In-beam PET imaging for on-line adaptive proton therapy: An initial phantom study

Yiping Shao, Xishan Sun, Kai Lou, Xiaorong R. Zhu, Dragon Mirkovic, Falk Poenisch, David Grosshans

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

We developed and investigated a positron emission tomography (PET) system for use with on-line (both in-beam and intra-fraction) image-guided adaptive proton therapy applications. The PET has dual rotating depth-of-interaction measurable detector panels by using solid-state photomultiplier (SSPM) arrays and LYSO scintillators. It has a 44mm diameter trans-axial and 30mm axial field-of-view (FOV). A 38mm diameter polymethyl methacrylate phantom was placed inside the FOV. Both PET and phantom axes were aligned with a collimated 179.2 MeV beam. Each beam delivered ∼50 spills (0.5s spill and 1.5s inter-spill time, 3.8 Gy at Bragg peak). Data from each beam were acquired with detectors at a given angle. Nine datasets for nine beams with detectors at nine different angles over 180 were acquired for full-tomographic imaging. Each dataset included data both during and 5min after irradiations. The positron activity-range was measured from the PET image reconstructed from all nine datasets and compared to the results from simulated images. A 22Na disc-source was also imaged after each beam to monitor the PET system's performance. PET performed well except for slight shifts of energy photo-peak positions (<1%) after each beam, due mainly to the neutron exposure of SSPM that increased the dark-count noise. This minor effect was corrected offline with a shifting 350-650keV energy window for each dataset. The results show a fast converging of activity-ranges measured by the prototype PET with high sensitivity and uniform resolution. Sub-mm activity-ranges were achieved with minimal 6s acquisition time and three spill irradiations. These results indicate the feasibility of PET for intra-fraction beam-range verification. Further studies are needed to develop and apply a novel clinical PET system for on-line image-guided adaptive proton therapy.

Original languageEnglish (US)
Pages (from-to)3373-3388
Number of pages16
JournalPhysics in Medicine and Biology
Volume59
Issue number13
DOIs
Publication statusPublished - Jul 7 2014

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Keywords

  • in-beam PET imaging
  • positron activity range
  • positron emission tomography
  • proton beam range
  • proton radiotherapy

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology
  • Medicine(all)

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