HAR §11-45-118. Fluoroscopic x-ray systems

(a) All fluoroscopic x-ray systems shall be image intensified or used in conjunction with a digital imaging system. (b) The useful beam shall be limited as follows: (1) Primary barrier: (A) The fluoroscopic imaging assembly shall be provided with a primary protective barrier which intercepts the entire cross section of the useful beam at any source-image receptor distance; and (B) The x-ray tube used for fluoroscopy shall not produce x-rays unless the barrier is in position to intercept the entire useful beam. (2) Fluoroscopic beam limitation: (A) For certified fluoroscopic systems with or without a spot film device, neither the length nor the width of the x-ray field in the plane of the image receptor shall exceed that of the visible area of the image receptor by more than three percent of the source-image receptor distance. The sum of the excess length and the excess width shall be no greater than four percent of the source-image receptor distance. (B) For uncertified fluoroscopic systems with a spot film device, the x-ray beam with the shutters fully opened (during fluoroscopy or spot filming) shall be no larger than the largest spot film size for which the device is designed. Measurements shall be made at the minimum §11-45-118 45-94 source-image receptor distance available but at no less than twenty centimeters table top to the film plane distance. (C) For uncertified fluoroscopic systems without a spot film device, the requirements of subparagraph (A) apply. (D) Other requirements for fluoroscopic beam limitation: (i) Means shall be provided to permit further limitation of the field. Beam-limiting devices manufactured after May 22, 1979, and incorporated in equipment with a variable source-image receptor distance and/or a visible area of greater than three hundred square centimeters shall be provided with means for stepless adjustment of the x-ray field; (ii) All equipment with a fixed source-image receptor distance and a visible area of three hundred square centimeters or less shall be provided with either stepless adjustment of the x-ray field or with means to further limit the x-ray field size at the plane of the image receptor to one hundred twenty-five square centimeters or less; (iii) If provided, stepless adjustment shall, at the greatest source-image receptor distance, provide continuous field sizes from the maximum attainable to a field size of five centimeters by five centimeters or less; (iv) For equipment manufactured after February 25, 1978, when the angle between the image receptor and beam axis is variable, means shall be provided to indicate when the axis of the x-ray beam is perpendicular to the plane of the image receptor; and (v) For rectangular x-ray fields used with circular image reception, the error in alignment shall be determined along the length and width dimensions of the x-ray field which pass through the center of the visible area of the image receptor. (E) Spot-film devices which are certified components shall meet the following additional requirements: (i) Means shall be provided between the source and the patient for adjustment of the x- ray field size in the plane of the film to the size of that portion of the film which has been selected on the spot film selector. Such adjustment shall be automatically accomplished except when the §11-45-118 45-95 x-ray field size in the plane of the film is smaller than that of the selected portion of the film. For spot film devices manufactured after June 21, 1979, if the x-ray field size is less than the size of the selected portion of the film, the means for adjustment of the field size shall be only at the operator's option; (ii) It shall be possible to adjust the x-ray field size in the plane of the film to a size smaller than the selected portion of the film. The minimum field size at the greatest source-image receptor distance shall be equal to, or less than, five centimeters by five centimeters; (iii) The center of the x-ray field in the plane of the film shall be aligned with the center of the selected portion of the film to within two percent of the source-image receptor distance; and (iv) On spot-film devices manufactured after February 25, 1978, if the angle between the plane of the image receptor and beam axis is variable, means shall be provided to indicate when the axis of the x-ray beam is perpendicular to the plane of the image receptor, and compliance shall be determined with the beam axis indicated to be perpendicular to the plane of the image receptor. (F) If a means exists to override any of the automatic x-ray field size adjustments required in subparagraph (E), that means: (i) Shall be designed for use only in the event of system failure; (ii) Shall incorporate a signal visible at the fluoroscopist's position which shall indicate whenever the automatic field size adjustment is overridden; and (iii) Shall be clearly and durably labeled