WO2002096280A2

WO2002096280A2 - Method and device for obtaining information relating to a bone fracture

Info

Publication number: WO2002096280A2
Application number: PCT/AT2002/000156
Authority: WO
Inventors: Oliver Ploder; Clemens Klug
Original assignee: Innovationsagentur Gesellschaft M.B.H.
Priority date: 2001-05-29
Filing date: 2002-05-22
Publication date: 2002-12-05
Also published as: WO2002096280A8; WO2002096280A3; AU2002344137A1; AU2002344137A8; ATA8372001A

Abstract

The invention relates to a method and a device for obtaining information relating to a bone fracture, especially an orbital floor fracture (11). According to the invention, produced layer images are subjected to image processing (2), e.g. by means of computer tomography (1), in order to obtain fracture image data from which information concerning the size of the fractured area is derived; dimensional values concerning the fractured area are taken from the fracture image data obtained by means of image processing (2) of the individual layer images; and, on the basis of said values collected by means of the layer images, a surface evaluation is carried out in order to represent the extent of the fracture (11).

Description

Method and device for obtaining information about a bone fracture

The invention relates to a method for obtaining information about a bone fracture, in particular an orbital (floor) fracture, e.g. slice images generated with the aid of computer tomography are subjected to image processing for obtaining fracture image data, from which information regarding the size of the fracture area is derived.

Furthermore, the invention relates to a device for carrying out such a method, with a layer image recording device, in particular a computed tomography device, an image processing unit connected thereto and an image display unit.

There are areas of bone, especially the walls of the eye socket (e.g. orbital floor), where a fracture is difficult to assess with conventional methods with regard to the need for treatment. Such orbital fractures typically result as so-called blow-out fractures when there are sudden impacts or pressure on the eye, for example when a ball strikes the eye area, with the extraordinarily thin wall (e.g. orbital floor) inward or inward in some areas breaks down below. The most common fractures in the area of the eye socket concern the floor (so-called orbital floor fracture) or the inner wall (so-called medial wall fractures). The mechanism of the eye socket causes tissue to sink, which can lead to disturbances in the mobility of the affected eye, which are clinically manifested in double images. Depending on the location and size of the fracture, treatment from the eye socket or from the maxillary sinus may be necessary. It is common to use slice imaging techniques to detect such fractures, such as ultrasound or x-ray slice images, in particular computed tomography (CT). In the case of an orbital floor fracture, so-called coronal tomography slice images are recorded, the image planes running parallel to the forehead. In the case of medial wall fractures, it is also common to perform axial computed tomography slices in addition to coronal computed tomography slices, corresponding to planes perpendicular to the end face. It has already been proposed, cf. Hong-Ryul Jin et al. , "Relationship between the extent of fracture and the degree of enophthalmos in isolated blowout fractures of the medial orbital wall ", Journal of Oral and Maxillofacial Surgery, June 2000, Volume 58, Number 6, pp. 617-620, on the basis of the coronal and axial layers to approximate the fracture area by an elliptical shape, the maximum length in the coronal CT slice and the maximum depth in the axial CT slice are used as ellipse axes, which is naturally extremely rough and inaccurate when it comes to determining the size or area of the fracture area in relation to the entire orbital floor The position of the fracture area within the eye socket cannot be determined with this method.

It is an object of the invention to provide an improved technique for obtaining information about the size and also about the location of the fractures in such critical bone areas, such as in particular in the bottom of eye sockets, the size of the fracture area and its location determining as precisely as possible should be able to be without being associated with excessive effort.

The method according to the invention of the type mentioned at the outset is characterized in that, from the fracture image data of the individual slice images obtained with the aid of image processing, dimension values relating to the fracture area are taken, on the basis of which an area determination for representing the extent of the fracture is carried out via the slice images.

In a corresponding manner, the device according to the invention of the type mentioned at the outset is characterized by computer means connected to the image processing unit or image reproduction unit, which are set up to determine an area for displaying the extent of the fracture from the fracture image data output by the image processing unit, specifying dimension values per layer image via the image reproduction unit ,

Advantageous embodiments and further developments are defined in the subclaims.

