Treating moving organs with particle beams Christoph Bert GSI - PowerPoint PPT Presentation

Treating moving organs with particle beams Christoph Bert GSI Helmholtz Centre for Heavy Ion Research, Department of Biophysics Darmstadt, Germany

Organ motion in radiotherapy A. Constantinescu Heart beat Friday, 9:30h Scale: seconds A. Rucinski Gut motion Prostate Gas Friday, 16:12h Scale: minutes 2

Organ motion in radiotherapy Respiration in particle therapy Respiration Scale: seconds 10cm 2cm 4cm 6cm 8cm tumor beam range 3

Respiratory motion - beam range [courtesy S.O. Grözinger, GSI] 12 C dose photons range ⇒ mitigation of range / longitudinal changes essential 2/28/2012 ICTR-PHE, Geneva 2012 4

Mitigation by margins (ICRU recommendation) ITV Internal target volume GTV Gross tumor volume [Rietzel et al., MGH] CTV Clinical target volume PTV Planning target volume 2/28/2012 ICTR-PHE, Geneva 2012 5

Range change dependence of margins Original treatment plan Original TP to 5 mm shifted tumor ⇒ Margins have to incorporate range and are thus field specific [M. Koto et al. / Radiotherapy and Oncology 71 (2004)] 2/28/2012 ICTR-PHE, Geneva 2012 6

Margins incorporating range changes • Propage CTV to ITV by manual exchange of HU-numbers (i.e. replace lung tissue by tumor tissue) [Koto et al. 2004] • Scattered beams: Change of compensator + aperture to cover all motion states of 4DCT [Engelsman et al. 2006, Mori et al. 2008] mitigation needed additional motion • Beam scanning, single field: ITV = union of CTVs in water-equivalent space [Bert & Rietzel 2007] • Beam scanning, IMPT: Beam specific WEPL-LUT and common geometric ITV [Graeff et al., GSI] 2/28/2012 ICTR-PHE, Geneva 2012 7

Water-equiv. Path Length ITV ITV Geometry WEPL-LUT CTV bone Water-Equivalent Path Length Field 1 Field 2 A B C (ref) Union of A,B,C Geometric union in WEPL of C Motion Phase [Graeff et al., GSI] 2/28/2012 ICTR-PHE, Geneva 2012 8

Field specific WEPL-LUT [Graeff et al., GSI] 2/28/2012 ICTR-PHE, Geneva 2012 9

Static Dose: DVH End Exhale (Reference) End Inhale [Graeff et al., GSI] 2/28/2012 ICTR-PHE, Geneva 2012 10

Static Dose: ITV Comparison Range-ITV Geo-ITV End-Inhale [Graeff et al., GSI] 11 2/28/2012 ICTR-PHE, Geneva 2012

4D-Dose (15 rescans): ITV Comparison Range-ITV Geo-ITV [Graeff et al., GSI] 12 2/28/2012 ICTR-PHE, Geneva 2012

4D-Dose (15 rescans): DVH [Graeff et al., GSI] 13 2/28/2012 ICTR-PHE, Geneva 2012

Interplay - simulation data → IM / ITV / PTV not sufficient [Bert et al, Phys Med Biol, 2008] 2/28/2012 ICTR-PHE, Geneva 2012 14

Motion mitigation techniques • Rescanning [Phillips et al., Phys Med Biol 1992] • multiple scans of ITV • several modalities investigated recently [Seco et al. 2009, Furukawa et al. 2010, Zenklusen et al. 2010] • Beam Tracking [Grözinger et al., Phys. Med. Biol. 2006] • compensate target motion by real-time adjustment of Bragg peak • 4D treatment plan optimization required • Gating [Minohara et al., IJROBP 2000] • beam on, if tumor within gating window (e.g. 30% around end-exhale) • used at NIRS for scattered beams >10 years • reduced ITV size • beam scanning: mitigation of residual motion 2/28/2012 ICTR-PHE, Geneva 2012 15

Motion mitigation techniques • Abdominal compression • supress motion • used at HIT for treatment of hepato cellular cancer • scanned beam: influence of residual motion • Apnea • anesthetized and intubated patient • used at RPTC, Munich since > 1 year • Breath hold • could be an option for sites with fast delivery (e.g. PSI with 80ms energy change time or NIRS with energy change on flat-top) 2/28/2012 ICTR-PHE, Geneva 2012 16

Rescanning [courtesy of A. Knopf, PSI and Knopf et al. Phys Med Biol 2011] 2/28/2012 ICTR-PHE, Geneva 2012 17

[courtesy of A. Knopf, PSI and Knopf et al. Phys Med Biol 2011] 2/28/2012 ICTR-PHE, Geneva 2012 18

[courtesy of A. Knopf, PSI] 2/28/2012 ICTR-PHE, Geneva 2012 19

Beam Tracking • Incorporated into GSI TPS TRiP4D [Bert & Rietzel, Radiat Oncol 2007; Saito et al.. Phys Med Biol 2009; • Implemented and experimentally validated at GSI for C12 irradiations of simple geometries • Procedure: pre-calculate compensation data for each combination of beam position and 4DCT motion state Bert et al. Med Phys 2007] 2/28/2012 ICTR-PHE, Geneva 2012 20

Real-time dose compensated beam tracking (RDBT) • Dose change depends on temporal correlation between beam and tumor motion • Real-time dose compensation necessary (RDBT) – Beam tracking: change of beam position and energy – RDBT: additionally change of deposited dose i.e. change of all treatment plan parameters based on target motion state and pre-calculated data [Lüchtenborg et al. Med. Phys. 2011] 2/28/2012 ICTR-PHE, Geneva 2012 21

