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Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter waves and acoustic waves can also be considered forms of radiative energy, and recently gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO).
Optical coherence tomography (OCT) is an imaging technique that uses low-coherence light to capture micrometer-resolution, two- and three-dimensional images from within optical scattering media. It is used for medical imaging and industrial nondestructive testing (NDT). Optical coherence tomography is based on low-coherence interferometry, typically employing near-infrared light. The use of relatively long wavelength light allows it to penetrate into the scattering medium. Confocal microscopy, another optical technique, typically penetrates less deeply into the sample but with higher resolution.
Near-infrared spectroscopy (NIRS) is a spectroscopic method that uses the near-infrared region of the electromagnetic spectrum. Typical applications include medical and physiological diagnostics and research including blood sugar, pulse oximetry, functional neuroimaging, sports medicine, elite sports training, ergonomics, rehabilitation, neonatal research, brain computer interface, urology, and neurology. There are also applications in other areas as well such as pharmaceutical, food and agrochemical quality control, atmospheric chemistry, combustion research and knowledge
Two-photon excitation microscopy is a fluorescence imaging technique that is particularly well-suited to image scattering living tissue of up to about one millimeter in thickness. Unlike traditional fluorescence microscopy, where the excitation wavelength is shorter than the emission wavelength, two-photon excitation requires simultaneous excitation by two photons with longer wavelength than the emitted light. The laser is focused onto a specific location in the tissue and scanned across the sample to sequentially produce the image. Due to the non-linearity of two-photon excitation, mainly fluorophores in the micrometer-sized focus of the laser beam are excited, which results in the spatial resolution of the image. This contrasts with confocal microscopy, where the spatial resolution is produced by the interaction of excitation focus and the confined detection with a pinhole.
Functional near-infrared spectroscopy (fNIRS) is an optical brain monitoring technique which uses near-infrared spectroscopy for the purpose of functional neuroimaging. Using fNIRS, brain activity is measured by using near-infrared light to estimate cortical hemodynamic activity which occur in response to neural activity. Alongside EEG, fNIRS is one of the most common non-invasive neuroimaging techniques which can be used in portable contexts. The signal is often compared with the BOLD signal measured by fMRI and is capable of measuring changes both in oxy- and deoxyhemoglobin concentration, but can only measure from regions near the cortical surface. fNIRS may also be referred to as Optical Topography (OT) and is sometimes referred to simply as NIRS.
Optical tomography is a form of computed tomography that creates a digital volumetric model of an object by reconstructing images made from light transmitted and scattered through an object. Optical tomography is used mostly in medical imaging research. Optical tomography in industry is used as a sensor of thickness and internal structure of semiconductors.
Bruce J. Tromberg is an American photochemist and a leading researcher in the field of biophotonics. He is the director of the National Institute of Biomedical Imaging and Bioengineering (NIBIB) within the National Institutes of Health (NIH). Before joining NIH, he was Professor of Biomedical Engineering at The Henry Samueli School of Engineering and of Surgery at the School of Medicine, University of California, Irvine. He was the principal investigator of the Laser Microbeam and Medical Program (LAMMP), and the Director of the Beckman Laser Institute and Medical Clinic at Irvine. He was a co-leader of the Onco-imaging and Biotechnology Program of the NCI Chao Family Comprehensive Cancer Center at Irvine.
Ballistic light, also known as ballistic photons, is photons of light that have traveled through a scattering (turbid) medium in a straight line.
Modeling photon propagation with Monte Carlo methods is a flexible yet rigorous approach to simulate photon transport. In the method, local rules of photon transport are expressed as probability distributions which describe the step size of photon movement between sites of photon-matter interaction and the angles of deflection in a photon's trajectory when a scattering event occurs. This is equivalent to modeling photon transport analytically by the radiative transfer equation (RTE), which describes the motion of photons using a differential equation. However, closed-form solutions of the RTE are often not possible; for some geometries, the diffusion approximation can be used to simplify the RTE, although this, in turn, introduces many inaccuracies, especially near sources and boundaries. In contrast, Monte Carlo simulations can be made arbitrarily accurate by increasing the number of photons traced. For example, see the movie, where a Monte Carlo simulation of a pencil beam incident on a semi-infinite medium models both the initial ballistic photon flow and the later diffuse propagation.
The photoacoustic Doppler effect is a type of Doppler effect that occurs when an intensity modulated light wave induces a photoacoustic wave on moving particles with a specific frequency. The observed frequency shift is a good indicator of the velocity of the illuminated moving particles. A potential biomedical application is measuring blood flow.
Ultrasound-modulated optical tomography (UOT), also known as Acousto-Optic Tomography (AOT), is a hybrid imaging modality that combines light and sound; it is a form of tomography involving ultrasound. It is used in imaging of biological soft tissues and has potential applications for early cancer detection. As a hybrid modality which uses both light and sound, UOT provides some of the best features of both: the use of light provides strong contrast and sensitivity ; these two features are derived from the optical component of UOT. The use of ultrasound allows for high resolution, as well as a high imaging depth. However, the difficulty of tackling the two fundamental problems with UOT have caused UOT to evolve relatively slowly; most work in the field is limited to theoretical simulations or phantom / sample studies.
