NAC459.582. Therapeutic X-ray systems: Leakage radiation; diaphragms and beam-limiting devices.

     1. When the tube is operated at its leakage technique factors, the leakage radiation must not exceed the value specified at the distance specified for the classification of that X-ray system.

     2. For systems of contact therapy, leakage radiation must not exceed 100 mR/hr at 5 centimeters from the tube housing and must meet the following standards:

     (a) In 0-150 kVp systems which are manufactured or installed prior to February 28, 1980, the leakage radiation must not exceed 1 R in 1 hour at 1 meter from the source.

     (b) In 0-150 kVp systems which are manufactured on or after February 28, 1980, the leakage radiation must not exceed 100 mR in 1 hour at 1 meter from the source.

     (c) In 151 to 999 kVp systems, the leakage radiation must not exceed 1 R in 1 hour at 1 meter from the source except systems that operate in excess of 500 kVp may have a leakage radiation at 1 meter from the source equivalent to the useful beam multiplied by a factor of 0.001.

     3. Permanent fixed diaphragms or cones used for collimating the useful beam must provide the same degree of protection as required by the tube housing assembly.

     4. Removable beam-limiting devices such as diaphragms or cones must, for the portion of the useful beam to be blocked by these devices, transmit not more than 1 percent of the original X-ray beam at the maximum kilovoltage and maximum treatment filter.

     5. Adjustable beam-limiting devices installed after February 28, 1980, must meet the criteria of subsection 4.

     6. Adjustable beam-limiting devices installed before February 28, 1980, must, for the portion of the X-ray beam to be blocked by these devices, transmit not more than 5 percent of the original X-ray beam at the maximum kilovoltage and maximum treatment filter.

     [Bd. of Health, Radiation Control Reg. §§ 6.8-6.8.1.3.3, eff. 2-28-80]