Diffusion weighted MR imaging of parotid gland tumors.

Transcription

1 Diffusion weighted MR imaging of parotid gland tumors. Poster No.: C-2604 Congress: ECR 2012 Type: Scientific Exhibit Authors: H. ZAGHOUANI BEN ALAYA, M. Gaha, W. Karmani, S. MAJDOUB, L. BEN CHERIFA, H. AMARA, D. BAKIR, K. Bouzouita, C. KRAIEM; Sousse/TN Keywords: DOI: Salivary glands, Oncology, MR, MR-Diffusion/Perfusion, Diagnostic procedure, Neoplasia, Pathology /ecr2012/C-2604 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 14

2 Purpose Several MR imaging based techniques have been evaluated for the diagnosis of benign and malignant salivary gland tumors. In contrast to fine-needle aspiration cytology (FNAC), a noninvasive examination such as MR imaging might provide a diagnosis and also stage the disease. Among the evaluated image-based techniques, diffusionweighted imaging (DWI) seems to have the highest potential to determine different histological subtypes of salivary gland tumors noninvasively. The purposes of this study were to identify the values of the apparent diffusion coefficient (ADC) with diffusion-weighted MR sequences in parotid gland tumors; and to investigate the potential of DWI in differentiating various entities of parotid gland tumors. Methods and Materials Twenty-one patients (9 m, 12 f; mean age 52.3 years) with biopsy-proven parotid masses were examined on a 1,5 T MRI. In addition to conventional MR sequences, a diffusion- weighted MR sequence in the axial plane was acquired using b-values of 0 and 800 mm 2 / s. ADC maps were calculated automatically. The tumors' ADC values as well as the ADC value of the controlateral parotid gland were measured by region of interest (ROI). Results Results: Histopathology revealed 10 pleomorphic adenomas, 4 Warthin tumors, 4 malignant tumors, 1 cyst, and 2 inflammatory masses (pseudotumors). Benign tumors showed a mean ADC value of 1.69±0.45 x10-3 mm 2 /s, which was thus significantly higher (p < 0.001) than mean ADC values of normal parotid tissue (1.04±0.13 x10-3 mm 2 /s) or malignant tumors (1.01±0.37 x10-3 mm 2 /s). The highest ADC values (1.7±0.4 x10-3 mm 2 /s) among all entities were found in pleomorphic adenomas. Warthin tumors showed a mean ADC of 1.37±0.37 x10-3 mm 2 /s. Page 2 of 14

3 Discussion: We investigated the potential of DWI in differentiating various entities of parotid gland tumors. Our results demonstrate that benign parotid tumors can be differentiated with more confidence from malignant entities. In a recently published study by Eida et al, consecutive patients with a single tumor in the parotid or submandibular gland were evaluated. The authors concluded that ADC may provide preoperative tissue characterization of salivary gland tumors by using different b factors (500 and 1000 s/mm 2 ). The predictive ability of the MR imaging criteria based on the ADC levels was assessed by dividing the calculated values in 4 groups (extremely low, low, intermediate, or high). Additionally, ADC levels were calculated from different areas of each tumor. Regarding the areas with extremely high ADCs, the difference between benign and malignant lesions was statistically significant. A comparable evaluation method was performed by Matsushima et al in 32 patients with salivary gland tumors (17 benign, 15 malignant). Considering different degrees of extracellular components, they made comparisons of mean ADC values between benign and malignant tumors and among tumors showing different degrees of extracellular components. In contrast to Eida et al, no significant difference in mean ADC values was found between benign and malignant tumors, and the mean ADC values increased with the degree of extracellular components. On the basis of these results, Matsushima et al concluded that ADC values alone are not sufficient to differentiate benign from malignant salivary gland tumors. In another study, including 45 patients, the drawn conclusion was very promising (b factors, 0, 500, and 1000 s/mm 2 ). Only an overlap within the malignant tumors was observed and additionally between myoepithelial adenomas (n=3) and salivary duct carcinomas (n=3). Pleomorphic adenomas were distinguishable from all 6 other examined entities solely on the basis of the calculated ADC values. In a recent published study by Prades et al, the offered results for determining whether a tumor is benign or malignant on the basis of the morphologic appearance are very promising and might be improved by combining morphologic features and DWIs in a diagnostic noninvasive approach. This is especially promising with regard to the differentiation of pleomorphic adenomas, which were diagnosed with an accuracy of 83%, and Warthin tumors, which were diagnosed with an accuracy of 85%, on the basis of the morphologic appearance. Page 3 of 14

