Characterization of time of flight and resolution modeling on image quality in positron emission tomography.

Time-of-flight (TOF) and resolution modeling (RM) algorithms are frequently used in clinical PET images, and inclusion of these corrections should measurably improve image quality. We quantified the effects of these correction algorithms on reconstructed images via the following metrics: recovery coefficients (RCs), contrast-to-noise ratio (CNR), noise-power spectrum (NPS), modulation transfer function (MTF), and the full width at half maximum (FWHM) of a point source. The goal of this experiment was to assess the effects of the correction algorithms when applied singly or together. Two different phantom tests were performed and analyzed by custom software. FWHM and MTF were measured using capillary tube point sources, while RCs, CNR, and NPS were measured using an image quality body phantom. Images were reconstructed with both TOF and RM, only TOF, only RM, or neither correction. The remaining reconstruction parameters used the standard clinical protocol. RM improved RCs, FWHM, and MTF, without increasing overall noise significantly. TOF improves CNR for small objects FWHM or MTF but did not decrease noise. RCs were not statistically improved by enabling these algorithms. Inclusion of both correction algorithms in image reconstruction provides an overall improvement to all metrics relative to the uncorrected image, but not by a significant margin in multiple aspects.

The helically-acquired CTDIvol as an alternative to traditional methodology.

PURPOSE: Most clinical computed tomography (CT) protocols use helical scanning; however, the traditional method for CTDIvol measurement replaces the helical protocol with an axial scan, which is not easily accomplished on many scanners and may lead to unmatched collimation settings and bowtie filters. This study assesses whether CTDIvol can be accurately measured with a helical scan and determines the impact of pitch, collimation width, and excess scan length. METHODS: CTDIvol was measured for 95 helical protocols on 31 CT scanners from all major manufacturers. CTDIvol was measured axially, then again helically, with the scan range set to the active area of the pencil chamber seen on the localizer image. CTDIvol measurements using each method were compared to each other and to the scanner-displayed CTDIvol . To test the impact of scan length, the study was repeated on four scanners, with the scan range set to the phantom borders seen on the localizer. RESULTS: It was not possible to match the collimation width between the axial and helical modes for 12 of the 95 protocols tested. For helical and axial protocols with matched collimation, the difference between the two methods averaged below 1 mGy with a correlation of R2  = 0.99. The difference between the methods was not statistically significant (P = 0.81). The traditional method produced four measurements that differed from the displayed CTDIvol by >20%; no helical measurements did. The accuracy of the helical CTDIvol was independent of protocol pitch (R2  = 0.0) or collimation (R2  = 0.0). Extending the scan range to the phantom borders increased the measured CTDIvol by 2.1%-9.7%. CONCLUSION: There was excellent agreement between the two measurement methods and to the displayed CTDIvol , without protocol or vendor dependence. The helical CTDIvol measurement can be accomplished more easily than the axial method on many scanners and is reasonable to use for QC purposes.

Assessment of volumetric absorbed dose for mobile fluoroscopic 3D image acquisition.

Mobile fluoroscopy (c-arm) units offering 3D image reconstruction are becoming more common in surgical settings. Although these images are "CT-like" and sometimes replace the postoperative CT, the acquisition is technically very different from a traditional CT acquisition. Dose assessment is complicated by a large beam width, automatic exposure rate control, and a rotation of less than 360°. The purpose of this work was to explore the impact of these factors on the volumetric dose calculation and to provide practical recommendations for clinical physicists assessing dose from these units using commonly available equipment. CTDIW was calculated using the IAEA method for dosimetry of wide beams and compared to scans of the 32-cm CTDI phantom using the full beam width and a 20-mm collimated beam width. The impact of the partial rotation on the CTDIW calculation was assessed by acquiring measurements at four and twelve positions on the phantom periphery. For the system tested, the CTDIW was calculated to be 16.1 mGy using the IAEA method with default clinical protocol. Results showed that measuring CTDIW with the full beam width or a collimated beam width alone resulted in CTDI values of 19.0 mGy and 19.5 mGy, respectively. Using four peripheral measurements instead of 12 resulted in a difference of 4% for a collimated beam and 6% for an open beam. Variations in positioning on the order of a few centimeters resulted in a variation of only 4% with an open beam. The excellent reproducibility of the measurements using the full beam width suggests that this simple method is adequate for year-to-year comparisons. In contrast, the IAEA method is difficult to employ, particularly with 180° acquisitions. Use of peripheral measurements in excess of the usual four is time-consuming and not necessary for most applications obtained with the geometry specific to this system.

