Potential use of a single scatter model in breast CBCT applications

Abstract

A model based on singly scattered photons could potentially be of use to correct for scatter effects in breast CBCT applications. Consider a simple phantom consisting of a 14 cm diameter 10.5 cm long cylindrical 50:50 mixture of fibroglandular and fat tissue with 21 cylindrical segments embedded along its central axis. One group of segments were 2 mm in diameter with compositions 0:100, 20:80, 35:65, 50:50, 65:35, 80:20, and 100:0. The remaining two groups had diameters of 5 mm and 10 mm. In order to reduce the computational time required, GEANT4 was used to simulate a scatter profile for a single projection which was then utilized in generating the large number of unique projections required for CBCT reconstruction. The scatter model was applied in an attempt to correct the cupping artifact caused by x ray scatter in the reconstructed images. The model assumed a homogeneous 50:50 phantom. The SPR generated by the model near the phantom center was at most 8% below that simulated by GEANT4. The scatter corrected images showed an almost complete removal of the cupping artifact. This simple model shows considerable promise in correcting scatter, though more research is required to determine its validity in more realistic imaging tasks.

Scatter point models for breast cone-beam computed tomography: preliminary study

“…The scatter from beamlet k that reaches pixel η was assumed to originate from a single point located at a depth given by d ´dk where d k represents the thickness of the phantom material that the beamlet encountered and δ is a value between 0 and 1. Mathematically, the SSP model is given by [24,31]…”