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

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

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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.

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Treating moving organs with particle beams

Christoph Bert

GSI Helmholtz Centre for Heavy Ion Research, Department of Biophysics

Darmstadt, Germany

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2

Organ motion in radiotherapy

Gas Prostate

Gut motion

Scale: minutes

Heart beat

Scale: seconds

  • A. Constantinescu

Friday, 9:30h

  • A. Rucinski

Friday, 16:12h

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3

Organ motion in radiotherapy Respiration

Scale: seconds

2cm 4cm 6cm 8cm 10cm range

tumor beam

Respiration in particle therapy

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2/28/2012 ICTR-PHE, Geneva 2012 4

Respiratory motion - beam range

range dose

photons

12C

[courtesy S.O. Grözinger, GSI]

⇒ mitigation of range / longitudinal changes essential

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2/28/2012 ICTR-PHE, Geneva 2012 5

Mitigation by margins (ICRU recommendation)

GTV CTV PTV

Gross tumor volume Clinical target volume Planning target volume

ITV Internal target volume

[Rietzel et al., MGH]

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Range change dependence of margins

2/28/2012 ICTR-PHE, Geneva 2012 6 [M. Koto et al. / Radiotherapy and Oncology 71 (2004)]

Original treatment plan Original TP to 5 mm shifted tumor ⇒ Margins have to incorporate range and are thus field specific

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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]

  • 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

additional motion mitigation needed

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ICTR-PHE, Geneva 2012 Geometry Water-Equivalent Path Length A B C (ref) Union of A,B,C Geometric union in WEPL of C Motion Phase

Water-equiv. Path Length ITV

[Graeff et al., GSI] 2/28/2012 8

WEPL-LUT Field 1 Field 2

CTV bone ITV

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Field specific WEPL-LUT

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

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Static Dose: DVH

End Exhale (Reference) End Inhale

2/28/2012 10 ICTR-PHE, Geneva 2012 [Graeff et al., GSI]

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Static Dose: ITV Comparison

Range-ITV Geo-ITV End-Inhale

11 2/28/2012 ICTR-PHE, Geneva 2012 [Graeff et al., GSI]

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4D-Dose (15 rescans): ITV Comparison

Range-ITV Geo-ITV

2/28/2012 ICTR-PHE, Geneva 2012 [Graeff et al., GSI]

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4D-Dose (15 rescans): DVH

2/28/2012 ICTR-PHE, Geneva 2012 [Graeff et al., GSI]

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2/28/2012 ICTR-PHE, Geneva 2012 14

Interplay - simulation data

→ IM / ITV / PTV not sufficient

[Bert et al, Phys Med Biol, 2008]

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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

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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

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Rescanning

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

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

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

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Beam Tracking

  • Incorporated into GSI TPS TRiP4D
  • 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

2/28/2012 ICTR-PHE, Geneva 2012 20

[Bert & Rietzel, Radiat Oncol 2007; Saito et al.. Phys Med Biol 2009; Bert et al. Med Phys 2007]

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2/28/2012 ICTR-PHE, Geneva 2012 21

Real-time dose compensated beam tracking (RDBT)

  • 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

  • Dose change depends on temporal correlation between beam

and tumor motion

[Lüchtenborg et al. Med. Phys. 2011]

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Beam tracking technique comparison

  • Treatment planning study (TRiP4D)

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
  • Plan design:
  • 4 fields, 4 fractions
  • 8.2 Gy (RBE) / fraction
  • based on NIRS protocol
  • 81 motion combinations calculated
  • Report of V95

2/28/2012 ICTR-PHE, Geneva 2012 22

[Lüchtenborg PhD-Thesis 2011]

Stationary dose distribution

Patient #5

V95

interplay RDBT

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2/28/2012 ICTR-PHE, Geneva 2012 23

4D dose calculation: beam tracking

[Lüchtenborg et al., PhD-Thesis, 2011]

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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

2/28/2012 ICTR-PHE, Geneva 2012 24

[Lüchtenborg PhD-Thesis 2011]

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2/28/2012 ICTR-PHE, Geneva 2012 25

Gating: clinical for passively shaped beams

[Minohara et al., IJROBP 2000, Miyamoto et al., Radioth. Oncol. 2003, IJROBP 2007, Mori et al. IJROBP 2008 ]

  • 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

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2/28/2012 ICTR-PHE, Geneva 2012 26

Gating: Residual motion – scanned beams Irradiation under abdominal compression, e.g. liver cancer (HCC) similar residual motion

time residual motion (gating) residual motion (abd. compr.)

