The SPECTacular study will enroll patients who are already undergoing a FDA approved PSMA-targeted Radioligand treatment cycle. During each treatment cycle, patients will receive 5 additional SPECT/CT scans to investigate the limits of agreement between dosimetry (absorbed radiation dose) approximation methods and dosimetry using the triexponential fitting method.

All patients with PSMA-positive tumor and/or Metastases of Prostate Cancer (PSMA-TMPC) who would be undergoing a PSMA-targeted Radioligand Therapy (PRLT) based on independent eligibility criteria for the same, will receive 6 serial SPECT-CT scans for every treatment cycle as a part of our study. The purpose of this investigation is to assess the limits of agreement of commonly employed dosimetry methods used to determine or approximate absorbed doses for organs and tumors compared to a dosimetry method using a triexponential fit requiring 6 post-injection SPECT-CT scans for all treatment cycles.

Inclusion Criteria:

1. Provision of signed and dated informed consent form
2. Stated willingness to comply with all study procedures and availability for the duration of the study
3. Male, 18 years old or older
4. Histologically or pathologically confirmed prostate adenocarcinoma without predominant small cell component.
5. Patient is receiving PSMA-targeted Radioligand Therapy (PRLT) for treatment of PSMA-positive tumor and/or metastases of prostate cancer. Therapy may be FDA approved or investigational in nature under an approved clinical trial.
6. Ability to lay flat on scanner for duration of SPECT-CT imaging studies (1-2 hours)

Exclusion Criteria:

1. Assessment by the Investigator as unable or unwilling to comply with the requirements of the protocol.
2. Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≥ 2
3. All criteria which may preclude a PSMA-radioligand therapy using Lu-177 PSMA-617 or Lu-177 PSMA I&T to be performed as per standardized guidelines and protocols laid down for these treatments and per decision by the treating physician.