CA1236935A

CA1236935A - Apparatus for orthoradial panoramic tomography

Info

Publication number: CA1236935A
Application number: CA000500296A
Authority: CA
Inventors: Hanspeter Delnon
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-01-25
Filing date: 1986-01-24
Publication date: 1988-05-17
Also published as: FI860338A0; AU5260386A; EP0193650B1; CH666803A5; DE3568303D1; EP0193650A1; JPS61172545A; ATE40852T1; FI87982B; JPH07100062B2; AU574886B2; DE8601539U1; US4694478A; FI860338A; FI87982C

Abstract

ABSTRACT OF THE DISCLOSURE

An apparatus for orthoradial panoramic tomography com-prises a radiation source for motion relative to a point of reference; a cassette means also for motion relative to said point of reference; a support for holding said radiation source and said cassette relative to said point of reference; a head positioning means including a first or intraoral device and a second or extraoral device for positioning the patient's head relative to said point of reference; a carriage connected with said support 11 and including a grip; a substantially vertical column for slidingly holding said carriage in a vertically defined position and having a vertical axis distanced from said point of reference; the apparatus further comprises a foot positioning means having a substantially horizontal reference face for defining a vertical distance from said horizontal reference face to said point of reference and a substantially vertical reference face for maintaining toe and/or heel portions of the patient's feet in a pre-determined position; a distancing means is provided for maintaining said at least one vertical reference face at a reproducible horizontal distance from said vertical ax-is of said column; and a means is arranged for determin-ing and reproducibly setting a vertical distance between said horizontal reference face and said point of refer-ence; said foot positioning means is arranged relative to said point of reference and to said vertical column axis for maintaining said patient, when standing on said foot positioning means and engaging said grip, in a re-producible and inclined position in which his longitudin-al body axis relative to said vertical column axis is at an angle (.alpha.) sufficient to cause an isotonic strain of brachial and dorsal muscles.

Description

~236935 BACKGROUND OF THE INVENTION

, (a) Field of the Invention This invention relates to radiography and specifically to an apparatus for orthoradial panoramic tomography.

(b) Description of the Prior Art Orthoradial panoramic tomography also termed orthopantomo-graphy (herein called OPT-technique for short) is a known X-ray method developed and described by Y, V. Paatero since about 1960 for radiographing curved surfaces, most frequent-ly the entire tooth-bearing area of both the upper and the lower jaw, to obtain a sharp and well defined yet flat image, photograph or other type of reproducible record, the ortho-radial pantomogram also termed orthopantomogram (herein called OPT for short).

For taking an OPT of the dental or another curved portion of a human patient's head region the entire part, e.g. dentition and adjacent mandibular areas, of interést must be penetrated perpendicularly by a narrow X-ray beam passing from a radiation source to a receptor or film that is sensitive to, and indicative of, X-rays in the radiolog-ical wave length.

While pantomography can be made with a stationary apparatusand a moving object, OPT-technique uses an apparatus where both the X-ray source and the film are moved; the film, in *

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~Z36935 turn, is held in a predetermined and generally curved con-figuration within an enclosure or cassette which, in gener-al, is moved by secondary motion; depending upon the shape of the area or stratum of radiological interest for the S particular OPT, X-ray soùrce and cassette means will each move along a more or less complex path around the immobile head of the patient. Fpr example, in order to take a con-centric pantomogram of a cylindrical object or plane one would rotate both the X-ray source and the film cassette carrier around a single common axis of rotation which, in turn, would coincide with the axis of the cylindrical ob-ject while the cassette is also moved relative to the cas-sette support.

Howe`ver, since typical objects of interest, such as the jaws, are not cylindrical, sharp X-ray imageing may require that the X-ray source and the cassette are moved along a particular path each involving more than one, say three or an infinite number of axes of rotation, i.e. a more or less continuously shifting position of the common axis of rota-_ 20 tion; in other words, orthoradial pantomography of a non-cylindric layer or stratum requires an excentric pantomo-gram including other than circular motion of the X-ray source and/or the cassette support. Numerous detailed stu-dies about optimizing such motion for specific OPT purpose can be found in the literature, cf. Acta Orthodontica 13 (1985) 445-453.

While the particular type of movement of X-ray source and cassette or film support is not believed to be essential , for the present purpose, the coordinated movement must be definitive, i.e. fully defined and reproducible with rela-tion to an arbitrary, yet fixed, point of reference gener-~6935 ally assumed to be positioned in a vertical plane ofsymmetry of the object of interest and/or the apparatus which plane, in turn, preferably will coincide with the mediosagittal plane of the patient when the OPT is taken.

For convenience and simplicity, such point is assumed here-in to be located at a fixed, or fixable, point of the ap-paratus such that the point of reference will be within I` the oral cavity of the patient when an OPT is taken with the apparatus.

Another reqùirement for the present apparatus is that the OPT can be taken of a patient in "erect position", i.e.
standing on his feet as opposed to sitting or lying;
from this further requirement it will be apparent that the predetermined motion of each the radiation source and the cassette means will be in an essentially horizontal plane, i.e. intersecting perpendicularly with the stand-ing patient's head axis in the mediosagittal plane.

OPT-apparatus meeting these requirements are available commercially from various sources; illustrative apparatus examples will be given below.

