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A device for production of PAGAT dosimetry gel
Christina Stengl1,2,3, Maike Kleiss2, Ronald E Teto2
1Department of Radiation Oncology, Heidelberg University Hospital (UKHD), Heidelberg, Germany.
Background:
PAGAT (PolyAcrylamide Gelatine gel fabricated at ATmospheric conditions) gel dosimetry provides a valuable three-dimensional (3D) measurement tool for photon therapy, particularly in the context of advanced radiotherapy techniques such as volumetric modulated arc therapy or intensity-modulated radiation therapy. However, the production of PAGAT gel is highly sensitive to variations in the preparation process, particularly in open environments.
Methods:
To ensure reliable production of PAGAT gel and a simplified workflow for inexperienced users, a gel preparation device was designed. This device enables (i) single-component preparation, (ii) transfer of gel components, and (iii) filling of gel in 3D-printed vials. The gel batches prepared with this device were analyzed for stability and reproducibility. Furthermore, sensitivity to oxygen exposure was tested with and without Tetrakis(hydroxymethyl)phosphonium chloride (THPC). Additionally, vials used for gel storage and irradiation were fabricated using two different PolyJet 3D printers, with either internal support material (opaque finish) or no internal support material (glossy finish). Post-processing of the printed vials was carried out using either sodium hydroxide (NaOH) cleaning or water rinsing.
Results:
The PAGAT gel produced with this device demonstrated high reproducibility, with a standard error of the mean below 1.8%. The gel remained stable for up to 14 days post-preparation. However, THPC was necessary to remove the residual oxygen from the solution. While the choice of 3D printer did not influence gel performance, the cleaning method played a critical role, with NaOH-cleaned opaque prints showing reduced gel response.
Conclusions:
The gel preparation device enabled low-cost PAGAT gel production. The system provided a stable and closed environment to ensure consistent gel properties, reducing variability in dosimetry applications. Its design also offers potential for use with other polymer gel formulations requiring controlled conditions.
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