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Medico-Technical Complex

Proton-beam therapy

Radiation therapy (radiotherapy) plays an important part in the treatment of malignant, as well as many nonmalignant neoformations. The main goal or ideology of the radiation therapy is to transport a high radiation dose to the tumour, with minimal or, ideally, no impact on normal tissues and organs.

Radiotherapy today is applied in the world mainly with gamma-rays obtained from either radioisotopes (for example, in cobalt guns) or from high-energy accelerated electrons’ bremsstrahlung. In most cases, this radiation is sufficient to solve the above-mentioned task. However, if vital radiosensitive structures and organs are located near the exposure target, the traditional radiotherapy is often impotent. It can be explained by the fact that the harmful action of gamma radiation decreases exponentially while penetrating the substance, bringing an even higher dose to healthy tissues along the route of the beam than to the target itself. Moreover, tissues and organs behind the target are also irradiated. Another drawback of gamma-rays is an insufficiently acute dose decrease on the side borders of the beam, due to the specific interaction of this radiation with the substance. For this reason, the dose distribution is not always focused on the target effectively that primarily makes the traditional radiation therapy limited.

Unlike gamma-rays, the dose from the proton beam grows while the beam is penetrating the tissue and has a distinct maximum (the so-called Bragg peak); overcoming it, the dose decreases very quickly at a distance of several millimeters practically to zero. Besides, the side gradients of such a beam are also significantly better than those of gamma-rays. All this made it possible to expect growing efficiency of radiotherapy and extend the method potentialities.

The first studies to use proton beams in practical radiotherapy were started in the mid-1950s at the US nuclear physics centres. For the present time, about 50 thousand patients have already been treated at proton beams in over 20 nuclear physics and medical centres of the world.  The accumulated clinical experience has fully come up to the expectations. As a confirmation of it, the first specialized centre for proton therapy was built in the late 1980s – early 1990s that had its own accelerator and was based on a large hospital (Loma-Linda, California, USA). Several more similar centres are under construction or come into operation in the world today. The proton beam therapy in oncology becomes a real alternative to surgery.

Historical facts about the Medico-Technical Complex

 First experiments on using a proton beam for radiotherapy of malignant tumours in the Laboratory of Nuclear Problems of the Joint Institute of Nuclear Research were started as far as in 1967. To day the unique six-box Medico-Technical Complex (MTC) was constructed and put into operation. It was designed for radiotherapy to treat oncological patients with heavy nuclear particles.

The Complex is based on the proton accelerator phasotron – a research facility with particle maximum output energy of 660 MeV.

Various methods to treat oncological diseases have been developed and technically implemented at MTC, such as application of a proton beam of different energies for a wide range of neoformations’ locality (box 1), the so-called “shoot-through” technique with a proton beam of maximum energy of 660 MeV (box 3), treatment of onco-gynecological patients (box 2), experiments to use such exotic particles in radiotherapy as negative pi-mesons which give some biological advantages to kill cancer cells in comparison to protons (box 4), neutron therapy (box 5) and standard gamma therapy at the “Rokus” device (box 6).

When in December 1999 a specialized radiological department was opened at the local hospital, the studies were given a fresh impetus that made it possible to attract qualified radiologists from Moscow, Obninsk, and Omsk to Dubna.

Rapid progress of recent decades in medical diagnostics and computing has brought about the establishment of a new branch in radiology – the 3D computer scheduling and exposure sessions. Thereby, the method of 3D conformal irradiation of deep-seated tumours with a proton beam was implemented for the first time in Russia and is still applied today in one of the Complex treatment rooms. With this method, the maximum of the dose distribution conforms most precisely (up to millimeters) to the target shape. In addition, the dose sharply decreases beyond the target borders; it allows exposure of localizations that used to be inaccessible for conventional radiotherapy.

Long-standing cooperation of MTC with the Medical Radiological Research Centre of the Russian Academy of Medical Sciences in Obninsk has made it possible to implement powerful programmes of proton therapy research. Today, about 100 patients annually take treatment at the phasotron proton beams.

The efficiency of the treatment at MTC is sufficiently high for a wide range of localizations: these are, primarily, neoformations in brain, cancer of naso- and oropharynx, neck, lung, prostate, vesical cervix etc. This list is growing year by year, due to constant efforts on new methods of fixation and exposure of patients.

Innovation projects: Proton beam therapy centre

Apart from the centre in Dubna, there are two other centres for proton beam therapy in Russia which are also based on large research accelerators – at the Institute of Theoretical and Experimental Physics (ITEP) in Moscow and the Petersburg Institute of Nuclear Physics (PINP) in Gatchina. But in these centres the task of conformal (conforming to the target shape and structure) irradiation with the proton beam has not been solved yet. Thus, the range of diseases to be treated at these centres is rather limited.

At the same time, even today Dubna is the apparent leader in Russia in the field of precise proton therapy, with its patient capacity of 100 people a year. It is only here that the method of conformal 3D irradiation of deep-seated tumours, when the dose distribution precisely conforms (up to millimeters) to the target shape, has been worked out and is successfully applied.

The Centre for proton therapy on the basis of the cyclotron with the patient capacity of 1000 patients a year is being developed at the Laboratory of Nuclear Problems, JINR, as a basic variant. At present, a proton 235 MeV cyclotron is constructed together with the Belgian company IBA. It can become the basic model of proton therapy centres to be replicated in Russia.

 The advantage of a proton therapy centre based on a cyclotron is in its operation safety and compactness. Long-term JINR cooperation with the company IBA – a world leader in this field that developed equipment for nine proton centres in various parts of the globe - considerably extends JINR potential in the development of unique systems for proton therapy centres in Russia that have no Russian analogues, such as, for example, the gantry systems.  A big team of physicists, radiobiologists and physicians at JINR have been efficiently working for 40 years to develop schedule programmes, diagnostics and application of advanced methods of proton therapy. The experience in construction of accelerators and medical equipment at JINR makes it possible to produce and deliver the equipment for proton therapy centres in the “ready-to-operate” mode.