Figure 3.

Illustration of the preHQ‐guided NLM image filtering for sparse‐view CT: (a) one transverse CT image of a patient; (b) FBP reconstruction from sparse‐view projection data; (c) conventional NLM filtering of low‐dose image in (b); (d) a deformed version of (a) serving as the prior image for preHQ‐guided NLM filtering; (e) prior image registered to (a); (f) registered prior image with simulated view‐aliasing artifacts; (g) the corresponding preHQ‐guided NLM filtering result with Eq. (11); (h) corresponding preHQ‐guided NLM filtering result with Eq. (13). (Figure reprinted from the work of Xu and Mueller²⁶).