A new technique to measure micromotion distribution around a cementless femoral stem.

The interfacial micromotion is closely associated to the long-term success of cementless hip prostheses. Various techniques have been proposed to measure them, but only a few number of points over the stem surface can be measured simultaneously. In this paper, we propose a new technique based on micro-Computer Tomography (μCT) to measure locally the relative interfacial micromotions between the metallic stem and the surrounding femoral bone. Tantalum beads were stuck at the stem surface and spread at the endosteal surface. Relative micromotions between the stem and the endosteal bone surfaces were measured at different loading amplitudes. The estimated error was 10μm and the maximal micromotion was 60μm, in the loading direction, at 1400N. This pilot study provided a local measurement of the micromotions in the 3 direction and at 8 locations on the stem surface simultaneously. This technique could be easily extended to higher loads and a much larger number of points, covering the entire stem surface and providing a quasi-continuous distribution of the 3D interfacial micromotions around the stem. The new measurement method would be very useful to compare the induced micromotions of different stem designs and to optimize the primary stability of cementless total hip arthroplasty.

A novel technique using echocardiography to evaluate venous cannula performance perioperatively in CPB cardiac surgery.

OBJECTIVE: Transthoracic echocardiography (TTE) has been used clinically to disobstruct venous drainage cannula and to optimise placement of venous cannulae in the vena cava but it has never been used to evaluate performance capabilities. Also, little progress has been made in venous cannula design in order to optimise venous return to the heart lung machine. We designed a self-expandable Smartcanula (SC) and analysed its performance capability using echocardiography. METHODS: An epicardial echocardiography probe was placed over the SC or control cannula (CTRL) and a Doppler image was obtained. Mean (V(m)) and maximum (V(max)) velocities, flow and diameter were obtained. Also, pressure drop (DeltaP(CPB)) was obtained between the central venous pressure and inlet to venous reservoir. LDH and Free Hb were also compared in 30 patients. Comparison was made between the two groups using the student's t-test with statistical significance established when p<0.05. RESULTS: Age for the SC and CC groups were 61.6+/-17.6 years and 64.6+/-13.1 years, respectively. Weight was 70.3+/-11.6 kg and 72.8+/-14.4 kg, respectively. BSA was 1.80+/-0.2 m(2) and 1.82+/-0.2 m(2), respectively. CPB times were 114+/-53 min and 108+/-44 min, respectively. Cross-clamp time was 59+/-15 min and 76+/-29 min, respectively (p=NS). Free-Hb was 568+/-142 U/l versus 549+/-271 U/l post-CPB for the SC and CC, respectively (p=NS). LDH was 335+/-73 mg/l versus 354+/-116 mg/l for the SC and CC, respectively (p=NS). V(m) was 89+/-10 cm/s (SC) versus 63+/-3 cm/s (CC), V(max) was 139+/-23 cm/s (SC) versus 93+/-11 cm/s (CC) (both p<0.01). DeltaP(CPB) was 30+/-10 mmHg (SC) versus 43+/-13 mmHg (CC) (p<0.05). A Bland-Altman test showed good agreement between the two devices used concerning flow rate calculations between CPB and TTE (bias 300 ml+/-700 ml standard deviation). CONCLUSIONS: This novel Smartcanula design, due to its self-expanding principle, provides superior flow characteristics compared to classic two stage venous cannula used for adult CPB surgery. No detrimental effects were observed concerning blood damage. Echocardiography was effective in analysing venous cannula performance and velocity patterns.

