Mr. Roshan Karunamuni Profile

Roshan Karunamuni

at Univ of Pennsylvania

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Proceedings Article | 19 March 2013 Paper

Exploring the relationship between SDNR and detectability in dual-energy breast x-ray imaging

Roshan Karunamuni, Swathiu Kanamaluru, Kristen Lau, Sara Gavenonis, Predrag Bakic, Andrew Maidment

Proceedings Volume 8668, 866863 (2013) https://doi.org/10.1117/12.2008114

KEYWORDS: Iodine, Breast, Tomography, Digital breast tomosynthesis, Signal detection, Interference (communication), Signal to noise ratio, X-ray imaging, Visualization, Tissues

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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.

Proceedings Article | 19 March 2013 Paper

Quantification of a silver contrast agent in dual-energy breast x-ray imaging

Roshan Karunamuni, Andrew Maidment

Proceedings Volume 8668, 866862 (2013) https://doi.org/10.1117/12.2008105

KEYWORDS: Silver, Breast, Tissues, X-ray imaging, Iodine, Signal attenuation, X-rays, Computer simulations, Breast imaging, Sensors

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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.

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