A Unique Acoustic Thermometer Was Created at FEL

Innovative devices for medical diagnosis, created at the Department of Acoustic and Multimedia Electronic Systems (AMES) under the leadership of Professor Serhii Naida, are traditionally recognized and in demand among specialists, and receive funding from sponsors.

In autumn, the "Acoustic Thermometer" project became the winner of the XI Festival of Innovation Projects "Sikorsky Challenge 2022: Innovative Transformation of Ukraine" and received GIST Support Funding as part of the The U.S. State Department's Global Innovations through Science and Technology Initiative (GIST). And in 2021, scientists presented the project "Broadband acoustic ear echo spectrometer" at the X Festival, and it was recognized as the winner in the nomination "Best technological solution" (See "KP" No. 31-32 for 2021).

The acoustic thermometer was worked on by a team of lecturers, students and postgraduate students of the AMES Department of the Faculty of Electronics of the Igor Sikorsky Kyiv Polytechnic Institute in the composition of: Serhii Naida - project manager; Tetiana Zheliaskova, Anton Naida and Mykyta Naida - solution development; Yurii Onikiienko - technical implementation, Oleksandr Drozdenko - technological implementation, Pavlo Popovych – marketing and finance.

About diagnosis. According to the developers, a new direction of early disease detection - measuring the deep temperature of the human body using its own heat radiation - occupies an important place among the modern methods of prevention and treatment of various diseases. This radiation occurs in the ranges of ultra-high frequencies, infrared radiation and acoustic radiation in the ultrasonic range. Therefore, the methods of measuring the internal temperature differ: infrared thermovision, radio and acoustic thermometry. At the same time, acoustic thermometry is characterized by better spatial resolution, greater sounding depth, lower attenuation, and is also simpler in technical implementation, which indicates the prospects for its use.

It was the problem of the lack of an acoustic thermometer on the market as a developed device with the accuracy of determining the depth temperature required for the purposes of passive diagnostics that became the impetus for the research carried out at the Department of Acoustic and Multimedia Electronic Systems. As a result of the research, the team developed a non-invasive diagnostic device of a new generation - an acoustic thermometer, which registered the thermal acoustic radiation of the human body and therefore was absolutely safe. According to scientists, there are no analogues of such a device in the world currently.

Intended use. The acoustic thermometer created by Kyiv polytechnicians can be used in the early detection of oncological diseases, including at home; early diagnosis of babies, as well as for constant monitoring and functional tests; studying thermoregulation of the human body as a whole in combination with other methods, for example, when diagnosing blood circulation by Doppler methods; measurement and long-term control of the temperature of internal organs (for example, the liver in chronic hepatitis); temperature control during hyperthermic treatment of malignant tumors and during physiotherapy, which is currently used in every physiotherapy office.

How the measurement is done. The physical cause of thermal radiation of the human body - both electromagnetic (radio-frequency) and acoustic - is the chaotic movement of its atoms and molecules. The higher the temperature, the intenser the noise that this movement causes. Infrared radiation has the greatest intensity in the wavelength range of 3-14 μm, where it reaches 10-2 W/cm2. Since the characteristic length of penetration of this radiation is only 100 μm, it carries information about the surface temperature, which is related to the conditions of capillary blood flow in the skin. Radiothermal radiation is much weaker. Its intensity on decimeter waves in the frequency band of hundreds of megahertz is approximately 10-12 W/cm2. The characteristic length of its penetration into biological tissues is several centimeters, but the spatial distribution capacity is 1-2 cm. Dynamic images of various human organs have already been obtained with the help of infrared thermal imaging and radio thermography, and devices are being produced.

Much better spatial resolution (~1 mm) at the same depth of the location of internal organs can be achieved when recording acoustic thermal radiation in the megahertz range. However, its intensity is even lower than radio-thermal, and is 10-13 W/cm2. The lack of industrial models of acoustic thermometer with the accuracy of determining the depth temperature required for the purposes of passive diagnosis became the impetus for this project.

About the project. "The innovative thing in the project is the use of a modified modulation method for temperature measurement using a focused piezo sensor, which works in a completely passive mode, does not emit anything, but only receives oscillations, therefore it is absolutely safe for humans, - Professor Serhii Naida explains. - Basic characteristics of the acoustic thermometer are: accuracy of temperature measurement is 0.2 °C; operating frequency range is 1-3 MHz; maximum depth of temperature measurement is 7 cm; spatial resolution is 1 mm".

And he goes on to talk about the advantages of the acoustic thermometer over other devices of a similar purpose: "We used a piezoelectric sensor as a receiver of the acoustic radiation of the human body, which provided high measurement accuracy - 0.2°С - together with circuits for amplification and detection of a weak noise signal. That made it possible to use the device for functional early disease detection, in particular, long-term monitoring of babies from the day of their birth. The use of electronic switching of a piezo receiver and a noise standard made it possible to measure the deep temperature of the human body in real time. The use of an elliptical lens to focus the received ultrasound beam allows you to measure the deep temperature of the human body using a single-frequency and single-channel method, which provides a greater depth of temperature measurement."

It is worth adding that the intellectual property right for the project is covered by a utility model patent of Ukraine and an application for an invention, the owner of which is the Igor Sikorsky Kyiv Polytechnic Institute.

What is the current status of project implementation? As of now, the methodological basis for the calculation of the acoustic thermometer has been developed and its experimental verification has been carried out, the laboratory model of the dynamic single-frequency acoustic thermometer with focusing has been developed and experimentally tested. Work on the creation of a portable acoustic thermometer continues.

Nadiia Libert