Information Notice 2009-17, Reportable Events Involving Treatment Delivery Errors Caused by the Use of Differing Units for the Calibration of Brachytherapy Sources
| ML080710054 | |
| Person / Time | |
|---|---|
| Issue date: | 08/28/2009 |
| From: | Robert Lewis NRC/FSME/DMSSA |
| To: | |
| Flannery C, FSME/DMSSA, 301-415-0223 | |
| References | |
| IN-09-017 | |
| Download: ML080710054 (6) | |
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 sourcesspecifically, 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 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 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 manufacturers
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).
NRCs Advisory Committee on Medical Uses of Isotopes endorses the concept of using air- kerma strength when ordering brachytherapy sources and in patient treatment planning. By all
licensees and manufacturers specifying the intensity of brachytherapy sources in units of air- kerma strength for every order and treatment plan, a standard of practice would be established 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:
(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 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:
(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
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 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 Accelerator- Produced 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/gen- comm/index.html.