Si-Cheol Noh

Study on Changes in Shape of Denatured Area in Skull-mimicking Materials Using Focused Ultrasound Sonication

Recently, ultrasound therapy has become a new and effective treatment for many brain diseases. Therefore, skull-mimicking phantoms have been developed to simulate the skull and brain tissue of a human and allow further research into ultrasound therapy. In this study, the suitability of various skull-mimicking materials(HDPE, POM C, Acrylic) for studies of brain-tumor treatments was evaluated using focused ultrasound. The acoustic properties of three synthetic resins were measured. The skull-mimicking materials were then combined with an egg white phantom to observe the differences in the ultrasound beam distortion according to the type of material. Highintensity polyethylene was found to be suitable as a skull-mimicking phantom because it had acoustic properties and a denatured-area shape that was close to those of the skull,. In this study, a skull-mimicking phantom with a multi-layer structure was produced after evaluating several skullmimicking materials. This made it possible to predict the denaturation in a skull in relation to focused ultrasound. The development of a therapeutic protocol for a range of brain diseases will be useful in the future.

The study of correlation between foot-pressure distribution and scoliosis

The foot-pressure while walking represents the status of the geometrical balance of the human’s musculoskeletal system. The foot-pressure in unbalanced anatomical position causes physiological disorders to the human body and accumulates stress to the musculoskeletal system. Repetitious abnormal impacts become the direct cause of vertebrae disease. The purpose of this study is to evaluate the correlation between the degree of scoliosis and the foot-pressure distribution in twenty males who have no clinical history of vertebral disease. The F-scan system(Tekscan Inc., USA, 850Hz sampling frequency) was used to measure the foot-pressure. The sole was divided into 7 regions of interest(ROI), and an analysis was performed for these ROIs. The degree of scoliosis was expressed as the angle, calculated with X-ray image, which showed lumbar vertebra number 5 to thoracic vertebra number 7. This angle was used to evaluate the correlations with the result of the foot-pressure analysis. Measurement of footpressure on the subjects was executed using the same protocol. The correlation between the measured foot-pressure and the degree of scoliosis was evaluated under a 0.05 level of significance. The results of the evaluation revealed the tendency that, as the degree of scoliosis increases, a difference in footpressure also increases. The variables used for analysis showed high correlations. The obtained results will be used to determine the occurrence of vertebra and lower limb disease and to present a qualitative evaluation basis for the rehabilitation of patients with lower limb disease.

The Study on Design of Customized Radiation Protective Layer for Medical Radiation Dose Reduction

Abstract The fact is that in addition to an increase in social needs that must be managed systematically unnecessary exposure in the field of medical Recent important that the shield has emerged. However, products that are now in practical use, are not subdivided as compared to various medical radiology. Therefore, in the present study, we tried to present with the help of Monte Carlo simulation the structure of the shielding material that has been optimized. Simulated estimation result, the energy of the mammography for (30 kVp) spectrum, check the shielding rate of 90% or more 30μmPb, at 2 mmAl case of shielding material of a single, at design time of 1 mmAl and 0.03 mmPb a double shield structure it is determined that more efficient. Also, check the blocking rate of 90% or more 340μmPb, at 30 mmAl energy captured general in (80 kVp) spectra, it is considered that a double shield structure, design 1 mmAl and 0.3 mmPb is useful . These results, be used as basic material for the development of commercialization customized products for dose reduction is expected.

Thermal characteristics of non-biological vessel phantoms for treatment of varicose veins using high-intensity focused ultrasound

The ultrasonic treatment of varicose veins uses high-intensity focused ultrasound, in which a blood vessel is contracted by converting acoustic energy into thermal energy. In this study, we propose a phantom of varicose veins that can be applied for the efficient evaluation of ultrasonic treatment in varicose veins. The proposed phantom consisted of glycerol base tissue equivalent material, vessel mimic tube, and blood mimic substances. The vessel mimic tube was placed inner glycerol phantom and it was filled with blood mimic substances. Blood-mimicked substances are prepared by adjusting the concentration of the glycerol solution to be similar to the acoustic properties of the blood, and vessel-mimicking materials are selected by measuring acoustic properties and thermal shrinkage of various materials in a heat-shrinkable tube. The blood vessels surrounding the tissue are replaced with the phantom similar to glycerol-based organization, and venous blood flow is implemented using a DC motor. The heating characteristics according to the ultrasonic wave using the manufactured varicose veins phantom were evaluated. As the sound wave irradiation time and power increased, the contractility of the vessel mimicking materials and the temperature of the surrounding tissues were increased. When the blood-mimicking material was circulated, the highest temperature in the focused region and the contractility of vessel mimicking materials were reduced under the same conditions as used for sonication. The manufactured phantom may contribute to the treatment of varicose veins and can be used to predict the ultrasonic therapeutic efficiency of varicose veins.

Evaluation of Acoustic, Thermal, and Morphological Properties in the Egg White Phantom

The egg white phantom is a thermal lesion visualization phantom able to illustrate a thermal lesion. It is often used to evaluate the performance of HIFU and is less expensive than the BSA phantom. This study determined the optimal phantom composition for evaluated therapeutic ultrasound machines by varying the egg white concentration in the egg white phantom and demonstrated its utility as a therapeutic ultrasound phantom. The egg white phantom at varying egg white concentrations (10-40% in 10% intervals) was fabricated, and its thermal properties and acoustic properties were assessed. In addition, the size and shape of the formed lesion were compared between the egg white phantom and bovine liver tissue according to the electrical power. The results showed that 30% egg white phantom was optimal for the performance evaluation due to its thermal and acoustic properties. The generated thermal lesions formed sequentially as a cigar, ellipse, tadpole, and cone shapes according to the electrical power; a similar tendency was observed in the liver tissue. Hence, we conclude that the egg white phantom will prove useful in quantitatively evaluating the thermal effects of therapeutic ultrasound.

