FI125761B - Generating panoramic images of a tooth - Google Patents

Generating panoramic images of a tooth Download PDF

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Publication number
FI125761B
FI125761B FI20130379A FI20130379A FI125761B FI 125761 B FI125761 B FI 125761B FI 20130379 A FI20130379 A FI 20130379A FI 20130379 A FI20130379 A FI 20130379A FI 125761 B FI125761 B FI 125761B
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panoramic
image
images
ray
curve
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FI20130379A
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Finnish (fi)
Swedish (sv)
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FI20130379A (en
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Lasse Toimela
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Planmeca Oy
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    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/02Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03Computerised tomographs
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/02Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03Computerised tomographs
    • A61B6/032Transmission computed tomography [CT]
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/14Applications or adaptations for dentistry
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/46Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with special arrangements for interfacing with the operator or the patient
    • A61B6/461Displaying means of special interest
    • A61B6/466Displaying means of special interest adapted to display 3D data
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/52Devices using data or image processing specially adapted for radiation diagnosis
    • A61B6/5205Devices using data or image processing specially adapted for radiation diagnosis involving processing of raw data to produce diagnostic data
    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T3/00Geometric image transformation in the plane of the image
    • G06T3/40Scaling the whole image or part thereof
    • G06T3/4038Scaling the whole image or part thereof for image mosaicing, i.e. plane images composed of plane sub-images
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/02Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/027Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/42Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis
    • A61B6/4208Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector
    • A61B6/4233Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector using matrix detectors
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/44Constructional features of the device for radiation diagnosis
    • A61B6/4429Constructional features of the device for radiation diagnosis related to the mounting of source units and detector units
    • A61B6/4435Constructional features of the device for radiation diagnosis related to the mounting of source units and detector units the source unit and the detector unit being coupled by a rigid structure
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/52Devices using data or image processing specially adapted for radiation diagnosis
    • A61B6/5211Devices using data or image processing specially adapted for radiation diagnosis involving processing of medical diagnostic data
    • A61B6/5223Devices using data or image processing specially adapted for radiation diagnosis involving processing of medical diagnostic data generating planar views from image data, e.g. extracting a coronal view from a 3D image
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/52Devices using data or image processing specially adapted for radiation diagnosis
    • A61B6/5211Devices using data or image processing specially adapted for radiation diagnosis involving processing of medical diagnostic data
    • A61B6/5229Devices using data or image processing specially adapted for radiation diagnosis involving processing of medical diagnostic data combining image data of a patient, e.g. combining a functional image with an anatomical image
    • A61B6/5235Devices using data or image processing specially adapted for radiation diagnosis involving processing of medical diagnostic data combining image data of a patient, e.g. combining a functional image with an anatomical image combining images from the same or different radiation imaging techniques, e.g. PET and CT
    • A61B6/5241Devices using data or image processing specially adapted for radiation diagnosis involving processing of medical diagnostic data combining image data of a patient, e.g. combining a functional image with an anatomical image combining images from the same or different radiation imaging techniques, e.g. PET and CT combining overlapping radiation images, e.g. by stitching
    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T11/002D [Two Dimensional] image generation
    • G06T11/003Reconstruction from projections, e.g. tomography
    • G06T11/006Inverse problem, transformation from projection-space into object-space, e.g. transform methods, back-projection, algebraic methods

Description

GENERATING DENTAL PANORAMIC IMAGES TECHNICAL FIELD

The invention generally relates to dental panoramic imaging and, more particularly, to generating digital dental panoramic images from multiple frame images acquired during a dental panoramic imaging scan about a patient's head.

BACKGROUND OF INVENTION

A traditional operation principle of panoramic X-ray apparatuses includes driving an X-ray source and a film cassette around a patient's head while a film is moved with respect to the X-ray beam in such a way that the dental arch will be imaged as a planar picture on the film.

This basic operation of the traditional dental panoramic imaging includes creating a respective mutual movement between the X-ray source, the image information receiver and the patient. While there are number of possibilities to create such movement, the most common arrangement has been to attach the X-ray source and the image information receiver to a support arm at a distance from each other, which arm is then moved in a specific way with respect to a stationary patient. In such context, in order to obtain a sharp image of a desired layer within the object, i.e. the layer of a dental arch within a patient's head, the velocity of movement of the film has to be specifically correlated with the sweep velocity of the X-ray beam along the desired layer to be imaged. By this arrangement, the undesirable structures in front of and behind the desired layer within the patient's head are blurred invisible.

