Surgery is a practical art! The surgeon is often required physically to intervene to effect a treatment. To minimize operative morbidity and mortality, and to maximize therapeutic success, surgical strategies are tailored to each patient and must be carefully planned using the best possible anatomical information. The traditional way for a surgeon to gain basic experience, without risk to the patient, is to dissect cadavers and to examine carefully preserved pathological specimens. This serves to provide an anatomical and pathological understanding from which operative interventions may be safely made. As every patient is unique, there is a need for the surgeon to attain a specific understanding of the individual's anatomy preoperatively. Thorough physical examination may be all that is needed for common conditions with which the surgeon is experienced. Detailed information displaying the morphology of internal structures is often required by the surgeon to understand more complicated pathological conditions. To obtain this internal anatomical information non-invasively, the surgeon relies on medical imaging.
The discovery of the diagnostic value of X-rays by Wilhelm Conrad Roentgen in 1895 first introduced a way of studying internal anatomy without direct physical intervention. Plain X-rays were quickly accepted for the display of skeletal pathology. The introduction of radio opaque contrast agents enhanced the power of plain X-rays to display the anatomical morphology of soft tissues in many conditions. Major advance came with the introduction of computed tomography (CT) by Sir Godfrey Newbold Hounsfield in 1973 (Hounsfield, 1973). This technology allowed visualization as never before. Neurosurgeons could study direct cross-sectional images of intracranial soft tissue tumour masses. This illustration of neuroanatomy was a great advance compared with angiography, myelography and pneumo-encephalography. As CT became widely used in neurosurgery, applications soon followed in many other specialities. Ultrasound and more recently magnetic resonance (MR) imaging have followed the use of X-ray, and each has come to have specific indications for imaging internal anatomy.
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These advances in medical imaging have created ever increasing volumes of complex data. The interpretation of such information has become a speciality in itself and the surgeon at times may be left bewildered as to how best to apply the available information to the practicalities of physical intervention. The surgeon seeks to understand the exact morphology of the abnormality, its relationships to surrounding anatomy and the best way to access and correct the pathology operatively. Such specific information is not readily available in the radiologist's report and, however experienced the surgeon may be at interpreting radiological films, it can be difficult to interpret the data so that such questions can be easily answered.
Three-dimensional (3D) imaging has been developed to narrow the communication gap between radiologist and surgeon. By using 3D imaging, a vast number of complex slice images can be combined into a single 3D image which can be quickly appreciated. The term 'three-dimensional', however, is not a truly accurate description of these images as they are still usually displayed on a radiological film or flat screen in only two dimensions.
The advent of 3D imaging has not only dramatically improved data display but also promoted the development of even more useful technologies to assist the surgeon in diagnosis and planning. Ideally in surgery an exact copy of the patient would allow complete preoperative simulation. The yearning of the surgeon for this most realistic portrayal of data initiated the evolution of 3D imaging and has now fuelled the development of solid biomodelling.
'Biomodelling' is the generic term that describes the ability to replicate the morphology of a biological structure in a solid substance. Specifically, biomodelling has been defined by the author as 'the process of using radiant energy to capture morphological data on a biological structure and the processing of such data by a computer to generate the code required to manufacture the structure by rapid prototyping apparatus' (D'Urso and Thompson, 1998). A 'biomodel' is the product of this process. 'Real virtuality' is the term coined to describe the creation of solidreality from the virtual imagery (D'Urso and Thompson, 1998). Virtual reality, in contrast, creates a computer-synthesized experience for the observer without a real basis. In medicine, biomodelling has been used to create anatomical real virtuality. Biomodels are a truly remarkable and exciting tool in the practice of surgery, and the applications of such a generic technology will be discussed in this chapter.
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