Physicians engaged in complex medical interventions such as cranial reconstruction, orthognathic surgery and radiotherapy, among others, increasingly rely on technologies that facilitate preprocedural planning and simulation. Parallel progress in imaging and computer techniques for virtual data manipulation provides the framework for detailed planning of complex medical treatments. Despite the increasing levels of detail possible with more and more powerful computer hardware and software, virtual representation of medical image data remains, for the most part, limited to on-screen displays that provide no means for true 3D understanding or tactile interaction. In addition, the transfer of treatment parameters from the planning environment to the actual patient for intervention is challenging. Virtual planning environments often allow data visualization and manipulation on a scale that is much finer that can be appreciated practically. In addition, most virtual planning systems are unencumbered by such real-world challenges as patient motion, bleeding, limited visibility through small incisions and sterility issues. Therefore, while it may be possible, for instance, to plan the perfect trajectory for a spinal pedicle screw in a virtual environment, actually implementing this treatment plan in a stable, repeatable and reliable fashion is more difficult. There is certainly a value in the exercise of virtual planning, in that the surgeon will have the opportunity to gain understanding of unique patient anatomy. This can be a valuable preparation tool for physicians, providing a detailed preview that complements their trained expertise. As the trend towards less invasive and time-consuming procedures continues, physicians will likely rely more heavily on advanced tools, including use of digital manufacturing, for planning and delivery treatment interventions.
Advanced manufacturing methods including rapid prototyping (RP) afford the means to fabricate solid objects based on medical imaging data. RP-generated anatomical models provide the means for tactile interaction with anatomy, and for rehearsal of tasks like osteotomy and surgical planning utilizing the actual instruments that will be used in a procedure. Models are used frequently in fields such as cranio-maxillofacial surgery, giving surgeons a highly accurate replica of patient anatomy for surgical rehearsal and customization of treatment devices.
RP techniques can also be used to create custom treatment devices that incorporate anatomic features, in addition to designed treatment parameters such as drill trajectories, cut planes and movement of bone segments. These rapid digital manufacture (RDM) techniques present elegant solutions to many medical problems, including the design of patient-specific implants and robust vehicles to bring treatment parameters to the patient in a truly custom way. Fabrication, through RP or RDM, of custom treatment aides such as templates, drill guides and cutting jigs provides specialized intermediary devices for accurate implementation of the custom-designed treatment intervention.
This chapter gives a general overview of the current status of computerized planning for medical intervention, with an emphasis on the role of RDM.
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