physics of carbon ions and principles of beam scanning g. kraft biophysik, gsi, darmstadt, germany...
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Physics of carbon ions and principles of beam scanning
G. KraftBiophysik, 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)
vacuumwindow
monitors air skin patient
FW
HM
(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
Pituitary Lacrimal gland
BrainPTV
Vol.(%)
Vol.(%)
Vol.(%)
Vol.(%)
Dose (Gy)Dose (Gy)
ScattScatt
ScattScatt
Dose (Gy) Dose (Gy)
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 1.5.10 10 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
measured simulated
W.Enghardt et al. , FZR Dresden
precision of stereotactic fixation:
1mm in the head to3mm 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
3D online motion compensation (3D-OMC)
magnetic scanner system PMMA wedge system suitable motion tracking system
dynamic treatment plan
static moving, non-compensated
moving, compensated
real-time, highest precision
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
Thank you