Parallel to the long axis of the body and separates the body from left to right.
Perpendicular to the long axis of the body and separates body from top (superior) to bottom (inferior).
Parallel to the long axis of the body and separates the body from front (anterior) to back (posterior).
Oblique imaging planes refer any plane that uses a combination of those planes.
Short Axis and Long Axis Orientation:
Cylindrical and non-circular structures can additionally be described using the terms Short vs Long axis.
Long Axis: plane parallel to the maximal length of a structure.
Short Axis: plane perpendicular to the long-axis of a structure.
These views can be obtained by rotating 90 degrees relative to each other. These terms are helpful in structures such as vascular and cardiac applications. Also, this is useful when deciding to perform a procedure in a short versus long-axis approach.
Below we are rotating between a short-axis and long-axis of the brachial artery using a clockwise rotation of 90 degrees.
Here is an example of the long axis and short axis of the heart. The parasternal short axis is obtained by rotating 90 degrees clockwise from the parasternal long axis view.