US2523050A - Method and apparatus used in - Google Patents

Description

Sept. 19, 1950 v s. H. NIGHSWANDER I METHOD AND APPARATUS USED IN X-RAYING OBJECTS Filed Oct. 16, 194s '32 5P3: as

INVENTOR: 5151mm H Mam upm av %TTOR NEX S.

Patented Sept. 19, 1950 METHOD AND APPARATUS USED IN X-RAYING OBJECTS Sterling H. Nighswander, Davenport, Iowa, assignor to International Basic Technique Research Institute, Inc., St. Louis County, Mo., a

corporation of Missouri Application October 16, 1946, Serial No. 703,598

I 13 Claims.

1 r This invention relates to improvements in methods andapparatus that'are used in X-raying objects. More particular1y,'this invention relates to improvements in methods and apparatus that areused to determine the true relative positions of two spaced objects by means of X-rays and X-ray film.

"It is, therefore, an object of the present invention to provide an improved method and apparatus for determining the true relative positions of two spaced objects by 'means of X-rays andX-rayfilm. 1' i V I In certain methods fof treatinggpersons for various ills and bodily ailments, it is'important to. determine with considerable accuracy the true relative positions of the top portionsof the femur bones of those persons. Obviously, because of the layers of muscle and tissue of those persons,

relative positions of the shadows cast by the top portions of the femur bones disagreed with the by the other diagnostic methods.

determination ofzthe relative positions of those portions of the femur bones that was obtained In some of those other "instances, nationof the persons bone structure by means of X-ray photographs showed different relative positions of the top portions of the femur bones,

although each time the person had his or her feet on the same leveled surface. Investigation provedthat where the photographic plate gave a true indication of the relative positions ofthe top portions of the femur bones, the persons had I stood in such a way that the top portions of the femur bones were equidistant from the photoit is impossible to make directphysical measurej ments ,of the positions of those particular portions ofthe femur bones relative to'a common base or point. Accordingly, a method has been devised that permits measurement of the true relative positions of the top portions of the femur bonesof a person despite the presence of the layers of muscle and'tissue of that person and that method utilizesX-rays which passthrougnthe graphic plate. Where 7 the photographic plate did not give a true indication of the relative positions of those portions of the femur bones, the persons had stood in such a way that the top -por-' tions of the femur bones were not equidistant from the photographic plate. This result is due to the fact that the X-rays emanate from a virtual point source and diverge as they move toward the photographic plate and that, therefore, two horizontally-spaced objects must be at persons muscle and tissue. In practicing that method, itis customary to have the personstand with'his or her feet ona leveled surface,.and to stand immediately in front of a large size;pho-tographic,platewhileiX-rays are projected through his or her body onto the photographic plate.

Thereafter, the photographic plate is developed and mounted on the front of an X-ray viewing box. Where the X-ray viewing box is perfectly vertical and where the photographic plate is made precisely parallelto the X-ray viewing box, the positions of the shadows cast on the photographic plate by the top portions of the femur bones can be determined relative to a common base or point. Sincethe shadows on the photo- A graphic plate were cast, by the top portions of the femur bones, a determination of the-positions of those shadows relative to'a common base or point would seem to provide a true determination the same level, at the same distance from the photographic plate, and must be disposed at equal distances on opposite sides of the ray-emitting aperture to cast shadows which have the same positions relative toa common base or point.

Accordingly, whenever the top portions of the femur bones of a person are at different distances from the photographic plate, the shadows cast by those portions on that plate will not be truly indicative of the relative positions of those portions of thefemur bones. In recognition of this fact, it is customary to have'the person align his or her body between the ray-emitting aperture and the photographic plate in such a way that the top portions of the femur bones are equidistant from the photographic X-ray plate but this is not possible in all instances because the various bones of a persons body do not have precisely of the positions of those portions of the femur bones relative to a common base or point. many instances the determination of the relative positions of the shadows cast by the top pore tions of the femur bones did corroborate and make definite the determination of the relative positions of those portions of the femur bones that was obtained by otherdiagnostic methods;

but in other instances, the determination of the the same positions and proportions in .all instances, and there may be some shifting of the various portions of the bone structure relative to each other because of disease or accidental injury, As a result, it sometimes happens that the top portions ofthe'femur bones cannot, be set precisely equidistant from the photographic plate and in those instances, distortion of the picture on the photographic plate will result and the shadow cast by the top portionof one femur bone will not bear the same relation to the shadow cast shown on the photographic plate.

