Xiangyang Tang PhD, Presenter: Nothing to Disclose

Yi Yang PhD, Abstract Co-Author: Nothing to Disclose

Shaojie Tang PhD, Abstract Co-Author: Nothing to Disclose

As a new imaging method, grating based differential phase contrast CT (DPC-CT) has been drawing increasing attention. We have reported that there exists a substantial difference in the noise transfer property – noise power spectrum NPS(k) – between the DPC-CT (trait 1/|k|) and conventional attenuation-based CT (trait |k|). In this work, we investigate the spectrum of noise equivalent quanta NEQ(k) – the joint signal and noise transfer properties – of the DPC-CT and compare it with that of the conventional CT.

We analytically derive the functional form of the NPS(k) and NEQ(k) of the DPC-CT and evaluate and verify the derived equations through simulation study. The imaging chain of DPC-CT is simulated through Fresnel and Fourier analyses and validated with an extensive phantom study, while that of the conventional CT is carried out as usual. At given x-ray exposure, an air phantom is used to acquire the NPS(k) of both DPC-CT and conventional CT. Due to DPC-CT’s imaging mechanism, a thick cylindrical object, rather than a thin wire, is employed to gauge the modulation transfer function MTF(k), in which the edge spread function is acquired initially, followed by a numerical operation to obtain the line spread function and then MTF(k). Finally, the NEQ(k) of DPC-CT is obtained using the functional form derived in this work, while that of the conventional CT is attained using the method established in the literature.

The preliminary results show that both MTF(k) and NEQ(k) of the DPC-CT are comparable to that of the conventional CT, even though there exist a substantial difference in their noise transfer property - NPS(k).

The joint signal and noise transfer properties of the DPC-CT and conventional CT are essentially identical. Thus the extent to which the DPC-CT can outperform the conventional CT in differentiating soft tissues is essentially dependent on the extent to which the contrast in soft tissue's refractive index is larger than their counterpart in attenuation index.

Providing an insightful understanding of the;DPC-CT;s potential imaging performance and guidelines on thDPC-CT;s performance optimization for extensive preclinical and ultimately clinical applications

Tang, X, Yang, Y, Tang, S, Spectrum of Noise Equivalent Quanta NEQ(k) – Differential Phase Contrast CT vs Conventional CT.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12037921.html