Comparison of calibration coefficients for a vinten ionization chamber simulated using four Monte Carlo methods.

The Vinten 671 ionization chamber (VIC) was modelled using Monte Carlo (MC) programs EGSnrc, Penelope, and TOPAS. Several national measurement institutes have VICs with well-characterized response relationships and have measured calibration coefficients for many radionuclides. Twelve radionuclides with various decay emissions were assessed as well as 14 monoenergetic photon sources and 10 monoenergetic electron sources. Calibration coefficients were calculated based on the energy deposited in the simulated VIC nitrogen gas volume and compared to experimental values from the literature.

Reliability of radiographic assessment of growth modulation from anterior vertebral body tethering surgery in pediatric scoliosis.

PURPOSE: To assess the reliability of vertebral height and angular measurements for anterior vertebral body tethering (AVBT). METHODS: Eight observers measured PA radiographs of 15 idiopathic scoliosis patients treated with AVBT, pre-operative and 4-year follow-up. Vertebral wedging, disc wedging, convex vertebral body heights, and concave vertebral body heights of the 3 apical vertebrae were measured. For each observer, there were a total of 90 measurements for vertebral body height and 75 measurements for all wedging types At least 14 days elapsed between first and second round measurements. RESULTS: From the pre-operative to the 4-year follow-up time-point, the total wedging angle over the 3 peri-apical levels fell from 30 ± 7° to 16 ± 6° (p < 0.001) and the difference between the convex and concave vertebral heights decreased from 9 ± 4 to 6 ± 3 mm (p < 0.001). Interobserver agreement for pre-operative vertebral body heights was good [ICC = 0.80; 95% CI (0.74-0.85)]. At 4-year follow-up there was a moderate agreement [ICC = 0.67 (0.59-0.74)]. There was a poor interobserver agreement for pre-operative wedging angle measurements [ICC = 0.41 (0.32-0.52)] and 4-year follow-up [ICC = 0.45 (0.36-0.56)]. The Limits of Agreement with the Mean (LOAM) for pre-op heights was ± 2.4 mm, similar to the follow-up ± 2.6 mm. When raters are averaged in random groups of two the agreement limits decrease to ± 1.8 mm pre-op and ± 1.6 mm at follow-up. Similarly for wedging angles, LOAM values among the 8 observers of ± 4.6° pre-op and ± 4.2° dropped to ± 2.7° for both pre-op and follow-up when random groups of two raters were averaged together. Intraobserver agreement ranged from good to excellent per individual (ICC = 0.84-0.94) for pre-operative vertebral body heights, but this decreased at 4-year follow-up (ICC = 0.52-0.88). Intraobserver agreement was low overall for wedging (pre-operative ICC = 0.41-0.71; 4-year follow-up ICC = 0.41-0.76). CONCLUSION: Based on 8 individual observers, interobserver agreement ranged from good (pre-operative vertebral body heights) to moderate (4-year follow-up vertebral body heights) to poor (all wedging angles). To improve the reliability of the measurement of wedging angles, we recommend averaging the measurements of at least two observers.

Association of Socioeconomic Status With Relapse After Ponseti Method Treatment of Idiopathic Clubfeet.

