Photoplethysmography-based derivation of physiological information using the BioPoint

The BioPoint is a new wireless and wearable device, targeting both the ambulatory and on-site monitoring of biosignals. It is described as being capable of streaming and recording the i) electromyography, ii) electrocardiography, iii) electrodermal activity, iv) photoplethysmography, v) skin temperature and vi) actigraphy simultaneously, while making the raw signals recorded by the sensors readily available. However, an in-depth assessment of the biophysical signals recorded by this device, as well as its ability to derive vital signs and other health metrics, remains to be carried out. Consequently, this work proposes a preliminary study to evaluate the quality of the signals that can be acquired by this wearable with a focus on the derivation of heart rate and peripheral blood oxygenation via photoplethysmography. The device is quantitatively compared to the medical-grade pulse oximeter NoninConnect 3245, by Nonin inc. This study was performed with participants wearing the BioPoint at different positions on the body (finger, wrist, forearm, biceps and plantar arch), while the NoninConnect was worn on the fingertip and used as the ground truth. The results show that the BioPoint can accurately determine both heart rate and oxygen saturation from various locations on the body. However, as the BioPoint's photoplethysmograph is not calibrated it cannot be used for medical purposes (non-medical-grade).

Enhancing OSA Assessment with Explainable AI. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023;2023:1-6. [PMID: 38083271 DOI: 10.1109/embc40787.2023.10341035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Explainable Artificial Intelligence (xAI) is a rapidly growing field that focuses on making deep learning models interpretable and understandable to human decision-makers. In this study, we introduce xAAEnet, a novel xAI model applied to the assessment of Obstructive Sleep Apnea (OSA) severity. OSA is a prevalent sleep disorder that can lead to numerous medical conditions and is currently assessed using the Apnea-Hypopnea Index (AHI). However, AHI has been criticized for its inability to accurately estimate the effect of OSAs on related medical conditions. To address this issue, we propose a human-centric xAI approach that emphasizes similarity between apneic events as a whole and reduces subjectivity in diagnosis by examining how the model makes its decisions. Our model was trained and tested on a dataset of 60 patients' Polysomnographic (PSG) recordings. Our results demonstrate that the proposed model, xAAEnet, outperforms models with traditional architectures such as convolutional regressor, autoencoder (AE), and variational autoencoder (VAE). This study highlights the potential of xAI in providing an objective OSA severity scoring method.Clinical relevance- This study provides an objective OSA severity scoring technique which could improve the management of apneic patients in clinical practice.

Biases in BCI experiments: Do we really need to balance stimulus properties across categories?

Brain Computer Interfaces (BCIs) consist of an interaction between humans and computers with a specific mean of communication, such as voice, gestures, or even brain signals that are usually recorded by an Electroencephalogram (EEG). To ensure an optimal interaction, the BCI algorithm typically involves the classification of the input signals into predefined task-specific categories. However, a recurrent problem is that the classifier can easily be biased by uncontrolled experimental conditions, namely covariates, that are unbalanced across the categories. This issue led to the current solution of forcing the balance of these covariates across the different categories which is time consuming and drastically decreases the dataset diversity. The purpose of this research is to evaluate the need for this forced balance in BCI experiments involving EEG data. A typical design of neural BCIs involves repeated experimental trials using visual stimuli to trigger the so-called Event-Related Potential (ERP). The classifier is expected to learn spatio-temporal patterns specific to categories rather than patterns related to uncontrolled stimulus properties, such as psycho-linguistic variables (e.g., phoneme number, familiarity, and age of acquisition) and image properties (e.g., contrast, compactness, and homogeneity). The challenges are then to know how biased the decision is, which features affect the classification the most, which part of the signal is impacted, and what is the probability to perform neural categorization per se. To address these problems, this research has two main objectives: (1) modeling and quantifying the covariate effects to identify spatio-temporal regions of the EEG allowing maximal classification performance while minimizing the biasing effect, and (2) evaluating the need to balance the covariates across categories when studying brain mechanisms. To solve the modeling problem, we propose using a linear parametric analysis applied to some observable and commonly studied covariates to them. The biasing effect is quantified by comparing the regions highly influenced by the covariates with the regions of high categorical contrast, i.e., parts of the ERP allowing a reliable classification. The need to balance the stimulus's inner properties across categories is evaluated by assessing the separability between category-related and covariate-related evoked responses. The procedure is applied to a visual priming experiment where the images represent items belonging to living or non-living entities. The observed covariates are the commonly controlled psycho-linguistic variables and some visual features of the images. As a result, we identified that the category of the stimulus mostly affects the late evoked response. The covariates, when not modeled, have a biasing effect on the classification, essentially in the early evoked response. This effect increases with the diversity of the dataset and the complexity of the algorithm used. As the effects of both psycho-linguistic variables and image features appear outside of the spatio-temporal regions of significant categorical contrast, the proper selection of the region of interest makes the classification reliable. Having proved that the covariate effects can be separated from the categorical effect, our framework can be further used to isolate the category-dependent evoked response from the rest of the EEG to study neural processes involved when seeing living vs. non-living entities.

