Definition of Variables
TEE protocol duration was defined by the timestamp of the first and last
image acquisition for each protocol (manual versus automated). The echo
machine console keyboard was videotaped during each TEE exam for the
duration of each protocol performed. The number of keystrokes performed
by the sonographer during each protocol (manual or automated protocols)
was counted by a review of video from each TEE. The number of keystrokes
obtained was further subdivided into seven categories: image
acquisition, angle correction, gain control, 2D control, 4D control, XYZ
control, or miscellaneous. Miscellaneous keystrokes amount to the number
of non-specific keystrokes performed by the sonographer during imaging
in contrast to pre-specified task-specific keystrokes: image acquisition
(when the sonographer presses a specific knob to capture an image),
angle correction (when the sonographer presses or rotates a specific
knob to view the image from a desired angle), and the various techniques
of gain optimization. The number of keystrokes for gain control refers
to an instance when the sonographer adjusts the time gain compensation
(TGC) keys on the console until a desired overall gain is achieved.
Likewise, the 2D control stands for 2D imaging gain adjustment whereas
the 4D control adjusts the gain for the volume and the multiplane
reference planes. The XYZ control is the combined number of keystrokes
performed for adjusting and navigating the imaging volumes around the
individual X, Y, and Z axes.