• Journal of Institute of Control, Robotics and Systems
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• v.18 no.3
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• pp.161-167
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• 2012

It is known that big brown bats can distinguish echo of a prey at various angles. In this paper, we suggest a new object localization strategy using ultrasonic echolocation. We calculate the relative energy ratio between a high frequency component of ultrasound signal and a low frequency component of ultrasound signal for a target object. We found the measure depends on bearing angle of the object in space. We also tested energy ratio of echoed FM ultrasound signals depending on frequency, based on cross-correlation. It can determine the relative angular position of objects even though the reflected signals are congested form each object.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.463-465
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• 2022

The high-intensity focused ultrasound device intermittently operates abnormally due to communication signal interference between the devices during use due to the high frequency radiated during the skin treatment procedure. Communication interference between multi-frequency ultrasound devices can be reduced through CAN communication controller and transceiver design, firmware S/W program and CAN communication module development.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.297.2-297.2
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• 2016

Photoacoustic generation of ultrasound is an effective approach for development of high-frequency and high-amplitude ultrasound transmitters. This requires an efficient energy converter from optical input to acoustic output. For such photoacoustic conversion, various light-absorbing materials have been used such as metallic coating, dye-doped polymer composite, and nanostructure composite. These transmitters absorb laser pulses with 5-10 ns widths for generation of tens-of-MHz frequency ultrasound. The short optical pulse leads to rapid heating of the irradiated region and therefore fast thermal expansion before significant heat diffusion occurs to the surrounding. In this purpose, nanocomposite thin films containing gold nanoparticles, carbon nanotubes (CNTs), or carbon nanofibers have been recently proposed for high optical absorption, efficient thermoacosutic transfer, and mechanical robustness. These properties are necessary to produce a high-amplitude ultrasonic output under a low-energy optical input. Here, we investigate carbon nanotube (CNT)-polydimethylsiloxane (PDMS) composite transmitters and their nanostructure-originated characteristics enabling extraordinary energy conversion. We explain a thermoelastic energy conversion mechanism within the nanocomposite and examine nanostructures by using a scanning electron microscopy. Then, we measure laser-induced damage threshold of the transmitters against pulsed laser ablation. Particularly, laser-induced damage threshold has been largely overlooked so far in the development of photoacoustic transmitters. Higher damage threshold means that transmitters can withstand optical irradiation with higher laser energy and produce higher pressure output proportional to such optical input. We discuss an optimal design of CNT-PDMS composite transmitter for high-amplitude pressure generation (e.g. focused ultrasound transmitter) useful for therapeutic applications. It is fabricated using a focal structure (spherically concave substrate) that is coated with a CNT-PDMS composite layer. We also introduce some application examples of the high-amplitude focused transmitter based on the CNT-PDMS composite film.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.4 no.1
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• pp.49-61
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• 2006

This study conducted the following experiment to examine and compare transdermal permeation effects according to parameters of ultrasound and physiochemical characteristics of meloxicam. Permeation by ultrasound among these experimental drugs was relatively higher and it was involved in COX-2 inhibition unlike other drugs. Recently use of oral agents has been rapidly increased, but it was not generalized to transdermal agent and this study selected meloxicam that transdermal permeation research using ultrasound was not performed and conducted transdermal permeation experiment with skin of hairless mouse and analyzed permeation with HPLC. It made gel first and analyzed permeation depending on frequency and intensity of ultrasound of meloxicam with the same experimental procedures as the above experiment. The results of this study can be summarized as follows. Transdermal permeation by ultrasound frequency was higher in 1.0 MHz and it was higher as intensity increased. In comparison by parameters of ultrasound, there was similar permeation in $1.0\;W/cm^2$ of continuous mode and $3.0\;W/cm^2$ of pulsed mode and it was effective to high intensity for using pulsed mode. It was found that duty cycle of ultrasound affected transdermal permeation in meloxicam gel used in this experiment and transdermal permeation was higher in used ultrasound as phonophoresis than non-ultrasound for anti-inflammatory effects.

• Korean journal of applied entomology
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• v.51 no.3
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• pp.223-230
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• 2012

Some high frequency sounds alter physiological processes of the beet armyworm, Spodoptera exigua. This study investigated the effect of ultrasound (${\geq}$ 20 kHz) on larval feeding, pupal development, and adult mating behavior of S. exigua. Ultrasound suppressed feeding behavior of fifth instar larvae, and 30 or 45 kHz treatment inhibited more than 50% of feeding activity. Larvae treated with ultrasound exhibited alterations in major nutrient compositions in the hemolymph plasma. Plasma protein levels decreased with an increase in ultrasound frequency. In contrast, sugar levels increased with an increase in ultrasound frequency. Lipid levels increased with an increase in ultrasound frequency up to 30 kHz and then decreased at treatments > 30 kHz. Hemocytes, the fat body, and epidermis expressed three heat shock proteins and apolipophorin III. Ultrasound treatment markedly inhibited expression of some stress-related genes. Ultrasound treatment also inhibited S. exigua pupal development by extending the pupal developmental period and preventing adult emergence. Last, ultrasound treatment significantly inhibited adult mating behavior, which resulted in a significant decrease in female fecundity. These results show that ultrasound is a physiological stress to S. exigua.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.2
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• pp.855-860
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• 2014

