Cardiovascular impact of intravenous caffeine in preterm infants.

AIM: To evaluate the acute effect of intravenous caffeine on heart rate and blood pressure variability in preterm infants. METHODS: We extracted and compared linear and nonlinear features of heart rate and blood pressure variability at two time points: prior to and in the two hours following a loading dose of 10 mg/kg caffeine base. RESULTS: We studied 31 preterm infants with arterial blood pressure data and 25 with electrocardiogram data, and compared extracted features prior to and following caffeine administration. We observed a reduction in both scaling exponents (α1 , α2 ) of mean arterial pressure from detrended fluctuation analysis and an increase in the ratio of short- (SD1) and long-term (SD2) variability from Poincare analysis (SD1/SD2). Heart rate variability analyses showed a reduction in α1 (mean (SD) of 0.92 (0.21) to 0.86 (0.21), p < 0.01), consistent with increased vagal tone. Following caffeine, beat-to-beat pulse pressure variability (SD) also increased (2.1 (0.64) to 2.5 (0.65) mmHg, p < 0.01). CONCLUSION: This study highlights potential elevation in autonomic nervous system responsiveness following caffeine administration reflected in both heart rate and blood pressure systems. The observed increase in pulse pressure variability may have implications for caffeine administration to infants with potentially impaired cerebral autoregulation.

On the Einthoven Triangle: A Critical Analysis of the Single Rotating Dipole Hypothesis.

Since its inception, electrocardiography has been based on the simplifying hypothesis that cardinal limb leads form an equilateral triangle of which, at the center/centroid, the electrical equivalent of the cardiac activity rotates during the cardiac cycle. Therefore, it is thought that the three limbs (right arm, left arm, and left leg) which enclose the heart into a circuit, where each branch directly implies current circulation through the heart, can be averaged together to form a stationary reference (central terminal) for precordials/chest-leads. Our hypothesis is that cardinal limbs do not form a triangle for the majority of the duration of the cardiac cycle. As a corollary, the central point may not lie in the plane identified by the limb leads. Using a simple and efficient algorithm, we demonstrate that the portion of the cardiac cycle where the three limb leads form a triangle is, on average less, than 50%.

Near infrared spectroscopy for body fat sensing in neonates: quantitative analysis by GAMOS simulations.

BACKGROUND: Under-nutrition in neonates is closely linked to low body fat percentage. Undernourished neonates are exposed to immediate mortality as well as unwanted health impacts in their later life including obesity and hypertension. One potential low cost approach for obtaining direct measurements of body fat is near-infrared (NIR) interactance. The aims of this study were to model the effect of varying volume fractions of melanin and water in skin over NIR spectra, and to define sensitivity of NIR reflection on changes of thickness of subcutaneous fat. GAMOS simulations were used to develop two single fat layer models and four complete skin models over a range of skin colour (only for four skin models) and hydration within a spectrum of 800-1100 nm. The thickness of the subcutaneous fat was set from 1 to 15 mm in 1 mm intervals in each model. RESULTS: Varying volume fractions of water in skin resulted minimal changes of NIR intensity at ranges of wavelengths from 890 to 940 nm and from 1010 to 1100 nm. Variation of the melanin volume in skin meanwhile was found to strongly influence the NIR intensity and sensitivity. The NIR sensitivities and NIR intensity over thickness of fat decreased from the Caucasian skin to African skin throughout the range of wavelengths. For the relationship between the NIR reflection and the thickness of subcutaneous fat, logarithmic relationship was obtained. CONCLUSIONS: The minimal changes of NIR intensity values at wavelengths within the ranges from 890 to 940 nm and from 1010 to 1100 nm to variation of volume fractions of water suggests that wavelengths within those two ranges are considered for use in measurement of body fat to solve the variation of hydration in neonates. The stronger influence of skin colour on NIR shows that the melanin effect needs to be corrected by an independent measurement or by a modeling approach. The logarithmic response obtained with higher sensitivity at the lower range of thickness of fat suggests that implementation of NIRS may be suited for detecting under-nutrition and monitoring nutritional interventions for malnutrition in neonates in resource-constrained communities.

