In 2005, Canadian-based St. Jude Medical issued an advisory to doctors, warning that SEUs to the memory of its implantable cardiac defibrillators could cause excessive drain on the unit’s battery.
As with other industries, there is a slow, but growing recognition of SEUs and their impact on medical equipment. For example, in 1998 Bradley and Normand reported on the incidence of SEUs in implantable cardiac defibrillators. This report presented the first clinical data set obtained indicating the effects of cosmic radiation on implantable devices.
While Bradley and Normand were investigating errors induced at ground level, modern medical equipment, such as portable infusion pumps, aircraft-based defibrillators, pacemakers, and implantable cardiac defibrillators, must also operate when flying in commercial aircraft (with the high neutron flux at altitude).
The error rate for a given circuit is generally proportional to the relative neutron flux of the operating environment. The neutron flux for aircraft operating at altitudes near 40,000 feet on near polar flight paths is roughly 600 times that at ground level at New York City (the reference point defined by JESD98A) — representing a significant increase in the risk of SEUs for devices operating on aircraft. As a result, the FIT rate for any device operating at this altitude near the poles is nearly 600 times greater than when operating at sea-level at lower latitudes.
However, cosmic rays and device materials are not the only sources of ionization radiation in the medical environment. With rise of new technologies such as radiation therapy, where ionizing radiation is used to target cancers, designers must also consider this locally generated flux. In fact, Guo, et al. investigated the flux generated by a Varian linear accelerator (LINAC) operating in high-energy mode, estimating that a typical radiation therapy room could experience 38 SEUs/MB/day. Given the memory content of modern electronics, the estimated error rate is indeed significant.
Source: Single-Event Upsets (SEUs) and Medical Devices | 2010