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Molecular Imaging glossary & taxonomy
Evolving terminology for emerging technologies. & taxonomy
Comments? Questions? Revisions?  Mary Chitty MSLS mchitty@healthtech.com
 Last revised July 09, 2019 

Technologies term index   Related glossaries include Biomarkers    Labels, Signaling & Detection,  Mass Spectrometry,  Microarrays Microscopy   NMR & X-ray crystallography   Molecular Diagnostics  Biology: Cells & Cell biology  

2-photon: See two photon excitation. 
3-photon: See three photon excitation
anisotrophy: See under Near-field Scanning Optical Microscopy NSOM Microscopy

biophotonic imaging: A novel approach to functional genomics, target validation, and drug screening and preclinical testing. Uses a bioluminescent reporter gene to tag a target of interest - which can be a gene, a cell, or a microorganism - in a whole mouse. Because light passes through tissue, the labeled mouse can be anesthetized and photographed with a camera capable of detecting the bioluminescence. This method can be used to label bacteria, infect an organism, and study the effect of antibiotics on the infection, or the effects of various physiological conditions or drugs that can modify response to infection. In oncology, this approach can be used to label tumor cells and follow the effects of chemotherapeutic treatments on the cancer. One can do assays both in cell culture and in whole animals with a gene tagged with the same reporter, and one can follow changes in gene expression in real time both in cell culture and in whole animals.

biphotonic excitation: Also called two-photon excitation. The simultaneous (coherent) absorption of two photons (either same or different wavelength) the energy of excitation being the sum of the energies of the two photons. IUPAC Photochemistry

brain mapping: a set of neuroscience techniques predicated on the mapping of (biological) quantities or properties onto spatial representations of the (human or non-human) brain resulting in maps. According to the definition established in 2013 by Society for Brain Mapping and Therapeutics (SBMT), brain mapping is specifically defined, in summary, as the study of the anatomy and function of the brain and spinal cord  through the use of imaging, immunohistochemistry, molecular & optogenetics, stem cell and cellular biology, engineering, neurophysiology and nanotechnology. Wikipedia accessed 2018 August 24 https://en.wikipedia.org/wiki/Brain_mapping

Cancer imaging Program, NCI  The NCI Cancer Imaging Program fosters advances in in vivo medical imaging sciences through support of basic and applied research in cancer imaging as well as promotion of imaging in clinical trials in order to gain greater understanding of the pathways of cancer biology for the benefit of cancer patients and people at cancer risk. https://imaging.cancer.gov/

CAT scan: See computed tomography

CCD Charged Coupled Device: a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time. CCDs move charge between capacitive bins in the device, with the shift allowing for the transfer of charge between bins. In recent years CCD has become a major technology for digital imaging. In a CCD image sensor, pixels are represented by p-doped metal-oxide-semiconductors (MOS) capacitors. These capacitors are biased above the threshold for inversion when image acquisition begins, allowing the conversion of incoming photons into electron charges at the semiconductor-oxide interface; the CCD is then used to read out these charges. Although CCDs are not the only technology to allow for light detection, CCD image sensors are widely used in professional, medical, and scientific applications where high-quality image data are required. In applications with less exacting quality demands, such as consumer and professional digital cameras, active pixel sensors, also known as complementary metal-oxide-semiconductors (CMOS) are generally used; the large quality advantage CCDs enjoyed early on has narrowed over time. Wikipedia accessed 2018 Aug 24 https://en.wikipedia.org/wiki/Charge-coupled_device

circular dichroism spectroscopy: Is observed when optically active matter absorbs left and right hand circular polarized light slightly differently. It is measured with a CD spectropolarimeter, which is relatively expensive (~$70k). ...  CD spectra for distinct types of secondary structure present in peptides, proteins and nucleic acids are different. The analysis of CD spectra can therefore yield valuable information about secondary structure of biological macromolecules.  Bernhard Rupp, Circular Dichroism Spectroscopy http://www.ruppweb.org/cd/cdtutorial.htm 

computational nanophotonics:    Broader term: nanophotonics

confocal detection: See under Drug discovery & development miniaturization uHTS

detector instrumentation:: Includes CCD cameras, lasers. See Labels, signaling & detection glossary for detection technologies.

