## 3 Results
### Assessing the Impact of Object Position in the Phantom on Empirical Frequency Selection  
Figure 15 illustrates a cross-sectional reconstruction of the phantom in Experiment I within a homogeneous environment, examining the impact of the position of the object on the contrast within a specific frequency range. The results reveal a gradual decrease in object contrast as the distance from the electrode increases at the same survey frequency. In particular, the empirical frequency range, ranging from 15 to 40 kHz, aligns with the findings of previous experiments, emphasizing the robustness of this frequency window. Furthermore, Figures 16-20 illustrate the impact of different object positions.  
Figure 14: Graph of the analytical indices in Experiment V.1: (**A**) the profile line at the 128 th pixel row. The dashed square represents the positions of the objects; (**B**) the normalized sharpness values; (**C**) the normalized CNR values correspond to the surveyed frequency range.  
Figure 16: EIT image of Experiment I.2 shows the impact of object positions in a homogeneous environment.  
Figure 15: EIT image of Experiment I.1 shows the impact of object positions in a homogeneous environment.  
Figure 17: EIT image of Experiment I.3 shows the impact of object positions in a homogeneous environment.  
Figure 18: EIT image of Experiment I.4 shows the impact of object positions in a homogeneous environment.  
Figure 19: EIT image of Experiment L5 shows the impact of object positions in a homogeneous environment.  
Figure 20: EIT image of Experiment L6 shows the impact of object positions in a homogeneous environment.  
Figure 21A shows the variations in linear intensity through the CNR index, providing valuable information on contrast dynamics. This phenomenon suggests that the influence of object position on contrast is a significant factor within the explored frequency range. The consistent empirical frequency range from 15 to 40 kHz at different positions of objects indicates a robust characteristic, which underscores the reliability of this frequency window in achieving high contrast. Additionally, Figure 21B shows deviations in frequency ranges corresponding to the object's shift toward the center in a heterogeneous environment. This shift leads to an expanded frequency range and a non-linear decrease in CNR value intensity. The dynamic adaptation of the empirical frequency range emphasizes the importance of considering environmental heterogeneity in optimizing contrast for EIT imaging in scenarios with varied material compositions. These findings improve our understanding of contrast dynamics in EIT and advance imaging methodologies, and provide insights for optimizing contrast in diverse scenarios.  
This result illustrates the spatial impact of the object's position on contrast and emphasizes the resilience of the empirical frequency range. The observed variations in linear intensity and the effects of heterogeneous environments introduce additional intricacies to the discourse, fostering a more detailed comprehension of contrast dynamics in EIT. These  
Figure 21: CNR values across the surveyed frequency range with object position variation: (**A**) homogeneous environment; (**B**) heterogeneous environment.  
insights play an essential role in the advancement of imaging methodologies and present valuable factors to be considered in order to enhance contrast optimization in a multitude of scenarios.