Diffuse optical imaging of the whole head

Abstract

Functional optical brain imaging measurements require a fast image acquisition rate and coverage of a large area of the brain. A fast acquisition rate permits simple filtering of faster hemoglobin changes arising from, for example, cardiac pulsation from the relatively slow evoked hemodynamic response to brain activation. A spatial coverage not limited to the activation area but extended to areas not involved with the stimulation allows separation of evoked hemodynamic changes from global systemic oscillations of hemoglobin at similar frequencies, such as Mayer waves and respiration.¹ With this purpose in mind, we have developed a fast multichannel optical imaging system with a large number of channels and a parallel acquisition scheme to allow a fast acquisition rate with a sufficiently high signal-to-noise ratio (SNR) to characterize brain activation and the background physiological fluctuations.