Summary and Insights into the TG-43U1S2 Report on...
Transcript of Summary and Insights into the TG-43U1S2 Report on...
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Summary and Insights into the TG-43U1S2Report on brachytherapy dosimetry
Mark J. Rivard,1 Wayne M. Butler,2 and Facundo Ballester3
on behalf of the report authors1Alpert Medical School of Brown University, Providence, RI
2Schiffler Cancer Center and Wheeling Jesuit University, Wheeling, WV3Departamento de Física Atómica, Molecular y Nuclear Universitat de Valencia, Burjassot, ESPAÑA
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Disclosures
This session may be interpreted as societal guidance.
Specific commercial equipment, instruments, and materials are listedto fully describe the necessary procedures. Such identification does not
imply endorsement by the presenters, nor that these products are necessarily the best available for these purposes.
For work performed preceding this report, Dr. Rivard has received research support from GE Healthcare, CivaTech Oncology, and IsoRay Medical; Dr. Ballester from
Elekta; Dr. DeWerd from GE Healthcare, CivaTech Oncology, and IsoRay Medical; Dr. Ibbott from IsoRay Medical; Dr. Meigooni from Intl. Brachytherapy and IsoAid;
and Dr. Papagiannis from Elekta AB and BEBIG GmbH
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Learning Objectives
1. understand method for deriving consensus datasetssee 11 practical examples
2. become familiar with recommendations to vendors of BT sources and TPSs
3. identify reference data for BT dosimetry investigations:radionuclide source spectra and half-lives,reference dose scoring media, andTLD methodological corrections
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Radial Dose Functions
Pd-103
I-125
Cs-131
S18, I-125
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1D Anisotropy Functions
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1D Anisotropy Functions
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Summary and Insights into the TG-43U1S2Report on brachytherapy dosimetry:
Report summary, methods to formulate consensus data, and presentation of the consensus datasets
Mark J. Rivard,1 Wayne M. Butler,2 and Facundo Ballester3
on behalf of the report authors1Alpert Medical School of Brown University, Providence, RI
2Schiffler Cancer Center and Wheeling Jesuit University, Wheeling, WV3Departamento de Física Atómica, Molecular y Nuclear Universitat de Valencia, Burjassot, ESPAÑA
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AAPM Task Group 43 formed in 1988 and published its report in 1995
• Included data on 192Ir and 3 permanent seed LDR sources
• 125I models 6711 and 6702 and 103Pd model 200
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Subsequent TG-43 reports
• 2004, TG-43 U1
• Updated 3 models
• Added 5 new seed models
• Included Bebig and Best 125I models
• 2007, TG-43 U1S1
• Added 8 new seed models
• Included IsoAid 125I and Best 103Pd models
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Finally…!
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The latest report, TG-43 U1S2(Med Phys, 44:e297–e338, 2017)
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TG-43 Update 1, Supplement 2
• Added 11 new seed models
• Included Elekta and Theragenics 125I, CivaTech and IsoAid 103Pd and
IsoRay 131Cs models
• Data for 5 discontinued models included for retrospective analyses
• Contains 38 data tables
• > 6,800 data points
• 42 pages in Med Phys
• Considerable manual labor!
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in TG-43 U1S2
• Dose rate tables for each source for r vs. polar
angle
• r range from 0.1 cm to 10 cm
• Angles from 0° to 90°
• Dose rate tables for each source in Cartesian
coordinates (along and away)
• r from 0 to 7 cm
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TABLE XVIII. Dose rates (cGy h-1 U-1) per unit source strength (Theragenics model AgX100 125I source)
• Easily check your TPS (use Tavg)
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There is, of course, an erratum
• Med Phys, 45:971–974, 2018
• 6 data tables republished with errors corrected
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TG-43 dose equation for a line source
SK = air-kerma strength in cGy·cm²/h = U
Λ = dose rate constant in cGy / h·U
gL(r) = radial dose function (atten & scatter)
F(r,θ) = 2D anisotropy function
Tavg = average life of the radionuclide = t½/ln2
GL(r,θ) = geometry function of source distribution
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Reference quality published data necessary for consensus
• Effective active length, Leff, determined for geometry function calculations
• Two methods used to determine dosimetry parameters
• Experimental: TLD
• Solid to liquid corrections used
• Monte Carlo transport is up-to-date
• cross section library
• scoring estimator
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The consensus dose rate constant, Λ
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The radial dose and 2D anisotropy functions
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Geometry functions
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All candidate data was checked for consistency
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Calculated g(r) were plotted to reveal outliers(Elekta model 130.002)
0.0
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0 1 2 3 4 5 6 7 8 9 10
g(r
)
r [cm]
ratio TLD/PC
MC low res
TLD
PC high res
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F(r,θ) for r ≤ 1 cm (Elekta model 130.002)
0.15
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0 10 20 30 40 50 60 70 80 90
F(r
,8)
fro
m P
C
degrees
0.1
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F(r,θ) for r ≥ 1 cm (Elekta model 130.002)
0.35
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0.55
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0.65
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0.75
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0.95
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1.05
0 10 20 30 40 50 60 70 80 90
F(r
,8)
fro
m P
C
degrees
1
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Interpolation and extrapolation
g(r) r linear log-lin
ri 0.1 0.576 0.576
rx 0.15 0.679 0.664
rf 0.25 0.884 0.884
• Interpolation of F(r,θ) uses a bi-linear approach
• Interpolation of g(r) uses a log-linear approach
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Log-linear interpolation for g(r) compared to linear interpolation
0.5
0.6
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0.1 0.15 0.2 0.25
g(r)
r
linear log-lin
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In TG-43 U1S2, interpolated data is bold and extrapolated is underlined
Interpolated from r = 0.7 and 0.8
Extrapolated from θ = 6º or from 11º
• Those values are not derived from numbers in the printed report but from nearby high resolution values.