dichroism: In optics, a dichroic material is either one which causes visible light to be split up into distinct beams of different wavelengths (colours) (not to be confused with dispersion), or one in which light rays having different polarizations are absorbed by different amounts.[1] The original meaning of dichroic, from the Greek dikhroos, two-coloured, refers to any optical device which can split a beam of light into two beams with differing wavelengths. Such devices include mirrors and filters, usually treated with optical coatings, which are designed to reflect light over a certain range of wavelengths, and transmit light which is outside that range. An example is the dichroic prism, used in some camcorders, which uses several coatings to split light into red, green and blue components for recording on separate CCD arrays, however it is now more common to have a Bayer filter to filter individual pixels on a single CCD array. This kind of dichroic device does not usually depend on the polarization of the light. The term dichromatic is also used in this sense. The second meaning of dichroic refers to the property of a material in which light in different polarization states traveling through it experiences a different absorption coefficient; this is also known as diattenuation. When the polarization states in question are right and left-handed circular polarization, it is then known as circular dichroism. Since the left- and right-handed circular polarizations represent two spin angular momentum (SAM) states, in this case for a photon, this dichroism can also be thought of as Spin Angular Momentum Dichroism.  Wikipedia accessed 2018 Nov 8 https://en.wikipedia.org/wiki/Dichroism

diffusion tensor imaging: Determination of axonal pathways provides an invaluable means to study the connectivity of the human brain and its functional network. Diffusion tensor imaging (DTI) is unique in its ability to capture the restricted diffusion of water molecules which can be used to infer the directionality of tissue components. In this paper, we introduce a white matter tractography method based on anisotropic wavefront propagation in diffusion tensor images. A front propagates in the white matter with a speed profile governed by the isocontour of the diffusion tensor ellipsoid. By using the ellipsoid, we avoid possible misclassification of the principal eigenvector in oblate regions. Jackowski M, Kao CY, Qiu M, Constable RT, Staib LH. White matter tractography by anisotropic wavefront evolution and diffusion tensor imaging Med Image Anal 9(5): 427- 440, Oct 2005  Broader term: MRI Magnetic Resonance Imaging 

Diffusion-weighted magnetic resonance imaging (DWI or DW-MRI): the use of specific MRI sequences as well as software that generates images from the resulting data, that uses the diffusion of water molecules to generate contrast in MR images.[1][2][3] It allows the mapping of the diffusion process of molecules, mainly water, in biological tissues, in vivo and non-invasively. Molecular diffusion in tissues is not free, but reflects interactions with many obstacles, such as macromolecules, fibers, and membranes. Water molecule diffusion patterns can therefore reveal microscopic details about tissue architecture, either normal or in a diseased state. A special kind of DWI, diffusion tensor imaging (DTI), has been used extensively to map white matter tractography in the brain. Wikipedia accessed 2018 Nov 8 https://en.wikipedia.org/wiki/Diffusion_MRI

Einstein: One mole of photons. Although widely used, it is not an IUPAC sanctioned unit. It is sometimes defined as the energy of one mole of photons. This use is discouraged. IUPAC Photochemistry

excitation: Narrower terms: biphotonic excitation, three photon, two photon

fiber optics, optical fibre: <communications> (fibre optics, FO, US "fiber", light pipe) A plastic or glass (silicon dioxide) fibre no thicker than a   human hair used to transmit information using infra- red or even visible light as the carrier (usually a laser). The light beam is an electromagnetic signal with a frequency in the range of 10^14 to 10^15 Hertz. Optical fibre is less susceptible to external noise than other transmission media, and is cheaper to make than copper wire, but it is much more difficult to connect. Optical fibres are difficult to tamper with (to monitor or inject data in the middle of a connection), making them appropriate for secure communications. The light beams do not escape from the medium because the material used provides total internal reflection. FOLDOC

Fluorescence Correlation Spectroscopy: is a correlation analysis of fluctuation of the fluorescence intensity. The analysis provides parameters of the physics under the fluctuations. One of the interesting applications of this is an analysis of the concentration fluctuations of fluorescent particles (molecules) in solution. In this application, the fluorescence emitted from a very tiny space in solution containing a small number of fluorescent particles (molecules) is observed. Wikipedia accessed 2018 Sept 2 https://en.wikipedia.org/wiki/Fluorescence_correlation_spectroscopy   Related terms: Photon Correlation Spectroscopy; Ultrasensitivity glossary single molecule...

fluorescence spectrometry: Measurement of the intensity and quality of fluorescence. MeSH, 1974

