In-Line Phase Contrast Mammography, Phase Contrast Digital Breast Tomosynthesis, and Phase Contrast Breast Computed Tomography With a Dedicated CT Scanner and a Microfocus X-Ray Tube: Experimental Phantom Study

Abstract

We performed laboratory investigations of the image quality for 2-D [digital mammography (DM)] and 3-D [digital breast tomosynthesis (DBT) and computed tomography (CT)] in-line phase contrast imaging dedicated to the breast. We employed the cone-beam, microfocus CT scanner developed in-house. Planar imaging tests were carried out with BR50/50 and polymethylmethacrylate test objects, at tube voltages of 60 kV, 80 kV, and 100 kV. CT volume images, acquired at 80 kV at dose levels comparable to two-view mammography (mean glandular dose <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cong ~4$ </tex-math></inline-formula> mGy), as well as at 120 kV, were reconstructed from phase contrast projection images as well as from the corresponding phase retrieved projection images (Paganin’s algorithm). We assumed 3-D spatial uniform distribution of the ratio <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta /\beta $ </tex-math></inline-formula> of the X-ray optical coefficients of the sample material, at the effective energy of the X-ray beam. In 2-D imaging, all phantom details showed higher contrast after phase retrieval. In particular, contrast-to-noise ratio between a simulated mass and phantom background in phase retrieved images resulted up to 6.5 times higher than for absorption-based images. CT and DBT phase retrieval images of a homogeneous 50/50 test object at 120 kV produced higher signal-to-noise ratio of microcalcifications than in phase contrast DBT and CT of the same object, at the same glandular dose. In CT reconstructed volume images, microcalcifications down to 0.230–0.290-mm size presented an increased visibility after phase retrieval, in a two-components 50/50 breast phantom. For the first time, the advantages of in-line phase imaging in microfocus breast imaging have been shown with one setup for all techniques (DM, DBT, and breast CT). These results motivate further research on in-line phase contrast 2-D and 3-D imaging of the breast with a microfocus X-ray tube for potential application in the clinic of in-line phase contrast DM, DBT, and breast CT at dose levels comparable with corresponding attenuation-based exams.