Evaluation of mediastinal lymph node with diffusion weighted imaging (DWI)

AIM: Diffusion-weighted magnetic resonance imaging (DWI) make it possible to detect malignant lesions based on the difference in the diffusion of water molecules among tissues. The aim of this study are to evaluate DWI, in the differentation between malignant and benign mediastinal lymph nodes.MATERIAL AND METHODS: 43 consecutive patient with 75 enlarged (>10 mm) mediastinal lymph nodes underwent MR imaging at 1,5T. DWI was performed using a sigle-shot echo-planar (SSEPI) MR imaging sequence with b-values (b: diffusion factor) of 0-600 s/mm². Apparent diffusion coefficent (ADC) maps were reconstructed for all patients and ADC values were calculated for each lymph node. ROC ( receiver operating characteristic) curve analysis was performed.RESULTS: Mediastinal lymph node enlarment was secondary to granulomatous disease (27), non-small cell cancer (13), reactive lymphadenitis (14), sinus hystiositosis (7), small cell cancer (7), prostate cancer (3), breast cancer (2), neuroendocrine cancer (1), and mantle zone lymphoma (1). The mean ADC values (x10?³ mm²/s) were 0,765±0,277 for metastatic lymph nodes and 1,429±472 for benign mediastinal lymph nodes. ADC values of the mediastinal lymph nodes were significantly lower than ADC values of benign lymph nodes. %84 of lesions were correctly classified as benign or malign using a threshold ADC value of 1008x10?³ mm²/sCONCLUSION: According to our first experience, DWI using a SSEPI sequence allows reliable differentiation between benign and malign mediastinal lymph nodes.KEY WORDS: Mediastinal lymph nodes, diffusion-weighted MR imaging, apparent diffusion coefficiency