Fourier Transform Infrared Spectroscopy: A spectroscopic technique in which a range of wavelengths is presented simultaneously with an interferometer and the spectrum is mathematically derived from the pattern thus obtained. MeSH, 1994

Functional Magnetic Resonance Imaging fMRI: a technique for measuring brain activity. It works by detecting the changes in blood oxygenation and flow that occur in response to neural activity – when a brain area is more active it consumes more oxygen and to meet this increased demand blood flow increases to the active area.  http://psychcentral.com/lib/what-is-functional-magnetic-resonance-imaging-fmri

measures brain activity by detecting changes associated with blood flow.[1][2] This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.[3]  Wikipedia accessed 2018 Oct 18 http://en.wikipedia.org/wiki/Functional_magnetic_resonance_imaging

imaging contrast agents: contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging.[1]Contrast agents absorb or alter external electromagnetism or ultrasound, which is different from radiopharmaceuticals, which emit radiation themselves. In x-rays, contrast agents enhance the radiodensity in a target tissue or structure. In MRI's, contrast agents shorten (or in some instances increase) the relaxation times of nuclei within body tissues in order to alter the contrast in the image. Contrast agents are commonly used to improve the visibility of blood vessels and the gastrointestinal tract. Several types of contrast agent are in use in medical imaging and they can roughly be classified based on the imaging modalities where they are used. Most common contrast agents work based on X-ray attenuation and magnetic resonance signal enhancement. Wikipedia accessed 2018 Dec 2 https://en.wikipedia.org/wiki/Contrast_agent

imaging (photoimaging): The use of a photosensitive system for the capture, recording, and retrieval of information associated with an object using electromagnetic energy. IUPAC Photochemistry
Narrower terms: biophotonic imaging, functional imaging, imaging - data mining, imaging contrast agents, imaging outcomes measurement, in vivo imaging, Magnetic Resonance Imaging MRI, quantitating imaging data, receptor imaging, spectral imaging; Related terms: image analysis - microarrays, image cytometry

in vivo imaging: The dynamic real-time localization and translocation of molecules in living cells is an integral aspect of cellular function. Scientists are pioneering new applications for in vivo cellular and molecular imaging. These applications are based on genetic engineering advances and improved imaging technologies. In vivo imaging has become quantifiable, highly sensitive and amenable to high-throughput study design. The high sensitivity and utility of in vivo imaging, is exemplified by use of the Fluorescence Resonance Energy Transfer (FRET) method, which quantitates enzyme activity, protein-protein interactions and second messenger dynamics. Optical in vivo imaging methods are being applied in pre-clinical research studies. Real time in vivo imaging studies in whole animals have been used to track cell-based therapies, and monitor response to chemotherapies (1).  New England BioLabs, In Vivo Imaging https://www.neb.com/applications/cellular-analysis/in-vivo-imaging

Infrared spectroscopy: (IR spectroscopy or vibrational spectroscopy) involves the interaction of infraredradiation with matter. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic techniques, it can be used to identify and study chemicals. Wikipedia accessed 2018 Sept 2 https://en.wikipedia.org/wiki/Infrared_spectroscopy

laser: Light Amplification by Stimulated Emission of Radiation. This phenomenon is brought about using devices that transform light of varying frequencies into a single intense, nearly nondivergent beam of monochromatic radiation in the visible region. Lasers operate in the visible, infrared, or ultraviolet regions of the spectrum. They are capable of producing immense heat and power when focused at close range and are used in surgical procedures, in diagnosis, and in physiologic studies. MeSH, 1965  Related terms: CCD, image analysis, scanning technology Narrower terms: Microscopy glossary Laser Fluorescence Microscopy, laser scanning, laser scanning microscopy 

Light-sheet fluorescence microscopy: enables relatively gentle imaging of biological samples with high resolution in three dimensions (3D) and over long periods of time. Especially when combined with high-speed cameras, it is fast enough to capture cellular or subcellular dynamics. For its potential for fast, relatively gentle, volumetric imaging of biological samples, we have chosen light-sheet fluorescence microscopy as Method of the Year 2014. Nature Methods Jan 2015 doi:10.1038/nmeth.3251 Published online 30 December 2014  http://www.nature.com/nmeth/journal/v12/n1/full/nmeth.3251.html  

