Photoacoustic/Ultrasound Imaging of Brown Adipose Tissue Activity

Criteria for Healthy Subjects: (INCLUSION CRITERIA) 1. Healthy individuals over 18 years of age. 2. Body Mass Index (BMI) \< 30. 3. No history of metabolic diseases, rheumatic immune diseases, or cardiovascular and cerebrovascular diseases. 4. Not currently using any sympathomimetic or sympatholytic drugs. 5. Non-smoker and does not consume excessive alcohol. (EXCLUSION CRITERIA) 1. Weight change \> 5% within 3 months prior to enrollment. 2. BMI ≥ 30. 3. Diagnosis of metabolic disease, rheumatic immune disease, cardiovascular and cerebrovascular disease, or malignant tumor. 4. Use of sympathomimetic or sympatholytic drugs within 3 months prior to enrollment. 5. Smoker or consumes excessive alcohol. 6. Diagnosis of Raynaud's disease, or intolerance/allergy to cold stimulation. 7. Currently pregnant, lactating, or menstruating. 8. Contraindications to the injection of the radionuclide tracer Fluorodeoxyglucose (18F-FDG) or other conditions unsuitable for PET-CT examination. Criteria for Patients with Metabolic Syndrome and Insulin Resistance-Related Diseases: (INCLUSION CRITERIA) 1. Age between 18 and 60 years. 2. Must meet 3 or more of the following criteria: 1. Waist circumference ≥ 90 cm for males, ≥ 85 cm for females. 2. Fasting blood glucose ≥ 6.10 mmol/L (110 mg/dl) OR 2-hour postprandial blood glucose ≥ 7.80 mmol/L (140 mg/dl) OR previously diagnosed diabetes. 3. Blood pressure ≥ 130/85 mmHg OR previously diagnosed hypertension and under treatment. 4. Fasting triglycerides (TG) ≥ 1.7 mmol/L (150 mg/dl). 5. Fasting high-density lipoprotein cholesterol (HDL-C) \< 1.0 mmol/L (40 mg/dl). 3. Patients diagnosed with Polycystic Ovary Syndrome (PCOS), defined as meeting two or more of the following criteria and excluding other endocrine diseases that could cause similar symptoms: hyperandrogenism, ovulatory dysfunction, polycystic ovary morphology. (EXCLUSION CRITERIA) 1. Diagnosis of Type 1 diabetes or other specific types of diabetes. 2. Presence of acute diabetic complications or severe chronic diabetic complications. 3. History of acute or chronic pancreatitis, or pancreatic tumors. 4. Heart failure, unstable angina, myocardial infarction within the past 12 months, cerebral infarction, severe arrhythmia, or severe hypertension (blood pressure \> 180/110 mmHg despite antihypertensive medication). 5. Severe hepatic or renal dysfunction. 6. Comorbid malignant tumors or other severe chronic diseases. 7. Received glucose-lowering therapy within 3 months prior to enrollment OR a total of more than 3 months of glucose-lowering therapy in the past 2 years. 8. Diagnosis of rheumatic immune diseases. 9. Diagnosis of Raynaud's disease, or intolerance/allergy to cold stimulation. 10. Currently pregnant, lactating, or menstruating. 11. Contraindications to the injection of the radionuclide tracer Fluorodeoxyglucose (18F-FDG) or other conditions unsuitable for PET-CT examination.