[3.0T MR diffusion-weighted imaging: evaluating diagnosis potency of pulmonary solid benign lesions and malignant tumors and optimizing b value].

BACKGROUND AND OBJECTIVE: Diffusion is caused by random translational molecular motion, also known as Brownian water motion. Diffusion-weighted imaging (DWI) is the only imaging method that can be used to evaluate the diffusion process in vivo. The aim of this study is to evaluate 3.0T magnetic resonance imaging (MRI) DWI with phased-array coil and the array spatial sensitivity encoding technique (ASSET) of diagnosis potency in the discrimination of pulmonary solid benign lesions and malignant tumors. This study also aims to optimize b value.

METHODS: One hundred and sixteen patients with 120 lesions confirmed by pathology and clinical diagnosis underwent T2 weighted imaging (T2WI), T1 weighted imaging, T2WI fat suppression, and DWI (diffusion factors of 200 s/mm², 500 s/mm², 800 s/mm², 1,000 s/mm²) examinations by ASSET with 3.0T MR. The signal intensity of DWI images and the apparent diffusion coefficient (ADC) values of the lesions were measured. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and ADC were compared among different b values. Receiver operating characteristic (ROC) curves were analyzed and the b values were optimized.

RESULTS: Both the SNR and CNR significantly differed among varied b values (P<0.001, P=0.002). The ADC values of pulmonary solid benign lesions and malignant tumors were gradually reduced with increasing b value, and the differences were statistically significant (P<0.001, P<0.001). ROC analysis shows that the area under curve (AUC) values were 0.831, 0.876, 0.813, 0.785 (b=200 s/mm², 500 s/mm², 800 s/mm², 1,000 s/mm², respectively). The AUC with a b value of 500 s/mm² was the largest. The optimal threshold of ADC was 1.473×10⁻³ mm²/s, and the sensitivity and specificity were 80% and 84%, respectively.

CONCLUSION: 3.0T MR DWI with phased-array coil and ASSET has moderate diagnosis potency in differentiating pulmonary solid benign lesions and malignant tumors. The optimal b value is 500 s/mm².