Speaker
Description
X-ray phase imaging techniques has been developing for the last decade because of its attractive potentials [1–7]. X-ray phase imaging provides three images such absorption, differential-phase, and visibility-contrast images. This future causes to higher resolution density variations in the sample than that conventional absorption-contrast X-ray imaging. Medical and biological imaging is the main target of X-ray phase imaging, and several trials using synchrotron radiation sources and laboratory sources have been made. In X-ray Talbot-Lau interferometry, single or mulch absorption gratings between a sample and X-ray generate detector differential-phase, and visibility-contrast images. The absorption gratings generate Moire fringes and differential-phase, and visibility-contrast images are obtained from analysis of the spatial frequency of the Moire fringes. However absorption gratings absorbed the transmitted X-ray and sensitivity is degraded. So exposure dose can become a problem in medical and biological imaging.
Recently submicron-diameter phase-separated scintillator fibers (PSSFs) were reported and they possessed both the properties of an optical fiber and a radiation-to-light conversion. The PSSFs were fabricated using a directionally solidified eutectic (DSE) system. Our group reported high-resolution X-ray imaging using Ce doped GdAlO3(GAP)/a-Al2O3 eutectic[9,10]. In this study, Tb and Eu doped GAP/a-Al2O3 eutectic scintillator was grown by the micro pulling down (-PD) method with varius growth rate. Radiomuninescence intensity, decay time and scintillation fibers diameter were evaluated for X-ray imaging detecrtor.
1~15mol% Tb and Eu doped GAP/-Al2O3 eutectics were grown by the -PD method. Tb3+ and Eu3+ 4f4f emission were observed in 470-700nm and 580-750nm ranges , respectively. Tb 8mol% and Eu 5mol% samples showed 5.5 and 4.4 times higher emission intensity than Ce doped one. Diameter pf scintillation fibers were 2.43-0.38mm for growth rate of 0.07-3.0 mm/min in the grown Tb 8mol% doped GAP/a-Al2O3 eutectics. The best contrast transfer function@122lp/mm of 0.28 was archived at the sample of growth rate at 0.3mm/min. The grown eutectic wafers were mounted on a CMOS sensor (SONY, 2.5μm pitch, 2080x1552pizels, 5.2x3.9mm sensitive area) with a fiber optic plate (FOP, Hamamatsu J5734, 3m fiber diameter). By using this sensor, a prototype of X-ray Talbot-Lau imaging system was developed. Absorption, differential-phase, and visibility-contrast images were simultaneously obtained without absorption grating. Comparing to X-ray Talbot-Lau imaging system using CsI scintillator and a absorption grating, 2 time higher signal difference-to-noise ratio was achieved at the same radiation dose of 10mGy. This is the first result of direct X-ray phase imaging. Details on eutectic growth, detector design and X-ray phase imaging will be showed in the presentation.
References
1. A. Momose, et al., Jpn. J. Appl. Phys. 42, L866–L868 (2003).
2. T. Weitkamp, et al., Appl. Phys. Lett. 86, 054101 (2005).
9. Y. Ohashi, , et al., Appl. Phys. Lett. 102 (2013) 05190
10. Y. Ohashi, et al., J. Eur. Ceram. Soc. (2014), in press, [doi:10.1016/j.jeurceramsoc.2014.04.042]
