In this paper, we for the first time define the concept of 3D skew lambda tomography (SLT) based on the 3D Calderon
Operator, and formulate an approximate local reconstruction algorithm for cone beam data collected along an arbitrary
scanning curve. The main idea is to rewrite the filtering operator in an exact filtered-backprojection reconstruction
formula as a local projection. While the practical cone-beam lambda tomography works well for spirals with small
pitches, the proposed SLT is more suitable to the spirals with large pitch. Simulation using the 3D differentiable Shepp-
Logan phantom is performed to demonstrate the utility of this new technique.