A Review of Pneumatic Actuators Used for the Design of Medical Simulators and Medical Tools

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Theme F "medical robotics for training and guidance": Results and future work

International audienceThis paper presents the projects of the Theme F "medical robotics for training and guidance" inside the GdR STIC-Santé. Three scientific meeting days have been organized during the period 2011-2012. They were devoted to physical simulators of behavior for gesture learning, command of hand prostheses by myoelectric signals or brain activity and the manipulation of objects by the artificial hand, and the last to the use of robots for medical gestures. The next event, scheduled for early 2013, will focus on the evaluation of gesture and especially "evaluation of gesture - to do what?"

Towards a realistic in vitro experience of epidural Tuohy needle insertion.

The amount of pressure exerted on the syringe and the depth of needle insertion are the two key factors for successfully carrying out epidural procedure. The force feedback from the syringe plunger is helpful in judging the loss of pressure, and the depth of the needle insertion is crucial in identifying when the needle is precisely placed in the epidural space. This article presents the development of two novel wireless devices to measure these parameters to precisely guide the needle placement in the epidural space. These techniques can be directly used on patients or implemented in a simulator for improving the safety of procedure. A pilot trial has been conducted to collect depth and pressure data with the devices on a porcine cadaver. These measurements are then combined to accurately configure a haptic device for creating a realistic in vitro experience of epidural needle insertion

Stiffness control of pneumatic actuators to simulate human tissues behavior on medical haptic simulators

In order to increase the realism of medical simulators, haptic interfaces could be used to simulate the patient's body behavior. It is especially interesting to reproduce the stiffness of different soft tissues with corresponding haptic behaviors. In this paper, two control laws, impedance control and back-stepping associated with a closed-loop stiffness tuning, are introduced and applied to a pneumatic actuator. Both controllers have been obtained by using the A-T transform which is suitable to model the behavior of a pneumatic system, in a strict-feedback form. Both control laws allow to tune the system stiffness. A comparison of their performances is presented, based on experimental results

Towards increased realism of a computer simulation of human childbirth.

A virtual childbirth simulator is normally associated with a computer analogue of mechanical mannequins used for training purposes in obstetrics. Such a simulator would allow acquiring a deeper understanding of labour and provide the necessary expertise for students in obstetrics. A patient-specific childbirth simulator, in turn, would be capable of predicting difficult birth scenarios in advance based on ultrasound or magnetic resonance imaging scans of the maternal pelvis and fetus. This would give midwives and obstetricians time to prepare for predicted worst­case scenarios and potentially reduce morbidity and mortality of both babies and their mothers. The existing virtual childbirth simulator successfully simulates physiologic labour. This thesis is concerned with taking the software one step closer towards being a patient-specific virtual childbirth simulator and to simulate difficult birth scenarios. The core content of this thesis is concerned with the development of computational feta I neck models. A number of neck models were developed and tested in the simulator. The methods used to simulate the feta I neck are the following: ball and socket joint for intervertebral discs, spring-and-damper systems for ligaments and six-degrees­of-freedom bushing element to simulate a coupled behaviour of the discs, ligaments and neck muscles. The latest one-pivot neck model is using a six-degrees-of-freedom bushing element to simulate the behaviour of the feta I head. The developed neck model, together with the approximated complete mechanical properties of the feta I spine, facilitated running the experiments with a higher variety of biomechanical parameters such as the neck's length, strength and a full range of feta I bi parietal diameters. The experiments are reported in this thesis. An additional simulation software, using haptic devices, was developed specifically for validation of the developed computational neck models. The software allows manipulating of a virtual feta I head on the screen, using two haptic devices. It is used to validate the resistance of the feta I head, during flexion, extension and rotation. It was clinically tested by midwives and obstetricians at the hospital. The results showed that the software is capable of providing biomechanical properties of a newborn's head motion, with the help from the clinicians. Experiments were conducted to validate the accuracy of the Total Lagrangian Explicit Dynamics (TLED) contact method, used in the software. The validation setup consisted of a finite element cube and a rigid body plate, pushing vertically down on the cube with a gravitational force of 9.81N. Similarly, the experiment was repeated for a rigid body sphere pushing on the top of the cube. The results showed that TLED is less sensitive to the number of tetrahedral elements as compared to the Abaqus Explicit contact method. Another set of experiments were conducted for resolving a direct occipito-posterior position (OP) of the fetal head, which is considered to be a difficult birth scenario. In OP, midwives advise their patients to tilt their pelvises anteriorly to help with labour. This method was experimentally tested in the childbirth simulator and the results showed that tilting a pelvis anteriorly could potentially ease the dilation during the first stage of labour. However, no significant difference was observed as compared to the non-tilted pelvis during the second stage of labour. Experiments were run to observe shoulder dystocia in the childbirth simulator. Initially it was not possible to observe shoulder dystocia due to the rigid fetal trunk coming into contact with the maternal sacrum. A number of adjustments were made in order to allow the rigid feta I trunk to follow the feta I head, such as increasing the feta I shoulders to the average width, cutting the trunk in half and disabling the spring keeping the trunk vertical. Shoulder dystocia was observed in the simulator even in the absence of the complete birth canal, articulated fetal shoulders and flexible fetaI chest. Finally, a new maternal pelvis was introduced in the software with a mobile sacrum. The sacrum was attached to the rest of the pelvis using the six degrees-of-freedom bushing element. The effects of the sacrum mobility on a childbirth were studied. The results show that a mobile sacrum contributes toward the full internal rotation of the fetaI head during a childbirth, whereas the absence of the mobility leads to the arrest of the head in the anteroposterior diameter of the pelvis