An international phantom study of inter-site variability in Technetium-99m image quantification: analyses from the TARGET radioembolization study.

BACKGROUND: Personalised multi-compartment dosimetry based on [99mTc]Tc-MAA is a valuable tool for planning 90Y radioembolization treatments. The establishment and effective application of dose-effect relationships in yttrium-90 (90Y) radioembolization requires [99mTc]Tc-MAA SPECT quantification ideally independent of clinical site. The purpose of this multi-centre phantom study was to evaluate inter-site variability of [99mTc]Tc-MAA imaging and evaluate a standardised imaging protocol. Data was obtained from the TARGET study, an international, retrospective multi-centre study including 14 sites across 8 countries. The impact of imaging related factors was estimated using a NEMA IQ phantom (representing the liver), and a uniformly filled cylindrical phantom (representing the lungs). Imaging was performed using site-specific protocols and a standardized protocol. In addition, the impact of implementing key image corrections (scatter and attenuation correction) in the site-specific protocols was investigated. Inter-site dosimetry accuracy was evaluated by comparing computed Lung Shunt Fraction (LSF) measured using planar imaging of the cylindrical and NEMA phantom, and contrast recovery coefficient (CRC) measured using SPECT imaging of the NEMA IQ phantom. RESULTS: Regarding the LSF, inter-site variation with planar site-specific protocols was minimal, as determined by comparing computed LSF between sites (interquartile range 9.6-10.1%). A standardised protocol did not improve variation (interquartile range 8.4-9.0%) but did improve mean accuracy compared to the site-specific protocols (5.0% error for standardised protocol vs 8.8% error for site-specific protocols). Regarding the CRC, inter-system variation was notable for site-specific SPECT protocols and could not be improved by the standardised protocol (CRC interquartile range for 37 mm sphere 0.5-0.7 and 0.6-0.8 respectively), however the standardised protocol did improve accuracy of sphere:background determination. Implementation of key image corrections did improve inter-site variation (CRC interquartile range for 37 mm sphere 0.6-0.7). CONCLUSION: Eliminating sources of variability in image corrections between imaging protocols reduces inter-site variation in quantification. A standardised protocol was not able to improve consistency of LSF or CRC but was able to improve accuracy.

The current state of mental health services in Canada's paediatric emergency departments.

OBJECTIVE: To describe emergency mental health services in major paediatric centres across Canada. METHODS: A cross-sectional study of mental health services in emergency departments (EDs) from all 15 Canadian tertiary care paediatric centres was conducted. RESULTS: Fifteen individuals participated and were either a paediatric emergency physician with administrative responsibilities (60%) or an emergency mental health care provider (40%). Four participants reported that their ED used an evidence-based guideline, tool or policy, and one participant reported their ED based its services on published research evidence. Reported ED-based mental health resources included a crisis intervention team (five EDs), a mental health nurse (six EDs) and a social worker (five EDs). Thirteen participants reported on-site consultation with child psychiatry and six reported urgent follow-up as an adjunct service to ED care. CONCLUSIONS: There is a wide variety of mental health care practices in Canadian paediatric EDs. Consideration of which resources are required to ensure evidence-based, effective services are provided to children and youth is necessary.

