If a cat scan shows no cancer,what are the chances of a pet scan finding it?

I am 73 excellent health

CAT scans don't show everything. ( my gma has cancer)
Her CAT scan only showed one tumor, but the pet scan found 7.
So, obviously pet scans show alot more than cat scans do.
also the doctor said that pet scans show deeper things than regualr cat scans even mri's.

A PET scan is extremely good at detecting cancer, particularly tumours that are too small to be easily detected on a CAT scan. A CAT (or CT) scan simply contains images of the inside of your body.

A PET scan can actually tell which cells in your body are growing faster than normal - this abnormal growth is a consistent feature of cancer cells. To do this, a special type of glucose is administered to the patient, then the machine can measure how much glucose is being used by different cells in the body (glucose use is related to how much/how fast the cell is growing).

Different colors or degrees of brightness on a PET image represent different levels of tissue or organ function. For example, because healthy tissue uses glucose for energy, it accumulates some of the tagged glucose, which will show up on the PET images. However, cancerous tissue, which uses more glucose than normal tissue, will accumulate more of the substance and appear brighter than normal tissue on the PET images.