Tractography reproducibility challenge with empirical data (TraCED): The 2017 ISMRM diffusion study group challenge.

BACKGROUND: Fiber tracking with diffusion-weighted MRI has become an essential tool for estimating in vivo brain white matter architecture. Fiber tracking results are sensitive to the choice of processing method and tracking criteria. PURPOSE: To assess the variability for an algorithm in group studies reproducibility is of critical context. However, reproducibility does not assess the validity of the brain connections. Phantom studies provide concrete quantitative comparisons of methods relative to absolute ground truths, yet do no capture variabilities because of in vivo physiological factors. The ISMRM 2017 TraCED challenge was created to fulfill the gap. STUDY TYPE: A systematic review of algorithms and tract reproducibility studies. SUBJECTS: Single healthy volunteers. FIELD STRENGTH/SEQUENCE: 3.0T, two different scanners by the same manufacturer. The multishell acquisition included b-values of 1000, 2000, and 3000 s/mm2 with 20, 45, and 64 diffusion gradient directions per shell, respectively. ASSESSMENT: Nine international groups submitted 46 tractography algorithm entries each consisting 16 tracts per scan. The algorithms were assessed using intraclass correlation (ICC) and the Dice similarity measure. STATISTICAL TESTS: Containment analysis was performed to assess if the submitted algorithms had containment within tracts of larger volume submissions. This also serves the purpose to detect if spurious submissions had been made. RESULTS: The top five submissions had high ICC and Dice >0.88. Reproducibility was high within the top five submissions when assessed across sessions or across scanners: 0.87-0.97. Containment analysis shows that the top five submissions are contained within larger volume submissions. From the total of 16 tracts as an outcome relatively the number of tracts with high, moderate, and low reproducibility were 8, 4, and 4. DATA CONCLUSION: The different methods clearly result in fundamentally different tract structures at the more conservative specificity choices. Data and challenge infrastructure remain available for continued analysis and provide a platform for comparison. LEVEL OF EVIDENCE: 5 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2020;51:234-249.

Predicting Mortality Following Traumatic Brain Injury or Subarachnoid Hemorrhage: An Analysis of the Validity of Standardized Mortality Ratios Obtained From the APACHE II and ICNARC H-2018 Models.

INTRODUCTION: Standardized mortality ratios (SMRs), calculated using the Acute Physiology, Age, Chronic Health Evaluation II (APACHE II) and Intensive Care National Audit and Research Centre H-2018 (ICNARC H-2018 ) risk prediction models, are widely used in UK intensive care units (ICUs) to measure and compare the quality of critical care delivery. Both models incorporate an assumption of Glasgow Coma Score (GCS) if an actual GCS without sedation is not recordable in the first 24 hours after ICU admission. This study assesses the validity of the APACHE II and ICNARC H-2018 models to predict mortality in ICU patients with traumatic brain injury (TBI) or aneurysmal subarachnoid hemorrhage (aSAH) in whom GCS is related to outcomes. METHODS: In a retrospective analysis, the SMR calculated by the APACHE II and ICNARC H-2018 models for all UK ICU admissions in a 1-year period was compared with calculated SMRs in TBI/aSAH patients and at 3 GCS groups. Data for patients admitted to a single tertiary neurocritical care unit were similarly analyzed. RESULTS: Both models predicted mortality well for the overall TBI/aSAH population; SMR (95% confidence interval) was 1.00 (0.96-1.04) and 0.99 (0.95-1.03) for the APACHE II and ICNARC H-2018 models, respectively. When analyzed by GCS grouping, both models underpredicted mortality in TBI/aSAH patients with GCS ≤8 (SMR, 1.1 [1.05-1.15]) and "unrecordable" GCS (SMR, 1.88 [1.77-1.99]). Similar findings were identified in the local data analysis. DISCUSSION: The APACHE II and ICNARC H-2018 models predicted mortality well for the overall TBI/aSAH ICU population but underpredicted mortality when GCS was ≤8 or "unrecordable." This raises questions about the accuracy of these risk prediction models in TBI/aSAH patients and their use to evaluate treatments and compare outcomes between centers.

Race-based sexual stereotyping and sexual partnering among men who use the internet to identify other men for bareback sex.

This qualitative study used sexual scripting theory to explore sexual stereotyping and sexual partnering practices among a racially diverse sample of men who use the Internet to engage in "bareback" sex with other men. The sample included 81 (73%) HIV-negative and 30 (27%) HIV-positive men who were recruited on Web sites where men seek other men to have bareback sex. Participants completed a semi-structured interview that included topics on their racial identification, their sexual experiences tied to race, and their experiences having sex with men of different racial groups. The findings suggested that a variety of race-based sexual stereotypes were used by participants. Sexual stereotyping appeared to directly and indirectly affect the sexual partnering decisions of participants. Sexual scripts may reinforce and facilitate race-based sexual stereotyping, and this behavior may structure sexual networks.