This clinical trial evaluates \[18F\]-rh PSMA positron emission tomography (PET)-computed tomography (CT) imaging performance in patients with prostate cancer. PET is an established imaging technique that utilizes small amounts of radioactivity attached to very minimal amounts of tracer, in the case of this research, 18F-rhPSMA. Because some cancers take up \[18F\]-rhPSMA, cancer cells can be seen with PET. CT utilizes x-rays that traverse body from the outside. CT images provide an exact outline of organs and potential inflammatory tissue where it occurs in patient's body. Posluma (18F-rhPSMA) is an approved prostate-specific membrane antigen (PSMA) imaging agent for prostate cancer. The RefleXion Medical Radiotherapy System (RMRS) is designed to facilitate delivery of biology-guided radiotherapy (BgRT). The system uses PET emissions to guide radiotherapy delivery in real-time and has been studied for use with fludeoxyglucose (FDG) (which is an agent used in standard PET-CT scans that targets glucose). Information gathered from this study may help researchers to improve PET-CT imaging on the RefleXion system. This information will be used in the future to improve planning and delivery of radiation therapy that will target (in real time) the signal released from the \[18F\]-rhPSMA PET-CT tracer. Comparing the imaging from the standard of care \[18F\]-rh PSMA PET-CT with the imaging from RMRS may help improve the quality of the imaging captured on the RMRS for detection of imaging signals in patients with prostate cancer.