by'the top portion of the other femur bone as that portion of the one bone actually bears to the top portion of the other bone. Consequently, in using the X-ray photographs to determine the relative positions of the top portions of the femur bones,,itis "necessary to calculate a correction factor based on the angle of divergence'of the X-rays and the distances of the top portions of the femur bones from the photographic plate.

and to apply that correction factor to the data obtained from the photographic plate.

In making his calculation, the diagnostician must remember that the' X-rays, which pass through the ray-emitting'aperture of the X-ray device diverge vertically and horizontally and will cast shadows that are distorted in both directions.

Accordingly, the calculation must take into account both the vertical and horizontal divergence of the X-rays. Consequently, in usingX-ray'pho tographs to determine the relative heights of two spaced objects that arenot'accessible for direct a physical measurement, it has become necessary I to make complicated and laborious'mathematicalcalculations' .and determinations before the diagnostician can trust the information obtained from the photographic plate'i The making of v thefmathernatical calculations is not only laborivous but it is always subject to error andsuch error can be harmful where the relative positions of the top portions of the femur bones aroused '7 n gauging the amount of treatment the bone structure of theperson should receive. The present invention obviates the :labor. and possible errors involved in. the use-,oi these mathematical 1 the objects is spaced a'considerable-distance fartier from the photographic plate than theother is spaced from that plate. It is, therefore; .an :object of the present invention to provide a disand. vertical divergence of .X-rays.

In the reading of X-ray photographic plates,

it is customary to affix the photographic plate to the front of a viewing boxand to provide a source or" illumination in the box behind the photographicplate. The distortion meter of the present invention can be used with such a box by making themeter of a transparent material, and

by securing it to a transparent support that is attached to the viewing box. Moreover,- theidistortion meter can be pivoted to the transparent su'pportso it can be rotated to any part of .the photographic plate to provide accurate reading oi all portions of-that plate.

-The X-rays-which emerge from the aperture of the X-ray machine and follow a path that is precisely perpendicular to the plane of the photog'raphicplate will pass 1 through the body of the person being X-rayed in such away that they'iwill cause the portion or the body immediate l-y in iro'nt of the faperture to cast. ashadow t-hat ha's the same positio'n' as-the aperture, :but ail-ofthe other X ra'ys will diverge fromth'at' path and will cast shadows that do not have the same position as the objects through which those rays passed. As a result, one portion of the distortion meter must make no correction for distortion while other portions of the distortion meter mustmake corrections of varying degree for distortion, and thesaid one portion of the distortion meter must be superimposed over that -...Lpart of the photographic plate which was directly opposite the aperture of the X-ray machine. The

present invention makes this possible by providihg a pivot at that point on the distortion meter 2 which corresponds to the point of impingement of the distortion-free perpendicular path on the photographic-plate, and by securing that pivot to a transparent support on an X-ray viewing box so it will overlie the portion of the photographic plate that was opposite the aperture of the X- 'ray machine. This arrangement not only enables the distortion meter to correct for the distortion of .variousrsp'aced shadows on -the. photographic plate, but it also'enables the distortion meter to be moved overall portionsoi. the-photographic plate to correct for the distortion of all shadows on that plate. It is; therefore, anobject of the present invention torprovide aviewing box with a transparent support that maintains the pivot of a distortion'meter .in-register with that portion of the photographic plate which was directly opposite the aperture of theX-ray machine.

Other objects and advantages of the present invention should become apparentfrom an examination of the drawing and accompanying description.

