title: Proton computed tomography using a 1D silicon diode array.
abstract: OBJECTIVE
  Proton radiography (PR) and proton computed tomography (PCT) can be used to measure proton stopping power directly. However, practical and cost effective proton imaging detectors are not widely available. In this study, the authors investigated the feasibility of proton imaging using a silicon diode array.
  
  
  METHODS
  A one-dimensional silicon diode detector array (1DSDA) was aligned with the central axis (CAX) of the proton beam. Polymethyl methacrylate (PMMA) slabs were used to find the correspondence between the water equivalent thickness (WET) and 1DSDA channel number. Two-dimensional proton radiographs were obtained by translation and rotation of a phantom relative to CAX while the proton nozzle and 1DSDA were kept stationary. A PCT image of one slice of the phantom was reconstructed using filtered backprojection.
  
  
  RESULTS
  PR and PCT images of the PMMA cube were successfully acquired using the 1DSDA. The WET of the phantom was measured using PR data. The resolution and maximum error in WET measurement are 2.0 and 1.5 mm, respectively. Structures down to 2.0 mm in size could be resolved completely. Reconstruction of a PCT image showed very good agreement with simulation. Limitations in spatial resolution are attributed to limited spatial sampling, beam collimation, and proton scatter.
  
  
  CONCLUSIONS
  The results demonstrate the feasibility of using silicon diode arrays for proton imaging. Such a device can potentially offer fast image acquisition and high spatial and energy resolution for PR and PCT.
authors: Texas Center for Proton Therapy, Irving, Texas 75063.
authors: Peng
authors: P
authors: Wang
authors: The College of Liberal and Professional Studies of the School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors: Jochen
authors: J
authors: Cammin
authors: IBA Dosimetry GmbH, Schwarzenbruck 90592, Germany and Friedrich-Alexander University Erlangen-Nürnberg, Erlangen 91058, Germany.
authors: Francesca
authors: F
authors: Bisello
authors: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors: Timothy D
authors: TD
authors: Solberg
authors: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors: James E
authors: JE
authors: McDonough
authors: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors: Timothy C
authors: TC
authors: Zhu
authors: IBA Dosimetry GmbH, Schwarzenbruck 90592, Germany.
authors: David
authors: D
authors: Menichelli
authors: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors: Boon-Keng Kevin
authors: BK
authors: Teo
mesh_terms: D002138:Calibration; D055615:Electrical Equipment and Supplies; D019047:Phantoms, Imaging; D011522:Protons; D012825:Silicon; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
chemical_list: D011522:Protons; D012825:Silicon