OBJECTIF: Décrire les services de santé mentale d'urgence dans les principaux centres pédiatriques du Canada. MÉTHODOLOGIE: Les chercheurs ont mené une étude transversale des services de santé mentale offerts aux départements d'urgence (DU) des 15 centres pédiatriques de soins tertiaires du Canada. RÉSULTATS: Quinze personnes ont participé à l'étude. Il s'agissait de pédiatres d'urgence pédiatrique ayant des responsabilités administratives (60 %) ou de dispensateurs de services de santé mentale d'urgence (40 %). Quatre participants ont indiqué que leur DU faisait appel à des lignes directrices, un outil ou une politique probants et un participant a indiqué que les services de son département se fondaient sur des résultats de recherche publiés. Les ressources de santé mentale utilisées au DU incluaient une équipe d'intervention en cas de crise (cinq DU), une infirmière en santé mentale (six DU) et un travailleur social (cinq DU). Treize participants ont déclaré obtenir des consultations en pédopsychiatrie sur place et six, un suivi urgent en services complémentaires aux soins d'urgence. CONCLUSIONS: On constate une grande variété de pratiques de soins de santé mentale dans les départements d'urgence pédiatrique du Canada. Il faut se pencher sur les ressources nécessaires pour garantir des services probants et efficaces aux enfants et aux adolescents.

Resident education in the radiological sciences: what now?

OBJECTIVE: With the dizzying changes in the rapidly evolving profession of radiology, the structure of resident education in the associated sciences of imaging, physics, radiobiology, and radiation effects must be reevaluated continually. What roles do these basic radiologic sciences play in bolstering the neophyte radiologist on a career of patient care? How should we define the spectrum of material that should be learned? How should that spectrum be taught? Who decides these things? With the impending changes in the radiology board certification process, questions have been raised as to how these changes will affect education in a residency program. Should the basic science curriculum be enhanced or scaled back? With the emphasis on practical applied physics, what is considered old school and what is new school material? CONCLUSION: This article describes one approach adopted by a large residency program to address these issues.

Accuracy and reproducibility of effective atomic number and electron density measurements from sequential dual energy CT.

PURPOSE: This study assesses the accuracy of effective atomic number (Zeff ) and electron density measurements acquired from dual energy CT and characterizes the response to clinically relevant variables representative of challenges in patient imaging, including: phantom size, material position within the phantom, variation over time, off-center positioning, and large cone beam angle. METHODS: The Gammex Multi-Energy CT head and body phantoms were used to measure Zeff and electron density from 35 rod inserts that mimic tissues and varying concentrations of iodine and calcium. Scans were performed on a Canon Aquilion ONE Genesis CT scanner over a period of 6 months using default dual energy protocols appropriate for each phantom size. Theoretical Zeff and electron density values were calculated using data provided by the phantom manufacturer and compared to the measurements. Sources of variance were separated and quantified to identify the influences of random photon statistics, ROI placement, and variation over time. A subset of measurements were repeated with the phantom shifted in the vertical and horizontal directions, and over all slices in the volumetric scan. RESULTS: All measurements showed strong correlation (r > 0.98) with their corresponding theoretical values; however, the system did demonstrate a bias of -0.58 atomic units in the body phantom and 0.28 atomic units in the head phantom for Zeff measurements. The mean absolute percent error (MAPE) was 6.3% for the body phantom and 3.2% for the head phantom. Electron density measurements of the body and head phantoms gave MAPE values of 4.6% and 1.0%, respectively. Zeff and electron density measurements significantly varied within the solid water background, showing a positional dependence within the phantom that dominated the total standard deviation in measurements. Zeff values dropped by 0.2 atomic units when the phantom was off-center; electron density measurements were less affected by phantom position. Along the z-axis, the accuracy drops off markedly at more than 50-60 mm from the central slice. CONCLUSION: The Canon dual energy system offers an accurate way of measuring the Zeff and electron density of clinically relevant materials. Accuracy could be improved further by calibration to remove bias, careful attention to centering within the FOV, and avoiding measurements at the edges of the cone beam.

Comparison of CT image quality between the AIDR 3D and FIRST iterative reconstruction algorithms: an assessment based on phantom measurements and clinical images.

