An independent monitor unit calculation by commercial software as a part of a radiotherapy treatment planning system quality control

For the independent calculation of the monitored unit (MU) the commercial software RadCalc (Lifeline Software Inc., Tyler TX) was used as the choice of some available similar programs. The program was configured and used to verify the doses calculated by commercially accessible planning system Eclipse version 8.6.17 (Varian Medical System Inc., Palo Alto). This system is being used during the clinical running for the creation of the treatment plans. The results of each plan were compared to the dose phantom measurements by the ionization chamber at the same point in which the calculation were done (Eclipse, RadCalc) - in the izocentre. TPS is configured by the beam data (PDD and OAR). Those beam data were exported and afterwards the same data were imported to the program RadCalc. The consistent and independent data between TPS and RadCalc were gained by this process. The reference conditions were set the identical in RadCalc as in TPS, so the consistency between TPS and RadCalc output factors has been achieved (Collimator Scatter Factor: Sc, Phantom Scatter Factor: Sp). Those output factors were also measured by the ionizing chamber in the water phantom and compared with the TPS. Based on the clinical data of the response to the doses, ICRU recommends ensuring the ability of dosimetric systems to deliver the doses with accuracy of at least 5%. Many factors, such as layout of anatomic structures, positioning of a patient, factors related to an accelerator (a dose calibration and mechanic parameters) cause random and systematic failures in a dose delivery. The source of some problems can be also caused by the system databases and relating information transfer; and the TPS containing besides other things other dose calculation algorithms. (authors)