Study on The Detection Method of Fat Infiltration in Muscle Tissue Based on Phase Angle Electrical Impedance Tomography

<trans-abstract abstract-type="key-points" xml:lang="en"><sec><title>Objective</title> Fat infiltration has been shown to be closely related to muscle mass loss and a variety of muscle diseases. This study proposes a method based on phase-angle electrical impedance tomography (<italic>Φ</italic>EIT) to visualize the electrical characteristic response caused by muscle fat infiltration, aiming to provide a new technical means for early non-invasive detection of muscle mass deterioration. </sec><sec><title>Methods</title> This study was divided into two parts. First, a laboratory pork model was constructed to simulate different degrees of fat infiltration by injecting 1 ml or 2 ml of emulsified fat solution into different muscle compartments, and the phase angle images were reconstructed using <italic>Φ</italic>EIT. Second, a human experiment was conducted to recruit healthy subjects (<italic>n</italic>=8) from two age groups (20-25 years old and 26-30 years old). The fat content percentage <italic>η</italic>_fat of the left and right legs was measured by bioelectrical impedance analysis (BIA), and the phase angle images of the left and right calves were reconstructed using <italic>Φ</italic>EIT. The relationship between the global average phase angle <italic>Φ</italic>_M and the spatial average phase angle <italic>Φ</italic>_M<italic>_i</italic> of each muscle compartment and fat infiltration was further analyzed. </sec><sec><title>Results</title> In the laboratory pork model, the grayscale value of the image increased with the increase of <italic>η</italic>_fat and <italic>Φ</italic>_M showed a downward trend. The results of human experiments showed that at the same fat content percentage, the <italic>Φ</italic>_M<italic> </italic>of the 26-30-year-old group was about 20%-35% lower than that of the 20-25-year-old group. The fat content percentage was significantly negatively correlated with <italic>Φ</italic>_M. In addition, the M₂ (soleus) compartment was most sensitive to fat infiltration, and the spatial average phase angles of the M₂ (soleus), M₃ (tibialis posterior and flexor digitorum longus), and M₄ (tibialis anterior, extensor digitorum longus, and peroneus longus) compartments all showed significant inter-group differences. </sec><sec><title>Conclusion</title> <italic>Φ</italic>EIT imaging can effectively distinguish different degrees of fat infiltration, especially in deep, small or specially located muscles, showing high sensitivity, demonstrating the potential application of this method in local muscle mass monitoring and early non-invasive diagnosis. </sec></trans-abstract>