ML080710054

UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

OFFICE OF FEDERAL AND STATE MATERIALS 

AND ENVIRONMENTAL MANAGEMENT PROGRAMS 

WASHINGTON, DC 20555 

August 28, 2009 

NRC INFORMATION NOTICE 2009-17: REPORTABLE MEDICAL EVENTS INVOLVING 

TREATMENT DELIVERY ERRORS CAUSED BY 

CONFUSION OF UNITS FOR THE 

SPECIFICATION OF BRACHYTHERAPY 

SOURCES. 

ADDRESSEES 

All U.S. Nuclear Regulatory Commission (NRC) medical use licensees and NRC master 

materials licensees. All Agreement State Radiation Control Program Directors and State 

Liaison Officers. 

PURPOSE 

The NRC is issuing this information notice (IN) to alert addressees to treatment delivery errors 

and associated medical events caused by confusion of units for the specification of low-energy 

photon-emitting brachytherapy sources implanted into patients. The NRC expects recipients to 

review the information for applicability to their facilities and to consider actions, as appropriate, 

to avoid similar problems. However, suggestions contained in the IN are not new NRC 

requirements; therefore, no specific action or written response is required. The NRC is 

providing this IN to the Agreement States for their information and for distribution to their 

medical licensees as appropriate. 

DESCRIPTION OF CIRCUMSTANCES

The NRC has received reports of numerous medical events caused by errors in confusing the 

units of source strength in the specification of sources—specifically, units of air-kerma strength 

and apparent activity in units of millicurie (mCi). Although the details of the medical events 

varied, human error, not the design or functioning of the equipment, caused all of these events. 

These events illustrate the following three main areas of concern: 

(1) data entry error, whereby the source strength was entered into a computerized treatment 

planning system in units not used by the system 

(2) ordering error, whereby sources of an incorrect source strength were delivered and used 

because either the licensee or the manufacturer made an error in the requested units 

(3) conversion error, whereby a conversion between two different units was omitted or 

performed incorrectly 
IN 2009-17 

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The NRC recognizes that other pathways may lead to treatment delivery errors, such as the 

mislabeling of source strength or errors in patient dose calculations caused by incorrect 

programming of the treatment planning software (e.g., incorrect conversion factor or decay 

correction values within the software programming). However, this IN only addresses events 

caused by errors in the use of differing source-strength units. 

Data Entry Error

One recent data entry error for a manual implant of iodine-125 resulted in the patient receiving a 

dose higher than the intended dose when the wrong units were entered into the treatment 

planning system. 

Another event reported to the NRC in which the patient received a higher-than-intended dose 

because of a data entry error was caused by a licensee staff member who entered the 

numerical value for mCi instead of the default units of air-kerma strength used in the treatment 

planning system. Based on the 27-percent lower activity per source entered, the treatment 

planning system calculated a higher quantity of seeds to deliver the intended dose. 

Both events were avoidable human errors associated with entering information into a treatment 

planning system using the wrong units to specify the source strength of the brachytherapy 

sources. 

Ordering Error

As a result of a licensee error when ordering brachytherapy sources, a patient received a 

27-percent overdose. The treatment planning system calculated the source strength in 

air-kerma strength per seed; however, when placing the order, the licensee specified the source 

activity in mCi per seed using the same numerical value. 

A similar medical event occurred at another facility when the licensee ordered the 

brachytherapy sources in units of mCi per seed instead of ordering them with the same 

numerical value but in units of air-kerma strength per seed. Because of this error, 10 different 

patients received doses 27 percent higher than those prescribed in the written directive. 

The NRC also received reports of medical events that were caused by differences in the units 

used by the individual who ordered the sources and the vendor that supplied them. In one such 

case that resulted in a 28-percent overdose, a seed manufacturer delivered seeds in units of 

mCi per seed, but the individual who had ordered the sources actually requested the seeds of 

the same numerical value but in units of air-kerma strength per seed. 

