chāo shēng chéng xiàng
2 English ReferenceUSG
3 OverviewUltrasound is a sound wave that exceeds what can be heard by the normal human ear, with a frequency of 20,000 hertz (Hertz, Hz) or more. Ultrasonography is an examination method that utilizes the physical properties of ultrasound and the differences in the acoustic properties of human organs and tissues to display and record in the form of waveforms, curves, or images for the diagnosis of disease.The use of ultrasound to examine the human body was explored in the early 1940s, and the use of ultrasound to make organs form ultrasound level images was studied and used in the 1950s, and real-time ultrasound technology was developed in the early 1970s, which allows observation of the heart and fetal activity. The early 1970s saw the development of real-time ultrasound technology to visualize the heart and fetal activity. Ultrasound diagnostic equipment is not as expensive as CT or MRI equipment, can obtain any cross-section of the organ image, but also to observe the activities of moving organs, imaging fast, timely diagnosis, no pain and danger, belong to the non-invasive examination, therefore, the application of the clinic has been popularized, is an important part of medical imaging. The disadvantage is that the contrast resolution and spatial resolution of images are not as high as CT and MRI. This article only introduces gray scale ultrasonic tomography.
Ultrasound imaging is the use of ultrasound beam scanning the human body, through the reception of the reflected signal, processing, in order to obtain the image of the body organs. Commonly used ultrasound instruments have a variety of: A type (amplitude modulation type) is to the amplitude of the wave expressed in the strength of the reflected signal, the display is a kind of "echogram"; M type (point of light scanning type) is to the vertical direction on behalf of the shallow to the deep spatial location, the horizontal direction on behalf of the time, the display of the point of light in the movement of the curve of the different time. The above two types are one-dimensional displays with a limited range of applications, while the B-type (brightness modulation type) is an ultrasound sectional imager, or "B-ultrasound" for short. It is a point of light with different brightness to indicate the strength of the received signal, in the probe moves along the horizontal position, the display of the point of light along the horizontal direction of the synchronized movement of the point of light trajectory into the ultrasound beam scanned cross-section, for two-dimensional imaging. Because the B-type ultrasound image is clear, intuitive, strong sense of hierarchy, it is widely used in clinical practice. As for the D-type is made according to the principle of ultrasound Doppler. C-type is similar to the scanning method of television, showing a perpendicular to the beam of the cross-section of the acoustic image. In recent years, ultrasound imaging technology continues to develop, such as grayscale display and color display, real-time imaging, ultrasound holography, penetrating ultrasound imaging, ultrasound meter and machine tomography spam, three-dimensional imaging, intracorporeal ultrasound imaging.
Ultrasound imaging methods are commonly used to determine the location of the organs, size, morphology, determine the scope of the lesion and physical properties, to provide some of the anatomical map of the glandular tissue, to identify normal and abnormal fetal, in ophthalmology, obstetrics and gynecology, and cardiovascular system, the digestive system, the urological system, is very wide range of applications. At present, ultrasound imaging technology is also applied in the field of traditional Chinese medicine, such as the use of Doppler flowmeter to detect the blood flow of various pulse images. Thus, to provide indicators for the objectivity and quantification of the pulse; ultrasound imaging can also be used to carry out the objectivity of the Chinese medicine certificate research.
4 USG imaging basic principles and equipment 4.1 Physical properties of ultrasound
Ultrasound is a mechanical wave, generated by the mechanical vibration of the object. It has physical quantities such as wavelength, frequency and propagation speed. Used for medical ultrasound frequency of 2.5 ~ 10MHz, commonly used is 2.5 ~ 5MHz. ultrasound needs to be propagated in the medium, its speed varies depending on the medium, the fastest in the solid, followed by the liquid, the slowest gas. In the human soft tissue is about 150m/s. The medium has a certain acoustic impedance, acoustic impedance is equal to the density of the medium and the product of ultrasound velocity.
Ultrasound propagates in a straight line in the medium, with good directivity. This is the basis of ultrasound can be used to detect human organs. When the ultrasound transmitted through the interface of two different acoustic impedance of neighboring media when the difference in acoustic impedance is greater than 0.1%, and the interface is significantly larger than the wavelength, that is, the large interface, the reflection occurs, a part of the acoustic energy in the interface behind the neighboring media in the refraction of ultrasound continues to propagate, encountered another interface and then reflect until the exhaustion of acoustic energy. The reflected ultrasound is an echo. The larger the difference in acoustic impedance, the stronger the reflection, and if the interface is smaller than the wavelength, i.e., a small interface, scattering occurs. Ultrasound propagating in a medium also undergoes attenuation, i.e., the amplitude and intensity decrease. The attenuation is proportional to the attenuation coefficient of the medium, inversely proportional to the distance squared, and is also related to the absorption and scattering of the medium. Ultrasound also has Doppler should (Doppler effect), active interface to the source of relative motion can change the reflected echo rate. This effect allows ultrasound to detect cardiac and fetal activity and blood flow.
