Photon and electron specific absorbed fractions for the...

$: Photon and electron specific absorbed fractions for the ...nucleus.iaea.org/HHW/MedicalPhysics/IDOS/3b_Wayson_134.pdf · The University of Florida. Department of Nuclear and Radiological$
Michael B. Wayson

November 10, 2010

The University of Florida

Department of Nuclear and Radiological Engineering

The United States of America

IAEA IDOS Symposium

Vienna, Austria

Photon and electron specific absorbed fractions for the University of Florida

paediatric hybrid computational phantoms

Outline

IntroductionComputational dosimetry

Internal dosimetry formalism

Materials and MethodsPhoton specific absorbed fractions (SAFs)

Electron SAFs

ResultsPhoton SAFs

Electron SAFs

Conclusion

The University of Florida -


Introduction

Computational dosimetryUse of virtual representations of humans in conjunction with radiation transport codes

“Quick” dose estimation

Accurate and detailed

Logistically feasible

Measures of interestAbsorbed fraction (AF)

Unitless

Specific absorbed fraction (SAF)Units of kg-1



sourceby emittedEnergy by target absorbedEnergy )( =← ST rrAF

T

STST m

rrAFrrSAF )()( ←=←

Introduction

MIRD Pamphlet No. 21 internal dosimetry formalism

( ) ( ) ( ) ( ) ( )∑∑ ∫ ←=←⎥⎦⎤

⎢⎣⎡=

∞

SS rSTS

rSTST rrSrArrSdttrArD ~,

0

( ) ( ) ( )∑∑ ←ΦΔ=←

=←i

STii T

STiiST rr

mrrYE

rrSφ

( )srA~

( )ST rrS ←

iE

iY

( )ST rr ←φ

iΔ

( )ST rr ←Φ= number of decays occurring in rS

= radionuclide S value (mGy/MBq s)

= energy of the ith

radiation

(MeV)

= yield of the ith

radiation

= delta value for the ith

radiation (MeV/decay)

= AF for rS

irradiating rT

= SAF for rS

irradiating rT

(g-1)



Photon SAFs

Monte Carlo N-Particle eXtended (MCNPX), Version 2.6

Phantom preparation – VoxelizationThree-dimensional continuous surface geometry converted to a three-dimensional matrix of voxels (rectangular prisms)

In-house MATLABTM code (Choonsik Lee, Ph.D.) to voxelize

Desired voxel dimensions equal to the skin thickness of the phantom of interest (ideally isotropic)

Skin added with in-house MATLABTM code (replaces outermost voxels with skin voxels)



Photon SAFs

Figure 1. (A) Axial, (B) coronal, and (C) sagittal views of the UFH00F phantom voxelized at an isotropic resolution of 0.663 mm.

(A) (B) (C)



Photon SAFs

Reading phantom geometry into MCNPXLattice file

In-house MATLABTM code to generate

Communicates to MCNPX the organ tags associated with each voxel

Creating internal sourceSource file

In-house MATLABTM code to generate

Defines source organ voxel coordinates

Defines sampling probability

For most organs, sp = 1

For active marrow and trabecular bone, sp ≠ 1AM and TB not explicitly modeled in NURBS/voxel phantom

Utilize skeletal AM and TB volume distribution for sampling probabilities

55 unique source organs for each phantom



Photon SAFs

21 photon energies ranging from from 10 keV to 4 MeVNumber of histories selected according to initial photon energy (based on experience)Tallies

General OrgansEnergy deposition averaged over target cell – Thick-target bremsstrahlung model

10 keV ≤ E ≤ 100 keVUnits of MeV/g

Total energy deposition in target cell100 keV < E ≤ 4 MeVUnits of MeV

Spongiosa (for skeletal targets)Volume-averaged photon fluence

10 keV ≤ E ≤ 4 MeVGeneral organ SAFs

SAFTTB = tallyTTB / Ephoton

SAFE-dep = tallyE-dep / (Ephoton mT)



Photon SAFs

Figure 2. (A) Hand, (B) right humerus, (C) pelvis, and (D) L-spine of the UFH00MF skeleton.

