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A (Quick) Survey of (Some) Medical Accelerators

A (Quick) Survey of (Some) Medical Accelerators. Dr. Todd Satogata Brookhaven National Laboratory SUNY Stony Brook PHY 684 – September 5, 2007. The NASA Space Radiation Laboratory at BNL X-Rays for imaging and cancer therapy Dose advantage for hadron cancer therapy

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A (Quick) Survey of (Some) Medical Accelerators

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  1. A (Quick) Survey of (Some)Medical Accelerators Dr. Todd Satogata Brookhaven National Laboratory SUNY Stony Brook PHY 684 – September 5, 2007 • The NASA Space Radiation Laboratory at BNL • X-Rays for imaging and cancer therapy • Dose advantage for hadron cancer therapy • Cyclotrons vs synchrotrons in hadron therapy • PET imaging

  2. The NASA Space Radiation Laboratory • Long-range space travelers (e.g. to Mars) are exposed to high radiation doses • Most concern is about heavy ions from galactic cosmic rays, solar wind • Less expensive to simulate/study on earth • Biological effects of high radiation doses of this type are controversial • DNA damage, repair • Mutagenesis • Carcinogenesis • Cellular necrosis • p-Fe, 200-1000 MeV/u T. Satogata - PHY 684

  3. X-Ray Imaging • By far the most common use of medical radiation • X-ray tubes: 1-2% efficiency • Typical energies from 10-100 keV • X-rays made by brehmsstrahlung • Follows dose attenuation curve • Image shadow of X-rays stopped T. Satogata - PHY 684

  4. X-Ray Cancer Therapy • Conventional X-ray cancer treatment accelerators are “small” • Nearly all of it visible here • 5-25 MeV X-rays • x100 diagnostic X-ray • Generated by a small linac • A few MV/m • (Linac lecture 9/19) • 500+ US locations • Treatment planning and beam shaping are challenging on patient-by-patient basis T. Satogata - PHY 684

  5. X-Rays vs Protons X-rays deposit most of their dose near the surface (skin) of the patient Most proton dose is deposited in the sharp "Bragg Peak", with no dose beyond 100-250 MeV protons penetrate 7-37 cm Scanning the proton energy makes a Spread Out Bragg Peak (SOBP) that spans the depth of the tumor Carbon and other light hadrons also work – but beware of nuclear dissociation T. Satogata - PHY 684

  6. X-Rays vs Protons II • Photons/X-rays do not stop at a well-defined boundary • Dose conformity is much better with protons than X-rays T. Satogata - PHY 684

  7. X-Rays vs Protons III • With multiple angles/fields, protons excel even better • The “spine” is better protected • Dose to surrounding (healthy) tissues is intrinsically lower T. Satogata - PHY 684

  8. Cancer Therapy Accelerators • X-rays, protons, and light ion beams are all used in modern cancer radiotherapy • Need to minimize side-effects • Minimize dose to healthy tissue • But dose cancer enough (~5 krem) • X-rays are: • less expensive (>500 US locations) • better for peripheral/surface tumors • Protons/Ions are: • more expensive (~5 US locations) • better for deeper, critical tumors • CAT, MRI, PET imaging all came from accelerator technology T. Satogata - PHY 684

  9. Two Existing US Proton Therapy Facilities Loma Linda (California) - synchrotron source - built/commissioned at Fermilab - world leading patient throughput Mass General Hospital (Boston) - cyclotron source (IBA) - 1st patient Nov 2001 - coming up to speed T. Satogata - PHY 684

  10. Cyclotron vs Synchrotron: Cyclotron (ACCEL superconducting cyclotron for RPTC, Munich) • Fixed energy output at constant current • Energy degrader reduces beam energy • Collimators scrape beam to size • Large intrinsic beam size in all three dimensions T. Satogata - PHY 684

  11. Cyclotron vs Synchrotron: Synchrotron (Rapid Cycling Medical Synchrotron, RCMS) • Accelerate variable beam intensity to variable energy • 50-250 MeV • No energy degrader • Smaller beam sizes • Accelerate either • Small beam intensity rapidly (30-60 Hz), extract in one turn • Large beam intensity slowly, extract in many turns T. Satogata - PHY 684

  12. Cyclotron vs Synchrotron: Table T. Satogata - PHY 684

  13. The Rapid Cycling Medical Synchrotron Bragg Peak Treatment Room Treatment Room Tumor Scanning Synchrotron T. Satogata - PHY 684

  14. Dielectric Wall Accelerators • A recent new development in hadron therapy accelerators • Alternating fast-switching transmission lines – gradients up to 100 MV/m (!!) • Requires advanced materials • Very high-gradient insulators • High-frequency/voltage switches • In development by LLNL and Tomotherapy Group • 10+ years from delivery T. Satogata - PHY 684

  15. Metastasized prostate cancer PET Imaging • PET: Positron Emission Tomography • Tag metabolically active compounds with positron emitters • e.g. 18F deoxyglucose • Emitted positrons annihilate with nearby electrons producing back to back 511 keV gamma rays • Coincident gamma rays detected with photomultiplier tubes or avalanche photodiodes T. Satogata - PHY 684

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  17. T. Satogata - PHY 684

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