Abstract
Purpose
To prospectively determine whether the diffusion‐weighted magnetic resonance imaging is useful to distinguish between malignant and benign mediastinal lymph nodes.
Materials and Methods
Thirty‐five patients (14 women, 21 men; mean age 52 years) with 91 lymph nodes in the mediastinum detected by computed tomography underwent 1.5 Tesla (T) diffusion‐weighted MR imaging before mediastinoscopy (n = 29) and mediastinotomy (n = 6). Diffusion‐weighted MR images were acquired with a b factor of 50, and 400 s/mm^2^ using single‐shot echo‐planar sequence.
Results
Of the 35 patients, 18 had diagnosis of malignant tumor. Of the 18 patients with tumor, 8 had nonsmall cell carcinoma, and 10 had small cell carcinoma. Ninety‐one mediastinal lymph nodes were detected in the 35 untreated patients: 19 were pathologically diagnosed as metastatic lymph nodes, and 72 lymph nodes were diagnosed as nonmetastatic lymph nodes, including 50 sarcoidosis, 14 reactive lymphoid hyperplasia, and 8 necrotizing granulamatous lymphadenitis. The apparent diffusion coefficient (ADC) was significantly lower in metastatic lymph nodes (1.012 ± 0.025 × 10^−3^ mm^2^/s; P < 0.0005) than in benign lymph nodes (1.511 ± 0.075 × 10^−3^ mm^2^/s). On the ADC map, malignant nodes showed hyperintense (n = 2, 10.52%), hypointense (n = 14, 73.68%), and mixed intensity (n = 3; 15.78%), whereas benign nodes showed hyperintense (n = 57; 79.16%), hypointense (n = 3; 41.6%), isointense (n = 6; 8.33%), and mixed intensity (n = 6; 8.33%).
Conclusion
Diffusion‐weighted MR with ADC value and signal intensity can be useful in differentiation of malignant and benign mediastinal lymph nodes. J. Magn. Reson. Imaging 2009;30:292–297. © 2009 Wiley‐Liss, Inc.