Marcel Beister, Presenter: Employee, Artemis Imaging GmbH

Ronny Hendrych, Abstract Co-Author: Employee, Artemis Imaging GmbH

Daniel Kolditz, Abstract Co-Author: Employee, Artemis Imaging GmbH

Willi A. Kalender PhD, Abstract Co-Author: Consultant, Siemens AG Consultant, Bayer AG Founder, CT Imaging GmbH Scientific Advisor, CT Imaging GmbH Shareholder, CT Imaging GmbH Founder, Artemis Imaging GmbH CEO, Artemis Imaging GmbH Shareholder, Artemis Imaging GmbH

To develop a dose-efficient iterative reconstruction method for imaging of the female breast and to compare it to a conventional reconstruction algorithm on a dedicated breast CT setup.

Model-based iterative reconstruction algorithms model the CT acquisition process more accurately than conventional techniques based on filtered backprojection (FBP). Since dedicated CT competes with mammography, the expected dose levels have to be low. Our iterative reconstruction uses photon statistic modeling, geometrical modeling of focus, detector and voxels and modeling of a realistic local image-neighborhood. It was implemented for a graphical processing unit (GPU) using the CUDA framework (NVIDIA, Santa Clara, USA). Noise, spatial resolution, noise power spectra and low contrast detectability were evaluated with simulated datasets of our planned setup. Two proposed reconstruction modes were investigated: A standard mode for soft-tissue lesion (STL) detectability and a high-resolution mode for microcalcifications (µCa). The results were verified with measured data of an experimental test system. The evaluation was done using breast phantoms including clusters of calcifications of different sizes, lesions in different sizes and structures of glandular tissue. Three dose levels (1.5, 3 and 6 mGy) per scan were investigated, simulated and verified using Monte Carlo simulation software. Dose levels in the measurements were verified using a calibrated ionization chamber.

Iterative reconstruction allowed a significant reduction of noise levels in both low-contrast (60-72%) and high-resolution reconstruction modes (81-84%). Detectability of soft-tissue lesions was also significantly improved. Spatial resolution in the STL mode was significantly higher (3 vs. 1 Lp/mm) compared to the FBP results. In the µCa mode, resolution was nearly identical (5 Lp/mm), but microcalcifications were better perceptible with iterative reconstruction due to the reduced background noise.

The proposed dose-efficient reconstruction method provided superior image quality in breast CT imaging compared to FBP methods.

The use of dose-efficient reconstructions with a dedicated breast CT scanner can provide improved diagnostic information at dose levels accepted for mammography screening.

Beister, M, Hendrych, R, Kolditz, D, Kalender, W, Dose Efficient Model-based Iterative Reconstruction for a Dedicated Female Breast CT Scanner.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11005205.html