Code of Massachusetts Regulations › 105 CMR - DEPARTMENT OF PUBLIC HEALTH › Title 105 CMR 120.000 - The Control of Radiation › RECORDKEEPING REQUIREMENTS › Section 120.432 - Definitions

Current through Register 1525, July 5, 2024
As used in 105 CMR 120.430, the following definitions
				  apply:
Absorbed Dose (D)
means the mean
				  energy imparted by ionizing radiation to matter. Absorbed dose is determined as
				  the quotient of dE by dM, where dE is the mean energy imparted by ionizing
				  radiation to matter of mass dM. The SI unit of absorbed dose is joule per
				  kilogram and the special name of the unit of absorbed dose is the gray (Gy).
				  The previously used special unit of absorbed dose (rad) is being replaced by
				  the gray.
Absorbed Dose Rate
means absorbed
				  dose per unit time, for machines with timers, or dose monitor unit per unit
				  time for linear accelerators.
Accessible Surface means
surface of
				  equipment or of an equipment part that can be easily or accidentally touched by
				  persons without the use of a tool.
Added Filtration
means any
				  filtration which is in addition to the inherent filtration.
Air Kerma (K)
means the kinetic
				  energy released in air by ionizing radiation. Kerma is determined as the
				  quotient of dE by dM, where dE is the sum of the initial kinetic energies of
				  all the charged ionizing particles liberated by uncharged ionizing particles in
				  air of mass dM. The SI unit of air kerma is joule per kilogram and the special
				  name for the unit of kerma is the gray (Gy).
Barrier
(
See
Protective Barrier
in
				  105 CMR 120.005
				  ).
Beam Axis
means the axis of rotation
				  of the beam limiting device.
Beam-limiting Device
means a field
				  defining collimator, integral to the therapeutic radiation machine, which
				  provides a means to restrict the dimensions of the useful beam.
Beam Monitoring System
means a
				  system designed and installed in the radiation head to detect and measure the
				  radiation present in the useful beam.
Beam Scattering Foil
means a thin
				  piece of material (usually metallic) placed in the beam to scatter a beam of
				  electrons in order to provide a more uniform electron distribution in the
				  useful beam.
Bent Beam Linear Accelerator
means a
				  linear accelerator geometry in which the accelerated electron beam must change
				  direction by passing through a bending magnet.
Certified Health Physicist
means and
				  individual certified by the American Board of Health Physics as a health
				  physicist.
Changeable Filters
means any filter,
				  exclusive of inherent filtration, which can be removed from the useful beam
				  through any electronic, mechanical, or physical process.
Contact Therapy System
means a
				  therapeutic radiation machine with a short target to skin distance (TSD),
				  usually less than five centimeters.
Conventional Simulator
means any
				  x-ray system designed to reproduce the geometric conditions of the radiation
				  therapy equipment.
Detector
(
See
Radiation Detector
in
				  105 CMR 120.402
				  ).
Dose Monitor Unit (DMU)
means a unit
				  response from the beam monitoring system from which the absorbed dose can be
				  calculated.
Dosimetry System
means a device
				  which can measure radiation dose.
Electronic Brachytherapy
means a
				  method of radiation therapy using an electrically generated source of ionizing
				  radiation to deliver a radiation dose at a distance of up to a few centimeters
				  by intracavitary, intraluminal or interstitial application, or by applications
				  with the source in contact with the body surface or very close to the body
				  surface.
Electronic Brachytherapy Device
means the system used to produce and deliver therapeutic radiation including
				  the x-ray tube, the control mechanism, the cooling system, and the power
				  source.
Electronic Brachytherapy Source
means the x-ray tube component used in an electronic brachytherapy
				  device.
External Beam Radiation Therapy
means therapeutic irradiation in which the source of radiation is at a distance
				  from the body.
Field-flattening Filter
means a
				  filter used to flatten the absorbed dose rate over the radiation field.
Filter
means material placed in the
				  useful beam to change beam quality in therapeutic radiation machines subject to
				  105 CMR
				  120.436.
Gantry
means that part of a
				  radiation therapy system supporting and allowing movements of the radiation
				  head about a center of rotation.
Gray (Gy)
means the SI unit of
				  absorbed dose, kerma, and specific energy imparted equal to one joule per
				  kilogram. The previous unit of absorbed dose (rad) is being replaced by the
				  gray. [one Gy=100 rad].
Intensity Modulated Radiation Therapy
				  (IMRT)
means radiation therapy that uses non-uniform radiation
				  beam intensities which have been determined by various computer-based
				  optimization techniques.
Interlock
means a device preventing
				  the start or continued operation of equipment unless certain predetermined
				  conditions prevail.
Interruption of Irradiation
means
				  the stopping of irradiation with the possibility of continuing irradiation
				  without resetting of operating conditions at the control panel.
Isocenter
means the center of the
				  sphere through which the useful beam axis passes while the gantry moves through
				  its full range of motions.
Leakage Radiation
means radiation
				  emanating from the radiation therapy system except for the useful beam.
Light Field
means the area
				  illuminated by light, simulating the radiation field.
mA
means milliampere.
