Magnetic resonance current density imaging (MRCDI)

 
#Sensing #RemoteSensing Is there a RADAR for electric activity?
 
Sensing of electric activity with magnetic resonance-based magnetometry
 
Magnetic resonance current density imaging (MRCDI)
 
Current density imaging with magnetic resonance
 
In different scientific disciplines, the process of obtaining information for an object or a process is termed "sensing" and in the case of non-physical contact, it is termed "remote sensing". Fundamental techniques for remote sensing include RADAR, LIDAR and SONAR. RADAR which stands for "RAdio Detection And Ranging" uses radio waves to detect an object and to determine its range (distance, position) and its velocity. Similarly, LIDAR uses light and SONAR uses sound.
 
Is there a remote sensing technique for determining the electric current or electric activity of an object e.g. of a circuit?
 
The electric current which flows through a unit area of defined cross section is termed current density.
 
Sensing of current density is performed with magnetic resonance-based magnetometry. We refer to current density imaging performed with magnetic resonance imaging (magnetic resonance current density imaging or MRCDI).
 
"Current-induced magnetic resonance phase imaging" by Bodurka et al 1999 (https://www.ncbi.nlm.nih.gov/pubmed/10053158
 
"An electrically insulated thin copper wire (60mm diameter) was formed into a 3-inch long and 2-inch wide rectangle that was supported by a plastic frame. The orientation of the wire was perpendicular to the main magnetic field B0. A 10-k resistor was connected in series. A pulse generator was employed to provide a 0-, 10-, 20-, 30-,50-, 70-, or 100-mA current with 2s on and 2s off cycle through the wire." (Figure 1)
 
Electric current-induced phase alternations are imaged by fast magnetic resonance imaging (MRI) technology.
The authors calculated the average value of the Z component of Bc parallel to B0 produced by electric current I.
The findings are discussed in terms of possible direct MRI detection of neuronal activity.
 
Figure 2 shows the current-induced (70 mA) phase images (A) and time series of induced phase changes (B).
The induced change of magnetic field was calculated to be 1.7 +- 0.3 nT.
 
Further studies: Optically detected magnetic resonance-based magnetometry

 

Figure 1: Wire formed in rectangular shape and correlation map.

 

 

Figure 2: Waveform and phase changes induced by a 70 uA current.