An investigation of a PRESAGE®in vivodosimeter for brachytherapy

Abstract

Determining accurate in-vivo dosimetry in brachytherapy treatment with high dose gradients is challenging. Here we introduce, investigate, and characterize a novel in-vivo dosimeter and readout technique with the potential to address this problem. A cylindrical (4 mm x 20 mm) tissue equivalent radiochromic dosimeter PRESAGE® In-Vivo (PRESAGE®-IV) is investigated. Two readout methods of the radiation induced change in optical density (OD) were investigated: (i) volume-averaged readout by spectrophotometer, and (ii) a line profile readout by 2D projection imaging utilizing a high-resolution (50 micron) telecentric optical system. Method (i) is considered the gold standard when applied to PRESAGE® in optical cuvettes. The feasibility of both methods was evaluated by comparison to standard measurements on PRESAGE® in optical cuvettes via spectrophotometer. An end-to-end feasibility study was performed by a side-by-side comparison with TLDs in an 192Ir HDR delivery. 7 and 8 Gy was delivered to PRESAGE®-IV and TLDs attached to the surface of a vaginal cylinder. Known geometry enabled direct comparison of measured dose with commissioned treatment planning system. A high-resolution readout study under a steep dose gradient region showed 98.9% (5%/1 mm) agreement between PRESAGE®-IV and Gafchromic® EBT2 Film. Spectrometer measurements exhibited a linear dose response between 0–15 Gy with sensitivity of 0.0133 ± 0.0007 ΔOD/(Gy·cm) at the 95% confidence interval. Method (ii) yielded a linear response with sensitivity of 0.0132 ± 0.0006 (ΔOD/Gy), within 2% of method (i). Method (i) has poor spatial resolution due to volume averaging. Method (ii) has higher resolution (~1mm) without loss of sensitivity or increased noise. Both readout methods are shown to be feasible. The end-to-end comparison revealed a 2.5% agreement between PRESAGE®-IV and treatment plan in regions of uniform high dose. PRESAGE®-IV shows promise for in-vivo dose verification, although improved sensitivity would be desirable. Advantages include high-resolution, convenience and fast, low-cost readout.

Dosimetric feasibility of an anthropomorphic three-dimensional PRESAGE® dosimeter for verification of single entry hybrid catheter accelerated partial breast brachytherapy

“…The formulation of PRESAGE ® used in this study has Z eff of 7•6 and a physical density of 1•07 g/cm 3 . The physical dimensions of breast PRE-SAGE ® dosimeter were 13•8 cm (length) by 12•4 cm (width) and 4•6 cm (height) [15][16][17][18][19][20][21][22][23][24][25] as shown in Figure 2a. The dosimeter was scanned with the Duke midsized optical scanner dedicated for the RPC (DMOS-RPC) (Duke University, Durham, NC, USA) using 1°per step to produce 360 projection images.…”

Radiation Dosimetry by Use of Radiosensitive Hydrogels and Polymers: Mechanisms, State-of-the-Art and Perspective from 3D to 4D

“…Some dependence of the dose sensitivity on oxygen content in PRESAGE ® was also found [ 179 ]. Despite these unfavorable properties, the relative dose distribution was found to be reproducible within a 2% dose difference for an allowable distance-to-agreement of 2 mm [ 178 ], and PRESAGE ® was applied in some clinical dosimetric validation studies including IMRT [ 180 , 181 ], VMAT [ 182 , 183 ] in the determination of output factors of gamma knife radiosurgery [ 184 ] and in brachytherapy [ 185 , 186 , 187 ]. PRESAGE ® was also tested with hadron therapy, where a 20% dose underestimation was found in the Bragg peak for protons [ 188 ], but in another study with 400 MeV carbon ions, no significant LET effect on the dose response was observed [ 189 ].…”

A Review of PRESAGE Radiochromic Polymer and the Compositions for Application in Radiotherapy Dosimetry

“…Meanwhile, the TLD has a deviation of 13.08%. In addition, PRESAGE also has a 98.9% agreement with the EBT2 film dose delivery in brachytherapy treatment [ 166 ]. Another study reported that PRESAGE provides an acceptable relative dose measurement for Ir-192 and Cs-137 brachytherapy sources [ 167 ].…”