fan_cosine_weights#

diffct.analytical.fan_cosine_weights(num_detectors, detector_spacing, sdd, detector_offset=0.0, device=None, dtype=torch.float32)[source]#

Per-detector-cell cos(gamma) weight for fan-beam FBP.

cos(gamma) = sdd / sqrt(sdd^2 + u^2) where u is the in-plane detector coordinate. Multiplying the sinogram by this weight before the ramp filter compensates for the extra path length that off- principal-ray fans traverse.