ECG or other physiological waveforms associated with an Enhanced US Volume (item 1d in the use case hierarchy) are to be conveyed via a one or more companion instances of Waveform IODs linked bidirectionally to the Enhanced US Volume instance. Physiological waveforms associated with Ultrasound image acquisition may be represented using any of the Waveform IODs, and are linked with the Enhanced US Volume instance and to other simultaneous waveforms through the Referenced Instance Sequence in the image instance and each waveform instance. The Synchronization module and the Acquisition DateTime Attribute (0018,1800) are used to synchronize the waveforms with the image and each other.