METHOD AND APPARATUS FOR PROVIDING TWO DIGITAL PANORAMIC LAYER IMAGES

Abstract

The invention relates to a method for providing a first and a second digital panoramic layer image optimized for a comparison, wherein the first and second panoramic layer images each have multiple projections detected and stored for them by means of at least one digital detector during an at least partial revolution of a recording unit around an object to be recorded, and the first and second panoramic layer images are each produced from the multiple projections in accordance with a computation code and by forming a panoramic layer. Differences between the first and second panoramic layer images are minimized by altering at least one parameter of the computation code for fresh production of the first and/or second panoramic layer image. In addition, the invention relates to a corresponding apparatus.

Claims

1. Method for providing a first and a second digital panoramic layer image, the method comprising detecting and storing multiple projections of the first and second panoramic layer images with at least one digital detector during at least one partial revolution of a recording unit around an object to be recorded, and producing the first and second panoramic layer images multiple projections in accordance with a computation rule and forming a panoramic layer, wherein differences between the first and second panoramic layer images are minimized due to variation of at least one parameter of the computation rule in case of a new production of the first and/or second panoramic layer images.

2. Method according to claim 1, wherein the parameter to be changed is a position and/or a shape of the panoramic layer.

3. Method according to claim 2, wherein the position of the panoramic layer is altered with regard to three translation and three rotation axes.

4. Method according to claim 2, wherein the shape of the panoramic layer is advantageously altered by a spreading and/or compression and/or scaling.

5. Method according to claim 1, wherein the differences are minimized an optimization method.

6. Method according to claim 5, wherein the optimization method is a brute force method, or a gradient method, or a structure search method.

7. Method according to claim 1, wherein the panoramic layer is varied in at least two different areas of the panoramic layer image.

8. A device for providing a first and a second digital panoramic layer image, the device comprising a calculation unit, a dental x-ray device having an x-ray source and at least one digital x-ray detector that can respectively be moved at least partially around a recording space, and means for transmitting projections detected with the detector to the calculation unit, wherein the calculation unit is designed to produce the first and second panoramic layer images respectively from multiple projections detected during a revolution, according to a computation rule and with formation of a panoramic layer, wherein the calculation unit is capable of executing the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The method according to the invention and the apparatus according to the invention are explained using the drawings. Shown are:

[0025] FIG. 1 an apparatus for providing a first and a second digital panoramic layer image;

[0026] FIG. 2 a method for providing a first and a second digital panoramic layer image.

EMBODIMENTS OF THE INVENTION

[0027] Drawn in FIG. 1 is a dental x-ray device 1 for producing panoramic layer images P1, P2. A patient is typically positioned by means of a positioning device 2 in a recording space between an x-ray source 3 and at least one digital x-ray detector 4, wherein the x-ray source 3 and the x-ray detector 4 are arranged on a rotatable arm 5 and can be moved in at least partial circles around a recording space and a patient positioned therein, so as to produce a panoramic layer image P1, P2. During this at least partial revolution, a projection is respectively detected by means of the x-ray detector 4 for various angle positions of the arm 5 relative to the positioned patient, and said projection is transmitted to a calculation unit 6 by means of a transmission system 7. 3000 such projections, for example, may be detected during a full revolution.

[0028] Following the revolution, a panoramic layer image P1, P2 is produced by means of the calculation unit 6 from the detected projections, in that these are added or superimposed according to a computation rule, so that a classical panoramic layer image results, with a sharp layer (the panoramic layer) and a blurry portion. The more projections that are produced or form the basis for the panoramic layer image, the more distinct the resulting panoramic layer.

[0029] In order to monitor a course of growth or therapy, such a digital panoramic layer image of the same patient may be respectively generated at time intervals, for example. At a first point in time, a first panoramic layer image P1 is thus produced from projections produced during a first revolution and, after some time, a second panoramic layer image P2 is produced from projections of the same patient that are produced during a second revolution, wherein the patient should be positioned as identically as possible for both panoramic layer images P1, P2, and, respectively, the same computation rule is used to produce the two panoramic layer images P1, P2 from the respective projections.

[0030] In order to further optimize the two panoramic layer images for the comparison, according to the invention, the difference between the panoramic layer images P1, P2 is minimized. Differences which are based only upon a different positioning of the patient or different conditions in the recording should in this way be eliminated as completely as possible, or at least to the extent possible, so that real differences in the object to be recorded (the patient, for example) are more simply and clearly recognizable in the images at the two recording points in time.

[0031] For example, for this purpose, differences U1 between the two panoramic layer images P1, P2 are determined in a first step S1, based upon two panoramic layer images P1, P2 produced according to the same computation rule, and by forming a respective panoramic layer from the respective projection images. For example, in a second step S2, the first panoramic layer image P1 is produced again from the projection images detected during the first revolution, wherein a position and/or a shape of the panoramic layer is varied by changing the computation rule. Step S2 may also provide for calculating only the second panoramic layer image P2 again with a modified computation rule, or for producing both panoramic layer images P1, P2 again, with a respectively new computation rule.

[0032] In the subsequent step S3, depending upon the selection of step S2, the newly produced first panoramic layer image P1 is compared with the second panoramic layer image P2, or the first panoramic layer image P1 is compared with the newly produced second panoramic layer image P2, or the newly produced first panoramic layer image P1 is compared with the newly produced second panoramic layer image P2, and differences U2 are determined.

[0033] Steps S2 and S3 are repeated until the determined difference between the current panoramic layer image P1, P2 is optimally small or is no longer present, or a termination condition A is satisfied.

[0034] For example, a limit value for the differences U1, U2 may be provided, and a termination of the minimization may take place as soon as this limit value is underrun. Or, an optimization method for minimizing the differences U1, U2 is used which has a different termination condition.

[0035] In the final step S4, the two current panoramic layer images P1, P2 are stored and/or output, in order to provide them to a user for comparison.

[0036] The difference between the panoramic layer images P1, P2 may be determined or evaluated by means of a mutual information method, for example. A minimization may then include the following method steps, for example: A first parameter (the position, for example) is varied (via translation, for example). At least one of the two panoramic layer images P1, P2 is re-calculated with the modified parameter. The difference between the re-calculated panoramic layer images P1 and P2, or between the re-calculated and unmodified panoramic layer images P1, P2, is evaluated according to the mutual information method. These steps are repeated until a minimum is reached. A corresponding minimization in the difference is subsequently produced with regard to one or more additional parameters, for example. To minimize the difference, for example, the first parameter is subsequently varied again, then the second parameter, etc., until a general minimum in the difference or a general maximum in the identity has been found or is achieved.

REFERENCE CHARACTERS

[0037] 1 digital x-ray device

[0038] 2 positioning device

[0039] 3 x-ray source

[0040] 4 x-ray detector

[0041] 5 rotatable arm

[0042] 6 calculation unit

[0043] 7 transmission system

[0044] A termination condition

[0045] P1 panoramic layer image

[0046] P2 panoramic layer image

[0047] S1 step 1

[0048] S2 step 2

[0049] S3 step 3

[0050] S4 step 4

[0051] U1 differences

[0052] U2 differences