Joseba Alonso1,2, Daniel Grau2,3, Juan Pablo Rigla3, Eduardo Pallás1,2, José Miguel Algarín1,2, José Borreguero1,2, Rubén Bosch1,2, Guillermo Comazzi1,2, Elena Díaz3, Fernando Galve1,2, José Manuel González3, Carlos Gramage1,2, Rubén Pellicer1,2, Alfonso Ríos3, and José María Benlloch1,2
1Spanish National Research Council (CSIC), Valencia, Spain, 2Universitat Politècnica de València, Valencia, Spain, 3Tesoro Imaging S.L., Valencia, Spain
1Spanish National Research Council (CSIC), Valencia, Spain, 2Universitat Politècnica de València, Valencia, Spain, 3Tesoro Imaging S.L., Valencia, Spain
We present an
apparatus for PNS threshold determination on a subject's limb, where we perform
a systematic study on 51 volunteers in a regime relevant to small, dedicated
MRI and MPI scanners. We propose this system for fast offline determination of
a subject's limits prior to scanning.
a) Photograph of PNS measurement setup. b) Coil design, consisting on two pairs of coils. We define the center of the coordinate system to be at the mid-point between the centers of the coil pairs (the z-axis is shown for further reference). c) Magnetic field strength distributions for homogeneous (left) and inhomogeneous (right) configurations, simulated in Comsol for a current of 1 A running through the coils, and plotted for the x = 0 plane, with 82 mm gap between plates. The structure along the contours is due to finite numeric precision in the simulations.
Experimental PNS threshold determination of sinusoidal (left), triangular (middle) and trapezoidal (right) trains of 1,000 pulses on 51 volunteers. Blue circles are semi-transparent and represent the threshold for every individual. Orange squares denote the mean for a given waveform and time parameters. The dashed orange lines are fits to standard models [6], with rheobase 30.3 ± 0.3 mT (30.4 ± 0.5 mT) and chronaxie 770 ± 110 us (519 ± 53 us) for the sinusoidal (triangular) scans. The red curves in the scans with linear magnetic ramps correspond to the IEC default thresholds.
