0
`
`United States Patent [191
`White
`
`[11]
`[45]
`
`4,436,684
`Mar. 13, 1984
`
`[54] METHOD OF FORMING IMPLANTABLE
`
`3,796,129 3/1974 Cruikshank ....................... .. 409/115
`
`PROSTHESES FOR RECONSTRUCI‘IVE
`
`4,053,779 10/1977 Barbieri . . . . . . . . . . .
`
`. . . . . .. 378/9
`
`SURGERY
`
`4,096,390 6/1978 Houns?eld . . . . . .
`
`. . . . . .. 378/ 5
`
`[75] Inventor: David N. White, P2110 A110, Calif.
`.
`[73] Assrgnee: Contour-‘Med Partners, Ltd.,
`Mountain VIeW, Cahf-
`[21] App1-No-= 384,646
`[22] Fi1ed=
`Jun- 3, 1982
`
`1
`
`4,145,614 3/1979 Kowalski . . . . . . . . . . . . .
`
`. . . . . .. 378/9
`
`4,149,079 4/1979 Ben-Zeev et a1. .................... .. 378/9
`4,298,800 11/1981 Goldman .
`4,352,018 9/1982 Tanaka et a]. ........................ .. 378/4
`4,360,028 11/1982 Barbier et a1. ................ .. 128/303 B
`FOREIGN PATENT DOCUMENTS
`820576 8/1969 Canada ................................ .. 434/82
`
`Primapy Examiner_Donald E_ Czaja
`Assistant Examiner__]ames C. Housel
`Attorney, Agent, or Firm-C. Michael Zimmerman
`
`[56]
`
`1126-4
`’
`
`1
`
`[51] Int. Cl.3 ........................................... .. BZSQ 15/14
`UaS- Cl. ....................................... .
`128/92 C; 128/653; 264/163; 264/219; 373/ 4;
`378/21; 434/82; 434/267; 434/274
`ABSTRACT
`[57]
`[58] Field of Search ............... .. 434/22, 267, 270, 274;
`Non-invasive method of forming prostheses of skeletal
`373/4, 5, 6, 7, 8, 9, 10, 11» 12, 13, 14, 15! 16, 17!
`structures internal to a body for use in reconstructive
`18, 19, 20, 21; 123/303 13, 653; 264/138, 1639
`219; 3/ 1.9; 28/92 C surgery. The selected internal skeletal structure is mea
`References Cited
`sured by subjecting the body to radiant energy to pro
`duce radiant energy responses that are detected to ob
`tain representations delineating the skeletal structure.
`U'S' PATENT DOCUMENTS
`20y‘; --------------------------------- -
`Three dimensional coordinate data de?ning the skeletal
`structure is generated from the obtained representa
`0° ----------------- "
`tions. The coordinate data is employed to control a
`31kg; zilg'e‘t'a ' '
`‘ D
`3:259:022 7/1966 Vietorisz ................... .. 364/561 x Sculpting t°°1 ‘0 form the Prosthesis
`3,673,394 6/1972 Hartmann . . . . .
`. . . . .. 364/558 X
`3,746,872 7/1973 Ashe et a1. ...................... .. 378/21 X
`
`31 Claims, 14 Drawing Figures
`
`RADIANT ENERGY
`SCAN
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`__.
`
`DATA
`DETECTION
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`DATA
`PROCESSING
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`COORDINATE GENERATION
`AND MANIPULATION
`
`84
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`MODEL
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`85
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`-1-
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`Smith & Nephew Ex. 1039
`IPR Petition - USP 7,534,263
`
`

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`US. Patent Mar. 13, 1984
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`Sheet 1 of4
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`4,436,684
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`RADIANT ENERGY
`SCAN
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`/82
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`/85
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`DATA
`DETECTION
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`DATA
`PROCESSING
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`84-
`AND MANIPULATION
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`MODEL
`SCULPTING
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`U.S. Patent Mar. 13, 1984
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`Sheet2 of4
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`-U.S. Patent Mar. 13, 1984
`US. Patent Mar. 13, 1984
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`Sheet4of4 4
`Sheet4of4 ‘
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`4,436,684
`4,436,684
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`1
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`METHOD OF FORMING IMPLANTABLE
`PROSTHESES FOR RECONSTRUCI‘ IVE
`SURGERY
`
`5
`
`40
`
`45
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`50
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`4,436,684
`2
`the morbidity associated with the prolonged anesthesia
`presently required.
