Category: Ultrasound
Biophysical aspects of ultrasound
Ultrasound is an acoustic wave with a frequency of more than 20 kHz, which is not captured by the human ear. The ultrasound, as a diagnostic method, was based on the piezoelectric effect discovered by the Curie brothers in 1880. Subsequently, this served as a starting point for the creation of ultrasonic transducers, piezoelements which can alternately serve as a source or receiver of ultrasonic waves.
The principles of the operation of medical ultrasound scanners were borrowed from flaw detectors and sonar used in aviation and navigation. In the 1950s, the first experimental studies were carried out using ultrasound on a man, and in 1957 a prototype of a contact scanner operating in B mode was created.
The extensive use of ultrasound in medical diagnosis began in the 60s. the last century.
All ultrasonic devices generate ultrasonic vibrations that propagate in biological tissues. The propagation of ultrasonic waves depends on the properties of the medium (its physical state, density, elasticity, pressure, temperature, etc.).
Different tissues of the body have different acoustic resistance. When the interface between two media with different acoustic impedance is reached, the ultrasonic signals begin to be reflected. These reflected signals are captured by the acoustic transducer and displayed on the monitor screen in the form of images of organs and tissues.
To conduct ultrasound in the seroscale mode, ultrasound is used in the range of 2-15 MHz. Scanning of organs located at different depths is carried out using a certain frequency of radiation. Surface structures and soft tissues (thyroid gland, mammary glands, scrotum organs, joints, etc.) are studied by sensors working at a frequency of 7.5 MHz and higher. For visualization of deep internal organs, the frequency is 3.5 MHz. Modern ultrasonic devices have a resolving power of 1-3 mm.
The ultrasound procedure is performed in a darkened room (for better perception of gray tones on the monitor). Scanner operation mode is selected depending on the type and tasks of the study. For more complete contact of the sensor of the device with the patient’s body on the skin, a hypoallergenic conducting gel is applied in the area of the study.
Ultrasound in diagnostics: Types of research
To obtain diagnostic information in the conduct of ultrasound, different modes are used:
A-mode (one-dimensional echography, amplitude mode) – provides information on the intensity of the reflected signal and the distance between the sensor and the reflecting structures. Used in ophthalmology (echobiometry), neurology (Echo-EG), otolaryngology (ultrasound of the paranasal sinuses).
B-mode (two-dimensional echography, brightness mode) – reproduces a two-dimensional tomographic image of anatomical structures in real time. The main mode used for most types of ultrasound.
M-mode (motion mode) – displays temporary changes in the A-echogram. It is used mainly in cardiology during Echocardiography.
C-mode – in this type of scanning, the A-mode is used to determine the depth of the object under study, and a two-dimensional mode is used to form its image at a given depth.
D-mode (Doppler mode) – is based on the principle of frequency shift, which allows you to visualize and measure the flow of blood in the vessels. Dopplergrams can be presented in the form of color images (color Doppler) or graphic / acoustic waves (spectral Doppler). Special techniques of ultrasound are color Doppler mapping (DCC), energy doppler (EDC), tissue doppler (TDK). The combination of the B-mode with the CDC is a triplex scan; combination of B-mode and ultrasound-ultrasonic duplex scanning.
Depending on the model of the image received on the screen, 2D ultrasound (flat, two-dimensional), 3D ultrasound (three-dimensional, static) and 4D ultrasound (volumetric, dynamic, in real time) are distinguished. Despite the fact that almost any internal organs can be examined with the help of 3D / 4D technologies, these techniques were most widely used in obstetrics (3D / 4D ultrasound of the fetus).
Ultrasound may be performed by external (percutaneous) or intracavitary (intracorporeal) access. The transthoracic ultrasound of the mediastinum, the transabdominal ultrasound of the pelvic organs or abdominal organs, etc., belong to the first category of studies.
Intracavitary studies include transesophageal echocardiography, transvaginal ultrasound, endo rectal ultrasonography of the rectum, laparoscopic echography and many others.
Depending on the purpose of the study, ultrasound may be planned or urgent; screening (prophylactic) or diagnostic. Ultrasound studies are widely used for monitoring, intraoperative diagnosis, postoperative testing, control of the accuracy of instrumental manipulation (biopsy, puncture, drainage).
Taking into account the anatomical region or organ system, subjected to ultrasonic scanning, emit ultrasound structures of the head and neck ultrasound of the chest cavity, ultrasound of the abdomen and retroperitoneal space, US female genitalia ultrasound of male sexual organs, ultrasound of the urinary system, ultrasound musculoskeletal systems, etc.
Ultrasound: Areas of use
Ultrasound diagnostics is used in various fields of medicine for examining adults and children.
Complex ultrasound of the abdominal organs includes echoscanization of the liver, gallbladder and bile ducts, pancreas, spleen. It can be performed both for preventive purposes, and in the presence of signs indicating the defeat of the digestive organs (abdominal pain, jaundice, weight loss, biochemical deviations in blood, etc.).