Modern CT iterative reconstruction algorithms are transitioning from a statistical-based to model-based approach. However, increasing complexity does not ensure improved image quality for all indications, and thorough characterization of new algorithms is important to understand their potential clinical impacts. This study performs both quantitative and qualitative analyses of image quality to compare Canon's statistical-based Adaptive Iterative Dose Reduction 3D (AIDR 3D) algorithm to its model-based algorithm, Forward-projected model-based Iterative Reconstruction SoluTion(FIRST). A phantom was used to measure the task-specific modulation transfer function (MTFTask), the noise power spectrum (NPS), and the low-contrast object-specific CNR (CNRLO) for each algorithm using three dose levels and the convolution algorithm (kernel) appropriate for abdomen, lung, and brain imaging. Additionally, MTFTaskwas measured at four contrast levels, and CNRLOwas measured for two object sizes. Lastly, three radiologists participated in a preference study to compare clinical image quality for three study types: non-contrast abdomen, pulmonary embolism (PE), and lung screening. Nine questions related to the appearance of anatomical features or image quality characteristics were scored for twenty exams of each type. The behavior of both algorithms depended strongly on the kernel selected. Phantom measurements suggest that FIRST should be beneficial over AIDR 3D for abdomen imaging, but do not suggest a clear overall benefit to FIRST for lung or brain imaging; metrics suggest performance may be equivalent to or slightly favor AIDR 3D, depending on the size of the object being imaged and whether spatial resolution or low-contrast resolution is more important for the task at hand. Overall, radiologists strongly preferred AIDR 3D for lung screening, slightly preferred AIDR 3D for non-contrast abdomen, and had no preference for PE. FIRST was superior for the reduction of metal artifacts. Radiologist preference may be influenced by changes to noise texture.

Dose simulations of an early 20th century kilovoltage pneumonia radiotherapy technique performed with a modern fluoroscope.

To simulate an early 20th century viral pneumonia radiotherapy treatment using modern fluoroscopy and evaluated it according to current dose guidelines. Monte Carlo was used to assess the dose distribution on an anthropomorphic phantom. Critical organs were: skin, breasts, esophagus, ribs, vertebrae, heart, thymus, and spinal cord. A 100 kVp beam with 3 mm Al HVL, 25 × 25 cm2 posterior-anterior (PA) field and 50 cm source-to-surface distance were simulated. Simulations had a resolution of 0.4 × 0.4 × 0.06 cm3 and a 6% uncertainty. Hundred percent dose was normalized to the skin surface and results were displayed in axial, coronal, and sagittal planes. Dose volume histograms were generated in MATLAB for further analysis. Prescription doses of 0.3, 0.5, and 1.0 Gy were applied to the 15% isodose for organ-dose comparison to current tolerances and potential risk of detriment. Ninety-five and ninety-seven percent of the right and left lung volumes, respectively, were well-covered by the 15% isodose line. For the 0.3, 0.5, and 1.0 Gy prescriptions, the maximum skin doses were 2.9, 4.8, and 9.6 Gy compared to a 2.0 Gy transient erythema dose threshold; left/right lung maximum doses were 1.44/1.46, 2.4/2.4, and 4.8/4.9 Gy compared to a 6.5 Gy pneumonitis and 30 Gy fibrosis thresholds; maximum heart doses were 0.5, 0.9, and 1.8 Gy compared to the 0.5 Gy ICRP-recommendation; maximum spinal cord doses were 1.4, 2.3, and 4.6 Gy compared to 7.0 Gy single fraction dose threshold. Maximum doses to other critical organs were below modern dose thresholds. A 100 kVp PA field could deliver a 0.3 Gy or 0.5 Gy dose without risk of complications. However, a 1.0 Gy dose treatment could be problematic. Critical organ doses could be further reduced if more than one treatment field is used.

Family Factors and Repeat Pediatric Emergency Department Visits for Mental Health: A Retrospective Cohort Study.