Conversion Error

In the case of a medical event involving an interstitial brachytherapy treatment using iridium-192 

seeds, the conversion from units of milligram radium-equivalent (mg Ra-eq) to units of air-kerma 

strength was omitted before the numerical value was entered into the treatment planning 

system. The numerical value in mg Ra-eq was entered into the treatment planning system 

using units of air-kerma strength. This medical event was further compounded by the use of a 

dose rate factor being based on the wrong isotope because the licensee omitted acceptance 
IN 2009-17 

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testing of the treatment planning software for iridium-192. Together, these two errors resulted in 

a delivered dose of 4,590 centigray (cGy), rather than the intended 2,500-cGy dose. 

In a separate medical event, four different patients received overdoses of 56 to 78 percent 

higher than those prescribed when the conversion from mg Ra-eq to activity in units of mCi was 

omitted before entry into the treatment planning system. 

DISCUSSION

Human error, not the design or functioning of the equipment, was the cause of all of these 

events. To prevent these types of occurrences, licensees should have the written directive and 

treatment plan readily available when they order brachytherapy seeds from the manufacturer 

and when they receive the seeds from the manufacturer for comparison with the calibration 

certificate. Licensees should use written forms that capture key data (i.e., dates, quantities, and 

units) rather than relying on verbal telephone orders when ordering brachytherapy seeds from a 

manufacturer to limit the potential for miscommunication and minimize the likelihood of errors. 

However, if licensees order brachytherapy seeds by telephone, they could request that the 

manufacturer fax or e-mail a copy of the order for their immediate review. This procedure would 

allow licensees to find discrepancies before the manufacturer transfers the sources to them. 

Additional precautions that licensees may take include developing and implementing working 

procedures that require independent confirmation of key processes, a system of redundant 

checks, and reviews of the treatment plan. Independent confirmations should include an 

independent verification of the accuracy of the dose calculation algorithms. Redundant checks 

should include checking the quantity of seeds, numerical values, and units for specifying the 

source strength of the seeds before ordering from the manufacturer and upon receipt of the 

seeds. Treatment plan reviews should include verifying the consistency and accuracy of the 

following information among the written directive, treatment plan, and calibration certificate: 

(1) all dates, (2) radioactive decay, (3) numerical values, (4) quantities, and (5) units. 

Furthermore, licensees should check that the correct data was entered into the treatment 

planning system. A good standard of practice accepted by many physicists is that an individual 

other than the person who entered the data perform these redundant checks. 

Users of treatment planning systems are reminded to refer to the software manufacturer’s 

instructions for appropriate data entry methods. Effective communication among all involved 

persons (e.g., licensee staff, the seed manufacturer, and the treatment planning software 

manufacturer) is vital to an effective process. 

As an additional reference for specifying the source strength, licensees may refer to guidance 

and practical standards contained in the American Association of Physicists in Medicine (AAPM) 

Report No. 21, “Specification of Brachytherapy Source Strength,” Report of AAPM Task Group 

No. 32, issued 1987 (http://www.aapm.org/pubs/reports/rpt 21.pdf). 

NRC’s Advisory Committee on Medical Uses of Isotopes endorses the concept of using airkerma strength when ordering brachytherapy sources and in patient treatment planning. By all 

licensees and manufacturers specifying the intensity of brachytherapy sources in units of airkerma strength for every order and treatment plan, a standard of practice would be established 
IN 2009-17 

Page 4 of 4 

that would reduce the number of medical events caused be errors in confusing the units of 

source strength in the specification of sources. 

CONTACT

This IN requires no specific action or written response. If you have any questions about the 

information in this notice, please contact the technical contact below or the appropriate regional 

office. 

 

 Robert J. Lewis, Director /RA/ 

 Division of Materials Safety 

 and State Agreements 

 Office of Federal and State Materials 

 and Environmental Management Programs 

Technical Contact: Cindy Flannery, FSME 

 (301) 415-0223 

 E-mail: cindy.flannery@nrc.gov 

Enclosure: 

List of Recently Issued Office of Federal 

 and State Material and Environmental 

 Management Programs Generic 

 Communications 
IN 2009-17 

Page 4 of 4 

that would reduce the number of medical events caused be errors in confusing the units of 

source strength in the specification of sources. 

