Validating a Diffuse Reflectance near Infrared Spectroscopy Method for Measuring a Coating on a Highly-Scattering Surface

NIR news ◽  
2014 ◽  
Vol 25 (8) ◽  
pp. 13-15
Author(s):  
Gary E. Ritchie ◽  
Emil W. Ciurczak ◽  
Sharon Flank
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Diffuse Reflectance ◽  
Near Infrared ◽  
Spectroscopy Method

Quantifying contact force artefact in near infrared spectroscopy

2021 ◽  
Author(s):  
◽  
Timothy Schwab
Keyword(s):  
Experimental Investigation ◽  
Adipose Tissue ◽  
Infrared Spectroscopy ◽  
Contact Force ◽  
Near Infrared Spectroscopy ◽  
Muscle Activation ◽  
Diffuse Reflectance ◽  
Near Infrared ◽  
Photon Propagation ◽  
Superficial Tissues

Transcutaneous near infrared spectroscopy (NIRS) of muscle requires coupling between the device and the skin. An unfortunate by-product of this coupling is contact force artefact, where the amount of contact force between the device and the skin affects measurements. Contact force artefact is well known, but largely ignored in most NIRS research. We performed preliminary investigations of contact force artefact to quantify tissue behaviour to inform future NIRS designs. Specifically, we conducted three studies on contact force artefact: (i) an experimental investigation of static load at varied levels of contact force and muscle activation, (ii) an experimental investigation of oscillating load at varied levels of contact force and frequency, and (iii) a Monte Carlo simulation of photon propagation through skin, adipose tissue, and muscle. Our results confirmed that contact force artefact is a confounding factor in NIRS muscle measurements because contact force affects measured hemoglobin concentrations in a manner consistent with muscle contractions. Further, the effects of contact force are not altered by muscle contraction and a likely candidate for the mechanism responsible for contact force artefact is the viscoelastic compression of superficial tissues (skin and adipose) during loading. Simulation data suggests that adipose tissue plays a key role in diffuse reflectance of photons, so any compression of the superficial tissues will affect the reflected signal. Further research is required to fully understand the mechanisms behind contact force artefact, which will, in turn, inform future NIRS device designs.

Interpreting Diffuse Reflectance and Transmittance: A Theoretical Introduction to Absorption Spectroscopy of Scattering Materials

2007 ◽  
Author(s):  
Donald Dahm ◽  
Kevin Dahm
Keyword(s):  
Infrared Spectroscopy ◽  
Absorption Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Mathematical Description ◽  
Diffuse Reflectance ◽  
Near Infrared ◽  
Diffuse Reflection ◽  
Theoretical Understanding ◽  
Famous Book ◽  
Father And Son

A jar of sweets may not appear to be a serious introduction to the attempt to progress the understanding of the challenging nature of what is usually termed "diffuse reflection". However, this book by the father and son team of Don and Kevin Dahm is the first such attempt since the famous book by Wendlandt and Hecht some forty year ago. The sweets are not only useful models, they also indicate the desire of the authors to make this a readable and entertaining book as well as a very serious attempt to advance our theoretical understanding of this complex and confusing topic. The Dahms have been developing and advancing a new theory for the last few years. This book brings it together. It explains the nature of reflected radiation and then the problem of finding a mathematical description of it. In their quest, they have rediscovered and used mathematics that was invented by Sir George Strokes in the 1860s! Much of the current use of near infrared spectroscopy utilizes diffuse reflection or transmission. According to Karl Norris "The development of NIR analysis is being restricted by our lack of a theoretical understanding of diffuse reflection" and he should know!

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