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Master Thesis

Caractérisation des masses médiastinales antérieures en IRM avec séquence de diffusion

Abstract : Purpose: to assess the effectiveness of MRI using chemical-shift sequence and DWI to characterize mediastinal anterior masses (MAM). Methods: a retrospective analysis was performed of patients referred for a MAM between 2000 and 2017. Patients were classified as benign (rebounds, lipoma, normal thymus) and a ‘non-typically benign’ (lesions needing further investigations or malignant) MAM. Thymic epithelial tumors were classified as low-risk (type A, AB, B1), high-risk thymomas (type B2, B3) and thymic carcinomas. Qualitative analysis of morphological criteria and quantitative analysis of the chemical-shift ratio (CSR) and Apparent Diffusion Coefficient (ADC) were performed. The discrimination capacity of CSR and ADC was evaluated with ROC curves and optimal cutoff points were determined according to the Youden index. The relationship between diagnosis and MRI findings were evaluated with logistic regression models. Results: 64 patients were eligible, 20 with benign MAM (9 males, 11 females, mean age 30.7 years) and 44 with a non-typically benign MAM (25 males, 19 females, mean age 56.7 years). CSR and ADC significantly differed between groups (P<0.01). The CSR optimal cutoff point was 0.885 (sensitivity 93.5%, specificity 88.9%). The ADC optimal cutoff point was 1.3 10-3 mm2/sec (sensitivity 73.3%, specificity 87.5%). MAM tumor probability increased with higher CSR (P=0.02) and lower ADC (P=0.04). A small (P=0.02) homogeneous mass (P=0.02) with homogeneous enhancement (P<0.01) and high ADC value (P=0.03) suggested a low-risk thymoma. Conclusion: CSR and ADC are two independent factors which can be used to characterize MAM.
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Master Thesis
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Marie Gavrel. Caractérisation des masses médiastinales antérieures en IRM avec séquence de diffusion. Médecine humaine et pathologie. 2018. ⟨dumas-01909981⟩

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