A simple version of X-ray computerized tomograph for receiving topometric information

The 128-channel computerized X-ray tomograph operating on-line with HP-21MX computer has been developed for receiving topometric information about inside organs of patient body in a proton beam plane and for subsequent planning of radiation treatment. In the chosen variant of installation X-ray apparatus and detector block are fixed immovably on the walls of a procedure box, and an examined object is rotated with a rotational stand included into the arrangement for proton therapy. The detector system consists of 128 CsI(Tl) scintillation counters working in a combination with FEU-85 photomultipliers. Information from the detctors passes to a special designed logarithmic ADC. The results are displayed on a colour or a half-tone black-white displays. Preliminary tests of the device make it possible to use it for increasing the proton therapy effectiveness. It has been found that the error in determining the total thickness of the substance to a centre of dose maximum localization is no more than 0.5 g/cm2. It is significantly less than in the case of the calculation mehod. The irradiation dose is no more than 20 mrad during one diagnostic procedure