Monte Carlo study of a 3D Compton imaging device with GEANT4

Abstract

In this paper we investigate, with a detailed Monte Carlo simulation based on Geant4, the novel approach of Lenti (2008) [1] to 3D imaging with photon scattering. A monochromatic and well collimated gamma beam is used to illuminate the object to be imaged and the photons Compton scattered are detected by means of a surrounding germanium strip detector. The impact position and the energy of the photons are measured with high precision and the scattering position along the beam axis is calculated. We study as an application of this technique the case of brain imaging but the results can be applied as well to situations where a lighter object, with localized variations of density, is embedded in a denser container. We report here the attainable sensitivity in the detection of density variations as a function of the beam energy, the depth inside the object and size and density of the inclusions. Using a 600 key gamma beam, for an inclusion with a density increase of 30% with respect to the surrounding tissue and thickness along the beam of 5 mm, we obtain at midbrain position a resolution of about 2 mm and a contrast of 12%. In addition the simulation indicates that for the same gamma beam energy a complete brain scan would result in an effective dose of about 1 mSv

GEANT4 simulation of a 3D Compton imaging device

“…A correction for the attenuation of the beam has been obtained [3] considering the passage of our pencil beam through the object: on its path it will impinge on a small cylinder of material with length equal to length of the object. This cylinder can be subdivided into small voxels of equal thickness.…”

“…In this paper we want to explore the potential of the novel method to image the electron density in the human body proposed in [I ] by means of a detailed Monte Carlo simulation using GEANT4 [2] with a realistic set-up. The application [3] presented here refers to brain imaging but the results can be applied as well to situations where a lighter object, with localized variations of density, is embedded in a denser container.…”