Definitions

As used in this chapter, the following definitions apply: 1. "Absorbed dose" means the energy imparted by ionizing radiation per unit mass of irradiated material. The units of absorbed dose are the gray (Gy) and the rad. 2. "Accessible surface" means surface of equipment or of an equipment part that can be touched by persons without the use of a tool. 3. "Added filtration" means any filtration which is in addition to the inherent filtration. 4. "Air kerma" means kerma in air (see "kerma"). 5. "Air kerma rate" means the air kerma per unit of time. 6. "AKR" means air kerma rate. 7. "Allied health" means occupations of medical personnel who are not physicians and are qualified by special training to undergo cross-training into x-ray as a limited x-ray machine operator. Refer to appendix G for qualifying professions. 8. "Aluminum equivalent" means the thickness of type 1100 aluminum alloy affording the same attenuation, under specified conditions, as the material in question. (The nominal chemical composition of type 1100 aluminum alloy is ninety-nine percent minimum aluminum, twelve-hundredths percent copper.) 9. "As low as reasonably achievable" (ALARA) means making every reasonable effort to maintain the exposures to radiation as far below dose limits as is practicable. 10. "Assembler" means 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 the employee or agent who assembles components into an x-ray system that is subsequently used to provide professional or commercial services. 11. "Attenuation block" means a block or stack, having dimensions twenty centimeters by twenty centimeters by three and eight-tenths centimeters, of type 1100 aluminum alloy or other materials having equivalent attenuation. 12. "Automatic exposure control" means a device which automatically controls one or more technique factors in order to obtain at a preselected location or locations a required quantity of radiation (includes devices such as phototimers and ion chambers). 13. "Barrier" (see "protective barrier"). 14. "Beam axis" means the axis of rotation of the beam-limiting device from the source through the centers of the x-ray fields. 15. "Beam-limiting device" means a device which provides a means to restrict the dimensions of the useful beam. 16. "Biennium" means a two-year cycle. 17. "Board certified" means an individual who has completed an accredited school of medical radiography or chiropractic radiography and has passed a national registry examination. 18. "Board eligible" means an individual who has obtained eligibility to take a national registry examination in radiologic technology or chiropractic radiologic technology. 19. "Bone densitometry system" means a medical device which uses electronically produced ionizing radiation to determine the density of bone structures of human patients. 20. "Calibration" means the determination of: a. The response or reading of an instrument relative to a series of known radiation values over the range of the instrument; or b. The strength of a source of radiation relative to a standard. 21. "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. 22. "Cephalometric device" means a device intended for the radiographic visualization and measurement of the dimensions of the human head. 23. "Certified components" means components of x-ray systems which are subject to regulations promulgated under the Radiation Control for Health and Safety Act of 1968 [Pub. L. 90-602]. 24. "Certified system" means any x-ray system which has one or more certified component or components. 25. "CEU" (see "continuing education unit"). 26. "CFR" means Code of Federal Regulations. 27. "Changeable filters" means any filter, exclusive of inherent filtration, which can be removed from the useful beam through any electronic, mechanical, or physical process. 28. "Coefficient of variation" or "C" means the ratio of the standard deviation to the mean value of a set of observations. It is estimated using the following equation: where: s = Estimated standard deviation of the population. = Mean value of observations in sample. Xi = ith observation in sample. n = Number of observations in sample. 29. "Computed tomography" means the production of a tomogram by the acquisition and computer processing of x-ray transmission data. 30. "Contact therapy system" means an x-ray system used for therapy with the x-ray tube port placed in contact with or within five centimeters of the surface being treated. 31. "Continuing education" means a planned, organized, and administered learning activity that enhances the knowledge and underlying skills of an x-ray operator. 32. "Continuing education unit" means a unit of measure for continuing education. One continuing education unit is equal to one contact hour. 33. "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. 34. "Cooling curve" means the graphical relationship between heat units stored and cooling time. 35. "CT" (see "computed tomography"). 36. "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. 37. "Department" means the department of environmental quality. 38. "Detector" (see "radiation detector"). 39. "Diagnostic source assembly" means the tube housing assembly with a beam-limiting device attached. 40. "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. 41. "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. 42. "Direct scattered radiation" means that scattered radiation which has been deviated in direction only by materials irradiated by the useful beam (see "scattered radiation"). 43. "Direct supervision" requires direct observation and observer must be in the room during the time the x-ray image is obtained. 