16 Del. Admin. Code § 4465-X-2.0
As used in this Regulation, 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".
"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.
"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 5 centimeters.
"Conventional Simulator" means any x-ray system designed to reproduce the geometric conditions of the radiation therapy equipment.
"Detector" (See "Radiation detector").
"Dose monitor unit (DMU)" means a unit response from the beam monitoring system from which the absorbed dose can be calculated.
"Electronic brachytherapy" means a method of radiation therapy where an electrically generated source of ionizing radiation is placed in or near the tumor or target tissue to deliver therapeutic radiation dosage.
"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 homogenize 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 6.4. "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 1 joule per kilogram. The previous unit of absorbed dose (rad) is being replaced by the gray [1 Gy=100 rad].
"Half-value layer (HVL)" 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-half of the value measured without the material at the same point.
"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.
"Irradiation" means the exposure of a living being or matter to ionizing radiation.
"Isocenter" means the center of the sphere through which the useful beam axis passes while the gantry moves through its full range of motions.
"Kilovolt (kV) [kilo electron volt (keV)]" means the energy equal to that acquired by a particle with one electron charge in passing through a potential difference of one thousand volts in a vacuum. [Note: current convention is to use kV for photons and keV for electrons.]
"Lead equivalent" means the thickness of the material in question affording the same attenuation, under specified conditions, as lead.
"Leakage radiation" means radiation emanating from the radiation therapy system except for the useful beam.
"Licensed Practitioner" means an individual licensed to practice medicine, dentistry, podiatry, chiropractic, osteopathy, or veterinary medicine in this state. For the purpose of this regulation, Advanced Practice Registered Nurses (APRN) and Physicians Assistants (PA) may order diagnostic or supportive x-ray procedures for patients in accordance with Title 24, Delaware Code. APRNs and PAs who supervise, perform, view, or interpret x-ray procedures do so within their scope of practice, as governed by Title 24, Delaware Code.
"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.]
"Misadministration" means an event that meets the criteria in 5.2.
"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:
"Patient" means an individual subjected to machine produced radiation for the purposes of medical therapy.
"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 parameter or condition continues to be valid.
"Phantom" means an object behaving in essentially the same manner as tissue, with respect to absorption or scattering of the ionizing radiation in question.
"Practical range of electrons" corresponds to classical electron range where the only remaining contribution to dose is from bremsstrahlung x-rays. A further explanation may be found in "Clinical Electron Beam Dosimetry: Report of AAPM Radiation Therapy Committee Task Group 25" [Medical Physics 18(1): 73-109, Jan/Feb. 1991] and ICRU Report 35, "Radiation Dosimetry: Electron Beams with Energies Between 1 and 50 MeV", International Commission on Radiation Units and Measurements, September 15, 1984.
"Prescribed dose" means the total dose and dose per fraction as documented in the written directive. The prescribed dose is a estimation from measured data from a specified therapeutic machine using assumptions that are clinically acceptable for that treatment technique and historically consistent with the clinical calculations previously used for patients treated with the same clinical technique.
"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 "Protective barrier").
"Protective barrier" means a barrier of radiation absorbing material(s) used to reduce radiation exposure. The types of protective barriers are as follows:
"Qualified expert" means an individual who has demonstrated to the satisfaction of the Agency that such individual possesses the knowledge and training to measure ionizing radiation, to evaluate safety techniques, and to advise regarding radiation protection needs, for example, individuals certified in the appropriate field by the American Board of Radiology, or the American Board of Health Physics, or the American Board of Medical Physics, or those having equivalent qualifications. With reference to the calibration of radiation therapy equipment, an individual, in addition to the above qualifications, must be qualified in accordance with 4465 Part F and 4465 Part X of these regulations as amended.
"Qualified Medical Physicist (QMP)" means an individual who meets each of the following credentials:
"Radiation detector" means a device which, in the presence of radiation provides, by either direct or indirect means, a signal or other indication suitable for use in measuring one or more quantities of incident radiation.
"Radiation field" (see "Useful beam").
"Radiation head" means the structure from which the useful beam emerges.
"Radiation Therapist" means an individual who is certified and registered by the American Registry of Radiologic Technologists in Radiation Therapy and who has successfully completed an accredited radiation therapy educational program.
"Redundant beam monitoring system" means a combination of two independent dose monitoring systems in which each system is designed to terminate irradiation in accordance with a pre-selected number of dose monitor units.
"Scattered radiation" means ionizing radiation emitted by interaction of ionizing radiation with matter, the interaction being accompanied by a change in direction of the radiation. Scattered primary radiation means that scattered radiation which has been deviated in direction only by materials irradiated by the useful beam.
"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").
"Shadow tray" means a device attached to the radiation head to support auxiliary beam blocking material.
"Shutter" means a device attached to the tube housing assembly which can totally intercept the useful beam and which has a lead equivalency not less than that of the tube housing assembly.
"Sievert (Sv)" means the SI unit of dose equivalent. The unit of dose equivalent is the joule per kilogram. The previous unit of dose equivalent (rem) is being replaced by the sievert. [1 Sv=100 rem.]
"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 a beam of accelerated particles is directed to produce ionizing radiation or other particles.
"Target-skin distance (TSD)" means the distance measured along the beam axis from the center of the front surface of the x-ray target and/or electron virtual source 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 these regulations, 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 in writing for the administration of radiation to a specific patient or human research subject, as specified in 5.1.
"X-ray tube" means any electron tube which is designed to be used primarily for the production of x-rays.
16 Del. Admin. Code § 4465-X-2.0
23 DE Reg. 306 (10/1/2019)
28 DE Reg. 312 (10/1/2024) (Final)