Diffusion-weighted MRI of pulmonary lesions: Comparison of apparent diffusion coefficient and lesion-to-spinal cord signal intensity ratio in lesion characterization.

PURPOSE: To evaluate the diagnostic performance of minimum apparent diffusion coefficient (ADCmin ) and lesion-to-spinal cord signal intensity ratio (LSR) in the differentiation of benign and malignant pulmonary lesions. MATERIALS AND METHODS: Forty-seven patients (36 men, 11 women; range, 17-81 years) with 62 pulmonary lesions underwent magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) performed using a 1.5T scanner during free-breathing using b 600 s/mm2 . The ADCmin values and LSR were calculated. A receiver operating characteristic (ROC) curve analysis was performed to detect the threshold value of the ADCmin and LSR values for discrimination between benign and malignant pulmonary lesions. RESULTS: There were 42 malignant (33 primary tumors, 9 metastases) and 20 benign lesions. The mean ADCmin ± standard deviations (×10-3 mm2 /s) were 1.45 ± 0.33 for malignant tumors, and 2.4 ± 0.69 for benign lesions (P < 0.001). The mean LSR ± standard deviations for lung cancer was 1.24 ± 0.78, and for benign lesions was 0.55 ± 0.57 (P < 0.001). The area under the ROC curve for ADCmin (0.931; 95% confidence interval [CI]: 0.868-0.993) was greater than that for LSR (0.801; 95% CI: 0.675-0.926) (P = 0.029). For benign/malignant discrimination, the ROC curve showed threshold value of ADCmin to be 1.78 × 10-3 mm2 /s and that of LSR to be 0.86. Using these cutoff values, accuracy of ADCmin and LSR were 89%, 74%, respectively (P = 0.383). CONCLUSION: Being a contrast-free and radiation-free technique, DWI allows discrimination of benign and malignant lung lesions. The ADCmin value performed marginally better than LSR values in distinction of benign and malignant lesions. LEVEL OF EVIDENCE: 1 J. Magn. Reson. Imaging 2017;45:845-854.