AAPM Administrative Policy AP 75B (12/15/2010):
Joint AAPM/RPC Registry of Brachytherapy Sources
Complying with AAPM Dosimetric Prerequisites
A. Purpose and Rationale
Many individual users contact the Radiological Physics Center (RPC) and the AAPM
Brachytherapy Subcommittee (BTSC) asking which of the available photon-emitting
brachytherapy source models conform to the AAPM’s guidelines. The AAPM guidelines
are based on reports for low-energy and high-energy photon-emitting brachytherapy
sources:
1.
R. Nath, L. L. Anderson, G. Luxton, K. A. Weaver, J. F. Williamson, and A. S. Meigooni, "Dosimetry of interstitial
brachytherapy sources: Recommendations of the AAPM Radiation Therapy Committee Task Group No. 43," Med.
Phys. 22, 209–234 (1995).
2. R. Nath, L. L. Anderson, J. A. Meli, A. J. Olch, J. A. Stitt, and J. F. Williamson, "Code of practice for brachytherapy
physics: Report of the AAPM Radiation Therapy Committee Task Group No. 56," Med. Phys. 24, 1557–1598 (1997).
3. H. D. Kubo, G. P. Glasgow, T. D. Pethel, B. R. Thomadsen, and J. F. Williamson, "High dose rate brachytherapy
treatment delivery: Report of the AAPM Radiation Therapy Committee Task Group No. 59," Med. Phys. 25, 375–403
(1998).
4. J. F. Williamson, B. M. Coursey, L. A. DeWerd, W. F. Hanson, R. Nath, and G. Ibbott, ‘‘Guidance to users of Nycomed
Amersham and North American Scientific, Inc. I-125 Interstitial Sources: Dosimetry and calibration changes:
Recommendation of the American Association of Physicists in Medicine Radiation Therapy Committee Ad Hoc
Subcommittee on Low-Energy Seed Dosimetry,’’ Med. Phys. 26, 570–573 (1999).
5. J. F. Williamson, B. M. Coursey, L. A. DeWerd, W. F. Hanson, R. Nath, M. J. Rivard, and G. Ibbott, ‘‘On the use of
apparent activity (Aapp) for treatment planning of 125I and 103Pd interstitial brachytherapy sources: Recommendations of
the American Association of Physicists in Medicine Radiation Therapy Committee Subcommittee on Low-Energy
Brachytherapy Source Dosimetry,’’ Med. Phys. 26, 2529–2530 (1999).
6. M. J. Rivard, B. M. Coursey, L. A. DeWerd, W. F. Hanson, M. S. Huq, G. S. Ibbott, M. G. Mitch, R. Nath, and J. F.
Williamson, "Update of AAPM Task Group No. 43 Report: A revised AAPM protocol for brachytherapy dose
calculations," Med. Phys. 31, 633–674 (2004).
7. L. A. DeWerd, M. S. Huq, I. J. Das, G. S. Ibbott, W. F. Hanson, T. W. Slowey, J. F. Williamson, and B. M. Coursey,
"Procedures for establishing and maintaining consistent air-kerma strength standards for low-energy, photon-emitting
brachytherapy sources: Recommendations of the Calibration Laboratory Accreditation Subcommittee of the American
Association of Physicists in Medicine," Med. Phys. 31, 675–681 (2004).
8. Z. Li, R.K. Das, L. A. DeWerd, G. S. Ibbott, A. S. Meigooni, J. Perez-Calatayud, M. J. Rivard, R. S. Sloboda and J. F.
Williamson, "Dosimetric prerequisites for routine clinical use of photon emitting brachytherapy sources with average
energy higher than 50 keV," Med. Phys. 34, 37-40 (2007).
9. M. J. Rivard, W. M. Butler, L. A. DeWerd, M. S. Huq, G. S. Ibbott, A. S. Meigooni, C. S. Melhus, M. G. Mitch, R. Nath,
and J. F. Williamson, "Supplement to the 2004 update of the AAPM Task Group No. 43 Report," Med. Phys. 34, 2187–
2205 (2007).
