Local blood flow into tumors during artificial hyperglycemia

The blood flow in the rat Guerin carcinoma was measured by the hydrogen clearance method. It was shown that the blood flow in the tumour tissue decreased almost 3.5 times to the 3 hours of the intravenous glucose infusion at a dose of 80 mg X kg-1 X min-1. In some tumours the microcirculation ceased completely. The results obtained help developing the new schemes of local hyperthermia and induced hyperglycemia in the complex antitumour therapy.     

激光治疗恶性肿瘤的进展

激光诞生不久就用来进行杀伤癌细胞的研究,这给治疗癌肿提供了一种新的手段。本文介绍上海激光治疗恶性肿瘤的进展情况可以看到,激光应用的潜力尚未得到充分地发挥,必须努力研究,合理应用,以造福于人类。     

Ultrafast Doppler imaging of blood flow dynamics in the myocardium

Imaging intramyocardial vascular flows in real-time could strongly help to achieve better diagnostic of cardiovascular diseases. To date, no standard imaging modality allows describing accurately myocardial blood flow dynamics with good spatial and temporal resolution. We recently introduced a novel ultrasonic Doppler imaging technique based on compounded plane waves transmissions at ultrafast frame rate. The high sensitivity of this ultrafast Doppler technique permits to image the intramyocardial blood flow and its dynamics. A dedicated demodulation-filtering process is implemented to compensate for the large tissue velocity of the myocardium during the cardiac cycle. A signed power Doppler processing provides the discrimination between arterial and venous flows. Experiments were performed in vivo in a large animal open chest model ( N = 5 sheep) using a conventional ultrasonic probe placed at the surface of the heart. Results show the capability of the technique to image intramyocardial vascular flows in normal physiological conditions with good spatial (200 μm) and temporal resolution (10 ms). Flow dynamics over the cardiac cycle were investigated and the imaging method demonstrated a phase opposition of flow waveforms between arterial and venous flows. Finally, ultrafast Doppler combined with tissue motion compensation was found able to reveal vascular flow disruption in ischemic regions during occlusion of the main diagonal coronary artery.     

Multivariate dynamic analysis of cerebral blood flow regulation in humans

The contributions of beat-to-beat changes in mean arterial blood pressure (MABP) and breath-by-breath fluctuations in end-tidal CO2 (EtCO2) as determinants of the spontaneous variability of cerebral blood flow velocity (CBFV) were studied in 16 normal subjects at rest. The two input variables (MABP and EtCO2) had significant cross-correlations with CBFV but not between them. Transfer functions were estimated as the multivariate least mean square finite impulse response causal filters. MABP showed a very significant effect in explaining CBFV variability (p < 10(-11), Fisher's aggregated-p test) and the model mean square error was significantly reduced (p < 0.001) by also including the contribution of EtCO2. The estimated mean CBFV step response to MABP displayed the characteristic return to baseline caused by the cerebral autoregulatory response. The corresponding response to EtCO2 showed a gradual rise taking approximately 10 s to reach a plateau of 2.5%/mmHg. This study demonstrated that spontaneous fluctuations in EtCO2 can help to explain the CBFV variability at rest if appropriate signal processing techniques are employed to address the limited power and bandwith of the breath-by-breath EtCO2 signal.     

Mathematical simplification of a PET blood flow model

The positron emission tomography (PET) H(2)(15)O bolus injection model for cerebral blood flow (CBF) requires calculation of a certain double integral that, when calculated, provides the pixel values of a reconstructed image (PET number) in terms of the tissue flow, the arterial input function, a decay constant for (15)O, the partition coefficient and a camera calibration constant that relates the flow-dependent integrated tissue activity to the measured PET number (cts/pixel). The tissue activity is assumed to be zero at the time of injection. A mathematical simplification, changing the order of integration, enabled the integration with respect to time to be performed analytically before the integration of the arterial input function. As a result of this simplification, only single integrals remain to be calculated numerically; cubic spline integration was used to calculate numerically these remaining integrals. This technique increases the accuracy and speed of evaluating blood flow without making simplifying assumptions. Similar simplifications may be applicable to other physiological models.     

