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Published on: October 20, 2023
Fat deposition decreases diffusion parameters at MRI: a study in phantoms and patients with liver steatosis
Helena S Leitão1, Sabrina Doblas, Gaspard d'Assignies
1Center for Neuroscience and Cell Biology, PhD Program in Experimental Biology and Biomedicine, University of Coimbra, Coimbra, Portugal. helenasleitao@netcabo.pt
Purpose:
Assess the effect of fat deposition on the MRI diffusion coefficients in lipid emulsion-based phantoms and patients with proven isolated liver steatosis.
Materials And Methods:
Diffusion-weighted MRI with 11 b values from 0-500 s/mm(2) was performed in phantoms (fat fractions 0-18 %) with and without fat suppression and in 19 patients with normal liver (n = 14) or isolated liver steatosis (n = 5) proven by histopathology. The apparent, pure and perfusion-related diffusion coefficients and the perfusion fraction were measured. Spearman correlation coefficient and Mann-Whitney U test were used for comparisons.
Results:
A strong correlation between the apparent and pure diffusion coefficients and fat fractions was seen in phantoms. The pure diffusion coefficient decreased significantly in patients with liver steatosis (0.96 ± 0.16 × 10(-3) mm(2)/s versus 1.18 ± 0.09 × 10(-3) mm(2)/s in normal liver, P = 0.005), whereas the decrease in apparent diffusion coefficient did not reach statistical significance (1.26 ± 0.25 × 10(-3) mm(2)/s versus 1.41 ± 0.14 × 10(-3) mm(2)/s in normal liver, P = 0.298).
Conclusions:
Fat deposition decreases the apparent and pure diffusion coefficients in lipid emulsion-based phantoms and patients with isolated liver steatosis proven by histopathology.
Insights
Fat deposition significantly lowers MRI diffusion coefficients in liver steatosis. This finding in phantoms and patients highlights diffusion MRI
Area of Science:
- Radiology
- Medical Imaging
- Biophysics
Background:
- Liver steatosis, characterized by fat accumulation in hepatocytes, affects liver function and can progress to more severe liver diseases.
- Diffusion-weighted magnetic resonance imaging (DW-MRI) is a non-invasive technique sensitive to water molecule movement, which can be influenced by tissue composition.
Purpose of the Study:
- To investigate the impact of varying fat fractions on MRI diffusion coefficients.
- To assess the relationship between fat deposition and diffusion coefficients in patients diagnosed with isolated liver steatosis.
Main Methods:
- Diffusion-weighted MRI was performed on lipid emulsion phantoms with fat fractions ranging from 0% to 18%.
- DW-MRI was also conducted on 19 patients (14 normal liver, 5 with isolated liver steatosis confirmed by histopathology) using 11 b-values (0–500 s/mm²).
- Apparent diffusion coefficient (ADC), pure diffusion coefficient (PDC), and perfusion fraction were calculated and analyzed using Spearman correlation and Mann-Whitney U tests.
Main Results:
- Phantoms demonstrated a strong correlation between fat fraction and both ADC and PDC.
- Patients with isolated liver steatosis showed a statistically significant decrease in PDC compared to those with normal livers (0.96 × 10⁻³ mm²/s vs. 1.18 × 10⁻³ mm²/s, P=0.005).
- The decrease in ADC in patients with steatosis did not reach statistical significance (1.26 × 10⁻³ mm²/s vs. 1.41 × 10⁻³ mm²/s, P=0.298).
Conclusions:
- Fat deposition demonstrably alters MRI diffusion coefficients.
- The pure diffusion coefficient is a sensitive indicator of fat deposition in the liver, showing significant reduction in isolated liver steatosis.
- These findings support the utility of diffusion MRI in quantifying fat content and diagnosing liver steatosis.
