KEYWORDS: Iodine, Breast, Tomography, Digital breast tomosynthesis, Signal detection, Interference (communication), Signal to noise ratio, X-ray imaging, Visualization, Tissues
Contrast-enhanced (CE) digital breast tomosynthesis (DBT) provides a technique to increase the contrast of radiographic
imaging agents by suppressing soft-tissue signal variation. By reducing the effect of the soft-tissue anatomical noise, it is
then possible to quantify the signal from an iodinated contrast agent. The combination of dual-energy and tomographic
acquisitions allows for both the accurate quantification and localization of an iodinated lesion. Here, we present our
findings demonstrating the relationship that exists between the signal difference to noise ratio (SDNR) and reader
detectability of iodinated lesions in a physical anthropomorphic phantom. The observer study was conducted using the
ViewDEX software platform with a total of nine readers. The readers were asked to score each of the iodinated lesions
on a scale from 1 (entire boundary and area are visible) to 5 (not visible). Both SDNR and lesion detectability were
found to improve as the concentration of the iodine increases, and the thickness of the phantom decreases. Lesion
detectability was better in the tomographic slice that best matches the focal plane of the imaged object. However, SDNR
does not significantly change with focal plane. Our results demonstrated that observer lesion detectability correlated well
with SDNR. Lesions whose SDNR fell below 1 were difficult to distinguish from the background and were in general
not visible. Lesions that were rated entirely visible corresponded to those with SDNR values above 3. Lesions with
intermediate SDNR values were visualized but not confidently from the surrounding background. These threshold SDNR
values can be used to optimize the imaging parameters in CE-DBT.
Dual-energy (DE) breast x-ray imaging involves acquiring images using a low- and high-energy x-ray spectral pair.
These images are then subtracted with a weighting factor that eliminates the soft-tissue signal variation present in
the breast leaving only contrast that is attributed to an exogenous imaging agent. We have previously demonstrated
the potential for silver (Ag) as a contrast material for DE breast imaging. Theoretical analysis shows that silver can
provide better contrast to clinically-used iodine. Here, we present the subtraction method developed to eliminate the
contrast between adipose and glandular tissue; the two major component materials in the breast. The weighting
factor is calculated from the attenuation coefficients of the two tissue types and varies between values of 0 and 1 for
the energy combinations studied. A spectral search was performed to identify the set of clinically-feasible imaging
parameters that will optimize the contrast of silver using our subtraction technique. The subtraction methodology
was tested experimentally using step-phantoms and demonstrated that we are able to a) nullify the soft-tissue
contrast that arises from differences in glandularity, and b) preserve an image contrast for silver that is independent
of the underlying soft-tissue composition. By applying the DE subtraction proposed, a silver-based agent will
outperform an iodinated contrast agent on a commercially-available CEDE breast x-ray imaging system.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.