• Clinical Endoscopy
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• v.56 no.2
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• pp.229-238
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• 2023

Background/Aims: Shear wave elastography (SWE) is used for liver fibrosis staging based on stiffness measurements. It can be performed using endoscopic ultrasound (EUS) or a transabdominal approach. Transabdominal accuracy can be limited in patients with obesity because of the thick abdomen. Theoretically, EUS-SWE overcomes this limitation by internally assessing the liver. We aimed to define the optimal technique for EUS-SWE for future research and clinical use and compare its accuracy with that of transabdominal SWE. Methods: Benchtop study: A standardized phantom model was used. The compared variables included the region of interest (ROI) size, depth, and orientation and transducer pressure. Porcine study: Phantom models with varying stiffness values were surgically implanted between the hepatic lobes. Results: For EUS-SWE, a larger ROI size of 1.5 cm and a smaller ROI depth of 1 cm demonstrated a significantly higher accuracy. For transabdominal SWE, the ROI size was nonadjustable, and the optimal ROI depth ranged from 2 to 4 cm. The transducer pressure and ROI orientation did not significantly affect the accuracy. There were no significant differences in the accuracy between transabdominal SWE and EUS-SWE in the animal model. The variability among the operators was more pronounced for the higher stiffness values. Small lesion measurements were accurate only when the ROI was entirely situated within the lesion. Conclusions: We defined the optimal viewing windows for EUS-SWE and transabdominal SWE. The accuracy was comparable in the non-obese porcine model. EUS-SWE may have a higher utility for evaluating small lesions than transabdominal SWE.

• Journal of the Korean Society of Radiology
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• v.11 no.4
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• pp.221-225
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• 2017

To evaluate the performance of ultrasound imaging system, we investigated the change of spatial resolution according to changing sonic velocity change parameter provided by ultrasound equipment. Ultrasound phantom images were obtained using a 3.0 ~ 5.0 MHz convex transducer in an ultrasound diagnostic device used at a medical institution located at Iksan. N-365 multi-purpose ultrasound phantom was used to measure longitudinal distance measurement accuracy and longitudinal and transverse resolution. In the same manner, the sonic velocity of the ultrasound equipment was changed from 1580 m/sec to 1400 m/sec in six steps, and the full width at half maximum(FWHM) was measured using the image J program to determine whether the measured values were different. As a result, lateral resolution was measured from 1.91 mm to 5.3 mm according to the speed change, and the smallest FWHM was 1.91 mm at 1420 m/sec. The axial resolution was measured from 1.03 mm to 1.14 mm according to the speed change, and the smallest FWHM was 1.03 mm at 1400 m/sec. The slower the sound velocity of the ultrasound equipment, the shorter the length of longitudinal measurement.

• The Journal of the Acoustical Society of Korea
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• v.18 no.5
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• pp.68-77
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• 1999

The paper looked into the effects of the spectral properties (waveform) of the high intensity focused ultrasound on suppression of the ultrasonic cavitation. Three different types of ultrasound were considered in the study, which were sinusoidal (1 MHz, 5 MPa), frequency modulated (from 1 MHz to 6 MHz for 10 ㎲, 5 MPa), asymmetrically shocked (fundamental frequency 1 MHz, peak positive pressure 12 MPa, peak negative pressure -4 MPa). The temporal response of an air bubble in water initially 1 ㎛ in radius to each type of the ultrasound was predicted using Gilmore bubble dynamic model and Church's rectified gas diffusion equation. It was shown that the radially pulsating amplitude of the bubble was greatly reduced for the frequency modulated wave and was little decreased for the shock wave, compared to the case that the bubble was exposed to the sinusoidal wave. It is interesting that the bubble response to the frequency modulated wave remains similar when the frequency component of the modulated ultrasound is beyond the bubble resonant frequency 3 MHz. This implies that, although the ultrasound is modulated up to 3MHz rather than up to the present 6 MHz, it is likely to produce similar cavitation suppression effects. In practice, it means that a typical narrow band ultrasonic transducer can be taken to generate an appropriate frequency modulated ultrasound to reduce cavitation activity. The present study indicates that ultrasonic cavitation may be suppressed to some extent by a proper spectral modification of high intensity ultrasound.

