following summarises and defines in outline the most important terms
used in photo therapy and related areas of application.
N D E X
A | B
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D | E
| F | G
| H | I
| J | K
| L | M
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O | P
Q | R
| S | T
| U | V
| W | X
| Y| Z
radiant energy (e.g. light) by interaction with matter therefore
creating a decrease in the power of light passing through a substance.
spectrum The relationship
of absorption depending on the wavelength.
spectrum A plot of the relative
efficiencies of different wavelengths of light in their ability
to create a biological response.
energy The energy that must be
provided in to a molecule to allow a chemical reaction to proceed
Cell respiration in which
molecular oxygen is used to take part in the oxidation or organic
Cell respiration which no oxygen is used to break down organic
substrates during metabolism.
Adenosin triphosphate. A high energy phosphate ester
which serves as the principal energy-storage compound of the cell.
Reduction of radiant energy (light) by interaction with matter,
including absorption and scattering.
average amount of power (usually measured in watts) emitted by a
are small lymphocytes which synthesize and secrete hormonal antibodies
upon antigenic stimulation.
The range of continuous frequencies or wavelengths in an electrical,
optical or acoustic signal.
diameter The diameter of a light beam extends to a point
where the intensity of the light in the beam had dropped to 1/e2
(0.135) of the peak intensity. Note that according to this definition,
some light in the beam falls outside of Gaussian profile of intensity.
Clocks Mechanisms which allow the expression of certain
biological structure's at periodic intervals.
The fundamental unit of life; the
smallest body capable of independent reproduction. Cells vary considerably
in size and shape. But all have the common features of metabolism.
timed sequence of events occurring in a cell in the period between
differentiation The process whereby
descendants of a common parental cell achieve and maintain specialization
of structure and function.
line Cultured cells of single origin
capable of stable growth for many generations.
immunity Immune response directly mediated by T lymphocytes
rather than circulating (humoural) antibody molecules.
respiration A complicated series of chemical reactions
in which molecular oxygen is used to oxidize carbohydrates or other
organic substances, releasing energy and producing carbon dioxide
and water. During the process ADP is changed to ATP, and ATP provides
the energy for biological processes.
A theory which accounts for the coupling of electron transfer and
ATP formation by populating the formation of H* gradients across
the mitochondria membrane.
The two daughter strands of a duplicated chromosome that are still
joined by a single centromere.
The nucleoprotein fibers of which eukaryotic chromosomes are composed.
A light absorbing atom, molecule or molecular unit.
A long, thin thread like body in the dividing nucleus of an eukaryotic
cell. They are only observable during nuclear division. Contains
DNA, RNA and protein and these constitute the genetic material of
aberrations During meioses the chromosomes or chromatids
may become broken and subsequently rejoined and the result is a
mutation of the genres in the chromosomes.
A group of cells all descended from a single common ancestor.
Small molecules which associate with protein to form
active enzymes (e.g. NAD, NADP).
refers to the inherent 'synchronicity' of light; such light
is described as both spatially and temporarily coherent, signifying
that the light is monochromatic, in phase/ in step or out of phase.
See also Temporal coherence, Spatial
A tough, inelastic,fibrous protein, formed
and maintained in tissues by fibroblasts.
filter A filter which absorbs some of
the incident light and transmits the rest.
is a term which describes the high degree of parallelity light.
Divergence is more commonly specified by manufacturers and researchers;
this is essentially the opposite of collimation.
that are synthesised in fixed amounts irrespective of the growth
wave (CW) describes
the output of those therapeutic units where radiant
power output is relatively constant over time.
Iron containing proteins taking part in cellular respiration. They
are oxidized by dissolved oxygen in a cell and reduced by oxidizable
substances in a cell.
of a light wave by an object of dimensions comparable to the wavelength.
is sometimes used when describing light therapy treatments as an
alternative to either radiant exposure
or energy. See fluence
(deoxyribonucleic acid) A
polymer of deoxyribonucleotids. The genetic material for all cells.
Energy flow formed by any oscillating electric and magnetic field
at right angles and lying transverse to the deflection of energy
flow. Examples are X-rays, ultraviolet light, visible light, infrared
radiation and radio waves, all of which occupy various portions
of the electromagnetic spectrum and differ in frequency, wavelength
and energy of a quantum.
can be thought of as the amount of work one or photons delivered
by a given unit; it is measured in J and is given by multiplying
the average radiant power output by the irradiation in s
content per unit volume see
which acts as a covering or lining for any organ or organism.
molecules capable of catalyzing chemical reactions.
Haemoglobin-rich nucleated red blood cell involved in oxygen transportation.
process that increases the internal energy of an atom or molecule.
cells which have a spindle shape and growth rate of connective tissue
A material put in the pat of the light allowing only certain
wavelengths to pass.
