“Fake” images in ultrasound diagnosis

  I believe many people are aware of ultrasound examinations, and even a large number of people have undergone ultrasound examinations. Ultrasound examination can dynamically display the movement of organs and blood flow conditions, and obtain real-time functional and morphological information of various parts of the body, thereby discovering abnormal conditions of the body. However, in the ultrasound examination, the gas in the bones, lungs, and gastrointestinal tract may totally reflect the incident light generated by the ultrasound, resulting in “false” images and affecting the examination effect. This is clinically called an ultrasound artifact .
  Ultrasonic artifacts refer to the position of any echo signal displayed by the ultrasonic diagnostic equipment, which does not match the actual position of the echo interface in the subject, or the displayed signal amplitude and grayscale changes are not consistent with the displayed echo interface characteristics Change related. Ultrasonic sound beams with certain parameters such as wavelength, amplitude, phase, and sound intensity are incident at a certain direction and angle into non-uniform and anisotropic human tissues and complex interfaces with different density, sound speed, acoustic characteristic impedance and other parameters. When propagating in a granular medium, complex physical phenomena such as sound reflection, refraction, diffraction, diffraction, transmission, scattering, as well as attenuation, absorption, frequency shift, wave mode conversion, and nonlinear effects will occur. This is the result of ultrasound imaging. The foundation is also the cause of acoustic artifacts. Facts show that the existence of artifacts is universal and absolute. These fake images may affect our observation of the disease, and of course, sometimes they can help us diagnose.
  Common clinical ultrasound artifacts include the following types-
  reverberation artifacts: due to the ultrasound beam being irradiated perpendicularly to the flat large interface such as the chest wall and abdominal wall, part of the ultrasound returns to the probe surface and is reflected again by the smooth surface of the probe Enter the human body. In this way, the ultrasonic waves reflect back and forth between the probe surface and the large interface, forming a reverberation form. Strong reverberation is more common on the surface of the lungs and intestines with more gas; weak reverberation can cause false echoes on the surface of the bladder, liver, kidney, and gallbladder, which can easily be misdiagnosed as thickening of the organ wall or tumor. In order to avoid this situation, the doctor will appropriately move the probe sideways during operation to prevent the sound beam from entering the interface perpendicularly; and also pressurize or decompress the probe to reduce or increase the distance of multiple reflections.
  Multiple internal reverberation and ringing effects: Internal reverberation refers to the ultrasound beam reflecting back and forth in foreign bodies in tissues and organs until attenuation, forming a comet tail sign. The ringing effect refers to that the ultrasonic beam is strongly reflected back and forth in a very small amount of liquid wrapped by several microbubbles, resulting in a long strip of image interference. The use of internal reverberation can indicate aerobacterial infection, such as aerobacter infectious liver abscess, subdiaphragmatic abscess, and intrauterine infection. Ringing artifacts are sometimes helpful for diagnosis, such as identifying intrahepatic bile duct gas, gastrointestinal gas, gallbladder adenomyosis, etc.
  Partial volume effect: the thickness of the slice of the ultrasound tomogram is wider, which makes the echo of the lesion overlap with the echo of the surrounding tissues, and is more common in smaller hypoechoic or anechoic structures, such as blood vessels. In order to avoid this effect, the doctor will constantly adjust the cut surface during the operation to make the lesion fall into the ultrasound beam as much as possible; for smaller lesions, a probe with a thinner ultrasound beam will be used; move the probe back and forth according to the image Changes can also determine whether the structure is in the same plane.
  Sidelobe artifact: It is caused by sidelobe reflections other than the main sound beam. The “veil sign” and “dog ear sign” appearing on both sides of strong echoes such as stones and intestinal gas are all side lobe artifacts. Changing the probe position and scanning direction, adjusting the focus position, using dynamic apodization technology and variable aperture technology, etc., can eliminate this artifact.
  Acoustic shadow: refers to the strip-shaped anechoic zone that appears behind the sound beam when the sound beam encounters a strong reflection or a material with a high degree of sound attenuation. On the one hand, the acoustic shadow is helpful for clinical ultrasound diagnosis, such as finding stones and identifying the nature of the tumor; on the other hand, it also has an adverse effect on the diagnosis, such as a wide acoustic shadow obstructing the rear tissue and causing missed diagnosis, or a large number of gallbladder stones The sound shadow covered the gallbladder tumor.
  In addition, there are more than ten kinds of common ultrasound artifacts in clinical practice, such as mirror artifacts and prism artifacts. Patients should not worry about it when undergoing the examination, because the causes of these artifacts have been clearly understood clinically, which can effectively avoid misdiagnosis or missed diagnosis caused by artifacts, and can also use the characteristics of some artifacts to help doctors diagnosis.

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