Thin-layer liquid crystal thermometry of cells in vitro during hyperthermal microwave irradiation

A nonperturbing technique of thin-layer liquid crystal thermometry was developed to quantitate heating of Chinese hamster ovary cells and the bacterium Serratia marcescens when exposed to 2450-MHz microwave fields at 0.2–0.5 W/cm². Cells suspended in culture medium were injected into 5-cm glass microcapillary tubes coated on the inside with a thin layer of liquid crystal. The tubes were sealed and placed parallel to the electric field in a watertight waveguide exposure chamber where they were heated by circulating temperature-controlled water. Even at high circulation rates, liquid crystal color changes indicated local microwave capillary tube heating of 0.1–0.25 °C. Precision of measurement was 0.02 °C. Observations during microwave heating were significantly different from observations without microwaves at the 1% level, and heating increased as circulating water flow was reduced from 300 ml/s to 100 ml/s. The results of a cell survival assay following hyperthermal treatment were in good agreement with expectations based on the observations of microwave heating using liquid crystals.     

Noninvasive in vivo glucose detection in human finger interstitial fluid using wavelength‐modulated differential photothermal radiometry

We present a noninvasive and noncontacting biosensor using Wavelength Modulated Differential Photothermal Radiometry (WM‐DPTR) to monitor blood glucose concentration (BGC) through interstitial fluid (ISF) probing in human middle fingers. WM‐DPTR works in the interference‐free mid‐infrared range with differential wavelengths at the peak and baseline of the fundamental glucose molecule absorption band, giving rise to high glucose sensitivity and specificity. In vivo WM‐DPTR measurements and simultaneous finger pricking BGC reference measurements were performed on diabetic and nondiabetic volunteers during oral glucose tolerance testing. The measurement results demonstrated high resolution and large dynamic range (~80 deg) change in phase signal in the normal‐to‐hyperglycemia BGC range (5 mmol/L to higher than 33.2 mmol/L), which were supported by negative control measurements. The immunity to temperature variation of WM‐DPTR yields precise and accurate noninvasive glucose measurements in the ISF.      

Contactless passive diagnosis for brain intracranial applications: A study using dielectric matching materials

A prototype system for passive intracranial monitoring using microwave radiometry is proposed. It comprises an ellipsoidal conductive wall cavity to achieve beamforming and focusing, in conjunction with sensitive multiband receivers for detection. The system has already shown the capability to provide temperature and/or conductivity variations in phantoms and biological tissue. In this article, a variant of the initially constructed modality is theoretically and experimentally investigated. Specifically, dielectric matching materials are used in an effort to improve the system's focusing attributes. The theoretical study investigates the effect of dielectric matching materials on the system's detection depth, whereas measurements with phantoms focus on the investigation of the system's detection level and spatial resolution. The combined results suggest that the dielectric matching layers lead to the improvement of the system's detection depth and temperature detection level. Also, the system's spatial resolution is explored at various experimental setups. Theoretical and experimental results conclude that with the appropriate combination of operation frequencies and dielectric layers, it is possible to monitor areas of interest inside human head models with a variety of detection depths and spatial resolutions. Bioelectromagnetics 31:335–349, 2010. © 2010 Wiley‐Liss, Inc.     

Active microwave tomographic imaging of isolated, perfused animal organs

The relative transparency of biological materials to high-frequency electromagnetic waves has encouraged the development of new systems for imaging. This report describes experiments of microwave tomography conducted on a prototype. The object to be analyzed is submerged in water and is illuminated by a plane wave. The total electric field is analyzed by a microwave camera. The recorded data are then processed numerically in order to reconstruct the image that corresponds to the distribution of equivalent currents in a defined plane of a section. Experiments have been conducted on isolated kidneys with and without perfusion. The influence of the perfusing solution temperature has also been studied. These experiments show the potential of this system, especially through the correlation between microwave images and the biological structures. They also confirm previous results concerning spatial resolution and depth of exploration. Finally, the results demonstrate the influence of temperature and support the applicability of this imaging system in non-invasive thermometry, especially for clinical hyperthermia.     

