# Implementation of a Breast Phantom with Acoustic Properties for Ultrasonic Thermometry
## 3 Methodology
### System Setup and Ultrasonic Signal Acquisition
#### 3.2.1 Design of Experiment: Single-Layer Phantom  
For the setup configuration of the ultrasonic inspection system for the single-layer phantom case, the mounting device was designed using SolidWorks, 2024 (Dassault Systemes--SolidWorks Corporation). The mounting device consists of two sections: one for monitoring temperature using K-type thermocouples within the single phantom, and the other for acquiring ultrasonic signals with a transducer probe. Figure 2a illustrates the design, which is divided into four quadrants, while Figure 2b provides a view of the model without the bases, highlighting the position of the phantoms, temperature sensors, and acquisition devices; Figure 2c indicates the individual phantom mold. In Figure 2a, Quadrant I includes support S1 for K-type thermocouples T1, T2, and T3, connected to a digital thermometer (Lutron) used to monitor the temperature at different depths within Phantom 2; each of them has a length of 150 mm, labeled as LT. The thermocouples are positioned at depths of 5 mm (T1), 7.5 mm (T2), and 10 mm (T3), considering that the total thickness of the phantom, G, is 15 mm. The thermocouples are spaced 12.5 mm apart and are distributed across the 50 mm diameter, labeled as DP, in Phantom 2. This ensures that ultrasonic acquisition is performed once the temperature has stabilized at the three central points. In Figure 2a, Quadrant II contains the thermocouples immersed in a solid mass, Phantom 2, encased by walls with a T-shaped flange, S2. This design prevents the phantom from leaking through any openings and ensures the thermocouples remain properly immersed, avoiding potential leaks of water or air that could lead to undesired temperature gradients. In Figure 2a, Quadrants III and IV are dedicated to fixing the area where ultrasound is transmitted through the phantom to obtain the signal. In Quadrant III, Phantom 1 is secured to the base by two rectangular structures labeled as S3 and S4; this facilitates ultrasound passage without interference and prevents the phantom from floating when submerged in distilled water. It is important to note that Phantom 1 is not directly poured into the device; instead, it is cast in a separate, circular mold, IPM. This mold shapes the phantom into a cylinder and allows for the incorporation of a circular aluminum disk, SD, which is 48 mm in diameter and 10 mm thick, with a 5 mm central elevation to maintain a controlled distance within the phantom. This setup facilitates the collection of echoes inside the phantom, enhancing the efficiency of SOS characterization, as depicted in Figure 2c.  
The near field, focal spot, and far field for the 1 MHz transducer were calculated using a transducer diameter, DT, of 0.0158 m and a sound velocity of water at 1500 m/s. These calculations served as a reference for determining the optimal distance between the transducer face and the phantom, which is 0.0416 m, labeled as LPF. The focal point was positioned at the water-phantom interface. Quadrant IV displays the fixed geometry of the transducer TR, including the defined radiation area used for the experiment.