Evaluation of the spatial resolution of Gafchromic (TM) HD-V2 radiochromic film characterized by the modulation transfer function

The Modulation Transfer Function (MTF) characteristics of radiochromic film (RCF) dosimetry with optical systems were evaluated with an RCF, HD-V2, which is transferred with the line patterns of the resolution test chart. In the evaluation using a GT-X980 flatbed scanner, a high contrast spatial resolution with an MTF of >= 0.8 is limited to about 83.3 mu m due to artifacts such as scattering of the HD-V2 transmitted light. To achieve high contrast at higher spatial frequencies, a test bench microdensitometer (TBMD) was developed, and its optical performance, dose equivalent response, and spatial resolution characteristics with MTF were evaluated. The TBMD had a minimum readout focal diameter of 13 mu m, and its high contrast spatial resolution with an MTF of >= 0.8 is about 11.9 mu m. The result that the optical density error increases with decreasing focal diameter in the TBMD supports our hypothesis that these errors are based on the non-uniformity of the shading and surface roughness of the HD-V2 active layer monomers. (c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

The MTF characteristics of radiochromic film dosimetry with optical systems were evaluated using an RCF, HD-V2, and a resolution test chart. The evaluation showed that a high contrast spatial resolution with an MTF of >= 0.8 is limited to about 83.3 μm due to artifacts. To achieve higher contrast at higher frequencies, a test bench microdensitometer (TBMD) with a high contrast spatial resolution of about 11.9 μm was developed. The optical density error in the TBMD was found to increase with decreasing focal diameter, supporting the hypothesis of non-uniform shading and surface roughness in the HD-V2 active layer monomers.