A review of the issues surrounding three-dimensional computed tomography for medical modelling using rapid prototyping techniques

This technical note aims to raise awareness amongst radiographers of the application of Computed Tomography data in the production of models using Rapid Prototyping technologies. It also aims to provide radiographers with recommendations that will assist them in providing three-dimensional Computed Tomography data that can fulfil the requirements of medical modelling. Potential problem areas in data acquisition and transfer are discussed and suggestions are given for methods that aim to avoid these

Medical rapid prototyping technologies: state of the art and current limitations for application in oral and maxillofacial surgery

Purpose We describe state of the art software and hardware requirements for the manufacture of high quality medical models manufactured using medical rapid prototyping. The source of the medical model artefacts and there physical appearance are illustrated along with remedies for their removal. Materials and Methods Medical models were built using predominantly stereolithography and fused deposition modelling at both institutions over a period of 6 years. A combined total of 350 models have been produced for a range of maxillofacial, neurosurgical and orthopaedic applications. Stereolithography, fused deposition modelling computerised numerical milling and other technologies are described. Results A range of unwanted artefacts that create distortions on medical models have been identified. These include, data import, CT gantry distortion, metal, motion, surface roughness due to support structure removal or surface modelling and image data thresholding. The source of the artefact has been related to the patient, imaging modality performance or the modelling technology. Discussion as to the significance of the artefacts on clinical use is provided. Conclusions It is recommended that models of human anatomy generated by medical rapid prototyping are subject to rigorous quality assurance at all stages of the manufacturing process. Clinicians should be aware of potential areas for inaccuracies within models and review the source images in cases where model integrity is in doubt

Design of human surrogates for the study of biomechanical injury: a review

Human surrogates are representations of living human structures employed to replicate “real-life” injurious scenarios in artificial environments. They are used primarily to evaluate personal protective equipment (PPE) or integrated safety systems (e.g., seat belts) in a wide range of industry sectors (e.g., automotive, military, security service, and sports equipment). Surrogates are commonly considered in five major categories relative to their form and functionality: human volunteers, postmortem human surrogates, animal surrogates, anthropomorphic test devices, and computational models. Each surrogate has its relative merits. Surrogates have been extensively employed in scenarios concerning “life-threatening” impacts (e.g., penetrating bullets or automotive accidents). However, more frequently occurring nonlethal injuries (e.g., fractures, tears, lacerations, contusions) often result in full or partial debilitation in contexts where optimal human performance is crucial (e.g., military, sports). Detailed study of these injuries requires human surrogates with superior biofidelity to those currently available if PPE designs are to improve. The opportunities afforded by new technologies, materials, instrumentation, and processing capabilities should be exploited to develop a new generation of more sophisticated human surrogates. This paper presents a review of the current state of the art in human surrogate construction, highlighting weaknesses and opportunities, to promote research into improved surrogates for PPE development

The computer-aided design and rapid prototyping fabrication of removable partial denture frameworks

This study explores the application of computer-aided design and manufacture (CAD/CAM) to the process of electronically surveying a scanned dental cast as a prior stage to producing a sacrificial pattern for a removable partial denture (RPD) metal alloy framework. These are designed to retain artificial replacement teeth in the oral cavity. A cast produced from an impression of a patient's mouth was digitally scanned and the data converted to a three-dimensional computer file that could be read by the computer-aided design (CAD) software. Analysis and preparation were carried out in the digital environment according to established dental principles. The CAD software was then used to design the framework and generate a standard triangulation language (STL) file in preparation for its manufacture using rapid prototyping (RP) methods. Several RP methods were subsequently used to produce sacrificial patterns, which were then cast in a chromium-cobalt alloy using conventional methods and assessed for accuracy of fit. This work demonstrates that CAD/CAM techniques can be used for electronic dental cast analysis, preparation, and design of RPD frameworks. It also demonstrates that RP-produced patterns may be successfully cast using conventional methods and that the resulting frameworks can provide a satisfactory fit

