SU965424A1 - Ultrasonic apparatus for ophtalmological investigations - Google Patents

Description

(5) ULTRASOUND DEVICE

FOR OPHTHALMOLOGICAL STUDIES

The invention relates to medicine, namely to ultrasound diagnostic devices, and can be applied in medical practice in ophthalmology in the diagnosis of diseases of the eye and orbit. Closest to the invention is a device comprising an ultrasound probe, a probe pulse generator, a receiver, a cathode tube with a time scan system, a marker signal generator with a reading device, a probe delay time delay, a tag pulse former, a delay delay, and a synchronizer J1. A disadvantage of this device is that, due to the lack of means for eliminating the influence of the thickness of the matching and protective layers of the ultrasound probe, on the measurement results, measuring means and means allowing the direct determination of the sizes of intraocular structures. Accuracy of the study is not sufficiently high. To determine the size of intraocular structures, one has to successively measure the distance from the surface of the eye to each of the structures and then calculate the sought-for distance as the difference between the values obtained. This increases the study time and reduces the accuracy of the measurement, since in a living object, such as eye sight, the first of the signals may be shifted when measuring the distance to the second. Lack of tools in the apparatus; Bil measurement leads to the need to check and adjust it during operation. The purpose of the invention is to improve the accuracy of the study by eliminating the influence of the thickness of the matching and protective layers of the probe on the measurement results. It is supplied that the device, a probe connected directly to the probe pulse generator and through a receiver with a cathode ray tube, a synchronizer that is connected to the probe pulse generator and to the timebase unit of the cathode ray tube, is connected to a cathode ray tube generator. adjustable delay markers, connected between the synchronizer and the generator of marker signals, the driver connected between the synchronizer and the receiver, and digital meter connected to the output of the generator of marker signals. In addition, in it, the image driver is made in the form of serially connected pulse width converter and transistor switch. FIG. 1 shows a structural electrical circuit diagram of the device in FIG. 2, diagrams of electrical voltages; in fig. 3 is a diagram of the occurrence of an error due to the influence of the matching and protective layers of the ultrasound probe. The device contains an ultrasonic probe 1, a probe pulse generator 2, a receiver 3, an electron beam tube, a synchronizer 5, a timebase 6 unit of the electron beam tube, a marker signal generator 7, a variable delay marker generator 8, a driver 9 and a digital meter 10. The driver 9 is in the form transducer 11 of pulse duration and transistor switch 12 interconnected. Ultrasonic probe 1 consists of a piezoplate, onto which a matching and protective layers are applied, damper and agree transformer (not shown). It is connected to the probe pulse generator 2 and the receiver 3. And the probe pulse generator 2 is connected to the synchronizer 5 and home zones 1. The receiver 3 is connected to the probe 1 and the electron-beam tube k. In this case, the time sweep unit 6 is connected to the synchronizer 5 and the cathode ray tube k, and the generator 7 of the marker signals is connected to the generator 8 of the adjustable delay of the marker signals, the meter 10 and the electron loop 394, which is achieved by means of the tube k. Moreover, the generator 8 containing ultrasound-controlled delay markers is connected to the synchronizer 5 and the generator 7 marker signals. The meter 10 is connected to the generator 7 of the marker signals, and the driver 9 is connected to the synchronizer 5 and the receiver 3. The device operates as follows. The synchronizer 5 generates a synchronization pulse (Fig. 2a), which starts the generator 2, which produces a powerful electrical pulse, which excites ultrasonic and electrical oscillations in probe 1, the so-called oscillator pulse (Fig. 2b) With acoustic contact of the probe 1 with the test the impulse of ultrasonic vibrations spreads in the eye in a straight line and practically at a constant speed, reflected from structural inhomogeneities located in its path. The reflected ultrasonic pulses reach the probe 1, n They are formed into pulses of electrical oscillations and are fed to the input of receiver 3 in which amplification and detection of received signals occurs. From the output of receiver 3, signals are sent to vertically deflecting plates of a cathode-ray tube A. Simultaneously with generator 2, synchronizer 5 also starts a sweep, in which a sawtooth-shaped voltage is produced, providing a time-proportional deflection of the beam of the cathode-ray tube k horizontally (Fig. 2c). Thus, an echogram is formed on the screen of the cathode-ray tube k, on which the generator pulse and pulses reflected from internal structural inhomogeneities have the form of vertical signals of positive polarity, whose position on the horizontal, time axis is determined by the depth of the reflecting structure: the deeper the reflecting structure, the later the reflected signal arrives and it is located on the echogram the farther from the generating pulse and from the beginning of the sweep (Fig. 2d). Simultaneously with the launching of the timebase block 6 and the generator 1, the synchronizer 5 starts the generator 8 of adjustable delay markers. which produces a pulse of adjustable duration (Fig. 2e), with the help of which the position of the markers on the time axis of the echogram is changed. The generator 7 produces two short pulses, a marker I and a mark II (Fig. 2e). The position of the markers on the time axis of the echogram is smoothly adjusted. Markers are fed to vertically deflecting plates of a cathode ray tube. On the echogram, the markers have the form of narrow negative signals (Fig. 2d), the markers are inserted below the images of the signals, the distances between which are measured. In addition, the marker signals go to meter 10, 6 of which measures the interval-time between them. The measurement result is recorded in digital form. The meter 10 is calibrated in such a way that it does not fix the actual size of the measured time interval, but proportional to the distance between the two intraocular structures presented on the echogram (Fig. 2d) with two reflected signals, to which markers I and M. The distance is measured in millimeters with an accuracy of 0.1 mm. Such accuracy is achieved by stabilizing the meter 10 with quartz. In this way, the distance between the surface of the eye and the inner structure is directly measured, as well as between the two within the eye structures, while eliminating the need for repeated manipulations and additional calculations. The use of stabilization using quartz in the meter 10 ensures high accuracy and stability of its operation, thereby eliminating the need for any adjustment or calibration during operation. When measuring the distance between the surface, the eye and its internal structure, an additional error occurs due to the influence of the thickness of the matching and protective layers of the probe on the measurement results (Fig. 3). With the direct contact of the ultrasound probe 1 with the surface of the rjia, it is not possible to receive on the echogram individual signals from the structures of the eye closest to the probe. These signals are merged with the generator pulse, which is the result of the total effect of the exciting electric pulse, the oscillations of the piezoplate and the reflected signals from the eye structures closest to the probe. Therefore, the counting of the distance on the echogram in this case is conducted from the front of the generator pulse. The time of the generator pulse corresponds to the moment of initiation of the piezoplate. The acoustic impulse arising as a result of the excitation, extending straight into the depths of the object, passes through the matching and protective layer of the probe 1 and only then reaches the surface of the eye (Figure Za). Therefore, the measured distance d is greater than true c by the total thickness f of these layers, which is on average several tenths of a millimeter (Fig. 36). In the study of relatively large objects whose dimensions are 5Q mm or more, the error introduced does not significantly affect the accuracy of measurement, and it can be neglected. However, when measuring the eye, when dealing with distances in units and fractions of a millimeter Such an error significantly affects accuracy ;: measurements. To eliminate this error in this device, the image of the generator pulse on the screen of the cathode-ray tube k is narrowed — the initial section is cut off from it, the duration of which corresponds to the transit time of the matching and protective layers of the ultrasound beam of probe 1. When measured, marker I is brought to the newly formed image of the generator pulse which is now offset to the right from the real front by an amount o, marker II is brought to the front of the signal from the reflecting structure, as usual (Fig. 13). In this case, the reading of the meter 10 is free from the error created by the matching and protective layers of the probe. The correction introduced in this way eliminates the error in measuring the distance between the surface of the eye and the internal structure and does not disturb the accuracy of measuring the distance between the two internal structures, in which the influence of the matching and protective layers is absent .. The narrowing of the generator pulse by cutting off its initial portion is provided by the driver 9 of FIG. }

