Literature Survey for In-Vivo Reynolds and Womersley Numbers of Various Arteries and Implications for Compliant In-Vitro Modelling.

PURPOSE: In-vitro modelling can be used to investigate haemodynamics of arterial geometry and stent implants. However, in-vitro model fidelity relies on precise matching of in-vivo conditions. In pulsatile flow, velocity distribution and wall shear stress depend on compliance, and the Reynolds and Womersley numbers. However, matching such values may lead to unachievable tolerances in phantom fabrication. METHODS: Published Reynolds and Womersley numbers for 14 major arteries in the human body were determined via a literature search. Preference was given to in-vivo publications but in-vitro and in-silico values were presented when in-vivo values were not found. Subsequently ascending aorta and carotid artery case studies were presented to highlight the limitations dynamic matching would apply to phantom fabrication. RESULTS: Seven studies reported the in-vivo Reynolds and Womersley numbers for the aorta and two for the carotid artery. However, only one study each reported in-vivo numbers for the remaining ten arteries. No in-vivo data could be found for the femoral, superior mesenteric and renal arteries. Thus, information derived in-vitro and in-silico were provided instead. The ascending aorta and carotid artery models required scaling to 1.5× and 3× life-scale, respectively, to achieve dimensional tolerance restrictions. Modelling the ascending aorta with the comparatively high viscosity water/glycerine solution will lead to high pump power demands. However, all the working fluids considered could be dynamically matched with low pump demand for the carotid model. CONCLUSION: This paper compiles available human haemodynamic information, and highlights the paucity of information for some arteries. It also provides a method for optimal in-vitro experimental configuration.

Optimal Positioning of Inertial Measurement Units in a Smart Shirt for Determining Respiratory Volume.

Tidal volume can be estimated using the surface motions of the upper body induced by respiration. However, the precision and instrumentation of such estimation must be improved to allow widespread application. In this study, respiration induced changes in parameters that can be recorded with inertial measurement units are examined to determine tidal volumes. Based on the data of an optical motion capture system, the optimal positions of inertial measurement units (IMU) in a smart shirt for sets of 4, 5 or 6 sensors were determined. The errors observed indicate the potential to determine tidal volumes using IMUs in a smart shirt.Clinical Relevance- The measurement of respiratory volumes via a low-cost and unobtrusive smart shirt would be a major advance in clinical diagnostics. In particular, conventional methods are expensive, and uncomfortable for conscious patients if measurement is desired over an extended period. A smart-shirt based on inertial sensors would allow a comfortable measurement and could be used in many clinical scenarios - from sleep apnoea monitoring to homecare and respiratory monitoring of comatose patients.

Improving the Generalisability of Deep CNNs by Combining Multi-stage Features for Surgical Tool Classification.

Dataset characteristics play an important role in training convolutional neural networks (CNNs) to evolve optimal features required to perform a specific task. Due to the high cost of recording and labelling surgical data, available datasets are relatively small in size and have been predominantly acquired at single sites. CNN-based approaches have been widely adapted to analyse surgical workflow using single-site datasets. Therefore, assessing generalised performance on data from different institutions has not been investigated. In this work, a CNN model that combines features from multiple stages to develop more accurate and generalised tool classification was introduced. An extensive evaluation of the proposed approach on three different datasets showed better generalised performance of our approach compared to base CNN models. The proposed approach achieved mAP values of 91.46%, 69.02% and 37.14% on the Cholec80, Cholec20 and Gyna05 datasets, respectively. The generalisation performance was improved on the achieved base CNN models mAP by about 7%. Clinical Relevance- In this research, we proposed a method to improve generalisation capability of CNN models which will have positive impact on developing more robust assistive systems that can support the surgeon and improve patient care.

Effects of Intra-Abdominal Pressure on Lung Mechanics during Laparoscopic Gynaecology.

Investigating the relations between surgical actions and physiological reactions of the patient is essential for developing pre-emptive model-based systems. In this study, the effects of insufflating abdominal cavity with CO2 in laparoscopic gynaecology on the respiration system were analysed. Real-time recordings of anaesthesiology and surgical data of five subjects were acquired and processed, and the correlation between lung mechanics and the intra-abdominal pressure was evaluated. Alterations of ventilation settings undertaken by the anaesthesiologist were also considered. Experimental results demonstrated the high correlation with a mean Pearson coefficient of 0.931.Clinical Relevance- This study demonstrates the effects of intra-abdominal pressure during laparoscopy on lung mechanics and enables developing predictive models to promote a greater awareness in operating rooms.