Diseño, implementación y evaluación de un juego educativo basado en puzles con scaffolding enfocado a las redes de ordenadores

En los últimos años, el sector de las TIC (Tecnologías de la Información y la Comunicación) está contemplando cómo va creciendo la demanda de profesionales y, a la vez, el número de matriculaciones universitarias está cayendo. Esta situación está comenzando a ser alarmante dentrodel mundo de las empresas y profesionales de este campo.Con el fin de buscar una solución, se ha demostrado que existen una serie de metodologías pedagógicas basadas en la teoría Constructivista que, combinadas con la tecnología software necesaria, pueden incrementar el nivel de interés de los estudiantes por el mundo de las TIC. Apesar de ello, actualmente hay una escasez de herramientas que implementen dichas metodologías pedagógicas y que proporcionen al mismo tiempo los mecanismos necesarios para dar apoyo a los estudiantes durante el aprendizaje de conceptos TIC. Una posible solución a este problema es la creación de juegos educativos que implementen este tipo de metodologías y que integren mecanismos de scaffolding, es decir, mecanismos de apoyo al aprendizaje del estudiante.Dentro de este marco, siguiendo la propuesta de un modelo conceptual que define los elementos necesarios para crear juegos basados en puzles con scaffolding, el propósito que tiene este proyectoes dar a conocer conceptos relacionados con las TIC mediante la implementación de un juego educativo con la intención de despertar el interés de los estudiantes por esta área. En concreto, el proyecto se basa en el diseño, implementación y evaluación de un juego educativo dentro del área de las redes de ordenadores que proporcione mecanismos de ayuda a los estudiantes para guiarlos a que alcancen soluciones correctas.

Diseño, implementación y evaluación de un juego educativo basado en puzles con Scaffolding orientado al aprendizaje de arquitectura de computadores

Las matriculaciones en el área de las Tecnologías de la Información y la Comunicación (TIC)están sufriendo un grave descenso en estos últimos años. Diversos estudios corroboran que la manera como se instruye al alumnado en estas áreas no es la adecuada y para resolver este problema se han investigado diversos métodos de aprendizaje basados en la teoríaConstructivista. En este sentido, los juegos educativos parecen ser una buena solución para implementar este tipo de metodologías, ya que además, se adecuan a las características y motivaciones de los estudiantes de hoy en día, y son una buena solución para enseñar conceptos complicados. Además, la integración de mecanismos de apoyo al aprendizaje (conocidos como,scaffolding) en los juegos educativos juega un importante papel ya que permite al alumnoguiarlo durante su proceso de aprendizaje. Teniendo en cuenta todo esto, este PFC se centra en el diseño e implementación de un juego educativo con scaffolding, regido por una metodología de aprendizaje basada en el Constructivismo para que los alumnos aprendan conceptos relacionados con arquitectura de computadores. Una vez completado el diseño, se evaluará el funcionamiento con diferentes alumnos y se analizarán los resultados obtenidos.

Diseño, implementación y evaluación de un juego educativo basado en puzles con scaffolding orientado a la programación

Existe una falta de interés por parte de los estudiantes en el área de las Tecnologías de la Información y la Comunicación (TIC) que se ve reflejada en el descenso de las matriculaciones en este ámbito. El uso de metodologías de aprendizaje basadas en el Constructivismo combinadas con tecnología software, se ha observado que es una buena solución para afrontar dicha falta de interés. Sin embargo, actualmente no existen aplicaciones software que implementen estas metodologías pedagógicas y que proporcionen a los estudiantes los mecanismos de ayuda necesarios (Scaffolding) para darles soporte durante el aprendizaje de conceptos TIC. Una posible solución a este problema es el uso de juegos educativos, los cuáles implementarán técnicas de Scaffolding que den el soporte necesario al estudiante para alcanzarlos objetivos de aprendizaje fijados. Por tanto, en este proyecto se diseñará e implementará un juego educativo basado en puzles orientado a la Programación que estará basado en un método aprendizaje basado en el Constructivismo en el que el estudiante construye su propio conocimiento. Una vez implementado, será evaluado en un centro escolar por parte deestudiantes de últimos cursos de ESO o Bachillerato.

Progress in cardiovascular anastomoses: will the vascular join replace Carrel's technique?

