Device for digital imaging of the patient's head area

Abstract

A device for digital imaging of a patient's head region is disclosed, comprising: a source (9) for generating X-ray radiation; a sensor (11) for detecting the X-ray radiation generated by the source (9) and penetrating a patient (14); a rotating arm (6) for arranging the source (9) and the sensor (11) on the rotating arm (6) in a manner opposite to each other, wherein the rotating arm (6) is provided with an adjustment device (10, 12) for changing the distance between the source (9) and the sensor (11); and a supporting structure (2, 3, 4, 5) for supporting the rotating arm (6), wherein a translation and rotation device (7) driven by a motor is disposed between the rotating arm (6) and the sensor (11). between the swivel arm (6) and the support structure (2, 3, 4, 5); wherein the device comprises a single sensor (11) for both panoramic imaging and computed tomography, and the device comprises a control unit (16) which controls the source (9), the sensor (11), the adjustment means (10, 12) and the translation and rotation means (7), and the control unit (16) is arranged to operate the device in a basic working mode for larger patients and in an alternative working mode for smaller patients, in which the distance between the source (9) and the sensor (11) is reduced compared to the distance used in the basic working mode.

Description

Technical Field

[0001] The invention relates to a device for digital imaging of the head region of a patient, comprising:

[0002] - a source for generating X-ray radiation;

[0003] - a sensor for detecting the X-ray radiation generated by the source and penetrating the patient;

[0004] - a swivel arm for arranging the source and the sensor thereon in a manner opposite to one another, wherein the swivel arm is provided with adjustment means for varying the distance between the source and the sensor;

[0005] - A support structure for supporting the rotating arm, wherein the translation and rotation means driven by the motor are interposed between the rotating arm and the support structure. Background Art

[0006] US 2007 / 0030950 A1 discloses a combined panoramic and computed tomography (CT) device for dental imaging. The device comprises an X-ray source and an X-ray sensor unit provided with a panoramic sensor component or a CT sensor component for detecting X-rays generated from the X-ray source and penetrating a patient. The device further comprises a rotating arm for arranging the X-ray source and the X-ray sensor unit thereon in a manner opposite to each other. The rotating arm is supported by a supporting member. A driving device is provided to change the distance between the X-ray source and the X-ray sensor unit arranged opposite to each other relative to the rotating arm.

[0007] The known device can perform panoramic imaging and CT imaging and provides an optimum magnification depending on whether the device is operating in panoramic imaging mode or CT imaging mode. The optimum magnification can be obtained by varying the distance between the X-ray source and the X-ray sensor unit.

[0008] Known devices are only optimally suited for use with adult patients of normal size. However, imaging of smaller patients, especially children, may require modification. Summary of the invention

[0009] Starting from this related art, the present invention aims to provide a device for digital imaging of the head area, which is optimized for patients with smaller bodies, especially children.

[0010] This object is achieved by a device having the features of the independent claim. Advantageous embodiments and developments are described in the dependent claims.

[0011] The device comprises a single sensor for both panoramic imaging and computed tomography of the area of ​​the patient's head and a control unit for controlling the source, the sensor, the adjustment means and the translation and rotation means. The control unit is arranged to operate the device in a basic operating mode for larger patients and in an alternative operating mode for smaller patients, in which the distance between the source and the sensor is reduced compared to the distance used in the basic operating mode. By reducing the relative distance between the source and the sensor, the dose rate and / or the exposure time can be reduced, thereby reducing the radiation risk to the child to be examined.

[0012] For an alternative operating mode, the control unit may move both the source and the sensor towards each other such that the amplification remains constant.

[0013] In an alternative embodiment, the device is set into an alternative operating mode by the control unit only moving the sensor towards a source fixed to the rotating arm. Thus, the rotating arm only needs to be provided with means for moving the sensor towards the source.

[0014] In a modified embodiment, the distance of the alternative operating mode is reduced by moving the axis of rotation. The source remains fixed relative to the rotating arm, and the control unit reduces the distance by moving the axis of rotation of the rotating arm in the direction of the sensor and by moving the sensor towards the source. This keeps the magnification constant for both operating modes.

[0015] In a modified embodiment, a special operating mode can be used for computed tomography, since for computed tomography the axis of rotation can be moved on a trajectory which surrounds a virtual axis of rotation which is located at the object to be imaged.

[0016] To increase the safety of the device, the sensor moves in a housing that is stationary relative to the swivel arm.

[0017] The adjustment means may include means for positioning the sensor selected from:

[0018] - a mechanism comprising means for transverse movement relative to the longitudinal axis of the swivel arm,

[0019] - a mechanism comprising means for rotational movement relative to the rotating arm,

[0020] - a scissor mechanism for varying the distance between a base attached to the rotating arm and the supporting structure of the sensor,

[0021] - a linear mechanism for moving the sensor along the guide structure in the direction of the source, and

[0022] - A combination of the above.

