• This is the author's version of a work that was accepted for publication in Journal of Oral and Maxillofacial Surgery. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication.A definitive version was subsequently pub- Keywords Medical rapid prototyping, Computed Tomography, Stereolithography, Fused Deposition Modelling, Artefacts Abstract PurposeWe 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 MethodsMedical 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. ResultsA 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. ConclusionsIt 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.

This report describes a new method of custom making cranial titanium plates for the repair of skull defects. We have combined 3D CT imaging and surface modelling with rapid prototyping (RP) technology to produce physical models of our patients' skulls from which custom titanium plates were made. We have expanded the use of image processing tools applied to the CT image data to fabricate a representation of the skull defect. Medical RP models are relatively expensive and particular attention has been paid to developing image processing methods to reduce costs. Our technique used the patient as their own model and generated data from the contralateral side of the head where appropriate. We present the results of 10 patients who have had a custom made cranial titanium plate fitted and discuss the models for these cases. The benefits of our custom made titanium plates are reduced patient attendances to hospital and a more accurate titanium plate which has improved fitting and cosmesis.

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.

Citation: BIBB, R. and WINDER, J., 2010. A review of the issues surrounding three-dimensional computed tomography for medical modelling using rapid prototyping techniques. Radiography, 16 (1), pp. 78 -83.Additional Information:• AbstractThis 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.

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