Gamma-ray apparatus

Gamma apparatus - installation for remote gamma-therapy, mainly patients with malignant tumors, as well as for experimental studies. Radiation source in gamma-ray apparatus is radioactive cobalt (60) and much less radioactive cesium (Cs -137).
Gamma apparatus consists of a tripod, which strengthened deliver radiation to the head (protective cover), and devices for the control system. Deliver radiation to the head has the shape of a sphere or cylinder in the center of which is the source of radiation, located against a conical window to exit the radiation beam. To obtain fields of different shape and size of the output window is supplied with a diaphragm. At the end of radiation window overlaps the shutter avoid exposure of medical personnel. The phone has a special mechanism for automatic opening and closing of the shutter and the regulation of the size and shape of the aperture. In case of emergency gate may be closed manual drive. Protective housing made of heavy metals (inner layers of tungsten and subsequent of the lead) and the outside is covered with steel cover.
The design of the tripod on which suspended deliver radiation to the head, move it allows for the convenience of exposure to fields of different localization. Depending on the design of the tripod distinguish gamma-ray apparatus for static exposure at which the radiation beam and the patient is in the process of irradiation motionless relative to each other, and rotary and rotary-convergent gamma-ray devices for rolling exposure at which the beam is moved around the stationary patient or the patient still revolves around a fortified radiation source. As a result of this rotation gamma apparatus generates the highest dose of gamma radiation in the tumor, subject to treatment, and the skin and tissue surrounding the tumor, are much lower dose.
Gamma devices have radiation sources with different activity. For irradiation from great distances apply With60 and for small distances Cs137. When activity With60 2000-4000 Curie irradiation is performed from a distance of 50 to 75 cm (remote gamma-ray apparatus), which creates at the depth of the location of the tumor high interest dose, for example at a depth of 10 cm dose is 55-60% of the surface. The exposure time is only a few minutes, and therefore bandwidth gamma apparatus is large. The use of this gamma-ray apparatus for radiation treatment of superficial tumors impractical because, in addition to the tumor, radiation exposed to a large amount of normal tissue. For radiation therapy of tumors, lying at a depth of 2 to 4 cm, use gamma-ray apparatus with a source of Cs -137 activity of not more than 100-200 Curie, and the patient is exposed to a distance of 5-15 cm (korotkometrazhnye gamma-ray apparatuses). Gamma apparatus The now commonly used remote gamma-ray apparatus for static exposure: "Ray" source With60 activity 4000 Curie (Fig. 1)GUT With60-800-1200 Curie and for rolling exposure - "Rocus" source With60 activity 4000 Curie (Fig. 2). For korotkovremennouu therapy is applied gamma apparatus "Rita". For experimental irradiation of animals, microorganisms, plants used gamma-ray apparatus with a source With60 great activity (in the tens of thousands of curies).
The premises intended for carrying out gamma-therapy, is located in the ground floor or basement corner of the building, which is on the outside perimeter is fenced off by a protective zone width 5 M. It includes the following facilities.
1. One, but more often 2 treatment rooms with a height of 2.5-3.5 m and the area of 30 - 42 m2. Procedural room partitioned off by a concrete wall 2/3-3/4 of its width, forming a kind of a maze to protect service personnel from scattered radiation. In procedural hall, in addition to the gamma-ray machine and a table for laying sick, no furniture should not be. 2. Panel room area of 15-20 m2 for one or two remote control apparatus; it is the observation of patients through the observation window of lead and tungsten glass density of 3.2-6.6 g/cm2 or using the TV channel. Panel and procedural connected to the intercom. The door in the procedural protected from scattered radiation sheet lead. Protection of walls, doors, Windows should ensure workplace dose rate not exceeding 0,4 Mr/hour. 3. Gamma apparatus For the gamma apparatus of type "Rocus" there is an additional soundproof room 10-12 m2 for electric starting equipment and devices of food. 4. The Plenum.
In addition to main rooms, there are more, which is necessary for maintenance of patients (dosimetry laboratory for calculation of dose fields irradiated patient, dressing, a physician's room, a waiting room for patients).