An experimentally validated finite element method for augmented vertebral bodies

Background Finite element models of augmented vertebral bodies require a realistic modelling of the cement infiltrated region. Most methods published so far used idealized cement shapes or oversimplified material models for the augmented region. In this study, an improved, anatomy-specific, homogenized finite element method was developed and validated to predict the apparent as well as the local mechanical behavior of augmented vertebral bodies. Methods Forty-nine human vertebral body sections were prepared by removing the cortical endplates and scanned with high-resolution peripheral quantitative CT before and after injection of a standard and a low-modulus bone cement. Forty-one specimens were tested in compression to measure stiffness, strength and contact pressure distributions between specimens and loading-plates. From the remaining eight, fourteen cylindrical specimens were extracted from the augmented region and tested in compression to obtain material properties. Anatomy-specific finite element models were generated from the CT data. The models featured element-specific, density-fabric-based material properties, damage accumulation, real cement distributions and experimentally determined material properties for the augmented region. Apparent stiffness and strength as well as contact pressure distributions at the loading plates were compared between simulations and experiments. Findings The finite element models were able to predict apparent stiffness (R2 > 0.86) and apparent strength (R2 > 0.92) very well. Also, the numerically obtained pressure distributions were in reasonable quantitative (R2 > 0.48) and qualitative agreement with the experiments. Interpretation The proposed finite element models have proven to be an accurate tool for studying the apparent as well as the local mechanical behavior of augmented vertebral bodies.

Augmented environments for the targeting of hepatic lesions during image-guided robotic liver surgery

BACKGROUND Stereotactic navigation technology can enhance guidance during surgery and enable the precise reproduction of planned surgical strategies. Currently, specific systems (such as the CAS-One system) are available for instrument guidance in open liver surgery. This study aims to evaluate the implementation of such a system for the targeting of hepatic tumors during robotic liver surgery. MATERIAL AND METHODS Optical tracking references were attached to one of the robotic instruments and to the robotic endoscopic camera. After instrument and video calibration and patient-to-image registration, a virtual model of the tracked instrument and the available three-dimensional images of the liver were displayed directly within the robotic console, superimposed onto the endoscopic video image. An additional superimposed targeting viewer allowed for the visualization of the target tumor, relative to the tip of the instrument, for an assessment of the distance between the tumor and the tool for the realization of safe resection margins. RESULTS Two cirrhotic patients underwent robotic navigated atypical hepatic resections for hepatocellular carcinoma. The augmented endoscopic view allowed for the definition of an accurate resection margin around the tumor. The overlay of reconstructed three-dimensional models was also used during parenchymal transection for the identification of vascular and biliary structures. Operative times were 240 min in the first case and 300 min in the second. There were no intraoperative complications. CONCLUSIONS The da Vinci Surgical System provided an excellent platform for image-guided liver surgery with a stable optic and instrumentation. Robotic image guidance might improve the surgeon's orientation during the operation and increase accuracy in tumor resection. Further developments of this technological combination are needed to deal with organ deformation during surgery.

Design and Implementation of a Laparoscope Calibration Method for Augmented Reality Navigation

Intraoperative laparoscopic calibration remains a challenging task. In this work we present a new method and instrumentation for intraoperative camera calibration. Contrary to conventional calibration methods, the proposed technique allows intraoperative laparoscope calibration from single perspective observations, resulting in a standardized scheme for calibrating in a clinical scenario. Results show an average displacement error of 0.52 ± 0.19 mm, indicating sufficient accuracy for clinical use. Additionally, the proposed method is validated clinically by performing a calibration during the surgery.

Generation of an hTERT-restricted, CMV-augmented oncolytic adenovirus capable of tumor-specific transgene expression: Development, characterization, and optimization