In the traditional panoramic imaging, the thickness of the layer that will be photographed sharp is directly proportional to the distance of the instantaneous center of rotation of the support arm from the film level, and inversely proportional to the magnification and to the width of the beam.

This basic equation of panoramic imaging can be expressed as follows : vl/vO = L1/L0 vO - cor where : LO = distance from the X-ray tube focus F to a point of the object being imaged at a given moment;

Ll = distance from the X-ray tube focus F to the X-ray film (or detector) plane; ω = angular velocity of rotational movement about the instantaneous center of rotation; r = distance of the point of the object being imaged from the instantaneous center of rotation; and vl = velocity of the image point on the film (detector) plane.

The velocity vl thus relates to the speed by which the film is moved during the panoramic imaging scan relative to the x-ray beam hitting the film. As to digital imaging, when a so-called TDI imaging technique (Time Delayed Integration) is used, the transfer velocity of pixel charges across the detector is made to correspond to the velocity of film movement. Thus, the image data read out from the sensor will correspond to the panoramic film image in the sense that blurring of the layers outside the desired layer is already done when the scanning process and charge transfer are carried out so as to follow this imaging equation. In this context, as far as selecting the tomographic layer to be shown is concerned, post exposure image processing is not needed nor would it even be possible, as the data read out from the sensor already represents the very layer the velocity vl corresponds to.

Prior art digital panoramic imaging also includes a so-called FT (Frame Transfer) technigue. When using FT or any other tech-nigue in which a number of individual overlapping frames are shot during the imaging scan, when one wishes to view the same layer as one would get when following the traditional panoramic imaging equation presented above, the degree of overlap of the frames when constructing the layer to be viewed as sharp shall be made to correspond to the velocity vl.

One advantage the frame technique brings along is that since the degree of overlap of the frames used in the image processing determines the layer that will be relatively intensified while the others will be blurred, by altering the degree of overlap on can change the tomographic layer to a certain degree after the exposure. The extent one is able to alter the layer depends on how and by which kind of means the frame data has been acquired. Typically, however, only marginal changes in the location of the layer are possible.

Still, while the prior art frame panoramic systems include the possibility to marginally alter the sharp layer, the degree of overlap used in the image construction is based on some predetermined scheme. These schemes typically include using a standard overlap of the frames and the actual calculation of the panoramic image does not include any parameter which would relate to the actual imaging geometry of the imaging system at the exposure positions of the frames.

Further, as the viewing direction of the anatomy is primarily dictated by the imaging geometry used to obtain the frame data, i.e. by the geometry according to which the imaging means (the x-ray source and the image information receiver) move when the frame data is acquired, the prior art systems are stuck with that viewing direction as they lack means to alter a viewing direction from which the panoramic images or sections of them are shown.

Further, even though the frame imaging technique makes it possible to use wider detector areas than possible in practice when using the more traditional continuous scanning techniques, there are criteria such as those relating to the necessity to be able to read out a frame fast enough during the imaging scan, as well as not to have major alterations in the magnification ratio within a single frame, which have set practical limits also to the width of the detectors one can use in the prior art dental panoramic frame imaging.

SUMMARY OF THE INVENTION

The main objective of the invention and its preferable embodiments is to provide a system by which the frame image data acquired in a single panoramic imaging scan can be used in relation to knowledge of the true imaging geometry used in the imaging procedure, regarding each exposure position, so as to provide new possibilities for generating dental panoramic images from the frame data after the exposure. Secondary objectives of the invention include making it possible to not only generate more than one tomogaphic layer from the frame image data acquired in a single panoramic imaging scan but also to construct and display images or partial images of dental arch as viewed from different directions.

These and other objectives of the invention that will be discussed below can be reached by embodiments of the invention as defined in the attached claims. The core of the invention is to implement the panoramic scan so that information of the imaging geometry, that is location and orientation of the detector and of the focus of the x-ray tube and, and thus of the x-ray beam, is known at their exposure positions and this information is then used in calculating a dental panoramic image.

