Multiparametric Magnetic Resonance Imaging for Assessing Thymic Epithelial Tumors: Correlation With Pathological Subtypes and Clinical Stages

Abstract

Background 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. Purpose To investigate the value of multiparametric MRI in evaluating TETs. Study Type Retrospective. Subjects 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). Field strength/Sequence A 3 T, turbo spin echo imaging, echo planar imaging, volumetric interpolated breath‐hold examination with radial acquisition trajectory. Assessment DCE‐MRI and apparent diffusion coefficient (ADC) variables were compared. Diagnostic performances of single significant factor and combined model were compared. Statistical Tests 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. Results ADC, Ktrans, and kep values were significantly different among low‐risk, high‐risk and carcinoma group (ADC, 1.279 ± 0.345 × 10−3 mm2/sec, 0.978 ± 0.260 × 10−3 mm2/sec, 0.661 ± 0.134 × 10−3 mm2/sec; Ktrans 0.167 ± 0.071 min−1, 0.254 ± 0.136 min−1, 0.393 ± 0.110 min−1; kep 0.345 ± 0.113 min−1, 0.560 ± 0.269 min−1, 0.872 ± 0.149 min−1). They were significantly different for early stage and advanced stage (ADC, 1.270 ± 0.356 × 10−3 mm2/sec vs. 0.845 ± 0.251 × 10−3 mm2/sec; Ktrans 0.179 ± 0.092 min−1 vs. 0.304 ± 0.142 min−1; kep 0.370 ± 0.181 min−1 vs. 0.674 ± 0.362 min−1). The combination of them had highest diagnostic efficiency for WHO classification (AUC, 0.925; sensitivity, 83.7%; specificity, 89.5%), clinical stage (AUC, 0.879; sensitivity, 80.9%; specificity, 82.5%). Data Conclusion Multiparametric MRI model may be useful for discriminating WHO classification and clinical stage of TETs. Evidence Level 4 Technical Efficiency Stage 2

The value of diffusion-weighted and dynamic contrast-enhanced imaging in the diagnosis of thymic epithelial tumors

“…In the same study, the AUC was 0.804 when using an ADC cutoff of 1.25 × 10 -3 mm 2 /sec to differentiate low-risk thymomas from high-risk thymomas and thymic carcinomas. A recent study by Shen et al 18 reported that the mean ADC values of low-risk thymoma, high-risk thymoma, and TC were 1.279 × 10 -3 mm 2 /sec, 0.978 × 10 -3 mm 2 /sec, and 0.661 × 10 -3 mm 2 /sec, respectively. The optimal ADC cutoff to distinguish low-risk thymomas from high-risk thymomas and TCs in the research of Shen et al 18 was 1.193 × 10 -3 mm 2 /sec, which was also lower than the value reported by Razek et al 17 .…”

“…A recent study by Shen et al 18 reported that the mean ADC values of low-risk thymoma, high-risk thymoma, and TC were 1.279 × 10 -3 mm 2 /sec, 0.978 × 10 -3 mm 2 /sec, and 0.661 × 10 -3 mm 2 /sec, respectively. The optimal ADC cutoff to distinguish low-risk thymomas from high-risk thymomas and TCs in the research of Shen et al 18 was 1.193 × 10 -3 mm 2 /sec, which was also lower than the value reported by Razek et al 17 . The ADC values of the TETs in our study were lower compared with the results of both Razek et al 17 and Shen et al 18 .…”

“…Technically, the ADC value decreases when the b values increase 19 . Our study employed b values of 0, 500, and 2000, while Razek et al 17 and Shen et al 18 used values of 0, 400, and 800 sec/mm 2 and 0 and 1000 sec/mm 2 , respectively. Additionally, due to the rarity of TETs, the sample sizes of all three studies were relatively small, making them prone to selection bias.…”

“…The optimal ADC cutoff to distinguish low-risk thymomas from high-risk thymomas and TCs in the research of Shen et al [18] was 1.193 × 10 -3 mm 2 /sec, which was also lower than the value reported by Razek et al [17]. The ADC values of the TETs in our study were lower compared with the results of both Razek et al [17] and Shen et al [18]. The difference may be due to variations in the chosen DW-MRI parameters, specifically b values.…”

Editorial for “Multiparametric MRI for Assessing Thymic Epithelial Tumors: Correlation With Pathological Subtypes and Clinical Stages”

“…In this issue of Journal of Magnetic Resonance Imaging, a publication by Shen et al entitled "Multiparametric MRI for assessing TETs: Correlation with Pathological Subtypes and Clinical Stages" evaluated biomarkers to be integrated into an improved risk prediction model for thymic tumors. 7 The study assessed the value of a combination of DCE-MRIderived parameters and ADC values for differentiation in the WHO classification and Masaoka-Koga staging system. The authors concluded that the quantitative parameters ADC, Ktrans, and Kep were valuable for discrimination of both WHO classification and clinical stage of TETs.…”