生体医工学
Online ISSN : 1881-4379
Print ISSN : 1347-443X
ISSN-L : 1347-443X
44 巻, 3 号
選択された号の論文の15件中1~15を表示しています
解説特集 クリニカルバイオインフォマティクス
研究
  • 岩瀬 英仁, 姫野 龍太郎, 加藤 陽子
    2006 年 44 巻 3 号 p. 428-434
    発行日: 2006年
    公開日: 2008/05/01
    ジャーナル フリー
    The numerical simulation system of hemodynamics has been developed for the purpose of advanced medicine. The simulation system we have developed realizes a highly efficient simulation process by adopting the voxel model of blood vessels obtained by medical images and a newly developed scheme based on VOF-FVM corresponding to voxel models. The new simulation system does not require mesh generation because of the use of rectangular coordinates. The voxel model of a blood vessel can be constructed very quickly using the voxel model builder we developed. Furthermore, we developed an input system for boundary conditions, which makes it possible for the user to input boundary conditions easily and quickly through a user-friendly interface. To certify the numerical results rapidly, software for animating the blood flow has been developed. We examined the preciseness of the hemodynamics simulation system in the case of a linear tube and a U-shaped tube. The results were in agreement with experimental results and theoretical solutions. As an example of hemodynamics simulation, we examined the blood flow of an internal carotid artery. The simulation system attained high performance compared with the result obtained using the authors' previous method. It especially improves the efficiency of modeling and mesh generation.
  • 小田 敍弘, 青木 隆敏, 岡崎 浩子, 掛田 伸吾, 興梠 征典, 矢原 勝哉, 庄野 逸
    2006 年 44 巻 3 号 p. 435-444
    発行日: 2006年
    公開日: 2008/05/01
    ジャーナル フリー
    The purpose of this study was to develop a novel computerized scheme to automatically select similar chest radiographs for image subtraction of patients who have no previous chest radiographs and to assist the radiologist's interpretation by presenting “similar subtraction images”. A large database of approximately 15,000 posteroanterior chest radiographs, which were diagnosed as normal, was used for searching similar images of different patients. First, in this scheme, two clinical parameters (age and sex) were used for selecting similar images. Next, 100 images of candidates in the database were selected according to similarity in height and the area of the lung field in the target image. We used quantitative measurement for searching similar images; namely, the correlation value of cheat region in the 100 images of the candidates. The similar subtraction images were obtained by subtracting the similar images selected from the target image. The performance of the proposed system was evaluated in comparison with 95 chest radiographs with a temporal subtraction image. The experimental results showed that the average of the correlation values in the temporal subtraction image and similar subtraction images were 0.9794 and 0.9574, respectively. Three radiologists subjectively evaluated various lung artifacts on the temporal subtraction image and similar subtraction images of 95 chest radiographs using a five-point rating scale (1: very poor, 2: poor, 3: adequate, 4: good, 5: excellent). Ratings higher than “adequate” were given for 70% of the similar subtraction images. This computerized scheme seems useful for the automatic selection of similar images for similar-image subtraction of chest radiographs and has potential use for assisting interpretations by radiologists.
  • 笈田 武範, 藤原 卓矢, 天野 晃, 姜 有峯, 堤 定美, 松田 哲也
    2006 年 44 巻 3 号 p. 445-453
    発行日: 2006年
    公開日: 2008/05/01
    ジャーナル フリー
    Magnetic resonance elastography (MRE) is one of the non-invasive methods to measure the viscoelastic properties of tissue. In MRE measurement, viscoelastic properties are estimated from the wavelength and damping factor of the viscoelastic waves in the object; however, the influence of reflection and refraction are not considered in the estimation methods applied (e.g., algebraic inversion of the differential equation and elastic wave fitting). Therefore, in general, reflection and refraction are avoided by shortening the interval between object oscillation and acquisition of the MRE signal. However, the viscoelastic properties of transient-state oscillation can be measured using this method, since a specific time period is necessary to realize steady-state oscillation. This may lead to a less accurate measurement of the viscoelastic properties. In this paper, we first show that the viscoelastic properties in transient-state oscillation are measured when the interval between object oscillation and MRE signal acquisition is short, and show that the accuracy of viscoelastic properties is high when using steady-state oscillation. Then, we propose a reflection reduction method using a spatio-temporal directional filter (STDF). The experiments using a silicon gel phantom showed that the viscoelastic properties during transient-state oscillation were measured when the interval between object oscillation and MRE signal acquisition was short. These results suggest that steady-state oscillation improves the accuracy of viscoelastic property measurement. In addition, the reflection wave could be reduced using the STDF, which leads improved accuracy in measuring the viscoelastic properties of MRE images with reflected waves.
