33.1-10-06-06. Radiographic systems other than fluroscopic, dental intraoral, bone densitometry, or computed tomography x-ray systems.

1. Beam limitation requirements for systems without positive beam limitation including portable x-ray systems. The useful beam shall be limited to the area of clinical interest.

a. General purpose stationary and mobile x-ray systems including veterinary systems (other than portable) installed after January 1, 1998.

(1) There shall be provided a means for independent length and width stepless adjustment to the size of the x-ray field.

(2) Means 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.

(3) The department may grant an exemption to paragraphs 1 and 2 on noncertified x-ray systems, provided the registrant makes a written application for such exemption and demonstrates in the application:

(a) That it is impractical to comply with paragraphs 1 and 2; and

(b) The purpose of paragraphs 1 and 2 will be met by other means.

b. Additional requirements for stationary general purpose x-ray systems. In addition to the requirements of subdivision a, all stationary x-ray systems both certified and noncertified shall meet the following requirements:

(1) Means 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.

(2) The beam-limiting device shall numerically indicate the field size in the plane of the image receptor to which it is adjusted.

(3) Indication of field size dimensions and source-image receptor distances shall be specified in inches 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 distance when the beam axis is indicated to be perpendicular to the plane of the image receptor.

c. X-ray systems designed for one image receptor size. Radiographic equipment designed for only one image receptor size at the fixed source-image receptor distance 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.

d. Systems designed for or provided with special attachments for mammography. Radiographic systems designed only for mammography shall be provided with means to limit the useful beam such that the x-ray field at the plane of the image receptor does not extend beyond any edge of the image receptor at any designated source-image receptor distance except the edge of the image receptor designed to be adjacent to the chest wall where the x-ray field may not extend beyond this edge by more than two percent of the source-image receptor distance. This requirement can be met with a system which performs as prescribed in paragraph 3 of subdivision e. When the beam-limiting device and image receptor support device are designed to be used to immobilize the breast during a mammographic procedure and the source-image receptor distance may vary, the source-image receptor distance indication specified in subparagraphs a and b of paragraph 3 of subdivision e shall be the maximum source-image receptor distance for which beam limiting device or aperture is designed. In addition, each image receptor support intended for installation on a system designed only for mammography shall have clear and permanent markings to indicate the maximum image receptor size for which it is designed.

e. X-ray systems other than those described in subdivisions a, b, c, and d and veterinary systems installed prior to January 1, 1998, and all portable veterinary x-ray systems.

(1) 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.

(2) 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.

(3) Paragraphs 1 and 2 may be met with a system that meets the requirements for a general purpose x-ray system as specified in subsection 1, or, when alignment means are also provided, may be met with either:

(a) 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 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

(b) 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.

2. Beam limitation requirements applicable to certified systems only. Diagnostic x-ray systems incorporating one or more certified components shall be required to comply with the following additional requirements which relate to those certified components.

a. Beam limitation for stationary and mobile general purpose x-ray systems.

(1) There shall be provided a means of independent length and width stepless adjustment of the size of the x-ray field. The minimum field size at a source-image receptor distance of one hundred centimeters shall be equal to or less than five centimeters by five centimeters. (2) 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 foot candles 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. (3) 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 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.

b. Beam limitation for portable x-ray systems. Beam limitation for portable x-ray systems shall meet the beam limitation requirements of subdivision a of subsection 1 and subdivision a of this subsection.

c. Beam limitation and alignment on stationary general purpose x-ray systems equipped with positive beam limitation (PBL). 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 meeting manufacturer's specifications and the requirements of this subdivision have been properly used.

(1) Positive beam limitation (PBL), when provided, shall function as described in paragraph 2 whenever all of the following conditions are met:

(a) The image receptor is inserted into a permanently mounted cassette holder. (b) The image receptor length and width are each less than fifty centimeters. (c) The x-ray beam axis is within plus or minus three degrees of vertical and the source-image receptor distance is ninety centimeters to one hundred thirty centimeters inclusive, or the x-ray beam axis is within plus or minus three degrees of horizontal and the source-image receptor distance is ninety centimeters to two hundred five centimeters inclusive.

