Information Notice No. 84-62Therapy Misadministrations to Patients Undergoing Cobalt-60 Teletherapy Treatments

                                                            SSINS No.: 6835 
                                                            IN 84-62       
                                UNITED STATES
                           WASHINGTON, D.C. 20555

                               August 10, 1984

                                   UNDERGOING COBALT-60 TELETHERAPY 


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

This information notice is intended to bring to the attention of medical 
licensees two recent therapy misadministration cases to patients undergoing 
teletherapy treatments. They illustrate what can happen when internal 
policies and procedures for checking dose calculations are not clear, and/or
are not followed, by the licensee's personnel. Licensees are expected to 
review the information for applicability to their facilities and take 
actions, as appropriate. Suggestions contained in this notice do not 
constitute NRC requirements and, therefore, no specific action or written 
response is required. 

Description of Circumstances: 

In the first case, an NRC medical licensee who is authorized to use a 
cobalt-60 teletherapy unit has reported a therapy misadministration to a 
patient undergoing treatments for a brain tumor. The radiation therapy 
physician gave a written prescription of a total radiation dose of 6,000 rad
to be delivered in fractions of 200 rad per day, 5 days per week for 6 
weeks. The 200 rad per day were to be delivered to the central axis midplane 
of the head, equally divided between the right and left lateral portals. 

The dosimetrist reviewed the physician's prescription, but wrote down on the
Physics Dose Calculations form a dose of 200 rad per treatment for each 
field rather than the desired 100 rad for each field. Beam on-time was 
calculated for 200 rad per field and, therefore, was twice the time needed 
for the prescribed dose. 

The licensee's radiation therapy technologists, typically, do not review the
Physics Dose Calculations form. They refer to the Treatment Planning Chart 
before each treatment. In this instance, the treatment planning chart showed
a beam on-time which would deliver 200 rad per field. Subsequent Treatment 
Planning Chart checks by department supervisors (chief therapy 
technologists) failed to find the error because these Treatment Planning 
Chart checks do not include review of the dose calculations form. 

Although the licensee has an internal procedure that requires all dose 
calculations to be checked for accuracy before the second treatment, the 
delegation of such responsibility, as to who is supposed to check for 
accuracy, was not 


                                                           IN 84-62       
                                                           August 10, 1984 
                                                           Page 2 of 2    

clearly described in the procedure. Consequently, the procedure was not 
implemented in this case. After 15 treatments at the elevated dose, the 
patient exhibited erythema. Because this reaction was not uncommon, the 
treating physician was not suspicious. To reduce patient discomfort, the 
physician reduced the prescribed dose to a total dose of a 150 rad per 

New exposure times were calculated by another dosimetrist who, continuing 
with the same Physics Dose Calculations form, repeated the original error 
and calculated times which would deliver 150 rad to each side of the 
patient's head. Again, no checks were made on the second set of 
calculations. Nine treatments were given at 150 rad per field until the 
patient exhibited severe reaction and the physician requested that exposure 
times be recalculated. The error was discovered and treatments were 

The patient had received a dose 45% higher than the prescribed dose, 15 
treatments of 400 rad and 9 treatments of 300 rad (total of 8,700 rad) 
instead of the prescribed 30 treatments of 200 rad (total of 6,000 rad). 

In the second case, a therapy misadministration to a patient undergoing 
teletherapy treatments resulted from similar causes. After the patient 
received 16 of the scheduled 20 treatments, the error was, found during a 
review of the patient's treatment record by the attending physician. The 
patient received 6,400 rad instead of the prescribed total of 4,000 rad. The
licensee plans to take corrective action by having the attending physician, 
who originally prescribed the dose, review the patient's treatments on a 
timely basis. 


Even though there are no NRC requirements to have formal written procedures 
for prescribing and administering teletherapy doses, good practice indicates
the desirability of establishing and implementing a written procedure to 
prevent future misadministrations of this type. The procedure should define 
the format of the dose prescription and the responsibility of the licensee's
personnel to check dose calculations. 

If you have any questions regarding this matter, please contact the 
Administrator of the appropriate NRC regional office, or this office. 

                              J. Nelson Grace, Director 
                              Division of Quality Assurance, Safeguards 
                                and Inspection Procedures, IE 

Contact:  H. Karagiannis
          (301) 492-9655

List of Recently Issued IE Information Notices

Page Last Reviewed/Updated Wednesday, March 24, 2021