15 years of ¹⁰⁶ Ru eye plaque dosimetry at Memorial Sloan-Kettering Cancer Center and Weill Cornell Medical Center using radiochromic film in a Solid Water phantom

Abstract

Purpose. 106 Ru eye plaques are used for treatment of intraocular malignancies, providing a good alternative to enucleation. We perform our own acceptance testing and commissioning of 106 Ru eye plaques using radiochromic film as recommended by ISO standard 21439:2009 'Clinical dosimetrybeta radiation sources for brachytherapy'. A Solid Water 'eye' phantom with several novel features and related tools were developed for accurate radiochromic film dosimetry of eye plaques. Methods. The phantom enables full 3D dosimetric characterization of eye plaques. Films perpendicular to the central axis of the eye plaques are sandwiched between inserts in the phantom. Small holes in the phantom inserts enable marking the films with respect to the eye plaques, assuring exact geometrical coregistration. Special thin unlaminated radiochromic films were utilized, enabling dosimetric measurements virtually at the surface of the eye plaques. Precise film punches were developed in order to cut films with diameters as small as 8.5 mm and make cutouts in films without damaging the cut edges. Results. Full dosimetric characterization of three CCX type and partial characterization of a CIA type 106 Ru eye plaques is presented. Replicate film results were reproducible to within 4%-5%. Even 4% non-uniformities in planar dose rates were easily detected. Comparison with Monte Carlo calculations by Hermida-López 2013 Med. Phys. 40 101705-1-101705-13, found good agreement along the central axis, but some lateral differences. Conclusions. Accurate and precise 106 Ru eye plaque dosimetry was achieved utilizing radiochromic film in the phantom introduced here. Co-registration of eye plaques and films permits not only precise treatment planning calculations along the central axis of the plaque, but also accounts for dosimetric non-uniformities using 2D or 3D methodologies. Dose measurements on the inner surface of the plaques provide precise assessment of the scleral dose, its homogeneity, and the active area of the plaques for coverage determination.

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

“…103,105 The LDR source dosimetry studies using the EBT film series include 106 Ru/ 106 Rh eye plaques, 325 125 I eye plaques, 145,147 new concept 125 I plaques, 3 125 I seeds, 103,105 and 131 Cs seeds 105 in solid water phantoms, and 137 Cs sources in GYN applicators. 326 In 2018, Trichter et al 327 described in detail a specially designed Solid Water eye phantom used for dosimetry of 106 Ru/ 106 Rh eye plaques with regular and unlaminated RCFs. The active layer of the unlaminated films was either unprotected (EBT3 unlaminated) on the surface of the film or covered by just a few microns of protective layer (EBT unlaminated).…”

“…In 2018, Trichter et al 327 described in detail a specially designed Solid Water eye phantom used for dosimetry of 106 Ru/ 106 Rh eye plaques with regular and unlaminated RCFs. The active layer of the unlaminated films was either unprotected (EBT3 unlaminated) on the surface of the film or covered by just a few microns of protective layer (EBT unlaminated).…”

Modified Geometry of 106Ru Asymmetric Eye Plaques to Improve Dosimetric Calculations in Ophthalmic Brachytherapy

“…To the best of our knowledge, only three works [ 8 , 9 , 10 ] included some experimental results for asymmetric Ru plaques. All these works used in-house developed phantoms for the radiochromic film-based dosimetry.…”

“…All these works used in-house developed phantoms for the radiochromic film-based dosimetry. Taccini et al [ 8 ] and Trichter et al [ 10 ] presented dosimetric results in the form of isodose distributions and lateral profiles for the BEBIG asymmetric plaque models CIB and CIA, respectively, without comparing to other published data or calculations. Heileman et al [ 9 ] performed film measurements of the asymmetric COB plaque dose, showing important discrepancies with respect to simulations with the MC code MCNP6, especially in the cut-out region.…”

A convex windowless extrapolation chamber to measure surface dose rate from 106Ru/106Rh episcleral plaques

“…27 Additional dosimetry studies have included the use of scintillation detectors, thermoluminescent dosimeters, semiconductor detectors, radiochromic films, diamond detectors, diode detectors, alanine pellets, alanine-polymer film, and ionization chambers. [28][29][30][31][32][33][34][35][36][37][38] For 106 Ru/ 106 Rh plaques, all current measurement techniques rely on the use of a calibrated device to perform relative dosimetry, as opposed to an extrapolation chamber where dose is determined directly as a primary measurement device.…”