## 4 Discussion
This option sets safety limits under specific patient exposure conditions. This addition essentially ensures that, during MRI operation, by applying fixed parameters, the patient's safety limits are maintained. However, in this study, for the first time, it was observed that, during the Tier 3 process, the application of different options of the standard results in a different distribution of the induced electric field and consequently the calculated absorbed power. This does not always make the FPO:B approach more conservative. This highlights the need to adopt both options of the IEC 60601-2-33 standard in the Tier 3 process to compare results and consider the most adverse patient radiation condition. Thus, the necessity arises to include this specific condition not covered in existing versions of ISO TS 10974. Apart from the impact of the imaging position and the coil configuration on the deposited energy, the effect of the implant path inside the human body was also evaluated, indicating some paths that consistently reduced the RF deposited power over different resonant frequencies, human models and imaging landmarks. In particular, the induced W values for the leads implanted along the axillary vein were lower by 0.4 to 0.7 dB than the corresponding ones along the subclavian vein. On the other hand, the effect of the terminating point inside the heart was found to depend on the anatomy of the human model. Moreover, the excited W on the left side trajectories was lower by 0.2 to 2.2 dB than the corresponding one on the right side of the imaging position LD3 for both 64 and 128 MHz The reason for this right-left asymmetry is the clockwise polarization of the MRI, which for the supine position of the patient leads to a higher electric field at the posterior right edge and at the anterior left edge than estimated in previous works [15; 50]. Therefore, an additional margin of safety could be achieved for patients with CIEDs undergoing MRI procedures for both 1.5 T and 3 T systems by considering the path of the lead. In particular, when the cardiac lead inserts into the left axillary vein instead of the right subclavian vein, the deposited power at the tip of a pacemaker could be on average lower by 1.6 and 2.1 dB at 64 and 128 MHz, respectively. This is an observation that has not been reported before and has not been exploited in clinical practice until now. In previous works, the main goal was the reduction in the localized heating in patients with implants by modifying the device to reduce the coupling with the electric field [10; 44; 47] or by monitoring the induced current [13; 51; 52], even by modifying the RF coil [43; 53; 54; 55]. However, the above-mentioned approaches are not compatible with the existing implants and birdcage coils as they are applied after the implantation of the device. Hence, based on the analysis of the factors affecting the induced power on a pacemaker,we propose a more appropriate solution based on varying the placement of the device inside the human body. Therefore, from a practical perspective, optimal cardiac paths could be implemented in patients with minimum disruption to surgical flow, improving safety issues without added cost. It should further be noted that lead trajectories that reduce RF heating could also reduce image artifact as it is caused by induced currents, which are responsible for tissue heating and for production of the secondary magnetic fields that distort the B1 field [56]. The entire applied process relied on electromagnetic simulations, and, recently, in order to avoid the required computational time and memory requirements, novel machine learning methods have been proposed for the assessment of MRI RF heating. Specifically, the application of neural networks has been proposed to predict the worst-case heating of orthopedic fixation plates in the MRI environment, with the only input being the geometric properties of the implant [57].