1. A method comprising: obtaining a raw speckle image of a sample; converting the raw speckle image to a laser speckle contrast image using a laser speckle contrast algorithm; and converting the laser speckle contrast image to a relative correlation time image using a relative correlation time algorithm; wherein the laser speckle contrast algorithm is a direct algorithm that uses the following formula: k = s I 〈 I 〉 = ∑ i = 1 N ⁢ ( I i - 〈 I 〉 ) 2 N - 1 〈 I 〉 where speckle contrast k is equal to the standard deviation of time-integrated intensity s I divided by the mean time-integrated intensity (I) and where N is a positive integer.