• Journal of Trauma and Injury
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• v.20 no.2
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• pp.130-137
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• 2007

Purpose: Ultrasound is of proven accuracy in abdominal and thoracic trauma and may be useful for diagnosing extremity injury in situations where radiography is not available, such as disasters and military and space applications. However, the diagnosis of fractures is suggested by history and physical examination and is typically confirmed with radiography. As a alternative to radiography, we prospectively evaluated the utility of extremity ultrasound performed by trained residents of emergency medicine (EM) one patient with wrist and ankle extremity injuries. Methods: Initially, residents of EM performed physical examinations for fractures. The emergency ultrasound (EM US) was performed by trained residents, who used a portable ultrasound device with a 10- to 5-MHz linear transducer, on suspected patients before radiography examination. The results of emergency ultrasound and radiography and the final diagnosis were recorded, and correlation among them were determined by using Kappa s test Results: Thirty-nine patients were enrolled in our study. The average age was $36.6\;{\pm}\;19.3$ years. There were radius Fx. (n=21), radius-ulna Fx. (n=1), ulna Fx. (n=1), and contusion (n=2) injuries among the wrist injury and lat.-med. malleolar Fx. (n=13), lat. malleolar Fx. (n=6), and med. malleolar Fx. (n=3) injuries among the ankle injury. Comparing EM US with radiography, we found the sensitivity, specificity, positive predictive value, and negative predictive value of EM US for Fx. diagnosis to be 100%, 66.7%, 97.3%, 100% and those of radiography to be 97.2%, 100%, 100%, and 75%, respectively. Kappa s test for a correlation between the Fx. diagnosis of EM US and the final diagnosis of Fx was performed, and Kappa's value was 0.787 (P = 0.004).Conclusion: EM US for Fx. can be performed quickly and accurately by EM residents with excellent accuracy in remote locations such as disaster areas and in military and aerospace applications. EM US was as useful as radiography in our study and had a high correlation to the final diagnosis of Fx. Therefore, ultrasound should performed on patients with extremity injury to determine whether extremity evaluation should be added to the FAST (focused abdominal sonography trauma) examination.

• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.250-257
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• 2007

Functional gastrointestinal disorders affect millions of people of all age regardless of race and sex. There are, however, rare diagnostic methods for the functional gastrointestinal disorders because functional disorders show no evidence of organic and physical causes. Our research group identified recently that the gastrointestinal tract well in the patients with the functional gastrointestinal disorders becomes more rigid than healthy people when palpating the abdominal regions overlaying the gastrointestinal tract. The aim is, therefore, to develop a diagnostic method for the functional gastrointestinal disorders based on quantitative measurement of the rigidity of the gastrointestinal tract well using ultrasound technique. For this purpose, a preliminary ultrasound diagnostic system was developed and verified through phantom tests. The system consisted of transmitter, ultrasonic transducer, receiver, TGC, and CPLD, and verified via a phantom test. For the phantom test, ten soft-tissue specimens were harvested from porcine. Five of them were then treated chemically to mimic a rigid condition of gastrointestinal tract well, which was induced by functional gastrointestinal disorders. Additionally, the specimens were tested mechanically to identify if the mimic was reasonable. The customized ultrasound system was finally verified through application to human subjects with/without functional gastrointestinal disorders(Normal and Patient Groups). It was identified from the mechanical test that the chemically treated specimens were more rigid than normalspecimen. This finding was favorably compared with the result obtained from the phantom test. The phantom test also showed that ultrasound system well described the specimen geometric characteristics and detected an alteration in the specimens. The maximum amplitude of the ultrasonic reflective signal in the rigid specimens $(0.2{\pm}0.1Vp-p)$ at the interface between the fat and muscle layers was explicitly higher than that in the normal specimens $(0.1{\pm}0.0Vp-p)$ (p<0.05). Clinical tests using our customized ultrasound system for human subject showed that the maximum amplitudes of the ultrasonic reflective signals nea. to the gastrointestinal tract well for the patient group$(2.6{\pm}0.3Vp-p)$ were generally higher than those in normal group$(0.1{\pm}0.2Vp-p)$ (p<0.05). These results suggest that newly designed diagnostic system based on ultrasound technique may diagnose enough the functional gastrointestinal disorders.

