Alexander L. C. Kwan PhD, Presenter: Nothing to Disclose

Kai Yang, Abstract Co-Author: Nothing to Disclose

Nikula Shah MS, Abstract Co-Author: Nothing to Disclose

Shih-Ying Huang, Abstract Co-Author: Nothing to Disclose

John Michael Boone PhD, Abstract Co-Author: Nothing to Disclose

To quantify the important parameters in optimizing the spatial resolution of a prototype pendant-geometry cone-beam breast CT system, and how the spatial resolution varies spatially in the reconstructed volume.

The modulation transfer function (MTF) was calculated by scanning a 0.070 mm nickel-chromium wire in the breast CT scanner. The wire produced a point spread function (PSF) in the reconstructed images, which was then used to compute the MTF. The MTF measurements were made as a function of the radial position in the field of view (from isocenter to edge), and as a function of the number of projections (500 and 1000) acquired for reconstruction. MTFs were assessed for different cone angles as well. The CT images were reconstructed with the Shepp-Logan filter for different matrix sizes (512, 800, and 1024 pixels squares).

For the 500 projection acquisition with a 512 square reconstructed image size, the MTF at a frequency of 0.5 mm^-1 dropped from 0.73 at the isocenter to 0.35 at a radius of 8 cm from isocenter. Similar trends were observed for other acquisitions and matrix sizes. While the increase in the number of acquired projection images has minimal impact on the MTF at the isocenter, the MTF at 0.5 mm^-1 increased from 0.35 to 0.44 for the radial position of 8 cm with a 512-by-512 matrix size. Lastly, the size of the reconstruction matrix had little effect on the computed MTF for the current setup.

The MTF of the dedicated cone-beam breast CT scanner was examined. The spatial resolution is determined to be best at the isocenter, and degrades slightly towards the periphery. While the reconstructed image size has minimal effect on the computed MTF, the increase in the number of acquired projection images improved the MTF at the periphery of the reconstructed image.

Kwan, A, Yang, K, Shah, N, Huang, S, Boone, J, Evaluation of the Spatial Resolution Characteristics of a Breast CT Scanner.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4414669.html