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An automated geometric modeling framework in GATE for the design and optimization of high-sensitivity converging-beam SPECT collimators.

Objective.The trade-off between detection sensitivity and spatial resolution is a fundamental challenge in designing organ-dedicated Single-photon emission computed tomography (SPECT) collimators. While converging-hole geometries offer a solution, their optimization is often hindered by the lack of flexible computational tools capable of modeling large-scale, non-parallel hole arrays. This study aims to develop an automated geometric modeling framework to facilitate the design and evaluation of complex converging- and diverging-hole collimators within standard Monte Carlo environments.Approach.We developed a specialized modeling framework by implementing custom C++ classes and a vector-based alignment algorithm within GATE. This platform enables automated, orientation-consistent construction of large-scale converging arrays not natively supported by standard implementations. A high-sensitivity pure cone-beam collimator (CBC) was designed using this framework. The evaluation used hot-rod, disc, and Jaszczak phantoms for physical characterization, while XCAT and dedicated brain models were employed for clinical tasks, including cardiac, brain perfusion, and DaTscan SPECT simulations.Main results.The CBC achieved a nearly fourfold sensitivity increase compared to a conventional low-energy high-resolution parallel-hole collimator at a 20 cm radius of rotation, while maintaining comparable spatial resolution. Despite a 52.3% field of view reduction, the CBC yielded a 2.2-fold noise reduction (CV: 11.7% vs 25.9%) and mitigated partial volume effects via geometric magnification. XCAT and brain phantom simulations confirmed enhanced anatomical definition and contrast recovery in cardiac, perfusion, and DaTscan tasks.Significance.This work provides an efficient computational tool for rapid design space exploration of advanced collimator geometries. The results demonstrate that the proposed CBC design offers a significant sensitivity advantage, making it highly suitable for high-performance, small-volume clinical applications such as brain and cardiac molecular imaging.

Tomography, Emission-Computed, Single-Photon

Genomic and food-safety evaluation of Staphylococcus chromogenes in Chinese dairy milk.

Non-aureus staphylococci and mammaliicocci (NASM) cause mastitis and may contaminate milk and dairy products. Milk samples (n&#xa0;=&#xa0;1916) from cows with subclinical or clinical mastitis (SCM and CM, respectively) were collected from 28 large-scale (> 500 lactating cows) Chinese dairy farms. Overall, 999 NASM isolates representing 19 species were identified by MALDI-TOF MS and cpn60 sequencing, with Staphylococcuschromogenes, Mammaliicoccus sciuri and Staphylococcus haemolyticus being most prevalent. Antimicrobial resistance (AMR) was determined with disc diffusion; non-susceptible to penicillin was most common (SCM, 30% and CM, 29%) whereas cefoxitin non-susceptible NASM accounted for 8-10% of isolates; among these, 12.5% carried mecA but none carried mecC. Galleria mellonella was used to assess virulence of 78 strains of S. chromogenes, a dominant species; subsequently, 32 strains, representing higher- and lower-virulence in the Galleria model, were selected for whole-genome sequencing and comparative genomics. S. chromogenes isolates from CM had higher virulence (p&#xa0;<&#xa0;0.05) than those from SCM. The 32 genomes comprised 20 sequence types, indicating high genetic diversity. No robust genomic marker of Galleria virulence phenotype was identified in this selected WGS subset. Acquired resistance genes (n&#xa0;=&#xa0;5) were detected, including a first report of fusC in S. chromogenes; the fusC-positive isolate had an elevated fusidic acid MIC (8&#xa0;mg/L). Although S. chromogenes persisted in milk at 4&#xa0;&#xb0;C, pasteurization (64&#xa0;&#xb0;C for 30&#xa0;min) reduced viable counts to below detection. This study provided new insights into the prevalence, AMR, genomic diversity, and dairy-chain relevance of milk-derived NASM, particularly S. chromogenes. However, the genomic findings were based on an intentionally selected WGS subset and should be interpreted as hypothesis-generating rather than population-representative.

Animals

Noncombustible Nicotine or Tobacco Product Use After Smoking Cessation and Major Vision-Impairing Diseases: A Nationwide Cohort Study.

OBJECTIVE: We assessed the risk of major vision-impairing eye diseases among smokers who quit combustible cigarettes (CC) and switch to noncombustible nicotine or tobacco products (NNTPs) compared with those who completely quit using tobacco. DESIGN: Retrospective cohort study. PARTICIPANTS: About 179 273 adults from the Korean National Health Insurance Service who smoked CC in 2011 to 2012 and reported cessation in 2018 to 2019, classified into complete quitters and NNTP switchers. METHODS: This nationwide longitudinal cohort study followed participants for up to 6 years and identified incident major vision-impairing eye diseases (cataract, glaucoma, age-related macular degeneration, diabetic retinopathy, and refractive and accommodation disorders) using standardized diagnostic codes. Propensity score matching was applied to emulate a pseudo-randomized comparison, balanced on key demographic, clinical, comorbidity, and lifestyle characteristics. Subdistribution hazard ratios (SHRs) were evaluated using the Fine-Gray subdistribution hazards model accounting for all-cause mortality as a competing risk. MAIN OUTCOME MEASURES: Adjusted SHRs for incident major vision-impairing eye diseases. RESULTS: Among 32 316 matched participants followed for a mean of 4.6 years, 6328 incident major vision-impairing eye disease events occurred. The incidence was 41.1 and 44.0 per 1000 person-years for complete quitters and NNTP switchers, respectively. Switching to NNTPs was associated with an increased risk of major vision-impairing eye disease (SHR, 1.07; 95% CI, 1.02-1.13). The risk elevation was most pronounced for diabetic retinopathy (SHR, 1.24; 95% CI, 1.00-1.53) and refractive and accommodation disorders (SHR, 1.07; 95% CI, 1.01-1.12). These findings were robust across inverse probability-weighted and Cox proportional hazards models. The association remained consistent in sensitivity analyses and across clinical subgroups. CONCLUSIONS: Transitioning from CC to NNTPs is associated with a modest but consistent increase in the risk of major vision-impairing eye diseases compared with complete nicotine abstinence. These findings challenge the assumption that substituting NNTPs for CCs is visually harmless and indicate that, from an ophthalmic perspective, complete cessation of all nicotine products should remain the preferred cessation goal.

Humans