TU‐EF‐207‐02: Spectral Mammography Based on Photon Counting Detectors
Authors: Molloi S. 
Published: June 2015

Breast imaging technology is advancing on several fronts. In digital mammography, the major technological trend has been on optimization of approaches for performing combined mammography and tomosynthesis using the same system. In parallel, photon‐counting slot‐scan mammography is now in clinical use and more efforts are directed towards further development of this approach for spectral imaging. Spectral imaging refers to simultaneous acquisition of two or more energy‐windowed images. Depending on the detector and associated electronics, there are a number of ways this can be accomplished. Spectral mammography using photon‐counting detectors can suppress electronic noise and importantly, it enables decomposition of the image into various material compositions of interest facilitating quantitative imaging. Spectral imaging can be particularly important in intravenously injected contrast mammography and eventually tomosynthesis. The various approaches and applications of spectral mammography are discussed.

Digital breast tomosynthesis relies on the mechanical movement of the x‐ray tube to acquire a number of projections in a predefined arc, typically from 9 to 25 projections over a scan angle of +/−7.5 to 25 degrees depending on the particular system. The mechanical x‐ray tube motion requires relatively long acquisition time, typically between 3.7 to 25 seconds depending on the system. Moreover, mechanical scanning may have an effect on the spatial resolution due to internal x‐ray filament or external mechanical vibrations. New x‐ray source arrays have been developed and they are aimed at replacing the scanned x‐ray tube for improved acquisition time and potentially for higher spatial resolution. The potential advantages and challenges of this approach are described.

Combination of digital mammography and tomosynthesis in a single system places increased demands on certain functional aspects of the detector and overall performance, particularly in the tomosynthesis mode due to lower photon fluence per projection. This may require fast‐frame acquisition and symmetric or asymmetric pixel binning in some systems. Recent studies investigated the performance of increased conversion layer thickness for contrast‐enhanced imaging of the breast in dual‐energy acquisition mode. In other direct conversion detectors operating in the avalanche mode, sensitivities close to the single photon response are also explored for mammography and breast tomosynthesis. The potential advantages and challenges of this approach are described.

Dedicated breast CT brings x‐ray imaging of the breast to true tomographic 3D imaging. It can eliminate the tissue superposition problem and does not require physical compression of the breast. Using cone beam geometry and a flat‐panel detector, several hundred projections are acquired and reconstructed to near isotropic voxels. Multiplanar reconstruction facilitates viewing the breast volume in any desired orientation. Ongoing clinical studies, the current state‐of‐the art, and research to advance the technology are described.

Learning Objectives:

To understand the ongoing developments in x‐ray imaging of the breast

To understand the approaches and applications of spectral mammography

To understand the potential advantages of distributed x‐ray source arrays for digital breast tomosynthesis

To understand the ongoing developments in detector technology for digital mammography and breast tomosynthesis

To understand the current state‐of‐the‐art for dedicated cone‐beam breast CT and research to advance the technology.

Research collaboration with Koning Corporation.