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Frequency domain diffuse optical spectroscopy with a near-infrared tunable vertical cavity surface emitting laser.
We present an approach for performing frequency domain diffuse optical spectroscopy (fd-DOS) utilizing a near-infrared tunable vertical cavity surface emitting laser (VCSEL) that enables high spectral resolution optical sensing in a miniature format. The tunable VCSEL, designed specifically for deep tissue imaging and sensing, utilizes an electrothermally tunable microelectromechanical systems topside mirror to tune the laser cavity resonance. At room temperature, the laser is tunable across 14nm from 769 to 782nm with single mode CW output and a peak output power of 1.3mW. We show that the tunable VCSEL is suitable for use in fd-DOS by measuring the optical properties of a tissue-simulating phantom over the tunable range. Optical properties were recovered within 0.0006mm-1 (absorption) and 0.09mm-1 (reduced scattering) compared to a broadband fd-DOS reference system. Our results indicate that tunable VCSELs may be an attractive choice to enable high spectral resolution optical sensing in a wearable format
Does Traumatic Brain Injury Attenuate The Exposure Therapy Process?
Research indicates that exposure therapy is efficacious for combat-related posttraumatic stress disorder (PTSD) comorbid with traumatic brain injury (TBI) as is shown by reduced PTSD treatment outcome scores. What is unknown, however, is whether the process of fear extinction is attenuated in veterans with TBI history. Increased PTSD symptomatology and possible cognitive deficits associated with TBI sequelae may indicate additional or longer exposure sessions to achieve habituation and extinction comparable to individuals without TBI history. As such, a more extensive course of treatment may be necessary to achieve comparable PTSD treatment outcome scores for individuals with TBI history. Using a sample of veterans with combat-related PTSD, some of whom were comorbid for TBI, this study compared process variables considered relevant to successful treatment outcome in exposure therapy. Individuals with and without TBI demonstrated similar rates of fear activation, length and number of exposure sessions, within-session habituation, between-session habituation, and extinction rate; results remained consistent when controlling for differential PTSD symptomatology. Furthermore, results indicated that self-perception of executive dysfunction did not impact the exposure process. Results suggest that individuals with PTSD and TBI history engage successfully and no differently in the exposure therapy process as compared to individuals with PTSD alone. Findings further support exposure therapy as a first-line treatment for combat-related PTSD regardless of TBI history