Information Notice 2004-02, Strontium-90 Eye Applicators: New Calibration Values and Use
ML040330279 | |
Person / Time | |
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Issue date: | 02/05/2004 |
From: | Chris Miller NRC/NMSS/IMNS |
To: | |
References | |
IN-04-002 | |
Download: ML040330279 (7) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
WASHINGTON, D.C. 20555 February 5, 2004 NRC INFORMATION NOTICE 2004-02: STRONTIUM-90 EYE APPLICATORS: NEW
CALIBRATION VALUES AND USE
Addressees
All U.S. Nuclear Regulatory Commission (NRC) medical-use licensees and NRC master
materials license medical-use permittees.
Purpose
NRC is issuing this Information Notice (IN) to inform all medical-use licensees and permittees of
information regarding the use of newly calibrated strontium-90 (Sr-90) eye applicators. It is
expected that recipients will review this information for applicability to their facilities and
consider actions, as appropriate, to avoid similar problems. However, suggestions contained
in this IN are not new NRC requirements; therefore, no specific action nor written
response is required.
Description of Circumstances
This notice alerts medical-use licensees and permittees to discrepancies associated with new
and older calibration values for Sr-90 eye applicators and effects this may have on their use
under the regulatory requirements in 10 CFR Part 35, Medical Use of Byproduct Material.
Discussion:
NRC issued an IN, in 1994, on the calibration and use of Sr-90 eye applicators (IN 94-17, March 11, 1994) that, among other things, informed licensees that: (1) researchers at the
National Institute of Standards and Technology (NIST) recognized large discrepancies among
calibrated outputs assigned to Sr-90 eye applicators; (2) original manufacturer calibrations were
expressed in older (traditional) units, which differed from the System Internationale (SI) units;
(3) calibration values were not comparable for units from different manufacturers; and (4)
discrepancies larger than 10 percent could exist when comparing output measurements
between competent measurement laboratories using state-of-the-art techniques.
At that time, the Advisory Committee on the Medical Uses of Isotopes (ACMUI) advised the
staff that calibration was not a critical factor in the use of Sr-90 eye applicators for treating
pterygium because licensees treated for response rather than to tolerance. Members of the
ACMUI recommended that the Sr-90 eye applicator licensees continue to treat patients as they
had using the original manufacturers Sr-90 activity values and treatment times derived from
decay correction charts. The ACMUI further recommended cautioning licensees that if they
were to use an applicator other than the one currently in their possession, or if they were to buy
a new one, their current technique might not be applicable to another device because of
variances in stated and actual exposure rates for the different applicators.
In 1991, NIST implemented major revisions to its method for performing these calibrations. The
major changes involved using a collecting electrode smaller than the source being calibrated
and restricting measurements to air gaps less than 0.2 millimeter (mm). These changes
yielded current-versus-air-gap data that are linear and which extrapolate unambiguously at
distances down to zero air gap. NIST reviewed additional changes in the recombination
corrections, stopping-power averages, and corrections for electrode backscatter. NIST
continues to review and refine its calibration calculations and techniques for
Sr-90 eye applicators.
Before October 2002, if a medical-use licensee or permittee had a calibration certificate for its
eye applicator, the licensee or permittee was not required to re-calibrate its eye applicators.
Effective October 24, 2002, NRC amended its regulations at 10 CFR 35.432, Calibration
measurements of brachytherapy sources. This section of the regulations requires, among
other things, that brachytherapy sources be calibrated before first medical use on or after the
effective date of the rule. The effect of this requirement on Sr-90 eye applicator licensees and
permittees was that they all had to have their applicators calibrated using the new techniques
that more accurately measure the actual exposure rate for the eye applicator and provide the
calibration results in SI units. Thus, the calibration values and units may be significantly
different from those provided in the original manufacturers calibrations or more
recent calibrations.
