The ultrasound is superior in certain aspects than any other diagnostc scan such as in nodal involvement than the PET, CT, MRI. I just did one last week for a cervical neck lymph node, after a PET/CT scan. Each of the diagnostc scans are sometimes used interchangeably or to show more detail depending on area, and what they're looking for. When I was diagnosed, a salivary stone was found in the duct in floor of my mouth also. I don't recall off hand, which scan showed it or if it was the ENT's palpable exam, combination. As mentioned, see an ENT who sees hundreds, if not thousands of patients with similar symptoms. Good luck.