On the correction of lateral response artifact in accelerated radiochromic film dosimetry protocols

This study investigates the correction of the lateral response artifact (LRA) in accelerated protocols for radiochromic film dosimetry that shorten the time between irradiation and read-out. In these protocols, the LRA is assessed by pixel profiles along the longest axis of radiochromic film strips that are scanned parallel to the axis of artifact. The interplay between the non-uniform response of flatbed scanners and unavoidable heterogeneities in the radiation fields of linear accelerators modifies these pixel profiles, deviating them from their real behavior. This phenomenon has a negative impact on radiochromic film dosimetry. To solve this issue, first-order variations in the homogeneity of the radiation fields were subtracted from the pixel profiles. We studied dose distributions of 30 × 30 cm² square fields at different dose levels and realistic radiotherapy treatment plans, using 6 MV and 6 MV flattening filter free energies. The radiochromic film models utilized were EBT4 and EBT-XD. For evaluation, gamma analysis (2 %,2 mm) and relative root mean square error metrics were employed. Comparisons against reference measurements demonstrate this novel correction is highly effective in suppressing radiation field heterogeneities, leading to enhanced dosimetric accuracy. Moreover, this study presents a semi-analytical expression for the LRA correction, which contributes to reducing uncertainties.