Heavy Ion Tumor Therapy

Transcription

1 Heavy Ion Tumor Therapy Applications Bence Mitlasoczki

2 Heidelberg 1. Source (H 2 /CO 2 ) 2. Linac 3. Synchrotron 4. Guide 5. Treatment rooms 6. X-ray system 7. Gantry 8. Treatment room with rotating x-ray systems 1

3 Target Bragg-peak RBE = D ref /D ion Lateral beam spread More fragmentation tail 11 C, 10 C: in vivo PET Tumor Therapy with Heavy Ions P.J. Bryant: Gantries for Tumor Therapy 2

4 Aiming at the target Near critical organs: base of skull (acoustic neuroma), eye (uveal melanoma), lung cancer Passive or active targeting Patient fixation: individual mask/full body mould Check position: X-ray/CT compared to treatment planning CT Example: lung cancer at HIMAC (Japan) The number of patients enrolled in heavy ion radiotherapy at the National Institute of Radiological Sciences (June 1994 to February 2016) 3

5 Lung cancer at HIMAC Expansion of PTV, rescanning, gating, tracking Two iridium markers Irradiation: when tumor volume is lowest Longer time 4

6 The guide 16 cm in water: 150 MeV vs MeV (250 MeV/u) High momentum high magnetic rigidity R = Bρ = p q : max. 400 MeV/u: 6.3 Tm vs 2.2 Tm (protons with same range) 1.8 T: 1.2 m vs 3.5 m larger magnets and/or larger radius (structure) M. Pullia, F. Ebskamp: Introduction to Gantries and Comparison of Gantry Design 5

7 Passive targeting: transversal shaping Double-scattering system: spread out beam, scatter the dense centre to the edges High Z: favour scattering, low Z (longitudinal shaping): less scattering Wobbling magnets: less material in beam path Collimator: multi-leaf or patient specific 6

8 Passive targeting: longitudinal shaping Rotary modulator: time-dependent Ridge filters (aluminium): time-independent Disadvantage: constant SOBP width unwanted dose Range shifter: adjust to maximum depth; binary plastic plates Patient specific compensator: fine-tuning Used at HIMAC (2005: layer-stacking) (Japan) More fragments: increase of dosis in entrance region 7

9 Layer-stacking method 10 mm mini-sobp : thin ridge filter, MLC HIMAC: step and shoot Dose level constant in each layer: pre-irradiation cannot be compensated 8

10 Active targeting Spot scanning (PSI, protons) Beam monitoring system, kicker magnet turns beam off, sweeper magnet for targeting Vertical movement: patient table, depth: dynamic range shifter Hot and cold spots Raster scanning (GSI) Continuous irradiation: intensity fluctuations can be compensated Depth: range shifter or variable source 9

11 Gantry Criteria: 3-27 cm depth, cm 2 treatment field Isocentric or exocentric 90 magnet: t design should minimise elastic deformations Alternative example (HIMAC): horizontal, vertical, 45 angle beams 10

12 Riesenrad gantry Preferred: independent-cabin gantry (PIMMS) Vertical movement: low-precision lift structure Horizontal movement: Telescopic floor High precision alignment: couch Independent patient cabin: smaller counterweight necessary 130 t central cage Safety: quick access to patient 11

13 Riesenrad gantry 12

14 HIT gantry system 600 t moving weight 25% of total cost 15 years lifetime P. Bryant: Gantries for Hadron Therapy 13

15 Accelerator Cyclotron 100% duty factor Easy to control Large at required energies No energy variability 250 MeV to 70 MeV: factor of 1000 decrease in intensity Synchrotron 25-50% duty factor Energy variability Larger than cyclotron Need injector m diameter 14

16 Alternative designs Superconductors: Compact, expensive Cyclotron: IBA (Belgium): 4.5 T, 400 MeV/u Fixed-Field Alternating-Gradient accelerator: Synchrotron-like setup Fixed field: spiraling beam like in cyclotron Proof-of-principle projects in Japan, UK, France Laser acceleration Chao, A., Chou, W.: Reviews of Accelerator Science and Technology Wikipedia 15

17 The HIMAC >9000 patients (>50% of all carbon ion therapy) 3D scanning system (2011) Depth: coarse (accelerator), fine (range shifter) Respiratory gating system Isocentric gantry (SC) 16

18 The HIT Heidelberg University Hospital Proton, C; He, O Heavy ion therapy since end 2012, 2500 patients by 2014, 2/3 with C Jointly run with Marburg center First heavy ion gantry First raster-scanning system 17

19 Future 18

20 References Schardt, D., Thilo, E. Heavy-ion tumor therapy: Physical and radiobiological benefits Linz, U. Ion Beam Therapy. Fundamentals, Technology, Clinical Applications. Tumor Therapy with Heavy Ions. (Association for the Promotion of Tumor Therapy with Heavy Ions) Jkel, O. Heavy Ion Radiotherapy. Amaldi, U., Kraft, G. Radiotherapy with beams of carbon ions. Robin, D. Novel Design of Gantry Optics for Carbon Cancer Therapy Accelerator. Bryant, P.J. Accelerator Design Issues in Cancer Therapy. Jongen, Y. Cyclotrons from protons to Carbon for Hadron Therapy. 19