BriefCommunicationFreefulltextavailablefromwww.cancerjournal.netMultileafcollimatortransmissionfromthefirstHi-ArtIIhelicaltomotherapymachineinIndiaABSTRACTRajeshAKinhikarThepurposeofthisstudywastomeasurethemultileafcollimator(MLC)transmissionfromthefirstHi-ArtIItomotherapymachineDepartmentofMedicalinstalledattheAdvancedCenterforTreatment,Research,andEducationinCancer(ACTREC).TheMLCtransmissionwasmeasuredPhysics,TataMemorialwithanA1SLionchamberandtheradiographicextendeddoserange(EDR2)filminvirtualwaterslabsat1.5-cmdepthwithasource-Hospital,Parel,Mumbai,Indiato-surfacedistanceof85cm.TheMLCtransmissionwasmeasuredfor30swithallleavesopenandfor360swithallleavesclosed.Themovablejawsweresettothecalibrationfieldsizeof5×40cmatisocenter.TheMLCtransmissionwasfoundtobe0.3%withtheForcorrespondence:ionchamberand0.32%withthefilm.Thus,theMLCtransmissionvaluewasfoundwellwithinthemanufacturertoleranceof0.5%.MLCDr.RajeshA.Kinhikar,cansafelybeusedforthebeammodulationduringintensity-modulatedradiotherapy(IMRT)todeliveraccuratedosestothepatients.DepartmentofMedicalPhysics,TataMemorialHospital,Parel,Mumbai-400012,India.KEYWORDS:Film,ionchamber,multileafcollimatortransmission,tomotherapyE-mail:rkinhikar@rediffmail.comHelicaltomotherapyrepresentsanewapproachtomovement.Amoveablesetoftungstenjawsintensity-modulatedradiationtherapy(IMRT).[1-6]collimatesthebeamfromclosedto5-cmwideinIMRTrequiresstringentmodulationfromthetheinferior-superiordirectionofthepatient.Themultileafcollimators(MLC).Patientleakagedosedetailofthedesignofthismachineisdiscussedfromhelicaltomotherapyresultsfromtwosources:elsewhere.[7]Figure1showstheHiArttomotherapyLeakagethroughandbetweenclosedMLCleavesmachineinstalledatourcenter.andfromthejaws.TheleakagefromtheMLCshouldbeexactlymeasuredandmodeledintheMultileafcollimatorstreatmentplanningsystemtoaccuratelydeliverSixty-fourinterlockedbinaryleavesareusedtothedesireddosestothepatients.modulatetheslitbeam.Thebinaryreferenceindicatesthatinoperationth