At present, the development direction of ultrasound in the medical field is color ultrasound, the following we will talk about the characteristics of color ultrasound.
Color ultrasound is simply high-definition black and white B ultrasound plus color Doppler. First of all, let’s talk about the ultrasound frequency shift diagnosis method, namely D ultrasound, which applies the principle of Doppler effect. When there is relative movement between the sound source and the receiver (i.e., the probe and the reflector), the frequency of the echo changes, and such frequency changes are called frequency shift.
Color Doppler ultrasound generally uses autocorrelation technology for Doppler signal processing, and the blood flow signal obtained by autocorrelation technology is color-coded and superimposed on the two-dimensional image in real time, which forms a color Doppler ultrasound blood flow image. Thus, color Doppler ultrasound (i.e., color ultrasound) has the advantages of two-dimensional ultrasound structure images and provides rich information on hemodynamics at the same time, and its practical application has been widely valued and welcomed, and it is clinically known as “non-invasive angiography”.
The main advantages of color Doppler ultrasound are.
①It can quickly visualize the two-dimensional distribution of blood flow.
(2) It can show the direction of blood flow.
③It helps to identify arteries and veins.
④It is good for identifying vascular and non-vascular lesions.
⑤It is beneficial to understand the nature of blood flow.
⑥It is convenient to understand the temporal phase and speed of blood flow.
⑦It can reliably detect shunts and reflux.
⑧It can quantitatively analyze the origin, width, length, and area of blood flow bundles.
However, the relevant technology used in color ultrasound is pulse wave, and the color flow color will be erroneous when the speed of the detector is too high, which is obviously inferior to spectral Doppler in quantitative analysis. Nowadays, all color Doppler ultrasound instruments have the function of spectral Doppler, which is color ── dual function ultrasound.
Color Doppler ultrasound flow diagram (CDF), also known as color Doppler ultrasound imaging (CDI), it obtains the same source of echo information and spectral Doppler, the distribution and direction of blood flow is displayed in two dimensions, and different speeds are distinguished by different colors. Duplex Doppler ultrasound systems, i.e., B-mode ultrasound images show the location of blood vessels. Doppler measures blood flow, and this combination of B-mode and Doppler systems can more precisely locate any particular vessel.
1. In spectral Doppler display, the direction of blood flow is distinguished by a zero baseline. Those above the zero baseline indicate blood flow toward the probe, and those below the zero baseline indicate blood flow away from the probe. In CDI, color coding indicates blood flow direction, red or yellow chromatography indicates blood flow toward the probe (hot color); while blue or blue-green chromatography indicates blood flow away from the probe (cold color).
2.Vascular distribution CDI shows the blood flow in the lumen of blood vessels, thus it is a flow channel type display, which cannot show the vessel wall and outer membrane.
3.Identify the vascular types of cancer nodules with CDI can classify the vasculature of liver cancer nodules. Distinguish them as peri-nodal circumferential vessels, arcuate vessels to the inner edge of the nodule. The flow vessels of nodules, internal vessels of nodules and outflow vessels of nodules, etc.
Clinical applications of color ultrasound
(I) Vascular diseases
Using 10MHz high frequency probe can find the calcification point less than 1mm in the blood vessel, which has good diagnostic value for carotid artery sclerotic occlusive disease. It can also use blood flow probe to determine the degree of luminal stenosis by local magnification, whether the embolus is likely to be dislodged, whether the ulcer is produced, and prevent the occurrence of cerebral embolism. Ultrasound can be the best diagnostic method for all types of arteriovenous fistulas, and the diagnosis can be confirmed when a colorful mosaic of the circumferential color spectrum is probed.
For carotid body aneurysm, abdominal main vein aneurysm, vaso-occlusive vasculitis, chronic lower extremity venous diseases (including lower extremity varicose veins, primary lower extremity deep vein valve insufficiency, lower extremity deep vein reflux disorder, thrombophlebitis and venous thrombosis), the high definition, local magnification and blood flow spectrum of ultrasound can make a more correct diagnosis.
