Neutron Therapy with Cf Source
Development of Treatment Methods, Technical Means and Small Sized Cf-252 Sources for Neutron Brachytherapy
Tech Area / Field
3 Approved without Funding
VNIITFA, Russia, Moscow
- NIIAR (Atomic Reactors), Russia, Ulianovsk reg., Dimitrovgrad\nNIIIT (Pulse Techniques), Russia, Moscow
- Oak Ridge National Laboratory / Nuclear Science and Technology Division / Radiochemical Inggineering Development Center / Int. Calif.-252 Brachytherapy Society, USA, TN, Oak Ridge\nUniversitatsklinikum Essen / Westdeutches Tumorzentrum, Klinik und Poliklinik fur Strahentherapie, Germany, Essen\nArgonne National Laboratory (ANL), USA, IL, Argonne
The malignant tumors radiotherapy investigations show that radiosensitivity of biological cells to irradiation depends in great extent on sell oxygen concentration. Cancer cells are less saturated with oxygen than healthy ones. The irradiation with high linear energy transfer (LET) radiation can be more effective for poor oxygenated cells. As a rule, in practical radiotherapy gamma-radiation is used with a LET ranging from 2 to 10 keV/. The sensitivity of high-oxygenized cells for such LET radiation is by a factor of 3 higher as compared to low- oxygenated cells. These low oxygenized cells can be under-irradiated during radiation therapy course and lead to recurrence of disease. On the other hand, surrounding healthy cells can be over-irradiated.
Because of that it is preferable to use neutrons with high LET (> 60 keV/), where secondary radiation (mostly recoil protons) is formed as a result of interaction of neutrons with biological tissue. Spontaneous Cf-252 fission neutrons can be used for this purpose.
Such high LET (> 60 keV/micron) ensures radiosensitivity ratio 1.5 (instead of 3 for gamma-therapy) of well oxygenated to low oxygenated cells, which leads to unification of radiosensitivity of healthy and malignant tissues. Thus, the same therapy effect is achieved as in case of gamma-therapy, while load on healthy tissue decreases at least twice. It leads to decreasing of radiation-caused complications of healthy organs and tissues. On the other hand, efficiency of treatment in this case must be much higher.
Preliminary investigations carried out by foreign and Russian experts from Russian Oncological Scientific Center and Medical Radiotherapy Scientific Center (Obninsk) using experimental equipment and Cf-252 sources have shown high efficiency of neutron brachytherapy for various tumors localizations especially for recurrences, as well as for bulky and late staged tumors. However in order to examine more possible advantages of Cf-252 neutron brachytherapy further investigations are to be carried out. That is why the development of tiny high flux neutron sources and proper technical means are necessary.
The goal of the Project is the development of experimental treatment apparatus for contact neutron brachytherapy of malignant tumors based on newly developed small-sized and high power neutron flux Cf-252 sources of radiation, which enable to increase the efficiency of treatment of various local tumors and decrease the number of recurrences of disease. The objective is achieved not only due to high LET radiation but also due to optimum program modes of irradiation. Another very important goal will also be achieved: decreasing of harmful irradiation to medical personnel.
Nowadays Californium-252 is the only material, which can be used for fabrication of such source. Technology of Cf-252 production is so complicated and source manufacturing needs so highly specific equipment, that creation of such kind characteristics of sources (Cf-252 content up to 3 mg, outer diameter 1.2 mm and length 5 mm) is possible only in the USA and Russia. Russian Research Institute of Atomic Reactors (RIAR) has accumulated great experience in production of prototypes of similar sources. Many sources for gamma therapy are produced in RIAR. Development of small sized
Cf-252 source with high neutron flux is the first objective of the Project.
The second objective is to ensure automatic delivery and retracting of radiation sources in several seconds, thus eliminating manual operations and minimizing irradiation of personnel. This problem is achieved through creating of special machine – Neutron Brachytherapy Afterloading Device (NBAD).
This device operates according to the principle of remote controlled afterloading of the radiation source. It is supplied either with special treatment applicators, which are placed at the nearest vicinity of the tumor before exposure, or with flexible hoses for transportation of radiation source to the treatment applicator by means of special driver. It enables not only automatic transportation of radiation source, but also to perform its displacement inside applicator according to prescribed program.
Variety of dose distributions created by source movement inside applicator enables to ensure inpidual treatment of each patient.
VNIITFA scientists and engineers will carry out NBAD design. VNIITFA is known as leading institution in radiation technologies. Special electronic equipment and software (according to doctors recommendations) will be carried out by the experts from NIIIT – one of the leading institutions on electronics in atomic industry.
The third objective is to be achieved along with two others and consists of development of new promising medical methods of treatment, to facilitate application of newly- created equipment. Preliminary clinical trials in investigating efficiency of Cf-252 treatment carried out by Dr. Y.Maruyama at USA and by leading Russian radiologists (participants of this Project) academician, Prof. Y.S.Mardinskiy, Prof. B.Vtyurin, Prof. L.Maryina and others  have developed scientific basis to this Project.
NBAD development enables to come from experimental investigation to routine treatment methods for wide circle of deseases, not only for gynaecological and rectum cancer, but also for prostate, bladder, oral cavity, oesofagus and others.
The Projects meeets all goals and objectives of the ISTC. It enables to involve a large team of “weapon” scientists and engineers (83% of total number of participants) to solving of important humanitarian problems. This work has also significant commercial potential. Original technical findings enable to decrease cost of future serial production of the machine and provide large oncological centers with this installation.
Leading expert on Boron Neutron Capture Therapy (BNCT) Prof. W.Sauerwein from Essen University (Germany) and Cf-252 production expert Dr.R. Martin from Oak-Ridge National Laboratory (USA) kindly agreed to collaborate the Project and take part in discussion of scientific and technical results in machine development and treatment methods, providing assistance in international certification.
Ref.1. Californium-252 Isotope for 21-st Century Radiotherapy. Proceedings of the NATO Advanced Research Workshop on Californium-252. Detroit U.S.A., April 24-27, 1996. NATO ASI Series. 3.High Technology – Vol.29
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