# X-ray Visualization and Quantification Using Fibrous Color Dosimeter Based on Leuco Dye
## 3 Results and Discussion
During the first stage of the TGA, the fibrous color dosimeter showed a slight weight loss due to the presence of water at approximately 100 \({}^{\circ}\)C. In addition, no weight loss was observed up to 230 \({}^{\circ}\)C due to decomposition derived from the MBTT, and some weight losses of the materials contained in the fiber were observed in high temperature regions of 360 \({}^{\circ}\)C and 530 \({}^{\circ}\)C. Based on the result of the TGA, it was suggested that the thermal stability of the PS-based fibrous color dosimeters with MBTT/Black305 would be guaranteed up to the glass-transition temperature of PS of 100 \({}^{\circ}\)C. That is, if the color changing reaction processes thermodynamically, generally, increasing temperature can promote reaction activity (Figure S4); however, this thermodynamic property of the fibrous color dosimeters will be one of the issues in practical application because making a quantitative assessment of radiation exposure doses requires maintaining a constant temperature during use. Therefore, it is pointed out that the recommended operating temperature of the fibrous color dosimeter will be room temperature from the viewpoint of thermal stability. The humidity of the ambient can affect the dosimeter response as well [35]. Therefore, the effect of humidity on dose-response of the fibrous color dosimeter will need to be considered in the future. We conducted a preliminary experiment of X-ray exposure visualization using a fabric based on the fibrous color dosimeter (3.0/3.0 _w/w_), which presents photographic images of color changes during X-ray exposure at room temperature (RT; 20 \({}^{\circ}\)C). The leftmost photograph in Figure 3a shows the fabric before X-ray exposure. The color of the fabric before X-ray exposure is based on the absorption characteristics of MBTT. The circular black colors on the fabrics indicate the actual color change due to the X-ray exposure, and the dose dependence of the coloration is shown in Figure 3b. In addition, the black circles on the fabrics completely trace the shape of a window formed on a lead plate placed on the fabric. Figure 3b exhibits the UV\(-\)visible reflectance spectral changes of the color of the fabric during X-ray exposure at an interval of 20 Gy. Before the X-ray exposure, the broad reflection band where the reflection bands of PS and MBTT overlap appears in the region \(<\)532 nm. Under X-ray exposure, the color of the fabric gradually changes to black, and the reflection spectra with a peak of 610 nm are attributed to the colored zwitterionic form of Black305 [25]. Consequently, the reflectivity of the fabric changed drastically from 58% for yellow to 32% for black. Photographs of the fabric before and after an X-ray exposure dose of 80 Gy are presented in Figure 3c. An important property of the fabric is that its color changes can be uniformly confirmed as a whole, which indicates that the MBTT and Black305 dispersed entirely and would not form aggregates in the fabric. For future applications on the personal wearable dosimeter, the mechanical properties of the fabric were investigated as well. The mechanical properties of the fabric must be strong enough to build a wearable device. Figure 3d shows the stress-strain curve of the fabric. As a result, the maximum tensile stress and elongation at maximum tensile stress for the fabric are 0.36 \(\pm\) 0.01 MPa and 1.3 \(\pm\) 0.4%, respectively, and the properties are consistent with a nonwoven fabric derived from PS fibers [23]. Therefore, the mechanical strength of the fabric has a sufficient performance as a wearable dosimeter. Finally, a practical demonstration of X-ray visualization using the fabric that was processed into an apron is presented in Figure 3e. We put the fibrous color dosimeter apron on a teddy bear and placed it in inside the X-ray exposure apparatus. Then, we put a lead plate with a \"\(\blacktriangledown\)\" shape hole on the teddy bear to distinguish the contrast between the exposed area and unexposed one.