as follows: FOR X-RAY FIELD LIMITATION SYSTEM FAILURE (c) X-ray production in the fluoroscopic mode shall be controlled by a device which requires continuous pressure by the fluoroscopist for the entire time of any exposure. When recording serial fluoroscopic images, the fluoroscopist shall be able to terminate the x-ray exposure(s) at any time, but means may be provided to permit completion of any single exposure of the series in process. (d) Entrance exposure rate allowable limits: (1) Fluoroscopic equipment which is provided with §11-45-118 45-96 automatic exposure rate control shall not be operable at any combination of tube potential and current which shall result in an exposure rate in excess of ten roentgens (2.58 millicoulombs per kilogram) per minute at the point where the center of the useful beam enters the patient, except: (A) During recording of fluoroscopic images, or (B) When an optional high level control is provided. When so provided, the equipment shall not be operable at any combination of tube potential and current which shall result in an exposure rate in excess of five roentgens (1.29 millicoulombs per kilogram) per minute at the point where the center of the useful beam enters the patient unless the high level control is activated. Special means of activation of high level controls shall be required. The high level control shall only be operable when continuous manual activation is provided by the operator. A continuous signal audible to the fluoroscopist shall indicate that high level control is being employed. (2) Fluoroscopic equipment which is not provided with automatic exposure rate control (manual mode) shall not be operable at any combination of tube potential and current which shall result in an exposure rate in excess of five roentgens (1.29 millicoulombs per kilogram) per minute at the point where the center of the useful beam enters the patient, except: (A) During recording of fluoroscopic images, or (B) When an optional high level control is activated. Special means of activation of high level controls shall be required. The high level control shall only be operable when continuous manual activation is provided by the operator. A continuous signal audible to the fluoroscopist shall indicate that the high level control is being employed. (3) Fluoroscopic equipment which is provided with both automatic exposure rate control mode and a manual mode shall not be operable at any combination of tube potential and current which shall result in an exposure rate in excess of ten roentgens (2.58 millicoulombs per kilogram) per minute in either mode at the point where the center of the useful beam enters the patient, except: (A) During recording of fluoroscopic images; or (B) When the mode or modes have an optional high level control, in which case that mode or modes shall not be operable at any combination of tube potential and current which shall result in an exposure rate in excess of five roentgens (1.29 millicoulombs per kilogram) per minute at the point where the center of the useful beam enters §11-45-118 45-97 the patient, unless the high level control is activated. Special means of activation of high level controls shall be required. The high level control shall only be operable when continuous manual activation is provided by the operator. A continuous signal audible to the fluoroscopist shall indicate that the high level control is being employed. (4) Any fluoroscopic equipment manufactured after May 19, 1995 which can exceed five roentgens (1.29 millicoulombs per kilogram) per minute shall be equipped with an automatic exposure rate control. All entrance exposure rate limits shall be ten roentgens (2.58 millicoulombs per kilogram) per minute with an upper limit of twenty roentgens (5.16 millicoulombs per kilogram) per minute when high level control is activated. (5) Compliance with the requirements of this subsection shall be determined as follows: (A) If the source is below the x-ray table, the exposure rate shall be measured one centimeter above the tabletop or cradle. (B) If the source is above the x-ray table, the exposure rate shall be measured at thirty centimeters above the tabletop with the end of the beam-limiting device or spacer positioned as closely as possible to the point of measurement. (C) For a C-arm type of fluoroscope, the exposure rate shall be measured thirty centimeters from the input surface of the fluoroscopic imaging assembly, with the source positioned at any available SID, provided that the end of the beam-limiting device or spacer is no closer than thirty centimeters from the input surface of the fluoroscopic imaging assembly. (D) For a lateral type fluoroscope, the exposure rate shall be measured at a point fifteen centimeters from the centerline of the x-ray table and in the direction of the x-ray source with the end of the beam-limiting device or spacer positioned as closely as possible to the point of