[0023] Mechanisms that allow lateral movement of the sensor can be used to adjust the sensor to panoramic and CT imaging modes. If a rotary mechanism is used to adjust the distance between the source and the sensor, then this can also be used to compensate for lateral movement of the sensor. Mechanisms designed to perform rotary movement have the added advantage of being able to change position quickly. The same is true for scissor mechanisms. Linear mechanisms change position more slowly but are particularly stable and reliable.

[0024] The adjustment mechanism is usually motor driven so that the operator does not have to adjust the distance between the source and the sensor.

[0025] The device may be provided with a primary collimator located between the source and the patient, and the primary collimator is opened wider in the alternative operating mode than in the basic operating mode to take into account the need for a wider beam for the alternative operating mode.

[0026] In an embodiment, in an alternative operating mode, the radiation intensity and therefore the absorbed dose rate is reduced by reducing the current and / or voltage of the source generating the X-rays.

[0027] Specifically, the radiation intensity can be reduced and thus the absorbed dose rate can be reduced by the square of the ratio of the distance between the source and the sensor in the alternative operating mode to the distance between the source and the sensor in the basic operating mode, so that the exposure time can remain unchanged.

[0028] Furthermore, the exposure time of the sensor is shorter in the alternative operating mode than in the basic operating mode.

[0029] Typically, the magnification of the alternative operating mode and the basic operating mode is identical, so that the image provided to the medical personnel always has the customary magnification.

[0030] The basic operating mode may be an adult operating mode and the alternative operating mode may be a pediatric operating mode, so that the dose rate may be optimized for children.

[0031] In a particular embodiment, the source is provided with a collision detection device for detecting a possible collision of the source with the patient and / or the patient positioning device during the movement of the source, and / or the sensor is provided with a collision detection device for detecting a possible collision of the sensor with the patient and / or the patient positioning device during the movement of the sensor. The collision detection device increases the safety of the device. The distance between the source and the sensor can be reduced to a minimum, so that the maximum benefit of the reduced distance between the source and the sensor can be utilized.

[0032] The collision detection device is selected from: a capacitive distance sensor, an ultrasonic distance sensor, an optical distance sensor, and a time-of-flight optical sensor or any other suitable sensor.

[0033] The distance between the source and the sensor may also be adjusted according to the output of the sensor device used to determine the patient's physical parameter. Thus, the distance between the source and the sensor may be adjusted according to the individual needs of a particular patient. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further advantages and features of the invention are disclosed in the following description, in which exemplary embodiments of the invention are explained in detail based on the accompanying drawings:

[0035] Figure 1 is a perspective view showing a combined panoramic and CT imaging device;

[0036] Figure 2 To show Figure 1 Side view of the device in action while capturing images of an adult patient;

[0037] Figure 3 To show Figure 1 A side view of the device working while taking images of a pediatric patient;

[0038] Figure 4 is a schematic diagram showing the benefits of a specific imaging modality for children;

[0039] Figure 5 a side view of the device modified for operation in an adult operating mode;

[0040] Figure 6 for Figure 5 A side view of the modified device operating in a child working mode;

[0041] Figure 7 Shows the use Figure 5 The trajectory of the rotation axis of the device when generating CT images for children;

[0042] Figure 8 To show the use Figure 5 The trajectory of the rotation axis of the device when generating a panoramic image for the child;

[0043] Fig. 9 is a perspective view showing components for moving the sensor;

[0044] Fig.10 for Fig. 9 perspective views of components of a component;

[0045] Fig.11 To observe from below Fig.10 A perspective view of the components of

[0046] Fig.12 is a perspective view of another component for moving the sensor;

[0047] Fig.13 is a perspective view of another component for moving the sensor as viewed from below;

[0048] Fig.14 Shows possible collisions that may occur while operating the equipment;

[0049] Fig.15 A modified device provided with a collision detector is shown;

[0050] Fig.16 shows the working principle of capacitive collision detector;

[0051] Fig.17 The working principle of ultrasonic collision detector is shown;

[0052] Fig.18 shows how an optical distance sensor works;

[0053] Fig.19 The principle of a time-of-flight optical sensor is shown. DETAILED DESCRIPTION

[0054] Figure 1 A perspective view of a combined panoramic and CT imaging device 1 is shown. Panoramic imaging in dentistry is typically imaging of a vertical image plane along the dental arch. An image of the entire dental arch is thereby formed. Panoramic imaging may also cover the temporomandibular joint (TMP), sinus, or mandible or maxilla. Dental CT is typically intended to generate a three-dimensional image of a selected region of interest (ROI) along the dental arch. The ROI typically includes a group of teeth or at least a single tooth. CT may also be used to image any area of ​​the head, particularly the ears, nose, and throat.

