R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

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4.4 Two-dimensional formats Working with medical scan data 47 Typically in radiography the output of medical scanning modalities is in the form of two-dimensional images. These images are usually prepared from the scan data by the radiographer according to instructions from doctors and surgeons, and they may be from the slices taken through the body or three-dimensional reconstructions. Often these images are printed on fi lm and treated in much the same way as X-ray fi lms. As medical scan data images are made up of pixels, the images can be exported in familiar computer graphics formats such as bit maps or JPEGs. 4.5 Pseudo three-dimensional formats Data can be exported in formats that allow three-dimensional operations to be undertaken without being true three-dimensional forms. The objects are defi ned by a series of two-dimensional contours arranged in increments in the third dimension. These types of fi le are often referred to as 2 1 / 2D data or ‘slice’ formats. More typically, however, these formats are used as an intermediate step in creating true three-dimensional CAD representations. The formats typically are in the form of lines delineating the inner and outer boundaries of structures isolated by thresholding and region growing techniques. The lines are usually smooth curves, or polylines that are derived from the pixel data. This technique results in smooth contours that more closely approximate the original anatomical shape than the pixelated data. For example, if we consider the original CT data shown in Fig. 4.13 we can see that there is a high-density bone structure surrounded by lower density soft tissue. The effect of specifying upper and lower threshold and region growing is shown in Fig. 4.14. The inner and outer boundaries of the selected region are smooth polylines. The pseudo-three-dimensional effect arises when the two-dimensional polylines are stacked in correct orientation and spacing to provide a layered model, similar in effect to a contour map. Figure 4.15 shows a threedimensional rendering derived from CT data of the proximal tibia alongside the same data exported in a 2 1 / 2D polyline or ‘slice’ format. When such formats are used in CAD, it is common to create surfaces between the slices to generate true three-dimensional surfaces. However, when these formats are used to interface directly with rapid prototyping machines, it is common to interpolate intermediate layers between the original slices so that data exists at layer intervals that correspond with the build layer thickness of the machine being used. The formats that follow are essentially the same and appear similar to that shown in Fig. 4.15. The differences between them are concerned with the order and amount of information stored in them.
48 Medical modelling 4.13 Original pixelated CT image. 4.5.1 IGES contours IGES (Initial Graphics Exchange Specifi cation) is an international standard CAD data exchange format that has been used for many years. More information about the standard can be found at http://www.nist.gov/iges/. The standard consists of lists of geometric entities, which can be assigned with size and position properties in three dimensions. When dealing with layer data, two-dimensional contours can be described as simple polylines at increments in the third dimension. These contours can be imported into CAD packages which can then form true three-dimensional surfaces on them. IGES fi les have the three-letter suffi x IGS. 4.5.2 SLC Derived from the word ‘slice’, the SLC is a relatively simple fi le format that describes the perimeter of individual slices through three-dimensional forms. The inner and outer boundaries are expressed as a set of vectors. The format, therefore, is an approximation but, in practice, the vectors can
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Medical modelling
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Medical modelling The application o
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Contents Preface ix Acknowledgement
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Contents vii 6.10 Rehabilitation ap
Page 11 and 12: x Preface Therefore, it is hoped th
Page 14 and 15: 1.1 Background 1 Introduction The p
Page 16 and 17: Introduction 3 Whilst this book is
Page 18 and 19: Long axis 1.1 The anatomical positi
Page 20 and 21: Introduction 7 1.3 The major refere
Page 22 and 23: Medical imaging for rapid prototypi
Page 26 and 27: 2.2.3 Anatomical coverage Medical i
Page 30 and 31: 2.6 X-ray scatter artefact in a CT
Page 32 and 33: 2.9 Close up of noise. Medical imag
Page 34 and 35: 2.12 Smooth data. Medical imaging f
Page 40 and 41: 1 Medical imaging for rapid prototy
Page 46 and 47: Export data format and media 33 (NE
Page 48 and 49: 3.3 Media Export data format and me
Page 50 and 51: 4.1 Pixel data operations 4 Working
Page 52 and 53: 4.3 Effect of a high threshold. 4.4
Page 54 and 55: Working with medical scan data 41 4
Page 58 and 59: Working with medical scan data 45 S
Page 64 and 65: Working with medical scan data 51 I
Page 66 and 67: 4.18 Close up view showing facets.
Page 72 and 73: 5.1 Background to rapid prototyping
Page 74 and 75: Physical reproduction 61 developing
Page 76 and 77: Physical reproduction 63 will displ
Page 78 and 79: Physical reproduction 65 As there i
Page 80 and 81: Physical reproduction 67 However, t
Page 82 and 83: Data quality Physical reproduction
Page 84 and 85: Physical reproduction 71 In some ca
Page 86 and 87: Physical reproduction 73 Overhangin
Page 88 and 89: Physical reproduction 75 5.10 SL mo
Page 90 and 91: Physical reproduction 77 5.12 Selec
Page 92 and 93: 5.13 A Perfactory ® model of a man
Page 94 and 95: 5.15 FDM TM model of the mandible.
