Genetic Predisposition to Ischemic Stroke

Background and Purpose—The prediction of genetic predispositions to ischemic stroke (IS) may allow the identification of individuals at elevated risk and thereby prevent IS in clinical practice. Previously developed weighted multilocus genetic risk scores showed limited predictive ability for IS. Here, we investigated the predictive ability of a newer method, polygenic risk score (polyGRS), based on the idea that a few strong signals, as well as several weaker signals, can be collectively informative to determine IS risk.Methods—We genotyped 13 214 Japanese individuals with IS and 26 470 controls (derivation samples) and generated both multilocus genetic risk scores and polyGRS, using the same derivation data set. The predictive abilities of each scoring system were then assessed using 2 independent sets of Japanese samples (KyushuU and JPJM data sets).Results—In both validation data sets, polyGRS was shown to be significantly associated with IS, but weighted multilocus genetic risk scores was not. Comparing the highest with the lowest polyGRS quintile, the odds ratios for IS were 1.75 (95% confidence interval, 1.33–2.31) and 1.99 (95% confidence interval, 1.19–3.33) in the KyushuU and JPJM samples, respectively. Using the KyushuU samples, the addition of polyGRS to a nongenetic risk model resulted in a significant improvement of the predictive ability (net reclassification improvement=0.151; P<0.001).Conclusions—The polyGRS was shown to be superior to weighted multilocus genetic risk scores as an IS prediction model. Thus, together with the nongenetic risk factors, polyGRS will provide valuable information for individual risk assessment and management of modifiable risk factors

Evaluation of Antimony Tri-Iodide Crystals for Radiation Detectors

This study was carried out to examine the potential of antimony tri-iodide (SbI3) as a material for radiation detectors that operate at room temperature. SbI3 is a compound semiconductor with an AsI3-type crystal structure, high atomic number (Sb: 51, I: 53), high density (4.92 g/cm3), and a wide band-gap energy (2.2 eV). In addition, crystalline SbI3 is easy to grow by conventional crystal growth techniques from melting phase because the material exhibits a low melting point (171°C) and undergoes no phase transition in the range of its solid phase. In this study, SbI3 crystals were grown by the Bridgman method after synthesis of SbI3 from 99.9999% pure Sb and 99.999% pure I2. The grown crystals consisted of several large grains with red color and were confirmed to be single-phase crystals by X-ray diffraction analysis. SbI3 detectors with a simple planar structure were fabricated using the cleavage plates of the grown crystals, and the pulse-height spectra were recorded at room temperature using an 241Am alpha-particle (5.48 MeV) source. The detector showed response to the alpha-particle radiation

Timing resolution of TlBr and TlBr-TlCl PET detectors based on Cerenkov radiation measurement

TlBr is a high density (7.56 g/cm) semiconductor material composed of high effective atomic number elements. Therefore, TlBr has sufficient detection efficiency for 511 keV annihilation radiation in PET. In addition, TlBr detectors have high energy resolution due to the direct conversion to electrons. On the other hand, timing performance of typical semiconductor detectors is poor compared with scintillation detectors However, detection of Cerenkov light from TlBr offers an alternative method to get better timing resolution. This paper reports our feasibility study on the timing performance of TlBr detectors using Cerenkov light.In the experiment, a conventional TlBr crystal and TlBr mixed with TlCl (TlBr-TlCl crystal) were used. The TlBr crystals were fabricated at Tohoku University. Each TlBr crystal was 3 × 3 × 3 mm3. The TlBr crystals were covered with ESR films and Teflon tape. Cerenkov light was detected with a multi-pixel photon counter (Hamamatsu S13360-3075CS). Coincidence detection measurement was carried out using a LYSO scintillator coupled with another MPPC (Hamamatsu S13360-3050CS) as a reference detector. Signals from the detectors were amplified with high frequency amplifiers and then waveforms were recorded with a digitizer (CAEN, DT5742). We obtained the timing spectra by Cerenkov light from the TlBr and scintillation light from the LYSO. From them, the timing resolution better than 600 ps was obtained for all the event data. After selecting the events by optimizing a trigger level, the timing resolutions better than 450 ps was obtained for both the TlBr detector and the TlBr-TlCl detector.2021 Virtual IEEE Nuclear science symposium and medical imaging conferenc