[0055] The device 1 comprises a base 2, to which a rod 3 extending in a vertical direction is attached. On the rod 3, a height adjustment member 4 is mounted which can slide on the rod 3 to adjust the device 1 to the height of a patient to be examined by the device 1. A support arm 5 is fixed to the height adjustment member 4. The support arm 5 extends in a horizontal direction, and its end supports a rotating arm 6. A translation and rotation device 7 driven by a motor is interposed between the support arm 5 and the rotating arm 6. The translation and rotation device 7 can be used to rotate and / or translate the rotating arm 6 according to the needs of panoramic and CT imaging. The rotating arm 6 can specifically rotate around a rotation axis 8, and the position of the rotation axis 8 can be moved in the x-direction and the y-direction of a plane extending perpendicular to the rotation axis 8.

[0056] The X-ray source 9 is located at one end of the rotating arm 6. By using an adjustment device 10, the X-ray source 9 can be moved along the rotating arm 6. An X-ray sensor 11 is further arranged at the other end of the rotating arm 6. The X-ray sensor 11 is a digital area sensor, usually a flat panel detector. By using an adjustment device 12, the sensor 11 can be moved along the rotating arm 6.

[0057] The adjustment means 10 and 12 are preferably means for performing a translational movement along the rotating arm 6, but may also be alternative means for changing the position along the rotating arm 6. For example, the adjustment means 10 and 12 may also include means for performing a pivoting movement to change the relative distance between the source 9 and the sensor 11.

[0058] The X-ray source 9 emits X-ray radiation that penetrates the head 13 of the patient 14, who is usually in a standing position during the X-ray examination. During the acquisition of the X-ray images, the head 13 of the patient 14 is fixed in a fixed position relative to the support arm 5 by a head support 15. To this end, the head support 15 can be attached to the height adjustment member 4. The head support 15 can be a simple bite-type, which the patient 14 can bite into during the examination, but can also include other devices for supporting the head 13 in a predetermined position during the acquisition of the X-ray images. For example, the head support 15 can also include a device for supporting the head 13 of the patient 14 in the area of ​​the temples. The elements of the head support 15 can be fixed or movable, so that the head support 15 can be adapted to the size of the patient 14, in particular the head 13.

[0059] The operation of the device 1 is controlled by a control unit 16, which may be a conventional computer comprising the usual components for executing programs, such as a processor, means for data transmission and storage, and various interfaces. The control unit 16 is connected to the components of the device 1 and executes programs for controlling these components. For example, the control unit 16 controls the motors associated with the translation and rotation means 7. The control unit 16 may also set the operating parameters of the source 9, such as the current and voltage of the source 9, since the source 9 is usually an X-ray tube. As is known in the art, the current affects the radiation power of the X-ray radiation emitted by the X-ray tube, while the voltage affects the spectrum of the emitted X-ray radiation. The control unit 16 also reads the acquired image data from the digital area sensor 11, processes the image data and displays the obtained image on a display 17. The control unit 16 is also usually provided with some input means 18, such as a computer mouse or keyboard, allowing an operator to enter commands to the control unit 16. The display 17 may also be used to enter commands. For example, the display 17 may be a touch screen on which the operator can select commands from a displayed command menu. Finally, the control unit 16 may also be arranged to control the regulating devices 10 and 12.

[0060] The height adjustment member 4 is usually manually operated. Before acquiring an X-ray image, the operator adjusts the height of the height adjustment member 4 so that the patient 14 can stand comfortably in the device 1 .

[0061] Now device 1 can work in adult working mode and child working mode. Figure 2 and Figure 3 Further explain the adult working mode and child working mode.

[0062] Figure 2 The basic adult operating mode is shown, which is adopted if the patient 14 to be examined is an adult. The X-ray radiation emitted from the anode 19 of the source 9 forms a beam 20. The angular extension of the beam 20 is limited by a primary collimator 21, which is located between the anode 19 of the source 9 and the patient 14 and is usually arranged in a housing 22 of the source 9. In the case of panoramic imaging, the beam 20 is a vertically aligned fan beam, while in the case of CT, a so-called cone beam is used. The beam 20 penetrates the patient. The beam 20 further passes through an optional secondary collimator 23, which is located in front of a sensor plane 24 supporting the X-ray-sensitive pixels of the sensor. The secondary collimator 23 can be located in a housing 25 of the sensor 11.

[0063] A pixel may be an element that converts X-rays into visible light, which is detected by an associated photosensitive element and converted into an electrical signal, or a pixel may be an element that directly converts the impinging X-rays into electrical signals. These electrical signals are converted into image data by associated sensor electronics. The image data is read by the control unit 16.

[0064] To generate a panoramic image of the dental arch, only selected areas of the flat-panel area sensor 11 are used, typically only a few columns of pixels, whereas in the case of CT all pixels of the sensor 11 or at least a larger area of ​​the sensor 11 are used.

[0065] The distance between the anode 19 of the source 9 and the sensor plane 24 of the sensor 11 is called the source-sensor distance (= SSD). The distance between the anode 19 and the object 26 to be imaged inside the head 13 is called the source-object distance (= SOD). In the case of panoramic imaging, the object 26 is a vertical line passing through the point of the dental arch to be imaged by panoramic imaging. In the case of dental CT, the object 26 can be the vertical axis of a typical cylindrical ROI centered on a single tooth or a group of teeth, for which a three-dimensional image is generated using CT. In the case of CT, the object 26 coincides with the rotation axis 8. The ratio of SSD to SOD defines the magnification.

