The protonthérapie is a particular technique of Radiothérapie aiming at destroying the cancer cells in the irradiant with a beam of particles. Contrary to the radiotherapy " conventionnelle" , the protonthérapie does not irradiate the tumors by using Photon S but, as its name indicates it, by focusing a beam of Proton S on the lesions. For this reason, the protonthérapie is a branch of the Hadronthérapie which gathers the techniques of radiotherapy using of the heavy Ion S in the place of the photons.

Introduction

The protonthérapie represents an interest by its capacity to target precisely and to destroy the tumors at the same time on the surface but also installed in-depth in the body, by minimizing the damage caused with the biological fabrics surrounding. For this reason, it is preferentially used to treat certain types of tumors for which the conventional Radiothérapie containing photons X would damage surrounding and radiosensitive healthy fabrics on an unacceptable level. This is of an particular importance in the case of patient pediatric where the long run effects such as release of secondary tumors caused by the total amount of radiation in the body would be problematic. Because of more low dose delivered with healthy fabrics, the protons have collateral effects less severe than the conventional Radiothérapie.

Historically, a field where the protonthérapie had very early beneficial applications was the treatment of the malignant melanomists of the Choroïde, a type of Cancer of the Oeil for which the only known treatment was the enucleation (extraction of the eye). Today, the protonthérapie is one of the techniques which is able to treat this tumor without mutilation. The protonthérapie is used on cancers which were not propagated yet.

How it goes

The protonthérapie, like all the forms of Radiotherapy, functions by sending energy particles ionizing (in our case, of the Proton S in the target tumor. These particles damage DNA cells until finally causing their death. Because of their strong propensity with the cellular Division, and of their aptitude reduced to the repair of the damaged bits of DNA, the cancer cells are particularly vulnerable to this attack on their DNA.

As the protons disperse less easily in fabrics, there is very little of side Dispersion; The beam of protons remains concentrated on the shape of the tumor without too much side damage to surrounding fabrics. All the protons of a certain energy have a certain distance from penetration; no proton penetrates behind this distance. Moreover, the amount delivered with fabric is maximum right on the last millimetres this penetration depth, this maximum is called Pic of Bragg (see Stopping power), of the name of William Henry Bragg which discovered the phenomenon in 1903. This depth depends on the energy to which the particles were accelerated by the Accélérateur of proton, energy which can be adjusted to the maximum of the capacities of the accelerator. It is of this fact possible to concentrate the destruction of the cells due to the beam of protons to deepest of the body where the tumor is located. The fabrics located on the race of the peak of Bragg will receive a reduced amount, and the fabrics located after the peak will not receive anything.

The protonthérapie, however, requires large equipment. For example, the Center of Protonthérapie d' Orsay, in France, uses a Synchrocyclotron of 900 tons. Such equipment was at the origin available only in the centers studying the Physique particles. And in the case of the installation of Orsay, the processing machine was converted of a use of research into Physique towards a medical use.

Nowadays, it has there several centers dedicated to the protonthérapie under operation or construction in North America, Europe, Asia and South Africa. The therapy by beam of protons had remarkable successes in the treatment of several types of cancers, including the tumors of the brain and those of the spinal column, as well as those of the prostate. Certain researchers put forward the idea that the antiprotons could be even more effective to destroy the cancer cells than their opposite proton. For the moment, only of preliminary research on culture of cells were carried out.

History of the protonthérapie in France

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