Leipzig Applicator HDR End-to-End Testing Using In-House Fabricated 16 Mm EBT4 Radiochromic Film Discs
Abstract
Purpose
Commissioning of horizontal Leipzig applicators in HDR typically includes determination of the effective distal source position and output verification using a suitable chamber. In addition to those methods, we previously described an end-to-end testing procedure using optically stimulated luminescent dosimeters (OSLDs) in which measured doses were compared to published Monte Carlo simulation data. In this work, we refine that methodology by implementing in-house fabricated EBT4 radiochromic film discs in place of OSLDs.
Methods
EBT4 film discs were prepared in-house and calibrated with a 6MV linac using a custom treatment jig designed in CAD and fabricated via 3D printing. Custom CAD-designed and 3D-printed holders were also developed for both the film discs and horizontal Leipzig applicators. These fixtures reproducibly aligned the film along the central axis of irradiation while allowing variation in solid water thickness to simulate measurement depth. Expected doses to water at 3 mm depth were determined from published Monte Carlo–based dose tables for horizontal Leipzig applicators with nominal diameters of 3 cm, 2 cm, and 1 cm. Measured doses obtained using in-house calibrated EBT4 film were compared to calculated values to assess dosimetric agreement.
Results
Measured doses for the 3 cm, 2 cm, and 1 cm Leipzig applicators were within 2% of published Monte Carlo–derived values at 3 mm depth. This level of agreement is comparable to the percentage differences observed with our previously described OSLD-based methodology.
Conclusion
Calibrated EBT4 radiochromic film discs demonstrated comparable dosimetric accuracy to OSLDs and provide a reliable alternative for end-to-end testing in HDR brachytherapy commissioning.