Diagnostic Value Of3.0T MR Diffusion-weighted Imaging In Pulmonary Solid Benign Lesions And Malignant Tumors

Objective To evaluate3.0T MR DWI with phased-array coil and array spatial sensitivity encoding technique (ASSET) of diagnosis potency in discrimination of pulmonary solid benign lesions and malignant tumors, and to optimize b value; To investigate the application value of DWI signal intensities characters and ADC values in discrimination and evaluation of pulmonary solid benign lesions and malignant tumors.Materials and Methods One hundred and fifty-four patients (92men,62women; mean age,57.47years) with one hundred and sixty-seven lesions collected from Tianjin Medical University General Hospital from June2009to October2011were enrolled in this study.116patients with120lesions underwent conventional MR and DWI examinations with different b values (200,500,800,1000s/mm2) using ASSET with3.0T MR. The signal intensity of DWI images and the apparent diffusion coefficient (ADC) values of the lesions were measured respectively. Signal to noise ratio (SNR), contrast to noise ratio (CNR) and ADC were compared among different b values. ROC curves were analyzed to compare the diagnosis potency in discrimination of pulmonary solid benign lesions and malignant tumors, and to optimize b value. All154patients underwent conventional MR and DWI examinations with the optimal b value using ASSET with3.0T MR. DWI and ADC images were obtained by post processing. Signal intensities of DWI and ADC images were evaluated referring to the thoracic muscles, and ADC values of the lesions were measured. The following analysis was subsequently done:①The signal intensities characters of DWI and ADC images in discrimination of pulmonary solid benign lesions and malignant tumors.②Quantitatively analyse of ADC values in discrimination and evaluation of pulmonary solid benign lesions and malignant tumors with the optimal b value.Results①The SNR of DWI images attenuated seriously with the increase of b value with a statistical significance (P<0.001), The SNR with b value of200s/mm2had the largest SNR. The CNR of DWI images increased at first with the increase of b values to some extent and then gradually dropped down with a statistically significance (P=0.002). The CNR was largest when b value was500s/mm2. ADC values of both pulmonary solid benign lesions and malignant tumors attenuated significantly with the increase of b value (P<0.001, P<0.001). The ROC analysis showed the area under curve (AUC) were0.831,0.876,0.813,0.785, respectively, for four different b values. AUC was largest when b value was500s/mm2. The optimal threshold of ADC was1.473×10-3mm2/s, and the sensitivity and specificity were80%and84%.②With b value of500s/mm2, most malignant lesions had a tendency to demonstrate moderate intensity or hyperintensity, while most benign lesions tended to show moderate intensity or hypointensity on DW images.③With b value of500s/mm2, ADC values of malignant lesions((1.242±0.274) X10-3mm2/s) were significantly lower than that of benign lesions((1.815±0.485)×10-3mm2/s)(P=0.000). As a ADC values of1.473×10-3mm2/s was considered as a threshold, the sensitivity and specificity were78.6%,84.9%, respectively. And the AUC was0.843. There was significant difference between the ADC values of SCLC and NSCLC, and among those of the malignant pulmonary lesions (P=0.000,P=0.024).Conclusion3.0T MR DWI with phased-array coil and ASSET has moderate diagnosis potency to differentiate pulmonary solid benign lesions and malignant tumors. The optimal b value is500s/mm2. ADC values are helpful to differentiate pulmonary solid benign lesions from malignant tumors, and it can provide a valuable tool in the evaluation of pulmonary malignant tumors to some extent as well. Therefore, DWI is a beneficial complement for conventional MR examination.