Filter optimization in respect to the type of feature characteristics is important before the reconstruction. The MPA combined with median and sinc filters results in improved reconstruction of microcalcifications and low-contrast features. The latter are better visualized at extended arc length, while microcalcifications are less sensitive to this acquisition parameter. Use of monochromatic beams may result in tomographic images with higher contrast acquired at lower incident exposures.
Objective: This study aims to investigate the use of 3D printing techniques for the fabrication of physical breast phantoms, suitable for conventional and phase contrast breast imaging. Such phantoms could provide essential information for the design, development and optimization of emerging X-ray imaging modalities. Materials and Methods: Physical phantoms were constructed using two 3D printing techniques: Fused Deposition Modeling and Stereolithography. Eight materials suitable for 3D printing, including thermoplastic filaments and photopolymer resins, were investigated for the optimal representation of breast tissues, based on their attenuation and refractive characteristics. The phantoms consisted of a 3D-printed mold, which was then manually filled with paraffin wax. Additionally, a 3D complex-patterned layer and details representing abnormalities were embedded in different depths. Images of the phantoms were obtained in attenuation and phase contrast mode. Experiments were conducted using an X-ray microfocus tube with Tungsten anode set to 55kVp, combined with a photon-counting detector. The distance between source and detector was 56.5cm. The images were acquired at different object-to-detector distances starting from 5cm up to 40cm in a free space propagation set-up. Results and Conclusion: Results show that among all combinations with paraffin used as an adipose substitute, phantoms created with the Stereolithography technique and resins (especially Flex) as glandular equivalent, were found to be more appropriate for both attenuation and phase contrast imaging. The edge enhancement effect was well observed in the experimental images acquired at 35cm object-to-detector distance, indicating the potential for improved feature visualization using this set-up in phase contrast compared to attenuation mode.
The aim of the study is to investigate the impact on image quality of using monochromatic beams for lower dose breast tomosynthesis (BT). For this purpose, modeling and simulation of BT and mammography imaging processes have been performed using two x-ray beams: one at 28kVp and a monochromatic at 19keV at different entrance surface air kerma ranging between 0.16 and 5.5 mGy. Two 4cm thick computational breast models in a compressed state were used: one simple homogeneous and one heterogeneous based on CT breast images, with compositions of 50% glandular-50% adipose and 40% glandular-60% adipose tissues by weight, respectively. Modeled lesions representing masses and calcifications were inserted within these breast phantoms. X-ray transport in the breast models was simulated with previously developed and validated Monte Carlo application. Results showed that for the same incident photon fluence, the use of the monochromatic beam in BT resulted in higher image quality compared to the one using polychromatic acquisition, especially in terms of contrast. For the homogenous phantom, the improvement ranged between 15% and 22% for calcifications and masses, respectively, while for the heterogeneous one this improvement was in the order of 33% for the masses and 17% for the calcifications. For different exposures, comparable image quality in terms of signal-difference-to-noise ratio and higher contrast for all features was obtained when using monochromatic 19keV beam at lower mean glandular dose compared to the polychromatic one. Monochromatic images provide also better detail and in combination with BT can lead to substantial improvement in visualization of features and particularly better edge detection of low-contrast masses.
The MPA which had been applied previously to reconstruct tomograms from projections acquired at synchrotron facilities, is a time efficient algorithm, and is fully compliant with and can be successfully used in BT clinical systems. Compared to 2D mammography, BT shows advantage in visualizing features of small size and for increased phantom thickness or features within a dense background with superimposed structures.
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