Current shortcomings in cancer therapy require the generation of new, broadly applicable, potent, targeted treatments. Here, an adenovirus is engineered to replicate specifically in cells with active human telomerase promotion using a modified hTERT promoter, fused to a CMV promoter element. The virus was also modified to contain a visible reporter transgene, GFP. The virus, Ad/hTC-GFP-E1 was characterized in vitro and demonstrated tumor specific activity both by dose and over time course experiments in a variety of cell lines. In vivo, Ad/hTC-GFP-E1 was affected at suppressing tumor growth and providing a survival benefit without causing any measurable toxicity. To increase the host range of the vector, the fiber region was modified to contain an RGD-motif. The vector, AdRGD/hTC-GFP-E1, was recharacterized in vitro, revealing heightened levels of infectivity and toxicity however maintaining a therapeutic window between cancer and normal cell toxicity. AdRGD/hTC-GFP-E1 was administered in vivo by limb perfusion and was observed to be tumor specific both in expression and replication. To further enhance the efficacy of viral vectors in lung delivery, asthma medications were investigated for their abilities to enhance transgene delivery and expression. A combination of bronchodilators, mast cell inhibitors, and mucolytic agents was devised which demonstrated fold increases in expression in immunocompetent mouse lungs as single agents and more homogenous, intense levels of expression when done in combination of all agents. To characterize the methods in which some cancers are resistant or may become resistant to oncolytic treatments, several small molecule inhibitors of metabolic pathways were applied in combination with oncolytic infection in vitro. SP600125 and PD 98059, respective JNK and ERK inhibitors, successfully suppressed oncolytic toxicity, however did not affect infectivity or transgene expression of Ad/hTC-GFP-E1. JNK and ERK inhibition did significantly suppress viral replication, however, as analyzed by lysate transfer and titration assays. In contrast, SB 203580, an inhibitor for p38, did not demonstrate any protective effects with infected cells. Flow cytometric analysis indicated a possible correlation with G1 arrest and suppressed viral production, however more compounds must be investigated to clarify this observation. ^

Cuando el Estado no dice todo: la relación entre la rendición de cuentas gubernamental y el monitoreo ciudadano en el caso uruguayo

Presentación en la 4ta. Conferencia Regional del CLACAI. Reafirmando el legado de Cairo: Aborto legal y seguro. Lima, 21 y 22 de Agosto de 2014

¿Qué se enseña, cuando "se dice que se enseña", educación física en el Jardín de Infantes?

La elección del tema del presente proyecto, es a consecuencia de las preocupaciones que iban surgiendo cuando me desempeñaba como Profesora en Educación Física en distintos Jardines de Infantes urbanos y suburbanos de la ciudad de La Plata. A medida que daba clases, se iban presentando dificultades que tenía que resolver, como por ejemplo, la comunicación y la organización de los alumnos, el uso del lenguaje particular del nivel, la selección de los contenidos y de las estrategias para la enseñanza. El trabajo se presenta a partir de la formulación de interrogantes de investigación que dan el marco para explicar el estado de la cuestión. El título es una pregunta que contiene los núcleos de análisis que se desarrollarán a lo largo de la ponencia. ¿Qué se enseña, "cuando se dice que se enseña", educación física en el jardín de infantes?

¿Yo soy quien dice "yo"? : Consideraciones sobre la primera persona en la poesía yámbica de la Grecia arcaica

Dentro del marco de los estudios contemporáneos sobre la poesía griega antigua, dos corrientes críticas han adquirido relevancia interpretativa acerca de la naturaleza y la funcionalidad del "yo" en las composiciones líricas, elegíacas y yámbicas de la Grecia arcaica. La primera corriente entiende los textos como expresión personal del propio poeta. Desde esta perspectiva, el campo referencial que entra en juego en un poema remite siempre a la experiencia vivida por el poeta o a su reflexión íntima. Esta concepción postula una exégesis crítica tendiente a develar la poética a través de la biografía. La segunda corriente, concibe el "yo" como una construcción estereotipada o ficcional. De este modo, aquella primera persona funcionaría como un artilugio poético convencional. Nuestra presentación tiene como objetivo indagar las distintas vertientes interpretativas sobre la referencialidad del "yo" en las composiciones yámbicas de Arquíloco de Paros

"'Herramientas' se dice de muchas maneras". Reflexiones sobre las secciones iniciales de las Investigaciones de Wittgenstein

Fil: Karczmarczyk, Pedro. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

¿Por qué fantaseamos con el apocalipsis zombie? Lo que dice de "nosotros" el éxito The Walking Dead y otras ficciones del capitalismo tardío

Fil: Labra, Diego. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

"Lo que se dice y se hace. Lo que se calla y se niega" : Apropiaciones de la literatura en el aula

Fil: Mattioli, Luz. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.