Detailed explanations of prior art OPT-apparatus will be found in the literature, e.g. U.S. Patent 3,673,408 (issu-ed June 27, 1972) and U.K. Patent 2,006"590 (published May 2, 1979); such apparatus may include head positioning means comprising separate devices for the upper head por-tion and the lower head portion so that the patient's head can be positioned relative to the above-defined point of reference so as to obtain reasonably well-defined OPTs.
However, even with the most stringent prior art head pos---_ , . . . , _ ,, ~X36935 itioning devices (intraoral support or "bit" structurecombined with extracranial points of contact so as to align the vertical axis of the patient's head) the OPTs, while sharp in the area of interest, are not fully repro-ducible, that is, "congruent" to the extent that a firstand a subsequent OPT taken some time after the other could be mutually superimposed and then match in all those por-tions that have not changed since the first OPT was taken.
In fact, the degree of reproducibility reported in the clinical studies that were discussed in the above-mention-ed review by Marxer, H. in Acta Orthodontica was not suff-icient to permit comparative measurements as pointed out by that author.

For diagnostic purposes, i.e. to determine time-dependent changes in a patient's head region, such as tumor dia-gnosis, control and treatment of undesirable dental chan-ges and the like purposes, it would be extremely desirable to provide for congruent OPTs in the sense defined above, i.e. permitting measurements of time-dependent changes be-cause unchanged portions would be apparent as reference - positions from congruent OPTs.

The research leading to the present invention has shown that reliable congruence of sequential OPTs cannot be achieved safely with prior art apparatus even if the pati-ent does not leave the apparatus at all,and even if thetime span between the first OPT and a sequential OPT is but a few minutes, not to speak of congruence of OPTs af-ter time intervals of weeks, months or even years between the first (or preceding) and a second (or subsequent) OPT.

~6935 osJscTs AND SUMMARY OF THE INVENTION

Accordingly, it is a main object of the invention to provide for an OPT apparatus that is capable of yielding congruent OPTs, even after passage of a time interval in the range of several weeks or months between a first or preceding OPT
and a subsequent OPT as would be typical for normal observ-ation intervals in a given medical field.

A further object of the invention is to provide for an app-aratus which allows congruent OPTs having a degree of con-gruence (expressed as linear divergence) of better than about + 1 % between a preceding and a subsequent OPT with a time lapse in the order of several weeks or months and probably up to some years (based on present experience).

Another object of the invention is to provide for an apparat-us that is capable of producing congruent OPTs with a struct-ure that requires neither substantial sophistication abovethat of prior art OPT-apparatus, nor a substantial increase in apparatus costs.

Yet a further object of the invention is to provide for an apparatus capable of producing congruent OPTs with an ess-entially minor structural variation of presently availableOPT-apparatus.

Further objects of the invention will become apparent as the specification proceeds.

Generally, I have found that even the most accurate position-ing of merely the patient's head relative to the point of reference is not sufficient for congruent OPTs and that the apparatus used must co-act with a body portion substanti-ally remote from the head so as to achieve a patient's pos-.. .. ... . . _ . . . .

12369;~5 ition that is not only reproducible but, additionally, cau-ses what can be termed a "muscularly induced body rigor"
lasting for the normal time of OPT-exposure typically from a few seconds to half a minute, and being of the type caus-ed intentionally by a patient who stands erect and is in-structed to hold himself by hi.s hands on a defined grip while his feet are po,sitioned in a forward direction in the apparatus such that the patient's center of gravity is I`
posterior to his heels. In other words, the OPT-apparatus must be modified such that it causes the patient to pro-duce "body rigor" effective to immobilize his vertebra by isotonically straining his brachial and dorsal muscles to the extent required for maintaining a reproducible back-ward inclination. Generally, the apparatus should cause that the patient's occipital joint will be in a reproduc-ible position during OPT-exposure as well and permit main-taining the vertical head axis at an angle of from about 175 to about 150 relative to the inclined longitudinal body axis; in other words, the plane of mastication of the patient should be substantially horizontal-even though the body axis is held in inclined position.
.

Specifically, I have found that the above objects and fur-ther advantages will be achieved, according to the invent-ion, by means of an apparatus for orthoradial panoramic tomography of a head region (term used herein to include any cranial, facial, oral, nasal, foraminal or cervico-vertebral area of radiological interest in addition to the dental area of prime importance) of a human patient in an erect position defined essentially by a longitudinal body axis when the appara-tus comprises:
(a) a radiation source arranged for predetermined motion, generally in an essentially horizontal plane relative to a point of reference (as defined above);

~236935 (b) a cassette means (generally including a film, an enclos-ure or cassette and a cassette support)for selective ex-posure of a film sensitive to X-ray radiation from the radiation source, said cassette means also being arrang-ed for predetermined motion, generally in an essenti-ally horizontal plane relative to the point of refer-ence;

f (c) a means for movably supporting the radiation source and the cassette means relative to the point of reference;

(d) a head positioning means including first and second de-vices for positioning the patient's head relative to the point of reference;

(e) a carriage connected with the support means and includ-ing a grip;

(f) a substantially vertical column for holding the carri-age in a vertically defined position and having a vert-ical axis (A ) distanced from said point of reference, and for slidingly displacing the carriage in a vertical direction, and when the apparatus additionally is provïded with:

(g) a foot positioning means having a s,ubstantially horizont-al reference face for defining a vertical distance be-tween the patient's foot soles (planta pedis) and the point of reference, and a substantially vertical refer-ence face for maintaining toe and/or heel portions of the patient's feet in a predetermined position;
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~236935 (h) a distancing means for maintaining the vertical refer-ence face at a reproducible horizontal distance from the vertical axis of column (f);

(i) a means for determining and reproducibly setting a vertical distance between the horizontal reference fa-ce and the point of reference; and wherein r the foot positioning means (g) is arranged relative to the point of reference and to the vertical column axis (Al) for maintaining the patient, when standing on the foot pos-10 itioning means and engaging said grip, in a reproducibly inclined position in which his longitudinal body axis (A2) relative to the vertical column axis (Al) is at an angle ( d ). that will cause an isotonic strain of brachial and dorsal muscles of the patient while engaging said grip 15 means, preferably at an angle (d) of between 5 and 30, more preferably between 15 and 25 and, typically, at ab-out 20.

