Administrative Rules of Montana › Department 37 - PUBLIC HEALTH AND HUMAN SERVICES › Chapter 37.14 - RADIATION CONTROL › Subchapter 37.14.10 - X-Rays in the Healing Arts › Rule 37.14.1022 - THERAPEUTIC X-RAY INSTALLATIONS

Current through Register Vol. 13, July 5, 2024
(1) The
				equipment used in therapeutic x-ray installations shall be as follows:
(a) The tube housing shall be of therapeutic
				type. Contact therapy machines shall meet the additional requirement that the
				leakage radiation at 2 inches from the surface of the housing not exceed 0.1
				R/h.
(b) Permanent diaphragms or
				cones used for collimating the useful beam shall afford the same degree of
				protection as the tube housing. Adjustable or removable beam-defining
				diaphragms or cones shall transmit not more than 5% of the useful beam obtained
				at the maximum possible kilovoltage and with maximum treatment
				filter.
(c) The filter system shall
				be so arranged as to minimize the possibility of error in filter selection and
				alignment. The filter slot shall be so constructed that the radiation escaping
				through it does not produce an exposure exceeding 1 roentgen per hour at 1
				meter, or, if the radiation from the slot is accessible to the patient, 30
				roentgens per hour at 2 inches from the external opening. Each removable filter
				shall be marked with its thickness and material.
(d) A filter indication system shall be used
				on all therapy machines using changeable filters. It shall indicate from the
				control panel the presence or absence of any filter and it shall be designed to
				permit easy recognition of the filter in place.
(e) The x-ray tube shall be so mounted that
				it cannot turn or slide with respect to the aperture. A mark on the housing
				should show the location of the focal spot.
(f) Means shall be provided to immobilize the
				tube housing during stationary portal treatment.
(g) There shall be on the control panel an
				easily discernible indicator which will give positive information as to whether
				or not the x-ray tube is energized.
(h) A suitable exposure control device shall
				be provided to terminate the exposure after a preset exposure or dose limit. It
				shall be designed to preserve its accumulated response in the event of
				equipment failure during patient treatment. If a timer is used, it should
				permit accurate presetting and determination of exposure times as short as 1
				second.
(i) Unless it is possible
				to bring the x-ray exposure rate to the prescribed value within 5 seconds after
				the x-ray "on" switch is energized, the tube housing on machines operating
				below 500 kVp shall be fitted with an "ON-OFF" shutter operated from the
				control panel and of lead equivalent not less than that of the tube housing.
				The "ON-OFF" positions of the shutter shall be indicated at the control
				panel.
(j) Mechanical or electrical
				stops shall be provided on x-ray machines capable of operating at 150 kVp or
				above to insure that the useful beam is oriented only toward primary
				barriers.
(k) Interlocks shall be
				provided for x-ray therapy equipment capable of operating above 75 kVp so that
				when any door to the treatment room is opened, either the machine will be shut
				off automatically or the radiation level within the room will be reduced to an
				average of not more than 2 mR/hr and a maximum of 10 mR/hr at a distance of 1
				meter in any direction from the source. After such a shutoff or reduction in
				exposure rate, it shall be possible to restore the machine to full operation
				only from the control panel.
(l)
				The x-ray control circuit shall be so designed that it is not possible to
				energize the x-ray tube without resetting the x-ray "on" switch at the control
				panel.
(m) X-ray therapy machines
				shall be provided with a locking device to prevent unauthorized use.
(n) When a beam interceptor is provided, it
				shall transmit not more than 0.1% of the useful beam under any operating
				conditions. It shall also reduce by the same factor the radiation scattered by
				the patient through an angle up to 30 E from the central ray.
(o) When the relationship between the beam
				interceptor and the useful beam is not permanently fixed, mechanical or
				electrical stops shall be provided to insure that the beam is oriented only
				toward primary barriers.
(p)
				Special consideration shall be given to the safety design of x-ray machines
				with electron beam extraction capability such as linear accelerators.