  • 大橋 俊朗, 瀬川 圭, 坂元 尚哉, 佐藤 正明
    2006 年 44 巻 3 号 p. 454-459
    発行日: 2006年
    公開日: 2008/05/01
    ジャーナル フリー
    To study endothelial cell remodeling in response to hydrostatic pressure, human umbilical vein endothelial cells (HUVECs) were exposed to hydrostatic pressure of 25 and 100 mmHg and changes in morphology and expression of VE-cadherin were studied. After exposure to hydrostatic pressure, HUVECs exhibited elongated and tortuous shape without predominant orientation, together with development of centrally located, thick stress fibers. Particularly, HUVEs exposed to 25 mmHg exhibited more tortuous shape compared to those both under control conditions and 100 mmHg. HUVECs did not exhibit a multilayered structure unlike BAECs after exposure to hydrostatic pressure. Fluorescence staining demonstrated that VE-cadherin expression was lower under pressure than under control conditions. These results suggest that hydrostatic pressure may induce a decrease in VE-cadherin expression in HUVECs, leading to the formation of numerous randomly distributed intercellular gaps followed by the formation of tortuous shape.
研究速報
  • —肺の熱伝導シミュレータの構築—
    二見 光, 荒井 恒憲, 屋代 英樹, 中塚 誠之, 栗林 幸夫, 泉 陽太郎, 塚田 紀理, 川村 雅文
    2006 年 44 巻 3 号 p. 460-466
    発行日: 2006年
    公開日: 2008/05/01
    ジャーナル フリー
    To develop an evaluation method for the curative field when using X-ray CT imaging during percutaneous transthoracic cryoablation for lung cancer, we constructed a finite-element heat conduction simulator to estimate temperature distribution in the lung during cryo-treatment. We calculated temperature distribution using a simple two-dimensional finite element model, although the actual temperature distribution spreads in three dimensions. Temperature time-histories were measured within 10 minutes using experimental ex vivo and in vivo lung cryoablation conditions. We adjusted specific heat and thermal conductivity in the heat conduction calculation and compared them with measured temperature time-histories ex vivo. Adjusted lung specific heat was 3.7 J/(g·°C) for unfrozen lung and 1.8 J/(g·°C) for frozen lung. Adjusted lung thermal conductivity in our finite element model fitted proportionally to the exponential function of lung density. We considered the heat input by blood flow circulation and metabolic heat when we calculated the temperature time-histories during in vivo cryoablation of the lung. We assumed that the blood flow varies in inverse proportion to the change in blood viscosity up to the maximum blood flow predicted from cardiac output. Metabolic heat was set as heat generation in the calculation. The measured temperature time-histories of in vivo cryoablation were then estimated with an accuracy of ±3°C when calculated based on this assumption. Therefore, we successfully constructed a two-dimensional heat conduction simulator that is capable of estimating temperature distribution in the lung at the time of first freezing during cryoablation.
  • 田中 志信, 本井 幸介, 野川 雅道, 山越 健弘, 山越 憲一
    2006 年 44 巻 3 号 p. 467-474
    発行日: 2006年
    公開日: 2008/05/01
    ジャーナル フリー
    The daily monitoring of health conditions at home is a very important subject not only as an effective scheme for the early diagnosis and treatment of cardiovascular and other diseases, but also for the prevention and control of such diseases. From this point of view, we have been developing a fully automated “non-conscious” monitoring system for home healthcare. In this paper, we describe the structural details of a newly developed blood pressure (BP) measurement system built into a toilet seat and some results obtained using the system. The principle used for BP measurement was the volume-oscillometric method. A reflectance-type photoplethysmographic sensor was installed in an appropriate position on the toilet seat, and it was automatically lifted and lowered using a newly designed helicoid-type actuator. Systolic (SBP) and mean BP (MBP) were obtained using the arterial volume pulsation signal obtained by the sensor. In order to evaluate the accuracy of the BP measurements, simultaneous measurements were carried out using two types of commercially available BP monitors (upper arm and wrist). Simultaneous measurement using an “invasive technique” via catheterization to the right brachial artery was also conducted. From the results obtained (bias[s.d.] for SBP; Upper arm: -1.20 [7.90] mmHg, Wrist: 0.44 [7.28] mmHg, Invasive: -0.41 [4.91] mmHg, bias [s.d.] for MBP; Upper arm: 4.40 [6.91] mmHg, Wrist: 5.07 [8.04] mmHg, Invasive: 3.68 [5.69] mmHg), reasonable accuracy of the present system was clearly demonstrated. This system, which requires no cumbersome procedures for BP measurement such as cuff setting, proper positioning of measuring site and so on, appears to be a useful means for long-term home healthcare monitoring.
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