RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP INITIAL STUDIES on PROTON COMPUTED TOMOGRAPHY USING SILICON STRIP DETECTORS L. Johnson, B. Keeney, G. Ross, H. F.-W. Sadrozinski, A. Seiden, D.C. Williams, L. Zhang Santa Cruz Institute for Particle Physics, UC Santa Cruz, CA V. Bashkirov, R. W. M. Schulte, K. Shahnazi Loma Linda University Medical Center, Loma Linda, CA Proton Tomography / Proton Transmission Radiography Proton Transmission Radiography Data Proton Transmission Radiography MC Study

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Computed Tomography (CT) X-ray tube Detector array Based on X-ray absorption Faithful reconstruction of patient’s anatomy Stacked 2D maps of linear X-ray attenuation Coupled linear equations Invert Matrices and find (hopefully) non- malignant structures

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Radiography: X-rays vs. Protons Attenuation of Photons, z N(x) = N o e -  x Energy Loss of Protons,  NIST Data

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Proton Radiography: Density Map NIST Data

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Development of Proton Beam Computed Tomography Exploratory Study in Proton Radiography –two detector planes –Crude phantom in front Experimental Study –two detector planes –water phantom on turntable Theoretical Study –GEANT4 MC simulation –influence of MCS and range straggling –importance of angular measurements –Optimization of energy

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Proton Energy Measurement with LET Simple 2D Silicon Strip Detector Telescope built for Nanodosimetry (based on GLAST Design) 2 single-sided SSD 194um Pitch 400um thick 1.3us shaping time Binary readout Time-over-Threshold TOT Large dynamic range Measure particle energy via LET

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP GLAST Front-End Electronics ASIC Binary Readout: Low-power (~200uW/channel) Peaking time ˜ 1.3 ms Low noise (Noise occupancy <10 -5 ) Threshold set in every ASIC Separate Masks for Trigger and Readout in every Channel Self - Trigger = OR of one Si plane (1536 channels) Pulse Charge: Time – over-Threshold on the OR of every Si plane Distinguish single tracks from two tracks in one strip Electron Events Photon Events

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP TOT  charge  LET! Charge ~ Time-Over-Threshold (TOT): Digitization of Position and Energy with large Dynamic Range Pulse Threshold Time-over-Threshold TOT

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Proton Energy Measurement with LET TOT Spectra as for several proton energies Mean TOT vs. Proton Energy Good agreement between measurement and MC simulations

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Proton Energy Measurement with LET TOT Spectra vs. energy TOT Resolution “~flat”. Energy Measurement possible where slope dTOT/dE is large

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Proton Localisation: M.S. vs. Energy Resolution

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Exploratory Proton Radiography Set-up Beam from Synchrotron 30 cm SSD modules Object Wax block SSD detector planes y x x y Air 27.3 cm Air 250MeV 130MeV MeV Use Loma Linda University Medical Ctr 250 MeV Proton Beam Degraded down to 130 MeV by Wax Block Object is Aluminum pipe 5cm long, 3cm OD, 0.67cm ID Very large effects expected, but beam quite non-uniform

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Image ! Subdivide SSD area into pixels 1.Strip x strip 194um x 194um 2. 4 x 4 strips (0.8mm x 0.8mm) Image given by average TOT or Energy in pixel

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Issues Features: Washed out image in 2 nd plane Fuzzy edges Hole filled partially Energy diluted at edges and in hole Migration of events All explained by Multiple Coulomb Scattering

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Loss of Resolution in Back: Data

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Migration and Energy Dilution in Slice Data shows increased frequency of hits in boundary of the pipe: the hole and the outside perimeter. These events are associated with a dilution of the energy profile Hit frequency vs. Location Mean Energy vs. Location Approx. Beam Profile Excess Events Energy lowered Blurred Edges

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Multiple Scattering: Emigration Protons scatter OUT OF Target (not INTO). Those have larger energy loss larger angles fill hole dilute energy

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Energy Resolution = Position Resolution Simulation reproduces spread of energy and loss of resolution Data (LET converted to Energy) GEANT4 MC (LET in SSD) RMS

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Energy Resolution Data: LET converted to Energy MC: LET in SSD plane ObjectBackground

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Migration: MC Dilution by events entering the Object but leaving it before the end

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP MC: Loss of Resolution in Back First Plane, 2cm behind Object Second Plane, 30cm behind Object

RESMDD'02 pCT: Hartmut F.-W. Sadrozinski, SCIPP Conclusions Imaging with protons is working! GEANT4 program describes the data well (energy and position resolution, migration) Issues: Energy needs Optimization depending on Target Improve resolution with cut on exit angle? Investigate independent Energy measurement Dose – Contrast - Resolution Relationship to be explored Next steps: pCT