Evaluation of material heterogeneity dosimetric effects using radiochromic film for COMS eye plaques loaded with ¹²⁵I seeds (model I25.S16)

Abstract

Substantial heterogeneity effect on the (125)I dose distributions in an eye phantom for COMS plaques was verified using radiochromic EBT film dosimetry. The calculated doses for uniformly loaded plaques using PS with heterogeneity correction option enabled were corroborated by the EBT film measurement data. Radiochromic EBT film dosimetry is feasible in measuring absolute dose distributions in eye phantom for COMS eye plaques loaded with single or multiple (125)I seeds. Plaque Simulator is a viable tool for the calculation of dose distributions if one understands its limitations and uses the proper heterogeneity correction feature.

I‐125 ROPES eye plaque dosimetry: Validation of a commercial 3D ophthalmic brachytherapy treatment planning system and independent dose calculation software with GafChromic® EBT3 films

“…These dose differences may be attributed to uncertainties in the film measurements due to positioning uncertainties, or the algorithm used in PS to account for the collimating lip. 19 The effect was also observed by Acar et al 19 in their measurements of the dose distribution produced by COMS plaques using EBT film. Deviations of up to 17% at 5 mm depth and 9% at 12 mm depth occurred between their film measurements and the heterogeneous PS calculation.…”

“…Radiochromic film dosimetry has recently been established as a reliable method in measuring dose distributions produced by COMS type eye plaques loaded with various I-125 seed models. 10,[19][20][21][22] Acar 22 and Acar et al 19 have used GafChromic R EBT film in a polystyrene eye phantom to measure absolute doses along the plaque CAX and in off-axis directions at depths of 5 and 12 mm for four types of COMS plaques loaded with model I25.S16 I-125 seeds. Krintz et al 10 measured relative dose distributions from COMS eye plaques uniformly loaded with model 6711 I-125 seeds in a Solid Water TM phantom using GafChromic model MD55-2 films.…”

Report of AAPM Task Group 235 Radiochromic Film Dosimetry: An Update to TG‐55

“…One or two (one above and one below the brachytherapy source) film pieces are irradiated at a time. Each film is positioned in contact, or at a given distance (such as 0.5 to 3 cm) from a brachytherapy source of the same radionuclide with a known dose to water at the film center 15,103,104,140,146–148 . For low dose rate (LDR) sources, this method can demand very long exposure times.…”

Multidimensional dosimetry of 106Ru eye plaques using EBT3 films and its impact on treatment planning

“…They were able to reduce the uncertainty down to ±15% as compared to the 95% confidence interval of ±25% specified by the manufacturer. 11 Other studies investigated the use of radiochromic films, 10,[12][13][14][15][16][17] TLDs, 15,16,[18][19][20][21][22][23] extrapolation ionization chambers, 24 and diodes 25 which are considered to be a standard for 125 I eye plaque dosimetry. Other dosimetric techniques which are less widely used, such as plastic scintillators, 11,26,27 threedimensional liquid scintillators, 28 and polymer gel dosimetry 29 were explored as well.…”