Experimental study of neutron-induced soft errors in modern cardiac pacemakers

Abstract

Purpose: Density of circuits and size reduction of microelectronic devices increase the sensitivity to natural terrestrial radiation environment. Atmospheric particles, mainly neutrons can cause non-destructive or destructive failures in most electronic circuits, including volatile static memories. The failure occurrence probability of a soft error in real life is very low. However, in the last few years, a safety alert had to be communicated to the physicians for a few defibrillator models potentially affected by background levels of atmospheric ionizing cosmic radiation. The aim of this study was to test in vitro a variety of currently available pacemakers exposed to experimental neutron irradiation.

Methods: The neutron irradiation at high flux fast neutron beam was performed using Cyclone facility, with the cyclotron of the University of Leuven, Belgium. The neutron energy spectrum was obtained with a peak around 20 mega-electron volt (MeV) energy range from 3 to 50 MeV, and tests were performed at three fluence levels: 1E9, 5E9, and 1E10 neutrons/cm(2).

Results: A total of 14 tests were conducted on 14 devices from four manufacturers. Following the test, the devices were functioning normally in eight cases. In six cases, the response at interrogation was a message on the programmer screen announcing an electrical reset. In all of these cases, the programmer reset command was activated and immediately restored normal functioning and programmability. For a same model, the electrical reset was present at high fluence (1E10 or/and 5E9 n/cm²) and not at the lower level (1E9 n/cm²). Obvious differences among manufacturers were shown in this small sample study.

Conclusions: This experiment shows the sensibility of modern pacemakers to neutron-induced soft errors and effectiveness of backup reversion in response to irradiation. The lower neutron fluence associated with a positive test was used to propose the calculation of the very low soft error rate for the tested devices in real-life atmospheric radiation.