The value of diffusion-weighted imaging based on monoexponential and biexponential models for the diagnosis of benign and malignant lung nodules and masses.

OBJECTIVES: The objective is to compare the efficacy of diffusion-weighted imaging (DWI) parameters of mean and minimum apparent diffusion coefficient (ADCmean and ADCmin) and intravoxel incoherent motion (IVIM) in the differentiation of benign and malignant lung nodules and masses. METHODS: Lung lesions measured larger than 1.5 cm on CT were included between August 2015 and September 2018. DWI (10 b-values, 0-1000 s/mm2) scans were performed, and the data were post-processed to derive the ADCmean, ADCmin and IVIM parameters of true diffusion coefficient (D), pseudodiffusion coefficient (D*) and perfusion fraction (f). An independent sample t-test or Mann-Whitney U test was used to compare benign and malignant parameters. Receiver operating characteristic curves were generated and a Z test was used. RESULTS: 121 patients were finally enrolled, each with one lesion. Examined 121 lesions were malignant in 88 (72.7%) and benign in 33 (27.3%). The ADCmean of malignant pulmonary nodules was significantly lower than that of benign pulmonary nodules (t = 3.156, p = 0.006), whereas the other parameters revealed no significant differences (p = 0.162-0.690). Receiver operating characteristic curve analysis revealed that an ADCmean threshold value of 1.43 × 10-3 mm2/s yielded 88.57% sensitivity and 64.29% specificity. While for lung masses, the ADCmean, ADCmin, D and D* values in malignant pulmonary masses were significantly lower (P﹤0.001-0.011). Among them, the D value exhibited the best diagnostic performance when the threshold of D was 1.23 × 10-3mm2/s, which yielded a sensitivity of 90.57% and a specificity of 89.47% (Z = 2.230, 3.958, 2.877 and p = 0.026, ﹤0.001 and 0.004, respectively). CONCLUSION: ADC is the most robust parameter to differentiate benign and malignant lung nodules, whereas D is the most robust parameter to differentiate benign and malignant lung masses. ADVANCES IN KNOWLEDGE: This is the first study to compare all the quantitative parameters of DWI and IVIM mentioned in the literatures for assessing lung lesions; Second, we divided the lesions into lung nodules and lung masses with the size of 3 cm as the boundary.

Lung Cancer: Short-Term Reproducibility of Intravoxel Incoherent Motion Parameters and Apparent Diffusion Coefficient at 3T.

PURPOSE: To prospectively evaluate the short-term reproducibility of intravoxel incoherent motion (IVIM) parameters and apparent diffusion coefficient (ADC) in lung cancer patients. MATERIALS AND METHODS: In all, 50 patients (50 lesions) underwent free-breathing diffusion-weighted imaging (DWI) (b = 0, 300, 800 s/mm2 ) and IVIM (10 b-values, 0-1000 s/mm2 ) scans twice (0.5-1-hour interval) at 3T. Regions of interests (ROIs) were drawn on ADC maps and IVIM images to derive the mean ADC value and IVIM parameters D, D*, and f. Intra- and interobserver, test-retest reproducibility were assessed with intraclass correlation coefficients (ICCs), within coefficient-of-variations (WCVs), and Bland-Altman analysis. The effects of type, size, and location of lung lesions were compared with WCVs. RESULTS: D and ADC showed good intraobserver reproducibility and interobserver agreement, while D* and f showed relatively larger variability (WCV 20.89-34.97%). The test-retest reproducibility of D and ADC were good (ICC 0.763-0.837; WCV 11.12-12.55%), while those of D* and f were relatively poor (ICC 0.604-0.842; WCV 36.54-72.62%). D and ADC had decreased reproducibility for lesions <2 cm (WCV 14.20%, 16.34%, respectively) and for lesions in the lower lung zones (WCV 16.52%, 14.78%, respectively). f had decreased reproducibility in central lung cancers (WCV 50.11%) and lesions >2 cm (WCV 42.64%). D* had even worse reproducibility in peripheral lung cancers (WCV 84.11%) and lesions in the lower lung zones (WCV 80.84%). CONCLUSION: If the change in ADC, D, D*, and f values is less than ∼31%, 34%, 170%, and 130%, respectively, it may be caused by measurement error. The type, size, and location of lung lesions have an effect on measurement errors. LEVEL OF EVIDENCE: 1 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2018;47:1003-1012.