NAC459.570. Fluoroscopic X-ray systems: Exposure rate limits.

     1. The exposure measured at the point where the center of the useful beam enters the patient must not exceed 10 roentgens (100 millisieverts) per minute, except during recording of fluoroscopic images or when provided with optional high level control.

     2. When provided with optional high level control, the equipment must not be operable at any combination of tube potential and current which will result in an exposure rate, measured at the point where the center of the useful beam enters the patient, in excess of:

     (a) Five roentgens (50 millisieverts) per minute if the high level control is not activated; and

     (b) Twenty roentgens (200 millisieverts) per minute if the high level control is activated and the unit was manufactured on or after May 19, 1995.

Ê Special means of activation of high level controls, such as additional pressure applied continuously by the operator, will be required to avoid accidental use. A continuous signal audible to the fluoroscopist must indicate activation and use of the high level control.

     3. Any new equipment installed after February 28, 1980, which does not incorporate an automatic exposure control, for example, an automatic brightness control or ionization chamber control, must not be operable at any combination of tube potential and current which will result in an exposure rate in excess of 5 roentgens (50 millisieverts) per minute at the point where the center of beam enters the patient except during recording of fluoroscopic images or when provided with an optional high level control.

     4. Compliance with this section is determined as follows:

     (a) If the source is below the table, exposure rate must be measured 1 centimeter above the tabletop or cradle.

     (b) If the source is above the table, the exposure rate must be measured at 30 centimeters above the tabletop with the end of the beam-limiting device or spacer positioned as closely as possible to the point of measurement.

     (c) In a C-arm type of fluoroscope, the exposure rate must be measured 30 centimeters from the input surface of the fluoroscopic imaging assembly.

     (d) In a miniature C-arm type of fluoroscope, the exposure rate must be measured with the end of the beam-limiting device or spacer positioned as closely as possible to the point of measurement.

     (e) In a lateral type of fluoroscope, the exposure rate must be measured at a point 15 centimeters from the centerline of the tabletop and in the direction of the X-ray source, with the end of the beam-limiting device or spacer positioned as closely as possible to the point of measurement. If the tabletop is movable, it must be positioned as closely as possible to the lateral X-ray source.

     5. Periodic measurements of the exposure rate must be made annually or after any maintenance of the system which might affect the exposure rate. If the equipment is provided with optional high level control, measurements of the exposure rates must be made both with and without the high level control activated.

     6. Results of these measurements must be made available at a place where any fluoroscopist will have ready access to them while using that fluoroscope. Results of the measurements must include the maximum possible r/minute, as well as the physical factors used to determine all data, the name of the person performing the measurements and the date the measurements were performed.

     7. Use of monitoring devices, for example, commercially available film badges, thermoluminescence dosimeters or low energy dosimeters, may be used to perform the test if the measurements are made as in subsection 8.

     8. The measurement must be made under the conditions that satisfy the requirements of subsection 4:

     (a) The kVp must be the peak kV that the X-ray system is capable of producing;

     (b) If determining the maximum dose rate below 5 roentgens (50 millisieverts) per minute, the high level control, if present, must not be activated;

     (c) The X-ray system that incorporates automatic exposure control, for example, automatic brightness control, must have sufficient material, for example, lead or lead equivalent, placed in the useful beam to produce the maximum radiation output of the X-ray system; and

     (d) The X-ray system that does not incorporate automatic exposure control must utilize the maximum milliamperage of the X-ray system. The material, for example, an attenuation block, must be placed in the useful beam to protect the imaging system.

     [Bd. of Health, Radiation Control Reg. §§ 6.5.3-6.5.3.1.5.4.5, eff. 2-28-80]—(NAC A by Dep’t of Human Resources by R137-01, 5-30-2003)