,,,ok, David, here I am...
mj, in the vast majority of cases this is done in 2 separate procedures. The volume study is done several weeks before the seeding. The volume study allows the radiation oncologist to accurately judge the volume of the prostate and map the prostate for seed placement. A very few doctors will do this just before seeding as they believe that they want the most current info possible on the size of the prostate. My doc believed that that was not a good tradeoff, i.e. he felt taking the time to accurately determine seed placement was the best approach, hence my volume study was a month before my seeding.
Incidentally, the volume study for me was the worst part of the whole deal, as you can read if you choose to click the link on my journey below. I recommend some mild relaxant pre-volume study if your doc's camera is as big as my doc's was.