---
kind: "section"
citation: "10 C.F.R. § 35.645"
title: "10"
number: "35.645"
heading: "Periodic spot-checks for gamma stereotactic radiosurgery units."
url: "https://uscodex.org/cfr/10/35.645"
---

# §35.645. Periodic spot-checks for gamma stereotactic radiosurgery units.

- (a) 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—
  - (1) Monthly;
  - (2) Before the first use of the unit on a given day; and
  - (3) **After each source installation.**
- (b) **A licensee shall—**
  - (1) Perform the measurements required by [paragraph (a)](#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.
  - (2) **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.
- (c) **To satisfy the requirements of paragraph (a)(1) of this section, spot-checks must, at a minimum—**
  - (1) **Assure proper operation of—**
    - (i) Treatment table retraction mechanism, using backup battery power or hydraulic backups with the unit off;
    - (ii) Helmet microswitches;
    - (iii) Emergency timing circuits; and
    - (iv) **Stereotactic frames and localizing devices (trunnions).**
  - (2) **Determine—**
    - (i) The output for one typical set of operating conditions measured with the dosimetry system described in [§ 35.630(b)](/cfr/10/35.630.md?p=b);
    - (ii) The difference between the measurement made in [paragraph (c)(2)(i)](#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);
    - (iii) Source output against computer calculation;
    - (iv) Timer accuracy and linearity over the range of use;
    - (v) On-off error; and
    - (vi) **Trunnion centricity.**
- (d) To satisfy the requirements of paragraphs [(a)(2)](#a-2) and [(a)(3)](#a-3) of this section, spot-checks must assure proper operation of—
  - (1) Electrical interlocks at each gamma stereotactic radiosurgery room entrance;
  - (2) Source exposure indicator lights on the gamma stereotactic radiosurgery unit, on the control console, and in the facility;
  - (3) Viewing and intercom systems;
  - (4) Timer termination;
  - (5) Radiation monitors used to indicate room exposures; and
  - (6) **Emergency off buttons.**
- (e) A licensee shall arrange for the repair of any system identified in [paragraph (c)](#c) of this section that is not operating properly as soon as possible.
- (f) If the results of the checks required in [paragraph (d)](#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.
- (g) A licensee shall retain a record of each check required by paragraphs [(c)](#c) and [(d)](#d) and a copy of the procedures required by [paragraph (b)](#b) of this section in accordance with [§ 35.2645](/cfr/10/35.2645.md).

## Notes

### Authority

Authority: Atomic Energy Act of 1954, secs. 81, 161, 181, 182, 183, 223, 234, 274 (42 U.S.C. 2111, 2201, 2231, 2232, 2233, 2273, 2282, 2021); Energy Reorganization Act of 1974, secs. 201, 206 (42 U.S.C. 5841, 5846); 44 U.S.C. 3504 note.

### Source

Source: 67 FR 20370, Apr. 24, 2002, unless otherwise noted.