CT And MRI Analysis In Nasopharyngeal Carcinoma After Radiotherapy

Objective:To improve the cognition of the recurrence and changes of CT and MRI in nasopharyngeal carcinoma (NPC) after radiotherapy.Methods:CT imaging of 118 patients and MRI imaging of 49 patients confirmed by followed-up or pathology in NPC after radiotherapy were analyzed in details.Results:There were 53 cases recurrence in 118 CT imaging. In those, nasopharyngeal wall thicken/lump (n=28), medial soft tissue of styloid process (MSTSP) thicken and compact (n=40), skull base invaded (n=24). In the 65 cases non-recurrent, nasopharyngeal wall thicken (n=35), nasopharyngeal wall lump(n=5), MSTSP thicken and compact(n=18), skull base residues encroached (n=6). There was significant difference between the non-recurrent and the recurrence in the thicken and compact of the MSTSP (P<0.05), and there was no significant difference in the nasopharyngeal wall thicken/lump (P>0.05). There were 28 non-recurrent cases and 21 recurrent cases in 49 MRI imaging. In the 28 non-recurrent cases, justo of cavum nasopharyngeum (n=2), distortion of cavum nasopharyngeum (n=15), nasopharyngeal wall thicken (n=19), medial soft tissue of styloid process (MSTSP) thicken(n=7), narrowing of parapharyngeal space (n=3), skull base residues encroached (n=5). In the 21 recurrent cases, each nasopharyngeal wall and MSTSP thicken (n=12), skull base destruction (n=18) tumor in infratemporal fossa (n=4), tumor in oropharynx (n =2), fossa orbitalis, maxilla and maxillary sinus invaded (n=2), temporomandibular joint invaded (n=1), in 1 case with mastoid process invaded and tumor of bilateral parotid glands and encircling collare, narrowing or disappearance of parapharyngeal space (n=9). By statistical analysis, there were significant difference between the non-recurrent and the recurrence among the MSTSP thicken and narrowing or disappearance of parapharyngeal space (P<0.05). In the non-recurrent,7 cases with MSTSP thicken were displayed with a tumor of isointensity to hypo-intensity on T1WI and T2WI; on the enhanced MRI,5 cases with no enhancement,2 cases with slight enhancement. In the recurrence,12 cases with MSTSP thicken were displayed with a irregular mass of isointensity to hyperintensity on T1WI and T2WI; 11 cases were done with enhanced MRI,9 cases with strong enhancement,2 cases with slight enhancement.Conclusions:1.CT and MRI can show the changes in NPC after radiotherapy.2.The change of MSTSP is important to decide whether or not the tumor has recurred.3.CT and MRI can play important roles in differentiating recurrent NPC from radio-fibrosis.