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Radiotherapy, hadrontherapy and treatment planning systems.

Faiza Bourhaleb INFN-Torino

University Med 1er-Morocco Radiotherapy Optimization techniques Hadrontherapy Treatment planning ANCOD++ Perspectives

NURT-Havana 25 October 2001

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Radiotherapy, the history:

RT as an inter-disciplinary technique.

Conventional RT !!??No: Too many error sources due to

a large rectangularly shaped fields bad definition of tager volume to irradiate.

Since 1973, conformational RT.

The Intensity Modulated RT birth => MLC

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Optimization and treatment planning

Patient steps before treatment CT and 3D definition of the global volume for treatment.Doctors prescription. Planning of the treatment?

Optimizing a TP Forward planning Monte Carlo simulation Inverse planning

ANCOD++ !??

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Why we should think to some thing else!!!

The solution is it an inverse planning, and what about optimization of beam intensities.

The beams intensities are the unique free parameter.

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Inverse planning:

Asking help from mathematics and numerical calculation

Big variety of algorithm already exciting:

Conjugate Gradient minimization.

Quasi Newton minimization.

Simulated annealing minimization.

All to resolve a simple linear system:

voxel),()( beamdwvoxelDbeam

beamrequired

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Physical properties of protons and carbon ions

Particularities of hadrontherapy.

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Biological properties

Alpha particles

Carbon ions

Double strand break

Lethal event

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Relative biological efficiency:

For the same biological effect show that we need much less dose delivering. Possibility of cell repair decrease in a considerable way.

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Treatment planning in hadrontherapy.

Patient information: AnatomyCT images for treatment

Doctors prescriptions considering devices limitations for the treatment.

Optimization technique: Mathematic algorithm2D or 3D optimization!

Display of final 3D dose distribution and notion of DVH.

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Voxel scan technique adopted:

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ANCOD++ description

VOXELCTTarget

AcceleratorFieldEnergyOptimize

Dose

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ANCOD++, results

100

40

Dose

X

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DVH inside target

DVH outside target

NB:comparison with IMRT ?

Vol

ume%

Dose%

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Comparison: IMRT Protons

Abdomen

Brain

Between eyes

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ANCOD++ GEANT 3

ANCOD++ and GEANT3 simulation

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The future !!??

Hadrontherapy has a big chance to be the therapy of the future since it has really minimum possible side effects, sparing as no other technique can do the organs at risk. It adopts the newest techniques of treatment planning, optimizing time and in that way money also. It is now a technique a bit expensive comparing with therapies with photon or electrons but like all the new technologies at the beginning the precision costs a lot but then the expenses decrease quickly with time.

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Thanks!!

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Filter degrader

Cancer

Bolus

Final collimator

scatterer

Ridge filter

Ridge filter

First collimator

Bolus

Final collimator

Body

Revolution and era of Conformational RT:

Blocks

Filters

Wedges

Compensators

Collimators…..

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The IMRT birth => MLC.

Gantry with an DMLC

The Multivane Intensity modulating Collimator (MIMIC).

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Iterative method used in our software.

Dose required in a specific voxel is changed in each iteration for the new one with correction.

We start considering the supervising weight the one of the beam steered in the actual voxel to have the Bragg peak there and so the maximun of energy deposition.

However it is necessary to iterate many times to join the compromise between different beams to respond the best to our requirements and prescriptions.