4 Images for this section: Fig. 1: Case 1 : Pleomorphic adenoma ; ADC value 1.98x10-3 mm2/s. Page 4 of 14

5 Fig. 2: Case 1 : Pleomorphic adenoma ; ADC value 1.98x10-3 mm2/s. Page 5 of 14

6 Fig. 3: Case 1 : Pleomorphic adenoma ; ADC value 1.98x10-3 mm2/s. Page 6 of 14

7 Fig. 4: Case 2A : A, Transverse T1-weighted spin-echo MR image from a 47-year-old female patient with a histologically proved Warthin tumor in the left parotid gland (arrow). B, The T2-weighted image also shows a bright signal intensity of the lesion (arrow) with a lesser extent but appearance similar to that of the pleomorphic adenoma C, On the basis of ADC maps, the difference between the pleomorphic adenoma and the Warthin tumor shown (arrow) becomes obvious (mean ADC value: 0.85x10-3 mm2/s). Page 7 of 14

8 Fig. 5: Case 2B : A, Transverse T1-weighted spin-echo MR image from a 47-year-old female patient with a histologically proved Warthin tumor in the left parotid gland (arrow). B, The T2-weighted image also shows a bright signal intensity of the lesion (arrow) with a lesser extent but appearance similar to that of the pleomorphic adenoma C, On the basis of ADC maps, the difference between the pleomorphic adenoma and the Warthin tumor shown (arrow) becomes obvious (mean ADC value: 0.85x10-3 mm2/s). Page 8 of 14

9 Fig. 6: Case 2C : A, Transverse T1-weighted spin-echo MR image from a 47-year-old female patient with a histologically proved Warthin tumor in the left parotid gland (arrow). B, The T2-weighted image also shows a bright signal intensity of the lesion (arrow) with a lesser extent but appearance similar to that of the pleomorphic adenoma C, On the basis of ADC maps, the difference between the pleomorphic adenoma and the Warthin tumor shown (arrow) becomes obvious (mean ADC value: 0.85x10-3 mm2/s). Page 9 of 14

10 Fig. 7: Case 3 : High-grade carcinosarcoma : gadolinium-enhanced images show a welldefined, low-signal encapsulated tumor, with homogeneous and moderate enhancement; on DWI, the ADC was mm2/s. Page 10 of 14

11 Fig. 8: Case 3 : High-grade carcinosarcoma : gadolinium-enhanced images show a welldefined, low-signal encapsulated tumor, with homogeneous and moderate enhancement; on DWI, the ADC was mm2/s. Page 11 of 14

12 Fig. 9: Case 3 : High-grade carcinosarcoma : gadolinium-enhanced images show a welldefined, low-signal encapsulated tumor, with homogeneous and moderate enhancement; on DWI, the ADC was mm2/s. Page 12 of 14

13 Fig. 10: Case 3 : High-grade carcinosarcoma : gadolinium-enhanced images show a welldefined, low-signal encapsulated tumor, with homogeneous and moderate enhancement; on DWI, the ADC was mm2/s. Page 13 of 14

14 Conclusion With DWI, benign parotid tumors can be differentiated with more confidence from malignant entities. However, because of the considerable overlap of ADC values, further differentiation within the benign group is difficult. References 1- Eida S, Ohki M, Sumi M, et al.mrfactor analysis: improved technology for the assessment of 2D dynamic structures of benign and malignant salivary gland tumors. J Magn Reson Imaging 2008;27: Eida S, Sumi M, Sakihama N, et al. Apparent diffusion coefficient mapping of salivary gland tumors: prediction of the benignancy and malignancy. AJNR Am J Neuroradiol 2007;28: Habermann CR, Gossrau P, Graessner J, et al. Diffusion-weighted echo-planar MRI: a valuable tool for differentiating primary parotid gland tumors? Rofo 2005;177: Matsushima N, Maeda M, Takamura M, et al. Apparent diffusion coefficients of benign and malignant salivary gland tumors: comparison to histopathological findings. J Neuroradiol 2007;34: Okahara M, Kiyosue H, Hori Y, et al. Parotid tumors:mrimaging with pathological correlation. Eur Radiol 2003;13(suppl 4):L Thoeny HC. Imaging of salivary gland tumours. Cancer Imaging 2007;7:52-62 Personal Information Page 14 of 14