Sheng Quan Xie

Design of a Parallel Long Bone Fracture Reduction Robot with Planning Treatment Tool

The principals and procedure of long bone surgery are presented and the need for robotic assistance is established. Existing problems include radiation exposure from fluoroscopy, mental strain from reconstructing 3-dimensional images and physical fatigue from overcoming fracture deforming forces. These problems are addressed by a proposed fracture reduction robot which aids in treatment planning and reduction of the fracture. A flexible parallel robot (FleP) with an active force/position controller is designed to perform the operation. A computer-aided planning treatment tool (CAPTT) provides image analysis, path planning and simulation. An advanced human machine interface (AHMI) attempts to provide a companion feeling between robot and surgeon by using human forms of communication. The result is a reduction in radiation exposure, removal of the need to reconstruct images mentally and there is no longer any physical strain

Diagnostic radiograph based 3D bone reconstruction framework: Application to the femur

Three dimensional (3D) visualization of anatomy plays an important role in image guided orthopedic surgery and ultimately motivates minimally invasive procedures. However, direct 3D imaging modalities such as Computed Tomography (CT) are restricted to a minority of complex orthopedic procedures. Thus the diagnostics and planning of many interventions still rely on two dimensional (2D) radiographic images, where the surgeon has to mentally visualize the anatomy of interest. The purpose of this paper is to apply and validate a bi-planar 3D reconstruction methodology driven by prominent bony anatomy edges and contours identified on orthogonal radiographs. The results obtained through the proposed methodology are benchmarked against 3D CT scan data to assess the accuracy of reconstruction. The human femur has been used as the anatomy of interest throughout the paper. The novelty of this methodology is that it not only involves the outer contours of the bony anatomy in the reconstruction but also several key interior edges identifiable on radiographic images. Hence, this framework is not simply limited to long bones, but is generally applicable to a multitude of other bony anatomies as illustrated in the results section.

Closed loop control of dielectric elastomer actuators

Sensing the electrical characteristics of a Dielectric Elastomer Actuator(s) (DEA) during actuation is critical to improving their accuracy and reliability. We have created a self-sensing system for measuring the equivalent series resistance of the electrodes, leakage current through the equivalent parallel resistance of the dielectric membrane, and the capacitance of the DEA whilst it is being actuated. This system uses Pulse Width Modulation (PWM) to simultaneously generate an actuation voltage and a periodic oscillation that enables the electrical characteristics of the DEA to be sensed. This system has been specifically targeted towards low-power, portable devices. In this paper we experimentally validate the self-sensing approach, and present a simple demonstration of closed loop control of the area of an expanding dot DEA using capacitance feedback.

Dielectric elastomer memory

Life shows us that the distribution of intelligence throughout flexible muscular networks is a highly successful solution to a wide range of challenges, for example: human hearts, octopi, or even starfish. Recreating this success in engineered systems requires soft actuator technologies with embedded sensing and intelligence. Dielectric Elastomer Actuator(s) (DEA) are promising due to their large stresses and strains, as well as quiet flexible multimodal operation. Recently dielectric elastomer devices were presented with built in sensor, driver, and logic capability enabled by a new concept called the Dielectric Elastomer Switch(es) (DES). DES use electrode piezoresistivity to control the charge on DEA and enable the distribution of intelligence throughout a DEA device. In this paper we advance the capabilities of DES further to form volatile memory elements. A set reset flip-flop with inverted reset line was developed based on DES and DEA. With a 3200V supply the flip-flop behaved appropriately and demonstrated the creation of dielectric elastomer memory capable of changing state in response to 1 second long set and reset pulses. This memory opens up applications such as oscillator, de-bounce, timing, and sequential logic circuits; all of which could be distributed throughout biomimetic actuator arrays. Future work will include miniaturisation to improve response speed, implementation into more complex circuits, and investigation of longer lasting and more sensitive switching materials.

Biomimetic control for DEA arrays

Arrays of actuators are ubiquitous in nature for manipulation, pumping and propulsion. Often these arrays are coordinated in a multi-level fashion with distributed sensing and feedback manipulated by higher level controllers. In this paper we present a biologically inspired multi-level control strategy and apply it to control an array of Dielectric Elastomer Actuators (DEA). A test array was designed consisting of three DEA arranged to tilt a set of rails on which a ball rolls. At the local level the DEA were controlled using capacitive self-sensing state machines that switched the actuator off and on when capacitive thresholds were exceeded, resulting in the steady rolling of the ball around the rails. By varying the voltage of the actuators in the on state, it was possible to control the speed of the ball to match a set point. A simple integral derivative controller was used to do this and an observer law was formulated to track the speed of the ball. The array demonstrated the ability to self start, roll the ball in either direction, and run at a range of speeds determined by the maximum applied voltage. The integral derivative controller successfully tracked a square wave set point. Whilst the test application could have been controlled with a classic centralised controller, the real benefit of the multi-level strategy becomes apparent when applied to larger arrays and biomimetic applications that are ideal for DEA. Three such applications are discussed; a robotic heart, a peristaltic pump and a ctenophore inspired propulsion array.