In the drawingand accompanying description, a preferred embodiment of the present invention is shown and described'but it isto be understood that the drawing and accompanying description are for the purposes of illustration only and do not'limitthe invention a'nol'the'inventio-n will be defined -by-theappended claims.

In the drawing, Fig; 1 is a perspective view of an Xray viewingbox' which is equipped with the distortion meter of the-present invention, and

Fig. 2 is a frontelevationalview of the distortion meter shown in Fig. 1. w

Referring to the-drawingin detail, the number 16 denotes an X-ray viewingbox which has tortion meter that compensates for the horizontal opaque sides and top and-has a translucent plate i2fat the fronttloerect-Borderingthe plate [2 is a retaining frame'id that has spaced clips '16 attached thereto. The'clips I6 extendover and bear against portions of theplate" i2. Whenever the edges of aphotographic p'late are inserted between the clips IE and the plate'-l2, that phoftographic p'late willbe held in position against *the -plate l2 bythe clips lfi.

Also mounted on the frame M are projectingstuds, bolts or screws [8 and the studs lli support a'horizont'ally disposed transpar'entsupport ZO. -The support 20 has notches 22 at the-opposite-ends thereof and these notches cooperate with the studs E8 to i maintain the support 20 in position relative to the viewing boxia.

Positioned -in'the approximate center of the "supportid is a pivot 24,and' this pivot rotatably carries a distortion meter 28'. The distortion meter-25 is of transparent-material and it has an opening 28 therethrough that can receive and fit over the pivot ii -carried by the' support 20.

Extending: downwardly 'from the opening 28 is a series of spaced openings 3il that lie on a True line which would,if -extended, pass through the opening 28. :Angularl'yspaced fromthe aligned openings 35E 1 of the"Tr-ue lineare other lines '32,

' val: of two inches.

' .yr Formed on the left hand tion meter 26 is a scale :56 that can be a metric 34, 36, 38 and 48 that are positioned on one half of the meter 26, and angularly spaced from the aligned openings 38 of the True line are other lines 42, 44, 46, 48 and 58, that are positioned on the other half of the meter 26. The lines 32, 34, 36, 38, 48, 42,44, 46, 48 and 58 may be marked on the distortion meter 26 in any suitable manner, but they can easily be inscribed in the material ofwhich the meter '26 is made. Each of the lines 32, 34, 36, 3B, 48, 42, 44, 46,48 and 58 is positioned relative to the openin 28 so extensions of those lineswo-uld pass through the opening 28. .As a result, the lines 32, 34, 36, 38, 40, 42, 44, 46, 48 and 58 can be said to extend radially outward from the opening 28. Inclined at an angle to the lines 32, 34, 36,38 and 48 and to the 7 True? line are a number of straight lines 52 that terminate in the spaced openings 38 of the True line One half of the 1ines.52 are shown as being dotted, but this is done to make the meter 26 easier to read and if desired,the dotted lines can allbe madesOlid. Inclined at an angle to theines 42, 44, .46, 48 and58 and to the True lineare a number of lines 54. that also terminate 38;,and48 are figures which correspond to the number of inches between the photographic plate andthe object being X-rayed. These figures,

which are even numbers, ar e given in terms of inchesv and are separated by the common interlines; 52 are straight and have the same slope. Adjacent the lower ends of lines 42, 44, 46, 48 and .58; are figures, which areodd numbers and are vjgiven; in terms of inches However, it will be noted thatwhile lines 42,44, 46, 48 and. 58 are or Englishsoale. Only a portion of the scale 56 is shown in, the drawing, but the scale 56 will preferably extend along theentire length ofthe distortion meter 26 so it can be used to measure the distance between points on the photographic plate. The left hand edge ofthe distortion meter 26 is,"and the right hand edge of that meter nation of the-lines 52 and will be determined to a large extent'by the perpendicular distance between the photographic plate and the aperture of the -X-r-ay machine, but those spacingspan be determinedwith great precision in each case, With the distortion metershown, at a reduced "scale, in the'drawing, the perpendicular distance from the photographic plate to the aperture of the Xfray machine was sixtyinches.