Live-Cell Imaging  See high content

Magnetic Resonance Imaging MRI: Non- invasive method of demonstrating internal anatomy based on the principle that hydrogen nuclei in a strong magnetic field absorb pulses of  radiofrequency energy and emit them as radiowaves which can  be reconstructed into computerized images. The concept includes proton spin tomographic techniques. MeSH, 1988

Magnetic Resonance Spectroscopy MRS: Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING). MeSH, 1966  Narrower terms:  functional MRI, structural MRI  Related term: diffusion tensor imaging

microimaging: Cell technologies

micro-PET: Positron emission tomography (PET) is a nuclear imaging tool for molecular and functional imaging of biological processes. While functional imaging is used to monitor parameters such as perfusion and metabolic rate, molecular imaging is done to study and measure cellular events like gene expression and receptor binding. The miniaturized version of PET called the micro-PET is used in small animal imaging. The development of micro-PET imaging has opened up new possibilities for non-invasive and repetitive imaging of small animals in preclinical studies. With the development of new probes and reporter genes, the applications of micro-PET in research studies focusing on enzyme activity, protein-protein interactions, metabolism, and gene expression has been enhanced. Also, the results of small animal PET imaging is extrapolatable and can be easily translated to the clinic. Micro-PET can reduce the number of animals needed for experiments by allowing non-invasive and serial studies. MicroPET principles strengths & weaknesses 2018  https://www.news-medical.net/life-sciences/Micro-PET-Principles-Strengths-and-Weaknesses.aspx    Broader term: Positron Emission Tomography PET.  See also under nanomanufacturing Miniaturization & Nanoscience  glossary

microscopy: Microscopy glossary Narrower terms: include atomic force microscopy AFM, Confocal Scanning Laser Scanning Microscopy CLSM, confocal microscopy, electron microscopy, fluorescence microscopy, ion microscopy, Laser Fluorescence Microscopy LFM, laser scanning microscopy, Multiphoton Laser Scanning Microscopy MLSM, Magnetic Resonance Force Microscopy MRFM, multiple- photon excitation fluorescence microscopy, Near- field Scanning Optical Microscopy NSOM, Scanning Electron Microscopy SEM, Scanning Transmission Electron Microscopy STEM, Scanning Tunneling Microscopy STM, scanning probe microscopy, Surface Plasmon Resonance microscopy, Total Internal Reflectance Fluorescence Microscopy TIR-FM, Transmission Electron Microscopy TEM, two- photon Laser Fluorescence Microscopy

molecular imaging: can be broadly defined as the in vivo characterization and measurement of biologic processes at the cellular and molecular levels. In contradistinction to “conventional” diagnostic imaging, it sets forth to probe the specific molecular abnormalities that are the basis of disease. Glossary of Molecular Imaging Terminology,  Douglas J Wagenaar, Ralph Weissleder, Arne Hengerer, Academic Radiology May 2001  http://www.academicradiology.org/article/S1076-6332(03)80549-4/fulltext  DOI: https://doi.org/10.1016/S1076-6332(03)8054 

Molecular imaging originated from the field of radiopharmacology due to the need to better understand fundamental molecular pathways inside organisms in a noninvasive manner. ..Molecular Imaging emerged in the mid twentieth century as a discipline at the intersection of molecular biology and in vivo imaging. It enables the visualisation of the cellular function and the follow-up of the molecular process in living organisms without perturbing them. The multiple and numerous potentialities of this field are applicable to the diagnosis of diseases such as cancer, and neurological and cardiovascular diseases. This technique also contributes to improving the treatment of these disorders by optimizing the pre-clinical and clinical tests of new medication. They are also expected to have a major economic impact due to earlier and more precise diagnosis. Wikipedia accessed 2018 Oct 18  http://en.wikipedia.org/wiki/Molecular_imaging 

Multi-isotope Imaging Mass Spectrometry MIMS: Mass spectrometry glossary

NAMIC National Alliance for Medical Image Computing: A multi- institutional, interdisciplinary team of computer scientists, software engineers, and medical investigators who develop computational tools for the analysis and visualization of medical image data. The purpose of the center is to provide the infrastructure and environment for the development of computational algorithms and open source technologies, and then oversee the training and dissemination of these tools to the medical research community. 2004  http://www.na-mic.org/   

nanophotonics or nano-optics is the study of the behavior of light on the nanometer scale, and of the interaction of nanometer-scale objects with light. It is a branch of optics, optical engineering, electrical engineering, and nanotechnology. It often (but not exclusively) involves metallic components, which can transport and focus light via surface plasmon polaritons. The term "nano-optics", just like the term "optics", usually refers to situations involving ultraviolet, visible, and near-infrared light (free-space wavelengths from 300 to 1200 nanometers). Wikipedia accessed 2018 Aug 24 https://en.wikipedia.org/wiki/Nanophotonics  Narrower term: computational nanophotonics