(A) (B) (C) (D)



Photon SAFs

Skeletal target SAFs (skeletal averaged dose)

( ) ( )( ) ( )∑ ∑ ←Φ⎥

⎦

⎤⎢⎣

⎡Φ

=←j i

isi

TTST Erj

ErDw

EkrrSAF

j,

0

jTw( )is Erj ,←Φ

k

= 6.24142 x 1013

(cm2

MeV kg) / (m2

J g)

E0 = initial monoenergetic photon energy (MeV)

= mass fraction of target tissue T

in each bone site j

= fluence incident on spongiosa of each bone site j

for

photons of energy Ei

(photons / cm2

/ history)

Ei = upper energy bin boundary for fluence tally and DRF (MeV)

( ) ( )iT ErD Φ = skeletal photon DRF (Gy m2

/ photon)



Electron SAFs

Novel method for minimizing poor statistics anticipated for cross-organ dose from bremsstrahlung photons

Spectrum of energies with many low energy photonsNumber of photons emitted is less than the number of starting electron historiesPTRAC file

In lieu of conventional talliesTracks many parameters for event of interest (e.g. source, bank, collision …)

Type of interactionCell of interactionX-, Y-, and Z-coordinatesU-, V-, and W-cosinesWeightEnergyTimeOther parameters

Assume bremsstrahlung emission is isotropic



Electron SAFs

Low error photon SAFs already calculated

Bremsstrahlung photons are still photons!

Weight energy spectrum of bremsstrahlung photons by previously calculated photon SAFs



Reliable cross-organ photon-attributed dose from primary electron sources

Reliable cross-organ photon-attributed dose from primary electron sources

Electron SAFs

( ) ( )T

STSWSTSW m

rrAFrrSAF

←=←

( )( )

( )electronelectron

o

i

photoni

photoniST

Eelectronelectron

Ephotonphotonphoton

ST

electronsemitted

photonsdeposited

STSW

NE

EErrAF

dEEn

dEEnErrAF

EE

rrAF electron

photon

⋅

⋅←=

⋅←==←

∑

∫

∫

;

)(

)(;

max

max

0

0

( )( )

electronelectrono

i

photoni

photoniST

STSW NE

EErrSAFrrSAF

⋅

⋅←=←∑ ;



Electron SAFs

Deviations from photon transport methodsTTB and fluence tallies not used, only E-depositionTwo separate simulations for each source organ

Simulation 1Primary electrons onlySame number of histories as used in photon transportE-deposition tallies for primary electron energy deposition

Simulation 2Coupled photon/electron transportNPS set to 105

No tallies used

Obtaining SAFs from tally dataSAFe-only = tallyE-dep / (Eelectron mT)SAFtotal = SAFe-only + SAFSW



Results –

Photon SAFs

Raw photon SAFs computed for the UFH00M and UFH00F phantoms

Reciprocity theorem

Adjoint Monte Carlo performed for UF00M phantom

Average MCNP uncertainty ~1% to 5% across all energies (most <<1%)

Variance reduction conditions and actionsSAFfinal = 0 at low initial photon energies

SAFfinal is log-linearly back-extrapolated to E = 10 keV

All target organsєadjoint < єforward at E = 4 MeV

SAFforward is replaced by SAFadjoint

Otherwise, SAFforward is retained

SAFfinal still displays poor behaviorSmoothing done subjectively by hand based on known shapes of the SAF curves



)()( TSST rrSAFrrSAF ←=←

Figure 3. Variance reduction techniques for the case where (A) adjoint MC is performed and SAF = 0 at low photon energies and where (B) SAF presents poor statistics after variance reduction and manual

smoothing is performed. E

indicates back-extrapolation, and S

indicates subjective smoothing.

(A) (B)



Figure 4. Photon SAFs for a uniform liver source in the UFH00M phantom before

variance reduction.



Figure 5. Photon SAFs for a uniform liver source in the UFH00M phantom after variance reduction.



Results –

Electron SAFs

Raw electron SAFs computed for the UFH00M liver source using full photon and electron transport

Separate “electron only” and “spectrum generation” simulations performed for the same source organ and phantom

Full transport uncertainties at E = 4 MeVє < 1% – 17 target organs

1% < є < 5% – 7 target organs

5% < є < 10% – 3 target organs

10% < є – 10 target organs



Figure 6. Full photon/electron transport versus bremsstrahlung spectrum weighting for a uniform electron source in the UFH00M phantom.



