T₂* Mapping from Multi-Echo Dixon Sequence on Gadoxetic Acid-Enhanced Magnetic Resonance Imaging for the Hepatic Fat Quantification: Can It Be Used for Hepatic Function Assessment?

OBJECTIVE: To evaluate the diagnostic value of T₂* mapping using 3D multi-echo Dixon gradient echo acquisition on gadoxetic acid-enhanced liver magnetic resonance imaging (MRI) as a tool to evaluate hepatic function. MATERIALS AND METHODS: This retrospective study was approved by the IRB and the requirement of informed consent was waived. 242 patients who underwent liver MRIs, including 3D multi-echo Dixon fast gradient-recalled echo (GRE) sequence at 3T, before and after administration of gadoxetic acid, were included. Based on clinico-laboratory manifestation, the patients were classified as having normal liver function (NLF, n = 50), mild liver damage (MLD, n = 143), or severe liver damage (SLD, n = 30). The 3D multi-echo Dixon GRE sequence was obtained before, and 10 minutes after, gadoxetic acid administration. Pre- and post-contrast T₂* values, as well as T₂* reduction rates, were measured from T₂* maps, and compared among the three groups. RESULTS: There was a significant difference in T₂* reduction rates between the NLF and SLD groups (−0.2 ± 4.9% vs. 5.0 ± 6.9%, p = 0.002), and between the MLD and SLD groups (3.2 ± 6.0% vs. 5.0 ± 6.9%, p = 0.003). However, there was no significant difference in both the pre- and post-contrast T₂* values among different liver function groups (p = 0.735 and 0.131, respectively). A receiver operating characteristic (ROC) curve analysis showed that the area under the ROC curve for using T₂* reduction rates to differentiate the SLD group from the NLF group was 0.74 (95% confidence interval: 0.63–0.83). CONCLUSION: Incorporation of T₂* mapping using 3D multi-echo Dixon GRE sequence in gadoxetic acid-enhanced liver MRI protocol may provide supplemental information for liver function deterioration in patients with SLD.

Diagnosis of Acute Global Myocarditis Using Cardiac MRI with Quantitative T1 and T2 Mapping: Case Report and Literature Review

The diagnosis of myocarditis can be challenging given that symptoms, clinical exam findings, electrocardiogram results, biomarkers, and echocardiogram results are often non-specific. Endocardial biopsy is an established method for diagnosing myocarditis, but carries the risk of complications and false negative results. Cardiac magnetic resonance imaging (MRI) has become the primary non-invasive imaging tool in patients with suspected myocarditis. Myocarditis can be diagnosed by using three tissue markers including edema, hyperemia/capillary leak, and necrosis/fibrosis. The interpretation of cardiac MR findings can be confusing, especially when the myocardium is diffusely involved. Using T1 and T2 maps, the diagnosis of myocarditis can be made even in cases of global myocarditis with the help of quantitative analysis. We herein describe a case of acute global myocarditis which was diagnosed by using quantitative T1 and T2 mapping.

Single-exponential and dual-exponential fitting methods of MR T2-Map / 中国医学影像技术

Objective To assess the single-exponential and dual-exponential fitting methods of MR T2-Map, and to get T2 value of each pixel. Methods Single and dual-exponential methods with linear fitting and non-linear regression fitting techniques were used for a series images with different TE; then T2-Map images were achieved. T2-Map software was realized on MATLAB and it had the function of compute, display, save and so on. Results T2-Map software with single-exponential and dual-exponential fitting methods was achieved, able to calculate T2 value of tissues everywhere and form the T2-Map image. Conclusion Single-exponential T2-Map method is convenient, having obvious merit-high speed, but can not show the area with obvious different contents very well. However, dual-exponential fitting method can deal with this question with providing different T2 values, thus is accurate with the sacrifice of costing too much time. Dual-exponential fitting method of T2-Map is a beneficial supplement to single-exponential method.