Rui Li Zhuoxin Sun Cishen Zhang Adaptive filter for speckle reduction with feature preservation in medical ultrasound images. 1787-1792 2008 ICARCV http://dx.doi.org/10.1109/ICARCV.2008.4795799 conf/icarcv/2008 db/conf/icarcv/icarcv2008.html#RuiZC08