| Part I:Value of Manifestations of Magnetic Resonance Imaging?MRI?in Differential Diagnosis of Salivary Gland TumorsObjective:To evaluate the value of the morphological features of MRI in differential diagnosis of salivary gland tumors.Methods:MRI manifestations of 108 cases with salivary gland tumors confirmed pathologically were retrospectively analyzed.Conventional T1WI and CHESS T2WI sequence were used in MRI unenhancement scan,and all cases were examined with both unehancement and enhancement.The localization,contour,margin,signal intensity,enhancing type,homogeneity,infiltration into the adjacent structures,and lymph node metastasis detected by MRI were compared with relevant pathologic results.We then analyzed the imaging characteristics among different types of salivary gland tumors.Results:?1?108 cases?116 lesions?of salivary gland tumors were located in parotid gland?101 lesions?,submandibular gland?6 lesions?and minor salivary gland of nasal cavity?1 lesions?,including 98 benign tumors?52 pleomorphic adenomas,32 Wathin tumors,6 basal cell adenomas,5 myoepitheliomas,2 hemangiomas and 1 lipoma?and 18malignant tumors?5 mucoepidemoid carcinomas,4 acinic cell carcinomas,3 adenoid cystic carcinomas,2 lymphoepithelial carcinomas,1 squamous cell carcinoma,1carcinoma ex pleomorphic adenoma,1 lymphoma,1 metastatic tumor?.?2?The MRI features of common salivary gland benign tumors were as follows:The majority of benign mass showed regular shape?71/98?and clear margin?66/98?.All 52 cases of pleomorphic adenoma demonstrated high signal intensity in T2WI and were characterized by delayed enhancement.Of these 52 cases,40 cases showed inhomogeneous signal intensity,and 6cases appeared as multiple separate nodules in a single parotid gland.All 32 cases of Warthin's tumor enhanced moderately and 18 cases showed equal signal intensity in T2WI.Of these 32 cases,24 lesions demonstrated cystic degeneration with multiple signal intensity.In 6 cases of basal cell adenoma,3 cases presented cystic changes as mottled or crack form.In 5 myoepitheliomas,3 lesions showed lobulated configuration and 4 lesions showed predominantly cystic degeneration.2 cases of hemangioma were characterized by their irregular shape and marked enhancement.?3?The MRI features of common salivary gland malignant tumors were as follows:The majority of malignant masses showed irregular shape?11/18?and unclear margin?14/18?.In 5 cases of mucoepidermoid carcinoma,3 cases of low-and moderate-grade malignant mucoepidermoid carcinomas were cystic solid masses with well-defined margin.However,2 cases of moderate-and high-grade malignant mucoepidermoid carcinoma were solid masses with ill-defined margin.In 3 cases of adenoid cystic carcinoma,2 lesions were characterized by extensive invasion of surrounding parotid gland.In 4 cases acinic cell carcinoma,1 case showed low-grade malignant acinic cell carcinoma,which had regular shape and clear margin,and was difficult to distinguish from benign tumor.1 case with lesion diameter greater than 3cm showed obvious infiltration characteristics.1 case of malignant pleomorphic adenoma showed high signal and predominantly cystic degeneration in T2WI together with irregular shape and ill-defined margin.Conclusion:MRI is an important modality for the diagnosis of salivary gland tumors.Most of the common salivary gland tumors have characteristic MRI features,which make the differential diagnosis of these tumors possible.Part?Diagnostic Value of Diffusion-weighted Imaging Combined with Dynamic Contrast-enhanced MR Imaging in Salivary Gland TumorsObjective:To explore the value of DWI combined with dynamic contrast-enhanced MR imaging?DCE-MRI?in differential diagnosis of benign and malignant salivary gland tumors,and to determine the possibility of appling the two methods in differentiating various types of primary salivary gland tumors.Methods:106 consecutive patients?61 men,45 women;mean age,47.86±16.15years?with clinically suspected salivary gland tumors were examined on a 3.0T MR scanner.DWI was performed by using a single-shot spin-echo echo-planar?SS-SE-EPI?sequence with 3 b-values?0,500,100 s/mm2?.Dynamic contrast-enhanced MR imaging was performed by using GRE T1WI?VIBE?sequence.Time of peak enhancement(Tpeak)and washout ratio?WR?were determined from time-intensity curve?TIC?.TIC patterns were categorized as follows:type A,the Tpeak was more than 120 seconds,and this type was considered to have gradual enhancement;type B,the Tpeak was 120 seconds or less with high WR??30%?,and this type was considered to have early enhancement and high washout;type C,the Tpeak was 120 seconds or less with low WR?