• Journal of Biomedical Engineering Research
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• v.40 no.2
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• pp.39-47
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• 2019

Ultrasound sonication along with microbubble (MB) could enhance drug delivery to promote the absorption of anticancer drugs into cancers in a noninvasive and targeted manners. In this study, we verify the acute drug delivery enhancement (within an hour) of two representative focused ultrasound driven drug delivery enhancement methods (MB and Doxorubicin-coated Nanoparticle complex (MB-NP) based). Experiments were conducted using in vivo mouse model with MDA-MB-231 breast cancer cell line. Ultrasound generated by single-element 1 MHz focused ultrasound transducer was delivered in pulsed sonication consisted of 0.125 msec bursts at a pulse repetition frequency of 2 Hz for 20 seconds without a significant increase in local temperature (less than $0.1^{\circ}C$) or hemorrhage. Doxorubicin concentrations in tumors were improved by 1.97 times in the case of MB-NP, and 1.98 times by using Doxorubicin and MB separately. These results indicate anticancer drug delivery based on MB and MB-NP can significantly improve the effect of anticancer drugs delivered to tumors in a short time period by using low-intensity focused ultrasound.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.4
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• pp.65-71
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• 1984

The design formular of optical focusing systems cannot be applied to ultrasonic B scanners, which use broadband pulses instead of continuous wave. In this paper, a calculation method is studied for analyzing the propagation of ultrasonic broadband pulse excited by ultrasonic array transducers. Using the results, seveial design parameters such as the number of transducer elements, delay time, and the focal point are determined to obtain high resolution in the ultrasonic dynamic focusing system. A dynamic focusing system with low-noise switching characteristics; which attains lateral resolution of 2-3mm all along the axial direction up to 18 cm with a 3.5 MHz linear array transducer, was implemented.

• Smart Structures and Systems
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• v.17 no.1
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• pp.17-29
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• 2016

Ultrasonic tomography is a powerful tool for identifying defects within an object or structure. But practical application of ultrasonic tomography to solids is often limited by time consuming transducer coupling. Air-coupled ultrasonic measurements may eliminate the coupling problem and allow for more rapid data collection and tomographic image construction. This research aims to integrate recent developments in air-coupled ultrasonic measurements with current tomography reconstruction routines to improve testing capability. The goal is to identify low velocity inclusions (air-filled voids and notches) within solids using constructed velocity images. Finite element analysis is used to simulate the experiment in order to determine efficient data collection schemes. Comparable air-coupled ultrasonic signals are then collected through homogeneous and isotropic solid (PVC polymer) samples. Volumetric (void) and planar (notch) inclusions within the samples are identified in the constructed velocity tomograms for a variety of transducer configurations. Although there is some distortion of the inclusions, the experimentally obtained tomograms accurately indicate their size and location. Reconstruction error values, defined as misidentification of the inclusion size and position, were in the range of 1.5-1.7%. Part 2 of this paper set will describe the application of this imaging technique to concrete that contains inclusions.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.11
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• pp.1060-1066
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• 2007

When a high-energy ultrasound propagates through a solid body that contains a crack or a delamination, the two faces of the defect do not ordinarily vibrate in unison, and dissipative phenomena such as friction, rubbing and clapping between the faces will convert some of the vibrational energy to heat. By combining this heating effect with infrared imaging, one can detect a subsurface defect in material efficiently. In this paper a detection of the welding defect of thin SUS 304 plates using the UIR (ultrasonic infrared imaging) technology is described. A low frequency (20kHz) ultrasonic transducer was used to infuse the welded thin SUS 304 plates with a short pulse of sound for 280ms. The ultrasonic source has a maximum power of 2kW. The surface temperature of the area under inspection is imaged by a thermal infrared camera that is coupled to a fast frame grabber in a computer. The hot spots, which are a small area around the defect tip and heated up highly, are observed. From the sequence of the thermosonic images, the location of defective or inhomogeneous regions in the welded thin SUS 304 plates can be detected easily.

• Korea-Australia Rheology Journal
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• v.17 no.2
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• pp.87-95
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• 2005

In this study, we performed RTD measurement at the die exit of co-rotating twin-screw extruder using a non-destructive ultrasonic device. The ultrasonic device was attached at slit die and was composed of a steel buffer rod and 10 MHz longitudinal piezoelectric ultrasonic transducer. This in-line ultrasonic monitoring method is based on the ultrasonic response of $CaCO_3$ filled in polymer. The RTD is evaluated by variation of ultrasonic attenuation with time caused by change of the tracer concentration during extrusion. The ultrasonic tracer, pellet type of compounded $CaCO_3$ in polymer was used in this study. The effects of tracer concentration on RTD and flow patterns were studied. Evaluation for the residence functions at different screw speeds, feeding rates and screw configurations were also carried out.