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

Abstract

To evaluate the diagnostic performance of minimum apparent diffusion coefficient (ADC_min) and lesion-to-spinal cord signal intensity ratio (LSR) in the differentiation of benign and malignant pulmonary lesions. 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 ADC_min values and LSR were calculated. A receiver operating characteristic (ROC) curve analysis was performed to detect the threshold value of the ADC_min and LSR values for discrimination between benign and malignant pulmonary lesions. There were 42 malignant (33 primary tumors, 9 metastases) and 20 benign lesions. The mean ADC_min ± 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 ADC_min (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 ADC_min to be 1.78 × 10⁻³ mm²/s and that of LSR to be 0.86. Using these cutoff values, accuracy of ADC_min and LSR were 89%, 74%, respectively (P = 0.383). Being a contrast-free and radiation-free technique, DWI allows discrimination of benign and malignant lung lesions. The ADC_min 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.