Methods (Exp. Cal.) Methods (Exp.)

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1 8 cm 8 cm 6 cm 6 cm Bchmark of EGS5 for 25 brachytherapy n comparson to glass rod dosmeter and treatmt plannng system usng AAPM-TR43U formalsm K. Tanaka, K. Tateoka, O. Asanuma 2, K. Kamo, G. Bgua 3, K. Sato 2,T.Ueda 4, H. Takeda 2, M. Takag 3, M. Hareyama 3, and J. Takada Purpose To develop a dose calculaton method applcable to - nter-seed attuaton (sheldng by seeds already mplanted) - geometry lackng the equlbrum radaton scatter condtons ( scatterng margn below 5 cm, small organ such as tongue ) Amercan Assocaton of Physcsts n Medcne Task Group No 43 Updated Protocol (TG43U) s N/A 2 Graduate School of Sapporo Medcal Unversty, Japan 2 Sapporo Medcal Unversty Hosptal, Japan 3 Auckland Cty Hosptal, New Zealand 4 Hokkado Unversty Hosptal, Japan 5Teshn-ka Radaton Therapy nsttute, Japan e-mal: tanakak@sapmed.ac.jp Comparson - Monte Carlo code EGS5 wth a source geometry - Glass Rod Dosmeter (GRD) ( Data accumulaton) - TG43U Methods () 3 Methods ( ) 4 rradaton for day Phantom cterlne φ GRD supportng plate GRD supportng plate phantom (8cm dam. X 6cm) Lne along whch GRDs were set. Phantom cterlne GRD θ r 25 seed:.44 U, 2. MBq (Oncra nc. Oncoseed 67) Radophotolumnesct glass rod dosmeter (Asah Techno Glass GD-32M) Calbraton: 6MV, cm nto Tough, STD cm,.mu (8mGy) 8 cm dameter 8 cm 9 cm GRD poston (r: or 2 cm nt., 45 deg. nt.) Some GRDs close to phantom surface : Backscatter margn less than 5 cm (nsuffct)

2 Methods ( Correcton) 5 Methods ( Correcton) 6 Calbraton at 6MV to correct sstvty dfferce among detectors Absorbed dose to water by 25 6MV D R 6MV 6MV D F R E MV Absorbed dose to water by 25 D ( / ) 6 MV, 6MV E 6 MV, Glass ( / ) 6 MV, Glass R 6MV D F R E MV ( / ) 6MV Detector devaton etc. Normalzaton to TG43U at referce pont (cm, 9deg) To compare relatve dstrbuton Readng of dosmeter Energy response correcton Mass ergy -absorpton coeffct μ/ρ (cm2/g). Glass dosmeter.... Energy (MeV) Readng: glass dose Needed: water dose J.H. Hubbell and S.M.Seltzer, NSTR 5632 (Ver.4); 24 Methods ( Correcton) 7 Methods ( for GRD measuremt) 8 μ/ρ (cm2/g). Absorbed dose to water by MV Glass dosmeter D F R E ( / ) E ( / ) ( / ) x, / Glass 25, / Glass 6 MV, / Glass ( / ) ( / ) x, x, Glass EGS5 Geometry : phantom, GRD, seed, Styroforam stand (,Pb, wall) Seed: RM.Knedy et al. Med. Phys. 33 (2) mm Ar.7mm thck T.... Energy (MeV) E=.29 ( / ) 25 m, ( / ) E, m -25 coated onto Ag rod 2.8mm 4.5mm.5mm.8mm

3 Methods () 25 : NuDat2 ( ) Energy E (kev) ntsty (%) Methods ( Correcton) Absorbed dose to water by 25 μ/ρ (cm2/g). ( / ) D F O N 25, ( / ) 25 Glass dosmeter.... Energy (MeV) E D Glass, EGS output (Glass dose) Energy correcton (.328) Amount of dsntegraton complcated to nclude source ar kerma ntegraton of appart actvty wth tme, and determned F for ths N D Photon/ntegraton Methods ( for TG43U parameters) cterlne sphere Tally θ r Methods (TG43U) Dosmetry used for brachytherapy Dose rate Radal dose functon (absorpton and buldup depdt on r at 9 deg. Ar kerma strgth Dose rate constant (to water dose) 2 5 cm Radal dose functon g (r), 2D ansotropy functon, F(r,) EGS5 Vared r and followng TG43U Tally radus : 4 % of r Geometry functon /r^2 Ansotropy functon (absorpton and buldup depdt on theta at r)