From the ^* technology according to the invention, the (axial or coronal) slice images are used one after the other to obtain length dimensions, these dimensions expediently directly from the representation of the slice images on the image display device by "clicking" on the ends of the respective as Line in the slice image recognizable area (left and right end of the orbital floor and left and right end of the fracture area), that is, can be removed in order to be processed. With a suitable design of the image processing unit, length sizes can be immediately entered into the computer unit, where corresponding length dimensions are determined on the basis of the scale known from the image processing unit and multiplied by the "layer thicknesses" or more precisely by the distances between the layer image levels are so that partial areas of the fracture area or the surrounding affected bone area, for example orbital floor, are obtained from layer image to layer image. In this case, averaging is expediently carried out by determining these partial areas as trapezoidal areas, the arithmetic mean values from the length specifications of two adjacent slice images being used for the area calculation. These trapezoidal partial areas are expediently used for determining the fracture area as well as for calculating the area of the entire orbital floor - in the case of an orbital floor fracture.

In practice it has been shown that in the case of an orbital floor the latter can be assumed to be essentially planar; in exceptional cases there is a slight concave curvature, and in correspondence to this curvature a correction of the length dimensions, as they are taken from individual slice images, can be carried out; it has been shown that this consideration can be done simply by assuming an arcuate curvature, seen in section in each layer image plane. The partial areas obtained as well as the total area can be output or printed out in tables. In addition or instead of this, it is also conceivable to provide a graphical representation of the affected bone area and the fracture area located therein, i.e. in particular the orbital floor including the fracture area, wherein this graphical representation can in fact correspond to a schematic plan view of this bone area including the fracture area. Such a top view has so far not been possible using conventional imaging techniques (e.g. computed tomography, ultrasound) alone.

One possible treatment for a fracture in the orbital floor is to place suitable implants in the eye socket or in a socket Introducing balloon catheters into the maxillary sinus, and for this purpose it is also desirable to obtain an approximate estimate of the extent of the fracture and the volume of the displaced orbital contents affected by the fracture area. Based on this data, the surgeon can make a diagnosis or plan the operation from the maxillary sinus, from the eye socket or from both access routes. Furthermore, the type and size of the implant used, which is necessary to support the fracture, can be determined before the surgical intervention. Accordingly, it is also preferably provided according to the invention that, in the event of a fracture of the orbital floor, the fracture piece projecting obliquely downward is not only calculated in terms of area, but also a calculation of the volume defined above this folded-away fracture piece, in order thus to carry out the so-called herniation (displacement of the orbital contents ) to be able to fix it rationally. In this embodiment, in order to create a targeted diagnosis, not only is information about the area size of the fracture area obtained, but also about the extent of the sinking or the sinking volume. This volume calculation can also be carried out layer by layer, with a partial volume being calculated for each layer thickness, and these partial volumes being able to be calculated on the basis of the partial areas determined and of height information taken from the layer image data. In addition to a tabular representation of the volume data, a graphical representation is also useful here.

A major advantage of the technique according to the invention is that information about the location and the size of the respective fracture can be obtained with great accuracy, so that the diagnosis and consequently the therapy are made considerably easier for the attending doctor. In particular, the tabular and graphical representation of the areas and volumes of the fracture areas enables the surgeon in the event of a fracture of the orbital floor (or other walls of the orbit) to make a quick and exact diagnosis, so that an immediate decision about the treatment method is subsequently made - Intervention from the eye socket with insertion of an implant or lifting of the fracture area with the help of a balloon catheter inserted below it - can be decided. Sometimes the decision can also be that Surgical treatment is not required for smaller fractures.

