Differentiation of malignant and benign lung lesions with diffusion-weighted MR imaging

BACKGROUND: The aim of the study was to evaluate the role of diffusion-weighted magnetic resonance imaging in the differential diagnosis of lung lesions. PATIENTS AND METHODS. Sixty-seven patients with lung lesions (48 malignant, 19 benign) were included in this prospective study. Signal intensities (SIs) were measured in diffusion-weighted MR images that were obtained with b=0, 500 and 1000 s/mm(2) values. Apparent diffusion coefficient (ADC) maps were calculated by using images with b=0 and 1000 s/mm(2) values. The statistical significance was determined using the Student-t test. RESULTS: The SIs of malignant lesions were significantly higher than those of benign lesions (p<0.004 for b=0 s/mm(2) and p<0.000 for the other b values). Using b=500 s/mm(2), SI≥391 indicated a malignant lesion with a sensitivity of 95%, specificity of 73% and positive predictive value of 87%. Using b=1000 s/mm(2), SI≥277 indicated a malignant lesion with a sensitivity of 93%, specificity of 69% and positive predictive value of 85%. There was no significant difference between malignant and benign lesions regarding ADC values (p=0.675). There was no significant difference in SIs or ADC values between small cell carcinoma and non-small cell carcinoma. When comparing undifferentiated with well- partially differentiated cancers, SIs were higher with all b values, but the difference was statistically significant only with b=1000 s/mm(2) (p<0.04). CONCLUSIONS: Diffusion-weighteted MR trace image SI is useful for the differentiation of malignant versus benign lung lesions.