OBJECTIVES: Approximately 45% of youth presenting to the emergency department (ED) for mental health (MH) concerns will have a repeat ED visit. Since youth greatly depend on their caregivers to access MH services, the objective of this study was to determine if family characteristics were associated with repeat ED visits. METHODS: A retrospective cohort study of youth aged 6-18 years (62% female) treated at a tertiary pediatric ED for a discharge diagnosis related to MH was conducted. Data were gathered from medical records, telephone interviews, and questionnaires. Family factor contribution was analyzed using a multivariable logistic regression model controlling for demographic, clinical and service utilization factors. Variables associated with earlier and more frequent visits were determined using cox regression and negative binomial regression. RESULTS: Of 266 participants, 70 (26%) had a repeat visit. While caregiver history of MH treatment decreased the odds of having a repeat ED visit, family functioning and perceived family burden were not associated with repeat visits. Post-visit MH services, prior psychiatric hospitalization, higher severity of symptoms, and living closer to the hospital increased the odds of repeat visits. CONCLUSIONS: This study examined the contribution of multiple family factors in predicting repeat MH visits to the ED. Results suggest caregiver characteristics may impact the decision to return. Healthcare providers should therefore consider caregiver and youth service utilization factors to inform patient management and discharge planning.

OBJECTIFS: Environ 45 % des adolescents qui se présentent au service d'urgence (SU) pour des raisons de santé mentale (SM) auront une visite répétée au SU. Puisque les adolescents dépendent beaucoup de leurs aidants pour avoir accès aux services de SM, l'objectif de cette étude était de déterminer si les caractéristiques familiales étaient associées aux visites répétées au SU. MÉTHODES: Une étude de cohorte rétrospective a été menée sur des adolescents de 6 à 18 ans (62 % de sexe féminin) traités dans un SU pédiatrique tertiaire pour un diagnostic lié à la SM posé au moment du congé. Les données ont été recueillies d'après les dossiers médicaux, les entrevues téléphoniques et les questionnaires. La contribution des facteurs familiaux a été analysée à l'aide d'un modèle de régression logistique multivariable après contrôle des facteurs démographiques, cliniques et d'utilisation des services. Les variables associées à des visites précédentes et plus fréquentes ont été déterminées à l'aide de la régression de Cox et la régression binomiale négative. RÉSULTATS: Sur les 266 participants, 70 (26 %) avaient une visite répétée. Les antécédents de traitement de SM des aidants diminuaient les probabilités d'avoir une visite répétée au SU, et le fonctionnement familial et le fardeau familial perçu n'étaient pas associés à des visites répétées. Les services de SM ultérieurs à la visite, une hospitalisation psychiatrique précédente, une gravité plus élevée des symptômes et le fait d'habiter à proximité de l'hôpital augmentaient les probabilités de visites répétées. CONCLUSIONS: Cette étude a examiné la contribution de multiples facteurs familiaux à la prédiction de visites répétées au SU pour raisons de SM. Les résultats suggèrent que les caractéristiques des aidants puissent influer sur la décision de retourner au SU. Les prestataires de soins de santé devraient donc prendre en compte les facteurs d'utilisation des services des aidants et des adolescents afin d'éclairer la prise en charge des patients et la planification du congé.

Comparison of skin dose measurement using nanoDot® dosimeter and machine readings of radiation dose during cardiac catheterization in children.

OBJECTIVES: Direct measurement of skin dose of radiation for children using optically stimulated luminescence (OSL) technology using nanoDot® (Landauer, Glenwood, IL, USA). BACKGROUND: Radiation dose is estimated as cumulative air kerma (AK) and dosearea product based on standards established for adult size patients. Body size of pediatric patients who undergo cardiac catheterization for congenital heart disease vary widely from newborn to adolescence. Direct, skindose measurement applying OSL technology may eliminate errors in the estimate. MATERIALS AND METHODS: The nanoDot® (1 cm × 1 cm × flat plastic cassette) is applied to patient's skin using adhesive tape during cardiac catheterization and radiation skin doses were read within 24 hrs. nanoDot® values were compared to the currently available cumulative AK values estimated and displayed on fluoroscopy monitor. RESULTS: A total of 12 children were studied, aged 4 months to 18 years (median 1.1 years) and weight range 5.3-86 kg (median 8.4 kg). nanoDot® readings ranged from 2.58 mGy to 424.8 mGy (median 84.1 mGy). Cumulative AK ranged from 16.2 mGy to 571.2 mGy (median 171.1 mGy). Linear correlation was noted between nanoDot® values and AK values (R2 = 0.88, R = 0.94). nanoDot® readings were approximately 65% of the estimated cumulative AK estimated using the International Electrotechnical Commission standards. CONCLUSIONS: Application of OSL technology using nanoDot® provides an alternative to directly measure fluoroscopic skin dose in children during cardiac catheterization. Our data show that the actual skin dose for children is approximately one-third lower than the AK estimated using international standards for adult size patients.