近红外无创伤血糖测量的组织光学基础研究

人体血糖浓度无创伤测量是当今学术界和医学界普遍关注的课题。在分析了血糖浓度无创伤测量的意义、现有的测量方法及其进展后,从组织光学角度分析血糖浓度无创伤测量中包含的研究内容,并根据当前的研究现状,提出血糖浓度无创伤测量所存在的问题。通过组织光学角度对血糖浓度无创伤测量方法的剖析,更加明确血糖测量的研究任务,有望促使其更进一步的发展以及血液中其他成分的无创测量。     

The Knysna elephants: a population study conducted using faecal DNA

The elephants of the Knysna region continue to survive, despite fears that there was only a single surviving female. Their range is larger than previously believed, and includes the Afromontane forest and mountain fynbos. The five individuals detected in this study were all females, and share a single mitochondrial DNA control region haplotype with individuals from Addo Elephant National Park. At least two of these elephants appear to be first‐order relatives, and the others may be part of a single matrilineal group. The genetic diversity detected is lower than that found in most African savanna populations, but is higher than that found at Addo, where individuals represent the descendents of a severe population size bottleneck. Levels of genetic diversity are more similar to those detected at Kruger National Park, suggesting that the Knysna elephants represent a remnant of the once widespread populations of South Africa.     

Noninvasive fluid dynamic power loss assessments for total cavopulmonary connections using the viscous dissipation function: a feasibility study

The total cavopulmonary connection (TCPC) has shown great promise as an effective palliation for single-ventricle congenital heart defects. However, because the procedure results in complete bypass of the right-heart, fluid dynamic power losses may play a vital role in postoperative patient success. Past research has focused on determining power losses using control volume methods. Such methods are not directly applicable clinically without highly invasive pressure measurements. This work proposes the use of the viscous dissipation function as a tool for velocity gradient based estimation of fluid dynamic power loss. To validate this technique, numerical simulations were conducted in a model of the TCPC incorporating a 13.34 mm (one caval diameter) caval offset and a steady cardiac output of 2 L x min(-1). Inlet flow through the superior vena cava was 40 percent of the cardiac output, while outflow through the right pulmonary artery (RPA) was varied between 30 and 70 percent, simulating different blood flow distributions to the lungs. Power losses were determined using control volume and dissipation function techniques applied to the numerical data. Differences between losses computed using these techniques ranged between 3.2 and 9.9 percent over the range of RPA outflows studied. These losses were also compared with experimental measurements front a previous study. Computed power losses slightly exceeded experimental results due to different inlet flow conditions. Although additional experimental study is necessary to establish the clinical applicability of the dissipation function, it is believed that this method, in conjunction with velocity gradient information derived from imaging modalities such as magnetic resonance imaging, can provide a noninvasive means of assessing power losses within the TCPC in vivo.     

Noninvasive genetic analysis in birds: testing reliability of feather samples

Noninvasive samples are useful for molecular genetic analysis of free‐ranging animals. I tested whether moulted feathers collected in the field are a reliable source of DNA for genotyping microsatellite loci. I prescreened extracts for DNA quantity and, using only samples with higher amounts of DNA, obtained reliable genotyping results. Polymerase chain reaction (PCR) amplification success was higher from extracts of plucked feathers than moulted feathers. DNA quantity in larger feathers was higher than that in smaller feathers. This study clearly demonstrates that moulted feathers could be used for genetic studies in birds.     

Noninvasive measurement of mucosal immunity in a free-ranging baboon population

Ecoimmunological patterns and processes remain understudied in wild primates, in part because of the lack of noninvasive methods to measure immunity. Secretory immunoglobulin A (sIgA) is the most abundant antibody present at mammalian mucosal surfaces and provides an important first line of defense against pathogens. Recent studies show that sIgA can be measured noninvasively in feces and is a good marker of mucosal immunity. Here we validated a commercial ELISA kit to measure fecal IgA in baboons, tested the robustness of its results to variation in collection and storage conditions, and developed a cost-effective in-house ELISA for baboon fecal IgA. Using data from the custom ELISA, we assessed the relationship between fecal IgA concentrations and gastrointestinal parasite burden, and tested how sex, age, and reproductive effort predict fecal IgA in wild baboons. We find that IgA concentrations can be measured in baboon feces using an in-house ELISA and are highly correlated to the values obtained with a commercial kit. Fecal IgA concentrations are stable when extracts are stored for up to 22 months at −20°C. Fecal IgA concentrations were negatively correlated with parasite egg counts (Trichuris trichiura), but not parasite richness. Fecal IgA did not vary between the sexes, but for males, concentrations were higher in adults versus adolescents. Lactating females had significantly lower fecal IgA than pregnant females, but neither pregnant nor lactating female concentrations differed significantly from cycling females. Males who engaged in more mate-guarding exhibited similar IgA concentrations to those who engaged in little mate-guarding. These patterns may reflect the low energetic costs of mucosal immunity, or the complex dependence of IgA excretion on individual condition. Adding a noninvasive measure of mucosal immunity will promote a better understanding of how ecology modulates possible tradeoffs between the immune system and other energetically costly processes in the wild.     