*Accm'ding to the principles and teachings of the present invention, a person or object is 'placedbetween an X-raymachine and a photo- I graphic plate, the distances between the photo- "graphic plate and the particular portions of the object or 'per'sonto be X-ra'yed are carefully A cordingly, the reference,

edge of the distor photographic plate.

measured and recorded, and then theX-rays are projected through the body of the person or object and are caused to fall upon the photographic plates Thereafter, the photographic plate is developed and is held in front ofthe translucent plate 12 of viewing boX I8 by clips 16. Thereupon'the support 28 can be set so the notches 22 thereof rest on and are held by the studs l8and at this time, because of predetermined positioning of the photographic plate relative to the aperture of the X-ray machine,,the pivot24 of the support 28 will overlie that point on the photographic plate which was directly opposite the aperture of the X-ray machine. As a result, telescoping of the opening 28 of the distortion meter 26 over the pivot 24 will correctly position the meter 26 relative to the photographic plate.

0nce this has beendona; the various, Objects whose'true relative heightsare to the determined are located on the photographic plate and-reference is madeto the previously recorded dis,- tances between each of those objects and the photographic plate. Thereafter the one particular line, of the group of lines 32, 34, 36, 38, 48, 42, 44, 46, 48 and 58, which most closely corresponds to the distance between the object being measured and the photographic plate is placedso it intersects the shadow cast by that object onthe Then, that inclined line, of the groups of lines 52 and 54, which is closest to the intersection of the shadow and the one particular line. of the group of lines 132, 34, 36, 38, 48, 42, 44, 46,48 and 58 is followed to the opening 38 at the end thereof and a pen, pencil on other objectyis inserted through that opening 38and is used tomake a mark on the photographic plate as the distortion meter 26 is rotated about the pivot 24. This forms anarc on ,the photo,-

graphic plate and whenthe dist0rtion meter 26- is set so its left hand edge intersects the shadow of the object being measured and when ,a linegis drawn along that edge to form an intersection with the arc, that intersection represents the true relative position of the object which cast the shadow on the photographic plate. The intersection will indicate the true vertical position of the object and will also indicate the truehori zontal position of the object since the distortion meter 26 compensates for thevertical; and ,horizontal divergence of the 'X-rays. In other words, the intersection will be the point, ,th'at 'was directly opposite the object, when the photo,- graphic plate was made,and'i s thus the perpendicular projection of that object. Having es tablished the true position of the onepbject, the

52 and 54, which is closest to the intersectioniof ''the shadow and the one particular line" of the group of lines 32,34, 36,38, 40, 42, 4,4, 46, 48 and 58 is followed to the opening 38 at the end there;-

of,'and a pen, pencil or otherobjectis inserted through that opening 38- and is used to make a mark on ,the photographic plate as the distortion meteris rotated about the pivot 24. .This

forms an are on the photographic plate and when the distortion meter .26 is (set so its left hand edge intersects the shadow of the other object and when a line is drawnalong'thatiedge to form' an intersection' with the are; thatinte'rsection represents the true horizontal" and Vrti 7 seal zppsition .ofrthe secondiobject. A measurement of the position of the-two intersections-rel- :ative ;to .-a common ,base or level {will provide ,a true'and; accurate indication of the relative .posi- ;tions of zthe objects. which cast, the shadows .on the photographic plate. :In determining :the :rel- :ative :positions of the intersections on the photo- Lgrap'hicplate, a T -.square, a try-squareror other similar vdevice can be set against the irame :lzil and canibe used :to draw. two horizontal :lines and two vertical "lines through the intersections .on the photographic plate. Thereafter, rotation of the meter .26 until its left hand edge is .vertical permits the-scale 56 on that edge .to indicatethe distance between the two horizontal lines; rotationof the meter 26 until its left hand edgeis horizontal permits the scale 56 to indicate the distance hetween -thetwo vertical lines. These distances are true indications of the differences "between the vertical and horizontal positions oi--the-objects"that cast the shadows on the photographic plate.