Optimization & Characterization of Interdigitated Electrodes for Microbial Growth Monitoring

This study optimally designed and implemented highly sensitive microscale interdigitated electrodes (IDEs) to monitor microorganisms' growth in diverse environments. Gold interdigitated electrodes (AuIDE) with 4 mm×4 mm effective sensing area and varying microscale interdigitate gaps were designed and fabricated. The electrodes were electrically characterized voltametrically. Electrochemical impedance spectroscopy (EIS) measurements were conducted to determine the optimal geometry by observing the impedance spectra of microelectrodes through varying pH and temperature. Furthermore, the sensors sensitivity was evaluated by measuring the impedance properties of a microscale volume of microorganism concentrations in growth media solution.

A versatile wearable sEMG recording system for long-term epileptic seizure monitoring

Surface electromyography (sEMG) can be used to detect motor epileptic seizures non-invasively. For clinical use, a compact-size, user-friendly, safe and accurate sEMG measurement system can be worn by epileptic patients to detect and characterize a seizure. Such devices must be small, wireless, power-efficient minimally invasive and robust to avoid movement artefacts, friction, and slipping of the electrode, which can compromise data integrity and/or generate false positives or false negatives. This paper presents a highly versatile device that can be worn in different locations on the body to capture sEMG signals in a freely moving user without movement artefact. The system can be safely worn on the body for several hours to capture sEMG from wet Ag/AgCl electrodes, while sEMG data is wirelessly transmitted to a host computer within a range of 20 m. We demonstrate the versatility of our sensor by recording sEMG from five different body locations in a freely moving volunteer. Then, simulated seizure data was captured while the device was placed on the extensor carpi ulnaris. We show that sEMG bursts were successfully recorded to characterize the seizure afterward. The presented sensor prototype is small (5 cm x 3.5 cm x 1 cm), lightweight (46 g), and has an autonomy of 12 hrs from a small 110-mAh battery.

Similarities and Differences Between Eye and Mouse Dynamics During Web Pages Exploration

The study of eye movements is a common way to non-invasively understand and analyze human behavior. However, eye-tracking techniques are very hard to scale, and require expensive equipment and extensive expertise. In the context of web browsing, these issues could be overcome by studying the link between the eye and the computer mouse. Here, we propose new analysis methods, and a more advanced characterization of this link. To this end, we recorded the eye, mouse, and scroll movements of 151 participants exploring 18 dynamic web pages while performing free viewing and visual search tasks for 20 s. The data revealed significant differences of eye, mouse, and scroll parameters over time which stabilize at the end of exploration. This suggests the existence of a task-independent relationship between eye, mouse, and scroll parameters, which are characterized by two distinct patterns: one common pattern for movement parameters and a second for dwelling/fixation parameters. Within these patterns, mouse and eye movements remained consistent with each other, while the scrolling behaved the opposite way.

Forearm High-Density Electromyography Data Visualization and Classification with Machine Learning for Hand Prosthesis Control

Electromyography offers a way to interface an amputee's resilient muscles to control a bionic prosthesis. While myoelectric prostheses are promising, user acceptance of these devices remain low due to a lack of intuitiveness and ease-of-use. Using a low-cost wearable flexible electrodes array, the proposed system leverages high-density surface electromyography (HD-EMG) and deep learning techniques to classify forearm muscle contractions. These techniques allow for increased intuitiveness and ease-of-use of a myoelectric control scheme with a single easy-to-install electrodes apparatus. This paper proposes a flexible electrodes array construction using standard printed circuit board manufacturing processes for low-cost and quick design-to-production cycles. HD-EMG dataset visualization with t-distributed Stochastic Neighbor Embedding (t-SNE) is introduced, and offline classification results of the wearable gesture recognition system for hand prosthesis control are validated on a group of 8 able-bodied subjects. Using a majority vote on 5 successive inferences, a median recognition accuracy of 98.61 % was obtained across the group for an 8 gestures set. For a 6 gestures set containing commonly used prosthesis positions, the median accuracy reached 99.57 % with the majority vote.

The EcoChip 2: An Autonomous Sensor Platform for Multimodal Bio-environmental Monitoring of the Northern Habitat

This paper presents the EcoChip 2, an autonomous multimodal bio-environmental sensor platform for the monitoring of microorganisms in the northern habitat. The EcoChip 2 prototype includes an array of 96-wells for the continuous monitoring of microbiological growth through a multichannel electrochemical impedance analyzer circuit. In addition, the platform includes luminosity, humidity, temperature sensors and monitoring. The developed electronic board uses an ultra-low-power microcontroller unit, a custom power management unit, a low-power wireless ISM-2.45 GHz transceiver, and a flash memory to accumulate and store the sensor data over extended monitoring periods. When a wireless base station is placed within the transmission range of the EcoChip 2, an embedded low-power wireless transceiver transmits the 96-wells impedance data and the other sensor data stored in the flash memory to the user interface. We present the measured performance of the prototype, along with laboratory test results of bacterial growth measurements inside the 96 wells in parallel. We show that the EcoChip 2 can successfully measure the impedances associated with bacterial growth over several hours using an excitation frequency of 2 kHz with power consumption of 114.6 mW under operating mode.