Local tumor hyperthermia using a computer-controlled microwave system

A minicomputer-based system was designed to control the microwave (2.45-GHz) power to four local hyperthermia applicators. Errors in temperature measurement, due to electromagnetic field interactions with small thermocouple probes, are minimized by sampling the temperature only when the microwave power is off. The programmable controller can regulate the temperature in tumors in 0.1 °C increments from 30 to 60 °C. This technique reduces temperature differences throughout the tumor at steady state to less than 0.4 °C and prevents skin burns.     

光闪烁方法测算区域蒸散研究进展

蒸散是土壤-植物-大气连续体(SPAC)水热运移的一个重要环节,是全球水量平衡的重要组成,一直是气象学、水文学、地理学及生态学等相关学科重要的研究主题。区域尺度地表蒸散的时空变化过程十分复杂。迄今为止,在像元尺度水平上,特别在非均匀下垫面和地形起伏条件下,有代表性的进行地表蒸散的观测仍然十分困难。虽然遥感方法可获得区域尺度水平蒸散,但其主要根据经验或半经验模型对区域蒸散进行估算,模型选用的参数以及结果还需地面实测数据进行改进、优化,如何获得与遥感尺度相应的地面蒸散实测数据成为模型验证的重点和难点,光闪烁方法的出现为上述问题的解决带来了希望。光闪烁方法能够适应复杂下垫面,测量结果准确且具有时空平均等优点,成为测量区域蒸散的有效方法、验证遥感模型结果的最佳手段。从理论原理、计算方法、主要应用情况等方面,概述了光闪烁方法观测区域蒸散研究进展,指出了影响测算精度的不确定性因素,并提出了研究展望,旨在进一步推动该方法在区域蒸散观测研究中的应用,促进相关学科的发展。     

Subject-specific body segment parameters' estimation using biplanar X-rays: a feasibility study

In order to improve the reliability of children's models, the aim of this study was to determine the subject-specific masses and 3D locations of the centres of mass (CoM) of body segments using biplanar X-rays. Previous methods, validated on upper leg segments, were applied to the whole body. Six children and six adults were studied. The low-dose X-ray system EOS(?) was used to simultaneously get head-to-foot biplanar X-rays in the upright position. Specific methods were used to get 3D reconstructions of bones and body shape. The densities from the literature were used to define the masses. To assess the accuracy of the reconstructions, a force plate was used to compare the mass and the projection of the CoM. A mean distance of 4.5?mm between the measured and the calculated projections of the CoM was found. The mean error between the estimated and the actual body mass was 2.6%. Such a method will be useful in obtaining the body segment parameters in children, hard to obtain using direct measurement techniques.     

Li4Zn(PO4)2:Mn2+ thermosensitive phosphor with dual luminescent centres for optical thermometry

An optical thermometry strategy based on Mn²⁺-doped dual-wavelength emission phosphor has been reported. Samples with different doping content were synthesized through a high-temperature solid-phase method under an air atmosphere. The electronic structure of Li₄Zn(PO₄)₂ was calculated using density functional theory, revealing it to be a direct band gap material with an energy gap of 4.708 eV. Moreover, the emitting bands of Mn²⁺ at 530 and 640 nm can be simultaneously observed when using 417 nm as the exciting wavelength. This is due to the occupation of Mn²⁺ at the Zn²⁺ site and the interstitial site. Further analysis was conducted on the temperature-dependent emission characteristics of the sample in the range 293–483 K. Mn²⁺ has different responses to temperature at different doping sites in Li₄Zn(PO₄)₂. Based on the calculations using the fluorescence intensity ratio technique, the maximum relative sensitivity at a temperature of 483 K was determined to be 1.69% K⁻¹, while the absolute sensitivity was found to be 0.12% K⁻¹. The results showed that the Li₄Zn(PO₄)₂:Mn²⁺ phosphor has potential application in optical thermometry.     