Page 96 and 97: Table 5.3 Advantages and disadvanta
Page 98 and 99: Physical reproduction 85 In medical
Page 100 and 101: Table 5.5 Advantages and disadvanta
Page 102 and 103: 5.7 Jetting head technology 5.7.1 P
Page 104 and 105: 5.23 ThermoJet ® model of the mand
Page 106 and 107: 5.24 LOM TM model of the mandible.
Page 108 and 109: 5.26 LOM TM model of a partial face
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6 Case studies The following case s
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IMPLEMENTATION 6.1 Implementation c
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Post model Hospital department Pati
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Case studies 103 When using this so
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Case studies 105 (Mimics). Image ma
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Case studies 107 full co-operation
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Case studies 109 communication and
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• to achieve patient’s agreemen
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6.2.4 Rapid prototyping technologie
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Case studies 115 not be suitable. A
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Case studies 117 scale of the data
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6.7 SL model with signifi cant stai
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Case studies 121 6.9a Smooth surfac
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Case studies 123 slice editing of t
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Case studies 125 6.12 Removal of bo
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Case studies 127 18. Williams R J,
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Case studies 129 and passing throug
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Case studies 131 6.14 The effect of
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Case studies 133 6.18 The block ove
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Case studies 135 create template (3
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6.4.3 Materials and methods Case st
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6.22 Resected bone compared to SLA
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Case studies 141 9. Robinson R P, C
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Case studies 143 multi-plane reform
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Case studies 145 6.25 The custom ti
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Case studies 147 6.28 Plain radiogr
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Case studies 149 reproduction of ex
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Case studies 151 manner. The softwa
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Case studies 153 surface on which t
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6.33 The guide being fi tted to the
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Case studies 157 The more fundament
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Case studies 159 25. Sarment D P, A
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6.37 Stereolithography models. 6.38
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Case studies 163 6.41 Merged pre- a
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REHABILITATION APPLICATIONS 6.8 Reh
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6.8.3 Methods Preliminary trial of
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Case studies 169 prototyping system
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Case studies 171 The aperture for t
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Case studies 173 7. Manners C R (19
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Case studies 175 during the acquisi
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6.46 Smoothing the data (exaggerate
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6.49 Plaster fi lled SL mould. Case
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Case studies 181 diffi cult for hos
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Case studies 183 extremely diffi cu
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Case studies 185 back as shown in F
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6.54 The result of the Boolean subt
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6.56 The SLA model of the plate. Ca
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6.59 SLA implant on SLA model of de
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Case studies 193 In the near future
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Case studies 195 anatomical forms a
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Case studies 197 Establishing the c
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Case studies 199 6.63 The rough (a)
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Case studies 201 The fi nal prosthe
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Case studies 203 grating the techno
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Case studies 205 6.12 Rehabilitatio
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Case studies 207 • Data capture N
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Case studies 209 placement of two i
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Case studies 211 technique that has
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Case studies 213 6.72 The bar locat
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Case studies 215 Stereolithography
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Case studies 217 authors intend to
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Case studies 219 17. Kau C H, Zhuro
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Case studies 221 310, Sainte-Foy, Q
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6.77a The physically surveyed cast.
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Creation of relief Case studies 225
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6.81 Construction curves. Case stud
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6.83 The support structure in 3D Li
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Finishing Case studies 231 The cast
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Case studies 233 6.14 Rehabilitatio
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6.86 The RPD framework designed in
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Second experiment Case studies 237
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Case studies 239 6.90 Close up view
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Table 6.2 Process steps and associa
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Case studies 243 9. Budtz-Jorgensen
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Case studies 245 micro-computed tom
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Case studies 247 supports became av
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Case studies 249 However, the probl
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6.96 Model of one of the samples su
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6.15.9 Reference Case studies 253 1
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Case studies 255 mummies. Mimics so
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Case studies 257 6.101 3D reconstru
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Case studies 259 6.103 The stages o
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6.16.5 Conclusions Case studies 261
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Case studies 263 the patient’s de
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Case studies 265 and sharp radii re
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Suitable technologies identifi ed C
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Case studies 269 6.107 A close-up p
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6.110 The selected region of facial
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Case studies 273 patterns were buil
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Case studies 275 7. Cheah C M, Chua
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Future developments 277 slices to b
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Future developments 279 ments that
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Glossary and explanatory notes 281
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Glossary and explanatory notes 283
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Further reading on anatomy Last’s
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Fundamentals of Facial Prosthetics
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Rapid Prototyping and Tooling Resea
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Contacts 3D Systems 26081 Avenue Ha
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Marcam Engineering GmbH Fahrenheits
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3D Lightyear TM 229, 247, 249-51, 2
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Removable Partial Denture 219-20, 2
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4.10 A three-dimensional shaded ima
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6.41 Merged pre- and post-operative
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