THE EVOLUTION OF FIELD DEPLOYABLE fNIR SPECTROSCOPY FROM BENCH TO CLINICAL SETTINGS

In the late 1980s and early 1990s,Dr.Britton Chance and his colleagues,using picosecond-long laser pulses,spearheaded the development of time-resolved spectroscopy techniques in an effort to obtain quantitative information about the optical characteristics of the tissue.These efforts by Chance and colleagues expedited the translation of near-infrared spectroscopy(NIRS)-based techniques into a neuroimaging modality for various cognitive studies.Beginning in the early 2000s,Dr.Britton Chance guided and steered the collaboration with the Optical Brain Imaging team at Drexel University toward the development and application of afield deployable continuous wave functional near-infrared spectroscopy(fNIR)system as a means to monitor cognitive functions,particularly during attention and working memory tasks as well as for complex tasks such as war games and air tra±c control scenarios performed by healthy volunteers under operational conditions.Further,these collaborative efforts led to various clinical applications,including traumatic brain injury,depth of anesthesia monitoring,pediatric pain assessment,and brain
computer interface in neurology.In this paper,we introduce how these collaborative studies have made fNIR an excellent candidate for specified clinical and research applications,including repeated cortical neuroimaging,bedside or home monitoring,the elicitation of a positive effect,and protocols requiring ecological validity.This paper represents a token of our gratitude to Dr.Britton Chance for his influence and leadership.Through this manuscript we show our appreciation by contributing to his commemoration and through our work we will strive to advance thefield of optical brain imaging and promote his legacy.

FUNCTIONAL NEAR-INFRARED SPECTROSCOPY-BASED ASSESSMENT OF ATTENTION IMPAIRMENTS AFTER TRAUMATIC BRAIN INJURY

A frequent consequence of traumatic brain injury(TBI)is cognitive impairment,which results in significant disruption of an individual's everyday living.To date,most clinical rehabilitation interventions still rely on behavioral observation,with little or no quantitative information about physiological changes produced at the brain level.Functional brain imaging has been extensively used in the study of cognitive impairments following TBI.However,its applications to rehabilitation have been limited.This is due in part to the expensive or invasive nature of these modalities.The objective of this study is to apply functional near-infrared spectroscopy(fNIR)to the assessment of attention impairments following TBI.fNIR provides a localized measure of prefrontal hemodynamic activation,which is susceptible to TBI,and it does so in a noninvasive,affordable and wearable way,thus partially overcoming the limitations of other modalities.Participants included 5 TBI subjects and 11 healthy controls.Brain activation measurements were collected during a target categorization task.Significant differences were found in the hemodynamic response between healthy and TBI subjects.In particular,the elicited responses exhibited reduced amplitude in the TBI group.Overall,the results providefirst evidence of the ability of fNIR to reveal differences between TBI and healthy subjects in an attention task.fNIR is therefore a promising neuroimaging technique in thefield of neurorehabilitation.The use of fNIR in neurorehabilitation applications would benefit from its noninvasiveness and cost-effectiveness and the neurophysiological information obtained through the evaluation of the hemodynamic activation could provide invaluable information to guide the choice of intervention.