skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: SU-F-J-200: An Improved Method for Event Selection in Compton Camera Imaging for Particle Therapy

Abstract

Purpose: The uncertainty in the beam range in particle therapy limits the conformality of the dose distributions. Compton scatter cameras (CC), which measure the prompt gamma rays produced by nuclear interactions in the patient tissue, can reduce this uncertainty by producing 3D images confirming the particle beam range and dose delivery. However, the high intensity and short time windows of the particle beams limit the number of gammas detected. We attempt to address this problem by developing a method for filtering gamma ray scattering events from the background by applying the known gamma ray spectrum. Methods: We used a 4 stage Compton camera to record in list mode the energy deposition and scatter positions of gammas from a Co-60 source. Each CC stage contained a 4×4 array of CdZnTe crystal. To produce images, we used a back-projection algorithm and four filtering Methods: basic, energy windowing, delta energy (ΔE), or delta scattering angle (Δθ). Basic filtering requires events to be physically consistent. Energy windowing requires event energy to fall within a defined range. ΔE filtering selects events with the minimum difference between the measured and a known gamma energy (1.17 and 1.33 MeV for Co-60). Δθ filtering selects events with themore » minimum difference between the measured scattering angle and the angle corresponding to a known gamma energy. Results: Energy window filtering reduced the FWHM from 197.8 mm for basic filtering to 78.3 mm. ΔE and Δθ filtering achieved the best results, FWHMs of 64.3 and 55.6 mm, respectively. In general, Δθ filtering selected events with scattering angles < 40°, while ΔE filtering selected events with angles > 60°. Conclusion: Filtering CC events improved the quality and resolution of the corresponding images. ΔE and Δθ filtering produced similar results but each favored different events.« less

Authors:
;  [1]; ;  [2];  [3]
  1. UT MD Anderson Cancer Center, Houston, TX (United States)
  2. University of Maryland School of Medicine, Baltimore, MD (United States)
  3. University of Cape Town, Rondebosch, Cape Town (South Africa)
Publication Date:
OSTI Identifier:
22634796
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; ALGORITHMS; ANIMAL TISSUES; BIOMEDICAL RADIOGRAPHY; CAMERAS; COBALT 60; ENERGY ABSORPTION; FILTERS; GAMMA RADIATION; GAMMA SPECTRA; IMAGES; PARTICLE BEAMS; PATIENTS; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; RADIOTHERAPY; SCATTERING; CDZNTE SEMICONDUCTOR DETECTORS

Citation Formats

Mackin, D, Beddar, S, Polf, J, Draeger, E, and Peterson, S. SU-F-J-200: An Improved Method for Event Selection in Compton Camera Imaging for Particle Therapy. United States: N. p., 2016. Web. doi:10.1118/1.4956108.
Mackin, D, Beddar, S, Polf, J, Draeger, E, & Peterson, S. SU-F-J-200: An Improved Method for Event Selection in Compton Camera Imaging for Particle Therapy. United States. doi:10.1118/1.4956108.
Mackin, D, Beddar, S, Polf, J, Draeger, E, and Peterson, S. Wed . "SU-F-J-200: An Improved Method for Event Selection in Compton Camera Imaging for Particle Therapy". United States. doi:10.1118/1.4956108.
@article{osti_22634796,
title = {SU-F-J-200: An Improved Method for Event Selection in Compton Camera Imaging for Particle Therapy},
author = {Mackin, D and Beddar, S and Polf, J and Draeger, E and Peterson, S},
abstractNote = {Purpose: The uncertainty in the beam range in particle therapy limits the conformality of the dose distributions. Compton scatter cameras (CC), which measure the prompt gamma rays produced by nuclear interactions in the patient tissue, can reduce this uncertainty by producing 3D images confirming the particle beam range and dose delivery. However, the high intensity and short time windows of the particle beams limit the number of gammas detected. We attempt to address this problem by developing a method for filtering gamma ray scattering events from the background by applying the known gamma ray spectrum. Methods: We used a 4 stage Compton camera to record in list mode the energy deposition and scatter positions of gammas from a Co-60 source. Each CC stage contained a 4×4 array of CdZnTe crystal. To produce images, we used a back-projection algorithm and four filtering Methods: basic, energy windowing, delta energy (ΔE), or delta scattering angle (Δθ). Basic filtering requires events to be physically consistent. Energy windowing requires event energy to fall within a defined range. ΔE filtering selects events with the minimum difference between the measured and a known gamma energy (1.17 and 1.33 MeV for Co-60). Δθ filtering selects events with the minimum difference between the measured scattering angle and the angle corresponding to a known gamma energy. Results: Energy window filtering reduced the FWHM from 197.8 mm for basic filtering to 78.3 mm. ΔE and Δθ filtering achieved the best results, FWHMs of 64.3 and 55.6 mm, respectively. In general, Δθ filtering selected events with scattering angles < 40°, while ΔE filtering selected events with angles > 60°. Conclusion: Filtering CC events improved the quality and resolution of the corresponding images. ΔE and Δθ filtering produced similar results but each favored different events.},
doi = {10.1118/1.4956108},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}