary determined by a threshold (SUVmean of blood pool × 1.5).

RESULTS

The SUVmean of the blood pool measured in the descending aorta (DA) (r = 0.86, intraclass correlation coefficient [ICC] = 0.93, P < 0.0001) and that in the left ventricle (LV) cavity (r = 0.87, ICC = 0.90, P < 0.0001) showed high inter-operator reproducibility. However, the SUVmean in the LV cavity showed a significant correlation with the CMV (P = 0.0002, r = 0.26). The CMV in the patients who fasted < 18 hours were significantly higher (49.7  ±  73.2 vs. 18.0  ±  53.8 mL, P = 0.0013) compared to the patients with > 18-hour fasting. The multivariate analysis demonstrated that only the fasting period > 18 hours was independently associated with CMV = 0.

CONCLUSION

Our findings revealed that the DA is suitable to decide the threshold for the volume-based analysis. The fasting time was significantly associated with the cardiac FDG uptake.

Hybrid FDG-PET/MR imaging of chronic osteomyelitis: a prospective case series

Background

Magnetic resonance imaging (MRI) and 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography paired with computed tomography (PET/CT) are two commonly used imaging modalities in the complicated diagnostic workup of osteomyelitis. Diagnosis using these modalities relies on, respectively, anatomical (MRI) and metabolic (PET) signs. With hybrid PET/MRI being recently available, our goal is to qualitatively compare hybrid FDG PET/MRI to FDG PET/CT in the diagnosis and operative planning of chronic osteomyelitis.

Methods

Five patients with suspected chronic osteomyelitis in an extremity underwent an ¹⁸F-FDG single-injection/dual-imaging protocol with hybrid PET/CT and hybrid PET/MR. Images and clinical features were evaluated using a standardized assessment method. Standardized uptake value (SUV) measurements were performed on all images. Concordant and discordant findings between PET/MRI and PET/CT were analysed.

Results

The consensus diagnoses based on PET/MRI and PET/CT images were identical for all five patients. One discrepancy between PET/MRI and PET/CT was found in the assessment of the features in one patient. PET signal intensities and target-to-background ratios were on average highest for PET/MRI. On PET/MRI, the location of infection based on FDG uptake could clearly be correlated with certain soft tissue structures (oedema, fluid collection, or muscle), which is paramount for surgical planning.

Conclusions

In the presented cases, FDG PET/MRI led to the same diagnosis and provided at least the same diagnostic information as PET/CT. PET/MRI was able to provide additional soft-tissue information for the physician planning treatment. Because of this, we suggest that PET/MRI could be used for osteomyelitis diagnosis and treatment planning.

FDG PET-CT findings of extra-thoracic sarcoid are associated with cardiac sarcoid: A rationale for using FGD PET-CT for cardiac sarcoid evaluation

PURPOSE

This retrospective study investigates the relationship between cardiac and extra-thoracic sarcoid findings on FDG PET-CT using a 72-hour pretest high-fat, high-protein, and very low-carbohydrate (HFHPVLC) diet.

PATIENTS AND METHODS

A total of 196 consecutive FDG PET-CT scans with 72-hour HFHPVLC diet preparation were performed between December 2014 and December 2015 in known sarcoid patients. Of these scans, 5 were excluded for non-adherence to diet preparation or underlying cancer. Cardiac and extra-thoracic sarcoid lesions were categorized and measured for radiotracer uptake.

RESULTS

A total of 188 patients had 191 eligible FDG PET/CT scans (3 follow-up scans), of which there were 20 (10%) positive, 6 indeterminate (3%), and 165 (86%) negative for CS. Among the 20 scans positive for CS, 8 (40%) had findings of both cardiac and extra-thoracic sarcoid.

CONCLUSION

Our study shows that 40% of CS patients also have FDG PET-CT findings of extra-thoracic sarcoid. This makes an intriguing case for FDG PET-CT use with pretest diet prep over cardiac MRI (CMR) for cardiac sarcoid evaluation, given that CMR is likely to overlook these extra-thoracic sites of disease.

PET/CT Evaluation of Cardiac Sarcoidosis

The increasing implementation of advanced cardiovascular imaging in the form of cardiac PET/CT has had a significant impact on the management of cardiac sarcoidosis, which continues to evolve. This review summarizes the role of PET/CT imaging in sarcoidosis with a specific focus on (1) indications, (2) patient preparation, (3) test performance, (4) study interpretation, (5) clinical relevance of findings, (6) comparison to alternative imaging modalities, and finally (7) introduction of areas of anticipated development and research.

Cardiac sarcoidosis classification with deep convolutional neural network-based features using polar maps

AIMS

The aim of this study was to determine whether deep convolutional neural network (DCNN)-based features can represent the difference between cardiac sarcoidosis (CS) and non-CS using polar maps.

METHODS

A total of 85 patients (33 CS patients and 52 non-CS patients) were analyzed as our study subjects. One radiologist reviewed PET/CT images and defined the left ventricle region for the construction of polar maps. We extracted high-level features from the polar maps through the Inception-v3 network and evaluated their effectiveness by applying them to a CS classification task. Then we introduced the ReliefF algorithm in our method. The standardized uptake value (SUV)-based classification method and the coefficient of variance (CoV)-based classification method were used as comparative methods.

RESULTS

Sensitivity, specificity and the harmonic mean of sensitivity and specificity of our method with the ReliefF algorithm were 0.839, 0.870 and 0.854, respectively. Those of the SUVmax-based classification method were 0.468, 0.710 and 0.564, respectively, and those of the CoV-based classification method were 0.655, 0.750 and 0.699, respectively.

