Glossary
A
- absorption
- In the context of light propagation in a medium — the process by which photons have some probability of being captured by the molecules of the medium. Energy transferred to the molecule is converted into a form other than in the original photon, resulting in an apparent loss in incident light intensity to the observer. In the context of in vivo optical imaging — the absorption of light in tissue is one of two parameters that must be accounted for to obtain quantitative results about the tissue's physiological processes.
- adjuvant therapy
- Is given immediately after radiation or surgery to destroy any cancer cells that may remain following radiation or surgery.
- ADME
- Administration, distribution, metabolism, excretion.
- angiogenesis
- The process of developing new blood vessels. Angiogenesis is a naturally occurring process that may also be triggered by certain pathological conditions, such as cancer, where the continuing growth of solid tumours requires nourishment from new blood vessels.
- anatomical imaging
- Imaging of the body’s structure, morphology and the relationship between its parts.
- anatomical information
- Information pertaining to the body’s anatomy.
- antibody
- A type of protein made by certain white blood cells (called leukocytes) in response to a foreign substance (antigen). Each antibody can bind only to a specific antigen to neutralize it. Another type of white blood cell (phagocytes) destroys the neutralized antigen.
- antigen
- A substance that triggers a specific reaction from the immune system.
- attenuation
- In the context of optical imaging — the combination of absorption and scattering of light observed when it propagates through a medium.
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B
- benign
- A non-cancerous tumour whose cells do not spread (metastasize) to other parts of the body.
- biodistribution
- The spatial pattern of a chemical compound's distribution throughout an organism at a specific point in time.
- bioluminescence
- Light produced within an organism, where the excitation energy is supplied by a biochemical reaction rather than a light source. In the context of molecular imaging — refers generally to the enzymatic production of visible light by luciferase, a chemical substance naturally produced by some organisms such as glow worms, fireflies, some jellyfish, some fungi and some deep-sea fish.
- bio-optical imaging
- The application of optical imaging to biological organisms using a method that measures the interaction of light with tissue in the visible and near-infrared regions.
- biopsy
- The removal of cells or tissues for examination.
- BRCA1 / BRCA2
- An inherited gene. Alterations in this gene may increase the risk of breast cancer.
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C
- cancer
- The growth of abnormal cells that proliferate in an uncontrolled way and, in some cases, metastasize (spread).
Cancer is a group of more than 100 different and distinctive diseases, usually designated by the type of cell or organ in which they start. Some cancers are curable, while others may be fatal.
- cell
- The smallest biological unit capable of reproduction. All living things are made up of one or more cells.
- chemotherapy
- Treatment with powerful drugs that attack cancer cells but may also harm certain types of healthy cells.
- clinical trial
- A type of research study aimed at evaluating the effectiveness and safety of new medication or medical devices by monitoring their effects on patients and healthy volunteers. Such studies test new methods of screening, prevention, diagnosis, or treatment of a disease. A successful preclinical study is required before conducting a clinical trial. Clinical studies are regulated by government health agencies.
Also called clinical investigation or clinical study.
- computed tomography scan
- Also known as CAT or CT scan; an x-ray test that uses safe amounts of radiation to take a picture of organs and tissues, and uses a computer to create a 3D x-ray.
- continuous wave optical imaging
- An optical imaging modality where the intensity of the light source is constant or the detector is not providing sufficient, or any, time-resolution. In this configuration, only attenuation properties can be measured; absorption and scattering properties cannot be distinguished from one another.
- contrast agent
- In the context of medical imaging — refers to an exogenous substance administered to an organism or tissue to enhance the ability to distinguish details in the resulting image. Substances include fluorescent dyes, radioactive isotopes, microbubbles and nanoparticles such as quantum dots, metallic ions solutions and others. Depending on the chemistry of the agent, it can target specific tissues (targeted probes) or a specific physiological process (activatable probes).
See also probe.
- core biopsy
- A biopsy procedure using a large needle to remove a small tissue sample and examine it for cancer, for example.
- CW
- Continuous wave.
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D
- detection wavelength
- In the context of fluorescence imaging — wavelength to which a light detector is tuned. Often interchanged with emission wavelength.
