JerryB-UK,
Glad someone who also has had HIFU has joined me! And you sound like you are glad you chose HIFU.
I believe that the doctor can choose what tissue to ablate, and so some of the gland can be treated, leaving other areas, so the capsule can be left unharmed, but I believe the entire capsule can be ablated, and turn to ash and leave the body, I found this that I believe backs up my thinking in the wikipedia page that I posted above:
"This technology can achieve precise ablation of diseased tissue, therefore it is called HIFU surgery. Because it destroys the diseased tissue non-invasively, it is also known as "Non-invasive HIFU surgery". Anesthesia is not required, but should be recommended." and again: "HIFU may also be used to ablate the entire prostate gland using a transrectal probe."
Now I am thinking that the PSA score may tell us how much was ablated. Mine is 0.2, so maybe a bit near the nerves was left. I see you had your treatment not quite 3 months ago, please do post your score.
Interesting your thoughts on BPH, no one diagnosed me with it, but it did take a while to start the flow, and a while to finish before HIFU, however I had no issues after HIFU except ED for several months, not total ED, just not able without Cialis.