A post‐reconstruction method to correct cupping artifacts in cone beam breast computed tomography

Abstract

In cone beam breast computed tomography (CT), scattered radiation leads to nonuniform biasing of CT numbers known as a cupping artifact. Besides being visual distractions, cupping artifacts appear as background nonuniformities, which impair efficient gray scale windowing and pose a problem in threshold based volume visualization/segmentation. To overcome this problem, we have developed a background nonuniformity correction method specifically designed for cone beam breast CT. With this technique, the cupping artifact is modeled as an additive background signal profile in the reconstructed breast images. Due to the largely circularly symmetric shape of a typical breast, the additive background signal profile was also assumed to be circularly symmetric. The radial variation of the background signals was estimated by measuring the spatial variation of adipose tissue signals in front view breast images. To extract adipose tissue signals in an automated manner, a signal sampling scheme in polar coordinates and a background trend fitting algorithm were implemented. The background fits compared with targeted adipose tissue signal value (constant throughout the breast volume) to get an additive correction value for each tissue voxel. To test the accuracy, we applied the technique to cone beam CT images of mastectomy specimens. After correction, the images demonstrated significantly improved signal uniformity in both front and side view slices. The reduction of both intraslice and interslice variations in adipose tissue CT numbers supported our observations.

Artefacts in CBCT: a review

“…Many of them are post-processing algorithms operating on the 3D volume data. 25,[36][37][38] Although this may result in considerable reduction of some apparent artefact structures, from a physical point of view post-processing is like putting the cart before the horse since the error has been integrated into the volume already. Consequently, more modern approaches attempt to avoid reconstruction errors either by supplementing missing or incorrect information in the projection images 8,39,40 or by integrating some sort of meta-information into an iterative reconstruction process.…”

“…25 The basic concept behind the radiographic imaging process as described in Equation 1 is that only photons travelling directly (i.e. in a linepath) from the source to the detector are measured.…”

On The Effect Of Image Brightness And Contrast Nonuniformity On Statistical Texture Parameters

“…Other modalities, e.g. visual light camera [7] or computed tomography images [1] may feature additive variations as well. To keep the discussion more general, we investigated and compared both cases -additive and multiplicative nonuniformity artifacts and their effects on texture analysis in the presented example.…”

“…The recognized texture attributes such as "smoothness", "roughness", "granularity", "directionality", etc. [4] have their origin in the physical microstructure of tissues and organs that are visualized in the image [2], [1].…”

Methodology for generating a 3D computerized breast phantom from empirical data

“…44 The cupping artifact due to scatter radiation is modeled as a circularly symmetric additive background signal profile in the reconstructed breast images. The artifact lowers the true tissue signal in a nonuniform way with a greater bias toward the breast center.…”