Beam Test for Proton Computed Tomography PCT

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Beam Test for Proton Computed Tomography PCT
(aka Mapping out The Banana)

• Hartmut F.-W. Sadrozinski
• Santa Cruz Inst. for Particle Physics SCIPP

• The pCT Project
• Most likely Path MLP
• Beam Test Set-up
• Comparison with MLP
• Localization Accuracy

Florence Catania
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Authors

• 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)

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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
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Proton CT System (Final prototype)
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Comparison pCT - X-ray CT
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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) 28992911
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
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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
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First Data Beam Profile

• Measured Beam profile
• Angle-position correlation
• qx -0.0050.0002x/mm
• qy -0.0030.0002y/mm
• FuzzySource 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
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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
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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
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First Results lt 500 mm Localization within
Absorber

• 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

RMS 490um MLP width 380 um
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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
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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
  lt 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)
• ------gtPoster 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