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Abstract: TH-PO745

A Quantitative 23Na-MRI Protocol to Assess Muscle Na Concentrations: Protocol Reliability and Na Level Heterogeneity Between the Anterolateral and Superficial Posterior Compartments of the Lower Leg

Session Information

  • Bioengineering
    October 25, 2018 | Location: Exhibit Hall, San Diego Convention Center
    Abstract Time: 10:00 AM - 12:00 PM

Category: Bioengineering

  • 300 Bioengineering

Authors

  • Fang, Hsin-Yu, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
  • Perez, Luis M., University of Illinois, Urbana, Illinois, United States
  • Burrows, Brett, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
  • Larsen, Ryan J., University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
  • Wilund, Ken, University of Illinois, Urbana, Illinois, United States

Group or Team Name

  • Renal and Cardiovascular Disease Research Laboratory UIUC
Background

Previous sodium magnetic resonance imaging (23Na-MRI) studies demonstrated that sodium (Na) can be stored in muscle without thoroughly describing the image quantification methodology. 23Na-MRI image region of interest (ROI) analysis is a subjective process that depends on user experience. We sought to develop a reliable protocol to quantify Na concentrations in two lower leg muscle compartments. The intra- and inter-rater reliability of our quantification protocol and the heterogeneity of Na level between two assessed muscle compartments were also examined.

Methods


Twenty-five 23Na-MRI (3T system) images from 21 subjects (16 healthy subjects/5 hemodialysis patients) were quantified for muscle Na concentrations. We de-identified and randomized all images into two sets for ROI analysis by two trained researchers. Two ROIs were designated as the anterolateral (AL) and superficial posterior (SP) lower leg muscle compartments.

We calculated Intraclass correlation coefficient (ICC) estimates based on 2-way mixed-effects models to determine the intra- and inter-rater reliability of our protocol on muscle Na concentrations of AL and SP compartments. Simple linear regression (SLR) analysis was used to investigate the relationship between the average muscle Na concentration of AL and SP (AL-SP mean) and the difference between AL and SP muscle Na concentrations (AL-SP difference).

Results

The ICCs of inter and intra-rater reliability for muscle Na concentrations of AL and SP compartments were all above 0.97, indicating excellent reliability. SP compartment muscle Na was higher than in the AL compartment (SP=20.32±8.69 mM, AL=15.57±5.92 mM, p=0.001). However, Na concentrations of the two compartments were strongly correlated (r=0.697, p<0.01). Linear regression of the AL-SP mean versus the AL-SP difference was significant (β1=-0.444, p=0.013; R2=0.232).

Conclusion

The reliability of our 23Na-MRI image analysis protocol in the measurement of Na concentrations in lower leg muscular compartments was high. Muscle Na concentrations varied between muscle compartments, suggesting a heterogenous Na distribution among different muscle groups. The variance of muscle Na concentrations between compartments increased as the total muscle Na level elevated.

Funding

  • Private Foundation Support