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61.
骨骼肌介电行为的理论模型仿真 总被引:1,自引:1,他引:1
在 10 0 Hz~ 10 0 MHz范围内 ,应用椭圆壳介电理论模型 ,经过模拟仿真蛙骨骼肌细胞的介电行为 ,确定了蛙骨骼肌细胞的椭圆壳模型各相参数。为将来对骨骼肌疲劳、肌营养不良和肌肉萎缩等病症的模型分析奠定理论基础。 相似文献
62.
背景:应力遮挡效应会导致植入假体修复骨缺损手术失败,其主要原因是由于植入假体的弹性模量大于骨组织弹性模量。目的:分析植入假体弹性模量对应力分布的影响,寻求消除应力遮挡现象的方法。方法:通过CT扫描的方式获取实验犬与人体骨组织的模型,分别对其优化后进行梯度赋值,建立较为可靠的骨骼力学模型,并与植入假体组合后进行有限元仿真。首先,通过对比格犬骨骼模型和人体骨骼模型及其对应的植入假体进行有限元仿真,模拟了不同弹性模量对植入假体修复术后的应力和位移分布情况;其次,分析了较小弹性模量差仍会形成应力遮挡现象的原因,建立了骨骼模型及植入假体模型,确立了材料属性赋予方法;最后,验证了该模型及材料属性赋予方法的可行性,并通过随机选取受力点的方式,定量分析植入假体弹性模量与骨骼弹性模量之间的关系对应力遮挡形成的影响。结果与结论:通过梯度赋值法建立与骨骼力学性质更加接近的实验犬骨骼模型和人体骨骼模型,该方法重建的力学模型与真实骨骼的力学性质更为接近;通过有限元仿真力学测试证明,不同弹性模量植入假体对假体本身与周围骨骼间相对位移的影响较小;另外量化弹性模量对假体植入骨骼后对应力分布的影响,可为后续的相关研究提供帮助。 相似文献
63.
A computer model was designed as a relational database to assess breast cancer screening in a cohort of women where the growth and development of breast cancer originates with the first malignant cell. The concepts of thresholds for growth, axillary spread, and distant sites are integrated. With tumor diagnosis, staging was performed that includes clinical and sub-clinical states. The model was parameterized to have staging characteristics similar to data published by the Surveillance, Epidemiology, and End-Results (SEER) Program. Validation was accomplished by comparing simulated staging results with non-SEER sources, and simulated survival with independent clinical survival data. 相似文献
64.
The study aimed to model the cerebrovascular system, using a linear ARX model based on data simulated by a comprehensive physiological
model, and to assess the range of applicability of linear parametric models. Arterial blood pressure (ABP) and middle cerebral
arterial blood flow velocity (MCAV) were measured from 11 subjects non-invasively, following step changes in ABP, using the
thigh cuff technique. By optimising parameters associated with autoregulation, using a non-linear optimisation technique,
the physiological model showed a good performance (r=0.83±0.14) in fitting MCAV. An additional five sets of measured ABP of length 236±154 s were acquired from a subject at rest.
These were normalised and rescaled to coefficients of variation (CV=SD/mean) of 2% and 10% for model comparisons. Randomly
generated Gaussian noise with standard deviation (SD) from 1% to 5% was added to both ABP and physiologically simulated MCAV
(SMCAV), with ‘normal’ and ‘impaired’ cerebral autoregulation, to simulate the real measurement conditions. ABP and SMCAV
were fitted by ARX modelling, and cerebral autoregulation was quantified by a 5 s recovery percentage R5% of the step responses
of the ARX models. The study suggests that cerebral autoregulation can be assessed by computing the R5% of the step response
of an ARX model of appropriate order, even when measurement noise is considerable. 相似文献
65.
为了研究不同心电序列转换方式及不同谱估计方法对心率变异性(HRV)信号谱分析结果的影响,本文对积分脉冲频率调制(IPFM)模型及修正积分脉冲频率调制(MIPFM)模型在输入不同振幅与频率的正弦信号时所产生的随机点过程,用两种心电序列转换方法进行转换得到仿真HRV信导;然后,采用周期图与自回归(AR)谱估计方法计算这种厉真HRV信号的功率谱。研究结果表明:①对于MIPFM模型产生的随机点过程,同一心电序列转换方法所得出的仿真HRV信号的AR谱与周期图的谱峰功率估计基本一致;而对IPFM模型则不完全一致。②MIPFM模型仿真实验表明,对实际HRV信号谱分析,使用低,高频谱峰功率比(RF)作为反映心脏自主神经张力平衡的指标时,除心电序列传换及谱估计方法可能造成的误差外,当低频谱峰靠近极低频谱峰时,根据RF值解释生理实验结果会有校大误差。③座分析实际HRV信号的工作中,不同心电序列转换方式产生的伪谐波对HRV谱分析结果的影响不大。 相似文献
66.
