Development and Evaluation of a Dual-Layer-Offset PET Detector Constructed with Different Reflectors

Dual-layer-offset or multi-layer-offset design of a PET detector can improve spatial resolution while maintaining high sensitivity. In this study, three dual-layer-offset LYSO detectors with three different reflectors (ESR, Toray, and BaSO4) were developed. The top layer consisted of a 17 × 17 array of crystals 1 × 1 × 6.5 mm3 in size and the bottom layer consisted of an 18 × 18 array of crystals 1 × 1 × 9.5 mm3 in size. Neither light guides nor optical glue were used between the two layers of crystals. A custom-designed electronics system, composed of a 6 × 6 SiPM array, two FPC cables, and a custom-designed data processing module, was used to read out signals. An optimized interaction-decoding algorithm using the center of gravity to determine the position and threshold of analog signals for timing methods was applied to generate decoding flood histograms. The detector performances, in terms of peak to valley ratio of the flood histograms and energy resolutions, were calculated and compared. The dual-layer-offset PET detector constructed with BaSO4 reflectors performed much better than the other two reflectors in both crystal identification and energy resolution. The average peak-to-valley ratio and the energy resolution were approximately 7 and 11%, respectively. In addition, the crystals in the bottom layer showed better performance at crystal identification than those in the top layer. This study can act as a reference providing guidance in choosing scintillator reflectors for multi-layer dedicated DOI detectors designed for small-animal PET imaging.

Fiber-optic light guides as secondary sources of light for hen keeping in cage batteries

The method of local illumination of cage batteries with LED lamps, previously developed by us, made it possible to increase the livability and productivity of hens in comparison with the traditional method. In this case, the placement of low-power LED sources directly in each cage requires a large number of rather complex electronic devices across the whole metal structure of the cage battery and extended power transmission lines. This work compares the efficiency of local LED lighting and fiber-optic light guides when keeping hens of the productive flocks of cross SP-789 in traditional cages. The 120-day-old hens were divided by the method of analogs in 2 groups of 100 heads. In the control group, LED lamps were used for local illumination of hens, and in the experimental group, fiber-optic light guides were used with LEDs as the primary source of illumination. The color temperature of light-emitting diodes was 3000 K. Up to 260 days of age, hens were kept in triple-tiered cage batteries, 5 animals per cage. The results of the study showed that in the control and experimental groups, the livability of the livestock was 95.0 and 99.0%, the egg production per initial hen was 99.2 and 102.5 pieces. The weight of eggs was 57.9 and 58.3 g, the yield of the egg weight per initial hen was 5.81 and 5.98 kg, feed consumption for 10 eggs and 1 kg of egg weight were 1.37, 2.35 and 1.30, 2.23 kg, respectively, without significant changes in the morphological and chemical qualities of eggs.

Thermal conductivity measurement of infrared optical fibers based on silver halide solid solution crystals

The aim of the study is to measure the thermal conductivity of silver halide light guides based on crystals of the AgCl-AgBr system used in PSD production technologies. The conductivity temperature coefficient of the samples under study were determined by the laser flash method using the LFA 467 (Hyper Flash) installation. We studied mono- and polycrystalline samples of solid solutions with the composition AgCl0,25AgBr0,75 in the temperature range 298–523 K. The thermal conductivity of the investigated materials was then calculated using literature data on density and heat capacity. The thermal conductivity coefficient ranges from 0.80±0,04 to 0.53±0,03 (W/mK), depending on the microstructure of the sample.

Characterization and Pilot Human Trial of Dedicated Breast Ring Positron Emission Tomography (BRPET) System

We describe the design and performance of BRPET, a novel dedicated breast PET (dbPET) scanner designed to maximize visualization of posterior regions of the breast. BRPET uses prone imaging geometry and a 12-module detector ring built from pixelated LYSO crystals coupled to position sensitive photomultiplier tubes (PSPMTs). Optical coupling via slanted plastic fiber optic light guides permits partial insertion of the crystals into the exam table’s breast aperture. Image quality testing procedures were adapted from the NEMA NU4-2008 protocol. Two additional phantom tests quantified the posterior extent of the usable volume of view (VoV). BRPET axial, radial, and tangential FWHM spatial resolutions at the isocenter were 1.8, 1.7, and 1.9 mm, respectively. The peak absolute system sensitivity was 0.97% using an energy window of 460–562 keV. The peak noise equivalent counting rate was 5.33 kcps at 21.6 MBq. The scanner VoV extends to within ~6 mm of the plane defining the location of the chest wall. A pilot human study (n = 10) compared the diagnostic performance of FDG-BRPET to that of contrast enhanced MRI (CEMRI), with biopsy as ground truth. Averaged over three expert human observers, the sensitivity/specificity for BRPET was 0.93/1.0, compared to 1.0/0.25 for CEMRI.

Quartz-quartz type light guides with low losses and a thin polymer shell for the near-IR spectral range.

The issues of obtaining silica optical fibers with SiO2/SiO2-F composition (where SiO2 is a core, and SiO2-F is a light-reflecting cladding) with low optical losses for the near-IR spectral range are considered. This fiber type is widely used in various fields of science and technology, including laser medicine. The study results of the dependence of the numerical aperture and fluorine concentration in silica glass of the formed fiber preforms on the Freon (C3F8) consumption in the gas phase when using a waveguide-type microwave plasmotron at the H10 wavelength, are presented. It is showed that to increase the fluorimeters sensitivity in the near-IR spectral range as probe fibers for detecting luminescence, it is promising to use quartz-quartz fibers with the “Heraeus” glass core and the reflective SiO2-F cladding with an increased fluorine content in the glass (up to 7 wt. %). In this case, the numerical aperture of such fibers will reach values up to 0.32. For laser procedures in ophthalmology, surgery, phlebology and etc., optical fibers with a standard numerical aperture 0.20-0.24 can be used (with a fluorine concentration in the glass up to 3 wt. %).