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Microwave Electron Linear Accelerators for Cancer Therapy and Non-Destructive Testing: History, Application & Theory Mark Trail, Manager Microwave & Physics R&D April 10, 2008 University of Idaho Research Colloquium What is a Medical Linear Accelerator? A Medical Device designed to deliver ionizing radiation to a tumor. University of Idaho Research Colloquium What is an Electron Linear Accelerator? A high-Q, resonantly coupled, microwave circuit that accelerators electrons to many MeV University of Idaho Research Colloquium Electron Gun (-25kV) Standing Wave Microwave Circuit (3Ghz) A Little History… It all started with Wilhelm Roentgen 1895: Roentgen discovered X-rays Shortly thereafter folks discovered that radiation kills cells Definition: RADIOTHERAPY – The therapeutic application of ionizing radiation University of Idaho Research Colloquium More History… Sigurd Varian 1948: Varian Associates Founded 1950: Sigurd Varian prepared proposal for 10MeV Medical X-Ray Linac 1955: Dr. Henry Kaplan builds 1st 6MV Medical Linac 1960: Varian Clinac-6 Treats Patients Russell Varian University of Idaho Research Colloquium 1955: 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 Colloquium 1962: Henry Kaplan with Varian Clinac 6 University of Idaho Research Colloquium Cancer 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 169,500 lung 192,200 breast 135,400 colorectal Men – if you live long enough you will get prostate cancer Treatment Options Surgery, Chemotherapy, Radiation Therapy, or combination University of Idaho Research Colloquium Radiation Therapy Facts… Non-Invasive Eradicates tumors, stops cancer cell replication or relieves pain, Treats 50% of all cancer cases in USA Typically, ~15min treatments, delivered 5 day/wk over 6-8 wks Treatment is Painless - like having an X-Ray taken University of Idaho Research Colloquium Radiation Therapy Facts… (cont) Side effects usually temporary; Depending on treatment site, can include nausea, loss of energy & appetite. Millions of patients have been treated ~5000 Varian medical accelerators presently treating patients world-wide We ship 2-3 machines a day from Palo Alto and build ~1km of accelerators/year University of Idaho Research Colloquium Modern Medical Linacs Generates High-Energy X-rays and/or electrons for Therapy Rotates around the patient delivering radiation from multiple beam angles Capable of Volumetric ConeBeam CT Imaging Work in special treatment rooms with 7-ft thick walls How Do They Work? University of Idaho Research Colloquium Inside a Varian Medical Linac beam transport electron linac beam shaping University of Idaho Research Colloquium Treatment Planning… Process: 1) Acquire CT and/or PET Images 2) Plan treatment 3) Irradiate from different angles 4) 5) Goal Dose the tumor – spare healthy tissue & minimize Shape Beam to conform to tumor exposure to critical structures. Treatment is Vary penetration by varying beam energy typically “fractionated” 20 – 30 “fractions” in 4 to 6 weeks (outpatient) University of Idaho Research Colloquium Accelerating the electrons the “Guide” or “Accelerator” University of Idaho Research Colloquium Accelerator: Side-Coupled Standing-Wave Design Varian core technology! University of Idaho Research Colloquium Accelerator: Side-Coupled Standing-Wave Design First we bake at 450C. Then pull a high-vacuum (Vacion pump) Operate at ~10-8 torr (remove 99.999999999% of the air) University of Idaho Research Colloquium Accelerator: Side-Coupled Standing-Wave Design Fill with high power RF at 3 GHz Insert electrons Up to 5.5 Megawatts peak, 5 kilowatts average University of Idaho Research Colloquium University of Idaho Research Colloquium Accelerator: Side-Coupled Standing-Wave Design Side cavities couple rf Resonant cavities electrons Axial electric fields RF power input University of Idaho Research Colloquium Beam Transport: The Bend Magnet University of Idaho Research Colloquium Bend Magnet Directs the beam from accelerator towards patient Three 90 degree bends + drift spaces Doubly Achromatic (achromatic & nondispersive) One-to-one imaging, radial and accelerator transverse Energy slits limit the energy acceptance Beam is ~ 1.5 – 2 mm diameter University of Idaho Research Colloquium Bend Magnet Directs the beam from accelerator towards patient Beam is directed onto a “target” to make x-rays Or passes through for electron treatments Up to ~ 1 kw of beam University of Idaho Research Colloquium e- Scattering Foils & X-Ray Flattening Filters Scatter e-beams and flatten X-beams to make uniform at patient University of Idaho Research Colloquium Ion Chamber Monitor dose delivered to patient University of Idaho Research Colloquium Collimate/Shape The Beam Limit the extent of the beam – only treat tumor University of Idaho Research Colloquium Collimator or “Jaw” System Tungsten blocks coarsely collimate the beam University of Idaho Research Colloquium Multi-Leaf Collimator Fine beam collimation Because tumors don’t have corners Irregularly shaped field 120 tungsten “leaves” University of Idaho Research Colloquium University of Idaho Research Colloquium IMRT Intensity Modulated RadioTherapy Dynamic motion of the MLC leaves while the beam is on. “Paints” irregular dose distribution Improved dose distributions, better sparing of normal tissues Treatment planning must optimize many variables Improved efficacy of treatments Good for the patient and… University of Idaho Research Colloquium IMRT Dynamic motion of the MLC leaves while the beam is on. “Paints” irregular dose distribution • improved dose distributions, better sparing of normal tissues • treatment planning must optimize many variables • information management is very important • complex treatments – lots of work for the physicist Very good for VAR stock price! University of Idaho Research Colloquium Security & Inspection Products Same technology as Medical Linacs Very different applications Primary business is Cargo Inspection University of Idaho Research Colloquium Mobile Cargo Inspection Systems Linatron™ University of Idaho Research Colloquium Other Security and Inspection Applications: • Mega-Voltage Computed Tomography (CT) • Sterilization of Medical Disposables • Food Irradiation (sterilize fruit flies or kill pathogens in food) Picture of Steriliz ation Linatrons Each Accelerator Delivers: - 10 MeV electrons - 15kWavg Beam Power University of Idaho Research Colloquium Job Opportunities at Varian: Presently, 30 openings in USA for all levels of engineers Complete list available at www.varian.com Please take a Varian Brochure Thanks for Your Attention University of Idaho Research Colloquium