[0066] Figure 3An alternative child operating mode of the device 1 is shown. In the child operating mode, the relative distance between the source 9 and the sensor 11 is reduced by using the adjustment means 10 and 12. Figure 3 In the example, both SSD and SOD are reduced by the same factor, so that the magnification remains unchanged, although this is not a mandatory requirement. It is also possible to move only the source 9 or the sensor 11, or both in an asymmetrical manner. Reducing the relative distance between the source 9 and the sensor 11 results in a reduced SSD. r and reduced SOD r .

[0067] Figure 4 The advantages of the alternative child working mode are shown. The solid line shows the beam 20 during the adult working mode, while the dashed line shows the beam 20 in the child working mode. For simplicity, both SSD and SOD are reduced by the same factor, as shown in FIG. Figure 3 shown.

[0068] In order to achieve a certain signal-to-noise ratio, a certain amount of radiation energy (joules = J) must be deposited in each pixel of the sensor 11. If the SSD is reduced, the angular extension of the sensor 11, seen from the source 9, will be greater. If the radiation intensity (watts / steradian) of the source 9 is kept constant, the energy required to achieve a certain signal-to-noise ratio can be obtained in less time than in the adult mode of operation. On the other hand, if the exposure time is kept constant, the radiation intensity can be reduced. If there is no such Figure 4 If the SOD is not reduced as shown, but kept constant, the reduced radiation intensity will result in a reduced absorbed dose rate (J / kg second = Gray / second) of the radiation absorbed by the head 13. Since a lower absorbed dose rate is less harmful than a higher absorbed dose rate, a reduced absorbed dose rate is preferred. If the SOD is kept constant, the reduction in radiation intensity and the resulting reduction in absorbed dose rate are similar to (SSD r / SSD) 2 Proportional, where SSD r is the reduced SSD. If SOD is also reduced to SOD r , then the reduction in dose rate will be less, since object 26 also appears larger from source 9. Therefore, the reduction in dose rate will be roughly the same as (SOD / SOD r ) 2 (SSD r / SSD) 2 If the SOD and SSD are reduced by the same factor, and if the radiation intensity is reduced by the square of that factor, the absorbed dose rate will remain unchanged.

[0069] It should be noted that a substantial reduction in the absorbed dose rate can be obtained by moving the sensor 11 as close as possible to the object 26. For example, if the SSD r / SSD=0.85, corresponding to a 15% reduction, the absorbed dose rate will be reduced by about 30%.

[0070] In practice, the radiation intensity and thus the absorbed dose rate is reduced by reducing the current of source 9. It should be noted that the dose rate can also be reduced by reducing the voltage of source 9, taking into account that the optical thickness of hard tissue in children is less than that in adults.

[0071] If Figure 4 If the SOD is reduced as shown, it should be noted that for the child working mode, the primary collimator 21 must be opened wider and the optical path of the light passing through the patient 14 is different in the adult and child working modes, which can be seen from Figure 4 Seen from Figure 4 It can also be seen in FIG. 1 that the dashed light beam and the solid light beam intersect the line of the object 26 at the same point. As a result, various parts of the object 26 are imaged at the same pixels on the sensor plane 24. Therefore, the spatial resolution of the object 26 can remain essentially the same. It should also be noted that the magnification in the child working mode is the same as the magnification in the adult working mode, since both the source 9 and the sensor plane 24 are moved symmetrically with respect to the rotation axis 8.

[0072] The secondary collimator 23 may also be omitted.

[0073] exist Figure 1 In the embodiment shown, the adjustment means 10 and 12 are driven by motors and operated by a control unit 16. However, in a simplified embodiment, the adjustment means 10 and 12 can also be operated manually by an operator, for example by moving the source 9 and / or the sensor 11 along the rotating arm 6 to the mark. In this case, the device can be provided with position sensors to allow the control unit 16 to check the correct position of the source 9 and / or the sensor 11. The control unit 16 can then adapt the operating parameters of the source 9 to the selected SSD. For example, if the SSD is reduced, the radiation intensity can be reduced accordingly.

[0074] Figure 5 and Figure 6 Another modified embodiment is shown. Figure 5 and Figure 6 The embodiment shown comprises an enlarged housing 27 in which the sensor 11 can perform a translational movement to adjust the distance between the source 9 and the sensor 11. In a modified embodiment, the source 9 is fixed to a rotating arm 6, which itself moves with the source 9 to reduce the SOD. At the same time, the sensor 11 moves within the housing 27 towards the source 9, so that the SSD is also reduced.

[0075] The movement of the swivel arm 6 can be performed by means of the translation and rotation device 7, in particular by means that allow the axis of rotation 8 to be moved in the x and y directions. If the source 9 moves together with the swivel arm 6, the axis of rotation 8 is no longer centered on the object 26, but is shifted to an eccentric position. This may affect the movement of the swivel arm 6 in the child working mode.