Advantages the various embodiments of the invention provide includes a possibility to be able to generate dental panoramic images from a single frame data set as viewed from more than one direction. When it is possible to virtually change the viewing angle, features of an anatomy may become visible which are not visible from a particular other viewing direction. Thus, e.g. re-exposure of a patient to x-radiation due to a need for a re-take of the image may be avoided. Further, embodiments discussed below provide a possibility to use wider detectors than typically used in dental frame panoramic imaging.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and some of its preferable embodiments will be discussed below, by also referring to the attached Figs, out of which

Fig. 1 shows an example of a panoramic imaging apparatus,

Fig. 2 shows some of the basic components of a system to implement the embodiments discussed below,

Fig. 3a shows a dental panoramic image and Fig. 3B an individual frame image out of number of which a dental panoramic image may be generated,

Fig. 4 shows individual overlapping frames together with a line representing a vertical section of an anatomy which is projected at different locations of the frames as an imaging detector is moved to new exposure positions,

Fig. 5 shows a schematic drawing of the principle of the panoramic imaging process according to an embodiment of the invention,

Fig. 6 shows steps of a method in which principles of the invention are applied and

Fig. 7 shows a schematic drawing illustrating a hardware configuration of an information handling/computer system which can be used when implementing the invention.

DETAILED DESCRIPTION OF INVENTION

The embodiments discussed herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

It should also be understood that the embodiments are exemplary. For example, in case the specification refers somewhere to "an", "one", or "some" embodiment (s), this does not necessarily mean that each such reference is to the same embodiment(s) , or that the feature only applies to a single embodiment. Single features of different embodiments may be combined to provide other embodiments, even if that has not been explicitly disclosed in a given context.

The embodiments of the invention discussed herein use location and orientation information of an x-ray beam and an x-ray detector when taking overlapping frames along a dental arch to generate a dental panoramic image. For example, embodiments discussed below permit a user to view specific points of inter est of the dental arch from an angular area, i.e. from more than one viewing direction. Thus, the embodiments described herein may permit the user to view specific features between a patient's teeth in a dental panoramic radiograph, for example, which features may be invisible in another dental panoramic radiograph generated using prior art methods and arrangements.

Of the attached figures, Fig. 1 presents a structure of an exemplary panoramic X-ray imaging apparatus. The apparatus comprises a base 27 and a column-like frame part 12 fixed by its lower end to the base 27. A supporting arm 13 (shown without its cover) is rotatably mounted on the upper end of the frame part 12. Correspondingly, rotatably mounted on the outer end of the supporting arm 13 is another, intermediate supporting arml4 on the outer end of which is further rotatably mounted an imaging arm 15, or a C-arm as it is often called. The C-arm 15 supports the imaging means, i.e. an x-ray source 26 and an image detector 16. Moreover, a positioning support 25 is attached to the column-like frame part 12 to help in positioning the person to be imaged. Instead of on the column-like frame part 12, the rotatable supporting arm 13 may as well be mounted on wall or ceiling structures.

The structure illustrated in Fig. 1 has been simplified for the sake of clarity. For example, force receiving means serving as transmission means of the arm structures 13-15 are not shown in the figure. Likewise, the stepping motors 1 to rotate the arm structures 13-15 are depicted in a simplified form.

The apparatus as shown in Fig. 1 and its control system (not shown in Fig. 1) provides an example of a structure for moving the rotation centre of the C-arm 15 which carries the imaging means to perform a panoramic imaging scan about a patients head using basically any shape of trajectory of the rotation centre one desires. Structures of dental panoramic imaging apparatus vary and at the simplest, the imaging apparatus may allow for just one fixed imaging geometry.

The basic components of a system to implement the invention, as shown in Fig. 2, include a control system CS of the imaging apparatus, which includes or is in operational connection with motors 1 that drive the arm or the arms 13-15 of the apparatus, and with operating electronics of the detector 16. The system includes a memory M for, amongst other, recording frame image information and information regarding the related imaging geometry, processing means IP to create a panoramic image, a screen S on which to show images and a user interface UI.

