Technology and Health Care - Volume 13, issue 4

Authors: Ohta, Makoto | Jacobson, J. Paul | Hiltbrand, Emile | Kelekis, Alexis | Ivancevic, Marko | A. Rüfenacht, Daniel | Iwata, Hiroo | Tsutsumi, Sadami

Article Type: Research Article

Abstract: This paper describes the development of a Polyvinyl alcohol hydrogel (PVA-H) model for calibration and measurement of temperature using image contrast on MRI using DMSO/H2 O as a solvent to alter the freezing and melting points of PVA-H. Tissues exposed to temperature changes above 41°C or below 0°C exhibit increasingly extensive and irreversible damage, depending on the exposure duration. MR images can provide a map of temperature if there is sufficient tissue signal. To evaluate treatment principles using temperature changes (hyperthermia, cryotherapy), a model simulating tissue may be useful to provide a reproducible test environment. PVA-H is water soluble and …can be seen on MRI. It can be used to construct complicated shapes such as vascular structure, soft tissues, and so on. Therefore, PVA-H can be useful to measure temperatures and assume the distribution of temperature under treatment. In this paper, we applied PVA-H as a temperature detector and calibrated temperature from image contrast. The results exhibit good capability as a temperature detector not only of high temperature (around 41°C), but also of low temperature (as low as −23°C). Show more

DOI: 10.3233/THC-2005-13401

Citation: Technology and Health Care, vol. 13, no. 4, pp. 221-228, 2005

Authors: Wang, Qingtian | Yambe, Tomoyuki | Shiraishi, Yasuyuki | Duan, Xudong | Yoshizawa, Makoto | Tabayashi, Kouichi | Nitta, Shinichi | Umezu, Mitsuo

Article Type: Research Article

Abstract: Artificial heart (AH) and ventricular assist devices (VAD) are widely used in the clinical setting to assist severe heart failure patients. The concept of direct cardiac compression (DCC) has been in use for several decades and has advantages over intravascular VAD. The process involves compressing the dysfunctional heart from its epicardial surface to avoid the thromboembolic events and decrease the complications and mortality. An Electro-hydraulic Artificial Myocardium (EHAM) system was designed and fabricated by Tohoku University. This system may assist cardiac contraction and create pulsatile blood flow. The aim of this study was to clearly define the hemodynamic …efficiency of the EHAM system in myocardial tissue perfusion during its application in acute animal experiment. Eight healthy adult goats were used; left lateral thoracotomy was performed and the chest was opened by the resection of the 4th and 5th ribs. Hemodynamic parameters including ECG, blood pressure and cardiac output were continuously monitored. Myocardial tissue perfusion was measured by using Omega flow laser fiber attached to the surface of the heart. During the EHAM compression, and increase in blood pressure and myocardial tissue perfusion was observed in all animals when compared with pre-assisted mode. To conclude, EHAM effectively improves myocardial tissue perfusion and increases the pressure on the initiation of direct cardiac compression immediately. Thus it can be a potentially valuable adjunct in the management of severe heart failure. Show more

DOI: 10.3233/THC-2005-13402

Citation: Technology and Health Care, vol. 13, no. 4, pp. 229-234, 2005

Authors: Gillies, George T. | Smith, Joshua H. | Humphrey, Joseph A. C. | Broaddus, William C.

Article Type: Research Article

Abstract: Positive pressure infusion is a clinical means of achieving convection-enhanced delivery of therapeutic agents within the tissues of the central nervous system for the treatment of glioblastoma multiforme and other diseases of the brain. We have developed a mathematical model of the technique and an in vitro gelatin surrogate for it, which provide biophysical insights into the performance characteristics of candidate infusion systems and drug delivery protocols. We present a brief overview of the clinical problems that are being addressed, succinctly describe the mathematical and in vitro models used in our laboratories, and highlight some representative results from our studies. …A number of references to related work are provided for those seeking further details. Show more

DOI: 10.3233/THC-2005-13403

Citation: Technology and Health Care, vol. 13, no. 4, pp. 235-243, 2005

Authors: Baheux, Kenji | Yoshizawa, Makoto | Tanaka, Akira | Seki, Kazunori | Handa, Yasunobu

Article Type: Research Article

Abstract: Victims of a stroke or an accident with damage on the parietal lobe can suffer from hemispatial neglect. This disorder is characterized by misperception of the space contralateral to the damaged area. Paper and pencil tests, such as line bisection tests, are used to diagnose hemispatial neglect. Unfortunately, they fail to quantify the degree of the neglect. Moreover, the neglect has different manifestations in each sensorial space and frame of references. In order to diagnose disorders of spatial recognition and analyze the neglected area in visual and somatic spaces, we developed a 3D-haptic virtual reality system coupled with an eye-tracking …device. The haptic interface was used to interact with virtual objects. The virtual world can use the eye-gaze information to let patients overcome the neglect. We tested the system at a rehabilitation center and observed different approaches between normal subjects and hemiplegics patients. The first group was getting close to the target and then slowed down to grab it, whereas the later group proceeded by trial and error. The feature of trajectories of the hand in the 3D space could be used to determine the degree of the motion handicap. However, more specific virtual worlds are needed for efficiently extracting the feature of the patients. Show more