It will be understood that the use of foot positioning means or "foot plates" has been known, per se, in radiology 20 for many years, e.g. in the distortion apparatus of U.S.
Patent 3,256,611 (issued 1966), or as an optional body support for the X-ray machine of U.S. Patent 3,514,606 (issued 1970).

However, as the hitherto unsuccessful search for means and 25 ways of obtaining congruent OPTs would seem to indicate, Kit was not to be expected that such a relatively simple means in proper arrangement as a complement would be suff-icient to resolve the problem.

.. , . . , . . . . , , As regards the foot positioning means of the inventive apparatus it will be understood that the substantially horizontal reference face of the foot positioning means ~g) preferably is a structural surface of a foot position-ing plate suitable to support, without significant deform-ation, the weight of a patient standing thereon; by the same token, the substantially vertical reference face pre-ferably is a stationary wall port,ion of such a foot plate f' and, generally, will intersect perpendicularly with the mediosagittal plane of the patient.

The distancing means (i) can be a discrete element, such as a securing device, that holds the foot positioning means, or plate, at a reproducible distance from the vert-ical axis of column (f); alternatively, the distancing means is an integral part of the foot plate, e.g. a stop-surface or plate for abutting and/or locking engagement with column (f).

Further, according to a generally preferred embodiment, the foot positioning means according to the invention in-cludes at least one longitudinal reference face, i.e."longitudinal" in the sense of extending in the direction from the axis of column (f) to a vertical projection of the point of reference onto the plane which extends through the horizontal reference face or parallel to such direct-ion.

The longitudinal reference face or, preferably, a pair ofparallel longitudinal reference faces is intended for pos-itioning the patient's feet at mutually equidistanced pos-itions relative to a vertical plane defined by the point of reference and the vertical axis of column (f); further, such vertical plane should be essentially coplanar with g ., _._ _.. . ... . _., .. .. ._ . . .. ..

the mediosagittal plane of the erect patient when the OPT
is taken; also the longitudinal body axis of the patient should essentially be in that plane when the OPT is taken.

Generally, the preferred positioning plate has a straight longitudinal ridge for contact with the adjacent "inner"
sides (i.e. those next to the mediosagittal plane) of the patient's feet.

That ridge may further serve as a rail or guide for a sec-ond and movable vertical face, e.g. a transverse plate, that can be positioned in contact with both heels of the patient's feet after the same have been brought into con-tact with the stationary vertical face or surface that is in contact with the toe portions of both feet of the pa-tient.

lS It will be understood that the term "in contact with" the toes of the patient's feet means that type of contact that occurs when a patient is positioned so that the most pro-minent toe portion of each of his feet is in contact with a vertical plane which, in turn, is perpendicular to the mediosagittal plane of the erect patient.

Further, it should be noted in this context that it is not believed to be essential whether the foot position of the patient in the OPT-apparatus according Jo the invention is defined but by the toe position, or by the heel position, or both, of the patient's feet.

. ,~ __. _ . _ ... _ . _ .. _ .. .... _ _ .. , ~693s For practical reasons, the foot positioning means (g) of the inventive apparatus comprises the vertical reference face as a stationary surface for contact with the patient's toes while a second adjustable vertical surface substanti-S ally parallel with the reference face is for contact withthe patient's heels.
Pressure sensors may be used to ascertain contact or achie-I` vement of a predetermined contact pressure as explained be-low.

From the requirement that the inventive apparatus is cap-able of positioning the patient's feet in the manner needed to cause the inclined body position explained above and to do so in a reproducible manner, it will be understood that the point of reference should be in a fixed position relat-ive to the carriage means as is conventional for commerci-ally available OPT-apparatus. Thus, in order to determine, or reproducingly set, the vertical distance between the horizontal reference face of the foot positioning means (g) and the point of reference, the distancing means (i) provided for this purpose may be any conventional device for measuring a distance, e.g. a scale mounted on column (f) for cooperation with a marker mounted on carriage (e);
mechanical or non-mechanical means to determine a distance and indicating it, e.g. in terms of a digital value, or to reset a previously determined distance ,may be used.

Here, it will be understood that the term "vertical dist-ance" between the point of reference and the horizontal reference face of the foot positioning means (g) refers to the distance between the plane defined by the horizont-al reference face and a plane parallel thereto extending I, .

., ~236935 through the point of reference. For convenience, the pointof reference may be conceived as a "determinative site" of the bite structure which, in turn, is held in a defined spatial relation to carriage (e) explained below in more detail.

