A parametric study of the effect of 3D plaque shape on local hemodynamics and implications for plaque instability

The vast majority of heart attacks occur when vulnerable plaques rupture, releasing their lipid content into the blood stream leading to thrombus formation and blockage of a coronary artery. Detection of these unstable plaques before they rupture remains a challenge. Hemodynamic features including wall shear stress (WSS) and wall shear stress gradient (WSSG) near the vulnerable plaque and local inflammation are known to affect plaque instability. In this work, a computational workflow has been developed to enable a comprehensive parametric study detailing the effects of 3D plaque shape on local hemodynamics and their implications for plaque instability. Parameterized geometric 3D plaque models are created within a patient-specific coronary artery tree using a NURBS (non-uniform rational B-splines)-based vascular modeling pipeline. Realistic blood flow features are simulated by using a Navier-Stokes solver within an isogeometric finite-element analysis framework. Near wall hemodynamic quantities such as WSS and WSSG are quantified, and vascular distribution of an inflammatory marker (VCAM-1) is estimated. Results show that proximally skewed eccentric plaques have the most vulnerable combination of high WSS and high positive spatial WSSG, and the presence of multiple lesions increases risk of rupture. The computational tool developed in this work, in conjunction with clinical data, -could help identify surrogate markers of plaque instability, potentially leading to a noninvasive clinical procedure for the detection of vulnerable plaques before rupture.

Image-guided subject-specific modeling of glymphatic transport and amyloid deposition

The glymphatic system is a brain-wide system of perivascular networks that facilitate exchange of cerebrospinal fluid (CSF) and interstitial fluid (ISF) to remove waste products from the brain. A greater understanding of the mechanisms for glymphatic transport may provide insight into how amyloid beta (A β ) and tau agglomerates, key biomarkers for Alzheimer's disease and other neurodegenerative diseases, accumulate and drive disease progression. In this study, we develop an image-guided computational model to describe glymphatic transport and A β deposition throughout the brain. A β transport and deposition are modeled using an advection-diffusion equation coupled with an irreversible amyloid accumulation (damage) model. We use immersed isogeometric analysis, stabilized using the streamline upwind Petrov-Galerkin (SUPG) method, where the transport model is constructed using parameters inferred from brain imaging data resulting in a subject-specific model that accounts for anatomical geometry and heterogeneous material properties. Both short-term (30-min) and long-term (12-month) 3D simulations of soluble amyloid transport within a mouse brain model were constructed from diffusion weighted magnetic resonance imaging (DW-MRI) data. In addition to matching short-term patterns of tracer deposition, we found that transport parameters such as CSF flow velocity play a large role in amyloid plaque deposition. The computational tools developed in this work will facilitate investigation of various hypotheses related to glymphatic transport and fundamentally advance our understanding of its role in neurodegeneration, which is crucial for the development of preventive and therapeutic interventions.

Extra Biliary Complications of Laparoscopic Cholecystectomy: Experience from a Study of 1420 Cases

To evaluate the extra biliary complications of laparoscopic cholecystectomy and the outcome of management of those complications. This descriptive observational study was carried out at CMH Dhaka and CMH Jashore, Bangladesh from March 2016 to March 2022. A total of 1420 patients who underwent Laparoscopic cholecystectomy were included in this study. Extra biliary complications of laparoscopic cholecystectomy were divided into i) Access related ii) Intraoperative (procedure related) and iii) Postoperative complications. The incidence of access-related, intra-operative or procedure-related and postoperative complications was 2.88%, 4.91% and 1.82% respectively. Access related complications were extra-peritoneal insufflations 1.34%, port site bleeding 1.26%, small bowel laceration 0.21% and transverse colon injury 0.07%. Intraoperative or procedural extra biliary complications were liver injury 0.56%, duodenal perforation 0.07%, colon injury 0.07%, bleeding through cystic artery 0.49% and bleeding from gall bladder bed 1.12%. Postoperative complications were port site infection (PSI) 1.05%, port site hernia (PSH) 0.56%, major sepsis 0.14% and ischemic stroke 0.07%. Two of colonic injuries were the major complications encountered in this series, diagnosed during the procedure and converted to open procedure. Duodenal perforation encountered in one case during difficult dissection in the Callot's triangle, diagnosed during the procedure and managed laparoscopically by intra-corporeal suturing. No mortality reported in this series. Extra biliary complications are almost equally common as biliary complications in laparoscopic cholecystectomy and can be life-threatening. An early diagnosis and effective management of complications accordingly, are the utmost requirement for favorable outcome in laparoscopic cholecystectomy.

