Comparison study of various beam modulation schemes on image quality in chest digital tomosynthesis (CDT) system

Abstract Recently, digital tomosynthesis systems have been actively investigated to reduce radiation dose in medical imaging. In this work, we present various beam modulation schemes for low-dose digital tomosynthesis; we compared the effects of the various acquisition schemes on image quality. A prototype chest digital tomosynthesis (CDT) system (LISTEM, Korea) and the LUNGMAN phantom (Kyoto Kagaku, Japan) with lung nodules were used in this study. A total of 81 projection data obtained through various beam modulation schemes over a 40° angular range were reconstructed using the filtered back projection (FBP) algorithm. The contrast noise ratio (CNR), structural similarity index (SSIM), and peak signal-to-noise ratio (PSNR) of the lung nodules were calculated to evaluate the image quality depending on the acquisition scheme. The reconstructed images obtained based on the proposed beam modulation schemes showed enhanced contrast in addition to a reduction of the area dose. It was determined that the beam modulation schemes affect the image quality. Among beam modulation schemes we investigated, the bunched view acquisition (outer focused) showed promising results within the region of interest (ROI). The reconstructed image obtained using the bunched view showed an increase of the CNR value by 63% compared to the conventional acquisition method. In addition, shutter scan acquisition showed promising results for the restoration information for the outside ROI. We determined that the beam modulation schemes in the prototype CDT system affect the image quality. It is also expected that the patient exposure dose can be reduced by modulating the beam size in the prototype CDT system.