An experimental investigation of light emission produced in the process of positronium formation in matter

The excess energy emitted during the positronium (Ps) formation in condensed matter may be released as light. Spectroscopic analysis of this light can be a new method of studying the electronic properties of materials. We report the first experimental attempt, according to our knowledge, to verify the existence of this emission process. As a result, the possibility of the emission of photons during Ps formation is within the experimental uncertainty in two different solids: an n-alkane and porous silica. However, it seems that the Ps formation on the alkane surface is not accompanied by the emission of photons with energy in the detection range of 1.6-3.8 eV. Various processes that can influence the energy of the photon emitted during the Ps formation are discussed to elucidate this issue. To aid future experiments, equations were developed to estimate the expected ratio of light emission events to annihilation events with the presence or absence of a photon during the Ps formation.

Diagnosis and management of tropomyosin receptor kinase (TRK) fusion sarcomas: expert recommendations from the World Sarcoma Network

Sarcomas are a heterogeneous group of malignancies with mesenchymal lineage differentiation. The discovery of neurotrophic tyrosine receptor kinase (NTRK) gene fusions as tissue-agnostic oncogenic drivers has led to new personalized therapies for a subset of patients with sarcoma in the form of tropomyosin receptor kinase (TRK) inhibitors. NTRK gene rearrangements and fusion transcripts can be detected with different molecular pathology techniques, while TRK protein expression can be demonstrated with immunohistochemistry. The rarity and diagnostic complexity of NTRK gene fusions raise a number of questions and challenges for clinicians. To address these challenges, the World Sarcoma Network convened two meetings of expert adult oncologists and pathologists and subsequently developed this article to provide practical guidance on the management of patients with sarcoma harboring NTRK gene fusions. We propose a diagnostic strategy that considers disease stage and histologic and molecular subtypes to facilitate routine testing for TRK expression and subsequent testing for NTRK gene fusions.

A new mechanism for void-cascade interaction from nondestructive depth-resolved atomic-scale measurements of ion irradiation-induced defects in Fe

The nondestructive investigation of single vacancies and vacancy clusters in ion-irradiated samples requires a depth-resolved probe with atomic sensitivity to defects. The recent development of short-pulsed positron beams provides such a probe. Here, we combine depth-resolved Doppler broadening and positron annihilation lifetime spectroscopies to identify vacancy clusters in ion-irradiated Fe and measure their density as a function of depth. Despite large concentrations of dislocations and voids in the pristine samples, positron annihilation measurements uncovered the structure of vacancy clusters and the change in their size and density with irradiation dose. When combined with transmission electron microscopy measurements, the study demonstrates an association between the increase in the density of small vacancy clusters with irradiation and a remarkable reduction in the size of large voids. This, previously unknown, mechanism for the interaction of cascade damage with voids in ion-irradiated materials is a consequence of the high porosity of the initial microstructure.

Integration of the M6 Cyberknife in the Moderato Monte Carlo platform and prediction of beam parameters using machine learning

PURPOSE

This work describes the integration of the M6 Cyberknife in the Moderato Monte Carlo platform, and introduces a machine learning method to accelerate the modelling of a linac.

METHODS

The MLC-equipped M6 Cyberknife was modelled and integrated in Moderato, our in-house platform offering independent verification of radiotherapy dose distributions. The model was validated by comparing TPS dose distributions with Moderato and by film measurements. Using this model, a machine learning algorithm was trained to find electron beam parameters for other M6 devices, by simulating dose curves with varying spot size and energy. The algorithm was optimized using cross-validation and tested with measurements from other institutions equipped with a M6 Cyberknife.

RESULTS

Optimal agreement in the Monte Carlo model was reached for a monoenergetic electron beam of 6.75 MeV with Gaussian spatial distribution of 2.4 mm FWHM. Clinical plan dose distributions from Moderato agreed within 2% with the TPS, and film measurements confirmed the accuracy of the model. Cross-validation of the prediction algorithm produced mean absolute errors of 0.1 MeV and 0.3 mm for beam energy and spot size respectively. Prediction-based simulated dose curves for other centres agreed within 3% with measurements, except for one device where differences up to 6% were detected.

CONCLUSIONS

The M6 Cyberknife was integrated in Moderato and validated through dose re-calculations and film measurements. The prediction algorithm was successfully applied to obtain electron beam parameters for other M6 devices. This method would prove useful to speed up modelling of new machines in Monte Carlo systems.

Molecular point-of-care testing for influenza A/B and respiratory syncytial virus: comparison of workflow parameters for the ID Now and cobas Liat systems

Aims

Point-of-care (POC) tests for influenza and respiratory syncytial virus (RSV) offer the potential to improve patient management and antimicrobial stewardship. Studies have focused on performance; however, no workflow assessments have been published comparing POC molecular tests. This study compared the Liat and ID Now systems workflow, to assist end-users in selecting an influenza and/or RSV POC test.

Methods

Staffing, walk-away and turnaround time (TAT) of the Liat and ID Now systems were determined using 40 nasopharyngeal samples, positive for influenza or RSV. The ID Now system requires separate tests for influenza and RSV, so parallel (two instruments) and sequential (one instrument) workflows were evaluated.

Results

The ID Now ranged 4.1–6.2 min for staffing, 1.9–10.9 min for walk-away and 6.4–15.8 min for TAT per result. The Liat ranged 1.1–1.8 min for staffing, 20.0–20.5 min for walk-away and 21.3–22.0 min for TAT. Mean walk-away time comprised 38.0% (influenza positive) and 68.1% (influenza negative) of TAT for ID Now and 93.7% (influenza/RSV) for Liat. The ID Now parallel workflow resulted in medians of 5.9 min for staffing, 9.7 min for walk-away and 15.6 min for TAT. Assuming prevalence of 20% influenza and 20% RSV, the ID Now sequential workflow resulted in medians of 9.4 min for staffing, 17.4 min for walk-away, and 27.1 min for TAT.

