WO1983000403A1

WO1983000403A1 - Three dimensional assembly of cross-sectional images derived by computer assisted tomography and the like

Info

Publication number: WO1983000403A1
Application number: PCT/US1982/000952
Authority: WO
Inventors: Robert N Egbert
Original assignee: Egbert, Robert, N.
Priority date: 1981-07-20
Filing date: 1982-07-15
Publication date: 1983-02-03

Abstract

A device (10) for three-dimensional illustration of an object includes a plurality of parallel cross-sectional images (12) of the object carried on a substantially transparent support such as a film. The cross-sectional images are mounted in a parallel, spaced, aligned relationship to one another and are embedded in, or surrounded by a substance (14) that has substantially the same refractive index as the transparent support of the images.

Description

THREE DIMENSIONAL ASSEMBLY OF

CROSS-SECTIONAL IMAGES DERIVED BY

COMPUTER ASSISTED TOMOGRAPHY AND THE LIKE

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a three- dimensional assembly or display of a plurality of succes¬ sive, parallel cross-sectional images of an object. More particularly, the present invention is directed to a three-dimensional assembly or display of a plurality of tomographic images of an organ or portion of the body of a human patient. The present invention is also directed to a process of preparing the three-dimensional assembly or display of the images.

2. Brief Description of the Prior Art Anatomical models are well known in the prior art. An anatomical model described in United States Patent No. 3,276,146 comprises a plurality of panels hav¬ ing depicted thereon, a plurality of cross-sectional fac¬ simile images of a human organ. The panels, which may be transparent, are in a parallel spaced relationship to one another, and are mechanically fastened to a substan¬ tially horizontally disposed base panel.

United States Patent Nos. 1,104,067 and 1,141,180 describe an anatomical model wherein facsimile, cross-sectional images of a human organ, such as the brain, are secured to a plurality of glass plates. The cross-sectional images are taken in parallel planes and the glass plates are attached to one another in a parallel, spaced relationship. The patents teach that the assembled glass plates, when placed between a light source and a viewer, provide a three-dimensional model of the brain.

In addition to attempting to provide three-dimen¬ sional models of various organs, the arts relating to the demonstration and preservation of anatomical and related medical specimen also provide substantially flat displays of microtomes, tissue sections and the like. United States Patent Nos. 3,130,099 and 4,010,544 describe dis¬ plays, wherein the microtome or tissue section is embedded or enclosed in transparent, solid plastic. Of course, the process of embedding various objects in transparent plas¬ tic for the purpose of preservation and display of the object is well known, and is widely practiced mainly for the purpose of providing gift and curiosity items.

Relatively recently, tomography and particularly computer assisted tomography has gained increasing accept¬ ance and application in the medical diagnostic field. Briefly, a tomogram is a cross-sectional image of an organ or a portion of the body of a patient. In present medical diagnostic practice, it is customary to obtain several successive parallel tomograms or cross-section images of an organ or body portion of a patient when the presence or absence of a malignancy or other seriour disease is suspected. Tomograms, and particularly computer assis¬ ted tomograms may be obtained by conventional x-ray. They may also be obtained by using other diagnostic tools such as various scanning techniques for internally administered radiosotopes, ultrasound scanning and nuclear magnetic resonance scanning. For the purpose of describing the background of the present invention, it is sufficient to understand that each of the several cross-sectional images represents a char¬ acteristic, such as x-ray or ultrasound absorption, or radiosotope emission of the organ or body portion under scrutiny. According to current practice, the several cross-sectional images or tomograms are viewed indivi¬ dually or side-by-side by the diagnosing physician.

As the above-noted patent disclosures, and particularly United States Patent Nos. 1,104,067 and 1,141,480 recognize, it is often desirable to view the plurality of cross-sectional images of an organ in a three-dimensional assembly. Viewing the state-of-the-art diagnostic tomograms in a three-dimensional assembly is particularly desirable because in a three-dimensional form the presence and particularly the extent of malig¬ nancies or deformities is better discernible than in the conventional two-dimensional form.

A serious disadvantage of the device and method disclosed in United Sates Patent 1,104,067 and 1,141,480 is that as the several glass plates or layers of the therein disclosed device are assembled,a plur¬ ality of light reflective surfaces are created. In other words, the device of United States Patent Nos. 1,104,067 and 1,141,480 has many interfacing optically ^* different surfaces, and therefore the device is not op¬ tically homogeneous. This renders viewing of the as¬ sembled images of the device cumbersome, and less than satisfactory from the utilitarian and aesthetic point of view as well.