The invention is explained in more detail below on the basis of particularly preferred exemplary embodiments, to which, however, it should not be restricted, with reference to the drawing. The drawing shows in detail:

Fig.l in a schematic block diagram of a device for obtaining information about bone fractures based on CT scans;

2 shows a schematic vertical section, corresponding to a coronal CT slice, through part of a skull;

3 shows a plan view of a left orbital floor with a fracture area;

4 shows schematically in a diagram the procedure for obtaining information about the areal size and the position of the fracture area and the orbital floor in the case of such an orbital floor fracture;

5 shows the finished area diagram of orbital floor and fracture area in a diagram representation corresponding to FIG. 4;

6 shows schematically in a diagram the calculation of the partial re-volumes; and

7 shows schematically the type of correction of linear dimensions in the event of a curvature of the orbital floor.

In Fig. 1, a device for obtaining information about a bone fracture is shown schematically in a block diagram, with particular attention being given to difficult bone areas in terms of diagnosis and therapy, in particular fractures of the floor of the eye sockets (orbital floor). A device 1 for recording slice images of the bone area in question is used, in particular a computer tomograph (CT) device 1, in order to slice images from the bone area to be examined, where the fracture is or is suspected, at the required intervals, e.g. in the case of slice images of the orbital floor at intervals of 3 mm. Instead of a CT device, it is also possible to use other imaging devices which generate slice images, such as those which operate on the basis of ultrasound.

The slice images recorded in the CT device 1 are processed in an image processing unit 2 and are displayed on an image display unit in the form of a screen 3 edited. The image processing unit 2 can be equipped with a conventional image processing module, such as the so-called "Easy Vision module", in order to process the images scanned by the CT device 1. If an orbital floor is examined, the images are recorded with the CT device 1 in coronal planes, ie in planes parallel to the forehead of the skull.

Such a slice image is shown schematically in a coronal plane in FIG. 2, the history skull 4 being visible, in which the right eye socket 5 has an intact orbital floor 6. During the display on the screen 3, the length dimension (strictly speaking the width of the orbital floor 6), as it is denoted by L in FIG. 2, can be reduced between points 7 and 8, the points 7, 8, for example, with the cursor With the aid of a mouse 9 (see FIG. 1) or a similar control device, for example cursor control keys on a keyboard, can be controlled and clicked on. This is carried out in a corresponding manner above all for the left eye socket 10 provided with a fracture in FIG. 2, where the corresponding length dimension between corresponding edge points 7 'and 8' is removed. Furthermore, the length dimensions X and Y at the beginning 18 and end 17 of the fracture area 11 are taken from the inner edge of the orbital floor, corresponding to the respective point 8 ′. To calculate the herniation volume (as described in more detail below), the herniation area given per slice (recording) - according to FIG. 2 the triangular, checkered area H with the corner points 17, 18 and 19 - can be moved around with the cursor on the screen be removed. In the present example, this area H is used by the image processing module, e.g. calculated directly by the "Easy Vision" module, and this calculation is carried out for all CT slices. The determined individual areas (= herniation area / CT slice) are used to calculate the herniation volume with a known slice thickness.

These dimensions L, X, Y and H of the orbital floor 6 (see fracture area 11 in FIG. 2) can be stored in tables, whereby they are transferred from the image processing unit 2 shown in FIG. 1 to a memory 13 belonging to a computer 12 be, s. Fig.l. As is further illustrated in FIG. 1 by a dashed line at 14, the image processing unit 2 and the computer 12 can be integrated into a single computer. be summarized unit, which may also include the memory 13.

A printer or similar output device 15 is then connected to the computer 12 according to FIG. 1 in order to obtain the values L, X, Y obtained for each slice image, generally L _n as well as X _n and Y _n , with n = number of the slice image, for example output in tabular form or graphically.

