"Do they have a way of using the one needle to sample at various depths / locations within the prostate?"
Don't know about various depths but, yes, the needle is normally presented transrectally to the hardest or lumpy part of the prostate. This area of the prostate is determined by a previous DRE (e.g. right side) and is the one most likely to render a positive result if cancer is present. The administering Physician determines the course of the probe by referring to an ultrasound screen during the process.
Mitch in SC