Dual-Tracer Theranostic PET

Inclusion Criteria:

* adults aged 18 years or greater.
* willing and able to sign a written informed consent and HIPAA authorization in accordance with local and institutional guidelines.
* presence of at least 1 measurable lesion ≥ 1 cm in size.
* willing to have their clinical records reviewed for at least 24 months after enrollment.
* willing to lie flat on their back in the PET/CT scanner for up to one hour to allow for the imaging data to be obtained.
* willing to undergo two separate PET/CT exams on different days within 2 weeks of each other.
* female participants who are not postmenopausal or surgically sterile will undergo a serum pregnancy test prior to baseline and the subsequent set of multi-tracer PET scans. The serum pregnancy test must be performed within 48 hours prior to research PET imaging. A negative test will be necessary for such patients to undergo research PET imaging. This only applies to Arms 1 and 2, since only males will be included in Arm 3 (only males can get prostate cancer).
* Arms 1 and 2 only: known or suspected somatostatin receptor-positive neuroendocrine tumor (NET) who could be considered for clinical use of DOTATATE PET/CT imaging under the approved indications for use of this radiopharmaceutical according to published appropriate use criteria. These indications include initial staging after the histologic diagnosis of NET, evaluation of an unknown primary; evaluation of a mass suggestive of NET not amenable to endoscopic or percutaneous biopsy, staging of NET before planned surgery, monitoring of NET seen predominantly on somatostatin receptor (SSTR) PET, evaluation of patients with biochemical evidence and symptoms of a NET, evaluation of patients with biochemical evidence of a NET without evidence on conventional imaging or a prior histologic diagnosis, restaging at time of clinical or laboratory progression without progression on conventional imaging, and new indeterminate lesion on conventional imaging with unclear progression.
* Arm 3 Only: known or suspected prostate cancer who could be considered for clinical use of PSMA PET/CT imaging under the approved indications for use of this radiopharmaceutical, including patients with suspected metastasis and patients with suspected recurrence based on elevated serum prostate-specific antigen (PSA) level.

Exclusion Criteria:

* received somatostatin receptor targeted therapy at any time prior to enrollment will be excluded from the study Arms involving DOTATATE (Arms 1-2).
* known intolerance or hypersensitivity to any somatostatin analogs will be excluded from the study Arms involving DOTATATE (Arms 1-2).
* participated in any therapeutic clinical study or received any investigational agent within the last 30 days.
* known allergic or hypersensitivity reactions to previously administered radiopharmaceuticals
* require monitored anesthesia for PET/CT scanning.
* too claustrophobic to undergo PET/CT scanning.
* exceed the 450 lb. weight limit of the PET/CT scanner.
* pregnant or currently breast feeding.