High spatial resolution thermal mapping of radiofrequency ablation lesions using a novel thermochromic liquid crystal myocardial phantom.

BACKGROUND: Radiofrequency (RF) ablation causes thermal mediated irreversible myocardial necrosis. This study aimed to (i) characterize the thermal characteristics of RF ablation lesions with high spatial resolution using a thermochromic liquid crystal (TLC) myocardial phantom; and (ii) compare the thermochromic lesions with in vivo and in vitro ablation lesions. METHODS AND RESULTS: The myocardial phantom was constructed from a vertical sheet of TLC film, with color change between 50 °C (red) to 78 °C (black), embedded within a gel matrix, with impedance titrated to equal that of myocardium. Saline, with impedance titrated to blood values at 37 °C, was used as supernatant. A total of 51 RF ablations were performed. This comprised 17 ablations in the thermochromic gel phantom, bovine myocardial in vitro targets and ovine in vivo ablations, respectively. There was no difference in lesion dimensions between the thermochromic gel and in vivo ablations (lesion width 10.2 ± 0.2 vs 10.2 ± 2.4, P = 0.93; and depth 6.3 ± 0.1 vs 6.5 ± 1.7, P = 0.74). The spatial resolution of the thermochromic film was tested using 2 thermal point-sources that were progressively opposed and was demonstrated to be <300 µm. CONCLUSIONS: High spatial resolution thermal mapping of in vitro RF lesions with spatial resolution of at least 300 µm is possible using a thermochromic liquid crystal myocardial phantom model, with a good correlation to in vivo RF ablations. This model may be useful for assessing the thermal characteristics of RF lesions created using different ablation parameters and catheter technologies.

Investigating the role of capacitive coupling between the operating table and the return electrode of an electrosurgery unit in the modification of the current density distribution within the patients' body.

BACKGROUND: Electrosurgery units are widely employed in modern surgery. Advances in technology have enhanced the safety of these devices, nevertheless, accidental burns are still regularly reported. This study focuses on possible causes of sacral burns as complication of the use of electrosurgery. Burns are caused by local densifications of the current, but the actual pathway of current within patient's body is unknown. Numerical electromagnetic analysis can help in understanding the issue. METHODS: To this aim, an accurate heterogeneous model of human body (including seventy-seven different tissues), electrosurgery electrodes, operating table and mattress was build to resemble a typical surgery condition. The patient lays supine on the mattress with the active electrode placed onto the thorax and the return electrode on his back. Common operating frequencies of electrosurgery units were considered. Finite Difference Time Domain electromagnetic analysis was carried out to compute the spatial distribution of current density within the patient's body. A differential analysis by changing the electrical properties of the operating table from a conductor to an insulator was also performed. RESULTS: Results revealed that distributed capacitive coupling between patient body and the conductive operating table offers an alternative path to the electrosurgery current. The patient's anatomy, the positioning and the different electromagnetic properties of tissues promote a densification of the current at the head and sacral region. In particular, high values of current density were located behind the sacral bone and beneath the skin. This did not occur in the case of non-conductive operating table. CONCLUSION: Results of the simulation highlight the role played from capacitive couplings between the return electrode and the conductive operating table. The concentration of current density may result in an undesired rise in temperature, originating burns in body region far from the electrodes. This outcome is concordant with the type of surgery-related sacral burns reported in literature. Such burns cannot be immediately detected after surgery, but appear later and can be confused with bedsores. In addition, the dosimetric analysis suggests that reducing the capacity coupling between the return electrode and the operating table can decrease or avoid this problem.

Pregnancy detection and monitoring in cattle via combined foetus electrocardiogram and phonocardiogram signal processing.

