10-144-220 Me. Code R. § F-2
As used in this part, the following definitions apply:
Accessible surface means the external surface of the enclosure or housing provided by the manufacturer.
Added filtration means any filtration that is in addition to the inherent filtration.
Aluminum equivalent means the thickness of type 1100 aluminum alloy1 affording the same attenuation, under specified conditions, as the material in question.
Assemblermeans any person engaged in the business of assembling, replacing, or installing one or more components into an x-ray system or subsystem. The term includes the owner of an x-ray system or his or her employee or agent who assembles components into an x-ray system that is subsequently used to provide professional or commercial services.
Attenuation block means a block or stack having dimensions 20 centimeters by 20 centimeters by 3.8 centimeters, of type 1100 aluminum alloy or other materials having equivalent attenuation.
Automatic exposure control means a device that automatically controls one or more technique, factors in order to obtain at a preselected location(s) a required quantity of radiation (Includes devices such as photo timers and ion chambers).
Barrier (See Protective barrier.)
Beam axis means a line from the source through the centers of the x-ray fields.
Beam-limiting device means a device that provides a means to restrict the dimensions of the x-ray field.
Beam monitoring system means a system designed to detect and measure the radiation present in the useful beam.
C-arm x-ray system means an x-ray system in which the image receptor and x-ray tube housing assembly are connected by a common mechanical support system in order to maintain a desired spatial relationship. This system is designed to allow a change in the projection of the beam through the patient without a change in the position of the patient. This definition does not refer to a conventional fluoroscopic system or to a dental cephalametric x-ray machine.
Cephalometric device means a device intended for the radiographic visualization and measurement of the dimensions of the human head.
Certified components mean components of x-ray systems, which components are subject to the X-ray Equipment Performance Standards promulgated under Public Law 90-602, the Radiation Control for Health and Safety Act of 1968.
Certified system means any x-ray system that has one or more certified component(s).
Changeable filters means any filter, exclusive of inherent filtration, which filter can be removed from the useful beam through any electronic, mechanical or physical process.
Coefficient of variation or "C" means the ratio of the standard deviation to the mean value of a population of observations. It is estimated using the following equation:
where
[SIGMA] = Estimated standard deviation of the population.
[PI] = Mean value of observations in sample.
[OMEGA]1 = with observation in sample.
[RETROFLEX HOOK] = Number of observations in sample
Computed tomography means the production of a tomogram by the acquisition and computer processing of x-ray transmission data.
Contact therapy system means an x-ray system used for therapy with the x-ray tube port placed in contact with or within 5 centimeters of the surface being treated.
Control panel means that part of the x-ray control upon which are mounted the switches, knobs, pushbuttons, and other hardware necessary for manually setting the technique factors.
Cooling curve means the graphical relationship between heat units stored and cooling time.
CT (see Computed tomography.)
Dead-man switch means a switch so constructed that a circuit closing contact can be maintained only by continuous pressure on the switch by the operator.
Diagnostic source assembly means the tube housing assembly with a beam-limiting device attached.
Diagnostic x-ray imaging system means an assemblage of components for the generation, emission, and reception of x-rays and the transformation, storage, and visual display of the resultant x-ray image.
Diagnostic x-ray system means an x-ray system designed for irradiation of any part of the human or animal body for the purpose of diagnosis or visualization.
Direct scattered radiation means that scattered radiation, which has been deviated in direction only by materials, irradiated by the useful beam (See Scattered radiation.)
Direct supervision means that during use of the radiation producing sources and devices, the supervisor is present to observe and correct, as needed, the performance of the individual being supervised who is using the radiation producing sources and devices.
Entrance exposure rate means the exposure free in air per unit time at the point where the center of the useful beam enters the patient.
Field emission equipment means equipment, which uses an x-ray tube in which electron emission from the cathode is due solely to the action of an electric field.
Filter means material placed in the useful beam to absorb preferentially selected radiations.
Fluoroscopic imaging assembly means a subsystem in which x-ray photons produce a fluoroscopic image. It includes the image receptor(s) such as the image intensifier and spot-film device, electrical interlocks, if any, and structural material providing linkage between the image receptor and diagnostic source assembly.
Focal spot (actual) means the area projected on the anode of the x-ray tube bombarded by the electrons accelerated from the cathode and from which the useful beam originates.
