# Feasibility of a Reusable Radiochromic Dosimeter
## 3 Results
### Reusability (Multiple Irradiations) Linearity and Dose Sensitivity  
For purposes of reusability, only Formulation 1 and Formulation 3 will be further considered, as the slow clearing response of Formulation 2 is not ideal. This will be explained in detail in the discussion. The linearity data for Formulation 1 (Figure 7, Tables 2 and 3) are shown for each of the five irradiations. A positive correlation ranging from R\({}^{2}\) = 0.9966 to 0.9993 was found for all linear fits.  
The linearity data for two separate groups (designated Group 1 and Group2) of Formulation 3 cuvettes (Figures 8 and 9, Tables 4 and 5) are shown for each of the five irradiations of both groups, indicating a positive correlation ranging from R\({}^{2}\) = 0.9963 to 0.9994 for all irradiations.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Irradiation \#** & \(\Delta\)**OD/Gy** & **\% Change** \\ \hline First & 0.0898 & 0 \\ Second & 0.0686 & \(-\)23.6 \\ Third & 0.0538 & \(-\)40.1 \\ Fourth & 0.0527 & \(-\)41.3 \\ Fifth & 0.0469 & \(-\)47.7 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Formulation 1 sensitivity measurements for five successive irradiations along with the percent change from the initial sensitivity.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Irradiation \#** & **MAPE \%** & **Least Squares R\({}^{2}\)** \\ \hline First & 3.05 & 0.9966 \\ Second & 1.24 & 0.9993 \\ Third & 2.14 & 0.9981 \\ Fourth & 4.46 & 0.9989 \\ Fifth & 3.92 & 0.9980 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Linearity values for Formulation 1 for five successive irradiations. The mean average percent error (MAPE) calculation includes cuvettes dosed with 1–10 Gy. The R\({}^{2}\) coefficient of linearity is also included.  
Figure 7: Five separate irradiations of Formulation 1 with seven cuvettes ranging from 0.5–10 Gy dose. The reirradiations were performed well after the cuvettes had cleared back to a stable baseline OD following the previous irradiation. Least squares linear fits to each of the five data sets are shown above, with the R\({}^{2}\) coefficient included for each.  
Figure 8: Five separate irradiations of Formulation 3 Group 1 with seven cuvettes ranging from 0.5–10 Gy dose. The reirradiations were performed well after the cuvettes had cleared back to a stable baseline OD following the previous irradiation. Least squares linear fits to each of the five data sets are shown above, with the R2 coefficient included for each.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Irradiation \#** & \(\boldsymbol{\Delta\text{OD/Gy}}\) **Group 1** & **\% Change** & \(\boldsymbol{\Delta\text{OD/Gy}}\) **Group 2** & **\% Change** \\ \hline First & 0.0710 & 0 & 0.0678 & 0 \\ Second & 0.0661 & \(-\)6.9 & 0.0677 & \(-\)1.5 \\ Third & 0.0723 & 1.8 & 0.0720 & 6.2 \\ Fourth & 0.0680 & \(-\)4.2 & 0.0689 & 1.6 \\ Fifth & 0.0680 & 4.2 & 0.0693 & 2.2 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Formulation 3 (Groups 1 and 2) sensitivity measurements for five successive irradiations along with the percent change from the initial sensitivity.  
Figure 9: Five separate irradiations of Formulation 3 Group 2 with seven cuvettes ranging from 0.5–10 Gy dose. The reirradiations were performed well after the cuvettes had cleared back to a stable baseline OD following the previous irradiation. Least squares linear fits to each of the five data sets are shown above, with the R2 coefficient included for each.  
Figure 10 shows the measured sensitivity values of all five irradiations of Group 1 and Group 2 of Formulation 3 cuvettes plotted together, with the one population standard deviation bands included to show the level of agreement between the two data sets. The average sensitivity for Groups 1 and 2 was 0.0691 \(\pm\) 0.0023 \(\Delta\)OD/Gy and 0.0691 \(\pm\) 0.0015 \(\Delta\)OD/Gy, respectively, with the uncertainty values representing one population standard deviation. Thus, all measured sensitivities were within two population standard deviations of the average.