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. September 5, 2007T. Satogata - PHY 6842 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

3. September 5, 2007T. Satogata - PHY 6843 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

4. September 5, 2007T. Satogata - PHY 6844 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

5. September 5, 2007T. Satogata - PHY 6845 X-Rays vs Protons Most proton dose is deposited in the sharp "Bragg Peak", with no dose beyond X-rays deposit most of their dose near the surface (skin) of the patient 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 100-250 MeV protons penetrate 7-37 cm

6. September 5, 2007T. Satogata - PHY 6846 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

7. September 5, 2007T. Satogata - PHY 6847 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

8. September 5, 2007T. Satogata - PHY 6848 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

9. September 5, 2007T. Satogata - PHY 6849 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) - 1 st patient Nov 2001 - coming up to speed

10. September 5, 2007T. Satogata - PHY 68410 Cyclotron vs Synchrotron: Cyclotron  Fixed energy output at constant current  Energy degrader reduces beam energy  Collimators scrape beam to size  Large intrinsic beam size in all three dimensions (ACCEL superconducting cyclotron for RPTC, Munich)

11. September 5, 2007T. Satogata - PHY 68411 Cyclotron vs Synchrotron: Synchrotron  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 (Rapid Cycling Medical Synchrotron, RCMS)

12. September 5, 2007T. Satogata - PHY 68412 Cyclotron vs Synchrotron: Table

13. September 5, 2007T. Satogata - PHY 68413 The Rapid Cycling Medical Synchrotron Synchrotron Treatment Room Tumor Scanning Bragg Peak

14. September 5, 2007T. Satogata - PHY 68414 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

15. September 5, 2007T. Satogata - PHY 68415 PET Imaging  PET: Positron Emission Tomography  Tag metabolically active compounds with positron emitters  e.g. 18 F 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 Metastasized prostate cancer

16. September 5, 2007T. Satogata - PHY 68416 ===============

17. September 5, 2007T. Satogata - PHY 68417