Keywords: haptic feedback, hemispatial neglect, rehabilitation, virtual reality

DOI: 10.3233/THC-2005-13404

Citation: Technology and Health Care, vol. 13, no. 4, pp. 245-260, 2005

Authors: Saijo, Yoshifumi | Sasaki, Hidehiko | Hozumi, Naohiro | Kobayashi, Kazuto | Tanaka, Motonao | Yambe, Tomoyuki

Article Type: Research Article

Abstract: Since 1985, we have been developing a scanning acoustic microscope (SAM) system for biomedical use and have been investigating the acoustic properties of various organs and disease states by using this SAM system. In biomedicine, SAM is useful for intraoperative pathological examination, study of low-frequency ultrasonic images, and assessment of biomechanics at a microscopic level. Recently, we have proposed a new concept – acoustic microscopy – using a single pulsed wave instead of continuous waves used in conventional SAM systems. In the present study, we compared two systems by measuring the same biological material. The sound speed image obtained by …sound speed microscopy corresponded well to that obtained using a conventional SAM system. Lesions with hyaline degeneration showed a lower sound speed when compared with that of normal myocardium. Frequency domain analysis of amplitude and phase by both methods also showed similar characteristics. Although the data acquisition time of one frame was greater than that in conventional SAM, the total time required for calculation was significantly shorter. The SAM system can be applied to intraoperative pathological examination. Show more

DOI: 10.3233/THC-2005-13405

Citation: Technology and Health Care, vol. 13, no. 4, pp. 261-267, 2005

Authors: Nakamura, Masanori | Wada, Shigeo | Karino, Takeshi | Yamaguchi, Takami

Article Type: Research Article

Abstract: Intraventricular hemodynamics during diastole was numerically analyzed in order to investigate effects of a ventricular untwisting on flow and a pattern of a color M-mode Doppler echocardiogram. Results showed that the ventricular untwisting affected secondary flows by inducing spiral flows in the ventricular cavity especially in the apical region. On the other hand, flows in the long-axis plane were not affected. Timing of formation, size and growing manner of the annular vortex were almost the same regardless of the presence of the ventricular untwisting; the vortex firstly arose in the base region, expanded towards the apex and eventually occupied the …upper half of the ventricular cavity. A pattern of a color M-mode Doppler echocardiogram, that is, a spatiotemporal map of velocity along the long axis, was topologically the same as quantitatively confirmed by comparison of propagation velocity (0.43 m/s and 0.42 m/s for the case without and with the ventricular untwisting, respectively). These results suggested that this technique can exclusively capture flow dynamics produced by ventricular expansion with little influence of the ventricular untwisting. Therefore, we concluded that this is advantageous for assessing a left ventricular diastolic function. Show more

DOI: 10.3233/THC-2005-13406

Citation: Technology and Health Care, vol. 13, no. 4, pp. 269-280, 2005

Authors: Feng, Yixiang | Wada, Shigeo | Tsubota, Ken-ichi | Yamaguchi, Takami

Article Type: Research Article

Abstract: The genesis and development of intracranial aneurysm have long been of interest but remain not understood. In the present study we simulate the progression of intracranial aneurysms by constructing a computational model of a curved artery. It is hypothesized that high local wall shear stress above a threshold value will lead to degeneration of the arterial wall mechanical properties. And this degenerative effect may continue even after the wall shear stress has become lower than the threshold, which is referred to as the “time remaining effect” in this study. We performed several groups of studies using both assumptions and aneurysm …development is observed as result of the interplay between high wall shear stress, wall degeneration and wall deformation. In the growth of aneurysms with “time-remaining effect”, the increase of aneurysmal height accelerates in later steps. It is concluded that computer simulation can yield insight into the understanding of the pathophysiology of aneurysmal initiation and growth, and help in clarifying the role of certain hemodynamic parameters. Show more

Keywords: biomechanics, intracranial aneurysm, progression, computer aided analysis, modeling, wall shear stress, material properties, time remaining effect, blood flow

DOI: 10.3233/THC-2005-13407

Citation: Technology and Health Care, vol. 13, no. 4, pp. 281-291, 2005

Authors: Mizuno, F. | Hayasaka, T. | Tsubota, K. | Wada, S. | Yamaguchi, T.