4.2 Fundamentals of Ultrasound ImagingThe human body is a complex medium for ultrasound, and various organs and tissues, including pathological tissues, have their own specific acoustic impedance (Table 141) and attenuation characteristics. Thus, there are differences in acoustic impedance and differences in attenuation. When ultrasound is injected into the body, from the surface to the depth, it will pass through organs and tissues with different acoustic impedance and different attenuation characteristics, thus producing different reflections and attenuation. This difference in reflection and attenuation is the basis of the ultrasound image. The received echoes, according to the echo strength, with different light and dark points sequentially displayed on the screen, can show a cross-section of the human body ultrasound image, which is called the sonogram (sonogram or echogram).
Table 141 The speed of sound and acoustic impedance of different media in the human body
medium Density (g/cm3) ultrasound longitudinal velocity (m / s) Characteristic impedance (105R *) test frequency (MHz) Air 0.001293 332 0.000429 2.9 Water 0.9934 1523 1.513 2.9 blood 1.055 1570 1.656 1.0 Soft tissue 1.016 1500 1.524 1.0 Muscle 1.074 1568 1.684 1.0 Bone 1.658 3860 5.571 1.0 Fat 0.955 1476 1.410 1.0 Liver 1.050 1570 1.648 1.0*R (Rayls) 1kg/m2.s
Surface of the human body organ The surface of human organs is surrounded by a membrane, and the difference in acoustic impedance between the membrane and the tissue underneath is so large that a good interface reflection is formed, and complete and clear peripheral echoes appear on the sonogram, thus revealing the contours of the organs. According to the peripheral echo can determine the shape and size of the organ.
The ultrasound passes through the interior of different normal organs or lesions, and the internal echoes can be anechoic, hypoechoic, or varying degrees of strong echoes.
No echo: the area where the ultrasound passes through is not reflected, and becomes a dark area without echo (black shadow), which may be caused by the following: ① liquid dark area: homogeneous fluid, acoustic impedance, no difference or very small difference, does not constitute a reflective interface, forming a liquid dark area, such as blood, bile, urine, and amniotic fluid, and so on. In this way, blood vessels, gallbladder, bladder and amniotic cavity, etc. are liquid dark areas. Pathologic conditions such as pleural effusion, pericardial effusion, ascites, pus, pyelonephrosis, and fluid-containing cystic masses and encapsulated cysts also present as fluid dark zones, which are well permeable. Echo enhancement and bright bands of light (white shadows) are common below the dark areas. ② Attenuated dark area: tumor, such as giant cancer, due to the absorption of ultrasound by the tumor, resulting in obvious attenuation and no echo, appearing as attenuated dark area. ③ Parenchymal dark area: homogeneous parenchyma with small difference in acoustic impedance may appear as a dark area without echo. Renal parenchyma, spleen and other normal tissues and renal cancer and hyaline degeneration and other lesions can be manifested as parenchymal dark zone.
Hypoechoic: Parenchymal organs such as the liver, internal echoes are evenly distributed point-like echoes, in the event of acute inflammation, exudation, its acoustic impedance is smaller than that of the normal tissues, transduced sound increases, and the appearance of hypoechoic areas (gray shadows).
Strong echoes: can be stronger echoes, strong echoes and very strong echoes. ① Stronger echoes: tumors with dense tissue or increased vascularity in parenchymal organs, the acoustic impedance difference is large, and the reflective interface is increased, so that the local echoes are strengthened, and there are dense light spots or light clusters (gray shadows), such as carcinoma, leiomyosarcoma, and hemangiomas. ② Strong echoes: the internal structure of the medium is dense, and the neighboring soft tissues or liquids have obvious acoustic impedance difference, causing strong reflections. For example, bone, stone, calcification, there can be a band or block of strong echo area (white shadow), due to poor sound transmission, the sound energy attenuation below, and the appearance of non-echoic dark area, that is, acoustic shadow (acoustic shadow). ③ very strong echo: gas-containing organs such as lungs, inflatable gastrointestinal, because of the difference in acoustic impedance with the neighboring soft tissues, acoustic energy is almost entirely reflected back, can not be transmitted, and the emergence of a very strong light band.
4.3 Ultrasound equipmentThere are many types of ultrasound equipment. Early application of amplitude modulation (amplitude mode), that is, A-type ultrasound, to reflect the echo of the wave amplitude change. Gray-scale modulation type (brightness mode), that is, B-type ultrasound, the Department of light and dark spots reflecting echo changes, in the shadow screen display 9 to 64 levels of gray-scale image, strong echo spot bright, weak echo spot dark.
According to the different imaging methods, divided into static imaging and dynamic imaging or real-time imaging (real timeimagimg) two kinds. The former to obtain static sonogram, image display a wider range of images, the image is clearer, but the inspection time is long, less application, the latter can be obtained in a short period of time, multi-frame images (20 ~ 40 frames / s) so you can observe the dynamic changes in the organ, but the image display range is small, the image is a little less clear.
Ultrasound equipment mainly consists of ultrasound transducer that is the probe (probe) and transmission and reception, display and recording, and power supply and other components (Figure 141).
