As I read Don's query it was free of value judgements. The tenor of replies on flownet suggest otherwise.
 I am an Australian Medical Imaging Technichian (we used to be Radiographers-your RT equivalent) with a post graduate qualification in vascular ultrasound. In our country people come into non-invasive vascular assessment from a variety of backgrounds. Medical imaging, nursing and medical science are most common professions from which vascular technologists are recruited.
In Australia technicians from an imaging background tend to examine carotids from the patient's side.
Those that are older and come from a nursing or science background are more likely to examine from the head of the patient. Good technicians use whichever position provides them with the most accurate results.
Either position, head end or side of couch, left or right hand, sitting, supine or even on occasions standing are all scanning techniques that are appropriate to the individual technician or the particular patient.
The aim is a quality scan performed in a fluent manner,
Doug O'Reilly