Surface applicator calibration and commissioning of an electronic brachytherapy system for nonmelanoma skin cancer treatmenta)
(a) Applicator source channel connecting to the 35 mm cone on the right end and the Touhy burst adaptor on the left. Below are four skin applicator cones with different sizes. (b) The Axxent® FlexiShield Mini with drawn circles representing different field sizes.
L-shaped in-air calibration fixture with the PTW T34013 parallel-plate chamber centrally placed under the 10 mm applicator for the in-air measurement.
Surface applicator QA test fixture with the PTW T34013 parallel-plate chamber centrally inserted under the applicator for shielded measurements.
(a) Patient setup with a thermoplastic facemask for skin treatment on the ear. (b) Radiation protection with the rolling shield in place.
Diagram of measurement points with clinical setup for the ear, scalp, and leg cases. Point A is right behind the controller. Points B, G, C, and D are 1 m from the source superior, inferior, right, and left. Point E is 1 m from the source to the left. Point F is behind the rolling shield.
Nominal dose rate of the 35 mm applicator at skin surface over 16 sources. Its average is 1.35 Gy/min with a variation of 5%.
Nominal dose rate variation for two individual sources measured on three different days. On each day the measurement was repeated five times. The variation is less than 1% for the same source.
Nominal dose rates of three sources at skin surface for four different cone sizes. The average nominal dose rate for each cone is shown.
(a) EBT GafChromic film exposure at surface for a 35 mm cone. (b) Relative dose profiles for the 35 mm cone from the EBT GafChromic films exposed to five sources. (c) Relative dose profiles for the 10 mm cone from the EBT GafChromic films exposed to five sources.
Factory data of PDDs for four applicator cones. Diamonds, squares, rectangles, and stars represent the PDD curves for 50, 35, 20, and 10 mm cones.
Depth dose comparisons of measurements performed in water vs solid water for the 35 mm applicator. The rectangles represent the measurement points in water provided by the vendor. The squares represent the measurement points obtained clinically in solid water setup using thin-window parallel-plate chamber.
The plot of vs corresponding air gap (squares) and the linear fit. The slope of the curve is used to determine the effective SSD for the 35 mm cone.
Different collimations using the FlexiShield lead material for targets located at (a) the temple, (b) the bridge of the nose, and (c) the left ear.
Room exposure at different locations during the treatment of several patient setups.
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