Positron Emission Tomography (PET) Contrast Agent Kinetics and Safety: [18F]-Fluoromannitol

Inclusion Criteria: Healthy volunteers, 18-75 years of age. * Female participants of childbearing age must not be lactating due to theoretical potential harm to the infant from exposure to radiation. * Informed consent signed by participant according to the guidelines of the institutional review board. Exclusion Criteria: Initial Eligibility Exclusion Criteria (Entry to Screening Phase - * Participant currently has a fever or other symptoms concerning for an active infection or is currently undergoing treatment for an active infection. * Participant has been diagnosed and/or treated for a known or suspected bacterial infection within the past 60 days. * Participant has known disease of the lung, liver, kidneys, gastrointestinal tract, bones/joints, or known immune suppression or autoimmune disease that is likely to have active inflammation (examples to exclude: Crohn's disease, COPD; example to i include: well controlled asthma) * Participant has prosthetic or indwelling device(s) currently or has had one in the past 60 days. * Participant is pregnant or breastfeeding. * Use of drugs known to have interaction or be affected by mannitol within 60 days of enrollment. * Participant has any condition that would, in the opinion of the investigator, place the subject at an unacceptable risk of injury or render the subject unable to meet the requirements of the protocol, including being unable to tolerate the PET scan procedures. * Inability or unwillingness of research participant or legal guardian/representative to give written informed consent. * Participant is currently participating in another study subject to an IND. Final Eligibility Exclusion Criteria (Entry to Study): At the time of the Final Eligibility Determination (Imaging Study Visit 1): * Participant no longer meets one or more of the Inclusion Criteria * Participant now fails one or more of the Initial Eligibility Exclusion Criteria * Estimated glomerular filtration rate is \< 45 ml/minute/1.73m2 * Positive pregnancy test (females only) * One or more of the results from laboratory (hematology, chemistries, inflammatory markers), vital signs, or ECG specified in the schedule of evaluations is outside the normal institutional range AND is clinically significant in the opinion of the investigator. Re-screening will not be allowed unless the Investigator considers the cause of the initial screen failure to be of an acute and/or completely reversible nature.