X-RAY TOMOGRAM IMAGING DEVICE

• US 20150305696A1
• Filed: 07/13/2011
• Published: 10/29/2015
• Est. Priority Date: 07/13/2010
• Status: Active Grant

• Current Assignee: Takara Telesystems Corp.
• Original Assignee: Telesystems Co., Ltd.
• Inventors: YAMAKAWA, Tsutomu, TSUJITA, Masahiro, KATSUMATA, Akitoshi, OGAWA, Koichi, AOKI, Hisatoshi
• Granted Patent: US 9,668,705 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 6/025 Tomosynthesis
• CPC Class Codes: A61B 6/035 Mechanical aspects of CT
• CPC Class Codes: A61B 6/466 adapted to display 3D data
• CPC Class Codes: A61B 6/51 for dentistry
• CPC Class Codes: A61B 6/547 involving tracking of position of the device or parts of the device
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: G06T 11/006 Inverse problem, transformation from projection-space into object-space, e.g. transform methods, back-projection, algebraic methods
• CPC Class Codes: G06T 2207/10081 Computed x-ray tomography [CT]
• CPC Class Codes: G06T 2207/30036 Dental; Teeth
• CPC Class Codes: G06T 2207/30196 Human being; Person
• CPC Class Codes: G06T 2211/436 Limited angle

Abstract

An X-ray tomographic imaging apparatus includes an X-ray and a direct conversion type of detector. The X-ray tube and the detector are supported by the support means so as to be rotatable along curved orbits mutually independently. Under instructions from a computer, scans and image reconstruction are performed. The X-ray tube and the detector are moved along the orbits mutually independently so that X-ray beams are always transmitted through a desired tomographic plane of an object at desired angles. Acquired frame data are used to produce a panoramic image of the plane, while the frame data and the panoramic image are used to produce a tomographic image in which structural components of the object are optically focused and distortions caused due to differences in X-ray paths are suppressed. The apparatus can be used as devices for dental, medical diagnosis and nondestructive inspection, and can have a CT imaging function.

Claims

1. An X-ray tomographic imaging apparatus, comprising:

a data acquiring device comprising;

an X-ray tube radiating X-rays whose intensities are dependent on an amount of current to be supplied thereto;

a detector provided with a detection section in which a plurality of pixels are arranged two-dimensionally, the pixels detecting the incoming X-rays and outputting, frame by frame, digital electric data;

support means having the capability to provide a curved orbit and support the X-ray tube and the detector such that the X-ray tube and the detector are movable along the orbit independently of each other,

moving means having the capability to move the X-ray tube and the detector along the orbit independently of each other such that the X-rays are transmitted through an object being imaged, at desired angles and at respective positions in a scanning direction of a desired tomographic plane of the object, wherein the object is located inside the orbit provided by the data acquiring device;

panoramic image procuring means having the capability to apply a tomosynthesis technique to the data acquired by the data acquiring device to produce a panoramic image of the tomographic plane based on the data; and

tomographic image producing means having the capability to produce a tomographic image based on the data acquired by the data acquiring device and the panoramic image produced by the panoramic image producing means, structural components existing in the object being optimally focused in the tomographic image and distortions due to differences in angles of paths of the X-rays being suppressed in the tomographic image.

2. The apparatus of claim 1, characterized in that the apparatus comprises

X-ray amount adjusting means having the capability to adjust amounts of the X-rays such that the amounts of the X-rays radiated per unit time become uniform at the respective positions during a period of time during which the X-ray tube and the detector are moved by the moving means.

3. The apparatus of claim 2, characterized in that the X-ray amount adjusting means is composed of one or more means designated among tube current adjusting means for adjusting a value of the current to the X-ray tube depending on the respective positions, tube voltage adjusting means adjusting a value of a tube voltage applied to the X-ray tube depending on the respective positions, and acquisition time adjusting means for adjusting an acquisition time necessary for the detector to acquire the data, the acquisition time being dependent on the respective positions.

4. The apparatus of claim 3, characterized in that

the object is a tooth row of a patient'"'"'s jaw, and

the tube current adjusting means has the capability to increase the value of the current for X-ray scanning of the tooth row along paths passing through a cervical spine acting as an obstacle shade, more than the value of the current for X-ray scanning of the tooth row along paths other than the paths passing through the cervical spine.

5. The apparatus of claim 3 or 4, characterized in that

the object is a tooth row of a patient'"'"'s jaw, and

the acquisition time adjusting means has the capability to widen the acquisition time for X-ray scanning of the tooth row along paths passing through a cervical spine acting as an obstacle shade, more than the acquisition time for X-ray scanning of the tooth row along paths other than the paths passing through the cervical spine.

6. The apparatus of any one of claims 1 to 5, characterized in that

enlargement factor correcting means having the capability to correct distortions in a height direction of the panoramic image produced by the panoramic image producing means, based on irregularities of an enlargement factor among the respective positions in the scanning direction, the enlargement factor showing enlargement of an image produced by the X-rays onto the tomographic plane in the height direction perpendicular to the scanning direction.

7. The apparatus of any one of claims 1 to 6, characterized in that

the data acquiring device is equipped with a collimator collimating the X-rays from the X-ray tube, the collimator being movable independently of the X-ray tube, and

the moving means is provided with means for moving the collimator relatively to the X-ray tube depending on angles of the X-rays transmitted across the tomographic plane at respective positions in the scanning direction.

8. The apparatus of claim 7, characterized in that the collimator is equipped to be movable in a direction perpendicular to radiation directions of the X-rays or rotatable in the radiation directions.