10. W. M. Butler, W. S. Bice Jr., L. A. DeWerd, J. M. Hevezi, M. S. Huq, G. S. Ibbott, J. R. Palta, M. J. Rivard, J. P.
Seuntjens, and B. R. Thomadsen, "Third-party brachytherapy source calibrations and physicist responsibilities: Report
of the AAPM Low Energy Brachytherapy Source Calibration Working Group," Med. Phys. 35, 3860–3865 (2008).
The Radiation Therapy Oncology Group (RTOG) has asked the RPC to identify those
brachytherapy sources that meet the AAPM dosimetric prerequisites, since participating
institutions will be expected to use sources meeting these prerequisites. This joint
AAPM/RPC Source Registry is intended to satisfy the RTOG request and similar
requests that might arise from other cooperative clinical trial study groups.
The RPC and AAPM work together to identify and register brachytherapy
sources that meet the AAPM criteria. A webpage-based Registry is maintained by the
RPC, listing sources that meet the AAPM criteria. RPC relies on the AAPM’s BTSC,
through its Brachytherapy Source Registry Work Group (WGBSR), to establish the
criteria for including or excluding source models from this Registry, and to determine
which source models meet the criteria. As the recommendations are intended to apply
internationally, some of the agencies, organizations and standard laboratories identified
within the U.S. could be, at the discretion of the BTSC, interpreted in the context of the
arrangements in other countries where applicable.
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B. Compliance Registry Appearance and Contents
The Registry is in the form of a webpage reachable via hot links from both the RPC and
AAPM websites, and is entitled “Joint AAPM/RPC Registry of Brachytherapy Sources
Meeting the AAPM Dosimetric Prerequisites.” The webpage displays the following
information for each source model listed on the Registry: The vendor (manufacturer if
different), radionuclide, model number, trade name, date of addition to the Registry, and
dosimetry publications taken as evidence of compliance.
Links to this Policy, the AAPM prerequisites publications, other publications
subsequently determined to be relevant, as well as an application form to be used by
source vendors are kept accessible on the webpage.
The following text appears verbatim on the webpage:
The AAPM, through its Brachytherapy Subcommittee, has determined that the following
brachytherapy source models comply with the AAPM’s dosimetric prerequisites as set
forth in one of two publications: "Dosimetric prerequisites for routine clinical use of new
low-energy photon interstitial brachytherapy sources: Recommendations of the
American Association of Physicists in Medicine Radiation Therapy Committee". Med.
Phys. 25, 2269-2270 (1998), or “Dosimetric prerequisites for routine clinical use of
photon emitting brachytherapy sources with average energy higher than 50 keV," Med.
Phys. 34, 37-40 (2007). The manufacturers must also satisfy criteria established by the
AAPM Subcommittee on Calibration Laboratory Accreditation and described in a
publication (hereafter referred to as “the 2004 CLA Report”): “Procedures for
establishing and maintaining consistent air-kerma strength standards for low-energy,
photon-emitting brachytherapy sources: Recommendations of the Calibration
Laboratory Accreditation Subcommittee of the American Association of Physicists in
Medicine”. Med. Phys., 35 671-685 (2004). The criteria are summarized here.
(Note: The final phrase is a link to a new page that lists the following text:
The AAPM dosimetric prerequisites for brachytherapy sources may be
summarized as follows The vendor provides air-kerma strength calibrations that
are directly or indirectly traceable to the air-kerma strength standards (SK,N99 for
low energy sources) for photon emitting brachytherapy sources maintained by
NIST, or in the case of HDR 192Ir, the standard developed by the University of
Wisconsin and maintained by the ADCLs.
• A full set of TG-43 dosimetric parameters is available, supporting both
calculation of the 2-D dose-rate distribution and, for low-energy seed
models, the 1-D isotropic point source approximation. This set of
dosimetric parameters must be based upon at least one experimental
study and at least one Monte Carlo study of the source model’s
dosimetric parameters. These studies must be performed by
investigators having independence from the manufacturer, and have
been accepted for publication in a peer-reviewed journal.
• The vendor has assured that the calibration from NIST has been
transferred to the ADCLs.
• The vendor has implemented a program that is compliant with the
2004 CLA Report for periodically comparing its air-kerma strength
calibrations with the NIST primary standard and the secondary
standards maintained by the ADCLs.
The complete text of the 2004 CLA report is available here.)