In addition to a comprehensive ultrasound, it is possible to study individual OBP: liver and gall bladder, spleen, pancreas. With the help of ultrasound, you can determine the presence of free fluid or blood in the abdominal cavity. Within the framework of a separate diagnostic procedure, the retroperitoneal space – the ultrasound of the adrenal gland and retroperitoneal tissue – is usually scanned.
The areas of application of ultrasound therapy ar:
therapy,
gastroenterology,
abdominal surgery,
oncology,
hematology,
infectology.
The ultrasound of the thoracic cavity can include such independent studies as echocardiography, ultrasound of the pleural cavity, ultrasound of the mediastinum. Echocardiography is the leading method for diagnosing the anatomical and functional state of the heart in cardiology.
It can be performed by transthoracic or transesophageal access, in conditions of rest, physical or medicamentous load, electrostimulation. Ultrasound of the pleural cavities is indicated for the detection of effusion, accumulation of blood and pus, examination of pleural sheets.
The ultrasound of the mediastinum is used to detect volumetric processes of mediastinal localization.
Ultrasound of the urinary system includes the examination of the kidneys, ureters and bladder. In urology, indications for the appointment of such studies can be dysuric disorders, low back pain and urination, changes in color and odor of urine, changes in laboratory urine tests. Kidney ultrasound is often performed in conjunction with an ultrasound of the adrenal glands.
Ultrasound of female genital organs is most often performed for the purpose of comprehensive assessment of the reproductive system in women of different ages. It can be performed transabdominal or transvaginal (more rarely – trinsrethal), as well as combined (TA + TV) access.
Self-sufficient types of ultrasound are folliculometry, USGSS, assessment of patency of the fallopian tubes. At the onset of pregnancy, ultrasound helps to monitor the development of the fetus, promptly detect intrauterine malformations, the threat of spontaneous abortion and premature birth. For this purpose, in the framework of the pregnancy management program, women are recommended to perform ultrasound in I, II and III, trimesters, UZDG utero-placental blood flow, cervicometry.
US male genitals in Andrology carried out in the framework of screening for the detection of adenomas and prostate cancer (TA ultrasound and prostate TRUS), pathology of the testes and epididymis (cryptorchidism, hydrocele, varicocele, cysts), determine the causes of erectile dysfunction (US penile Doppler ultrasound sex member). The study assumes an evaluation of the structure and vascularization of male genital organs.
The ultrasound of paired joints (arthrosonography) and the spine are included in the standards of diagnostic algorithms for the study of the musculoskeletal system. These types of ultrasound may be appointed traumatologist-orthopedist, rheumatologist, neurologist. UZ-visualization is also used for joint puncture, puncture biopsy. Ultrasonic densitometry is a convenient screening method for assessing bone tissue.
Diagnostic procedures grouped under ultrasound structures of the head and neck, include a number of independent in the diagnostic research plan, which find application in ophthalmology (US eyes), neurology (ultrasonography, Echo EG), Endocrinology (thyroid ultrasound), otorhinolaryngology (US paranasal sinuses ), dentistry (ultrasound of the salivary glands). To the category of ultrasound of soft tissues and surface structures include the study of muscles, tendons, lymph nodes, mammary glands.
Advantages and disadvantages of ultrasound method of conducting
In many cases, ultrasound does not require any special training of patients and can be performed as soon as possible. Ultrasound scanners can be delivered to any department for examination of bedridden and untransportable patients, in addition, the use of portable devices makes it possible to conduct ultrasound at home.
The big advantage is the possibility of a one-time examination of several organs at once. At the request of the patient, ultrasound can be recorded on an electronic carrier – in this case, it becomes possible to obtain a second expert opinion on this study, as well as comparing the results in the treatment process.
The price of ultrasound in USA is several times lower than on CT or MRI. Ultrasound can be used not only for diagnostic purposes, but also for invasive procedures (puncture and biopsy under the supervision of ultrasound).
Along with undeniable advantages, sonography has a number of limitations. The accuracy of the diagnosis and interpretation of the data depends largely on the equipment class, the qualifications of the specialist in ultrasound diagnostics, his experience and knowledge of the research methodology.
Small informativity of ultrasound may be associated with poor preparation for the procedure (for example, ultrasound of the abdominal cavity is recommended to be performed strictly on an empty stomach, the presence of gases in the intestine makes it very difficult to visualize).
Significant impact on image quality is the physique of the patient: a large layer of subcutaneous fat can reduce the informative value of ultrasound. Ultrasonic waves do not pass through the bone tissue, so it is almost impossible to obtain images of structures located in closed bone cavities (for example, the brain in adults) by means of ultrasound.
Cost of ultrasound in USA
Ultrasound research is an extremely popular type of diagnostics widely used in many areas of practical medicine. Today, ultrasound is performed in almost all municipal and federal institutions, private medical centers. Factors affecting the pricing of the diagnostic procedure are the equipment class, the research area and the access used. In addition, the price of ultrasound in USA may fluctuate depending on the form of ownership, the reputation and location of the clinic, the doctor’s qualifications, the urgency of the research and the level of service.