9. The apparatus of any one of claims 1 to 8, characterized in that the orbit is a circular orbit or an elliptical orbit.

10. The apparatus of any one of claims 1 to 9, characterized in that the orbit is a circular orbit in which the object of a patient is allowed to be located.

11. The apparatus of claim 10, characterized in that the orbit member provides the circular orbit with part of which opened.

12. The apparatus of any one of claims 1 to 11, characterized in that the X-ray tube has an X-ray focal point of which diameter is 0.3 mm or less,

the support means is configured to support the X-ray tube and the detector to hold a distance between the focal point of the X-ray tube and the detection section of the detector at 40 cm or less.

13. The apparatus of claim 12, characterized in that the data acquiring means is equipped with X-ray shielding means for shielding an outer side of the support means against the X-rays, at least, acquiring the data.

14. The apparatus of any one of claims 1 to 13, characterized in that

the tomographic image producing means comprises

referential-plane image reconstructing means for reconstructing, as a referential-plane image, a projection image of a desired tomographic plane of the object based on the data acquired by the data acquiring device, and

optimally-focused image producing means for producing the three-dimensional optimally focused image based on data of the referential-plane image and the frame data.

15. The apparatus of claim 14, characterized in that

the desired tomographic plane is a three-dimensional (3D) referential tomographic plane which is curved and rectangular in a space between the X-ray tube and the detector,

the object is a tooth row of a patient, and

the referential-plane image reconstructing means is configured to reconstruct a panoramic image of the tooth row.

16. The apparatus of claim 15, characterized in that

the image producing means comprises

tomographic plane setting means for setting a plurality of tomographic planes along the 3D referential tomographic plane in a direction opposed to the 3D referential tomographic plane,

pixel value calculating means for calculating pixel values of each of the plurality of tomographic planes,

position identifying mean for identifying optimally focused sampling points of the portion being imaged based on image data of both the 3D referential tomographic plane and the plurality of tomographic planes to which the pixel value calculating means provides the pixel values,

pixel value providing means for providing the sampling points identified by the position identifying means, with pixel values based on the pixel values at the sampling points corresponding to the panoramic image and being present in a viewing direction from the X-ray tube to the detector via the respective sampling points,

tooth row deciding means for deciding the tooth row by recognizing the 3D referential tomographic plane provided at the sampling points to which the pixel values are provided by the pixel value providing means and a characteristic pattern shown by pixel values of the plurality of tomographic planes, and

singularity removing means for removing singularities from the sampling points of the tooth row decided by the tooth row deciding means.

17. The apparatus of claim 16, characterized in that

the singularity removing means comprises

classification means for classifying substances every characteristic shown by the same type of substance based on the frequency characteristic at the respective sampling points, and

smoothing means for smoothly connecting each substance classified by the classification means.

18. The apparatus of any one of claims 1-17, characterized in that

the X-ray tomographic imaging apparatus comprises CT (Computed Tomography) image reconstructing means for reconstructing tomographic images, based on a CT reconstruction method, from the frame data acquired by the detector,

the movement means is configured to move, along the orbits, the X-ray tube and the detector which are directly opposed to each other, and

switching means for switching an attitude of the detector when CT imaging is desired to be performed instead of the tomosynthesis method.

19. The apparatus of claim 18, characterized in that

the switching means comprise

position changing means for positionally moving the X-ray tube and the detector toward a patient'"'"'s head in a body axis direction thereof by a predetermined distance, and

angle changing means for changing an angle of the detector such that a first attitude of the detector which is for performing the tomosynthesis method with a patient'"'"'s jaw serving as the object is changed to a second attitude of the detector which is for performing the CT method with the patient'"'"'s jaw.

20. The apparatus of claim 19, characterized in that

the detection section of the detector has first edges and second sides, the first and second sides being perpendicular to each other, the pixels mapped in a direction of the first sides being less in number than the pixels mapped in a direction of the second sides, and

the angle changing means is configured to change the angle of the detector such that the first attitude in which the first sides are directed laterally, which is for performance of the tomosynthesis method of the patient'"'"'s jaw, is changed to the second attitude in which the second edges are directed laterally, which is for performance of the CT method with the patient'"'"'s jaw.

21. The apparatus of claim 19, characterized in that

the data acquiring device comprises a collimator having an aperture changeable in area for changing an X-ray incident region of the detection section of the detector, and

first aperture controlling means for controlling the area of the aperture of the collimator in accordance with the first and second attitudes.

22. The apparatus of any one of claims 18-21, characterized in that

the orbit includes a first orbit having a predetermined radius from a rotation center provided when the X-ray tube and the detector are rotated around the patient'"'"'s jaw and a second orbit having a radius longer than the radius of the first orbit, and

the support means comprises a first arm movably supporting the X-ray tube along the second orbit, and a second arm movably supporting the detector along the first orbit.

23. The apparatus of claim 22, characterized in that

the first arm is configured to movably support the X-ray tube along the second orbit so that the X-ray tube is directly opposed to the detector, and

the second arm is configured to movably support the detector along the first orbit so that the detector is directly opposed to the X-ray tube.

24. The apparatus of any one of claims 20-23, characterized in that the apparatus comprises

CT imaging mode deciding means for deciding, interactively with an operator, whether the CT imaging is performed with a whole are of tooth rows of the jaw or a partial area of the tooth rows of the jaw, and

second aperture controlling means for controlling the area of the aperture of the collimator depending on a CT imaging mode decided by the CT imaging mode deciding means.