What is Ultrasound Gain–correct, over, under (with photos)

Gain refers to the control sonologists use to adjust the brightness with which returning sound waves are displayed by the ultrasound machine. When an echo returns from body tissue, it does so within an amplitude range.
The ultrasound device translates that amplitude range to a brightness, which it displays on the monitor. The overall gain allows the sonologist to adjust the brightness of all returning echoes. Decreasing the gain makes the overall image less bright, while increasing the gain makes the image more bright .

These figure shows the types of gain:

(A) (Correct) This image is correctly gained

(B) (Over) The image has too much gain applied to the image. Compared with image A, echoes are found where there should be none.

(C) (Under) The image is undergained. The image is too dark, potentially making it difficult for accurate diagnosis.