[0076] Figure 7 The movement of the swivel arm 6 during CT imaging in the adult and pediatric working modes is shown. Figure 7 Specifically depicted are various positions of the source 9, sensor 11, and central ray 28 of the light beam 20 during a CT scan of an object 26 in a pediatric working mode.

[0077] In accordance with Figure 2 and Figure 3 In the embodiment of the invention, the rotation axis 8 remains stationary in the adult working mode and the pediatric working mode to generate CT images, and the rotating arm 6 usually rotates more than 180° around the stationary rotation axis 8, so that the source 9 and the sensor 11 perform a semicircular motion around the rotation axis 8. Figure 5 and Figure 6 In the child working mode of the modified embodiment shown, the rotating arm 6 can be moved so that the source 9 and the sensor 11 are pivoted about the virtual rotation axis 29. The movement about the virtual rotation axis 29 is achieved by moving the rotation axis 8 along a circular trajectory 30. The circular trajectory 30 is centered on the virtual rotation axis 29, and the rotation angle representing the position of the rotation axis 8 on the circular trajectory 30 is This particular movement along the circular path 30 will keep the magnification constant. Figure 5 and Figure 6 The magnification can also be changed in the child operating mode of the modified embodiment shown by moving the sensor plane 24 toward the rotation axis 8 , keeping the position of the rotation axis 8 unchanged, and rotating the rotating arm 6 about the rotation axis 8 .

[0078] Figure 8 The movement of the rotating arm 6 during the panoramic imaging process is shown. Figure 7 2, the various positions of the source 9, the sensor 11 and the central ray 28 of the light beam 20 during panoramic imaging of an adult dental arch 31 and a child dental arch 32. During panoramic imaging, the rotation axis 8 is moved so that the central ray 28 of the light beam 20 is at right angles to the corresponding dental arch 31 or 32. The rotation axis 8 is further moved so that the magnification of the vertically aligned plane to be imaged remains unchanged. If using Figure 5 and Figure 6In the embodiment of the invention, the axis of rotation 8 is moved along the trajectory 33 in the adult working mode to image the dental arch 31 of an adult. If a child is to be examined, a modified trajectory 34 is obtained by moving the axis of rotation 8 and reducing the distance between the source 9 and the sensor 11 by moving the sensor 11 along the rotating arm 6 towards the source 9. This particular movement along the trajectory 34 keeps the magnification constant. However, it is also possible to change the magnification by moving the sensor plane 24 towards the axis of rotation 8 and by also using the trajectory 33 for the child working mode. Figure 5 and Figure 6 The magnification of the children's working mode of the modified embodiment shown. In this case, the magnification is preferably reduced by no more than 10% or 20%.

[0079] For the sake of completeness, it should be noted that if the dental arches are identical or approximately identical, then Figure 2 and Figure 3 The implementation scheme includes essentially the same trajectories for both adult and child working modes.

[0080] The movement of the sensor 11 can be achieved by various mechanisms.

[0081] Fig. 9 3 is a perspective view of a mechanism 35 for performing a rotational translation, wherein the sensor 11 is located within the housing 27 of the sensor 11. The mechanism 35 is oriented at right angles to the longitudinal axis 36 of the rotating arm 6. The longitudinal axis 36 of the rotating arm 6 is generally parallel to the central ray 28 of the light beam 20. A base plate 37 of the mechanism 35 is oriented at right angles to the longitudinal axis 36 of the rotating arm 6. A guide rail 38 is fixed to the base plate 37. A guide block 39 can slide on the guide rail 38 so that a movable plate 40 can move along the base plate 37. To control the movement of the movable plate 40, a motor plate 41 is fixed to one end of the base plate 37. The motor plate 41 supports a translation motor 42, which drives a lead screw 43 extending along the guide rail 38. The lead screw 43 is inserted into a lead screw barrel 44, and if the lead screw 43 is rotated, the lead screw barrel 44 moves along the lead screw 43. The lead screw barrel 44 is attached to a lead screw block 45 fixed to the movable plate 40. If the motor 42 drives the lead screw 43 , the movable plate 40 moves along the guide rail 38 .

[0082] The movable plate 40 supports an extension plate 46 which supports the other components of the mechanism 35. Fig.10These components can be seen in FIG. Bearings 47 are provided at opposite ends of the extension plate 46, on each of which a pivot 48 is supported. A pulley 49 is mounted at one end of each pivot 48. The two pulleys 49 stretch a cam belt 50, which is tensioned by a guide wheel 51, which is located on one side of the cam belt 50 between the two pulleys 49. At the opposite part of the cam belt 50, a fixed plate 52 and a drive plate 53 clamp the cam belt 50. A lead screw block 54 is attached to the drive plate 53. The lead screw block 54 supports a lead screw barrel 55 mounted on a lead screw 56. In order to drive the lead screw 56, a motor plate 57 is fixed to one end of the extension plate 46. The motor plate 57 supports a rotary motor 58 that drives the lead screw 56. If the motor 58 rotates the lead screw 56, the drive plate 53 and the fixed plate 52 move together with the cam belt 50. The movement of the cam belt 50 causes the rotation of the pivot 48.

