PET/CT vs Bone Scan

There ought to be someone out there in the field who can give a more concise answer.  But I'll tell you what I know.

The different tests are explained on this site under Symptoms and Diagnosis:

http://www.breastcancer.org/symptoms/testing/types/

ACS also talks about them but I think the explanations are so-so.

http://www.cancer.org/docroot/CRI/content/CRI_2_4_3X_How_is_breast_cancer_staged_5.asp?rnav=cri

Initially I had both a CT and a bone scan.  

The reason I got a CT was two-fold.  My symptoms indicated a quickly growing cancer and potential vascular involvement through the skin.  So the onc wanted to see if the cancer had spread to other organs.  The second reason was it was a requirement for the trial I went on - to confirm that I was locally advanced and didn't have mets.

The bone scan was standard for my onc.  It clearly outlines the bones and any mets (or arthritis!) "lights up" and is easy to see.

In my trial I went on to have multiple PETs.  Different machine and different contrast material.  It was checking for glucose uptake - cancer cells are very active so they have high glucose activity.  This was used to monitor the effectiveness of the chemo trial.  I'm sure I wouldn't have had this test had I gone through standard AC-T.