R 333.5312 X-ray equipment.

Rule 312. (1) The tube housing shall be of the therapeutic type. (2) Permanent diaphragms or cones used for collimating the useful beam shall afford the same degree of attenuation as is required of the housing. (3) Adjustable or removable beam-limiting devices shall transmit not more than 5% of the useful beam as determined at the maximum tube potential and with maximum treatment filter. (4) Filters shall be so mounted as to prevent their movement during the treatment. (5) The filter slot shall be so constructed that the radiation escaping through it does not produce an exposure rate exceeding 1 R/h at 1 meter, or if the patient is likely to be exposed to radiation escaping from the slot, 30 R/h at 5 centimeters (2 inches) from the external opening. (6) A removable filter shall be permanently marked with its thickness and material. (7) A filter indication system shall be used on therapy machines which use changeable filters. It shall indicate, from the control panel, the presence or absence of a filter and it shall be designed to permit easy recognition of the filter in place. (8) The x-ray tube shall be so mounted that it cannot turn or slide with respect to the housing aperture. A reproducible means of measuring the focal spot to patient distance shall be provided. (9) Means to immobilize the tube housing during stationary portal treatment shall be provided. (10) An easily discernible indicator which shows whether or not x-rays are being produced shall be on the control panel. (11) Beam monitoring devices shall be fixed in the useful beam to indicate an error due to incorrect filter, tube current, or tube potential, unless the device introduces more filtration than is clinically acceptable. (12) A suitable exposure control device, such as an automatic timer, exposure meter, or dose meter, shall be provided to terminate the exposure after a preset time interval or preset exposure or dose limit. If a timer is used, it shall permit accurate presetting and determination of exposure times as short as 1 second. Means for the operator to terminate the exposure at any time shall be provided. (13) Mechanical or electrical stops, or both shall be provided to insure that the useful beam is oriented only toward primary barriers. (14) Interlocks shall be provided so that, when a door to the treatment room is opened, the machine turns off automatically or the radiation level within the room is reduced to an average of not more than 2 mR/h and a maximum of 10 mR/h at a distance of 1 meter in any direction from the source. After the shut-off or reduction in exposure rate, it shall be possible to restore the machine to full operation only from the control panel. (15) The x-ray control circuit shall be so designed that it is not possible to energize the x-ray tube to produce x-rays without resetting the x-ray "ON-OFF" switch at the control panel. (16) When the relationship between the beam interceptor (when present) and the useful beam is not permanently fixed, mechanical or electrical stops shall be provided to ensure that the beam is oriented only toward primary barriers. (17) X-ray machines with electron beam extraction capability shall be provided with such additional safety devices as determined necessary and specified in writing by the department to prevent accidental electron beam exposure. (18) To reduce the electron contamination of high energy treatment beams, shadow trays, or other accessories placed in the primary beam shall be placed at a sufficient distance from the patient that the electron contamination contribution to the skin dose is minimal. Editor's Note: An obvious error in R 325.5312 was corrected at the request of the promulgating agency, pursuant to Section 56 of 1969 PA 306, as amended by 2000 PA 262, MCL 24.256. The rule containing the error was published in Michigan Register, 2016 MR 10. The memorandum requesting the correction was published in Michigan Register, 2016 MR 16.