`The present invention is a method of constructing a
`three dimensional corporeal model that accurately rep
`resents a selected structure internal to a body. The inter
`nal structure is measured by subjecting the body to
`radiant energy to produce radiant energy responses that
`are detected to obtain representions delineating the
`internal structure three dimensionally. A set of three
`dimensional coordinates de?ning a three dimensional
`representation of the selected internal structure is gen
`erated from the obtained representations and is em
`ployed to direct a sculpting tool to form a corporeal
`model of the selected structure. As will become more
`apparent upon consideration of the detailed description
`of a preferred embodiment of the method of the present
`invention found hereinafter, the formation of an accu
`rate corporeal model replica of the selected structure is
`facilitated by using the generated set of three dimen
`sional coordinates to control the trajectory of a ma
`chine-controlled sculpting tool for the purpose of
`formng the corporeal model. However, the method of
`the present invention can be practiced to provide three
`dimensional coordinates that de?ne a mold cavity
`model representation of the selected structure from
`which one or more corporeal model‘ replicas may be
`formed by conventional molding processes. In such
`implementations, the trajectory of the sculpting tool is
`directed by the provided three dimensional coordinate
`data to form the desired mold cavity.
`As will become more apparent upon consideration of
`the description of the preferred embodiment of the
`present invention, noninvasive radiographic image re
`construction techniques and automatically controlled
`machining techniques are adapted and combined to
`enable the precise measurement of internal structures
`and the construction of corporeal models that are accu
`rate representations of the internal structures. A radio
`graphic image reconstruction technique particularly
`useful in the method of the present invention is com
`puted tomography, according to which a cross sectional
`tomographic image is constructed from radiant energy
`transmitted through or re?ected from the interior of the
`body along paths at different angles relative to the
`body. The image is constructed by computer manipula
`tion of the detected radiant energy according to an
`algorithm whereby the localized radiant energy re
`sponses occurring at the cross section location of the
`body are computed. The computed radiant energy re
`sponses are characteristic of the substances located at
`the cross section location of the detected radiant energy
`responses and, therefore, enable formation of an image
`of the structure at the cross section location. A series of
`such images is obtained at locations distributed along a
`line perpendicular to the plane of cross section by sub
`jecting the body to radiant energy and detecting the
`transmitted or re?ected radiant energy at each of the
`distributed locations. Computerized tomographic de
`vices have employed x-ray, nuclear magnetic resonance
`(NMR), positron emission (PET) and ultrasonic radiant
`energy techniques to obtain data for the construction of
`images of internal structures. Both analog gray-scale
`pictures of the detected radiant energy responses and
`paper printouts of mapped numerical value representa
`tions of the gray-scale values are commonly provided
`by such computerized tomographic devices. Examples
`of such devices are described in US. Pat. Nos.
`
`DESCRIPTION
`The present invention relates generally to a method
`of constructing three dimensional corporeal models of
`structures internal to bodies and, more particularly, to a
`method of constructing such models from three dimen
`sional representations of the internal structures obtained
`without physical invasion of the bodies.
`A three dimensional corporeal model of a structure
`whose exact size and/or shape is unknown ordinarily is
`constructed from direct measurement of the dimensions
`of the structure. Direct measurement of the internal
`structure has the advantage of providing precise dimen
`sional information that enables the construction of a
`corporeal model which accurately represents the inter
`nal structure. Often, however, the structure is con?ned
`within a body so as not to be accessible for direct mea
`surement. In such cases, the body is either openedor
`diassembled to provide access for the measurement of
`the internal structure of interest. When such opening or
`25
`disassembly has not been practicable or desirable, cor
`poreal models have been constructed with the aid of
`visual inspections of standard radiographic images of
`the internal structure of interest, externally formed cast
`ings of the body and other techniques of indirect exami
`nation of the body. The de?ciencies of such techniques,
`however, have made it dif?cult to construct corporeal
`models that accurately represent internal structures.