3D Reconstruction of Patient Specific Bone Models from 2D Radiographs for Image Guided Orthopedic Surgery

Three dimensional (3D) visualization of anatomy plays an important role in image guided orthopedic surgery and ultimately motivates minimally invasive procedures. However, direct 3D imaging modalities such as Computed Tomography (CT) are restricted to a minority of complex orthopedic procedures. Thus the diagnostics and planning of many interventions still rely on two dimensional (2D) radiographic images, where the surgeon has to mentally visualize the anatomy of interest. The purpose of this paper is to apply and validate a bi-planar 3D reconstruction methodology driven by prominent bony anatomy edges and contours identified on orthogonal radiographs. The results obtained through the proposed methodology are benchmarked against 3D CT scan data to assess the accuracy of reconstruction. The human femur has been used as the anatomy of interest throughout the paper. The novelty of this methodology is that it not only involves the outer contours of the bony anatomy in the reconstruction but also several key interior edges identifiable on radiographic images. Hence, this framework is not simply limited to long bones, but is generally applicable to a multitude of other bony anatomies as illustrated in the results section.

Computer assisted 3D pre-operative planning tool for femur fracture orthopedic surgery

Femur shaft fractures are caused by high impact injuries and can affect gait functionality if not treated correctly. Until recently, the pre-operative planning for femur fractures has relied on two-dimensional (2D) radiographs, light boxes, tracing paper, and transparent bone templates. The recent availability of digital radiographic equipment has to some extent improved the workflow for preoperative planning. Nevertheless, imaging is still in 2D X-rays and planning/simulation tools to support fragment manipulation and implant selection are still not available. Direct three-dimensional (3D) imaging modalities such as Computed Tomography (CT) are also still restricted to a minority of complex orthopedic procedures. This paper proposes a software tool which allows orthopedic surgeons to visualize, diagnose, plan and simulate femur shaft fracture reduction procedures in 3D. The tool utilizes frontal and lateral 2D radiographs to model the fracture surface, separate a generic bone into the two fractured fragments, identify the pose of each fragment, and automatically customize the shape of the bone. The use of 3D imaging allows full spatial inspection of the fracture providing different views through the manipulation of the interactively reconstructed 3D model, and ultimately better pre-operative planning.

Diagnostic radiograph based 3D bone reconstruction framework: application to osteotomy surgical planning

Pre-operative planning in orthopedic surgery is essential to identify the optimal surgical considerations for each patient-specific case. The planning for osteotomy is presently conducted through two-dimensional (2D) radiographs, where the surgeon has to mentally visualize the bone deformity. This is due to direct three-dimensional (3D) imaging modalities such as Computed Tomography (CT) still being restricted to a minority of complex orthopedic procedures. This paper presents a novel 3D bone reconstruct technique, through bi-planar 2D radiographic images. The reconstruction will be pertinent to osteotomy surgical diagnostics and planning. The framework utilizes a generic 3D model of the bone of interest to obtain the anatomical topology information. A 2D non-rigid registration is performed between the projected contours of this generic 3D model and extracted edges of the X-ray image to identify the planar customization required. Subsequently a free-form deformation based manipulation is conducted to customize the overall 3D bone shape.

Patient-Specific Customization of a Generic Femur Model Using Orthogonal 2D Radiographs

Visualization of the patient-specific fractured bone in three dimensions (3D) plays an important role in image guided orthopedic surgery. Existing research often focuses on intra-operative registration of the patientspsila anatomy with pre-operatively obtained 3D volumetric data (e.g. CT scans) utilizing fiduciary markers. This expensive and invasive approach is not routinely available for diagnostics, and a majority of fracture reduction procedures currently solely relies on two dimensional (2D) x-ray/fluoroscopic images. This paper presents a new concept for the construction of a 3D model of a fractured human femur that eliminates the need to have the preoperative CT scan of the patientpsilas injured anatomy. It is based on two conventional orthogonal (in anterior and lateral views) 2D radiographic images and a supporting database of 3D intact (healthy) femurs. A search over the database initially finds the closest match to the patientpsilas femur. This best match is then customized through a non-rigid registration to the shape of the patientpsilas femur. Once the customization is complete a novel 2D-3D registration process separates the bone into the proximal and distal segments and identifies the pose (position and orientation) of each fragment.