Objective To discuss the X-ray and CT manifestations of keratocystic odontogenic tumour(KCOT)in mandible,to im-prove the diagnostic accuracy of the disease.Methods The X-ray and CT features of KCOT(n=25)in mandible,which were proved by surgery and pathology,were retrospectively analyzed.Results The KCOT,including solitary tumor(n=23)and multiple tumor (n=2),mainly displayed unilocular or multilocular in shape with distinct sclerosing margin.Disruption of the adjacent cortex was de-tected in 7 cases,growth along the long axis of mandible in 18 cases,compression and displacement of the adjacent teeth in 21 cases, resorption of bevel of roots in 2 cases.Conclusion Most lesions of KCOT in mandible have characteristic manifestation in X-ray and CT findings,which is helpful for diagnosis and differential diagnosis.

Objective To assess the value of low dose CT scanning applied in nasal sinus examination. Methods 100 cases were divided into two groups,including youth group and adult group,with 50 cases for each group.After scanned by standard dose(150mAs),all the patients were scanned with low dose. Those in youth group were scanned with 40mAs and 25mAs,and the others in adult group were scanned with 50mAs and 30mAs.CT images were evaluated by three doctors using blind method.The image quality was evaluated according to 3 grades:normal image,image with mild artifact,and image with serious artifact and the results were analyzed statistically. Results The CTDlw of low-dose CT scanning was obviously lower than that of standard dose(P