(A) The basic principle of ultrasound imaging
Ultrasonic diagnosis commonly used sound source vibration frequency of 2.5 ~ 5.0MHz, when the ultrasound propagates in the human body, through different organs, tissues, lesions, each interface on both sides of the medium acoustic impedance is different, different degrees of reflection, scattering, as well as the attenuation of ultrasound information, are obtained by the receiver, after information processing on the screen as a waveform or image. According to the type of ultrasound imaging and display mode, it is divided into A-type ultrasound, B-type ultrasound (two-dimensional ultrasound), M-type ultrasound, D-type ultrasound.
(B) Main features of 2D sonogram
1. The imaging records a two-dimensional section of the examination site, often labeled with the examination site and sweeping direction.
2. The image consists of black, white and gray light dots, representing the strength of the tissue structure echo, the whiter the color indicates the stronger the echo (distinguishing between X-ray, CT high density and low density).
3. The image display range is limited, and larger organs and lesions cannot be displayed as a whole.
4. Acoustic contrast examination changes the tissue structure echo on the image.
(C) Normal performance of two-dimensional ultrasound images
1. Liver
The size and contour of the liver are the same as those described above. The echogenic signal of the liver parenchyma is lower than that of the diaphragm and approximately equal to that of the pancreas.
2. Gallbladder
In transverse and longitudinal views, it appears round, round-like, or oblong, with a long diameter of less than 9 cm, an anterior-posterior diameter of less than 3.5-4 cm, and a wall thickness of 2-3 mm.
3. Kidney
Round, ovoid, bean-shaped, smooth and clear, hyperechoic peritoneum, uniform and weakly echogenic renal parenchyma, hypoechoic renal cone, ureter often not shown due to intestinal gas interference.
(D) Liver lesion performance
In cirrhosis, ultrasound can directly detect liver atrophy, total liver volume reduction, deformation, surface unevenness, diffuse thickening and enhancement of echogenicity, uneven and dense small abnormal echogenicity, thin, tortuous and stiff hepatic veins, indirect manifestations include splenomegaly, peritoneal fluid, thickening of main trunk and main branches of portal vein.
(E) Gallbladder lesion manifestation
1. Size
Shrinking gallbladder and thickening of gallbladder wall are seen in chronic cholecystitis, while enlargement of gallbladder suggests cholecystitis and biliary obstruction.
2. Calcification
Stones in the gallbladder and bile ducts show strong echogenicity with posterior acoustic shadowing, and gallbladder stones can move with position changes.
3. Dilatation
The internal diameter of intrahepatic bile duct is greater than 2mm, and the internal diameter of common bile duct is greater than 6mm, suggesting dilatation.
4. Filling defect
Stones and tumors can cause filling defects in the cystic cavity. The edges of stone defects are smooth and neat, and tumors are irregular.
(F) Renal lesion performance
Ultrasound is highly sensitive to the examination of kidney stones, and can detect hyperechoic, point-like or mass-like in the renal calyces, renal pelvis or ureter, and the sound shadow is visible in the posterior part, and the ureter and pelvis above are dilated and watery when obstruction is detected.
