L Huang*, X Chang, J Liu, J Chang, Y Cao, Northwell Health, North New Hyde Park, NY

• 
  L Huang

(Saturday, 3/26/2022)   [Central Time (GMT-5)]

Purpose: To characterize the in-water percent depth dose (PDD) curve and dose profiles of the novel Y-90 planar source (Liberty Vision, Portsmouth, NH) for treating ocular melanoma using Gafchromic EBT3 films and 3D-printed film holders

Methods: A low-cost desktop 3D printer (Ender 3 v2) and the TinkerCAD were used to design and manufacture the film holders with Polylactic Acid (PLA) filament and 0.4 mm nozzle. EBT3 film sheet was cut into 3x4 cm2 (size of the holding space of the film holders) pieces. Films were calibrated (0-10 Gy) on a Truebeam of our institution. In-water PDD (normalized to depth at 1 mm from the source surface) and profile measurements were performed with these film sheets irradiated by a Y-90 disc source (6mm in diameter). In-film PDD curve was also measured using a stack of 18 cut films. Following AAPM TG-235 recommendations, irradiated films were processed and scanned using an Epson-10000XL flat-bed scanner. The dose distributions were then determined from the calibration curve.

Results: Measured printing accuracy was within 0.5 mm. Exponential fit (y=A_1*e^(-x/t_1 )) of the in-water PDD curve yielded a R2 of 0.998. In-film PDD curve has a faster dose fall-off due to its higher density. However, after applying a scaling factor of 1.4, the in-film PDD agreed well with the in-water PDD (Correlations Coefficient=0.9993). Profiles were acquired at depths of 0.14, 1.28, 3.28 mm corrected for the film thickness. Full-width-half maximum (FWHM), calculated from RIT V6.8, were 5.191±0.014, 5.436±0.076, 7.29±0.37 mm, respectively.

Conclusion: This is the first experimental study on the dose distribution of the novel Y-90 planar source for episcleral brachytherapy. The 3D-printed film holders demonstrated effective in acquiring PDD curves and dose profile. The in-film measurement is easy to implement but requires a scaling factor of 1.4 in depth for conversion to in-water measurement

ePosters

• 174-60687-16021654-182477-1914628224.pdf (L Huang)

Keywords

Brachytherapy, Radiochromic Film, Phantoms

Taxonomy

TH- Brachytherapy: Beta emitting sources and applications

Contact Email