' -In;some instances, horizontal and vertical lines can be formed in the photographic plate itself and these linescan be used to measure the relative-positions of the intersections. In using these lines, the distances-between the intersections-and ;any-"horizonta-l -or vertical line can be measured to provide a-measure of the relative--positions o1" the objects which cast the shadows. The lines on the photographic plate can be preparedein a number of ways, but one way utilizes india ink lines in 'the -inner surface of the holder for the photographic-plate; and those india ink lines will cast shadows on thephotographic platewhichwill be aperman-ent'part of 'thatplate.

Where the distances between :the photographic plateand the' objects, whose relative heights are 'to be determined, are not integral inches, it is ,-r rece ssary--'to-interpolate; Similarly, where the "intersection between the shadow on the photographic p1 'ate and one of theradially extending lines- 3233!, F36, 3 8, fi0, 42, 14, 16,43 and-50 does not lie on one of theinclined lines 52 and 545mterpolation is necessary. This can be done visually. ;I n indicating the final interpolated intrsecftignjtiwould be advisable to maketwo preliminaryarcs through the openings '30 and then to page the; interpolated are at the right I distance between them; V 7 '.Where" the Objects, whose relative "positions are 'to'fbe Irreasuredp are pressed against the photograprrre iate, andiwhere those objects do not have an appreciable thickness; there, will he no distortion, and ;the true position of such objects can 'fbe indicated "by placing the "Irue" line, over 'thelshadows cast by those objects and making a mark thr u h the app o ate ng 30 f th iI lle, Where, .however,;the objects are spaced iroinjjthe photographic plate, there will be 3911s,, eralole distortion and .the appropriate radiallyextendingilinesfiz,'34,3638, '40, r2 44, es, 4 8,: nd 5.0, and the appropriatelines ;5.;2 an d54, will h 'veltohe used to indica e thetrue r la ire'posk t ig iislif those objects;

ent invention has. been shown and described ,in v

Th drawin and. a company d s iption, it

shonldhe obviou 1to-t,hos,e skilled in the .art ,that

Tea

8 various changes can be made in the ;form.of the invention without affecting the scope thereof.

What I claimis:

1. A Viewing box ,for X-ray photograph plates that comprises an enclosure with opaque sides and top, a translucent front plate, asource of illumination behind'sa'id translucent plate, means to secure a photographic plate adjacent to said translucent plate, a supporting bar of substantiall transparent material secured to said enclosure, a pivot carried by said bar, said platesecuring means and said supporting bar coacting ,to cause said pivot to overlie that point on the photographic plate which was directly opposite the aperture of the X-ray machine, and -a substantially transparent indicator rotatably secured to said pivot, said indicator having :a plurality of: spaced openings therethrough, said indicator also having :a plurality of lines that extend radially outwardly 'irom said pivot, said indicator also having a plurality of lines thatare angularly disposed relative to said radially extending lines and that terminate in said openings, said radially extending lines and saidangularly disposed lines being dimensioned and being spaced relative to said openings'whereb said indicator can be used in making marks on said photographic plate which will indicate the true positions of the objects that cast shadows on said photographic plate.

7 2. The method of determining the exact position of a plurality Of objects that comprises X-raying said objects, placing the photographic "X-ray plate-adjacent the translucentiront of an X-ray-viewing box, superimposing on said photographic plate a distortion-meter which has radially extendinglinesthat project outwardly from that point on the X-ray plate which was opposite the aperture of the X-ray machine and that also has angularly disposed lines which intersect said radially extending lines and that terminate in spaced openings, selecting the radially extending lines which correspond .to the distances between the photographic'plate and objects at the time the X-ray plate was made, selecting the angularly disposed lines which intersect the radiallyextending lines at the shadows of the objects being measured, following the angularly disposed lines to the openings, making marks through said openings as said meter is rotated, passing lines 'througheach of the shadows and said ,point of the X-ray plate which was opposite the aperture of the X-ray machine and extending those lines to form intersections with the marks that were made as the meter was rotated, and then com- ;paring the relative position of said intersections.