Article Type: Research Article

Abstract: We previously developed a network-based medical care support system called the Hyper Hospital, a computer network with an interface that is dedicated to patient care. In this study, we developed a wearable information system that is designed so that a caregiver can obtain information and control various support devices within the home-care environment. In our system, the wearable computer itself consists of a computer network built into a jacket. Each required function is implemented by a dedicated small computer connected to the in-jacket network. A new function may easily be added to the system by connecting additional computers. A network …comprising such a set of single-function computers becomes a highly efficient information system when applied to health care support. Show more

Keywords: hyper hospital, home care support, wearable computer, Electro-Oculo-Graph (EOG)

DOI: 10.3233/THC-2005-13408

Citation: Technology and Health Care, vol. 13, no. 4, pp. 293-300, 2005

Authors: Shirai, Atsushi | Fujita, Ryo | Hayase, Toshiyuki

Article Type: Research Article

Abstract: The concentration of neutrophils in the pulmonary microvasculature is higher than in systemic large vessels. It is thought that the high concentration of neutrophils facilitates their effective recruitment to sites of inflammation. Thus, in order to understand the role of neutrophils in the immune system, it is important to clarify their flow characteristics in the pulmonary microvasculature. In previous studies, we numerically investigated the motion of a neutrophil through a single capillary segment modeled by a moderate axisymmetric constriction in a straight pipe, developing a mathematical model for the prediction of the transit time of the cell through the segment. …In the present study, this model was extended for application to network simulation of the motion of neutrophils. First, we numerically investigated shape recovery of a neutrophil after expulsion from a narrow capillary segment. This process was modeled in two different phases: elastic recovery and viscous recovery. The resulting model was combined with the previously developed models to simulate motion of the cells and plasma flow in a capillary network. A numerical simulation of the motion of neutrophils and plasma flow in a simple lattice capillary network showed that neutrophils were widely dispersed in the network with an increased concentration. Show more

DOI: 10.3233/THC-2005-13409

Citation: Technology and Health Care, vol. 13, no. 4, pp. 301-311, 2005

Authors: Sigal, Ian A. | Flanagan, John G. | Tertinegg, Inka | Ethier, C. Ross

Article Type: Research Article

Abstract: Purpose: Glaucoma is a common ocular disease whose pathogenesis is hypothesized to involve biomechanical damage to optic nerve tissues. Here we describe a method for the construction of patient-specific models that can be used to evaluate the biomechanical environment within the optic nerve head. We validate the method using a virtual eye, and demonstrate its use in computing optic nerve head biomechanics. Methods: Human eyes were imaged and the optic nerve head region was processed to allow serial plastic histologic sections to be cut. These sections were photographed, unwarped and aligned so as to reconstruct three-dimensional patient-specific models …incorporating sclera, pre- and post-laminar nerve, lamina cribrosa, and pia mater. Deformations, stresses and strains were computed in the resulting model using finite element techniques. Results: The approach successfully reconstructed patient-specific optic nerve head models. Reconstruction of a virtual eye showed excellent agreement between the true and reconstructed geometries, and between the deformations and strains computed on the true and reconstructed geometries. A sample reconstruction showed reasonable agreement between computed and measured retinal surface deformations. Conclusion: The technique presented here is viable and can be used to accurately compute human optic nerve head biomechanics. Show more

Keywords: glaucoma, optic nerve head, IOP, biomechanics, finite elements, stress, strain

DOI: 10.3233/THC-2005-13410

Citation: Technology and Health Care, vol. 13, no. 4, pp. 313-329, 2005

Authors: Funamoto, Kenichi | Hayase, Toshiyuki | Saijo, Yoshifumi | Yambe, Tomoyuki

Article Type: Research Article

Abstract: Detailed information of real blood flows is essential to develop an accurate diagnosis or treatment for serious circulatory diseases such as aortic aneurysms. Ultrasonic-Measurement-Integrated (UMI) simulation, in which feedback signals from the ultrasonic measurement make the simulation converge to the real blood flow, is a key to solving this problem. However, aliasing in the ultrasonic blood velocity measurement causes UMI simulation to converge to an erroneous result. In this paper, we have investigated the detection and the correction of aliasing in UMI simulation. The artificial force in the feedback of UMI simulation can be used as an index to detect …the aliasing. We have proposed two ways for the correction of the aliasing. Correction A, in which measurement velocity is replaced with the computational one at the monitoring point where the aliasing is detected, substantially improves the accuracy of UMI simulation. Correction B, in which measurement velocity is replaced with an estimated Doppler velocity, can provide exactly the same result as that of UMI simulation using the nonaliased standard solution. Although correction B gives the most accurate result, correction A seems more robust and, therefore, a beneficial choice considering the other artifacts in the measurement. Show more

DOI: 10.3233/THC-2005-13411

Citation: Technology and Health Care, vol. 13, no. 4, pp. 331-344, 2005