BACKGROUND: Pregnancy testing in cattle is commonly invasive requiring manual rectal palpation of the reproductive tract that presents risks to the operator and pregnancy. Alternative non-invasive tests have been developed but have not gained popularity due to poor specificity, sensitivity and the inconvenience of sample handling. Our aim is to present the pilot study and proof of concept of a new non invasive technique to sense the presence and age (limited to the closest trimester of pregnancy) of the foetus by recording the electrical and audio signals produced by the foetus heartbeat using an array of specialized sensors embedded in a stand alone handheld prototype device. The device was applied to the right flank (approximately at the intercept of a horizontal line drawn through the right mid femur region of the cow and a vertical line drawn anywhere between lumbar vertebrae 3 to 5) of more than 2000 cattle from 13 different farms, including pregnant and not pregnant, a diversity of breeds, and both dairy and beef herds. Pregnancy status response is given "on the spot" from an optimized machine learning algorithm running on the device within seconds after data collection. RESULTS: Using combined electrical and audio foetal signals we detected pregnancy with a sensitivity of 87.6% and a specificity of 74.6% for all recorded data. Those values increase to 91% and 81% respectively by removing files with excessive noise (19%).Foetus ageing was achieved by comparing the detected foetus heart-rate with published tables. However, given the challenging farm environment of a restless cow, correct foetus ageing was achieved for only 21% of the correctly diagnosed pregnant cows. CONCLUSIONS: In conclusion we have found that combining ECG and PCG measurements on the right flank of cattle provides a reliable and rapid method of pregnancy testing. The device has potential to be applied by unskilled operators. This will generate more efficient and productive management of farms. There is potential for the device to be applied to large endangered quadrupeds in captive breeding programs where early, safe and reliable pregnancy diagnosis can be imperative but currently difficult to achieve.

Near-Infrared Spectroscopy to Monitor Nutritional Status of Neonates: A Review.

The World Health Organization reported that half or more of all under five deaths were caused by undernutrition in developing countries, with the majority of these deaths occurring in the first week of life. Even if the undernourished neonates manage to survive, they are exposed to long-term health impacts, including obesity, cardiovascular disease, and hypertension. Along with those health-impacts they can be exposed to risks related to detrimental early development, such as physical impairment, stunting, brain dysfunction, and reduced cognitive development. Body fat percentage has been recognized to be closely associated with undernutrition in neonates. In this article, the potential of near infrared spectroscopy (NIRS), along with previous methods to measure body fat in neonates, is reviewed and discussed.

Minimization of the Wilson's Central Terminal voltage potential via a genetic algorithm.

OBJECTIVE: The Wilson Central Terminal (WCT) is an artificially constructed reference for surface electrocardiography, which is assumed to be near zero and steady during the cardiac cycle; namely it is the simple average of the three recorded limbs (right arm, left arm and left leg) composing the Einthoven triangle and considered to be electrically equidistant from the electrical center of the heart. This assumption has been challenged and disproved in 1954 with an experiment designed just to measure and minimize WCT. Minimization was attempted varying in real time the weight resistors connected to the limbs. Unfortunately, the experiment required a very cumbersome setup and showed that WCT amplitude could not be universally minimized, in other words, the weight resistors change for each person. Taking advantage of modern computation techniques as well as of a special ECG device that aside of the standard 12-lead Electrocardiogram (ECG) can measure WCT components, we propose a software minimization (genetic algorithm) method using data recorded from 72 volunteers. RESULT: We show that while the WCT presents average amplitude relative to lead II of 58.85% (standard deviation of 30.84%), our minimization method yields an amplitude as small as 7.45% of lead II (standard deviation of 9.04%).

An anthropometric approach to characterising neonatal morbidity and body composition, using air displacement plethysmography as a criterion method.