Computer-based simulation of the effects of instrumental delivery on the fetal head

Fetal head moulding is a phenomenon that happens during the process of human childbirth. Due to the highly deformable fetal scalp being in contact with the maternal anatomy, the shape of the fetal head changes. This can be benefi�cial when the fetal head dimensions are very similar to the dimensions of the female pelvis hence allowing the baby to progress safely through the birth canal. Conversely, excessive head moulding may have serious eff�ects on the baby's wellbeing. The fi�rst part of this thesis presents a computer-based �finite element model of fetal head moulding as an improvement on previously developed models. The second part of the research focuses on another cause of potentially excessive fetal head moulding, i.e. the incorrect use of obstetric instruments including the obstetric forceps and the ventouse (vacuum extractor). The degree of damage that may be caused by incorrectly placing a forceps (i.e. asymmetric placement of the blades) or a ventouse (i.e. placement on top of soft parts of the skull such as the fontanelles) was assessed by means of fi�nite element analysis after developing a set of software tools to facilitate these experiments. The fi�nal results of this research included: an improved and more realistic model of fetal head moulding under conditions of normal delivery, and results that reveal the great potential of severe damage that obstetric forceps and/or the ventouse may cause to the baby's head when applied incorrectly

Enhanced e-learning and simulation for obstetrics education

Background: In medicine, new media technologies have been used in recent years to simulate situations and techniques that may not be common enough for students to experience in reality or may not be visible to the naked eye. Especially in areas of medicine focusing on important surgeries or procedures, these simulated designs could train students and ultimately prevent possible risk or morbidity. Aims: The aim of this thesis was to develop a multipurpose hybrid educational resource based on a physical/software driven simulator platform enabling the use of multimedia properties like 3D and video to enhance the educational training of obstetrics students through haptic interactions. All of this content was enabled by the learning preferences of the obstetric students involved. Method: The learning resource was developed using a combination of student learning preference, online learning content, 3D, video, human patient simulations and sensor technology interaction. These mediums were all interconnected to create a multipurpose resource. The learning preference was collected through a developed student online survey, the results consequently informed the creation of the other aspects of the finished resource. The interactive aspects were created through position and orientation sensors and the 3D/video influences which localised the position and orientation of an object like a fetal model relative to a human patient simulator. All of these methods combined with added assessment contributions for obstetric tutors, enabled the finalising of a prototype. Conclusion: This form of learning resource has a vital role in the progressing higher level education in the digital age. This proposal is the development of a new type of joint simulator that allows students and practitioners physically involve themselves in a series of processes while assessing their own progression through real time digital feedback in the form of video narrative and analytics. Usability test was not conducted on the full resource (one on the video platform) due to time limitations

Fast computation of soft tissue deformations in real-time simulation with Hyper-Elastic Mass Links

International audienceVirtual surgery simulators show a lot of advantages in the world of surgery training, where they allow to improve the quality of surgeons' gesture. One of the current major technical difficulties for the development of surgery simulation is the possibility to perform a real-time computation of soft tissue deformation by considering the accurate modeling of their mechanical properties. However today, few models are available, they are still time consuming and limited in number of elements by algorithm complexity. We present in this paper a new method and framework that we call 'HEML' (Hyper-Elastic Mass Links), which is particularly fast. It is derived from the finite element method, can handle visco-hyperelastic and large deformation modeling. Although developed initially for medical applications, the HEML method can be used for any numerical computation of hyperelastic material deformations based on a tetrahedral mesh. A comparison with existing methods shows a much faster speed. A comparison with Mass-Spring methods, that are particularly fast but not realistic, shows that they can be considered as a degenerate case of the HEML framework

Canine Abdominal Palpation Training Device

Palpation is used in medical diagnostics to determine the conditions of underlying parts or organs using pressure of the hands and fingers on the body’s surface. There are no existing devices that teach abdominal palpation of small animals. This project aimed to design and create a haptic teaching device for use by veterinary students to learn canine abdominal palpation skills. The device simulates the tactile sense of a canine abdomen including palpable organs and abnormalities to teach students diagnostic skills. The team developed ten palpation devices with a soft tissue component, hard tissue component, three palpable objects, and two abnormalities in each device. Validation from the client, veterinary professionals, and mechanical testing confirmed the device met the objectives

Mathematical models for educational simulation of uterine contractions during labor

Tese de mestrado. Engenharia Biomédica. Faculdade de Engenharia. Universidade do Porto. 201