Head positioning means comprise a first or intraoral (i.
e. in contact with a region within the oral cavity) and a l second or extraoral positioning device. Combinations of intraoral and extraoral positioning means are known in radiology, e.g. from U.S. Patent 3,514,606, and aim at optimum definition of the position of a patient's head.

Now, while even the best prior art head positioning means will not, per se, be capable to yield congruent OPTs, use of such best means is preferred in the inventive apparatus;
such best means include a bite structure made of a rigid yet radiologically transparent material and mounted in a fixed, or reproducibly adjustable or reproducibly exchange-able, manner on carriage te) combined with a three-point, external head positioning device of the type disclosed in the above mentioned U.K. specification (GB 2,006 590) and also being connected in a spatially defined manner with carriage (e).

Commercially available OPT-apparatus may have such position-ing means, or may be fitted therewith. , For simplicity of illustration it will be assumed herein that the point of reference mentioned above for definition of the foot positioning means and its function as part of the inventive apparatus can be a discrete (and visible) point on the bite structure even though the "theoretical"

_~,, , . _ . . .... .. ..... .. . . . . .. . . .

~36935 point of reference may be at a different point in space relative to the carriage means. This will be understood from the above explained view-point of congruence of se-quential OPTs and the fact that a reproducible definition S of the spatial relation of the patient's head relative to each and every position of both radiation source (a) and cassette means (b) while an OPT is taken is a necessary but not a sufficient condition that must be achieved with f the inventive OPT-apparatus (which, additionally defines a specific foot position).

Consequently, the actual location of the point of refer-ence is not essential as long as its relation to a "de-terminative site" (point, line or surface) is defined and reproducible.

It has been found that if such "determinative site" is at an upper portion of the intraoral positioning means or bi-te structure, congruent OPTs can be obtained with the in-ventive apparatus but since OPTs may be required both for patients with substantially complete or with substanti-,~
ally missing dentition, the inventive apparatus providesfor different bite structures: the first type will be called a "tooth-engaging" structure and used for patients that have all or mos-t incisors; the second type will be called "gum-engaging" structure and used for patients whe-re all or most incisors are missing.

The term "gum" is used herein to refer to the firm tissuesin the upper and lower jaw in which teeth, if present, would be set, and which remain when teeth are lost or ex-tracted; most OPTs can be taken with tooth-engaging struct-ures of the type known per se since most patients will havenative or prosthetic incisors.

_ _ . . ...

lZ36935 Such prior art structures may have the general shape of an inversed "L" or "cobra head" such that the longer leg or cobra neck serves for rigid connection with a holder or socket of carriage (e) while the shorter leg or cobra nose is a small block with at least one short groove at its upper surface for receiving a common edge portion of the frontal incisors, a traverse marker line may indicate a center site as "determinative site"; the lower block surface may, and preferably does, carry another short groove for engagement with edge portions of the lower frontal incisors.

In some cases, e.g. for extensive dental repair such as after an accident, a novel bite structure of the gum en-gaging type will be required as explained in more detail below; such structures may be standardized or taylor-made as required and a determination site at the upper side of the bite structure may be marked.

Hybrid bite structures may be provided if needed, e.g.
having a gum-engaging upper (or lower) and a tooth-engag-ing lower (or upper) side if required and would be taylor-made, e.g. by conventional dental molding techniques.

In tooth-engaging and/or gum-engaging bite structures opposed (i.e. at opposite sides of the mastication plane) jaw portions of the patient will be in,contact with the bite structure.

_ 14-. ,.

lZ36935 Carriage means (e) with grip means, e.g. a rail member, a pair of handles or the like elements, positioned at the lower side of the carriage structure may further include self-positioning controls that help the patient to find a 5 centered position of the head after positioning of the feet; such controls may include a mirror in the field of vision of the patient provided with crosswebs. Further, a lower edge portion of carriage (e) may serve as a stop r means for contact with a sternal portion of the patient 10 and/or have a protrusion for contact with a clavicular portion of the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

The,inventi,on will be better understood and objects other than those set forth above will become apparent when con-sideration is given to the following detailed description 15 Such description makes reference to the annexed drawings which illustrate exemplary embodiments of the apparatus according to the invention and of particular features of such apparatus and wherein Fig. 1 is a perspective view of an apparatus according to the invention with a patient positioned there-in for taking congruent OPTs.
Fig. 2 is a somewhat enlarged perspective view of the upper part of the apparatus of Fig. 1 shown with-out the patient and with the support structure turned to show details, Fig. 3 is a semidiagrammatic view of a foot position-ing means mounted at the lower end of the appara-tus of Fig. 1, Figs. 4A, 4B and 4C are perspective view of an intra-oral positioning device in the form of a bite structure of the gum-engaging type, and T 15 , . _ _ _ _ .. _ _ _ _ _ _ , .. _ .. ... _ . .. .. . . ... . .. .. . . . ... . .. . ... .
,,: . i -~236935 Figs. 5A, 5s, 5C and 5D are perspective views of a preferred foot positioning plate for use with an apparatus of the type shown in Fig. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The apparatus 10 depicted in Fig. 1 includes the portions r 5 of commercially available OPT apparatus, e.g. as manufact-ured by Philips, Holland, and sold under the trademark "orthoORALIX", or a comparable apparatus sold by Siemens, Germany; it will be understcod, how-ever, that no restriction to a particular type of OPT-10 apparatus is intended except that it must have the follow-ing features:

