Local Muscle Quality Imaging in Human Calf by Phase Angle Electrical Impedance Tomography (ΦEIT)

Panji Nursetia Darma, Bo Sun, Prima Asmara Sejati, Masahiro Takei

Abstract: Local muscle quality imaging in human calf by phase angle electrical impedance tomography (ΦEIT) has been proposed to monitor the local muscle aging (MA), local muscle fat infiltration (FI), and local muscle cross-sectional area (CSA) for the daily monitoring of muscle quality. The MA is assessed by the calf-specialized phase angle Jacobian matrix $^{\boldsymbol {\Phi }}$ J, the FI is estimated by the phase angle distribution $\Phi _{M}$ , and the high-intensity binarization of phase angle CSA predicts CSA ( $\widehat {\Phi _{M}}$ ). The ΦEIT is applied to 14 healthy subjects categorized into the young subject group (age $\le 30$ , $n = 7$ ) and middle-aged subject group (age > 30, $n = 7$ ). An independent samples t-test was conducted to elucidate the statistical significance of spatial-mean phase angle $\langle \Phi \rangle $ for MA assessment, spatial-mean phase angle $\langle \Phi \rangle _{M}$ for FI estimation as compared with FI by conventional ultrasound (uFI), and phase angle CSA ( $\widehat {\Phi _{M}}$ ) for CSA prediction compared to muscle area by the conventional ultrasound CSA (uCSA). The results from the independent t-test show that the ΦEIT correlates well with the subject’s age, uFI, and uCSA. The $\langle \Phi \rangle $ is significantly correlated to the MA ( $n \, =14$ , $p \lt 0.001$ ) in the young and middle-aged groups. The $\langle \Phi \rangle _{\mathbf {M}}$ is related substantially to FI ( $n =14$ , $p \lt 0.05$ ) in the young and middle-aged groups. the $\widehat {\Phi _{M}}$ is significantly related to CSA ( $n =14$ , $p \lt 0.05$ ) in the young and middle-aged subject groups.