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The AAPM dosimetric prerequisites for high-energy sources may be summarized
as follows:
• The single-source dose distribution used for clinical treatment planning
should be based upon two dose-rate determinations, one of which is a
theoretical calculation method such as the Monte Carlo method, and
the other an experimental measurement. Note that a single dosimetric
study is acceptable for certain 137Cs, 192Ir, and 60Co sources under
specific circumstances (see the complete text.)
• A full set of TG-43 dosimetric parameters is available, supporting
calculation of the 2-D dose-rate distribution. In addition, a set of “along
and away” tables must be provided.
• The vendor provides air-kerma strength calibrations that are directly or
indirectly traceable to the air-kerma strength standards for photon
emitting brachytherapy sources maintained by NIST.
• The vendor has implemented a program of periodically comparing its
air-kerma strength calibrations with the NIST primary standard or the
secondary standards maintained by the ADCLs that is compliant with
the CLA Report. Note, however, that while the CLA Report specifically
addresses low-energy sources, the AAPM has confirmed that
manufacturers are expected to comply with its requirements for highenergy sources also. The CLA Report was dedicated to low-energy
sources. Until a similar report is available for high-energy sources,
vendors must apply these guidelines with appropriate variations. For
example, it may be necessary to send a source or a measurement
system to NIST or an ADCL.
• In addition, the AAPM requires biennial comparisons for high-energy
sources through Measurement Quality Assurance (MQA) tests.
• In the case of experimental sources for which no ADCL interpolative or
NIST primary standard exists, the end user institution is responsible for
calibrating the sources with an ionization chamber of appropriate
dimensions that has calibrations directly traceable to an appropriate
NIST air-kerma standard.
The webpage will contain the following disclaimer (the disclaimer will be
displayed in a new page by clicking on a link labeled “Disclaimer”):
The AAPM and the RPC maintain this Registry solely as a service to their
members and clients. Neither the AAPM nor the RPC endorses or approves
specific products. No statement regarding the quality of construction, safety, or
clinical effectiveness of specific sources is expressed or implied by inclusion or
exclusion of sources from this Registry. The AAPM Brachytherapy Subcommittee
bases its decisions to place or exclude source models in this Registry on the
content of published papers and the vendor’s descriptions of its calibration
procedure. The AAPM and the RPC neither warrant nor are responsible for (a)
accuracy of the published dosimetry studies and applicability to the sources as
manufactured; (b) compliance of the vendor with its stated procedures; or (c) the
accuracy of any particular brachytherapy source calibration. The AAPM does not
monitor on a continuing basis the compliance of the vendor’s calibration
procedures with the AAPM prerequisites nor the compatibility of its source design
and manufacturing practices with the published dosimetry data.
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C. Procedures for Registry Inclusion
1. Request for inclusion of a source model is initiated by the vendor applying to the
AAPM BTSC for this purpose.
2. A special case exists for orphaned sources; those no longer commercially
available, but still in regular use in hospitals. These must be sources with long
half-life and suitable dose rates which consequently comprise only certain
models of 137Cs and 60Co sources. In the case of these sources, there is no
manufacturer available to submit the Registry application forms. For these
orphaned sources, the AAPM and RPC have agreed to an alternative procedure
for Registry application: a hospital that wishes to participate in a clinical trial that
involves brachytherapy sources not currently posted on the Registry may submit
the application, listing the dosimetric studies available and the dosimetry
parameters to be used for treatment planning. The hospital must also describe
their method of source strength traceability for review by the RPC to assure the
correct calibration of the sources. In the special case of source trains, in which
individual sources cannot be removed for calibration with a well chamber, the
hospital may describe a method of calibration at a distance in a phantom, in
accordance with calibration procedures described in the peer-reviewed literature.
3. Upon receipt, BTSC will deliver the application to WGBSR, which will review the
published/accepted dosimetry papers. WGBSR will review the vendor’s
statements regarding calibration procedures with appropriate NIST Group Leader
as well as the ADCL Directors and the AAPM CLA Subcommittee chair. WGBSR
may withhold entry into the Registry until any discrepancies between the
vendor’s statements and calibration lab personnel observations are resolved
satisfactorily. Following its review, WGBSR will forward a recommendation for or
against inclusion in the Registry to BTSC.
