Radiotherapy
- Preambule
- TERABALT Cobalt Irradiation Unit Model 80 and Model 100
- TERASIX simulator
- IRACEL blood irradiator
- Accessories
- Software
The treatment of tumour diseases is currently based on three main approaches: surgery, chemotherapy and radiotherapy, which are frequently combined together. Radiotherapy of timorous diseases is based on the action of ionizing radiation on living tissues, where sufficiently high radiation doses are capable of inactivating and killing cells.
The strategic aim of radiotherapy is to selectively destroy the tumour focus while causing minimal damage to the surrounding tissues. While a sufficiently high radiation dose must be sent to the target region, the surrounding healthy tissue should be left undamaged as much as possible. It is the aim of clinical radiotherapy to find an optimum compromise between the two contradictory requirements.
The routine radiotherapy procedure consists in irradiation using a collimated beam of penetrating radiation delivered by an external facility.
Currently, penetrating gamma rays produced by a radioactive cobalt 60Co (1173+1322 keV) is among the most frequently used types of radiation for radiotherapy. Such a type of irradiator for radiotherapy is manufactured by UJP PRAHA. |
 |
Two major factors contribute to attaining the main strategic aim of radiotherapy, which is efficient selective irradiation of the tumour while causing minimal damage to the surrounding tissue:
- The tumour is irradiated with a collimated beam from multiple directions intersecting in a point where their doses sum up – referred to as the focus or isocentre – coinciding with the location of the tumour. The surrounding tissues receive a much smaller dose, the total being distributed over a large volume.
- The tumorous tissue, which occurs in a state of vigorous – pathological – cell division, is normally more sensitive to ionizing radiation that the healthy tissue. Fractionated irradiation is practised, where the total dose is divided into a number of smaller daily doses, applied consecutively for several days (about 3 to 5 weeks). The cumulative biological effect on the tumour tissue is then usually higher than the effect on the healthy tissue, which has higher recovery capabilities.
Largely the two factors make possible a sufficiently efficient and selective irradiation of the pathological site. In clinical practice, the treatment is preceded by a demanding planning process, resulting in a treatment plan containing all the particular details of the irradiation procedure for the given patient. The treatment plan is mainly based on detailed X-ray images of the area to be treated (currently they are computed tomography (CT) scans). The radiographs serve not only to precisely locate the tumour focus and to determine its size and shape but also as a detailed anatomical picture showing the tissue density distribution and location of organs.
 RTG simulátor TERASIX |
A simulator facility mimicking the entire irradiation process and enabling this process to be optimized – is used for precise treatment planning purposes. A simulator is an X-ray facility for diagnosis equipped with an image intensifier whose tube is fixed to a rotatable isocentric arm and is fitted with a system of adjustable diaphragms making it possible to simulate a radiation beam such as is to be used in the irradiator itself. The simulator makes possible location of the target area and topometry of the tumour focus, aiming of the radiation beam and modelling of the field geometries and irradiation parameters, and indication of reference points on patient’s body. |
The data along with the required radiation dose to be delivered to the target tissue (which depends on the type of tumour, i.e. on its radiosensitivity) serve to calculate the intensity, energy and geometry parameters of the radiation beam, including a precise adjustment of the irradiation positions and angles, as well as the dose distribution patterns. The entire planning process and subsequent radiotherapy can be automated by means of dedicated software which processes the starting X-ray images, plots the isodose curves and calculated local doses, and creates an irradiation formula. Software that controls the performance and motions of the irradiator during the therapy with reference to the planned data is referred to as the verification system.