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 manufacturer’s 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.

ML040330279
IN 2004-02 

Page 2 of 4 

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 manufacturer’s 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 licensee’s or permittee’s 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 
IN 2004-02

Page 3 of 4

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 manufacturer’s 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 user’s 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 user’s 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 manufacturer’s 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.
IN 2004-02

Page 4 of 4

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
____________________________________________________________________________________

OL = Operating License

CP = Construction Permit

Attachment 1

IN 2004-02

Page 1 of 1

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

____________________________________________________________________________________

Information Date of 

Notice No. Subject Issuance Issued to

____________________________________________________________________________________

2004-01 Auxiliary Feedwater Pump

Recirculation Line Orifice

Fouling - Potential Common

Cause Failure

01/21/2004 All holders of operating licenses

or construction permits for

nuclear power reactors, except

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

Dryer After A Recent Power

Uprate

01/09/2004 All holders of an operating license

or a construction permit for

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 BottomMounted Instrumentation

Nozzles

01/08/2004 All holders of operating licenses

or construction permits for

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

Patients Containing Detectable

Amounts of Radiation from

Medical Administrations

12/09/2003 All medical licensees and NRC

Master Materials License medical

use permittees.

2003-21 High-Dose-Rate-RemoteAfterloader Equipment Failure11/24/2003 All medical licensees.

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

IN 2004-02

Page 1 of 1

LIST OF RECENTLY ISSUED

NMSS INFORMATION NOTICES

____________________________________________________________________________________

Information Date of 

Notice No. Subject Issuance Issued to

____________________________________________________________________________________

2003-22 Heightened Awareness for

Patients Containing Detectable

Amounts of Radiation from

Medical Administrations

12/09/2003 All medical licensees and NRC

Master Materials License medical

use permittees.

2003-21 High-Dose-Rate-RemoteAfterloader Equipment Failure11/24/2003 All medical licensees.

2003-20 Derating Whiting Cranes

Purchased Before 1980

10/22/2003 All holders of operating licenses

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

Bottom of Dry Storage System

and Storage Pad

10/06/2003 All 10 CFR Part 72 licensees and

certificate holders.

2003-12 Problems Involved in

Monitoring Dose to the Hands

Resulting from the Handling of

Radiopharmaceuticals

08/22/2003 All holders of 10 CFR Parts 32,

33, and 35 licenses.

2003-10 Criticality Monitoring System

Degradation at BWX

Technologies, Inc., Nuclear

Products Division, Lynchburg,

VA

08/04/2003 All U.S. Nuclear Regulatory

Commission (NRC) licensees

authorized to possess a critical

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