The Transducer Frame of Reference is a Right-hand Coordinate System consisting X X , Y X , and Z X axes originating at a reference “Transducer Origin” defined as the geometric center of the transducer face.
The orientation of the Transducer Frame of Reference relative to the Volume Origin is such that the Y X axis is normal to the transducer face and the “direction reference” ( i.e. transducer tactile marker or zero reference) is aligned with the positive X X axis. A transformation is specified between the Volume Frame of Reference and the Transducer Frame of Reference to define the position of the transducer relative to the volume. This transformation is specified by the Volume to Transducer Mapping Matrix (0020,9309).
The Transducer Frame of Reference recognizes two types of scan geometry: 1) a scan geometry with a real apex such as would be the case for a pyramid, toroid or rotational volume acquisition, or 2) a scan geometry for which there is no specific apex. The point (x A , y A , z A ) is the apex (or phase center) of the acquisition volume geometry in the Volume Frame of Reference. The apex (x A , y A , z A ) may be located in the volume or exterior to it.
Figure C.8.24.2-2: Transducer Frame of Reference