[0083] from Fig.11 As can be seen in FIG. 4 , the rotation of the pivot 48 causes the rotational movement of the rotating arm 59, which is mounted to the other end of the pivot 48 located below the extension plate 46. The other end of the rotating arm 59 is inserted into a bearing 60, which is supported by a rotating plate 61. The rotating plate 61 ultimately supports the sensor 11. The rotating plate 61 is provided with a channel 62, which allows the head of the pivot 48 to pass over the rotating plate 61.

[0084] The mechanism 35 can be used to move the sensor 11 in the lateral direction relative to the longitudinal axis 36 of the rotating arm 6 in order to adjust the position of the sensor 11 for panoramic or CT imaging. The mechanism 35 can further be used to adjust the distance between the source 9 and the sensor 11 by pivoting the rotating arm 59 so that the rotating plate 61 moves in the direction of the longitudinal axis 36 of the rotating arm 6. The rotating arm 59 is preferably pivoted by 180°, but can also be pivoted by a smaller angle. In this case, the lateral movement can be compensated by a corresponding lateral movement along the guide rail 38.

[0085] The main advantage of the mechanism 35 is that the sensor 11 can be moved relatively quickly in the direction of the source 9, since the lead screw barrel 55 only has to move a short distance in order to rotate the rotating arm 59 180°, and the rotation of the rotating arm 59 covers a distance twice the length of the rotating arm 59. Another advantage is that the mechanism 35 also allows lateral movement of the sensor to adjust the position of the sensor 11 according to the requirements of panoramic and CT imaging.

[0086] Fig.12An alternative mechanism is depicted, in which the distance between the source 9 and the sensor 11 is varied by using a scissor mechanism 63. The scissor mechanism 63 comprises a base 64 oriented at right angles to the longitudinal axis 36 of the rotating arm 6. Two parallel rails 65 are attached to the base 64. A slide 66 is mounted on the rails 65 and supports a folding bracket 67, which comprises a support 68, one end of which is movably attached to the slide 66. Each of the two supports 68 is connected by a central cross bearing 69, and the other ends of the two supports support a fixed block 70, which supports a support plate 71, on which the sensor 11 can be mounted. The folding bracket 67 is driven by a motor 72 mounted on the base 64. The motor 72 drives a lead screw 73, which meshes with a nut 74 fixed to a cross plate 75. The cross plate 75 is connected to a pair of slides 66, each of which is mounted on an opposite rail 65.

[0087] The scissor mechanism 63 also allows for rapid movement of the sensor 11 , since the nut 74 only has to move along the lead screw 73 a distance corresponding to half the distance that the support plate 71 , ie the sensor 11 , moves toward the source 9 .

[0088] Fig.13 A linear mechanism 76 is shown which can be used to vary the distance between the source 9 and the sensor 11. The mechanism 76 comprises a base 77 provided with tracks 78. The base 77 also supports a motor bracket 79 which supports a motor 80 which drives a lead screw 81 extending along the longitudinal axis 36 of the rotating arm 6 and which engages a nut 82 supported by a cross plate 83. The cross plate 83 extends between the tracks 78 and is supported by a slide 84 mounted on the rails 78. The sensor 11 is mounted on the cross plate 83 such that the longitudinal axis 36 of the rotating arm 6 extends along the lead screw 81.

[0089] A particular advantage of the linear mechanism 76 is that the linear mechanism 76 is particularly stable and reliable.

[0090] It should be noted that the described mechanisms may also be combined.

[0091] It should also be noted that the pediatric working mode can also be used for adults with smaller bodies. Several different working modes can also be provided, which are applied according to the height of the patient 14 to be examined. Each working mode then uses a different distance between the source 9 and the sensor 11 to adapt the device 1 to the specific size of the patient 14. The device 1 can also be provided with sensor means for determining the size of the patient and adjusting the distance stepwise or continuously according to the output of the sensor means. These sensor means can be used to determine one or more physical parameters of the head 13 or the patient 14. For example, these parameters can be the weight of the patient 14, the height of the patient 14, the size of the head 13 or any other suitable parameters. If no sensors are provided or there are not enough sensors, these parameters can also be manually entered by the operator of the device 1. The control unit 16 can then adapt the operating parameters of the source 9 to the selected SSD. For example, if the SSD is reduced, the radiation intensity can be correspondingly reduced by reducing the current of the source.

[0092] If you try to make the SSD as small as possible, collisions may occur. Specifically, Fig.14 As shown, the housing 25 of the sensor 11 may collide with the head 13 or the head support 15, in particular since the head support 15 may be provided with a protruding temple support 85. Fig.14 In the figure, the temple cradle 85 is shown in a closed position, wherein the temple cradle 85 is in contact with the head 13, and when the temple cradle 85 is in an open position, wherein the temple cradle is a distance away from the head 13. The dotted line represents the open position, and the solid line represents the closed position.