4. BTSC has adopted the following “Independence Policy” (reproduced from
“Update of AAPM Task Group No. 43 Report: A revised AAPM protocol for
brachytherapy dose calculations.” Med. Phys. 31, 633-674 (2004):
The first meaning of “independent studies” is that they are performed, written,
and published by investigators who are affiliated with institutions independent of
the source vendor and who have no major conflicts-of interest with that vendor.
The second meaning of “independent studies” is that they are scientifically
independent of one another, i.e., they represent independent and distinct
estimations of the same quantities. In the case of two measurement based studies,
this will usually mean that two different investigators have used their own
methodologies for measuring Λ and sampling the relative dose distribution, as
TLD dosimetry is highly technique and investigator dependent. In the case of an
empirical study and a Monte Carlo study, if properly executed, they will yield
scientifically independent estimates of the TG-43 parameters. Thus, so long as
the two studies are successfully scrutinized by the peer-review process and satisfy
the AAPM scientific requirements, the empirical and Monte Carlo investigator
author lists can overlap or even be identical. It is permissible to publish the
Monte Carlo and measured estimates in the same paper so long as the two datasets
are independently tabulated. In this context, “Not independent” means that the
one study is used to modify the outcomes and methods of the other to improve
agreement between the two datasets in a manner that is not scientifically justified.
5. BTSC has adopted the following “Data Overlap Policy”: We require that, for
sources other than conventionally-encapsulated 137Cs, 192Ir, and 60Co sources,
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two dosimetry studies each assess: (a) Λ; (b) gL(r) or gP(r); (c) F(r,θ) and φan(r)
with r and θ sampling resolution at least as good as that recommended in the
2004 AAPM TG-43U1 (low-energy) and Li et al. 2007 (high-energy) reports so
that overlap between the two studies may readily reveal significant discrepancies
if present; and (d) L or Leff. As provided in reference (8) above, a single
dosimetry study is acceptable for conventionally-encapsulated 137Cs 192Ir, and
60
Co sources.
6. BTSC expects that vendors will comply with the AAPM prerequisite requiring
periodic comparisons of their calibrations with those of an independent
laboratory. Vendors can best do this by participating in comparisons with both
NIST and the ADCLs offering calibration services for that source model. The
AAPM has recommended a procedure and a frequency for such comparisons in:
“Procedures for establishing and maintaining consistent air-kerma strength
standards
for
low-energy,
photon-emitting
brachytherapy
sources:
Recommendations of the Calibration Laboratory Accreditation Subcommittee of
the American Association of Physicists in Medicine.” Med. Phys. 31, 675-681
(2004). The AAPM High Energy Brachytherapy Source Dosimetry working group
(HEBD) has set a calibration comparison frequency of two years for 60Co, 137Cs,
and 192Ir. Vendors of these high-energy sources should comply with this
comparison frequency.
7. Inclusion into the Registry is by majority vote of the BTSC. Written notification of
any unfavorable decision will be provided to the vendor by the WGBSR chair
along with an explanation.
8. Upon completion of a positive vote for inclusion by the BTSC, the RPC will be
informed of the decision and instructed to add the source model to the Registry.
9. BTSC reserves the right to withhold entry into the Registry if it believes that the
dosimetry articles contain technical errors or omissions; or rely on unproven or
inappropriate computational or experimental dosimetry methodologies.
10. Upon receipt of notification of rejection of a source from the Registry, a
manufacturer may appeal the decision by submitting a written request for review
to the AAPM Therapy Physics Committee (TPC). The TPC will assign a
minimum of three physicists to review the materials submitted to the BTSC and
the decision made by BTSC. TPC may decide to endorse or reverse the
decision of the BTSC.
11. This Policy may be revised as new source models or technologies emerge.
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D. Procedures for Registry Removal
Vendors (or hospitals according to section C.2) may request that a source be removed
from the Registry on the grounds that it will no longer be available to the medical
community. Immediate steps will be taken to remove the source from the Registry upon
receipt of a specific written request from the manufacturer, source distributor, or
hospital.
While manufacturers are encouraged to contact the BTSC should there be any
changes in their source manufacturing processes, the BTSC retains the discretion to
remove a product from the Joint AAPM/RPC Registry should it have grounds to believe
that a product, as currently manufactured, is no longer accurately characterized by the
reference-quality dose-distribution data submitted in support of Registry posting.
