An MRI scan is not typically used to diagnose prostate cancer, according to Mayo Clinic. The condition is often detected through a biopsy of the gland.
A prostate biopsy is usually ordered after a prostate blood level test is performed and the results are abnormal or if the prostate exam indicates something is amiss. An MRI can be used to determine if the cancer has spread to other parts of the body or to determine whether the cancer has grown, as stated by the American Cancer Society. Other tests used includes ultrasounds of the prostate, bone scans, blood work and PET scans.