Phasor imaging with a widefield photon-counting detector

Fluorescence lifetime can be used as a contrast mechanism to distinguish fluorophores for localization or tracking, for studying molecular interactions, binding, assembly, and aggregation, or for observing conformational changes via Fo?rster resonance energy transfer (FRET) between donor and acceptor molecules. Fluorescence lifetime imaging microscopy (FLIM) is thus a powerful technique but its widespread use has been hampered by demanding hardware and software requirements. FLIM data is often analyzed in terms of multicomponent fluorescence lifetime decays, which requires large signals for a good signal-to-noise ratio. This confines the approach to very low frame rates and limits the number of frames which can be acquired before bleaching the sample. Recently, a computationally efficient and intuitive graphical representation, the phasor approach, has been proposed as an alternative method for FLIM data analysis at the ensemble and single-molecule level. In this article, we illustrate the advantages of combining phasor analysis with a widefield time-resolved single photon-counting detector (the H33D detector) for FLIM applications. In particular we show that phasor analysis allows real-time subsecond identification of species by their lifetimes and rapid representation of their spatial distribution, thanks to the parallel acquisition of FLIM information over a wide field of view by the H33D detector. We also discuss possible improvements of the H33D detector's performance made possible by the simplicity of phasor analysis and its relaxed timing accuracy requirements compared to standard time-correlated single-photon counting (TCSPC) methods.     

Visualization of left ventricular Purkinje fiber distribution using widefield optical coherence microscopy

Background: The distribution and connection of ventricular Purkinje fibers are known to be associated with idiopathic left ventricular arrhythmias. Unusual anatomy is one of the important factors associated with catheter ablation success rate. With the widefield high-speed, swept-source optical coherence microscopy (OCM) and light microscope, we visualized the left ventricular Purkinje fiber distribution. Methods: Left ventricular walls of five adult ovine hearts were incised from the mitral annulus to the apex. Using the widefield OCM technique and light microscopy, we observed the distribution, direction, depth, and dividing patterns of the Purkinje network with multiple tangential angles and without tissue destruction. Results: Widefield OCM was used to characterize the ovine heart Purkinje network system in a 4 × 4 mm² field. Left ventricular Purkinje fibers traveled in the sub-endocardial area near the left-sided peri-membranous septal area and ran like a wide hair bundle. The distal branching fibers penetrated to the endocardium and connected to the contractile muscle. In this distal area, Purkinje fibers were connected to each other, forming multiple layers. Some Purkinje fibers were directly connected within the false tendon between the papillary muscles or between the trabeculations. Some free-running Purkinje fibers were directly connected to the papillary muscle from the left bundle. Conclusion: Using widefield OCM, we were able to observe the left bundle and its branching patterns in ovine left ventricle without tissue destruction. This might be applied to future cardiac ablation procedures.     

In-vivo non-invasive study of the thermoregulatory function of the blood vessels in the rat tail using magnetic resonance angiography

In rats, a significant portion of total body heat loss occurs through sympathetically mediated changes in tail blood flow, making the rat tail a convenient model to study vasomotor activity during thermoregulation. Our aim was to perform a non-invasive study of the mechanisms of blood vessel control in the rat tail upon increasing body temperature. In anaesthetized rats, blood vessel temperature was monitored using non-invasive thermistors positioned on the skin surface, covering the ventral artery (Ta) and lateral vein (Tv), and changes in blood vessel size were measured using in-vivo magnetic resonance angiography (MRA). Two important regions of the tail (base and middle) were studied during a gradual rise of rectal temperature (Tr) from 37 to 40 degrees C. MRA data show that increasing Tr causes increased diameter of both arteries and veins of the tail, that venous diameter changes are greater than arterial diameter changes, and that diameter changes of both types of vessel are greater at the base of the tail than in the middle. Temperature data allowed calculation of (Ta - Tv), which we used as an index of flow through arteriovenous anastomoses (AVAs). The data suggest that AVAs near the base of the tail are important in heat exchange, and that they remain open only for Tr values between 38 and 39 degrees C.     