`For the most part, such indirect examination techniques
`are de?cient for such purposes because they provide
`imprecise dimensional information and structural delin
`eation of structures internal to a body.
`Accuracy is particularly important in the construc
`tion of corporeal models of internal tissue structures of
`mammalian anatomies. Such models will be referred to
`herein as prostheses, whether in the form of a surgically
`implantable prosthesis or an external prosthesis.
`Though exact measurement and accurate conformation
`are desirable in the construction of implantable prosthe
`ses for reconstructive surgery, non-invasive direct mea
`surement of internal anatomic tissue structures is not
`available by present methods and not practicable for the
`fabrication of prostheses. Present methods require fabri
`cation of an implantable prosthesis for correction of
`bony contour abnormalities on the basis of a plaster
`casting taken over the area of abnormality with soft
`tissue interposed between the structural defect and the
`cast. From this case, a model onlay prosthesis is con
`structed by a hand-sculpting method by a skilled pros
`thetist on a best-approximation basis, attempting to
`allow for the inaccuracies resulting from indirect mea
`surement. Residual inaccuracies must then be modi?ed
`at the time of implantation when direct surgical exami
`nation of deep structures is possible.
`If a bone graft from the patient is to be fashioned to
`correct a structural defect, the surgeon has no precise
`representation of the bony abnormality prior to direct
`examination at the time of surgery, and is then required
`to alter the abnormality and fashion the implant in the
`operating room without the bene?t of a prior working
`model.
`Construction of accurate preoperative models and
`correctional implants avoids the shortcomings of the
`above-noted hand sculpting technique and diminishes
`
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`4,436,684
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`3,673,394, 4,298,800 and Re 30,397, and references cited
`in the patents.
`Machine-controlled contour sculpting tool devices
`have been widely used to reproduce three dimensional
`object surfaces from representations of such surfaces.
`Some of these devices control tool trajectory relative to
`a work piece in accordance with numerical data ob
`tained from drawings or photographs of the desired
`object, for example, by the use of contour or pro?le
`following instruments. Other contour sculpting devices
`utilize contour followers adapted to follow a physical
`model of the desired object and generate coordinate
`control data used to control the trajectory of the sculpt
`ing tool. Some contour followers are mechanically
`linked to the sculpting tool whereby movement of the
`contour follower directly causes corresponding move
`ment of the sculpting tool. Examples of contour sculpt
`ing tool devices are described in U.S. Pat. Nos.
`2,852,189, 3,195,411, 3,259,022 and 3,796,129.
`In the preferred embodiment of the method of the
`present invention, a computerized x-ray tomographic
`device is operated to provide representations of the
`absorption coefficient of substances at locations internal
`to a body. The absorption coef?cient representations
`delineate the internal structures and are examined to
`derive three dimensional coordinate data de?ning a
`three dimensional representation of a selected delin
`eated internal structure. The coordinate data is derived
`in a format compatible with a machine-controlled
`sculpting tool device selected to form the desired cor
`poreal model of the selected internal structure. A model
`is formed from a workpiece of suitable material by oper
`ating the machine-controlled sculpting tool device to
`control the trajectory of its cutting sculpting tool rela
`tive to the workpiece in accordance with the coordinate
`data derived from the absorption coefficient representa
`tions of the structure obtained by the computerized
`x-ray tomographic device.
