beam test for proton computed tomography pct

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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. - PowerPoint PPT Presentation


  • Beam Test for Proton Computed Tomography PCTHartmut F.-W. SadrozinskiSanta Cruz Inst. for Particle Physics SCIPP Florence & Catania(aka Mapping out The Banana) The pCT Project Most likely Path MLP Beam Test Set-up Comparison with MLP Localization Accuracy

  • AuthorsLoma Linda UMCReinhartd Schulte, MDVladimir Bashkirov, PhDGeorge Coutrakon, PhDPeter Koss, MSSanta Cruz Institute for Particle PhysicsHartmut Sadrozinski, PhDAbe Seiden, PhDDavid C Williams, PhDJason Feldt (grad. Student) Jason Heimann (undergrad student)Dominic Lucia (undergrad student)Nate Blumenkrantz (undergrad student)Eric Scott (undergrad student)Florence U. Mara Bruzzi, PhDDavid Menichelli, PhDMonica Scaringella (grad student)INFN Catania Pablo Cirrone, PhDGiacomo Cuttone, PhDNunzio Randazzo, PhDDomenico Lo Presti, EngineerValeria Sipali (grad student)

  • 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 peakMaximum 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 variabilityGoal of pCT CollaborationDevelop proton CT for applications in proton therapy

  • Proton CT System (Final & prototype)

  • Comparison pCT - X-ray CT

  • Simulations: The most likely path (banana)Measurement of entrance and exit anglesconstrain the most likely pathThe most likely path of an energetic charged particle through a uniform mediumD C Williams Phys. Med. Biol. 49 (2004) 28992911200 MeV Protons, 20 cm water, most likely, 1 s and 2 s pathGoal of the Beam Test:Verify the MLP Predictions

  • Beam Test setupIn and out telescopes measure entrance and exit location and angleRoving module in between absorbers measures the 2-D displacement wrt beam = bananaMove roving module through the segmented absorber

    GLAST BT 97 Silicon Telescopesingle-sided SSD, pitch = 236 mm. 2nd rotated by 90oGLAST 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

  • First Data: Beam ProfileMeasured Beam profileAngle-position correlation:qx = -0.005+0.0002*x/mmqy = -0.003+0.0002*y/mmFuzzySource at L= 1/0.0002= 5mBeam Divergence sB = 0.005

    Translate and rotate coordinates such that entrance is at (0,0) with zero angleMeasure outside parameters: Displacement y exit angle qMeasure inside parameter:Displacement yl in roving module vs. absorber depthProton AngleProton Position

  • MCS at WorkCorrelation between exit displacement and angle

    Without AbsorberMap out Beam Dispersion Limited by Beam Spread

    With AbsorberAngular Spread given by multiple scattering ~ 3 degreesStrong correlation between angle and displacement due to multiple scatteringDisplacementExit Angle

  • Exit Displacement & Angle CorrelationsDisplacement in Roving Module is correlated with exit displacement YDisplacement in Roving Module is anti-correlated with exit angle blue: Displacement in AbsorberDisplacement in AbsorberExit DisplacementExit Angle

  • First Results: < 500 mm Localization within AbsorberDisplacement 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 mmResolution ultimately limited by Beam SpreadRMS = 490umMLP width = 380 um

  • 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 correlationResolution improves wrt no angle selection

    pCT design validated: measure pCT design validated: measure both exit displacement AND anglewith high precision

  • pCT Beam Test ConclusionsSi tracker affords high resolution position and angle measurementFirst results show localization within phantom to better than 400 umSimple 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 J03-25Improvements for Tracker: Reduce absorber-less gap around roving moduleIncreased 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


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