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Molecular Imaging glossary & taxonomy
Evolving terminology for emerging technologies. & taxonomy

Comments? Questions? Revisions?  Mary Chitty
Last revised January 12, 2015 


Technologies map  Finding guide to terms in these glossaries   Site Map  Related glossaries include Biomarkers    Labels, Signaling & DetectionMass SpectrometryMicroarrays 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.

BIP Biomedical Imaging Program: National Cancer Institute, US program

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 Photo

brain mapping: 

cancer imaging, quantitative: Neoplasms have an intrinsic spatially distributed nature. That is, tumors develop in different sites, metastasize to other sites and are internally heterogeneous. To study tumors one must make spatially distributed  measurements. Imaging is a means of making and displaying spatially coherent measurements and is therefore a key resource for studying the development, growth and therapeutic response of neoplasms. One of the important research directions for imaging research is to provide quantitative information in the setting of cancer diagnosis and therapy. Quantitation of image data for small animals will lead the way to application of quantitative methods in human beings. A major limitation to studying tumors in model systems with current imaging techniques is the limited availability of small animal imaging systems. Most biomedical imaging devices have been optimized for human studies and have suboptimal spatial resolution for small animals and their tumors. However, imaging techniques can be scaled down to yield very high resolution and signal sensitivity for in vivo images of mouse- sized organs. Furthermore, there are some applications of imaging techniques that could provide valuable knowledge from small animal models, but are not feasible for human subjects. [National Cancer Institute, US "Small Animal Imaging Resource Program" RFA July 31, 2000]

CAT scan: See computed tomography

CCD Charged Coupled Device: Captures photos on a grid array that can then be converted to digital images. CCDs can register as little as a single photon event. NCMIR Glossary

CCD camera: A CCD is a charge-coupled device – a silicon chip whose surface is divided into light- sensitive pixels. When a photon (light particle) hits a pixel, it registers a tiny electric charge that can be counted. With large pixel arrays and high sensitivity, CCDs can create high- resolution images under a variety of light conditions. A CCD camera incorporates a CCD to take such pictures. [Xenogen website, Glossary] 

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 

computational nanophotonics: The past years have witnessed dramatic progress and interest in the micro- and nano-fabrication techniques of complex photonic systems. These structures are characterized by controlled feature sizes of the order of the wavelength of light. As a consequence, multiple scattering and near field effects have a profound influence on the propagation of light and light-matter interaction. In turn, this leads to novel regimes for basic research as well as to novel applications in various disciplines. For instance, the modified dispersion relation of Photonic Crystals and Photonic Crystal Fibers lead to novel nonlinear wave propagation effects such as giant soliton shifts and supercontinuum generation with applications in telecommunication, metrology, and medical diagnostics. WE-Heraeus-Seminar Computational Nano-Photonics, Bad Honnef 2007   Broader term: nanophotonics

confocal detection: See under Drug discovery & development miniaturization uHTS

DCIDE Development of Clinical Imaging Drugs and Enhancers: A new program designed to expedite and facilitate both the development of promising imaging enhancers (contrast agents) or molecular probes and their translation from laboratory synthesis to IND application. Under this program, developers of a promising diagnostic agent or probe can apply to the National Cancer Institute (NCI) for assistance. NCI will make its pre- clinical development resources available to competitively- selected developers in order to remove the most common barriers between laboratory discoveries and IND status. The DCIDE program is intended to supply or enable missing steps to those who lack development capacity or resources so that promising discoveries may eventually be translated to the clinical research environment. The DCIDE program will focus on promising diagnostic agents that are not otherwise likely to undergo adequate pre- clinical testing to warrant an IND application. The DCIDE program itself will not provide full- scale clinical development but will facilitate the performance of the pre- clinical studies necessary to bring an imaging agent to IND status. National Cancer Institute, DCIDE, FAQ

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

dichroism: Wikipedia  Accessed Aug 20, 2007 discusses two separate [but related] meanings of dichroism. 

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 Photo]

electronic spectroscopy: Includes "photoelectron, Auger electron, electron energy loss, soft x-ray fluorescence, and soft x-ray absorption) as related to electronic structure and dynamics, as well as to atomic structure and dynamics, and in both gaseous and condensed phases. Topics will also include spectromicroscopy and microspectroscopy with incident photons and electrons, as well as basic and applied surface and interface analysis. 8th International Conference on Electronic Spectroscopy, Lawrence Berkeley Lab, Berkeley CA, Aug. 8- 12, 2000

enhancement agents: See imaging contrast agents.

epifluorescence: An optical set- up for a fluorescence microscope in which the objective lens is used both to focus ultraviolet light on the specimen and collect fluorescent light from the specimen. Epifluorescence is more efficient than transmitted fluorescence, in which a separate lens or condenser is used to focus ultraviolet light on the specimen. Epifluorescence also allows fluorescence microscopy to be combined with another type on the same Fluorescence Microscopy,, 2001 microscope.