A Study on the Safety and Performance Test Guideline of Low Intensity Therapeutic Ultrasound Device

In this study, we suggested the performance and safety testing guideline for low intensity pulsed ultrasound (LIPUS) represented by the ultrasound fracture treatment device and cartilage treatment device and low intensity focused ultrasound (LIFU) represented by ultrasonic face lifting device. For these study, the international standards and management regulations of Korea, Japan and United State were analyzed. And the usefulness and applicability were evaluated by testing with commercial equipment and reflecting the views of the industry and experts. As a result of this study, the safety and performance test guidelines for low intensity therapeutic ultrasound device were proposed by presenting the 10 items for LIPUS and 12 items for LIFU. The suggested guidelines are considered a high utilization in the domestic testing and approval authorities. And they are also thought to be useful to new technology development.

Quantitative Rehabilitation Extent Monitoring for Unilateral Lower Extremity Disabled Patients using Simulated Gait Pattern Analysis

Abstract: In this paper, to quantitatively evaluate the degree of rehabilitation for the disabled of unilateral lowerextremity, we compared the EMG pattern of normal and simulated abnormal gait. The EMG signal was measuredat a rate of 1 kHz on the quadriceps and biceps femoris, the pressure sensor was attached to the sole in order todistinguish the gait cycle. Integrated EMG (IEMG) was obtained by the gait cycle, and classified four patterns thatwere the normal gait pattern, amplitude decrease pattern, reversed pattern, and irregular pattern. For comparisonof the patterns, a curve fitting was performed using the trigonometric functions. The result of curve fitting, themethod using a variable A that corresponds to the amplitude of the regression curve was able to distinguish thereverse pattern and remaining pattern. The coefficient of determination (R 2 ) representing coincidence of the patternof the regression curve and EMG was confirmed the biggest value at the normal gait. Therefore, the degree of normalgait can be confirmed using the coefficient of determination. This results show that it is possible to quantitativelyconfirm the degree of unilateral lower extremity disabled rehabilitation, and it will be contributed to the study of effi-cient rehabilitation methods by objective analysis.Key words: Gait analysis, IEMG, Curve fitting, Comparison of EMG pattern, Evaluation of rehabilitation

Ultrasonic Cavitation Effect Observation Using Bubble Cloud Image Analysis

In this study, in order to evaluate the yield of bubble by ultrasonic cavitation in HIFU sonication, the bubble image analysis was performed. The changing phenomenon of cavitation effect according to the sonication condition was discussed by analyzing the bubble image. Especially the appearance of bubble cloud, the size of micro-bubble, and the yield of bubble were considered. The 500 KHz and 1.1 MHz concave type ultrasonic transducers were used for HIFU sonication. Computer controlled digital camera was used to obtain the bubble image, and the binary image processing(binarization coefficient : 0.15) was performed to analyze them. In results of 500 KHz and 1.1 MHz transducer, the area of bubble cloud was increased in proportion to the rise in sonication intensity( : 0.7031 and 0.811). The mean size of single microbubble was measured as 98.18 um in 500 KHz sonication, and 63.38 um in 1.1 MHz sonication. In addition, the amount of produced bubble was increased in proportion to sonication intensity. Through the result of this study and further study for variable image processing method, the quantitative evaluation of ultrasonic cavitation effects in HIFU operation could be possible with the linearity associated with the sonication conditions.

Quantitative evaluating method for diagnostic ultrasound probe using 3-dimensional acoustic field analysis

In this study, in order to overcome the weakness of acoustic field analysis which is generally used for ultrasonic probe performance evaluation, automatic acoustic field measurement system and evaluation parameters were proposed. The comparisons between acoustic field simulation and measured acoustic distribution data of normal and abnormal channels were conducted to evaluate the availability of proposed system and evaluation parameters. First, the impulse response characteristic of sample probe was investigated to classify the normal elements and abnormal elements. And then, normal channels and abnormal channels with abnormal element were chosen. The suggested 12 evaluation parameters were calculated using the acoustic fields of these channels. The availability of proposed automatic acoustic field measurement system and evaluation parameters was confirmed. And the performance evaluation of ultrasonic probe using acoustic field analysis could be easier and faster.

Ultrasound field measuring using hydrophone for quantitative evaluation of medical ultrasonic probe

The quality of ultrasonic images is crucially affected by the applied ultrasonic probe; thus, it is necessary to evaluate the ultrasonic probe to achieve optimal performance. In this paper, the 3D acoustic field analysis method using a hydrophone, one of the probe evaluation methods, was performed, and the efficacy of this evaluation method for quantitative evaluation was evaluated. To acquire the acoustic field distribution of ultrasound at 7.5 MHz, a 128-multi-element medical ultrasonic array probe, that is considered to be inferior, was attached to a shaft. The shaft could be controlled in the x, y, and z directions. The hydrophone was attached in a water bath. The acoustic field distribution of each channel was displayed, and some parameters such as maximum acoustic pressure, the volume of -3dB field, and the symmetry of acoustic field were calculated. Using these parameters, the acoustic fields of normal, abnormal and simulated channels were compared. Comparing acoustic field characteristics of each channel proves that the proposed 3D acoustic field parameters are reliable and efficient to assess the performance of the ultrasonic probe.