Patient-Specific Modeling Could Predict Occurrence of Pediatric Stroke

Moyamoya disease (MMD) is a progressive steno-occlusive cerebrovascular disease leading to recurrent stroke. There is a lack of reliable biomarkers to identify unilateral stroke MMD patients who are likely to progress to bilateral disease and experience subsequent contralateral stroke(s). We hypothesized that local hemodynamics are predictive of future stroke and set out to noninvasively assess this stroke risk in pediatric MMD patients. MR and X-ray angiography imaging were utilized to reconstruct patient-specific models of the circle of Willis of six pediatric MMD patients who had previous strokes, along with a control subject. Blood flow simulations were performed by using a Navier–Stokes solver within an isogeometric analysis framework. Vascular regions with a wall shear rate (WSR) above the coagulation limit (>5,000 s⁻¹) were identified to have a higher probability of thrombus formation, potentially leading to ischemic stroke(s). Two metrics, namely, “critical WSR coverage” and “WSR score,” were derived to assess contralateral stroke risk and compared with clinical follow-up data. In two patients that suffered a contralateral stroke within 2 months of the primary stroke, critical WSR coverages exceeding 50% of vessel surface and WSR scores greater than 6× the control were present in multiple contralateral vessels. These metrics were not as clearly indicative of stroke in two additional patients with 3–5 year gaps between primary and contralateral strokes. However, a longitudinal study of one of these two cases, where a subsequent timepoint was analyzed, suggested disease stabilization on the primary stroke side and an elevated contralateral stroke risk, which was confirmed by patient outcome data. This indicates that post-stroke follow-up at regular intervals might be warranted for secondary stroke prevention. The findings of this study suggest that WSR-based metrics could be predictive of future stroke risk after an initial stroke in pediatric MMD patients. In addition, better predictions may be possible by performing patient-specific hemodynamic analysis at multiple timepoints during patient follow-up to monitor changes in the WSR-based metrics.

Image-based patient-specific flow simulations are consistent with stroke in pediatric cerebrovascular disease

Moyamoya disease (MMD) is characterized by narrowing of the distal internal carotid artery and the circle of Willis (CoW) and leads to recurring ischemic and hemorrhagic stroke. A retrospective review of data from 50 pediatric MMD patients revealed that among the 24 who had a unilateral stroke and were surgically treated, 11 (45.8%) had a subsequent, contralateral stroke. There is no reliable way to predict these events. After a pilot study in Acta-/- mice that have features of MMD, we hypothesized that local hemodynamics are predictive of contralateral strokes and sought to develop a patient-specific analysis framework to noninvasively assess this stroke risk. A pediatric MMD patient with an occlusion in the right middle cerebral artery and a right-sided stroke, who was surgically treated and then had a contralateral stroke, was selected for analysis. By using an unsteady Navier-Stokes solver within an isogeometric analysis framework, blood flow was simulated in the CoW model reconstructed from the patient's postoperative imaging data, and the results were compared with those from an age- and sex-matched control subject. A wall shear rate (WSR) > 60,000 s-1 (about 12 × higher than the coagulation threshold of 5000 s-1 and 9 × higher than control) was measured in the terminal left supraclinoid artery; its location coincided with that of the subsequent postsurgical left-sided stroke. A parametric study of disease progression revealed a strong correlation between the degree of vascular morphology altered by MMD and local hemodynamic environment. The results suggest that an occlusion in the CoW could lead to excessive contralateral WSRs, resulting in thromboembolic ischemic events, and that WSR could be a predictor of future stroke.

