Quality assurance procedures required in modem radiotherapy would greatly benefit from the development of tissue equivalent dosimeters able to render three-dimensional dose profiles with a high spatial resolution. In this scenario, Fricke gel (FG) dosimeters could be good candidates, but some limitations have restricted their use in clinical practice. Recently, formulations based on gel matrices of poly(vinyl-alcohol) (PVA) chemically cross-linked with glutaraldehyde (GTA) have shown improvements compared to FGs with natural matrices.The purpose of this study is the characterization of the dosimetric properties of radiochromic PVA-GTA FG dosimeters by means of absorption spectroscopy measurements. Xylenol orange (XO) FG dosimeters, prepared in spectrophotometry cuvettes using 9.1 w/w of Mowiol (R)-PVA and 26.5mM of GTA, were uniformly irradiated with a Cs-137 source and with 6 and 15 MV x-rays generated by a medical linear accelerator. Ultraviolet-visible absorbance spectra collected at consecutive times post-irradiation showed that a time of approximately 15 min is sufficient to reach a stable absorbance value, indicating the achievement of a chemical equilibrium in the complexation processes between Fe3+ and XO. The analysis of the change of the absorbance spectra shape with the cumulated dose demonstrated that a linear dose-response curve of PVA-GTA FG dosimeters is obtained in the entire investigated dose interval of 0.5-15 Gy by properly choosing the wavelength used for the absorbance measurements. Furthermore, PVA-GTA FG dosimeters proved to be nearly water- and tissue-equivalent and characterized by a response independent of the energies and dose rates in the investigated intervals. These findings suggested that PVA-GTA FGs are promising tools for dosimetry applications in external x-ray radiation therapy.

Characterization of radiochromic poly(vinyl-alcohol)–glutaraldehyde Fricke gels for dosimetry in external x-ray radiation therapy / S. Gallo, E. Artuso, Maria Grazia Brambilla, G.L.C. Gambarini, C. Lenardi, Angelo Filippo Monti, A. Torresin, E. Pignoli, I. Veronese. - In: JOURNAL OF PHYSICS D. APPLIED PHYSICS. - ISSN 0022-3727. - 52:22(2019), pp. 225601.1-225601.9.

Characterization of radiochromic poly(vinyl-alcohol)–glutaraldehyde Fricke gels for dosimetry in external x-ray radiation therapy

S. Gallo
Primo
Investigation
;
E. Artuso
Membro del Collaboration Group
;
G.L.C. Gambarini
Conceptualization
;
C. Lenardi
Membro del Collaboration Group
;
A. Torresin
Membro del Collaboration Group
;
E. Pignoli
Membro del Collaboration Group
;
I. Veronese
Ultimo
Supervision
2019

Abstract

Quality assurance procedures required in modem radiotherapy would greatly benefit from the development of tissue equivalent dosimeters able to render three-dimensional dose profiles with a high spatial resolution. In this scenario, Fricke gel (FG) dosimeters could be good candidates, but some limitations have restricted their use in clinical practice. Recently, formulations based on gel matrices of poly(vinyl-alcohol) (PVA) chemically cross-linked with glutaraldehyde (GTA) have shown improvements compared to FGs with natural matrices.The purpose of this study is the characterization of the dosimetric properties of radiochromic PVA-GTA FG dosimeters by means of absorption spectroscopy measurements. Xylenol orange (XO) FG dosimeters, prepared in spectrophotometry cuvettes using 9.1 w/w of Mowiol (R)-PVA and 26.5mM of GTA, were uniformly irradiated with a Cs-137 source and with 6 and 15 MV x-rays generated by a medical linear accelerator. Ultraviolet-visible absorbance spectra collected at consecutive times post-irradiation showed that a time of approximately 15 min is sufficient to reach a stable absorbance value, indicating the achievement of a chemical equilibrium in the complexation processes between Fe3+ and XO. The analysis of the change of the absorbance spectra shape with the cumulated dose demonstrated that a linear dose-response curve of PVA-GTA FG dosimeters is obtained in the entire investigated dose interval of 0.5-15 Gy by properly choosing the wavelength used for the absorbance measurements. Furthermore, PVA-GTA FG dosimeters proved to be nearly water- and tissue-equivalent and characterized by a response independent of the energies and dose rates in the investigated intervals. These findings suggested that PVA-GTA FGs are promising tools for dosimetry applications in external x-ray radiation therapy.
Fricke gel; poly(vinyl alcohol); dosimetry; tissue equivalence; glutaraldehyde
Settore FIS/07 - Fisica Applicata(Beni Culturali, Ambientali, Biol.e Medicin)
Settore MED/36 - Diagnostica per Immagini e Radioterapia
Settore FIS/01 - Fisica Sperimentale
Settore CHIM/02 - Chimica Fisica
2019
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/640512
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