11C-5-HTP PET in Clinical Islet Transplantation

Inclusion Criteria: Subjects must meet all of the following criteria to be considered eligible for participation in the study: 1. Subjects who are able to provide written informed consent and comply with the procedures of the study protocol. 2. Patient that has received an islet transplant in or outside the CIT01 trial (post primary endpoint). Exclusion Criteria: Subjects who meet any of these criteria are not eligible for participation in the study: 1. For female subjects: Positive serum pregnancy test, presently breast-feeding, or unwillingness to use effective contraceptive measures at the time of PET scan +/- 2 weeks. 2. Known history of severe co-existing cardiac disease, characterized by any one of the following conditions: 1. Recent myocardial infarction (within past 6 months). 2. Evidence of ischemia on functional cardiac exam within the last year. 3. Left ventricular ejection fraction \<30%. 3. Persistent elevation of liver function tests at the time of study entry. Persistent Aspartate Aminotransferase (serum glutamic-oxaloacetic transaminase), Alanine Aminotransferase (serum glutamate pyruvate transaminase), Alkaline phosphatase or total bilirubin, with values \>1.5 times normal upper limits will exclude a patient. 4. Treatment with any anti-diabetic medication, other than insulin, within 4 weeks of enrollment. 5. Use of any investigational agents within 4 weeks of enrollment. 6. Any medical condition that, in the opinion of the investigator, will interfere with the safe completion of the trial.