Figure 7. Electron SAFs for a uniform liver source in the UFH00M phantom using full photon/electron transport (no bremsstrahlung spectrum weighting).



Figure 8. Electron SAFs for a uniform liver source in the UFH00M phantom using full using bremsstrahlung spectrum weighting.



Conclusion

Detailed hybrid computational phantoms

Improved skeletal dosimetry

Complete sets of photon and electron SAFs for the UF newborn male and female, 1-year-old male and female, 5-year-old male and female, 10-year-old male and female, and 15-year-old male and female hybrid computational phantoms

Results for the UF adult male and female produced at the National Cancer Institute

ApplicationsRadiopharmaceutical therapy

Administered activity optimization

Low-dose risk assessment

References

Attix, F H. Introduction to Radiological Physics and Radiation Dosimetry. Weinheim, Germany: WILEY-VCH Verlag GmbH & Co. KGaA, 2004.

Bolch, W E, K F Eckerman, G Sgouros, and S R Thomas. "MIRD Pamphlet No. 21: A Generalized Schema for Radiopharmaceutical Dosimetry -

Standardization of Nomenclature." Journal of Nuclear Medicine

50 (2009): 477-484.

Cristy, M, and K F Eckerman. "Specific Absorbed Fractions of Energy at Various Ages from Internal Photon Sources. I. Methods." ORNL/TM-8381/V1, 1987: 1-100.

Cristy, M, and K F Eckerman. "Specific Absorbed Fractions of Energy at Various Ages from Internal Photon Sources. VI. Newborn." ORNL/TM-8381/V6, 1987: 1-72.

Hadid, L, A Desbree, H Schlattl, D Franck, E Blanchardon, and M Zankl. "Application of the ICRP/ICRU reference computational phantoms to internal dosimetry: calculation of specific absorbed fractions of energy for photons and electrons." Physics in Medicine and Biology

55 (2010): 3631-3641.

Harrison, J D, and C Streffer. "The ICRP Protection Quantities, Equivalent and Effective Dose: Their Basis and Application." Radiation Protection Dosimetry

127 (2007): 12-18.

Hendricks, J S, et al. "MCNPX 2.6.0 Extensions." (Los Alamos National Laboratory) LA-UR-08-2216 (2008).Hendricks, J S, et al. "MCNPX Extensions Version 2.5.0." LA-UR-05-2675, 2005: 1-79.

International Commission on Radiation Units and Measurements. "Photon, Electron, Proton and Neutron Interaction Data for Body Tissues." ICRU Report 46 (1992).



International Commission on Radiological Protection (ICRP). "2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103." Annals of the ICRP

37 (2007): 1-332.

International Commission on Radiological Protection (ICRP). "Adult Reference Computational Phantoms. ICRP Publication 110." Annals of the ICRP, 2009.

—. Basic Anatomical and Physiological Data for Use in Radiological Protection: Reference Values.

Vol. ICRP Publication 89. Oxford, UK: Pergamon Press, 2002.

International Commission on Radiological Protection (ICRP). "Limits for Intakes of Radionuclides by Workers." Annals of the ICRP

ICRP Publication 30 (1979).

Johnson, P, A Bahadori, K Eckerman, C Lee, W Bolch. “Response Functions for Computing Absorbed Dose to Skeletal Tissues from Photon Irradiation –

An Update." Physics in Medicine and Biology

(submitted, 2010).

Lee, C. "Voxelizer, version 6: A Matlab Code." Gainesville, FL: University of Florida, 2008.

Lee, C, D Lodwick, D Hasenauer, J L Williams, C Lee, and W E Bolch. "Hybrid Computational Phantoms of the Male and Female Newborn Patient: NURBS-Based Whole-Body Models." Physics in Medicine and Biology

52 (2007): 3309-3333.

Los Alamos National Laboratory. "MCNPX (TM) User's Manual. Version 2.5.0." LA-CP-05-0369 (2005).