BACKGROUND: Vascular reconstructions are becoming challenging due to the comorbidity of the aging population and since the introduction of minimally invasive approaches. Many sutureless anastomosis devices have been designed to facilitate the cardiovascular surgeon's work and the vascular join (VJ) is one of these. We designed an animal study to assess its reliability and long-term efficacy. METHODS: VJ allows the construction of end-to-end and end-to-side anastomoses. It consists of two metallic crowns fixed to the extremity of the two conduits so that vessel edges are joined layer by layer. There is no foreign material exposed to blood. In adult sheep both carotid arteries were prepared and severed. End-to-end anastomoses were performed using the VJ device on one side and the classical running suture technique on the other side. Animals were followed-up with Duplex-scan every 3 months and sacrificed after 12 months. Histopathological analysis was carried out. RESULTS: In 20 animals all 22 sutureless anastomoses were successfully completed in less than 2 min versus 6 +/- 3 min for running suture. Duplex showed the occlusion of three controls and one sutureless anastomosis. Two controls and one sutureless had stenosis >50%. Histology showed very thin layer of myointimal hyperplasia (50 +/- 10 microm) in the sutureless group versus 300 +/- 27 microm in the control. No significant inflammatory reaction was detected. CONCLUSIONS: VJ provides edge-to-edge vascular repair that can be considered the most physiological way to restore vessel continuity. For the first time, in healthy sheep, an anastomotic device provided better results than suture technique.

Fat signal suppression for coronary MRA at 3T using a water-selective adiabatic T2 -preparation technique.

PURPOSE: To improve fat saturation in coronary MRA at 3T by using a spectrally selective adiabatic T2 -Prep (WSA-T2 -Prep). METHODS: A conventional adiabatic T2 -Prep (CA-T2 -Prep) was modified, such that the excitation and restoration pulses were of differing bandwidths. On-resonance spins are T2 -Prepared, whereas off-resonance spins, such as fat, are spoiled. This approach was combined with a CHEmically Selective Saturation (CHESS) pulse to achieve even greater fat suppression. Numerical simulations were followed by phantom validation and in vivo coronary MRA. RESULTS: Numerical simulations demonstrated that augmenting a CHESS pulse with a WSA-T2 -Prep improved robustness to B1 inhomogeneities and that this combined fat suppression was effective over a broader spectral range than that of a CHESS pulse in a conventional T2 -Prepared sequence. Phantom studies also demonstrated that the WSA-T2 -Prep+CHESS combination produced greater fat suppression across a range of B1 values than did a CA-T2 -Prep+CHESS combination. Lastly, in vivo measurements demonstrated that the contrast-to-noise ratio between blood and myocardium was not adversely affected by using a WSA-T2 -Prep, despite the improved abdominal and epicardial fat suppression. Additionally, vessel sharpness improved. CONCLUSION: The proposed WSA-T2 -Prep method was shown to improve fat suppression and vessel sharpness as compared to a CA-T2 -Prep technique, and to also increase fat suppression when combined with a CHESS pulse.

Absence of ectopic epithelial inclusions in 3,904 axillary lymph nodes examined in sentinel technique.

Intraoperative examination of sentinel axillary lymph nodes can be done by imprint cytology, frozen section, or, most recently, by PCR-based amplification of a cytokeratin signal. Using this technique, benign epithelial inclusions, representing mammary tissue displaced along the milk line, will likely generate a positive PCR signal and lead to a false-positive diagnosis of metastatic disease. To better appreciate the incidence of ectopic epithelial inclusions in axillary lymph nodes, we have performed an autopsy study, examining on 100 μm step sections 3,904 lymph nodes obtained from 160 axillary dissections in 80 patients. The median number of lymph nodes per axilla was 23 (15, 6, and 1 in levels 1, 2, and 3, respectively). A total of 30,450 hematoxylin-eosin stained slides were examined, as well as 8,825 slides immunostained with pan-cytokeratin antibodies. Despite this meticulous work-up, not a single epithelial inclusion was found in this study, suggesting that the incidence of such inclusions is much lower than the assumed 5% reported in the literature.