(dose) Radiant energy per unit area.
A mass of nervous tissue that is encapsulated in connective tissue.
stretch along a chromosome the codes for function production (either
RNA or its translation product, a polypeptide) A unit factor of
Time necessary for growing cells to double their mass under specific
The minimum complete set of all different chromosomes found in each
nucleus of a given species.
tissue mainly composed of a network of protoplasmic and long fibrous
branching dendrons and axons of nerve cells; it provides support
for nerve cell bodies and nerve fibers, especially in the brain
and spinal cord.
(Embden-Meyerhoff pathway) The fermentation of glucose
to lactic acid with the production of ATP. Glycolysis takes place
in the cytoplasm.
frequency of a periodic oscillation given in cycles per second.
Electromagnetic radiation for which the wavelengths are within the
spectrum range of 0.7 µm up to 100 µm. this portion
of the spectrum is often separated into three bands by wavelength:
IR-A (0.7µm - 0.78µm to 1.4µm ). or ear-infrared;
OR - B (1.4µm to 3µm ) and IR-C (3µm to 100µm
) or far - infrared.
The amount of light energy incident per unit area per second. For
human viewing of visible light, the usual term is illuminance; for
electromagnetic radiation in general. The term is usually radiant
resting stage of a cell between two mitotic divisions.
power density is the incident
power per unit area. It is typically specified in milliwatts per
square centimeter (mW/cm2). For the calculation of irradiance for
in-contact treatments, the unit's radiant
power output is divided
by the spot size.
is an acronym for Light Amplification by Stimulated Emission
of Radiation. Lasers generate or amplify electromagnetic oscillations
at wavelengths from the far infrared (submillimeter) to the ultraviolet.
The laser oscillator needs two basic elements: an amplifying medium
and a regeneration or feedback mechanism (resonant cavity). the
amplifying medium can be a variety of substances, such as gas, semiconductor,
dye solution etc.
Cell-aggulating proteins. Often used for mitogenic activation of
A light-emitting diode. A semiconductor device in which light is
produced when current carriers combine as a pnjunction. The
emission is spontaneous and there are no feedback mirrors, unlike
in diode lasers and specialist PhotoTherapy products of a specific
(white blood cell) A nucleated motile colourless cell found in the
blood and lymph.
Visible electromagnetic radiation
(400 nm to 700 nm).
absorption coefficient The reciprocal of the distance
(in units cm2) in a thick, nonscattering layer, in which the flux
density or intensity in the direction of an incident collimated
light beam decreases by a factor of 1/e; also the absorption cross
section (in units cm2).
laser therapy (LILT) is the recommended
terms to describe the use of laser devices as a therapeutic modality.
Alternative terms such as 'cold laser therapy', 'soft laser therapy'
and 'low power laser therapy' are inappropriate and misleading.
(reactive) level laser therapy (LLLT) is an acceptable
alternative to low-intensity laser therapy (LILT).
Factors released by antifenically stimulated T lymphocytes which
attract phagocytic monocytes.
White blood cell, found in large numbers in higher vertebrates,
which is characterised by a seemingly inert nucleus surrounded by
only traces of an endoplasatic reticulum - poor cytoplasm (Small
lymphocytes). they all into two groups, B and T cells, which are
indistinguishable under the light microscope.
A membrane bounded particle, smaller than a mitochondrion, occurring
in cytoplasm. They contain hydrolic enzymes which are liberated
when the cell is damaged.
Large, phagocytic white blood cell with one nucleus found at the
sites of corpuscle formation, e.g. in bone marrow, lymph nodes,
spleen etc. Their function is to remove foreign particles from blood
and lymph. Macrophages are also found in loose connective tissue,
but they only become active when tissue is damaged.
the central component if a device; the medium determines the wavelength(s)
of light or near infra-red radiation emitted by the device.
set of consecutive intracellular enzymatic reactions that convert
one molecule to another.
sum total of various chemical reactions occurring in a living cell.
Organelle about 0.5 µm in width and up to 10 µm in length
found in the cytoplasm of all aerobic eukaryotic cells; the centre
of ATP generation through oxidative phorphorylation.
Substance which provokes cell division
(mitosis). Examples are lectins like phytohemagglutinin and concanavalin
Process whereby chromosomes duplicate and segregate accompanied
by cell division. The process takes place in four phases: prophase,
metaphase, anaphase and telophase.
Light with narrow spectral bandwidth.
literally means 'single coloured'; monochromatic light is 'practically
all at one wavelength' with very narrow bandwidth.
the largest leukocyte (macrophage) found in the blood. They are
A layer of cells which is informally one cell thick.
Messenger RNA that serves as a
template for protein synthesis.
scattering Interactions involving light, in which the
photons are scattered more than once before being absorbed or escaping
from the medium.
