Photopletysmographic methods for cardiovascular parameters monitoring have been extensively investigated. Yet, there is still a lack of consensus on the signals origins and sensors are designed based on qualitative intuitions. We present the radiometric calibration of a versatile optical workbench that allows quantitative multi-spectral reflectance measurements on several distances source/detector simultaneously. We propose here a method to retrieve both incident and outgoing radiant fluxes on the studied medium that paves the way for quantitative diffuse optics on-vivo. Compared to existing designs and methods, we believe our protocol matches well the needs of modern simulation tools dedicated to sensor designs.
Non-invasive pulse wave monitoring is now widely used in health and wellness applications. Very often, the use of this measurement to trace physiological parameters is indirect. We propose here a bench for synchronized acquisition of optical and ultrasound signals at high rates (over 100 Hz). Optical acquisition is performed with an in-house system enabling us to perform multispectral PPG. We report here the description of the bench, the performances obtained, and the first bimodal acquisitions made on dynamic phantoms.
Photoplethysmography (PPG) is a high-speed optical measurement technique that resolves fast physiological phenomena and offers promising applications in the medical field. In order to have a better understanding of the cardiovascular dynamics through the PPG signal, we propose a comprehensive multilayered and optical biophysical skin model from the wrist that is able to simulate some characteristic physiological properties and the complex cardiovascular dynamics. Thanks to this dynamic optical model, we are able to identify and disentangle the microvascular, arterial and venous contributions retrieved from the PPG signal signature.
Photoplethysmography (PPG) is a promising optical measurement method for daily patient monitoring for a wide range of physiological parameters. Nevertheless, this measurement technique remains sensitive to external disturbances, inter/intra-subject physiology, and sensor configuration. In order to study the behavior of these optical signals, we report an original bench based on PPG measurement and Diffuse Reflectance Spectroscopy (DRS). Thanks to this setup, we are able to investigate several sensor configurations in terms of source-detector distances and wavelengths at kHz acquisition rate. These measurements are multi-wavelength in the visible and near infrared range, synchronized and performed on up to eight configurable source-detector distances (three reported in this paper). An optical calibration suited for comparative measurements is also implemented. We additionally present the first results obtained on a representative and dynamic medium. This study highlights the dependence between the optical signal measurement and the configuration of the sensor. These first results demonstrate the interest of the development of our optical bench to study in depth the complex processes occurring in heterogeneous scattering environments such as biological tissues. This work paves the way for robust, quantitative, accurate and continuous monitoring of vital signs based on PPG, and opens perspectives for physiological measurements on persons and sensor development.
We present initial evidence of the SOLUS potential for the multimodal non-invasive diagnosis of breast cancer by describing the correlation between optical and standard radiological data and analyzing a case study.
A machine learning classification algorithm is applied to the SOLUS database to discriminate benign and malignant breast lesions, based on absorption and composition properties retrieved through diffuse optical tomography. The Mann-Whitney test indicates oxy-hemoglobin (p-value = 0.0007) and lipids (0.0387) as the most significant constituents for lesion classification, but work is in progress for further analysis. Together with sensitivity (91%), specificity (75%) and the Area Under the ROC Curve (0.83), special metrics for imbalanced datasets (27% of malignant lesions) are applied to the machine learning outcome: balanced accuracy (83%) and Matthews Correlation Coefficient (0.65). The initial results underline the promising informative content of optical data.
A multimodal instrument for breast imaging was developed, combining ultrasound (morphology), shear wave elastography (stiffness), and time domain multiwavelength diffuse optical tomography (blood, water, lipid, collagen) to improve the non-invasive diagnosis of breast cancer.
To improve non-invasively the specificity in the diagnosis of breast cancer after a positive screening mammography or doubt/suspicious ultrasound examination, the SOLUS project developed a multimodal imaging system that combines: Bmode ultrasound (US) scans (to assess morphology), Color Doppler (to visualize vascularization), shear-wave elastography (to measure stiffness), and time domain multi-wavelength diffuse optical tomography (to estimate tissue composition in terms of oxy- and deoxy-hemoglobin, lipid, water, and collagen concentrations). The multimodal probe arranges 8 innovative photonic modules (optodes) around the US transducer, providing capability for optical tomographic reconstruction. For more accurate estimate of lesion composition, US-assessed morphological priors can be used to guide the optical reconstructions. Each optode comprises: i) 8 picosecond pulsed laser diodes with different wavelengths, covering a wide spectral range (635-1064 nm) for good probing of the different tissue constituents; ii) a large-area (variable, up to 8.6 mm2 ) fast-gated digital Silicon Photomultiplier; iii) the acquisition electronics to record the distribution of time-of-flight of the re-emitted photons. The optode is the basic element of the optical part of the system, but is also a stand-alone, ultra-compact (about 4 cm3 ) device for time domain multi-wavelength diffuse optics, with potential application in various fields.
Blood oxygenation in depth is a critical parameter to be monitored in many clinical applications. We are developing a pre-clinical instrument to monitor oxygenation up to 1.5 cm deep in biological tissues. The measures, based on time of ight, are in vivo, non invasive and without injection of any contrast agent. Developments have been implemented in a tomographic reconstruction algorithm to make it reconstruct chromophores by layers. These developments are presented here along with simulations we used to set up the algorithm. Buried aps on 20 pigs were undergone for pre-clinical tests of our reconstruction algorithm and instrument.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.