A Wearable Wireless Armband Sensor for High-Density Surface Electromyography Recording

This paper presents a portable and modular wireless multichannel sensor system for high-density surface electromyography (HD-sEMG) signals acquisition. Featuring low-power and high-quality off-the-shelf components such as the Intan Technologies RHD2132 digital electrophysiology interface chip, the current iteration of the proposed sensor system allows the recording of 32 surface electromyography (sEMG) channels, each at a sampling rate of 1 kHz, and a sample resolution of 16 bits. It features the RHD2132's typical input-referred noise of 2.4 μV_rms, with <; 15% variation with amplifier bandwidth as specified by the manufacturer, and a total power consumption of 49.5 mW. Data is sent in real-time to a base station using a 2.4-GHz industrial, scientific and medical (ISM) wireless link. Along with the recording platform, the integrated sensor system includes a dry surface electrodes array prototype directly built on a printed circuit board. Intended for complex muscles activity patterns detection on the forearm, the flexible 32 surface electrodes array is designed to be placed flat or to fit a curved area like the forearm in a hand gestures recognition prosthetic system. In such applications, this device will offer improved prosthesis control scheme intuitiveness and ease-of-use. Among other core features of the system are its compact, light-weight and easy to install physical design. The complete system fits on a 2 by 6.5 cm² printed circuit board mounted on a 7.6 by 11.8 cm² electrodes array. HD-sEMG user forearm output data collected with the system is presented with a proposed frequency-time-space cross-domain preprocessing method for visualization of HD-EMG data and building training datasets.

A Wireless Optoelectronic Neuroscience Platform for Chronic Fluorescence Sensing in Freely Behaving Rodents

We present a new head mountable wireless fiber biophotometry microsystem conceived to detect fluorescent signal fluctuations correlated with neuronal activity. The proposed system incorporates all aspects of a conventional tethered fiber-based biophotometry system encompassed into a wireless microsystem. The interface includes an LED as excitation light source, a custom designed CMOS biosensor, a multimode fiber, a microcontroller (MCU), and a wireless data transceiver enclosed within a 3D-printed, small and light weight, plastic housing. Precisely, the system incorporates a new optoelectronic biosensor merging two individual building blocks, namely a low-noise sensing front-end and $\mathrm {a}2 ^{nd}$ order continuous-time $\Sigma \Delta $ modulator (CTSDM), into a single module for enabling high-sensitivity and high energy-efficiency photo-sensing. The proposed CMOS biosensor is implemented in $\mathrm {a}0 .18- \mu m$ CMOS technology, consuming $41 \mu W$ from $\mathrm {a}1 .8- V$ supply voltage, while achieving a peak dynamic range of $86 dB$ over a $50- Hz$ input bandwidth at a 20-kS/s sampling rate. This new interface opens new avenues for conducting in-vivo experiments with live animals.

A 110-nW in-channel sigma-delta converter for large-scale neural recording implants

Advancement in wireless and microsystems technology have ushered in new devices that can directly interface with the central nervous system for stimulating and/or monitoring neural circuitry. In this paper, we present an ultra low-power sigma-delta analog-to-digital converter (ADC) intended for utilization into large-scale multi-channel neural recording implants. This proposed design, which provides a resolution of 9 bits using a one-bit oversampled ADC, presents several desirable features that allow for an in-channel ADC scheme, where one sigma-delta converter is provided for each channel, enabling development of scalable systems that can interface with different types of high-density neural microprobes. The proposed circuit, which have been fabricated in a TSMC 180-nm CMOS process, employs a first order noise shaping topology with a passive integrator and a low-supply voltage of 0.6 V to achieve ultra low-power consumption and small size. The proposed ADC clearly outperforms other designs with a power consumption as low as 110 nW for a precision of 9 bits (11-fJ per conversion), a silicon area of only 82 μm × 84 μm and one of the best reported figure of merit among recently published data converters utilized in similar applications.

A short-impulse UWB BPSK transmitter for large-scale neural recording implants

In this paper, a short-impulse ultra-wide band (UWB) transmitter is introduced to enable large-scale neural recordings within miniature brain implants including thousands of channels. The proposed impulse radio UWB transmitter uses a BPSK modulation scheme, the carrier signal of which uses only two delayed impulses to encode the transmitted signal. The proposed UWB transmitter has been implemented into a CMOS 180 nm technology. It occupies 300 μm × 230 μm, and consumes only 6.7 pJ/bit from a 1.8-V supply. Experimental results show that the transmitter has a bandwidth of 2.6 GHz to 5.6 GHz and achieves a maximum data rate of 800 Mbps, which outperforms existing low-power UWB transmitters for similar applications.

