Japanese Society for Medical and Biological Engineering Acta Medica Okayama 2187-5219 15 2026 Verification of a Skin Electrical Impedance Model for Evaluating Indicators of Skin Barrier Function of Older Adults 160 164 EN Osamu UEHARA Medical Engineering Laboratory, ALCARE Co., Ltd. Yuya FUNAKI Medical Engineering Laboratory, ALCARE Co., Ltd. Takao NAKAMURA Department of Radiological Technology, Graduate School of Health Sciences, Okayama University Skin barrier function has been quantitatively evaluated through trans-epidermal water loss, which has been difficult to measure in clinical settings owing to environmental factors and the measurement time. The thickness and surface water content of the stratum corneum are important indicators of skin barrier function, and current methods for measuring these two indicators are also difficult to implement in clinical settings. Therefore, we developed a model based on skin electrical impedance to estimate the thickness and water content of the stratum corneum, enabling measurement and estimation of these two indicators in a short time. In this study, we verified this model implemented in a portable skin electrical impedance measurement device for estimating the thickness and surface water content of the stratum corneum of the skin in older adults. Thirty-four older individuals were studied. The measurement electrodes were placed in contact with the forearm skin, and an alternating signal of two frequencies was applied to measure the impedance, from which the thickness and surface water content of the stratum corneum were estimated in approximately 5 s. The correlation coefficients between the estimated and measured thickness and between the estimated and measured surface water content were 0.732 and 0.604, respectively. Furthermore, the root mean square errors of the residuals for the thickness and surface water content were 1.66 µm and 3.50 points, respectively, indicating that the model accurately estimated the thickness and surface water content of the stratum corneum, even in the skin of older adults. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 1609-0985 2025 An Alternative Approach Based on Skin Electrical Impedance to Determine Transepidermal Water Loss for Skin Barrier Function Assessments EN Osamu Uehara Department of Radiological Technology, Graduate School of Health Sciences, Okayama University Takao Nakamura Department of Radiological Technology, Graduate School of Health Sciences, Okayama University Purpose: The transepidermal water loss (TEWL) has long been measured as an indicator to assess the skin barrier function in dermatological research and clinical practice. However, practical limitations such as time requirement, environmental sensitivity, and measurement complexity hinder the widespread uptake of conventional TEWL measurements in clinical settings and routine monitoring. Consequently, there is a growing need for rapid, robust, and clinically applicable alternatives to conventional TEWL measurements. Here, we present a simple, non-invasive, and time-efficient method based on the skin electrical impedance for skin barrier function assessments. Methods: The skin electrical impedance, TEWL, stratum corneum (SC) thickness, and SC surface water content of 25 healthy adult participants with no history of dermatological diseases were measured at two adjacent forearm sites: intact site with a normal skin barrier and tape-stripped site with an impaired skin barrier. The measured impedance was used to calculate the SC thickness and surface water content, from which the TEWL was estimated and then compared against the TEWL measured using a Tewameter. The estimation accuracy was evaluated by determining the correlation coefficient (R) and root mean square error (RMSE) between estimated and measured TEWL. Results: A strong correlation (R = 0.891) was observed between estimated and measured TEWL, with an RMSE of 6.05 g/m²/h, indicating high accuracy of the proposed method. Conclusion: This impedance-based method provides accurate estimations of the TEWL, indicating its potential as a practical alternative to conventional TEWL measurements for skin barrier function assessments, particularly in clinical or high-throughput settings. No potential conflict of interest relevant to this article was reported.

Japanese Society for Medical and Biological Engineering Acta Medica Okayama 2187-5219 12 2023 Transepidermal Water Loss Estimation Model for Evaluating Skin Barrier Function 1 8 EN Osamu Uehara Medical Engineering Laboratory, ALCARE Co., Ltd. Toshimasa Kusuhara Department of Radiological Technology, Graduate School of Health Sciences, Okayama University Takao Nakamura Department of Radiological Technology, Graduate School of Health Sciences, Okayama University Deterioration of skin barrier function causes symptoms such as allergies because it allows various chemical substances to enter the human body. Quantitative evaluation of the thickness and water content of the stratum corneum is useful as a measure of skin barrier function in fields such as dermatology, nursing science, and cosmetics development. The stratum corneum is responsible for most of the skin barrier function, and this function has conventionally been evaluated using transepidermal water loss (TEWL). In this paper, we propose a new model for estimation of TEWL from measurements of the thickness of the stratum corneum and water content of the surface of the stratum corneum, and discuss the results of the measurements. By measuring the thickness and water content of the stratum corneum using confocal laser microscopy and confocal Raman spectroscopy, respectively, and examining the relationship of these variables with TEWL, we established a new potential model for estimating TEWL from these two variables. The correlation coefficient of the validation data was 0.886 and the root mean squared error was 8.18 points. These findings indicate the feasibility of qualitative evaluation of TEWL by measuring the thickness and water content of the stratum corneum. No potential conflict of interest relevant to this article was reported.