(a) an X-ray fiource 111 of conventional structure for predetermined motion (drive not shown) relative to a point of reference Pb positioned intraorally in the patient's mouth as shown in Fig. 1 and seen best in Fig. 2 at the upper surface of bite structure 25;
I;, ~b) a cassette means 112 of conventional design for sel-ective exposure of an X-ray film (not depicted) to radiation from source 111 including a curved cassette for enclosing the film and a securing means for conn-ecting the cassette with a cassette, support (drive not shown);

(c) a conventional support means 113 for holding the X-ray source 111 and the cassette means 112 relative to re-ference point Pb such that they can be moved in acc-ordance with a predetermined program suited for the specific OPT purpose, here taking of a dental OPT in ~23G935 horizontal planes around the patient's head. To this effect, support means 113 forms a composite radiogra-phic structure 11 together with the X-ray source 111 and the cassette means 112; structure 11 is rotatably connected with the upper arm or bracket 120 of carri-age means 12. Conventional light beam sources (not shown) may be provided for overall positioning;

r (d) conventional head positioning means comprised of an intraoral positioning device 25 (within patient's oral cavity, not apparent from Fig. 1 but shownin Fig. 2) mounted on the lower arm or bracket 129 of carriage 12, and an extraoral head positioning device 16 (comprised of three adjustable contact arms 261, 262, 263 as shown in Fig. 2) mounted on head plate 125 (225, Fig.2) which, in turn, is connected rigidly with the upper arm 120 of carriage means 12 (Fig. 2: 22);

(e) a conventional carriage means 12 consisting of the up-per arm 120, the lower arm 129 and the connecting por-tion 122, in addition to rotatably holding support 113 r includes a grip 121 (Fig. 2: 221), e.g. a rail or bar secured to the lower arm 129;

(f) a conventional and substantially vertical column 14 provided for holding carriage means 12 such that the latter can be held in a vertically defined position, e.g. as shown in Fig. 1 or with a smaller or larger patient in a lower or higher position. The vertical axis of column 14 is a theoretical line Al assumed to be located in the vertical plane that is defined by reference point Pb.

~.236935 As shown in Fig. 1, column 14 may support carriage 12 in a conventional manner via two slits 141, 142 by means of connectors (not shown) for sliding engagement with a shaft or group of shafts (not shown) within column 14, and conventional mechanical or pneumatic devices (not shown) will normally be provided to balance the weight of carriage 12 and those components of apparatus 10 that are supported by the carriage and to provide for easy move-'I ment of carriage 12 in vertical directions.

According to the invention a foot positioning means isprovided, e.g. in the form of a plate 17, having a top surface 170 upon which the patient places his bare feet and which is in a defined vertical distance from reference point Pb (as measured between a horizontal plane through Pb and the horizontal plane defined by surface 170).

A stationary vertical front plate 171 is in contact with patient's toes as shown in Fig. 1 while the heels are in contact with a vertical back plate 172 that is guided by a longitudinal ridge or rail 173 which also contacts the inner sides of patient's feet so as to define their longi-tudinal orientation.

A distancing means 18 is required to definé the distance between the vertical reference face provided in ,Fig. 1 by the toe-contacting surface of the st,ationary vertical plate 171, and axis Al of column 14. The actual distance between axis Al and the vertical reference face is not be-lieved to be overly critical as long as the angle en-closed between axis Al of column 14 and the longitudinal body axis A of the erect patient is within the range re-quired for muscularly induced body rigor as explained ab-ove, and generally within the range of from about 5 to _ 18 _ ~236g35 30 (assuming 360 for a full circle). In the embodiment of Fig. 1 a front portion of foot plate 17 abutting with column 14 serves as fixed distancing means but adjustable distancing means for adaption to smaller or older and less flexible patients are within the scope of the invention and will be explained with reference to Fig. 3.

For determining the vertical distance between surface 170 l of foot plate 17 and reference point Pb a linear scale 191, e.g. a metric scale reading in millimeters, is provided on column 14 while a marker or arrow 192 is arranged on carri-age 12. Other onventional metering or distance reading and setting means including digital read-outs and digital sett-ings may be used for the inventive apparatus. Control and soling means for taking the OPT are provided within con-sole 13.

Fig. 2 shows a somewhat enlarged presentation of the upperpart of apparatus 10 of Fig. 1 without the patient and with support 21 turned from the position of 11 in Fig. 1 by a rotation on carriage 22 of about 90.
r Thus, it will be seen that the head plate 125 of Fig. 1 re-mains stationary (225) so that the pivotably adjustable arms 261, 262 and 263 may hold patient's head in a given position regardless of the position of support 21 because of the rigid connection of the head plat,e 225 with the top arm of carriage 22; by the same token, the lower arm 229 of carriage 22 maintains bite structure 25 ("cobra-head" type for normal dentition) as well as any body stops 259 and grip 221 in a set relation to the point of reference Pb ass-umed to be at the center of the top surface of bite struct-30 ure 25. Sometimes, such arrangements are called "kephalo-stats" in the art but are not preferred herein if the first device of the head positioning means is a chin support and, thus, not intraoral.

, -- 19 --.. . . ... . . . . .. ..

~23693S

An operating grip 226 may be provided at the side of carriage 22 for lifting or lowering the carriage by the operator and for blocking in or deblocking from a given carriage position.

A mirror 223 including a crosshair 224 is provided on carriage 22 for helping the patient to attain a well cent-ered head position in the course of the positioning se-quence explained in more detail below.