Low-grade Tubular Myxoid Renal Tumors: A Clinicopathological Study of 3 Cases

We report 3 cases of a new renal cell tumor entity with a review of the literature. These 3 cases were retrieved from the files of this institution from 1991 to 2002. The clinical data and all histologic slides were reviewed and an immunohistochemical study was performed. Patients were all females. Tumors were almost similar with well-defined margins. Tumor architecture was tubular and focally fusiform with an abundant myxoid stroma. Tumor cells were low cuboidal, slightly eosinophilic with low nuclear grade. Immunohistochemistry was in favor of a distal nephron differentiation. All patients were healthy after surgery. We describe 3 cases of a new clinicopathological entity entitled low-grade tubular myxoid renal tumor with a benign clinical course.

Intuitive wireless control of a robotic arm for people living with an upper body disability

Assistive Technologies (ATs) also called extrinsic enablers are useful tools for people living with various disabilities. The key points when designing such useful devices not only concern their intended goal, but also the most suitable human-machine interface (HMI) that should be provided to users. This paper describes the design of a highly intuitive wireless controller for people living with upper body disabilities with a residual or complete control of their neck and their shoulders. Tested with JACO, a six-degree-of-freedom (6-DOF) assistive robotic arm with 3 flexible fingers on its end-effector, the system described in this article is made of low-cost commercial off-the-shelf components and allows a full emulation of JACO's standard controller, a 3 axis joystick with 7 user buttons. To do so, three nine-degree-of-freedom (9-DOF) inertial measurement units (IMUs) are connected to a microcontroller and help measuring the user's head and shoulders position, using a complementary filter approach. The results are then transmitted to a base-station via a 2.4-GHz low-power wireless transceiver and interpreted by the control algorithm running on a PC host. A dedicated software interface allows the user to quickly calibrate the controller, and translates the information into suitable commands for JACO. The proposed controller is thoroughly described, from the electronic design to implemented algorithms and user interfaces. Its performance and future improvements are discussed as well.

Multichannel spike detector with an adaptive threshold based on a Sigma-delta control loop

In this paper, we present a digital spike detector using an adaptive threshold which is suitable for real time processing of 32 electrophysiological channels in parallel. Such a new scheme is based on a Sigma-delta control loop that precisely estimates the standard deviation of the amplitude of the noise of the input signal to optimize the detection rate. Additionally, it is not dependent on the amplitude of the input signal thanks to a robust algorithm. The spike detector is implemented inside a Spartan-6 FPGA using low resources, only FPGA basic logic blocks, and is using a low clock frequency under 6 MHz for minimal power consumption. We present a comparison showing that the proposed system can compete with a dedicated off-line spike detection software. The whole system achieves up to 100% of true positive detection rate for SNRs down to 5 dB while achieving 62.3% of true positive detection rate for an SNR as low as -2 dB at a 150 AP/s firing rate.

Low-power adaptive spike detector based on a sigma-delta control loop

This paper presents a resources-optimized digital action potential (AP) detector featuring an adaptive threshold based on a new Sigma-delta control loop. The proposed AP detector is optimized for utilizing low hardware resources, which makes it suitable for implementation on most popular low-power microcontrollers units (MCU). The adaptive threshold is calculated using a digital control loop based on a Sigma-delta modulator that precisely estimates the standard deviation of the amplitude of the neuronal signal. The detector was implemented on a popular low-power MCU and fully characterized experimentally using previously recorded neural signals with different signal-to-noise ratios. A comparison of the obtained results with other thresholding approaches shows that the proposed method can compete with high performance and highly resources demanding spike detection approaches while achieving up to 100% of true positive detection rate at high SNR, and up to 63% for an SNR as low as 0 dB, while necessitating an execution time as low as 11 μs with the MCU operating at 8 MHz.

Towards a wireless optical stimulation system for long term in-vivo experiments

This paper presents our recent progresses towards the development of a wirelessly powered head mountable optical stimulator for enabling long-term optogenetic experiments with small freely moving transgenic models. The proposed system includes a wireless power transmission chamber with uniform power distribution in 3D and a wireless head mountable optical stimulator prototype with power recovery. The wireless power link, which includes the inductive chamber and power recovery circuits, is robust against subject movements in all directions, and against angular misalignment. Such link provides uniform power distribution without the need for a closed-loop control system, and can localize the transmitted power towards the receiver, without using additional detection and control circuitry compared to other systems. Additionally, the chamber is equipped with a camera for capturing the animal motion and behavior after applying optical stimulation patterns. A low-power microcontroller unit is embedded with the stimulator prototype to generate arbitrary light stimulation patterns. Measurement results show that the inductive chamber can continuously deliver 70 mW to the stimulator prototype with a power efficiency of 59%.

