Modeling and Real-Time Simulation of a Vascularized Liver Tissue

International audienceIn Europe only, about 100,000 deaths per year are related to cirrhosis or liver cancer. While surgery remains the option that offers the foremost success rate against such pathologies, several limitations still hinder its widespread development. Among the limiting factors is the lack of accurate planning systems, which has been a motivation for several recent works, aiming at better resection planning and training systems, relying on pre-operative imaging, anatomical and biomechanical modelling. While the vascular network in the liver plays a key role in defining the operative strategy, its influence at a biomechanical level has not been taken into account. In the paper we propose a real-time model of vascularized organs such as the liver. The model takes into account separate constitutive laws for the parenchyma and vessels, and defines a coupling mechanism between these two entities. In the evaluation section, we present results of in vitro porcine liver experiments that indicate a significant influence of vascular structures on the mechanical behaviour of tissue. We confirm the val- ues obtained in the experiments by computer simulation using standard FEM. Finally, we show that the conventional modelling approach can be efficiently approximated with the proposed composite model capable of real-time calculations

Conformation of Adjacent Self-expanding Stents: A Cross-Sectional In Vitro Study

We examined the proximal conformation of three commonly used self-expanding stents when the stents were deployed adjacent to one another in a tubular model, simulating a “kissing” stent technique. The stent pairs were evaluated by computed tomogrphy to determine the cross-sectional area excluded by the stents within the model. The mean areas associated with each stent pair were compared and significance evaluated by a t -test. A statistically significant difference was found when the area excluded by adjacent Wallstents was compared with both the Luminexx and SMART stents ( p < 0.001 and p < 0.002, respectively). The difference in the area excluded and differences in conformation might play a role in the lower patencies that have been observed in “kissing” stent series.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41328/1/270_2005_Article_33.pd

Superior vena cava obstruction presenting with epistaxis, haemoptysis and gastro-intestinal haemorrhage in two men receiving haemodialysis with central venous catheters: two case reports

<p>Abstract</p> <p>Introduction</p> <p>Superior vena cava (SVC) obstruction secondary to central venous catheterization is an increasingly recognized complication.</p> <p>Case presentation</p> <p>We present two cases of superior vena cava obstruction secondary to indwelling central venous catheters used for haemodialysis access. One of the patients developed the unusual complications of torrential epistaxis and haemoptysis, which has been reported only once so far in the literature. The other patient developed melaena secondary to downhill oesophageal varices. We briefly discuss the pathophysiology, symptoms and signs, investigations and management of superior vena cava obstruction and thrombosis.</p> <p>Conclusion</p> <p>Increasing use of central venous access for haemodialysis will increase the incidence of central venous stenosis, thrombosis and exhaustion. Superior vena cava obstruction is likely to be an increasingly recognised complication of vascular access in the future.</p

Successful Angioplasty of a Superficial Femoral Artery StenosisCaused by a Suture-Mediated Closure Device

We report the successful angioplasty of an acutearterial narrowing after suture-mediated closure (SMC) of a femoralarterial puncture. A 75-year-old woman underwent a cerebral arteriogramvia a right common femoral artery puncture. The arteriotomy site wasclosed with a SMC device. Four days after placement the patientcomplained of pain in her right calf after walking. An arteriogram 7days after SMC showed a severe focal stenosis at the origin of thesuperficial femoral artery involving the presumed puncture site. Thelesion was successfully treated with balloon angioplasty. The patientat 6 months was asymptomatic.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41325/1/270_2003_Article_2649.pd

Persistent left superior vena cava: Review of the literature, clinical implications, and relevance of alterations in thoracic central venous anatomy as pertaining to the general principles of central venous access device placement and venography in cancer patients