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Use the report wisely, & thank you
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Summary and Insights into the TG-43U1S2Report on brachytherapy dosimetry:
Dosimetry parameter dependence on radionuclide, influence of dataset grid size, and recommendations to vendors of
brachytherapy sources and treatment planning systems
Mark J. Rivard,1 Wayne M. Butler,2 and Facundo Ballester3
on behalf of the report authors1Alpert Medical School of Brown University, Providence, RI
2Schiffler Cancer Center and Wheeling Jesuit University, Wheeling, WV3Departamento de Física Atómica, Molecular y Nuclear Universitat de Valencia, Burjassot, ESPAÑA
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Learning objectives
33
show dependence of TG-43 parameter values on radionuclide
highlight influence of consensus dataset grid size on TPS calculations
identify societal recommendations to vendors of
brachytherapy sources and treatment planning systems
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Contents
34
background
dependence of TG-43 parameter values on radionuclide
resolution grid size influence on TPS calculations
recommendations to seed and TPS vendors
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TG-43U1S2 seedsI-125
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TG-43U1S2 seedsPd-103
Cs-131
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Dose rate constant values: Dependence on radionuclide
37
dose rate constant, CONΛ
I-125
Pd-103
Cs-131
For seeds of the same
radionuclide,
the dose rate constant is
approximately constant
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Radial dose function: Dependence on radionuclide
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For seeds of the same
radionuclide,
the radial dose functions
are indistinguishable,
except for r < 0.5 cm.
special case: S18 125I sed
Pd-103I-125
Cs-131
S18, I-125
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2D anisotropy function values: Dependence on radionuclide
39
2D anisotropy function, CONF(r,θ)
For seeds of the same
radionuclide,
the 2D anisotropy
functions are similar.
special case: S18 125I seed
S18
r = 0.5 cm
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1D anisotropy function values: Dependence on radionuclide
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1D anisotropy function, CONφan(r)
For seeds of same
radionuclide, 1D anisotropy
functions exhibit specific
characteristics for
r < 0.5 cm
special case: S18 125I seed
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41
1D anisotropy function functions for the 11 seed models
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Influence of the grid size resolution on TPS calculations
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Data interpolation/extrapolation method recommendations
Perez-Calatayud, et al., Med. Phys. 39, 2904-2929 (2012)
Pérez-Calatayud, et al. Med. Phys. 39, 2904-2929 (2012)
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Influence of grid size resolution on TPS calculations
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The aim of this work is to evaluate performance of a commercial BT TPS with vendor TG-43 data,
analyze possible discrepancies with respect to a proper reference source and its implications for
standard treatments, and judge the effectiveness of certain widespread recommended quality
controls to find potential errors related with interpolations of TG-43 tables.
Valdés, et al., J. Appl. Clin. Med. Phys. 16, 3-17 (2015)
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Valdés, et al., J. Appl. Clin. Med. Phys. 16, 3-17 (2015)
differences > 2% encompass ~17% of surrounding source volume
low-E LDR seeds also exhibitdose anisotropy and are equally susceptible to interpolation errors
192Ir
Influence of grid size resolution on TPS calculations
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2D anisotropy function grids in TG-43U1S2
Influence of grid size resolution on TPS calculations
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Consensus datasets
46
preferences on dosimetry datasets origin for clinical use
� societal consensus data: TG-43U1, TG-43U1S1, TG-43U1S2 reports
� data posted on the AAPM/IROC Houston Brachytherapy Source Registry
� http://rpc.mdanderson.org/RPC/BrachySeeds/Source_Registry.htm
o for a seed not posted on the Registry: the user should perform a
study similar to the ones described in the TG-43U1S2 report.
