Structure Enhancement In Virtual Dental Panoramic Radiography Generated From CT

With the development of computer and3D visualization technology,computer aided diagnosis technology is widely used in clinical diagnosisand surgery planning. It is useful for improving the diagnostic accuracy,reducing misdiagnosis as the development of computer aided diagnosistechnology. The combination of computer technology and modern digitalimage technology has provided the foundation for clinical diagnosis andsurgery planning. It also provides a vivid and convenient method formedical education and research. And the most important is that it can guidethe operation, reduce the surgical trauma and risk.Computer and modern digital image technology is widely used indental diagnosis and implant surgery. X-ray panoramic machine andcomputed tomography technology is the commonly used technology instomatology. The panoramic radiography generated by X-ray panoramicmachine can be used to demonstrate the distribution of all the teeth. Usually,X-ray panoramic machine is cheap and dentists are well trained to diagnoseby using panoramic radiography. Dentists also can easily communicatewith patients by using this image. The data got from computed tomographyis high accuracy, it can be used to reconstruct the three-dimensional oral anatomical structure. Therefore, CT technology can help dentists analyzethe anatomical structure of patients and determine the location of implantsbefore surgery. The panoramic radiography and CT images play differentroles in dental diagnosis as they have their own advantages. From patients’point of view, if panorama scanning and CT scanning should be done ineach diagnosis, not only the high cost, but also they have to bear radiationfor twice. So we wonder whether we can use CT data to generate thepanoramic radiography. In this way, patients only need to be scanned oncewhich can reduce trauma for patients. This paper first discusses the methodto generate panoramic radiography by using CT data, then puts forward aroot enhancement method based on fuzzy classification, finally discusseshow to use spatial information of CT data to enhance mandibular canal inthe panoramic radiography.This paper used an improved curved surface projection method as thetraditional plane projection method can’t provide the overall structureinformation of teeth. The casting surface should be first determined whenusing curved surface projection method. The projection surface depends onthe shape of the dental arch. This paper discussed two kinds of dental archline fitting method, one method is based on image morphology corrosionto fit dental arch curve; the other is based on the interaction tracing pointsand uses cube B-spline to fit dental arch curve. This paper also analyzedthat there exists incisor distortion if sampling points in a same radian and put forward a method to decrease the distortion. The design of the transferfunction is the core procedure of volume rendering, which affects thequality of the panoramic radiography. In dental implantation surgery,dentists care about the orientation of teeth-root. This paper proposed amethod based on fuzzy classification to enhance teeth-root. According tothe distribution of CT values, this method designed different kinds oftransfer function for different substance in oral cavity to enhance teeth-root.It is important for dentists to know the position of mandibular canal beforedental implantation surgery. Due to the complexity of the composition ofthe mandibular canal, this article introduced spatial information to designtransfer function. Different transfer functions were used according towhether the sampling points are in the interested region of space. Toprovide dentists more information of an interested tooth, this paper used aninteractive method to segment a tooth from the reconstructed3D anatomicstructure of oral.All the methods proposed by this paper have been integrated in acomputer aided diagnosis system developed by our laboratory. This systemis easy to use and has a good interactive interface.