MedX3D: standards enabled desktop medical 3D.

This paper reports on the work of the Web3D Consortium's Medical Working Group to specify and implement MedX3D -- an extension to the X3D standard that will support advanced medical visualization functionality and medical data exchange. This initiative covers volume rendering, ontology support, and data import/export, for standalone applications and web-based plug-ins. It is our hypothesis that such a 3D medical standard will provide better access to data, and enable improvements in medical care.

Physics-based virtual environment for training core skills in vascular interventional radiological procedures.

Recent years have seen a significant increase in the use of Interventional Radiology (IR) as an alternative to open surgery. A large number of IR procedures commences with needle puncture of a vessel to insert guidewires and catheters: these clinical skills are acquired by all radiologists during training on patients, associated with some discomfort and occasionally, complications. While some visual skills can be acquired using models such as the ones used in surgery, these have limitations for IR which relies heavily on a sense of touch. Both patients and trainees would benefit from a virtual environment (VE) conveying touch sensation to realistically mimic procedures. The authors are developing a high fidelity VE providing a validated alternative to the traditional apprenticeship model used for teaching the core skills. The current version of the CRaIVE simulator combines home made software, haptic devices and commercial equipments.

Web-based surgical simulation for ventricular catheterization.

We have used new developments in computer technology and the Internet to create a small program that simulates catheterization of the lateral ventricle. The program can run on most personal computers connected to the Internet. The program allows trainee surgeons to practice the technique with varying degrees of visual feedback--and no risk to the patient. It allows them to learn both the technique and the associated anatomy. The trainees can be assessed while performing the procedure. This is a small, early-stage application of virtual reality in surgical education. There is a demand for surgical training techniques that expose the patient to no risk; the use of computers is appropriate to meet this demand. The technique presented here requires further development; in particular, it needs a standardized assessment element that will allow it to be tested by established surgeons and trainees. The real test of a good training technique is how well it discriminates between trainee and trainer.

Noninvasive 3-D ultrasound of atherosclerotic plaques in the Watanabe rabbit.

We have investigated the ability to quantitate atherosclerosis in the aortic arch of the Watanabe rabbit using noninvasive 3-D ultrasound. Our methodology utilizes postprocessing of videotaped freehand 2-D interrogations to form a compound 3-D data block. Structures may then be segmented on the attributed grey-scale level and volumes measured. Analysis of 3-D reconstructions revealed a low echo structure in the aortic arch of atherosclerotic rabbits, absent in nonatherosclerotic rabbits, at recognized sites of plaque predilection. This structure volume correlated closely with fatty streak volume determined from histology (r = 0.890). During a 30-week study, this structure volume increased in untreated animals, but was blocked by treatment with the antiatherosclerotic agent probucol. Thus, a new 3-D ultrasound methodology has been used noninvasively to detect and quantitate a low echo structure corresponding to fatty streaks in the Watanabe rabbit aortic arch. This new methodology could potentially aid plaque burden quantification in human peripheral arteries.

Three-dimensional freehand ultrasound: image reconstruction and volume analysis.

A system is described that rapidly produces a regular 3-dimensional (3-D) data block suitable for processing by conventional image analysis and volume measurement software. The system uses electromagnetic spatial location of 2-dimensional (2-D) freehand-scanned ultrasound B-mode images, custom-built signal-conditioning hardware, UNIX-based computer processing and an efficient 3-D reconstruction algorithm. Utilisation of images from multiple angles of insonation, "compounding," reduces speckle contrast, improves structure coherence within the reconstructed grey-scale image and enhances the ability to detect structure boundaries and to segment and quantify features. Volume measurements using a series of water-filled latex and cylindrical foam rubber phantoms with volumes down to 0.7 mL show that a high degree of accuracy, precision and reproducibility can be obtained. Extension of the technique to handle in vivo data sets by allowing physiological criteria to be taken into account in selecting the images used for construction is also illustrated.

Navigating and visualizing three-dimensional data sets.

This paper provides an overview of the main techniques being used for three-dimensional (3D) visualization of medical data sets and highlights some of the clinical benefits that can be obtained. One of the major advantages of using a 3D representation is that all of the slice data produced by the latest multislice CT and high gradient MR scanners can be utilized, and then presented to the clinician in an intuitive format. Continued advances in technology mean that high resolution 3D representations of patient specific anatomy can now be routinely obtained and so provide valuable input to diagnosis, planning and navigation tasks. Examples from these areas are presented and illustrated below. Future developments and possibilities are also discussed.

Modelling concepts of proton eye radiotherapy.