BER performance of implant-to-air high-speed UWB data communications for neural recording systems

Implant-to-air ultra-wideband communication systems are interesting for neural recording systems due to their low power consumption and high data-rates. In this paper we investigate the performance of an implant-to-air wireless link using a realistic model of the biological channel for neural recording systems. We propose an optimized fifth-derivative Gaussian pulse as a transmitted waveform for different modulations: binary phase shift keying (BPSK), on-off keying (OOK) and differential phase shift keying (DPSK). Monitoring of neural responses with high resolution in the brain requires a high data rate link as the number of electrodes is increased. Each electrode needs a data rate around 800 kb/s to support its neural channel. As we target more than 512 electrodes, we require a data link higher than 400 Mbps.

Flexible sixteen monopole antenna array for microwave breast cancer detection

Radar based microwave imaging (MI) has been widely studied for breast cancer detection in recent times. Sensing dielectric property differences of tissues over a wide frequency band has been made possible by ultra-wideband (UWB) techniques. In this paper, a flexible, compact monopole antenna on a 100 μm Kapton polyimide is designed, using a high frequency structure simulator (HFSS), to be in contact with biological breast tissues over the 2-5GHz frequency range. The antenna parameters are optimized to obtain a good impedance match over the required frequency range. The designed antenna size is 18mm × 18mm. Further, a flexible conformal 4×4 ultra-wideband antenna array, in a format similar to that of a bra, was developed for a radar-based breast cancer detection system.

A low-power current-reuse dual-band analog front-end for multi-channel neural signal recording

Thoroughly studying the brain activity of freely moving subjects requires miniature data acquisition systems to measure and wirelessly transmit neural signals in real time. In this application, it is mandatory to simultaneously record the bioelectrical activity of a large number of neurons to gain a better knowledge of brain functions. However, due to limitations in transferring the entire raw data to a remote base station, employing dedicated data reduction techniques to extract the relevant part of neural signals is critical to decrease the amount of data to transfer. In this work, we present a new dual-band neural amplifier to separate the neuronal spike signals (SPK) and the local field potential (LFP) simultaneously in the analog domain, immediately after the pre-amplification stage. By separating these two bands right after the pre-amplification stage, it is possible to process LFP and SPK separately. As a result, the required dynamic range of the entire channel, which is determined by the signal-to-noise ratio of the SPK signal of larger bandwidth, can be relaxed. In this design, a new current-reuse low-power low-noise amplifier and a new dual-band filter that separates SPK and LFP while saving capacitors and pseudo resistors. A four-channel dual-band (SPK, LFP) analog front-end capable of simultaneously separating SPK and LFP is implemented in a TSMC 0.18 μm technology. Simulation results present a total power consumption per channel of 3.1 μw for an input referred noise of 3.28 μV and a NEF for 2.07. The cutoff frequency of the LFP band is fc=280 Hz, and fL=725 Hz and fL=11.2 KHz for SPK, with 36 dB gain for LFP band 46 dB gain for SPK band.

Multicoil resonance-based parallel array for smart wireless power delivery

This paper presents a novel resonance-based multicoil structure as a smart power surface to wirelessly power up apparatus like mobile, animal headstage, implanted devices, etc. The proposed powering system is based on a 4-coil resonance-based inductive link, the resonance coil of which is formed by an array of several paralleled coils as a smart power transmitter. The power transmitter employs simple circuit connections and includes only one power driver circuit per multicoil resonance-based array, which enables higher power transfer efficiency and power delivery to the load. The power transmitted by the driver circuit is proportional to the load seen by the individual coil in the array. Thus, the transmitted power scales with respect to the load of the electric/electronic system to power up, and does not divide equally over every parallel coils that form the array. Instead, only the loaded coils of the parallel array transmit significant part of total transmitted power to the receiver. Such adaptive behavior enables superior power, size and cost efficiency then other solutions since it does not need to use complex detection circuitry to find the location of the load. The performance of the proposed structure is verified by measurement results. Natural load detection and covering 4 times bigger area than conventional topologies with a power transfer efficiency of 55% are the novelties of presented paper.

Segmentation of Opacified Thorax Vessels using Model-driven Active Contour

We propose a novel method, guided slice marching to segment opacified vessels tree in 3D image sets (CT scans). It combines a front propagation technique, slice marching, and an anatomical model to guide the propagation for solving the particular case of touching vessels. The formulation of this method, which is based on interface evolution theory, enables easy integration of an a priori model of knowledge of vessels topology to handle the case of touching vessels, where image-based method systematically fails. The a priori knowledge is expressed as parametric curves that model vessels centerline. That information is injected in the fast marching method through the speed of propagation, setting it to zero at missing vessels boundaries. The model is intended to be reused across patients, and must therefore be registered with the image.

