Design of a New Instrumented Forceps: Application to Safe Obstetrical Forceps Blade Placement

High-Frequency Ultrasonic Forceps for the In Vivo Detection of Cancer During Breast-Conserving Surgery

A major aim in the surgical management of soft tissue cancers is to detect and remove all cancerous tissues while ensuring noncancerous tissue remains intact. Breast-conserving surgery provides a prime illustration of this aim, since remaining cancer in breast margins results in multiple surgeries, while removal of too much unaffected tissue often has undesirable cosmetic effects. Similarly, resection of benign lymph nodes during sentinel lymph node biopsy can cause deleterious health outcomes. The objective of this study was to create an intraoperative, in vivo device to address these challenges. Instant diagnostic information generated by this device could allow surgeons to precisely and completely remove all malignant tissue during the first surgery. Surgical forceps based on Martin forceps were instrumented at the tips with high-frequency ultrasonic transducers composed of polyvinylidene difluoride, a thickness-sensing rotary potentiometer at the base, and a spring to provide the appropriate restoring force. Transducer wires within the forceps were connected to an external high-frequency pulser-receiver, activating the forceps' transmitting transducer at 50 MHz and amplifying through-transmission signals from the receiving transducer. The forceps were tested with tissue-mimicking agarose phantoms embedded with 58–550 μm polyethylene microspheres to simulate various stages of cancer progression and to provide a range of measurement values. Results were compared with measurements from standard 50 MHz immersion transducers. The results showed that the forceps displayed similar sensitivity for attenuation and increased accuracy for wave speed. The forceps could also be extended to endoscopes and laparoscopes.

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

Simulators have been traditionally used for centuries during medical gestures training. Nowadays, mechatronic technologies have opened the way to more evolved solutions enabling objective assessment and dedicated pedagogic scenarios. Trainees can now practice in virtual environments representing various kind of patient and body parts including physio-pathologies issues. Gestures, to be mastered, vary according to each medical specialty (e.g., ultrasound probe orientations, or forceps installation during assisted delivery). Hence, medical students need kinesthetic feedback in order to significantly improve their learning capabilities. Gesture simulators require haptic devices with variable stiffness actuators. Existing solutions do not always fit the requirements because of their significant size. Contrary to electric actuators, pneumatic technology is low-cost, available off-the-shelf and offers a better mass–power ratio. However, it presents two main drawbacks: nonlinear dynamics and need for a compressed air supply. During the last decade, we have developed several haptic solutions based on pneumatic actuation (e.g., birth simulator, epidural needle insertion simulator) and, recently, in a joint venture with Prisme laboratory, a pneumatic probe master device for remote ultrasonography. This paper recalls literature scientific approaches on pneumatic actuation developed in the medical context and illustrated with the aforementioned applications to highlight the benefits.

A computer-based simulation of childbirth using the partial Dirichlet-Neumann contact method with total Lagrangian explicit dynamics on the GPU

During physiological or 'natural' childbirth, the fetal head follows a distinct motion pattern-often referred to as the cardinal movements or 'mechanisms' of childbirth-due to the biomechanical interaction between the fetus and maternal pelvic anatomy. The research presented in this paper introduces a virtual reality-based simulation of physiological childbirth. The underpinning science is based on two numerical algorithms including the total Lagrangian explicit dynamics method to calculate soft tissue deformation and the partial Dirichlet-Neumann contact method to calculate the mechanical contact interaction between the fetal head and maternal pelvic anatomy. The paper describes the underlying mathematics and algorithms of the solution and their combination into a computer-based implementation. The experimental section covers first a number of validation experiments on simple contact mechanical problems which is followed by the main experiment of running a virtual reality childbirth. Realistic mesh models of the fetus, bony pelvis and pelvic floor muscles were subjected to the intra-uterine expulsion forces which aim to propel the virtual fetus through the virtual birth canal. Following a series of simulations, taking variations in the shape and size of the geometric models into account, we consistently observed the cardinal movements in the simulator just as they happen in physiological childbirth. The results confirm the potential of the simulator as a predictive tool for problematic childbirths subject to patient-specific adaptations.

A new design for the BirthSIM simulator to improve realism

This paper presents a new design of the BirthSIM simulator. Its goal is to help obstetricians and midwives to train and improve their skills during childbirth delivery. The new version of the BirthSIM is more actuated than the previous version in order to be more biofidelic and cover various scenarios. The direct and inverse geometric models of the haptic interface are presented. The working space reached by the fetal head is computed and validates the proposed design which allows to reproduce all fetal head trajectories inside the pelvis. The novelty is illustrated by an example which presents a simulated trajectory stemmed from a sacrum shape measure. The inverse geometric model allows to compute the actuators displacements and thus to validate the chosen components.

Simulation of an instrumental childbirth for the training of the forceps extraction: control algorithm and evaluation

This paper presents the control algorithm implanted on the childbirth simulator BirthSIM in order to provide training to novice obstetricians. The forceps extraction is an obstetric manipulation learned by experience. However, nowadays the training is mainly provided during real childbirths. This kind of training could lead to dramatic consequences due to the lack of experience of some operators. This paper explains the approach that has been used to simulate the dynamic process of a childbirth on the BirthSIM simulator. We especially focus on one procedure that reproduces a difficult instrumental delivery. The recorded tractive force to extract the fetus corresponds to the literature results that confirm the realism of the simulator. The novice results emphasize the need of a childbirth simulator in order to gain initial experience without any risks.