44. "Dose" is a generic term that means absorbed dose, dose equivalent, effective dose equivalent, committed dose equivalent, committed effective dose equivalent, total organ dose equivalent, or total effective dose equivalent. For purposes of these rules, "radiation dose" is an equivalent term. 45. "Dose limits" means the permissible upper bounds of radiation of doses established in accordance with these rules. 46. "Entrance exposure rate" means the radiation exposure free in air per unit time at the point where the center of the useful beam enters the patient. 47. "Equipment" (see "x-ray equipment"). 48. "Exposure" means being exposed to ionizing radiation. 49. "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. 50. "Filter" means material placed in the useful beam to absorb preferentially selected radiations. 51. "Fluoroscopic imaging assembly" means a subsystem in which x-ray photons produce a visible image. It includes the image receptor or receptors 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. 52. "Focal spot" means the location projected on the anode of the x-ray tube bombarded by the electrons accelerated from the cathode and from which the useful beam originates. 53. "General diagnostic operator" means an individual who is American registry of radiologic technologists (ARRT) or American chiropractic registry of radiologic technologists (ACRRT) board certified, is or has been board eligible, or has the equivalent educational and clinical training and received specific authorization from the department. 54. "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. 55. "Gonad shield" means a protective barrier for the testes or ovaries. 56. "Gray" (Gy) means the SI unit of absorbed dose. One gray is equal to an absorbed does of one joule per kilogram or 100 rad. 57. "Half-value layer" means the thickness of 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. 58. "Hand-held dental x-ray equipment" (see "x-ray equipment"). 59. "Healing arts" means diagnostic or healing treatment of human and animal maladies, including the following which are duly licensed by the state of North Dakota for the lawful practice of medicine and its associated specialties, dentistry, veterinary medicine, osteopathy, chiropractic, and podiatry. 60. "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. 61. "Heat unit" means a unit of energy equal to the product of the peak kilovoltage, milliamperes, and seconds, i.e., kVp x mA x seconds. 62. "HVL" (see "half-value layer"). 63. "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. 64. "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. 65. "Image receptor support" means, for mammographic systems, that part of the system designed to support the image receptor during a mammographic examination. 66. "Inherent filtration" means the filtration of the useful beam provided by the permanently installed components of the tube housing assembly. 67. "Inspection" means an official examination or observation, including tests, surveys, and monitoring to determine compliance with rules, regulations, requirements, and conditions of the department. 68. "Irradiation" means the exposure of matter to ionizing radiation. 69. "Kerma" means the sum of the initial kinetic energies of all the charged ionizing particles liberated by uncharged ionizing particles per unit mass of a specified material. The SI unit of measure is joule per kilogram, or gray (Gy). 70. "Kilovolts peak" (see "peak tube potential"). 71. "kV" means kilovolts. 72. "kVp" (see "peak tube potential"). 73. "kWs" means kilowatt second. It is equivalent to 103 kV . mA . s, i.e., kWs = (X)kV x (Y)mA x (Z)s x 10-3 = XYZ 103 74. "Lead equivalent" means the thickness of lead affording the same attenuation, under specified conditions, as the material in question. 75. "Leakage radiation" means radiation emanating from the diagnostic or therapeutic source assembly except for: a. The useful beam; and b. Radiation produced when the exposure switch or timer is not activated. 76. "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: a. For diagnostic source assemblies intended for capacitor energy storage equipment, the maximum-rated peak tube potential and the maximum-rated number of exposures in an hour for operation at the maximum-rated peak tube potential with the quantity of charge per exposure being ten millicoulombs, i.e., ten milliampere seconds, or the minimum obtainable from the unit, whichever is larger. b. For diagnostic source assemblies intended for field emission equipment rated for pulsed operation, the maximum-rated peak tube potential and the maximum-rated number of x-ray pulses in an hour for operation at the maximum-rated peak tube potential. c. For all other diagnostic or therapeutic source assemblies, the maximum-rated peak tube potential and the maximum-rated continuous tube current for the maximum-rated peak tube potential. 77. "Light field" means the area illuminated by light, simulating the radiation field. 78. "Limited x-ray machine operator" means any individual who has completed the necessary didactic and clinical training required to perform limited scope x-ray procedures. 79. "Linear attenuation coefficient" or "u" means the quotient of dN/N divided by dl when dN/N is the fraction of uncharged ionizing radiation that experience interactions in traversing a distance dl in a specified material. 80. "mA" means milliampere. 81. "mAs" means milliampere second. 82. "Milliampere" as used in this chapter applies to x-ray tube current. 