• Medical Lasers
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• 제10권3호
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• pp.146-152
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• 2021

Background and Objectives Although lasers have been widely applied in tissue treatment, the light penetration depth in tissues is limited by the tissue turbidity and affected by its absorption and scattering characteristics. This study investigated the effect of using an optical clearing agent (OCA) on tissue to improve the therapeutic effect of 1064 nm wavelength laser light by reducing the heat generated on the skin surface and increasing the penetration depth. Materials and Methods A diode laser (λ = 1064 nm) was applied to a porcine specimen with and without OCA to investigate the penetration depth of the laser light and temperature distribution. A numerical simulation using the finite element method was performed to investigate the temperature distribution of the specimen compared to ex-vivo experiments using a thermocouple and double-integrating sphere to measure the temperature profile and optical properties of the tissue, respectively. Results Simulation results showed a decrease in tissue surface temperature with increased penetration depth when the OCA was applied. Furthermore, both absorption and scattering coefficients decreased with the application of OCA. In ex-vivo experiments, temperatures decreased for the tissue surface and the fat layer with the OCA, but not for the muscle layer. Conclusion The use of an OCA may be helpful for reducing surface heat generation and enhance the light penetration depth in various near-infrared laser treatments.

• 대한의용생체공학회:의공학회지
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• 제20권2호
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• pp.199-204
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• 1999

생체조직내의 정확한 광선량 측정이 PDT 치료의 효과에 중요한 영향을 주므로 본 연구에서는 광선량 측정을 위해서 Monte Carlo 시뮬레이션을 이용하였다. 실험에 사용한 계수는 실제 생체조직의 광학계수이고 위상함수는 Henyey-Greenstein 위상함수를 사용하였다. 결과는 깊이에 따른 Fluency rate의 변화로 나타내었으며 기존 이론과의 차이는 0.35%에 지나지 않았다. 실험에 사용한 생체조직은 인체조직, 돼지조직, 쥐간조직, 토기근육조직이다. 대부분의 생체조직은 가시광선영역에서 큰 산란계수를 가지고 있으며 이것은 투과도에 큰 영향을 미치는 것으로 밝혀졌다. 가시광선 영역에서 인체조직의 투과 깊이는 1.5~2cm이었다. Monte Carlo 시뮬레이션을 이용하여 생체조직내의 광전파(light propagation), 광선량(light dosimetry), 에너지율(fluence rate), 투과깊이(penetration depth)를 효과적으로 측정할 수 있음을 보여주었다.

• The Journal of Korean Physical Therapy
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• 제23권6호
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• pp.77-84
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• 2011

Purpose: The objectives of this study were to determine the enhancing effect of iontophoresis method as it transdermally deliver methylene blue (MB) using visual examination, in terms of penetration depth and tissue distribution in the skin, and to determine the effect of application duration on the efficacy of iontophoresis. Methods: Twenty-four male Sprague-Dawley rats were randomly divided into 5-, 10-, 20-, and 40-minute groups. These rats were exposed to either topical or anodic iontophoresis of 1% MB using a direct current of $0.5mA/cm^2$ for 5, 10, 20, and 40 minutes. Using cryosections of rat tissues, the penetration depth of MB was measured using light microscopy. Results: Significant differences in the penetration depth (F=54.20, p<0.001) were detected among the four groups. Post hoc comparisons of the penetration depth of MB data pooled across groups showed no significant difference between all topical application groups and 5-minute iontophoresis group, but did reveal a significant difference in the penetration depth between all topical application groups and 5-minute iontophoresis group versus 10-minute group, between the 10-minute and 20-minute group, and between the 20-minute and 40-minute iontophoresis group (p<0.05). Conclusion: The results demonstrate that iontophoresis enhances transdermal delivery of MB across stratum corneum of skin barrier by visual examination. Furthermore, the penetration depth of iontophoretic transdermal delivery of MB was dependent on the application duration. The duration of iontophoresis is one of the important factor in the efficacy of iontophoresis application.