BACKGROUND: With the greatest burden of infant undernutrition and morbidity in low and middle income countries (LMICs), there is a need for suitable approaches to monitor infants in a simple, low-cost and effective manner. Anthropometry continues to play a major role in characterising growth and nutritional status. METHODS: We developed a range of models to aid in identifying neonates at risk of malnutrition. We first adopted a logistic regression approach to screen for a composite neonatal morbidity, low and high body fat (BF%) infants. We then developed linear regression models for the estimation of neonatal fat mass as an assessment of body composition and nutritional status. RESULTS: We fitted logistic regression models combining up to four anthropometric variables to predict composite morbidity and low and high BF% neonates. The greatest area under receiver-operator characteristic curves (AUC with 95% confidence intervals (CI)) for identifying composite morbidity was 0.740 (0.63, 0.85), resulting from the combination of birthweight, length, chest and mid-thigh circumferences. The AUCs (95% CI) for identifying low and high BF% were 0.827 (0.78, 0.88) and 0.834 (0.79, 0.88), respectively. For identifying composite morbidity, BF% as measured via air displacement plethysmography showed strong predictive ability (AUC 0.786 (0.70, 0.88)), while birthweight percentiles had a lower AUC (0.695 (0.57, 0.82)). Birthweight percentiles could also identify low and high BF% neonates with AUCs of 0.792 (0.74, 0.85) and 0.834 (0.79, 0.88). We applied a sex-specific approach to anthropometric estimation of neonatal fat mass, demonstrating the influence of the testing sample size on the final model performance. CONCLUSIONS: These models display potential for further development and evaluation in LMICs to detect infants in need of further nutritional management, especially where traditional methods of risk management such as birthweight for gestational age percentiles may be variable or non-existent, or unable to detect appropriately grown, low fat newborns.

Prediction of intraventricular haemorrhage in preterm infants using time series analysis of blood pressure and respiratory signals.

Despite the decline in mortality rates of extremely preterm infants, intraventricular haemorrhage (IVH) remains common in survivors. The need for resuscitation and cardiorespiratory management, particularly within the first 24 hours of life, are important factors in the incidence and timing of IVH. Variability analyses of heart rate and blood pressure data has demonstrated potential approaches to predictive monitoring. In this study, we investigated the early identification of infants at a high risk of developing IVH, using time series analysis of blood pressure and respiratory data. We also explore approaches to improving model performance, such as the inclusion of multiple variables and signal pre-processing to enhance the results from detrended fluctuation analysis. Of the models we evaluated, the highest area under receiver-operator characteristic curve (5th, 95th percentile) achieved was 0.921 (0.82, 1.00) by mean diastolic blood pressure and the long-term scaling exponent of pulse interval (PI α2), exhibiting a sensitivity of >90% at a specificity of 75%. Following evaluation in a larger population, our approach may be useful in predictive monitoring to identify infants at high risk of developing IVH, offering caregivers more time to adjust intensive care treatment.

Respiratory Artefact Removal in Forced Oscillation Measurements: A Machine Learning Approach.

GOAL: Respiratory artefact removal for the forced oscillation technique can be treated as an anomaly detection problem. Manual removal is currently considered the gold standard, but this approach is laborious and subjective. Most existing automated techniques used simple statistics and/or rejected anomalous data points. Unfortunately, simple statistics are insensitive to numerous artefacts, leading to low reproducibility of results. Furthermore, rejecting anomalous data points causes an imbalance between the inspiratory and expiratory contributions. METHODS: From a machine learning perspective, such methods are unsupervised and can be considered simple feature extraction. We hypothesize that supervised techniques can be used to find improved features that are more discriminative and more highly correlated with the desired output. Features thus found are then used for anomaly detection by applying quartile thresholding, which rejects complete breaths if one of its features is out of range. The thresholds are determined by both saliency and performance metrics rather than qualitative assumptions as in previous works. RESULTS: Feature ranking indicates that our new landmark features are among the highest scoring candidates regardless of age across saliency criteria. F1-scores, receiver operating characteristic, and variability of the mean resistance metrics show that the proposed scheme outperforms previous simple feature extraction approaches. Our subject-independent detector, 1IQR-SU, demonstrated approval rates of 80.6% for adults and 98% for children, higher than existing methods. CONCLUSION: Our new features are more relevant. Our removal is objective and comparable to the manual method. SIGNIFICANCE: This is a critical work to automate forced oscillation technique quality control.

Freezing of Gait Detection in Parkinson's Disease: A Subject-Independent Detector Using Anomaly Scores.