A review of wrist splint designs for additive manufacture

Currently, patients with wrist ailments may be prescribed wrist splints to aid in their treatment regime. The traditional fabrication process of custom-made splints is skill dependent, time-consuming and the splints themselves pose numerous problems with regards to patient compliance. To overcome this, the use of Additive Manufacture has been proposed in recent years and there has been an increase in public awareness and exploration. Many of these developments have been as a result of the Maker-movement, the Internet-of-Things and development of more accessible technologies and infrastructures to enable production of AM builds; hobbyists, industry and academia are exploring the use of AM for splints, all with strengths and weaknesses. This paper highlights and describes specific examples of AM wrist splints currently available in the public domain and summarises strengths, weaknesses, opportunities and threats for the future implementation into the healthcare sector

When design never ends - a future scenario for product development

One of the foundations of product design is the division between production and design. This division manifests as designers aspiring to create fixed iconic archetypes and production replicates endlessly in thousands or millions. Today innovation and technological change are challenging this idea of product design and manufacturing. The evolution of Rapid Prototyping into Additive Manufacturing (AM), is challenging the notion of mass manufacture and consumer value. As AM advances in capability and capacity, the ability to economically manufacture products in low numbers with high degrees of personalisation poses questions of the accepted product development process. Removing the need for dedicated expensive tooling also eliminates the cyclical timescales and commitment to fixed designs that investment in tooling demands. The ability to alter designs arbitrarily, frequently and responsively means that the traditional design process need not be applied and because of this, design processes and practice might be radically different in the future. In this paper, we explore this possible evolution by drawing parallels with principles and development models found in software development

Digitising the splinting process using computer aided design and additive manufacturing

The splinting process is considered a very challenging and demanding activity, requiring a considerable amount of skill, clinical expertise and creative prowess in order to design and fabricate splints which suit the patient, their condition and their lifestyle...

Maxillofacial prostheses challenges in resource constrained regions

Background: This study reviewed the current state of maxillofacial rehabilitation in resource-limited nations. Method: A rigorous literature review was undertaken using several technical and clinical databases using a variety of key words pertinent to maxillofacial prosthetic rehabilitation and resource-limited areas. In addition, interviews were conducted with researchers, clinicians and prosthetists that had direct experience of volunteering or working in resource-limited countries. Results: Results from the review and interviews suggest rehabilitating patients in resource-limited countries remains challenging and efforts to improve the situation requires a multifactorial approach. Conclusion: In conclusion, public health awareness programmes to reduce the causation of injuries and bespoke maxillofacial prosthetics training programmes to suit these countries, as opposed to attempting to replicate Western training programmes. It is also possible that usage of locally sourced and cheaper materials and the use of low-cost technologies could greatly improve maxillofacial rehabilitation efforts in these localities

A review of existing anatomical data capture methods to support the mass customisation of wrist splints

Anatomical data acquisition methods used within medicine exhibit various strengths and weaknesses, particularly with regards to accuracy, resolution, patient comfort and safety. Difficulties with data acquisition of wrist and hand geometry are often underestimated, and a suitable method is yet to be identified and standardised to capture skin surface topography to support the mass customisation of wrist splints. The aim of this investigation is to identify a suitable data acquisition method, capable of digitising collected data of the wrist and hand, for manipulation and conversion into a suitable file format to create customised wrist splints using additive manufacture. Literature suggests that scanning inanimate objects such as plaster casts using multiple three-dimensional laser scanners can provide adequate quality scans with suitable accuracy and resolution, with low cost and low risk to the patient. However, post processing would be required to create a “watertight” digital model suitable for additive manufacture

Computed tomography characterisation of additive manufacturing materials

Additive manufacturing, covering processes frequently referred to as rapid prototyping and rapid manufacturing, provides new opportunities in the manufacture of highly complex and custom-fitting medical devices and products. Whilst many medical applications of AM have been explored and physical properties of the resulting parts have been studied, the characterisation of AM materials in computed tomography has not been explored. The aim of this study was to determine the CT number of commonly used AM materials. There are many potential applications of the information resulting from this study in the design and manufacture of wearable medical devices, implants, prostheses and medical imaging test phantoms. A selection of 19 AM material samples were CT scanned and the resultant images analysed to ascertain the materials’ CT number and appearance in the images. It was found that some AM materials have CT numbers very similar to human tissues, FDM, SLA and SLS produce samples that appear uniform on CT images and that 3D printed materials show a variation in internal structure