I've had this (I have mets in bones in various places) I think I can answer you questions.
Yes, you are correct , this is concept to pet scan - instead of a radioactive form of glucose that is taken up by metabolic active areas in normal tissue, this scan uses a radioactive that mimic's calcuim and is taken up by the bones. The machine that images is a large table with a large box that slowly moves from head to toe lookng for the radition given off. you will eliminate the isopot form your body over about 18 hours via your urine. There is no pain, in fact no senstation at all.
they will give hte shot in the morning, want to eat lunch and then a few hours later (to give the tracer time to enter the bones) the scan takes a little over an hour.
This should have no impact whatever with the other radiaiton treatment.
by the way, when the doctors say that the radiation will continue working - it's not really any radiation left over in your body. The external beam radiation leaves no residual radiation - as soon as hte machine turns off, the radiation is gone. what they really mean is that a large number of cells that weren't killed off immediatlly with the radiation are "walking dead". they have been damaged by the radiation such that can't reproduce, but they are still alive - however they are so damaged, that over the next few days or weeks they will die off. but you aren't radioactive and weren't ever radiactive.
there are some radiaiton treatments where actualy radioactive materials are put in your body body for treatments - like SIRT Spheres or Radioactive Seeds placed in body for rectal cancer. with these, the radioactivity source inplanted in your body does continue to give off radiaton 24 hours a day for several days (depending upon the half-life of the particular material). this type of treatment might interfer with the bone can or pet scan. but that is not what you had.
DX 2/07 mets liver/bone/brain/spleen
bone mets 5 times
GammaKnife brain lesion 1/08
SIRT Spheres rlobe 7/08 llobe 8/08
cyberknife brain 10/08
Brain surgery 1/09