Fig. 3A shows a typical dental panoramic image 200. When a digital panoramic image 200 is constructed from frame image data acquired during a panoramic imaging scan, Fig. 3B can be considered representing one of hundreds or thousands of partially overlapping frame images 300 that are taken during the scan. Fig. 4 then shows a principle of how overlapping individual frames 310, 315, 320 acquired during a panoramic imaging scan can be used in constructing the digital panoramic image 200. Line 210 which vertically spans the frames 310, 315, 320 represents location of a pixel column in each of the frames which includes image information of the same thin vertical section of the anatomy being imaged. The image information these columns include is used to construct a pixel column C of the final digital panoramic image 200 to be generated, as to be discussed in more detail below. Frames taken before frame 310 and after frame 320 which do not do not intersect the line 210 and thus do not include information concerning the particular section of the anatomy the line 210 represents, will not contribute to that particular column C of the panoramic image 200 being generated .

Fig. 5 shows a schematic drawing to explain principles of the panoramic imaging process of the invention. The process uses what will be called here a virtual panoramic curve 400, together with data of location of and orientation of the imaging means during exposure in the coordinate system of this curve.

To put this in other words and as will be discussed in further detail below, the process includes placing a virtual panoramic curve 400 which represents location and shape of the tomographic layer to be generated in the coordinate system of the imaging geometry used when shooting the frame data.

In Fig. 5, a number of points (PI, P2, P3, P4) are shown on the panoramic curve 400, each of which can be considered corresponding to a location of a section of anatomy to be shown in the panoramic image. In other words, each point (PI, P2, etc.) represents location of a vertical layer of a dental arch which is to be shown as an individual pixel column in the generated digital panoramic image.

Fig. 5 further shows two exposure positions, i.e. positions (E', E'') of the x-ray source and the detector at the time of an exposure and, thus, that of the x-ray beam which penetrates the anatomy being imaged and hits the detector. When this imaging geometry is known, one will be able to determine the location of projection P' of each point P on the detector, at each of the exposure positions in which a projection P' falls on the detector. These projection points P' determine pixel columns on the detector which are to be used in constructing the column C of the panoramic image, which represents a given point PN of the anatomy, which projection P -> P' can be considered defining a projection direction of the point P concerning a particular individual frame 300.

As can be seen in Fig 5, in the first of the exposure positions E' the projection P'2 of point P2 as seen from the focus of the radiation source falls on the detector (a frame) at a location which is quite far from the centre of the detector while in the second position E'', the projection P''2 falls basically at the centre of the detector. This is an occurrence a prior art image constructing process might miss in summing columns of overlapping frames by some standard predetermined procedure, while the embodiments discussed here make it possible to select columns to be used in constructing the panoramic image based on actual knowledge of the imaging geometry. In other words, instead of just adding column information of overlapping frames according to some standard summing protocol, one determines that particular column of each of the frame images where a projection of any particular point PI, P2 etc. lies, when viewed from the instantaneous location of the focus of the X-ray beam at the time of shooting the image, and uses specifically those columns in calculating columns C of the panoramic image being generated.

Knowing the imaging geometry, i.e. location and orientation of the X-ray source and the detector during the imaging scan, it also becomes possible by changing the shape or orientation, or both, of the panoramic curve 400 to not only calculate different layers of the anatomy as such but also to construct and display object layers viewed from different directions. This feature of the invention can be understood by considering that the panoramic curve 400 of Fig. 5 would be say slightly turned counter-clockwise about point P4. Considering the imaging positions E' and E'', this would bring projections P'2 and P''2 more to the left on the detector (on a frame, as viewed from the direction of the focus of the x-ray source) and thus, different pixel column information would be selected to be used in constructing the panoramic image. These different columns would then represent not only a different layer but also a different angle of view of the object than that according to Fig 5.

In principle, one can use a virtual panoramic curve 400 of any shape and arranged in any orientation in the coordinate system of the imaging geometry. This allows for constructing tomographic layers having shapes even the very versatile apparatus of Fig. 1 could not create by mere mechanical movements of the arm construction of the apparatus.

