Report on results - the relationship between the power and the temperature difference for four implants

readme.md 7/10/2023 1 / 2 Activity 1 Introduction The activity aims at investigating the feasibility of using power measurements/results as a substitute for temperature measurements/results when testing the heating of metallic implants in line with the procedure recommended by the ISO/TS 10974:2018 standard. The evaluations will be carried out considering the implants selected in A3.1.1 with the only exception of the cranial plate whose 2D-like shape makes such an analysis less interesting (NOTE: we can consider also the cranial plate at a later stage if we deem it is useful). It is expected that the following points are investigated in the framework of the activity: 1. For each implant, the correlation between the magnetic field direction that maximises the power deposition into the implant and that that maximises the temperature increase after 5 minutes, 15 minutes and 30 minutes of exposure; 2. For each implant, the correlation between the power deposited into the implant and the following temperature increase as a function of the magnetic field direction. The correlation should be evaluated accounting for a temperature increase after 5 minutes, 15 minutes and 30 minutes of exposure; 3. For each implant, a coefficient, with associated uncertainty/confidence level, that allows to estimate the temperature increase after a specified time instant given the power deposited into the implant. NOTE: With reference to the 3rd point, a coefficient can be also investigated without focusing on a single implant but involving them all. Based on our previous experience, the implant surface turns out to be useful to normalise the deposited power in order to improve the correlation with the temperature increase. All the data to be studied have been obtained by INRIM through a home-made tool and are provided as .mat files with one file produced for each implant. Further details about the followed procedure can be found in the WP3 report uploaded in the STASIS repository. UPDATE The data provided are relevant to the exposure of the implants to a homogeneous magnetic field with a 1 A/m amplitude. The ISO 10974 standard suggests to perform the gradient induced heating considering a magnetic flux density of 35 mT. Therefore, it could be more meaningful to report the results for the 35 mT magnetic flux density. Since both the power and temperature increase are proportional to the square of the magnetic field value, it corresponds to multiply all temperature increases and powers (x and y axes) by . Data format Each implant is associated with a activity1_<Implant_name>.mat file containing the following variables: power_map : matrix of the total power expressed in watt deposited into the implant for a specific orientation of the unitary harmonic magnetic field expressed in polar coordinates. (0.035/(4 π ) 10 −7 ) 2 × N θ N ϕ readme.md 7/10/2023 2 / 2 is the polar angle (the angle between the magnetic field vector and the z-axis) and is the azimuth angle (the angle between the magnetic field vector and the x-axis). and are the number of and intervals at which the power has been computed; power_worst_H : 3 element vector representing the unitary magnetic field that results in the maximum power deposited into the implant; temp_map_<n>min : matrix of the maximum temperature increase expressed in kelvin, after <n> minutes of exposure, for a specific orientation of the unitary harmonic magnetic field expressed in polar coordinates with the same criteria used in the power_map matrix; temp_worst_H_<n>min : 3 element vector representing the unitary magnetic field that results in the maximum temperature incerase after <n> minutes of exposure; external_surface : external surface of the implant expressed in square meter (i.e., the interface between the implant and the background). θ : [0, π /2] ϕ : [− π , π ] N θ N ϕ θ ϕ × N θ N ϕ