General purpose radiographic x-ray system means any radiographic x-ray system, which, by design, is not limited to radiographic examination of specific anatomical regions.
Gonad shield means a protective barrier for the testes or ovaries.
Healing arts screening means the testing of human beings using x-ray machines for the detection or evaluation of health indications when such tests are not specifically and individually ordered by a licensed practitioner of the healing arts legally authorized to prescribe such x-ray tests for the purpose of diagnosis or treatment.
Heat unit means a unit of energy equal to the product of the peak kilovoltage, milliamperes, and seconds, i.e., kVp x mA x second.
Image intensifier means a device, installed in its housing, which instantaneously converts an x-ray pattern into a corresponding light image of higher energy density.
Image receptor means any device, such as a fluorescent screen or radiographic film, which transforms incident x-ray photons either into a visible image or into another form, which can be made into a visible image by further transformations.
Image receptor support means, for mammographic systems, that part of the system designed to support the image receptor during a mammography.
Inherent filtration means the filtration of the useful beam provided by the permanently installed components of the tube housing assembly.
Irradiation means the exposure of matter to ionizing radiation.
Kilovolts peak (See. Peak tube potential.)
kV means kilovolts. kVp (See Peak tube potential.)
kWs means kilowatt second.
Leakage radiation means radiation emanating from the diagnostic or therapeutic source assembly except for:
Leakage technique factors means the technique factors associated with the diagnostic or therapeutic assembly which are used in measuring leakage radiation.
They are defined as follows:
Light field means that area of the intersection of the light beam from the beam-limiting device and one of the set of planes parallel to and including the plane of the image receptor, whose perimeter is the locus of points at which the illumination is one-fourth of the maximum in the intersection.
Line-voltage regulation means the difference between the no-load and the load line potentials expressed as a percent of the load line potential. It is calculated using the following equation:
Percent line-voltage regulation = 100 (Vn-V1)/V1 where:
Vn = No-load line potential and
V1 = Load line potential.
mA means milliampere.
mAs means milliampere second.
Mammographic facility means a facility that has an x-ray machine that is used, exclusively or not, for taking breast radiographs. Some facilities, such as hospitals, may have mammographic x-ray machines. These x-ray machines shall comply with the requirements, which apply to mammographic facilities.
Maximum line current means the root-mean-square current in the supply line of an x-ray machine operating at its maximum rating.
Mobile x-ray equipment (See x-ray equipment.)
Mobile van means an x-ray facility housed within a vehicle, which facility is moved, or capable of being moved to different locations for the purpose of performing x-ray examinations.
PBL (positive beam limitation) means the automatic or semi-automatic adjustment of an x-ray beam to the size of the selected image receptor, whereby exposures cannot be made without such adjustment.
Peak tube potential means the maximum value of the potential difference across the x-ray tube during an exposure.
Phantom means a volume of material behaving in a manner similar to tissue with respect to the attenuation and scattering of radiation.
Phototimer means a method for controlling radiation exposures to image receptors by measuring the amount of radiation which reaches a radiation monitoring device(s). The radiation monitoring device(s) is part of an electronic circuit, which controls the duration of time the tube is activated (See "Automatic exposure control").
PID (See position indicating device.)
Portable C-arm x-ray system means an x-ray system in which the image receptor and x-ray tube housing assembly are connected by a common mechanical support system in order to maintain a desired spatial relationship.
Portable x-ray equipment(See x-ray equipment.)
Position indicating device means a device on dental x-ray equipment used to indicate the beam position and to establish a definite source-surface (skew) distance. It may or may not incorporate or serve as a beam-limiting device.
Primary dose monitoring system means a system that will monitor the useful beam during irradiation and which will terminate irradiation when a pre-selected number of dose monitor units have been acquired.
Primary protective barrier (See Protective barrier.)
Protective apron means an apron made of radiation absorbing materials used to reduce radiation exposure.
Protective barrier means a barrier of radiation absorbing material(s) used to reduce radiation exposure. The types of protective barriers are as follows:
Protective glove means a glove made of radiation absorbing materials used to reduce radiation exposure.
Quality assurance program (QA) means a program, including quality control, which program extends to administrative, educational, and preventive maintenance methods. For purposes of these rules, a QA program is directed at radiographic facilities and includes a continuing evaluation of the adequacy and effectiveness of the overall imaging program.
