The objective of our study was to evaluate the feasibility of using silver sulfide nanoparticles (Ag2S-NP) as a contrast agent for photon-counting mammography. The efficacies of Ag2S-NP and iodine contrast were evaluated using a contrastembedded gradient phantom. The phantom was constructed using tissue-equivalent materials and varied continuously in composition from 100% glandular tissue to 100% adipose tissue. Each contrast agent was prepared at eight different concentrations: 1, 2, 5, 10, 15, 20, 25, and 30 mg/mL. Tubes of contrast agent were inserted into holes bored through the phantom in the direction of varying glandularity. Various images of the phantom were acquired by altering the acquisition parameters (kV, mAs, and high bin fraction). A range of beam energies from 26 kV to 40 kV was tested in this study. Our results demonstrate that for a given contrast agent, the contrast-to-noise ratio (CNR) is linearly proportional to concentration, and its magnitude is dependent on the kV of the spectrum. At mammographic energies, the Ag2S-NP contrast increases with increasing kV and increasing solution concentration. Comparatively, the iodine signal becomes detectable only when the kV of the image is above iodine’s K-edge (33.2 keV). This indicates that the optimal energy for imaging iodine may exceed the clinical mammographic energy range. In summary, we have demonstrated the feasibility of using Ag2S-NP as a contrast agent for breast imaging. Preliminary results from spectral photon-counting mammography indicate that Ag2S-NP contrast has a significantly higher signal than iodine, especially when imaging at lower energies.
The objective of our study is to optimize the acquisition parameters for imaging Ag2S nanoparticles using contrast-enhanced digital mammography (CE-DM) by varying parameters such as kV, mAs, and filtration. The efficacies of three different contrast materials (Ag2S nanoparticles, silver nanoparticles, and iodine) were assessed using a contrast-embedded gradient phantom. The phantom was constructed using tissue-equivalent materials and varied continuously in composition from 100% glandular tissue to 100% adipose tissue. Each contrast agent was prepared at six different concentrations (1, 2, 5, 10, 15, and 25 mg/mL). Holes were bored through the phantom in the direction of varying glandularity, and tubes of contrast agents were inserted into the holes. Phantoms were imaged at four different energies (26 kV, 32 kV, 45 kV, and 49 kV); 5 energy pairs were considered in this study. Our results demonstrate that for a given contrast agent, the contrast-to-noise ratio is linearly proportional to concentration, and its magnitude is dependent on the energy of the low-energy (LE) image. In our study, it was shown that the LE images at 26 kV are better suited for imaging silver-based nanoparticles, and the LE images at 32 kV are better suited for imaging iodine contrast. Thus, the energy of the LE image should be chosen so that it is as close as possible to the k-edge of the contrast material. Preliminary results from CE-DM imaging indicate that silver contrast has a significantly higher signal than iodine contrast when imaging at lower energies, thus demonstrating the feasibility of using silver-based nanoparticles in breast imaging.
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