dr run some tests in case of lawsuits- they generally diagnose according to symptoms and likelyhood of a condition or disease
in the event of a rare condition they do not usually do not test for because its too expensive.
the rare case can be actionable in a court case and guess what the patient (plaintiff) will have an expensive pet scan to back up his claim and win big money
on one hand expensive tests drive up costs and lawsuits do also.
every time you hear of a plaintiff winning big in court- your paying for it
some people are very litigious and do not accept there own responsibility
hospitals often are right and settle because they do not want bad publicity.