83. "Milliampere second" as used in this chapter is the product of the tube current and x-ray exposure time measured in seconds. 84. "Mobile x-ray equipment" (see "x-ray equipment"). 85. "Monitoring" means the measurement of radiation and the use of the measured results to evaluate potential exposures and doses. 86. "Patient" means an individual or animal subjected to radiation for the purposes of diagnosis or treatment. 87. "PBL" has the same meaning as "positive beam limitation". 88. "Peak tube potential" means the maximum value of the potential difference across the x-ray tube during an exposure. 89. "Phantom" means a volume of material behaving in a manner similar to tissue with respect to the absorption and scattering of the ionizing radiation in question. 90. "Phototimer" means a method for controlling radiation exposures to image receptors by the amount of radiation which reaches a radiation monitoring device. The radiation monitoring device is part of an electronic circuit which controls the duration of time the tube is activated (see "automatic exposure control"). 91. "Physician" means a medical doctor, doctor of osteopathy, doctor of podiatry, or chiropractor licensed by a state or territory of the United States, the District of Columbia, or the Commonwealth of Puerto Rico. 92. "Portable x-ray equipment" (see "x-ray equipment"). 93. "Position indicating device" means a device on dental x-ray equipment used to indicate the beam position and to establish a definite source surface (skin) distance. It may or may not incorporate or serve as a beam-limiting device. 94. "Positive beam limitation" means the automatic or semiautomatic adjustment of an x-ray beam to the size of the selected image receptor, whereby exposures cannot be made without such adjustment. 95. "Primary dose monitoring system" means 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 delivered. 96. "Primary protective barrier" (see "protective barrier"). 97. "Protective apron" means an apron made of radiation attenuating materials used to reduce radiation exposure. 98. "Protective barrier" means a barrier of radiation absorbing material or materials used to reduce radiation exposure. The types of protective barriers are as follows: a. "Primary protective barrier" means the material, excluding filters, placed in the useful beam; and b. "Secondary protective barrier" means the material which attenuates stray radiation. 99. "Protective glove" means a glove made of radiation absorbing materials used to reduce radiation exposure. 100. "Qualified expert" means an individual having the knowledge, training, and experience 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, "qualified expert" means an individual having, in addition to the above qualifications, training and experience in the clinical applications of radiation physics to radiation therapy, for example, individuals certified in therapeutic radiological physics or x-ray and radium physics by the American board of radiology, or those having equivalent qualifications. 101. "Radiation" means x-rays and gamma rays, which are capable of producing ions. For purposes of this chapter, ionizing radiation is an equivalent term. 102. "Radiation detector" means a device which in the presence of radiation provides a signal or other indication suitable for use in measuring one or more quantities of incident radiation. 103. "Radiation exposure" means the quotient of dQ by dm where "dQ" is the absolute value of the total charge of the ions of one sign produced in air when all the electrons (negatrons and positrons) liberated by photons in a volume element of air having mass "dm" are completely stopped in air. The SI unit of radiation exposure is the coulomb per kilogram (C/kg). (See section 33.1-10-01-14 units of exposure, dose, and activity for the special unit equivalent "roentgen" (R).) 104. "Radiation exposure rate" means the radiation exposure per unit of time, such as R/min, mR/h, etc. 105. "Radiation machine" means any device capable of producing radiation except those devices with radioactive material as the only source of radiation. 106. "Radiation therapy simulation system" means a radiographic, fluoroscopic, or computed tomography 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. 107. "Radiograph" means an image receptor on which the image is created directly or indirectly by an x-ray pattern and results in a permanent record. 108. "Radiographic imaging system" means any system whereby a permanent or temporary image is recorded on an image receptor by the action of ionizing radiation. 109. "Radiological physicist" means an individual who: a. Is certified by the American board of radiology in therapeutic radiological physics, radiological physics, or x-ray and gamma-ray physics; b. Has a bachelor's degree in one of the physical sciences or engineering and three year's full-time experience working in therapeutic or diagnostic radiological physics under the direction of a physicist certified by the American board of radiology. The work duties must include duties involving the calibration and spot checks of a medical accelerator or a sealed source teletherapy unit; or c. Has a master's or a doctor's degree in physics, biophysics, radiological physics, health physics, or engineering; has had one year's full-time training in therapeutic or diagnostic radiological physics; and has had one year's full-time work experience in a radiotherapy facility where the individual's duties involve calibration and spot checks of a medical accelerator or a sealed source teletherapy unit. 110. "Rating" means the operating limits as specified by the component manufacturer. 