(B) Abdominal organs
It is mainly used for liver and kidney, but it has some auxiliary diagnostic value for differentiating benign and malignant lesions in the abdominal cavity, differentiating gallbladder cancer from large polyps and chronic inflammation, and differentiating common bile duct and hepatic artery.
For cirrhosis, ultrasound can make a better judgment from the size of the lumen of various vessels in the liver, the speed and direction of internal flow and the establishment of collateral circulation. For nodular sclerosis and diffuse hepatocellular carcinoma, which are difficult to distinguish in black and white ultrasound, high-frequency probing and blood flow spectrum probing can be used to make differential diagnosis.
For the differentiation of benign and malignant occupying lesions in the liver, cysts and various arteriovenous tumors have better diagnostic value, and primary and secondary hepatocellular carcinoma can also be differentiated by internal blood supply.
Ultrasound is used in the kidney mainly for renal vascular lesions, such as the aforementioned renal arteriovenous fistula, and has strong indications when the clinical manifestation is interval, painless hematuria without detecting the cause. For renal artery stenosis, which is one of the common causes of secondary hypertension, ultrasound can basically make a definite diagnosis, with 98.6% diagnostic accuracy and 100% sensitivity when the blood flow velocity at the stenosis is greater than 150 cm/s. On the other hand, it is also a differential diagnosis for renal cancer, renal pelvic transplantation cancer and benign tumors.
(C) Small organs
Among the small organs, color ultrasound has obvious diagnostic accuracy compared to black and white ultrasound mainly for thyroid, breast and eye. In a way, 10MHz probe without color flow Doppler has been much clearer than ordinary black and white ultrasound 5MHz, probe. Diagnosis and differential diagnosis of thyroid lesions are made mainly based on the internal blood supply of thyroid gland, among which hyperthyroidism image is the most typical and specific, as a “sea of fire sign”. In contrast, simple goiter shows no significant changes compared to normal thyroid blood flow. Subacute thyroiditis, Hashimoto’s thyroiditis is between the two and can be distinguished by this, while nodular goiter, thyroid adenoma and thyroid cancer can be well distinguished by the nodule and surrounding blood flow. Therefore, it is recommended that those whose thyroid diagnosis is less clear and whose patients have some financial means can have an ultrasound to further clarify the diagnosis.
Breast ultrasound is mainly used for the differential diagnosis of breast fibroid and breast cancer, while eye mainly has better diagnostic value for ocular vascular lesions.
(iv) Prostate and seminal vesicles
Because rectal exploration is currently the best method for diagnosing the prostate, it is specifically proposed here. In this method, the prostate is divided into a migratory zone, a central zone, a peripheral zone, and a part of the prostatic fibromuscular stroma. The migratory zone includes both sides of the periurethral sphincter and the abdomen, which is the origin of 100% of BPH, while in normal people the migratory zone accounts for only 5% of the prostate size. The central zone is around the ejaculatory duct, the pointed wall pointing to the seminal caruncle, and the peripheral zone includes the posterior part of the prostate, both sides of the tip, which is the origin of 70-80% of cancers, while the tip of the envelope book or even disappears, forming an anatomically weak zone, a common metastatic channel for cancer, and a key area for prostate biopsy. The incidence of prostate cancer is on the rise in China, and the incidence of prostate cancer is the second most prevalent cancer in Europe and the United States, even after lung cancer. The most important thing is that you can use rectal investigation to diagnose prostate disease without abdominal investigation.
(E) Obstetrics and gynecology
The main advantages of color ultrasound in obstetrics and gynecology are the differentiation of benign and malignant tumors and the evaluation of umbilical cord disease, fetal precocious heart disease and placental function, and it has a better auxiliary diagnostic value for trophoblastic diseases.
The use of vaginal probe has certain advantages over abdominal exploration, and its superiority is mainly reflected in.
① High sensitivity and display rate of uterine artery and ovarian blood flow.
②Shortening the examination time and obtaining an accurate Doppler spectrum.
③No need to fill the bladder.
④No interference from body fat, abdominal scars, intestinal cavity inflation, etc.
⑤Search for pelvic organ tenderness site with the activity of the probe tip to determine whether there are adhesions in the pelvis.