Information concerning the application of proton beams in radiotherapy of ocular tumours is provided using conventional website technology by a number of treatment facilities around the world. We hypothesized, however, that many of the key concepts would be better conveyed by an interactive computer model utilizing virtual reality technology. We describe the implementation, using Virtual Reality Modelling Language (VRML), of such a model, the Proton Therapy Concepts Demonstrator (PTCD). The World-Wide-Web-accessible PTCD is intended to provide information useful both to trainee and to qualified clinical staff and also to patients. A model was created of the radiotherapy room that was linked to an interactive model depicting a simple explanation of the process of proton eye radiotherapy. This model also allows the user to explore specific elements of the treatment planning and delivery process, such as beam collimation and range modulation. A further level of detail has been provided by a dynamic model demonstrating how a specific modulated dose distribution is achieved as the time integration of discrete modulated Bragg peaks. We believe this VR-based model has the potential of enabling users to gain more rapid insight into the proton therapy process. Its development as an educational tool is continuing, following feedback collected from clinical staff and patients.

Surgical simulators using the WWW.

This paper will describe a suite of surgical simulators that we have designed and implemented to run on the WWW. The procedures that have been modelled include simulations of ventricular catheterisation, and lumbar puncture. We will present a detailed overview of implementation and operation of these simulators, and indicate results from early use. The advantages and disadvantages of our approach will be discussed.

Force-feedback in Web-based surgical simulators.

There is a growing requirement in the field of surgical training to allow trainees to practice procedures in a way that does not place patients in any risk. Computer based simulators allow students to gain experience and develop three-dimensional awareness in a safe and controlled environment. Typically systems that have been developed to perform this task are, due to their specialist nature, expensive to buy. With the increasing availability of Force-Feedback devices for the gaming market, is there now a cost-effective alternative for surgical simulations? In this paper we investigate the possibility of using such a device as a haptic input tool for surgical simulations.

Medical volume rendering over the WWW using VRML and JAVA.

The rapid growth of the World Wide Web (WWW) enables access to huge amounts of data and applications. The diversity of data-structures and applications has led to the concept of network computing where the data is encapsulated within the application. The end-user does not have to worry about tools for data manipulation as they are bundled together with the data itself. However, the user usually has to pay a price in the form of degraded performance. While JAVA is gradually taking its place as the network cross platform programming language, it is clear that it currently does not support high-performance visualization. The purpose of this paper is to demonstrate that high performance volume rendering, traditionally reserved for high-end visual computing, can now be made widely available in a cross-platform fashion using VRML and JAVA.

Web-based surgical educational tools.

This paper describes work being undertaken as part of the WebSET (Web-based Standard Educational Tools) project. The project is producing a standardised suite of interactive three-dimensional educational tools, delivered across the WWW. The major focus will be the use of open technology and standards, and the production of learning components that can be used as building blocks for further development in a wide range of application areas. Two learning disciplines have been selected for the development of the WebSET tools: surgical training, and physiological education. A high quality consortium from across Europe has been assembled with complementary skills in the technologies needed by the project. The project is partly funded by the European Commission.

An integrated simulator for surgery of the petrous bone.

This paper describes work being undertaken as part of the IERAPSI (Integrated Environment for the Rehearsal and Panning of Surgical Intervention) project. The project is focussing on surgery for the petrous bone, and brings together a consortium of European clinicians and technology providers working in this field. The paper presents the results of a comprehensive user task analysis that has been carried out in the first phase of the IERAPSI project, and details the current status of development of a pre operative planning environment and a physically-based surgical simulator.

Interventional radiology virtual simulator for liver biopsy.

PURPOSE: Training in Interventional Radiology currently uses the apprenticeship model, where clinical and technical skills of invasive procedures are learnt during practice in patients. This apprenticeship training method is increasingly limited by regulatory restrictions on working hours, concerns over patient risk through trainees' inexperience and the variable exposure to case mix and emergencies during training. To address this, we have developed a computer-based simulation of visceral needle puncture procedures. METHODS: A real-time framework has been built that includes: segmentation, physically based modelling, haptics rendering, pseudo-ultrasound generation and the concept of a physical mannequin. It is the result of a close collaboration between different universities, involving computer scientists, clinicians, clinical engineers and occupational psychologists. RESULTS: The technical implementation of the framework is a robust and real-time simulation environment combining a physical platform and an immersive computerized virtual environment. The face, content and construct validation have been previously assessed, showing the reliability and effectiveness of this framework, as well as its potential for teaching visceral needle puncture. CONCLUSION: A simulator for ultrasound-guided liver biopsy has been developed. It includes functionalities and metrics extracted from cognitive task analysis. This framework can be useful during training, particularly given the known difficulties in gaining significant practice of core skills in patients.

UltraPulse--simulating a human arterial pulse with focussed airborne ultrasound.

Medical simulators provide a risk-free environment for trainee doctors to practice and improve their skills. UltraPulse is a new tactile system designed to utilise focussed airborne ultrasound to mimic a pulsation effect such as that of a human arterial pulse. In this paper, we focus on the construction of the haptics component, which can later be integrated into a variety of medical procedure training simulators.

ImaGiNe Seldinger: first simulator for Seldinger technique and angiography training.