<~10mm

mitigation & robustness studies needed!

amplitude

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2/28/2012 ICTR-PHE, Geneva 2012 27

Residual Motion Mitigation Optimize beam overlap:

F (FWHM) = 5 x ΔS beam spots ΔS ΔS F = 3 x ΔS

(standard)

(ΔS = grid spacing)

[Bert et al., IJROBP 2010]

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2/28/2012 ICTR-PHE, Geneva 2012 28

Residual Motion Mitigation

beam ripple filter increased longitudinal overlap modulated bragg peak width energy layers

larger peak width B

width B

reduced slice spacing ∆Z [courtesy D. Richter, GSI]

spacing ∆Z

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2/28/2012 ICTR-PHE, Geneva 2012 29

Gating-Experiments at HIT

Measured:

  • ellipsoidal target volume
  • 3D target motion
  • 18 beam overlap

parameter combinations

  • motion amplitutes up to

10 mm ⇒ ∼ 90 different parameter combinations Simulated (TRiP4D):

  • additional motion

amplitudes

  • 4 – 30 starting phases

⇒ ~ 900 different parameter combinations

Robot Beam Geiger Counter Target Volume 24 Ionisation Chambers Laser Sensor Anzai- Laser Sensor

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2/28/2012 ICTR-PHE, Geneva 2012 30

Influence of residual motion

[Steidl, Richter, Gemmel, Bert, GSI/Siemens]

CTV PTV

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2/28/2012 ICTR-PHE, Geneva 2012

Validation: Measured vs. TRiP4D calculated

Amplitude: 10mm (peak-peak) mean deviation: 0.0 ± 3.3% Amplitude: 4mm (peak-peak)

mean deviation: 2.5 ± 2.2 % beam 24 ionization chambers

Absolute Deviation

[Richter et al, Radioth. Oncol. 96(S1) 2010]

⇒ validated simulations

31

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2/28/2012 ICTR-PHE, Geneva 2012 32

Example: Variation of beam focus

F=5 mm F=8 mm F=10 mm variation of ϕ0

[Steidl, Richter, Gemmel, Bert, GSI/Siemens]

residual motion [mm] homogeneity

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2/28/2012 ICTR-PHE, Geneva 2012 33

Beam parameters – results

Variation grid spacing Variation beam focus Variation Bragg-Peak-width Variation IES spacing Order of influence: beam focus F > IES spacing ΔZ > grid spacing ΔS > Bragg-Peak width B

[Steidl, Richter, Gemmel, Bert, GSI/Siemens]

slope of linear fit [mm-1 ]

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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)
  • 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

ANZAI belt

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Example – abdominal compression

Δs=2mm, Δz=3mm, F=10mm Δs=2mm, Δz=3mm, F=6mm

[Richter, Härtig, Chaudhri, et al., GSI/HIT/RadioOnkol] 2/28/2012 ICTR-PHE, Geneva 2012 35

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Example – Gating – 3D dose

PTV CTV

2/28/2012 ICTR-PHE, Geneva 2012 36 [Richter, Härtig, Chaudhri, et al., GSI/HIT/RadioOnkol]

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Gating: 30%Ex->70In% GW (ANZAI based)

2/28/2012 ICTR-PHE, Geneva 2012 37 [Richter, Härtig, Chaudhri, et al., GSI/HIT/RadioOnkol]

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2/28/2012 ICTR-PHE, Geneva 2012 38

Summary

  • Particle therapy: Organ motion requires dedicated solutions
  • Range influence
  • Scanned beam: interplay ⇒ under-dosage
  • Motion mitigation techniques

– Rescanning, gating and beam tracking + combinations – Apnea (used at RPTC for respiratory motion), abdominal compression (used at HIT for HCC) – Gating patient treatments with scanned beams started at HIT in 2011

  • Still an active field of research

– Sensitivity of techniques against uncertainties – Reduction of dose to normal tissues – Precise motion monitoring – …

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2/28/2012 ICTR-PHE, Geneva 2012 39

Acknowledgements

Medical Physics Group at GSI Biophysics

  • R. Brevet, A. Constantinescu, C. Graeff, S. Hild, R. Kaderka,
  • R. Lüchtenborg, D. Müssig, D. Richter, N. Saito, P. Steidl,
  • J. Wölfelschneider

Colleagues at GSI

  • M. Durante, G. Kraft, N. Kurz, W. Ott, U. Scheeler,
  • P. Schütt, E. Schubert

Colleagues at HIT

  • S. Brons, T. Haberer, P. Heeg, O. Jäkel, J. Naumann,
  • R. Panse, K. Parodi

Third-party support Siemens AG, Particle Therapy German Research Foundation, KFO 214 EU FP-7 ULICE, ENVISION, ENTERVISION