Quality control (QC) means a series of distinct technical procedures with the aim to provide high quality images while emitting as low a dose as necessary. QC includes, but is not limited to, the frequent evaluations of film processing, cassettes and intensifying screens, the film and the x-ray equipment.
Radiation therapy simulation system means a radiographic or fluoroscopic x-ray system intended for localizing the volume to be exposed during radiation therapy and confirming the position and size of the therapeutic irradiation field.
Radiographmeans an image receptor on which the image is created directly or indirectly by an x-ray pattern and results in a permanent record.
Radiographic imaging system means any system whereby a permanent or temporary image is recorded on an image receptor by the action of ionizing radiation.
Rating means the operating limits as specified by the component manufacturer.
Recording means producing a permanent form of an image resulting from x-ray photons.
Response time means the time required for an instrument system to reach 90 percent of its final reading when the radiation-sensitive volume of the instrument system is exposed to a step change in radiation flux from zero sufficient to provide a steady state midscale reading.
Scattered radiation means radiation that, during passage through matter, has been deviated in direction (See direct scattered radiation).
Secondary dose monitoring system means a system that will terminate irradiation in the event of failure of the primary system.
Secondary protective barrier (See Protective barrier.)
Shutter means a device attached to the tube housing assembly which can intercept the entire cross sectional area of the useful beam and which has a lead equivalency not less than that of the tube housing assembly.
SID (See "Source-image receptor distance").
Source means the focal spot of the x-ray tube.
Source-image receptor distance means the distance from the source to the center of the input surface of the image receptor.
Spot check means a procedure that is performed to assure that a previous calibration, continues to be valid.
Spot film means a radiograph that is made during a fluoroscopic examination to permanently record conditions, which exist during that fluoroscopic procedure.
Spot-film device means a device intended to transport and/or position a radiographic image receptor between the x-ray source and fluoroscopic image receptor. It includes a device intended to hold a cassette over the input end of an image intensifier for the purpose of making a radiograph.
SSD means the distance between the source and the skin entrance plane of the patient.
Stationary x-ray equipment (See "x-ray equipment.)
Stray radiation means the sum of leakage and scattered radiation.
Technique factors means the conditions of operation. They are specified as follows:
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.
Traceable to a national standard means that a quantity or a measurement has been compared to a national standard directly or indirectly through one or more intermediate steps and that all comparisons have been documented.
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.
Tube rating chart means the set of curves that specify the rated limits of operation of the tube in terms of the technique factors.
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 system to produce radiation.
Variable-aperture beam-limiting device means a beam-limiting device, which has capacity for stepless adjustment of the x-ray field size at a given SID.
Visible area means that portion of the input surface of the image receptor over which incident x-ray photons are producing a visible image.
Wedge filter means an added filter effecting continuous progressive attenuation on all or part of the useful beam.
X-ray exposure control means a device, switch, button or other similar means by which an operator initiates and/or terminates the radiation exposure. The x-ray exposure control may include such associated equipment as timers and back-up timers.
X-ray equipment means an x-ray system, subsystem, or component thereof. Types of x-ray equipment are as follows:
Mobile x-ray equipment means x-ray equipment mounted on a permanent base with wheels and/or casters for moving while completely assembled.
Portable x-ray equipment means x-ray equipment designed to be hand-carried.
Stationary x-ray equipment means x-ray equipment which is installed in a fixed location.
X-ray field means that area of the intersection of the useful beam and any one of the set of planes parallel to and including the plane of the image receptor, whose perimeter is the locus of points at which the exposure rate is one-fourth of the maximum in the intersection.
X-ray high-voltage generator means a device that transforms electrical energy from the potential supplied by the x-ray control to the tube operating potential. The device may also include means for transforming alternating current to direct current, filament transformers for the x-ray tube(s), high-voltage switches, electrical protective devices, and other appropriate elements.
X-ray system means an assemblage of components for the controlled production of x-rays. It includes minimally an x-ray high-voltage generator, an x-ray control, a tube housing assembly, a beam-limiting device, and the necessary supporting structures. Additional components, which function with the system, are considered integral parts of the system.
X-ray tube means any electron tube that is designed to be used primarily for the production of x-rays.
1 The nominal chemical composition of type 1100 aluminum alloy is 99.00 percent minimum aluminum, 0.12 percent copper.
10-144 C.M.R. ch. 220, § F-2