Freezing of gait (FoG) is common in Parkinsonian gait and strongly relates to falls. Current clinical FoG assessments are patients' self-report diaries and experts' manual video analysis. Both are subjective and yield moderate reliability. Existing detection algorithms have been predominantly designed in subject-dependent settings. In this paper, we aim to develop an automated FoG detector for subject independent. After extracting highly relevant features, we apply anomaly detection techniques to detect FoG events. Specifically, feature selection is performed using correlation and clusterability metrics. From a list of 244 feature candidates, 36 candidates were selected using saliency and robustness criteria. We develop an anomaly score detector with adaptive thresholding to identify FoG events. Then, using accuracy metrics, we reduce the feature list to seven candidates. Our novel multichannel freezing index was the most selective across all window sizes, achieving sensitivity (specificity) of (). On the other hand, freezing index from the vertical axis was the best choice for a single input, achieving sensitivity (specificity) of () for ankle and () for back sensors. Our subject-independent method is not only significantly more accurate than those previously reported, but also uses a much smaller window (e.g., versus ) and/or lower tolerance (e.g., versus ).Freezing of gait (FoG) is common in Parkinsonian gait and strongly relates to falls. Current clinical FoG assessments are patients' self-report diaries and experts' manual video analysis. Both are subjective and yield moderate reliability. Existing detection algorithms have been predominantly designed in subject-dependent settings. In this paper, we aim to develop an automated FoG detector for subject independent. After extracting highly relevant features, we apply anomaly detection techniques to detect FoG events. Specifically, feature selection is performed using correlation and clusterability metrics. From a list of 244 feature candidates, 36 candidates were selected using saliency and robustness criteria. We develop an anomaly score detector with adaptive thresholding to identify FoG events. Then, using accuracy metrics, we reduce the feature list to seven candidates. Our novel multichannel freezing index was the most selective across all window sizes, achieving sensitivity (specificity) of (). On the other hand, freezing index from the vertical axis was the best choice for a single input, achieving sensitivity (specificity) of () for ankle and () for back sensors. Our subject-independent method is not only significantly more accurate than those previously reported, but also uses a much smaller window (e.g., versus ) and/or lower tolerance (e.g., versus ).

Design Considerations in Development of a Mobile Health Intervention Program: The TEXT ME and TEXTMEDS Experience.

BACKGROUND: Mobile health (mHealth) has huge potential to deliver preventative health services. However, there is paucity of literature on theoretical constructs, technical, practical, and regulatory considerations that enable delivery of such services. OBJECTIVES: The objective of this study was to outline the key considerations in the development of a text message-based mHealth program; thus providing broad recommendations and guidance to future researchers designing similar programs. METHODS: We describe the key considerations in designing the intervention with respect to functionality, technical infrastructure, data management, software components, regulatory requirements, and operationalization. We also illustrate some of the potential issues and decision points utilizing our experience of developing text message (short message service, SMS) management systems to support 2 large randomized controlled trials: TEXT messages to improve MEDication adherence & Secondary prevention (TEXTMEDS) and Tobacco, EXercise and dieT MEssages (TEXT ME). RESULTS: The steps identified in the development process were: (1) background research and development of the text message bank based on scientific evidence and disease-specific guidelines, (2) pilot testing with target audience and incorporating feedback, (3) software-hardware customization to enable delivery of complex personalized programs using prespecified algorithms, and (4) legal and regulatory considerations. Additional considerations in developing text message management systems include: balancing the use of customized versus preexisting software systems, the level of automation versus need for human inputs, monitoring, ensuring data security, interface flexibility, and the ability for upscaling. CONCLUSIONS: A merging of expertise in clinical and behavioral sciences, health and research data management systems, software engineering, and mobile phone regulatory requirements is essential to develop a platform to deliver and manage support programs to hundreds of participants simultaneously as in TEXT ME and TEXTMEDS trials. This research provides broad principles that may assist other researchers in developing mHealth programs.

Length-free near infrared measurement of newborn malnutrition.