[0093] from Fig.15 As can be seen in FIG, the temple support 85 includes two contact portions 86 that contact opposite sides of the head 13 above the ears 87. The contact portions 86 are supported by brackets 88, respectively, and the lower ends of the brackets 88 are supported by pivot bearings 89 located on a base 90. The base 90 may also support a chin support 91 and / or a bite piece 92, which the patient 14 may bite during the examination to fix the position of the teeth during the scanning process.

[0094] like Fig.14 As shown, collision of the housing 25 of the sensor 11 with the temple bracket 85 may occur, since the open and closed positions of the temple bracket 85 are not well defined. Collision of the housing 25 of the sensor 11 with the head 13 of the patient 14 may also occur due to an unusual shape of the head 13. For example, the back of the head 13 of the patient 14 may be unusually long, obstructing the movement of the housing 25 along the scanning trajectory.

[0095] These collisions can be avoided by direct measurement of the patient's head 13 or temple bracket 85. These measurements can be made using mechanical measuring tools such as a ruler or a vernier caliper. Optical laser scanning technology, such as LIDAR, can also be used. Another option is to use a camera in combination with subsequent image recognition to determine the size of the head 13 and the position of the temple bracket 85. In this case, passive optical markers can be set on the temple bracket 85 to ensure that the image recognition can safely identify the position of the temple bracket 85. The position of the temple bracket 85 can also be determined by a passive radio marker, and its position can be detected by signals transmitted and received by a radio frequency transmitter. Finally, the base 90 can also be equipped with a position encoder for detecting the angular position of the bracket 88. By using one of these methods or any combination of these methods, the size of the head 13 can be determined before the panoramic imaging or CT scan begins.

[0096] Despite the great care in determining the dimensions of the head 13, there is still a risk of collision during imaging. The risk of collision can be reduced or even completely avoided if the sensor 11 is provided with a collision detector 93. For example, the collision detector 93 can be located in the housing 25 above the sensor plane 24, since the protruding part of the head 13 and the temple bracket 85 are usually located above the dentition, the image of which is generated by panoramic or CT imaging.

[0097] In order to avoid collisions with the source 9 , the source 9 may also be associated with a collision detector 94 .

[0098] In the following, various possible embodiments of the collision detectors 93 and 94 are described. For simplicity, the description only relates to the area around the sensor 11 and the housing 25, the description being valid for the area around the source 9 and the housing 22 as well.

[0099] Fig.16 An embodiment is shown, in which a capacitive distance sensor 95 is used for detecting collisions. The capacitive distance sensor 95 comprises two electrodes 96 which are connected to some sensor electronics 97 which can be read by the control unit 17.

[0100] The electrode 96 generates an electric field 98 which is disturbed if an object, i.e. the head 13 or the temple rest 85, approaches the electrode 96. As a result, the capacitance of the electrode 96 changes and an impending collision of the housing 25 with the head 13 or the temple rest 85 can be detected by the sensor electronics 97 and thus by the control unit 17.

[0101] Fig.17Another embodiment is shown in which an ultrasonic distance sensor 99 is employed to detect a collision. The sensor electronics 97 of the exemplary ultrasonic sensor 99 operates an ultrasonic transceiver 100 that transmits and receives ultrasonic signals 101 that are reflected by the head 13 or temple support 85. The time of flight of the ultrasonic signal 101 is measured and used to determine the distance between the ultrasonic transceiver 100 and the head 13 or temple support 85. Thus, the sensor electronics 97 is also capable of detecting an impending collision.

[0102] Fig.18 Yet another embodiment is shown in which an optical distance sensor 102 is employed to detect a collision. The optical distance sensor 102 is based on the principle of triangulation. The optical distance sensor comprises a light source 103, such as a laser or LED, which emits a light beam 104. The light beam 104 can be reflected by the head 13 or the temple bracket 85. The reflected light 105 impinges on a position sensitive detector 106. The sensor electronics 97 uses the information about the position where the reflected light strikes the position sensitive detector 106 to determine the distance between the optical distance sensor 102 and the head 13 or the temple bracket 85. Thus, the sensor electronics 97 of this embodiment is able to detect an impending collision.

[0103] Fig.19 A fourth embodiment is shown, in which an optical time-of-flight (=TOF) sensor 107 is employed to detect a collision. The optical TOF sensor 107 comprises a light source 108 which emits a light pulse 109. The light pulse 109 is reflected at the head 13 or the temple support 85 and is received by a light detector 110. The time of flight is measured by the sensor electronics 97, and based on this measurement the distance the light pulse 109 has travelled between the light source 108 and the light detector 110 can be determined.

[0104] The advantage of this optical system is that the results are independent of ambient conditions such as temperature or air humidity.

[0105] Figures 16 to 19 The example of a collision detector shown should not be understood as limiting. Any other distance sensor may be considered, for example a vision system may also be employed which processes images from camera data for identifying the risk of collision with objects in the camera's field of view.

