The gain is a linear factor that is used in a device as a multiplier after calibration. The gain is the ratio of input to output in an amplifier. The sensitivity of a probe is adjusted by changing the gain.

See also Compress, and Reject.

Sonography of the gallbladder is a reliable technique for diagnosing e.g., gallstones, cholecystitis, tumors, polyps, or ductal obstruction. Patient should be examined with empty stomach and on a low fat diet the night before. Barium studies, endoscopy, ERCP, colonoscopy, and abdominal CT should be performed after this examination.
Gallbladder ultrasound is best performed with a 5 MHz curved array or a linear array transducer in cases of a very superficial gallbladder. In obese patients or in patients with difficult sonographic access, a 3.5 MHz sector or curved linear transducer is advantageous.
Gallbladder and biliary tree are usually imaged in supine and posterior oblique (LPO) positions. Sometimes very small gallstones are better visible in upright and prone position.

GE Healthcare is the result of the merger between GE Medical and Amersham Health in Nov. 2004, after GE acquired Amersham Health for 9.5 billion in Oct. 2003. Jeffrey R. Immelt, Chairman of the Board and Chief Executive of General Electric, said, 'Amersham's diagnostic pharmaceutical and life sciences business will add new, high growth platforms to GE Medical's diagnostic imaging, services and health care information technology businesses'. GE Healthcare, a UK company, is a unit of General Electric (NYSE: GE). GE Healthcare is a global leader in medical imaging, diagnostic imaging agents, interventional procedures, health care services, and information technology. For more than 100 years, health care providers have relied on GE Medical Systems, now GE Healthcare, for high quality medical technology and productivity solutions. GE Healthcare, headquartered now at the formerly seat of Amersham Healthcare in Great Britain, operates facilities around the world. Global Operations include organizations on the Americas, Europe, and Asia, including India, Japan, Korea China, Thailand and Vietnam

Ultrasound Contrast Agents:

Ultrasound Contrast Agents:

The dimension of the ultrasound beam and the transducer array are the origin of grating-lobe artifacts (also called side lobe artifact). Grating lobes as side lobes are off-axis secondary ultrasound beams projecting at predictable angles to the main lobe. Side lobes are too small to produce important artifacts.

See also Apodization, and Subdicing.

Gray scale [also grayscale, grey scale = brit.] produces basically black and white images with series of shades of gray. Solid areas appear white and fluid areas appear black, varying from black at the weakest intensity to white at the strongest. Gray scale resolves artifacts as small as 1 mm. The display is made by transmitting bursts of energy and analyzing the returning signal. Gray scale pictures are limited to the gray scale tones; color pictures display more information because the color is added to the gray scale.
Most ultrasound contrast agents also improve gray scale visualization of the flowing blood to such a degree that the tissue echogenicity increases. Gray scale enhancement of flow in an organ promises to improve lesion detection, along with the ability to differentiate between normal and abnormal areas, using many of the criteria already routinely used in CT and MRI.

See also Compress, Densitometry, Triplex Exam and QB-Mode.