In accordance with the foregoing, there exists a need in the prior art for a device wherein a plurality of cross-sectional images or tomograms of an object and particularly of an organ or body portion of a patient are assembled to provide a three-dimensional representa¬ tion of the organ. SUMMARY OF THE INVENTION

It is an object of the present invention to provide a three-dimensional assembly or display of a plurality of parallel, successive, cross-sectional images of an object, and particularly of an organ or body por¬ tion of a human patient.

The above and other objects and advantages are attained by a device wherein a plurality of success¬ ive, parallel, cross-sectional images of the object are mounted in closely aligned substantially evenly spaced positions relative to one another. The cross-sectional images, are carried on a substantially transparent sup¬ port and are embedded in a plastic material which has a refractive index that is substantially identical with the refractive index of the support. The support con¬ veniently may be a polyester film. The entire assembly of the images in the embedding plastic is substantially optically homogeneous and comprises a three-dimensional representation of the object under scrutiny.

The features of the present invention can be best understood, together with further objects and ad¬ vantages, by reference to the following description, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic perspective view of a preferred embodiment of the present invention:

Figure 2 is a cross-sectional view taken on lines 2,2 of Figure 1;

Figure 3 is a schematic perspective view of a mold wherein the device of the present invention may be fabricated, the mold having a first layer of a plas¬ tic material poured thereinto; Figure 4 is a cross-sectional view of the mold taken on lines 4,4 of Figure 3;

Figure 5 is a schematic perspective view of the mold, the view showing a cross-sectional image or tomogram placed on top of the first layer of the plastic material in the mold;

Figure 6 is a cross-sectional view of the mold taken on lines 6,6 of Figure 5;

Figure 7 is a cross-sectional view of the mold showing several layers of plastic embedding a plurality of images in the mold;

Figure 8 is a perspective view of several tomo¬ grams disposed in an aligned spaced relationship adapted for assembly in the second preferred embodiment of the present invention;

Figure 9 is a perspective view of the second preferred embodiment of the present invention, and

Figure 10 is a cross-sectional view, the cross- section being taken on lines 10,10 of Figure 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following speci ication taken in conjunc¬ tion with the drawings sets forth the preferred embodi¬ ment of the present invention in such a manner that any person skilled in the arts relating to medical illus¬ trating devices and the arts relating to application of plastic materials, can use the invention. The em¬ bodiments of the invention disclosed herein are the best modes contemplated by the inventor for carrying out his invention in a commercial environment, although it should be understood that various modifications can be accomp¬ lished within the parameters of the present invention. Referring now to the drawing figures and par¬ ticularly to Figures 1-7, a first preferred embodiment of a display or assembly 10 providing a three-dimensional image of an object, is disclosed. It should be noted at the outset, that although the ensuing description is pri¬ marily directed to a three-dimensional assembly of a plurality of tomograms used in the medical diagnostic field, the scope of the present invention is not so limited. Rather, the display or assembly of the present invention may be utilized to provide a three-dimensional image of any object from a plurality of cross-sectional images of the object. The cross-sectional images may be facsimile images or drawings, even technical, blue¬ print type drawings, so that a three-dimensional image of a machine, component or structure may be created in accordance with the present invention.

Referring now specifically to the medical diag¬ nostic field, conventional x-ray tomograms have been in use for a long time. A conventional x-ray tomogram is an x-ray image wherein shadows of structures before and behind a section in scrutiny, do not show. Thus, a tomo¬ gram is a cross-sectional image. Although conventional x-ray tomograms can be obtained with certain prior art_- techniques without the assistance of a computer, pre¬ sently tomograms are customarily obtained by computer assistance, and therefore are often called computer assis¬ ted^* tomograms, or c.a.t. scans.

As it was stated above in the introductory section of the present application for patent, presently computer assisted tomograms are obtained by using a wide variety of scanning techniques. Such techniques include conventiona x-ray, ultrasound, radiation emission by in¬ ternally administered radioactive isotopes, and nuclear magnetic resonance. The hereinbelow disclosed princi¬ ples of the present invention are applicable to tomo¬ grams regardless of the specific technique employed for obtaining the tomograms. The only rela/ant limitations in this regard are the following. A plurality of tomo¬ grams, i.e. cross-sectional images, of an organ or a body portion must be obtained. The tomograms must be affixed to a substantially transparent support such as a film. Furthermore, in order to provide a true three-dimensional image of the organ or body portion un¬ der scrutiny, the tomograms should be taken at regularly spaced intervals, or at least at spaced intervals which are known.

