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World Health Organization classification and Masaoka-Koga stage are widely used for thymic epithelial tumors (TETs). Reduced field-of-view (rFOV) diffusion-weighed imaging (DWI) proved to improve the image quality. Dynamic contrast-enhanced (DCE) MRI was commonly used in evaluating tumors.To investigate the value of multiparametric MRI in evaluating TETs.Retrospective.Eighty-seven participants including 38 low risk (52.08 ± 14.19 years), 30 high risk (52.40 ± 11.35 years), and 19 thymic carcinoma patients (59.76 ± 10.78 years).A 3 T, turbo spin echo imaging, echo planar imaging, volumetric interpolated breath-hold examination with radial acquisition trajectory.DCE-MRI and apparent diffusion coefficient (ADC) variables were compared. Diagnostic performances of single significant factor and combined model were compared.Parameters were compared using one-way ANOVA or independent-samples t test. Logistic regression was employed to investigate the combined model. Receiver operating curves (ROC) and DeLong's test were used to compare the diagnostic efficiency.ADC, KMultiparametric MRI model may be useful for discriminating WHO classification and clinical stage of TETs.4 TECHNICAL EFFICIENCY: Stage 2.

Background Previous studies indicated that dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) could serve as a useful biomarker for differentiating malignant from benign orbital lymphoproliferative disorders (OLPDs). Purpose To investigate the influence of different region of interest (ROI) selection methods on the measurements of DCE-MRI parameters, and their diagnostic ability in discriminating malignant from benign OLPDs. Study Type Retrospective study. Population In all, 46 patients with OLPDs (22 benign and 24 malignant). Field Strength/Sequence 3.T DCE-MRI using a 2D turbo fast low angle shot sequence postcontrast. Assessment DCE-MRI data were analyzed using three different ROI selection methods, including whole-tumor ROI (ROIWT), single-slice ROI (ROISS) and hot-spot ROI (ROIHS). Quantitative parameters (Ktrans, Kep, Ve) were calculated based on a modified Tofts model. Statistical Testing Analysis of variance test, intraclass correlation coefficient (ICC), Bland–Altman plots, independent t-test, and receiver operating characteristic curve analyses were used for statistical analyses. Results The time required for outlining ROIWT was significantly longer than ROISS and ROIHS (P < 0.001). The measurements of DCE-MRI-derived parameters based on ROIHS demonstrated lowest ICC, followed by ROISS and ROIWT. Malignant OLPDs showed significantly higher Kep than benign mimics (P < 0.001), while no significant differences were found on Ktrans (ROIWT, P = 0.535; ROISS, P = 0.557; ROIHS, P = 0.400) and Ve (ROIWT, P = 0.071; ROISS, P = 0.079; ROIHS, P = 0.057). Kep-ROIWT showed the highest area under curve for differentiating malignant from benign OLPDs, followed by Kep-ROISS, and Kep-ROIHS; however, the differences were not significant (ROIWT vs. ROISS, P = 0.407; ROIWT vs. ROIHS, P = 0.363; ROISS vs. ROIHS, P = 0.887). Data Conclusion ROI selection methods could have an influence on the measurements of DCE-MRI parameters. Taking measurement time, reproducibility, and diagnostic ability into account, we suggest single-slice ROI to be used for differentiating malignant from benign OLPDs in clinical practice. Level of Evidence: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017.

Purpose To evaluate the diagnostic performance of extended models of diffusion-weighted (DW) imaging to help differentiate the epidermal growth factor receptor (EGFR) mutation status in stage IIIA-IV lung adenocarcinoma. Materials and Methods This retrospective study had institutional research board approval and was HIPAA compliant. Preoperative extended DW imaging including intravoxel incoherent motion (IVIM) and diffusional kurtosis imaging (DKI) 3 Tesla MRI were retrospectively evaluated in 53 patients with pathologically confirmed non-early stage (IIIA-IV) lung adenocarcinoma. EGFR mutationsat exons 18–21 were determined by using polymerase chain reaction-based ARMS. Quantitative parameters (mean, kurtosis, skewness, 10th and 90th percentiles) of IVIM (true-diffusion coefficient D, pseudo-diffusion coefficient D*, and perfusion fraction f) and DKI (kurtosis value Kapp, kurtosis corrected diffusion coefficient Dapp) were calculated by outlining entire-volume histogram analysis. Receiver operating characteristic analysis was constructed to determine the diagnostic performance of each parameter. Multivariate logistic regression was used to differentiate the probability of EGFR mutation status. Results Twenty-four of 53 patients with lung adenocarcinoma were EGFR mutations, which occurred most often in acinar (10 of 13 [76.9%]) and papillary predominant tumors (9 of 13 [69.2%]). Patients with EGFR mutation showed significant higher 10th percentile of D, lower D* value in terms of kurtosis, and lower Kapp value in terms of mean, skewness, 10th and 90th percentiles (all P values

