Ultrasound in urology

Ultrasound is one of the most accessible diagnostic methods in medicine. In urology, ultrasound is used to detect structural and functional changes in the urogenital organs. With the help of the Doppler effect - echodopplerography - hemodynamic changes in organs and tissues are evaluated. Under the supervision of ultrasound, minimally invasive surgery is performed. In addition, the method is used and with open interventions to determine and record the boundaries of the pathological focus (intraoperative echography). Developed ultrasonic sensors of a special form make it possible to carry them through the natural openings of the body, using special instruments for laparo-, nephro- and cystoscopy into the abdominal cavity and along the urinary tract (invasive or interventional ultrasound methods).

Advantages of ultrasound include its availability, high information content with the majority of urological diseases (including urgent states), harmlessness for patients and medical personnel. In this regard, ultrasound is considered a screening method, the starting point in the diagnostic search algorithm for instrumental examination of patients.

In the arsenal of physicians there are various ultrasound devices (scanners) capable of reproducing two- and three-dimensional images of internal organs in real time scale by technical characteristics.

Most modern ultrasonic diagnostic devices operate at frequencies of 2.5-15 MHz (depending on the type of sensor). Ultrasonic sensors in form are linear and convective; they are used for transcutaneous, transvaginal and transrectal studies. For ultrasonic intervention methods, transducers of the radial type of scanning are usually used. These sensors have the shape of a cylinder of different diameter and length. They are divided into rigid and flexible and used for carrying out in organs or cavities of the body both independently and by special tools (endoluminal, transurethral, intracranial ultrasound).

The greater the ultrasound frequency used for the diagnostic study, the greater the resolving and less penetrating ability. In this connection, it is advisable to use sensors with a frequency of 2.0-5.0 MHz for the investigation of deep-seated organs, and for scanning surface layers and surface-located organs 7.0 MHz or more.

With ultrasound, the body tissues on the echogram in the gray scale have different echolarsity (echogenicity). Tissues of high acoustic density (hyperechoic) on the screen of the monitor look lighter. The densest - the concrements are visualized as clearly contoured structures behind which the acoustic shadow is determined. Its formation is due to the complete reflection of ultrasonic waves from the surface of the stone. Tissues of low acoustic density (hypoechoic) appear darker on the screen, and liquid formations are as dark as possible - echo-negative (anechogenous). It is known that the energy of sound penetrates into the liquid medium practically without loss and is amplified when passing through it. Thus, the wall of the liquid formation located closer to the sensor has less echogenicity, and the distal wall of the liquid formation (relative to the sensor) has an increased acoustic density. Fabrics outside the liquid formation are characterized by increased acoustic density. The described property is called the effect of acoustic amplification and is considered a differential diagnostic feature, which makes it possible to detect liquid structures. In the arsenal of doctors there are ultrasonic scanners equipped with instruments capable of measuring the density of tissues depending on the acoustic resistance (ultrasonic densitometry).

Vascularization and evaluation of blood flow parameters are performed with the help of ultrasound dopplerography (UZDG). The method is based on a physical phenomenon discovered in 1842 by the Austrian scientist I. Doppler and received his name. The Doppler effect is that the frequency of the ultrasonic signal when it is reflected from a moving object varies in proportion to the speed of its movement along the propagation axis of the signal. When the object moves toward the sensor that generates ultrasonic pulses, the frequency of the reflected signal increases and. On the contrary, when a signal from a deletion object is reflected, it decreases. Thus, if the ultrasonic beam meets a moving object, then the reflected signals differ in frequency composition from the oscillations generated by the sensor. By the frequency difference between the reflected and sent signal, it is possible to determine the speed of movement of the object under study in a direction parallel to the path of the ultrasonic beam. The image of the vessels is then superimposed in the form of a color spectrum.

At present, three-dimensional ultrasound has become widely used in practice, which makes it possible to obtain a volumetric picture of the organ under study, its vessels and other structures, which certainly increases the diagnostic capabilities of ultrasonography.

Three-dimensional ultrasound has given rise to a new diagnostic technique for ultrasound tomography, also called multi-slice (Multi-Slice View). The method is based on the collection of voluminous information obtained with three-dimensional ultrasound, and its further decomposition into sections with a given step in three planes: axial, sagittal and coronary. The software performs post-processing of information and presents images in gradations of a gray scale with a quality comparable to that of magnetic resonance imaging (MRI). The main difference between ultrasound tomography and computer is the absence of X-rays and absolute safety of the study, which becomes especially important in its conduct in pregnant women.