An evaluation of the resistance element method for measuring detonation velocity of AN-FO mixtures confined in small diameter boreholes

Instrumentation and techniques employing a constant current in a 4 ft. length of Nichrome resistance wire embedded in an explosive mixture were developed to measure detonation velocity in small diameter boreholes. The resistance element technique was evaluated by detonating mixtures in iron and clay pipes, and it was shown that the current in the circuit was not constant. Velocity measurements varied from 8,000 fps to 16,000 fps. Low velocity material provided poor time - voltage traces. The resistance element method was compared to a pin oscillograph technique, and an explanation was offered for observed differences in velocity. The standard deviation for the corrected resistance element velocity records was found to be approximately two and one-half times larger than the standard deviation for pin oscillograph velocity records --Abstract, page ii

What volume increase is needed for the management of raised intracranial pressure in children with craniosynostosis?

Craniosynostosis describes a fusion of one or more sutures in the skull. It can occur in isolation or as part of a syndrome. In either setting, it is a condition which may lead to raised intracranial pressure. The exact cause of raised intracranial pressure in craniosynostosis is unknown. It may be due to; a volume mismatch between the intracranial contents and their containing cavity, venous hypertension, hydrocephalus or airway obstruction, which is often a sequela of an associated syndrome. At Great Ormond Street Hospital, after hydrocephalus and airway obstruction have been treated, the next surgical treatment of choice is cranial vault expansion. This expansion has been shown to reduce intracranial pressure, interestingly despite its success, the reasons behind its benefits are not fully understood. Using reconstructed 3-dimensional imaging, accurate measurement of cranial volumes can now be achieved. The aim of this project is to use the advances in 3-dimensional imaging and image processing to provide novel information on the volume changes that occur following cranial vault expansion. This information will be combined with clinical metrics to create a greater understanding of the causes of raised intracranial pressure in craniosynostosis, why cranial vault expansion treats them and whether there is an optimal volume expansion

Migrant health professionals’ systemic human rights vulnerabilities

This article investigates whether the methods by which states implement citizens’ human rights possess serious weaknesses for ensuring migrant health professionals’ rights. Stemming from the discipline of normative philosophy, the moral approach to human rights sees rights as implemented through multiple waves of duties delivered by state-managed integrity systems. We argue that this otherwise comparatively reliable method can fail to deliver adequate outcomes to migrant health professionals. These professionals can encounter problems stemming from the following: their lack of political priority as non-citizens; the challenges to effective monitoring of migrant health professional pathways and outcomes; the incapacity of federal lawmakers to impact on key policy levers; the ever-present threat of “pathways to nowhere”; and state-enabled employee exploitation. The findings provide a philosophically grounded foundation for acknowledging the human rights concerns of even high-skilled migrants, and show why special regimes for rights protection, facilitation and monitoring are necessary for migrant health professionals

Intracranial volume measurement: A systematic review and comparison of different techniques

The ability to calculate intracranial volume (ICV) from 3-dimensional imaging is a useful tool in a craniofacial team's armamentarium. Intracranial volume uses range from decision making to assessment. Various methods to calculate ICV exist including fully manual, semiautomatic, and fully automatic techniques and they are used with varying frequency in craniofacial centres globally.This study aimed to systematically analyze and compare ICV calculations across the 3 methods and provide information to allow the reader to utilize these processes in practice.Twenty-six computed tomography scans from Apert patients were used to compare ICV measurements calculated using the following techniques: fully manual segmentation with OsiriX (taken as the gold standard); semiautomatic segmentation using Simpleware ScanIP; and fully automatic segmentation using FSL neuroimaging software. In addition, to assess the effect that a reducing CT scan slice number had on ICV measurement, 13 scans were remeasured using half, quarter, and an eighth of the slices of the full scan.The manual and semiautomatic techniques had intraclass correlation coefficients of 0.997, and 0.993 respectively. Intracranial volume measurements using the semi- and fully automatic techniques showed high linear correlation with manual techniques (R = 0.993 and R = 0.995). The coefficients of determination for full scan versus half, quarter, and eighth scan were R = 0.98, 0.96, and 0.94 respectively.Similar ICV results can be obtained using manual, semiautomatic, or automatic techniques with decreasing amount of time required to perform each method. Command line code for the fully automatic method is provided

Validation of an in-silico modelling platform for outcome prediction in spring assisted posterior vault expansion

BACKGROUND: Spring-Assisted Posterior Vault Expansion has been adopted at Great Ormond Street Hospital for Children, London, UK to treat raised intracranial pressure in patients affected by syndromic craniosynostosis, a congenital calvarial anomaly which causes premature fusion of skull sutures. This procedure aims at normalising head shape and augmenting intracranial volume by means of metallic springs which expand the back portion of the skull. The aim of this study is to create and validate a 3D numerical model able to predict the outcome of spring cranioplasty in patients affected by syndromic craniosynostosis, suitable for clinical adoption for preoperative surgical planning. METHODS: Retrospective spring expansion measurements retrieved from x-ray images of 50 patients were used to tune the skull viscoelastic properties for syndromic cases. Pre-operative computed tomography (CT) data relative to 14 patients were processed to extract patient-specific skull shape, replicate surgical cuts and simulate spring insertion. For each patient, the predicted finite element post-operative skull shape model was compared with the respective post-operative 3D CT data. FINDINGS: The comparison of the sagittal and transverse cross-sections of the simulated end-of-expansion calvaria and the post-operative skull shapes extracted from CT images showed a good shape matching for the whole population. The finite element model compared well in terms of post-operative intracranial volume prediction (R2 = 0.92, p < 0.0001). INTERPRETATION: These preliminary results show that Finite Element Modelling has great potential for outcome prediction of spring assisted posterior vault expansion. Further optimisation will make it suitable for clinical deployment

Statistical shape modelling for the analysis of head shape variations

The aim of this study is, firstly, to create a population-based 3D head shape model for the 0 to 2-year-old subjects to describe head shape variability within a normal population and, secondly, to test a combined normal and sagittal craniosynostosis (SAG) population model, able to provide surgical outcome assessment. 3D head shapes of patients affected by non-cranial related pathologies and of SAG patients (pre- and post-op) were extracted either from head CTs or 3D stereophotography scans, and processed. Statistical shape modelling (SSM) was used to describe shape variability using two models - a normal population model (MODEL1) and a combined normal and SAG population model (MODEL2). Head shape variability was described via principal components analysis (PCA) which calculates shape modes describing specific shape features. MODEL1 (n = 65) mode 1 showed statistical correlation (p < 0.001) with width (125.8 ± 13.6 mm), length (151.3 ± 17.4 mm) and height (112.5 ± 11.1 mm) whilst mode 2 showed correlation with cranial index (83.5 mm ± 6.3 mm, p < 0.001). The remaining 9 modes showed more subtle head shape variability. MODEL2 (n = 159) revealed that post-operative head shape still did not achieve full shape normalization with either spring cranioplasty or total calvarial remodelling. This study proves that SSM has the potential to describe detailed anatomical variations in a paediatric population