An alternative way to measure respiration induced changes of circumferences: a pilot study.

Various measurement systems can be used to obtain dynamic circumferences of the human upper body, but each of these systems has disadvantages. In this feasibility study we introduce a non-invasive and wearable thoracic belt to measure dynamic changes of circumferences of thorax or abdomen. To evaluate this approach, five subjects undertook various breaths of disparate tidal volumes, which were measured by the belt and simultaneously by a motion capture system which provided a reference metric.The results of the belt concurred with the reference system. A coefficient of determination (adjusted R2) of 0.99 and a mean squared error of less than 0.87 mm2 showed that the belt is capable of measuring changes accurately and a couple of respiratory parameters, such as the respiratory rate, can be obtained.Clinical Relevance-The introduced system links surface motions of the upper body with the underlying respiratory mechanics. Thus it provides some respiratory parameters without the disadvantages of a facemask or a mouthpiece. The system could allow the analysis of breathing status in some clinical applications and could be used for low-cost monitoring in homecare or to analyse respiratory parameters during sports.

Radiographer reporting: A literature review to support cancer workforce planning in England.

OBJECTIVE: Clinical Imaging contributes to screening, diagnosis, planning and monitoring of treatment and surveillance in cancer care. This literature review summarises evidence about radiographer reporting to help imaging service providers respond to Health Education England's 2017 Cancer Workforce Plan project to expand radiographer reporting in clinical service provision. KEY FINDINGS: Papers published between 1992 and 2018 were reviewed (n = 148). Evidence related to dynamic examinations (fluoroscopy, ultrasound) and mammography was excluded. Content was analysed and summarised using the following headings: clinical scope of practice, responsibilities, training, assessment, impact in practice and barriers to expansion. Radiographer reporting is well established in the United Kingdom. Scope of practice varies individually and geographically. Deployment of appropriately trained reporting radiographers is helping the NHS maintain high quality clinical imaging service provision and deliver a cost-effective increase in diagnostic capacity. CONCLUSION: Working within multiprofessional clinical imaging teams, within a defined scope of practice and with access to medical input when required, reporting radiographers augment capacity in diagnostic pathways and release radiologist time for other complex clinical imaging responsibilities.

Tidal volume via circumferences of the upper body: a pilot study.

The gold standard for tidal volume measurement is spirometry. Based on retrospective data, this study evaluates different geometric lung models in their ability to deliver accurate tidal volumes from changes in thoracic and abdominal circumference. The geometric lung models showed good coefficients of determination (adjusted R2 >0.97) compared to the tidal volumes measured by a body plethysmograph. Tidal volumes obtained by circumference changes might be used in surveillance systems to analyze respiration without a face mask.

PIV Analysis of Stented Haemodynamics in the Descending Aorta.

Cardiovascular diseases (CVD) are the leading cause of death in the developed world and aortic aneurysm is a key contributor. Aortic aneurysms typically occur in the thoracic aorta and can extend into the descending aorta. The Frozen Elephant Trunk stent (FET) is one of the leading treatments for the aneurysms extending into the descending aorta. This study focuses on the in-vitro experimentation of a stented descending aorta, investigating the haemodynamics in a compliant phantom. A silicone phantom of the descending aorta was manufactured using a lost core casting method. A PVC stent was manufactured using the same mould core. Particle Image Velocimetry (PIV) was used for pulsatile studies, focusing specifically on the passive fixation at the distal end of the FET. The results showed an apparent expansion in the diastolic period that was identified to be a collapse in the lateral plane. Flow recirculation regions were identified during the collapse. The collapse was attributed to low upstream and high downstream pressures causing a vacuum effect. The findings may imply a potential risk introduced by the FET stent that requires further investigation.

A virtual patient model for mechanical ventilation.

