Application of the optimal 4D BFs (Table 2, highlighted in yellow) to a slice of phase 3 of the MOBY phantom reconstructed with noise (“Noisy Recon.” From Figure 2). For 4D BF, the filtering kernel expands to the phases before and after (phases 2 and 4, respectively) the phase being filtered (phase 3). Red labels highlight anatomic structures: LV, left ventricle; RV, right ventricle; RA, right atrium. Blue arrows denote a point of interest referenced in the text. The top intensity calibration bar applies to all grayscale images. The bottom intensity calibration bar applies to all difference images. All intensities are reported in HU.