# Developing a Specific MRI Technology to Identify Complications Caused by Breast Implants
## 4 Discussion  
In this study, MRI scans of implants were initially conducted to identify the qualitative characteristics of each material's signals. The signals of various tissues were then compared. Figure 6: Both saline and silicone bags were implanted in the breasts, the former on the outside of the latter. (**A**) The T2-weighted (T2W) fat-saturation image; (**B**) the same with a chemical shift of \(-61\) Hz from the water peak; (**C**) the short-tau inversion recovery water-saturation image with the center frequency at the fat peak. Figure 7: Signal intensity curves of the magnetic resonance images of the three materials (fat, silicone, and saline) with IR. The polynomial smooth curves are shown as dotted lines. Special MRI techniques were developed and applied to breast implants made from a variety of materials. The use of STIR water-saturation to obtain silicone-enhanced images can help diagnose leakage from silicone-bag implants, as shown in Figure 4A, but the use of T2W fat-saturation to obtain water-enhanced images can help diagnose leakage from saline-bag implants, as shown in Figure 4B. Both these imaging techniques are based on the chemical saturation technique, which suppresses signals from water and fat or fat and silicone while enhancing signals from other tissues, further enhancing the specific tissue contrast. As shown in Figure 4A, a silicone-enhanced image using STIR water-saturation with TI values allows the fat signals to fall on the null point. Resonance frequency tuning was also performed for fat (about 63,866,515 Hz). The frequency difference between 1.5 T oil and water is 220 Hz. Therefore, the signals from oil and water were shifted by +220 Hz from the center frequency of fat. The silicone signals were not influenced (it has a resonance frequency of about 636,686,425 Hz). As shown in Figure 4B, a water-enhanced image is achieved using T2W fat-saturation with FSE aimed at the resonance frequency of water (about 63,866,706 Hz) with radiofrequency excitation. Moreover, the chemical shift saturation technique was applied at the water center frequency-191 Hz (the fat center frequency was about 63,866,515 Hz) to remove the signals from fat completely. As the frequency difference between silicone (63,866,425 Hz) and water (63,866,706 Hz) is -281 Hz, as shown in Figure 5, the intensity of the silicone signals was relatively low, allowing a rather high image contrast for the signals from water. As the chemical shift saturation technique is constrained by magnetic homogeneity, and the frequency difference between oil and water is only 191 Hz using auto-tuning, a silicone peak could easily be mistaken for a fat peak, leading to incomplete chemical shift saturation when applying STIR water-saturation and T2W fat-saturation. Moreover, MRI scanners can vary in magnetic field strength, leading to different T1 values. As a result, the frequency difference between oil and water might not always be 220 Hz, influencing the effect of the chemical shift saturation technique. Taken together, the recommended T1 value for STIR water saturation is between 150 ms and 170 ms. However, in reality, when the fat signals reach the null point, the corresponding T1 values were between 120 ms and 140 ms. This theory can also indirectly influence the frequency difference between oil and water (approximately 200 Hz to 210 Hz). With these three points in mind, we suggest that when applying either STIR water-saturation or T2W fat-saturation, fine-tuning should be performed to confirm the center frequencies of water, fat, and silicone. In addition, because the influence of magnetic homogeneity on IR is rather small, simply making use of each tissue's null point characteristics by setting up the TI value to achieve specific suppression would allow confirmation of a material's identity between water, fat, and silicone.