Diagnostic value of MR imaging for dentigerous cysts

Objectives It is known that the magnetic resonance (MR)imaging features of dentigerous cysts (DCs) are the same as those of other cysts. The cavities of DCs generally show low signal intensity (SI) on T1-weighted imaging (T1WI). However, in our experience, DCs often show high SI on T1WI, rendering them difficult to distinguish from keratocystic odontogenic tumors (KCOTs). In this study, we evaluated seven cases of DC and 23 cases of KCOT to assess whether MR imaging can provide additional information for the differential diagnosis of DC and KCOT. Methods Two trials were evaluated. The first trial was an analysis of the cystic cavity SI on T1WI. To compare the SI between patients, we performed T1WI with contrast (T1c). The second trial analyzed the SI uniformity (UR) on T1WI, T2-weighted imaging (T2WI), and short inversion time inversion recovery (STIR) images of the cystic cavity, because it has been reported that an MR imaging feature of KCOT is heterogeneous SI. Statistical analyses were performed using the Mann-Whitney U test and a receiver operating characteristic (ROC) curve. Results The T1c values of DCs were significantly higher than those for KCOTs. The UR values on T1WI and STIR images were significantly higher for DCs than for KCOTs. The T1c cutoff values (0.66 and 0.84) and UR cutoff values for T1WI (82.1 %) and STIR images (79.8 %) were determined from the ROC analyses. Conclusions T1c and UR values provide useful additional information for the differential diagnosis of DC and KCOT.