Controlling jaw-related motion artifacts in functional near-infrared spectroscopy.

BACKGROUND: Functional near-infrared spectroscopy (fNIRS) as a non-invasive optical neuroimaging technique has demonstrated great potential in monitoring cerebral activity. Due to its portability and compatibility with medical implants, fNIRS has seen increasing applications in studying the hearing, language and cognitive functions. However, fNIRS is susceptible to artifacts related to jaw movements, such as teeth clenching, swallowing and speaking, which affect recordings over the temporal, parietal and frontal/prefrontal cortices. NEW METHOD: We investigated two new approaches to control the jaw-related motion artifacts, an individually customized bite bar apparatus and a denoising algorithm namely PCA-GLM based on multi-channel fNIRS recordings from long-separation and short-separation montage. We first recorded data while subjects performed a clenching task, then an auditory task and a resting-state task with and without the bite bar. RESULTS: Our results have shown that jaw clenching can introduce spurious, task-evoked-like responses in fNIRS signals. A bite bar customized for each participant effectively suppressed the movement-related activities in fNIRS, at both task and resting-state conditions. Moreover, the bite bar and the PCA-GLM denoising method are shown to improve auditory responses, by significantly reducing the within-subject standard deviation, increasing the task-related contrast-to-noise ratio, and yielding stronger activations to the auditory stimuli. COMPARISON WITH EXISTING METHOD(S): The current study has demonstrated a novel method to control the jaw-related motion artifacts in fNIRS signals. CONCLUSIONS: Our method will benefit the study of the hearing, language and cognitive functions in normal healthy subjects and patients.

Clenching-Related Motion Artifacts in Functional Near-Infrared Spectroscopy in the Auditory Cortex.

Functional near-infrared spectroscopy (fNIRS), a non-invasive optical neuroimaging technique, has demonstrated its great potential in monitoring cerebral activity as an alternative to functional magnetic resonance imaging (fMRI) in research and clinical usage. fNIRS has seen increasing applications in studying the auditory cortex in healthy subjects and cochlear implant users. However, fNIRS is susceptible to motion artifacts, especially those related to jaw movement, which can affect fNIRS signals in speech and auditory tasks. This study aimed to investigate the motion artifacts related to jaw movements including clenching, speaking, swallowing, and sniffing in a group of human subjects, and test whether our previously established denoising algorithm namely PCA-GLM can reduce the motion artifacts. Our results have shown that the jaw movements introduced artifacts that resemble task-evoked activations and that the PCA-GLM method effectively reduced the motion artifacts due to the clenching movements. The preliminary results of the present study underline the importance of the removal of the jaw-movement-related artifacts in fNIRS signals and suggest the efficacy of our PCA-GLM method in reducing the motion artifacts. Clinical Relevance- This work studies the motion artifacts due to jaw movements that frequently occur in speech perception and production tasks and validates the efficacy of an established denoising algorithm which benefits fNIRS studies on auditory and language functions.

A novel 3D video oculography system for measuring cross-axis vestibulo-ocular reflex.

We present a video oculography (VOG) system with 6-degree-of-freedom (6-DOF) mobility for real-time measurements of the binocular 3D eye position of a small animal. A hybrid hexapod that allowed for multi-axis complex motions with the resolution of the microscopic level was used to control the motion of the animal. The instantaneous eyeball movement of the animal was determined based on two approaches: (1) tracking of marker arrays affixed to the cornea; and (2) tracking the pupil outline. The tracking of the eyeball movement and the motion control of the hexapod were implemented with the LabVIEW virtual instruments. Compared with our previous measurements using a servo-motor-based single-axis VOG system, positional error reduced from more than 4% to less than 0.7%. Validation showed that the tracking errors in three rotational axes are less than 2% for the magnitude and less than 5° for the direction angle. The present VOG system is an effective tool for cross-axis 3D vestibulo-ocular reflex study on small animals.

Reducing Alarm Burden in a Level IV Neonatal Intensive Care Unit.

Introduction: Excessive alarm burden contributes to alarm fatigue, causing staff to ignore or delay response to clinically significant alarms. The objective of this quality improvement project was to reduce yellow self-resolving SpO2 alarms from a mean of 14 alarms/patient-hour (APH) to 7 APH (a 50% reduction) within a 6-month period, without significantly decreasing the amount of time spent in target SpO2 range (90%-95%). Methods: A multidisciplinary team used Define-Measure-Analyze-Improve-Control methodology to identify etiologies of alarm frequency and design improvement interventions to reduce alarm burden in a single-site Level IV NICU. Data-driven changes in alarm limit settings, alarm delay, and trial of a new pulse oximeter probe were used. Alarm data from the bedside monitor were analyzed following each improvement cycle. As a balancing measure, histograms monitored time spent in target SpO2 range. Results: SpO2 alarm data were collected for 4,320 patient-hours (180 patient-days) on 40 neonatal intensive care unit patients meeting inclusion criteria. Corresponding histograms were obtained for each patient day. Following 5 Plan-Do-Study-Act cycles, the mean number of yellow self-resolving SpO2 alarms decreased from 14 to 5 APH, a 64% decrease. There was no difference in time spent in target SpO2 range (50% versus 50%, P = 0.93). After achieving the project aim, 2 control phase measurements demonstrated sustained improvement (mean APH = 6). Conclusions: Yellow self-resolving SpO2 alarm frequency was reduced by 64% through the implementation of data-driven changes in alarm limit settings, alarm delays, and trial of a more sensitive oximeter probe without introducing harm to patients.