Prog Med Phys.  2024 Dec;35(4):135-144. 10.14316/pmp.2024.35.4.135.

Evaluating the Influence of Scan Timing on Dosimetric Accuracy in EBT3 and EBT4 Radiochromic Films

• Cho JD
• Han SC
• Lee JJB
• Lee H
• Nam H

• KMID: 2564152
• DOI: http://doi.org/10.14316/pmp.2024.35.4.135

Abstract

Purpose
This study compares the dosimetric properties of EBT3 and EBT4 GAFchromic films in transmission and reflection scanning modes, focusing on dose response, sensitivity, and postirradiation stability.
Methods
The EBT3 and EBT4 films were irradiated at doses of 0–10 Gy using a Varian TrueBeam linear accelerator at 6 MV. The films were scanned at intervals between 1 and 336 hours after irradiation in both transmission and reflection modes. Net optical density (NetOD) values from each scan were used to evaluate dose response and sensitivity, with calibration curves created for each film and scan mode. Dose differences between calculated and delivered doses were assessed over time.
Results
The EBT3 and EBT4 films exhibited similar dose–response curves and stable NetOD values across both scanning modes. However, EBT4 exhibited reduced sensitivity variability in response to dose changes. After irradiation, NetOD values increased up to 24 hours before stabilizing, suggesting that a 24-hour scan time is sufficient for consistent measurements. Dose differences between films and modes remained within ±4%.
Conclusions
EBT4 offers comparable dosimetric performance to EBT3, with additional benefits, such as improved dose–response linearity and reduced sensitivity fluctuations. The findings indicate that EBT4 can serve as a reliable successor to EBT3.

Keyword

Radiochromic film; Scan timing; Postirradiation stability; Film dosimetry; Dose sensitivity

Figure

• 

  Fig. 1 Net optical density (NetOD) changes over time for the EBT3 and EBT4 films according to scan time and mode. (a) EBT3 transmission represents EBT3 scanned in the transmission mode, (b) EBT4 transmission represents EBT4 scanned in the transmission mode, (c) EBT3 reflection represents EBT3 scanned in the reflection mode, and (d) EBT4 reflection represents EBT4 scanned in the reflection mode. a.u, arbitrary units.

• 

  Fig. 2 (a) EBT3 transmission, (b) EBT4 transmission, (c) EBT3 reflection, and (d) EBT4 reflection. Dose–response curves for the EBT3 and EBT4 films according to scan time and mode. NetOD, net optical density; a.u, arbitrary units.

• 

  Fig. 3 Dose sensitivity for the EBT3 and EBT4 films according to scan mode for the calibration film.

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  Fig. 4 (a) EBT3 transmission, (b) EBT4 transmission, (c) EBT3 reflection, and (d) EBT4 reflection. Box plot showing the mean dose difference between the delivered and calculated doses for the EBT3 and EBT4 films across scan modes over time. The graph illustrates the distribution of dose differences in the 0–10 Gy range as a function of time.

Reference

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