Japanese Society for Medical and Biological Engineering Acta Medica Okayama 2187-5219 11 2022 Skin Electrical Impedance Model for Evaluation of the Thickness and Water Content of the Stratum Corneum 98 108 EN Osamu Uehara Medical Engineering Laboratory, ALCARE CO., Ltd. Toshimasa Kusuhara Department of Radiological Technology, Graduate School of Health Sciences, Okayama University Kenichi Matsuzaki Medical Engineering Laboratory, ALCARE CO., Ltd. Yoshitake Yamamoto Okayama University Takao Nakamura Department of Radiological Technology, Graduate School of Health Sciences, Okayama University Deterioration of the skin barrier function causes symptoms such as allergies because various chemical substances may enter the human body. Quantitative evaluation of the thickness and water content of the stratum corneum is useful as a measure of the skin barrier function in domains such as dermatology, nursing science, and cosmetics development. The stratum corneum is responsible for most of the skin barrier function, and two factors—the thickness and water content of the stratum corneum—are thus important. In this paper, the stratum corneum is regarded as a parallel model of resistance and capacitance. From measurements of the electrical impedance of the skin, we propose a new model for simultaneous estimation of the thickness and water content of the stratum corneum conventionally measured by a confocal laser scanning microscope and a confocal Raman spectrometer, respectively, and we discuss the results of the measurements. The electrical impedance of the skin was measured using a device that we developed. The measurement began 3 seconds after the electrodes on the measurement head of the device came into contact with the skin, and parameters including the impedance, which was obtained by applying an alternating current signal at two frequencies, were measured. We measured the thickness and water content of the stratum corneum using confocal laser microscopy and confocal Raman spectroscopy, respectively; investigated the relationship of the thickness and water content of the stratum corneum with the electrical impedance of the skin; and established a new potential model for estimating the thickness and water content of the stratum corneum from the parallel resistance and capacitance. The correlation coefficients of the verification data were 0.931 and 0.776, respectively; and the root-mean-squared error of the thickness of the stratum corneum was 2.3 µm, while the root-mean-squared error of the water content at the surface of the stratum corneum was 5.4 points. These findings indicate the feasibility of quantitative evaluation of the thickness and water content of the stratum corneum by measuring skin electrical impedance. No potential conflict of interest relevant to this article was reported.

Cureus Inc. Acta Medica Okayama 2168-8184 13 12 2021 Evaluation of Skeletal Muscle Dysfunction Associated With Acute Inflammation by Electrical Impedance Myography: A Case Report on Skeletal Muscle Dysfunction After Cardiac Surgery and Literature Review e20166 EN Hiroki Sato Department of Radiological Technology, Graduate School of Health Sciences, Okayama University Takao Nakamura Graduate School of Health Sciences, Okayama University Electrical impedance myography (EIM) is an evaluation technique for skeletal muscles that uses electrical impedance technology. Recent reviews have shown that EIM is useful as a method to assess changes in skeletal muscle quality and quantity with aging. These may be utilized for functional changes in inflammatory skeletal muscles, such as disease and operation. In this report, the impedance parameters using EIM present perioperative skeletal muscle changes in patients after cardiac surgery. In addition, we will describe the efficacy of EIM in skeletal muscle dysfunction due to inflammation or disease. This study aimed to elucidate the efficacy of EIM in acute inflammation-associated skeletal muscle dysfunction. No potential conflict of interest relevant to this article was reported.