Pafundi, D, D Rajon, D Jokisch, C Lee, and W E Bolch. "An Image-Based Skeletal Dosimetry Model for the ICRP Reference Newborn -

Internal Electron Sources." Physics in Medicine and Biology

55, no. 7 (2010): 1785-1814.

Pafundi, D, et al. "An Image-Based Skeletal Tissue Model for the ICRP Reference Newborn." Physics in Medicine and Biology

54, no. 14 (2009): 4497-4531.

Shah, A P, W E Bolch, D A Rajon, P W Patton, and D W Jokisch. "A

Paired-Image Radiation Transport Model for Skeletal Dosimetry." Journal of Nuclear Medicine

46, no. 2 (2005): 344-353.



International Commission on Radiation Units and Measurements. "Photon, Electron, Proton and Neutron Interaction Data for Body Tissues." ICRU Report 46 (1992).

International Commission on Radiological Protection (ICRP). "2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103." Annals of the ICRP

37 (2007): 1-332.

International Commission on Radiological Protection (ICRP). "Adult Reference Computational Phantoms. ICRP Publication 110." Annals of the ICRP, 2009.

—. Basic Anatomical and Physiological Data for Use in Radiological Protection: Reference Values.

Vol. ICRP Publication 89. Oxford, UK: Pergamon Press, 2002.

International Commission on Radiological Protection (ICRP). "Limits for Intakes of Radionuclides by Workers." Annals of the ICRP

ICRP Publication 30 (1979).

Johnson, P, A Bahadori, K Eckerman, C Lee, W Bolch. “Response Functions for Computing Absorbed Dose to Skeletal Tissues from Photon Irradiation –

An Update." Physics in Medicine and Biology

(submitted, 2010).

Lee, C. "Voxelizer, version 6: A Matlab Code." Gainesville, FL: University of Florida, 2008.

Lee, C, D Lodwick, D Hasenauer, J L Williams, C Lee, and W E Bolch. "Hybrid Computational Phantoms of the Male and Female Newborn Patient: NURBS-Based Whole-Body Models." Physics in Medicine and Biology

52 (2007): 3309-3333.

Los Alamos National Laboratory. "MCNPX (TM) User's Manual. Version 2.5.0." LA-CP-05-0369 (2005).

Pafundi, D, D Rajon, D Jokisch, C Lee, and W E Bolch. "An Image-Based Skeletal Dosimetry Model for the ICRP Reference Newborn -

Internal Electron Sources." Physics in Medicine and Biology

55, no. 7 (2010): 1785-1814.

Pafundi, D, et al. "An Image-Based Skeletal Tissue Model for the ICRP Reference Newborn." Physics in Medicine and Biology

54, no. 14 (2009): 4497-4531.



Shah, A P, W E Bolch, D A Rajon, P W Patton, and D W Jokisch. "A

Paired-Image Radiation Transport Model for Skeletal Dosimetry." Journal of Nuclear Medicine

46, no. 2 (2005): 344-353.

Snyder, W S, M R Ford, and G G Warner. "Estimates of Specific Absorbed Fractions for Photon Sources Uniformly Distributed in Various Organs of Heterogeneous Phantom." MIRD Pamphlet No. 5, revised, 1978: 5-26.

Snyder, W S, M R Ford, G G Warner, and S B Watson. ""S," Absorbed Dose Per Unit Cumulated Activity for Selected Radionuclides and Organs." MIRD Pamphlet No. 11, 1975: 5-10.

Wayson, M B. "Input Generator: A Matlab Code." Gainesville, FL: University of Florida, 2010.—. "Lattice Generator: A Matlab Code." Gainesville, FL: University of Florida, 2010.—. "Output Processor: A Matlab Code." Gainesville, FL: University

of Florida, 2010.—. "Skin Generator: A Matlab Code." Gainesville, FL: University of Florida, 2010.—. "Source Generator: A Matlab Code." Gainesville, FL: University

of Florida, 2010.

X-5 Monte Carlo Team. MCNP -

A General Monte Carlo N-Particle Transport Code, Version 5.

Vols. LA-UR-03-1987. Los Alamos National Laboratories, 2003.



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