瘦素有望成为诊治肿瘤的一个关键点

对瘦素与肿瘤的最新研究进展进行综述,并阐明瘦素参与调节肿瘤发生、发展的可能机制,它可能有望成为早期诊治肿瘤的一个关键点。     

激光多普勒测量皮肤血流的Monte Carlo模拟

本文根据皮肤的双层模型,分别用两种相位函数给出光子与红血球碰撞的散射角,利用Monte carlo方法得出探测到的光子强度分布、光子数按频移的分布,以及总频移和平均频移与红血球浓度的关系。发现在低浓度时总频移与浓度呈线性,指出频移的强度涨落的一阶矩和带权重的一阶矩在低浓度时反映红血球的平均速率而在高浓度时反映均方根速率。     

GENI的启示

全球网络调研环境(GENI)是美国科学基金会提出的一项行动计划.本文首先介绍了什么是GENI,为何要搞GENI,然后,从作者的视角,提出了6点启示,与大家分享.     

A flexible blood flow phantom capable of independently producingconstant and pulsatile flow with a predictable spatial flow profile forultrasound flow measurement validations

The validation of the ultrasound time-domain correlation method of measuring blood flow has required the development of a flexible blood flow phantom capable of generating predictable flow profiles under a wide variety of conditions. The purpose of the phantom is to generate flow with well-known flow properties and not to mimic actual in vivo vessels. This paper describes a flow phantom which can independently generate both constant and pulsatile flow over a wide range of flow rates with a spatially fully developed laminar flow profile. It incorporates a computer-controlled pulsatile pump, which can produce different temporal pulsatile waveforms. The flow phantom also supports multiple vessels, different vessel sizes, as well as different attenuating media. The fluid most commonly used in the phantom is Sephadex mixed with water, and the probability density function of ultrasound reflected from Sephadex is experimentally determined and compared with that of blood. Examples of different constant and pulsatile flow experiments using the phantom are presented.     

Assessing blood flow control through a bootstrap method

In order to assess blood flow control, the relationship between blood pressure and blood flow can be modeled by linear filters. We present a bootstrap method, which allows the statistical analysis of an index of blood flow control that is obtained from constrained system identification using an established set of pre-defined filters.     

Estimation of coherence between blood flow and spontaneous EEG activity in neonates

Blood flow to the brain responds to changes in neuronal activity and, thus, metabolic demand. In earlier work, we observed correlation between cerebral blood flow and spontaneous electroencephalogram (EEG) activity in neonates. Using coherence, we now found that during Tracé Alternant EEG activity in quiet sleep of normal term neonates, this correlation is strongest at frequencies around 0.1 Hz, reaching statistical significance (p < 0.05) in six of the nine subjects studied (p < 0.07 in eight subjects). Due to noise, artifact, and spontaneous changes in the subjects' EEG patterns, the signals investigated included epochs of missing samples. We, therefore, developed a novel algorithm for the estimation of coherence in such data and applied a Monte Carlo (surrogate data) method for its statistical analysis. This process provides a test for the statistical significance of the maximum coherence within a selected frequency band. In addition to permitting further insight into the mechanisms of cerebral blood flow control, these algorithms are potentially of great benefit in a wide range of biomedical applications, where interrupted (gapped) recordings are often a problem.     

Dynamic modeling of renal blood flow in Dahl hypertensive and normotensive rats

A method is proposed in this paper which allows characterization of renal autoregulatory dynamics and efficiency using quantitative mathematical methods. Based on data from rat experiments, where arterial blood pressure and renal blood flow are measured, a quantitative model for renal blood flow dynamics is constructed. The mathematical structure for the dynamics is chosen as a "grey-box model," i.e. the model structure is inspired from physiology, but the actual parameters is found by numerical methods. Based on a number of experiments, features are extracted from the estimated parameters, which describe myogenic responses and tubuloglomerular feedback responses separately. The method is applied to data from normo- and hypertensive Dahl rats, and a discriminator that separates data from normotensive Dahl R rats and hypertensive Dahl S rats is constructed.     