Glycinergic input of widefield, displaced amacrine cells of the mouse retina

Glycine receptors (GlyRs) of displaced amacrine cells of the mouse retina were analysed using whole cell recordings and immunocytochemical staining with subunit-specific antibodies. During the recordings the cells were filled with a fluorescent tracer and 11 different morphological types could be identified. The studies were performed in wild-type mice and in mutant mice deficient in the GlyRα1 ( Glra1^spd-ot , 'oscillator' mouse), the GlyRα2 ( Glra2 ^−/−) and the GlyRα3 subunit ( Glra3 ^−/−). Based on their responses to the application of exogenous glycine in the retinas of wild-type and mutant mice, the cells were grouped into three major classes: group I cells (comprising the morphological types MA-S5, MA-S1, MA-S1/S5, A17, PA-S1, PA-S5 and WA-S1), group II cells (comprising the morphological types PA-S4, WA-S3 and WA-multi) and ON-starburst cells. For further analysis, spontaneous inhibitory postsynaptic currents (sIPSCs) were measured both in wild-type and mutant mouse retinas. Glycinergic sIPSCs and glycine induced currents of group I cells remained unaltered across wild-type and the three mutant mice (mean decay time constant of sIPSCs, τ∼25 ms). Group II cells showed glycinergic sIPSCs and glycine induced currents in wild-type, Glra1^spd-ot and Glra3 ^−/− mice (τ∼25 ms); however, glycinergic currents were absent in group II cells of Glra2 ^−/− mice. Glycine induced currents and sIPSCs recorded from ON-starburst amacrine cells did not differ significantly between wild-type and the mutant mouse retinas (τ∼50–70 ms). We propose that GlyRs of group II cells are dominated by the α2 subunit; GlyRs of ON-starburst amacrine cells appear to be dominated by the α4 subunit.     

A non-invasive Cochlear Microphonic measurement system

The Cochlear Microphonic is one of the electrical potentials generated by the ear in response to audible stimuli. It is very difficult to measure the CM non-invasively because it has a very small magnitude (less than 1μV). A high Common Mode Rejection Ratio (CMRR) and very large bandwidth (5Hz-20kHz) biomedical amplifier system is presented to measure the signal. The system also uses a driven right leg circuit to increase the CMRR.     

Functional angiography

The discovery of X-rays over a century ago enabled noninvasive examination of the human body. Contrast agents that enhanced X-ray images were soon developed that advanced angiology by allowing exploration of the vascular tree. Starting as a diagnostic tool, angiography underwent technological transformations over the last century and became a basis for interventional therapy as well. Initially a static two-dimensional record of the vasculature on screen films, angiography has evolved to real-time two-dimensional display of the vasculature on television monitors, three-dimensional reconstruction from computerized tomographic (CT) scans, and, more recently, three-dimensional cone-beam reconstruction. Cinematographic angiography is referred to as dynamic angiography in current terminology, but it essentially provides no more than images of vascular structures and changes therein. Although dynamic angiography has facilitated advances in image-guided interventions, the evaluation of blood flow rate, or perfusion, and blood flow velocity using angiography remains elusive. Many lines of research have been pursued toward enabling such evaluations, but none have found their way into clinical practice. This article reviews angiographic flow assessment methods attempted over the past several decades and explores some new avenues that may facilitate the transfer of such methods into the clinical practice of diagnostic and interventional angiography and, eventually, contribute to better patient care.     

孕早期无创性产前诊断的研究进展

随着社会进步和科学技术日新月异,孕早期无创性的产前诊断愈来愈受重视。国内外学者对孕妇外周血特别是早孕期宫颈胎儿滋养细胞应用于产前诊断来检测胎儿性别、非整倍体异常、单基因遗传病等进行了大量的实验研究,以期使这种早期,简便,无创性产前诊断的方法应用于临床。而从宫颈处获取的胎儿细胞量远高于从母体外周血获得的,结合现有的细胞检测技术,使其更具应用潜力。     

Computerized automatic non-invasive blood pressure monitoring system

A non-invasive, fully automatic blood pressure monitoring system was developed to make the diagnosis of hypertension more accurate and to help individualizing antihypertensive therapy. The system consists of two subunits: the automatic microprocessor-controlled blood pressure monitor (Nippon Colin Co. BP 203) and a microcomputer system (Commodore 64). The blood pressure monitor is fitted to the computer by our own interface and data transfer programme. Data-analysing, graphic displaying and plotting programmes were also developed by us. Circadian average blood pressure, its variability, the rhythm variabilities of chronobiological cosinor analysis: mesor, amplitude, acrophase and linear trend, have been calculated by means of these programmes. Results of blood pressure monitoring are demonstrated in a patient with essential hypertension and in a patient with renoparenchymal hypertension. The perspectives of this method in biomedical research and in clinical pharmacology are illustrated and discussed.     

