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Research Studies
Diabetes
| FDG Uptake on PET is a Marker for Internal Carotid and Aortic Plaque Instability
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Specific Aims: To test the hypothesis that F-18 FDG uptake is a marker of plaque instability in patients with documented plaque in the internal carotid arteries and/or in the aorta.
Subject Population: This study will enroll up to 30 patients with a lower age cut off of 40 years. Patients with atherosclerosis, including those with type II diabetes and vascular disease, will be referred for PET scanning from the vascular and cardiac (TEE) ultrasound laboratories. All patients will have laboratory evaluation of C-reactive protein at the time of enrollment. Positron emission tomography will be performed on all patients from the base of the skull to the proximal thighs after injection of F-18 fluorodeoxyglucose. Uptake of tracer will be localized and scored by extent and intensity.
Data Analysis: All patients will be followed for events including CNS events (stroke, TIA) as well as myocardial infarction since vascular inflammation may be a widespread process. Levels of CRP will also be correlated with events as well as with scan uptake. F-18 FDG PET scan results will be both dichotomized as +/- and considered as a continuous variable based on quantitative uptake.
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| Effect of Diabetes Control on Cardiac Autonomic Nerves () |
Approximately 16 million Americans have diabetes mellitus and about 1/3 of these patients demonstrate abnormal autonomic function on clinical testing. Autonomic dysfunction has been associated with increased morbidity and mortality. Because of our previous inability to measure damage in sympathetic neurons, little is known about the actual pathophysiology of cardiac sympathetic denervation in diabetic patients. PET imaging now allows us to quantitatively measure and study cardiac nerve function.
The objective of this study is to quantitatively assess cardiac carbon (C-11) hydroxyephedrine uptake as a marker for the imaging of postsynaptic sympathetic receptor occupancy (Bmax), and to correlate the regional Bmax with conventional markers of sympathetic and parasympathetic dysfunction in patients with autonomic neuropathy. We will also determine whether observed scintigraphic findings are due to irreversible or potentially reversible functional disturbances of sympathetic neurons.
We will study 15 diabetic patients and 7 normal control subjects. Diabetic patients will twice undergo both the standard 3-test American Diabetic Association (ADA) battery for the diagnosis of cardiac autonomic neuropathy and quantitative C-11 hydroxyephedrine imaging as evaluated by PET: first shortly after initial diagnosis and then again after 3-6 months of glycemic control. We believe there is a correlation between autonomic dysfunction, as assessed by ADA testing criteria, and regional variation in Bmax. We also believe that the degree of blood glucose control in diabetics is a determinant of autonomic nervous system function and that improvement in glycemic control will correlate with improved autonomic function and improvement in Bmax.
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Patients