BACKGROUND AND OBJECTIVES: Mechanical ventilation (MV) is a primary therapy for patients with acute respiratory failure. However, poorly selected ventilator settings can cause further lung damage due to heterogeneity of healthy and damaged alveoli. Varying positive-end-expiratory-pressure (PEEP) to a point of minimum elastance is a lung protective ventilator strategy. However, even low levels of PEEP can lead to ventilator induced lung injury for individuals with highly inflamed pulmonary tissue. Hence, models that could accurately predict peak inspiratory pressures after changes to PEEP could improve clinician confidence in attempting potentially beneficial treatment strategies. METHODS: This study develops and validates a physiologically relevant respiratory model that captures elastance and resistance via basis functions within a well-validated single compartment lung model. The model can be personalised using information available at a low PEEP to predict lung mechanics at a higher PEEP. Proof of concept validation is undertaken with data from four patients and eight recruitment manoeuvre arms. RESULTS: Results show low error when predicting upwards over the clinically relevant pressure range, with the model able to predict peak inspiratory pressure with less than 10% error over 90% of the range of PEEP changes up to 12 cmH2O. CONCLUSIONS: The results provide an in-silico model-based means of predicting clinically relevant responses to changes in MV therapy, which is the foundation of a first virtual patient for MV.

A Review of Arterial Phantom Fabrication Methods for Flow Measurement Using PIV Techniques.

Cardiovascular diseases (CVD) are the leading cause of morbidity and mortality in the western world. In the last three decades, fluid dynamics investigations have been an important component in the study of the cardiovascular system and CVD. A large proportion of studies have been restricted to computational fluid dynamic (CFD) modeling of blood flow. However, with the development of flow measurement techniques such as particle image velocimetry (PIV), and recent advances in additive manufacturing, experimental investigation of such flow systems has become of interest to validate CFD studies, testing vascular implants and using the data for therapeutic procedures. This article reviews the technical aspects of in-vitro arterial flow measurement with the focus on PIV. CAD modeling of geometries and rapid prototyping of molds has been reviewed. Different processes of casting rigid and compliant models for experimental analysis have been reviewed and the accuracy of construction of each method has been compared. A review of refractive index matching and blood mimicking flow circuits is also provided. Methodologies and results of the most influential experimental studies are compared to elucidate the benefits, accuracy and limitations of each method.

A fast generalizable solution method for glucose control algorithms.

In critical care tight control of blood glucose levels has been shown to lead to better clinical outcomes. The need to develop new protocols for tight glucose control, as well as the opportunity to optimize a variety of other drug therapies, has led to resurgence in model-based medical decision support in this area. One still valid hindrance to developing new model-based protocols using so-called virtual patients, retrospective clinical data, and Monte Carlo methods is the large amount of computational time and resources needed. This paper develops fast analytical-based methods for insulin-glucose system model that are generalizable to other similar systems. Exploiting the structure and partial solutions in a subset of the model is the key in finding accurate fast solutions to the full model. This approach successfully reduced computing time by factors of 5600-144000 depending on the numerical error management method, for large (50-164 patients) virtual trials and Monte Carlo analysis. It thus allows new model-based or model-derived protocols to be rapidly developed via extensive simulation. The new method is rigorously compared to existing standard numerical solutions and is found to be highly accurate to within 0.2%.

Reports of abnormal cervical cancer screening tests in systemic sclerosis.

OBJECTIVE: To assess the prevalence of abnormal cervical cancer screening (Pap tests) reported by women with SSc onset before the age of 50 yrs. METHODS: Female members of a Canadian multi-centre SSc cohort completed standardized assessments and were questioned regarding a history of an abnormal Pap test. Potential correlates examined included demographics, reproductive history, smoking, diffuse vs limited SSc type, immunosuppressant exposure and SSc duration. RESULTS: In the 320 women with SSc onset before the age of 50 yrs, the life-time prevalence of an abnormal Pap test (according to self-report) was 25.4% (95% CI CI 20.9, 30.4%). By comparison, self-reported prevalence of abnormal Pap tests among general population Canadian females was recently reported at 13.8% (95% CI 11.6, 16.4%). Women with diffuse SSc (n = 142), tended to have a higher prevalence of self-reported cervical dysplasia (31.7%) compared with those with limited disease (20.7%), but the CIs overlapped. A multivariate logistic regression found a significant positive association between self-reported abnormal Pap test and diffuse disease [odds ratio (OR) 1.87; 95% CI 1.01, 3.47]. An independent association of an abnormal Pap test with smoking (OR 2.43; 95% CI 1.23, 4.78) and with younger age at disease onset was also noted. CONCLUSIONS: We noted a high prevalence of abnormal Pap tests self-reported in our sample. Increased risk was seen among those with diffuse SSc, and also among smokers and those with a younger age at disease onset. Thus, it seems prudent to ensure that adequate attention is paid to cervical cancer screening for women with SSc.