- diagnosis
- Identification of a disease after an examination.
- DNA (Deoxyribonucleic acid)
- A double-stranded helix of nucleotides that carries the genetic information of cells. It encodes the information for the proteins and is able to self-replicate.
- drug efficacy
- The ability of a therapeutic compound to act against a known pathogen, cancer or other disease-causing agent in a living organism.
- drug toxicity
- The poisonous effect of a drug, depending on its dose, way of administration and secondary metabolism.
- duct
- Small tubes in the breast that carry milk from the lobules to the nipple during breast-feeding.
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E
- electromagnetic radiation
- Radiation of energy produced by accelerated charged particles. As an electromagnetic (sinusoidal) wave, electromagnetic radiation consists of oscillating electric and magnetic fields at right angles to one another and to the propagation direction. In a vacuum, electromagnetic radiation propagates at the speed of light. In addition to this “wavelike” behaviour, electromagnetic radiation also exhibits “particle-like” behaviour in that it comes in discreet packets known as photons. This dual wavelike and particle-like behaviour is referred to as the wave-particle duality of radiation and is a fundamental part of quantum physics.
The spectrum of electromagnetic radiation is continuous over all frequencies and is known as the electromagnetic spectrum.
- electromagnetic spectrum
- The total range of wavelengths of electromagnetic radiation, extending from zero to infinity.
- electromagnetic wave
- See electromagnetic spectrum.
- emission wavelength
- Wavelength of radiation emitted by a specimen. In the context of fluorescence imaging — refers to the wavelength emitted by the fluorescent agent when it is excited at the excitation wavelength.
- excitation wavelength
- Wavelength of the stimulation light source. More specifically in a fluorescence experiment — refers to the wavelength needed to illuminate the fluorescent agent to excite it.
- exogenous
- Refers to any compound, substance or tissue produced, prepared or grown outside a living organism.
- Ex vivo
- Latin meaning “out of or from life” — refers to tissues or cells that have been removed from a living organism for analysis
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F
- FDOI
- See frequency domain optical imaging.
- fluorescence
- A process by which a molecule excited by absorbing a photon re-emits the energy as another photon at a longer wavelength. The difference in wavelength between the absorbed and emitted photon is often called the Stokes shift.
- fluorescence intensity
- Intensity of radiation emitted by a fluorescence process.
- fluorescence lifetime
- The mean time that a fluorophore remains in its activated state — normally on the nanosecond-time scale for near-infrared fluorescent agents.
- fluorescent probe
- See probe.
- frequency
- The rate of oscillation of an electromagnetic wave. It is expressed in Hertz (cycles per second) and is inversely proportional to the wave's wavelength.
- frequency domain optical imaging
- An optical imaging modality where the intensity of the light source and sensitivity of the detector are frequency-modulated. Absorption and scattering coefficients can be separated in this modality, but not as well as with TD.
- functional imaging
- In vivo imaging and diagnosis of physiologic states and dynamic processes.
- functional information
- Information pertaining to the physiological processes of a body.
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H
- high-throughput screening
- Pertaining to various new technologies that allow a large numbers of interactions between chemicals and their intended targets to be studied and efficiently categorized at an increasingly fast rate.
- hormone replacement therapy
- Treatment that provides estrogen to women to help ease the symptoms of menopause.
- hyperplasia
- An increase in the number of normal cells in a tissue or organ.
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I
- ICG
- Indocyanine green. The only near-infrared fluorescent agent approved for clinical use.
- illumination wavelength
- The wavelength that a light source is tuned to emit. Often interchanged with excitation wavelength.
- immune system
- The group of tissues and cells that recognizes foreign substances in the body and defends it against infections and diseases.
- invasive breast cancer
- Cancer that penetrates ducts, lobules and other surrounding tissues.
- in vitro
- From the Latin meaning “in glass” — refers to tests or reactions taking place outside a living organism, on a microscope slide, in a test tube, etc.
- in vivo
- From the Latin meaning “in life” — refers to events that take place within a living organism.
- ionizing radiation
- Radiation (such as x-ray) that can convert organic molecules into more reactive specimens by ionizing some of their constituents. Reactive molecules can damage cellular structures such as DNA and proteins. In high doses, ionizing radiation can be a source of tumourgenesis.
