How does a veterinarian decide which dog diagnostic imaging tool to use?

Often, it depends on what we're looking for and what's going on with the pet. For instance, if it is limping on a leg, we would choose an x-ray over an ultrasound. If it has an upset stomach or is vomiting, we may want an ultrasound, which will show a little more detail in the abdomen than the big picture of an x-ray would. So it depends on what you need to find out, which kind of ties into the next question.