Abstract: An ultrasound catheter probe assembly capable of scanning a three-dimensional volume is provided. The ultrasound catheter probe assembly contains a plurality of ultrasonic transducers disposed along a central axis of the ultrasound catheter probe assembly. The plurality of ultrasonic transducers is disposed on a mechanism operable to reciprocally pivot the plurality of ultrasonic transducers enabling the plurality of ultrasonic transducers to scan a three-dimensional volume. A helically disposed electrical interconnection member may be disposed about a pivot axis of the plurality of ultrasonic transducers and may electrically interconnect the plurality of ultrasonic transducers to an ultrasound imaging system. The ultrasound transducer catheter probe assembly may be fluid-filled and contain bubble position control and fluid expansion compensation features.