measurement. If the tabletop is movable, it shall be positioned as closely as possible to the lateral x-ray source, with the end of the beam-limiting device or spacer no closer than fifteen centimeters to the centerline of the x-ray table. (6) Periodic measurement of entrance exposure rate shall be performed as follows: (A) Such measurements shall be made by, or under the supervision of, a qualified medical physicist at least annually or after any maintenance of the system which might affect the exposure rate. (B) Results of these measurements shall be posted §11-45-118 45-98 where any fluoroscopist may have ready access to such results while using the fluoroscope and in the record required in section 11-45-116 (a)(13)(C). The measurement results shall be stated in roentgens (coulombs per kilogram) per minute and include the technique factors used in determining such results. The name of the individual performing the measurements and the date the measurements were performed shall be included in the results. (C) Conditions of periodic measurement of maximum entrance exposure rate are as follows: (i) The measurement shall be made under the conditions that satisfy the requirements of this subsection; (ii) The kilovolts peak and milliamperes shall be typical of clinical use of the x-ray system; (iii) The x-ray system(s) that incorporates automatic exposure rate control shall have an appropriate phantom placed in the useful beam to produce a milliamperage and/or kilovoltage typical of the use of the x-ray system; and (e) Barrier transmitted radiation rate limits: (1) The exposure rate due to transmission through the primary protective barrier with the attenuation block in the useful beam, combined with radiation from the image intensifier, if provided, shall not exceed two milliroentgens (0.516 microcoulombs per kilogram) per hour at ten centimeters from any accessible surface of the fluoroscopic imaging assembly beyond the plane of the image receptor for each roentgen per minute of entrance exposure rate. (2) Measuring compliance of barrier transmission. (A) The exposure rate due to transmission through the primary protective barrier combined with radiation from the image intensifier shall be determined by measurements averaged over an area of one hundred square centimeters with no linear dimension greater than twenty centimeters. (B) If the source is below the tabletop, the measurement shall be made with the input surface of the fluoroscopic imaging assembly positioned thirty centimeters above the tabletop. (C) If the source is above the tabletop and the source-image receptor distance is variable, the measurement shall be made with the end of the beam-limiting device or spacer as close to the tabletop as it can be placed, provided that it shall not be closer than thirty centimeters. (D) Movable grids and compression devices shall be removed from the useful beam during the measurement. §11-45-118 45-99 (f) During fluoroscopy and cinefluorography the tube potential and tube current shall be continuously indicated. (g) The source-to-skin distance shall not be less than: (1) Thirty-eight centimeters on stationary fluoroscopic systems manufactured on or after August 1, 1974,; (2) A distance of 35.5 centimeters on stationary fluoroscopic systems manufactured before August 1, 1974; (3) Thirty centimeters on all mobile and portable fluoroscopes; and (4) Twenty centimeters for all image-intensified fluoroscopes used for specific surgical application. (h) Fluoroscopic timer: (1) Means shall be provided to preset the cumulative on- time of the fluoroscopic x-ray tube. The maximum cumulative time of the timing device shall not exceed five minutes without resetting. (2) A signal audible to the fluoroscopist shall indicate the completion of any preset cumulative on-time. Such signal shall continue to sound while x-rays are produced until the timing device is reset. (i) Control of scattered radiation: (1) Fluoroscopic table designs when combined with procedures utilized shall be such that no unprotected part of any staff or ancillary individual's body shall be exposed to unattenuated scattered radiation which originates from under the table. The attenuation required shall be not less than 0.25 millimeter lead equivalent. (2) Equipment configuration when combined with procedures shall be such that no portion of any staff or ancillary individual's body, except the extremities, shall be exposed to the unattenuated scattered radiation emanating from above the tabletop unless that individual: (A) Is at least one hundred twenty centimeters from the center of the useful beam; or (B) The radiation has passed through not less than 0.25 millimeter lead equivalent material including, but not limited to, drapes, bucky- slot cover panel, or self-supporting curtains, in addition to any lead equivalency provided by the protective apron. (j) Fluoroscopic systems equipped with spot film (radiographic) mode