Physics of carbon ions and principles of beam scanning G. Kraft Biophysik, GSI, Darmstadt, Germany PTCOG43 Educational Satellite Meeting: Principles of Carbon Ion Therapy December 9th,2005 GSI,Darmstadt

Physical and technical features of proton and carbon beams –Inverse depth dose profile –Lateral scattering and dose gradients –Intensity modulated beam delivery –In vivo PET control of the beam –Extension to moving targets

Depth dose distribution of various radiation modalities

fragmentation of heavy ions

Comparison of dose profiles of protons and carbon

Lateral Scattering

Edge effect; overrange induced by scattering

Treatment Plan with edge effects O. Jaekel et al., DKFZ

Scattering and irradiation geometry

Beam scattering for a real scanning setup (exit window, monitors, air, patient) vacuum window monitorsair skin patient FWHM (mm) U. Weber 2002

Comparison of Carbon Ions vs. Protons C-12 (GSI) Protons (Capetown/SA)  Advantage due to beam scanning and less lateral scattering

Passive beam modulation

CASE 2 BENIGN MENINGIOMA (recurrence after 2 surgeries) with invasive growth in the lateral and upper aspects of left orbit displacing the optic nerve PRESCRIPTION: AVERAGE DOSE to PTV (CTV + 3 mm) = 56 Gy

IMRT C ionsp+ passive p+ active

PituitaryLacrimal gland BrainPTV Vol. (%) Vol. (%) Vol. (%) Vol. (%) Dose (Gy) Scatt Dose (Gy)

Lt retina Lt optic nerve Chiasm Brainstem Vol. (%) Vol. (%) Vol. (%) Vol. (%) Dose (Gy) Scatt

Principle of raster scanning

Image of Albert Einstein produced with the GSI rasterscan system using a 430 MeV/u carbon beam of 1,7 mm width (FWHM). The picture consists of 105x120 pixel filled by particles given in 80 spills (5 sec. each) of the SOS accelerator. Original size of the picture: 15 x 18 cm

Slices of a tumor treated at GSI

Active Rasterscanning and Monitoring Rasterscan: Online- Monitor

Intensity distributon in a sphere

Intensity distribution of one slice

Clival Chordoma O. Jaekel et al., DKFZ

Positron Emission Tomography (PET)

In situ control with PET

Verifying the position of the irradiation field dose plan measuredsimulated W.Enghardt et al., FZR Dresden

Range measurements of carbon ions

precision of stereotactic fixation: 1mm in the head to 3mm in the pelvic region not feasible for regions with internal motion (e.g. respiration in thorax and abdomen) for ions: variations in radiological path length extremely important Extension to moving targets

Target Motion Destroys Volume Conformity time-dependent target positionfixed target position

intermittent irradiation in one motion state (gating) statistic averaging over many scans (rescanning)  elongation of treatment time or loss of precision staticmoving, 1 scanmoving, 3 scansmoving, 5 scans Minohara et al., 2000

3D online motion compensation (3D-OMC) magnetic scanner system PMMA wedge system suitable motion tracking system dynamic treatment plan staticmoving, non-compensated moving, compensated  real-time, highest precision

Patient treatment plan

Influence of target motion T=6.0s,  =270º staticcompensatednot compensated

Summary: Physical and technical properties of proton and carbon beams –Inverse depth dose profile –Lateral scattering and dose gradients –Intensity modulated beam delivery –In vivo PET control of the beam –Extension to moving targets

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