Noninvasive cardiac output estimation: a preliminary study

 The availability of a simple-to-use, automatic measurement system for noninvasive flow estimation is imperative, given the clinical demand for an acceptable noninvasive procedure rather than the standard invasive procedure of thermodilution. A method for calculating cardiac output from noninvasively derived pressure pulses has been developed, and the results of a preliminary evaluation study on post-cardiac surgery patients for whom invasive flow measures were readily available for comparison are provided in this report. The proposed method relies on fast Fourier transform (FFT) analysis of pulses measured externally at the carotid and femoral pressure points. A transfer function of the aorta is computed from digitally filtered pulse measurements, and a tapered model of the aorta is parametrically adapted using a simplex optimization algorithm so that its transfer function matches that derived experimentally. An aortic input impedance term is obtained from the optimized model and utilized along with the carotid pulse (analogous to input voltage) to compute aortic flow. In addition to its automation, attractive features of this method include the requirement for relatively few pulses for analysis as well as considerable resistance to noise artifact. For 59 data records collected from 54 post-cardiac surgery patients, the average flow measurements computed over several pulses compare well with the standard, invasive method of thermodilution. Preliminary results also indicate a strong potential for tracking changes in cardiac output over time, and invite further use of the method in monitoring hemodynamically unstable patients. Received: 18 February 1997 / Accepted in revised form: 12 May 1997     

Ambulatory impedance cardiography: a feasibility study

A wearable, ambulatory impedance monitor(AIM) has been developed to permit impedance cardiographic measurementswhile patients and volunteers engage in normal dailyactivities. The AIM system was developed for use with anew hybrid tetrapolar spot-band electrode configuration and wasdesigned to be comfortable and inconspicuous. Theobjective of the present study was to provide a preliminary evaluationof AIM comparability with the widely validated Minnesota model 304Bimpedance cardiograph with standard tetrapolar band electrodes.Orthostatic challenge was used to systematically alter cardiac functionin a laboratory setting in 11 healthy men and women. Both while thesubjects were sitting and while they were standing, the AIM yieldedmeasures of cardiac function, including heart rate, preejection period,left ventricular ejection time, and stroke volume, that were similar tothose acquired by using the reference Minnesota 304B system (allPearson R correlations > +0.87, allP < 0.001). Cardiac responses topostural shift, expressed as change measures from sitting to standing,were also comparable for the AIM and Minnesota reference monitoringsystems. Potential applications, including the assessment of 24-hhemodynamic profiles, are illustrated and discussed.

     

Microwave radiometry in biomedicine: a reappraisal.

Nearly 20 years ago the first papers appeared on biomedical applications of microwave radiometry, and many other papers have since appeared. Yet, despite its unique capabilities, microwave radiometry has so far received only limited acceptance by the medical community, and little commercial success. The chief reasons, we suggest, are the shallow depth of sensing and the difficulty of extracting imaging information from radiometry signals emitted by electrically heterogeneous media. A secondary factor has been the difficulty of validating many proposed clinical applications for the method--in particular, cancer detection. We suggest that microwave radiometry is a viable method of thermal sensing, but its successful applications are likely to be quite different than those that were originally conceived for the technique.     

Noninvasive population genetics: a review of sample source,diet, fragment length and microsatellite motif effects on amplification success and genotyping error rates

Noninvasive population genetics has found many applications in ecology and conservation biology. However, the technical difficulties inherent to the analysis of low quantities of DNA generally tend to limit the efficiency of this approach. The nature of samples and loci used in noninvasive population genetics are important factors that may help increasing the potential success of case studies. Here we reviewed the effects of the source of DNA (hair vs. faeces), the diet of focal species, the length of mitochondrial DNA fragments, and the length and repeat motif of nuclear microsatellite loci on genotyping success (amplification success and rate of allelic dropout). Locus-specific effects appeared to have the greatest impact, amplification success decreasing with both mitochondrial and microsatellite fragments’ length, while error rates increase with amplicons’ length. Dinucleotides showed best amplification success and lower error rates compared to longer repeat units. Genotyping success did not differ between hair- versus faeces-extracted DNA, and success in faeces-based analyses was not consistently influenced by the diet of focal species. While the great remaining variability among studies implies that other unidentified parameters are acting, results show that the careful choice of genetic markers may allow optimizing the success of noninvasive approaches.