Towards patient‐specific dosimetry in nuclear medicine associating Monte‐Carlo and 3D voxel‐based approaches

L.Hadid, N. Grandgirard, N. Pierrat, H. Schlattl, M. Zankl, A.Desbrée

IRSN, French Institute for radiation protection and nuclear safety, Fontenay-aux-roses, FranceInstitut Curie, Paris, France

Helmholtz Zentrum München-German Center for Environmental Health, Neuherberg, Germany

International Symposium on Standards, Applications and Quality Assurance in Medical Radiation Dosimetry

IAEA, 9-12 November 2010, Vienna

2IAEA International Symposium, 9‐12 November 2010, Vienna

Context Results ‐

SAF 

MIRD Formalism

Biokinetic aspect Geometric

aspect

Radiation Protection : Accurate and realistic dosimetry

EE

TT

/E/E

SS

MMT

SAF(rSAF(r

T      T      

rr

SS

) =       ) =       

)(~

STS

ST rrir i

irr SAFEnAD←∑ ∑= x

Results ‐

Patient‐based doses Results –

Reference doses 

Tabulated reference data

Mathematical phantom

SAFs tabulated for mathematical standard geometries

3

sourcemassSCSAF 1)( =←

Target region = Source region

Target region ≠

Source region

0)( =← SCSAF

Walled source regions

sourcemassSCSAF

*21)( =←

Approximations applied

for electron SAFs

S

SC

S=C

C

IAEA International Symposium, 9‐12 November 2010, Vienna

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

4

Monte Carlo calculations

OptimisationNew adult reference computational

phantoms of the ICRP

Male phantom Female phantom

Publication 110 

of the ICRP

SAFsPhotons + Electrons(10 keV<E<10MeV)

HMGU(EGSnrc)

IRSN(MCNPX 

+OEDIPE)

Absorbed dosesfrom radiopharmaceuticals

Standard

biokinetic of 

11 radiopharmaceuticalsused in nuclear medicine

IAEA International Symposium, 9‐12 November 2010, Vienna

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

Reference phantoms             Fixed geometry

5IAEA International Symposium, 9‐12 November 2010, Vienna

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

RESULTS

SAF Calculations

7

Comparison between voxelized and ORNL phantoms  PHOTONS, SAF (Lungs <‐

Liver), Male

Low energiesRatio

Voxelized/ORNL     25

Different shapes and  inter‐organ distances

High energiesRatio

Voxelized/ORNL      1,5

Small influence of the  organ shapes on the 

SAFs

Spe

cific

Abs

orbe

d Fr

actio

n (k

g-1)

Photon energy (MeV)

IAEA International Symposium, 9‐12 November 2010, Vienna

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

ELECTRONS, SAF ( Lungs <- Lungs), Male

8

Ratio0,99< EGSnrc/MCNPX< 1,01

Low energies :SAF          1

High energies:Electron escapeS

peci

fic A

bsor

bed

Frac

tion

(kg-1

)

Electron energy (MeV)

Prior

approximations

LungsmLungsLungsSAF 1)( =←

kg 1mLungs=

IAEA International Symposium, 9‐12 November 2010, Vienna

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

9

Application of the ICRP/ICRU reference computational phantoms to

internal dosimetry: calculation of specific absorbed fractions of energy for photons and electrons

L Hadid, A Desbrée, H Schlattl, D Franck, E Blanchardon and M Zankl

Phys.Med.Biol.55 (2010) 3631-3641

IAEA International Symposium, 9‐12 November 2010, Vienna

Cross-fire: for many organ pairs, voxel phantom SAFs higher than current values based on mathematical phantoms (inter-organ distances are larger in mathematical phantoms than in reality)

Photon SAFs

Electron SAFs

Cross-fire : SAFs can approach nearly the same order of magnitude as photon SAFs for higher electron energies and organs in close vicinity

Self-absorption : higher-energetic electrons escape, especially from small organs