`The foregoing and other objects, advantages and
`features characterizing the present invention will be
`come more apparent upon consideration of the follow
`ing description of speci?c embodiments and appended
`claims taken together with the drawings of which:
`FIG. 1 is a diagram schematically illustrating the
`steps of the preferred embodiment of the method of the
`present invention for obtaining three dimensional coor
`dinate data of a selected structure internal to a body and
`generating a corporeal model thereof;
`FIG. 2 is a perspective view of a head illustrating the
`manner in which three dimensional coordinates de?n
`ing a selected internal anatomic structure are obtained
`in accordance with the preferred embodiment of the
`method of the present invention;
`FIG. 3 is a schematic diagram of an exemplary gray
`scale tomographic axial image in a plane taken at lines
`3-3 of FIG. 2, with the image constructed from x-ray
`radiation responses obtained from the plane in accor
`dance with the preferred method of the present inven
`tion;
`FIG. 4 is a schematic diagram of an enhancement of
`60
`the exemplary image of FIG. 3 depicting a cross section
`of a mandible selected to be constructed in model form
`in accordance with the preferred method of the present
`invention;
`FIGS. 5A and 5B are schematic diagrams illustrating
`x-ray scanning equipment for obtaining radiation re~
`sponses from cross sections of a body in accordance
`with the preferred method of the present invention;
`
`4
`FIG. 6 is a schematic block diagram of a computer- ,
`ized x-ray tomographic apparatus for practicing the
`preferred method of the present invention;
`FIG. 7 is a schematic representation of an exemplary
`print of a mapped numerical value representation of a
`reconstructed tomographic image;
`FIGS. 8A, 8B and 8C together comprise a schematic
`diagram of a machine-controlled sculpting tool appara
`tus for forming corporeal models of selected structures
`in accordance with the preferred method of the present
`invention;
`FIGS. 9A and 9B together~comprise a schematic
`diagram illustrating the construction of an onlay pros
`thesis from three dimensional coordinate data translated
`in accordance with the preferred method of the present
`invention; and
`FIG. 10 is a schematic diagram illustrating the con»
`struction of an inlay prosthesis from three dimensional
`coordinate data translated in accordance with the pre
`ferred method of the present invention.
`The method of the present invention will be de
`scribed with reference to a preferred embodiment of the
`present invention arranged to construct a prosthesis of
`an internal anatomic tissue structure from three dimen
`sional coordinate data de?ning the internal structure
`obtained without the physical invasion of the anatomy.
`As will be appreciated from the following description
`of the preferred embodiment, however, the method of
`the present invention can be practiced to obtain de?ni
`tive three dimensional coordinate data and construct
`corporeal models of structures internal to bodies other
`than anatomies.
`_
`Generally and referring to FIG. 1, a corporeal model
`representation of a selected internal structure of a body
`is constructed by controlling a sculpting tool to follow
`a trajectory relative to a workpiece determined by three
`dimensional coordinate data that speci?es the contour
`of the selected internal structure. To obtain the three
`dimensional coordinate data in accordance with the
`method of the present invention, the selected internal
`structure is scanned as step 81 by subjecting it to radiant
`energy to produce radiant energy responses that deline
`ate the selected structure three dimensionally and are
`detectable at a location exterior to the body. The radi
`ant energy responses are detected at step 82 and the
`detected responses processed at step 83 to obtain data
`delineating the selected structure three dimensionally.
`At step 84, the three dimensional coordinate data re
`quired for the control of the sculpting tool in construct
`ing the desired corporeal model representation of the
`selected internal structure is generated from the data
`provided by the performance of step 83. As brie?y
`discussed hereinbefore and as will become more appar
`ant upon consideration of the detailed description of the
`preferred embodiment of the method of the present
`invention to follow, various corporeal model represen~
`tations of a selected structure can be constructed in
`accordance with the present invention. A scale replica
`of the internal structure in the state found within the
`body is constructed from three dimensional coordinate
`data de?ning the selected structure at scale. If other
`than a scale replica of the internal structure is desired,
`data is manipulated at step 84 to obtain transformed
`three dimensional coordinate data for constructing an
`altered corporeal model representation of the selected
`internal structure. The manipulation can be performed
`at the time of the generation of three dimensional coor
`dinate data from the data provided by the performance
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`of step 83, for example, by generating the three dimen
`path of thebeam. A computerized data processing sys
`sional coordinate data according to an algorithm relat
`tem 18 (FIG. 6) associated with the x-ray tomographic
`ing the untransformed three dimensional coordinate
`device 13 manipulates the measurements taken along
`the several paths according to an algorithm to calculate
`data to the desired transformed three dimensional coor
`dinate data. Alternatively, the transformed three dimen
`the attenuation coefficient of elements in each XY plane
`sional‘ coordinate data can be obtained by manipulation
`19_ (FIG. 2) through which the- x-ray beam 14 is di
`of generated untransformed three dimensional coordi
`rected. The attenuation coefficients of elements in other
`nate data, by manipulation of the data delineating the
`planes distributed at-spaced locations along the Z axis
`selecting structure before the generation of the three
`perpendicular to the _XY planes 19, hence the x-ray
`beam 14, are obtained by relatively moving the body 11
`dimensional coordinate data or by combinations of the
`aforementioned manipulations. As will be described in
`and the x-ray generation and detection apparatus in
`further detail hereinafter with reference to the'preferred
`increments along a line generally perpendicular to the
`plane of the x-ray beam. Typically, the body 11 is
`method of the present invention, interpolating, form or
`curve ?tting, scaling and translating are manipulations
`moved‘ through a stationary scanning station at which
`particularly useful in constructing external andimplant
`the x-ray measurements along the several paths in each
`XY plane are obtained by rotating oppositely disposed
`able prostheses and mold cavities for casting models of
`selected internal structures. In any case, the three di
`x-ray generator 26 and x-ray detector 17 devices (FIGS.
