An apparatus for intraoperative assessment of parathyroid gland viability in a surgery, comprising: a light source for emitting a beam of light; a diffuser coupled to the light source for diffusing the beam of light onto a tissue surface of a parathyroid gland of a patient to illuminate the tissue surface; a detector for acquiring images of the illuminated tissue surface, wherein each of the acquired images comprises a speckle pattern; and a controller arranged to operate the detector to acquire the images of the illuminated tissue surface, receive the acquired images from the detector, and process the acquired images to obtain speckle contrast images for the intraoperative assessment of parathyroid gland viability, characterized in that said processing the acquired images of the parathyroid gland by the controller is performed with calculating a plurality of speckle contrasts from the acquired images of the parathyroid gland, wherein said calculating a plurality of speckle contrasts from the acquired images of the parathyroid gland is performed with: defining a window with a number of pixels over which a speckle contrast is to be calculated; moving the window across the acquired image of the speckle pattern; and at each location, calculating the speckle contrast as a standard deviation of pixel intensity values σ s within the window divided by a mean intensity value (I) as follows: K s = σ s 〈 I 〉 wherein the resultant speckle contrast image has values that range from 0 to 1, with values closer to 0 representing regions of greater motion (perfusion) and 1 representing regions with no motion. a light source for emitting a beam of light; a diffuser coupled to the light source for diffusing the beam of light onto a tissue surface of a parathyroid gland of a patient to illuminate the tissue surface; a detector for acquiring images of the illuminated tissue surface, wherein each of the acquired images comprises a speckle pattern; and a controller arranged to operate the detector to acquire the images of the illuminated tissue surface, receive the acquired images from the detector, and process the acquired images to obtain speckle contrast images for the intraoperative assessment of parathyroid gland viability, characterized in that said processing the acquired images of the parathyroid gland by the controller is performed with calculating a plurality of speckle contrasts from the acquired images of the parathyroid gland, wherein said calculating a plurality of speckle contrasts from the acquired images of the parathyroid gland is performed with: defining a window with a number of pixels over which a speckle contrast is to be calculated; moving the window across the acquired image of the speckle pattern; and at each location, calculating the speckle contrast as a standard deviation of pixel intensity values σ s within the window divided by a mean intensity value (I) as follows: K s = σ s 〈 I 〉 wherein the resultant speckle contrast image has values that range from 0 to 1, with values closer to 0 representing regions of greater motion (perfusion) and 1 representing regions with no motion. defining a window with a number of pixels over which a speckle contrast is to be calculated; moving the window across the acquired image of the speckle pattern; and at each location, calculating the speckle contrast as a standard deviation of pixel intensity values σ s within the window divided by a mean intensity value (I) as follows: K s = σ s 〈 I 〉 wherein the resultant speckle contrast image has values that range from 0 to 1, with values closer to 0 representing regions of greater motion (perfusion) and 1 representing regions with no motion. <EOS>