3. The combination of a support, a distortion meter, and apivot that extendsbetween said sup- .port .and said distortion meter and permits rotation of said distortion meter relative to said support, said combination being adapted for use in determining the position of objects that cast shadows on Xray photographic plates, said dis tortion meter comprising a transparent body, a series of aligned openings extending radially outwardly from said pivot, angularly spaced lines that extend radially outwardly from said pivot, {the angular spacing-of said lines being a function graphic plate at the time'the X-ray photographic plate was exposed, saidsupport being disposable adjacent a photographic X-ray plate to'place said pivot in register'with that pointin said X-ray'photographicplate which was directly oppositetheap'erture of the X-ray machine;

4:A ;viewing box for X-ray photographic plates that comprises an' enclosure with opaque sides and top, a translucent plate, a-source of illumination behind said translucent plate, means to'secure a photographic plate adjacent to said translucent plate, a supporting bar of substan tially transparent-material secured to said enclosure, a pivot carried by said bar, and a substantially' transparent indicator rotatably secured to said pivot, said indicator having a pluplates that comprisesan enclosure with opaque sides and top, a translucent plate, a source'of illumination behind said translucent plate, means to secure a photographicplate adjacent to said,

translucent plate, a supporting bar of substantially transparent material secured to said enclosure, a pivot carried by said bar, and a substantially transparent indicator rotat'ably sccuredto said pivot, said indicatorhaving a plurality of reference points thereon and having a plurality of openings therethrough, said reference points being adapted to be placed in register with ,the shadows cast onlsaidphotographic plate' by objects being X-rayed, said openings being adaptedto overlieother portions of the photographic plate andfindicate the radial distance of thefperpendicular projections or the objects that cast the shadows on said photographic plate.

6. The combination of a support, a distortion meter, and a pivot that extends between said support and said distortionmeter and permits rotation of said distortion meter relative to said support, said combination being adapted for use in determining the position of objects that cast shadows on X-ray photographic plates, said distortion meter comprising a transparent body, a series of aligned openings extending radially outwardly from said pivot, angularly disposed lines that extend from said aligned openings and define the loci of points at various distances from the divergence-free path of the X-rays, and

,marks on said lines indicating the distances be tween said points and the photographic plate when the photographic plate was exposed, said support being disposable adjacent a photographic X-ray plate to place said pivot in register with that point in said X-ray photographic plate which was directly opposite the aperture of the X-ray machine.

7..The combination of a support, a distortion meter, and a pivot that extends between said i 1 support and said distortion meter and permits rotation of said distortion meter relative to said support, said combination being adapted for use in determining the position of objects that cast shadows on X-ray photographic plates, said dis tortion meter comprising a transparent body, a

. True line on said body, a plurality'o f lines on said body that are angularly spaced from said True line, said'plurality of lines defining the loci of all shadows of points spaced at predetermineddistances from the photographic -X-ray plate, and markings on'said body that correlate points on said plurality oflines with corresponding points on said True line, said support being disposable adjacent a photographic X-rayplate to place said pivot in register with that point in said X-ray photographic plate which was directly opposite the aperture of the X'-ray machine.

8. A distortion meter that comprises a transparent body, a True line on said body that is disposed radially of a reference point on said body, a plurality of lines that extend radially 0ut-' wardly from said reference point to define the loci of the shadows of all points that are be-' tween the X-ray machine and an X-ray photographic plate and are spaced at certain prede' termined distances from said photographic plate,

other lines on said body that are angularly dis- I posed to said radially extending lines and that extend'to said True line to correlate points on said radially extendinglines with corresponding line on said body, a plurality of lines on said body that are angularly spaced from said True line;

said lines including therein the loci of all shadows of points spaced certain predetermined distances 7 line} aplurality of openings that lie 'onsai-d True line of said meter and are at the termini of said inclined lines, and an edge which extends radially outward from said reference opening, theintersecticns of said plurality of lines and said inclined lines indicating the positions of shadows cast by objects, the openings on the True line indicating the distances between said reference opening and the perpendicular projections of the points which cast said shadows, and the edge cooperating with arcs, formed by the openings as the meter was rotated relative to the photographic plate, to indicate the true position of the points which cast the shadows.