National Institute of Biomedical Imaging and Bioengineering: The mission of the National Institute of Biomedical Imaging and Bioengineering (NIBIB) is to improve health by leading the development and accelerating the application of biomedical technologies. The Institute is committed to integrating the physical and engineering sciences with the life sciences to advance basic research and medical care. This is achieved through: research and development of new biomedical imaging and bioengineering techniques and devices to fundamentally improve the detection, treatment, and prevention of disease; enhancing existing imaging and bioengineering modalities; supporting related research in the physical and mathematical sciences; encouraging research and development in multidisciplinary areas; supporting studies to assess the effectiveness and outcomes of new biologics, materials, processes, devices, and procedures; developing technologies for early disease detection and assessment of health status; and developing advanced imaging and engineering techniques for conducting biomedical research at multiple scales. NIBIB Mission and History  https://www.nibib.nih.gov/about-nibib/mission

Near InfraRed spectroscopy NIR: Cell technologies

nuclear medicine: The medical specialty that involves the use of radioactive isotopes in the diagnosis and treatment of disease. Radiochemistry Society  http://www.radiochemistry.org/nuclearmedicine/definition.htm .

A specialty field of radiology concerned with diagnostic, therapeutic, and investigative use of radioactive compounds. MeSH 1967

a medical specialty that uses radioactive tracers (radiopharmaceuticals) to assess bodily functions and to diagnose and treat disease. Specially designed cameras allow doctors to track the path of these radioactive tracers. Single Photon Emission Computed Tomography or SPECT and Positron Emission Tomography or PET scans are the two most common imaging modalities in nuclear medicine.  Nuclear Medicine, NIH National Institute of Biomedical Imaging and Bioengineering https://www.nibib.nih.gov/science-education/science-topics/nuclear-medicine

optical biosensors: Include evanescent waves, fiber optical chemical sensors; Related terms: Labels, signaling & detection glossary

optical laser spectroscopy: See fluorescence, Raman

optoelectronics: The terms Electro-optics, Optoelectronics and Photonics are used to describe these subjects with no clear and universally accepted differentiation between the terms. Although Photonics could be restricted to the manipulation of Photons and Optoelectronics the combining of Photons and electrons with Electro-optics is a special case of Optoelectronics. The most probable introduction of the terms is time dependent, Electro-optic was used in the 1960s especially by the military and indeed defence related industry still uses the term. Optoelectronics appeared in the 1980s evidenced by its use by the Optoelectronics Industry and Technology Development Association (OITDA) of Japan founded in 1980, Photonics gaining common usage in the late 1990s. Scottish Optoelectrnics Association What is optoelectronics? http://optoelectronics.org.uk/what-is-optoelectronics/

phosphorimagers: Microarrays glossary

Photo Multiplier Tube PMT: A vacuum phototube with additional amplification by electron multiplication . It consists of a photocathode, a series of dynodes, called a dynode chain on which a secondary- electron multiplication process occurs, and an anode. According to the desired response time, transit time, time spread , gain, or low dark current, different types of dynode structures have been developed, e.g. circular cage structure, linear focused structure, venetian blind structure, box and grid structure . Some special dynode structures permit combination with additional electric or magnetic fields The term vacuum photodiode is not recommended. PART XI: Detection of Radiation IUPAC Recommendations 1995 Originally authored by K. Laqua, B. Schrader, D. S. Moore, and T. Vo-Dinh http://old.iupac.org/reports/V/spectro/partXI.pdf

photochemistry: Branch of chemistry concerned with the chemical effects of ultraviolet, visible, or infrared radiation. See also photochemical reaction. IUPAC Photochemistry

photon: The quantum of electromagnetic energy at a given frequency. This energy, E=hv, is the product of the Planck constant (h) and the frequency of the radiation (v). IUPAC Photochemistry