Fig. 3 shows a semi-diagrammatic perspective and enlarged view of the foot plate 17 of Fig. 1 as foot plate 37 with some modifications. The foot of the vertical column 34 for guiding the carriage (not shown) is depicted with a scale 391 for indicating the vertical distance between the hori-zontal reference face of an inventive apparatus that com-prises a foot positioning means (g) in the form of footplate 37 having a substantially rigid patient-supporting top surface 370 and a stationary vertical plate 371 for contact with the patient's toes. Again, a longitudinal rail or ridge 373 is provided for contact with the inner sides of patient's feet and for guiding the adjustable se-cond vertical plate 372 into contact with patient's heels.

In order to maintain the toe contacting vertical face or surface 375 at a reproducible yet variable distance from column 34 or its vertical axis (no-t shown in Fig. 3), a pair of rails 381, 382 is provided for sliding engagement with a pair of longitudinal recesses 378, 379 at the bot-tom side of foot plate 37. Rails 381, 382 will be secured (not shown) to the floor on which column 34 is mounted so that plate 37 may be set to either abut, by means of vert-ical plate 371, on column 34 or to be maintained at defin-ed distances thereform, e.g. by means of numbered fixed _ 20 -settings (not shown) or the like means that enable an easily reproducible placing of foot plate 37 relative to column 34.

As mentioned above, intraoral positioning devices of the tooth-engaging type suitable for use with the inventive apparatus are known per se while devices of the gum-en-gaging type for OPT use are believed to be novel in dent-al radiology. Accordingly, perspective views of a repres-entative example of such a device are shown in Figures 4A
(side view), 4B (posterior view) and 4C (front view) de-picting a bite structure 40 preferably made of an organic polymer that is essentially transparent to X-rays, e.g.
a polymethacrylate, polyamide, polycarbonate, epoxy resin or similar physiologically inert thermoplastic or duro-meric material capable of being sterilized.

A substantially rigid stem 401 serves for a positionallyreproducible connection of bite structure 40 by means of its massive end 411 with a socket or other holder (not shown) of the carriage in a similar manner as is used to position bite structure 25 in carriage 22 of Fig. 2.

The upper part of stem 401 may be provided with a recessed profile 412 providing sufficient rigidity to the connect-ion of the stem with the intraoral support 42 which, in turn, has an upper side 421 and a lower side 422; upper side 421 serves as a palate support and palate position-ing device frontally terminating in a stop ridge 46 which has a recess 461 to accomodate the patient's labial band, and comprises a groove smoothly curved (both in vertical and horizontal planes) from stop ridge 46 to palatum sup-port surface 48 and defined by its apex Sl (normally themost frontally located bottom point) which forms the de-, ~236935 terminative site of bite structure 40; consequently, pala-tum support wall 44 should be shaped so as to guide and position a toothless (incisors missing) upper jaw into the reproducible spatial relation relative to the carriage means required for congruence of sequential OPTs.

In an analoguous manner, lower side 422 of bite structure 40 serves to position the lower (toothless or dented) jaw of the patient into a reproducible position defined ess-entially by the location of apex s2 of recess or groove 45 that may, or may not, be curved when viewed in a horizontal plane; further, a protrusion base 41 is generally provided and may have a monolithic structure (extending into the portion shown in broken line) or a composite structure in that an exchangeable protrusion or riser 43 (as indicated lS in broken line) may be added to base 41 so as to adapt the total height of the resulting frontal bite wall to the toothed/untoothed structure of the patient's lower jaw.
Generally, apex S should be located more frontally, i.e.
closer to the vertical axis Al of the apparatus column, than apex Sl, -A preferred embodiment of the foot positioning means 17 of Fig. 1 is shown in various perspective views in Figures 5A
(operative position), 5B (reversed to show bottom struct-ure), 5C (cover plate of frontal portion removed) and SD
(posterior portion broken away).

Foot positioning means 5 comprises a frontal portion 51 rigidly connected with a massive bottom plate 54 having a flat horizontal top face 50 providing the horizontal ref-erence face explained above.

.. .. . . _ .. , .. , . ... .. . . , .. , . . , . .. . .. .. .. . .. . ...

The vertical reference face 56 (Fig. 5D) includes two (or more) contact faces 567, 568 connected via pressure sensit-ive switches (not shown) with a circuit, e.g. provided on a print plate 57 (Fig. SC) normally covered by a panel 58.

A battery arranged in a recess 593 is connected by the switches with indicator lights at the top of portion Sl so that one pair of indicator lights, e.g. 562, 563, will indicate that the pressure sensitive switches are energiz-ed but not activated, i.e. not in pressing contact with a patient's toes, while another pair of indicator lights, e.g. 561, 564, will indicate that one, some or all of the pressure sensitive switches connected with contact faces 567, 568 are operated by pressure of the patient's toes.

A longitudinal ridge 53 is mounted on the top face 50 of plate 54 and serves both as a rail to guide an adjustable vertical plate 52 in parallel alignment with reference fa-ce 56 into contact with both of a patient's heels, and to align the mediosagittal plane of the patient with the vert-ical plane defined by the center line of ridge 53 and axis A of the apparatus column (not shown in Figs. 5), Two longitudinal recesses 594, 595 in the bottom face S9 of plate 5 are provided to engage with a pair of rails S91, 592 secured to the floor (not shown) that also sup-ports the vertical column of the appara,tus; rails 591, 592 are secured in such manner that the center line of ridge 53 will intersect with the vertical axis Al of the appara-tus column; stopper means (not shown) are provided on rails 591, 592 or on plate 5 to reproducibly and securely define the distance between reference face 56 and axis when an OPT is taken.

