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Radiotherapy with Protons

by Dr. Ivan Rosenberg

Radiotherapy Physics, UCLH

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Why Proton Beam Radiotherapy ?

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A Schematic Cyclotron

Treatment Room 1 : isocentric gantry

Treatment Room 2 horizontal beam

Treatment Room 3: isocentric gantry

Research beam; radiobiology, gantry design, engineering and fundamental physics

Proton beam line

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Patient Positioning for Charged Particles

High precision in patient positioning is even more important for charged particle therapy, because of the sharp Bragg Peaks.

Depending on the disease site, extensive immobilisation procedures need to be adopted

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Head and Neck horizontal beam , LLMC

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Extreme accuracy needed for eye melanoma treatments

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Body mould immobilisation for pelvic sites

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Patient Positioning for Charged Particles

Patient in body mould in treatment position inside large proton beam gantry, LLMC.

Auxiliary retractable X-ray tube inside machine head used to produce port films

Deep false floor to allow gantry rotation

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Compact gantry at the Paul Scherrer Institute, Switzerland

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Practical Proton Radiotherapy BeamsRange modulation of a proton beam

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Practical Proton Radiotherapy BeamsRange modulator (passive)

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Practical Proton Radiotherapy BeamsCollimators and beam shaping

Irregular apertures are used to conform the beam to the shape of the tumour as projected along the direction of the incident beam

they need to be thick enough to expend all the incident energy (thicker than the range)

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Planning with Protons

Treatments for Ocular Melanoma can be achieved most successfully with about 70 MeV protons.

Because of its small volume, a single slightly modulated beam gives an ideal dose distribution

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Tumor divided in iso-energy slices

2-D dose distribution on the actually scanned slice

Bragg-peak

Scanning magnets in x

and y

ZX

Y

proton beam

Bragg peak

On-line monitor system

Practical Heavy Particle Radiotherapy Beams Beam Spreading by active scanning

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Intensity Modulated Proton Treatment

With active scanning, modulating the intensity and the energy depending on position, sophisticated plans can be achieved

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12 year old boy

Delivered single field plan

9 field IMRT plan9 field IMRT – second try

Factor 6 lower integral dose for protons

Some more Proton / IMXT comparisons

Unpublished data

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More IMPT vs. IMXT comparisons64Gy to target volume, doses to brainstem and optic structures as low as possible

IMXT(9 fields)

IMPT(3 fields)

z = 49

z = 49

z = 57

z = 57

z = 64

z = 64

Unpublished data

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Paraspinal tumour treated with IXRT vs. IPRT

From Weber et al, Int. J. Radiation Oncology Biol. Phys., Vol. 58, No. 5, pp. 1596–1606, 2004

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Paraspinal tumour treated with IXRT vs. IPRT

From Weber et al, Int. J. Radiation Oncology Biol. Phys., Vol. 58, No. 5, pp. 1596–1606, 2004

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Proton research at UCLH

• Non-clinical Proton treatment planning systems will be used to compare 3D-CRT with IMXT and with IMPT in selected patients with difficult paediatric and CNS tumours such as chordomas and chordosarcomas

• Analysis of dose distributions, DVH, TCP and NTCP, and possibility of dose escalation

• Identify patients who could benefit from referral to European or American Proton facility

• Develop understanding and expertise in proton planning among Clinicians and Physicists

• Prepare for the eventual availability of UK-based proton therapy facilities and strengthen the case for UCLH as one of those locations

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The case for protons at UCLHUCLH practice is highly specialised and serves nearby National Hospital for Neurology and Neurosurgery, Great Ormond Street Children`s Hospital, ENT and Dental Hospital (Gray`s Inn Rd) and North London Cancer Network. Strong academic presence.

Optimum Situation : University College Hospital near Euston Road/Station (excellent public transport access - train stations for Mid and North England/Scotland very close) .

Surrounding medical support & expertise is most impressive: specialist medicine, imaging, surgery, medical oncology, research oncology.

Several Large Radiation Oncology Centres nearby with large number of radiation oncology and medical physics experts. Use this expertise in patient selection, treatment planning and follow-up.