Springer Acta Medica Okayama 1880-6546 70 1 2020 Effectiveness of impedance parameters for muscle quality evaluation in healthy men 53 EN Hiroki Sato Department of Radiological Technology, Graduate School of Health Sciences, Okayama University Takao Nakamura Department of Radiological Technology, Graduate School of Health Sciences, Okayama University Toshimasa Kusuhara Department of Radiological Technology, Graduate School of Health Sciences, Okayama University Kobara Kenichi Department of Physical Therapist, Faculty of Rehabilitation, Kawasaki University of Medical Welfare Katsushi Kuniyasu Department of Physical Therapist, Faculty of Rehabilitation, Kawasaki University of Medical Welfare Takaki Kawashima Department of Physical Therapist, Kawasaki Junior College of Rehabilitation Kozo Hanayama Department of Rehabilitation Medicine, Kawasaki Medical School, 577, Matsushim We investigated the relationship between impedance parameters and skeletal muscle function in the lower extremities, as well as the effectiveness of impedance parameters in evaluating muscle quality. Lower extremity impedance of 19 healthy men (aged 23–31 years) measured using the direct segmental multi-frequency bioelectrical impedance analysis were arc-optimized using the Cole–Cole model, following which phase angle (PA), Ri/Re, and β were estimated. Skeletal muscle function was assessed by muscle thickness, muscle intensity, and isometric knee extension force (IKEF). IKEF was positively correlated with PA (r = 0.58, p < 0.01) and β (r = 0.34, p < 0.05) was negatively correlated with Ri/Re (r = − 0.43, p < 0.01). Stepwise multiple regression analysis results revealed that PA, β, and Ri/Re were correlated with IKEF independently of muscle thickness. This study suggests that arc-optimized impedance parameters are effective for evaluating muscle quality and prediction of muscle strength. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 3 1995 Automatic sensing device of electrical characteristics of living trees 729 732 EN Yoshitake Yamamoto Hiroshi Harada Kiyotaka Yasuhara Takao Nakamura The electrical impedance of a living tissue reflects its cell construction and physiological activity. For this purpose we developed an automatic sensing device of electrical tissue characteristics. The system is composed of a part measuring impedance at multifrequency points and a part analyzing parameters of dispersion of bioelectrical impedance, impedances are measured at eight frequency points of 1 kHz-500 kHz. The parameters for Cole-Cole arc's law are determined automatically by a personal computer program No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 45 1996 Instantaneous measurement of electrical parameters in a palm during electrodermal activity 483 487 EN Yoshitake Yamamoto Hiromi Isshiki Takao Nakamura The determination of impedance can be performed by means of a frequency-domain analysis or a time-domain analysis. The latter has the advantage of being able to measure instantaneously all the frequency characteristics of impedance. The method is hence well suited to obtain the biological impedance which changes with time. An instantaneous method of measuring skin impedance, by using time-domain analysis has thus been developed. The fast Fourier transform (FFT) of the step response for current to the skin can determine the palm impedance. This method can carry out the determination of the parameters of the palm skin impedance during a galvanic skin reflex (GSR), which is impossible by means of frequency-domain analysis No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 44 3 1995 Automatic sensing device of electrical characteristics of living trees 729 732 EN Yoshitake Yamamoto Hiroshi Harada Kiyotaka Yasuhara Takao Nakamura The electrical impedance of a living tissue reflects its cell construction and physiological activity. For this purpose we developed an automatic sensing device of electrical tissue characteristics. The system is composed of a part measuring impedance at multifrequency points and a part analyzing parameters of dispersion of bioelectrical impedance, impedances are measured at eight frequency points of 1 kHz-500 kHz. The parameters for Cole-Cole arc's law are determined automatically by a personal computer program No potential conflict of interest relevant to this article was reported.

