Biophotonic imaging has revolutionized the operation room by providing surgeons intraoperative image-guidance to diagnose tumors more efficiently and to resect tumors with real-time image navigation. Among many medical imaging modalities, near-infrared (NIR) light is ideal for image-guided surgery because it penetrates relatively deeply into living tissue, while nuclear imaging provides quantitative and unlimited depth information. It is therefore ideal to develop an integrated imaging system by combining NIR fluorescence and gamma-positron imaging to provide surgeons with highly sensitive and quantitative detection of diseases, such as cancer, in real-time without changing the look of the surgical field. The focus of this review is to provide recent progress in intraoperative biophotonic imaging systems, NIR fluorescence imaging and intraoperative nuclear imaging devices, and their future perspectives for image-guided interventions.

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

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A tightly focused pulsed laser beam can locally modify the crystal structure inside the bulk of a scintillator. The result is incorporation of so-called optical barriers with a refractive index different from that of the crystal bulk, that can be used to redirect the scintillation light and control the light spread in the detector. We here systematically study the scintillation light transport in detectors fabricated using the Laser Induced Optical Barrier technique, and objectively compare their potential performance characteristics with those of the two mainstream detector types: monolithic and mechanically pixelated arrays. Among countless optical barrier patterns, we explore barriers arranged in a pixel-like pattern extending all-the-way or half-way through a 20 mm thick LYSO:Ce crystal. We analyze the performance of the detectors coupled to MPPC arrays, in terms of light response functions, flood maps, line profiles, and light collection efficiency. Our results show that laser-processed detectors with both barrier patterns constitute a new detector category with a behavior between that of the two standard detector types. Results show that when the barrier-crystal interface is smooth, no DOI information can be obtained regardless of barrier refractive index (RI). However, with a rough barrier-crystal interface we can extract multiple levels of DOI. Lower barrier RI results in larger light confinement, leading to better transverse resolution. Furthermore we see that the laser-processed crystals have the potential to increase the light collection efficiency, which could lead to improved energy resolution and potentially better timing resolution due to higher signals. For a laser-processed detector with smooth barrier-crystal interfaces the light collection efficiency is simulated to >42%, and for rough interfaces >73%. The corresponding numbers for a monolithic crystal is 39% with polished surfaces, and 71% with rough surfaces, and for a mechanically pixelated array 35% with polished pixel surfaces and 59% with rough surfaces.

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We are developing a technique to fabricate high spatial resolution and cost-effective photon counting detectors using silicon photomultipliers (SiPMs) and microcolumnar structured scintillator. Photon counting detectors using SiPMs are of much interest to the gamma-and X-ray detector community, but they have limitations at low energy due to their dark noise. In this paper, we report on vapor deposition of CsI:Tl directly onto a SiPM, a technique that improves optical coupling and allows for detection of low energy gamma-and X-rays. It simultaneously addresses related issues of light loss and light spread in the scintillator, thereby improving the performance of the detector. Devices made by this technique may be used for both photon counting and gamma-and X-ray imaging.The SiPM used in this study comprises a 4 4 array of macropixels, each of which is 3.0 mm 3.0 mm, with 3.36 mm pitch. This SiPM was placed inside a physical vapor deposition chamber and a 0.75 mm thick layer of microcolumnar CsI:Tl was grown on its surface without any damage. Scanning Electron micrographs (SEM) show highly oriented microcolumnar CsI:Tl structure orthogonal to the SiPM surface. These microcolumnar structures are excellent for channeling scintillation light to the SiPM and provide sub-macro-pixel resolution, which is now limited to the size of the macro-pixels. In this study, we report the performance characteristics of the resultant detector in terms of position sensitivity, energy discrimination, optical crosstalk, and signal-to-noise ratio. The performance of the detector is evaluated against that of other CsI:Tl/SiPM combinations, such as mechanically coupled monolithic and laser-pixelated CsI:Tl scintillators. Success of the technique may be gauged by the fact that the photopeak can be realized for a wide range of energies, including those of (60 keV) and(122 keV).