Beam tracking technique comparison [Lüchtenborg PhD-Thesis 2011] Stationary dose distribution • Treatment planning study (TRiP4D) Patient #5 based on 4DCT data of 5 patients (courtesy MDACC, L.Dong) • Modalities • Beam Tracking (BT) • RDBT (dose compensated BT) • lateral BT (no range compensation) • interplay RDBT interplay • Plan design: • 4 fields, 4 fractions • 8.2 Gy (RBE) / fraction • based on NIRS protocol V95 • 81 motion combinations calculated • Report of V95 2/28/2012 ICTR-PHE, Geneva 2012 22

4D dose calculation: beam tracking [Lüchtenborg et al., PhD-Thesis, 2011] 2/28/2012 ICTR-PHE, Geneva 2012 23

Results V95 • BT and RDBT yield CTV coverage (with RBE-weighted dose) • RDBT not essential for lung cancer treatment • lat. BT sufficient for some patients [Lüchtenborg PhD-Thesis 2011] 2/28/2012 ICTR-PHE, Geneva 2012 24

Gating: clinical for passively shaped beams • NIRS (Chiba, Japan) uses gating for respiration influenced tumors since >10 years • Passively shaped carbon beams – No interference with target motion / simultaneous irradiation – Margins/PTV to account for motion amplitude – Compensator smearing to account for range changes • Great clinical results for lung cancer – Dose escalation studies – Hypo-fractionation studies [Minohara et al., IJROBP 2000, Miyamoto et al., Radioth. Oncol. 2003, IJROBP 2007, Mori et al. IJROBP 2008 ] 2/28/2012 ICTR-PHE, Geneva 2012 25

Gating: Residual motion – scanned beams Irradiation under abdominal compression, e.g. liver cancer (HCC) similar residual motion residual motion (gating) amplitude � <~10mm residual motion (abd. compr.) time � mitigation & robustness studies needed! 2/28/2012 ICTR-PHE, Geneva 2012 26

Residual Motion Mitigation � Optimize beam overlap: ( Δ S = grid spacing) F (FWHM) = 5 x Δ S Δ S F = 3 x Δ S Δ S (standard) beam spots [Bert et al., IJROBP 2010] 2/28/2012 ICTR-PHE, Geneva 2012 27

Residual Motion Mitigation � ripple larger peak width B filter width B beam energy layers spacing ∆ Z reduced slice spacing ∆ Z modulated bragg peak width increased longitudinal overlap [courtesy D. Richter, GSI] 2/28/2012 ICTR-PHE, Geneva 2012 28

Gating-Experiments at HIT Measured: Anzai- Laser Sensor • ellipsoidal target volume Robot • 3D target motion • 18 beam overlap parameter combinations Laser Sensor • motion amplitutes up to 10 mm ⇒ ∼ 90 different parameter combinations Simulated (TRiP4D): 24 Ionisation Chambers • additional motion amplitudes • 4 – 30 starting phases ⇒ ~ 900 different parameter combinations Beam Target Volume Geiger Counter 2/28/2012 ICTR-PHE, Geneva 2012 29

Influence of residual motion CTV PTV [Steidl, Richter, Gemmel, Bert, GSI/Siemens] 2/28/2012 ICTR-PHE, Geneva 2012 30

Validation: Measured vs. TRiP4D calculated � Amplitude: 4mm (peak-peak) mean deviation : 2.5 ± 2.2 % beam Absolute Deviation Amplitude: 10mm (peak-peak) 24 ionization mean deviation: 0.0 ± 3.3% chambers ⇒ validated simulations [Richter et al, Radioth. Oncol. 96 (S1) 2010] 2/28/2012 ICTR-PHE, Geneva 2012 31

Example: Variation of beam focus homogeneity F=5 mm F=8 mm F=10 mm variation of ϕ 0 residual motion [mm] [Steidl, Richter, Gemmel, Bert, GSI/Siemens] 2/28/2012 ICTR-PHE, Geneva 2012 32

Beam parameters – results Variation Variation Variation Variation grid spacing beam focus IES spacing Bragg-Peak-width slope of linear fit [mm -1 ] Order of influence: beam focus F > IES spacing Δ Z > grid spacing Δ S > Bragg-Peak width B [Steidl, Richter, Gemmel, Bert, GSI/Siemens] 2/28/2012 ICTR-PHE, Geneva 2012 33

Hepato Cellular Cancer treatment at HIT • HCC treatments started ~ 6 month ago, 6 patients so far • Protocol based on NIRS experience • 4 fractions each 8.1 Gy (RBE) (LEM I) ANZAI belt • Beam delivery • abdominal press (5 pat.) • Gating (1 pat.) • Motion surrogate: ANZAI belt • Treatment QA • 4DPET Ch. Kurz, Friday 12:00h • reconstruction of daily 4D dose distribution 2/28/2012 ICTR-PHE, Geneva 2012 34

Example – abdominal compression Δ s=2mm, Δ z=3mm, F=10mm Δ s=2mm, Δ z=3mm, F=6mm [Richter, Härtig, Chaudhri, et al., GSI/HIT/RadioOnkol] 2/28/2012 ICTR-PHE, Geneva 2012 35

Example – Gating – 3D dose CTV PTV [Richter, Härtig, Chaudhri, et al., GSI/HIT/RadioOnkol] 2/28/2012 ICTR-PHE, Geneva 2012 36