TG51_figures.pdf

AAPM’s TG–51 Protocol for Clinical Reference Dosimetry of

High-Energy Photon and Electron Beams

Peter R. Almond,Brown Cancer Center,Louisville, KY 40202

Peter J. Biggs,Department of Radiation Oncology, Massachusetts General Hospital,

Boston, MA 02114B.M. Coursey,

Ionizing Radiation Division, National Institute of Standards and Technology,Gaithersburg, MD 20899

W.F. Hanson,M.D. Anderson Cancer Center, University of Texas, Houston, TX 77030

M.Saiful Huq,Kimmel Cancer Center of Jefferson Medical College,Thomas Jefferson University, Philadelphia, PA 19107

Ravinder Nath,Yale Univ School of Medicine,New Haven, CT 06510

D.W.O. Rogers,Ionizing Radiation Standards, National Research Council of Canada,

Ottawa K1A OR6, Canada

∗ Developed by TG–51 of the Radiation Therapy Committee of the AAPM.

As published in Med Phys 26 (1999) 1847 – 1870

Abstract

This is the figures from TG-51 in a large scale and colour format. Note the postscript and/orpdf versions available at http://www.irs.inms.nrc.ca/inms/irs/tg51 figures/tg51 figures.html

1

AAPM’s TG–51 Protocol for Reference Dosimetry: Med Phys 26 (1999) 1847 – 1870 page 2

0 5 10 15 20depth /cm

50

60

70

80

90

100

%de

pth−

ioni

zatio

n

dmax A

I

II

%dd(10)

0 1 2 3 4 5 6 7 8depth / cm

0

20

40

60

80

100

I

II

a)b)

B

dose

I50

Figure 1: Effect of shifting depth-ionization data measured with cylindrical chambers upstream by0.6 rcav for photon beams (panel a) and 0.5 rcav for electron beams (panel b) (with rcav = 1.0 cm).The raw data are shown by curve I (long dashes) in both cases and the shifted data, which are takenas the depth-ionization curve, are shown by curve II (solid line). The value of the % ionization atpoint A (10 cm depth) in the photon beam gives %dd(10) and the depth at point B (solid curve, 50%ionization) in the electron beam gives I50 from which R50 can be determined (see section VIII.C). Forthe photon beams, curve II is effectively the percentage depth-dose curve. For the electron beams,curve II must be further corrected (see section X.D) to obtain the percentage depth-dose curve shown(short dashes - but this is not needed for application of the protocol).

∼dave/tex/tg51/tg51.tex: Edited 18 Aug 1999


0 2 4 6 8 10 12depth /cm

0

10

20

30

40

50

60

70

80

90

100

110

% d

epth

−do

se

dd_R50_dref

dmax

R50

dref = 0.6 R50 − 0.1 cm

Figure 2: R50 is defined as the depth, in cm, at which the absorbed dose falls to 50% of its maximumvalue in a ≥ 10 × 10 cm2 (≥ 20 × 20 cm2 for R50 > 8.5 cm) electron beam at an SSD of 100 cm.The depth for clinical reference dosimetry is dref = 0.6R50 − 0.1 cm, in the same sized beam at anSSD between 90 and 110 cm. Note that for low-energy beams, dref is usually at dmax.



� � � � � � � � � � � � ��

SAD Setup

10 cm

10x10 10 cm

SSD

10x10

SSD Setup

� � � � � � � � � � � � ��

SAD

Figure 3: Schematic of the SSD or SAD setups which may be used for photon beam referencedosimetry. In both cases the ion chamber is at a water equivalent depth of 10 cm in the waterphantom. The actual value of SSD or SAD is that most useful in the clinic (expected to be about100 cm).



55 60 65 70 75 80 85 90%dd(10)X

0.94

0.95

0.96

0.97

0.98

0.99

1.00

k Q

kQ_photon

A12,A1,PR05,PR05P,IC−5,IC−10

NE2561PR06C

NE2581

PTW N30002

PTW N30001,31003

NE2571, 25772505/3A, 30004

Figure 4: Values of kQ at 10 cm depth in accelerator photon beams as a function of %dd(10)x forcylindrical ion chambers commonly used for clinical reference dosimetry. When values were the samewithin 0.1%, only one curve is shown. Explicit values are given in Table I, as is a list of equivalentchambers. For 60Co beams, kQ = 1.000.



2 3 4 5 6 7 8 9R50 /cm

1.00

1.01

1.02

1.03

k’ R

50 a

t dre

f

kR50.prime

N23331

N30001

A12

NE2505.3A NE2571

NE2581PR06C/G

N30002IC10/5

N31003

PR06C/G

0.9905+0.071e(−R50/3.67)

NE2577 N30004

Exradin A1,PR05,PR05P

NE2561

Figure 5: Calculated values of k′R50at dref as a function of R50 for several common cylindrical ion

chambers. These values can be used with Eq.(6), (with a measured value of PQgr and a kecal value

from Table III) to determine the absorbed dose to water at the reference depth of dref = 0.6R50− 0.1cm.



2 3 4 5 6 7 8 9R50 /cm

0.99

1.00

1.01

1.02

1.03

1.04

1.05

1.06

k’ R

50 a

t dre

f

Attix

Exradin P11

Markus

NACP

PTB/Roos

kQ.prime_pp

Holt

Capintec

kR50.prime_pp

1.2239−0.145(R50)0.214

Figure 6: Calculated values of k′R50at dref as a function of R50 for several common plane-parallel cham-

bers. Note that the values for the 5 well-guarded chambers lie on the same line in the figure. Thesevalues can be used with Eq.(6) (with PQ

gr = 1.0) to determine the absorbed dose to water at thereference depth of dref = 0.6R50 − 0.1 cm.



9 10 11 12 13 14 15 16 17 18 19 20R50 /cm

0.96

0.97

0.98

0.99

1.00

k’ R

50 a

t dre

f

kR50.prime

N30002A12

A12

NE2505.3ANE2571

NE2581PR06C/G

N30002IC10/15

NE2581PR06C/G

NE2505.3A NE2571 NE2577N30001

N30004

NE2581 PR06C/G

NE2561 N23331

IC10/5

N31003

Exradin A1,PR05,PR05P

Figure 7: Calculated values of k′R50at dref for high-energy electron beams, as a function of R50 for

cylindrical ion chambers. These values can be used with Eq.(6), (with a measured value of PQgr

and a kecal value from Table III) to determine the absorbed dose to water at the reference depth ofdref = 0.6R50 − 0.1 cm.



9 10 11 12 13 14 15 16 17 18 19 20R50 /cm

0.95

0.96

0.97

0.98

0.99

1.00

k

’ R50

at d

ref

Attix

Exradin P11 Markus

NACP

PTB/Roos

kQ.prime_pp

’

Holt

Capintec

’

1.2239−0.145(R50)0.214

kR50.prime_pp.high

Figure 8: Calculated values of k′R50at dref for high-energy electron beams, as a function of R50 for

plane-parallel chambers. Note that the values for the 5 well-guarded chambers lie on the same linein the figure. These values can be used with Eq.(6) (with PQ

gr = 1.0 and a kecal value from Table II)to determine the absorbed dose to water at the reference depth of dref = 0.6R50 − 0.1 cm.


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