Analysis of Flow Through Extra-Anatomic Bypasses Between Supra-Aortic Branches Using Particle Image Velocimetry (PIV).

Supra-aortic extra-anatomic debranch (SAD) are prosthetic surgical grafts used to revascularize head and neck arteries that would be blocked during a surgical or hybrid procedure used in treating ascending and arch of the aorta pathologies. However, bypassing the supra-aortic arteries but not occluding their orifice might introduce potential for competitive flow that reduces bypass patency. Competitive flow within the bypasses across the supra-aortic arteries has not previously been identified. This research identified haemodynamics due to prophylactic inclusion of bypasses from the brachiocephalic artery (BCA) to the left common carotid artery (LCCA), and from the LCCA to left subclavian artery (LSA). Four model configurations investigated the risk of competitive flow and the necessity of intentionally blocking the proximal LSA and/or LCCA. Particle image velocimetry (PIV) was used to assess haemodynamics in each model configuration. We found potential for competitive flow in the BCA-LCCA bypass when the LSA was blocked, in the LSA-LCCA bypass, when the LCCA alone or LCCA and LSA were blocked. Flow stagnated at the start of systole within the RCCA-LCCA bypass, along with notable recirculation zones and reciprocating flow occurring throughout systolic flow. Flow also stagnated in the LCCA-LSA bypass when the LCCA was blocked. There was a large recirculation in the LCCA-LSA bypass when both the LCCA and LSA were blocked. The presence of competitive flow in all other configurations indicated that it is necessary to block or ligate the native LCCA and LSA once the debranch is made and the thoracic endovascular aortic repair (TEVAR) completed.

Analysing multi-perspective patient-related data during laparoscopic gynaecology procedures.

Fusing data from different medical perspectives inside the operating room (OR) sets the stage for developing intelligent context-aware systems. These systems aim to promote better awareness inside the OR by keeping every medical team well informed about the work of other teams and thus mitigate conflicts resulting from different targets. In this research, a descriptive analysis of data collected from anaesthesiology and surgery was performed to investigate the relationships between the intra-abdominal pressure (IAP) and lung mechanics for patients during laparoscopic procedures. Data of nineteen patients who underwent laparoscopic gynaecology were included. Statistical analysis of all subjects showed a strong relationship between the IAP and dynamic lung compliance (r = 0.91). Additionally, the peak airway pressure was also strongly correlated to the IAP in volume-controlled ventilated patients (r = 0.928). Statistical results obtained by this study demonstrate the importance of analysing the relationship between surgical actions and physiological responses. Moreover, these results form the basis for developing medical decision support models, e.g., automatic compensation of IAP effects on lung function.

A review of the hormones involved in the endocrine dysfunctions of polycystic ovary syndrome and their interactions.

Polycystic ovary syndrome (PCOS) affects up to 20% of women but remains poorly understood. It is a heterogeneous condition with many potential comorbidities. This review offers an overview of the dysregulation of the reproductive and metabolic systems associated with PCOS. Review of the literature informed the development of a comprehensive summarizing 'wiring' diagram of PCOS-related features. This review provides a justification for each diagram aspect from the relevant academic literature, and explores the interactions between the hypothalamus, ovarian follicles, adipose tissue, reproductive hormones and other organ systems. The diagram will provide an efficient and useful tool for those researching and treating PCOS to understand the current state of knowledge on the complexity and variability of PCOS.

Particle Image Velocimetry Evaluation of Hemodynamics Proximal to the Kissing Stent Configuration in the Aorto-Iliac Bifurcation.

PURPOSE: The kissing stent (KS) method is low-risk compared with open surgery techniques. It is often used to treat aorto-iliac occlusive disease (AIOD). Deployment of the KS geometry has a high technical success rate. However, stent patency reduces in the first 5 years potentially due to deleterious flow behavior. Potentially harmful hemodynamics due to the KS were investigated in vitro. METHODOLOGY: A compliant phantom of the aorto-iliac bifurcation was manufactured. Two surrogate stent-grafts were deployed into the phantom in the KS configuration to investigate effects of the presence of the stents, including the compliance mismatch they cause, on the hemodynamics proximal and distal to the KS. The investigation used pulsatile flow through a flow circuit to simulate abdominal aortic flow. Particle image velocimetry (PIV) was used to quantify the hemodynamics. RESULTS: PIV identified peak proximal and distal velocity in vitro was 0.71 and 1.40m·s-1, respectively, which were within physiological ranges. Throughout systole, flow appeared normal and undisturbed. A lumen wall collapse in the sagittal plane formed during late systole and continued to early diastole proximal to the aorto-iliac bifurcation, distal to the inlet stent position. The wall collapse led to disturbed flow proximal to the stented region in early diastole producing potential recirculation zones and abnormal flow patterns. CONCLUSION: The normal systolic flow behavior indicates the KS configuration is unlikely to cause an inflammatory response of the arterial walls. The collapse has not been previously identified and may potentially cause long-term patency reduction. It requires further investigation. CLINICAL IMPACT: The role of this article is to provide further insight into the haemodynamic behavior through a stented aorto-iliac artery. The results of this investigation will improve the understanding of the effects that using the kissing stent method may have on a patient and help to identify high risk regions that may require more detailed monitoring. This paper also develops the in vitro modelling techniques that will enable further research that cannot be carried out within patients.