Conclusions

The ID Now and Liat systems offer different workflow characteristics. Key considerations for implementation include value of both influenza and RSV results, clinical setting, staffing capacity, and instrument(s) placement.

B-54 Insights into a Novel Integrated Screening Clinic: Parent Perceptions of Emotional Functioning in Acute Recovery Phase Following Pediatric Neurocritical Care

Objective

Children with traumatic brain injury (TBI) requiring neurocritical care are at high risk for neurocognitive, emotional, physical, and psychosocial difficulties, collectively known as Post-Intensive Care Syndrome. Our study sought to characterize parent ratings of emotional functioning in the acute recovery phase based upon mechanism of injury.

Method

Twenty children (Mdn = 12.6 years, IQR = 9-15; 65% male) were screened as part of a multidisciplinary follow-up clinic 1-month following hospital discharge. Emotional functioning was assessed using PROMIS Parent Proxy Report for Anxiety and Depression. A brief neurocognitive battery estimated presence of cognitive impairment. MANCOVA was used to compare emotional functioning across injury mechanism (high velocity injury [HVI], 65%; fall, 35%).

Results

Groups did not differ on age, gender, and presence of cognitive impairment. After controlling for severity, mechanism of injury had a significant effect on both anxiety (p = .026) and depression (p = .004). The HVI group had mildly elevated anxiety (M = 50.5, SD = 12.2) and depression (M = 54.2, SD = 10.6) scores, while the fall group had anxiety (M = 38.0, SD = 6.2) and depression (M = 39.0, SD = 7.3) scores within normal limits.

Conclusions

In the acute recovery phase following TBI, anxiety and depression symptoms are more common after HVI than falls, even when controlling for severity of injury. The HVI group includes injuries resulting from motor vehicle accidents which may have a broader impact on the family and may explain higher rates of emotional distress in this patient group compared to other mechanisms of TBI. Additional research is needed to further explore variables related to emotional functioning following TBI and how they change over the course of recovery.

On defects' role in enhanced perpendicular magnetic anisotropy in Pt/Co/Pt, induced by ion irradiation

Modifications of magnetic and magneto-optical properties of Pt/Co(d _Co )/Pt upon Ar⁺ irradiation (with energy 1.2, 5 and 30 keV) and fluence, F at the range from 2 · 10¹³-2 · 10¹⁶ Ar⁺ cm^-2) were studied. Two 'branches' of increased perpendicular magnetic anisotropy (PMA) and enhanced magneto-optical response are found on 2D (d _Co , F) diagrams. The difference in F between 'branches' is driven by ion energy. Structural features correlated with magnetic properties have been analysed thoroughly by x-ray diffraction, Rutherford backscattering spectrometry and positron annihilation spectroscopy. Experimental results are in agreement with TRIDYN numerical calculations of irradiation-induced layers intermixing. Our work discusses particularly structural factors related to crystal lattice defects and strain, created and modified by irradiation, co-responsible for the increase in the PMA.

Laboratory comparison between cell cytotoxicity neutralization assay and ultrasensitive single molecule counting technology for detection of Clostridioides difficile toxins A and B, PCR, enzyme immunoassays, and multistep algorithms

Diagnostic tests for Clostridioides difficile infection (CDI) lack either specificity (nucleic acid amplification tests) or sensitivity (enzyme immunoassays; EIAs). The performance of the Singulex Clarity® C. diff toxins A/B assay was compared to cell cytotoxicity neutralization assay. Testing was also performed using an EIA for glutamate dehydrogenase (GDH) and C. difficile toxins A and B (C. Diff Quik Chek Complete®), polymerase chain reaction (PCR) (BD MAX™ Cdiff Assay), and 2 multistep algorithms: algorithm 1 (discordant GDH/toxin results arbitrated by PCR) and algorithm 2 (PCR-positive samples tested with toxin EIA). The Clarity assay and PCR both had 97% sensitivity, while specificity was 100% for Clarity and 79% for PCR. Algorithm 1 yielded 41% discordant results, and both toxin EIA and algorithm 2 had 58% sensitivity. Median toxin concentrations, as measured by the Clarity C. difficile toxin assay, were 3590, 11.5, 0.4, and 0 pg/mL for GDH+/toxin+, GDH+/toxin-/PCR+, GDH+/toxin-/PCR-, and GDH-/toxin- samples, respectively (P < 0.001). The Clarity assay may offer a single-test solution for CDI.

Elevated age-related cortical iron, ferritin and amyloid plaques in APPswe/PS1ΔE9 transgenic mouse model of Alzheimer’s disease

Iron is very important element for functioning of the brain. Its concentration changes with aging the brain or during disease. The aim of our work was the histological examination of content of ferritin and free iron (unbound) in brain cortex in association with Aβ plaques from their earliest stages of accumulation in amyloid plaque forming APP/PS1 transgenic mice. Light microscopy revealed the onset of plaques formation at 8-monthage. Detectable traces of free iron and no ferritin were found around plaques at this age, while the rate of their accumulation in and around Aβ plaques was elevated at 13 months of age. Ferritin accumulated mainly on the edge of Aβ plaques, while the smaller amount of free iron was observed in the plaque-free tissue, as well as in and around Aβ plaques. We conclude that free iron and ferritin accumulation follows the amyloid plaques formation. Quantification of cortical iron and ferritin content can be an important marker in the diagnosis of Alzheimer’s disease.

1088. Ultrasensitive Detection of C. difficile Toxins in Stool Using Single Molecule Counting Technology: A Multicenter Study for Evaluation of Clinical Performance

Background

Methods

Results

Conclusion

Disclosures