- IR
- Infrared.
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L
- label
- See marker.
- lesion
- An area of abnormal tissue change.
- light
- Refers to the visible region of the electromagnetic spectrum and to photons or electromagnetic radiation in general.
- lobule
- A small sac in the breast that makes milk during breast-feeding.
- longitudinal imaging
- In an imaging context — refers to the capability of obtaining measurements from the same organism over a given period of time.
- lumpectomy
- The surgical removal of a tumour and some surrounding tissue.
- lymph nodes
- Small bean-shaped structures scattered along the vessels of the lymphatic system. Lymph nodes may trap cells that travel through the lymphatic system.
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M
- magnetic resonance imaging
- A test that uses magnetic fields to create clear three-dimensional images of internal body parts, such as tissues, muscles, nerves and bones. Often referred to as MRI.
- malignant
- In the context of a tumour — capable of spreading (metastasizing) by invading nearby tissue and other parts of the body remote to the cancer.
- mammogram
- An x-ray picture of the breasts used to detect tumours and cysts and to help differentiate benign (noncancerous) and malignant (cancerous) disease.
- marker
- A fluorescent or radioactive chemical group or atom added to a molecule to spatially locate those molecules from non-labelled ones.
See also contrast agent.
- metabolism
- The rate at which blood is locally deoxygenated in tissue. Tumours need oxygen to proliferate and are shown as high metabolism regions in an image, relative to healthy tissue.
- metastasis
- A tumour or growth of cells in a part of the body other than the original or primary location.
- molecular imaging
- A growing research discipline aimed at imaging specific molecular events, particularly those that are key targets in disease processes. Molecular imaging merges the disciplines of molecular biology, genetic engineering, immunology and biochemistry with imaging. It is a term “used to define in vivo imaging of molecules and stands in contrast to anatomical or physiological imaging. In that sense, any type of imaging that uses molecules as indicators or addresses molecules as targets is molecular.”
(Tavitian B. Oligonucleotides as Radiopharmaceuticals. Molecular Imaging: An Essential Tool in Preclinical Research, Diagnostic Imaging, and Therapy, Ernst Schering Foundation Symposium Proceedings, Vol. 49, 2005)
- molecular probe
- See probe.
- molecule
- The joining of two or more atoms by chemical bonding resulting in a set of chemical properties that is not the simple summation of the individual atom's properties.
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N
- near-infrared fluorescence imaging
- Imaging of photons in the near-infrared range, typically 600-1100 nm.
- near-infrared spectral range
- The shortest wavelengths of the infrared region of the electromagnetic spectrum, ranging from 0.75 to 3 μm.
- neoadjuvant therapy
- Therapy used before surgery or radiation to reduce the size of the tumour.
- non-invasive breast cancer/carcinoma in situ
- Cancer within the ducts and lobules that does not spread to any other surrounding tissues.
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O
- OI
- Optical imaging.
- oncology
- From the Greek “o(n)glos” (bulk or mass, tumour) and “logos” (study), oncology literally means the “study of tumours”— refers generally to the field of medicine devoted to studying the causes, diagnosis and treatment of cancer.
- optical imaging
- An imaging method that provides optical properties of the radiation emanating from a body under investigation at a specific wavelength range of the electromagnetic spectrum. In the context of in vivo optical imaging — observing the behaviour of photons in the near-infrared region is favoured because of tissue's low absorption properties in this spectral band (typically, between 650 and 1100 nm), therefore allowing light to penetrate several centimetres.
Optical imaging allows the tissue's natural (endogenous) compounds, called chromophores, to be observed and monitored. A fluorescent or bioluminescent contrast agent may also be used for in vivo optical imaging to enhance the contrast of the physiological process of interest in the images.
Optical imaging measures an overall property called attenuation in the continuous wave technique, or the absorption and scattering properties in the frequency domain and time domain modalities.
- organ
- A part of the body that performs a specific function, such as the heart, the eyes, the liver, etc.
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P
- pathology
- The study of disease.
- perfusion
- The flow of blood per unit volume of tissue. Regional perfusion refers to perfusion of part of the body, especially a limb, and particularly with chemotherapeutic agents, to treat a malignant tumour.