A transcutaneous power transfer interface based on a multicoil inductive link

This paper presents a transcutaneous power transfer link based on a multicoil structure. Multicoil inductive links using 4-coil or 3-coil topologies have shown significant improvement over conventional 2-coil structures for transferring power transcutaneously across larger distances and with higher efficiency. However, such performance comes at the cost of additional inductors and capacitor in the system, which is not convenient in implantable applications. This paper presents a transcutaneous power transfer interface that takes advantage on a 3-coils inductive topology to achieve wide separation distances and high power transfer efficiency without increasing the size of the implanted device compared to a conventional 2-coil structure. In the proposed link, a middle coil is placed outside the body to act as a repeater between an external transmitting coil and an implanted receiving coil. The proposed structure allows optimizing the link parameters after implantation by changing the characteristics of the repeater coil. Simulation with a multilayer model of the biological tissues and measured results are presented for the proposed link.

A mixed-signal multichip neural recording interface with bandwidth reduction

We present a multichip structure assembled with a medical-grade stainless-steel microelectrode array intended for neural recordings from multiple channels. The design features a mixed-signal integrated circuit (IC) that handles conditioning, digitization, and time-division multiplexing of neural signals, and a digital IC that provides control, bandwidth reduction, and data communications for telemetry toward a remote host. Bandwidth reduction is achieved through action potential detection and complete capture of waveforms by means of onchip data buffering. The adopted architecture uses high parallelism and low-power building blocks for safety and long-term implantability. Both ICs are fabricated in a CMOS 0.18-mum process and are subsequently mounted on the base of the microelectrode array. The chips are stacked according to a vertical integration approach for better compactness. The presented device integrates 16 channels, and is scalable to hundreds of recording channels. Its performance was validated on a testbench with synthetic neural signals. The proposed interface presents a power consumption of 138 muW per channel, a size of 2.30 mm(2), and achieves a bandwidth reduction factor of up to 48 with typical recordings.

A low-power integrated bioamplifier with active low-frequency suppression

We present in this paper a low-power bioamplifier suitable for massive integration in dense multichannel recording devices. This bioamplifier achieves reduced-size compared to previous designs by means of active low-frequency suppression. An active integrator located in the feedback path of a low-noise amplifier is employed for placing a highpass cutoff frequency within the transfer function. A very long integrating time constant is achieved using a small integrated capacitor and a MOS-bipolar equivalent resistor. This configuration rejects unwanted low-frequency contents without the need for input RC networks or large feedback capacitors. Therefore, the bioamplifier high-input impedance and small size are preserved. The bioamplifier, implemented in a 0.18-mum CMOS process, has been designed for neural recording of action potentials, and optimised through a transconductance-ef-ficiency design methodology for micropower operation. Measured performance and results obtained from in vivo recordings are presented. The integrated bioamplifier provides a midband gain of 50 dB, and achieves an input-referred noise of 5.6 muVrms. It occupies less than 0.050 mm(2) of chip area and dissipates 8.6 muW.

Tumor detection using airways asymmetry

A novel tumor detection technique on CT Scan images of the neck area is detailed in this paper. This technique is based on an airways' symmetry evolution within slices. The algorithm proposes to the physician a set of three slices where a tumor (if it exists) should mostly be located. Then, he will just have to browse the three slices instead of almost 100 in a CT scan. Our method is very effective and shows no false alarms within the patients in our database. In each of our tests the tumors were found to be close to one of the three proposed slices.

Histologic structure and development of the laryngeal macula flava

The laryngeal maculae flavae (MF) have been previously described as cellular condensations at the extremities of the vocal cords, but the exact nature and role of the MF are unknown. The purpose of this study is a histomorphological analysis of the nature and development of the MF in human vocal cords, from the beginning of fetal life to adulthood. Eighty-six larynges, from the fetus at 12 weeks of amenorrhea (WA) to adulthood, were collected from autopsies and studied by light microscopy with hematoxylin and eosin, orcein, and Alcian blue staining and pS 100 immunostaining. Our observations allowed us to separate the fetal development of the MF into 4 periods. The first corresponds to the appearance of the posterior MF between 13 and 15 WA. In the second period, the anterior MF appeared between 16 and 18 WA, allowing definition of the intermacular space. Fibrous structures, composed of collagen and elastic fibers, of the MF and intermacular space developed between 20 and 33 WA. The last period, from 33 WA to birth, corresponded to a maturation of these structures. In adults, the histologic structure of the MF presented a concentric peripheral fibrous layer associated with a central cellular component. Structural analysis of the MF concludes in favor of the chondroid nature of the macular cell. These observations bring into question the current knowledge on the MF. From these observations, the role of the MF in the developing vocal cord is discussed.