111. "Recording" means producing a permanent form of an image resulting from x-ray photons. 112. "Registrant" means any person, group, or facility who is registered with the department and is legally obligated to register with the department pursuant to North Dakota Century Code chapter 23.1-02. 113. "Roentgen" or "(R)" means the special unit of exposure. One roentgen equals two hundred fifty-eight millionth of a coulomb per kilograph of air. 114. "Scattered radiation" means radiation that, during passage through matter, has been deviated in direction (see "direct scattered radiation"). 115. "Secondary dose monitoring system" means a system which will terminate irradiation in the event of failure of the primary dose monitoring system. 116. "Secondary protective barrier" (see "protective barrier"). 117. "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. 118. "SI" means the abbreviation for the international system of units. 119. "SID" has the same meaning as "source-image receptor distance". 120. "Source" means the location or material, or both, from which the radiation emanates. 121. "Source-image receptor distance" means the distance from the source to the center of the input surface of the image receptor. 122. "Spot check" means a procedure which is performed to assure that a previous calibration continues to be valid. 123. "Spot film" means a radiograph which is made during a fluoroscopic examination to permanently record conditions which exist during that fluoroscopic procedure. 124. "Spot-film device" means a device intended to transport 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. 125. "Stationary x-ray equipment" (see "x-ray equipment"). 126. "Stray radiation" means the sum of leakage and scattered radiation. 127. "Survey" means an evaluation of the radiological conditions which may include tests, physical examinations, and measurements of levels of radiation. 128. "Technique factors" means the conditions of operation. They are specified as follows: a. For capacitor energy storage equipment, peak tube potential in kilovolts and quantity of charge in milliampere second. b. For field emission equipment rated for pulsed operation, peak tube potential in kilovolts and number of x-ray pulses. c. For CT x-ray systems designed for pulsed operation, peak tube potential in kilovolts, scan time in seconds, and either tube current in milliampere, x-ray pulse width in seconds, and the number of x-ray pulses per scan, or the product of tube current, x-ray pulse width, and the number of x-ray pulses in milliampere second. d. For CT x-ray systems not designed for pulsed operation, peak tube potential in kilovolts, and either tube current in milliampere and scan time in seconds, or the product of tube current and exposure time in milliampere second and the scan time when the scan time and exposure time are equivalent. e. For all other equipment, peak tube potential in kilovolt and either tube current in milliampere and exposure time in seconds, or the product of tube current and exposure time in milliampere second. 129. "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. 130. "Tomogram" means the depiction of x-ray attenuation properties of a section through the body. 131. "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. 132. "Tube" means an x-ray tube, unless otherwise specified. 133. "Tube housing assembly" means the tube housing with tube installed. It includes high-voltage or filament transformers, or both, and other appropriate elements when such are contained within the tube housing. 134. "Tube rating chart" means the set of curves which specify the rated limits of operation of the tube in terms of the technique factors. 135. "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. 136. "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 source-image receptor distance. 137. "Visible area" means that portion of the input surface of the image receptor over which incident x-ray photons are producing a visible image. 138. "Wedge filter" means an added filter effecting continuous progressive attenuation on all or part of the useful beam. 139. "Whole body" means for purposes of external exposure, head, trunk including male gonads, arms above the elbows, or legs below the knees. 140. "X-ray exposure control" means a device, switch, button, or other similar means by which the operator initiates or terminates, or both, the radiation exposure. It may include equipment such as timers, phototimers, automatic brightness stabilizers, and similar devices. 141. "X-ray equipment" means an x-ray system, subsystem, or component thereof. Types of x-ray equipment are as follows: a. "Hand-held dental x-ray equipment" means any dental x-ray equipment which is designated to be physically held during x-ray exposure. b. "Mobile x-ray equipment" means x-ray equipment mounted on a permanent base with wheels or casters for moving while completely assembled. c. "Portable x-ray equipment" means x-ray equipment designed to be hand-carried. d. "Stationary x-ray equipment" means x-ray equipment which is installed in a fixed location. 142. "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 radiation exposure rate is one-fourth of the maximum in the intersection. 143. "X-ray high-voltage generator" means a device which 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, high-voltage switches, electrical protective devices, and other appropriate elements. 144. "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. 145. "X-ray tube" means any electron tube which is designed for the conversion of electrical energy into x-ray energy.