Section 325.5312. 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 and are manufactured after the effective date of these rules. 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.

(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)     On therapeutic machines manufactured after the effective date of these rules beam monitoring devices shall be fixed in the useful beam to indicate any 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 (e.g. 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 any door to the treatment room is opened, the machine will shut off automatically   or  the  radiation level within the room will be 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 insure that the beam is  oriented  only toward  primary barriers.

(17)      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.

(18)      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.

(19)     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.

(20)         X-ray machines capable of producing radioactive material in excess of exempt quantities listed in schedule B of rule 147 unless excluded from the particle accelerator definition in part 1 by design and use shall comply with the applicable requirements of part 11.

History: 1954 ACS 85, Eff. Dec. 3, 1975.