Child and Adolescent Mental Health Repeat Visits to the Emergency Department: A Systematic Review.

OBJECTIVES: Repeat visits represent up to 45% of mental health (MH) presentations to emergency departments (EDs) and are associated with higher health care costs. We aimed to synthesize available literature on predictors of pediatric MH repeat ED visits and differences between repeat visitors and nonrepeat visitors. METHODS: A systematic review was performed using PsycINFO, PubMed, and CINAHL databases. Reporting followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement checklist. Methodologic quality was assessed using the following 8 criteria: design, generalizability, breadth of predictors, reporting of effect sizes, additional outcomes, interaction terms, confounding variables, and clear definition of repeat visits. RESULTS: A total of 178 articles were retrieved; 11 articles met inclusion criteria. Quality assessment revealed that all studies used chart review or administrative data. Predictors were grouped into 3 categories: demographic, clinical, and MH care access and utilization factors. Common predictors associated with repeat ED MH visits included socioeconomic status, involvement with child protective services, and previous and current MH service use. For studies using a 6-month repeat window, the most common factors were previous psychiatric hospitalization and currently receiving MH services. Heterogeneity in statistical analyses and determinants explored precluded the use of meta-analysis. CONCLUSIONS: Findings revealed that repeat visits to the ED for MH concerns is a complex phenomenon that can be attributed to various demographic, clinical, and MH care access and utilization factors. To further elucidate the strongest predictors, future prospective research should consider prospective designs and include family factors. Investigating recency and frequency outcomes can also inform clinical practice.

Scratching the surface? Taxonomic revision of the subgenus Schizoptera (Odontorhagus) reveals vast undocumented biodiversity in the largest litter bug genus Schizoptera Fieber (Hemiptera: Dipsocoromorpha).

Schizoptera Fieber, currently the largest genus of litter bugs (Hemiptera: Dipsocoromorpha), comprises 61 extant species in 4 subgenera. Specimens are abundant in New World bulk and residue samples. Schizoptera species showcase stunning morphology including intricate, asymmetrical genitalia in males that have proven to provide excellent species diagnostic features in the past. Recent bulk sample sorting efforts have revealed a vast number of Schizoptera specimens from across the New World, with the majority representing undescribed species. We here taxonomically revise the subgenus Schizoptera (Odontorhagus) that has recently been shown to form a monophyletic group within Schizoptera. Characterized by the blunt tooth on the posterior margin of the propleuron, Schizoptera (Odontorhagus) previously comprised 10 species from Central and the northern part of South America. We here describe 20 new species in S. (Odontorhagus): S. acuta, n. sp., S. angularis, n. sp., S. ansata, n. sp., S. aspera, n. sp., S. brevis, n. sp., S. dentata, n. sp., S. dolosa, n. sp., S. enigmatica, n. sp., S. exacta, n. sp., S. gorgonensis, n. sp., S. insidiosa, n. sp., S. monstrosa, n. sp., S. piscicaudata, n. sp., S. quasicompleta, n. sp., S. radicata, n. sp., S. serrata, n. sp., S. simpla, n. sp., S. singularis, n. sp., S. trivialis, n. sp., S. ungulata, n. sp., increasing the species count of Schizoptera to 81. We provide morphological documentation including digital habitus images and genitalic drawings for all new species and document and redescribe existing species where feasible. Distribution maps and a key to the species of Schizoptera (Odontorhagus) are also presented. We predict that similar increases in species numbers are to be expected for the remaining subgenera of Schizoptera, making this genus a very diverse lineage of minute litter bugs.

Systematic review of depression in mild traumatic brain injury: study protocol.