� early adopters of a seed should collaborate with vendor, vendor
dosimetry consultant, and TPS vendor
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preferences on dosimetry datasets origin for clinical use
� seeds approved in Europe but new in North America:
follow GEC-ESTRO recommendations
� dataset on ESTRO and Carleton University websites as Excel spreadsheet formats
https://www.estro.org/about/governance-organisation/committees-activities/tg43
http://www.physics.carleton.ca/clrp
Consensus datasets
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Consensus datasets
preferences on dosimetry datasets origin for clinical use
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Seed and TPS vendor dosimetry recommendations
49
Seed vendors:
o source strength must be specified in terms of SK in U units
o contained activity should only be used for regulatory purposes:
NRC reported events due to the use of apparent activity instead of SK
https://www.nrc.gov/docs/ML0807/ML080710054.pdf
In the manufacturer’s certificate, the date format must be specified:
� DD/MM/YY or MM/DD/YY or YY/MM/DD?
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TPS vendors:
o use consensus datasets
o use of the correct L (or Leff)
o follow recommended methods for interpolation/extrapolation
o the date format must be specified: DD/MM/YY or MM/DD/YY or YY/MM/DD
o use QA tables in the report available to the user
o implement 1D approximation for dose calculation
o information on manu. certificate and TPS must be the same
Seed and TPS vendor dosimetry recommendations
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AcknowledgementsTG-43U1S2 members
Mark J Rivard, chairFacundo Ballester, vice chairWayne M. Butler
Larry A. DeWerdGeoffrey S. IbbottAli S. MeigooniChistopher S. MelhusMichael G. Mitch
Ravinder NathPaniagottis Papagiannis
Valencia University GroupJavier VijandeJosé Pérez-CalatayudCristian Candela-JuanDomingo Granero 51
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Summary and Insights into the TG-43U1S2Report on brachytherapy dosimetry:
Radionuclide Source Spectra and Half-Lives, Reference Dose Scoring Media, and TLD Methodological Corrections
Mark J. Rivard,1 Wayne M. Butler,2 and Facundo Ballester3
on behalf of the report authors1Alpert Medical School of Brown University, Providence, RI
2Schiffler Cancer Center and Wheeling Jesuit University, Wheeling, WV3Departamento de Física Atómica, Molecular y Nuclear Universitat de Valencia, Burjassot, ESPAÑA
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• Recommended source:National Nuclear Data Center (NNDC) of Brookhaven National Laboratory
http://www.nndc.bnl.gov/chart/
• The NNDC collects, evaluates, and disseminates nuclear physics data for basic nuclear research and applied nuclear technologies.
http://www.nndc.bnl.gov/chart/reCenter.jsp?z=46&n=57 103Pd
De Frenne, Nuclear Data Sheets 110, 2081 (2009) 16.991(34) days
http://www.nndc.bnl.gov/chart/reCenter.jsp?z=53&n=72 125I
Katakura, Nuclear Data Sheets 112, 495 (2011) 59.407(10) days
http://www.nndc.bnl.gov/chart/reCenter.jsp?z=55&n=76 131Cs
Khazov et al, Nuclear Data Sheets 107, 2715 (2006) 9.689(16) days
§ 5.B. Radionuclide Half-Lives
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• choice of reference data not a simple decision based on current evaluations
NNDC is comprehensive for gamma ray tabulations (limited for x rays)
NIST is thorough for x-ray transition energies, but not intensities
NCRP Report 58 is coarse and from a 1984 evaluation
Lund University (Sweden) and Lawrence Berkeley National Lab is from 1999
Laboratoire National Henri Becquerel (France) is missing 103Pd and 131Cs
• combine evaluations for AAPM+GEC-ESTRO 131Cs reference data
• choice of reference data weakly influences dose calculations
choice of reference data weakly influences TG-43 dosimetry parameters
§ 5.A. Radionuclide Photon Spectrum
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§ 5.A. Radionuclide Photon Spectrum: 131Cs