Physical and chemical agents, such as radiation, heat, or alkylating
or dominating agents, which raise the frequency of mutations greatly
above the spontaneous background level.
Marrow cell in the long bones which are possibly the precursor of
Nicotinamide adenine dinucleotide.
A coenzyme taking part in redox reactions. It oxidizes substrates
by removing NADH. The reduced form reduces substrates and is itself
oxidized to reconstitute NAD. This cyclical process is of fundamental
importance and the ratio of NAD to NADP in a cell plays an important
part in controlling the rate of energy production.
Nicotinamide adenine dinucleotide phosphate.
A coenzyme taking part in redox reactions. It oxidizes substrates
by removing hydrogen and is itself changed to the reduced form of
NADPH. The reduced form reduces substrates and is itself oxidized
to reconstitute NADP.
A uninucleated cell, with cytoplasm containing fibris and with long
thread like processes (axons and dendrites) arising from the cell
body. Nerve cells are usually taken to exclude the process but the
term is sometimes used instead of neuron.
Optical interactions which are proportional to the square or higher
powers of light intensities. Passive optical transmission of light,
such as by a lens, is linear transmission. Nonlinear effects generate
harmonies of optical frequencies and sum and difference frequencies
when two light waves are mixed. Nonlinear materials are materials
in which nonlinear effects are likely to occur at moderate power
Round granular structures found in nucleus of eukaryotic cells usually
associated with specific chromsomal site. Involved in rRNA synthesis
and ribosome formation.
spherical or ovoid body present in almost all living cells of animals
and plants but absent in bacteria and blue green algae. They contain
the structure controlling the reproduction and functioning of the
gene responsible for inducing the transformed phenotype.
A measurement of transmission equal to the base-10 logarithm of
the reciprocal of transmittance (the fraction of the incident light
transmitted). An object with optical density of zero is transparent;
an optical density of one corresponds to 10 percent transmission.
is lower in power reflecting the use of very very low
Coupled electron transfer and ATP formation which occurs on the
A modality which requires the presence of a photosensitizer and
The quantity of energy in a single light source commonly in laser
the pulse multiplied by the length of the pulse duration.
Intracellular organelles which contain a fine granular matrix and
often have cristaelike cores. They have been found to contain four
enzymes involved in hydrogen peroxide metabolism, including the
H2O2 - degradative enzyme catalase. They may be important in purine
degradation, hostorespiration and the metabolic pathway known as
the glyoxylate cycle.
mitogenic lectin, phytohaemagglutuinin.
white blood cell which engulfs foreign bodies particularly pathogens.
In mammals polymorponuclear leukocytes, monocytes and macrophages
process for food gathering employed by phagocytes. This process
involves the surrounding and subsequent digestion of cellular-sized
objects by pseudopod-like projections.
is the term used to describe the inhibitory effects of light upon
biological functions (see also below).
is the term used to describe the stimulatory effects of light upon
biological functions e.g. in clinical practice this might be various
wound healing processes. The term has been inappropriately used
as an alternative to the more precise generic terms such as
or low-intensity laser therapy (LILT)
action A biological photosensitization
that requires the presence of molecular oxygen.
system of optical units based on the visual response of the standard,
light adapted human eye.
quantum of electromagnetic radiation; photons travel at the speed
of light and have energy hv, where he is Planck's constant
(6.625x10-34 Jxs) and v is the frequency of Hz. Quantum properties
of electromagnetic radiation take place during absorption, emission
A photochemical reaction that is equivalent to electron transfer
from a donor molecule to an acceptor.
A process that requires both light and a chromophoric photosensitizing
agent in order to take place.
a Treatment unitizing
UV, visible or near IR radiation for medical purposes.
initiated by exposure of a biological object to light associated
with the presence of chemical or drug.
The cell differentiated from antigenically stimulated B lymphocyte.
They are characterized by a very rough endoplasmatic reticulum and
secretion of massive amounts of antibodies.
membrane (cell membrane, plasmalemma, plasmic membrane) Physical
barrier that surrounds the cell surface and encloses the cytoplasm.
The membrane is semipermiable and largely composed of lipids and
proteins. About 10 nm thick.
refers to the orientation of waves of light. The direction of the
electric vector of electromagnetic radiation in the plane perpendicular
to the direction of propagation.
A polynucleated, irregularly shaped white blood cell, exhibiting
amoeboid movement. Active phagocytes are continually produced in
the bone marrow and constitute about 70% of all leukocytes in humans.
Polymorphonclear leukocytes are divided into eosinophils, basophils
and neutrophils. All three types increase in number during infection.
density (intensity) The
power per unit area (W/m2 for example) contained in a light beam
or falling on a given target area. It is the same as the radiometric
term irradiance Intensity of light is the power per unit of area.