Geometric Generalization of Self Tapping Screw Insertion Model.

Bone screws are used in orthopaedic procedures to fix implants and stabilise fractures. These procedures require care, as improperly torquing the screws can lead to implant failure or tissue damage, potentially requiring revision surgery or causing further disability. It was proposed that automated torque-limit identification may allow clinical decision support to control the screw torque, and lead to improved patient outcomes. This work extends a previous model of the screw insertion process to model complex thread geometries used for bone screws; consideration was made for the variable material properties and behaviours of bone to allow further tuning in the future. The new model was simulated and compared with the original model. The model was found to be in rough agreement with the earlier model, but was distinct, and could model thread features that the earlier model could not, such as the fillets and curves on the bone screw profile. The new model shows promise in modelling the more advanced thread geometries of bone screws with higher accuracy.Clinical relevance: This work extends a self tapping screw model to support complex thread shapes, as common in bone screws, allowing more accurate modelling of the clinically relevant geometries.

Methoxyflurane toxicity: historical determination and lessons for modern patient and occupational exposure.

AIM: Historically methoxyflurane was used for anaesthesia. Evidence of nephrotoxicity led to abandonment of this application. Subsequently, methoxyflurane, in lower doses, has re-emerged as an analgesic agent, typically used via the Penthrox inhaler in the ambulance setting. We review the literature to consider patient and occupational risks for methoxyflurane. METHOD: Articles were located via PubMed, ScienceDirect, Google Scholar, Anesthesiology journal and the Cochrane Library. RESULTS: Early studies investigated pharmacokinetics and considered the resulting effects to pose minimal risk. Pre-clinical rodent studies utilised a species not vulnerable to the nephrotoxic fluoride metabolite of methoxyflurane, so nephrotoxicity was not identified until almost a decade after its introduction, and was initially met with scepticism. Further evidence of nephrotoxicity led to abandonment of methoxyflurane use for anaesthesia. Subsequent research suggested there are additional risks potentially relevant to recurrent patient or occupational exposure. Specifically, greater than expected fluoride production after repeated low-dose exposure, increased fluoride production due to medication-caused hepatic enzyme induction, fluoride deposition in bone potentially acting as a slow-release fluoride compartment, which suggests a risk of skeletal fluorosis, and hepatotoxicity. Gestational risk is unclear. CONCLUSIONS: Methoxyflurane poses a potentially substantial health risk in high (anaesthetic) doses, and there are a number of pathways whereby repeated exposure to methoxyflurane in lower doses may pose a risk. Single analgesic doses in modern use generally appear safe for patients. However, the safety of recurrent patient or occupational healthcare-worker exposure has not been confirmed, and merits further investigation.

Non-identifiability of the Rayleigh damping material model in magnetic resonance elastography.

Magnetic Resonance Elastography (MRE) is an emerging imaging modality for quantifying soft tissue elasticity deduced from displacement measurements within the tissue obtained by phase sensitive Magnetic Resonance Imaging (MRI) techniques. MRE has potential to detect a range of pathologies, diseases and cancer formations, especially tumors. The mechanical model commonly used in MRE is linear viscoelasticity (VE). An alternative Rayleigh damping (RD) model for soft tissue attenuation is used with a subspace-based nonlinear inversion (SNLI) algorithm to reconstruct viscoelastic properties, energy attenuation mechanisms and concomitant damping behavior of the tissue-simulating phantoms. This research performs a thorough evaluation of the RD model in MRE focusing on unique identification of RD parameters, µI and ρI. Results show the non-identifiability of the RD model at a single input frequency based on a structural analysis with a series of supporting experimental phantom results. The estimated real shear modulus values (µR) were substantially correct in characterising various material types and correlated well with the expected stiffness contrast of the physical phantoms. However, estimated RD parameters displayed consistent poor reconstruction accuracy leading to unpredictable trends in parameter behaviour. To overcome this issue, two alternative approaches were developed: (1) simultaneous multi-frequency inversion; and (2) parametric-based reconstruction. Overall, the RD model estimates the real shear shear modulus (µR) well, but identifying damping parameters (µI and ρI) is not possible without an alternative approach.