## 3 Results
### Visible Spectroscopy Analysis of Expired EBT3 Gafchromic Film  
#### 3.3.1 Spectrum of Absorbers of Expired EBT3 Film  
As mentioned previously, higher doses of radiation will result in a decrease in optical transparencies or optical absorptions. Figure 2 shows the net visible light absorption spectrum in the region between 500 and 720 nm for the exposed expired EBT3 films post-irradiation of all three radiation sources. The highest absorption value (primary) centered around 633.52 nm, while the lower (secondary) centered around 582.3 nm. The peaks obtained are similar to the observation by [PERSON] et al., where they located their EBT3 absorbance peaks at (582 \(\pm\) 2) and (633 \(\pm\) 2) nm [22]. According to Leon-Marroquin EY \begin{table}
\begin{tabular}{c c} \hline \hline
**Expired EBT3 Samples** & **Absorbed Dose (Gy)** \\ \hline
1 & 0.62 \\
2 & 1.12 \\
3 & 2.39 \\
4 & 2.90 \\
5 & 3.72 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Absorbed dose at each film samples for 90 kVp X-ray energy. Figure 1: Incremental changes to the color changes of expired EBT3 film. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Radiation Source** & **Prescribed Dose (MU)** & **Absorbed Dose (Gy)** \\ \hline X-rays: & 100 & 1.00 \\ Energy: 6 MV & 200 & 2.00 \\
**dmax**: 1.5 cm & 300 & 3.00 \\ Field size: 10 cm \(\times\) 10 cm SSD & 400 & 4.00 \\ calibration & 500 & 5.00 \\ \hline Electron beam: & 100 & 1.06 \\ Energy: 6 MeV & 200 & 2.12 \\
**dmax**: 1.3 cm & 300 & 3.20 \\ Field size: 10 cm \(\times\) 10 cm SSD & 400 & 4.28 \\ calibration & 500 & 5.34 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Absorbed dose at each film sample for 6 MV photon and 6 MeV electron beam. et al. [13], the net absorbance spectra showed two absorption bands centered around 634-636 nm (primary) and 583-585 nm (secondary) for clinical photon and electron beams with dose range of 1-50 Gy and they observed the highest absorbance peak at 636 nm and a less intense peak at around 585 nm. Therefore, from this study, the primary and the secondary peaks were slightly differing from previous studies with percentage differences of 0.39% and 0.46% respectively. From the obtained results, different sources of radiation and energies showed the primary peak band at \(\lambda\) = 633.52 nm. All primary absorption bands were located around 633.52 nm wavelength at every absorbed dose. As the absorbed doses increased, the values of the absorbance peak increased as well. For the 90-kVp X-rays experiment, the spectra indicated 0.594 as the highest absorbance value at absorbed dose of 3.72 Gy. For the 6-MV photon beam experiment, the absorbed dose of 5 Gy showed 2.002 as the highest absorbance value. For the 6-MeV electron beam experiment, the spectra indicated 1.187 as the highest absorbance value at absorbed dose of 5 Gy. Therefore, expired EBT3 films showed the highest sensitivity for the 6-MV photon beam compared with the other irradiation sources. According to [PERSON] et al. [13], no significant change was observed in the absorption spectra of the EBT3 film from the same batch irradiated with the same amount of dose using different beam qualities and type. Additionally, no spectral change with dose rate was observed. The measured net absorbance per Gy was independent of beam quality in the 1-50 Gy dose range. The spectral shape absorption of the expired EBT3 radiochromic films irradiated with photons and electron beams is beam type (photon/electron) and dose rate independent. However, it varies with the dose level, the batch of the film sample, and the spectroscopy system used. From the results obtained, one can show that the beam quality and dose rate, due to all primary absorption bands located around \(\lambda\) = 633.52 nm, had a quite different value of absorbance at every absorbed dose for 90 kVp X-rays, 6 MV photon, and 6 MeV electron beams. With different setups and different radiation detectors used, the discrepancy of measured absorbed doses will probably be affected.