Swartling J Pålsson S Platonov P Olsson SB Andersson-Engels S 《Medical & biological engineering & computing》2003,41(4):403-409
The optical properties of pig heart tissue were measured after in vivo ablation therapy had been performed during open-heart
surgery. In vitro samples of normal and ablated tissue were subjected to measurements with an optically integrating sphere
set-up in the region 470–900 nm. Three independent measurements were made: total transmittance, total reflectance and collimated
transmittance, which made it possible to extract the absorption and scattering coefficients and the scattering anisotropy
factor g, using an inverse Monte Carlo model. Between 470 and 700 nm, only the reduced scattering coefficient and absorption
could be evaluated. The absorption spectra were fitted to known tissue chromophore spectra, so that the concentrations of
haemoglobin and myoglobin could be estimated. The reduced scattering coefficient was compared with Mie computations to provide
Mie equivalent average radii. Most of the absorption was from myoglobin, whereas haemoglobin absorption was negligible. Metmyoglobin
was formed in the ablated tissue, which could yield a spectral signature to distinguish the ablated tissue with a simple optical
probe to monitor the ablation therapy. The reduced scattering coefficient increased by, on average, 50% in the ablated tissue,
which corresponded to a slight decrease in the Mie equivalent radius. 相似文献
67.
A PC-AT based program for conversion of magnetic resonance imaging (MRI) scans into coordinate input for finite element mesh generation is presented. The program is written in Borland C + +3.1 and is compatible with every general-use personal computer, permitting the use of MS-DOS 3.0 or higher with a Microsoft mouse. The program is menu driven and does not demand specialised knowledge from the user. The system and memory requirements are minimal -- 640 kB RAM -- and it runs as a stand-alone program. A second program allows the construction of a three-dimensional representation of the limb sub-structure and generation of the FE mesh from the converted cross-sectional scans. The capabilities of the program are demonstrated using cross-sectional scans of the upper arm; the fat, muscle and bone contours were obtained to a very high level of precision (0.4 mm). 相似文献
68.
基于美国BRG公司的运动及动力学仿真分析软件LifeMOD,建立包括股骨、胫骨、腓骨、4条主要韧带及肌肉在内的较完整的膝关节动力学模型,并用该模型模拟了人体下肢在平地行走时膝关节的动力学行为以及前交叉韧带缺损对膝关节接触力大小的影响。通过动力学分析,得到人体在平地行走时,胫股关节之间最大的接触力值为2645N,最大韧带张力为590N,发生在内侧副韧带上;当胫股关节之间的滑动受到限制时,最大的韧带张力发生在前交叉韧带上,为560N,研究结果与文献较接近。通过动力学模拟,可以得出结论:胫股关节之间的滑动对韧带张力有较大影响;前交叉韧带缺损使得胫股关节之间的接触力变小。 相似文献
69.
J. M. Maarek G. Jarry J. Crowe M. -H. Bui D. Laurent 《Medical & biological engineering & computing》1986,24(4):407-414
A Monte Carlo model has been developed to study the propagation of an ultrashort light pulse through a heterogeneous thick
biological specimen. A circular blood vessel is moved within a tissular slab to simulate biological specimen scanning using
a picosecond laser source and a collimated ultrafast multichannel opticl shutter. Features of the transmitted light are computed
for each position of the blood vessel. The computer program gives an account of the transmitted photons, the flight time which
does not exceed straightforward crossing time plus time gate of known duration. A small blood vessel (radius R=2 mm) placed
in a 40 mm thick slab is easily located when a time gate of 10 ps duration is employed. Such a time gate also allows the detection
of a middle-sized vessel (R=4 mm) embedded in a thicker sample (80 mm). The contrast computed for the transmittance profile
is greatly improved when a time gate is used. In addition, shifting of the blood vessel towards the unilluminated side of
the sample decreases the contrast. We demonstrate that the time selection process may provide a substantial improvement to
the laser tomoscopy technique when used for imaging biological media. 相似文献
70.
Killmann R. Jaros G. G. Wach P. Graumann R. Moshage W. Renhardt M. Fleischmann R. H. 《Medical & biological engineering & computing》1995,33(5):643-651
A computer simulation study is performed to investigate the method of current density reconstruction to localise myocardial
ischaemia. A computer model of the entire human heart is used to simulate the excitation and repolarisation process in eight
topographically different cases of myocardial ischaemia. The associated magnetocardiogram is calculated at 37 positions of
the KRENIKON* biomagnetic measurement equipment. The method of current density reconstruction is applied at the S-point (the last discemible
deviation from the ST-segment at the end of the QRS-complex) of the MCG to find characteristics of the myocardial ischaemia
simulated by the model. The results show that it is possible to determine the location of the ischaemia. The current density
distribution may be interpreted physiologically in terms of the so-called ‘injury current’. This indicates that magnetocardiography
might be a suitable method for noninvasive ischaemia diagnosis, and further investigations of the current density reconstruction
method for the injury current should be performed on patients with ischaemic heart disease. 相似文献