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Basic knowledge of ultrasound: 1. Physical properties of ultrasonic waves: the frequency range of sound that normal human ears can hear is 20 ~ 20000Hz (Hz), and those below 20 Hz are called infrasound waves, and those with sound source vibration frequency higher than 20000Hz are called ultrasonic waves. Ultrasonic wave belongs to mechanical wave, which can propagate at inherent speed in elastic medium. Ultrasonic wave has three vibration states in solid: longitudinal wave, transverse wave and surface wave, but only longitudinal wave in liquid and gas. The longitudinal wave of ultrasonic wave is used for medical diagnosis. Ultrasonic wave has three basic physical quantities, namely wavelength (λ), frequency (f) and speed of sound (c). The relationship between them is: C=λ. F wavelength (λ) represents the length between particles in two adjacent periods when sound waves propagate in the medium, and the unit is millimeter (mm). Frequency (f) indicates the number of times the particle vibrates in unit time, and the unit is hertz (Hz). In ultrasonic diagnosis, the frequency range is usually 2.5 ~ 10 MHz (MHz, 1 MHz = 100000 Hz). The speed of sound (c) indicates the speed at which ultrasonic waves propagate in a certain medium, that is, the distance per unit time, and the unit is meters per second (m/s). Generally speaking, the sound velocity is the highest when the solid content is high; The higher the fibrous tissue (mainly collagen fibers), the higher the sound velocity; The soft tissue with higher water content has lower sound velocity; The speed of sound in body fluids is low; The speed of sound in gas-containing organs is the lowest. In medical diagnosis, the average propagation speed of ultrasonic wave in human body is calculated as1500m/s. Ultrasonic beam: Because of its high frequency and short wavelength, ultrasonic wave propagates in a straight line in a uniform medium and has good beam or directivity, so it can be used for directional detection of human tissues and organs. The near-field sound beam near the sound source has almost equal width and good directivity, while the far-field sound beam has certain diffusibility, and the diffusion angle is related to the sound source diameter (d) and wavelength (λ), that is, sin θ =1.22λ/d. In order to improve the image quality in the far-field area, sound beam focusing technology should be added to ultrasonic imaging. Reflection of ultrasonic waves: When ultrasonic waves propagate in two different media, reflection will occur. Reflection refers to the process of sound waves returning partially or completely on the interface, which follows the following laws: ① reflection and incident sound beams are on the same plane; ② The reflected sound beam and the incident sound beam are on both sides of the normal; ③ The reflection angle is equal to the incident angle. The reflection of ultrasonic energy depends on the acoustic impedance difference between adjacent media. Acoustic impedance (z) can be understood as the resistance encountered when ultrasonic waves propagate in a medium, which is equal to the product of medium density (ρ) and sound speed (c), that is, Z=ρ. C, the unit is Rayleigh. The reflected energy of ultrasonic wave is determined by the reflection coefficient (R 1), where Z 1 and Z2 represent the acoustic impedance of medium 1 and medium 2. R1= [(z2-z1)/(z2+z1)] the square of 2. If the acoustic impedance is equal (Z 1=Z2), then R 1=0, and there is no reflection, which can be seen in bile in gallbladder, urine in bladder and vitreous body of eyeball in physiological state, and pleural effusion, ascites, pericardial effusion and cyst in pathological changes. If the acoustic impedance is different (Z 1≠Z2), then R 1≠0, and there is reflection; As long as the acoustic impedance difference is greater than 1‰, reflected echo will be generated, so the resolution of ultrasonic wave on human soft tissue is very high. When the acoustic impedance of the two media is very different (Z 1 15 mm 4), the motion amplitude of interventricular septum and left ventricular wall decreases, and the thickening rate decreases. C Doppler echocardiography: 1) Mitral and tricuspid valves. 1 coronary heart disease, heart failure, anemia, hyperthyroidism and rheumatic valvular heart disease. Hypertrophic cardiomyopathy is a kind of cardiomyopathy characterized by obvious asymmetric hypertrophy of ventricular muscle, smaller ventricular cavity with left ventricular hyperdynamic contraction, blocked left ventricular filling and decreased compliance. Pathophysiology: Cardiac hypertrophy and abnormal arrangement-impaired ventricular diastolic function-slow filling-decreased ventricular volume-decreased venous return-Most patients have asymmetric ventricular septal hypertrophy-left ventricular outflow tract stenosis-abnormal motion of the anterior mitral valve (SAM) in mid-systole-aggravated left ventricular stenosis-aortic valve closure in mid-systole. According