Association of Serum Vitamin D (25OHD) Level with Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Acute exacerbations of COPD is characterized by a change in the patients baseline dyspnoea, cough and/or sputum that is beyond normal day to day differences and guides to a change in standard medications in a patient with COPD. Vitamin D influences the innate & adaptive immune system, and exerts pleiotropic antimicrobial and anti-inflammatory responses. Vitamin D deficiency is frequent among COPD patients but its contributory role in disease exacerbations is widely debated. This study was aimed to assess relationship between reduced serum vitamin D (25-OHD) level with COPD severity and acute exacerbation. This observational cross-sectional study was carried out in the department of Respiratory Medicine, NIDCH, Mohakhali, Dhaka, Bangladesh from October 2016 to September 2017. Consecutive 80 hospital admitted patients with acute exacerbation of chronic obstructive pulmonary disease diagnosed on the basis of clinical history & pulmonary function tests and 78 age & sex matched controls were investigated for serum vitamin D (25-OHD) level. Among the COPD patients, 37% had Vitamin D deficiency (<20ng/ml) and 28.75% had Vitamin D insufficiency (20-29ng/ml). Mean vitamin D (25-OHD) level of COPD patients (25.82±10.62ngm/ml) was found to be significantly lower than healthy controls (32.57±11.32ngm/ml). Vitamin D deficiency was found, by Pearson correlation test, to be significantly associated with severity of COPD. Multivariate analysis showed that age (in years), FEV1 (percent predicted), frequent exacerbators (≥2 in the last year), and smoking (>40 pack year) were significantly associated with Vitamin D deficiency. Acute exacerbation of chronic obstructive pulmonary disease patients was found to have vitamin D deficiency and vitamin D deficiency was significantly associated with severity of COPD. Vitamin D deficiency was also associated with frequent disease exacerbation.

Liposome size and charge optimization for intraarterial delivery to gliomas

Nanoparticles such as liposomes may be used as drug delivery vehicles for brain tumor therapy. Particle geometry and electrostatic properties have been hypothesized to be important determinants of effective tumor targeting after intraarterial injection. In this study, we investigate the combined roles of liposome size and surface charge on the effectiveness of delivery to gliomas after intraarterial injection. Intracarotid injection of liposomes was performed in separate cohorts of both healthy and C6 glioma-bearing Sprague Dawley rats after induction of transient cerebral hypoperfusion. Large (200 nm) and small (60-80 nm) fluorescent dye-loaded liposomes that were either cationic or neutral in surface charge were utilized. Delivery effectiveness was quantitatively measured both with real-time, in vivo and postmortem diffuse reflectance spectroscopy. Semi-quantitative multispectral fluorescence imaging was also utilized to assess the pattern and extent of liposome targeting within tumors. Large cationic liposomes demonstrated the most effective hemispheric and glioma targeting of all the liposomes tested. Selective large cationic liposome retention at the site of glioma growth was observed. The liposome deposition pattern within tumors after intraarterial injection was variable with both core penetration and peripheral deposition observed in specific tumors. This study provides evidence that liposome size and charge are important determinants of effective brain and glioma targeting after intraarterial injection. Our results support the future development of 200-nm cationic liposomal formulations of candidate intraarterial anti-glioma agents for further pre-clinical testing.

