Helical CT in the evaluation of cranio-facial fibrous dysplasia

Purpose. To evaluate the role of helical CT in the evaluation of skull abno rmalities seen in fibrous dysplasia. Materials and Methods. Prospective study on 6 cases with cranio-facial fibr ous dysplasia (3 males and 3 females) aged 8 to 59 years old, evaluated wit h plain radiographs, helical CT and, in 1 case, MRI. Helical CT was perform ed in 3 cases on a CT Twin scan (Elscint), in 3 cases on a Somatom Plus sca n (Siemens). Multiplanar reconstructions and 3D reconstructions were done i n all cases. 4 cases had a histopathological confirmation of fibrous dyspla sia lesions by bone-biopsy (3 cases) or surgical biopsy (1 case). Results. The 6 cases included sclerotic form in 3 cases, cystic variety in 1 case, polyostotic variety in 1 case, mixed form in 1 case. Topographic lo calizations of fibrous dysplasia were skull base involvement in 1 case, mul tizonal skull involvement in 4 cases, maxillo-mandibulary involvement (cher ubism) in 1 case. Conclusion. Helical CT is an optimal method to evaluate the skull lesions o f fibrous dysplasia. The review of source images must always be done. 8-dim ensional bone reconstructions are better to visualize the anterior cranial vault and skull base dysmorphy. Helical acquisition is a compromise in case by case between the dose of irradiation and the quality of source images.