Comparing of the Sensitivity of Para - sialographic Images, Before and After Digital Subtraction Procedure in Lateral Oblique and True Lateral Views of Mandible

Lateral oblique and true lateral view of mandible are usually used for sialographyof major salivary glands. Panoramic view has been recently introduced as areplacement procedure. Among these techniques, true lateral view of mandible with900 horizontal and vertical angles of projection has the least distrotion in images ofsalivary glands and duct patterns. But this technique because of super imposition ofshadow of mandible of the opposite side, has lower diagnostic capability comparedwith the other two techniques. In the present study, probability of removingoverlapping shadows and improving of diagnostic power of true lateral views with invitro digital subtraction procedure has been evaluated. In this research a dry skull and12 angio-catheter tube sets with 29 artificial filling defects measuring about 2 to 5 mmprepared in them was used. A total of seven radiologists and residents of medical andmaxillo facial radiology evaluated digitized para-sialographic images before and afterdigital subtraction procedure. The results were analyzed with “Chi-square” and“Distribution-sensitivity frequency” tests. Data from analysis showed apparentimproved diagnostic capability in true lateral view of mandible by using digitalsubtraction technique (P<0.05) while there was no statistically significant difference inlateral-oblique view of mandible (P>0.05). In conclusion, the present study showed ifwe replace lateral oblique view by true lateral of mandible to decrease distortion ofsialography images, it is possible to improve image accuracy by digital subtractiontechnique.