Megavolt (MV) [Mega Electron Volt
				  (MeV)]
means the energy equal to that acquired by a particle with
				  one electron charge in passing through a potential difference of one million
				  volts in a vacuum. [
Note
: current convention is to use
				  MV for photons and MeV for electrons.]
Mobile Electronic Brachytherapy
				  Service
means transportation of an electronic brachytherapy device
				  to provide electronic brachytherapy at an address that is not the address of
				  record.
Monitor Unit (MU)
(
See
Dose Monitor Unit
).
Moving Beam Radiation Therapy
means
				  radiation therapy with any planned displacement of radiation field or patient
				  relative to each other, or with any planned change of absorbed dose
				  distribution. It includes arc, skip, conformal, intensity modulation and
				  rotational therapy.
Nominal Treatment Distance
means:
(a) For electron irradiation, the distance from the
				  scattering foil, virtual source, or exit window of the electron beam to the
				  entrance surface of the irradiated object along the central axis of the useful
				  beam.
(b) For x-ray irradiation, the virtual source or target to
				  isocenter distance along the central axis of the useful beam. For
				  non-isocentric equipment, this distance shall be that specified by the
				  manufacturer.
Peak Tube Potential
means the
				  maximum value of the potential difference across the x-ray tube during an
				  exposure.
Periodic Quality Assurance Check
means a procedure which is performed to ensure that a previous calibration
				  continues to be valid.
Prescribed Dose
means the total dose
				  and dose per fraction as documented in the written directive.
Primary Dose Monitoring System
means
				  a system which will monitor the useful beam during irradiation and which will
				  terminate irradiation when a pre-selected number of dose monitor units have
				  been delivered.
Primary Protective Barrier
(
See
105 CMR 120.005:
Protective Barrier
).
Qualified Medical Physicist
means an
				  individual qualified in accordance with
				  105
				  CMR 120.433(D).
Radiation Field
(See
Useful Beam
)
Radiation Head
means the structure
				  from which the useful beam emerges.
Redundant Beam Monitoring System
means a combination of two dose monitoring systems in which each system is
				  designed to terminate irradiation in accordance with a pre-selected number of
				  dose monitor units.
Secondary Dose Monitoring System
means a system which will terminate irradiation in the event of failure of the
				  primary dose monitoring system.
Secondary Protective Barrier
(
See
Protective Barrier
in
				  105 CMR 120.005
				  ).
Simulator (Radiation Therapy Simulation
				  System)
means any x ray system intended for localizing the volume
				  to be exposed during radiation therapy and establishing the position and size
				  of the therapeutic irradiation field. (
See
:
Conventional Simulator
and
Virtual
				  Simulator
.)
Source
means the region and/or
				  material from which the radiation emanates.
Source-skin Distance (SSD)
(
See
Target-skin Distance).
Stationary Beam Radiation Therapy
means radiation therapy without displacement of one or more mechanical axes
				  relative to the patient during irradiation.
Stray Radiation
means the sum of
				  leakage and scattered radiation.
Target
means that part of an x-ray
				  tube or accelerator onto which is directed a beam of accelerated particles to
				  produce ionizing radiation or other particles.
Target-skin Distance (TSD)
means the
				  distance measured along the beam axis from the target to the surface of the
				  irradiated object or patient.
Tenth-value Layer (TVL)
means the
				  thickness of a specified material which attenuates X-radiation or gamma
				  radiation to an extent such that the air kerma rate, exposure rate or absorbed
				  dose rate is reduced to one-tenth of the value measured without the material at
				  the same point.
Termination of Irradiation
means the
				  stopping of irradiation in a fashion which will not permit continuance of
				  irradiation without the resetting of operating conditions at the control
				  panel.
Therapeutic Radiation Machine
means
				  x-ray or electron-producing equipment designed and used for external beam
				  radiation therapy. For the purpose of 105 CMR 120.000, devices used to
				  administer electronic brachytherapy shall also be considered therapeutic
				  radiation machines.
Tube
means an x-ray tube, unless
				  otherwise specified.
Tube Housing Assembly
means the tube
				  housing with tube installed. It includes high-voltage and/or filament
				  transformers and other appropriate elements when such are contained within the
				  tube housing.
Useful Beam
means the radiation
				  emanating from the tube housing port or the radiation head and passing through
				  the aperture of the beam limiting device when the exposure controls are in a
				  mode to cause the therapeutic radiation machine to produce radiation.
Virtual Simulator
means a computed
				  tomography (CT) unit used in conjunction with relevant software which recreates
				  the treatment machine; and that allows import, manipulation, display, and
				  storage of images from CT and/or other imaging modalities.
Virtual Source
means a point from
				  which radiation appears to originate.
Wedge Filter
means a filter which
				  effects continuous change in transmission over all or a part of the useful
				  beam.
Written Directive
means an order,
				  such as a physician's prescription, in writing, by an authorized user for the
				  administration of radiation to a specific patient or human research subject, as
				  specified in
				  105 CMR
				  120.435(A).
X-ray Tube
means any electron tube
				  which is designed to be used primarily for the production of x-rays.