shall meet the exposure reproducibility requirements of section 11-45-119 when operating in the spot film mode. (k) Radiation therapy simulation systems shall be exempt from all the requirements of subsections (b), (d), (e), and (h) provided that: (1) Such systems are designed and used in such a manner that no individual other than the patient is in the x- ray room during periods of time when the system is producing x-rays; and §11-45-118 45-100 (2) Systems which do not meet the requirements of subsection (h) are provided with a means of indicating the cumulative time that an individual patient has been exposed to x-rays. Procedures shall require in such cases that the timer be reset between examinations. (l) All newly-assembled, installed, or reassembled fluoroscopic x-ray systems shall be evaluated by, or under the supervision of, a qualified medical physicist before use on human patients unless otherwise authorized by the director. [Eff 11/12/99] (Auth: HRS §§321-10, 321-11, 321-71) (Imp: HRS §§321-1, 321-11(21), 321-71) §11-45-119 Radiographic systems other than fluoroscopic, dental intraoral, or computed tomography systems. (a) The useful beam shall be limited to the area of clinical interest. This shall be deemed to have been met if a positive beam limiting device has been properly used or if evidence of collimation is shown on at least three sides or three corners of the film, (e.g., projections from the shutters of the collimator, cone cutting at the corners, or borders at the film's edge). (1) General purpose stationary, mobile, and portable x-ray systems, including veterinary systems installed after the effective date of this chapter: (A) Means shall be provided for independent stepless adjustment of the size of the x-ray field. Each dimension of the minimum field size at an source-image receptor distance of one hundred centimeters shall be equal to or less than five centimeters. (B) A method shall be provided for visually defining the perimeter of the x-ray field. The total misalignment of the edges of the visually defined field with the respective edges of the x-ray field along either the length or width of the visually defined field shall not exceed two percent of the distance from the source to the center of the visually defined field when the surface upon which it appears is perpendicular to the axis of the x-ray beam. (2) In addition to the requirements of paragraph (1), all stationary general purpose x-ray systems shall meet the following requirements: (A) A method shall be provided to indicate when the axis of the x-ray beam is perpendicular to the plane of the image receptor, to align the center of the x-ray field with respect to the center of the image receptor to within two percent of the source-image receptor distance, and to indicate the source-image receptor distance to within two percent; (B) The beam-limiting device shall indicate numerically the field size in the plane of the §11-45-119 45-101 image receptor to which it is adjusted; and (C) Indication of field size dimensions and source- image receptor distances shall be specified in inches and/or centimeters, and shall be such that aperture adjustments result in x-ray field dimensions in the plane of the image receptor which correspond to those indicated by the beam- limiting device to within two percent of the source-image receptor distances when the beam axis is indicated to be perpendicular to the plane of the image receptor. (3) Radiographic equipment designed for only one image receptor size at a fixed source-image receptor distances shall be provided with means to limit the field at the plane of the image receptor to dimensions no greater than those of the image receptor, and to align the center of the x-ray field with the center of the image receptor to within two percent of the source-image receptor distance, or shall be provided with means to both size and align the x-ray field such that the x-ray field at the plane of the image receptor does not extend beyond any edge of the image receptor. (4) Radiographic systems other than those designated in paragraphs (1), (2), and (3), and veterinary systems installed before the effective date of this chapter: (A) Means shall be provided to limit the x-ray field in the plane of the image receptor so that such field does not exceed each dimension of the image receptor by more than two percent of the source-image receptor distance when the axis of the x-ray beam is perpendicular to the plane of the image receptor. (B) Means shall be provided to align the center of the x-ray field with the center of the image receptor to within two percent of the source- image receptor distance, or means shall be provided to both size and align the x-ray field such that the x-ray field at the plane of the image receptor does not extend beyond any edge of the image receptor. Compliance shall be determined with the axis of the x-ray beam perpendicular to the plane of