Value of frozen section examination for the management of nonpalpable incidental testicular tumors

OBJECTIVES

To determine the value of frozen section examination for the management of small incidental testis tumors.

METHODS

We reviewed all cases of incidental nonpalpable testis tumors that have been examined in frozen section during the period 1996-2002. For each case, frozen section and definitive histological slides were available and were reviewed.

RESULTS

Fifteen cases were retrieved in the files of the Department of Pathology. Nine cases were discovered by ultrasonography examination in patients presenting with infertility. Six cases were discovered incidentally by sonography for testis trauma or scrotal pain. The patients were aged from 18 to 43 years. The tumors measured from 4 to 16 mm. Frozen section examination concluded in 9 cases to a benign lesion "Leydig cell nodule", in four cases a diagnosis of malignancy was retained and the last two cases were inconclusive. The standard microscopic examination confirmed the 9 cases of Leydig cell tumors; malignancy was confirmed in the 4 cases (3 seminomas and one teratoma) and the uncertain cases were benign Sertoli cells tumors. Benign lesions were treated by a conservative approach.

CONCLUSION

Frozen section examination is a useful method for the management of small incidental masses of the testis.

Diagnostic value of MUC4 immunostaining in distinguishing epithelial mesothelioma and lung adenocarcinoma

The distinction between pleural malignant mesothelioma and pleural infiltration by adenocarcinomas has complex therapeutic and medicolegal implications. Although the panel of adenocarcinoma-associated antibodies and one or two mesothelioma markers is useful in this purpose, most of these antibodies are not totally specific. We determined the diagnostic value of MUC4 immunostaining in this issue. MUC4 gene expression was also studied by in situ hybridization and RT-PCR. MUC4 is a membrane-bound mucin that has been suggested to be implicated in malignant progression in humans and rats. The MUC4 gene is expressed in various normal epithelial tissues of endodermic origin and carcinomas. In the respiratory tract, MUC4 transcripts have been detected in normal respiratory epithelium and lung carcinomas. MUC4 protein was expressed in 32 of 35 (91.4%) lung adenocarcinomas on paraffin-embedded tissue. None of the 41 malignant mesotheliomas nor the 32 cases of benign mesothelial cells expressed MUC4 at the protein and mRNA levels. We conclude that MUC4 is a very specific (100%) and sensitive (91.4%) marker of lung adenocarcinomas on paraffin-embedded tissue that could be useful in diagnostic practice in the distinction between malignant mesothelioma and adenocarcinoma.

Expression of human mucin genes during normal and abnormal renal development

Human mucin genes encode large O-glycoproteins, which are expressed in various epithelial tissues. The proteins are the main components of mucus, but also might be involved in morphogenesis of or carcinogenesis in many organs. We studied the expression of human mucin genes during fetal kidney development and in malformed cystic renal diseases in 10 normal fetal kidneys and 12 malformed kidneys by in situ hybridization and immunohistochemical analysis. MUC1, MUC3, and MUC6 were expressed in normal fetal kidney. MUC1 was expressed from 7.5 weeks of gestation in the metanephric blastema and throughout fetal life in the ureteric buds, distal convoluted tubules, and collecting ducts. MUC3 was expressed weakly in immature tubules from 8 weeks of gestation, after which it was expressed weakly and focally in the proximal convoluted tubules. MUC6 was expressed at 9.5 weeks of gestation in the tips of the ureteric buds and later in the collecting ducts. In malformative cystic diseases, only MUC1 expression was retained; no expression of MUC6 and MUC3 was observed. These results implicate human mucin genes (MUC1, MUC3, and MUC6) in renal morphogenesis processes.

Schwannoma of the sinonasal tract: a clinicopathologic and immunohistochemical study of 5 cases

CONTEXT

Peripheral nerve sheath tumors are soft tissue neoplasms rarely encountered in the nasal cavity and paranasal sinuses.

OBJECTIVE

To describe the clinicopathologic and immunohistochemical features of a series of schwannomas of the sinonasal tract.

DESIGN

Surgical pathology files were searched for the diagnosis "sinonasal schwannoma." All histologic documents and clinical data were reviewed. Immunohistochemistry was performed on paraffin-embedded tissue with antibodies to S100 protein, epithelial membrane antigen, CD34, and MIB-1. RESULSTS: Five cases of sinonasal schwannoma were retrieved; patients included 3 women and 2 men, aged 20 to 56 years. Three cases were located in the ethmoid sinus. Clinical symptoms were nonspecific (nasal obstruction, epistaxis, and anosmia). All tumors were treated with conservative surgical resection. Pathologic examination showed a spindle cell proliferation without encapsulation in all cases. No cytologic atypia was seen, and the mitotic activity was low (<3 mitotic figures/10 high-power fields). Immunohistochemistry showed diffuse positivity with S100 protein and negativity with CD34 and epithelial membrane antigen. MIB-1 staining was low (1%-5% of tumor cell nuclei stained). During the follow-up (median, 6 years), no recurrence or metastasis was observed.