CONTACT

This IN requires no specific action or written response. If you have any questions about the 

information in this notice, please contact the technical contact below or the appropriate regional 

office. 

 Robert J. Lewis, Director /RA/ 

 Division of Materials Safety 

 and State Agreements 

 Office of Federal and State Materials 

 and Environmental Management Programs 

Technical Contact: Cindy Flannery, FSME 

 (301) 415-0223 

 E-mail: cindy.flannery@nrc.gov 

Enclosure: 

List of Recently Issued Office of Federal 

 and State Material and Environmental 

 Management Programs Generic 

 Communications 

ML080710054 

OFC MSSA/MSEA MSSA/MSEA QTE OGC 

NAME CFlannery: sxg6 AMcIntosh KAzariah-Kribbs BJones 

DATE 05/27/09 06/01/09 06/03/09 08/11/09 

OFC MSEA MSSA MSSA 

NAME CEinberg JLuehman RLewis 

DATE 08/11/09 08/18/09 08/28/09 

OFFICIAL RECORD COPY
Enclosure 

IN 2009-17 

Page 1 of 1 

List of Recently Issued Office of Federal and State Material 

and Environmental Management Programs Generic Communications

Date GC No. Subject Addressees 

01/12/09 IN-2008-22 Molybdenum-99 Breakthrough in 

Molybdenum-99/Technetium-99m 

Generators 

All NRC medical, radiopharmacy, molybdenum-99/ 

technetium-99m generator manufacturers, and 

master materials licensees authorized to 

manufacture or use generators. All Agreement State 

Radiation Control Program Directors and State 

Liaison Officers. 

01/22/09 IN-2009-01 National Response Framework All holders of operating licenses or certificates for 

nuclear power plants, research and test reactors, 

independent spent fuel storage installations, fuel 

cycle facilities, and radioactive materials. All holders 

of operating licenses for uranium recovery facilities 

and all holders of licenses or certificates for the 

following types of facilities undergoing 

decommissioning: nuclear power plants, research 

and test reactors, fuel cycle facilities, and uranium 

recovery facilities. 

02/03/09 IN-2009-05 Contamination Events Resulting 

from Damage to Sealed 

Radioactive Sources during Gauge 

Dismantlement and Nonroutine 

Maintenance Operations 

All NRC materials licensees. All Agreement State 

Radiation Control Program Directors and State 

Liaison Officers. 

03/30/09 IN-2009-07 Withholding of Proprietary 

Information from Public Disclosure 

All current holders of and potential applicants for 

licenses, certificates of compliance, permits, or 

standard design certifications and any other persons 

submitting a request that information be withheld 

from public disclosure under the provisions of Title 

10 of the Code of Federal Regulations (10 CFR) 

2.390, “Public Inspections, Exemptions, Requests for 

Withholding.” 

05/07/09 RIS-2009-07 Status Update for the 

Implementation of NRC Regulatory 

Authority for Certain Naturally 

Occurring and AcceleratorProduced Radioactive Material 

All NRC material and fuel cycle licensees. All 

Radiation Control Program Directors and State 

Liaison Officers. 

07/13/09 RIS-2009-09 Use of Multiple Dosimetry and 

Compartment Factors in 

Determining Effective Dose 

Equivalent from External Radiation 

Exposures 

All NRC licensees, Agreement State Radiation 

Control Program Directors, and State Liaison 

Officers. 

Note: This list contains the six most recently issued generic communications issued by the Office of Federal and 

State Materials and Environmental Management Programs. A full listing of all generic communications may be 

viewed at the NRC public Web site at the following address: http://www.nrc.gov/reading-rm/doc-collections/gencomm/index.html.