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

FISH Fluorescence In Situ Hybridization: Gene Amplification & PCR glossary

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: FCS is a spectroscopic technique for the study of molecular interactions in solution. FCS monitors the random motion of fluorescently labelled molecules inside a defined volume element irradiated by a focused laser beam. These fluctuations provide information on the rate of diffusion or diffusion time of a particle and this, in turn, is directly dependent on the particle's mass. Carl Zeiss Microimaging GmbH, What is FCS?  Related terms: Photon Correlation Spectroscopy; Ultrasensitivity glossary single molecule...

fluorescence scanners: Microarrays glossary

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 imaging:   We are assessing these three techniques as potential functional imaging modalities, which can be hopefully used in humans to provide important physiologic information. FT EPR imaging. With this method, the free radicals are imaged by collecting their responses after pulsed excitation under static gradient magnetic fields ... Continuous wave EPR imaging. Using free radical contrast agents, which participate in redox reactions in tissue, it is possible to perform pharmacokinetic imaging experiments in which the free radical tracer is converted to a nonmagnetic species by intracellular redox processes. ... Overhauser enhanced MRI (OMRI). This is a hybrid technique, which uses the inherent sensitivity of EPR spectroscopy to enhance the intensity of images obtained by conventional MRI.  Our Science – Cherukuri Website,  National Cancer Institute, NIH  Related terms:  Functional genomics  

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.

image informatics: Encompassing far more than computer- based image analysis, image informatics enables image quantification and analysis along with powerful and complete image search technology ... a new area of data management that allows researchers to mine scientific images of all types using advanced image data storage, retrieval, mining and analysis capabilities. Image Informatics: The Key to Using Image Data, Suzanne Z. Mattingly, Proteome Society, 2002

imaging (photoimaging): The use of a photosensitive system for the capture, recording, and retrieval of information associated with an object using electromagnetic energy. IUPAC Photo
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

imaging contrast agents: Developments in image enhancement agents are improving our ability to capture changes in the biochemical makeup of cells and other living structures. Enhancement agents contribute to image formation in three ways. They may localize in certain body organs or structures (anatomic localization); they may attach to specific molecules in the body (receptor localization); or they may become activated by certain biochemical or physical conditions, such as the presence of a specific enzyme or low oxygen concentration in the cell (activatable agents). We anticipate that contrast agents of the future will be able to reveal the functional characteristics of tumors that determine clinical behavior and response to therapy.  [National Cancer Institute, US "Scientific Priorities for Cancer Research: NCI's Extraordinary Opportunities: Cancer Imaging" March 2000]   
Narrower term: smart contrast agents

imaging data mining: Data mining in brain imaging is proving to be an effective methodology for disease prognosis and prevention. This, together with the rapid accumulation of massive heterogeneous data sets, motivates the need for efficient methods that filter, clarify, assess, correlate and cluster brain- related information. Here, we present data mining methods that have been or could be employed in the analysis of brain images. These methods address two types of brain imaging data: structural and functional. We introduce statistical methods that aid the discovery of interesting associations and patterns between brain images and other clinical data. Megalooikonomou V, Ford J, Shen L, Makedon F, Saykin A. "Data mining in brain imaging" Stat Methods Med Res 2000 Aug; 9 (4): 359-94

imaging oncology: Translational Imaging in Cancer Drug Development June 10-11, 2015 • Boston, MA Program | Register | Download Brochure
Translational Imaging in Cancer Drug Development

in vivo
Imaging sciences are at a stage at which in vivo imaging can occur at near micron resolutions with image specificity at the physiological, cellular and molecular level. Although the molecular basis of may diseases are well defined, we do not have a full understanding of the mechanism by which they develop in vivo nor have we fully harnessed the potential for translating advances in molecular science into clinical practice of imaging. Increased understanding of these areas and development of novel techniques is likely to provide new important directions in the earlier detection, molecular characterization and treatment of cancers. NCI, BIP Funded Projects and Resources, Ralph Weissleder, Center for Imaging Research, Mass General Hospital, In Vivo Cellular and Molecular Imaging Centers