[0106] Finally, it should also be noted that the invention is described herein as a dental imaging device. However, the invention may also be used generally for instruments for imaging any part of the head 13 of a patient 14, such as instruments for imaging the mandible or maxilla, the temporomandibular joint or the sinuses by panoramic imaging, and / or instruments for imaging any other part of the head 13 by CT, in particular the areas around the ears, nose and throat of the patient 14.

[0107] Throughout the description and claims of this specification, the singular encompasses the plural, unless the context requires otherwise. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0108] Features, values, characteristics, components or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

Claims

1. A device for digital imaging of the head region of a patient (14), comprising: - a source (9) for generating X-ray radiation; - a sensor (11) for detecting X-ray radiation generated by the source (9) and penetrating the patient (14), wherein the sensor is a single sensor (11) for both panoramic imaging and computed tomography of the head region of the patient (14); - a rotating arm (6) for arranging the source (9) and the sensor (11) on the rotating arm (6) in a manner opposite to each other, wherein the rotating arm (6) is provided with adjustment means (10, 12) for varying the distance between the source (9) and the sensor (11); - a support structure (2, 3, 4, 5) for supporting a rotating arm (6), wherein a translation and rotation device (7) driven by a motor is interposed between the rotating arm (6) and the support structure (2, 3, 4, 5); and - a control unit (16) which controls the source (9), the sensor (11), the adjustment means (10, 12) and the translation and rotation means (7), and the control unit (16) is arranged to operate the device in a basic operating mode for larger patients and in an alternative operating mode for smaller patients, in which the distance between the source (9) and the sensor (11) is reduced by merely moving the sensor (11) towards the source (9) and the dose rate and / or exposure time is also reduced compared to the distance used in the basic operating mode.

2. The device according to claim 1, in, For an alternative operating mode, the control unit (16) merely moves the sensor (11) towards the source (9) fixed to the rotating arm (6).

3. The device according to claim 2, in, The control unit (16) also moves the axis of rotation (8) of the rotating arm (6) in the direction of the sensor (11).

4. The device according to claim 3, in, For a computed tomography scan, the axis of rotation (8) is moved on a trajectory (30) which surrounds a virtual axis of rotation (29) located at the object (26) to be imaged.

5. The device according to claim 1, in, The sensor (11) moves in a housing (25) which is stationary relative to the swivel arm (6).

6. The device according to claim 1, in, The adjustment means (10, 12) comprise means for positioning the sensor (11), said means being selected from: - a mechanism (35) comprising means (37-45) for transverse movement relative to the longitudinal axis (36) of the swivel arm (6), - a mechanism (35) comprising means (47-62) for rotational movement relative to the rotating arm (6), - a scissor mechanism (63) for varying the distance between a base (64) attached to the rotating arm (6) and the support structure (71) of the sensor (11), a linear mechanism (76) for moving the sensor (11) along the guide structure (74) in the direction of the source (9), and - A combination of the above.

7. The device according to claim 1, in, The adjusting device (10, 12) is driven by a motor.

8. The device according to claim 1, in, The device is provided with a primary collimator (21) located between the source (9) and the patient (14), which is opened wider in an alternative operating mode than in a basic operating mode.

9. The device according to claim 1, in, Compared to the basic operating mode, in the alternative operating mode, the radiation intensity of the source (9) is reduced and / or the exposure time of the sensor (11) is also reduced.

10. The device according to claim 1, in, In an alternative operating mode, the radiation intensity of the source (9) generating X-rays is reduced by reducing the current and / or the voltage of the source (9).

11. The device according to claim 1, in, The radiation intensity of the source (9) is reduced by the square of the ratio of the distance between the source (9) and the sensor (11) in the alternative operating mode to the distance between the source (9) and the sensor (11) in the basic operating mode.

12. The device according to claim 1, in, In the alternative operating mode, the exposure time of the sensor (11) is shorter than in the basic operating mode.

13. The device according to claim 1, in, The magnification of the alternative operating mode is the same as that of the basic operating mode.

14. The device according to claim 1, in, The basic working mode is an adult working mode, and the alternative working mode is a child working mode.

15. The device according to claim 1, in, The distance between the source (9) and the sensor (11) is adjusted according to the output of a sensor device for determining a physical parameter of a patient (14).

16. The device according to claim 1, in, The source (9) is provided with a collision detection device (94), and the collision detection device (94) is used to detect a possible collision between the source (9) and the patient (14) and / or the patient positioning device (15) during the movement of the source (9), and / or the sensor (11) is provided with a collision detection device (93), and the collision detection device (93) is used to detect a possible collision between the sensor (11) and the patient (14) and / or the patient positioning device (15) during the movement of the sensor (11).

17. The device according to claim 16, in, The collision detection devices (93, 94) are selected from: a capacitive distance sensor (95), an ultrasonic distance sensor (99) and an optical distance sensor (102).

18. The device according to claim 16, in, The collision detection device (93, 94) is selected from: a capacitive distance sensor (95), an ultrasonic distance sensor (99) and a time-of-flight optical sensor (107).

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