Photon-Correlation Spectroscopy: Involves the measurement of the dynamic fluctuations of the intensity of fluorescent or scattered light in a very small volume. Brownian motion causes the fluctuations in local concentrations of molecules- resulting in local inhomogeneities of fluorescence or refractive index from which details of molecular interactions and diffusive behavior can be extracted. Potentially important applications include determination of macromolecule interactions (forward and reverse rates for complex formation) and translational mobility in the cytoplasm of living cells. This method is also applicable to the study of aggregating systems. The extension of fluorescence correlation spectroscopy to multi- photon excitation regimes is logical, since smaller, better- defined excitation volumes can be optically interrogated. A limitation, and advantage, of fluorescence correlation spectroscopy methods is a requirement for low probe concentrations.  National Center for Research Resources "Integrated Genomics Technologies Workshop Report" Jan 1999

photonics: the physical science of light (photon) generation, detection, and manipulation through emission, transmission, modulation, signal processing, switching, amplification, and sensing.[1][2] Though covering all light's technical applications over the whole spectrum, most photonic applications are in the range of visible and near-infrared light. The term photonics developed as an outgrowth of the first practical semiconductor light emitters invented in the early 1960s and optical fibers developed in the 1970s. ..Photonics as a field began with the invention of the laser in 1960. Other developments followed: the laser diode in the 1970s, optical fibers for transmitting information, and the erbium-doped fiber amplifier. These inventions formed the basis for the telecommunications revolution of the late 20th century and provided the infrastructure for the Internet. Though coined earlier, the term photonics came into common use in the 1980s as fiber-optic data transmission was adopted by telecommunications network operators ...photonics covers a huge range of science and technology applications, including laser manufacturing, biological and chemical sensing, medical diagnostics and therapy, display technology, and optical computing. Wikipedia accessed 2018 Oct 18 https://en.wikipedia.org/wiki/Photonics
RP Photonics Glossary https://www.rp-photonics.com/glossary.html

Positron Emission Tomography PET:  a nuclear medicine functional imaging technique that is used to observe metabolic processes in the body as an aid to the diagnosis of disease. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide, most commonly fluorine-18. which is introduced into the body on a biologically active molecule called a radioactive tracer. Three-dimensional images of tracer concentration within the body are then constructed by computer analysis. In modern PET-CT scanners, three-dimensional imaging is often accomplished with the aid of a CT X-ray scan performed on the patient during the same session, in the same machine.  Wikipedia accessed 2018 Oct 18 https://en.wikipedia.org/wiki/Positron_emission_tomography

Complementary to the anatomic imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI). Related terms: molecular imaging, SPECT.  Narrower terms:  micro-PET, nano-PET
History of Positron Imaging, A HISTORY OF POSITRON IMAGING

probe: Probes used in atomic force and scanning probe microscopy.  How do these relate to the probes defined in Gene amplification & PCR and Microarrays.

quantum (of radiation): An elementary particle of electromagnetic energy in the sense of wave- particle duality. See also photon.  IUPAC Photochemistry  

Raman scattering: See under Raman spectroscopy

Raman spectroscopy: Involves the coupling of incident light with the internal vibrational states of molecules. Raman active transitions are about 12 orders of magnitude lower in intensity than fluorescence transitions. However, at resonance, i.e.., when the exciting light is tuned to an electronic absorption band of the molecule, the intensity of Raman scattering increases by as much as 6 orders of magnitude. When molecules are adsorbed onto appropriate metal surfaces, such as roughened silver, another 6 or more orders of magnitude increase in sensitivity is gained. Adsorption of molecules onto colloidal metal particles has yielded enhancement factors of as much as 15 orders of magnitude, permitting in advantageous cases single- molecule resonance (and non- resonance) Raman spectrum detection. SERS Surface- enhanced Raman Scattering  is thus viewed as a method with great potential for ultra- high resolution analysis of biological systems. National Center for Research Resources "Integrated Genomics Technologies Workshop Report" Jan 1999     Narrower term: SERS Surface- enhanced Raman Scattering

Raman spectrum analysis: Analysis of the intensity of Raman scattering of monochromatic light as a function of frequency of the scattered light. MeSH, 1977

