Laser Doppler Flowmeters Prototypes:Monte Carlo Simulations Validation Paired with Measurements - Biomedical Engineering Systems and Technologies - page 113

Laser Doppler Flowmeters Prototypes: Monte Carlo
Simulations Validation Paired with Measurements

Edite Figueiras 1 , Anne Humeau-Heurtier 2 , Rita Campos 1 , Ricardo Oliveira 1 ,
Luís F. Requicha Ferreira 1 , and Frits de Mul 3

1 Instrumentation Center (GEI-CI), Physics Department,
Faculty of Sciences and Technology of Coimbra University,
Rua Larga, 3004-516, Coimbra, Portugal
2 Laboratoire d'Ingénierie des Systèmes Automatisés (LISA), Université d'Angers,
62 avenue Notre Dame du Lac, 49000 Angers, France
3 previously at University of Twente, Department of Applied Physics,
Biomedical Optics Group, Enschede, Netherlands
{edite.figueiras,ffmdemul}@gmail.com,
[e-mail],

Abstract. Two new laser Doppler flowmeter prototypes are herein validated with
Monte Carlo simulations paired with measurements. The first prototype is a multi-
wavelength laser Doppler flowmeter with different spaced detection fibres that
will add depth discrimination capabilities to laser Doppler flowmetry skin mon-
itoring. The other prototype is a self-mixing based laser Doppler flowmeter for
brain perfusion estimation. Monte Carlo simulations in a phantom consisting of
moving fluid as well as in a skin model are proposed for the first prototype vali-
dation. We obtain a good correlation between simulations and measurements. For
the second prototype validation, Monte Carlo simulations are carried out on a rat
brain model. We show that the mean measurement depth in the rat brain with our
probe is 0.15 mm. This positioning is tested in vivo where it is shown that the
probe monitors the blood flow changes.

Keywords: Laser Doppler Flowmetry, Monte Carlo simulations, Microcircula-
tion.

1 Introduction

Laser Doppler flowmetry (LDF) is a Doppler effect based technique used for microcir-
culation blood flow monitoring where monochromatic light, guided by optical fibres,
is transmitted to the tissues under study. In the tissues the laser light can be reflected,
absorbed, transmitted or scattered. The photons scattered by moving particles, like red
blood cells (RBCs), are frequency shifted in accordance with the Doppler effect. These
photons get red blood cells velocity information. If they are detected, together with
photons scattered by static particles, they will produce a modulated photocurrent in the
photodetector. This photocurrent is related with the velocity and concentration of the
RBCs [1] [2].