IEEE Acta Medica Okayama 2003 Evaluating object and region of concentric electrode in bio-electrical impedance measurement 282 283 EN Yoshitake Yamamoto Kiyoko Shirai Noriko Goda Takao Nakamura Toshimasa Kusuhara Hiroyuki Okuda Concentric electrode is easy to use and used widely for measuring bio-electrical impedance. But, its evaluating region was not investigated in detail. Then, the characteristics of concentric electrode were studied from various points of view. In case of use without electrode paste, impedance is determined with the contacting condition between electrode and skin surface over all frequency range. In case of use with electrode past, impedance is composed of stratum corneum in the frequency range of 20 Hz-1 kHz and is mainly composed of subcutaneous tissue in the range of 200 kHz-1 MHz. In the high frequency range, evaluating region of concentric electrode is the area less than the radius or the gap of center electrode. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 45 2 1996 Instantaneous measurement of electrical parameters in a palm during electrodermal activity 483 487 EN Yoshitake Yamamoto Hiromi Isshiki Takao Nakamura The determination of impedance can be performed by means of a frequency-domain analysis or a time-domain analysis. The latter has the advantage of being able to measure instantaneously all the frequency characteristics of impedance. The method is hence well suited to obtain the biological impedance which changes with time. An instantaneous method of measuring skin impedance, by using time-domain analysis has thus been developed. The fast Fourier transform (FFT) of the step response for current to the skin can determine the palm impedance. This method can carry out the determination of the parameters of the palm skin impedance during a galvanic skin reflex (GSR), which is impossible by means of frequency-domain analysis No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1 1998 Consideration of conditions required for multi-channel simultaneous bioimpedance measurement 231 234 EN Yoshitake Yamamoto Takao Nakamura Toshimasa Kusuhara Mr. Adli Impedance techniques have been widely applied to the biomedical engineering field. In order to obtain definite results from bioimpedance, multi-channel measurement is effective. A linearity of biological tissue and fundamental technical parameters for the instrument must be confirmed. In this study, the fundamental conditions have been investigated for multi-channel bioimpedance measurement and the condition of measurement for biological tissue has been confirmed. The differences of every measurement frequency should be appropriate to 1 kHz and it has been shown that the linearity of biological tissue is maintained. Based on these results, a two-channel bioimpedance measurement instrument has been constructed No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 30 1 1995 Principle of Biodynamic Analysis Using Human Limb Electrical Impedance 19 24 EN Takao Nakamura Yoshitake Yamamoto 10.18926/15369 This paper describes a new measurement method and principle of detection of biodynamics using bioelectrical impedance method based on four-electrode technique with sinusoidal constant current. This method uses a human body itself as a part of the sensor. First, we show a bioelectrical impedance measuring device and the change of bioelectrical resistance is measured in human movement. Second, we proposes a principle of detection of biodynamics based on correspondence of magnitude, form and stability of movement to impedance waveform. Hence we can use this method for the judgement of sports skill using the impedance characteristics. No potential conflict of interest relevant to this article was reported.

岡山大学医学部保健学科 Acta Medica Okayama 1345-0948 12 1 2001 食道癌術後の嚥下感覚の変化に対する考察 ―頸部電気インピーダンスおよび嚥下音を用いた嚥下活動評価― 53 62 EN Keiko Mori Yoshitake Yamamoto Takao Nakamura Toshimasa Kusuhura 10.18926/15243 食道癌患者は腫瘍による狭窄のため,程度の差はあるものの,術前より通過障害を認めることが多い｡食道癌と診断され,手術を自己決定した患者の多くは,手術をして罹患前のように食事ができるようになりたいと思っている｡しかし,患者の多くが術後に嚥下感覚の変化に遭遇する｡現在,手術前に実施されるインフォームドコンセント(以下IC)では,術後に起こる嚥下感覚の変化については説明が行われていない｡そのため患者は,経口摂取が可能になった時点で嚥下感覚の変化を自覚し,強い不安を感じる｡今回, 5人の患者に術後の嚥下感覚の変化に関するインタビューを実施するとともに,術後の嚥下活動を頸部電気インピーダンスおよび嚥下音を用いて測定した｡インタビューの結果, 5人全てが,術後に嚥下感覚の変化を自覚し,不安を感じていた｡また,青年健常者と比較し,IPG波形の多相化と,嚥下音の咽頭期以外での発生が認められた｡患者が,術後に起こる嚥下感覚の変化についてのICを望んでいることからも,術後の嚥下感覚の変化についてのICを行なう必要がある｡ No potential conflict of interest relevant to this article was reported.

岡山大学医学部保健学科 Acta Medica Okayama 1345-0948 14 1 2003 浮腫評価のための体肢容積計の開発 31 35 EN Takao Nakamura Noriko Goda Kiyoko Shirai Toshimasa Kusuhara Yoshitake Yamamoto 10.18926/15205 周産期医学にとって浮腫の定量評価は重要である｡これまでは,測定部位の2箇所の周囲長をメジャーで測り,その変化により浮腫を評価している｡また周囲長により容積を推定する方法も提案されている｡しかしながら,この方法ではメジャーの測定部位への巻き付け方による誤差や容積を推定する根拠となる測定部位のモデル形状と実際の測定部位の形状との誤差など様々な誤差の影響により,精度の点からは十分とはいえない｡そこで,本研究では浮腫評価のための高精度で日常的な使用に適した体肢容積計を開発した｡この測定原理はアルキメデスの原理を適用したもので,水を入れた水槽に測定部位を入れる前後の質量変化により,その容積を量るしくみである｡まず,この容積計の出力の線形性,分解能,安定性,再現性について検討を行った｡この結果,本装置の仕様は最大計測容積25,000cm(3),分解能1cm(3),非直線性0.007%以下となり,非常に高精度であるといえる｡また,被験者3名の足部,下腿部の容積の日内変化を測定した結果,各被験者の容積変化の特徴を明らかにすることができ,浮腫評価への応用ができることを確認した。 No potential conflict of interest relevant to this article was reported.