Background: The Ponseti method is today's standard treatment of idiopathic talipes equinovarus (ITEV). Compliance with foot abduction bracing (FABO) and socioeconomic factors have been shown to impact treatment outcome. We wished to further study socioeconomic factors using the Area Deprivation Index (ADI), a more comprehensive way to evaluate socioeconomic status, which has not been done before. Methods: All TEV patients from 2010 through 2019 treated with the Ponseti method were reviewed. Standard demographic variables, as well as the number of casts to complete initial correction, FABO compliance, and occurrence of relapse were tabulated. Socioeconomic level was quantified with the 2018 ADI. Results: There were 168 children; 151 had typical and 17 complex TEV. Average follow-up was 4.3 ± 1.8 years; relapse occurred in 46%. There were no significant differences in the percentage of relapse by sex, race, or ADI. FABO noncompliance was present in 46%. Relapse increased with increasing time of follow-up and FABO noncompliance (76% vs 21%, P < 10-6). Multivariate logistic regression analysis revealed that only FABO compliance and length of follow-up were associated with relapse. The OR of relapse for FABO noncompliance was 17.9 (7.6, 42.4, P < 10-6) and for follow-up >4 years the OR was 4.97 (2.1, 11.70, P = .0003). Conclusion: The outcome of the Ponseti method for TEV treatment is dependent on local circumstances. In our state, socioeconomic status, as determined by the ADI, was not associated with the occurrence of relapse. Thus, each center needs to assess its results, and analyze its own reasons for relapse. There were no other demographic variables associated with relapse except FABO compliance and length of follow-up. Parents should be strongly advised that FABO compliance and follow-up appears paramount to achieving the best results, and that complex TEV are at greater risk for relapse. Level of Evidence: Level IV, case series.

Current dichotomous metrics obscure trends in severe and extreme child growth failure.

Historically, the prevalence of child growth failure (CGF) has been tracked dichotomously as the proportion of children more than 2 SDs below the median of the World Health Organization growth standards. However, this conventional "thresholding" approach fails to recognize child growth as a spectrum and obscures trends in populations with the highest rates of CGF. Our analysis presents the first ever estimates of entire distributions of HAZ, WHZ, and WAZ for each of 204 countries and territories from 1990 to 2020 for children less than 5 years old by age group and sex. This approach reflects the continuous nature of CGF, allows us to more comprehensively assess shrinking or widening disparities over time, and reveals otherwise hidden trends that disproportionately affect the most vulnerable populations.

Monte Carlo modelling of live-timed anticoincidence (LTAC) counting for Cu-64.

The radionuclide copper-64 is a promising candidate for nuclear medicine, but its complex decay creates challenges in the primary standardization of its activity. Monte Carlo simulations of live-timed anticoincidence (LTAC) counting of 64Cu were used to calculate corrections to extrapolation intercepts, resulting in improved activity determinations. A small correction (-0.33%) to the linear extrapolation of LTAC data acquired with a γ-gate over the 1346keV gamma peak was determined. We discuss the physical origin of the correction. We also use experimental data to demonstrate a Monte Carlo scaling that allows for inclusion of data acquired with a γ-gate set over the annihilation photon peak(s).

Intentionally forgetting other-race faces: costs and benefits?

Eyewitnesses to events with multiple actors might be aware that during a subsequent investigation some actors will need to be remembered and others can be forgotten. Research on the directed-forgetting procedure suggests that when some information is cued to be forgotten, retention of other information is enhanced. In three experiments, directed-forgetting conditions were compared with control conditions to assess potential costs and benefits of forgetting other-race faces. In Experiment 1, undergraduate students (N = 148; mostly Caucasian) viewed all Black faces or all Asian faces followed by overt remember or forget cues. Participants in the directed-forgetting conditions of Experiments 2 and 3 received more covert cues instructing them to remember the faces of one race and to forget the faces of another race. In Experiment 2, undergraduate students (N = 116; all Caucasian) viewed Black and Asian faces within the context of a criminal storyline. In Experiment 3, undergraduate students (N = 94; all Caucasian) again viewed Black and Asian faces; however, the remember and forget cues were embedded in a noncriminal narrative. Although faces generally were forgotten on cue, forgetting some faces did not enhance memory for other faces. Furthermore, recognition of remember-cued faces was impaired by exposure to forget-cued faces. These findings indicate that faces can be forgotten on cue, but that doing so confers no benefit for remembering other faces. Eyewitnesses are advised that exposure to irrelevant faces reduces the likelihood that relevant faces will be remembered, even when effort is allocated to forgetting the irrelevant faces.