颅内压检测技术研究进展

近年来,随着颅内压（ICP）检测精度的提高,其在临床上的应用也越来越多.多种检测技术被运用于临床,可分为侵入式硬脑膜外导管法、蛛网膜下腔螺栓法、脑室导管法、光纤探头检测、微型芯片和非侵入式诱发耳声刺激法、经眼检测法、经颅多普勒法、影像学方法及磁感应检测法.就ICP检测生理基础,常见ICP检测技术,特别对非侵入式ICP检测方法进行了综述,评价了ICP检测方法的优缺点,并展望了非侵入式ICP检测技术的发展.     

Implementation of non-invasive brain physiological monitoring concepts

The paper presents innovative methods and technology for non-invasive intracranial hemodynamics monitoring based on the measurement of brain parenchyma acoustic properties. The clinical investigation of new technology shows the similarity between the invasively recorded intracranial pressure (ICP) and non-invasively recorded intracranial blood volume (IBV) pulse waves, slow waves and slow trends under intensive care unit (ICU) conditions. Also, the applicability of the non-invasive IBV slow wave monitoring technique for cerebrovascular autoregulation non-invasive long-term monitoring is demonstrated by theoretical and experimental studies.     

Design of non-invasive glucose meter using near-infrared technique

Diabetics need to keep track of their blood glucose level and measure it regularly to determine their insulin dose intake and to ensure that glucose level is always within the normal range. In this article, a system that enables the measurement of blood glucose level non-invasively is designed. This article uses a near infra-red (NIR) transmittance spectroscopy, without drawing blood, puncturing the skin, or causing pain. It involves a light source and light detector circuits positioned on a certain region of the body. The attenuated received infra-red signal by the detector is a measure of the blood glucose level of that region. Data are collected from the receiving circuit and sent to a microcontroller using CoolTerm application, then exporting it to Excel Sheet, in which mean values and graphs are obtained. The performance of the circuit with and without Filtering is examined. A downward pattern was noticed, as the glucose concentration in the solution increased, the voltage output decreased, meaning that a less intensity light was detected by the receiving circuit. An improvement in the accuracy of measurements by 17% was achieved, when a notch filter is implemented to cut the voltage components corresponding to the power line noisy signals.     

Exploring non-invasive methods to assess pain in sheep

The aim of this study was to determine whether changes in eye temperature, measured using infrared thermography (IRT), and heart rate variability (HRV) can detect moderate levels of pain in sheep. Six ewes received the following treatments: 1) noxious ischaemic stimulus by application of a forelimb tourniquet (S), 2) noxious ischaemic stimulus and flunixin meglumine (S + F), and 3) flunixin meglumine (F). Maximum eye temperature, HRV, mechanical nociceptive threshold, blood pressure and behaviour were recorded for up to 60 min, including 15 min of baseline, 30 min during intervention and 15 min post-intervention. There was a tendency towards a decrease in the heart rate variability parameters RMSSD (the root mean square of successive R-R intervals) and SDNN (the standard deviation of all interbeat intervals) in treatment S compared to treatment F, and a significant increase in the same parameters between test day 1 and 3. A reduction in eye temperature was detected for all treatments during intervention, but no difference was found between S and F and S + N and F during intervention. The eye temperature decreased more in test day 2 and 3 compared to test day 1 during intervention. A significant reduction for both lip licking and vocalisation was observed between test day 1 and 3, and forward facing ears was the ear posture most frequently recorded in test day 1. We suggest that HRV is a sensitive, non-invasive method to assess mild to moderate pain in sheep, whereas IRT is a less sensitive method.