Effects of Brain Beta-Amyloid on Postoperative Cognition

Inclusion Criteria: * Scheduled for total knee arthroplasty or total hip arthroplasty under general anesthesia (primary arthroplasties and revisions) * English speaking * Anticipated stay in the hospital * Not anticipated to stay intubated postoperatively * Patients who live with or have regular visits from an individual ("study partner") willing to provide information about the patient's cognitive status * Willing and able to undergo all testing procedures including neuroimaging and agree to longitudinal follow up * Adequate visual and auditory acuity to allow neuropsychological testing * Subjects with Clinical Dementia Rating Scale (CDR) of 0-0.5 * Patients who are not demented * Subjects sho signed an IRB approved informed consent prior to any study procedures Exclusion Criteria: * Clinically significant hepatic, renal, pulmonary, metabolic, or endocrine disturbances as indicated by history, which in the opinion of the investigator might pose a potential safety risk to the subject * Current clinically significant cardiovascular disease. * History of drug or alcohol abuse within the last year, or prior prolonged history of abuse * Clinically significant infections disease, including Acquired Immune Deficiency Syndrome (AIDS) or Human Immunodeficiency Virus (HIV) infection or previous positive test for hepatitis * History of relevant severe drug allergy or hypersensitivity * Received an investigational medication under an FDA IND protocol within the last 30 days. * Current clinically significant unstable medical comorbidities, as indicated by history or physical exam, that pose a potential safety risk to the subject * Received a radiopharmaceutical for imaging or therapy within the past 24 hours prior to the imaging session for this study * Severe psychiatric disorders including schizophrenia, bipolar disorders, and major depression as described in DSM-IV within the past year (medical record, GDS score, interview with the patient and study partner) * Obvious causes for their cognitive impairment (e.g. onset coincides with recent head trauma or stroke) * Dementia of any cause * CDR score \> 0.5 * Expressed the preference to undergo the procedure under regional anesthesia in form of spinal or epidural anesthesia * Patients who, in the opinion of the investigator, are otherwise unsuitable for a study of this type