_ 23-. ,, . ..... ... . .. ... . . . . . . .

~236935 Finally, an electrical switch (not shown) will be provided to connect the battery in recess 593 with circuit plate 57.

A step-by-step description will now be given to illustrate the manner of operating an inventive apparatus when taking an OPT that will be congruent with at least one other OPT
taken previously or subsequently, i.e. sequentially with an intervening time interval of hours, days, weeks or ' months:

(1) X-ray-sensitive film is arranged within the cassette in a reproducible manner; film sizes and cassettes are standardized in the sense that same cassettes and film sizes will be used in sequential OPTs. This is the same for all patients.

(2) The cassette is mounted on the cassette support in re-lS producible if not standard position; this, normally, is the same for all patients.

(3) Position and type of the bite structure are controlled if standard, or selected and mounted in a defined and reproducible manner; identical structures and settings must be used for the same patient.

(4) Position of foot plate, and possibly type of plate, is controlled and, if required, moved into a defined re-producible position if patient's height so requires;
longitudinal axis A2 of patient should be at angle of between 15 and 25, optimally at about 20, relative to axis Al of apparatus column when his toes are in contact with the vertical reference face and an ident-ical setting must be used for all sequential OPTs of the same patient. Other patients may require a smaller angle I.

,:

.

(5~ Patient with bare feet is caused to step onto the foot positioning means, e.g. foot plate 5 (Figs. S), and - while engaging any grip of the apparatus - places both feet with their inner sides against ridge 53 and moves toes of both feet into contact with faces 567, 568 until control lights indicate that toe contact is established; then plate 52 is moved to contact both heels of the patient, and contact of inner side of ' patient's feet with ridge 53 is controlled. This oper-ation is the same for all patients except for the pos-ition of plate 52.

(6) Patient is caused to engage the grip as high as poss-ible; again, this is the same for all patients.

(7) The apparatus carriage is positioned such that patient is just able to engage the bite structure with his teeth edge to edge while his head is flexed backwards;
the patient is now in an erect yet hanging position with a stretched thorax and his longitudinal body axis will be at an angle relative to the axis of the apparatus column, but this angle may exceed that an-gle (~) which is finally desired.

(8) The horizontal line of the crosshairs of the self-pos-itioning control mirror is set along the bi-pupillar line and patient is requested to align his head pos-ition.

(9) While patient maintains his body position the apparatus carriage is moved downwards so as to cause a forward pitch of the atlanto occipital joint of the patient and maximum flexion of the cervical vertebra in ventral direction; referring to Fig. 1 of the drawing, the _ 25_ ., ~5 position of axis A2 of patient Pa should be maintained during this operation without change of angle while ax-is A3 is brought into an essentially vertical position;
this results in an op-timal elongation of the cervical vertebra and, at the same time, should align patient's plane of mastication parallel with surface 50 of foot plate 5.

(10) The head posi-tioning device, unless already in working position, is set for contact with patient's head; a final check of the head position is made and the sett-ing recorded if variable.

(11) Patient is required to draw his body into contact with the sternal and/or clavicular stop of the carriage and to retain this position; this will cause an isotonic muscular strain of his arm and back muscles; now his body axis shouid be at the final value, preferably about 20.

(12) The vertical level of the carriage is recorded, prefer-ably together with the time of day.

(13) The OPT is taken in accordance with the instructions given by the producer of the OPT-apparatus taking care that all variable settings are recorded for reproduct-ion in sequential OPTs.

(14) Any sequential OPT is made by repeating steps 1 to 13 with identical settings of all variable and, prefer-ably, at about the same time of the day in order to avoid as far as possible different degrees of compress-ion of the vertebra.

_ 26 -. ., Contrary to what has been believed feasible or, rather, im-possible in OPT-technique as regards congruence, the invent-ion provides for reproducibility and congruence of sequenti-al OPTs in the sense of true reproduction as evidenced by putting on top of each other two or more sequential OPTs ob-tained with the inventive apparatus in the manner explained;
true reproduction or congruence can be ascertained simply by aligning superimposed~OPTs so as to form a composite, or multilayer, OPT in which any unchanged area of one OPT layer is fully congruent and cannot be discriminated visually from the same area of any other OPT in the composite while any lack of congruence,or identical reproduction, indicates actu-al change of the object.

While actual physical superimposition of congruent OPTs is a preferred method of controlling change in the OPT-area of interest, comparison by projection onto a screen or by el-ectronic scanning and-computer evaluation etc. is feasible.

Two further surprising advantages have been observed when taking congruent OPTs with the inventive apparatus: One add-~`~ 20 itional benefit is a remarkable increase of sharp OPT-de-finition of the anterior bone structure (central area of dental OPTs including frontal jaws plus dental region from canine to canine) where prior art apparatus.produce an over-projection of the vertebra so as to blurr the jaw and tooth structure in that projection area and require use of another radiological projection, e.g. a posterior/anterior panoramic image of the lower jaw, for complete evaluation.

The second advantage is that the distorsion factor of a given OPT-area can be determined reproducibly and used for spatial orientation, e.g. for implantates and target surgery, in a head area of interest.