As a further aspect, an individual local viewing vector D for any number of points PI, P2 etc. may be determined. In addition to what has been discussed above referring to Fig. 5, a vector D is included in the drawing to denote a desired local viewing direction of point P2. Such vectors D can be used to determine weighting factors for pixel values of the columns of the frames representing particular points PI, P2 etc. of the anatomy. For example, as one can see in Fig. 5, the angle between vector D and the projection direction defined by the line starting from the focus of the radiation source and ending at a projected point P' is somewhat greater in the second E1' than in the first exposure position E' of Fig 5. When this type of embodiment is applied, relatively less weight in the image construction would be given to the pixel values of the column of the projected point P''2 of the second exposure than for values of the projected point P'2 of the first exposure. When this principle is applied to a projection P' of point P, i.e. when more weight is given to pixel values of a certain projection direction than to others, features of the anatomy as view from the favoured direction will become emphasized.

A flow diagram shown in Fig. 6 illustrates one preferred method to implement the principles of the invention. In the first step 500 of the Fig. 7 method, frames and respective exposure positions of the frames during a panoramic imaging scan which has been performed are read. Next, in step 510, the virtual panorama curve one wishes to use in the image construction is obtained, which curve is then divided in step 520 into a plurality of points P - or, in other words, a plurality of points P are selected from the curve, preferably equidistantly, to define points of the anatomy which are to correspond columns C of the panoramic image being generated. An individual viewing direction D for points P may be determined in step 530.

In practice, in view of the imaging geometry to be used in the panoramic imaging scan, it would be preferable that one is aware of the virtual panoramic curve or curves 400 planned to be used in the image construction so that the imaging geometry will reasonable enable generating such desired layer or layers.

Having all the data now available, generating columns C of the panoramic image 200 to be constructed may commence (step 540). First, a point P which corresponds to a column C of the panoramic image, and a related local viewing direction D if such has been determined for a point P is found in step 550. Then, as the panorama curve 400 and respective locations and orientations upon exposure of each frame and of the radiation source are known, a process can be performed for each of the frames (step 560) in which, first, a point P is projected to a frame along a line which originates from the focus of the radiation source in step 570. In practice, concerning most of the frames, there will be no projected point P' as a line originating from the focus of the x-ray source and going through a point P on the panorama curve does not intersect most of the frames but concerning the rest few, the projected point P' on a frame will define the pixel column of that particular frame which is to be used in constructing the column C of the panoramic image the point P in guestion represents (steps 580 and 610).

In case a local viewing direction D for a given point P has been determined, the process further includes determining the angle between the local viewing direction D and the line originating from the focus of the x-ray source and crossing the point P in question in step 590. This angle can be used as a weighting factor in step 600 to give the less weight in the image construction (step 610) to the frames (i.e. to the pixel values of the projected point P' of the frame) the more the direction of a projection of the point P (or, in other words, in reference to Fig 5, a vector from P to P') deviates from the desired local viewing direction D. After completion of this process (step 620), the pixel values of each column C of the final panoramic image are normalized by dividing values of a given column by the total sum of the weighting factors of that column.

The procedure discussed above can be presented in more general terms to include using several individual overlapping frames 300 taken along a dental arch by a dental panoramic x-ray imaging apparatus, said apparatus including an x-ray source for generating an x-ray beam and having a focus, and an image detector having pixel columns, the frames 300 being taken by moving the x-ray source and the image detector around a patient's head, and calculating the panoramic image 200 by summing information of the frames 300, and generating the panoramic image 200 by summing information of the frames 300 with respect to information of location and orientation of the x—ray beam and the x-ray detector at times when taking the frames. Summing of information may then include determining location of a desired point or points P with respect to information of location and orientation of the x—ray beam and the x—ray detector at times when taking the frames, whereby the summing of information of the frames 200 then includes summing a column or columns C of the panoramic image 200 with respect to the point or points P. On the other hand, at least two panoramic images 200 as viewed from different directions can be generated and at least two images representing views from different directions then be pre— sented on the display siinultsnGously/ in succession, bs b com bination image or as a moving image.

An embodiment can also include generating a virtual panorama curve 400 which represents a tomographic layer to be shown by the panoramic image 200, placing this curve 400 and information of location and orientation of the x-ray beam and the x-ray detector in the same set of coordinates, and generating a panoramic image 200 which represents a tomographic layer according to location of the curve 400 in this set of coordinates.

