# Implementation of a Breast Phantom with Acoustic Properties for Ultrasonic Thermometry
## 5 Discussion
### Comparative Analysis with Commercial Brands  
There are several brands of commercial phantoms for ultrasound imaging, and all of them have been developed for training purposes [79; 80; 81; 82; 83; 84; 85; 86]. Few can be used for equipment calibration too. They are constructed with patented materials that mimic parameters as SOS, attenuation coefficient, anatomical shape, and density. The SOS and attenuation coefficient can vary depending on the material, e.g., the SOS value is approximately 1540 m/s for phantoms based on a material called Zerdine, and 1450 m/s \(\pm\) 1.0% at 23\({}^{\circ}\) for phantoms based on urethane; the attenuation coefficient of Zerdine is within the range of 0.7 to 0.95 dB/cm/MHz and that of urethane is 0.5 dB/cm/MHz \(\pm\) 10% [79; 80].  
There is a wide variety of phantoms, from multipurpose to very specific ones; e.g., Sun Nuclear Inc. (FL, USA) provides ultrasound phantoms for many applications (Doppler, elastography, biopsy, etc.) and Elevate Health Care Inc. (FL, USA) provides phantoms for many specialties (abdominal, cardiology, musculoskeletal, small parts, among others). No information was found about commercial phantoms developed for thermometric purposes. Specifically, breast models [81; 84; 85; 86] are designed to help practitioners develop skills for invasive procedures such as needle biopsies, or on detecting breast masses. Important advantages are that they provide long duration (1 year or more), and they are reusable. Most of them are composed of background material with embedded masses simulating different kinds of lesions: cysts, microcalcifications, tumors, etc. Just one phantom called BREASTFAN (Kyoto Kagaku Co., Ltd., Kyoto, Japan) simulates different structures of the breast: the subcutaneous adipose, the mammary gland, the galactophore, Cooper's ligament, the retromammary adipose, the costae, the clavide, the pectoralis major, the lung, and the lymph nodes at axilla. However, this case is for training on imaging purposes too [84]. Not all providers give open information about the costs of the phantom, but based on the available information, we can establish that breast phantoms cost USD 350-650 [85; 86].  
In comparison with our breast phantom, developed and described in this work, we conclude with the following facts:  
Until now, there have been no reported commercial phantoms for thermometric applications; therefore, our phantom is a viable option, fulfilling the need for this specific application.  
The advantages of commercial phantoms are their durability and the fact that they are reusable; nevertheless, most of them do not consider the different tissue layers that compose the breast, which is relevant because different tissues present distinct thermal behaviors.  
One of the main challenges that arose during the development of our phantom was the need to preserve the distinct thermal behaviors of the layers (simulated tissues) despite the fact that they make up a single composed medium. Our breast phantom represents a low-cost option, where material costs per phantom are under USD 25. The initial investment in the equipment required is about USD 2500, but this is a one-off expense. This fact, in conjunction with the fact that agar is a non-dangerous and manageable component, makes our phantom an accessible and secure option.