Pennsylvania Code › Title 25 - ENVIRONMENTAL PROTECTION › Part I - Department of Environmental Protection › Subpart D - Environmental Health and Safety › Article V - Radiological Health › Chapter 228 - RADIATION SAFETY REQUIREMENTS FOR PARTICLE ACCELERATORS › GENERAL PROVISIONS › Section 228.2 - Definitions

Current through Register Vol. 54, No. 28, July 13, 2024
The following words and terms, when used in this
						  chapter, have the following meanings, unless the context clearly indicates
						  otherwise:
Accelerator
or
particle
						  accelerator
-A radiation-producing machine capable of accelerating
						  electrons, protons, deuterons, or other charged particles in a vacuum and of
						  discharging the resultant particulate or other radiation into a medium at
						  energies usually in excess of 1 megaelectron volt (MeV).
Applicator
-A structure which
						  determines the extent of the treatment field at a given distance from the
						  virtual source.
Beam-limiting device
-A device
						  providing a means to restrict the dimensions of the X-ray field.
Beam scattering filter
-A filter used
						  to scatter a beam of electrons.
Central axis of the beam
-A line
						  passing through the virtual source and the center of the plane figure formed by
						  the edge of the first beam limiting device.
Dose monitoring system
-A system of
						  devices for the detection, measurement and display of quantities of
						  radiation.
Dose monitor unit
-A unit response from
						  the dose monitoring system from which the absorbed dose can be
						  calculated.
Existing equipment
-Systems
						  manufactured on or before October 3, 1998.
Field flattening filter
-A filter used
						  to provide dose uniformity over the area of a useful beam of X-rays at a
						  specified depth.
Field size
-The configuration of the
						  radiation field along the major axes of an area in a plane perpendicular to the
						  specified direction of the beam of incident radiation at the normal treatment
						  distance and defined by the intersection of the major axes and the 50% isodose
						  line.
Filter
-Material placed in the useful
						  beam to modify the spectral energy distribution and flux of the transmitted
						  radiation and remove radiation that does not contribute to the efficacy of the
						  useful beam.
Isocenter
-A fixed point in space
						  located at the center of the smallest sphere through which the central axes of
						  the beams pass.
Leakage radiation
-Radiation emanating
						  from the source assembly except for the following:
(i) The useful beam.
(ii) Radiation produced when the exposure
						switch or timer is not activated.
Moving beam therapy
-Radiation therapy
						  with relative displacement of the useful beam and the patient during
						  irradiation.
New equipment
-Systems manufactured
						  after January 1, 1985.
Normal treatment distance
-
(i) For isocentric equipment, the
						isocenter.
(ii) For nonisocentric
						equipment, the target to patient skin distance along the central axis as
						specified by the manufacturer.
Particle accelerator
-See the
						  definition of "accelerator."
Phantom
-A volume of material behaving
						  in a manner similar to tissue with respect to the attenuation and scattering of
						  radiation.
Primary dose monitoring system
-A
						  system which will monitor the useful beam during irradiation and which will
						  terminate irradiation when a preselected number of dose monitor units have been
						  attained.
Radiation detector
-A device which
						  provides a signal or other indication suitable for measuring one or more
						  quantities of incident radiation.
Radiation head
-The structure from
						  which the useful beam emerges.
Secondary dose monitoring system
-A
						  system which will terminate irradiation in the event of failure of the primary
						  dose monitoring system.
Shadow tray
-A device attached to the
						  radiation head to support auxiliary beam limiting material.
Spot check
-A procedure to assure that
						  a previous calibration continues to be valid.
Stationary beam therapy
-Radiation
						  therapy without relative displacement of the useful beam and the patient during
						  irradiation.
Subsystem
-A combination of two or more
						  components of an accelerator.
Target
-The part of a radiation source
						  which intercepts a beam of accelerated particles with subsequent emission of
						  other radiation.
Tube housing assembly
-The term
						  includes high-voltage or filament transformers, or both, and other appropriate
						  elements when contained within the tube housing.
Useful beam
-The radiation which passes
						  through the tube housing port and the aperture of the beam-limiting device when
						  the exposure switch or timer is activated.
Virtual source
-The nominal location of
						  either the first scattering foil (for equipment providing electrons only) or
						  the photon focal spot (for equipment capable of delivering both photons and
						  electrons).
Wedge filter
-An added filter effecting
						  continuous progressive attenuation on all or part of the useful
						  beam.
This section cited in 25 Pa. Code §
														216.1 (relating to purpose and
							 scope).