Flow arrest intra-arterial delivery of small TAT-decorated and neutral micelles to gliomas

The cell-penetrating trans-activator of transcription (TAT) is a cationic peptide derived from human immunodeficiency virus-1. It has been used to facilitate macromolecule delivery to various cell types. This cationic peptide is capable of crossing the blood-brain barrier and therefore might be useful for enhancing the delivery of drugs that target brain tumors. Here we test the efficiency with which relatively small (20 nm) micelles can be delivered by an intra-arterial route specifically to gliomas. Utilizing the well-established method of flow-arrest intra-arterial injection we compared the degree of brain tumor deposition of cationic TAT-decorated micelles versus neutral micelles. Our in vivo and post-mortem analyses confirm glioma-specific deposition of both TAT-decorated and neutral micelles. Increased tumor deposition conferred by the positive charge on the TAT-decorated micelles was modest. Computational modeling suggested a decreased relevance of particle charge at the small sizes tested but not for larger particles. We conclude that continued optimization of micelles may represent a viable strategy for targeting brain tumors after intra-arterial injection. Particle size and charge are important to consider during the directed development of nanoparticles for intra-arterial delivery to brain tumors.

Surgical management of traumatic extradural haematoma: Experiences with 610 patients and prospective analysis

This study was carried out to find out the age, sex, mode of injury, localization, clinical presentation, CT findings, operative measures and outcome of extradural haematoma in the patient population at Dhaka Medical College. 610 consecutive patients with cranial extradural haematoma who underwent surgery in department of Neurosurgery from 1st January 2006 to 6th October 2008 were included in this prospective study. Each of the patients were evaluated in term of age, sex, mode of injury, localization of haematoma, clinical presentation, CT findings, operative measures and outcome. Out of 610 cases 86.32 % were male and 13.78 % were female. The male and female ratio was 6.27: 1. Age ranged from 2.5 to 83 years. Commonest age group was 21 to 30 years. Commonest mode of injury was Road traffic Accident 53.45%, followed by Assaults. Most common clinical presentation was headache / Vomiting 63.61 %, followed by altered sensorium 60.66 %. In this present prospective study of 610 cases of EDH, temporo parietal site was involved in 33.45 % followed by frontal region in 23.28 %. Sixty five patients (10.66 %) died; 19 of these had associated brain injuries and 28 cases were deeply unconscious. Extradural haematoma is a neurosurgical emergency where early surgical intervention is associated with the best prognosis. Many factors affects the outcome of extradural haematoma surgery and the most important one is the duration of time between incident/accident and operation in neurosurgical operation theater; mortality can be close to 0% if this time interval can be minimized.

Magnetic resonance imaging-based computational modelling of blood flow and nanomedicine deposition in patients with peripheral arterial disease

Peripheral arterial disease (PAD) is generally attributed to the progressive vascular accumulation of lipoproteins and circulating monocytes in the vessel walls leading to the formation of atherosclerotic plaques. This is known to be regulated by the local vascular geometry, haemodynamics and biophysical conditions. Here, an isogeometric analysis framework is proposed to analyse the blood flow and vascular deposition of circulating nanoparticles (NPs) into the superficial femoral artery (SFA) of a PAD patient. The local geometry of the blood vessel and the haemodynamic conditions are derived from magnetic resonance imaging (MRI), performed at baseline and at 24 months post intervention. A dramatic improvement in blood flow dynamics is observed post intervention. A 500% increase in peak flow rate is measured in vivo as a consequence of luminal enlargement. Furthermore, blood flow simulations reveal a 32% drop in the mean oscillatory shear index, indicating reduced disturbed flow post intervention. The same patient information (vascular geometry and blood flow) is used to predict in silico in a simulation of the vascular deposition of systemically injected nanomedicines. NPs, targeted to inflammatory vascular molecules including VCAM-1, E-selectin and ICAM-1, are predicted to preferentially accumulate near the stenosis in the baseline configuration, with VCAM-1 providing the highest accumulation (approx. 1.33 and 1.50 times higher concentration than that of ICAM-1 and E-selectin, respectively). Such selective deposition of NPs within the stenosis could be effectively used for the detection and treatment of plaques forming in the SFA. The presented MRI-based computational protocol can be used to analyse data from clinical trials to explore possible correlations between haemodynamics and disease progression in PAD patients, and potentially predict disease occurrence as well as the outcome of an intervention.

