Scatter in an uncollimated x-ray CT machine based on a Geant4 Monte Carlo simulation

Nicola Wadeson; Edward Morton; William Lionheart

doi:10.1117/12.843981

22 March 2010 Scatter in an uncollimated x-ray CT machine based on a Geant4 Monte Carlo simulation

Nicola Wadeson, Edward Morton, William Lionheart

Proceedings Volume 7622, Medical Imaging 2010: Physics of Medical Imaging; 76223E (2010) https://doi.org/10.1117/12.843981
Event: SPIE Medical Imaging, 2010, San Diego, California, United States

Abstract

A high-speed motionless-gantry x-ray CT machine has been designed to allow for 3D images to be collected in real time. By using multiple, switched x-ray sources and fixed detector rings, the time consuming mechanical rotation of conventional CT machines can be removed. However, the nature of this design limits the possibility of detector collimation since each detector must now be able to record the energy of x-ray beams from a number of different directions. The lack of collimation has implications in the reconstructed image due to an increase in the number of scattered photons recorded. A Monte Carlo computer simulation of the x-ray machine has been developed, using the Geant4 software toolkit, to analyse the behaviour of both Rayleigh and Compton scattered photons when considering airport baggage and medical applications. Four different scattering objects were analysed based on 50kVp, 100kVp and 150kVp spectra for a tungsten target. Two suitcase objects, a body and a brain phantom were chosen as objects typical of airport baggage and medical CT. The results indicate that the level of scatter is negligible for a typical airport baggage application, since the majority of space in a suitcase consists of clothing, which has a low density. Scatter contributes to less than 1% of the image in all instances. However, due to the large amounts of water found in the human body, the level of scatter in the medical instances are significantly higher, reaching 37% when the body phantom is analysed at 50kVp.

Citation Download Citation

Nicola Wadeson, Edward Morton, and William Lionheart "Scatter in an uncollimated x-ray CT machine based on a Geant4 Monte Carlo simulation", Proc. SPIE 7622, Medical Imaging 2010: Physics of Medical Imaging, 76223E (22 March 2010); https://doi.org/10.1117/12.843981

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