Yet another embodiment can include generating a virtual panorama curve 400 with respect to information of location and orientation of the x-ray beam and the x-ray detector which represents a desired tomographic layer to be shown by the panoramic image 200 and, for a column C of the panoramic image 200 being generated, determining the desired point P on the curve 400, and generating a column C of the panoramic image 200 by summing those columns of the individual frames 300 to which the point P as viewed from the focus of the radiation source is projected, this projection P -> P' defining a projection direction of the point P concerning the particular individual frame 300.

Concerning the weighting factor, the related process can be presented to include determining a desired viewing direction D for at least one point P whereby a weighting factor is calculated for a column on an individual frame 300 as based on an angle between the viewing direction D and a direction defined by a line from the focus of the radiation source to said point P, the weighting factor then being used when summing information of the frames 300 so as to give the less weight to a column of a frame the greater the angle between said directional vector D representing the desired viewing direction and the direction defined by a line from the focus of the radiation source to the point P.

The virtual panoramic curve used in the embodiment discussed above can be considered to be a tool which makes it possible to alter the tomographic layer in a controlled manner with respect to the imaging geometry used in acquiring the frame data and it can also be used to alter the direction from which the anatomy or a part thereof is viewed. By changing the shape or orientation of the virtual panoramic curve, or both, and even applying the local viewing direction vector discussed above, different images of dental arch can be constructed based on the one and the same set of original x-ray frame image data acquired in a single panoramic imaging scan.

A virtual panorama curve 400 to be used in generating a panoramic image may be defined in a number of different ways. One preferred way is to first generate a curve that fulfils the basic panorama equation discussed above with respect to movements of the imaging means. As movements of the imaging means in a panoramic imaging apparatus of a given type are often fixed, or the same few standard movements are typically used, a panorama curve 400 corresponding to a particular imaging procedure can be created and stored for later use. Additionally, a previously used or stored virtual panorama curve, or a virtual panorama curve just having been used, may be modified e.g. by means which include a linear transformation of all points P and the related viewing directions. The linear transformation may include rotational and translational parts. The modification can also include using a non-linear mapping function such as a two dimensional spline surface, which can be used to deform the panorama curve .

Embodiments of the invention include, as noted, novel ways not only to create dental panoramic images as such but also to show them on a display. For example, when information of location and orientation of the x-ray beam and the x-ray detector at times when taking the frames is available, two or more panoramic images as viewed from different directions can be generated by summing the frame information differently with respect to information of location and orientation of the x-ray beam and the x-ray detector, which in turn makes it possible to display images as viewed from different directions on a display e.g. simultaneously, in succession, as a combination image or as a moving image.

For example, a first and a second virtual panoramic curve with respect to information of location and orientation of the x-ray beam and the x-ray detector can be generated, both of the curves representing a desired layer to be shown by a panoramic image, the second curve being generated from the first one by-changing orientation of the first curve, and the two panoramic images then be calculated by summing information of the frames acquired in the panoramic imaging process with respect to these different curves. Of course, more than two curves can be used and e.g. an illusion of turning the dental arch can be generated by showing in succession panoramic images of altering viewing direction. In other words, this type of embodiment may include presenting images on a display in succession according to the order of their viewing direction so as to give an impression of the dental arch turning on the display.

A further embodiment can include generating several panoramic images as viewed from different directions, generating for each such viewing direction several images representing different sharp layers and then, concerning each such viewing direction, one of the several images representing different sharp layers can be selected to represent said viewing direction, after which the images thus selected can be presented on the display - in reference to above, e.g. simultaneously, in succession, as a combination image or as a moving image.

Use of the weighting factor as discussed above may enhance the effect of different viewing angles by emphasizing columns that have a primary x-ray travel path more in line with the viewing angle of the panoramic curve at a given point P.

