COMPFIT - A computer program for internal tissue-dose calculation

The internal tissue or organ dose from radionuclides taking part in the transport processes in the living organism is proportional to the total number of disintegrations, i.e. to the activity time integral for a given period of time. For the calculation of this integral the description of the activity time variation is needed. The most sophisticated method for obtaining the tissue activities in time is compartmental analysis, but the fitting of the sum of exponential functions can lead to good results as well. For this purpose the COMPFIT program consisting of five subprograms was elaborated: the program can handle measured or calculated activity data in time and it provides different parameters characterizing the movement of radionuclides as well as calculating the activity time integrals. The COMPFIT program can be widely applied in radiation protection, for dosimetry in nuclear medicine and for tracer-kinetic investigations. The different subprograms make it possible to solve the task at different levels and in a large variety of cases taking into account the measuring conditions and the calculated output information required. A short description of the principles underlying the program and its structure together with the main features from the viewpoint of the users, and the possible fields of application are presented. As a concrete example the way of internal tissue dose calculation is given in a case when 131I isotope has been ingested. (author)