Cardiac FDG-PET Research Articles

Clinical Characteristics of Definite or Suspected Isolated Cardiac Sarcoidosis: Application of Cardiac Magnetic Resonance Imaging and 18F-Fluoro-2-deoxyglucose Positron-Emission Tomography/Computerized Tomography

BackgroundIsolated cardiac sarcoidosis (iCS) is difficult to diagnose in patients without histologic evidence of sarcoidosis. We aimed to clarify the clinical characteristics of iCS, including imaging features on cardiac magnetic resonance imaging (MRI) and 18F-fluoro-2-deoxyglucose positron-emission tomography/computerized tomography (FDG-PET/CT) scans. We also reviewed the therapeutic effect of corticosteroids and determined the long-term prognosis. Methods and ResultsWe retrospectively reviewed 83 consecutive patients with suspicious CS from 1997 to 2013. Systemic sarcoidosis with CS (sCS, n = 30) and iCS (n = 11) were diagnosed according to clinical criteria. In iCS cases, sarcoidosis was not detected in any other organs. The clinical features did not significantly differ between sCS and iCS cases, except for ejection fraction, which was lower in iCS (P = .025). Nine sCS and 4 iCS cases showed late gadolinium enhancement, and the lesions tended to be on the epicardial side (76.9% P = .011) and septal wall (52.9% P < .001). The coefficient of variance for the myocardial standardized uptake value of FDG-PET/CT was higher in sCS (0.32 ± 0.13; n = 19) and iCS (0.32 ± 0.09; n = 7) than in control cases (n = 31; P < .001). B-Type natriuretic peptide level was improved after prednisolone treatment in both groups. Kaplan-Meier curve indicated that prognosis was not different between sCS and iCS cases. ConclusionsThe clinical cardiac characteristics of iCS cases were similar to those of sCS. Cardiac MRI and FDG-PET, noninvasive imaging modalities, could be useful modalities to detect myocardial involvement in the cases with definite or suspected iCS.

FDG gated cardiac PET at rest and immediately after dobutamine stress

Cardiac gated FDG PET images after injection of tracer at rest show (1a) relatively preserved tracer uptake (60 % of the maximum in the myocardium, inferior wall) in the anterior wall with marked hypokinesia. Images following obutamine stress (up to 20 μg/kg/min in 3-min steps) with no further injection of FDG reveal (1b) an apparent reduction in tracer uptake (40 % of the maximum in the myocardium, inferior wall) in the anterior wall (apical and mid-cavity segments) extending into the septum and apex. The left ventricular ejection fraction was measured at 56 % on both occasions. Gated cardiac FDG PET is a valuable tool [1] to assess patients with coronary artery disease when searching for viable myocardium [2]. Resting myocardial perfusion gated SPECT to search for viability in the anterior wall showed a perfusion defect with severe hypokinesia (1c). Gated cardiac FDG PET imaging at rest and after inotropic stress (with a single injection of FDG) demonstrates post-infarct viability in the anterior wall. The reduced contractility in the mid-cavity and apical segments of the anterior wall after inotropic stress with improvement at rest mimics ischaemia.

Identification of Inflamed Aortic Plaque in Conventional Fluorodeoxyglucose–Positron Emission Tomography Myocardial Viability Studies

BackgroundIt has been shown that 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is useful in identifying inflamed plaque in major arteries. This study evaluated the feasibility of inflamed plaque detection with routinely acquired cardiac FDG-PET viability studies in patients with severe coronary artery disease and left ventricular dysfunction. MethodsClinically indicated myocardial viability scans using FDG and PET combined with computed tomography from 103 patients were retrospectively analyzed for FDG uptake in the proximal, ascending, and descending thoracic aorta. Aortic uptake was graded on the basis of peak and mean target-to-background ratio (TBR): grade 0, < 1; grade 1, 1.01-1.49; grade 2, 1.5-1.99; and grade 3, > 2. ResultsOf the 103 patients, 71 (68.9%) had a history of myocardial infarction, 88 (85.4%) were on statins, and 70 (68%) were on angiotensin-converting enzyme (ACE) inhibitors. Increased FDG uptake (mean TBR grade 1-3) was seen in 79 of 103 patients (77%), and grade 3 aortic uptake based on peak TBR was found in 12 of 103 patients (12%). ConclusionsDetection of inflamed atherosclerotic plaque in the aorta with conventional FDG viability scans is feasible. The rate of very positive uptake in this population of ischemic heart disease patients is low, possibly reflecting aggressive secondary risk factor modification including statin and ACE inhibitor use.

