Just for clarity in the comments: there are needle biopsies, and there are needle hydrogel placement. The real estate is usually quite different. I believe most prostate biopsies are transrectal. The biopsies are then used to make the diagnosis and inform potential treatments.
Once the decision is to treat by radiation, some people precede that radiation by a couple of weeks with hydrogel insertion to minimize radiation damage to the colon, etc. Hydrogel placement is with an injection by an ultrasound guided needle in the area between the scrotum and the anus. This area is also known as the perineum. Numbing of the area immediately before the insertion was done by three injections.
It may be possible to do perineal biopsies of the prostate, it's just that I'm not aware of any.