CONCLUSION

The DCNN-based high-level features may be more effective than low-level features used in conventional quantitative analysis methods for CS classification.

Gallium-68 DOTA-NOC PET/CT as an alternate predictor of disease activity in sarcoidosis

INTRODUCTION

We evaluated the role of gallium-68-labeled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-1-Nal3-octreotide (Ga-DOTA-NOC) PET/CT in assessing sarcoidosis disease activity.

PATIENTS AND METHODS

Patients diagnosed with sarcoidosis underwent Ga-DOTA-NOC-PET/CT. The maximum standardized uptake value (SUVmax) at the pathological site and in the descending thoracic aorta (reference standard, SUVmed) were assessed. A SUVmax/SUVmed ratio (disease activity score) of more than one was considered a marker of active disease and was compared with the clinical symptoms and serum angiotensin-converting enzyme and computed tomography (CT) scan. The primary outcome was to assess the efficacy of the scan in estimating disease activity.

RESULTS

Of the 39 patients enrolled in the study, 27 patients were symptomatic and the rest were asymptomatic at enrollment. Increased disease activity was present in 25 (92%) of the 27 symptomatic patients and two (16%) of the 12 asymptomatic patients. The sensitivity and specificity of the test were 92.5% (95% confidence interval=75.7-99.0) and 83.3% (95% confidence interval=51.5-97.9), respectively. Seven out of nine patients who became asymptomatic after treatment showed a significant decrease in the mean disease activity score in post-treatment scans (3.38±1.05 vs 1.20±0.82, P<0.001).

CONCLUSION

Ga-DOTA-NOC PET/CT emerged as a useful tool to assess the disease activity and treatment response in patients with sarcoidosis with thoracic involvement.

11C-4DST PET/CT Imaging of Cardiac Sarcoidosis: Comparison With 18F-FDG and Cardiac MRI

A 75-year-old woman with a history of sarcoidosis presenting with low cardiac output and complete right bundle-branch block underwent 4'-[methyl-C]-thiothymidine (4DST) PET/CT after cardiac MRI and FDG PET/CT for the evaluation of suspected cardiac sarcoidosis (CS) before treatment. Cardiac MRI revealed late gadolinium enhancement on the anterior-to-lateral and posterior wall, indicating CS. FDG uptake was shown on the anterior-to-lateral wall, but not on the posterior wall. In contrast, 4DST uptake was demonstrated on both anterior-to-lateral and posterior walls. Use of 4DST appears promising for detecting CS without dietary restriction, due to the lack of physiological uptake in myocardium.

The "3M" Approach to Cardiovascular Infections: Multimodality, Multitracers, and Multidisciplinary

Cardiovascular infections are associated with high morbidity and mortality. Early diagnosis is crucial for adequate patient management, as early treatment improves the prognosis. The diagnosis cannot be made on the basis of a single symptom, sign, or diagnostic test. Rather, the diagnosis requires a multidisciplinary discussion in addition to the integration of clinical signs, microbiology data, and imaging data. The application of multimodality imaging, including molecular imaging techniques, has improved the sensitivity to detect infections involving heart valves and vessels and implanted cardiovascular devices while also allowing for early detection of septic emboli and metastatic infections before these become clinically apparent. In this review, we describe data supporting the use of a Multimodality, Multitracer, and Multidisciplinary approach (the 3M approach) to cardiovascular infections. In particular, the role of white blood cell SPECT/CT and [¹⁸F]FDG PET/CT in most prevalent and clinically relevant cardiovascular infections will be discussed. In addition, the needs of advanced hybrid equipment, dedicated imaging acquisition protocols, specific expertise for image reading, and interpretation in this field are discussed, emphasizing the need for a specific reference framework within a Cardiovascular Multidisciplinary Team Approach to select the best test or combination of tests for each specific clinical situation.

Effect of long fasting on myocardial accumulation in 18F-fluorodeoxyglucose positron emission tomography after chemoradiotherapy for esophageal carcinoma

This study sought to evaluate the effect of fasting time prior to 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) on myocardial accumulation of FDG in patients receiving radiotherapy for esophageal carcinoma, and the spatial relationship between the irradiated dose and myocardial accumulation of FDG. Forty-one patients with thoracic esophageal carcinoma received FDG-PET with <18-h (24 patients) or ≥18-h (17 patients) fasting status. Their myocardial accumulation patterns of FDG were categorized using the maximal standardized uptake value (SUVmax) into three types: physiological, focal and no pathological accumulation. The incidence rates of each pattern were then compared using the Fisher's exact test between two types of fasting, ≥18-h and <18-h, prior to FDG-PET. Additionally, the left ventricle was defined using four subsites depending on the irradiated doses, and the SUVmax values were compared among the subsites using the Kruskal-Wallis test. The incidence of the physiological accumulation pattern decreased significantly more in the ≥18-h fasting status group than in the <18-h fasting group (18% versus 71%, P = 0.002), and the focal accumulation of FDG was detected at a significantly higher rate (65% versus 13%, P = 0.001). The left ventricular subsites receiving the higher doses showed significantly higher SUVmax values than did the subsites receiving the lower doses (P < 0.001). In conclusion, radiotherapy was associated with abnormal myocardial accumulation of FDG. Long fasting for 18 h or more prior to FDG-PET would be useful in detecting subsequent myocardial damage from chemoradiotherapy compared with <18-h fasting prior to FDG-PET.