`mensional coordinate data is' generated in a format de
`5A and 5B) about the body. The calculated attenuation
`termined by the sculpting device used in constructing
`coefficients provide accurate representations of the
`the corporeal model representation of the selected inter
`densities of the substances within the anatomy. In the
`nal structure. The desired corporeal model representa
`processing of the measurements, gray-scale values are
`tion is obtained at step 85 by directing a sculpting tool
`assigned to the calculated attenuation coef?cient values
`to provide representations of the elements in each plane
`in accordance with the generated three dimensional
`19 suited for displaying an image of the structure of the
`coordinate data to follow a trajectory relative to a
`workpiece that produces the representation de?ned by
`anatomy 11 at the location of the plane.
`25
`the three dimensional coordinate data. The corporeal
`For example, FIGS. 3 and 4 schematically illustrate
`different image reconstructions 20 and 20' respectively,
`model is fabricated from suitable material selected ac
`cording to the expected use of the model.‘ Examples of
`of a single cross sectionof the, anatomy 11 shown in
`FIG. 2 taken at a plane 19 extending through the mandi
`material suitable for the construction of prostheses are
`Silastic and Proplast. “Silastic” is a trademark of Dow
`ble 10. As can be seen. by inspection of FIGS. 3 and 4,
`30
`Corning Corporation used to identify the material it
`tlie light gray scale mandible representative values 10
`are readily distinguishable from the darker surrounding
`markets. “Prop‘last” is a trademark of Vitek, Inc. used to
`identify the material it markets.
`gray scale representations of other substances. Greater
`contrast between the mandible representative grayrscale
`A preferred embodiment of the method of the present
`invention arranged to construct corporeal models of
`values and the gray scale representations of other ana
`35
`internal anatomic tissue structures will now be de
`tomic tissue substances at the cross section can be ob
`tained by enhancing the image reconstruction in. the
`scribed in detail with reference to FIGS. 2-7. The pre
`ferred embodiment will be described in connection with
`manner described hereinafter and shown in FIG. 4. In
`both image reconstructions of FIGS. 3 and 4, the gray
`the construction of prostheses of a mandible. More
`scale representations clearly delineate the surface loca
`specifically and referring to FIGS. 2-4, the mandible 10
`40
`of the anatomy 11 is speci?ed three dimensionally by
`tion 12 of the mandible 10, from which the three dimen
`subjecting the anatomy to radiant energy‘to produce
`sional coordinates of the mandible are derived. A series
`of such gray scale cross sectional representations of the
`radiant energy responses within the anatomy that are
`anatomy 11 obtained along the Z axis provides informa
`characteristic of a selected physical property of sub
`stances of and detectable at the exterior of the anatomy.
`tion from which three dimensionalcoordinate data can
`Different substances of the anatomy 11 produce‘ differ
`be derived. As will be described in further detail herein
`ent distinguishable characteristic _radiant energy re
`after, three dimensional coordinate data specifying a
`sponses which, upon detection, provide distinguishable
`selected structure 10 of which a model is to be con
`representations of the different substances‘ located
`structed is derived from a series of such cross sectional
`representations of the anatomy 11.