consisting of a pulse width converter 11 and a transistor switch 12.

A synchronizer impulse 5 is applied to the converter 11 input. At the same time, an output pulse is generated at the output of converter 1, synchronous with the synchronizer impulse 5, and equal in duration to the ultrasonic time of the matching layer and the protective layer of the probe 1. This impulse is supplied to the key 12 and controls it in such a way that during the time of action of the impulse, the key 12 is closed. In the absence of a pulse at the output of the converter 11 5, the key 12 is open, the latter is connected parallel to the output of the receiver 3. When there is a pulse at the output of the converter 11, the output of the receiver 3 is closed to the housing by the key 12, and there is no signal at the receiver's output. At the end of the pulse at the output of converter 11, key 12 is disconnected and before the next pulse arrives, it synchronizes and affects the output 25 signal of receiver 3, which freely passes to the vertical deflection plates of the CRT.

Thus, in this device, the measurement error due to the influence of the thickness of the matching and protective layers of the ultrasonic probe 1 is eliminated, the measurement accuracy is high, and the possibility of direct measurement of intraocular

distances, as a result of which an increase in the accuracy of the study has been achieved.

Claims (2)

Invention Formula An ultrasound device for ophthalmic examinations containing an ultrasound probe connected directly to a probe pulse generator and through a receiver with a cathode-ray tube, a synchronizer connected to a probe pulse generator and to a temporal sweep unit of the cathode ray tube, and a marker signal generator connected to the cathode ray tube, characterized by that, in order to increase the accuracy of the study by eliminating the influence of the thickness of the matching and protective layers On the measurement results, it has an adjustable marker delay generator connected between the synchronizer and the marker generator, a driver connected between the synchronizer and the receiver, and a digital meter connected to the generator output of the marker signals. 2. The device according to claim 1, which is based on the fact that in it the driver is designed as a series-connected pulse length converter and a transistor switch, Sources of information taken into account in the examination 1. USSR author's certificate 253999, cl. A 61 B 10/00, 19b7. Oma) I  and Mszhrker HapKe / S 1r Fs / .2.