CONCLUSIONS

Schwannoma is a very unusual tumor of the sinonasal tract and is associated with nonspecific symptoms. Histologically, sinonasal schwannomas differ from schwannomas of other locations by their lack of a peripheral capsule and possible ulceration of the epithelial covering. Sinonasal schwannomas are treated with conservative surgical resection and have an excellent prognosis.

MUC6 is a marker of seminal vesicle-ejaculatory duct epithelium and is useful for the differential diagnosis with prostate adenocarcinoma

The diagnosis of prostate adenocarcinoma is usually made on needle biopsies. Numerous benign lesions may mimic malignancy, especially when the focus of carcinoma is limited. The presence of seminal vesicle-ejaculatory duct epithelium on prostate biopsy is not rare and could cause confusion with adenocarcinoma. Lipochrome pigments are frequently encountered in seminal vesicle-ejaculatory duct but may be also seen in prostate adenocarcinoma. Prostate specific antigen immunostaining in difficult cases is sometimes used, but high-grade adenocarcinomas may be negative. In one previous report, MUC6 was found to be expressed in seminal vesicle but not in normal prostate. MUC6 belongs to the family of human mucin genes. So we investigated herein the immunohistochemical expression of MUC6 in prostate adenocarcinomas and seminal vesicle-ejaculatory duct. We have tested 30 prostate adenocarcinomas of various grade, 10 normal seminal vesicles, and 10 prostate adenocarcinomas invading the seminal vesicles. The tissues were fixed in 10% buffered formalin and embedded in paraffin. Immunohistochemistry was performed using the avidin-biotin-peroxidase complex technique. All adenocarcinomas and normal prostate structures tested were negative. In contrast, all seminal vesicles were diffusely immunostained with MUC6 antibody. We concluded that MUC6 is a valuable marker of seminal vesicle-ejaculatory duct and is useful for the differential diagnosis with prostate adenocarcinoma.

Minimal focus of adenocarcinoma on prostate biopsy: clinicopathological correlations

AIMS

To establish the clinicopathological features of minimal volume prostate adenocarcinoma on prostate biopsy.

METHODS

Twenty four cases of minimal adenocarcinoma diagnosed on prostate biopsy and treated by radical prostatectomy were reviewed.

RESULTS

The major microscopic criteria were nuclear enlargement (22 of 24), infiltrative pattern (19 of 24), prominent nucleoli (19 of 24), intraluminal eosinophilic secretions (15 of 24), and high grade intraepithelial neoplasia associated (11 of 24). Sixteen of 24 cases were assigned a Gleason score 6 on biopsy. When the whole gland was assessed, 22 of these tumours were localised to the prostate (stage pT2), and only two cases were stage pT3.

CONCLUSIONS

Minimal focus of adenocarcinoma on prostate biopsy is not an uncommon finding. It is usually an intermediate grade and localised stage neoplasm.

[Localized amyloidosis of the cavum]

INTRODUCTION

Amyloidosis is characterized by extracellular deposits of proteins.

OBSERVATION

A 66 year-old patient presented with a pseudo-tumoral amyloidosis of the cavum. Clinical and biological examinations confirmed the localized aspect of the disease and immunohistochemical exploration identified a type AL amyloidosis.

COMMENTS

The disease may be diffuse involving many organs and leading to various clinical manifestations. It can also be localized and take on a pseudo-tumoral aspect. Localised amyloidosis is a rare lesion of the upper aero-digestive tract, predominating in the larynx. Nasopharyngeal involvement is exceptional.

High frequency of a 30-bp deletion of Epstein-Barr virus latent membrane protein 1 gene in primary HIV non-Hodgkin's brain lymphomas

A characteristic 30-base pair (bp) deletion (del) in the 3' end of the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) gene, coding for the C-terminal NF-kappa B activation domain, has been identified in various lymphoproliferative disorders and nasopharyngeal carcinomas. In the single report to date of human immunodeficiency virus primary brain lymphomas (HIV-PBLs), del-LMP1 was noted in seven cases out of nine. The present study was designed to identify this deletion in a series of 31 diffuse large B-cell HIV-PBLs, with the aim of determining its possible oncogenic action. The presence of EBV was confirmed by EBER mRNA in situ hybridization. After genomic extraction from frozen tissue, two 20-base oligonucleotide primers flanking the site of the 30-bp deletion were used. DNA sequencing of the polymerase chain reaction (PCR) products confirmed an identical segment spanning 30-bp and 69-bp, frequently associated with mutational hotspots in 19 cases (61%). A role for del-LMP1 in the oncogenic potential of EBV in systemic proliferations is a matter of debate. Its high incidence suggests that the oncogenic mechanism of LMP1 in the brain might differ significantly from that in systemic lymphoid proliferations, and might be enhanced by HIV infection.