The large knob controls anteflexion/retroflexion, while the smaller knob controls left/right tilt. The two buttons increase or decrease the beam angle or "omniplane". Finally the lock knob locks the probe in place and in general is never used.
Gain is the degree of amplification of the returning ultrasound signal. The gain button alters the "brightness" of the whole image by adjusting the amplification of all returning echo signals. Minimal gain should be employed to provide an optimal image with good quality without dropout or "blooming" of signals. As a rule of thumb fluid and blood should appear black, myocardium a medium gray and pericardium and calcification a bright white color.
Adjusting "depth" alters the vertical field of vision (FOV) of the image and is used to get the region of interest (ROI) into view. Increasing the depth increases the time taken for the signal to return back to the transducer thereby decreasing the frame rate and vice versa. The highest frame rate possible should be sought as a lower frame rate lends a "swimmy" quality to the moving image. In order to maintain a higher frame rate the smallest FOV that allows the ROI should be employed. Zoom is different than depth as it is used to magnify the resolution of the selected ROI by decreasing sector size (fan shaped image) without sacrificing frame rate. In this ME 4 chamber view the LV (on the right side) is foreshortened and to see all of the LV the depth must be increased.
As the ultrasound beam passes deeper through tissue, there is a steady loss of transmitted intensity caused by attenuation of ultrasound. TGC toggles amplify the weak returning signal proportionate to the time delay and increase gain for that particular depth. Near field gain (closest to the transducer) is usually set low and far field gain (furthest from the transducer) is set high to compensate for the energy loss. Therefore the primary function of TGC is to ensure signals of similar magnitude at different deoths.
Too high or too low a Nyquist limit may affect interpretation of flow. Here Nyquist limit is adjusted to better appreciate flow across a smaller orifice as seen with this ASD
The buttons for calipers and the trackball measure the distance between two points. This can be used for measuring chamber dimensions, diameter of the aorta, valve annulus, left ventricular outflow tract, vegetation size and other essential measurements. Here the calipers are used to assess size of the left atrium in the ME two chamber view in a patient with mitral stenosis (normal 4 cm or less).
The trace tool is used to trace the size of an object of interest and quantify the delineated area. This can be used for measuring valve areas and other objects, seen here to assess aortic valve area in 2D in the midesophageal short axis view.
Dropout artifacts in transesophageal echocardiography are common imaging errors appearing as an absence of echoes (black, missing tissue) on 2D or 3D images distal to the strong reflector. They are caused by poor signal strength, excessive attenuation or the ultrasound beam hitting thin structures (like the interatrial septum or prosthetic valve leaflets) at an oblique angle. Seen here is dropout from prosthetic aortic valve leaflets in a midesophageal long axis view.
A mirror image artifact in ultrasound occurs when sound waves reflect off a strong smooth interface (like the diaphragm or pleura) creating a false, mirrored duplicate of a structure deeper in the image. The machine mistakenly displays the object on the other side f the reflector, as seen here with the left atrium visualized in the ascending aorta in the midesophageal short axis view.
Reverberation artifacts occur when ultrasound waves bounce between two reflective surfaces (e.g., metallic valves, pericardium, pleura) causing the probe to record multiple false equidistantly spaced echo lines deeper in the image. These common artifacts often mimic structures like the aorta or produce "comet tails".
Physics and Knobology
Air in the Lungs Probe in the Goose
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