NRC expects each Sr-90 eye applicator licensee and permittee to carefully review the results of
the new calibration with its authorized medical physicist to assure proper interpretation of the
calibration results. This review should include discussion of appropriate changes to the written
directives so that the patient treatments are based on the new calibration information. As
described below, the authorized user has several options and should select the best option, based on his/her medical judgment, for his/her practice. It is important for the licensee or
permittee to keep in mind that, although the units and calibration values may be different, the
actual amount of radioactive material (corrected for decreases from radioactive decay)
contained in each applicator and its distribution in the applicator remains the same.
The written directive regulations for eye applicator procedures require that the licensee (or
permittee) include the following information in the written directive:
- prior to implantation: treatment site, radionuclide, and dose;
- after implantation, but prior to completion of procedure: treatment site, radionuclide, number of sources, and total source strength and exposure time (or total dose).
Maintaining the same treatment regimen - revising total dose in the written directive.
If the licensees or permittees medical experience with its Sr-90 treatment regimen before the
October 2002 required recalibration indicated that the treatments provided appropriate medical
results, the authorized user may elect to administer the same amount of radiation to the treatment site and provide the same medical results after recalibration, as before. Even though
the units and calibration values may be different from those of an earlier calibration, the actual
exposure rate (corrected for decreases from radioactive decay) remains the same.
Therefore, to administer the same amount of radiation from a specific eye applicator, the
authorized user should keep the treatment time the same and adjust the total dose to a new
value, based on the new calibration exposure rate.
For example, based on the original manufacturers calibration data, the authorized user
believes that the exposure rate is 0.42 gray per second (Gy/sec), but the exposure rate based
on the new calibration certificate is really 0.55 Gy/sec, a value 31 percent higher. The
authorized users medical experience is that the treatment times used in the past provided good
medical results. To achieve the same medical results, the authorized user would keep the
administration time the same and increase the value of the total dose documented in the written
directive by 31 percent. The treatment times will change with time, because of the normal
radioactive decay of the Sr-90.
Changing the treatment regimen - retaining the same written directive total dose value.
Although the authorized users medical experience with his/her Sr-90 treatment regimen before
the October 2002 required calibration indicated that the treatments provided appropriate
medical results, the authorized user decides he/she wants to keep the value of the total dose
the same in future written directives. In this case, the authorized user will adjust the treatment
time so that the total dose value recorded in the written directive does not change. Because the
treatment regimen is changed, the authorized user should monitor his/her patients to see if the
expected medical results stay the same or change.
For example, based on the original manufacturers calibration data, the authorized user
believes that the exposure rate is 0.42 Gy/sec, but the exposure rate based on the new
calibration certificate is really 0.55 Gy/sec, a value 31 percent higher. In this example, the
authorized user decides to keep the total dose value the same in the written directive. To
achieve the same value for the total dose, the authorized user would have to reduce the
administration time by 31 percent. This IN requires no specific action nor written response. If you have questions about the
information in this notice, please contact the appropriate technical contact listed below.
/RA/ PKHolahan for
Charles L. Miller, Director
Division of Industrial and
Medical Nuclear Safety
Office of Nuclear Material Safety
and Safeguards
Technical contacts: Donna-Beth Howe, Ph.D., NMSS Jose M. Diaz, R-I, Atlanta Office
(301) 415-7848 (404) 562-4736 E-mail: dbh@nrc.gov E-mail: jxd2@nrc.gov
Attachments:
1. List of Recently Issued NRC Information Notices
2. List of Recently Issued NMSS Information Notices This IN requires no specific action nor written response. If you have questions about the
information in this notice, please contact the appropriate technical contact listed below.