Robert Alfano is an Italian-American experimental physicist. He is a Distinguished Professor of Science and Engineering at the City College and Graduate School of New York of the City University of New York, where he is also the founding Director of the Institute for Ultrafast Spectroscopy and Lasers (1982). He is a pioneer in the fields of Biomedical Imaging and Spectroscopy, Ultrafast lasers and optics, tunable lasers, semiconductor materials and devices, optical materials, biophysics, nonlinear optics and photonics; he has also worked extensively in nanotechnology and coherent backscattering. His discovery of the white-light supercontinuum laser is at the root of optical coherence tomography, which is breaking barriers in ophthalmology, cardiology, and oral cancer detection among other applications. He initiated the field known now as Optical Biopsy
Diffuse optical imaging (DOI) is a method of imaging using near-infrared spectroscopy (NIRS) or fluorescence-based methods. When used to create 3D volumetric models of the imaged material DOI is referred to as diffuse optical tomography, whereas 2D imaging methods are classified as diffuse optical imaging.
The Beckman Laser Institute is an interdisciplinary research center for the development of optical technologies and their use in biology and medicine. Located on the campus of the University of California, Irvine in Irvine, California, an independent nonprofit corporation was created in 1982, under the leadership of Michael W. Berns, and the actual facility opened on June 4, 1986. It is one of a number of institutions focused on translational research, connecting research and medical applications. Researchers at the institute have developed laser techniques for the manipulation of structures within a living cell, and applied them medically in treatment of skin conditions, stroke, and cancer, among others.
Photoacoustic microscopy is an imaging method based on the photoacoustic effect and is a subset of photoacoustic tomography. Photoacoustic microscopy takes advantage of the local temperature rise that occurs as a result of light absorption in tissue. Using a nanosecond pulsed laser beam, tissues undergo thermoelastic expansion, resulting in the release of a wide-band acoustic wave that can be detected using a high-frequency ultrasound transducer. Since ultrasonic scattering in tissue is weaker than optical scattering, photoacoustic microscopy is capable of achieving high-resolution images at greater depths than conventional microscopy methods. Furthermore, photoacoustic microscopy is especially useful in the field of biomedical imaging due to its scalability. By adjusting the optical and acoustic foci, lateral resolution may be optimized for the desired imaging depth.
The collimated transmission method is a direct way of measuring the optical properties of materials. It is especially useful for sensing the optical properties of tissues to guide developments of both diagnostic and therapeutic techniques. These optical properties are described by the absorption coefficient μa, scattering coefficient μs, and anisotropy factor g.
Multiple scattering low coherence interferometry(ms/LCI) is an imaging technique that relies on analyzing multiply scattered light in order to capture depth-resolved images from optical scattering media. With current applications primarily in medical imaging, has the advantage of a higher range since forward scattered light attenuates less with depth when compared to the specularly reflected light that is assessed in more conventional imaging methods such as optical coherence tomography. This allows ms/LCI to image through up to 90 mean free scattering paths, compared to roughly 27 scattering MFPs in OCT and 1-2 scattering MFPs in confocal microscopy.
Time-domain diffuse optics or time-resolved functional near-infrared spectroscopy is a branch of functional near-Infrared spectroscopy which deals with light propagation in diffusive media. There are three main approaches to diffuse optics namely continuous wave (CW), frequency domain (FD) and time-domain (TD). Biological tissue in the range of red to near-infrared wavelengths are transparent to light and can be used to probe deep layers of the tissue thus enabling various in vivo applications and clinical trials.
Diffuse optical mammography, or simply optical mammography, is an emerging imaging technique that enables the investigation of the breast composition through spectral analysis. It combines in a single non-invasive tool the capability to implement breast cancer risk assessment, lesion characterization, therapy monitoring and prediction of therapy outcome. It is an application of diffuse optics, which studies light propagation in strongly diffusive media, such as biological tissues, working in the red and near-infrared spectral range, between 600 and 1100 nm.
Igor Meglinski is a British, Finnish, New Zealand physicist, scientist, and biomedical engineer best known for his development of fundamental studies and translation research dedicated to imaging of cells and biological tissues utilising polarised light, dynamic light scattering and computational imitation of light propagation within complex tissue-like scattering medium.
References
- ↑ Durduran T; et al. (2010). "Diffuse optics for tissue monitoring and tomography". Rep. Prog. Phys. 73 (7): 076701. Bibcode:2010RPPh...73g6701D. doi:10.1088/0034-4885/73/7/076701. PMC 4482362 . PMID 26120204.
- 1 2 A. Gibson; J. Hebden; S. Arridge (2005). "Recent advances in diffuse optical imaging" (PDF). Phys. Med. Biol. 50 (4): R1–R43. doi:10.1088/0031-9155/50/4/r01. PMID 15773619. S2CID 23029891.[ permanent dead link ]
- ↑ S. Farsiu; J. Christofferson; B. Eriksson; P. Milanfar; B. Friedlander; A. Shakouri; R. Nowak (2007). "Statistical Detection and Imaging of Objects Hidden in Turbid Media Using Ballistic Photons" (PDF). Applied Optics. 46 (23): 5805–5822. Bibcode:2007ApOpt..46.5805F. doi:10.1364/ao.46.005805. PMID 17694130.
- ↑ Durduran, T; et al. (2010). "Diffuse optics for tissue monitoring and tomography". Rep. Prog. Phys. 73 (7): 076701. Bibcode:2010RPPh...73g6701D. doi:10.1088/0034-4885/73/7/076701. PMC 4482362 . PMID 26120204.
- ↑ "Harvard.edu Diffuse Optical Imaging". Archived from the original on June 16, 2012. Retrieved August 20, 2012.
- ↑ Lihong V. Wang; Hsin-i Wu (26 September 2012). Biomedical Optics: Principles and Imaging. John Wiley & Sons. pp. 3–. ISBN 978-0-470-17700-6.
