Biomedical subjects
Publications and source records attributed to A V Kruglov.
In this paper, the main concepts realized in a handheld OAE device are described. These concepts are: weighted averaging, non-linear MLS technique, acoustic probe with flat response, electronic passport of the probe, communication with clinical databases, special language for device control.
It is evident that the conventional technique for cochlear implant adjustment is not suitable for children in their first years of life. In order to find a solution to this problem, the possibility of electrically evoked auditory brainstem response (EABR) recording was investigated. EABRs were recorded in 9 patients with the Nucleus multichannel cochlear implant. The main problems that have to be solved during EABR recording in cochlear implantees are: i) EABR distortion due to the stimulus artefact: and ii) difference in the stimulus presentation rate during EABR registration (low pulse rate) and conventional psychophysical threshold estimation (high pulse rate) in cochlear implant patients. The influence of stimulus artefact on the recording results was minimized by setting the implant to the widest amplifier frequency band and by zeroing the initial segment containing the stimulus artefact with subsequent zero-phase digital filtering. The dependence of the EABR amplitude and latency on the stimulus intensity, width, electrode location and interstimulus interval was investigated. It was concluded that despite the difference revealed between absolute values of EABR thresholds and psychophysical threshold levels, it is possible to calculate implant adjustment parameters based on the EABR data with the proper correction applied.
Two alternative approaches for studying short-latency click-evoked otoacoustic emission (OAE) in normal-hearing subjects were employed. Growth of a click-evoked "ear canal response" with stimulus increase became progressively more non-linear and saturated when the latency of the analyzed segment of response increased. This relation between latency and shape of the response input/output function was observed even after linear component cancellation, indicating that it could be an intrinsic property of OAE. Hence, the existence of an essentially linear short-latency OAE component which is probably eliminated by commonly used artifact cancellation technique is suggested. Taking into account the fact that transient evoked otoacoustic emission (TEOAE) may be completely suppressed by simultaneously presented noise, a "true" artifact cancellation was performed by subtracting the ear canal response in the presence of a masker from the conventional click-evoked OAE recording. An additional TEOAE component with a latency of 2.5-5 ms was found. Its growth with stimulus intensity was indeed more linear than that of later components. However, latency and frequency of this TEOAE component, being specific for each subject, can hardly be explained by both a commonly assumed latency-frequency relationship of TEOAE and a generally used estimation of TEOAE latency as the sum of the forward and backward traveling wave propagation times.
The authors present the investigation of evoked otoacoustic emission (EOAE) as a part of the studies of the inner ear function. The EOAE was obtained in 10 normal hearing subjects during the routine recording conditions. In the investigation was used the adjustment of masking tone to obtain a reduction in the (EOAE) most stable component amplitude and suppression of the (EOAE) frequency components (FFT--derived).
The amplitude of gross microphonic potential of guinea pigs was used for output regulation of the generator of sinusoidal and narrow-band noise signals at continuous changing of frequencies. Thus isopotential contours of sound pressure levels (SPL) were obtained. The dynamics of the isopotential SPL on different levels within the range of 50-20 000 Hz, is described.
The spectral properties of click- and tone-evoked otoacoustic emission (OAE) under ipsilateral simultaneous tonal masking conditions as well as the changes of click-evoked OAE under ipsilateral forward masking by clicks were studied in normal-hearing subjects. It was found that (i) transiently evoked OAE (TEOAE) spectra consist of a number of peaks individual to the subject and distributed along a sufficiently wide cochlear region; (ii) each spectral peak is excited only when the stimulus energy was concentrated within the frequency range covering the frequency of the particular peak; (iii) different TEOAE spectral peaks can be masked independently under simultaneous tonal masking conditions; (iv) the TEOAE tuning curve shape is more closely related to the spectrum of TEOAE but not to that of the stimulus; (v) forward masking of TEOAE generation is most pronounced during the first few milliseconds after masker click onset and become significantly smaller with the longer latency. It is suggested that: (i) TEOAE is generated by a number of local generators individually distributed along the cochlear partition within a sufficiently wide region and characterized by different power; (ii) possible efferent effects in the ipsilateral TEOAE suppression are negligible as compared to the TEOAE reduction of exclusively cochlear origin.
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Screening of 1520 children living in the Khvalynsk district of the Saratov region, including assessment of urinary excretion of iodine and ultrasonic examinations of the thyroid in children and adults, revealed endemic goiter in the region. Special attention was paid to echographic examination of the thyroid; this method was used in examinations of 161 children aged 2 to 14 with thyroid enlargement of the I-III degree. 103 (64.0%) of there children had enlarged thyroid, in some children with diffusely enlarged thyroid of the I-II degree ultrasonic examination showed no enlargement, and in some children the gland was found even reduced in size. The greatest discrepancy between the data of palpation and ultrasonography was observed in first-degree thyroid enlargement, the least so in second-degree enlargement; in third-degree enlargement there was no such a discrepancy. Assessment of thyroid structure revealed various disorders of the organ in 29 of the 161 examined children, these disorders present both in enlarged glands and in those of normal or reduced size. Nodes that could not be palpated were detected in 2 children. Ultrasonic examinations of 56 adults aged 20 to 60 revealed changed structure of the thyroid in 35, with nodes of various sizes and localization detected in 15 of these.