The above requirements, however, are, generally speaking, readily met by state-of-the-art tomograms,ex¬ cept that for the purpose of practicing the present in¬ vention it is desirable that the tomograms be printed on good quality transparent film. The conventional posi¬ tive film used in hospitals and diagn.os.ti_c laboratories for recordation of x-rays, and tomograms in general, is relatively dark, yellowish or hazy, and not sufficiently transparent to provide really good results in the prac¬ tice of the present invention. Therefore, better re- . suits are obtained when the tomograms are recorded on a good quality substantially colorless positive film, such as Kodak fine grain positive film No. 7302. This film has a polyester material or base. Suitable color films may also be used.

Referring now specifically to Figures 1 and 2, the several layers of film or tomograms 12 are shown em¬ bedded in a suitable, clear plastic material 14. As the cross-sectional view of Figure 2 clearly illustrates, the layers of film 12 are evenly spaced from one another, and are aligned with one another. It is of course impor¬ tant that the layers of film or tomograms 12 be dis¬ posed in the embedding plastic 14 in the same sequence as they were taken out of the organ or body portion un¬ der scrutiny. The drawing Figures schematically illus¬ trate a three-dimensional facsimile of a skeleton 16, which may be assembled from a pluarlity of tomograms 12 in accordance with the present invention. It should be specifically understood, that the display 10 of the pre¬ sent invention is three-dimensional, which is practically impossible to illustrate within the two dimensional frame¬ work of the drawing.

A critical aspect of the three-dimensional display or assembly 10 of the present invention is that the refractive index of the solid transparent plastic 14 which embeds the layers of film or tomograms 12, must be substantially identical with the refractive index of the layers of film 12. A further critical aspect is that the entire plastic block 14 which embeds the tomograms 12 be substantially optically homogeneous. In other words, the embedding plastic 14 should not contain visually dis¬ cernible layers of plastic. As it will become more readily apparent in conjunction with the description of the novel process or method by which the three-dimensional display 10 of the present invention is produced, the above requirements are readily satisfied when a polyes¬ ter based film, and a polyester based embedding plastic 14 are used. More specifically, use of the above-noted Kodak fine grain positive film No. 7302, and a polyes¬ ter based "Clear Cast" embedding resin manufactured by Fibrelay Inc. of Seattle Washington is preferred.

It should be noted, however, that other film and resin combinations which will produce the desired _.optical homogeneity of the display 10 may become readily apparent to those skilled in the art. Therefore, such combinations are within the scope of the present inven¬ tion. It is possible to imbed all the layers at one time for example.

Typically, 5-25 cross-sectional images or tomo¬ grams 12 are embedded in the plastic block 14, and the layers of film or tomograms are located approixmately 0.05-0.15" from one another. In this regard, it should be understood, that within a given three-dimensional assembly 10, even spacing of the tomograms 12 from one another is important for the purpose of obtaining a good quality three-dimensional image.

The exact spacing of the tomograms 12 in the embedding plastic 14, is to a certain degree, a design choice and influences the viewing qualities of the re¬ sulting three-dimensional image. Generally speaking, within the above given range, the spacing ideally para¬ llels the spacing of the actual tomograms taken of the patient's body or organ.

A further important aspect of the present in¬ vention is, that the layers of film or tomograms 12 must be strictly aligned with one another, as is shown - on the drawing figures, particularly on Figure 2. All tomograms of a given three-dimensional display 10 must also be on the same scale. The latter requirement is, however, readily satisfied by state-of-the-art tomograms 12, which, in current practice, are viewed for diag¬ nostic purposes individually or side-by-side.

Although the two-dimensional drawing of Figure 1 is unable to truly illustrate it, the display 10 of the present invention provides a three-dimensional image of the organ or body portion under scrutiny. It was found in practice, that in certain instances, the three-dimen¬ sional display 10 permits diagnosis of tumors and other abnormalities which would otherwise be undetected from simple side-by-side viewing of the individual tomograms. Furthermore, the three-dimensional display 10 of the present invention facilitates the determination of the size and extent of tumors or other abnormalities and is also useful for anatomical demonstrations or as a teach¬ ing aid.

