Film-Based Commissioning of Valencia Skin Applicators—the Sutter Experience
Abstract
Purpose
To report clinical experience in commissioning Valencia surface applicators by applying published guidance and using fully film-based methods to assess source positioning, flatness/symmetry, depth dose, and output verification.
Methods
Commissioning of the 2-cm and 3-cm diameter Valencia applicators was performed using the Varian Bravos afterloader, Gafchromic EBT3 and EBT4 film calibrated with a 6 MV TrueBeam linear accelerator, and an EPSON 10000XL scanner using RIT for film analysis. Film batches were calibrated with doses ranging from 0-1000 cGy for purposes of absolute dose confirmation. Flatness and symmetry measurements were performed using film in solid water at a depth of 3 mm. Depth dose measurements were assessed using two different film orientations.
Results
For both the 2-cm and 3-cm diameter Valencia applicators, positioning the source 1 mm back from the applicator tip resulted in flatness and symmetry within +/-5% in both directions. Absolute dose measurements using the first film batch initially showed a systematic under-response relative to the planned dose. Subsequent measurements using a new film batch showed deviations of 4-6%, which is within the expected uncertainty. Depth dose values were largely within published specifications. One depth dose point initially exceeded tolerance when measured with the film oriented perpendicular to the applicator face. However, a spot check using film oriented parallel to the applicator face yielded agreement within 0.5%, and further measurements are ongoing to assess orientation-dependent effects. During end-to-end testing, improper applicator cap seating produced pronounced asymmetry ranging from -29% to 56%.
Conclusion
This clinical experience demonstrates that a fully film-based commissioning approach for Valencia applicators provides reliable data for quantifying source position, flatness, symmetry, depth dose, and output verification. It also reinforces the importance of accurate applicator assembly by highlighting the sensitivity of dose distribution to applicator cap seating.