scholarly journals Optimization of the phase and modulation depth signal-to-noise ratio for near-infrared spectroscopy of the biological tissue

2004 ◽  
Author(s):  
Vladislav Y. Toronov ◽  
Enrico D'Amico ◽  
Dennis M. Hueber ◽  
Enrico Gratton ◽  
Beniamino B. Barbieri ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Biological Tissue ◽  
Near Infrared ◽  
Modulation Depth ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Noise Ratio

scholarly journals Reduced semantic context and signal-to-noise ratio increase listening effort as measured using functional near-infrared spectroscopy

2021 ◽  
Author(s):  
Joseph Rovetti ◽  
Huiwen Goy ◽  
Michael Zara ◽  
Frank Russo
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Semantic Context ◽  
Signal To Noise ◽  
Listening Effort ◽  
Functional Near Infrared Spectroscopy ◽  
Noise Ratio ◽  
Linguistic Challenges

Objectives: Understanding speech in noise can be highly effortful. Decreasing the signal-to-noise ratio (SNR) of speech increases listening effort, but it is relatively unclear if decreasing the level of semantic context does as well. The current study used functional near-infrared spectroscopy (fNIRS) to evaluate two primary hypotheses: (1) listening effort (operationalized as oxygenation of the left lateral PFC) increases as the SNR decreases and (2) listening effort increases as context decreases. Design: Twenty-eight younger adults with normal hearing completed the Revised Speech Perception in Noise (R-SPIN) Test, in which they listened to sentences and reported the final word. These sentences either had an easy SNR (+4 dB) or a hard SNR (-2 dB), and were either low in semantic context (e.g., “Tom could have thought about the sport”) or high in context (e.g., “She had to vacuum the rug”). PFC oxygenation was measured throughout using fNIRS. Results: Accuracy on the R-SPIN Test was worse when the SNR was hard than when it was easy, and worse for sentences low in semantic context than high in context. Similarly, oxygenation across the entire PFC (including the left lateral PFC) was greater when the SNR was hard, and left lateral PFC oxygenation was greater when context was low. Conclusions: These results suggest that activation of the left lateral PFC (interpreted here as reflecting listening effort) increases to compensate for acoustic and linguistic challenges. This may reflect the increased engagement of domain-general and domain-specific processes subserved by the DLPFC (e.g., cognitive control) and IFG (e.g., predicting the sensory consequences of articulatory gestures), respectively.

scholarly journals Evaluation of Measurement Sites for Noninvasive Blood Glucose Sensing with Near-Infrared Transmission Spectroscopy

1999 ◽  
Vol 45 (9) ◽  
pp. 1621-1627 ◽  
Author(s):  
Jason J Burmeister ◽  
Mark A Arnold
Keyword(s):  
Blood Glucose ◽  
Body Fat ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Glucose Sensing ◽  
Infrared Transmission ◽  
Signal To Noise ◽  
Lower Lip ◽  
Percentage Of Body Fat ◽  
Noise Ratio

Abstract Six putative measurement sites were evaluated for noninvasive sensing of blood glucose by first-overtone near-infrared spectroscopy. The cheek, lower lip, upper lip, nasal septum, tongue, and webbing tissue between the thumb and forefinger were examined. These sites were evaluated on the basis of their chemical and physical properties as they pertain to the noninvasive measurement of glucose. Critical features included the effective optical pathlength of aqueous material within the tissue and the percentage of body fat within the optical path. Aqueous optical paths of 5 mm are required to measure clinically relevant concentrations of glucose in the first-overtone region. All of the tested sites met this requirement. The percentage of body fat affects the signal-to-noise ratio of the measurement and must be minimized for reliable glucose sensing. The webbing tissue contains a considerable amount of fat tissue and is clearly the worse measurement site. All other sites possess substantially less fat, with the least amount of fat in tongue tissue. For this reason, the tongue provides spectra with the highest signal-to-noise ratio and is, therefore, the site of choice on the basis of spectral quality.

Bioapplications and biotechnologies of upconversion nanoparticle-based nanosensors

The Analyst ◽  
2016 ◽  
Vol 141 (12) ◽  
pp. 3601-3620 ◽  
Author(s):  
Chengli Wang ◽  
Xiaomin Li ◽  
Fan Zhang
Keyword(s):  
Optical Properties ◽  
High Resistance ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Upconversion Nanoparticles ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Auto Fluorescence ◽  
New Generation ◽  
Narrow Emission

Upconversion nanoparticles (UCNPs), which can emit ultraviolet/visible (UV/Vis) light under near-infrared (NIR) excitation, are regarded as a new generation of nanoprobes because of their unique optical properties, including a virtually zero auto-fluorescence background for the improved signal-to-noise ratio, narrow emission bandwidths and high resistance to photo-bleaching.

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