- pharmacokinetics
- The process that quantitatively describes the time-dependant activity of drugs in the body, including the processes by which they are absorbed, distributed in the body, localized in the tissues, and excreted.
- photon
- The name given to a small bundle or “quantum” of electromagnetic energy. It is used when describing the particle-like behaviour of electromagnetic waves, including light. A photon has zero-mass and its energy is directly proportional to its frequency, where Planck's constant h is the proportionality factor.
- physiological process
- Refers to the functions of a living organism and its parts, and the physical and chemical factors involved.
- PKN
- Pharmacokinetics.
- positron emission tomography
- A test for cancer that produces an image of the body based on the uptake of glucose by cells; often referred to as a PET scan.
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R
- radiation
- See electromagnetic radiation.
- radiotherapy
- The use of ionizing radiation to treat cancer and other diseases.
- reflectance mode
- In an optical imaging context — an apparatus geometry where the light source and the detector are directed at the same surface of the organism under study.
- region of interest (ROI)
- A well-defined surface or volume of the organism chosen by an operator to be scanned. In digital imaging, the ROI contains a finite number of pixels and these have a mean, a variance, etc.
- RNA (Ribonucleic acid)
- A chemical found in the nucleus and cytoplasm of cells; it plays an important role in protein synthesis and other chemical activities of the cell.
- ROI
- See region of interest.
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S
- scattering
- Change of the spatial distribution of a beam of radiation when it interacts with a surface or a heterogeneous medium, in which process there is no change of wavelength of the radiation.
In the context of in vivo optical imaging — scattering of light in tissue is one of two parameters that must be accounted for to obtain quantitative results about the tissue's physiological processes.
- small animal imaging
- Any imaging technology that is optimized for the geometry and size of a mouse or similar sized small animal. This allows for higher spatial resolution, improved signal-to-noise ratio, and lower system costs compared with systems designed for human imaging.
- spectroscopy
- Spectroscopy is the science of measuring the emission and absorption properties of a sample over multiple wavelengths of visible and non-visible light.
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T
- targeted information
- In the context of molecular imaging — information pertaining to the phenomena of interest, highlighted by molecular probing.
- TD
- Time domain.
- temporal point spread function (TPSF)
- In the context of time domain optical imaging —, the number of detected photons as a function of time for each scan point, on the picosecond and nanosecond time scales. Essentially, it is the distribution of detected photons according to their time of flight in the medium or tissue.
Synonym: diffusion curve.
- time activity curve
- A curve representing the time-dependence of the radioactivity concentration in some region of interest.
- time domain optical imaging
- An optical imaging modality where the intensity of the light source is pulsed on a very short time-scale and the detector offers a high time-resolution. In this configuration, absorption and scattering properties can be extracted.
- tissue
- A group or layer of cells that are alike and that work together to perform a specific function. Major tissue types include epithelial, connective, skeletal, muscular, glandular and nervous tissues.
- TPSF
- Temporal point spread function.
- tracer
- A measurable substance used to mimic, follow or trace a chemical compound or process without disturbing the process under study.
- transgenic animal
- Genetically engineered animal or its offspring. A transgenic animal usually contains material from at least one unrelated organism, such as from a virus, plant or other animal.
- transmission mode
- In an optical imaging context — an apparatus geometry where the light source and the detector are directed at opposite surfaces of the organism under study.
- tomography
- An imaging technique based on combining multiple object views (projections) to derive maps of the object's interior properties in 3D.
- topography
- In the imaging context — refers to a given property of the object interior mapped to its surface.
- total mastectomy
- Removal of the entire breast.
- tumour
- An abnormal mass of tissue resulting from excessive cell division and that does not perform any useful body function. A tumour can be benign or malignant (cancerous).
- tumourgenesis
- The generation of a tumour.
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U
- ultrasound
- A diagnostic technique using sound waves to view different parts of the body, especially internal organs.
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V
- visible spectrum
- The visible region of the electromagnetic spectrum that extends from about 400 to 750 nm in wavelength.
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W
- wavelength
- The physical distance covered by one cycle of an electromagnetic wave, it is inversely proportional to frequency.
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