Self- Amplified Spontaneous Emission SASE: See under tunable lasers

Single-Photon Emission-Computed Tomography SPECT: A method of computed tomography that uses radionuclides which emit a single photon of a given energy. The camera is rotated 180 or 360 degrees around the patient to capture images at multiple positions along the arc. The computer is then used to reconstruct the transaxial, sagittal, and coronal images from the 3-dimensional distribution of radionuclides in the organ. The advantages of SPECT are that it can be used to observe biochemical and physiological processes as well as size and volume of the organ. The disadvantage is that, unlike positron- emission tomography where the positron- electron annihilation results in the emission of 2 photons at 180 degrees from each other, SPECT requires physical collimation to line up the photons, which results in the loss of many available photons and hence degrades the image. MeSH, 1990

spectral imaging: Wikipedia http://en.wikipedia.org/wiki/Spectral_imaging  Sometimes referred to as hyperspectral imaging http://en.wikipedia.org/wiki/Hyperspectral_imaging Accessed June 29, 2007

spectrophotometry:  The art or process of comparing photometrically the relative intensities of the light in different parts of  the spectrum. MeSH

spectrometry: Wikipedia disambiguation https://en.wikipedia.org/wiki/Spectrometry Narrower terms: Multi- isotopic Imaging Mass Spectrometry MIMS, mass spectrometry

spectroscopy: the study of the interaction between matter and electromagnetic radiation.[1][2] Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, by a prism. Later the concept was expanded greatly to include any interaction with radiative energy as a function of its wavelength or frequency. Spectroscopic data are often represented by an emission spectrum, a plot of the response of interest as a function of wavelength or frequency.   Wikipedia accessed 2018 Oct 18  https://en.wikipedia.org/wiki/Spectroscopy  Narrower terms: circular dichroism spectroscopy, Fluorescence Correlation Spectroscopy, Fourier Transform InfraRed Spectroscopy, Magnetic Resonance Spectroscopy, Near InfraRed Spectroscopy NIR, Photon Correlation Spectroscopy, Raman spectroscopy, Surface Enhanced Raman Spectroscopy SERS, X-ray Photoelectron Spectroscopy XPS

spiral computed tomography: Computed tomography where there is continuous X-ray exposure to the patient while being transported through a rotating fan beam. This provides improved three- dimensional contrast and spatial resolution compared to conventional computed tomography, where data is obtained and computed from individual sequential exposures. MeSH 2003

structural MRI: Magnetic resonance imaging (MRI) is often divided into structural MRI and functional MRI (fMRI). The former is a widely used imaging technique in research as well as in clinical practice. This review describes the more important developments in structural MRI in recent years, including high resolution imaging, T2 relaxation measurement, T2*-weighted imaging, T1 relaxation measurement, magnetisation transfer imaging, and diffusion imaging. M Symms1, H R Jäger2, K Schmierer3 and T A Yousry2 A review of structural magnetic resonance neuroimaging. Journal of Neurology Neurosurgery and Psychiatry 2004; 75:1235- 1244    Broader term: MRI

Synchrotron Radiation Circular Dichroism (SRCD) spectroscopy:  There is growing interest in using SRCD in structural biology because the high intensity of the SR light source ensures enhanced measurements compared with those from conventional lab- based instruments. As a result, measurements can be made to include lower wavelengths (and thus contain more information on protein secondary structures), have a higher signal- to- noise (and thus smaller amounts of material can be used), be done in a speedier manner (due to the requirement for less signal averaging due to the stronger signal), and be done in the presence of buffers and absorbing components (which better mimic "physiological" conditions). SRCD has many potential uses in the pharmaceutical industry. http://people.cryst.bbk.ac.uk/~ubcg25a/bbsrc_business.html  Narrower term: circular dichroism spectroscopy

three- photon excitation: Can also be used in certain circumstances. In this case three photons are absorbed simultaneously, effectively tripling the excitation energy. Using this technique, UV [ultraviolet] excited fluorophores may be imaged with IR [InfraRed] excitation. Because excitation levels are dependent on the cube of the excitation power, resolution is improved (for the same excitation wavelength) compared to two photon excitation where there is a quadratic power dependence. It is possible to select fluorophores such that multiple labeled samples by can be imaged by combination of 2- and 3 photon excitation, using a single IR excitation source. Laboratory for Optical and Computational Instrumentation, Univ. of Wisconsin Madison, 1999  Related terms:  two photon, multi- photon http://www.loci.wisc.edu/multiphoton/mp.html

tomography: Imaging methods that result in sharp images of objects located on a chosen plane and blurred images located above or below the plane. MeSH  Narrower terms: Positron Emission Tomography PET, Single Photon Emission Computed Tomography SPECT, spiral computed tomography

tractography: In neuroscience, tractography is a 3D modeling technique used to visually represent nerve tracts using data collected by diffusion MRI.[1] It uses special techniques of magnetic resonance imaging (MRI) and computer-based diffusion tensor imaging. The results are presented in two- and three-dimensional images called tractograms. Wikipedia http://en.wikipedia.org/wiki/Tractography  Related term: diffusion MRI

tunable lasers: a laser whose wavelength of operation can be altered in a controlled manner. While all laser gain media allow small shifts in output wavelength, only a few types of lasers allow continuous tuning over a significant wavelength range.  Wikipedia accessed 2018 Oct 18 https://en.wikipedia.org/wiki/Tunable_laser

