• Histopathological proven metastatic castration resistant prostate cancer. Castrationresistant disease is defined as a serum testosterone level of 50 nanogram per deciliter or lower (≤1.7 nanomol per liter) after bilateral orchiectomy or during maintenance treatment consisting of androgen-ablation therapy with a luteinizing hormone-releasing hormone agonist.

• Evidence of progressive disease, defined as 1 or more Prostate Cancer Work Grouping 3 (PCWG3) criteria: - PSA level ≥ 1 ng/mL that has increased on at least 2 successive occasions at least 1 week apart

• Progression as defined by RECIST 1.1 with PCGW3 modifications

• Progression after at least one line of chemotherapy and/or one line of nonsteroidal antiandrogen (NSAA).

• No active anti-tumor therapy, except for androgen deprivation therapy in combination with at least one androgen receptor-targeted agent

• Willing and able to undergo 2 cycles of 225Ac-PSMA I\&T therapy and 3 PET-MRI scans in 16 weeks and comply with protocol

• Signed and dated written informed consent by the patient (or legal representative) prior to any study-specific procedures.

• Age ≥ 18 years.

• Eastern Cooperative Oncology Group (ECOG) performance-status score 0-2.

• Use of highly effective methods of contraception (female partners of male participants)

• During the trial and 6 months after completion of the study or willing to practice sexual abstinence.