Reasonable grounds include, but are not limited to: change of manufacturing venue or
process, changes in source geometry and/or internal design, and discovery of
deficiencies in the published dosimetry data.
To retain Registry status, the vendor may submit for BTSC review a set of
revised dosimetry data that meet the standards specified by the AAPM dosimetric
prerequisites. Alternatively, the vendor may provide evidence to BTSC demonstrating
that the revised product is dosimetrically equivalent to the original source from which the
published and accepted dosimetry data were derived. Such information should include,
as applicable,
• Assurances from the vendor that manufacturing processes are unchanged and
the geometric and compositional structure of relevant source components are
unchanged.
• Review of quality assurance data (e.g., source radiograph, optical micrographs,
measurements, etc.) and vendor manufacturing processes with original
dosimetry investigators. These investigators must make a recommendation
regarding equivalence to BTSC and be willing to discuss findings with BTSC in
closed session.
• Review of NIST anisotropy and spectroscopy measurements before and after the
product change.
• A description of the vendor’s efforts and checks, along with their outcome, to
assure the equivalence of their current product with that at the time of original
dosimetric characterization.
The above information should be submitted to BTSC with sufficient lead-time that BTSC
can make a recommendation prior to the vendor distributing the modified product
commercially for routine clinical use.
Failure of a vendor to maintain a regular program of comparisons with NIST and
an ADCL, in accordance with the recommendations of the AAPM Calibration Laboratory
Accreditation (CLA) Subcommittee (Med. Phys. 31, 675-681 (2004) or Med. Phys. 34,
37-40 (2007)) may result in removal. When CLA determines that a vendor has
exceeded the recommended interval, the CLA chair will issue a warning. If a response
to the chair’s communication is not received within 60 calendar days, the CLA chair will
notify the BTSC chair that the source model should be removed from the Registry. The
decision to remove a source model from the Registry will be made by majority vote of
the BTSC. Upon completion of a vote to remove, the RPC will be instructed to remove
the source from the webpage Registry.
The following application is available for download from the Registry webpage:
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Application for Inclusion in the Joint AAPM/RPC Registry of Photon-Emitting
Brachytherapy Sources Complying with AAPM Dosimetric Prerequisites
To: Chair, Brachytherapy Subcommittee of the AAPM Therapy Physics Committee
From: __________________________________________________
(Manufacturer)
Technical contact and address:___________________________________________
The source identified below is believed by the manufacturer to meet the AAPM Prerequisites for dosimetry of
brachytherapy sources. The prerequisites for low-energy sources are defined in: "Dosimetric prerequisites for
routine clinical use of new low energy photon interstitial brachytherapy sources: Recommendations of the American
Association of Physicists in Medicine Radiation Therapy Committee". Med. Phys., 25, 2269-2270 (1998). The
prerequisites for high-energy sources are defined in: "Dosimetric prerequisites for routine clinical use of photon
emitting brachytherapy sources with average energy higher than 50 keV," Med. Phys. 34, 37-40 (2007). Note that
the recommendation regarding the calibration frequency of the vendor’s sources for in-house QA (recommendation
number 6 in the reference for high-energy sources) has been extended by the AAPM High Energy Brachytherapy
Source Dosimetry Working Group to 2 years for 192Ir, 137Cs, and 60Co sources. As the recommendations are
intended to apply internationally, some of the agencies, organizations, and standard laboratories identified within
the U.S. could be, at the discretion of the BTSC, interpreted in the context of the arrangements in other countries
where applicable.
The manufacturer hereby requests that the source be included by the AAPM and RPC on its web-based Registry of
sources complying with the Prerequisites.
Source Name: __________________________________
Model Number: _________________________________
Manufactured by: ________________________________
Marketed by: ____________________________________
Accredited Laboratory(s) providing initial reference calibration(s), and date of calibration(s):
________________________________________________
Dates of comparisons between accredited laboratory and vendor calibration procedures
during the last 2 years:
________________________________________________
Do you provide your clients with air-kerma strength calibrations directly or indirectly
traceable to the appropriate NIST standard?
________________________________________________
Please attach publications describing the dosimetric parameters of the source and
provide citations.
Please describe your program of measurement quality assurance and calibration
constancy. Indicate the laboratory(s) with which frequent comparisons will be made.
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