In vivo conductivity imaging of human knee using 3 mA injection current in MREIT

Recent in vivo human leg MREIT experiments showed successful conductivity image reconstructions using carbon-hydrogel electrodes and optimized RF coils. However, it is still difficult to perform in vivo human and disease model animal experiments primarily due to a long scan time and high injection current of about 9 mA. Compared to previous MREIT pulse sequences, a newly developed multi-echo pulse sequence provides a higher SNR of MR magnitude image and better quality of magnetic flux density data. Unlike the human calf, the knee has sensitive nerve bundles and mainly consists of the bone. In this study, we tried to obtain high-resolution conductivity images of in vivo human knees using the multi-echo pulse sequence. We injected as much as 3 mA current in the form of an 81 ms pulse into the knee without producing a painful sensation and motion artifacts. Reconstructed conductivity images well distinguish different parts of the subcutaneous adipose tissue, muscle, synovial capsule, cartilage and bone inside the knee. Considering clinical applications, future work should be focused on in vivo human and disease model animal experiments.