Instrumentation, modélisation, et traitement des signaux biomédicaux reflétant la microcirculation sanguine : contribution à la technique de fluxmétrie laser Doppler

National audienc

Some reasons to build a new laser Doppler flowmeter to monitor microvascular blood flow

Disturbance in the blood microcirculation is a frequent complication in a number of common diseases including diabetes, arteriosclerosis and Raynaud’s phenomenon. In order to effectively diagnose these diseases, clinical tools able to monitor non-invasively the microvascular perfusion are required. For that purpose several techniques have been proposed. Among them, laser Doppler flowmetry (LDF) has been developed over the years, from experimental tools into commercial products, and several thousands of publications cite its use in the scientific literature. Nowadays, the LDF technique is commonly proposed in diverse applications. However, the dependence of the LDF signal on the microvascular architecture is still not known. A scientific understanding and knowledge of the LDF signal origin is not yet accessible to clinicians. Some studies proposed the use of different fiber separations or several wavelengths in order to modify the sampling depth of the LDF technique. However, further work is required to have knowledge and control over the mean sampling depth (and hence volume) in skin tissue

Comparaison between laser Doppler flowmetry signals recorded in glabrous and non glabrous skin: time and frequency analyses

International audienc

A new laser Doppler flowmeter prototype for depth dependent monitoring of skin microcirculation

Laser Doppler flowmetry (LDF) is now commonly used in clinical research to monitor microvascular blood flow. However, the dependence of the LDF signal on the microvascular architecture is still unknown. That is why we propose a new laser Doppler flowmeter for depth dependent monitoring of skin microvascular perfusion. This new laser Doppler flowmeter combines for the first time, in a device, several wavelengths and different spaced detection optical fibres. The calibration of the new apparatus is herein presented together with in vivo validation. Two in vivo validation tests are performed. In the first test, signals collected in the ventral side of the forearm are analyzed; in the second test, signals collected in the ventral side of the forearm are compared with signals collected in the hand palm. There are good indicators that show that different wavelengths and fibre distances probe different skin perfusion layers. However, multiple scattering may affect the results, namely the ones obtained with the larger fibre distance. To clearly understand the wavelength effect in LDF measurements, other tests have to be performed

Use of laser speckle and entropy computation to segment images of diffuse objects with longitudinal motion

International audienc