Southwest Research Institute assistance to NASA in biomedical areas of the technology utilization program Final report, 1 Feb. 1969 - 24 Aug. 1970

Research progress in technology transfer by NASA Biomedical Application Tea

Southwest Research Institute assistance to NASA in biomedical areas of the technology utilization program

The activities are reported of the NASA Biomedical Applications Team at Southwest Research Institute between 25 August, 1972 and 15 November, 1973. The program background and methodology are discussed along with the technology applications, and biomedical community impacts

Low-Field NMR/MRI Systems Using LabVIEW and Advanced Data-Acquisition Techniques

International audienc

A Power-Efficient Bio-Potential Acquisition Device with DS-MDE Sensors for Long-Term Healthcare Monitoring Applications

This work describes a power-efficient bio-potential acquisition device for long-term healthcare applications that is implemented using novel microelectromechanical dry electrodes (MDE) and a low power bio-potential processing chip. Using micromachining technology, an attempt is also made to enhance the sensing reliability and stability by fabricating a diamond-shaped MDE (DS-MDE) that has a satisfactory self-stability capability and superior electric conductivity when attached onto skin without any extra skin tissue injury technology. To acquire differential bio-potentials such as ECG signals, the proposed processing chip fabricated in a standard CMOS process has a high common mode rejection ratio (C.M.R.R.) differential amplifier and a 12-bit analog-to-digital converter (ADC). Use of the proposed system and integrate simple peripheral commercial devices can obtain the ECG signal efficiently without additional skin tissue injury and ensure continuous monitoring more than 70 hours with a 400 mAh battery

Low Power CMOS Chopper Preamplifier Based on Source-Degeneration Transconductors

This paper describes the design of a low-power, low-noise flicker CMOS chopper preamplifier for sensor signal conditioning. The core amplifier and the Gm-C output low pass filter of the proposed fully differential preamplifier are based on a source degeneration transconductor. The circuit was designed in a standard 0.18µm CMOS process with 1.8V supply voltage. It shows 42dB gain, 1 kHz bandwidth and a total power consumption of 84 µW. The proposed configuration achieves a noise efficiency factor of 4.6 and a total input-referred noise of 560 nVrms integrated from 0.1 to 1 kHz

Front-end receiver for miniaturised ultrasound imaging

Point of care ultrasonography has been the focus of extensive research over the past few decades. Miniaturised, wireless systems have been envisaged for new application areas, such as capsule endoscopy, implantable ultrasound and wearable ultrasound. The hardware constraints of such small-scale systems are severe, and tradeoffs between power consumption, size, data bandwidth and cost must be carefully balanced. To address these challenges, two synthetic aperture receiver architectures are proposed and compared. The architectures target highly miniaturised, low cost, B-mode ultrasound imaging systems. The first architecture utilises quadrature (I/Q) sampling to minimise the signal bandwidth and computational load. Synthetic aperture beamforming is carried out using a single-channel, pipelined protocol in order to minimise system complexity and power consumption. A digital beamformer dynamically apodises and focuses the data by interpolating and applying complex phase rotations to the I/Q samples. The beamformer is implemented on a Spartan-6 FPGA and consumes 296mW for a frame rate of 7Hz. The second architecture employs compressive sensing within the finite rate of innovation (FRI) framework to further reduce the data bandwidth. Signals are sampled below the Nyquist frequency, and then transmitted to a digital back-end processor, which reconstructs I/Q components non-linearly, and then carries out synthetic aperture beamforming. Both architectures were tested in hardware using a single-channel analogue front-end (AFE) that was designed and fabricated in AMS 0.35μm CMOS. The AFE demodulates RF ultrasound signals sequentially into I/Q components, and comprises a low-noise preamplifier, mixer, programmable gain amplifier (PGA) and lowpass filter. A variable gain low noise preamplifier topology is used to enable quasi-exponential time-gain control (TGC). The PGA enables digital selection of three gain values (15dB, 22dB and 25.5dB). The bandwidth of the lowpass filter is also selectable between 1.85MHz, 510kHz and 195kHz to allow for testing of both architectural frameworks. The entire AFE consumes 7.8 mW and occupies an area of 1.5×1.5 mm. In addition to the AFE, this thesis also presents the design of a pseudodifferential, log-domain multiplier-filter or “multer” which demodulates low-RF signals in the current-domain. This circuit targets high impedance transducers such as capacitive micromachined ultrasound transducers (CMUTs) and offers a 20dB improvement in dynamic range over the voltage-mode AFE. The bandwidth is also electronically tunable. The circuit was implemented in 0.35μm BiCMOS and was simulated in Cadence; however, no fabrication results were obtained for this circuit. B-mode images were obtained for both architectures. The quadrature SAB method yields a higher image SNR and 9% lower root mean squared error with respect to the RF-beamformed reference image than the compressive SAB method. Thus, while both architectures achieve a significant reduction in sampling rate, system complexity and area, the quadrature SAB method achieves better image quality. Future work may involve the addition of multiple receiver channels and the development of an integrated system-on-chip.Open Acces