Persistent left superior vena cava (PLSVC) represents the most common congenital venous anomaly of the thoracic systemic venous return, occurring in 0.3% to 0.5% of individuals in the general population, and in up to 12% of individuals with other documented congential heart abnormalities. In this regard, there is very little in the literature that specifically addresses the potential importance of the incidental finding of PLSVC to surgeons, interventional radiologists, and other physicians actively involved in central venous access device placement in cancer patients. In the current review, we have attempted to comprehensively evaluate the available literature regarding PLSVC. Additionally, we have discussed the clinical implications and relevance of such congenital aberrancies, as well as of treatment-induced or disease-induced alterations in the anatomy of the thoracic central venous system, as they pertain to the general principles of successful placement of central venous access devices in cancer patients. Specifically regarding PLSVC, it is critical to recognize its presence during attempted central venous access device placement and to fully characterize the pattern of cardiac venous return (i.e., to the right atrium or to the left atrium) in any patient suspected of PLSVC prior to initiation of use of their central venous access device

Teaching Practicum in Biology

My teaching practicum was completed from August 2019 to December 2019 at Worcester Technical High School. I taught five freshman high school biology courses under the supervision of my supervising practitioner, Kevin Lauritsen. Through this experience, I created lesson plans which met the Massachusetts Science and Technology/Engineering Curriculum Framework standards, created course materials, engaged with students, and graded assignments. I adjusted my lessons and style according to my reflections, feedback from students, and feedback from my supervising practitioner, program supervisor (Irene Plonczak), and program director (Shari Weaver). I made progress to achieve growth and proficiency in each of the six CAP Element categories which are required for aspiring educators in Massachusetts. Overall, I created an engaging, supportive, and challenging learning environment for my students and developed my skills as a passionate and dedicated educator

Biofilm Sanitizer Tolerance of Vermont Dairy Listeria monocytogenes

Listeria monocytogenes is a foodborne pathogen found in biofilms on surfaces and equipment in the food processing environment. Sodium hypochlorite (SH) and quaternary ammonium compounds (QAC) are readily available and commonly used sanitizers. However, due to the structure and additional organic material produced in a biofilm, killing bacteria within the biofilm may be a challenge for one or both of these sanitizers. The objective of this work was to determine if immature and mature biofilms from L. monocytogenes isolated from Vermont artisan dairy environments were more tolerant to QAC and SH compared to planktonic cultures’ tolerance. To determine sanitizer minimum inhibitory concentration (MIC), cultures were incubated statically in 1x or 1/20x Brain Heart Infusion broth (BHI) in polystyrene microtiter plates for 24 hours at room temperature (22°C) with serial dilutions of sanitizer. Sanitizer efficacy on biofilms was determined by growing isolates on one cm stainless steel coupons in 1x or 1/20x BHI to simulate nutrient rich and poor conditions on a surface commonly seen in food processing environments. Coupons were incubated statically for 1, 3, or 10 days. Media was replaced every 48 hours to prevent nutrient depletion. After incubation, coupons were rinsed 3 times with phosphate buffered saline and placed into 0, 50, 100, or 200ppm SH or QAC for the manufacturer recommended contact time. Sanitizer was neutralized and adherent cells were removed by vortexing with beads. Cell suspensions were diluted and plated, then counted via spot plating on BHI agar. Significant differences for biofilm survival were assessed using Analysis of Variance in R (v.4.0.4). MICs for isolates grown in nutrient poor (1/20X BHI) conditions were lower than nutrient rich conditions (1X BHI) for both sanitizers. All isolates’ biofilms reached ~6-8 log10 CFU/coupon on stainless steel. Reductions from different QAC concentrations differed (padj \u3c0.05) in 1/20x BHI but were not significantly different in 1x BHI. In both biofilm growth conditions SH was more effective at 200 ppm than 50 ppm (padj \u3c 0.05). Biofilms from both persistent and transient L. monocytogenes environmental isolates from Vermont dairies are resistant to working concentrations of QAC sanitizer, but sodium hypochlorite bleach more adequately reduces L. monocytogenes biofilm on stainless steel