Finite Element Modeling, Computer Simulations, and Experiments of Shear Wave Propagation for Tissue Mechanical Property Assessment

The goal of this project is to develop a novel approach to tissue mechanical property measurement using Acoustic Radiation Force Ultrasound. This project aims to do so by incorporating the quantitative nature of shear wave imaging with the minimal lateral displacement requirement of acoustic radiation force impulse imaging to develop a novel approach to tissue mechanical property measurement using statistical signal separation techniques. By applying a wide tracking beam to a narrow push, it hypothesized that principal component analysis may be used to reconstruct the shear wave and get tissue mechanical property information. This new approach will not require spatial averaging, as alternative methods do, and will therefore better reflect the mechanical properties of heterogeneous tissues.Bachelor of Scienc

Scale-Invariant Specifications for Human-Swarm Systems

We present a method for controlling a swarm using its spectral decomposition -- that is, by describing the set of trajectories of a swarm in terms of a spatial distribution throughout the operational domain -- guaranteeing scale invariance with respect to the number of agents both for computation and for the operator tasked with controlling the swarm. We use ergodic control, decentralized across the network, for implementation. In the DARPA OFFSET program field setting, we test this interface design for the operator using the STOMP interface -- the same interface used by Raytheon BBN throughout the duration of the OFFSET program. In these tests, we demonstrate that our approach is scale-invariant -- the user specification does not depend on the number of agents; it is persistent -- the specification remains active until the user specifies a new command; and it is real-time -- the user can interact with and interrupt the swarm at any time. Moreover, we show that the spectral/ergodic specification of swarm behavior degrades gracefully as the number of agents goes down, enabling the operator to maintain the same approach as agents become disabled or are added to the network. We demonstrate the scale-invariance and dynamic response of our system in a field relevant simulator on a variety of tactical scenarios with up to 50 agents. We also demonstrate the dynamic response of our system in the field with a smaller team of agents. Lastly, we make the code for our system available.Comment: Journal of Field Robotics, Accepted for Publication. 25 page

A prospective, randomized, double-blinded single-site control study comparing blood loss prevention of tranexamic acid (TXA) to epsilon aminocaproic acid (EACA) for corrective spinal surgery

<p>Abstract</p> <p>Background</p> <p>Multilevel spinal fusion surgery has typically been associated with significant blood loss. To limit both the need for transfusions and co-morbidities associated with blood loss, the use of anti-fibrinolytic agents has been proposed. While there is some literature comparing the effectiveness of tranexamic acid (TXA) to epsilon aminocaproic acid (EACA) in cardiac procedures, there is currently no literature directly comparing TXA to EACA in orthopedic surgery.</p> <p>Methods/Design</p> <p>Here we propose a prospective, randomized, double-blinded control study evaluating the effects of TXA, EACA, and placebo for treatment of adolescent idiopathic scoliosis (AIS), neuromuscular scoliosis (NMS), and adult deformity (AD) via corrective spinal surgery. Efficacy will be determined by intraoperative and postoperative blood loss. Other clinical outcomes that will be compared include transfusion rates, preoperative and postoperative hemodynamic values, and length of hospital stay after the procedure.</p> <p>Discussion</p> <p>The primary goal of the study is to determine perioperative blood loss as a measure of the efficacy of TXA, EACA, and placebo. Based on current literature and the mechanism by which the medications act, we hypothesize that TXA will be more effective at reducing blood loss than EACA or placebo and result in improved patient outcomes.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov ID: NCT00958581</p

Are antifibrinolytic drugs equivalent in reducing blood loss and transfusion in cardiac surgery? A meta-analysis of randomized head-to-head trials