Figure 141 Pulse-echo ultrasound equipment basic structure schematic
The transducer is an electro-acoustic transducer, composed of piezoelectric crystals, complete the generation of ultrasound and echo reception, and its performance affects the sensitivity, resolution, and artifacts, such as interference. B ultrasound equipment, most of which are used in the pulse-echo. Electronic line array multi-probe line square scanning, electronic phased array probe line fan scanning (Figure 142). In order to guide the perforation with the help of sonograms, there are also perforating probes.
Figure 142 real-time scanning probe
a. Electronic line array b. Electronic phased array
Probe performance 3.0, 3.5, 5.8MHz, etc.. The larger the MHz, the smaller its permeability. According to the inspection part to choose the appropriate probe. For example, an 8MHz probe is used for eye scanning, while for pelvic scanning, a 3.0MHz probe is used. An ultrasound device can be equipped with several alternative probes of different performance.
Cathode ray tubes are used for displays, and multi-frame cameras and video recorders are used for recording.
5 USG image characteristicsThe acoustic image reflects the presence or absence and strength of echoes in different shades of gray between light (white) and dark (black), with no echoes as dark areas (black shadows) and strong echoes as bright areas (white shadows).
The sonogram is a level image. Changing the position of the probe gives a picture of the acoustic image in any direction, and allows observation of the movement of moving organs. However, the image does not show as much scope and clarity as an X-ray, CT or MRI image.
6 USG techniqueUltrasound exploration is mostly used in the supine position, but can also be used in the lateral position and other ***. The position can be changed during the exploration ***.
The orientation of the section can be transverse, longitudinal, or oblique.
The patient to take the appropriate ***, exposed skin, coated with coupling agent, in order to discharge the air between the probe and the skin, the probe close to the skin scanning, scanning to observe the image, if necessary, freezing, that is, stopping the frame, the line of careful observation, make a good record, and photographic or video.
Attention should be paid to the size and shape of the organ, peripheral echoes, especially the posterior wall echoes, internal echoes, the activity state, the relationship between the organ and neighboring organs, and the degree of activity.
7 USG image analysis and diagnosisWhen observing the sonogram, first of all, you should understand the orientation of the section, so as to facilitate the recognition of the included anatomical structures. Pay attention to the peripheral echoes, including the edge echoes of organs and large masses, so as to observe their size, shape, location and activity. Apply the vernier to measure its diameter, area or volume to determine whether it is enlarged or reduced; whether there is any localized bulging; whether there is any displacement and how to move. To observe the internal echoes of organs and larger masses, including the strength, amount, distribution, and surrounding of echoes (e.g., the presence or absence of acoustic shadows). Because it can reflect the internal nature of the tissue structure. Changes in neighboring organs should also be noted, including pressure displacement or infiltration destruction. Diffuse organ lesions are more difficult to diagnose based on changes in organ size, shape, and internal echogenicity, while intra-organ space-occupying lesions are easier to detect based on limited internal echogenicity.
The changes in the resulting sonograms are synthesized. In the case of localized lesions, the location of the lesion (e.g., in which part of an organ); the size and number of the lesion; the physical nature of the lesion, whether it is liquid, substantial, pneumatic, or mixed; and the pathological nature of the lesion, whether it is inflammatory or neoplastic, benign or malignant, primary or metastatic, and whether it is cancerous or sarcomatous, etc.
The sonogram is a combination of the changes obtained from the sonogram.
Echocardiography is easier to detect lesions, determine their location and size, and is more reliable in determining whether a lesion is liquid, substantial, or pneumatic. It is also possible to identify benign or malignant lesions, e.g. benign lesions have clear peripheral echoes, smooth margins, homogeneous internal echoes, and insignificant attenuation, whereas malignant lesions have unclear peripheral echoes, unsmooth margins, irregular contours, homogeneous internal echoes, and hemorrhagic necrotic areas that may be devoid of echoes, with more significant attenuation.
8 Clinical application of USG diagnosisUltrasound on the heart, abdomen and pelvic organs, including the examination of pregnancy more applications. For example, it is of considerable value in the diagnosis of hepatocellular carcinoma, hepatic hemangioma, hepatic abscess, cirrhosis of the liver, gallbladder stones and tumors, diseases of the pancreas and spleen, and ascites; in the examination of the kidneys, bladder, prostate, adrenals, uterus, and ovaries; in the examination of the eyes, the thyroid gland, and the mammary gland; and in the diagnosis of pregnancy, in the localization of the position of the fetus and the placenta, and in the determination of multiple births, stillbirths, fetal abnormalities, and gravid fetuses (Figure 143).
Figure 143 Sonogram
a. Normal uterus (↓) b. Ovarian dermoid cyst (↓) c. Pregnancy (↓) d. Fetal head halo (↓) e. Anterior wall of the uterus placenta (↓) f. Anterior placenta (↑ for the uterine internal os) BL. Bladder UT. Uterus C. Cyst P. Placenta AM. Amniotic fluid FA. Fetus