BACKGROUND: Of the over 1 million reported cases of traumatic brain injuries reported annually in the USA, a sizeable proportion are characterized as mild. Although it is generally well-accepted that most people who suffer a mild traumatic brain injury recover within 1 to 3 months, a proportion of individuals continue to experience physiological, psychological, and emotional symptoms beyond the expected window of recovery. Depression is commonly reported following mild traumatic brain injury; however, its course, consequences, and prognostic factors remain to be well understood. METHODS: A systematic review will be conducted of available prospective longitudinal studies of adult mild traumatic brain injury-related depression. The aim of the systematic review is to describe the course of mild traumatic brain injury-related depression, along with its prognostic factors and health consequences. The review will comply with the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. A thorough database search of peer-reviewed publications in English and French will be conducted in PubMed, Medical Literature Analysis and Retrieval System Online (MEDLINE), PsycINFO, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Cochrane, Embase, Scopus, Erudit, and Cairn. Independent investigators will perform study selection and data extraction. Risk of bias will be assessed using the Quality in Prognosis Studies tool, and methodological quality will be evaluated using a system inspired by the Scottish Intercollegiate Guidelines Network Methodology. Results will be presented through qualitative description and tabulation. DISCUSSION: This will be the first systematic review conducted with the aim of describing the course, prognostic factors, and health-related outcomes of depression in adults who have suffered a mild traumatic brain injury. The findings of the planned systematic review have the potential to guide research and clinical practice to effectively develop and implement evidence-based interventions aimed at preventing and alleviating mild traumatic brain injury-related depression. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42015019214.

Review of the genus Namadytes Hesse, 1969 (Insecta: Diptera: Mydidae: Syllegomydinae).

The Mydidae genus Namadytes Hesse, 1969 is reviewed. It is known from five species, primarily occurring in Namibia. The study of newly available material from both Namibia and South Africa deposited in several natural history collections results in the recognition of three species and new synonymy of two, i.e., Namadytespallidus Hesse, 1972 is a new junior synonym of Namadytesmaculiventris (Hesse, 1969) and Namadytesprozeskyi Hesse, 1969: 282 is a new junior synonym of Namadytesvansoni Hesse, 1969: 280. All three species are re-described and comments on sexual dimorphism and intraspecific variation are made, a dichotomous key for their identification is presented, and illustrations and photographs are provided to support the descriptions and facilitate future identification. Distribution, occurrence in biodiversity hotspots sensu Conservation International, and seasonal incidence with associated weather and climatic data are discussed for all species. A morphological structure ventral to the halter and posterior to the metathoracic spiracle, the infra-halter sclerite, is here newly termed.

Characterization of scatter in digital mammography from use of Monte Carlo simulations and comparison to physical measurements.

PURPOSE: Monte Carlo simulations were performed with the goal of verifying previously published physical measurements characterizing scatter as a function of apparent thickness. A secondary goal was to provide a way of determining what effect tissue glandularity might have on the scatter characteristics of breast tissue. The overall reason for characterizing mammography scatter in this research is the application of these data to an image processing-based scatter-correction program. METHODS: mcnpx was used to simulate scatter from an infinitesimal pencil beam using typical mammography geometries and techniques. The spreading of the pencil beam was characterized by two parameters: mean radial extent (MRE) and scatter fraction (SF). The SF and MRE were found as functions of target, filter, tube potential, phantom thickness, and the presence or absence of a grid. The SF was determined by separating scatter and primary by the angle of incidence on the detector, then finding the ratio of the measured scatter to the total number of detected events. The accuracy of the MRE was determined by placing ring-shaped tallies around the impulse and fitting those data to the point-spread function (PSF) equation using the value for MRE derived from the physical measurements. The goodness-of-fit was determined for each data set as a means of assessing the accuracy of the physical MRE data. The effect of breast glandularity on the SF, MRE, and apparent tissue thickness was also considered for a limited number of techniques. RESULTS: The agreement between the physical measurements and the results of the Monte Carlo simulations was assessed. With a grid, the SFs ranged from 0.065 to 0.089, with absolute differences between the measured and simulated SFs averaging 0.02. Without a grid, the range was 0.28-0.51, with absolute differences averaging -0.01. The goodness-of-fit values comparing the Monte Carlo data to the PSF from the physical measurements ranged from 0.96 to 1.00 with a grid and 0.65 to 0.86 without a grid. Analysis of the data suggested that the nongrid data could be better described by a biexponential function than the single exponential used here. The simulations assessing the effect of breast composition on SF and MRE showed only a slight impact on these quantities. When compared to a mix of 50% glandular/50% adipose tissue, the impact of substituting adipose or glandular breast compositions on the apparent thickness of the tissue was about 5%. CONCLUSIONS: The findings show agreement between the physical measurements published previously and the Monte Carlo simulations presented here; the resulting data can therefore be used more confidently for an application such as image processing-based scatter correction. The findings also suggest that breast composition does not have a major impact on the scatter characteristics of breast tissue. Application of the scatter data to the development of a scatter-correction software program can be simplified by ignoring the variations in density among breast tissues.