BACKGROUND: Aprotinin has been shown to be effective in reducing peri-operative blood loss and the need for re-operation due to continued bleeding in cardiac surgery. The lysine analogues tranexamic acid (TXA) and epsilon aminocaproic acid (EACA) are cheaper, but it is not known if they are as effective as aprotinin. METHODS: Studies were identified by searching electronic databases and bibliographies of published articles. Data from head-to-head trials were pooled using a conventional (Cochrane) meta-analytic approach and a Bayesian approach which estimated the posterior probability of TXA and EACA being equivalent to aprotinin; we used as a non-inferiority boundary a 20% increase in the rates of transfusion or re-operation because of bleeding. RESULTS: Peri-operative blood loss was significantly greater with TXA and EACA than with aprotinin: weighted mean differences were 106 mls (95% CI 37 to 227 mls) and 185 mls (95% CI 134 to 235 mls) respectively. The pooled relative risks (RR) of receiving an allogeneic red blood cell (RBC) transfusion with TXA and EACA, compared with aprotinin, were 1.08 (95% CI 0.88 to 1.32) and 1.14 (95% CI 0.84 to 1.55) respectively. The equivalent Bayesian posterior mean relative risks were 1.15 (95% Bayesian Credible Interval [BCI] 0.90 to 1.68) and 1.21 (95% BCI 0.79 to 1.82) respectively. For transfusion, using a 20% non-inferiority boundary, the posterior probabilities of TXA and EACA being non-inferior to aprotinin were 0.82 and 0.76 respectively. For re-operation the Cochrane RR for TXA vs. aprotinin was 0.98 (95% CI 0.51 to 1.88), compared with a posterior mean Bayesian RR of 0.63 (95% BCI 0.16 to 1.46). The posterior probability of TXA being non-inferior to aprotinin was 0.92, but this was sensitive to the inclusion of one small trial. CONCLUSION: The available data are conflicting regarding the equivalence of lysine analogues and aprotinin in reducing peri-operative bleeding, transfusion and the need for re-operation. Decisions are sensitive to the choice of clinical outcome and non-inferiority boundary. The data are an uncertain basis for replacing aprotinin with the cheaper lysine analogues in clinical practice. Progress has been hampered by small trials and failure to study clinically relevant outcomes

Postdural puncture headache in paediatric oncology patients

Previous studies have not determined the correlation between durai puncture and postural headache in paediatric patients. Furthermore, no studies have evaluated the correlation between atypical headache and durai puncture in the paediatric population. Therefore, we prospectively analyzed the incidence of typical postdural puncture headache (PDPHA) and atypical headache in paediatric oncology patients following durai puncture.The study population consisted of 66 paediatric patients undergoing 128 consecutive procedures, including 99 lumbar punctures and 29 bone marrow aspirations without concomitant lumbar puncture. Patients were prospectively randomized into four groups: Group I, preteens (< 13 yr) undergoing lumbar puncture, Group II, adolescents (13–21 yr) undergoing lumbar puncture, Group III, preteens undergoing bone marrow aspiration, and Group IV adolescents undergoing bone marrow aspiration. The presence and description of headache was documented immediately after durai puncture or bone marrow aspiration, and on post-procedure days #1,3 and 5 by personnel blinded to the type of procedure.There was an increase in the incidence of headache (9.1%) after lumbar puncture in patients < 21 yr relative to patients undergoing bone marrow aspiration (P < 0.05). No difference was found between the incidence of typical PDPHA after dural puncture in preteens and adolescents. There was also no difference in the incidence of atypical headache after durai puncture or after bone marrow aspiration among preteens and adolescents.Paediatric patients experience an increased incidence of typical postdural puncture headache after durai puncture compared with age-matched patients undergoing bone marrow aspiration only. Atypical headache is relatively common in the paediatric population after dural puncture or bone marrow aspiration.Les études antérieures n’ont pas établi de corrélation entre la ponction durale et la céphalée posturale chez les patients pédiatriques. En outre, aucune étude de cette population n’a évalué le lien entre la céphalée atypique et la ponction durale. Par conséquent, à la suite d’une ponction durale, nous avons analysé de façon prospective l’incidence d’une céphalée de ponction postdurale (CPPD) typique et atypique chez des patients d’oncologie pédiatrique.La population de l’étude était constituée de 66 patients de pédiatrie subissant 128 examens consécutifs, comprenant 99 ponctions lombaires et 29 ponctions médullaires sans ponction lombaire concomitante. Les patients ont été répartis au hasard en quatre groupes de façon prospective: Groupe I de pré-adolescents (< 13 ans) subissant une ponction lombaire; Groupe II d’adolescents (13–21 ans) subissant une ponction lombaire; Groupe III de pré-adolescents inscrits pour une ponction médullaire et Groupe IV d’adolescents pour une ponction médullaire. La présence de céphalée a été vérifiée et décrite immédiatement après la ponction durale ou la ponction médullaire et 1, 3 et 5 jours suivant les interventions par du personnel qui ignorait le type de technique employé.Il y a eu une incidence accrue de céphalée (9,1 %) à la suite de la ponction lombaire chez les patients < 21 ans par rapport aux patients qui ont subi une ponction médullaire (P < 0,05). Aucune différence n’est apparue dans l’incidence de CPPD typique après une ponction lombaire chez les pré-adolescents et chez les adolescents. Il n’y avait pas non plus de différence dans l’incidence de céphalée atypique après une ponction durale ou une ponction médullaire parmi les pré-adolescents et les adolescents.Les patients de pédiatrie ont connu une incidence accrue de céphalée de ponction postdurale à la suite d’une ponction durale quand on les compare aux patients du même âge qui ont subi une ponction médullaire seulement. La céphalée atypique est relativement fréquente dans la population pédiatrique après une ponction durale ou une ponction médullaire