Using weighting factors also contributes to the possibility to use wider detector surfaces than commonly used in dental frame panorama applications. When the prior art summing of the frame data is based on some standard overlapping procedure, the more likely it becomes that columns that are summed together do not represent the same section of the anatomy the further one goes from the centre of the detector. This is due to the summing protocol not knowing the exact changes in the overall imaging geometry during the exposure process, i.e. the changes there are in mutual positions and orientations of the imaging means and the layer desired to be generated. When using the principles discussed here, though, blurring of the panoramic image due to adding information to the columns C of the panoramic image 200 representing altering locations of the anatomy can be avoided. The weighting factor can also be used to compensate for an altering magnification.

Concerning embodiments of the invention, one possibility to create an illusion of turning an imaged anatomy is to use only one virtual panorama curve yet generate various panoramic images based on it by systematically changing orientation of the local viewing direction vectors D of points P discussed above. Overall, it is clear that the scope of the invention in view of displaying the imaged anatomy based on a frame data acquired in a single panoramic imaging scan includes any combination of modifying the virtual panorama curve 400 and orientation of the local direction vectors D of points P, including modifying only a selected number of the vectors D, so as to display different layers of the anatomy and from different angles of view, or only either of these.

The embodiments discussed here make it possible to use for dental frame panoramic imaging to realize the embodiments a dental panoramic imaging apparatus which includes an x-ray source having a focus and an image detector having a number of pixel columns, the x-ray source and the image detector being arranged to the apparatus at a first distance from each other, a drive means for moving the x-ray source and the detector around a patient' s head, a control system including means to control the apparatus to take several individual overlapping frames along a dental arch. The detector may be implemented as wide or wider than a second distance and the control system arranged to control the apparatus to take frames whose width is equal to the second distance, the second distance being of about 2-10 % of said first distance. In an embodiment, the distance between the x-ray source and the image detector may preferably be about 500 - 550 mm.

As discussed, embodiments discussed here may also make it possible for one being able to display anatomies which otherwise could not be made visible, not at least without exposing the patient to a further panoramic irradiation process. When one is able to change the angle of view, details of the imaged anatomy may become visible which otherwise would not be visible. For example, a tooth filling may hamper getting a tooth on the other side of the dental arch visible, but changing the viewing direction may be able to bring such tooth visible after all.

Shown in Fig. 7 is a schematic drawing which illustrates a hardware configuration of an information handling/computer system by which embodiments of the invention may be realized. System 1000 of Fig. 7 comprises at least one processor or central processing unit (CPU) 1010. The CPUs 1010 are interconnected via system bus 1012 to various devices such as a random access memory (RAM) 1014, read-only memory (ROM) 1016, and an input/output (I/O) adapter 1018. The I/O adapter 1018 can connect to peripheral devices, such as disk units 1011 and tape drives 1013, or other program storage devices that are readable by system 1000. System 1000 can read the inventive instructions on the program storage devices and follow these instructions to execute the methodology of the embodiments herein. The system further includes a user interface adapter 1019 that connects a keyboard 1015, mouse 1017, speaker 1024, microphone 1022, and/or other user interface devices such as a touch screen device (not shown) to the bus 1012 to gather user input. Additionally, a communication adapter 1020 connects the bus 1012 to a data processing network 1025, and a display adapter 1021 connects the bus 1012 to a display device 1023 which may be embodied as an output device such as a monitor, printer, or transmitter, for example.

Thus, a further embodiment includes a dental panoramic imaging apparatus which includes an x-ray source having a focus and an image detector having a number of pixel columns, the x-ray source and said image detector being arranged to the apparatus at a distance from each other, a drive means for moving the x-ray source and the detector around a patient's head, a control system including means to control the apparatus to take several individual overlapping frames along a dental arch, and a user interface to send control commands to said control system, the control system including recorded information on location and orientation of the x-ray source and the x-ray detector at times when taking the frames, and a means for calculating a panoramic image by summing information of the frames with respect to said information so as to generate panoramic images as viewed from at least two different directions, the user interface including a means to give at least one control command relating to showing the at least two panoramic images as viewed from the at least two different directions.

Δ dental panoramic imaging apparatus with structural features of the paragraph above may also be used as including a control system and/or image processing or other features relating to acquiring and constructing images according to any embodiments discussed here.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred em bodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.

