Study Of Generalized Mean Formula On The Estimation Of Equivalent Square

Objective1.To develop the methods of measuring photon beam relative dose factor for medical accelerator automatically.2.To propose a Generalized Mean(GM)formula for Equivalent Square(ES)estimation and compare it with other established formulae.Materials and methods1.The measuring sequence of beam relative dose factor was imported to MosaiQ system,which manage the state of the accelerator "beam on" or "beam off".The PC Electrometer reference dosimeter was turn on synchronously when the accelerator beam on,and the results were exported in excel format after the measurement.At last,the photon beam relative dose factor was worked out using formula.2.Two electron linear accelerators from different manufacturers were selected to measure 81 field relative dose factors(RDF)of 6MV open field respectively.The ES were calculated by the GM mathematical formula s =(?),and the accuracy was evaluated by the universal function formula of the RDF.Results1.The accelerator data collection of beam relative dose factor was measured automatically,gainning time about 40%,and the comparison of measuring result between manual set and automatic set had no statistical significance(P>0.05).2.The accuracy of the two accelerators’ RDF after ES by GM formula was<1%,which is better than by the traditional empirical formula(2%～5%).Conclusion1.Automatic measurement of beam relative dose factor could ensure quality and save time,which is worth to be popularized in clinical practice.2.The GM formula is universal,and it’s accuracy of ES is superior to the traditional empirical formula,but data fitting is needed for specific application conditions to determine the best variable value.