infrared: Infrared wavelengths of the electromagnetic spectrum are between the visible and microwave wavelengths of about 10-6 and 10-3 m. For infrared applications that are made through the atmosphere (and most are), it is appropriate to understand that the main method of attenuation of infrared wavelengths is absorption by carbon dioxide gas molecules and water vapor.  Colin Hockings, Infrared Equipment Terminology, American Society for Non-Destructive Testing,  Narrower terms: infrared spectroscopy, Near InfraRed

infrared spectroscopy: Has many applications in the fields of physics, chemistry, engineering, and more recently in the field of pathology. The method allows evaluation of complex heterogeneous mixtures based on the vibrational modes of chemical bonds present in biochemical entities. An important feature of infrared chemical images is that the image contrast is solely dependent on the chemical nature of the sample. This is extremely important for the application of this technique to the biological sciences since no special stains or dyes need to be utilized to visualize the structures of interest within samples. The technique is particularly well-suited as an adjunct tool for histopathological evaluation of neoplasia, since it provides quantitative chemical information while preserving the sample morphology that is critical for traditional histopathological assessment.  [NCI, CGAP IR Spectroscopie Imaging of Prostatic adenocarcinoma]

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 

laser scanning:  Microarrays glossary Related term: scanning technologies.

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  
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

I use a variety of magnetic resonance imaging (MRI) methods to study the brain including structural MRI to look at regional brain volumes, functional MRI to look at regional brain activity, and diffusion tensor MRI to look at the integrity of connections between structures. Hilary Blumberg MD, Dept of Psychiatry,  Yale University Medical School 

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

micro-PET: A dedicated PET scanner designed for high resolution imaging of small laboratory animals. It has been developed and built by a team of researchers at the Crump Institute for Biological Imaging, UCLA. The aim was to build a compact and relatively low cost PET scanner with unprecedented spatial resolution that would be useful to researchers in a wide range of biomedical research applications. MicroPET, Crump Institute for Molecular Imaging, UCLA, US
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

mid- infrared MID: See under infrared 

molecular imaging:
The rapidly emerging field of molecular imaging is poised to open new vistas for basic researchers, scientists working in drug discovery and development, and physicians. Little more than 5 years old, the postgenomic field of molecular imaging is undergoing rapid research and commercial development, driven largely by big pharma’s burgeoning interest in biomarkers as crucial for decision support in preclinical and early clinical development. Insight Pharma Reports, Molecular Imaging in Drug R&D and Medical Practice: Techno9logies, Applications, Markets,  2008

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   

nanophotonics: A better understanding of the fundamental interactions between nanoparticles in organized arrays is of paramount importance for the development of nanoscale photonic devices. This is because these interactions can serve as  communication mechanisms in nanometric regimes far below that of the conventional semiconductor regime in use today. Fundamental mechanisms of communication can involve transfer of energy in the form of photons, charge, or spin. Nanophotonics -- Experimental, Chemistry Div. Argonne National Lab    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 

nuclear medicine: The medical specialty that involves the use of radioactive isotopes in the diagnosis and treatment of disease. Radiochemistry Society .

optical biosensors: Include evanescent waves, fiber optical chemical sensors; Related terms: Labels, signaling & detection glossary
optical laser spectroscopy: See fluorescence, Raman

optoelectronics: The merger of optics and electronics is increasingly present in our everyday lives through familiar technology such as televisions, compact disc players, fibre optic communication systems, barcode scanners in the supermarket and mobile telephones. However this is the tip of the iceberg, as the technology expands in such fields as displays, transportation, medicine, environmental monitoring, computers and construction. Optoelectronics will be the all- pervasive technology that continues the propulsion of progress in the new millennium that has been driven by electronics over the past 35 years. Scottish Optoelectronics Association

phosphorimagers: Microarrays glossary

photochemical reaction: 

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

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 Glossary of 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 technology of transmission, control, and detection of light (photons). This is also known as fiber optics and optoelectronics. Silicon Photonics Glossary, Intel, 2006, 80 + terms

Positron Emission Tomography PET:  Builds images by detecting energy given off by decaying radioactive isotopes. Advanced Biomedical Technology Research, Dept of Energy, US, 2003

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
, Gordon Brownell, Oct. 1999

