There are disclosed embodiments of devices and methods for three-dimensional internal ultrasound usage, for example of the inside of a body part such as a blood vessel. In particular embodiments, a catheter has a tip chamber, within which is an ultrasound transducer mounted on a pivot mechanism, a motor for turning the transducer, and an implement for pivoting the transducer. Examples of such an implement are a second motor operating a shaft or a filament, and the pivot mechanism may be biased to return to a base position when the implement is not pivoting the transducer. In other embodiments, a mirror reflecting ultrasound signals from the transducer may be rotated and/or pivoted, using similar mechanisms.