~6935 Generally, the invention may lead to a break-through in maxillo-facial radiology and while preferred embodiments of the present invention were shown and described above, lt is to be understood that the invention is not limited to such embodiments but may be embodied and practiced with-in the scope of the following claims.

.~ .

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An apparatus for orthoradial panoramic tomography of a head region of a human patient in an erect position defined essentially by a longitudinal body axis; said apparatus comprising:
(a) a radiation source arranged for predetermined mo-tion relative to a point of reference;
(b) a cassette means for selective exposure of an X-ray sensitive film to radiation from said source, said cassette means also being arranged for pre-determined motion relative to said point of refer-ence;
(c) a support means for movably holding said radiation source and said cassette means relative to said point of reference;
(d) a head positioning means including a first or intra-oral device and a second or extraoral device for positioning said patient's head relative to said point of reference;
(e) a carriage means connected with said support means and including a grip means;
(f) a substantially vertical column means for slidingly holding said carriage means in a vertically defined position and having a vertical axis distanced from said point of reference;
(g) a foot positioning means having a substantially horizontal reference face for defining a vertical distance from said horizontal reference face to said point of reference, and a substantially vert-ical reference face for maintaining toe and/or heel portions of said patient's feet in a predetermined position;

(h) a distancing means for maintaining said at least one vertical reference face at a reproducible hor-izontal distance from said vertical axis of said column means;
(i) a means for determining and reproducibly setting a vertical distance between said horizontal reference face and said point of reference;
said positioning means being arranged relative to said point of reference and to said vertical column axis for maintaining said patient, when standing on said foot positioning means and engaging said grip means, in a re-producible and inclined position in which his longitudin-al body axis relative to said vertical column axis is at an angle (.alpha.) sufficient to cause an isotonic strain of brachial and dorsal muscles.

2. The apparatus of claim 1, wherein said foot positioning means additionally includes at least one longitudinal reference face for positioning said patient's feet in a mutually equidistanced position relative to a vertical plane defined by said point of reference and said vert-ical axis.

3. The apparatus of claim 1, wherein said column means com-prises a scale and wherein said carriage means comprises a marker for determining a reproducible distance between said point of reference and said horizontal reference face of said foot positioning means.

4. The apparatus of claim 1, wherein said vertical reference face or said positioning means includes a stationary sur-face for contact with both of said patient's toes.

5. The apparatus of claim 1, wherein said foot position-ing means further includes an adjustable second vert-ical face for contact with both of said patient's heels.

6. The apparatus of claim 1, wherein said first intraoral positioning device is a bite structure for contact with opposed jaw portions of said patient.

7. The apparatus of claim 2, wherein said longitudinal re-ference face is defined by a longitudinal ridge extend-ing transversely to said vertical reference face for contact with the inner sides of both of said patient's feet.

8. The apparatus of claim 7, wherein said ridge also ser-ves as a rail means for a movable vertical plate suit-able to contact both of said patient's heels.

9. The apparatus of claim 1, wherein said carriage means comprises a self-positioning control provided in the field of vision of said patient and including a cross-web means.

10. The apparatus of claim 1, wherein said carriage means further includes at least one stop means for contact with a sternal and/or clavicular body portion of said patient.

11. The apparatus of claim 1, wherein said vertical refer-ence face of said foot positioning means includes press-ure-sensitive portions for indicating a contact with said patient's toes.

12. The apparatus of claim 1, wherein said intraoral pos-itioning device includes a bite structure having a re-cessed curved surface for contact with a toothless up-per jaw portion, said surface being defined by a first apex.

13. The apparatus of claim 12, wherein said bite structure includes a recess portion at its lower side defined by a second apex for contact with a lower jaw portion, said second apex being closer to said axis of said col-umn than said first apex.

14. The apparatus of claim 1, wherein said head positioning means are arranged to position and maintain said pati-ent's plane of mastication in an essentially horizontal orientation when said longitudinal body axis is in said inclined position so as to cause a substantial elong-ation of the cervical vertebra.

15. In the method of taking an orthoradial panoramic tomo-graph of a head region of a human patient in an erect position by means of an apparatus having:
(a) a radiation source for predetermined motion relative to a point of reference;
(b) a cassette means for selective exposure of an X-ray sensitive surface to radiation from said source, said cassette means also being arranged for prede-termined motion relative to said point of reference;
(c) a support means for movingly holding said radiation means and said cassette means relative to said point of reference;
(d) a head positioning means including an intraoral positioning device and an extraoral positioning de-vice for placing said patient's head relative to said point of reference;

(e) a carriage means connected with said support means and including a grip means;
(f) a substantially vertical column means for sliding-ly holding said carriage means in a vertically de-fined position and having a vertical axis distanc-ed from said point of reference;
the improvement consisting essentially in causing said patient to manually engage said grip while his longi-tudinal body axis is maintained at an angle (.alpha.) of from about 15 to about 25° relative to said vertical column axis to cause a substantially isotonic strain of the patient's brachial and dorsal muscles while tak-ing a first tomograph; recording any variables of said first tomograph, and producing at least one congruent sequential tomograph of said patient under essentially iden-tical conditions.

16. The method of claim 15, wherein said head positioning means is arranged to maintain said patient's plane of mastication in an essentially horizontal orientation when said longitudinal body axis is maintained at said angle so as to cause a substantial elongation of said patient's cervical vertebra.