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
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.