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• density of water (H2O) at 22 ºC is 0.998 g/cm3
• standard temperature and pressure (STP) of air depends on locale
N. American STP is 22 ºC and 101.325 kPa
European STP is 20 ºC and 101.325 kPa
• density of dry air depends on ambient conditions
N. American ρair is 1.197 mg/cm3
European ρair is 1.205 mg/cm3
• air composition (by mass) is fixed
75.527% N, 23.178% O, 1.283% Ar, 0.012% C
§ 5.C. Reference Dose Scoring Media
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§ 5.D. TLD Dosimetry Methodological Corrections( ) ( ) ( )
,D Q M Q N Q
med D med=
( )( )
, ( )
M QS Q
AD med D Qmed
=
( )( ) ( ) 1 1( )
, ( ) ( ) ( ) ( )( )
D QM Q M Q TLDS QAD med D Q D Q k Q f QD Q
med med bqTLD
= = =
( ) 1 1,
, ( )0,
S QAD medrel
AD med rel relS Q k fAD med bq
S = =
( ) 1 1 1,( )
relS QAD med
rel relP Pkphant phantfbq
E r = =
(1)
(2)
(3)
(4)
(5)
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• understand relationship between detector measurement, medium corrections, detector corrections, and absorbed dose to the medium as function of radiation quality (i.e., photon energy)
• convert detector measurement
to absorbed dose to the medium
via the absorbed dose calibration coefficient
§ 5.D. TLD Dosimetry Methodological Corrections
( ) ( ) ( ),
D Q M Q N Qmed D med
=
( ) ( ) ( ),
D Q M Q N Qmed D med
( ) ( ) ( )D Q M Q N Qmed D med
( ) ( ) ( )D Q M Q N Qmed D med
=
(1)
( )S QAD med
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• inverse of the absorbed dose calibration coefficient
is the absorbed dose sensitivity coefficient
§ 5.D. TLD Dosimetry Methodological Corrections
(2)( )
( ), ( )
M QS Q
AD med D Qmed
=
( ),
S QAD med
( ) ( ) ( ),
D Q M Q N Qmed D med
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• partition into two components
avg. TLD dose for
radiation quality
intrinsic dependence
determined only by
measurement of signal formation
absorbed dose sensitivity ,
dependent on medium and detector,
may be estimated with Monte Carlo
§ 5.D. TLD Dosimetry Methodological Corrections
(3)
( )( ) ( ) 1 1( )
, ( ) ( ) ( ) ( )( )
D QM Q M Q TLDS QAD med D Q D Q k Q f QD Q
med med bqTLD
= = =
( )( ) ( ) 1 1
( ) ( ) ( ) ( )( )
D QM Q M Q TLD
D Q D Q k Q f QD Qmed med bqTLD
= = =
( ),
S QAD med
( )( ) ( ) 1 1
( ) ( ) ( ) ( )D Q D Q k Q f Qmed med bq
= = =( ),
S QAD med
( )S QAD med
( )S QAD med
( ) ( ) ( ) ( )D Q D Q k Q f Qmed med bq
= = =
( ) ( ) ( ) ( )D Q D Q k Q f Q
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• relative absorbed dose sensitivity coefficient uses ratios with and
ratio to calibration
relative intrinsic dependence of the detector
relative absorbed dose sensitivity of the detector
§ 5.D. TLD Dosimetry Methodological Corrections
(4)
( )S QAD med
( ) 1 1,
, ( )0,
S QAD medrel
AD med rel relS Q k fAD med bq
S = =
( )S Q= =
( )0S Q= =
rel relf
rel relkbq
= =
( ) 1 1
( ) rel relk fbq
= =,
relAD med
S
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• account for phantom presence different than calibration medium
• relative energy response function
dosimetry investigators should specify
assumptions and methods for deriving
the methodological corrections to dose
§ 5.D. TLD Dosimetry Methodological Corrections
(5)
( ) 1 1 1,( )
relS QAD med
rel relP Pkphant phantfbq
= =
P Pphant phant= =
( ) 1 1 1
rel relP Pkphant phantfbq
= =( )E r
( )E r
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• 11 new sources evaluated with consensus data provided
• CONΛ for 103Pd seeds all within 0.6% of 0.697 cGy/h/U
except for plastic encapsulated model 1032P and CS10 sources
• CONΛ for 125I seeds all within 1.2% of 0.942 cGy/h/U
except for plastic encapsulated model S18 source
• CONΛ for 131Cs (1.056) increased as expected relative to 103Pd and 125I
• MCΛ / EXPΛ = 0.961 on avg. for all 11 source models
• CONg(r) and CONφan(r) varied with energy and r as expected
• QA tables (along-away, polar coordinates) were provided
• medical physicists should document their TPS commissioning
Summary
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WAYNE’S SLIDES GO HERE