In FIG. 3, for better illustration of such a fracture of the orbital floor, a plan view of an orbital floor is shown, this orbital floor similarly designated as 6 ′ in FIG. 2, and FIG. 3 likewise showing a left orbital floor; Furthermore, the front of the skull is to be thought in Fig. 3 on the right side. The fracture area can be seen at 11 in FIG. 3, and the planes of the slice images according to the coronal stratification would be parallel to the right leaf edge of FIG. 3, the numbers of the CT slices according to the arrow n in FIG. 3 from the left ascending to the right. The points 8 ', from where the lengths L _n , X _n and Y _{n are} taken, lie on the slightly curved edge 8A' shown in FIG. The opposite, outer edge of the orbital floor 6 'is designated by 7A' in FIG.

4 shows schematically in a diagram how the individual slice images with the numbers n, for example 11 to 21, lead to the reduced length dimensions L _n , Xn and Y _n , specifically the left boundary points 8n 'and 812' as well the right edge points In 'and I12' are drawn in Fig.4. Since the points 8 _n 'are drawn on a straight coordinate in a map-based coordinate system, the right edge line 8A' according to FIG. 3 in FIG. 4 thus corresponds to the straight coordinate 8A '. However, this is not a problem for the doctor, who uses this representation and the other information obtained to make his diagnosis for the required therapy, since the basic shape of the orbital floor with the slight curve on. Inner edge is known in principle.

Instead of, as shown in FIG. 4, it would of course also be conceivable to record the inner edge of the orbital floor, for example 8A ', in accordance with its actual curvature (see FIG. 3), for example by using the layer images, see FIG. 2, starting from an image edge, for example the left image edge, as an absolute coordinate axis, provided that the slice images correspond to be displayed successively on the image display device 3 according to their actual position.

In the diagram of FIG. 4, points 17 and 18 (see FIG. 2) are also shown as edge points for the fracture area 11 for the layers with the numbers 14, 16 and 18 (points 17i4, 17i6, 17ιs and I814 18i6 and 18ιs. The length dimensions Xι ₄ and Yι ₄ , measured from the left edge 8A ', are also illustrated for layer No. 14. The fracture area 11 within the orbital floor 6' thus initially results as a series of rectangles, each correspondingly the individual layer thicknesses or distances of the layer planes from one another, for example with the depth S, which is uniform for the entire series of layer images and is, for example, 3 mm.

These rectangles still give a relatively rough approximation of the fracture area 11, so that from slice image plane to slice image plane a further approximation by oblique lines, forming triangles, such as e.g. shown at 19 in Figure 4. These triangles 19 result in a trapezoidal surface being obtained for each slice image n as a partial surface, the surface of which is obtained by averaging the length dimensions. Each partial area of the fracture area 11 can thus be written on as follows:

Fn = - - -. S; with a _{n +} ι = Y _n + ι - Xn + i and a _n = n - Xn.

2

The total area F for the fracture area 11 is thus obtained by the sum of the partial areas F _n , ie

F = _∑ Fn = _∑ -≥ ± ^S S.

The areas for the individual rectangles of the entire orbital floor 6 'are also determined in a similar manner, trapezoidal areas with the layer plane spacing S as the height of the trapezoidal areas also being used as partial areas. (The corresponding triangles for the formation of the trapezoidal surfaces are illustrated with dashed lines in FIG. 4.)

The following table shows, for example, corresponding values for an orbital floor with a fracture, belonging, for example, to the orbital floor of FIG. 4, the total area 0 for the orbital floor 0 = 5.42 cm ² and the total area F for the fracture area F = l, ll cm ² .

Furthermore, to compensate for the so-called "partial area The first length dimension (or area dimension) is used for the overall calculation:

0 + a _n

F ₀ = a-. S,

2 where a _n is the first relevant length dimension (according to Fig. 4 would be

To calculate the herniation volume V also contained in the table below, the individual volumes V _n already mentioned above are determined in layers on the basis of the removed herniation areas H _n , u. between according to the relationships

V = - ^{1 ± J.} S (single volume) or

2

n

V = V _n (total volume).