Under-nutrition in neonates can cause immediate mortality, impaired cognitive development and early onset adult disease. Body fat percentage measured using air-displacement-plethysmography has been found to better indicate under-nutrition than conventional birth weight percentiles. However, air-displacement-plethysmography equipment is expensive and non-portable, so is not suited for use in developing communities where the burden is often the greatest. We proposed a new body fat measurement technique using a length-free model with near-infrared spectroscopy measurements on a single site of the body - the thigh. To remove the need for length measurement, we developed a model with five discrete wavelengths and a sex parameter. The model was developed using air-displacement-plethysmography measurements in 52 neonates within 48 hours of birth. We identified instrumentation required in a low-cost LED-based screening device and incorporated a receptor device that can increase the amount of light collected. This near-infrared method may be suitable as a low cost screening tool for detecting body fat levels and monitoring nutritional interventions for malnutrition in neonates and young children in resource-constrained communities.

How to test bioinformatics software?

Bioinformatics is the application of computational, mathematical and statistical techniques to solve problems in biology and medicine. Bioinformatics programs developed for computational simulation and large-scale data analysis are widely used in almost all areas of biophysics. The appropriate choice of algorithms and correct implementation of these algorithms are critical for obtaining reliable computational results. Nonetheless, it is often very difficult to systematically test these programs as it is often hard to verify the correctness of the output, and to effectively generate failure-revealing test cases. Software testing is an important process of verification and validation of scientific software, but very few studies have directly dealt with the issues of bioinformatics software testing. In this work, we review important concepts and state-of-the-art methods in the field of software testing. We also discuss recent reports on adapting and implementing software testing methodologies in the bioinformatics field, with specific examples drawn from systems biology and genomic medicine.

Magnetic guidance versus manual control: comparison of radiofrequency lesion dimensions and evaluation of the effect of heart wall motion in a myocardial phantom.

BACKGROUND: Magnetic navigation system (MNS) ablation was suspected to be less effective and unstable in highly mobile cardiac regions compared to radiofrequency (RF) ablations with manual control (MC). The aim of the study was to compare the (1) lesion size and (2) stability of MNS versus MC during irrigated RF ablation with and without simulated mechanical heart wall motion. METHODS: In a previously validated myocardial phantom, the performance of Navistar RMT Thermocool catheter (Biosense Webster, CA, USA) guided with MNS was compared to manually controlled Navistar irrigated Thermocool catheter (Biosense Webster, CA, USA). The lesion dimensions were compared with the catheter in inferior and superior orientation, with and without 6-mm simulated wall motion. All ablations were performed with 40 W power and 30 ml/ min irrigation for 60 s. RESULTS: A total of 60 ablations were performed. The mean lesion volumes with MNS and MC were 57.5 ± 7.1 and 58.1 ± 7.1 mm(3), respectively, in the inferior catheter orientation (n = 23, p = 0.6), 62.8 ± 9.9 and 64.6 ± 7.6 mm(3), respectively, in the superior catheter orientation (n = 16, p = 0.9). With 6-mm simulated wall motion, the mean lesion volumes with MNS and MC were 60.2 ± 2.7 and 42.8 ± 8.4 mm(3), respectively, in the inferior catheter orientation (n = 11, p = <0.01*), 74.1 ± 5.8 and 54.2 ± 3.7 mm(3), respectively, in the superior catheter orientation (n = 10, p = <0.01*). During 6-mm simulated wall motion, the MC catheter and MNS catheter moved 5.2 ± 0.1 and 0 mm, respectively, in inferior orientation and 5.5 ± 0.1 and 0 mm, respectively, in the superior orientation on the ablation surface. CONCLUSIONS: The lesion dimensions were larger with MNS compared to MC in the presence of simulated wall motion, consistent with greater catheter stability. However, similar lesion dimensions were observed in the stationary model.

Unsupervised discrimination of motor unit action potentials using spectrograms.