A Lattice Boltzmann Model for pulsative blood flow in elastic vessels

Lattice Boltzmann Models (LBM) are widely used to solve fluid mechanical problems in engineering applications. In this work a brief introduction of LBM is given and a new boundary condition is proposed for the cardiovascular domain to support elastic walls in order to simulate blood flow in elastic vessels. The flow field is calculated in two spatial dimensions revealing characteristic flow patterns and geometrical changes of the arterial walls for different time dependent input contours of pressure and flow. For steady flow the results are compared to the predictions of the model proposed by Fung which is an extension of Poiseuille's theory. For unsteady flow the model was validated with the solution given by Womersley. The results are very promising for relevant Reynolds and Womersley numbers.      

A video system for measuring the blood flow velocity in microvessels

A video correlating system has been developed to measure the velocity of flowing blood in a microvessel. As the velocity of a red blood cell in a microvessel is given by the ratio of distance moved ?L to the incremental time At, we fix At in our system according to the framing rate of the video system and employ the video signal to find ?L by cross correlation.     

On the flow dependency of the electrical conductivity of blood

Experiments presented in the literature show that the electrical conductivity of flowing blood depends on flow velocity. The aim of this study is to extend the Maxwell-Fricke theory, developed for a dilute suspension of ellipsoidal particles in an electrolyte, to explain this flow dependency of the conductivity of blood for stationary laminar flow in a rigid cylindrical tube. Furthermore, these theoretical results are compared to earlier published measurement results. To develop the theory, we assumed that blood is a Newtonian fluid and that red blood cells can be represented by oblate ellipsoids. If blood flows through a cylindrical tube, shear stresses will deform and align the red blood cells with one of their long axes aligned parallel to the stream lines. The pathway of a low-frequency (< 1 MHz) alternating electrical current will be altered by this orientation and deformation of the red blood cells. Consequently, the electrical conductivity in the flow direction of blood increases. The theoretically predicted flow dependency of the conductivity of blood corresponds well with experimental results. This theoretical study shows that red blood cell orientation and deformation can explain quantitatively the flow dependency of blood conductivity.     

流体中血红细胞光散射信息的建模与仿真

为了获取流体中血红细胞精确的光散射信息,以反常衍射近似理论为基础,采用扁椭球构建了流体中血红细胞的数学散射模型。应用数值仿真模拟技术,分别讨论了血红细胞形体变化、体积变化、取向角和相对折射率变化对光散射幅值分布的影响,建立了相应的图谱分布,并通过实验对此模型进行了验证。结果表明,在前向小角度内,不同血红细胞大小、不同相对折射率对光散射信息有着较大影响。这一结果对于病理血红细胞的快速准确检测和流式细胞仪等细胞测量仪的精确测量是有帮助的。     

基于多普勒原理的血流速度计设计

血流速度对于检测各种重大疾病有非常重要的参考意义。基于多普勒原理,设计了一种血流速度检测系统,检测血流速度,检测系统的最终结果可以直观的显示在电脑上,并且保存到数据库中。通过实际应用,证明该方法具有很多优点:系统可扩展性强、系统的稳定性强、系统灵活、易于维护、技术兼容、简便易用、缩短开发周期、节约成本等。     

On-line determination of pulmonary blood flow using respiratoryinert gas analysis

An inert gas analysis method has been developed to perform on-line real time determination of pulmonary blood flow using a nonrebreathing approach. This technique is based on a mathematical model describing mass balance of two inert gases which are breathed using an open gas circuit. The measurements using this method are noninvasive, easy to perform, and do not disturb normal physiological processes. As well, since data are collected on a breath-by-breath basis, it is possible to estimate other respiratory, cardiopulmonary, and metabolic parameters simultaneously in a breath-by-breath manner. Special consideration was given to developing effective data processing algorithms to minimize the influence of measurement noise and respiratory variations. Experimental studies to compare this method with other accepted techniques were conducted to validate the present technique     

Activity of the natural killer cells in the peripheral blood of patients with brain tumors

Activity of natural killer cells (NK-cells) was determined in a 4-hour 51Cr-release test using K-562 as target cells in patients with brain tumours and donors. This activity was significantly (P less than 0.05) reduced in preoperative patients with metastatic brain tumours (mean--5.7%), gliomas of III-IV malignancy grades (mean--16.4%) as compared with the control (mean--32.5%). The activity of NK-cells remained low after surgical treatment irrespective of the length of remission.