Inclusion Criteria (Healthy Volunteers):  Adult 18 years of age or older No known hematological disorders Considered healthy based on assessment by Principal Investigator (PI). Able to provide informed consent Able to comprehend and willing to follow instructions for study procedures as called for by the protocol. Capable of lying still and supine within the PET/CT scanner for up to 1 hour at a time.  Exclusion Criteria (Healthy Volunteers):  No illicit drug use or other inhaled drug use (including pharmacologic agents, recreational agents or illicit drugs) within the past year per self-reporting mechanisms. No history of claustrophobia or other preventing condition that has previously or would interfere with completion of protocol specified imaging sessions. Not currently pregnant or nursing: Subject must be surgically sterile (has had a documented bilateral oophorectomy and/or documented hysterectomy), postmenopausal (cessation of menses for more than 1 year), non-lactating, OR of childbearing potential for whom a urine pregnancy test (with the test performed within the 24 hour period immediately prior to administration of 18 F-FAT) is negative  Inclusion Criteria (Participants with Diffuse Large B Cell Lymphoma):  Men or women 18 years of age or older New diagnosis of diffuse large B cell lymphoma (DLBCL) who will be treated with R-CHOP At least one measurable (RECIST 1.1), FDG-avid lesion that is accessible for ultrasound guided biopsy. Able to provide informed consent Able to tolerate standard of care systemic therapy as recommended by referring physician(s).  Exclusion Criteria (Participants with Diffuse Large B Cell Lymphoma):  Not currently pregnant or nursing: Subject must be surgically sterile (has had a documented bilateral oophorectomy and/or documented hysterectomy), postmenopausal (cessation of menses for more than 1 year), non-lactating, OR of childbearing potential for whom a urine pregnancy test (with the test performed within the 24 hour period immediately prior to administration of 18 F-FAT) is negative Not currently enrolled in another study using an investigational drug