Reassessing the Role of Intra-Arterial Drug Delivery for Glioblastoma Multiforme Treatment

Effective treatment for glioblastoma (GBM) will likely require targeted delivery of several specific pharmacological agents simultaneously. Intra-arterial (IA) delivery is one technique for targeting the tumor site with multiple agents. Although IA chemotherapy for glioblastoma (GBM) has been attempted since the 1950s, the predicted benefits remain unproven in clinical practice. This review focuses on innovative approaches to IA drug delivery in treating GBM. Guided by novel in vitro and in vivo optical measurements, newer pharmacokinetic models promise to better define the complex relationship between background cerebral blood flow and drug injection parameters. Advanced optical technologies and tracers, unique nanoparticles designs, new cellular targets, and rational drug formulations are continuously modifying the therapeutic landscape for GBM. Personalized treatment approaches are emerging; however, such tailored approaches will largely depend on effective drug delivery techniques and on the ability to simultaneously deliver multidrug regimens. These new paradigms for tumor-selective drug delivery herald dramatic improvements in the effectiveness of IA chemotherapy for GBM. Therefore, within this context of so-called "precision medicine," the role of IA delivery for GBM is thoroughly reassessed.

One Health: a perspective from the human health sector

Despite emerging consensus that the One Health concept involves multiple stakeholders, the human health sector has continued to view it from a predominantly human health security perspective. It has often ignored the concerns of other sectors, e.g. concerns that relate to trade, commerce, livelihoods and sustainable development, all of which are important contributors to societal well-being. In the absence of a culture of collaboration, clear One Health goals, conceptual clarity and operating frameworks, this disconnect between human health and One Health efforts has often impeded the translation of One Health from concept to reality, other than during emergency situations. If there are to be effective and sustainable One Health partnerships we must identify clear operating principles that allow flexible approaches to intersectoral collaborations. To convince technical experts and political leaders in the human health sector of the importance of intersectoral cooperation, and to make the necessary structural adjustments, we need examples of best practice models and trans-sectoral methods for measuring the risks, burden and costs across sectors. Informal collaborations between researchers and technical experts will play a decisive role in developing these methods and models and instilling societal well-being into the human health sector's view of One Health.

USNCTAM perspectives on mechanics in medicine

Over decades, the theoretical and applied mechanics community has developed sophisticated approaches for analysing the behaviour of complex engineering systems. Most of these approaches have targeted systems in the transportation, materials, defence and energy industries. Applying and further developing engineering approaches for understanding, predicting and modulating the response of complicated biomedical processes not only holds great promise in meeting societal needs, but also poses serious challenges. This report, prepared for the US National Committee on Theoretical and Applied Mechanics, aims to identify the most pressing challenges in biological sciences and medicine that can be tackled within the broad field of mechanics. This echoes and complements a number of national and international initiatives aiming at fostering interdisciplinary biomedical research. This report also comments on cultural/educational challenges. Specifically, this report focuses on three major thrusts in which we believe mechanics has and will continue to have a substantial impact. (i) Rationally engineering injectable nano/microdevices for imaging and therapy of disease. Within this context, we discuss nanoparticle carrier design, vascular transport and adhesion, endocytosis and tumour growth in response to therapy, as well as uncertainty quantification techniques to better connect models and experiments. (ii) Design of biomedical devices, including point-of-care diagnostic systems, model organ and multi-organ microdevices, and pulsatile ventricular assistant devices. (iii) Mechanics of cellular processes, including mechanosensing and mechanotransduction, improved characterization of cellular constitutive behaviour, and microfluidic systems for single-cell studies.

