Section 325.5373. X-ray equipment.

Rule 373. (1) The tube housing shall be of the diagnostic type.

(2)  The aluminum equivalent of the total filtration in the useful beam shall not be less than 2.0 millimeter aluminum for equipment capable of operating at potentials up to 70 kVp and shall not be less than 2.5 millimeter aluminum for equipment capable of operating at potentials greater than 70 kVp. The filter shall be located as near the window of the tube housing as possible.

(3)  For diagnostic x-ray machines manufactured after the effective date of these rules the aluminum equivalent of the total filtration in the useful beam shall not be less than that shown in table 1.

TABLE 1                                                                                                                    

Operating kVp                                    Minimum Total Filter (Inherent plus added)

Below 50 kVp                                     0.5 mm aluminum

50 - 70 kVp                                         1.5 mm aluminum

Above 70 kVp                                    2.5 mm aluminum

(4)  If the filter in the machine is not accessible for examination and the total filtration is not known subrule (3) may be assumed to have been met if the half-value layer is not less than

0.6 mm aluminum at 49 kVp

1.6 mm aluminum at 70 kVp

2.6 mm aluminum at 90 kVp

(5)  Under conditions of subrule (4) for tube potentials above 90 kVp subrule (3) may be assumed to have been met if the half-value layer is not less than that specified in table 2.

(6)  The half-value layer (HVL) of the useful beam for a given x-ray tube potential shall not be less than the values shown in table 2.

TABLE 2

Design operating range

(Kilovolts peak)

Measured

potential

(Kilovolts

Half-value

layer (milli- meters of

	peak)	aluminum)
Below 50	30	0.3
	40	0.4
	49	0.5
50 to 70	50	1.2
	60	1.3
	70	1.5
Above 70	80	2.3
	90	2.5
	100	2.7
	110	3.0
	120	3.2
	130	3.5
	140	3.8
	150	4.1

(7)   If it is necessary to determine the half-value layer at an x-ray tube potential which is not listed in table 2, linear interpolation or extrapolation may be made. Positive means shall be provided to insure that at least the minimum filtration needed to achieve these beam quality requirements is in the useful beam during each exposure.

(8)   Diaphragms or cones shall be provided for collimating the useful beam to a size no larger than clinically necessary and shall provide the same degree of protection as required of the tube housing.  The diameter of the useful beam at the cone tip shall not be greater than 3 inches.

(9)   Radiographic equipment manufactured after the effective date of these rules and designed for use with an intra-oral image receptor shall be provided with means to limit the x-ray beam so that:

(a)   If the minimum source-to-skin distance (SSD) is 18 centimeters or more, the x-ray field at the minimum SSD shall be containable in a circle having a diameter of not more than 7 centimeters.

(b)   If the minimum SSD is less than 18 centimeters, the x-ray field at the minimum SSD shall be containable in a circle having a diameter of not more than 6 centimeters.

(10)   For intra-oral film exposures, means (e.g. cones) shall be provided to limit the source-to- skin distance (SSD) to not less than 18 centimeters with apparatus operable above 50 kVp, and not less than 10 centimeters with apparatus not operable above 50 kVp. Open-ended cones are recommended to reduce scattered radiation.

(11)   Mechanical support of the tube head and pointer cone shall maintain the exposure position without drift or vibration of sufficient magnitude to cause the need for manually restraining the tube or retaking the x-ray.

(12)    A device shall be provided which terminates the exposure at a preset time interval or exposure limit. The operator shall be able to terminate the exposure at any time by discontinuing pressure upon the exposure switch except that during serial radiography means may be provided to permit completion of any single exposure of the series in progress.

(13)   If a recycling timer is employed, it shall not be possible to make a repeat exposure without release of the exposure switch to reset the timer.

(14)   The exposure control switch shall have a circuit-closing contact which can be maintained only by continuous pressure on the switch by the operator.

(15)   Unless protective shielding is provided for the operator, the length of the exposure control switch cord or remote control location shall be such that the operator shall be able to stand at least 1.8 meters (6 feet) away from the patient and the x-ray tube and out of the useful beam.

(17)   The control panel shall provide positive visual identification of the production of x-rays whenever the x-ray tube is energized.  A milliammeter may comply with this subrule.

(18)   On all diagnostic machines manufactured after the effective date of these rules a signal audible to the operator shall indicate that the exposure has ended.

(19)   The technique factors to be used during an exposure shall be indicated before the exposure begins, except when automatic exposure controls are used, in which case the technique factors which are set before the exposure shall be indicated. On equipment having fixed technique factors, this requirement may be met by permanent markings. Indication of technique factors shall be visible from the operator's position.

(20)   X-ray equipment installed after the effective date of these rules shall be installed and used in accord with the appropriate portions of the 1975 national electrical code (NFPA No. 70-1975) reproduced or referenced in rule 359. X-ray equipment installed before the effective date of these rules shall conform with the appropriate national electrical code in effect at the time of installation.

History: 1979 AC.