Particle Therapy, Protons & Neutrons

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Home Coming meetings Past meetings About the Society Galleries of the Virtual Museum Main Galleries Medicine Surgery Anaesthesia X-rays Hospitals,other organisations Individuals of note Small Galleries Dentistry Nursing Ethnic medicine - Aboriginal - Chinese - Mediterran	Particle Therapy, Protons & Neutrons Associate Professor Eva Bezak, Department of Medical Physics, The Royal Adelaide Hospital Protons have a definite range in matter in which the delivered dose is zero, and further range where the dose distribution increases with depth. These properties will result in geometrically better dose distribution (highly conformal high dose region) than can be achieved by conventional treatment with photons and electrons. Consequently dose to the target can be increased, improving the probability of tumour control while sparing normal tissue. Also the total integral dose delivered with protons is smaller compared to state-of-the-art conformal photon therapy, thus avoiding complications from late radiation injuries. As a result, the main clinical indications for proton therapy are the proximity of the target to critical structures, where maximum selectivity of dose distribution is of high importance, or low tumour sensitivity requiring high doses. Protons lose their energy mostly through Coulomb interactions with electrons of constituent atoms, with a small fraction of energy transferred through nuclear collisions. The energy loss per unit path length is relatively small and constant as the particles transverse tissue. However, as the proton comes to rest, there is a distinctive sharp increase in the absorbed dose in tissue known as the Bragg Peak . This peak is too narrow to irradiate most tumours so several beams of closely spaced energies are superimposed to create a range of uniform dose over the depth of the target, These extended regions of uniform dose are called “Spread out Bragg Peaks” (SOBP) . -o0o-

South Australian Medical Heritage Society Inc

Website for the Virtual Museum

Home
Coming meetings
Past meetings
About the Society

Galleries of the Virtual Museum

Main Galleries

Medicine
Surgery
Anaesthesia
X-rays
Hospitals,other organisations
Individuals of note

Small Galleries

Dentistry
Nursing

Ethnic medicine
     - Aboriginal
     - Chinese
     - Mediterran

Particle Therapy, Protons & Neutrons

Associate Professor Eva Bezak, Department of Medical Physics,
The Royal Adelaide Hospital

Protons have a definite range in matter in which the delivered dose is zero, and further range where the dose distribution increases with depth. These properties will result in geometrically better dose distribution (highly conformal high dose region) than can be achieved by conventional treatment with photons and electrons.

Consequently dose to the target can be increased, improving the probability of tumour control while sparing normal tissue. Also the total integral dose delivered with protons is smaller compared to state-of-the-art conformal photon therapy, thus avoiding complications from late radiation injuries. As a result, the main clinical indications for proton therapy are the proximity of the target to critical structures, where maximum selectivity of dose distribution is of high importance, or low tumour sensitivity requiring high doses.

Protons lose their energy mostly through Coulomb interactions with electrons of constituent atoms, with a small fraction of energy transferred through nuclear collisions. The energy loss per unit path length is relatively small and constant as the particles transverse tissue. However, as the proton comes to rest, there is a distinctive sharp increase in the absorbed dose in tissue known as the Bragg Peak . This peak is too narrow to irradiate most tumours so several beams of closely spaced energies are superimposed to create a range of uniform dose over the depth of the target, These extended regions of uniform dose are called “Spread out Bragg Peaks” (SOBP) .

-o0o-