Resolution-noise characteristics of common FDK filter kernels: A practical reference for preclinical cone-beam micro-CT.

Abstract

The ramp filter kernel and cutoff frequency are fundamental parameters of the Feldkamp-Davis-Kress (FDK) algorithm that determine the resolution and noise characteristics of the reconstructed image. Despite their importance, the filter configuration is frequently unreported in preclinical micro-CT studies. We reconstruct identical data from a GE eXplore CT 120 scanner using four filter kernels (ramp, Shepp-Logan, cosine, Hamming) at four cutoff frequencies (1.0, 0.8, 0.6, and 0.379× Nyquist, matched to the detector-to-voxel size ratio) and evaluate each of the sixteen configurations using the modulation transfer function (MTF), noise power spectrum (NPS), and non-prewhitening detectability index (NPW d'). Qualitative assessment is performed on a mouse lung specimen. Across the sixteen configurations, MTF10 ranges from 1.74 to 3.22 lp/mm, integrated NPS from 75 670 to 13 259 HU2, and the Rose criterion crossing diameter from 2.03 to 0.90 mm at ΔC=500 HU and from 6.89 to 3.56 mm at 100 HU. This note presents the data as a concise, primarily comparative visual and quantitative reference for FDK filter selection in preclinical cone-beam CT.