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Approximately 80–90% of salivary calculi form in the submandibular gland due to the chemistry of the secretions as well as the orientation and size of the duct in the floor of mouth. Eighty percent of submandibular calculi are radio‐opaque while approximately 40% of parotid sialoliths are radio‐opaque (see Chapter 5). CT without contrast is the imaging modality of choice as it easily depicts the dense calculi (Figures 2.56 through 2.58 ). MRI is less sensitive and may miss calculi. Vascular flow voids can be false positives on MRI. MR sialography as previously discussed may become more important in the assessment of calculi not readily visible by CT or for evaluation of strictures and is more important as part of therapeutic maneuvers. US can demonstrate stones over two millimeters with distal shadowing (Shah 2002; Bialek et al. 2006; Madani and Beale 2006a).