the image receptor. (C) The requirements of subparagraphs (A) and (B) may be met with a system that meets the requirements for a general purpose x-ray system as specified in paragraph (1) or, when alignment means are also provided, may be met with either: (i) An assortment of removable, fixed-aperture, beam-limiting devices sufficient to meet the requirement for each combination of image receptor size and source-image receptor distance for §11-45-119 45-102 which the unit is designed with each such device having clear and permanent markings to indicate the image receptor size and source-image receptor distance for which it is designed; or (ii) A beam-limiting device having multiple fixed apertures sufficient to meet the requirement for each combination of image receptor size and source-image receptor distance for which the unit is designed. Permanent, clearly legible markings shall indicate the image receptor size and source-image receptor distance for which each aperture is designed and shall indicate which aperture is in position for use. (b) Radiation exposure control: (1) Means shall be provided to initiate the radiation exposure by a deliberate action on the part of the operator, such as the depression of a switch. Radiation exposure shall not be initiated without such an action. In addition, it shall not be possible to initiate an exposure when the timer is set to a "zero" or "off" position if either position is provided. (2) Means shall be provided to terminate the exposure at a preset time interval, preset product of current and time, a preset number of pulses, or a preset radiation exposure to the image receptor. Termination of an exposure shall cause automatic resetting of the timer to its initial setting or to "zero." (A) When manual exposure control is provided, an x- ray exposure control shall be incorporated into each x-ray system such that an exposure can be terminated by the operator at any time ("deadman" switch) except for: (i) Exposure of one-half second or less; and (ii) During serial radiography when means shall be provided to permit completion of any single exposure of the series in progress. (B) When an automatic exposure control is provided: (i) Indication shall be made on the control panel when this mode of operation is selected; (ii) If the x-ray tube potential is equal to or greater than fifty-one kilovolts peak, the minimum exposure time for field emission equipment rated for pulsed operation shall be equal to or less than a time interval equivalent to two pulses; (iii) The minimum exposure time for all equipment other than that specified in clause (ii) shall be equal to or less than one-sixtieth second or a time interval required to deliver five milliamperes- §11-45-119 45-103 seconds, whichever is greater; (iv) Either the product of peak x-ray tube potential, current, and exposure time shall be limited to not more than sixty kilowatt-seconds per exposure, or the product of x-ray tube current and exposure time shall be limited to not more than six hundred milliamperes-seconds per exposure, except that when the x-ray tube potential is less than fifty-one kilovolts peak, the product of x-ray tube current and exposure time shall be limited to not more than two thousand milliamperes-seconds per exposure; and (v) A visible signal shall indicate when an exposure has been terminated at the limits required by clause (iv), and manual resetting shall be required before further automatically timed exposures can be made. (3) Means shall be provided for visual indication of x-ray production observable at or from the operator's protected position whenever x-rays are produced. In addition, a signal audible to the operator shall indicate that the exposure has terminated. (4) With a timer setting of 0.5 seconds or less, the difference between the maximum exposure time (Tmax) and the minimum exposure time (Tmin) shall be less than or equal to ten percent of the average exposure time (T), when four timer tests are performed: (Tmax - Tmin) < 0.1T (5) The x-ray exposure control shall be so placed that the operator can view the patient while making any exposure. (6) Operator protection, except veterinary systems: (A) Stationary x-ray systems shall be required to have the x-ray exposure control permanently mounted in a protected area so that the operator is required to remain in that protected area during the entire exposure. (B) Mobile and portable x-ray systems which are: (i) Used continuously for greater than one week in the same location, i.e., a room or suite shall be considered as stationary systems under subparagraph (A). (ii) Used for less than one week in the same location shall be provided with either a protective barrier at least 6.5 feet (two meters) high for operator protection during exposures, or means shall be provided to allow the operator to be at least twelve feet (3.7 meters) from the tube housing assembly during the exposure. §11-45-119 45-104 (7) Operators of all stationary, mobile or portable x-ray systems used for veterinary work shall be provided with a 6.5 foot (two meters) high protective barrier for operator protection during exposures, or a means to allow the operator to be at least twelve feet (3.7 meters) from the tube housing assembly during exposures, or a protective apron and protective gloves. (c) All mobile or portable radiographic systems shall be provided with means to limit the source-to-skin distance to equal to or greater than thirty centimeters, except for veterinary systems. (d) When all technique factors are held constant, including control panel selections associated with automatic exposure control systems, the coefficient of variation of exposure for both manual and automatic exposure control systems shall not exceed 0.05. This requirement shall be deemed to have been met if, when four exposures are made at identical technique factors, the difference between the maximum exposure (Emax) and the minimum exposure (Emin) shall be less than or equal to ten percent of the average exposure (E): (Emax - Emin) < 0.1E (e) Radiation from capacitor energy storage equipment in standby status: Radiation emitted from the x-ray tube when the exposure switch or timer is not activated shall not exceed a rate of two milliroentgens (0.516 microcoulombs per kilogram) per hour at five centimeters from any accessible surface of the diagnostic source assembly, with the beam-limiting device fully open. (f) Deviation of technique factors from indicated values shall not exceed the limits specified for that system by its manufacturer. In the absence of manufacturer's specifications, the deviation shall not exceed ten percent of the indicated value. (g) Linearity, uncertified x-ray systems only: The following requirements apply when the equipment is operated on a power supply as specified by the manufacturer for any fixed x-ray tube potential within the range of forty percent to one hundred percent of the maximum rated. (1) Equipment having independent selection of x-ray tube current: The average ratios of exposure to the indicated milliampere seconds product (mR/mAs (or C/kg/mAs)) obtained at any two tube current settings shall not differ by more than 0.10 times their sum: [X1 - X2] < 0.10(X1 + X2) where X1 and X2 are the average mR/mAs (or C/kg/mAs) values obtained at any two tube current settings. (2) Equipment having a combined x-ray tube current- exposure time product (mAs) selector, but not a separate tube current (mA) selector: The average ratios of exposure to the indicated milliampere seconds product (mR/mAs (or C/kg/mAs)) obtained at any §11-45-119 45-105 two mAs selector settings shall not differ by more than 0.10 times their sum: [X1 - X2] < 0.10(X1 + X2) where X1 and X2 are the average mR/mAs (or C/kg/mAs) values obtained at any two mAs selector settings. (3) Determination of compliance shall be based on four exposures, of no less than 0.05 seconds each, taken within a time period of one hour, at each of the two settings. These two settings may include any two focal spot sizes provided that neither focal spot size is equal to or less than 0.45 millimeter, in which case the two settings shall be restricted to the same focal spot size. For purposes of this requirement, focal spot size is the nominal focal spot size specified by the x-ray tube manufacturer. (h) Additional requirements applicable to certified systems only: diagnostic x-ray systems incorporating one or more certified component(s) shall be required to comply with the following additional requirement(s) which relate to that certified component(s). (1) Linearity: When the equipment is operated on a power supply as specified by the manufacturer in accordance with the requirements of applicable federal standards, for any fixed x-ray tube potential within the range of forty to one hundred percent of the maximum rated. (A) For equipment having independent selection of x- ray tube current, the average ratios of exposure to the indicated milliampere seconds product obtained at any two consecutive tube current settings shall not differ by more than 0.10 times their sum: [X1 - X2] < 0.10(X1 + X2) where X1 and X2 are the average mR/mAs (C/kg/mAs) values obtained at each of two consecutive tube current settings or at two settings differing by no more than a factor of two where the tube current selection is continuous. (B) For equipment having selection of x-ray tube current-exposure time product manufactured after May 3, 1994, the average ratios of exposure to the indicated milliampere seconds product obtained at any two consecutive milliampere seconds selector settings shall not differ by more than 0.10 times their sum: [X1 - X2] < 0.10(X1 + X2) where X1 and X2 are the average mR/mAs (C/kg/mAs) values obtained at each of two §11-45-119 45-106 consecutive milliampere seconds selector settings or at two settings differing by no more than a factor of two where