Program Information
Development and Evaluation of a Spatial Resolution Metric for Tomosynthesis
T Vent*, R Acciavatti , A Maidment , Univ Pennsylvania, Philadelphia, PA
Presentations
WE-G-601-2 (Wednesday, August 2, 2017) 4:30 PM - 6:00 PM Room: 601
Purpose: A novel method has been developed to measure the contrast transfer function (CTF) of digital breast tomosynthesis (DBT) systems.
Methods: Images of a resolution star pattern are reconstructed using commercial software to a pixel size of 32.3 μm which is 2.6 times smaller than the detector element size. The radial fast Fourier transform (FFT) is calculated for each quadrant of the star pattern. Specifically, starting at the inner ring of the star pattern, the plot profile is extracted radially for each quadrant (δω). The 1D FFT is computed for this profile. The radius is then incremented by one pixel and the process is repeated to the outer ring of the star pattern. The CTF of the quadrant is represented by the fundamental frequency of the radial FFT plot. Using software written in Matlab, the 3D radial FFT is plotted as a function of star pattern resolution (lp/mm) and period (cycles/δω). Each quadrant of the star pattern is investigated independently to assess super-resolution and aliasing due to scan directionality.
Results: This method was evaluated using our next-generation DBT system for star pattern images acquired at 28 kV and 10 mAs per projection (15 projections total) in contact mode. Super-resolution is present in the scan direction, but is not present perpendicular to the scan direction. In the perpendicular direction, spectral leakage of the radial FFT is evidenced as aliasing in the images. By contrast, traditional methods of calculating the MTF show comparable resolution in both directions, and do not demonstrate the effects of aliasing.
Conclusion: This work suggests that the radial FFT of a star pattern is a valid analysis technique for evaluating spatial resolution of DBT systems. These systems are non-linear and intrinsically include aliasing; this method demonstrates aliasing separate from the fundamental frequency.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by Komen grants PDF14302589 and IIR13264610, and NIH/NCI grant 1R01CA196528. TLV had an AAPM Summer Undergraduate Research Fellowship. Equipment was provided by Analogic, Barco, and Real-Time Tomography (RTT). ADAM is a scientific advisor to RTT and is the spouse of an employee and shareholder of RTT.
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