A processor implemented method, comprising: recording, via one or more hardware processors, an image stack consisting of N speckle images, wherein size of each of the speckle image is equal to K ∗ L which is recorded sequentially over a period of time, and wherein K indicates the number of rows and L indicates the number of columns of each of the speckle image; dividing, via the one or more hardware processors, the image stack into a spatial window of size K p ∗ L p and a temporal window of N p around each pixel of each of the speckle image, wherein the spatial window comprises speckle intensity data, and wherein p denotes a subset of K and L comprised in each of the speckle image; converting, via the one or more hardware processors, the speckle intensity data comprised in the spatial window into a column vector V p of length K p ∗ L p ∗ 1 for each of the speckle image to obtain a plurality of column vectors V p; constructing, via the one or more hardware processors, a diagonal matrix Σ p based on K p, N p and L p; extracting, via the one or more hardware processors, a singular value σ i from the diagonal matrix Σ p, wherein a total number of a plurality of singular values σ i is represented by min ( K p L p V p); defining, via the one or more hardware processors, a speckle intensity correlation metric using the plurality of singular values σ i: CM = σ 1 ∑ i = 1 i = min K p L p, N p σ i defining, via the one or more hardware processors, a speckle activity using the defined speckle intensity correlation metric, wherein a plurality of regions of high activity is represented by high speckle activity values and a plurality of regions of low activity is represented by low speckle activity values, wherein the speckle activity is expressed using the equation: SA = 1 − CM SA = 1 − σ 1 ∑ i = 1 i = min K p L p, N p σ i and generating, via the one or more hardware processors, a speckle contrast image by graphically plotting the speckle activity values to generate an activity map and performing an interpolation across the activity map to obtain an interpolated activity map. recording, via one or more hardware processors, an image stack consisting of N speckle images, wherein size of each of the speckle image is equal to K ∗ L which is recorded sequentially over a period of time, and wherein K indicates the number of rows and L indicates the number of columns of each of the speckle image; dividing, via the one or more hardware processors, the image stack into a spatial window of size K p ∗ L p and a temporal window of N p around each pixel of each of the speckle image, wherein the spatial window comprises speckle intensity data, and wherein p denotes a subset of K and L comprised in each of the speckle image; converting, via the one or more hardware processors, the speckle intensity data comprised in the spatial window into a column vector V p of length K p ∗ L p ∗ 1 for each of the speckle image to obtain a plurality of column vectors V p; constructing, via the one or more hardware processors, a diagonal matrix Σ p based on K p, N p and L p; extracting, via the one or more hardware processors, a singular value σ i from the diagonal matrix Σ p, wherein a total number of a plurality of singular values σ i is represented by min ( K p L p V p); defining, via the one or more hardware processors, a speckle intensity correlation metric using the plurality of singular values σ i: CM = σ 1 ∑ i = 1 i = min K p L p, N p σ i defining, via the one or more hardware processors, a speckle activity using the defined speckle intensity correlation metric, wherein a plurality of regions of high activity is represented by high speckle activity values and a plurality of regions of low activity is represented by low speckle activity values, wherein the speckle activity is expressed using the equation: SA = 1 − CM SA = 1 − σ 1 ∑ i = 1 i = min K p L p, N p σ i and generating, via the one or more hardware processors, a speckle contrast image by graphically plotting the speckle activity values to generate an activity map and performing an interpolation across the activity map to obtain an interpolated activity map.