Single motor unit activity study is a major research interest because changes of MUAP morphology, MU activation, and MU recruitment provide the most informative part in diagnosis and treatment of neuromuscular disorders. Intramuscular recordings often provide a more than one motor unit activities, thus MUAP discrimination is a crucial task to study single unit activities. Most neurology laboratories worldwide still need specialists who spend hours to classify MUAPs. In this study, we present a new real-time unsupervised method for MUAP discrimination. After automatically detect MUAPs, we extract features of spectrogram images from the wavelet coefficients of MUAPs. Unlike benchmark methods, we do not calculate Euclidean distances which assumes a spherical distribution of data. Instead, we measure correlation between spectrogram images. Then MUAPs are automatically discriminated without any prior knowledge of the number of clusters as in previous works. MUAP were detected on a real data set with a precision PPV of 94% (tolerance of 2 ms). We obtained a similar result in MUAP classification to the reference. The difference in percentages of MU proportions between our method and the reference were 3% for MU1, 0.4% for MU2, and 12% for MU3. In contrast, F1-score for MU3 reached the highest level at 91% (PPV at the highest of 96.64% as well).

Electrical impedance tomography for assessing ventilation/perfusion mismatch for pulmonary embolism detection without interruptions in respiration.

Recent studies have shown high correlation between pulmonary perfusion mapping with impedance contrast enhanced Electrical Impedance Tomography (EIT) and standard perfusion imaging methods such as Computed Tomography (CT) and Single Photon Emission Computerized Tomography (SPECT). EIT has many advantages over standard imaging methods as it is highly portable and non-invasive. Contrast enhanced EIT uses hypertonic saline bolus instead of nephrotoxic contrast medium that are utilized by CT and nuclear Ventilation/Perfusion (V/Q) scans. However, current implementation of contrast enhanced EIT requires induction of an apnea period for perfusion measurement, rendering it disadvantageous compared with current gold standard imaging modalities. In the present paper, we propose the use of a wavelet denoising algorithm to separate perfusion signal from ventilation signal such that no interruption in patient's ventilation would be required. Furthermore, right lung to left lung perfusion ratio and ventilation ratio are proposed to assess the mismatch between ventilation and perfusion for detection of Pulmonary Embolism (PE). The proposed methodology was validated on an ovine model (n=3, 83.7±7.7 kg) with artificially induced PE in the right lung. The results showed a difference in right lung to left lung perfusion ratio between baseline and diseased states in all cases with all paired t-tests between baseline and PE yielding p <; 0.01, while the right lung to left lung ventilation ratio remained unchanged in two out of three experiments. Statistics were pooled from multiple repetitions of measurements per experiment.

Towards true unipolar bio-potential recording: a preliminary result for ECG.

We present a bio-potential front-end capable of recording unipolar ECG leads without making use of the Wilson central terminal (WCT). The information contained in the new unipolar recordings may yield unique diagnostic information as it avoids the need to essentially subtract data or make use of the averaging effect imposed by the WCT. The system also allows a direct, real-time software calculation of signals corresponding to standard ECG leads for standard diagnosis. These calculated standard ECG leads have a correlation in excess of 92% with a gold standard ECG recorded in parallel. The circuit is wideband, compatible with both the standard and the dry electrodes, and of low power (requiring less than 20 mW powered at 12 V). It is therefore well suited for long-term applications.

A local region of interest imaging method for electrical impedance tomography with internal electrodes.

Electrical Impedance Tomography (EIT) is a very attractive functional imaging method despite the low sensitivity and resolution. The use of internal electrodes with the conventional reconstruction algorithms was not enough to enhance image resolution and accuracy in the region of interest (ROI). We propose a local ROI imaging method with internal electrodes developed from careful analysis of the sensitivity matrix that is designed to reduce the sensitivity of the voxels outside the local region and optimize the sensitivity of the voxel inside the local region. We perform numerical simulations and physical measurements to demonstrate the localized EIT imaging method. In preliminary results with multiple objects we show the benefits of using an internal electrode and the improved resolution due to the local ROI image reconstruction method. The sensitivity is further increased by allowing the surface electrodes to be unevenly spaced with a higher density of surface electrodes near the ROI. Also, we analyse how much the image quality is improved using several performance parameters for comparison. While these have not yet been studied in depth, it convincingly shows an improvement in local sensitivity in images obtained with an internal electrode in comparison to a standard reconstruction method.