Referring now to Figures 3-7, a process or method for the preparation of the three-dimensional dis¬ play 10 of the present invention, is disclosed. A sub¬ stantially rectangularly shaped molding tray or mold 18 is used in the process. The mold 18 has a bottom 20, having a smooth flat surface 22.' A pair of vertically disposed aligning pins 24 are attached to the bottom 20, and a pair of apertures 26 are provided in each tomo¬ gram 12 in locations precisely matching the position of the aligning pins 24 in the mold 18.

In the first step of the process, a first layer 28 of a first liquid plastic material 30 is poured into the mold 18, and is allowed to solidify therein. In accordance with the above-noted requirements of the present invention, the first liquid plastic material, must, after it solidifies, have substantially the same refractive index as the layers of films 12 which com¬ prise the tomograms. Furthermore, in order to yield substantially invisible interfaces with the successive layers of the same plastic 30, the first plastic mater¬ ial must not cure or solidify where it is exposed to air. These requirements are readily met, e.g. by the above-noted commercially available, polyester based "Fibrelay" "Clear Cast" liquid plastic. In accordance

^ - with standard practice in the plastic embedding arts, the first liquid plastic material 30 is admixed with a suitable catalyst (not shown) before it is placed in the mold 18. When the above-noted "Fibrelay"^* "Clear Cast" polyester is used, the catalysts is methyl ethyl ketone peroxide. The plastic 30 then cures or solidifies as a result of further polymerization or cross-linking under the action of the catalyst. The above-noted "Fibrelay" "Clear Cast" plastic material 30 substantially cures in approximately 4 hours. The curing time, however, may be affected by the amount of catalyst (not shown) used. After the first layer 28 of the first plastic material 30 has cured, the first tomogram 12 is placed flat on the top of the first layer 28 so that the aper¬ tures 26 of the tomogram 12 register with the aligning pins 24. Then a new layer of the first liquid plastic material 30 is poured into the mold 18 to cover the first tomogram 12. The thickness of the new, second layer 32 determines the spacing between the several tomograms 12 embedded in the display 10. As the several layers of the first liquid plastic material 30 are ap¬ plied, special care must be taken to prevent foaming and remove air bubbles from the respective layer and from behind the substantially horizontally disposed tomogram 12. Removal of air bubbles is facilitated, and foaming of the above-noted Fibrelay "Clean Cast" plastic is substantially prevented by application of a small amount of styrene monomer upon the uncured layer of plastic.

After the second layer 32 of the first plas¬ tic material has substantially cured, the steps of laying a tomogram 12 on top of the cured layer, pour¬ ing of a new intermediate layer 34 of the first liquid plastic material 30, and allowing the curing of the same, is repeated until all the tomograms 12 are deposited in the mold 18. Because the first liquid plastic mater¬ ial 30 does not cure where it is exposed to aid, each subsequent layer cross-polymerizes or cures with a top surface of the previously laid layer. Consequently, the interfaces of the individual layers of plastic are not visible in the final display 10. While the several intermediate layers 34 of the first liquid plastic mater¬ ial 30 are poured, care must be taken that each of the resulting layers be of the same thickness as the previ¬ ous one. This is necessary to ensure even spacing of the tomograms 12.

After the last tomogram has been positioned on top of the last cured layer of the first plastic material 30, a layer 36^' of a second plastic material 38 is poured. The layer 36 of the second plastic material 38 comprises an outer surface of the display. There¬ fore the second plastic material 38 must cure even where it is exposed to air, and also must have, after curing, substantially the same optical properties as the layers of film carrying the tomograms 12. A suit¬ able second plastic material 38 for the practice of the present invention is sold under the name "Hi-Glow" and is manufactured by the above-noted Fibrelay Inc. This material is also a polyester based plastic, and is ad¬ mixed with methyl ethyl ketone peroxide catalyst before final curing is affected. Foaming of this material may be prevented, and air bubbles may be removed by ap¬ plication of acetone.

After curing of the last layer 36, the entire block of solid plastic 14 which comprises the three- dimensional display 10, is removed from the mold 18. The aligning pins 24 are usually left within the block 14. Referring now to Figures 8-10, a second pre¬ ferred embodiment 40 of the three-dimensional display of the present invention is disclosed. In contrast to ^* the first preferred embodiment 10, the second preferred embodiment 40 does not comprise a permanent display. The second preferred embodiment is not intended pri¬ marily for preservation of the three-dimensional image of an object, organ or body portion under scrutiny, for later reference. Nor is the second preferred embodi¬ ment primarily used as a demonstration model or study aid. Instead, it is intended for quick temporary assem¬ bly so that a diagnosing physician (not shown) may in¬ spect the assembled tomograms in a three-dimensional view for diagnostic purposes without rendering impos¬ sible a later viewing of the same tomograms in a con¬ ventional "two-dimensional" manner.