5 shows, in correspondence with the diagram of FIG. 4, an illustration of the orbital floor 6 'including the fracture area 11 in the contour approximated by the triangles (19 in FIG. 4). Such a representation can be displayed on the image display unit 3 and / or printed out with the help of the printer 15, for example after it has been determined by the computer 12 according to FIG. 1, so as to give the surgeon treating the diagnosis help with the necessary therapy.

Additional help is also obtained in that, as described, the volume defined by the broken down piece of bone 16 in the fracture area 11 (see FIG. 2) between this piece of bone 16 and the imaginary orbital floor 6 'in the fracture area 11 is determined, for which purpose the respective individual herniation area (H _n ) (see FIG. 2) is taken from the individual slice images, as a result of which the individual volumes V _{n are} determined in layers, from which the total volume V is then calculated by adding them up.

The partial volumes V _n obtained may also, for example, as shown in Figure 6 shown and printed, are, and that ^'cumulative total gives the physician an indication of the decision on the urgency of surgical intervention.

In the table above, the corresponding partial volumes Vn and the total volume V (herniation volume) are also included as an example. For the calculation of the partial volumes (see, for example, V _i5 in FIG. 6), the procedure was such that the area of the herniation shown in FIG. 2, which is defined by points 17, 18 and 19, was determined for each slice image; this herniation area H was then multiplied by the layer plane distance S (= 3 mm in the present example).

As a rule, the orbital floor 6 or 6 'can be assumed to be flat; For a higher precision or for those cases where the orbital floor 6 or 6 'has a noticeable curvature, a correction can be made for the respective length dimensions, as will be illustrated below with reference to FIG. 7.

The curvature of the orbital floor 6 or 6 'is concave, and it can be assumed to be approximately circular in section be, s. 7, where a circular arc for the orbital floor 6 ', with the edge points 7', 8 ', is shown. The associated radius is labeled R. The maximum deviation of one plane is equal to dimension d, and the angle α is the arc angle associated with the circular arc 6 '. Half the length L between the points 7 ', 8' can thus be written to

From this it can further be deduced that

2d ex

The angle - can also be written as follows:

2

L

- = arctg, 2 _\ . ^{2 (} R ^ ^}

Based on the known equation for the circular arc corresponding to the arc angle, the following relationship thus results for the circular arc b:

(-) ² + cl ² Ld 2 arctg b =

2

This calculation is of course then for each layer image level, i.e. for each layer number n.

Practical investigations on human skulls, on which the corresponding dimensions could also be determined directly, showed that excellent measurement results can be achieved with the method explained above, the deviations from the actual sizes of the areas being in the range of at most 5%. This shows that the technique described above provides an excellent basis for the diagnosis and selection of therapy in the treatment of critical bone fractures, in particular in the so-called blow-out fractures of the orbit. Compared to obtaining information on the basis of three-dimensional images, this also saves time in a ratio of 1: 5 to 1:10, i.e. it only takes a fifth to a tenth of the time that was previously required to obtain useful image information he- hold, on the basis of which the doctor can take his further measures. In the case of orbital floor fractures, it has also been shown that as a rule approx. 10 slice images at intervals of 3 mm are sufficient.

Claims

Claims:

1. A method for obtaining information about a bone fracture, for example an orbital floor fracture, wherein layer images generated with the aid of a recording device are subjected to image processing for the purpose of generating fracture image data from which information regarding the size of the fracture area is derived, characterized in that from the the fracture image data of the individual slice images obtained with the aid of image processing are taken from the dimension values relating to the fracture area, on the basis of which an area determination is carried out via the slice images to represent the extent of the fracture.

2. The method according to claim 1, characterized in that in the course of determining the area, information about the position of the fracture in the affected bone area is also derived from the fracture image data.

3. The method according to claim 1 or 2, characterized in that the fracture is graphically represented in the affected bone area.

4. The method according to any one of claims 1 to 3, characterized in that the area of the fracture area is approximated by the calculation of trapezoidal areas on the basis of length measurements taken from the fracture image data of each slice image and of the distance values between the respective slice image levels and the addition of these trapezoidal areas becomes.

