Abstract
Objective: To clarify the diagnostic accuracy of CT in detecting the extent of tumor invasion into the surrounding soft tissues by squamous cell carcinoma of the mandibular gingiva.
Method: Axial CT scans of 77 patients with carcinoma of the mandibular gingiva were evaluated by three Oral and maxillof acial radiologists for the tumor invasion into the surrounding soft tissues. All patients underwent excision of the tumor in Kyushu University Dental Hospital from 1992 to 1999, and the presence and the extent of tumor invasion were confirmed by the macroscopic or histopahological findings following surgery. The observers rated their level of confidence for the presence of tumor invasion into genioglossus muscle (GGM), mylohyoid muscle (MHM), intrinsic lingual muscles (ILM), internal pterygoid muscle (IPM), masseter muscle (MM), labiobuccal tissues (LBT), and platysma muscle (PM) on the following five-point scale : 1, negative ; 2, probably negative ; 3, unsure ; 4, probably positive; 5, positive. The mean ROC curve area (Az) of each observer for tumor invasion into each tissue was obtained, and used as the index of diagnostic accuracy.
Results : The mean Az values for the detection of tumor invasion on CT was 0.86 for GGM and IPM, 0.82 for MHM, 0.80 for MM, 0.76 for ILM, 0.71 for LBT, and 0.65 for PM.
Conclusion : We should carefully interpret the tumor invasion into ILM, LBT and PM on CT images referring to the various clinical information, including inspection or palpation.
