Development and evaluation of venous oximetry

Photoplethysmography, a technique to measure by optical means volume changes, has been known and applied for many years. One of its most popular applications is pulse oximetry, a non-invasive method to measure oxygen content in arterial blood. It is based on the principle of arterial blood volume changes due to heart contractions, known as systoles. Systolic pulsations appear on the arterial vascular system, while blood flow in veins does not normally present pulsations, especially at remote parts of the peripheral vascular system, such as the fingers. Therefore, pulse oximetry is only applicable to arteries as their pulsations allow for separation of the pulsatile components from the rest of the absorbing components. A novel non-invasive technique permits the measurement of venous oxygen saturation by introducing a series of pulsations in the veins thus allowing the separation of venous signal components for calculation of venous oxygen saturation. This thesis presents a theoretical model describing the mechanical coupling of arteries and veins and its effects in the accuracy of oxygen saturation measurement. [Continues.

BioThreads: a novel VLIW-based chip multiprocessor for accelerating biomedical image processing applications

We discuss BioThreads, a novel, configurable, extensible system-on-chip multiprocessor and its use in accelerating biomedical signal processing applications such as imaging photoplethysmography (IPPG). BioThreads is derived from the LE1 open-source VLIW chip multiprocessor and efficiently handles instruction, data and thread-level parallelism. In addition, it supports a novel mechanism for the dynamic creation, and allocation of software threads to uncommitted processor cores by implementing key POSIX Threads primitives directly in hardware, as custom instructions. In this study, the BioThreads core is used to accelerate the calculation of the oxygen saturation map of living tissue in an experimental setup consisting of a high speed image acquisition system, connected to an FPGA board and to a host system. Results demonstrate near-linear acceleration of the core kernels of the target blood perfusion assessment with increasing number of hardware threads. The BioThreads processor was implemented on both standard-cell and FPGA technologies; in the first case and for an issue width of two, full real-time performance is achieved with 4 cores whereas on a mid-range Xilinx Virtex6 device this is achieved with 10 dual-issue cores. An 8-core LE1 VLIW FPGA prototype of the system achieved 240 times faster execution time than the scalar Microblaze processor demonstrating the scalability of the proposed solution to a state-of-the-art FPGA vendor provided soft CPU core

A remote approach to measure blood perfusion from the human face

A CMOS camera-based imaging photoplethysmography (PPG) system has been previously demonstrated for the contactless measurement of skin blood perfusion over a wide tissue area. An improved system with a more sensitive CCD camera and a multi-wavelength RCLED ring light source was developed to measure blood perfusion from the human face. The signals acquired by the PPG imaging system were compared to signals captured concurrently from a conventional PPG finger probe. Experimental results from eight subjects demonstrate that the camera-based PPG imaging technique is able to measure pulse rate and blood perfusion

Development of a remote photoplethysmographic technique for human biometrics

Non-contact reflection photoplethysmography (NRPPG) is being developed to trace pulse features for comparison with contact photoplethysmography (CPPG). Simultaneous recordings of CPPG and NRPPG signals from 22 healthy subjects were studied. The power spectrum of PPG signals were analysed and compared between NRPPG and CPPG. The recurrence plot (RP) was used as a graphical tool to visualize the time dependent behaviour of the dynamics of the pulse signals. The agreement between NRPPG and CPPG for physiological monitoring, i.e. HRV parameters, was determined by means of the Bland-Altman plot and Pearson’s correlation coefficient. The results indicated that NRPPG could be used for the assessment of cardio-physiological signals

Remote simultaneous dual wavelength imaging photoplethysmography: a further step towards 3-D mapping of skin blood microcirculation

This paper presents a camera-based imaging photoplethysmographic (PPG) system in the remote detection of PPG signals, which can contribute to construct a 3-D blood pulsation mapping for the assessment of skin blood microcirculation at various vascular depths. Spot measurement and contact sensor have been currently addressed as the primary limitations in the utilization of conventional PPG system. The introduction of the fast digital camera inspires the development of the imaging PPG system to allow ideally non-contact monitoring from a larger field of view and different tissue depths by applying multi-wavelength illumination sources. In the present research, the imaging PPG system has the capability of capturing the PPG waveform at dual wavelengths simultaneously: 660 and 880nm. A selected region of tissue is remotely illuminated by a ring illumination source (RIS) with dual-wavelength resonant cavity light emitting diodes (RCLEDs), and the backscattered photons are captured by a 10-bit CMOS camera at a speed of 21 frames/second for each wavelength. The waveforms from the imaging system exhibit comparable functionality characters with those from the conventional contact PPG sensor in both time domain and frequency domain. The mean amplitude of PPG pulsatile component is extracted from the PPG waveforms for the mapping of blood pulsation in a 3-D format. These results strongly demonstrate the capability of the imaging PPG system in displaying the waveform and the potential in 3-D mapping of blood microcirculation by a non-contact means

