One aspect of the invention relates to a method for intraoperative assessment of parathyroid gland viability in a surgery. The method includes diffusing a beam of light onto a tissue surface of a parathyroid gland of a patient to illuminate the tissue surface； acquiring images of the illuminated tissue surface, where each of the acquired images includes a speckle pattern； and processing the acquired images to obtain speckle contrast images for the intraoperative assessment of parathyroid gland viability.
