Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Cancer Facts…Radiation Therapy Facts…Radiation Therapy Facts… (cont)Modern Medical LinacsSlide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34University of Idaho Research ColloquiumMicrowave Electron Linear Accelerators for Cancer Therapy and Non-Destructive Testing: History, Application & TheoryMark Trail, ManagerMicrowave & Physics R&DApril 10, 2008University of Idaho Research ColloquiumWhat is a Medical Linear Accelerator?A Medical Device designed to deliver ionizing radiation to a tumor.University of Idaho Research ColloquiumWhat is an Electron Linear Accelerator?Electron Gun (-25kV)A high-Q, resonantly coupled, microwave circuit that accelerators electrons to many MeVStanding Wave Microwave Circuit (3Ghz)University of Idaho Research Colloquium 1895: Roentgen discovered X-rays  Shortly thereafter folks discovered that radiation kills cellsIt all started with Wilhelm RoentgenDefinition: RADIOTHERAPY – The therapeutic application of ionizing radiationA Little History…University of Idaho Research ColloquiumMore History…Russell VarianSigurd Varian1948:  Varian Associates Founded 1950:  Sigurd Varian prepared proposal for 10MeV Medical X-Ray Linac 1955:  Dr. Henry Kaplan builds 1st 6MV Medical Linac1960:  Varian Clinac-6 Treats PatientsUniversity of Idaho Research Colloquium1955: Dr. Henry Kaplan’s 1st 6MV Medical Linac(Stanford Medical School)1st retinoblastoma patient. Vision intact at last check (1996)photos copyright Radiology Centennial, Inc.University of Idaho Research Colloquium1962: Henry Kaplan with Varian Clinac 6University of Idaho Research ColloquiumCancer Facts… In the USA,Leading Cause of Death40% of us in this room will be diagnosed with cancer14% of us will be treated on a Varian Linac1.25 million new cancer cases annually 198,100 prostate  192,200 breast  169,500 lung  135,400 colorectalMen – if you live long enough you will get prostate cancerTreatment OptionsSurgery, Chemotherapy, Radiation Therapy, or combinationUniversity of Idaho Research ColloquiumRadiation Therapy Facts… Non-InvasiveNon-InvasiveEradicates tumors, stops cancer cell Eradicates tumors, stops cancer cell replication or relieves pain,replication or relieves pain,Treats 50% of all cancer cases in USATreats 50% of all cancer cases in USATypically, ~15min treatments, delivered 5 Typically, ~15min treatments, delivered 5 day/wk over 6-8 wksday/wk over 6-8 wksTreatment is Painless - like having an X-Ray Treatment is Painless - like having an X-Ray takentakenUniversity of Idaho Research ColloquiumRadiation Therapy Facts… (cont)Side effects usually temporary; Depending Side effects usually temporary; Depending on treatment site, can include nausea, loss on treatment site, can include nausea, loss of energy & appetite.of energy & appetite.Millions of patients have been treatedMillions of patients have been treated~5000 Varian medical accelerators ~5000 Varian medical accelerators presently treating patients world-widepresently treating patients world-wideWe ship 2-3 machines a day from Palo Alto We ship 2-3 machines a day from Palo Alto and build ~1km of accelerators/yearand build ~1km of accelerators/yearUniversity of Idaho Research ColloquiumModern Medical LinacsGenerates High-Energy X-rays Generates High-Energy X-rays and/or electrons for Therapyand/or electrons for TherapyRotates around the patient Rotates around the patient delivering radiation from delivering radiation from multiple beam angles multiple beam angles Capable of Volumetric Cone-Capable of Volumetric Cone-Beam CT ImagingBeam CT ImagingWork in special treatment Work in special treatment rooms with 7-ft thick wallsrooms with 7-ft thick wallsHow Do They Work?University of Idaho Research ColloquiumInside a Varian Medical Linacelectron linacbeam transportbeam shapingUniversity of Idaho Research ColloquiumTreatment Planning…Treatment is typically “fractionated”20 – 30 “fractions” in 4 to 6 weeks (outpatient)Dose the tumor – spare healthy tissue & minimize exposure to critical structures.GoalProcess: 1) Acquire CT and/or PET Images2) Plan treatment3) Irradiate from different angles4) Vary penetration by varying beam energy5) Shape Beam to conform to tumorUniversity of Idaho Research ColloquiumAccelerating the electrons - the “Guide” or “Accelerator”University of Idaho Research ColloquiumAccelerator: Side-Coupled Standing-Wave DesignVarian core technology!1.5 mUniversity of Idaho Research ColloquiumFirst we bake at 450C. Then pull a high-vacuum(Vacion pump)Operate at ~10-8 torr (remove 99.999999999% of the air)Accelerator: Side-Coupled Standing-Wave DesignUniversity of Idaho Research ColloquiumUp to 5.5 Megawatts peak, 5 kilowatts averageFill with high power RF at 3 GHzInsert electronsAccelerator: Side-Coupled Standing-Wave DesignUniversity of Idaho Research ColloquiumUniversity of Idaho Research ColloquiumRF power inputSide cavities couple rfResonant cavitiesAxial electric fieldselectronsAccelerator: Side-Coupled Standing-Wave DesignUniversity of Idaho Research ColloquiumBeam Transport: The Bend MagnetUniversity of Idaho Research ColloquiumBend MagnetDirects the beam from accelerator towards patient  Three 90 degree bends + drift spaces  Doubly Achromatic (achromatic & non-dispersive) One-to-one imaging, radial and transverse Energy slits limit the energy acceptance Beam is ~ 1.5 – 2 mm diameteracceleratorUniversity of Idaho Research ColloquiumBend MagnetDirects the beam from accelerator towards patient  Beam is directed onto a “target” to make x-rays Or passes through for electron treatmentsUp to ~ 1 kw of beamUniversity of Idaho Research Colloquiume- Scattering Foils & X-Ray Flattening FiltersScatter e-beams and flatten X-beams to make uniform at patientUniversity of Idaho Research ColloquiumIon ChamberMonitor dose delivered to patientUniversity of Idaho Research ColloquiumCollimate/Shape The BeamLimit the extent of the beam – only treat tumorUniversity of Idaho Research Colloquium Tungsten blocks coarsely collimate the