A comparison of the frequency of antibodies to cyclic citrullinated peptides using a third generation anti-CCP assay (CCP3) in systemic sclerosis, primary biliary cirrhosis and rheumatoid arthritis.

The objective was to investigate the frequency of anti-cyclic citrullinated peptides (CCP) antibodies in systemic sclerosis (SSc) and primary biliary cirrhosis (PBC), utilizing a new "third generation" anti-CCP ELISA (anti-CCP3) kit and a conventional anti-CCP2 assay. Patients with PBC, SSc, RA, and normal controls were included in the study. Serum samples were screened for autoantibodies by indirect immunofluorescence (IIF), antibodies to CCP by a second- and third-generation ELISA, antibodies to "scleroderma" antigens (CENP B, Scl-70, PM/Scl and fibrillarin-Scl-34) by a line immunoassay (LIA), and IgM RF by ELISA. The frequency of anti-CCP2 antibodies in SSc and PBC samples was 14.8% (11/74) and 6.2% (5/80), respectively, and the frequency of anti-CCP3 antibodies in SSc was 13.5% (10/74) and in PBC was 3.7% (3/80). By comparison, in the RA group the frequency of anti-CCP3 and anti-CCP2 antibodies was 79.1% (38/48) and 77% (37/48), respectively. Anti-CCP3 ELISA had a sensitivity, specificity, and positive and negative likelihood ratios (LR) of 79% (95% confidence interval [CI] = 64-89%), 93% (95% CI = 88-96%), 11.8 (95% CI = 6.8-20.3), and 0.22 (95% CI = 0.12-0.38), respectively. By comparison, the anti-CCP2 assay had a sensitivity, specificity, and positive and negative LRs of 77% (95% CI = 62-87), 90% (95% CI = 85-94), 8.3 (95% CI = 5.2-13.2), and 0.25 (95% CI = 0.15-0.42), respectively. In patients with SSc, there was an association of anti-CCP2 antibodies with the presence of arthritis, but there was no association of anti-CCP2 or anti-CCP3 with anti-CENP B, anti-Scl 70, or RF. This study confirmed the high specificity and sensitivity of both anti-CCP assays for the diagnosis of RA. The presence of anti-CCP antibodies in SSc was only correlated with the presence of arthritis.

The relationship of dyspnoea to function and quality of life in systemic sclerosis.

AIM: Up to 50% of patients with systemic sclerosis (SSc) have complaints of dyspnoea. We evaluated the independent contributions of dyspnoea to function and health related quality of life (HRQoL) in SSc and also assessed the contributions of pulmonary hypertension, measured by the pulmonary artery systolic pressure (PASP), and interstitial lung disease, measured by the forced vital capacity (FVC), to dyspnoea. METHODS: We assessed dyspnoea, PASP, FVC, function and HRQoL in a cohort of unselected patients with SSc. Multiple linear regression was used to assess the independent contributions of dyspnoea, PASP and FVC to function and HRQoL, after controlling for possible confounding variables. RESULTS: A total of 194 patients with mean disease duration of 11.6 years were studied. Dyspnoea was a significant independent predictor of function and HRQoL. A model including age, gender, disease duration, disease severity and dyspnoea explained 33.3%, 10.6%, 39.2% and 29.4% of the variance of the Stanford Health Assessment Questionnaire, the Short-Form 36 (SF-36) mental component summary score, the SF-36 physical component summary score and the World Health Organization Disability Assessment Schedule II. PASP and FVC were significant independent predictors of dyspnoea but only 21.9% of the variance in dyspnoea was explained by age, gender, disease duration, FVC and PASP. The FVC was a significant independent predictor of function and HRQoL. CONCLUSION: In an unselected population of SSc patients, dyspnoea is a very important contributor to function and HRQoL. Interstitial lung disease, as measured by the FVC, contributes significantly to the sense of dyspnoea, function and HRQoL in SSc. Pulmonary hypertension, assessed echocardiographically by the PASP, predicts the degree of dyspnoea but not function and HRQoL in SSc.

Blood digestion in the mosquito, Anopheles stephensi: the effects of Plasmodium yoelii nigeriensis on midgut enzyme activities.