Background: The purpose of this study was to assess the relationship between different sonographic features of papillary thyroid carcinoma (PTC) on high-frequency ultrasound and cervical lymph node metastasis (CLNM). Materials and Methods: We enrolled 548 patients who underwent initial surgery for PTC between May 2011 and December 2012 in our hospital at diagnosis. The sonographic features of 513 PTC nodules in 513 eligible patients, who had single PTC nodules in their thyroid glands, were retrospectively investigated. All patients with a suspect malignant nodule (d<0.5cm) among multiple nodules were initially diagnosed by fine-needle aspiration biopsy (FNAB) to ascertain if the suspect nodule was PTC. The final diagnosis of all the thyroid nodules and existence of CLNM were based on postoperative pathology. Patients were divided into two groups: a positive group with CLNM (224 nodules) and a negative group without CLNM (289 nodules). The following factors were investigated: gender, age, echogenicity, echotexture, size, shape, location, margin, contour, calcification morphology, distance between the nodule and pre- or post-border of the thyroid capsule, vascularity and the differences between the two groups. Results: Correlation analysis showed that shorter distances between the nodule and pre- or postborder of thyroid capsule resulted in greater risk of CLNM (Spearman correlation coefficient=-0.22, p<0.0001). The significant factors in multivariate analysis were age<45yrs, larger size (d>1cm), "wider than tall" shape, extrathyroid extension and mixed flow (internal and peripheral) (p<0.05, OR=0.406, 2.093, 0.461, 1.610, 1.322). Conclusions: Significant sonographic features of PTC nodules in preoperative high-frequency ultrasound are crucial for predicting CLNM.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.5
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• pp.481-488
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• 2015

It is difficult to see a therapeutic effect from cardiovascular disease treatment methods in the case of a hardened chronic total occlusion (CTO), owing to the calcification of the deposition materials. However, lesion cells, such as CTOs, can be selectively necrotized without affecting the normal tissue using high-intensity ultrasound focused on one point. In this study, a phantom CTO was necrotized by a high-intensity focused ultrasound (HIFU) energy system, and the acoustic characteristics in the focal region were analyzed. An experimental HIFU device was constructed to discover the appropriate conditions for the necrosis of a phantom CTO. The transfer characteristics of the ultrasound changed in the focal region by the density difference of the phantom CTO. These changes were acoustically analyzed to choose the available frequency band for each density. On-off temperature control in the focal region was applied to prevent rapid temperature rises, which would otherwise affect normal tissue.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.2
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• pp.80-87
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• 1994

Fetal monitoring is a routine procedure to obtain a record of physiologic functions during pregnancy and labor. It is required to determine fetal heart frequency accurately. There are various types of fetal heart rate(FHR) determination and the most frequently applied method is transabdominal Doppler ultrasound. However, in the case of weak or noise corrupted Doppler ultrasound signals, conventional peak detections and the autocorrelation function method have many difficulties to determine FHR precisely. Also the autocorrelation function is effected by threshold level and window size. To solve these problems, the high resolution pitch determination algorinthm is introduced to detect FHR from Doppler ultrasound signals. This scheme digitally processes Doppler ultrasound signal for digital rectification, envelope detection, decimation and correlation calculation of two interconnected segments and then FHR is determined by its maximal value. Even in the case of a greatly smeared noise signal, this algorithm is able to search FHR more accurately than autocorrelation function by means of compensating FHR with a constant correlation threshold. This algorithm is simulated by 386-MATLAB on PC 486/DX and verified that it is superior to the autocorrelation function method.

• Laser Solutions
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• v.15 no.4
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• pp.1-5
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• 2012

We demonstrate that reduced graphene oxide (rGO) coated thin aluminum film is an effective optoacoustic transmitter for generating high pressure and high frequency ultrasound previously unattainable by other techniques. The rGO layer of different thickness is deposited between a 100 nm-thick aluminum film and a glass substrate. Under a pulsed laser excitation, the transmitter generates enhanced optoacoustic pressure of 64 times the aluminum-alone transmitter. A promising optoacoustic wave generation is possible by optimizing thermoelasticity of metal film and thermal conductivity of rGO in the proposed transmitter for laser-induced ultrasound (LIUS) applications.

• Journal of Biomedical Engineering Research
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• v.27 no.1
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• pp.22-29
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• 2006

This paper proposes an efficient array beamforming method using spatial matched filtering for ultrasound imaging. In the proposed method, ultrasound waves are transmitted from an array subaperture with fixed transmit focus as in conventional array imaging. At receive, radio frequency (RF) echo signals from each receive channel are passed through a spatial matched filter that is constructed based on the system transmit-receive spatial impulse response. The filtered echo signals are then summed. The filter remaps and spatially registers the acoustic energy from each element so that the pulse-echo impulse response of the summed output is focused with acceptably low side lobes. Analytical beam pattern analysis and simulation results using a linear array show that the proposed spatial filtering method can provide more improved spatial resolution and contrast-to-noise ratio (CNR) compared with conventional dynamic receive focusing (DRF) method by implementing two-way dynamically focused beam pattern throughout the field.