5. The method according to any one of claims 1 to 4, characterized in that in the event of a fracture of the orbital floor, the area of the orbital floor together with the area of the fracture area by the calculation of trapezoidal areas on the basis of length measurements taken from the fracture image data of each slice image and from the distance values between the respective slice planes and the addition of these trapezoidal surfaces is approximated.

6. The method according to claim 4 or 5, characterized in that in each case the arithmetic co-determination of two consecutive lengths, from two adjacent slice images, is used.

7. The method according to any one of claims 4 to 6, characterized in that the length dimensions taking into account a in the affected bone area, e.g. Orbital floor, given curvature can be determined.

8. The method according to claim 7, characterized in that the curvature, seen in section according to the respective layer image plane, is approximated by an arc.

9. The method according to any one of claims 1 to 8, characterized in that in the event of a fracture of the orbital floor, the herniation volume defined by the fracture piece projecting obliquely from the rest of the orbital floor in relation to the original orbital floor is also determined.

10. The method according to claim 9 and one of claims 4 to 8, characterized in that the herniation volume is determined by layer-by-layer calculation of partial volumes on the basis of area dimensions obtained from the fracture image data of the layer images and addition of these partial volumes.

11. The method according to claim 10, characterized in that the partial volumes are graphically represented for each slice image.

12. The method according to any one of claims 1 to 11, characterized in that the slice images are generated with the aid of computer tomography.

13. Device for performing the method according to one of claims 1 to 12, with a layer image recording device (1), an associated image processing unit (2) and an image reproduction unit (3), characterized by with the image processing unit (2) or Image display unit (3) connected computer means (12), which are set up, from the image processing unit (2) output fracture image data by specifying dimension values per layer image via the image display unit (3) an area determination for displaying the The extent of the fracture (11).

14. Device according to claim 13, characterized in that the computer means (12) are further set up to derive information about the position of the fracture in the affected bone area (6 ') from the fracture image data in the course of the area determination.

15. Device according to claim 13 or 14, characterized in that the computing means (12) for graphical representation of the fracture (11) in the affected bone area (6 ') / e.g. on the image display unit (3).

16. Device according to one of claims 13 to 15, characterized in that the computing means (12) are set up to calculate the area of the fracture area (6 ') by calculating trapezoidal areas on the basis of length dimensions (X, Y.) Taken from the fracture image data of each layer image ) as well as from the

Distance values (S) between the respective slice planes and the addition of these trapezoidal surfaces.

17. Device according to one of claims 13 to 16, characterized in that the computing means (12) are set up, in the event of a fracture of the orbital floor (6 '), the area of the orbital floor together with the area of the fracture area (11) by the calculation of To approximate trapezoidal areas on the basis of length dimensions (X, Y, L) taken from the fracture image data of each layer image and of the distance values (S) between the respective layer image levels and the addition of these trapezoidal areas.

18. Device according to claim 16 or 17, characterized in that the computer means (12) are set up to use the arithmetic mean of two successive length dimensions from two adjacent slice images to calculate the trapezoidal areas.

19. Device according to one of claims 16 to 18, characterized in that the computing means (12) are set up, the length dimensions taking into account a bone in the affected area, e.g. orbital floor (6 ') / given curvature.

20. Device according to one of claims 13 to 19, characterized in that the computer means (12) are set up, in the event of a fracture of the orbital floor (6 ') also defined by the fracture piece projecting obliquely from the rest of the orbital floor in relation to the original orbital floor Determine herniation volume.

21. Device according to claim 20, characterized in that the computing means (12) are set up to determine the herniation volume by layer-by-layer calculation of partial volumes on the basis of area dimensions (H) obtained from the fracture image data of the layer images and addition of these partial volumes.

22. Device according to claim 21, characterized in that the computing means (12) are set up to graphically, e.g. on the image display unit (3).

23. Device according to one of claims 13 to 22, characterized in that the layer image recording device (1) is formed by a computed tomography device.