岡山大学医学部保健学科 Acta Medica Okayama 1345-0948 14 2 2004 歩行能力の評価･訓練のための足踏み測定器の開発 135 139 EN Takao Nakamura Hitoshi Konishi Hiroaki Tsuji Toshimasa Kusuhara Yoshitake Yamamoto 10.18926/15199 日常生活で杖をついたり,老人車などを押したりなど歩行能力の低下した人に対する簡便･安価で効果的な歩行訓練方法,訓練機器はない｡歩行能力の低下した人が体の移動を伴う歩行訓練をする場合,常に転倒の危険性を伴うために,介護者が必要であったり,転倒の不安のために動作が消極的になり,訓練の効果が半減する｡これに対して,ゆっくりとした足踏みは歩行能力の低下した人に対しては下肢筋力の強化,バランス訓練となり,歩行能力を向上させる｡しかし,足踏みが適切におこなわれているか,訓練の効果の程度についての評価ができなかった｡そこで,歩行能力の評価･訓練のために足踏み状態をモニタすることができる足踏み測定器を開発した｡本装置は,足踏みをするマット2枚およびノートパソコンなどから構成されている｡足踏み中における両脚立脚,左右それぞれの片脚遊脚の状態をマットスイッチのON,OFF状態にて判断する｡測定後,歩数,平均両脚立脚時間,平均片肺立脚時間などの解析･表示を行う｡最後に歩行能力が低下した被験者の足踏みを測定して,杖歩行など日常の歩行状態と足踏みの状態との関係を示し,足踏み測定の有効性についても検討した｡ No potential conflict of interest relevant to this article was reported.

岡山大学医学部保健学科 Acta Medica Okayama 1345-0948 15 1 2004 インピーダンス咽頭図(IPG)を用いた加齢による嚥下機能減退の定量的評価法 1 7 EN Toshimasa Kusuhara Takao Nakamura Keiko Mori Yoshitake Yamamoto Yasuhiro Shirakawa Yoshio Naomoto 10.18926/15189 インピーダンス咽頭図(Impedance Pharyngography, 以下IPG)は嚥下活動中の頸部電気インピーダンスを測定するもので,嚥下機能評価を簡便かつ無侵襲に行うことができる手法である｡IPG波形は嚥下機能を反映するものであるが嚥下機能の減退による波形への影響はその原因により様々である｡すなわち嚥下機能の状態が異なる被験者のIPG波形を直接比較･診断することは測定者の主観に依存することになり客観性に欠ける｡本研究では,まず青年健常者のNormal IPGをもとに嚥下機能が反映される波形の特徴を評価するパラメータとして,咽頭通過時間,インピーダンス変化率,類似度,嚥下音タイミングの4つを採用し,IPCを定量的に評価する手法を提案した｡また,この評価法を高齢者のIPGに適用し,青年健常者に比べて嚥下活動に関与する器官が円滑に活動を履行する能力に減退が生じる様子を定量的に示した｡ No potential conflict of interest relevant to this article was reported.

岡山大学医学部保健学科 Acta Medica Okayama 1345-0948 17 1 2007 Quantitative evaluation of micromotion of cultured cells using electrical cell-substrate impedance sensing (ECIS) method - cell-to-cell distance and cell-to-substrate distance - 9 15 EN Noriko Goda Yoshitake Yamamoto Takao Nakamura Toshimasa Kusuhara Toshinori Maruyama 10.18926/15168 We have proposed a mathematical model for the micro-dynamics for cultured cells measured with ECIS system for the detection of nanometer-order dynamics of cells cultured on a small gold electrode and could separately evaluate cell-to-cell distance (A) and cell-to-substrate distance (h). For wide applications of this method, we constructed mathematical models which express cell-to-electrode impedances for some kinds of confluent conditions. Based on this mathematical model, we defined new parameters S(A) and S(h) in order to evaluate cell-to-cell distance and cell-to-substrate distance. As the application, we investigated the effect of X-irradiation to bovine aortic endothelial cell (BAEC). We analyzed the micro-dynamics of cells from the impedance of BAEC before and after X-irradiation. It was proved that the stimulation of 100 Gy X-irradiation to the BAEC resulted in the large scale of increase in the cell-to-cell distances (A), and the slight increase in the cell-to-substrate distances (h) accompany with continuous fluctuations. No potential conflict of interest relevant to this article was reported.

