# X-ray Visualization and Quantification Using Fibrous Color Dosimeter Based on Leuco Dye
## 1 Introduction  
In recent years, radiotherapy has made great strides, and it is now possible to intensively irradiate only cancer cells with radiation and to suppress the effects on surrounding healthy cells as much as possible. Besides this, it is well-known that amounts of radiation doses have a harmful impact; however, small amounts of radiation doses have another aspect of stimulating various activities of the human body as physiological stimulation (radiation hormesis effect [1, 2]). In other words, radiation workers need to accurately measure and manage radiation doses, especially workers working at nuclear power plants, who must always manage their doses. In general, Geiger-Muller counters or semiconductor radiation detector devices have been used for detecting weak radiation. In facilities handling radiation, workers entering the controlled area must carry radiation meters and manage external exposure doses during the working time. Various types of personal dosimeters, such as fluorescent glass dosimeters [3, 4], thermoluminescent dosimeters (TLD) [5, 6, 7, 8], photostimulated luminescence dosimeters (PSL) [9, 10, 11], film badges [12, 13, 14], ionization chamber dosimeters [15, 16, 17], electronic dosimeters [18, 19, 20], GaFchromic film dosimetry [21, 22], and fiber-like systems dosimeters [23, 24], are currently available and the appropriate type of dosimeter is used according to the purpose of use and function. Among the abovementioned personal dosimeters, fluorescent glass dosimeters are currently the most widely used personal dosimeters. However, the fluorescent glass dosimeters require a dedicated reading device to measure the radiation exposure dose and have a fatal disadvantage in that the radiation exposure dosecannot be known immediately. This is because the fluorescent glass dosimeters use a mechanism to convert the radiation dose obtained using silver-activated phosphate glass into UV-excited fluorescence. Therefore, to overcome these problems, it is necessary to develop a new system that differs from existing radiation dosimeters and can visually, intuitively, and reliably measure the radiation exposure dose [25; 26]. In a previous study, we proposed a composite resin dosimeter (CRD) consisting of 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine (MBTT) as the photoacid generator, 2-(phenylamino)-6-(dipentylamino)-3-methylspiro[9\(H\)-xanthene-9,3'-phthalide] (Black305) as the color former, and cerium-doped yttrium aluminium perovskite YAlO\({}_{3}\):Ce (YAP:Ce) as the scintillator, that changes its color from yellow to thermally stable black upon monochromatic X-ray exposure in the range of 18-170 Gy at a wavelength of 0.154 nm [27]. A mechanism for the color change of the CRD film under the X-ray exposure doses was also proposed. The YAP:Ce scintillator powder in the CRD film absorbs the X-ray radiation and then emits the ultraviolet light inside the film. A free radical Cl\({}^{\bullet}\) is released from the MBTT that absorbs the ultraviolet light, and a photoacid-generating reaction occurs to produce a proton (H\({}^{+}\)). The H\({}^{+}\) reacts with the Black305 to open a lactone ring and eventually change the color of the material to black. However, as described above, the proposed composite material contained the YAP:Ce powder in the film, so the flexibility of the material was poor, and it was difficult to process the composite material into a fibrous form. Recently, fiber centrifugal spinning (or force spinning) has been used to fabricate fibers on the micro or nanoscale [28; 29; 30]. This method has high productivity and low cost and does not depend on the conductivity of the polymer solution, unlike the alternative technique of electrospinning. The centrifugal spinning process uses the centrifugal force arising from the high-speed rotation of a spinneret and exploits the properties of the polymer solution such as viscoelasticity and mass transfer characteristics to produce micro/nanofibers with controlled fiber diameter.