In vascular interventional radiology, procedures generally start with the Seldinger technique to access the vasculature, using a needle through which a guidewire is inserted, followed by navigation of catheters within the vessels. Visual and tactile skills are learnt in a patient apprenticeship which is expensive and risky for patients. We propose a training alternative through a new virtual simulator supporting the Seldinger technique: ImaGiNe (imaging guided interventional needle) Seldinger. It is composed of two workstations: (1) a simulated pulse is palpated, in an immersive environment, to guide needle puncture and (2) two haptic devices provide a novel interface where a needle can direct a guidewire and catheter within the vessel lumen, using virtual fluoroscopy. Different complexities are provided by 28 real patient datasets. The feel of the simulation is enhanced by replicating, with the haptics, real force and flexibility measurements. A preliminary validation study has demonstrated training effectiveness for skills transfer.

A stable and real-time nonlinear elastic approach to simulating guidewire and catheter insertions based on Cosserat rod.

Interventional Radiology procedures (e.g., angioplasty, embolization, stent graft placement) provide minimally invasive therapy to treat a wide range of conditions. These procedures involve the use of flexible tipped guidewires to advance diagnostic or therapeutic catheters into a patient's vascular or visceral anatomy. This paper presents a real-time physically based hybrid modeling approach to simulating guidewire insertions. The long, slender body of the guidewire shaft is simulated using nonlinear elastic Cosserat rods, and the shorter flexible tip composed of a straight, curved, or angled design is modeled using a more efficient generalized bending model. Therefore, the proposed approach efficiently computes intrinsic dynamic behaviors of guidewire interactions within vascular structures. The efficacy of the proposed method is demonstrated using detailed numerical simulations inside 3-D blood vessel structures derived from preprocedural volumetric data. A validation study compares positions of four physical guidewires deployed within a vascular phantom, with the co-ordinates of the corresponding simulated guidewires within a virtual model of the phantom. An optimization algorithm is also implemented to further improve the accuracy of the simulation. The presented simulation model is suitable for interactive virtual reality-based training and for treatment planning.

The Role of Haptics in Medical Training Simulators: A Survey of the State of the Art.

This review paper discusses the role of haptics within virtual medical training applications, particularly, where it can be used to aid a practitioner to learn and practice a task. The review summarizes aspects to be considered in the deployment of haptics technologies in medical training. First, both force/torque and tactile feedback hardware solutions that are currently produced commercially and in academia are reviewed, followed by the available haptics-related software and then an in-depth analysis of medical training simulations that include haptic feedback. The review is summarized with scrutiny of emerging technologies and discusses future directions in the field.

Integrating Haptics with Augmented Reality in a Femoral Palpation and Needle Insertion Training Simulation.

This paper presents a virtual environment for training femoral palpation and needle insertion, the opening steps of many interventional radiology procedures. A novel augmented reality simulation called PalpSim has been developed that allows the trainees to feel a virtual patient using their own hands. The palpation step requires both force and tactile feedback. For the palpation haptics effect, two off-the-shelf force feedback devices have been linked together to provide a hybrid device that gives five degrees of force feedback. This is combined with a custom built hydraulic interface to provide a pulse like tactile effect. The needle interface is based on a modified PHANTOM Omni end effector that allows a real interventional radiology needle to be mounted and used during simulation. While using the virtual environment, the haptics hardware is masked from view using chroma-key techniques. The trainee sees a computer generated patient and needle, and interacts using their own hands. This simulation provides a high level of face validity and is one of the first medical simulation devices to integrate haptics with augmented reality.

A prototype percutaneous transhepatic cholangiography training simulator with real-time breathing motion.

PURPOSE: We present here a simulator for interventional radiology focusing on percutaneous transhepatic cholangiography (PTC). This procedure consists of inserting a needle into the biliary tree using fluoroscopy for guidance. METHODS: The requirements of the simulator have been driven by a task analysis. The three main components have been identified: the respiration, the real-time X-ray display (fluoroscopy) and the haptic rendering (sense of touch). The framework for modelling the respiratory motion is based on kinematics laws and on the Chainmail algorithm. The fluoroscopic simulation is performed on the graphic card and makes use of the Beer-Lambert law to compute the X-ray attenuation. Finally, the haptic rendering is integrated to the virtual environment and takes into account the soft-tissue reaction force feedback and maintenance of the initial direction of the needle during the insertion. RESULTS: Five training scenarios have been created using patient-specific data. Each of these provides the user with variable breathing behaviour, fluoroscopic display tuneable to any device parameters and needle force feedback. CONCLUSIONS: A detailed task analysis has been used to design and build the PTC simulator described in this paper. The simulator includes real-time respiratory motion with two independent parameters (rib kinematics and diaphragm action), on-line fluoroscopy implemented on the Graphics Processing Unit and haptic feedback to feel the soft-tissue behaviour of the organs during the needle insertion.