4 8 cm 6 cm Result (Normalzaton factor F) Normalzaton at referce pont of TG43U (cm, 9 deg) especally relable : abundant data for composng formalsm GRD (.97 Gy at 9 deg,.98 Gy at 27 deg) EGS5 (.53 Gy) F =.8 Low value s reasonable because we used ntegraton of appart actvty wth tme as amount of dsntegraton Avalable : kerma strgth appart actvty. Purpose : relatve dstrbuton, absolute to be normalzed Agrees wthn 3 % : valdty of GRD F =.97 TG43U (.95 Gy) GRD supportng plate Phantom cterlne θ r 8 cm GRD 9 cm 3 Result (normalzed, dstrbuton n/on phantom) r = 9cm 2 3 ( ) EGS5 reproduces dose dstrbutons by GRDs to wthn 25% n geometry lackng equlbrum radaton scatter condtons Method (Uncertanty estmaton) 5 Method (factors to make uncertanty) 6 Formalsm Partal dervatve Y:value requred g: parameters wth uncertanty Standard devaton (rectangular probablty dstrbuton) Combned standard uncertanty wth coverage factor : CSU(k=) Y Y( gmax ) Y( gmn ) g g g g g max max g 2 3 mn mn Y 2 ( Y Geo) g g 2 g 2 Parameters g for EGS5 () the poston of the slver rod n the T shell (±.4 mm n longtudnal drecton and ±.8 mm n transversal drecton wth respect to the source cterlne) (2) the angle ( 3 ) betwe the rod and T shell axes (3) d weld thckness varatons (±.5 mm) (4) radoactve layer thckness (. 2.5 mm) (5) T capsule thckness varatons (±. mm) (6) rod d face dameter (6% 8% of the maxmum rod dameter) (7) GRD poston varatons (±.5 mm n transversal drecton wth respect to the GRD cterlne) only for GRD setup Parameters g for GRD () Photon ergy from 25 (3.77 to kev)

5 Result (Uncertanty estmaton) Uncertanty for EGS5 calculated dose usng GRD expermtal setup. 7 Result (Uncertanty estmaton) Uncertanty for GRD measuremt Result (Dstrbuton n/on phantom) r = 9cm 2 3 ( ) EGS5 reproduces dose dstrbutons by GRDs to wthn 25% n geometry lackng equlbrum radaton scatter condtons. the combned standard uncertanty wth the coverage factor of 2 to g(r) F(r,).5 Result ( EGS TG43U parameter) Radal dose functon r =cm 5 ( deg) Ths work TG43U Ths work TG43U F(r,) F(r,) r =.5cm.5 Ths work TG43U 5.5 2D ansotropy functon deg r =.5cm Ths work TG43U 5 (deg) 2

6 g(r) rato F(r,) rato Result (Rato EGS5 / TG43U) r =cm (degree) F (r, ) rato r =.5cm (degree) Agreemt consstt wth prevous study g(r) to wthn 9% F(r,) to wthn 5% except for 4 %(.5cm, deg), 27 %(.5cm, 5deg), 32%(.5cm, deg), 6%(.5cm, 2deg), 3%(cm, deg), 2%(cm, deg) %(cm, 2deg) and (2cm, deg) 2 Summary Agreemts betwe EGS5 wth Knedy s source, GRD, TG43U EGS5 agreed GRD n 25%. Absolute value of GRD agreed wth TG43U n 3%. F(r,q) and g(r) by EGS5 agreed wth TG43U. Supports valdty of EGS5, GRD, TG43U EGS5 calculaton s a pottal opton for treatmt plannng applcable to nter-seed attuaton and geometry lackng equlbrum radaton scatter. GRD can also be used n brachytherapy dosmetry. Detales n : K.Tanaka et al. Med. Phys. 38 (2) Part of the prest study was supported by Grant-n-Ad for Sctfc Research from the Japan Socety for the Promoton of Scce under grant #27923, and by Grant-n-Ad from Sappro Medcal Unversty n