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Understanding how the two‐dimensional image is formed from scanning through a three‐dimensional object is crucial not only to image interpretation but also communication of that information. The first piece of information is the imaging or scanning plane. The imaging plane may refer to the whole body, a part of the body (such as a leg or the head), or to a specific structure within the body, the left kidney, for instance (Figures 4.1 and 4.2).

The first of these, transverse, is any plane along the short axis of the structure being imaged.

Figure 4.1. Longitudinal and transverse orientation shown on anatomical planes.

Source: Illustration courtesy of Randi Taggart, Richmond, VA.

Figure 4.2. Examples of image planes for the kidney. In (A) the kidney is shown with longitudinal (sagittal) and transverse planes. In (B) the longitudinal (sagittal) plane is contrasted to (C) in transverse orientation on actual B‐mode ultrasound images. For most nonradiologist sonographers, the kidney is more readily recognized in the longitudinal (sagittal) orientation.

Source: Courtesy of Robert M. Fulton, DVM, Richmond, VA.

The second, longitudinal, is any plane that is perpendicular to the transverse plane or the long axis of the structure. Technically, the longitudinal plane has several specific types.

 Median – this plane splits a symmetrical structure into equal left and right halves along the long axis.

 Sagittal or paramedian – this plane is any plane that is parallel to the median plane. While technically incorrect, many will use sagittal interchangeably with longitudinal.

 Dorsal – this plane splits a structure into dorsal and ventral segments and is analogous to the coronal plane in biped scanning terminology.

Commonly, veterinary sonographers tend to talk about only two planes, transverse and longitudinal, and this suffices for most communication and image understanding (see Figures 4.1 and 4.2).