Media coverage of youth suicides and its impact on paediatric mental health emergency department presentations.

BACKGROUND: To examine mental health (MH) presentations to the emergency department (ED) of a paediatric hospital following two highly publicized local teen suicides. METHODS: Youths aged 12-18 years with a MH chief complaint and/or diagnosis were included. Differences in frequencies were analyzed using chi-square tests, and relative risks were evaluated using generalized linear modelling. RESULTS: Significant increases in the number of ED presentations were found within the months of the publicized suicides compared to the same months of previous years. No differences were found in symptom acuity, suicidal status and psychiatric hospitalization rates. Significant increases were found in relative risk of presenting to the ED 28 and 90 days post both publicized suicides. CONCLUSIONS: RESULTS suggest there was an association between highly publicized suicides and an increase in the number of MH presentations to the local paediatric ED. Considerations of media's potentially positive role in MH awareness are needed.

Characterization of scatter in digital mammography from physical measurements.

PURPOSE: That scattered radiation negatively impacts the quality of medical radiographic imaging is well known. In mammography, even slight amounts of scatter reduce the high contrast required for subtle soft-tissue imaging. In current clinical mammography, image contrast is partially improved by use of an antiscatter grid. This form of scatter rejection comes with a sizeable dose penalty related to the concomitant elimination of valuable primary radiation. Digital mammography allows the use of image processing as a method of scatter correction that might avoid effects that negatively impact primary radiation, while potentially providing more contrast improvement than is currently possible with a grid. For this approach to be feasible, a detailed characterization of the scatter is needed. Previous research has modeled scatter as a constant background that serves as a DC bias across the imaging surface. The goal of this study was to provide a more substantive data set for characterizing the spatially-variant features of scatter radiation at the image detector of modern mammography units. METHODS: This data set was acquired from a model of the radiation beam as a matrix of very narrow rays or pencil beams. As each pencil beam penetrates tissue, the pencil widens in a predictable manner due to the production of scatter. The resultant spreading of the pencil beam at the detector surface can be characterized by two parameters: mean radial extent (MRE) and scatter fraction (SF). The SF and MRE were calculated from measurements obtained using the beam stop method. Two digital mammography units were utilized, and the SF and MRE were found as functions of target, filter, tube potential, phantom thickness, and presence or absence of a grid. These values were then used to generate general equations allowing the SF and MRE to be calculated for any combination of the above parameters. RESULTS: With a grid, the SF ranged from a minimum of about 0.05 to a maximum of about 0.16, and the MRE ranged from about 3 to 13 mm. Without a grid, the SF ranged from a minimum of 0.25 to a maximum of 0.52, and the MRE ranged from about 20 to 45 mm. The SF with a grid demonstrated a mild dependence on target/filter combination and kV, whereas the SF without a grid was independent of these factors. The MRE demonstrated a complex relationship as a function of kV, with notable difference among target/filter combinations. The primary source of change in both the SF and MRE was phantom thickness. CONCLUSIONS: Because breast tissue varies spatially in physical density and elemental content, the effective thickness of breast tissue varies spatially across the imaging field, resulting in a spatially-variant scatter distribution in the imaging field. The data generated in this study can be used to characterize the scatter contribution on a point-by-point basis, for a variety of different techniques.