Novel laser-processed CsI:Tl detector for SPECT

Abstract

Purpose: The aim of this work is to demonstrate the feasibility of a novel technique for fabrication of high spatial resolution CsI:Tl scintillation detectors for single photon emission computed tomography systems. Methods: The scintillators are fabricated using laser-induced optical barriers technique to create optical microstructures (or optical barriers) inside the CsI:Tl crystal bulk. The laser-processed CsI:Tl crystals are 3, 5, and 10 mm in thickness. In this work, the authors focus on the simplest pattern of optical barriers in that the barriers are created in the crystal bulk to form pixel-like patterns resembling mechanically pixelated scintillators. The monolithic CsI:Tl scintillator samples are fabricated with optical barrier patterns with 1.0 × 1.0 mm 2 and 0.625 × 0.625 mm 2 pixels. Experiments were conducted to characterize the fabricated arrays in terms of pixel separation and energy resolution. A 4 × 4 array of multipixel photon counter was used to collect the scintillation light in all the experiments. Results: The process yield for fabricating the CsI:Tl arrays is 100% with processing time under 50 min. From the flood maps of the fabricated detectors exposed to 122 keV gammas, peak-to-valley (P/V ) ratios of greater than 2.3 are calculated. The P/V values suggest that regardless of the crystal thickness, the pixels can be resolved. Conclusions:The results suggest that optical barriers can be considered as a robust alternative to mechanically pixelated arrays and can provide high spatial resolution while maintaining the sensitivity in a high-throughput and cost-effective manner. C 2016 American Association of Physicists in Medicine. [http://dx

Light Spread Manipulation in Scintillators Using Laser Induced Optical Barriers

“…In our earlier experiments, we applied the LIOB technique to CsI:Tl to fabricate detectors for SPECT imaging [10]. It is noteworthy that CsI:Tl has a cubical structure and also is tolerant with respect to intense laser pulse energy, and therefore we did not observe any processing problems.…”

“…Detailed descriptions of the LIOB technique as well as the similar Sub-Surface Laser Engraving (SSLE) technique are given by our group and others [10]- [14]. The basic concept of the LIOB technique is illustrated in Fig 1a. Interaction of laser light with crystal material is a function of many parameters including laser pulse energy, duration, repetition rate, crystal thermal expansion, and crystal structure.…”

“…Our scintillator fabrication technique, called laser-induced optical barriers (LIOB), is based on local modifications of the scintillator crystal structure to control the light spread and thus achieve spatial resolution [10], [11]. In this paper, we report on simulations and experimental results of cerium-doped lutetium yttrium orthosilicate (LYSO:Ce) processed by the LIOB technique for PET applications.…”

Simulation study of light transport in laser-processed LYSO:Ce detectors with single-side readout

“…These techniques have found their way in a variety of medical imaging applications including Positron Emission Tomography (PET) (Moriya et al 2010, Sabet et al 2012a, Hunter et al 2015, Sabet et al 2016a, Uchida et al 2016, Bläckberg et al 2016b), Single Photon Emission Computed Tomography (SPECT) (Sabet et al 2016b), and Computed Tomography (CT) (Bläckberg et al 2016a). In LIOB a high power pulsed laser is tightly focused inside the bulk of a scintillator crystal, causing a local modification of the crystal structure.…”

Recent Advances of Radiation Detector Systems in Nuclear Medicine Imaging

“…and body-function studies [3] . The types of detectors encountered in nuclear medicine are gas-filled detectors, solid-state (semiconductor) detectors, and scintillation (organic and inorganic) detectors.…”