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

Quantitative Nuclear Grade QNG See under Nuclear Morphometric Descriptors NMD

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

receptor imaging: The human brain is highly complex and for normal function relies on the interaction of over 100 neurotransmitters with 300 receptors. Few techniques are available for investigating the molecular bases of human brain pathophysiology in vivo. A powerful technique is Positron Emission Tomography (PET). When used with appropriate radioligands, PET can reveal the distribution of neuroreceptors in living human brain, and their interactions with neurotransmitters or administered drugs.  [Christer Halldin (Coordinator)  Serotonin 5-HT1A Receptor Imaging in the Human Brain with PET. Coordination of the Standardization and Dissemination of Methodology STUDY, Karolinska Institut 1/11-98 - 31/10-99) Updated 6/ 21/00]

receptor mapping: Maps genomic & genetic

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

smart contrast agents: When smart contrast agents are injected into the body, they are undetectable. However, when they come into contact with tumor- associated enzymes called proteases, the smart agents change shape and become fluorescent. The fluorescent signal can then be detected using sophisticated imaging devices.  This first generation of smart agents are being further refined and developed by ICMIC [In Vivo Cellular and Molecular Imaging Centers] investigators and will have important applications in tumor detection and therapy assessment in the future. Scientific Priorities for Cancer Research: Cancer Imaging, National Cancer Institute, 2003  Broader term: imaging contrast agents 

spectral imaging: Wikipedia  Sometimes referred to as 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: Narrower terms: Multi- isotopic Imaging Mass Spectrometry MIMS, mass spectrometry

spectroscopy: The study of methods of producing and analysing spectra using spectroscopes, spectrometers, spectrographs, and spectrophotometers. The interpretation of the spectra so produced can be used for chemical analysis, examining atomic and molecular energy levels and molecular structures, and for determining the composition and motions of celestial bodies. [ physics]  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 

Surface Enhanced Raman Spectroscopy SERS: Used to investigate the vibrational properties of adsorbed molecules. Metal surfaces have to be of high reflectivity and of a suitable roughness. Increasing sensitivity of detectors these days means that Raman spectra can be observed in very thin films without the need for the surface enhancement effect. Surface Analysis Forum, Surface Science Site, 2001  Broader term: Raman Spectroscopy

Surface Plasmon Resonance  : Microscopy glossary
succesive absorption: See under two photon excitation

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.  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

time-resolved spectroscopy TRS: Although TRS is not new, the development of ultrafast lasers and pulseshaping techniques, among other innovations, has opened up a wide range of nascent application areas, including test and measurement in the semiconductor industry, materials characterization, biological analysis, and archeological dating. Jennifer Oullette, Time Resolved Spectroscopy Comes of Age,  Industrial Physicist, Feb-Mar 2004 

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: Wikipedia  Broader term: MRI

T-rays terahertz rays: Terahertz (THz) radiation is electromagnetic radiation in a frequency band from 0.1 to 10 terahertz between the infrared and microwave bands and is the next frontier in imaging science and technology. The laboratory of Zhang et al is currently studying uses for T-rays. T-rays (1012 Hz or THz waves) have been used to sense images at a cell level [6]. These images have also been used to monitor the moisture content of leaves, the chemical elements in flames, skin burn severity, skin cancer, and bacteria. Most recently Zhang’s laboratory used the terahertz band to develop a T-ray microscope for biomedical applications [6] and a 3 dimensional T-ray imaging system [7]. C.M. Lathers1, B. Ferguson2, S. Wang3, T. Yuan4, and X.-C. Zhang5 TERAHERTZ-RAYS: NEW TECHNIQUE TO MODEL BONE DEGRADATION AND TO DEVELOP AND PREDICT COUNTERMEASURE EFFECTIVENESS FOR LONG DURATION SPACE FLIGHT TO MARS? Head Out Water Immersion Symposium, Houston, TX, 2002

tunable lasers: Lasers that can be adjusted to emit one of several different wavelengths or channels. Intel, Silicon Photonics glossary 

Optical Devices Tunable Lasers Glossary, EE Times, 2002, 18 terms
Tunable lasers
, Light Reading, Aug, 18, 2001

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 

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

Crump Institute for Molecular Imaging, UCLA.  Includes glossary, based, in part, upon: D. Wagenaar, R. Weissleder, A. Hengerer. Glossary of Molecular Imaging Terminology. Acad Radiol 2001; 8:409- 420., 600+ terms
Fonar, MRI Glossary 
Intel, Silicon Photonics Glossary, 2010 
IUPAC International Union of Pure and Applied Chemistry, Glossary of Terms used in Photochemistry 3rd ed. 2006
MedCyclopedia, GE Healthcare, 1997-2005  17,500 topics, 8,500 images
MIPS Molecular Imaging Program at Stanford, Molecular Imaging Central, Glossary of Terms, Based, in part, upon: D. Wagenaar, R. Weissleder, A. Hengerer. Glossary of Molecular Imaging Terminology. Acad Radiol 2001; 8:409-420.
Photonics Dictionary, Laurin Publishing Co. Inc., 2013 6K terms, 2K abbreviations

Insight Pharma Reports Imaging

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

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