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, MTF 10 ranges from 1.74 to 3.22 lp/mm, integrated NPS from 75 670 to 13 259 HU 2 , and the Rose criterion crossing diameter from 2.03 to 0.90 mm at Δ C = 500 H U 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.