Beam Test for Proton Computed Tomography PCT

1. Loma Linda University Medical Center UCSC Santa Cruz Institute of Particle Physics Beam Test for Proton Computed Tomography PCT (aka Mapping out “The Banana”) • The pCT Project • Most likely Path MLP • Beam Test Set-up • Comparison with MLP • Localization Accuracy Hartmut F.-W. Sadrozinski Santa Cruz Inst. for Particle Physics SCIPP Florence & Catania

2. Loma Linda UMC Reinhartd Schulte, MD Vladimir Bashkirov, PhD George Coutrakon, PhD Peter Koss, MS Santa Cruz Institute for Particle Physics Hartmut Sadrozinski, PhD Abe Seiden, PhD David C Williams, PhD Jason Feldt (grad. Student) Jason Heimann (undergrad student) Dominic Lucia (undergrad student) Nate Blumenkrantz (undergrad student) Eric Scott (undergrad student) Florence U. Mara Bruzzi, PhD David Menichelli, PhD Monica Scaringella (grad student) INFN Catania Pablo Cirrone, PhD Giacomo Cuttone, PhD Nunzio Randazzo, PhD Domenico Lo Presti, Engineer Valeria Sipali (grad student) Authors

3. Why Proton CT? • Major advantages of proton beam therapy: • Finite range in tissue (protection of critical normal tissues) since cross section fairly flat and low away from peak • Maximum dose and effectiveness at end of range (Bragg peak effect) • Major uncertainties of proton beam therapy: • range uncertainty due to use of X-ray CT for treatment planning (up to several mm) • patient setup variability • Goal of pCT Collaboration • Develop proton CT for applications in proton therapy

4. Proton CT System (Final & prototype)

5. Comparison pCT - X-ray CT

6. Simulations: The most likely path (“banana”) The most likely path of an energetic charged particle through a uniform medium D C Williams Phys. Med. Biol. 49 (2004) 2899–2911 Measurement of entrance and exit angles constrain the most likely path 200 MeV Protons, 20 cm water, most likely, 1 s and 2 s path’ • Goal of the Beam Test: • Verify the MLP Predictions

7. Beam Test setup • In and out telescopes measure entrance and exit location and angle • “Roving” module in between absorbers measures the 2-D displacement wrt beam = “banana” • Move roving module through the segmented absorber GLAST BT 97 Silicon Telescope single-sided SSD, pitch = 236 mm. 2nd rotated by 90o GLAST GTFE32 readout chips, 32 channels each, serial data flow. Replace large scale GLAST readout (VME, Vxworks software) by commercial FPGA and NI 6534 PCI card

8. First Data: Beam Profile Measured Beam profile Angle-position correlation: qx = -0.005+0.0002*x/mm qy = -0.003+0.0002*y/mm “Fuzzy”Source at L= 1/0.0002= 5m Beam Divergence sB = 0.005 Proton Angle Proton Position Translate and rotate coordinates such that entrance is at (0,0) with zero angle Measure outside parameters: Displacement y exit angle q Measure inside parameter: Displacement yl in roving module vs. absorber depth

9. MCS at Work Correlation between exit displacement and angle • Without Absorber Map out Beam Dispersion Limited by Beam Spread • With Absorber Angular Spread given by multiple scattering ~ 3 degrees Strong correlation between angle and displacement due to multiple scattering Exit Angle Displacement

10. Exit Displacement & Angle Correlations Displacement in Absorber Displacement in Absorber Exit Displacement Exit Angle Displacement in Roving Module is correlated with exit displacement Y Displacement in Roving Module is anti-correlated with exit angle blue:

11. First Results: < 500 mm Localization within Absorber RMS = 490um MLP width = 380 um Displacement from incoming direction in the “Roving planes” as a function of exit displacement bins of 500 mm (all angles). Analytical calculation of the most likely path MLP (open symbols: the size of the symbol is close to the MLP spread). • Good agreement data - MLP, but systematically growing difference with larger displacements: need to incorporate absorber-free distance (M.C.) • Resolution inside Absorber better than 500 mm vs. MLP width of 380 mm • Resolution ultimately limited by Beam Spread

12. Angle Cut improves Localization Displacement in the “roving” modules for an exit displacement of 2 mm, Select 3 narrow exit angle bins : Mean Mean + 1 s Mean –1 s Observe expected negative correlation Resolution improves wrt no angle selection pCT design validated: measure pCT design validated: measure both exit displacement AND angle with high precision

13. pCT Beam Test Conclusions • Si tracker affords high resolution position and angle measurement • First results show localization within phantom to better than 400 um • Simple analysis confirms prediction of MLP on the < 200 um level (improvement expected when air gaps are included) • Data await detailed comparison with simulations using GEANT4 and analytical “banana” (INFN, SLAC and Japanese Geant4 groups) ------>Poster J03-25 • Improvements for Tracker: • Reduce absorber-less gap around “roving module” • Increased precision of input parameters (entrance angle) needed to correct for beam divergence • Next step: image NON-uniform density phantom using the energy loss measurement in the calorimeter