Lateral Gain Compensation: Adjusting the sector image brightness horizontally.
©Walter Rasmussen, R.D.C.S.
Lateral gain compensation consists of the same tabular array as TGC, except that it is arranged horizontally rather than vertically. The goal of LGC is to have control over the image brightness from side to side. LGC can make a great deal of difference in the diagnostic quality of an image.
LGC (top tabular array) and TGC (bottom)
Ultrasound machines that have LGC controls have a distinct advantage due to their ability to adjust the brightness of areas horizontally adjacent to each other, either from highly reflective areas or hypo-reflective (shadowed) areas.
When using an ultrasound machine which has LGC, it is important to set the tabs at the mid-point detent. This allows for brightening or darkening the image in the horizontal plane. In a busy echocardiography lab, it is not uncommon to find a machine that has the LGC optimized for a previous patient or that has the LGC tabs slid all the way to the bottom of their track. When LGC tabs are set at minimum, there is a reduction of the overall brightness of the image making increase the overall gain necessary and increased fogging of the image (noise) because of higher amplification.