Evaluation of biological speckle activity: Using variational mode decomposition

The physical description of the dynamic speckle behind biological tissues is often unknown or not known at all. In this paper, we investigate the application of the variational mode decomposition in dynamic speckle sequences. The proposed VMD indexes are used to adaptively determine the bands related to the dynamic speckle sequence, which can obtain more selective information about the characteristics of speckles in biological samples and isolate undesired covariates. The method is exemplified with speckle sequences of bruising apple. The difference of energy and phase between artificial scratch and natural fruit scar is successfully distinguished. The results are also compared with EMD results, confirming that the method can be used to extract the expected components in the raw signal. On this basis, through the proposed region-specific index and measuring the biological activity of bone tissue, the effect of the rupture and contraction of the water film on the bone surface on the dynamic speckle measurement is successfully eliminated, which can be used to judge the time of bone in vitro, as well as a novel index of the biospeckle activity.