Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4532_Библиотеки_им_академика_М_И_Перельмана

on CT scans – of a radiodense mass occupying the frontal sinus (more commonly) or, less frequently, the ethmoid or maxillary sinus (Gillman et al. 1997). According to the amount of mineralized bone within the lesion, osteomas may exhibit very high density, resembling cortical bone, or a gradually decreasing X-ray opacity/density to a “ground-glass” pattern (Fig. 8.1). All different patterns can be found at once in the same lesion (Som and Brandwein 1996). No enhancement is to be expected; nonetheless, contrast administration is normally unnecessary to obtain a diagnosis. MR is intrinsically inferior to CT in imag­ing osteomas, as both the low water content and the lack of mobile protons within osteomas result in very low signal intensity in all sequences. The possible presence of small amounts of fat tissue within the intertrabecular spaces may result in the detection of scattered hyperintense foci on both T1 and T2 se­quences (Rao et al. 2001). The differential diagnosis includes osteoblastoma, osteosarcoma, and fi brous dysplasia, calcifi ed hematoma being just an anec­dotal alternative (Huang and Misko 1998). On CT, high density, well-defi ned borders, lack of contrast enhancement and lytic bone destruction, are gener­ally suffi cient clues to suggest a correct diagnosis. In addition, osteomas are generally confi ned to the sinus of origin. Obstruction of mucus drainage path­ways (particularly the frontal recess) is the more fre­quent concern in sinonasal osteomas (Fig. 8.2). High quality CT multiplanar reconstructions – obtained with multidetector equipment – may be necessary to precisely identify the sinusal wall from which the lesion arises, to fully depict course and patency of