United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-70: Teletherapy Unit Full Calibration and Qualified Expert Requirements (10 CFR 35.23 and 10 CFR 35.24)

                                                          SSINS No.: 6835 
                                                            IN 85-70       

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C. 20555

                               August 15, 1985

Information Notice No. 85-70:   TELETHERAPY UNIT FULL CALIBRATION AND 
                                   QUALIFIED EXPERT REQUIREMENTS (10 CFR 
                                   35.23 and 10 CFR 35.24) 

Addressees: 

All NRC licensees authorized to possess and use sealed sources in medical 
teletherapy units. 

Purpose: 

This information notice is provided to alert medical licensees of a 
potential safety problem in reference to 10 CFR 35.23 (requirement to 
calibrate instruments used for full calibration and spot-check measurements) 
and 10 CFR 35.24 (criteria to determine qualified expert). 

It is expected that medical licensees using teletherapy units will review 
this notice for applicability to their activities, if appropriate, to 
preclude incorrect measurement of teletherapy output that could result in 
excessive radiation exposures to patients during therapeutic 
administrations. However, suggestions contained in this information notice 
do not constitute NRC requirements; therefore, no specific action or written 
response is required. 

Description of Circumstances: 

It was determined during recent routine NRC inspections that full 
calibration measurements of Co-60 teletherapy units, performed by a 
qualified expert, were conducted using a dosimetry system that was not 
calibrated by the National Bureau of Standards or by a Regional Calibration 
Laboratory accredited by the American Association of Physicists in Medicine. 
The institutions where the events were discovered were requested by the NRC 
to have their units checked with a dosimetry system that had been calibrated 
by an accredited laboratory. The output check at one facility showed the 
dosimetry system to be underestimating machine output by 4.8 percent, which 
is greater than the 3 percent limit specified in 10 CFR 35.21. The 
institution had to adjust patient treatments accordingly. It also was 
determined that this dosimetry system had been used at one other institution
and a similar request for corrections was made of that institution. 



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                                                            IN 85-70       
                                                            August 15, 1985 
                                                            Page 2 of 2    

Discussion: 

Licensees authorized to possess and use sealed sources in medical 
teletherapy units should be aware of their responsibilities with respect to 
10 CFR 35.23, 35.24, and 35.27. It is required by 10 CFR 35.23 that full 
calibration measurements of the teletherapy unit be performed using a 
dosimetry system which has been calibrated by the National Bureau of 
Standards or by a Regional Calibration Laboratory accredited by the American 
Association of Physicists in Medicine. In addition, 10 CFR 35.21 requires 
that the full calibration measurements set forth in 10 CFR 35.23 be 
performed by a qualified expert who meets the criteria outlined in 10 CFR 
35.24. Records of the full calibration measurements and the licensee's 
evaluation of the qualified expert's training must be preserved for a 
minimum of 5 years and maintained for NRC inspection pursuant to 10 CFR 
35.27. It is important that licensees are aware that compliance with these 
regulations is their responsibility, regardless of who performs the 
measurements. 

No specific action or written response is required by this information 
notice. If you have any questions regarding this matter, please contact the 
Regional Administrator of the appropriate NRC regional office or this 
office. 


                                   James G. Partlow, Director 
                                   Division of Inspection Programs 
                                   Office of Inspection and Enforcement 

Technical Contact:  J. R. Metzger, IE
                    (301) 492-4947 

Attachment: List of Recently Issued IE Information Notices 
Page Last Reviewed/Updated Tuesday, November 12, 2013