CCMod: a GATE module for Compton camera imaging simulation

Abstract

Compton cameras are gamma-ray imaging systems which have been proposed for a wide variety of applications such as medical imaging, nuclear decommissioning or homeland security. In the design and optimization of such a system Monte Carlo simulations play an essential role. In this work, we propose a generic module to perform Monte Carlo simulations and analyses of Compton Camera imaging which is included in the open-source GATE/Geant4 platform. Several digitization stages have been implemented within the module to mimic the performance of the most commonly employed detectors (e.g. monolithic blocks, pixelated scintillator crystals, strip detectors...). Time coincidence sorter and sequence coincidence reconstruction are also available in order to aim at providing modules to facilitate the comparison and reproduction of the data taken with different prototypes. All processing steps may be performed during the simulation (on-the-fly mode) or as a post-process of the output files (offline mode). The predictions of the module have been compared with experimental data in terms of energy spectra, angular resolution, efficiency and back-projection image reconstruction. Consistent results within a 3-sigma interval were obtained for the energy spectra except for low energies where small differences arise. The angular resolution measure for incident photons of 1275 keV was also in good agreement between both data sets with a value close to 13 • . Moreover, with the aim of demonstrating the versatility of such a tool the performance of two different Compton camera designs was evaluated and compared.

Influence of sub-nanosecond time of flight resolution for online range verification in proton therapy using the line-cone reconstruction in Compton imaging

“…In order to realistically study the effect of the temporal resolution of the Compton camera on the precision of the fall-off position retrieval, the BGO absorber was replaced by a 35 × 35 × 4 cm 3 block of CeBr 3 . The energy resolutions of the scatterer and absorber detectors were modelled using an inverse square root law (Etxebeste et al, 2020) based on the known resolutions of 1.1% FWHM at 1 MeV for Si (Fontana et al, 2020) and 6.9% FWHM at 511 keV for CeBr 3 (Iltis et al, 2018). The centre-to-centre distance between the last silicon plane detector and the CeBr 3 absorber was set to 15 cm.…”

“…Resolution (σ) Scatterer Absorber spatial (mm) 2 2 energy 1.1% at 1 MeV 7% at 511 keV temporal (ns) 15 variable (0-1.3) in position was to investigate the effect of the decreased detection efficiency of the camera off-axis as a result of the limited field of view. Interactions of particles with the Compton camera were digitised using the Gate Compton camera imaging module, CCMod (Etxebeste et al, 2020). The three dimensional position, time and energy deposition of each interaction were stored, and lists of coincidences within a 40 ns window were created.…”

Hybrid PET/Compton-camera imaging: an imager for the next generation

“…8c; the latter is inspired in the MACACO system [131], whereas the PET part is an extension of the current MERMAID PET prototype [149]. These first studies with 89 Zr and 124 I have been carried out employing CCMod, the GATE module for Compton-camera simulation [150].…”

The OpenGATE ecosystem for Monte Carlo simulation in medical physics

“…All these parameters are critical in image quantification for oncology applications. GATE is also widely used for prototype detector developments and the next imaging system generations integrating concepts like heterostructured scintillators for ultra-fast TOF-PET scanners [76], total body acquisition [98; 146], or Compton Camera systems [40; 41; 43; 101; 102] with a dedicated module [37]. GATE has been also used to optimize PET detector design for proton therapy range monitoring that is particularly challenged by low signal-to-noise ratio with respect to the diagnostic PET scanners (see section 3.1).…”