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Liver T2 Mapping in a Large Cohort of Healthy Subjects: Normal Ranges and Correlation with Age and Sex1Fondazione G. Monasterio CNR-Regione Toscana, Pisa, Italy, 2University of Ferrara, Ferrara, Italy, 3University of Padua, Padova, Italy
Synopsis
Keywords: Liver, Tissue Characterization
Motivation: To ensure successful integration of hepatic T2 mapping into clinical workflow it is critical to establish normal reference values.
Goal(s): We defined normal ranges for hepatic T2 values using a 1.5T General Electric scanner.
Approach: Multi-echo fast-spin-echo sequences were acquired in 100 healthy volunteers and T2 values were quantified in the visible hepatic segments.
Results: Segmental and global liver T2 values exhibited a good intra- and inter-observer reproducibility. No significant regional T2 variability was detected. Global T2 values were not associated with aging but were significantly lower in males than in females.
Impact: In healthy subjects liver T2 mapping is feasible and reproducible and T2 values are influenced by gender, suggesting the need for the use of normative values differentiated by gender.
Introduction
T2 relaxometry has the potential to serve as non-invasive biomarker for the assessment of liver function and disease progression in various conditions 1,2. To ensure successful integration of T2 mapping of the liver into clinical workflow, it is critical to standardize data acquisition and analysis, as well as establish normal reference values, and assess the reproducibility of the techniques with different sequences and scanners.Aims
We aimed to define normal ranges for native T2 values in the human liver using a 1.5 T General Electric scanner and to evaluate their variation across hepatic segments and their association with age and sex.Methods
A retrospective analysis of CMR images from a large cohort of healthy volunteers was performed. One-hundred healthy volunteers aged 20-70years (mean age:44.7±14.2years; 50% females) were included in this study. The left lobe of the liver was mostly included in the field of view of the acquired multi-echo fast-spin-echo sequences (basal, medium and apical short-axis views of the left ventricle) 3. On the generated pixelwise T2 maps, polygonal regions of interest (ROI) were drawn in the visible and detectable functionally independent segments of the liver, according to the Couinaud segmentation 4.Results
The caudate lobe (segment 1) was measurable in a small minority of cases. In the right liver, segments 5 (anteroinferior), 6 (posteroinferior), and 8 (anterosuperior) were measurable in 1–7% of the healthy subjects, while segment 7 (posterosuperior) was not visible in any subject. In all participants there was at least one segment in the left hepatic lobe with good diagnostic image quality (Table 1). Therefore, segments 2 (left lateral superior), 3 (left lateral inferior), and 4 (left medial) were considered. The global liver T2 value was calculated as the mean of T2 values from the three regions.The results of the intra- and inter-observer variability analysis for segmental and global T2 values are summarized in Table 2. Intra-observer variability and inter-observer variability were low, with a coefficient of variability always <5%. The Bland-Altman analysis showed no systematic differences between assessments.
For the subgroup of 40 subjects for whom it was possible to measure T2 values in segments 2, 3, and 4, no significant regional T2 variability was detected (segment 2: 45.11±4.55ms, segment 3: 45.13±4.45ms, segment 4: 45.10±4.30ms; p=0.479). A significant correlation was found between T2 values in segments 2 and 3 (R=0.671; p<0.0001), segments 2 and 4 (R=0.732; p<0.0001), and segments 3 and 4 (R=0.686; p<0.0001).
Table 3 shows the correlation of T2 values with age and sex. With the exclusion of segment 3, no significant association was detected between segmental T2 values and age. When considering males and females separately, the association between T2 values in segment 3 and age did not reach statistical significance. Global native T2 values were significantly lower in males than in females, and a significant sex difference was also obtained for segments 3 and 4.
Since T2 values were influenced by sex, sex-specific reference values for segments 2, 3, and 4 were defined (Table 4). In males, the lower and upper limits of normal for global T2 values were, respectively, 35ms and 54ms. In females, the lower and upper limits of normal for global T2 values were, respectively, 39ms and 54ms.
Conclusions
Liver T2 mapping is feasible and reproducible and the provided normal ranges may help to establish diagnosis and progression of various liver diseases.Acknowledgements
We thank all subjects for their cooperation.References
1. Guimaraes AR, Siqueira L, Uppal R, et al. T2 relaxation time is related to liver fibrosis severity. Quant Imaging Med Surg. 2016;6(2):103-114.
2. Chow AM, Gao DS, Fan SJ, et al. Measurement of liver T₁ and T₂ relaxation times in an experimental mouse model of liver fibrosis. J Magn Reson Imaging. 2012;36(1):152-158.
3. Meloni A, Nicola M, Positano V, et al. Myocardial T2 values at 1.5 T by a segmental approach with healthy aging and gender. Eur Radiol. 2022;32(5):2962-2975.
4. Couinaud C. [Liver lobes and segments: notes on the anatomical architecture and surgery of the liver ]. Presse Med (1893). 1954;62(33):709-712.
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