• 대한물리의학회지
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• 제9권2호
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• pp.133-140
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• 2014

PURPOSE: The purpose of this study was to compare the effect of current density on penetration depth, tissue concentration and transdermal transport of methylene blue(MB) by iontophoretic transdermal delivery. METHODS: Twenty-four male Sprague-Dawley rats were randomly divided into 1 mA($0.11mA/cm^2$), 2 mA($0.22mA/cm^2$), 4 mA($0.44mA/cm^2$), and 8 mA($0.89mA/cm^2$) groups. These rats were exposed to anodic iontophoresis of 1% MB using a direct current for 15 minutes. The penetration depth were measured using light microscopy from cryosections of skin tissue. The tissue concentration and transdermal transport were measured using biochemical analysis from target skin tissues. The data were analyzed with one-way analysis of variance. RESULTS: The significant differences in the penetration depth, tissue concentration and transdermal transport were detected among the groups(p<.001). Post hoc comparisons of the penetration depth, tissue concentration and transdermal transport of he 2 mA, 4 mA, and 8 mA iontophoresis groups were greater than in the 1 mA iontophoresis group(p<.05). There was no significant difference, however, among 2 mA, 4 mA, and 8 mA iontophoresis group. CONCLUSION: There was no difference in the efficiency of iontophoresis from 2 mA($0.22mA/cm^2$) to 8 mA($0.89mA/cm^2$). Higher current density can cause skin injury and discomfort sensation. In general, $0.5mA/cm^2$ is proposed to be the maximum iontophoretic current which should be used on human. The appropriate current amplitude should be selected by considering the safety current density and the depth of the target tissue.

• Restorative Dentistry and Endodontics
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• 제10권1호
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• pp.161-168
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• 1984

The purpose of this study was to examine the effect of heat generated by rotating bur on the dental hard tissue in vitro. Freshly extracted molar teeth with normal appearance from early 20's male were collected and experimental teeth were divided into 4 groups and the teeth in each group were prepared class I cavity with different clinical procedures as follows. The four methods were. I. 20,000rpm without coolant II. 20,000rpm with coolant III. 500,000rpm without coolant IV. 500,000rpm with coolant Five teeth were reserved intact as a control group. These teeth were longitudinally split into two parts by means of chisel after class I cavity preparation. In a control group 5 parts were boiled in water for 20 minutes and the other 5 specimens were not boiled. All specimens were immersed in 2% methylene blue dye solution and the image of dye penetration was examined and photographed under stereomicroscope. Followings were the results obtained through the study. 1. In control group, dye penetration of the unboiled specimens was increased than with the boiled group. 2. The specimens prepared cavity without coolant showed decreased dye penetration than with the coolant group. 3. 20,000rpm without coolant group showed the least dye penetration. 4. 500,000rpm with coolant group showed similar level of dye penetration to the unboiled specimens from the control group.

• Journal of Microbiology and Biotechnology
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• 제32권9호
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• pp.1209-1216
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• 2022

To better understand the effects of PEGylation and biotinylation on the delivery efficiency of proteins, the cationic protein lysozyme (LZ) and anionic protein bovine serum albumin (BSA) were chemically conjugated with poly(ethylene glycol) (PEG) and biotin-PEG to primary amine groups of proteins using N-hydroxysuccinimide reactions. Four types of protein conjugates were successfully prepared: PEGylated LZ (PEG-LZ), PEGylated BSA (PEG-BSA), biotin-PEG-conjugated LZ (Bio-PEG-LZ), and biotin-PEG-conjugated BSA (Bio-PEG-BSA). PEG-LZ and Bio-PEG-LZ exhibited a lower intracellular uptake than that of LZ in A549 human lung cancer cells (in a two-dimensional culture). However, Bio-PEG-BSA showed significantly improved intracellular delivery as compared to that of PEG-BSA and BSA, probably because of favorable interactions with cells via biotin receptors. For A549/fibroblast coculture spheroids, PEG-LZ and PEG-BSA exhibited significantly decreased tissue penetration as compared with that of unmodified proteins. However, Bio-PEG-BSA showed tissue penetration comparable to that of unmodified BSA. In addition, citraconlyated LZ (Cit-LZ) showed reduced spheroid penetration as compared to that of LZ, probably owing to a decrease in protein charge. Taken together, chemical conjugation of targeting ligands-PEG to anionic proteins could be a promising strategy to improve intracellular delivery and in vivo activity, whereas modifications of cationic proteins should be more delicately designed.

• 대한방사선기술학회지:방사선기술과학
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• 제39권2호
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• pp.157-161
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• 2016

본 연구에서는 자체 제작한 3종의 초음파 TM 팬텀의 음향학적 특성 및 온도 민감도를 측정하였으며, 초음파 영상학적 특성을 관찰, 평가하였다. TM 팬텀은 폴리우레탄을 주재료로 국제전기표준회의(International Electronical Committee, IEC) 기준안에 따라 제작하였으며 외부 온도 변화 따른 초음파 영상학적 특성은 $22^{\circ}C$ 이하에서 온도감소에 따라 휘도 및 영상투과심도가 비례하여 감소하는 것이 확인되었다. 본 연구를 통하여 산란재 특성이 상이한 TM 팬텀을 제작하는 기초자료를 제공하였으며, TM 팬텀의 사용 온도는 $22^{\circ}C$ 이상에서 사용하는 것이 적합한 것으로 판단되었다.