Midgut proteases contribute to the success or failure of Plasmodium infection of the mosquito. This paper examines the reciprocal effect of Plasmodium yoelii nigeriensis on midgut trypsin, chymotrypsin, aminopeptidase and carboxypeptidase in the mosquito Anopheles stephensi. The total protein ingested and the rate of protein digestion were unaffected by the parasite, but more protein was ingested at the first than the second bloodmeal. All peptidases were unaffected by the presence of the parasite during the first gonotrophic cycle, when ookinetes were penetrating the midgut. In the second gonotrophic cycle, trypsin and chymotrypsin were unaffected by growing oocysts, but aminopeptidase activity was reduced in the midguts of infected mosquitoes. Chymotrypsin activity was depressed and aminopeptidase activity elevated during the second gonotrophic cycle. Plasmodium infection has a negligible effect on bloodmeal digestion and does not limit the availability of the protein for egg production. The significance of changes in aminopeptidase activity when oocysts are present is discussed.

Nurse or doctor: biometry for intraocular lens power calculation, who should measure?

Biometry for intraocular lens power calculation is critical to the refractive success of cataract surgery with intraocular lens implantation. The majority of ophthalmology departments in Scotland currently entrust this procedure to junior medical staff. In an attempt to streamline preoperative assessment of cataract patients we have changed our practice so that nurses now carry out biometry. This prospective study, in which the results of 336 eyes undergoing cataract surgery and intraocular lens implantation were examined, shows that appropriately trained nursing staff in our department are able to perform the measurements for biometry at least as accurately as junior medical staff.

Single photon emission computed tomography in the diagnosis of inflammatory spondyloarthropathies.

OBJECTIVE: The role of bone scintigraphy in the evaluation of patients with inflammatory spondyloarthropathy is controversial and previous studies have reported a lack of sensitivity and specificity. The aim of our study was to determine whether single photon emission computed tomography (SPECT) scanning would enhance the clinical utility of bone scintigraphy in the detection of inflammatory axial disease, in particular sacroiliitis. METHODS: Twenty patients with definite sacroiliitis (New York criteria > 1) on plain film radiographs and 20 age matched controls were studied. Bone scintigraphy and SPECT scanning were carried out 2 h after an intravenous injection of 99mTc imidodiphosphonate (IDP). A quantitative and qualitative assessment of radiopharmaceutical uptake in the sacroiliac (SI) joints was derived from planar films and a qualitative analysis of uptake in the SI joints was derived from SPECT scans. All films were read without knowledge of patient identification. RESULTS: Quantitative analysis of planar films did not identify any difference between study and control groups (p > 0.05). Qualitative assessment of planar films identified features of sacroiliitis more frequently in patients than in controls (p < 0.05) with a sensitivity of 25% and a specificity of 95%. SPECT scanning also revealed enhanced radiopharmaceutical uptake in the SI joints more frequently in patients than in controls (p < 0.001) with a sensitivity of 85% and a specificity of 90%. Increased uptake in the lumbar facet joints and costovertebral joints was identified in 3 patients. Similar abnormalities were not detected in the control group. CONCLUSION: Our results indicate that SPECT scanning is both sensitive and specific for the detection of established sacroiliitis and may also identify inflammatory disease at other sites in the spine.

Magnetic resonance imaging in the detection of sacroiliitis.

The value of magnetic resonance imaging (MRI) in establishing the diagnosis of sacroiliitis was studied in 20 patients with established or suspected disease on conventional radiographs and in 10 healthy subjects. Coronal T1 weighted, axial T2 weighted and proton density MRI images of the sacroiliac joints in addition to plain film radiographs were obtained. All films were graded from 0 to 4 according to the modified New York criteria and independently for changes in joint width, erosions, sclerosis and ankylosis. Using the modified New York criteria, more abnormalities were detected by MRI than by conventional radiography (p = 0.04). This was due to the detection of definite abnormalities (grades 2-4) by MRI in joints that were graded normal or suspicious (grades 0-1) on plain films (p = 0.01). MRI tended to be superior to plain films in visualizing erosions. Only MRI detected abnormalities of articular cartilage (19 patients) and in subchondral bone marrow (7 patients). The latter 2 types represented fatty infiltration and inflammatory change. Intraobserver and interobserver variation were similar for the interpretation of MRI scans and plain film radiographs. These results suggest that MRI detects changes of established sacroilitis. Due to its ability to directly image articular cartilage it may be particularly useful in patients with early disease.