Diagnostic Performance of Diffusion - Weighted Imaging for Multiple Hilar and Mediastinal Lymph Nodes with FDG Accumulation

Background: It is sometimes difficult to assess patients who have multiple hilar and mediastinal lymph nodes(MHMLN) with FDG accumulation in PET-CT. Since it is uncertain whether diffusion-weighted magneticresonance imaging (DWI) is useful in the assessment of such patients, its diagnostic performance was assessed.Materials and
Methods: Twenty-three patients who had three or more stations of hilar and mediastinal lymphnodes with SUVmax of 3 or more in PET-CT were included in this study.
Results: For diagnosis of disease, therewere 20 malignancies (lung cancers 17, malignant lymphomas 2 and metastatic lung tumor 1), and 3 benigncases (sarcoidosis 2 and benign disease 1). For diagnosis of lymph nodes, there were 7 malignancies (metastasisof lung cancer 7 and malignant lymphoma 1) and 16 benign lymphadenopathies (pneumoconiosis/silicosis 7,sarcoidosis 4, benign disease 4, and atypical lymphocyte infiltration 1). The ADC value (1.57±0.29 ×10-3mm2/sec) of malignant MHMLN was significantly lower than that (1.99±0.24 ×10-3mm2/sec) of benign MHMLN(P=0.0437). However, the SUVmax was not significantly higher (10.0±7.34 as compared to 6.38±4.31) (P=0.15).The sensitivity (86%) by PET-CT was not significantly higher than that (71%) by DWI for malignant MHMLN(P=1.0). The specificity (100%) by DWI was significantly higher than that (31%) for benign MHMLN (P=0.0098).Furthermore, the accuracy (91%) with DWI was significantly higher than that (48%) with PET-CT for MHMLN(P=0.0129).
Conclusions: Evaluation by DWI for patients with MHMLN with FDG accumulation is useful fordistinguishing benign from malignant conditions.