Can you see what a person is thinking - optical measurements of brain activity

Optical spectroscopy/imaging of brain physiology is developing quickly. It has been proven to be possible to monitor changes in local blood concentration stimulated by small physical activity (for instance by tapping a finger) or even by visual stimulation from the outside of the head. This yields promising prospects of being able to use optical measurements to further develop the understanding of the function of the brain and also for diagnostic purposes of diseases affecting the brain, such as for instance Alzheimer’s disease or epilepsy.

The aim of this project is to estimate the magnitude of the blood concentration increase required for allowing transcutaneous detection.  

You should especially consider the optical properties of the brain and scull, the thickness of the scull bone, the measurement geometry, the location and size of the brain activity yielding the increased local blood content, and the light power used.

The intention is that the project should include the following:

• You are supposed to briefly study the field of optical monitoring of brain activation. You should especially focus on the techniques utilised, the measurement geometries for imaging the brain and the models used to simulate the measurements. Also discuss the resolution obtained. This background should be included in the introduction of the report. Make sure to cite the appropriate literature.
• You should find the values for the optical properties of the tissues of interest in the literature (or measure them yourselves, probably quite difficult).
• You should model the diffuse reflectance varying the blood concentration and other parameters of interest (for instance the measurement geometry) (during the computer exercises and by yourself, if necessary).
• You should calculate the temperature distribution following such a diagnostic procedure (during the laboratory exercise in laser thermotherapy and by yourself).
• Discuss how small a change in blood content you estimate would be possible to measure. Compare this with what is obtained in the literature and if this is relevant for the applications.

Suggested key-words: brain imaging, optical, lasers, tissue optics, time-resolved, frequency domain