[18F] Dihydro-testosterone Pet and MR Imaging In Patients With Localized Prostate Cancer

Inclusion Criteria: * Male aged 21 years or older and below 80 years of age. * Signed written informed consent and willingness to comply with protocol requirements. * Histologically confirmed diagnosis of prostate cancer. * Staging imaging workup including a baseline MRI of the prostate and pelvis performed at MSKCC. * Baseline imaging to rule out distant metastatic disease (99mTc bone scan, NaF PET, total body MRI, or CT chest/abdomen/pelvis) * Karnofsky performance status ≥ 70 * Clinical criteria required to be eligible: a. One of the following i.Pre-treatment PSA ≥10 ng/dL, OR ii. Clinical T-stage assessed by digital rectal exam of ≥T2a, OR ii . Radiographic ≥T3a on MRI, OR iv. Gleason score of ≥3+4=7 c. Visible intraprostatic tumor foci ≥1 cm in largest dimension on T2-weighted images based on initial pre-treatment MRI * Physician recommendation of ADT. Exclusion Criteria: * Metastatic disease on standard staging imaging (beyond regional lymph node involvement). o Absence of metastatic disease (beyond regional lymph node involvement) as defined by a negative bone scan, NaF PET, CT chest/abdomen/pelvis, or total body MRI. * Prior treatment of the prostate gland for malignant conditions (surgery, cryotherapy, radiotherapy, or photodynamic therapy). * Physician prescription of androgen receptor antagonist therapy (examples: bicalutamide, flutamide, or enzalutamide) during time of protocol scans. o Note: ADT consists of chemical castration (i.e. degarelix) to remove endogenous DHT. Androgen receptor antagonists will bind to the androgen receptor and inhibit FDHT from binding. * Patients receiving testosterone supplementation . * Any contraindication to baseline MRI based on departmental MR questionnaire, or inability to cooperate for an MRI scan. * History of allergic reactions attributed to compounds of similar chemical or biologic composition to FDHT. * Hepatic laboratory values: 1. Bilirubin \>1.5 x ULN (institutional upper limits of normal) 2. AST/ALT \>2.5 x ULN 3. Albumin \<2 g/dL * Creatinine \>2.5 mg/dL * Calcium \>11 mg/dL * Other serious illness(es) which might preclude completion of this study or interfere with determination of causality of any adverse effects experienced in this study.