Three-dimensional gesture comparison using curvature analysis of position and orientation

This paper describes a new analysis method dedicated to the comparison of human gestures. The orientations and the positions of the gestures are first digitized using active 3D sensors and then compared to a 6-D template using curvature analysis. The proposed algorithm first starts by computing the invariant curvature of 3D position and orientation of a surgical tool using Frenet-Serret frames in 3D and quaternion space. The resulting curvature calculation is matched and compared to the template using a Dynamic Time Warping method. The proposed method is invariant to sensor position and orientation. An experimental study shows the efficiency of the new algorithm for an application in obstetrics, where the aim is to compare forceps blade placements between a senior medical doctor and a novice.

Evaluation of medical gestures based on a global performance index

This paper presents a method to evaluate medical gestures. The objective is to objectively assess a gesture carried out by novice doctors. The proposed method is based on the study of the curvature of the 3D gesture and provide a global performance index for one manipulation. The study of the number of peaks on the curvature indicates if the gesture is smooth or not. The application is the obstetric gestures linked to the forceps use but the method can be applied to different gestures without loss of generality. Seven residents carried out 30 forceps blade placements. The results clearly show a difference between the gestures carried out. This highlights the difficulty of the gesture according to the fetal head presentation.

A dry lab for medical engineers?

Introduction

We describe a teaching and training method with objective evaluation to improve medical engineering students' knowledge and analysis skills about Minimally Invasive Surgery (MIS) instrumentation and techniques through hands-on experience. Training has been scheduled during a three-month course.

Methods

Twenty medical engineering students were trained to perform three times on a pelvic trainer a sequence of standardized drills connected with the selected MIS techniques, in order to improve their dexterity. The time required to perform each dexterity drill was recorded in seconds.

Then, the participants were divided into groups and asked to write an essay about an instrument they chose, analyzing and criticizing the instrument itself.

Results

All the trainees showed steady improvement in skill acquisition on the laparoscopic simulator and discussed their essays, making proposals in order to improve the instrument they tested.

Conclusion

Significant improvement in performance with increasing skillness has been measured; during the course and during their discussion the participants showed deep knowledge of the instrument, ability to analyze and criticize it and ability to make improvement proposals.

Dry lab experience for medical engineering students is useful for teaching and improving analysis and management of laparoscopic devices, allowing identification of problems and developing better devices.

Evaluation of obstetric gestures: an approach based on the curvature of quaternions

This paper presents a method to evaluate a gesture carried out by a resident obstetrician by comparing it to a gesture carried out by an expert obstetrician. The studied gesture is the forceps blade placement. Resident paths were recorded on a childbirth simulator while placing forceps blades instrumented with six degrees of freedom sensors. The path is characterized by the positions and the orientations. In this paper we particularly focus on the orientations. Forceps orientations are expressed in the quaternion unit space and the curvature of quaternion path is compared by correlation to a reference defined by an expert. Residents have been trained on a simulator and their gestures are evaluated by comparing their orientation path curvatures to reference path curvatures. Quantitative results confirm the qualitative analysis, residents become more similar to the reference while training on simulator.

A biomechanical model of the female reproductive system and the fetus for the realization of a childbirth virtual simulator

Our main work consists in modeling of the female pelvis and uterus, as well as the human fetus. The goal of this work is to recover the different forces generated during the delivery. These forces will be input to the haptic obstetric training tool BirthSim which has already been developed by the Ampère Laboratory at the INSA of Lyon. This modeling process will permit us to develop a new training device to take into account different anatomies and different types of delivery. In this paper, we will firstly show the different existing haptic and virtual simulators in the obstetric world with their advantages and drawbacks. After, we will present our approach based on a biomechanical modeling of concerned organs. To obtain interactive time performance, we proceed by the simplification of the organs anatomy. Then, we present some results showing that FEM analysis can be used to model forces during childbirth. In the future, we plan to use this work to more accurately control a childbirth simulator.

A medical simulator for subcutaneous contraceptive implant insertion

New contraceptive methods like the subcutaneous implant offers a new kind of comfort for women with an efficiency similar to the contraceptive pill. Unfortunately the few numbers of unintended pregnancies that have been reported are generally due to a bad insertion of the implant. In order to give more security to patients, we have designed, in close collaboration with physicians, a new kind of medical simulator. This paper focuses on a device dedicated to a specific subcutaneous implant but it is worth noting that this simulator is relatively generic since it will be used for other subcutaneous techniques or other implant instruments. This simulator can be used for two purposes: one for training novice physicians in the correct manipulation and the other for physician certification which will help determine if they are capable of inserting the implant in vivo. This paper describes the approach which has led to the design of this simulator. It describes its functionalities, its several components but also methods used to analyze the manipulation of the implant insertion inside the patient. Finally first experimental results are reported and discussed. The system used in this paper makes possible to carry out training in a constraint-free context and provides the first mean of visualizing a maneuver that, until now, has been performed blindly.

Evaluation of obstetric gestures: an approach based on the curvature of 3-D positions

This paper presents a method to evaluate a gesture carried out by a resident obstetrician doctors by comparing it to a gesture carried out by an expert obstetrician doctors. The studied gesture is the forceps blade placement. Residents were recorded on a childbirth simulator while placing forceps blades. Their paths were compared in order to evaluate how similar they are to a reference path defined by an expert. The comparison method is developed with respect to expert requests: time independence and in considering the whole set of data and not only particular points. In order to respect these requests, the developed method lies on the correlation coefficient between the path curvatures. Residents have been trained on a simulator and their gestures were evaluated by comparing their path curvatures to reference path curvatures. Quantitative results confirm the qualitative analysis, residents become more similar to the reference while training on simulator.