Reflections - Abstract

Glass Reflections
Cambridge 7th to 9th September

Presenting Author:
Safa Kasap
<safa.kasap@usask.ca>
article posted 30 Apr 2015

Safa Kasap

Safa Kasap is currently Canada Research Chair (Tier 1) and Professor of Electronic and Optoelectronic Materials and Devices at the University of Saskatchewan in Canada. He works closely with scientists at the Canadian Light Source (The Canadian Synchrotron) on campus, and with industry, for the development of new functionalities in glasses for applications in radiation detection and medical imaging. He has two widely used textbooks: Principles of Electronic Materials and Devices, 3rd Ed (McGraw-Hill) and Optoelectronics and Photonics, 2nd Ed (Prentice-Hall: Pearson). He is the Deputy Editor of J. Materials Science: Materials in Electronics (Springer) and a Co-Editor of the Springer Handbook of Electronic and Photonic Materials. Professor Kasap is Fellow of the Royal Society of Canada, the American Physical Society and SGT in the UK.

Development of Sm-Doped Glass-Ceramics for High-Dose,
High-Resolution Dosimetry in Microbeam Radiation Therapy
at the Canadian Light Source
Safa Kasap^1*, Go Okada², Jumpei Ueda³, Setsuhisa Tanabe³, George Belev⁴, Tomasz Wysokinski⁴ and Dean Chapman^4,5
There is a need to develop high-dose, high-resolution dosimetric detectors to characterize the microstructured x-ray beams used in microbeam radiation therapy (MRT). In this paper, we report a technique that is based on the reduction of Sm³⁺ to Sm²⁺ within CaF₂ nanocrystals embedded in an oxyfluoride glass-ceramic (SiO₂-Al₂O₃-CaF₂-CaO-SmF₃) plate [1]. We use the extent of Sm³⁺ --> Sm²⁺ valence reduction caused by x-ray irradiation as a probe of the x-ray dose delivered.

A confocal fluorescence microscope is used to read out the distribution of reduced Sm²⁺-ions by their characteristic photoluminescence (PL) emission. The PL emission from Sm³⁺ and Sm²⁺ ions have distinctly different PL characteristics and can be distinguished. The technique is similar to that reported for Sm-doped fluorophosphate and fluoroaluminate glasses for MRT where the x-ray induced Sm³⁺ --> Sm²⁺ valence reduction occurred within the glass matrix [2].

We demonstrate that the Sm³⁺ --> Sm²⁺ valence reduction takes place in CaF₂ nanocrystals, and not in the glass matrix. The PL emission from the Sm²⁺-ion is mainly due to the fast 4f₅5d¹ --> ⁷F₀ transition (in contrast to the f-f transitions in Sm²⁺ in a glass host), which allows us to read out the

irradiated dosimetric plate at a high scanning speed in confocal fluorescence microscopy. In addition, we show that the dose range that can be detected is several thousands of gray, and x-ray dose distribution is detected at a micrometer scale. Further, the x-ray induced Sm²⁺ signal can be erased by heating the irradiated sample at a suitable high temperature; or by exposing it to UV light. The erased glass-ceramic plate can be used again with very little variation in its response characteristics as a dosimetric detector. The new Sm-doped oxyfluoride glass ceramic containing dispersed CaF₂:Sm³⁺ nanocrystals reported in this work shows potential for practical use in high-dose, high-resolution dosimetry for MRT.

References:

1. G. Okada, J. Ueda, S. Tanabe, G. Belev, T. Wysokinski, D. Chapman, D. Tonchev, and S. Kasap, J. Am. Ceram. Soc., 97, 2147 (2014)

2. Go Okada, B. Morrell, C. Koughia, A. Edgar, C. Varoy, G. Belev, T. Wysokinski, D. Chapman and S. Kasap, Appl. Phys. Lett., 99, 121105 (2011)

Institutions:

1Electrical Engineering, University of Saskatchewan, Saskatoon, Canada

2Materials Science, Nara Institute of Technology, Nara, Japan

3Graduate School of Global Environmental Studies, Kyoto University, Japan

4Canadian Light Source Inc., Saskatoon, SK, Canada

5Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, Canada