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Optical Imaging
Published in George C. Kagadis, Nancy L. Ford, Dimitrios N. Karnabatidis, George K. Loudos, Handbook of Small Animal Imaging, 2018
For additional, focused coverage of specific types of optical imaging, the interested reader is directed to the various excellent reviews covering diffuse optical imaging (Arridge and Hebden 1997; Arridge and Schweiger 1997; Hebden et al. 1997; Arridge 1999; Boas et al. 2001; Schweiger et al. 2003; Gibson et al. 2005; Arridge and Schotland 2009; Arridge 2011), fluorescence imaging (Weissleder and Ntziachristos 2003; Graves et al. 2004; Stuker et al. 2011; Darne et al. 2014), bioluminescence imaging (Wang et al. 2008a; Darne et al. 2014; Qin et al. 2014), Cerenkov imaging (Qin et al. 2012; Thorek et al. 2012; Das et al. 2014), and instrumentation (Ntziachristos et al. 2005; Zhang 2014).
Functional Near-Infrared Spectroscopy
Published in Yu Chen, Babak Kateb, Neurophotonics and Brain Mapping, 2017
Carlos G. Treviño-Palacios, Karla J. Sanchez-Perez, Javier Herrera-Vega, Felipe Orihuela-Espina, Luis Enrique Sucar, Oscar Javier Zapata-Nava, Francisco F. De-Miguel, Guillermo Hernández-Mendoza, Paola Ballesteros-Zebadua, Javier Franco-Perez, Miguel Ángel Celis-López
Diffuse optical imaging (DOI) is an emerging modality of medical imaging based on the use of near-infrared light. This technique permits to study living tissue noninvasively (Villringer and Chance 1997; Strangman et al. 2002). Its working principle capitalizes on the characteristic spectroscopic signatures of the molecules of interest. Its practical manifestation involves irradiating a narrow collimated beam over the biological tissue, where the light is scattered, and in response, part of it abandons the tissue to be collected by a detector. The sensed light encodes information about the physiological changes in the tissue in the form of changes in absorption and scattering. In the adult head, DOI becomes a practical form of functional neuroimaging known as functional near-infrared spectroscopy (fNIRS).
Lasers in Medicine: Healing with Light
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
One novel application of the ideas from optics in medicine involves the use of infrared radiation, not for therapy, but for imaging inside the body. It may seem surprising that light can be used for this purpose, since the body seems opaque to radiation near the visible. However, everyone has likely had the experience of shining a flashlight through a cupped hand and noticing that some reddish light shines through one's fingers. This light is diffuse – it has been scattered so many times that its original direction is entirely corrupted. A similar effect occurs in milk or frosted glass, either of which can transmit a glow from a light source even though neither is transparent. A new technique called diffusive optical imaging uses this diffuse light to diagnose breast cancer and other diseases (Figure 3.35). The idea is simple: in the infrared, the absorption of water and many body tissues is small compared with that for visible wavelengths, so light can travel a significant distance without being absorbed. If the light's wavelength is chosen to coincide with values differentially absorbed by, for example, oxy- or deoxyhemoglobin, then the light will be absorbed preferentially by tissues with differing patterns of blood oxygenation, such as tumors or brain tissue affected by a stroke; similar results can be obtained by a wise choice of chemical tags with interesting optical properties. Scattering is still a problem, however, since it prevents one from simply using a lens to form an image from light transmitted from these regions. How can this diffuse light be used to create an image? If the infrared light is shone into the body at a well-defined time and location using an optical fiber, and then detected at a different location and time using a second optical fiber, its path inside the body can be inferred using mathematical techniques established to model the flow of diffusive light. These methods are being explored in research settings, establishing the feasibility of imaging with typical millisecond time resolution and several millimeters spatial resolution. These techniques are being investigated in combination with other imaging modalities, which can provide anatomical information to use in constructing the basic mathematical models, and with new biochemical techniques designed to provide tracers for interesting body functions and disease processes.
Whole body measurements using near-infrared spectroscopy in a rat spinal cord contusion injury model
Published in The Journal of Spinal Cord Medicine, 2023
Brianna Kish, Seth Herr, Ho-Ching (Shawn) Yang, Siyuan Sun, Riyi Shi, Yunjie Tong
Near infrared spectroscopy (NIRS) is a diffuse optical imaging tool used for measuring the relative concentrations of oxyhemoglobin (Δ[HbO]) and deoxyhemoglobin (Δ[Hb]). Though blood flow is believed to be the predominant contributing factor in the NIRS signal, with increases of flow corresponding to an increase in Δ[HbO] and decrease in Δ[Hb], changes in blood volume and metabolic rate impact the signal as well, altogether reflecting complex hemodynamic changes. NIRS is a low cost, portable optical technology easily adaptable to record real-time physiologic changes from many locations over the body at once with high temporal resolution. While the system can act invasively, it also works noninvasively, allowing for examinations over long periods of time. Additionally, the system is easily set up and operated, making it ideal for quick and accurate measurements. Together, NIRS is a promising technique for assessing hemodynamic changes in SCI models.