# Analysis of the Refraction Effect in Ultrasound Breast Tomography
## 5 Practical Conclusions  
Considering the conducted studies, it can be concluded that the water temperature for in vivo breast measurements using the developed UBT scanner can be set in the range of \(25\,\,^{\circ}\mathrm{C}\leq T<30\,\,^{\circ}\mathrm{C}\). It should be considered that in most cases, the in vivo breasts studied have a relatively low ultrasound velocity, less than \(1500\) m/s. For this reason, the UBT scanner currently uses a water temperature of \(25\,\,^{\circ}\mathrm{C}\). It is also advantageous due to energy savings, a faster tank heating process, easier stabilization, and comfort for the patient. To further analyze the phenomenon of refraction, the authors perform complex calculations and measurements for a wide range of variations in ultrasonic velocity in the breast and refine the model developed. Research has shown that the geometry of the breast should be slightly changed during measurements by vertical stretching or loading of the breast nipple to limit the possibility of obtaining large angles of incidence of ultrasound beam rays on the breast tip in the vertical plane. This can be done by using a sinker attached to the nipple with a rubber suction cup or by using a magnetic disc attracted by a magnet attached to an extension arm (Figure 19). The developers of ultrasound breast tomography scanners use different approaches. The authors used a suction cup with a weight of \(350\) g. The force to pull the breast in water in this way is so small that it does not cause permanent deformation of the breast or any pain to the patient. These improvements have been implemented in the prototype of the hybrid UTB scanner, enabling better imaging quality. In this way, there is no need for costly upgrades to the electronics of the device that would be necessary to register long signals, enabling the application of complex computational algorithms based on waveform or inverse theory. There is no doubt that significant improvements in image quality can be achieved with these methods, but it would necessitate the use of expensive and power-consuming high-bandwidth systems for fiber-optic data transmission, as well as graphics cards with GPU processors. In our applied solution, acquisition of fragments of received pulses is sufficient, which enables precise measurements of their transition time and pulse amplitude. Figure 20 shows the results of ultrasound imaging of the left breast of a 66-year-old woman (Patient 2) in vivo using the UBT scanner prototype with sinker application (Figure 19), at a water temperature of \(25\,\,^{\circ}\mathrm{C}\). Cross-sectional MPR images visualizing both velocity and attenuation distributions of ultrasound clearly show an area with values of these parameters increased compared to the surrounding tissue. This indicates a high probability of malignant  
Figure 19: Simple ways to stretch a breast submerged in a tank with a sinker or with a magnet. carcinoma. Ultrasound examination performed by an experienced radiologist showed a solid hypoechoic tumor with blurred outlines 19 \(\times\) 17 \(\times\) 17 mm, which cancerous in nature. Histopathological examination showed an invasive carcinoma of the breast of no special type, grade 3 (high malignancy). The carcinoma occupied about 60% of the surface of the samples sent for examination. Significant surges and negative values of attenuation on the borders of heterogeneous areas in UTT ultrasound attenuation images are the result of measurement errors, as the weakening of the amplitude of ultrasound wave pulses measured after passing through the breast is caused not only by attenuation but also by refraction, diffraction, anisotropy, reflection, scattering on heterogeneity borders, and beam divergence. Therefore, this image may be rather treated as a quantitative-qualitative one.