Can diffusion weighted MRI differentiate between inflammatory-infectious and malignant pleural effusions?

To assess exudative pleural effusions with diffusion-weighted magnetic resonance imaging (DW-MRI) in order to determine non-invasive differentiation criteria for inflammatory-infectious and malignant effusions.

Thirty-two patients with pleural effusions underwent DW-MRI with 4 different b values (10, 500, 750 and 1000 s/mm2). ADC maps were generated automatically. Signal intensity and ADC values were measured. Following MRI, pleural fluid of 10-15 ml was obtained and analyzed. AUC values were compared for different diffusion levels of ADC and SI measurements. The relationship between ADC values and pleural effusion LDH and total protein levels was examined.

The cut-off values obtained from signal intensity and ADC measurements to differentiate exudates with malignant pathology were not found to be statistically significant. In the inflammatory-infectious group, a significant negative correlation was observed between ADC values and pleural fluid LDH measurements in all b values. In the malignant group, a significant positive correlation was observed between ADC values and pleural fluid total protein measurements in b values of 500 and 1000.

Infectious/inflammatory and malignant effusions overlap strongly and cannot therefore be differentiated using DW MRI.