A Bayesian framework for the extraction of input function for 18F-FDG metabolism study for both healthy and infarcted rats' hearts

The quantitative analysis of tracers in positron emission tomography (PET) studies requires the measurement uptake and retention of tracer in tissue over time. This analysis applied to the heart allows to diagnose its state. It could provide a means to identify areas of myocardial viability and to assess myocardial ischemia. However, the input function (IF), quite commonly used in quantitative analysis, can be corrupted by undesirable effects such as spillover. In this paper, we propose a new approach to correct the cross contamination effect on PET dynamic image sequences. It is based on the decomposition of image pixel intensity into blood and tissue components using Bayesian statistics. The method uses an a priori knowledge of the probable distribution of blood and tissue in the images. Likelihood measures are computed by a General Gaussian Distribution (GGD) model. Bayes’ rule is then applied to compute weights that account for the concentrations of the radiotracer in blood and tissue and their relative contributions in each image pixel. We tested the method on a set of dynamic cardiac FDG-PET of healthy and unhealthy rats. The results show the benefit of our correction on the generation of pixel-wise images of myocardial metabolic rates for glucose (MMRG).

516 Cardiac fdg pet results impact decisions and identify patients likely to benefit from revascularization in a multi-center provincial registry (CADRE)

516 Cardiac fdg pet results impact decisions and identify patients likely to benefit from revascularization in a multi-center provincial registry (CADRE)

Diagnosis of Myocardial Viability by Fluorodeoxyglucose Distribution at the Border Zone of a Low Uptake Region

PurposeIn cardiac 2-[F-18]fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) examination, interpretation of myocardial viability in the low uptake region (LUR) has been difficult without additional perfusion imaging. We evaluated distribution patterns of FDG at the border zone of the LUR in the cardiac FDG-PET and established a novel parameter for diagnosing myocardial viability and for discriminating the LUR of normal variants.Materials and MethodsCardiac FDG-PET was performed in patients with a myocardial ischemic event (n = 22) and in healthy volunteers (n = 22). Whether the myocardium was not a viable myocardium (not-VM) or an ischemic but viable myocardium (isch-VM) was defined by an echocardiogram under a low dose of dobutamine infusion as the gold standard. FDG images were displayed as gray scaled-bull's eye mappings. FDG-plot profiles for LUR (= true ischemic region in the patients or normal variant region in healthy subjects) were calculated. Maximal values of FDG change at the LUR border zone (a steepness index; Smax scale/pixel) were compared among not-VM, isch-VM, and normal myocardium.ResultsSmax was significantly higher for n-VM compared to those with isch-VM or normal myocardium (ANOVA). A cut-off value of 0.30 in Smax demonstrated 100% sensitivity and 83% specificity for diagnosing n-VM and isch-VM. Smax less than 0.23 discriminated LUR in normal myocardium from the LUR in patients with both n-VM and isch-VM with a 94% sensitivity and a 93% specificity.ConclusionSmax of the LUR in cardiac FDG-PET is a simple and useful parameter to diagnose n-VM and isch-VM, as well as to discriminate thr LUR of normal variants.

Abstract 3302: Contribution of Cardiac F-18 FDG PET Imaging to the Management of Patients with Cardiac Sarcoidosis

Early detection and correct assessment of disease activity are critical for the optimal management of patients with cardiac sarcoidosis (CSRD). There are some recent reports showing F-18 FDG (FDG) uptake by sarcoid granulomas. In the present study, we estimated the significance of cardiac FDG PET imaging in 47 patients (57+/−11 years, 16 males and 31 females) with proven diagnosis of CSRD and receiving steroid therapy (30 – 60 mg prednisolone on alternate days) based on clinical signs of acute myocardial involvement. We interpreted regionally enhanced myocardial FDG uptake as positive in the 5-hr fasting FDG PET imaging. In addition, we determined standardized uptake value (SUV) of the FDG uptake. Before steroid therapy, positive myocardial finding was 89% (42/47) in FDG PET, 55% (21/38) in Tc-99m pyrophosphate tomographic imaging, 68% (30/44) in Ga-67 tomographic imaging, 49% (23/47) in echocardiographically estimated septal wall thinning and 35% (13/37) in biopsy. SUV was above 2.5 in all with positive FDG finding. In 3 patients with severe heart failure and with positive finding in biopsy, myocardial FDG uptake showed diffuse patterns and was hardly interpreted positive. The follow-up studies after steroid therapy revealed that the enhanced FDG uptake gradually reduced and disappeared in 6 months in most of the patients, while positive Ga-67 uptake disappeared soon after therapy. Afterwards, recurrence of active inflammation was symptomatically suspected in 4 patients. Performing FDG PET imaging, they all showed re-enhancement of myocardial FDG uptake, which contributed to decision-making of increasing steroid dose. These results suggest that the FDG PET imaging is a sensitive means in detecting disease activity of CSRD and contributes to the decision-making and evaluation of steroid therapy.