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

RESULTS

Dose CalculationsMathematical versus computational

reference phantoms

11IAEA International Symposium, 9‐12 November 2010, Vienna

Reference voxel  phantoms

Standard biokinetic of 

radiopharmaceuticals

(ICRP 53 + ICRP 80 + ICRP 106)

Absorbed doses for 11 radiopharmaceuticals  used in nuclear medicine

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

12

Absorbed doses for 18F-FDG

0,00

0,02

0,04

0,06

0,08

0,10

0,12

0,14

Adre

nals

Blad

der w

all

Bone

s sur

face

sBr

ain

Brea

st

Stom

ach

wall

Smal

l int

estin

eCo

lon

Gall

blad

der

Hear

tKi

dney

sLi

ver

Lung

sMus

cles

Oeso

phag

usOv

arie

sPa

ncre

asRe

d m

arro

w

Skin

Sple

enTe

stes

Thym

usTh

yroi

dUt

erus

Rem

aini

ng o

rgan

s

Effe

ctive

dos

eAbs

orbe

d do

se p

er u

nit

acti

vity

adm

inis

tere

d (m

Gy/

MBq

)

Reference mathematical phantom

Reference voxel male phantom

Reference voxel female phantom

IAEA International Symposium, 9‐12 November 2010, Vienna

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

13IAEA International Symposium, 9‐12 November 2010, Vienna

Absorbed doses Mathematical versus voxel reference phantoms

Differences depend on target organ and radiopharmaceutical

131I - thyroid uptake 55 %

306 % (lungs) 272 % (lungs)

11C-Methionine

56 % (uterus) 59 % (Urinary bladder wall)

-Geometric: topology and distances between organs

- Physic: approximations previously used for electrons transport

Reasons

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

RESULTS

Dose CalculationsMathematical phantoms using OLINDA/EXM

versus patient-based phantoms using OEDIPE

15IAEA International Symposium, 9‐12 November 2010, Vienna

Creation of the patient‐based voxel phantoms

Creation of a voxel phantom : ~ 8H

Specific voxel phantoms

Attribution

of the densities

TPS ISOGrayTM

Segmentation

of 27 organs

Voxelization

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

16IAEA International Symposium, 9‐12 November 2010, Vienna

M1 M2 M3 M4 M5 M6

6 malephantoms

F1 F2 F3 F4 F5 F6

6 female 

phantoms

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

17

Absorbed doses for 18F-FDG for male phantoms

IAEA International Symposium, 9‐12 November 2010, Vienna

0,00E+00

2,00E‐02

4,00E‐02

6,00E‐02

8,00E‐02

1,00E‐01

1,20E‐01

1,40E‐01

Brain

Colon

 wall

Gall b

ladde

r wall

Hear

t wall

Left 

kidne

yRig

ht ki

dney

Liver

Left 

lung

Right

 lung

Panc

reas

Splee

nSt

omac

h wall

Testi

sTh

yroid

Urina

ry bla

dder

 wall

Oeso

phag

us

Mean absorbed

 dose pe

r un

ité activity adm

inistered (m

Gy.MBq

‐1)

M1M2M3M4M5M6Male reference mathematicalRCP‐AM

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

18IAEA International Symposium, 9‐12 November 2010, Vienna

Determination of patient‐based doses : between 9H

and 16H

OEDIPE + MCNPX

Maximum dose differences between patient‐based phantoms  and

Reference mathematical phantoms : ~ 400 %

(walled organs)174 %

(brain for 131I_55%)

Reference voxel phantoms : 113 %

(thyroid for 131I_55%)

Maximum absorbed dose differences among patients: factor 3,4 

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

19IAEA International Symposium, 9‐12 November 2010, Vienna

Context Results ‐

SAF  Results ‐

Patient‐based doses Results –

Reference doses 

+

Absorbed dose to target organs 

or tumors

DVHIsodoses curves superimposed 

on anatomical images

Thank you for your attention

aurelie.desbree@irsn.fr