WO2020158644A1 - Tomosynthesis device and method for driving same - Google Patents

Abstract

[Problem] To provide a compact tomosynthesis device that uses a plurality of cold cathode X-ray sources. [Solution] This tomosynthesis device includes a plurality of cold cathode X-ray sources that irradiate a subject with X-rays, wherein the plurality of cold cathode X-ray sources is arranged two-dimensionally on a predetermined plane. This drive method for a tomosynthesis device is for a tomosynthesis device in which a plurality of cold cathode X-ray sources that illuminates a subject with X-rays is arranged two-dimensionally on a predetermined plane, and the plurality of cold cathode X-ray sources are caused to flash in turn.

Description

Tomosynthesis device Driving method

The present invention relates to a tomosynthesis device using a plurality of cold cathode X-ray sources and a method of blinking these X-ray sources.

Tomosynthesis is one of the widely used methods for obtaining high-resolution tomographic images in X-ray fluoroscopy, and a plurality of objects obtained by scanning an object while irradiating X-rays in a certain angle range are used. It is a method of reconstructing a tomographic image of a subject from image information. Compared with computed tomography (abbreviated as CT), the imaging range and the number of tomography are limited, but since tomographic images can be obtained with a small X-ray dose, the digital processing technology for image information is rapidly advancing, It is expected to be applied in various fields including medical applications.

Digital radiography (digital X-ray photography), which has been in full swing since the beginning of the 21st century, uses a flat panel image sensor in the X-ray photosensitive section, which used to rely on the film until then. It is to be taken out as a digital signal. As an X-ray source which is a light source, a traditional hot cathode X-ray tube is used in which thermoelectrons from a filament are accelerated by a high voltage and collide with an anode to obtain X-rays from the braking energy. Even with the current tomosynthesis device, one X-ray tube is moved in one direction on an arc or parallel straight line trajectory with respect to the image sensor, and the irradiated X-rays from this X-ray tube are transmitted to the object in the vicinity of the image sensor. Scanning against.

Due to the nature of thermoelectrons, it is not possible to quickly switch the blinking of X-ray irradiation by a simple and inexpensive method, and it is physically necessary to arrange multiple hot cathode X-ray tubes that tend to be large due to exhaust heat treatment or high voltage introduction. Nor was it economically rational.

However, if the bremsstrahlung electrons for generating X-rays are supplied by the cold cathode by the field emission method, the irradiation X-rays can be blinked easily and reliably, and the need for exhaust heat treatment is reduced, so that the X-ray tube can be downsized. It is possible, and a method of arranging a plurality of them and sequentially lighting them becomes practical. This eliminates the need for a drive mechanism for moving one X-ray tube, eliminates deterioration of image quality due to mechanical drive, shortens imaging time, and simplifies the entire imaging apparatus.

Therefore, an object of the present invention is to provide a tomosynthesis device using a plurality of cold cathode X-ray sources. Another object of the present invention is to provide a method of driving a tomosynthesis device using a plurality of cold cathode X-ray sources.

The tomosynthesis device according to the present invention includes a plurality of cold cathode X-ray sources for irradiating a subject with X-rays, and the plurality of cold cathode X-ray sources are two-dimensionally arranged on a predetermined plane. ..

A method of driving a tomosynthesis device according to the present invention is a method of driving a tomosynthesis device in which a plurality of cold cathode X-ray sources for irradiating a subject with X-rays are two-dimensionally arranged on a predetermined plane. , A plurality of cold cathode X-ray sources are sequentially blinked.