The effect of glucose load on both cardiac and skeletal muscle FDG uptake

Background: The augmentation of the myocardial FDG uptake after a glucose load is very well established. However, the response of the skeletal muscle to the same glucose load has not been clearly demonstrated. The aim of this study is to demonstrate an increased skeletal muscle FDG uptake after a standard oral glucose load. To this end, we compared myocardial and skeletal muscle FDG uptake in a group of fasted patients to that of a second group of patients who underwent FDG PET scanning following oral glucose load. Methods: We included 41 patients (20 Male, 21 Female; age:26–72 years) without any cardiac pathology who had whole body FDG PET scan after several hours of fasting (4–24) in the first group. In the second group, we included 9 patients (8M; 1F; age 52–80 years) who had cardiac FDG PET imaging following a 50 g of oral glucose load. PET images were acquired with a Phillips Allegro scanner. We calculated the standard uptake values (SUV= Cts/injected dose/pt weight) of myocardium, arterial blood and skeletal muscle for both groups using regions of interest over the left ventricular myocardium, left ventricular cavity and skeletal muscle. Statistical analysis was performed using unpaired t test. Results: The results for both groups are given in table below. * Groups Heart SUV * Blood SUV Muscle SUV * Heart/Blood * Heart/Muscle Gp1 (n = 41) 4.8 ± 3.07 1.9 ± 0.64 0.88 ± 0.29 5.78 ± 3.70 2.54 ± 1.17 Gp2 (n = 9) 8.9 ± 5.25 2.39 ± 0.83 1.52 ± 0.50 6.62 ± 5.24 3.72 ± 1.70 * p < 0.05 There were statistically significant difference (p<0.05) between p values for heart and skeletal muscle uptake and for the heart to blood ratio. Conclusions: Both myocardial and skeletal muscle FDG uptake were higher in patients that received glucose load. However, the arterial concentration was similar. Skeletal muscle uptake could be used as an indicator of fasting status in patients undergoing FDG PET imaging.

Correction of spillover radioactivities for estimation of the blood time-activity curve from the imaged LV chamber in cardiac dynamic FDG PET studies

In dynamic cardiac PET FDG studies for measurement of myocardial metabolic rate of glucose (MMRGlc), the plasma FDG time-activity curve (input function) is commonly obtained from the left ventricular (LV) region on the PET images. The input function is contaminated by spillover of radioactivity from the surrounding myocardium and this could cause significant error in the estimated MMRGlc. In this study, the authors determined the effect of myocardial to blood pool spillover on MMRGlc and developed a method to correct for this spillover of activity. The method is based on a reformulation of the FDG model equation in terms of the spillover contaminated input function that includes both the myocardium to blood pool and blood pool to myocardium spillover fractions as variable parameters (Fmb and Fbm) The reformulated model equation can be used to fit the global myocardial tissue activity curve to estimate Fmb and thus yields a spillover corrected input function. The MMRGlc estimate with the corrected input function was within 95% of the true value (compared to 85% using the uncorrected input function) in a set of computer simulation studies. Dynamic PET FDG data were obtained in eight human studies and blood samples were obtained during the study. As compared to the results with the uncorrected input function, the estimates of k4 by the new method were reduced by 69% into a range consistent with in vitro results. The method is effective in correcting Fmb spillover and leads to more accurate estimates of MMRGlc. The method also allows larger regions of interest (up to 150 mm2) to be drawn over the LV in dynamic PET images, thereby reducing the noise level in the input function.