the milliampere seconds selector provides continuous selection. (2) Beam limitation for stationary and mobile general purpose x-ray systems: (A) There shall be provided a means of stepless adjustment of the size of the x-ray field. The minimum field size at an source-image receptor distance of one hundred centimeters shall be equal to or less than five centimeters by five centimeters. (B) When a light localizer is used to define the x- ray field, it shall provide an average illumination of not less than one hundred sixty lux or fifteen footcandles at one hundred centimeters or at the maximum source-image receptor distance, whichever is less. The average illumination shall be based upon measurements made in the approximate center of each quadrant of the light field. Radiation therapy simulation systems manufactured on and after May 27, 1980, are exempt from this requirement. (C) The edge of the light field at one hundred centimeters or at the maximum source-image receptor distance, whichever is less, shall have a contrast ratio, corrected for ambient lighting, of not less than four in the case of beam-limiting devices designed for use on stationary equipment, and a contrast ratio of not less than three in the case of beam-limiting devices designed for use on mobile equipment. The contrast ratio is defined as I1/I2 where I1 is the illumination three millimeters from the edge of the light field toward the center of the field; and I2 is the illumination three millimeters from the edge of the light field away from the center of the field. Compliance shall be determined with a measuring instrument aperture of one millimeter in diameter. (3) Beam limitation for portable x-ray systems shall meet the beam limitation requirements of paragraphs (1) and (2). (4) Stationary, general purpose x-ray systems which contain a tube housing assembly, an x-ray control, and, for those systems so equipped, a table, all certified in accordance with 21 C.F.R. ? 1020.30(c) shall have manual collimation for field limitation and alignment. (5) If positive beam limitation is installed on stationary, general purpose x-ray systems after the effective date of these rules, the following requirements shall be met: §11-45-119 45-107 (A) Positive beam limitation shall prevent the production of x-rays when: (i) Either the length or width of the x-ray field in the plane of the image receptor differs, except as permitted by subparagraph (E), from the corresponding image receptor dimensions by more than three percent of the source-image receptor distance; or (ii) The sum of the length and width differences as stated in clause (i) without regard to sign exceeds four percent of the source-image receptor distance. (iii) The beam limiting device is at an source- image receptor distance for which positive beam limitation is not designed for sizing. (B) If a means of overriding the positive beam limitation system exists, that means shall be designed for use only in the event of positive beam limitation system failure or if the system is being serviced. (C) If in a position that the operator would consider it part of the operational controls or if it is referenced in the operator's manual or in other materials intended for the operator, (i) Shall require that a key be utilized to defeat the positive beam limitation; (ii) Shall require that the key remain in place during the entire time the positive beam limitation system is overridden; and (iii) Shall require that the key or key switch be clearly and durably labeled as follows: FOR X-RAY FIELD LIMITATION SYSTEM FAILURE (D) Compliance with subparagraph (A) shall be determined when the equipment indicates that the beam axis is perpendicular to the plane of the image receptor. Compliance shall be determined no sooner than five seconds after insertion of the image receptor. (E) The positive beam limitation system shall be capable of operation, at the discretion of the operator, such that the size of the field may be made smaller than the size of the image receptor through stepless adjustment of the field size. The minimum field size at an source-image receptor distance of one hundred centimeters shall be equal to or less than five centimeters by five centimeters. (F) Positive beam limitation shall be designed such that if a change in image receptor does not §11-45-119 45-108 cause an automatic return to positive beam limitation function as described in subparagraph (B), then any change of image receptor size or source-image receptor distance shall cause the automatic return. (6) Except for dental panoramic systems, termination of exposure shall cause automatic resetting of the timer to its initial setting or to "zero." (i) A tube stand or other mechanical support shall be used for portable x-ray systems so that the x-ray tube housing assembly need not be hand-held during exposures. [Eff 11/12/99] (Auth: HRS §§321-10, 321-11, 321-71) (Imp: HRS §§321-1, 321-11(21), 321-71)