FIG. 1A is a schematic perspective view showing a conventional tomosynthesis device (using a rotating mechanism) using a hot cathode X-ray tube. FIG. 1B is a schematic perspective view showing a conventional tomosynthesis apparatus (using a parallel movement mechanism) using a hot cathode X-ray tube. FIG. 1C is a schematic diagram for explaining an imaging method of a conventional tomosynthesis apparatus using a hot cathode X-ray tube. FIG. 2A is a schematic diagram showing a tomosynthesis device (small X-ray tubes arranged in an arc shape) using a plurality of small cold cathode X-ray sources. FIG. 2B is a schematic diagram showing a tomosynthesis device using a plurality of small cold cathode X-ray sources (a plurality of X-ray sources arranged linearly in a single X-ray generator). FIG. 3A is a schematic diagram showing a tomosynthesis device according to an example in which a plurality of small cold cathode X-ray sources are arranged in an arc shape. FIG. 3B is a schematic diagram showing a tomosynthesis device according to an example in which a plurality of small cold cathode X-ray sources are two-dimensionally arranged on a predetermined plane. FIG. 4A is a schematic diagram showing a tomosynthesis device according to an example in which some small cold cathode X-ray sources are arranged on different planes while avoiding obstacles. FIG. 4B is a schematic diagram showing a tomosynthesis apparatus according to an example in which a plane on which a plurality of small-sized cold cathode X-ray sources is arranged has an inclination. FIG. 5 is a schematic diagram for explaining an example of the blinking order of a plurality of small cold cathode X-ray sources. FIG. 6 is a schematic diagram for explaining an example of blinking order and dose of a plurality of small cold cathode X-ray sources. FIG. 7 is a schematic diagram for explaining an example of the blinking order and dose of a plurality of small cold cathode X-ray sources, and shows an example in which different anode voltages are applied in advance to specific X-ray sources.

By arranging a plurality of cold cathode X-ray tubes side by side or by arranging a plurality of X-ray sources in an integrated X-ray apparatus, a method of sequentially blinking driving of angled X-rays for tomosynthesis imaging can be considered. .. According to these methods, a plurality of X-ray tubes or X-ray sources are arranged on an arc or a straight line in accordance with a conventional mechanical X-ray tube driving method, and they are sequentially blinked in a fixed direction. It is assumed that. However, the arrangement of the cold cathode X-ray tube or the X-ray source, which is small and can blink easily, is not limited to the conventional mechanically driven track, and the blinking order is free. The present invention introduces a new usage and merit by introducing into the tomosynthesis the arrangement and blinking method of the cold cathode X-ray source that did not exist in the past.

The trajectory of the X-ray tube in the conventional tomosynthesis device that mechanically drives one traditional hot cathode X-ray tube, that is, the locus of the X-ray source, follows the drive mechanism, and therefore, the arc (Fig. 1A) or straight line (Fig. 1B). A rotary mechanism drives the arcuate track, and a parallel mechanism drives the linear track. The width of the arc (symbol A shown in FIG. 1A) and the length of the straight line (symbol B shown in FIG. 1B) are several tens cm to hundreds of tens of cm, and since there is also a drive mechanism, the tomosynthesis device itself is moved to take an image. I can't. The tomosynthesis device is fixed, and an object to be photographed (affected part) is placed at a predetermined photographing place for photographing.

In these X-ray source trajectories, X-rays are emitted ten to several dozen times in the order from one end of the orbit to the other end (Fig. 1C). Since it is difficult for the hot cathode X-ray tube to quickly and reliably blink the thermoelectrons from the filament, the X-ray tube is kept irradiating X-rays while moving in orbit, and There was also a method of sequentially capturing only the image information from the position from one end of the trajectory to the other end, but with this, most of the X-ray dose does not contribute to imaging, and the object (affected part) becomes useless. You will be exposed. Therefore, at present, measures are taken to prevent the X-rays from being irradiated from the orbital positions other than the time of photographing by using a high-cost method such as blinking the anode voltage of the X-ray tube.

At this time, if the X-ray tube is moved while moving in orbit, the light source moves during the shooting, which causes the problem of blurring the image. For this reason, a method may be adopted in which the movement is stopped after every ten to several tens of photographing positions and the X-ray tube is photographed at a stationary position. In this method, since the X-ray tube drive mechanism is repeatedly moved and stopped, it takes a long time to finish photographing a dozen to several tens of times, during which the object to be imaged (affected part) changes and the image quality is impaired. There is a problem. Also in this case, imaging is performed in the order from one end of the X-ray tube trajectory to the other end.

