In vivo measurement of human brain elasticity using a light aspiration device

The brain deformation that occurs during neurosurgery is a serious issue impacting the patient "safety" as well as the invasiveness of the brain surgery. Model-driven compensation is a realistic and efficient solution to solve this problem. However, a vital issue is the lack of reliable and easily obtainable patient-specific mechanical characteristics of the brain which, according to clinicians' experience, can vary considerably. We designed an aspiration device that is able to meet the very rigorous sterilization and handling process imposed during surgery, and especially neurosurgery. The device, which has no electronic component, is simple, light and can be considered as an ancillary instrument. The deformation of the aspirated tissue is imaged via a mirror using an external camera. This paper describes the experimental setup as well as its use during a specific neurosurgery. The experimental data was used to calibrate a continuous model. We show that we were able to extract an in vivo constitutive law of the brain elasticity: thus for the first time, measurements are carried out per-operatively on the patient, just before the resection of the brain parenchyma. This paper discloses the results of a difficult experiment and provide for the first time in-vivo data on human brain elasticity. The results point out the softness as well as the highly non-linear behavior of the brain tissue.Comment: Medical Image Analysis (2009) accept\'

A 3D multi-scale skeletal muscle model to predict active and passive responses. Application to intra-abdominal pressure prediction

Computational models have been used extensively to study the behavior of skeletal muscle structures, however few of these models are able to evaluate their 3D active response using as input experimental measurements such as electromyography. Hence, improving the activation mechanisms in simulation models can provide interesting and useful achievements in this field. Therefore, the purpose of this paper was to develop a multi-scale chemo-mechanical material model to consider the active behavior of skeletal muscle in 3D geometries. The model was used to investigate the response of abdominal muscles which represent a challenging scenario due to their complex geometry and anatomical conditions. Realistic muscle geometries and other tissues of the human abdomen, including transverse abdominis (TA), internal oblique (IO), external oblique (EO), rectus abdominis (RA), rectus sheath (RSH), linea alba (LA) and aponeurosis (APO) were considered. Since the geometry of these tissues was obtained from magnetic resonance images, an iterative algorithm was implemented to find the initial stress state that achieve the equilibrium of them with the intra-abdominal pressure. In order to investigate the functionality of the proposed model, the increase of intra-abdominal pressure was calculated during cough in the supine position while the Ca2+ signal for activating the muscles was set in regard to experimentally recorded electrical activity from previous studies. The amount of intra-abdominal pressure calculated by the model is consistent with reported experimental results. This model can serve as a virtual laboratory to analyze the role of the abdominal wall components in different conditions, such as the performance of meshes used for repairing hernia defects

Intraperitoneal chemotherapy for peritoneal metastases : an expert opinion

Introduction: The rationale for intraperitoneal (IP) drug delivery for patients with peritoneal metastases (PM) is based on the pharmacokinetic advantage resulting from the peritoneal-plasma barrier, and on the potential to adequately treat small, poorly vascularized PM. Despite a history of more than three decades, many aspects of IP drug delivery remain poorly studied. Areas covered: We outline the anatomy and physiology of the peritoneal cavity, including the pharmacokinetics of IP drug delivery. We discuss transport mechanisms governing tissue penetration of IP chemotherapy, and how these are affected by the biomechanical properties of the tumor stroma. We provide an overview of the current clinical evidence on IP chemotherapy in ovarian, colorectal, and gastric cancer. We discuss the current limitations of IP drug delivery and propose several potential areas of progress. Expert opinion: The potential of IP drug delivery is hampered by off-label use of drugs developed for systemic therapy. The efficacy of IP chemotherapy for PM depends on cancer type, disease extent, and mode of drug delivery. Results from ongoing randomized trials will allow to better delineate the potential of IP chemotherapy. Promising approaches include IP aerosol therapy, prolonged delivery platforms such as gels or biomaterials, and the use of nanomedicine

Towards the in vivo mechanical characterization of abdominal wall in animal model: application to hernia repair

El trabajo presentado en esta tesis se centra en el diseño e implementación de una metodología que permita caracterizar in vivo el comportamiento mecánico pasivo de la pared abdominal. Esta metodología permitiría a los cirujanos disponer de información mecánica relevante sobre un paciente especí co, lo que podría contribuir a mejorar el tratamiento quirúrgico de hernias mediante malla protésica. El tratamiento quirúrgico de hernias consiste en cerrar la debilidad creada en el músculo, ya sea directamente con puntos de sutura o mediante la implantación de una malla protésica. En el caso de la malla, ésta es la responsable de absorber las tensiones a las que el músculo se ve sometido durante el tiempo en el que se produce la regeneración de tejido. Para reducir el riego de aparición de dolor postoperatorio, rotura o rasgadura de tejido o incluso una recidiva, la malla debe mimetizar la respuesta mecánica de la zona de la pared donde vaya a ser colocada, que a su vez puede variar de un paciente a otro en función de su edad, género, índice de masa corporal u otras características físicas. Un mejor conocimiento de las propiedades mecánicas del abdomen en paciente especí co ayudaría al cirujano a determinar qué malla protésica se puede considerar la ideal, mecánicamente hablando. Por todo ello, el trabajo que aquí se presenta plantea una aproximación in vivo para caracterizar la pared abdominal sobre un modelo animal y su posterior implementación en casos de patologías herniarias. En un primer paso, se ha realizado un estudio biomecánico del cierre en línea alba, que ayudase a entender los aspectos mecánicos y biológicos que tienen lugar durante la curación de la herida a corto y largo plazo. A continuación, se han llevado a cabo ensayos mecánicos de in ado sobre la pared, que combinados con el uso de cámaras y técnicas de adquisición de imagen han permitido extraer la respuesta del tejido de una manera no invasiva. Este estudio experimental, se ha llevado a cabo sobre especímenes sanos y otro herniados y reparados con distintas mallas quirúrgicas, lo que ha permitido extrapolar el efecto in vivo que provocan estas mallas. A partir de los datos experimentales también se ha desarrollado un análisis numérico que permitiese caracterizar la respuesta mecánica especí ca de cada espécimen. A este efecto, dicha caracterización se ha tratado como un problema inverso y resuelto primeramente mediante un análisis de super cies de respuesta y después con un algoritmo propio aplicado a modelos hiperelásticos. Finalmente, también se ha reconstruido un modelo de elementos nitos de la cavidad abdominal que permite simular el efecto producido por distintas mallas protésicas así como su alteración respecto al tejido sano

Landmarks in vaginal mesh development: polypropylene mesh for treatment of SUI and POP

Vaginal meshes used in the treatment of stress urinary incontinence (SUI) and pelvic organ prolapse (POP) have produced highly variable outcomes, causing life-changing complications in some patients while providing others with effective, minimally invasive treatments. The risk:benefit ratio when using vaginal meshes is a complex issue in which a combination of several factors, including the inherent incompatibility of the mesh material with some applications in pelvic reconstructive surgeries and the lack of appropriate regulatory approval processes at the time of the premarket clearance of these products, have contributed to the occurrence of complications caused by vaginal mesh. Surgical mesh used in hernia repair has evolved over many years, from metal implants to knitted polymer meshes that were adopted for use in the pelvic floor for treatment of POP and SUI. The evolution of the material and textile properties of the surgical mesh was guided by clinical feedback from hernia repair procedures, which were also being modified to obtain the best outcomes with use of the mesh. Current evidence shows how surgical mesh fails biomechanically when used in the pelvic floor and materials with improved performance can be developed using modern material processing and tissue engineering techniques