10. The method of determining the exact position of a plurality of objects that comprises X- raying said objects, measuring the distance between said objects and the photographic plate which th X-rays struck, developing that photographic plate, drawing lines between the shadows of said objects and that point on the photographic plate which wasdirectly opposite the aperture of the X-ray machine when the objects were X-rayed, superimposing a distortion meter over said photographic plate that will indicate the shortest distances between the divergencefree path for the X-rays and the objects which cast said shadows, and using that meter to indicate the positions on said lines of the perpendicular projection of the objects which cast the shadows, as by locating on that meter points spaced 'from said divergence-free path of the X-rays distances corresponding to the'distances between.saiddivergencesfree path and the objects which cast said shadows and'superimposing thosefpoints over said lines to indicate the True positions of the objects which cast the shadows on the photographic plate.

11. .The method of determining the exactposition of a plurality of objects that comprises X- raying said objects, measuring the distance between saidobjects and the photographic plate which the X-rays struck, developing that photographic plate, indicating on the photographic platedshe loci of all objects that could have cast the-shadows on'the plate, superimposing on the photographic plate a distortion mete provided with lines that facilitate determination of the shortest distances between that point on the photographic plate which was directly opposite theapertureof the X-ray machine and various points on that plate corresponding to objects at=various distances from the X-raypl-atanusing said distortion meter and the measured distances between the objects being X-rayedand thephotographic-plate 'todetermine the shortest distances between that point on the photographic plate which was directly opposite the aperture of the X-raymachine andthe points onthat plate corresponding to the objects which cast said shadows, and using those distances to indicate on thesloci theaperpendicular projections of the objects'that cast the shadows.

12. The method ofmeasuringthe true position ofrobjectswhich cast shadows on 'a photographic X-ray plate, that comprises establishing-the loci cfsall objects that could have cast said shadows by drawing lines between-said shadows and that point on thephotographic plate which .was directly opposite-the aperture of the X-ray machine when the photographic-plate was made, superimposing .an indicator over said photographic plate, that has lines thereon and openingstherethrough whichcorrect for the increased distances between the shadows on the photographic plateand that point on said plate which was directly opposite the aperture of'the X-ray machine due to the spacing of these objects from said photographic plate when said photographic plate was exposed, and using that indicator to make marks along said' lines that compensate for the divergence of the X-rays passing through said objects, as byinserting amarking implement through-said holes when'said'holes arein-register with said lines.

13. 'A'distortion meter that comprises a substantially triangular transparent body, a series of aligned openings extending from a point adjacent'the apex to a point adjacent the base of said triangle, lines thatextendradially from said point adjacent said apex. and are angularly.- spaced apart. andithatextendto points-adjacent the base of said triangle, one of the edges of, said'triangle being radially disposed of said point adjacent said apex and being registerable with shadows on an X-ray photographic plate and angularly disposed lines that extend from said aligned openings and intersect :said radially. extending lines, said radially extending lines including the loci of shadows-of points spaced at predetermined distances from'the X-:ray plateat the time the X- ray plate was made.

STERLING H. NIGHSWANDER.

REFERENCES CITED The foilowingireferences-are of ,record in the file of this 'patent:

UNITED STATES PATENTS Number Name Date 1,311,995 FitaPower Aug. 5, 1919 1,553,229 Fraser Sept. ;8, .1925 2,043,729 :Bilder June 9, 1936 2,118,773 Ball May 24, 1938 2,268,632 Anderson Jan. 6, 1942 FOREIGN PATENTS Number Country Date 13,199 Great Britain .July 21, 1900 23236 Great Britain Nov.. 28, 1914 353,426 iGreatBritain .July 20, 1931 56,864 Switzerland Apr. 15, 1911

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