/ energy meter An
instrument which measures the amount of optical power (typically
in watts) or energy (joules). I can operate in the visible, infrared,
or ultraviolet region, and detect pulsed or continuous beams.
output see Irradiance
the output of those devices which allow the
radiant power output to be delivered as short pulses
of energy. Pulsing can be produced by chopping the output of continuous
wave devices, modulating the diode's output or by using
a diode which is inherently pulsed.
A photochemical reaction specifying the initial chemical species
generated by light absorption.
A photochemotherapy for skin disorders utilizing the combined action
of a psoralen drug and UVA.
duration (pulse width)
The time period between the half peak power points at the front
and trailing edges of a pulse.
A laser that generates energy in pulses rather than continuously.
small portion of energy associated with discrete events (absorption,
emission) of interaction of light and matter.
efficiency (quantum yield)
The probability that the absorption of a photon of a specified wavelength
will induce a selected molecular response; also referred to as quantum
energy density is the energy
delivered per unit area. It is usually measured and specified in
joules per square centimeter (J/cm2) and is given by multiplying
the radiant power output (in
watts) by the time of irradiation (in seconds) and dividing the
product by the area of irradiation (in square centimeters).
power output of
a therapeutic laser ir phototherapy unit is usually specified in
milliwatts. This gives a measure of the number of photons emitted
The rate at which pulses are repeated. For lasers, typically measured
as pulses per second (Hz). Sometimes lasers are said to be repetitively
pulsed when they produce pulses regularly at fixed intervals, rather
than producing single pulses.
Small cellular particles (10 to 15 nm in diameter) made up of rRNA
and protein. Ribosomes are the site of protein synthesis. They occur
mainly in the endoplasm of a cell, but also on the nuclear membrane.
(ribonucleic acid) A
polymer of riobonucleotids. A molecule of RNA consists of one strand.
Ribosmal RNA. The nucleic acid component of ribosomes,
making up two thirds of the mass of the ribosome in E. coli
and about one-half the mass of mammalian ribosomes.
cell A long thing uninucleated
cell forming part of a the neurilemma (a think outer coat surrounding
rRNA Ribosomal RNA The
nucleic acid component of ribosome's, making up two thirds of the
mass of ribosome in E. coli and about one half the mass of
molecular oxygen Molecular
oxygen that is in the lowest excited electronic state. gather are
two singlet states of the oxygen.
The intermolecular transfer of energy fro the excited singlet state
of a donor to the singlet ground state of an acceptor, resulting
in the acceptor being in the excited singlet state.
notation for an atom, a molecule, or an ion in which all electron
spins are paired resulting in a total spin of zero.
The coherence (or phase correlation) of light over an area of the
wavefront of a beam.
emission of radiation occurs
when an excited electron spontaneously returns to its resting level
and gives off a photo of light energy as a result
emission of radiation typically occurs when a photon
of a precise quantal energy interacts with an excited atom to give
rise to a second photon, which will carry exactly the same energy
as the first.
diode (SLD) is
a diode source, the output of which is exactly like that of a laser
diode, except for the property of coherence. The clinical relevance
of coherence remains a subject of ongoing debate.
Small lymphocyte which processes the surface antigen and direct
cell medicated immune response.
The coherence (or phase correlation) of light over time. Light is
temporarily coherent when the phase change during a time interval
remains constant regardless of when the interval is measured.
A process in which the observable response does not start until
a threshold or conditioning dose has accumulated. Tissue optics
Trends in optics dealing with light propagation (including absorption,
scattering etc) in biological tissues.
Spectroscopic notation for an atom, molecule, or ion in which two
electron spins are unpaired.
I photosensitization A photosensitized chemical reaction
in which the initial interactions of the excited photosensitizer
occur with the substrate.
II photosensitization A photosensitized chemical reaction
in which the initial interactions of the excited photosensitizer
occur with molecular oxygen, resulting in the production of singlet
Electromagnetic radiation that has wavelengths
from soft X-rays down to visible, violet light. This spectral region
is frequently categorized into three separate nads of wavelength:
UV-A (315 - 400 nm) UV-B (280 - 315 nm) and UV-C (200 - 280 nm).
When white light is passed through a prism
of diffraction grating a contentious spectrum is formed. The centre
part of this is visible from the blue to the red end.
Electromagnetic radiation that can be sensed
by the human eye. Generally used to describe wavelengths between
400 nm to 700 nm.
(w) The unit of power or radiant
flux - one joules per second.
is typically expressed in nanometres (nm) (or less commonly micrometers
- µm) and, expressed in terms of the wave theory of light,
is the distance between one positive maximum of the electromagnetic
field and the next. At a given wavelength of light, all photons
carry exactly the same energy.
light Mixture of colours - specific wavelengths of visible
light that appear white to the eye. Mixture of three colours or
specific wavelengths is sufficient to produce white light.
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