1. (d) The x-ray beam axis is perpendicular to the plane of the image receptor to within plus or minus three degrees.
2. (e) Neither tomographic nor stereoscopic radiography is being performed.
3. (f) The positive beam limitation system has not been intentionally overridden. The override provision is subject to paragraph 3.(2) Positive beam limitation (PBL), when provided, shall prevent the production of x-rays when:- (a) Either the length or width of the x-ray field in the plane of the image receptor differs, except as permitted by paragraph 5, from the corresponding image receptor dimensions by more than three percent of the source-image receptor distance.
4. (b) The sum of the length and width differences as stated in subparagraph a, without regard to sign, exceeds four percent of the source-image receptor distance.
5. (c) The beam-limiting device is at a source-image receptor distance for which positive beam limitation (PBL) is not designed for sizing.(3) If a means of overriding the positive beam limitation (PBL) system exists, that method:- (a) If located 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.
6. [1] Must require that a key be utilized to defeat the positive beam limitation;
7. [2] Must require that the key remain in place during the entire time the positive beam limitation system is overridden; and
8. [3] Must require that the key or key switch be clearly and durably labeled as follows:

FOR X-RAY FIELD LIMITATION

SYSTEM FAILURE

1. (b) Must include a label visible to the operator that override of the positive beam limitation system is engaged.(4) Compliance with paragraph 2 must be determined when the requirements of paragraph 1 are met. Compliance must be determined no sooner than five seconds after insertion of the image receptor.(5) The positive beam limitation system must 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 the source-image receptor distance of one hundred centimeters must be equal to or less than five centimeters by five centimeters.(6) The positive beam limitation system must be designed such that if a change in image receptor does not cause an automatic return to positive beam limitation

function as described in paragraph 2, then any change of image receptor size or source-image receptor distance must cause the automatic return.

3. Radiation exposure control.

1. a. Exposure initiation. 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. b. Exposure indication. Means shall be provided for visual indication 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.
3. c. Exposure termination. 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. Except for dental panoramic systems, termination of an exposure shall cause automatic resetting of the timer to its initial setting or to 'zero'. It shall not be possible to make an exposure when the timer is set to a zero or off position if either position is provided.
4. (1) Manual exposure control. An x-ray control which shall be the equivalent of a dead-man switch shall be incorporated into each x-ray system such that an exposure can be terminated by the operator at any time except for:
   1. (a) Exposure of one-half second or less; or
   2. (b) During serial radiography when means shall be provided to permit completion of any single exposure of the series in process.
5. (2) Automatic exposure controls. When an automatic exposure control is provided:
   1. (a) Indication shall be made on the control panel when this mode of operation is selected;
   2. (b) If the x-ray tube potential is equal to or greater than fifty kVp, 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;
   3. (c) The minimum exposure time for all equipment other than that specified in subparagraph b shall be equal to or less than one-sixtieth second or a time interval required to deliver five mAs, whichever is greater;
   4. (d) Either the product of peak x-ray tube potential, current, and exposure time shall be limited to not more than sixty kVs per exposure, or the product of x-ray tube current and exposure time shall be limited to not more than six hundred mAs per exposure except that, when the x-ray tube potential is less than fifty kVp, the product of x-ray tube current and exposure time shall be limited to not more than two thousand mAs per exposure; and
   5. (e) A visible signal shall indicate when an exposure has been terminated at the limits required by subparagraph d, and manual resetting shall be required before further automatically timed exposures can be made.
6. d. Exposure duration (timer) linearity. For systems having independent selection of exposure time settings, the average ratios $[X_i]$ of exposure to the indicated timer setting,

in units of coulombs per kilogram per second [milliroentgen per second], obtained at any two clinically used timer settings shall not differ by more than ten-hundredths times their sum. This is written as:

$$(X_1 - X_2) < 0.1 (X_1 + X_2)$$

where $X_1$ and $X_2$ are the average C kg⁻¹s⁻¹ (mR/s) values.

e. Exposure control location. The x-ray exposure control shall be so placed that the operator can view the patient while making exposures (see appendix B). f. Operator protection, except veterinary systems.

