Depending upon the scan, Debbie, you need to hold your breath.  Here in Brazil we have only doctors who do the sonograms and they tend to like to have the picture with as little motion as possible so they ask for the patient to hold their breath depending upon the area being examined.  With the MRIs and CTs, most of the scans I've had to do have to do with my aorta and I believe that the reason why they ask to take a deep breath and hold it is because it stops the breathing action, thus stopping the movement in the chest.  When I had to do an abdominal US looking at my kidneys and my abdominal aorta, I was again asked to hold my breath by the doctor.  My fainting kept causing her trouble because I couldn't keep a full breath!  I don't know why this helps for that exam, the next time I do it I'll ask the doctor why.



Lisa