岡山大学医学部保健学科 Acta Medica Okayama 1345-0948 10 2 2000 Modelling of interface construction relating to power-line interference phenomenon in biopotential signal measurement system 107 115 EN Yoshitake Yamamoto Takao Nakamura 10.18926/11726 A modelling of interface construction relating to power-line interference phenomenon was described. Source of interference was displacement currents which flowed from AC power-line configuration (APC) to a model. The interference depends on some factors: distance between the APC and a model ; length of unshielded leads ; position of the APC in vertical or horizontal direction ; and skin-electrode impedances which were balance or unbalanced. The position of APC and skin-electrode impedances were important in contributing of the interference. The interference was still large even though skin-electrode impedances were balance. This was caused by the disagreement in two displacement currents. It was overcame by adjustment of APC in vertical direction. As a result, total interference would be very small or zero. The result shows that interference in ECG signal recording can be eliminated to about 10 μV. Although interference of power-lines is a complicated phenomenon, the problem is easier to understand by using this modelling. No potential conflict of interest relevant to this article was reported.

岡山大学医学部保健学科 Acta Medica Okayama 1345-0948 10 1 1999 上肢運動に伴う生体電気インピーダンスのパラメータの変動 15 22 EN Takao Nakamura Yoshitake Yamamoto 10.18926/11716 これまでに生体電気インピーダンスを用いて身体運動の解析を行ってきた。インピーダンスの変動原因は測定部位の等価断面積変化および貯血量変化と説明できるが，直接的に断面積変化や貯血量変化を測定することは困難であるため，その変動原因の定量的な検討は不十分であった。そこで，本研究では上肢運動に伴う生体電気インピーダンスの変動原因を生体の等価回路のパラメータの変動で説明する。インピーダンスのモデルはCole－Cole型であり，等価回路は，細胞外液抵抗Re，細胞内液抵抗Ri，分散の特性周波fm　fm，緩和時間の分布の程度を表すα，βの独立した5パラメータで表現した。上肢の肘関節および手関節の屈曲運動野に伴う前腕部および上腕部の電気インピーダンスを測定した。まず，電気インピーダンスの等価直列抵抗Rの変動率をパラメータの変動率で線形近似し，その信頼性と各パラメータ変動のRへの影響を確認した。Rへの影響はReとRiが支配的であるが，測定部位や運動の違いにより，それぞれの影響が異なることを示した。これは測定部位の筋活動状態の違いを表すものである。さらに，肘関節最大屈曲におけるRの変化にはfmの変化が大きく依存しており，上肢運動のインピーダンス変化には細胞膜の分極特性の変化も影響していることを明らかにした。本研究の結果は，運動強度の違いや疲労状態における身体運動評価に有意義である。 No potential conflict of interest relevant to this article was reported.

岡山大学医学部保健学科 Acta Medica Okayama 1345-0948 11 2 2001 流動血液の電気インピーダンスと透過光強度との関係 65 70 EN Takao Nakamura Yoshitake Yamamoto 10.18926/11688 流動する血液についての力学的，光学的および電気的な特性についての研究が数多く報告されている。本研究では，狭窄がある人工血管を流れる血液の電気インピーダンス（周波数10kHz）を近赤外光（波長940nm）の透過度と同時に測定し，血液の電気インピーダンスの特性について検討を行った。内径2mmのアクリル製の血管モデルを作製し，その内部に断面積の小さい狭窄部位を1ヵ所設置し，ヒトの血液（Hct40％）を流した。定常流においては血流速度の増加に伴いインピーダンスの相対変化量および透過光強度ともに減少した。しかし，狭窄部に近い部位では，インピーダンスと透過光強度の変化パターンに違いがみられた。インピーダンスおよび透過光強度は流動する血球の動きや配向等を反映していると考えられた。 No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1992 生体電気インピーダンスの身体運動解析への応用に関する研究 EN No potential conflict of interest relevant to this article was reported.