In this study, investigators propose to use PET imaging to study the pharmacokinetics of 18F-TPP and develop methods for imaging membrane potential (ΔΨT) in humans.

The aims of this study are:

1. Assessment of the pharmacokinetics of primed constant infusion of 18F-TPP in humans.
2. Assessment of normal variation of membrane potential (ΔΨT) and extracellular space (ECS) in a cohort of "normal" subjects.
3. Assessment of the pharmacokinetics of bolus injection of 18F-TPP in humans. Studies will be performed on a PET/CT scanner. A separate MRI will be collected.

Each scan may or may not have arterial blood sampling for measurement of the time course of radioactivity in the whole-blood, plasma and radiometabolite analysis on selected plasma samples.

Inclusion Criteria:

• Willing and able to give voluntary written informed consent
• Stated willingness to comply with all study procedures and availability for the duration of the study
• In good general health as evidenced by medical history, physical examination, ECG, serum/urine biochemistry and hematology tests.
• If female of childbearing potential, must agree to use an acceptable method of birth control, as determined by the principal investigator, for the duration of the study.

Exclusion Criteria:

• Know structural heart disease (e.g. myocardial infarction)
• Abnormal and clinically significant ECG (as determined by the Investigator or his/her designee) at screening.
• Laboratory tests with clinically significant abnormalities at screening
• Pregnancy or Lactation
• MRI incompatible implants (i.e., such as pacemaker, artificial joints, non-removable body piercings) and other contraindications for MRI, such as claustrophobia, having implanted or embedded metal objects/fragments or fragments in the head or body that would present a risk during the MRI scanning procedure, or have worked with ferrous metals either as a vocation or hobby (for example, as a sheet metal worker, welder, or machinist).
• Participation in other research studies involving ionizing radiation within one year of the PET scans that would cause the subject to exceed the yearly dose limits followed by the Yale University PET Center.
• Subject who has current, past, or anticipated exposure to radiation in the workplace within one year of the proposed research scans that in combination with the study tracer would result in a cumulative exposure that exceeds recommended exposure limits.
• Has any condition that, in the opinion of the investigator, would prevent compliance with the study protocol.
• Arterial Line Exclusion: Blood donation within eight weeks of the start of the study.
• Arterial Line Exclusion: History of a bleeding disorder or are currently taking anticoagulants (such as Coumadin, Heparin, Pradaxa, Xarelto).
• Arterial Line Exclusion: Prothrombin Time (PT) and Partial Thromboplastin Time (PTT) greater than 5msec above the upper limit of normal.
• Arterial Line Exclusion: Unable to safely discontinue or hold aspirin and other NSAID use