SECTION 252:410-11-55. Beam monitors

(a)   Radiation detectors and dose monitors. All systems of 1 MeV or more must have radiation detectors in the radiation head. Post-1989 systems must have at least two radiation detectors which are incorporated into two separate dose monitoring systems. Pre-1989 systems must have at least one radiation detector which is incorporated into the primary dose monitoring system. The detector and the dose monitor system into which that detector is incorporated must meet the following requirements:

(1)   The detector must be removable only with tools and be interlocked to prevent incorrect positioning;

(2)   Each detector must form part of a dose monitoring system. The detector must show dose monitor units which can be used to calculate the absorbed dose at a reference point in the treatment volume; and

(3)   Each dose monitoring system must be capable of independently monitoring, interrupting and terminating irradiation. For post-1989 systems with two or more dose monitoring systems, the malfunctioning of one system must not affect the correct functioning of the second system. If any element common to both systems that could affect the correct function of both systems fails, the dose monitoring system must terminate irradiation.

(b)   Display. Each dose monitoring system shall have a legible display at the control panel. Post-1989 systems displays shall:

(1)   maintain a reading until intentionally reset to zero;

(2)   have only one scale and no scale multiplying factors;

(3)   show increasing dosage as increasing numbers; and

(4)   in the event of an overdosage of radiation, ensure the absorbed dose may be accurately determined.

(c)   Dose monitor data retrieval. In the event of power failure, the dose monitor information displayed at the control panel at the time of failure shall be retrievable in at least one system for at least 20 minutes.

[Source: Added at 17 Ok Reg 1136, eff 6-1-00]