A licensee authorized to use a gamma stereotactic radiosurgery unit for medical use shall perform spot-checks of each gamma stereotactic radiosurgery facility and on each unit—

Monthly;

Before the first use of the unit on a given day; and

After each source installation.

A licensee shall—

Perform the measurements required by paragraph (a) of this section in accordance with written procedures established by the authorized medical physicist. That individual need not actually perform the spot check measurements.

Have the authorized medical physicist review the results of each spot-check within 15 days. The authorized medical physicist shall notify the licensee as soon as possible in writing of the results of each spot-check.

To satisfy the requirements of paragraph (a)(1) of this section, spot-checks must, at a minimum—

Assure proper operation of—

Treatment table retraction mechanism, using backup battery power or hydraulic backups with the unit off;

Helmet microswitches;

Emergency timing circuits; and

Stereotactic frames and localizing devices (trunnions).

Determine—

The output for one typical set of operating conditions measured with the dosimetry system described in § 35.630(b);

The difference between the measurement made in paragraph (c)(2)(i) of this section and the anticipated output, expressed as a percentage of the anticipated output (i.e., the value obtained at last full calibration corrected mathematically for physical decay);

Source output against computer calculation;

Timer accuracy and linearity over the range of use;

On-off error; and

Trunnion centricity.

To satisfy the requirements of paragraphs (a)(2) and (a)(3) of this section, spot-checks must assure proper operation of—

Electrical interlocks at each gamma stereotactic radiosurgery room entrance;

Source exposure indicator lights on the gamma stereotactic radiosurgery unit, on the control console, and in the facility;

Viewing and intercom systems;

Timer termination;

Radiation monitors used to indicate room exposures; and

Emergency off buttons.

A licensee shall arrange for the repair of any system identified in paragraph (c) of this section that is not operating properly as soon as possible.

If the results of the checks required in paragraph (d) of this section indicate the malfunction of any system, a licensee shall lock the control console in the off position and not use the unit except as may be necessary to repair, replace, or check the malfunctioning system.

A licensee shall retain a record of each check required by paragraphs (c) and (d) and a copy of the procedures required by paragraph (b) of this section in accordance with § 35.2645.