`within the anatomy. As will be described in greater
`detail hereinafter, a computerized tomographic imaging
`As mentionedthereinbefore, other noninvasive radio
`graphic imaging devices can be utilized in the practice
`device 13 (FIG. 6) utilizing x-ray radiation is employed
`in the practice of the_ preferred embodiment of the
`of the method of the present invention to obtain cross
`sectional representations of the body 11 from which the
`method of the present invention to obtain distinguish
`desired three dimensional coordinate data de?ning the
`able representations of different substances within the
`anatomy 11. "As‘described hereinbefore, computerized
`structure 10 of interest can be obtained. In PET devices,
`tomography ,d'evices provide cross sectional representa
`for example, radiant energy originates within the anat
`omy 11 from an intravenouslyadministered biologically
`tions of the internal structure of the anatomy 11 recon
`active substance labeled with a positron-emitting radio
`structed from radiant energy transmitted through or
`active isotope. The isotope'decays by emitting positrons
`reflected from the interior of the anatomy along paths at
`that travel a short distance in tissue before colliding
`different angles relative to the anatomy. In the x-ray
`with electrons. ‘A collision between a positron and elec
`tomographic device 13, a narrow x-rayvbeam 14 (FIGS.
`tron annihilates both particles, converting the mass of
`5A and 5B) is directed through the anatomy 11 along
`the two particles into energy divided equally between
`several paths (such as depicted by arrows 16) in a plane
`two gamma rays emitted simultaneously along oppo
`and the radiation transmitted through the anatomy is
`sitely directed paths. One PET device in use includes
`measured by x~ray detectors 17. A transmission mea
`arrays of scintillation detectors encircling the subject
`surement taken along each'path represents a composite
`supported by a mobile table with the region of interest
`of the absorption characteristics of allelements in the
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`at the axis about which the detectors are disposed. The
`arrays of detectors record simultaneously emitted
`gamma rays at a plurality of spaced axial cross sections
`of the subject during an imaging cycle, the detectors
`being linked in opposite pairs so that emitted gamma
`rays are recorded only when both detectors of a pair
`simultaneously sense gamma rays. All gamma ray pairs
`originating within a volume of the subject de?ned by
`the cylindrical, colinear ?eld of view joining paired
`detectors are sensed. Gamma rays orginating outside
`that volume are not sensed by the detectors. The sensed
`gamma ray responses are processed to obtain ‘represen
`tations delineating the substances in the ?eld of view.
`The mobile table moves the subject axially relative to
`the encircling detectors to enable the detection of radi
`ant energy events and concomitant generation of repre
`sentations of substances at a plurality of spaced axial
`cross sections of the subject.
`NMR imaging devices have the advantage of using a
`non-ionizing form of radiant energy. In NMR devices,
`the subject is placed in a strong magnetic ?eld while a
`brief high frequency signal is beamed at the body. Dif
`ferent atoms of substances of the body respond by send
`ing out different characteristic radio signals that are
`detected by tunable receiving antennas placed about the
`body. The tunable receiving antennas are adjusted to be
`responsive to selected radio signals and thereby obtain
`representations of selected substances, which are pro
`cessed by an associated computerized data processing
`system to generate a distinguishable characteristic rep
`resentation of such substance in a plane of the subject.
`Representations of substances in other parallel planes at
`spaced locations along a de?ned line are obtained by
`moving the subject in increments through the magnetic
`?eld and past the receiving antennas.
`Ultrasonic radiographic imaging devices also can be
`employed to obtain representations of the internal struc
`ture of a body. Like NMR imaging devices, ultrasonic
`devices have the advantage of using a non-ionizing form
`of radiant energy in obtaining the data from which
`40
`representations of the internal structure of bodies are
`derived. Most ultrasonic imaging devices generate rep
`resentations of anatomic structures from detected re
`?ections of high frequency pulsed sound waves directed
`through the anatomy. A series of pulsed sound waves
`are sent forth into the anatomy by electrically pulsed
`piezoelectric transducers in contact with the anatomy.
