Unravelling instrumental challenges in heating power measurements for magnetic hyperthermia

Heating powers of magnetic nanoparticles for magnetic hyperthermia are typically measured by non-adiabatic AC calorimetry. This technique is, however, reported to have a standard deviation in the intrinsic loss power (ILP) of 30–40% by the RADIOMAG EU COST Action TD1402 round-robin study involving 21 European laboratories. In the present study, we re-examine the RADIOMAG dataset and reveal four common sources of error: i) Insufficient temperature resolution, ii) AC-field sensitive thermometers, iii) Non-physical temperature oscillations, and iv) Apparent non-linear heat losses. In total, 16 of the 21 laboratories were observed to suffer from one or more of these four measurement issues. Based on these findings, we propose minimum criteria for sufficient measurement quality and apply them to re-estimate the ILP values only for datasets with sufficient quality. Given these criteria, we demonstrate that addressing instrumentation and analysis issues can decrease the inter-laboratory ILP deviation to 17–30%, corresponding to reductions in errors of around 30% compared to previous reporting. Based on our analysis, we introduce a diagnostic protocol for identifying and solving common instrumentation challenges proactively before the data acquisition phase. In future applications, the inter-laboratory ILP deviations are anticipated to be reduced further than the 17-30% observed in this work, given that the identified instrumentation issues are resolved and the corrected slope method can be properly implemented.