Determination of Correction Coefficient of the Sterlling's Formula

[摘要] BackgroundandObjective:Forhighenergyx-raybeamsusedinradiationtherapythehead-scatterfactor(Sc)accountforthevariationinscatteredradiationwithcollimatorsettingoftheincidentbeamthatreachesthepointofmeasurementonthecentralaxis.Thescatteredradiationfromthejawsthatdeterminedimensionsoftreatmetfield,isduetohighthicknessofjawsthatarenotlocatedatthesamelevelofthepatient#039;sbody.Thereforescatteredofthemonthetreatmentareaisnotthesame.ThismakesthereplaceoftreatmentfieldBeacuaseofarenotsymmetric.theSterlling#039;sformulafortheequivalentfieldsmustbecorrected.ThecorrectionofeachsystemtakesplacebyapplyingthecoefficientinSterlling#039;sformulathatiscalledtheVadash̒sfactorwhichisimportantinthetreatmentplaningofpatients.SubjectsandMethod:BymeasuringtheamountofScforsquarefields,thevariationofScintermsofsquarefieldsizewasplotted,therelationshipbetweenScandfieldsizewasdeterminedbyExelsoftware.Bythisrelation,theequivalentsquarefieldsforrectangularfieldsattainedandaverageVadash#039;sfactor)wascalculatedforthem.Aselectionofdifferentvaluesaroundthisaverage,foreveryenergy(6MVand18MV)thevalueofAweredetermined,finallyAthattotalvariancearoundtheaveragewasminimumisdesirableforVadash,sfactor.Results:Vadash#039;sfactorforenergy6MVand18MVLinacVarian2100CDareobtained2.14and2.29respectively.Conclusion:Accordingtothecollimatorexchangeeffect,theSterlling#039;sformulaneedsacorrectionbyapplyingthephysicalanalysisofScforvariousenergy,thiscorrectionisextractable.

[学科分类] 基础医学