Nuclear Data for Radiation Therapy

Transcription

1 Symposium on Nuclear Data 2004 Nov. 12, JAERI, Tokai Nuclear Data for Radiation Therapy ~from macroscopic to microscopic~ Naruhiro Matsufuji, Yuki Kase and Tatsuaki Kanai National Institute of Radiological Sciences Research Center for Charged Particle Therapy

2 Résumé 2 Introduction radiations used for radiotherapy what to estimate to carry out heavy ion therapy Macroscopic effect nuclear reaction dose Microscopic effect beam quality biological effect spatial distribution advanced irradiation microdosimetry nature of heavy ion radiotherapy neutrons Summary

3 Radiations used for tumor therapy 3 direct ionizing radiation electron proton Heavy ion helium, carbon, neon, silicon, indirect ionizing radiation photon neutron

4 HIMAC (Heavy Ion Medical Accelerator in Chiba) Established in Aimed at finding optimal heavy ion therapy scheme. 4

5 Clinical trials at HIMAC Targets of carbon therapy brain, scull base eye head and neck nasal passage cancer 5 lung liver pancreas prostate, uterus rectum bone, soft tissue Nov. 1, 2003: approved as a Highly Advanced Medical Technology 3.14M / treatment

6 Basis of clinical dose prescription 6 cell survival loss of capacity for multiplication (inactivation) radiation survival 1 Surviving Fraction 0.1 reference test RBE D = D reference_ radiation test _ radiation same _ effect carbon: 2~3 Dose (Gy)

7 Characteristic of heavy-ion therapy 7 Fragmentation of incident particles MeV/n projectile (carbon) participant projectile fragment target spectator Projectile fragments have almost - same velocity - same direction with those of primaries. Therapeutic beam is contaminated by fragments!

8 Why? 6 5 C290 MeV/n in Water HIBRAGGs measurement 8 Effect by fragmentation from clinical point of view Relative Dose Production of fragment particles Depth in Water (mm) causes unwanted dose beyond the range makes estimation of biological effect complex. makes it possible to monitor beam range. T. Nishio (NCC-east), private comm. M. Scholz et al., Radiat. Environ. Biophys., 36, 59 (1997).

9 9 Macroscopic effect Depth dose distribution

10 10 Depth-dose distribution Dose quantity of radiation Dose = J / kg[ Gy] the most fundamental factor to be controlled on radiotherapy physical factors reaction cross section stopping power multiple scattering and straggling : Disintegration of primaries loss of dominant dose carrier Production of fragments deliver dose but form fragment tail beyond the range

11 11 Depth-dose distribution Depth-dose distribution in water measured at HIMAC C290 MeV/n in Water C400 MeV/n in Water Relative Dose HIBRAC measurement Relative Dose HIBRAC measurement Depth in Water (mm) Depth in Water (mm) Dose can be controlled in clinically enough precision. basis of ongoing carbon therapy

12 12 Macroscopic to Microscopic What? particle identification

13 Importance of P. I. 13 LET and particle species dependency of RBE (CHO cell) M. Scholz and G. Kraft, Rad. Prot. Dos., 52, 29 (1994) How should we take into account this complexity? Radiation quality (fluence and energy)

14 How? - NIRS scheme 14 fragment simulation LET Biological data HSG cell dose LQ model: S= exp(-αd-βd 2 ) Biol. dose dose depth depth survival α mix f α = i i β mix f β = i i

15 How many? - fluence C-290MeV/n Calculation: hibrac (old) Z=6,2,1 1 Z=6 Z=2 Z=1 Z=6 Z=2 Z=1 Z=6 (CR39) Z=5,4,3 0.1 Z=5 Z=4 Z=3 Z=5 Z=4 Z=3 Z=5 (CR39) Z=4 (CR39) Normalized Fluence Normalized Fluence PMMA Thickness (mm) PMMA Thickness (mm) Need improvement on simulation model N. Matsufuji et al Phys. Med. Biol., 48, 1605 (2003)

16 Comparison with PHITS C-290MeV/n Calculation: PHITS 1.80 Z=6,2,1 Z=5,4,3 1.5 Z=6 Z=2 Z=1 Z=6 Z=2 Z=1 0.1 Z=5 Z=4 Z=3 Z=5 Z=4 Z= Normalized Fluence Normalized Fluence BF Thickness (mm) BF Thickness (mm)

17 LET spectra C-290MeV/n Relative Dose Depth in Water (mm) Z=6 Z=5 Z=4 Z=3 Z=2 Z= PMMA = 0 mmh 2 O 10 4 PMMA = 90 mmh 2 O 10 4 PMMA = 130 mmh 2 O Dose (Arbitrary Unit) 10 3 Dose (Arbitrary Unit) 10 3 Dose (Arbitrary Unit) LET (kev/µm) LET (kev/µm) LET (kev/µm) 100% 81% 77%

18 18 Heavy-ion therapy sites 1997~ GSI LBL 1977~1991 Hyogo 2002~ NIRS 1994~

19 19 Where? spatial distribution

20 20 Importance of the spatial distribution Scanning irradiation with pencil beam stopping power multiple scattering production cross section reaction cross section momentum transfer : lateral nonuniformity (picture from SIEMENS) Not fully understood both experimentally / theoretically

21 21 More microscopic! - microdosimetric approach

22 22 Microdosimetric problem Random energy deposition in cell nucleus amorphous (averaged) track actual (sparse) track

23 What? neutrons 23

24 24 Neutrons in therapy room 12 C-290MeV/n particles simulation with PHITS carbon neutron scatterer ridge filter collimator patient Geometry: from Nose (IHI)

25 25 Neutrons in therapy room 12 C-290MeV/n particles simulation with PHITS Neutron dose distribution scatterer ridge filter collimator patient Risk estimation for the induction of the secondary cancer Dependency to irradiation scheme Optimal treatment method

26 26 Summary Macroscopic effect Charge-changing cross section Depth-dose distribution is given in good precision Dose is delivered to tumor accurately Need further investigation for heavier elements

27 Summary 27 Microscopic effects Fluence and LET distribution (broad beam) Feedback to biology (ex. survival simulation) Spatial distribution (pencil beam) Input data for RTP of scanning irradiation Angular distribution, double differential production cross section, momentum transfer, Development of simulation code including spatial information, advanced RTP (inhomogeneous structure) Microdosimetric approach Understanding of the nature of heavy ion therapy

28 28 Thank you for your attention. Mt. Fuji from Chiba city A part of this work was carried out as the Research Project with Heavy Ions at HIMAC.