(1) Stationary systems. Stationary x-ray systems shall be required to have the x-ray control permanently mounted in a protected area so that the operator is required to remain in that protected area during the entire exposure (see appendix B). (2) Mobile and portable systems. Mobile and portable x-ray systems which are:

(a) Used continuously for greater than one week in the same location, i.e., a room or suite, shall meet the requirements of paragraph 1; and (b) Used for less than one week at the same location shall be provided with either a protective barrier at least two meters [6.5 feet] high for operator protection during exposures, or means shall be provided to allow the operator to be at least two and seven-tenths meters [9 feet] from the tube housing assembly during the exposure.

(3) Mammography systems shall be operable from a shielded position.

g. Operator protection for veterinary systems. All stationary, mobile, or portable x-ray systems used for veterinary work shall be provided with either a two-meter [6.5-foot] high protection barrier for operator protection during exposures, or shall be provided with means to allow the operator to be at least two and seven-tenths meters [9 feet] from the tube housing assembly during exposures.

4. Source-to-skin distance. All mobile or portable radiographic systems shall be provided with means to limit the source-to-skin distance equal to or greater than thirty centimeters, except for veterinary systems.

5. Radiation exposure reproducibility. 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 five hundredths. This requirement applies to clinically used techniques. This requirement shall be deemed to have been met if, when four radiation exposures are made at identical technique factors, the value of the average radiation exposure (E) is greater than or equal to five times the maximum radiation exposure ($E_max$) minus the minimum radiation exposure ($E_min$),

$$\bar{E} \ge 5(E_max - E_min)$$

6. Radiation from capacitor energy storage equipment in standby status. Radiation emitted from the x-ray tube when the system is fully charged and the exposure switch or timer is not

activated shall not exceed a rate of two milliroentgens per hour at five centimeters from any accessible surface of the diagnostic source assembly, with the beam-limiting device fully open.

7. Accuracy. Deviation of measured technique factors from indicated values of kVp and exposure time 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 for kVp and twenty percent for time.

8. mA/mAs linearity. 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:

a. Equipment having independent selection of x-ray tube current (mA). The average ratios (X₁) of exposure to the indicated milliampere-seconds product in units of coulombs per kilogram per milliampere second (or milliroentgen per milliampere seconds) obtained at any two consecutive tube current settings shall not differ by more than ten hundredths times their sum:

$$X_1 - X_2 \le 0.10 (X_1 + X_2)$$

where X₁ and X₂ are the average 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. Equipment having a combined x-ray tube current exposure time product (mAs) selector, but not a separate tube current (mA) selector. The average ratio (X₁) of exposure to the indicated milliampere-seconds product, in units of coulombs per kilogram per milliampere second (or milliroentgen per milliampere seconds), obtained at any two consecutive mAs selector settings shall not differ by more than ten hundredths times their sum:

$$X_1 - X_2 < 0.10 (X_1 + X_2)$$

where X₁ and X₂ are the average values obtained at any two consecutive mAs selector settings, or at two settings differing by no more than a factor of two where the mAs selector provided continuous selection.

c. Measuring compliance. Determination of compliance shall be based on four exposures taken within a time period of one hour, at each of the two settings. These two settings may include any two focal spot sizes except where one is equal to or less than forty-five hundredths millimeters and the other is greater than forty-five hundredths millimeters. For purposes of this requirement, focal spot size is the nominal focal spot size specified by the x-ray tube manufacturer.

9. Other requirements:

a. Transmission limit for image receptor supporting devices used for mammography. For x-ray systems manufactured after September 5, 1978, which are designed only for mammography, the transmission of the primary beams through the image receptor support provided with the system will be limited such that the exposure five centimeters from any accessible surface beyond the plane of the image receptor supporting device does not exceed twenty-five and eight-tenths microcoulomb per kilogram [.01 milliroentgen] for each activation of the tube. Exposure shall be measured with the system operated at the minimum source-image receptor distance for which it is designed. Compliance shall be determined at the maximum rated peak tube potential for the

system and at the maximum rated product of tube current and exposure time (milliampere second) for that peak tube potential. Compliance shall be determined by measurements averaged over an area of one hundred square centimeters with no linear dimension greater than twenty centimeters.

b. Tube stands for portable x-ray systems. 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 handheld during exposures.

History: Effective January 1, 2019.

General Authority: NDCC 23.1-03-04; S.L. 2017, ch. 199, § 1

Law Implemented: NDCC 23.1-02-03, 23.1-03-03, 23.1-03-04; S.L. 2017, ch. 199, §§ 17, 18