/RA/ PKHolahan for
Charles L. Miller, Director
Division of Industrial and
Medical Nuclear Safety
Office of Nuclear Material Safety
and Safeguards
Technical contacts: Donna-Beth Howe, Ph.D., NMSS Jose M. Diaz, R-I, Atlanta Office
(301) 415-7848 (404) 562-4736 E-mail: dbh@nrc.gov E-mail: jxd2@nrc.gov
Attachments:
1. List of Recently Issued NRC Information Notices
2. List of Recently Issued NMSS Information Notices
DISTRIBUTION:
IMNS r/f RPDC RIDSRGNSMAIL CENTER
ADAMS Accession#: ML040330279 DOCUMENT NAME: G:\HOWE\TAR FY 2004\New OJOS Sr-90 IN.wpd
- see previous concurrence
OFC MSIB E R-I Tech. Ed. MSIB MSIB IMNS
NAME DBHowe* JDiaz* EKraus* RTorres* TEssig* CMiller/PKH for
DATE 12/ 3 /03 1/ 14 /04 1/ 16 /04 12/ 3 /03 1/ 23 /04 1/30/04 OFFICIAL RECORD COPY
Attachment 1 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
______________________________________________________________________________________
Information Date of
Notice No. Subject Issuance Issued to
______________________________________________________________________________________
2004-01 Auxiliary Feedwater Pump 01/21/2004 All holders of operating licenses
Recirculation Line Orifice or construction permits for
Fouling - Potential Common nuclear power reactors, except
Cause Failure those that have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor.
2002-26, Sup 2 Additional Failure of Steam 01/09/2004 All holders of an operating license
Dryer After A Recent Power or a construction permit for
Uprate nuclear power reactors, except
those that have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor.
2003-11, Sup 1 Leakage Found on Bottom- 01/08/2004 All holders of operating licenses
Mounted Instrumentation or construction permits for
Nozzles nuclear power reactors, except
those that have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor.
2003-22 Heightened Awareness for 12/09/2003 All medical licensees and NRC
Patients Containing Detectable Master Materials License medical
Amounts of Radiation from use permittees.
Medical Administrations
2003-21 High-Dose-Rate-Remote- 11/24/2003 All medical licensees.
Afterloader Equipment Failure
Note: NRC generic communications may be received in electronic format shortly after they are
issued by subscribing to the NRC listserver as follows:
To subscribe send an e-mail to <listproc@nrc.gov >, no subject, and the following
command in the message portion:
subscribe gc-nrr firstname lastname
______________________________________________________________________________________
OL = Operating License
CP = Construction Permit
Attachment 2 LIST OF RECENTLY ISSUED
NMSS INFORMATION NOTICES
______________________________________________________________________________________
Information Date of
Notice No. Subject Issuance Issued to
______________________________________________________________________________________
2003-22 Heightened Awareness for 12/09/2003 All medical licensees and NRC
Patients Containing Detectable Master Materials License medical
Amounts of Radiation from use permittees.
Medical Administrations
2003-21 High-Dose-Rate-Remote- 11/24/2003 All medical licensees.
Afterloader Equipment Failure
2003-20 Derating Whiting Cranes 10/22/2003 All holders of operating licenses
Purchased Before 1980 for nuclear power reactors, except those who have
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor vessel; applicable
decommissioning reactors, fuel
facilities, and independent spent
fuel storage installations.
2003-16 Icing Conditions Between 10/06/2003 All 10 CFR Part 72 licensees and
Bottom of Dry Storage System certificate holders.
and Storage Pad
2003-12 Problems Involved in 08/22/2003 All holders of 10 CFR Parts 32, Monitoring Dose to the Hands 33, and 35 licenses.
Resulting from the Handling of
Radiopharmaceuticals
2003-10 Criticality Monitoring System 08/04/2003 All U.S. Nuclear Regulatory
Degradation at BWX Commission (NRC) licensees
Technologies, Inc., Nuclear authorized to possess a critical
Products Division, Lynchburg, mass of special nuclear material.
Note: NRC generic communications may be received in electronic format shortly after they are issued by
subscribing to the NRC listserver as follows:
To subscribe send an e-mail to <listproc@nrc.gov >, no subject, and the following command in the
message portion:
subscribe gc-nrr firstname lastname
______________________________________________________________________________________
OL = Operating License
CP = Construction Permit