Thus, in accordance with the above-stated ob¬ jectives, a plurality of the layers of film carrying the sequential tomograms 12 are assembled in a parallel, spaced, aligned relationship on^* a suitable rack 42. The rack 42, which is schematically shown on Figures 8-10, includes four pins 44 which are inserted into suitably located apertures 46 in the respective corners of the tomograms 12. Proper spacing of the individual tomo¬ grams 12 from one another is accomplished by insertion of spacers 48 between the tomograms 12. For the sake of simplicity of illustration, the spacers 48 are only shown on the cross-sectional view of Figure 10.

In accordance with the above-noted basic principles of the present invention, the assembly of the tomograms 12 on the rack 42 is inserted into a container or tank 50 which contains a liquid 52 having substanti¬ ally the same refractive index as the refractive index of the film carrying the tomograms 12. As a result, the films become substantially invisible in the li¬ quid 52, and a three dimensional image of the organ or body portion under scrutiny becomes visible in the con¬ tainer 50. Several liquid compositions, particularly mixtures of organic solvents, may be suitable for the above-stated purpose,a further requirement in this re¬ gard being that the liquid not be destructive to the tomograms 12. After an examining physician (not shown) has viewed the assembly^* of tomograms 12 as a three- dimensional picture, the tomograms 12 may be disassem¬ bled from the rack 42 for conventional viewing and safe keeping. If desired, a holographic photograph of the three-dimensional assembled tomograms 12 can be taken by conventional holographic methods. In this case, the three-dimensional image of the organ or body portion under scrutiny may be recreated at a later time by con¬ ventional holographic techniques.

What has been described above is a device comprising a novel assembly of a plurality of cross- sectional images of an object, which provides a unique three-dimensional image of the object. Several modifi¬ cations of the above-described novel device and of the method of making the same, may become readily apparent to those skilled in the art in light of the above dis¬ closure. Therefore, the scope of the present invention should be interpreted solely from the following claims.

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Claims

WHAT IS CLAIMED IS:

1. A device for effectively providing a three- dimensional image of an object, the device comprising: a plurality of cross-sectional images of the object, each cross-sectional image of the object being a substantially flat, sub¬ stantially two-dimensional transparent image, carried on a substantially transparent support layer, the cross-sectional images being taken in substantially regularly spaced parallel planes within the object, in the device the cross-sectional images being aligned with one another and being disposed at substantially regularly spaced intervals in the same order as cross-sectional images were taken of the object, and a substance having^*** substantially the same refractive index as the support layers of the cross-sectional images, the cross-sectional images being fully embedded in the substance.

2. The invention of Claim 1 wherein the images are carried on conventional film, and the substance is clear, solid plastic.

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3. The invention of Claim 2 wherein the film ia a polyester film and the plastic is a substantially polyester based plastic.

4. The invention of Claim 1 wherein the de¬ vice comprises a substantially rectangularly shaped solid block of plastic.

5. The invention of Claim 1 wherein approxi¬ mately 5-25 cross-sectional images are embedded in the substance.

6. The invention of Claim 5 werein the cross- sectional images are mounted at an approximate distance of 0.05-0.15" from one another. ^•

7. A device for providing a three-dimensional simulation of an anatomical object, comprising a part or the entire body of a live human being, the device com¬ prising: a plurality of parallel, cross- sectional images of the anatomical object, the cross-sectional images being taken at substantially regularly spaced intervals in the object by medically accepted non-des¬ tructive techniques such as computer assist¬ ed tomography, the images being carried on substantially transparent support layers and being aligned with one another and mounted at substantially regularly spaced intervals relative to one another, and an embedding substance completely sur¬ rounding the plurality of images assembled in the device, said embedding substance having a refractive index relative to visible light which is substantially the .same as the refrac¬ tive index of the support layers.

8. The invention of Claim 7 wherein the embedding substance is a clear, unitary block of plastic having no interior visually discernible interfaces.

9. The invention of Claim 8 wherein the support layers are polyester based films, and the clear plastic comprises polyester.

