Particle therapy

Particle therapy or particle therapy (english particle therapy ), or more precisely Hadron therapy is a method of radiation therapy in which, in the context of cancer treatment, the tumor with high-energy positive ions ( mostly protons or carbon ions ) is irradiated. The particles are accelerated in a cyclotron or synchrotron. For carbon ions, a synchrotron accelerator is necessary in order to achieve acceptable penetration depths (up to 30 cm).

Properties

The advantage of particle therapy compared with conventional radiation therapy with photons is completely different penetration of the particles ( particles). The interaction of the charged particles with the tissue is strongly dependent on speed: The power output is approximately inversely proportional to the velocity squared. During the passage through the tissue, the particles are thus decelerated continuously stronger, the deeper they penetrate. As long as they have (> 50 MeV / u energies spec. ) high speed, its effect is relatively small. Only at the end of their range they unfold their powerful effect. There, the effect on a range of a few millimeters is increasing very strongly to then drop to zero (for protons ) or close to zero ( at carbon ions). The depth-dose profile thus generated is referred to as the Bragg peak. The energy of the particle leaving the accelerator and controls the penetration depth of the location of the maximum effect. This behavior makes it possible, in the tumor a very high dose of radiation to be deposited at the same time the surrounding tissue or organs of risk. Because the particle beam distracted transverse to the beam direction with fast electromagnet can with the magnetic raster scan method (combined with the energy variation ), the target volume can be scanned in layers and thus an extremely tumor -conform radiotherapy can be achieved. This is the main advantage over the conventional irradiation with photons.

Despite the high equipment requirements ( cyclotron or synchrotron ) particle therapy is routinely used already in thirteen countries around the world, and over 70,000 patients have been treated by the end of 2008, over 7000 patients with particles heavier than protons ( mostly helium and carbon). The list of treatments worldwide up to now has been taken from the Particle Therapy Co-Operative Group constantly up to date.

In Germany, the particle therapy only on installations was initially possible, their main purpose was to physics research. On the ion beam laboratory ISL of the Hahn- Meitner Institute in Berlin over 1200 eye cancer patients treated with protons in the years 1998-2008. By October 2007, there was a small treatment facility at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, where carbon ions were used ( a total of 450 patients). 2009 received a private proton therapy facility in Munich approval. In November 2009, the Heidelberg Ion -Beam Therapy Center (HIT ) was put in service. A planned system from Siemens at the University Hospital Schleswig- Holstein, Campus Kiel, is realized only as a conventional radiotherapy center.

Proton Therapy

Therapy with carbon ions

For carbon ions still gives a strong additional advantage: the high local ionization density at the end of the range are more common correlated damage (mainly to the DNA structures ) in the target volume, resulting in the DNA of cancer cells can be worse repair of repair enzymes than in front of it healthy tissue ( Eindringkanal ). This effect causes an increase in the efficiency of dose factor of about 1.5 to 3 in the target volume. The effect is typical of the particles such as carbon or oxygen. Photons or the light protons do not own it (photons) or very weak ( protons).

The Particle Therapy Co-Operative Group is constantly updated lists of active and planned hadron therapy centers. The end of 2008 there were only two centers for carbon ions in operation, both in Japan World: HIMAC in Chiba and Hyogo HIBMC. In Germany the first hadron therapy center was opened with the Heidelberg Ion -Beam Therapy Center on 2 November 2009 at the University Hospital Heidelberg.

View

Protons and carbon ions are on offer to develop also for problematic cases (malignant tumors that are accessible due to its proximity to sensitive organs, neither the surgery nor the conventional radiotherapy) a local, aiming at healing effect therapy technique.

In the current state of clinical research is an advantage from for highly ionizing radiation ( carbon ion ) is characterized for treating certain malignant tumors of the major salivary glands of adenocarcinoma of the prostate, soft tissue sarcoma, local recurrence of the rectum and of adenoid cystic tumors of the nasal cavities. Radiation therapy with protons is well suited for tumors near the surface, such as choroidal melanoma, chordoma and chondrosarcoma, and shows positive approaches to esophageal carcinoma, hepatocellular tumors, adenocarcinomas of the prostate, meningiomas and pituitary tumors.

Because the deposited total dose is less ion beam for radiotherapy than in the conventional irradiation with X-ray or gamma radiation or neutron radiation, the ion therapy for almost all tumors which are radiation therapy, the advantageous concept, as well as tumors of the major salivary glands of nasal cavities, the central nervous system, the non-small cell lung cancer, and tumors in children. Whether protons or carbon ions are the clinically favorable particle beams, can not yet be conclusively assessed. But it is clear that the particle therapy with protons, but especially with carbon ions, significantly better than the neutron therapy.