A novel direct-indirect dual-layer flat-panel detector for contrast-enhanced breast imaging: Experimental assessment

In contrast-enhanced digital mammography (CEDM) and contrast-enhanced digital breast tomosynthesis (CEDBT), low-energy (LE) and high-energy (HE) images are acquired after injection of iodine contrast agent. Weighted subtraction is then applied to generate dual-energy (DE) images, where normal breast tissues are suppressed, leaving iodinated objects enhanced. Currently, clinical systems employ a dual-shot (DS) method, where LE and HE images are acquired with two separate exposures. However, patient motion between these exposures can cause residual breast tissue structure to appear in the recombined DE images, reducing the visibility of iodinated lesions. To address this issue, we propose a direct-indirect dual-layer flat-panel detector (DI-DLFPD), which eliminates patient motion artifact by acquiring LE and HE images simultaneously.

This study aims to: (1) experimentally validate CEDM and CEDBT imaging using a first-generation prototype DI-DLFPD, (2) compare lesion conspicuity with images obtained using the DS method, (3) optimize the k-edge filter for the DI-DLFPD based on breast thickness.

CEDM and CEDBT images were acquired using both the prototype DI-DLFPD and a conventional DS single-layer detector at comparable dose levels to evaluate image quality and iodine target conspicuity. The figure of merit (FOM) was defined as the square of signal difference to noise ratio (SDNR) divided by the mean glandular dose. The selection of k-edge filter for DI-DLFPD was assessed based on varying breast thickness.

By eliminating patient motion artifacts, DI-DLFPD images exhibit a significant improvement (∼233%) in iodine object FOM compared to DS images affected by patient motion. Iodine quantification accuracy was also improved. The results suggest using a sliver filter for average breast thickness (4 cm) and a Tin filter for thicker breasts (8 cm) to achieve optimal iodine SDNR for DI-DLFPD.

This study presents experimental results from the first-generation prototype DI-DLFPD for CEDM and CEDBT. A practical strategy was recommended, where the x-ray filter for DI-DLFPD was optimized based on the compressed breast thickness.