3.3.4. Beam Profile Comparison at Reference Dose (*dref*) and Maximum Dose (*dmax*)

The comparison of the relative dose plots against distance from the central axis of sample A15 and solid water phantoms for the beam profile curves for 6 and 10 MV photons are presented in Figures 8 and 9. As can be seen from the figures, the DSF-based particleboards reveal remarkable beam profiles with good dose homogeneity and beam symmetry in comparison to those of solid water phantoms. There was a consistency between the constructed particleboard and solid water phantom plots in both the dose plateau and the penumbra regions. Table 10 addressed the variation of flatness of the beam profiles at *dref* and *dmax* between the DSF-based particleboards and solid water phantoms for both photon energies. Overall, the beam uniformity enhanced as the photon energy increased, with 10 MV photons having a reduced percentage discrepancy of beam flatness values at *dref* and *dmax* compared with that of 6 MV photons relative to solid water phantom. This has demonstrated the appropriateness of DSF/NaOH/IA-PAE/*R.* spp. particleboards to be utilized as phantom material for high-energy photons in medical health applications.

**Figure 8.** Beam profile for 6 MV photons evaluated at: (**a**) *dmax* and (**b**) *dref* .

**Figure 9.** Beam profile for 10 MV photons measured at: (**a**) *dmax* and (**b**) *dref* .

**Table 10.** Beam profile flatness for DSF/NaOH/IA-PAE/*R.* spp. particleboards (sample A15) compared to that of solid water phantom for 6 MV and 10 MV photons.


3.3.5. Determination of PDD for Electron Beams Using IC

The PDD curves of the electron beams for the particleboard phantoms showed an improved surface dose when compared with that of water and solid water phantoms, as displayed in Figure 10a–d. DSF-based phantom delivers a reasonably homogeneous dose from the surface to a specific depth, after which the dose falls off rapidly with increasing depth, eventually to near zero values. As can be seen from the figures, the percentage dose variations in *dmax* between the DSF-based *R.* spp. Particleboards, with respect to water and solid water phantoms for the four electron beam energies, were within 2.40–3.87%, 3.52–3.59%, 4.36–4.55%, and 2.82–4.63%, respectively. In addition, the percentage difference at which the electron PDD beyond the depth of *zmax* drops off sharply as a result of the scattering and continuous energy loss by the incident electrons. The therapeutic range (R90 and R80) and half-value depth range (R50) were found to be within the limit and similar to those of water and solid water phantoms for 6, 9, 12, and 15 MeV electrons (Table 11).

**Table 11.** Comparison of PDD curves between DSF/NaOH/IA-PAE/*R.* spp., water and solid water phantoms for different electron beams.


**Figure 10.** PDD curves for water, solid water, and DSF/NaOH/IA-PAE/*R.* spp. particleboard phantoms using IC for: (**a**) 6 MeV, (**b**) 9 MeV, (**c**) 12 MeV, and (**d**) 15 MeV electrons.

3.3.6. Evaluation of PDD for Electron Beams Using Gafchromic EBT3 Radiochromic Film

Figure 11a–d depicts the PDD profiles between DSF-based particleboard phantom, water, and solid water phantom evaluated from their surfaces for 6, 9, 12, and 15 MeV electron beams using Gafchromic EBT3 radiochromic films. As shown in the figures, comparable results were found in the constructed particleboards at the selected electron beams range to those of water and solid water phantoms. In this case, for 6, 9, 12, 15 MeV electrons discrepancies found were within 1.49–1.90%, 1.89–3.01%, 1.74–3.53%, and 2.38–3.84%, respectively. These findings indicate that, at 6 MeV, DSF-based particleboards depicted good agreement to those of water and solid water phantom with minimum discrepancies, whereas 9, 12, and 15 MeV give maximum values of percentage of discrepancies. Additionally, it can be observed that variations in percentage between the examined phantoms were lower at a depth beyond *zmax* in comparison to that in the build-up region. According to the obtained results, the dissimilarities in the discrepancy of the surface dose values were found to improve in the range between 1.45–1.63%, 1.51–1.79%, 1.53–2.17%, and 1.98–2.70%, which showed good agreement with the results of the IC. The observed reduction in surface dose can be assigned to a slight reduction in backscatter. This confirms that EBT3 radiochromic film is suitable and provided surface dosimetry measurements in 6, 9, 12, and 15 MeV electrons beam fields.

**Figure 11.** PDD plots for water, solid water, and DSF/NaOH/IA-PAE/*R.* spp. particleboard phantoms with the use of Gafchromic EBT3 radiochromic film for: (**a**) 6 MeV, (**b**) 9 MeV, (**c**) 12 MeV, and (**d**) 15 MeV electrons.

#### **4. Conclusions**

The RAPs and dosimetric characterization of DSF/NaOH/*R.* spp. particleboard phantoms as a tissue-equivalent phantom material with different amounts of IA-PAE (0, 5, 10, and 15 wt%) have been demonstrated. The ascertained average mass density exhibited acceptable quality values to those of water and solid water phantom in the range between 0.99 ± 0.01 gcm−3–1.04 ± 0.03 gcm−3. The PMDSP, *zeff* , and *Nel* values were found to be satisfactory. Comparison between the calculated RAPs values shows a reasonable agreement with 15 wt% IA-PAE, solid water phantom, and theoretical values of water (XCOM), as indicated by the *χ*<sup>2</sup> values (0.044). The dosimetric computation results of DSF/NaOH/IA-PAE/R. spp. particleboard phantoms from IC showed good agreement with Gafchromic EBT3 radiochromic films, and they were benchmarked with those of water and solid water phantoms for the selected high energy photons and electrons, demonstrating the possibility to use these dosimeters under extremely intense radiation fields and confirming the effectiveness of the DSF/NaOH/IA-PAE/*R.* spp. particleboards. The fabricated particleboard phantom (sample A15) was shown to be ideal for use in radiation therapy dosimetry as tissue-equivalent phantom material within the range of 1% variations to those of water and solid water phantoms.

**Author Contributions:** Conceptualization, D.O.S., M.Z.A.A., A.S., N.A.A.H. and R.H.; Data curation, D.O.S., M.Z.A.A. and S.H.Z.; Formal analysis, D.O.S., M.Z.A.A., M.F.M.Y. and N.A.R.; Funding acquisition, M.Z.A.A., A.S., R.H. and M.F.M.Y.; Investigation, D.O.S., R.H. and S.J.G.; Methodology, D.O.S., M.Z.A.A., N.A.A.H., S.H.Z. and M.F.M.Y.; Project administration, A.S.; Resources, A.S. and S.J.G.; Software, D.O.S., S.H.Z. and N.A.R.; Supervision, A.S. and M.F.M.Y.; Validation, D.O.S., M.Z.A.A., N.A.A.H. and M.F.M.Y.; Visualization, R.H., N.A.R. and S.J.G.; Writing—original draft, D.O.S.; Writing—review and editing, D.O.S., M.Z.A.A., A.S. and R.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Universiti Sains Malaysia under Fundamental Grant Research Scheme, Ministry of Higher Education [Grant No. FRGS/1/2022/STG07/USM/02/2].

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** We express our appreciation and gratitude to the Advanced Medical and Dental Institute, Universiti Sains Malaysia and the Malaysian Nuclear Agency for allowing this research to be conducted using their facilities.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
