1 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2018;47:1003-1012.

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.

Background T1 mapping can potentially quantitatively assess the intrinsic properties of tumors. B1 correction can reduce the magnetic field inhomogeneity. Purpose To assess the repeatability and reproducibility of B1‐corrected T1 mapping for lung cancer and the ability to identify pathological types. Study Type Prospective reproducibility study. Population Sixty lung cancer patients (22 with emphysema) with a total of 60 lesions (adenocarcinoma [n = 23], squamous cell carcinoma [n = 19], and small‐cell lung cancer [SCLC] [n = 18]). Field Strength/Sequence A 3 T/B1‐corrected 3D variable flip angle T1 mapping and free‐breathing diffusion‐weighted imaging. Assessment Intraobserver, interobserver, and test–retest reproducibility of minimum, maximum, mean, and SD of lung tumor T1 values were assessed. The correlation between mean T1 and apparent diffusion coefficient (ADC) and differences between different histological types of lung cancer were evaluated. Statistical Tests Intraclass correlation coefficients (ICCs), within‐subject coefficients of variation (WCVs), Bland–Altman plots, Pearson's correlation coefficient (r), and analysis of variance (ANOVA). A P value <0.05 was considered to be statistically significant. Results No significant differences were found in minimum, maximum, mean, and SD T1 values for repeated measurements (intraobserver and interobserver) and repeated examinations (P = 0.103–0.979). All parameters showed good intraobserver, interobserver and test–retest reproducibility (ICC, 0.780–0.978), except the maximum T1 value (ICC, 0.645–0.922). The mean T1 exhibited the best reproducibility and repeatability, with an average difference <6% for repeated measurements, <8% for repeated scans in lung cancer patients, and<10% for repeated scans in those with emphysema. The mean T1 correlated moderately with ADC (r = −0.580, −0.516, and −0.511 for observers A, B, and C). Both mean T1 and mean ADC were significantly different in SCLC patients compared with those in adenocarcinoma and squamous cell carcinoma patients. Data Conclusion The mean T1 from B1‐corrected T1 mapping is a repeatable parameter with the potential to identify histological types of lung cancer and thus may be a promising imaging biomarker for characterizing lung cancer. Evidence Level 1 Technical Efficacy Stage 2