It is known that the greatest sensitivity to radiation have been actively dividing cells. The mechanism of influence of ionizing radiation on cancer cells at the molecular level is reduced to the formation of ions of different signs and, as a consequence, the formation of chemically active free radicals. The latter, in turn, can damage the structure and hence function of basic biological molecules in the cell, especially DNA, which at the time of cell division is most vulnerable.
Nondividing or weakly dividing cells of the body more resistant to ionizing radiation and therefore do not perish under the influence of radiation therapy. However, some cancer cells at the time of irradiation in the interphase, ie, at rest and as a consequence, resistance to radiation comes close to the normal cells.
For this reason, radiation therapy is not carried out simultaneously and in a few sessions. The single and total dose are selected in such a way as not to cause damage to healthy tissue and the maximum impact on the tumor.
X-rays and gamma rays in particular, at doses that are hundreds of thousands of times higher than the dose from a single fluorographic image is used to treat many types of tumors. The most intensively they are used in the treatment of cancer in adults. In children, radiation therapy is a very important limitation. The fact that the body of any child is growing, which means that many cells are in the process of division and as a consequence, the difference in the sensitivity of normal and tumor cells are not as great as in adults. It is for this reason it is necessary to take into account features of the radiosensitivity of different organs at different times of life, take a package of measures to reduce the impact on them.
First, you must plan carefully to minimize the exposure of radiation exposure to surrounding healthy tissues and organs of the child. This helps prevent the development of immediate complications of treatment, as well as remote, such as impaired growth and development of various organs and systems.
Secondly, the radiation therapy in children requires immobilization of the irradiated parts of the body, and sometimes the use of anesthesia to prevent movement of the body, and, consequently, reduce the exposure to healthy tissue.
Third, it requires psychological preparation of any patient.
Fourth, it requires careful preparation predluchevaya, whose objectives are: Preparation of topographic information about the patient and tumor. Carried out using three-dimensional computed tomography (CT, MRI or ultrasound)
Select the source and exposure conditions. The most frequently used external beam radiation, which requires, as a rule, two or more fields of radiation at different angles in order to reduce radiation dose to healthy tissue.
The modeling of irradiation. In the simulation, a physicist and dosimetrists a radiologist calculated and compared the possible effects of dose and exposure. Then worked through the practical implementation of the model simulator.
Quality control predluchevoy training. By using gammagraphy, ie careful analysis of images obtained during the practical implementation of the model simulator.
Complications of radiation therapy
In adult patients during radiation therapy, the risk of immediate and long-term complications is minimal. In children, the risk several times higher, and therefore has many limitations. Long-term effects on the development of the musculoskeletal system of children (slowing its growth and development) is most revealing. However, the recovery ability of some other organs and systems in children is higher than in adults. Most sensitive to radiation in children and adults, red bone marrow, gonads, the epithelium of the gastrointestinal tract, the lens of the eye. In addition, the red bone marrow of children is increasingly common, which imposes additional restrictions on radiation therapy.
It is due to increased radiosensitivity of normal tissues of the child lately more and more attention paid to the development of chemotherapy and radiation therapy is used is limited and is usually combined with other treatments.