`The transducers employed are capable of reversibly
`converting electrical to vibratory mechanical energy at
`the pulse frequency of interest. After the transmission of
`50
`each short burst or pulse of sound energy, the circuitry
`associated with the transducer is switched to act as a
`receiver for returning or re?ected echos of the transmit
`ted sound waves. Echos are reflected when the pulsed
`sound encounters an interface of tissues of different
`densities. Tissues of different acoustic impedances re
`turn different echos. The re?ected echos are converted
`to representative electrical signals by the piezoelectric
`transducers, from which planar representations of the
`internal structure of the anatomy are obtained. The data
`processing system associated with the ultrasonic device
`converts elapsed time between transmission of a sound
`pulse and reception of each echo into a measurement of
`the distance from the transducer to each location of
`echo re?ection.
`65
`Each of the radiographic imaging devices described
`above provides representations of the internal structure
`of a body by subjecting the body to selected radiant
`
`8
`energy. In x-ray, NMR and ultrasonic devices, the body
`is subjected to radiant energy projected at it from a
`location external to the body. With PET devices, how
`ever, the body is subjected to radiant energy generated
`within the body itself. In any case, each of the imaging
`devices produces radiant energy responses within a
`body from which distinguishable representations of
`different internal structures of the body are generated
`and from which, in turn, three dimensional coordinates
`de?ning a selected structure internal to the body are
`generated for directing a sculpting tool to form a corpo
`real model representation of the selected internal struc
`ture.
`A computerized x-ray tomographic system suited for
`use in obtaining three dimensional coordinate data de
`?ning the mandible 10 of the anatomy 11 in accordance
`with the preferred embodiment of the method of the
`present invention is marketed by General Electric Com
`pany under the model designation CT/T 8800 Scanner
`System. The preferred method of obtaining three di
`mensional coordinate data de?ning the mandible 10 in
`accordance with the present invention will now be
`described with reference to the CT/T 8800 Scanner
`System, which is schematically illustrated in FIGS. 5
`and 6. The computerized x-ray tomographic system 13
`(FIG. 6) is arranged to produce computer reconstructed
`cross sectional images of any part of the anatomy from
`multiple x-ray absorption measurements. The system 13
`includes a radiation scanning assembly 27 having a mo
`bile table 21 (FIG. 5B) for supporting and transporting
`a subject through the x-ray scanning station 22 along a
`path indicated by arrow 23. Thetable 21 is configured
`to aid in centering and con?ning the anatomy 11 in a
`selected orientation relative to the x-ray generator 26
`and detector 17 (FIGS. 5A and 5B) of the scanning
`assembly.
`The radiation scanning assembly 27 also includes a
`gantry 24 (FIG. 5B) positioned along the path 23 for
`supporting the x-ray generator 26 and x-ray detector 17
`for rotation about the mobile table 21 in a selected plane
`perpendicular or at an. angle to the path 23. The x-ray
`generator 26 emits an x-ray fan beam 14 that is directed
`at an array of x-ray radiation sensitive cells forming the
`detector 17 at the opposite side of the gantry 24. The
`beam 14 is formed and the detector 17 is arranged to
`permit scanning of an object detection zone 29 (FIG.
`5A) located in the plane of the beam. Each cell of the
`detector 17 detects a portion of the x-ray beam 14 after
`its passage through the object detection zone 29 (and
`any part of a body 11 located in the zone) and provides
`data representative of the composite x-ray radiation
`attentuation coef?cient along a path between the x-ray
`generator 26 and the data cell. The data provided by the
`detector 17 as it and the X-ray generator 26 are rotated
`about the subject (borne by the table 21) is processed to
`generate an attenuation coef?cient representation for
`each volume element 31 (FIG. 4) of the cross sections of
`the anatomy 11 scanned by the x-ray beam 14. The
`resolution capability of the CT/T 8800 system 13 is
`dependent upon the fan thickness of the x-ray beam 14
`and the power of the data reconstruction algorithm
`characterizing the software program employed in the
`system. A typical CT/T 8800 system generates an atten
`uation coef?cient representation for a volume element
`31 having a size on the order of 1.5 mmX0.8 mmXO.8
`mm, with the long 1.5 mm dimension of the volume
`element 31 extending in the direction of the fan thick
`ness dimension of the beam 14, he