3-D Hemorrhage Imaging by Cambered Magnetic Induction Tomography

Magnetic induction tomography (MIT) is a promising imaging technique for hemorrhage detection due to the features of initial diagnosis and continuous monitoring. The dispersed nature of the electromagnetic field makes the MIT difficult to image the intraaxial hemorrhage. An open cambered MIT was proposed to improve the sensitivity of extraaxial hemorrhage which is located 14-20 mm below the scalp. Realistic head models with different hemorrhage volumes and positions are used for simulation. The imaging performance of the cambered MIT is compared with the cylindrical MIT based on the time-difference and frequency-difference imaging methods, respectively. Different levels of noise (standard deviation of phase difference at 0.5 and 0.75 m°) were added to the phase difference measurements of time difference at 1 MHz. 3-D images were reconstructed by the single-step Tikhonov regularization method. Two factors of correlation coefficient rpd and localization error Le are introduced to assess the quality of the images. The results show that the cambered MIT obtains a better imaging performance of extraaxial hemorrhage than cylindrical MIT. In particular, for the hemorrhage of 7 mL at the lower position by time-difference imaging, rpd of the cambered MIT is increased by 42.3% and Le is reduced by 37.7% relative to the cylindrical MIT. The cambered MIT obtained twice the signal-to-noise ratio of phase difference for the frequency-difference method than the cylindrical MIT. The cambered MIT improves the sensitivity of near-subsurface locations, which provides a high resolution and portable way to monitor the extraaxial hemorrhage.