• 대한방사선기술학회지:방사선기술과학
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• 제33권3호
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• pp.245-252
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• 2010

본 연구는 주제인 폴리우레탄(polyurethane, PU)과 새로운 형태의 n-type 산란재를 사용하여 합성한 조직모사물질(tissue mimicking materials : TMM)에 대해 국제표준규격 IEC 60601-2-37(2007)의 Annex D.D가 권고한 인체 연조직(soft tissue)의 음향학적 특성 기준에 준해, 전파속도, 임피던스, 감쇠계수 특성 등을 분석하였으며, 영상특성은 SONOACE 9900C PRIME(MEDESON Co.), 3.5 MHz 컨벡스 프로브(2.5-5.0 MHz)로 초음파 휘도와 최대투과심도를 분석 평가하여 다음과 같은 결론을 얻었다. 주제인 prepolymer와 polyol mixture를 혼합하고 n-type 산란재를 0~8%로 점차 증가하여 합성하였을 때, 1. 조직모사물질의 전파속도는 산란재가 증가할수록 연조직에 더 가깝게 수렴(convergence)하였다. 2. 음향임피던스는 산란재가 감소할수록 연조직에 더 가깝게 수렴하였다. 3. 감쇠계수는 산란재가 증가할수록 증가하였다. 4. 영상 평균휘도는 산란재가 증가할수록 증가하였으나 역치가 있었다. 5. 최대투과심도는 산란재 6% 조직모사물질에서 연조직에 가깝게 수렴하였다.

• The Journal of Korean Physical Therapy
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• 제22권6호
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• pp.77-83
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• 2010

Purpose: The aim of this study was to do numerical analysis of the wavelength dependence in low level laser therapy (LLLT) using a finite element method (FEM). Methods: Numerical analysis of heat transfer based on a Pennes' bioheat equation was performed to assess the wavelength dependence of effects of LLLT in a single layer and in multilayered tissue that consists of skin, fat and muscle. The three different wavelengths selected, 660 nm, 830 nm and 980 nm, were ones that are frequently used in clinic settings for the therapy of musculoskeletal disorders. Laser parameters were set to the power density of 35.7 W/$cm^2$, a spot diameter of 0.06 cm, and a laser exposure time of 50 seconds for all wavelengths. Results: Temperature changes in tissue based on a heat transfer equation using a finite element method were simulated and were dominantly dependent upon the absorption coefficient of each tissue layer. In the analysis of a single tissue layer, heat generation by fixed laser exposure at each wavelength had a similar pattern for increasing temperature in both skin and fat (980 nm > 660 nm > 830 nm), but in the muscle layer 660nm generated the most heat (660 nm ${\gg}$ 980 nm > 830 nm). The heat generation in multilayered tissue versus penetration depth was shown that the temperature of 660 nm wavelength was higher than those of 830 nm and 980 nm Conclusion: Numerical analysis of heat transfer versus penetration depth using a finite element method showed that the greatest amount of heat generation is seen in multilayered tissue at = 660 nm. Numerical analysis of heat transfer may help lend insight into thermal events occurring inside tissue layers during low level laser therapy.

• Journal of the Optical Society of Korea
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• 제17권2호
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• pp.205-212
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• 2013

Pain is one of the quite common symptoms in clinics and many treatment methods have been applied to relieve pain. Among the treatments, high-intensity light therapy for pain has been introduced, but this therapy has not been fully supported by confirmed efficacy due to the absence of quantitative assessments and treatment feedback data in real time. In this study, the evaluation of light distribution in tissue was performed with current high-intensity light sources quantitatively using light-tissue interaction simulations. The diffuse reflectance in tissue was generated using Monte Carlo simulation that traces photons as they undergo multiple scattering and absorption within each tissue layer (skin, fat, and muscle) and within multi-layered tissue. The results showed that the highest diffuse reflectance and the deepest penetration of tissue were achieved at ${\lambda}$=830 nm when compared with other wavelengths like ${\lambda}$=650 nm, 980 nm and 1064 nm.