Whole Body Phantom with Pacemaker Implant, in Generic MRI System, 64 MHz

Model

The previous model of the patient in the generic MRI system is extended to include the influence of an implanted pacemaker in the patient.  The pacemaker model includes the metallic housing, pins, leads and a small PIFA antenna with curve slot.

Simulation

Due to the detailed structure of the pacemaker and leads the minimum grid step must be reduced and the resulting grid size is much larger than the model previous model which does not include the pacemaker. In this case a minimum step of 0.3 mm is used in the region of the PIFA antenna and the resulting grid contains 17.5 MCells. The operational frequency  is still 64 MHz. Since the minimum grid step is very small in terms of the wavelength the time step also becomes very small, which implies that a large number of  time steps are required for the simulation to reach steady-state. However, using the latest hardware acceleration solutions, e.g. a CIB 800, the simulation time is about 5 hrs.

Results

In order to access the influence of the implanted device the SAR distribution is compared to the model without the implant. The SAR distribution is noticeably higher in the region of the  metallic housing of the device. Furthermore, when comparing the 1 g Spatial Peak averaged SAR, the model containing the pacemaker is significantly higher. It is also possible to extract  other significant parameters, e.g. the coupling interference current, which is induced  at the feed of the pacemaker antenna.