Vascular deposition patterns for nanoparticles in an inflamed patient-specific arterial tree

Inflammation, a precursor to many diseases including cancer and atherosclerosis, induces differential surface expression of specific vascular molecules. Blood-borne nanoparticles (NPs), loaded with therapeutic and imaging agents, can recognize and use these molecules as vascular docking sites. Here, a computational model is developed within the isogeometric analysis framework to understand and predict the vascular deposition of NPs within an inflamed arterial tree. The NPs have a diameter ranging from 0.1 to 2.0 μm and are decorated with antibodies directed toward three endothelial adhesion molecules, namely intravascular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin, whose surface density depends on the local wall shear stress. Results indicate VCAM-1 targeted NPs adhere more, with ICAM-1 directed NPs adhering least efficiently, resulting in approximately an order-of-magnitude lower average particle surface density. ICAM-1 and E-selectin directed 0.5 μm NPs are distributed more uniformly (heterogeneity index ≈ 0.9 and 1.0, respectively) over the bifurcating vascular branches compared to their VCAM-1 counterparts (heterogeneity index ≈ 1.4). When the NPs are coated with antibodies for VCAM-1 and E-selectin in equal proportions, a more uniform vascular distribution is achieved compared with VCAM-1-only targeted particles, thus demonstrating the advantage of NP multivalency in vascular targeting. Furthermore, the larger NPs (2 μm) adhere more (≈ 200%) in the lower branches compared to the upper branch. This computational framework provides insights into how size, ligand type, density, and multivalency can be manipulated to enhance NP vascular adhesion in an individual patient.

Surgery for primary intracerebral haemorrhage: is it safe and effective?

This prospective study was conducted to compare the outcome between medical and surgical treatment of primary intracerebral haemorrhage at the department of Neurosurgery, Dhaka Medical College Hospital from January 2006 to October 2007. All patients with primary intracerebral haematoma with Glasgow Coma Scale (GCS). 5-15 (on admission) and heamatoma volume 30 cc or above admitted at Neurosurgery department managed conservatively or surgically were included in this study. Total 60 patients were selected, of them 30 patients managed conservatively and 30 patients managed surgically. Conservatively managed patients regarded as control group (Group-A) and surgically managed patients regarded as experimental group (Group-B). Patients or attendants refused to operate were included in the conservative group. All the selected patients were evaluated on the basis of detailed history, clinical examination (general and neurological examination) and CT scan findings. Outcome was evaluated in term of Glasgow Outcome Scale (GOS). Best medical treatment was given for conservative group and operations were done for surgical group and followed up after surgery till discharge by observing GCS and GOS at discharge. Number of death were 15 (50%) patients in group-A and 13 (43%) patients in group-B. There was no significant difference in mortality rate between two groups but outcome was relatively better in group-B. According to Glasgow Outcome Scale, dependency in group-A and group-B was 26.6% and 23.4% respectively. So dependency were more in group-A. But there was no significant difference statistically. Seven (23.4%) patients were independent in group-A but 10(43.3%) patients were independent in group-B. However in relative terms of outcome of group-B was better than that of group-A. In our study we found no statistically significant difference in outcome between medical and surgical management of primary intracerebral haemorrhage.

In silico vascular modeling for personalized nanoparticle delivery

AIMS

To predict the deposition of nanoparticles in a patient-specific arterial tree as a function of the vascular architecture, flow conditions, receptor surface density and nanoparticle properties.

MATERIALS & METHODS

The patient-specific vascular geometry is reconstructed from computed tomography angiography images. The isogeometric analysis framework integrated with a special boundary condition for the firm wall adhesion of nanoparticles is implemented. A parallel plate flow chamber system is used to validate the computational model in vitro.

RESULTS

Particle adhesion is dramatically affected by changes in patient-specific attributes, such as branching angle and receptor density. The adhesion pattern correlates well with the spatial and temporal distribution of the wall shear rates. For the case considered, the larger (2.0 µm) particles adhere two-times more in the lower branches of the arterial tree, whereas the smaller (0.5 µm) particles deposit more in the upper branches.

CONCLUSION

Our computational framework in conjunction with patient-specific attributes can be used to rationally select nanoparticle properties to personalize, and thus optimize, therapeutic interventions.