to left flow stenosis, it can be divided into obstructive type and non-obstructive type, and divided into four types+apical hypertrophy type: type ⅰ: anterior ventricular septum is obviously thickened; Type ⅱ: thickening of anterior and posterior interventricular septum; Type ⅲ: all ventricular walls were thickened; Type ⅳ: thickening of interventricular septum and anterior and lateral walls of left ventricle; Apical hypertrophy: apical ventricular cavity stenosis and occlusion. Clinical manifestations: it often ends in sudden death, and congestive heart failure may occur in the late stage of the disease. In addition to the long-axis section and four-chamber section of the left ventricle, the short-axis section of the mitral valve and papillary muscle were taken to observe the thickening position and thickness of the ventricular wall, the width of the left ventricular outflow tract, the SAM of the anterior mitral valve and the closure of the aortic orifice in the middle systolic period. The left beam flow and valve regurgitation were detected by color Doppler. Sonographic features A, transect echocardiography 1) Asymmetric myocardial hypertrophy, especially the ratio of the middle and upper ventricular septum to the posterior wall of the left ventricle > 1.3. 2) due to SAM in the anterior leaflet of mitral valve, the process of ventricular septal thickening, left rheology narrowing, left ventricular outflow tract narrowing < < 20mm 3= = myocardial hypertrophy, echo disorder rough as rice grains, left ventricular cavity narrowing B, Doppler echocardiography 1 = jet beam from left ventricular outflow tract in systole, and the spectrum is in the shape of a single peak dagger. 2 = Reflux bundles of mitral valve and aortic valve orifice can be detected. C-mode and M-mode echocardiography 1 = It can be seen that the CD segment of the anterior mitral valve moves forward in systolic phase (SAM). 2 = the left ventricular outflow tract is narrow, which often makes the E peak collide with the ventricular septum, and the decline rate of EF is obviously weakened. 3 = Abnormal aortic valve movement, early valve closure in mid-systole, reopening in late systole or rapid left blood flow, differential diagnosis of impact on aorta: 1) Hypertension 2) SAM and aortic valve insufficiency and mitral valve prolapse. 3) The incidence of restrictive cardiomyopathy is 3%. Pathophysiology: Endocardia and myocardium are extensively fibrotic, and the cardiac cavity is partially occluded due to fibrosis and thrombosis, which limits ventricular filling and leads to the decline of ventricular diastolic function. Pericardial effusion: Pericardium can be caused by bacteria, virus, autoimmune, physical and chemical factors, and chronic diseases such as pericardial adhesion and constriction. The common causes are tuberculosis, rheumatism, virus, inflammation and tumor. Pathophysiology The pericardium consists of two parts: cellulose and serous fluid. The slurry is divided into dirty layer and wall layer, and there is a pericardial cavity between the two layers, which contains 20-30 ml slurry for lubrication. Pericardium has the functions of protecting the heart and lungs, fixing the heart, reducing the impact of heart beating on the lungs and preventing the influence of external forces on the heart. Due to the above reasons, pericardial effusion → pericardial effusion → pericardial cavity pressure gradually increases → exceeds the degree of pericardial dilatation → cardiac dilatation is limited → leads to decreased ventricular filling → decreased cardiac output → systemic blood stasis → increased venous pressure → hepatosplenomegaly → inferior vena cava dilatation → edema of both lower limbs. A large amount of fluid in pericardium accumulates or exceeds the degree of pericardial dilatation, even if the amount of fluid is small, pericardial tamponade syndrome occurs. Clinical manifestations: Examination methods: mainly examine the long-axis section, apical four-chamber section and a series of short-axis sections of the left ventricle, and observe the amount of fluid in the pericardial cavity of the anterior wall of the right ventricle, the posterior wall of the left ventricle, the apical part and the atrial apex, as well as the expansion of the low-level fluid dark area with the change of body position. Ultrasonographic features: There is anechoic dark area in pericardial cavity, which changes with body position to diagnose pericardial effusion. A. Sectional echocardiography: 1 A small amount of pericardial effusion (that is, the fluid volume is less than 200ml) is distributed in the pericardial cavity of the left ventricular posterior wall, with a width of 0.5- 1.0cm, and the heart movement is not affected. 2. Moderate pericardial effusion (200-500ml), except that the width of the fluid in the pericardial cavity of the left ventricular posterior wall is 1.0-2.0cm, and that in the pericardial cavity of the right ventricular anterior wall is 0.5- 1.0cm. ..