| Abstract |
The first aim of our study was to estimate the sensitivity of the US, CT, MR imaging, CT Sialography and MR Sialography in the detection of parotid lesions and differentiation of the malignant from the benign masses. The second aim was to explore the possibility of delineation of the facial nerve and the parotid duct within the parotid gland and to differentiate between deep and superficial parotid lesions in relationship to the facial nerve and parotid duct using all the above imaging diagnostic methods. We examined 124 patients (136 cases ) with clinically suspected parotid lesions, 70 males and 54 females, 1-83 years old (mean 46,9 years old). From these, 59 cases underwent US, 72 CT, 82 MR imaging, 39 CT Sialography, 20 MR Sialography and 14 cases underwent CT and MR Sialography. The size of the parotid lesions was 0,5-8 cm (mean 2,7 cm) and their commonest location was the inferior pole (42%). In addition the normal values of 100 parotid glands were measured. All cases underwent surgery and the histologic diagnosis was obtained: 69 benign lesions (38 pleomorphic adenomas, 22 adenolyphoma, 9 other benign tumors, 21 malignant tumors (7 squamous cell Ca, 3 mucoepidermoid, 3 adenocarcinoma, 3 metastatic deposits, 1 malignant lymphoma, 1 adenocystic Ca, 1 rabdomyosarcoma, 1 malignant mixed tumor and 1 leukaemia), 19 inflammatory masses, 13 other pathologies and 14 extraparotid lesions. The sensitivity of US in the detection of the parotid lesion was 100%, of CT without IV Contrast injection 68,6% and with contrast 92,8%, of MR T1 weighted imaging 97,2%, of CT Sialography 89,7% and of MR Sialography 100%.The specificity of all methods was 100% The differentiation of the malignant from the benign lesions using imaging criteria such as echogenicity, density, signal intensity, homogeneity and outline of the mass was not possible.Distal enhancement of the echos on US was shown only with benign lesions and lymphoma but not with malignant tumors. The irregular outline was seen with malignant but also with large benign tumors. The majority of lymphadenomas (92%) however showed well defined outline and in 62% homogenous parencyma. Insertions of Lipiodol within the lesions on CT Sialography was demonstrated with malignant but also with inflammatory and benign masses. Associated lymphadenopathy in older than 45 years old patients was malignant in all cases, where in the majority of the younger than 45 years old patients was inflammatory in origin. Infiltration of the subcutaneous fat and regional muscles was seen mainly with malignant tumors, however similar findings were shown also with inflammatory processes. The low intensity curvilinear structures seen on T1 weighted MR images (shown in 84% of the normal and 69% of the cases with parotids tumors) were delineated better after the intraductal gadolinium injection (MR Sialography) and proved to represent parotid ducts on CT Sialography. The facial nerve itself was indistinguishable form the parotid gland in all our imaging methods. However, using the main parotid duct as a landmark we tried to distinguish the deep from the superficial parotid lesions in relationship to the facial nerve in the cases we delineated both the parotid duct and tumor. The way of displacement of the main parotid duct (but not the parotid duct branches) was helpfull in this differentiation. In the 76% of the intraparotid tumors without displacement of the main parotid duct, lesions medially to the parotid duct plane were deep lesions and lesions lateral to the parotid duct were superficial. In the 24% of the intraparotid lesions with displacement of the parotid duct by the lesion, the medial, anterior, posterior, upwards and downwards displacement of the parotid duct was shown with superficial lobe lesions and the lateral displacement with deep lobe lesions. Deep lesions beyond the mandibular angle were not involving the main parotid duct but were displacing the vessels (retromandibular vein and superficial temporal artery) laterally. However superficial lesions within the lower pole of the parotid gland inspite their extension beyond the mandibular angle they were not involving the main parotid duct but they displaced the above vessels anteriorly or and medially. The normal size of the parotid gland was 10-40 mm (measured from the posterior point of the mandibular angle to the outer surface of the parotid gland) (mean 21,1 mm). The distance of the parotid duct from the posterior aspect of the mandibular angle was 4-23 mm (mean 11,5 mm). This distance was increasing according to the size of the parotid gland suggesting the possibility of similar variation of the position of the facial nerve within the parotid gland .
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Απεικονιστική διερεύνηση παρωτιδικών μαζών, συγκριτική μελέτη με υπέρηχους, αξονική τομογραφία, μαγνητική τομογραφία, αξονική και μαγνητική σιελογραφία