Claims (8)

  1. A method for generating a digital dental panoramic image, comprising: using a plurality of individual overlapping dental panoramic x-ray imaging (300) images, said imaging device comprising: an image detector around the patient's head, and - calculating the panoramic image (200) by summing the information of the images (300), wherein the panoramic image (200) is generated by summing the information of the images (300) in that said generating a panoramic image (200) includes generating a virtual panoramic curve (400) taking into account said X-ray data the location and orientation of the decal and the image detector representing the virtual panoramic curve (400) that the panoramic image (200) is desired to display, (200) generating a column C by summing the columns of individual images (300) projected from a point of view of the X-ray source, which projection P -> P 'defines the projection direction of P for that single image, defining the desired viewing direction D Calculating P and weighting for column C of a single image (300) based on the angle between desired viewing direction D and projection direction, and - applying said weighting to summing said image (300) information by providing image (300) for granule C, always the less weight, the greater the angle between the direction vector representing the desired viewing direction and said projection direction.
  2. The method of claim 1, wherein said virtual panoramic curve (400) and said X-ray and image detector location and orientation information are located in the same coordinate system, and a panoramic image (200) is generated according to the location of said virtual panoramic curve (400).
  3. The method of claim 1 or 2, wherein the pixel values in columns C of the panoramic image (200) are normalized by dividing the pixel values of the column C in question by the sum of the weight coefficients of the column C in question.
  4. A method for generating and displaying digital dental panoramic images, comprising: - using a plurality of individual overlapping dental panoramic x-ray imaging devices (300) in conjunction with said imaging device, said images (300) being taken by moving an X-ray source and an image detector around a patient's head, - calculating a panoramic image (200) by killing the information of the images (300) and displaying a panoramic image (200) depicting the tomography layer thus generated a viewed panoramic image (200), said generation comprising: generating a virtual panoramic curve (40); 0) representing the tomography layer shown in the panoramic image (200), and said curve (400) and said X-ray and image detector position and orientation information are placed in the same coordinate system, said at least two panoramic images (200) viewed from different directions said virtual panoramic curve (400) such that the virtual panoramic curve (400) is arranged at least to the first and second orientations in said coordinate system such that for each orientation: 200) column C is generated by killing the columns of the individual images (300) into which point P, projected from the focus of the X-ray source, which projection P -> P 'defines the point P pro for that single image (300) and, said at least two images representing views from different directions being displayed on the screen simultaneously, sequentially, in a composite image, or as a moving image.
  5. The method of claim 4, wherein generating said at least two panoramic images (200) includes killing the information of said images (300) in at least two different ways, taking into account X-ray and image detector location and orientation information when taking the images.
  6. The method of claim 4 or 5, wherein at least two panoramic images (200) are sequentially displayed on the display to give an impression of a rotating tooth arc on the display.
  7. The method of claim 6, generating a plurality of panoramic views (200) viewed from different directions, generating a plurality of tomography images for each viewing direction, selecting, for each viewing direction, one of said plurality of tomography layers representing said viewing direction, and on the screen.
  8. The method of any one of claims 4 to 7, wherein the location of the desired point or points P relative to said X-ray and image detector location and orientation information is determined and said summing of the images (300) comprises summing a column (s) of to P.
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CN201910704924.2A CN110353717A (en) 2013-12-18 2014-12-18 Generate panoramic dental image
PCT/FI2014/000041 WO2015092119A1 (en) 2013-12-18 2014-12-18 Generating dental panoramic images
RU2016125711A RU2677830C1 (en) 2013-12-18 2014-12-18 Generating dental panoramic images
EP14871134.4A EP3082609A4 (en) 2013-12-18 2014-12-18 Generating dental panoramic images
CN201480074309.3A CN105934201B (en) 2013-12-18 2014-12-18 Generate panoramic dental image
JP2016540978A JP6595480B2 (en) 2013-12-18 2014-12-18 Generating dental panoramic images
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KR101740851B1 (en) 2016-02-04 2017-06-09 (주)제노레이 X-ray imaging machine, method for generating panorama image using the same
KR101880150B1 (en) * 2016-09-06 2018-07-19 오스템임플란트 주식회사 Method and apparatus for generating panoramic image, panoramic x-ray imaging apparatus, computer-readable recording medium and computer program
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