Image quality of opportunistic breast examinations in photon-counting computed tomography: A phantom study

Purpose: To compare the breast imaging performance of a clinical whole-body photon-counting CT (PCCT) to that of a dedicated breast CT (BCT) to determine the image quality of opportunistic breast examinations in clinical PCCT.

Materials and methods: To quantify image quality for breast cancer applications, acquisitions of a breast phantom including representations of calcifications, fibers, and masses were performed using a clinical PCCT and a dedicated BCT. When imaging with the PCCT, the phantom was also combined with a thorax phantom to simulate realistic patient positioning, while only the breast phantom was imaged in the BCT. Images in BCT were acquired at 7.0 mGy (CTDI_{16 cm}) and using 2.6 mGy-25.0 mGy in the PCCT. Spatial resolution between the BCT and PCCT images was matched and data were reconstructed using the default methods of each system. The dose-normalized contrast-to-noise ratio (CNRD) of masses and the structural visibility of fibers and calcifications were evaluated as figures of merit for all reconstructions.

Results: CNRD between masses and background was 0.56 mGy^-½, on average with BCT and varied between 0.39 mGy^-½ to 1.46 mGy^-½ with PCCT over all dose levels, phantom configurations, and reconstruction algorithms. Calcifications down to a size of 0.29 mm and fibers down to a size of 0.23 mm could be reliably identified in the images of both systems.

Conclusions: Clinical PCCT provides an image quality superior to that obtained with BCT in terms of CNRD and allows for the identification of calcifications and fibers at comparable dose levels.