10. The invention of Claim 7 wherein the number of the cross-sectional images is approximately 5-25.

11. The invention of Claim 10 wherein the cross- sectional images are located approximately 0.05-0-15" from one another.

12. The invention of Claim 7 wherein the embedding substance is a clear liquid.

13. A process for providing an assembly of a plur¬ ality of parallel two-dimensional cross-sectional images of an object, carried on a substantially transparent and substantially two-dimensional support, said assembly com¬ prising an effective three-dimensional simulation of the object, the process comprising the steps of: placing a first layer of suitable first liquid plastic material into a suitable mold, said first liquid plastic material being adapted to harden upon passage of time where not exposed to air; allowing said first layer of said first plastic material to substantially harden; placing a first cross-sectional image of the object upon the first layer; pouring a second layer of the first liquid plastic material upon the first layer so as to cover the first cross-sectional image with the first liquid plastic material; allowing the second layer to substanti¬ ally harden; successively repeating the steps of placing a cross-sectional image on top of a hardened layer of the first liquid plastic material, pouring a layer of the first liquid plastic material on top of the hardened layer so as to cover the cross-sectional image, and allowing the poured layer to harden, until substantially all of the cross-sectional images are embedded in the first plastic material, the cross-sectional images being placed in align¬ ment with one another in the same order as they were taken of the object, a thickness of the second and of each successive layer of the first plastic material being substantially equal so that the cross-sectional images are substantially evenly spaced in the assembly, the first liquid plastic material when hardened being transparent and having substantially the same refractive index toward visible light as the support of the cross-sectional images; pouring a layer of a second liquid plas¬ tic material on the last hardened layer of- the first liquid plastic material, said second liquid plastic material being adapted to har¬ den upon passage of time regardless of ex¬ posure to air, and after hardening being transparent and having substantially the same refractive index toward visible light as the support of the cross-sectional images; allowing said layer of the second liquid plastic material to harden, and removing the assembly of the cross- sectional images and of the hardened first and second liquid plastic materials from the mold.

14. The process of Claim 13 wherein the support of the cross-sectional images is a polyester film, and wherein the first and second liquid plastic materials are polyesters.

15. The process of Claim 13 wherein all but the last of the cross-sectional images is covered by the suc¬ cessive layers of said first liquid plastic material, and wherein the process additionally comprises the step of placing the last cross-sectional image on the last har¬ dened layer of said first liquid plastic material, and wherein said second liquid plastic material is poured to cover the last cross-sectional image.

16. The process of Claim 16 wherein the support of the cross-sectional images is a polyester film, the first and second liquid plastic materials comprise poly¬ esters, and wherein each of the steps of allowing the poured layers of the first and second plastic materials to harden is of approximately four hours duration.

17. A process for assembling for the purpose of three-dimensional viewing and illustrating a plurality of successive, parallel cross-sectional images obtained by computer assisted tomography and the like of an ana¬ tomical object, such as a portion of the body of a live human, the process comprising the steps of: pouring into a suitable mold several successive layers of a first liquid plastic material which is adapted to harden upon passage of time except where it is exposed to air.; successively allowing each layer of the first liquid plastic material to harden except on its upwardly located surface wherein the layer is exposed to air; successively placing one cross-sec¬ tional image on top of each hardened layer of the first liquid plastic material, each cross-sectional image being covered after said placing step by the next layer of the first liquid plastic material, the layers of the first plastic material which separate the cross-sectional images from one another being of substantially equal thickness, the cross-sectional images successively placed on the hardened layers being in substantial alignment with one another, and being placed in the same order as they were taken off the anatomical object; pouring a layer of a second liquid plas¬ tic material on top of the last hardened layer of the first liquid plastic material, the second liquid plastic material being adapted to harden upon passage of time regardless of exposure to air; allowing the layer of the second li¬ quid plastic material to harden, and removing the assembled cross-sectional images and hardened plastic materials from the mold, the first and second plastic mater¬ ials when hardened being -transparent and having substantially identical refractive in¬ dex with a support carrying the cross-sectional images.

18. The process of Claim 17 wherein the support of the cross-sectional images is a transparent polyester film, and the first and second plastic materials com¬ prise polyester.

19. The process of Claim 17 wherein the number of cross-sectional images assembled is approximately 5 to 25.

20. The process of Claim 17 wherein the thickness of each hardened layer of the first plastic material is approximately 0.05-0.15".