Optimisation and realisation of a portable NMR apparatus and Micro Antenna for NMR

International audienceThis paper is focused on two designs and realizations. The first one concerns a prototype of a portable NMR (nuclear magnetic resonance) apparatus. The second one concerns NMR micro antenna realization. For the first part, our goal is the NMR magnetic field homogeneity and the signal-to-noise ratio (SNR) improvement. Since de the volume of the sample to analyse is around 1 cm 3 , the design is optimized to obtain a good SNR. Particularly, the magnet is chosen to obtain a high magnetic field with limited inhomogeneities. The receiver antenna is designed and optimized to have high feeling factor and then more sensitivity. A mixer and a low-pass filter are used in order to limit the bandwidth and reduce the thermal noise. The FID is digitized and addressed to a FPGA which averages successive acquisitions in order to increase the SNR. The final acquisition is processed for determining the FID spectrum. In the second part, a new concept of micro coil is presented in order to measure the small volumes and small concentrations samples by NMR spectroscopy at 4.7 T (200 MHz proton frequency resonance). This micro sensor would offer the possibility of new investigation techniques based on micro coils' implantation used for in vivo study of local cerebral metabolites of animals models

Design of a Non-Dispersive Infra-Red (NDIR) based CO2 sensor to detect the human respiratory CO2

Respiratory Carbon dioxide (CO2) contains substantial amount of information that can be used to diagnose and treat pulmonary diseases. Many devices have been developed for this purpose, such as capnography, vital monitor, peak flow meter, spirometer etc. There are many CO2 sensor are available in the market but among them NDIR based sensors are considered to be most inexpensive with its accuracy in terms of sensitivity and fast response time. There are commonly two types of technology available for detection; mainstream and sidestream. Mainstream technology is preferable than sidestream because sidestream is not applicable in intubated patients and at the same time it tends to give delay in detection due to longer transmission tube. Most of the NDIR CO2 sensor are being used for the environmental CO2 detection and there are very few mainstream NDIR based CO2 sensor are available in the market. These sensor have a vast number of advantages with some disadvantages as well; such as high response time, thermal noise, temperature increase and others. This project proposed the specification of the electrical circuit of the NDIR CO2 sensor combined with a gas chamber to detect human respiratory CO2. To determine the specification of the CO2 sensor circuit, the components value has been calculated and then the circuit design has been carried out by using Multisim Software. The overall CO2 sensor circuit has six circuit blocks named oscillator, driver circuit, preamplifier, voltage regulator, rectifier, LPF and each of the blocks were built and simulated in the Multisim software. After the simulation the circuit has been built on breadboard to test the output. An IR source from International Light Technologies (ILT) 4115-2A and pyroelectric photodetector L2100X2020 from laser component were used for this project as NDIR components. After the successful simulation from breadboard a gas acquisition cell has been designed to acquire the human CO2 gas. The design has been done by using Solid Works software and printed from a 3D printing machine. The material used for this chamber was ABS. After placing all the calculated components with the source and detector the output has been observed on the digital oscilloscope as a capnograph wave form showing the voltage range. These waveforms are being used in a capnometer determining respiratory diseases. The circuit shows a response time of 6 second with less noise and the waveform showed clear view of detected CO2 without any temperature increase