<30%?,and this type was considered to have early enhancement and low washout;type D,the TIC was flat,and this type was considered to be non-enhanced or cystic.ROC curve was used to analyze the diagnostic efficacy of ADC values,TIC types and combination of these two methods in diagnosing benign and malignant tumors.Results:?1?90 patients with parotid gland tumors?94 lesions?included 75 benign tumors?39 pleomorphic adenomas,24 Warthin tumors,5 myoepitheliomas,4 basal cell adenomas,2 hemangiomas,1 lopoma?and 19malignant tumors?6 mucoepidermoid carcinoma,4 acinic cell carcinomas,3 adenoid cystic carcinomas,2 lymphoepithelial carcinomas,1 carcinoma ex pleomorphic adenoma,2 lymphomas,1 metastatic tumor?.?2?Benign and malignant parotid tumors had statistical differences in ADC values?P<0.001?.The ADC values of malignant tumors([1.02±0.25]×10-3 mm2/s)were significantly smaller than those of pleomorphic adenomas([1.70±0.26]×10-3 mm2/s;P<0.001)but higher than those of Warthin tumors([0.88±0.16]×10-3 mm2/s;P<0.05).The ADC values of pleomorphic adenomas were significantly higher than those of all other benign epithelial tumors?P=0.001?,except for myoepitheliomas?P=0.123?,and the ADC values of Warthin tumors were significantly smaller than those of all other benign tumors?P<0.001?.?3?Of the 39 pleomorphic adenomas,34 were type A tumors,and 5 were type C tumors.19 of 24 Warthin tumors were type B neoplasms,and 5 were type C neoplasms.2 of 5 myoepitheliomas were type A tumors,and 3 were type C tumors.All basal cell adenomas and hemangiomas were type C neoplasms.All of the malignant tumors,except 1 mucoepidermoid carcinoma and 1carcinoma ex pleomorphic adenoma,were type C neoplasms.1 lopoma had a type D curve.?4?The sensitivity was 0.62 and the specificity was 0.92,when type A?persistent?,B?washout?,and D?flat?tumors were regarded as benign and type C?plateau?tumors as malignant.Sensitivity and specificity were significantly improved?0.92 and 0.95,respectively?in diagnosis of malignant tumors when type C and ADC<1.36×10-3 mm2/s were combined.Conclusion:?1?Due to an overlap within benign and malignant parotid tumors,the diagnosis should not be addressed on the basis of ADC values alone.The TIC manifestations,type A,B or D on DCE-MRI indicates benign parotid tumors,and type C indicates malignant diseases in most cases.When the TIC is type C,combining ADC value can improve the differential diagnostic efficacy of benign and malignant parotid tumors.?2?There are differences in ADC values among benign parotid epithelial tumors,and DWI may have the potential to differentiate histologic subtypes of parotid tumors.Part?Preliminary Study of Intravoxel Incoherent Motion Diffusion-weighted Imaging of Salivary Gland tumorsObjective:To prospectively determine the value of intravoxel incoherent motion?IVIM?parameters?pure diffusion coefficient,D,perfusion-related inxoherent microcirculation,D*and microvascular volum fraction,|?in differentiating various histological types of primary salivary gland tumors.Methods:101 consecutive patients?58 men,43 women;median age,47 years?with clinically suspected salivary gland tumors were examined on a 3.0T MR scanner.DW imaging was performed by using a single-shot echo-planar sequence with 11 b-values?0,10,20,30,50,80,100,200,300,400,800 s/mm2?.The perfusion and diffusion of salivary gland tumors were assessed on the basis of the IVIM theory.The Mann-Whitney test was used to compare IVIM parameters in various histologic types of salivary gland tumors.ROC curve was used to analyze the diagnostic power of each parameter.Results:?1?Successful IVIM DWI were acquired in 87 patients?91 lesions?with a total of 76 benign salivary gland tumors?42 pleomorphic adenomas,23 Warthin tumors,5myoepitheliomas,4 basal cell adenomas,2 hemangiomas?and 15 malignant tumors?4mucoepidermoid carcinoma,4 acinic cell carcinomas,2 adenoid cystic carcinomas,2lymphoepithelial carcinomas,1 carcinoma ex pleomorphic adenoma,1 lymphoma,1metastatic tumor?.Tumors were located in parotid gland?85 cases?and submandibular gland?6 cases?.?2?The D values of malignant tumors(0.98×10-3 mm2/s±0.30)were significantly different from those of pleomorphic adenomas(1.61×10-3 mm2/s±0.24)[P<0.01]and Warthin tumors(0.72×10-3 mm2/s±0.17)[P<0.01].The D*values of malignant tumors(26.63×10-3 mm2/s)were significantly higher than those of pleomorphic adenomas(14.27×10-3 mm2/s)[P<0.01]but smaller than those of Warthin tumors(44.90×10-3 mm2/s)[P<0.01].The D values of pleomorphic adenomas were significantly higher than those of all other benign epithelial tumors[P<0.05],except for myoepitheliomas.Differences were significant for D*values among benign epithelial tumors[P<0.05].?3?ROC curve disclosed that the area under curves?AUC?were 0.997,0.997 for differential diagnosis of pleomorphic adenomas from Warthin tumors for the D and D*value,and the sensitivity and specificity were 0.98,0.95 and 0.95,0.98 respectively.The area under curves?AUC?were 0.94,0.85 for differential diagnosis of pleomorphic adenomas from malignant tumors,and the sensitivity and specificity were 0.95,0.80 and 0.80,0.81 respectively.The area under curves?AUC?were 0.75,0.80 for differential diagnosis of Warthin tumors from malignant tumors,and the sensitivity and specificity were 0.73,0.95 and 0.95,0.77respectively for D and D*value.Conclusion:The IVIM parameters?D,D*?have high efficacy in differentiating pleomorphic adenomas,Warthin tumors and malignant tumors.Different histologic types of salivary gland tumors have different IVIM parameters.IVIM DWI may has the potential to differentiate benign and malignant tumors,and different histologic subtypes of salivary gland tumors. |
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