Thanks for that added information.

It's my own speculation, but here's something I wrote previously: "How do you do stick a needle there without damaging prostate, rectum, etc.? ". In other words, even when ultrasound guided, positioning a long sharp needle in that small space has to have some risk associated with it, like nicking something you want to avoid.

I would note that hydrogel itself worked well for me. I would recommend it. It's the placement of it that's tricky. So is would suggest that the "prostatectomy rule" applies: don't go with a surgeon who only does one radical prostatectomy a month. Same with hydrogel placement.