In breast X-ray images, texture has been characterized by a noise power spectrum (NPS) that has an inverse power-law shape described by its slope β in the log-log domain. It has been suggested that the magnitude of the power-law spectrum coefficient β is related to mass lesion detection performance. We assessed β in reconstructed digital breast tomosynthesis (DBT) images to evaluate its sensitivity to different typical reconstruction algorithms including simple back projection (SBP), filtered back projection (FBP) and a simultaneous iterative reconstruction algorithm (SIRT 30 iterations). Results were further compared to the β coefficient estimated from 2D central DBT projections. The calculations were performed on 31 unilateral clinical DBT data sets and simulated DBT images from 31 anthropomorphic software breast phantoms. Our results show that β highly depends on the reconstruction algorithm; the highest β values were found for SBP, followed by reconstruction with FBP, while the lowest β values were found for SIRT. In contrast to previous studies, we found that β is not always lower in reconstructed DBT slices, compared to 2D projections and this depends on the reconstruction algorithm. All β values estimated in DBT slices reconstructed with SBP were larger than β values from 2D central projections. Our study also shows that the reconstruction algorithm affects the symmetry of the breast texture NPS; the NPS of clinical cases reconstructed with SBP exhibit the highest symmetry, while the NPS of cases reconstructed with SIRT exhibit the highest asymmetry.
This work investigates a dual-energy subtraction technique for cone-beam breast CT combined with an iodinated
contrast agent. Simulations were performed to obtain optimally enhanced iodine-equivalent and morphological images.
The optimal x-ray beam energies and average glandular dose allocation between the LE and HE images were identified.
Cylindrical phantoms were simulated with 10, 14 and 18 cm diameters and composed of 50% fibroglandular breast tissue
equivalent material. They contained spherical lesion inserts composed of 0, 25, 75 and 100% fibroglandular equivalent
tissues, homogeneous mixtures of 50% fibroglandular equivalent tissue and 0.5, 1.0, 2.5 and 5.0 mg/cm3 iodine, as well
as pure calcium hydroxyapatite, emulating calcifications. An acquisition technique with 600 projection images is
proposed. Only primary x-ray photons were simulated and a perfect energy-integrating detector was considered. LE and
HE beams ranging from 20 keV to 80 keV were investigated. The LE and HE projections were reconstructed using a
filtered backprojection algorithm. The LE volume provided the morphological image while the iodine-equivalent volume
was obtained by recombining the LE and HE volumes. Contrast-to-noise ratio (CNR) between the spherical inserts and
background breast tissue normalized to the square root of the total AGD (CNRD) was used as figure-of-merit for lesion
detectability. Based on maximizing CNRD, a 30keV/34keV LE/HE pair and a ~50/50% LE/HE AGD allocation were
found to provide the best possible performance for iodine and morphological imaging for an average size breast.
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