Purpose To evaluate the feasibility of intravoxel incoherent motion (IVIM) for the measurement of diffusion and perfusion parameters in hyperacute strokes. Materials and Methods An embolic ischemic model was established with an autologous thrombus in 20 beagles. IVIM imaging was performed on a 3.0 Tesla platform at 4.5 h and 6 h after embolization. Ten b values from 0 to 900 s/mm2 were fitted with a bi-exponential model to extract perfusion fraction f, diffusion coefficient D, and pseudo-diffusion coefficient D*. Additionally, the apparent diffusion coefficient (ADC) was calculated using the mono-exponential model with all the b values. Statistical analysis was performed using the pairwise Student's t test and Pearson's correlation test. Results A significant decrease in f and D was observed in the ischemic area when compared with those in the contralateral side at 4.5 h and 6 h after embolization (P

Purpose To determine the optimal combination of parameters derived from 3T multiparametric (conventional magnetic resonance imaging [MRI], diffusion-weighted [DW] and dynamic contrast-enhanced [DCE]) MRI for differentiating malignant from benign orbital lymphoproliferative disorders (OLPDs). Materials and methods Forty patients with OLPDs (18 benign and 22 malignant) underwent conventional 3.0T MR, DW, and DCE-MRI examination for presurgery evaluation. Conventional MRI features (including tumor laterality, shape, number of involved quadrants, signal intensity on T1 -weighted imaging (WI) and T2 WI, flow void sign on T2 WI, and findings suggestive of sinusitis) were reviewed, and multivariate logistic regression analysis was used to identify the most significant conventional MRI features. Apparent diffusion coefficient (ADC) and DCE-MRI derived parameters (area under curve [AUC], time to peak [TTP], maximum rise slope [Slopemax ]) were measured and compared between two groups. Receiver operating characteristic (ROC) curve analyses were used to determine the diagnostic ability of each combination that was established based on identified qualitative and quantitative parameters. Results Multivariate logistic regression analysis showed that the presence of flow void sign on T2 WI significantly associated with benign OLPDs (P = 0.034). Malignant OLPDs demonstrated significantly lower ADC (P = 0.001) and AUC (P = 0.002) than benign mimics. ROC analyses indicted that, ADC alone showed the optimal sensitivity (threshold value, 0.886 × 10-3 mm2 /s; sensitivity, 90.9%), while a combination of no presence of flow void sign on T2 WI + ADC ≤ 0.886 × 10-3 mm2 /s + AUC ≤ 7.366 showed optimal specificity (88.9%) in differentiating benign from malignant OLPDs. Conclusion Multiparametric MRI can help to differentiate malignant from benign OLPDs. DWI offers optimal sensitivity, while the combination of conventional MRI, DWI, and DCE-MRI offers optimal specificity. Level of evidence 3 J. Magn. Reson. Imaging 2017;45:167-176.

Purpose To determine whether intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) could detect parotid gland abnormalities in Sjogren's syndrome (SS) patients who were not identified by conventional MRI. Materials and methods Ten consecutive patients with clinically proven SS who were not identified by conventional MRI were assessed by IVIM MRI with a 3.0T MRI scanner. Quantitative parameters (tissue diffusivity, D; pseudodiffusion coefficient, D*; perfusion fraction, f) derived from IVIM MRI were compared between the SS group and healthy control group (n = 15). A receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of each significant parameter. Results Excellent inter- and intrareader agreements were obtained during the measurement of D, f, and D* values (interreader, 0.980, 0.942, and 0.883; intrareader, 0.991, 0.952, and 0.896, respectively). All three parameters of the SS group were significantly higher than those of the healthy group (D, 1.049 ± 0.056 × 10(-3) mm(2) /s vs. 0.976 ± 0.116 × 10(-3) mm(2) /s, P = 0.012; D*, 20.410 ± 1.786 × 10(-3) mm(2) /s vs. 18.764 ± 2.433 × 10(-3) mm(2) /s, P = 0.013; f, 0.207 ± 0.003 vs. 0.182 ± 0.002, P = 0.004). ROC analysis showed that the f value had the best diagnostic performance (AUC, 0.712; Sensitivity, 0.80; Specificity, 0.57; Cutoff value, 0.185) in detecting the parotid gland abnormalities in early SS patients. Conclusion IVIM MRI detected parotid gland abnormalities in early-stage SS patients. J. Magn. Reson. Imaging 2016;43:1455-1461.