Optical Devices Tunable Lasers Glossary, EE Times, 2002, 18 terms http://www.eetimes.com/document.asp?doc_id=1145121
Tunable lasers, Light Reading, Aug, 18, 2001 http://www.lightreading.com/document.asp?site=lightreading&doc_id=3308

two- photon excitation: Excitation resulting from successive or simultaneous absorption of two photons by an atom or molecular entity. This term is used for successive absorption only if some of the excitation energy of the first photon remains in the atom or molecular entity before absorption of  the second photon. The simultaneous two- photon absorption can also be called biphotonic excitation.  IUPAC Photo

Two-photon excitation results from high laser fluxes leading to simultaneous absorption of two photons whose energies sum, permitting excitation of chromophores at /2. Thus, two- photon excitation using 900 nm light will excite a chromophore absorbing at 450 nm. Two- photon excited fluorescence intensity is proportional to the square of the exciting laser intensity. The confined two- photon excitation volume greatly reduces out of focus excitation. The capability of using near- IR excitation wavelengths provides two- photon excitation scanning microscopy the advantage of much- reduced cell damage compared to single- photon confocal microscopy, since there are few intrinsic near- IR absorbing chromophores. Two- photon illumination has been used to release caged compounds in femtoliter volumes. National Center for Research Resources "Integrated Genomics Technologies Workshop Report" Jan 1999  
Related term: biphotonic excitation.  

wavelet: <mathematics> A waveform that is bounded in both frequency and duration. Wavelet transforms provide an alternative to more traditional Fourier transforms used for analysing waveforms, e.g. sound. The Fourier transform converts a signal into a continuous series of sine waves, each of which is of constant frequency and amplitude and of infinite duration. In contrast, most real-world signals (such as music or images) have a finite duration and abrupt changes in frequency. Wavelet transforms convert a signal into a series of wavelets. In theory, signals processed by the wavelet transform can be stored more efficiently than ones processed by Fourier transform. Wavelets can also be constructed with rough edges, to better approximate real- world signals. For example, the United States Federal Bureau of Investigation found that Fourier transforms proved inefficient for approximating the whorls of fingerprints but a wavelet transform resulted in crisper reconstructed images. FOLDOC

x-ray crystallography: See NMR & X-ray Crystallography glossary.  X-ray crystallography is an experimental technique that exploits the fact that X-rays are diffracted by crystals. It is not an imaging technique. Bernhard Rupp, Crystallography 101  http://ruppweb.dyndns.org/Xray/101index.html 

X-ray Photoelectron Spectroscopy XPS: Technique for determining the elemental composition at a solid surface by measuring the energy of electrons emitted in response to X-rays of different frequency. Has been applied to solid- phase combinatorial chemistry by incorporating a tracer atom in the linker. IUPAC Combinatorial

Imaging resources
FOLDOC computing glossary http://foldoc.org/
Fonar, MRI Glossary http://fonar.com/glossary.htm 
IUPAC International Union of Pure and Applied Chemistry, Glossary of Terms used in Photochemistry 3rd ed. 2006  https://www.iupac.org/publications/pac/79/3/0293/
GE Healthcare, Glossary of Low Dose Terms http://www3.gehealthcare.com/en/products/dose_management/glossary  Patient radiation exposure
 Photonics Dictionary, Laurin Publishing Co. Inc., 2013 8K plus terms http://www.photonics.com/edu/Dictionary.aspx
Society of Nuclear Medicine & Molecular Imaging, Glossary of Molecular Imaging terms http://www.snmmi.org/AboutSNMMI/Content.aspx?ItemNumber=5646

Insight Pharma Reports Imaging http://www.insightpharmareports.com/Reports_All_Reports.aspx?t=470359

How to look for other unfamiliar  terms

IUPAC definitions are reprinted with the permission of the International Union of Pure and Applied Chemistry.

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