Dixie,
Is it your ALT level that your dr is concerned (about)? My ALT stays mildly elevated and the guideline is to stay less than 3 x the top end of the normal level (my lab uses 36 as the top range). Do you take Tylenol (acetaminophen) on a regular basis? It is a very common cause of elevated liver panel as are certain anti-biotics.
As to your ultrasound, it would show any visible damage to your liver, however, the most accurate test is the biopsy. I think the biopsy is used as a last resort and I would imagine your levels would have to be pretty high on a prolonged basis before biopsy.
As I stated, my ALT levels have remained mildly elevated for five years or so. My former dr ordered the ultrasound of my liver last year. My liver appeared normal however gallstones were discovered

. Don't be surprised if you too have gallstones found due to prolonged statin use

.
Check webmd for treatment of elevated liver enzymes if you wish.