Real-time VLSI architecture for bio-medical monitoring

This paper discusses the architecture and implementation of SSS2, a high-performance real-time signal processing system developed with a hybrid ESL/RTL methodology and targeted to biomedical image processing. Traditional methodologies, as well as new tools, such as Cebatech's C2R untimed-C synthesizer have been employed in the design of the system. The SSS2 platform specifies a parametric number of scalar processing elements, based on multiple 32-bit Sparc-compliant engines, augmented with LE2, an ESL-designed 2-way LIW/SIMD accelerator. LE2, which is purely designed in C, exposes a consistent interface to its SIMD datapath directly which is directly derived from the C-source of open-source image processing codes. It is synthesized to Verilog RTL with C2R. Behaviorally-synthesized SIMD datapaths are then 'plugged-in' into the exposed LE2 datapath interface. The LE2 memory interface can be either a cache- based configurable vector load/store unit or a multi-banked, multi-channel streaming local memory system. Results drawn from this work strongly suggest a shift towards a hybrid approach in designing multi-core systems for high bandwidth streaming and for dealing with large scale medical image transfers and non-linear bio-signal processing algorithms

Non-contact reflection photoplethysmography towards effective human physiological monitoring

A non-contact reflection photoplethysmography (NRPPG) with its engineering model was created to access human physiological information. The NRPPG engineering setup with a vertical cavity surface emitting laser (VCSEL) as a light source and a high-speed PiN photodiode as a photodetector was configured based upon the principles of light-tissue interaction and Beer-Lambert’s law. In this paper, we present three aspects of the NRPPG performance: (1) photonics engineering work to capture photoplethysmographic signals with a non-contact manner in an optimal setup of the NRPPG; (2) a 5-minute protocol with 22 participants to determine a good agreement between NRPPG and contact photoplethysmography (CPPG) by means of Bland-Altman statistical analysis and Pearson’s correlation coefficient; and (3) a physiological experiment designed for cardiac-physiological monitoring utilizing NRPPG. The experimental results suggest that clean PPG signal can be obtained between 30-110 mm. The outcome from agreement study indicates that the performance of NRPPG is compatible with CPPG. The NRPPG technique has great potential in cardiac-physiological assessment in a required clinical circumstance

Imaging

Use of photoplethysmographic processes in order to determine blood pulsing is known. By providing illumination over a range of excitation frequencies or wavelengths and using a multi time gating technique with regard to returned light, images are created which provide a spectral depth due to the varying scatter and absorption effects at the different excitation wavelengths. These images can be consolidated in order to provide a substantially real time view of pulsing action dependent upon blood oxygen saturation within the blood circulation system

Innovation for personalization: A healthcare case study

This paper describes a research and innovation platform for the development of ideas relating to the investigation of blood perfusion in peripheral tissue. The Loughborough Innovation Platform for Health Technologies (LIPHT) can be used to demonstrate the use of the research and innovation pipe-line in more than one dimension. For this paper the first dimension considered is that of `blue sky' idea through to their exploitation for the benefit of users and at the same time creating a wealth stream; the second dimension is the changing market as the ideas develop - from a hospital-based instrument operated by clinicians through to a point and click device for the use by the knowledgeable layman in the community. The starting point for these developments is a medical device known to many people as the `finger clip' that measures arterial blood oxygen saturation; the end point is an optical device capable of imaging blood perfusion

Development of effective photoplethysmographic measurement techniques: From contact to non-contact and from point to imaging

This paper provides an overview of the most recent developments in photoplethysmography (PPG). Existing contact point measurement techniques, i.e. pulse oximetry probes, are contrasted with the next generation non-contact and imaging implementations, i.e. non-contact reflection and camera-based PPG. The development of effective PPG monitoring techniques relies on novel approaches to opto-physiological modeling