Berlin 2001 – scientific programme

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Q: Quantenoptik

Q 30: Poster: Laser in Medicine

Q 30.3: Poster

Friday, April 6, 2001, 12:30–15:00, AT2

Time-resolved diffuse reflectance measurements for depth localisation of absorption changes in the human head — •Heidrun Wabnitz¹, Jens Steinbrink¹, Herbert Rinneberg¹, Hellmuth Obrig², and Arno Villringer² — ¹Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, D-10587 Berlin — ²Neurologische Klinik, Charité, Humboldt-Universität, Schumannstr. 20-21, D-10098 Berlin

We have simultaneously measured time-resolved diffuse reflectance of the adult head at three wavelengths using a portable setup based on three picosecond diode lasers emitting at 684, 780 and 826 nm and time-correlated single photon counting. The data were analysed employing a layered model of the head and the concept of time-dependent mean partial pathlenghts of photons. Changes in reflectance related to small absorption changes in different layers are described by a set of linear equations. The corresponding coefficient matrix consists of the time-dependent mean partial pathlenghts associated with different layers and obtained from Monte-Carlo simulations. We analysed changes in reflectance induced by various stimulation experiments on healthy volunteers and determined separately intra- and extracerebral concentration changes of oxy- and deoxyhaemoglobin.