IMO, these are questions you really need to be asking of your
family physician and not here.  Without knowing your past history,
all you will get is speculation and conjecture, which will
only make you worry even more.  Usenet is a fine place to get
information, but a lousy place to get a diagnosis.

Ga-67 is normally used in infection and inflammation imaging.
I don't believe it normally localizes in tumours.  Besides, by
the time any cancer is visible in a nuclear medicine scan,
especially lung cancer, it is easily visible in a radiograph
or CT scan.  If it was a lung cancer, it would have showed up in
the chest x-ray you had.  Trying to pinpoint a location on any
Ga-67 scan is also going to be difficult because there is usually
little or no uptake in areas that can be easily used as a landmark
or reference point.

Have the CT done, wait for your doctor to get the results and
let her come up with the next step.  Ask your doctor to see
if she can have the radiology department (or wherever you are
having the imaging done) do image fusion on the Ga-67
scan and the CT scan.  This will overlay the Ga-67 scan onto
the CT scan and help correlate any physiologic abnormality
seen on the Ga-67 scan with any anatomical abnormality that might
be seen on the CT.  The image fusion process requires some specialized
software though, which the imaging center may or may not have.

Eugene