Transcranial time-of-flight estimation using backscattered infrared data

Abstract

Recently, we reported on our observation that diffuse infrared (IR) light transmitted through human skull bone exhibits an intensity that correlates positively with acoustic (1 MHz) time-of-flight data acquired at equivalent locations [POMA 22, 020002 (2015)]. Presently, we investigate the potential to exploit this correlation as a means of correcting for skull-induced aberration. For measurement, a dual ultrasonic/infrared array capable of illuminating a localized region of the skull bone and recording the backscattered light was constructed. The array design utilized 940 nm IR emitters (TSAL4400, 3-mm-diameter) and a single detector (TEFD4300-3 mm) configured to transmit and record under the face of an ultrasonic PZT ring transducer. Initial tests consisted of a three-emitter configuration, with fiberglass-reinforced foil used to isolate the direct infrared signal between the emitters and the receiver. Effects of skin were considered by attaching a skin-mimicking layer to the skull and comparing results with and without the layer. Data acquired on a set of eight skull samples will be presented. Preliminary results show good correlation between ultrasound and IR intensity. [Work supported by NIH award R01EB014296.] Posters will be on display and contributors will be at their posters during the session break from 2:40 p.m. to 3:05 p.m.