| Objective:To study the feasibility of diffusion-weighted imaging (DWI) features in lung benign lesions and malignancy, and choose the optimal scan method and b value. To evaluate the DWI performance and apparent diffusion coefficient (ADC) of differential diagnostic value and limits on lung benign lesions and malignancy. Materials and Methods Sixty-four patients with seventy-six lesions of The Affiliated Hospital of Luzhou Medical College from June 2009 to March 2011, who's the diameter of nodules, bump or solid lesions was more than 1 cm, were enrolled in this study,63 cases in them were malignancy and 13cases are benign lesions.38 males,26 females, age from 35 to 77, mean 56.28±10.38 years.64 patients include 51 lung careinomas (22 cases of squamous cell careinoma,14 cases of adenocarcinomas,9 cases of small cell lung carcinoma,4 cases of large cell carcinomas and 2 cases of sarcoma kind cancer),and 12 benign lesions (5 cases of tuberculosis tumor,4 cases of pneumonia,2 cases of inflammatory pseudotumor,2 cases of pulmonary abscess). All of them achieved pathologic confirmation either by operation, biopsy or bronchoscopy etc. All 64 patients underwent DWI examinations, and fifteen of them had both breathless and free breath scan. By comparing the image signal to noise ratio (SNR), contrast to noise ratio (CNR) and ADC values to evaluate the imaging quality differences between breathless scanning and free breathe scanning. Scanning with different b values (0 s/mm2,300 s/mm2,500 s/mm2,600 s/mm2,800 s/mm2) gets DWI and ADC images, measuring signal intensities of DWI and ADC values of the lesions under different b values.Then doing the following analysis:①Observing the performance of DWI and ADC images calculates and compares the differences between groups of SNR, CNR and ADC values under different b values;②Applying ROC curves under different b values analysis the different diagnostic performances of ADC values between malignant pulmonary tumors and solid benign lesions, then selecting the optimal b value and confirm the diagnostic threshold;③Quantitatively analyse the ADC values of lung benign lesions or malignancy with the optimal b value and compare the differences of ADC values between lung benign lesions and malignancy, central and peripheral lung cancer of different histologic types. Results:The images quality of DWI had no significant difference in 1.5 cases with breathless and free breath scan. The SNR of different b values had statistical significance (P=0.000); the SNR with b=300 s/mm2 is the largest. The CNR increases with the b value increased gradually at first and then gradually decreased, when b=500 s/mm2, the group average is the maximum, but the CNR difference between the groups under different b values was not statistically significant (p> 0.05). ADC values of benign and malignant lesions decreased with the increase of b values, the ADC value differences under different b values between groups were statistically significant (p<0.05); when b value=500 s/mm2, ADC values has the highest performance in the diagnosis, ROC area under the curve (Az) is 0.878, the best ADC threshold is 1.473×10-3mm2/s, the sensitivity and specificity were 84.6%,77.8%. When the optimal b value is 500 s/mm2,ADC values of malignancy were 1.241±0.316×10-3 mm2/s,ADC values of benign lesions were 1.819±0.409×10-3 mm2/s,there was statistical significance between ADC values for malignant pulmonary tumors and solid benign lesions(P=0.000),ADC values of malignant tumors were significantly lower than those benign lesions. ADC values of central lung cancer lesions parenchyma were 1.237±0.251×10-3 mm2/s;ADC values of peripheral lung cancer lesions parenchyma were 1.254±0.196×10-3 mm2/s, and the differences didn't have statistical significance (P>0.05). ADC values of adenocarcinoma, squamous cell careinoma, large cell carcinomas, small cell carcinomas and arcoma kind cancer have statistical significance (P<0.05),ADC values of adenocarcinoma were higher than other pathologic types. Conclusion:DWI examination is feasible for assessing malignant pulmonary tumors and solid benign lesions, and realizes quantitative analysis of ADC values of pulmonary lesions, and it may be a new ideal method in diagnosis pulmonary tumors and solid benign lesions. Therefore DWI examination is a beneficial complement for conventional MR examination.
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