Current density imaging sequences with separation of mobile-ion current from immobile-ion current

Enhanced sensitivity current density imaging

“…The phase shift is proportional to the current amplitude and to the time of its application, i.e., to the current encoding period. In conventional CDI sequences (DC-CDI, AC-CDI, DC-AC-CDI) [16] the current encoding period is relatively short and normally does not exceed a few tens of milliseconds. Therefore, to obtain a large enough phase shift, the short current encoding period has to be compensated by larger current amplitude.…”

“…The long encoding period, that was achieved by the use of the train of hard refocusing RF pulses with no slice-selection gradients and with superimposed electric pulses of alternating polarity in-between the RF pulses [16,17], is combined with fast signal acquisition enabled by the two-shot RARE approach [18]. Fast signal acquisition enables many signal averages in the same experiment time as is normally needed for the conventional CDI and additionally improves the CDI sensitivity.…”

“…The diffusion signal attenuation is further reduced by exclusion of imaging magnetic field gradients in the current encoding part of the sequence so that the signal decays with the T 2 relaxation rate. The polarity of electric pulses is changed after each refocusing RF pulse in order to sum phase shifts accumulated during individual electric pluses [16,17]. Namely, each refocusing RF pulse reverses the magnetization phase.…”