Many tomosynthesis images are taken under equal conditions while the X-ray tube moves from one end on the orbit to the other end (except for the position of the X-ray source on the orbit). That is, the X-ray irradiation of ten to several tens of times is performed with the same position interval, irradiation time, tube voltage, and tube current (X-ray dose).

In medical X-ray photography, the same object (affected part) is imaged with two types of X-rays with different energy levels, and these images are combined to make it possible to see multiple tissues with different X-ray absorption rates. It is possible to use a so-called dual energy method for improving tomosynthesis in tomosynthesis. In this case, if the tube voltage of the X-ray tube is switched during one movement on the orbit and two images are taken at the same position, a series of images on one orbit will be performed under different conditions. However, it is exceptional because there is a problem that it takes longer to finish all the shooting.

When a small cold cathode X-ray tube is used as an X-ray source for tomosynthesis imaging, a dozen to several tens of cold cathode X-ray tubes are placed on the orbit of the hot cathode X-ray tube in the conventional tomosynthesis device. By arranging the individual tomosynthesis images a number of times and sequentially blinking these to irradiate X-rays, the same imaging as the method described in FIGS. 1A to 1C can be performed (FIG. 2A). .. The same applies to an X-ray generator including a mechanism in which a plurality of cold cathode X-ray sources are arranged on the orbit (FIG. 2B). Even in these cases, each cold cathode X-ray tube or cold cathode source is arranged along an arc or straight line in the conventional tomosynthesis device. The size of the X-ray source portion of the tomosynthesis device (reference A in FIG. 1A or reference B in FIG. 1B) does not change except that the X-ray tube drive mechanism is not required.

Furthermore, the blinking method of multiple cold cathode tubes or cold cathode sources is performed under the same condition from one end of the arc or linear array to the other end.

As described above, in tomosynthesis imaging, whether a device that mechanically drives a traditional hot cathode X-ray tube or a device that arranges a plurality of cold cathode X-ray sources and blinks them, arranges the X-ray sources and drives X-ray irradiation. The method is no different from the conventional method.

A plurality of X-ray irradiations from different angles with respect to the object (X-ray image sensor) necessary for tomosynthesis imaging are arranged one-dimensionally when viewed from the object (X-ray image sensor) ( 3A) is not necessary and may be realized by dispersing the cold cathode X-ray source in two dimensions (FIG. 3B). That is, a plurality of small cold cathode X-ray sources may be arranged two-dimensionally on a predetermined plane. As a result, the maximum length of the X-ray source portion can be reduced even if the same number of irradiations and the same intervals as those in the conventional arrangement are arranged (reference numeral C in FIG. 3A to reference numeral C in FIG. 3A), and the object to be photographed is reduced. It is possible to change the position of the X-ray source portion and take an image according to the (affected part) and the imaging environment. In the example shown in FIG. 3B, a plurality of cold cathode X-ray sources are arranged so as to surround the object to be viewed when viewed from directly above the object.

The plurality of cold cathode sources arranged two-dimensionally when viewed from the object (X-ray image sensor) does not need to be equidistant from the object (X-ray image sensor), and different distances depending on the purpose. In addition, they may be dispersed in a three-dimensional space. As a result, the X-ray source portion of the tomosynthesis device can be placed in the restricted space shape (FIG. 4A), and it can also be arranged so as to ensure imaging from a specific direction (FIG. 4B). In the example shown in FIG. 4A, some small cold cathode X-ray sources are arranged on another plane closer to the object to be photographed, avoiding obstacles. Further, in the example shown in FIG. 4B, the plane on which the plurality of small cold cathode X-ray sources are arranged has an inclination, and the small cold cathode X-ray source located at the center is directly above the object to be photographed. It is arranged. In the example shown in FIGS. 4A and 4B, the distances between the plurality of cold cathode X-ray sources and the object to be photographed are not the same, and at least two cold cathode X-ray sources are different from each other in the object to be photographed.

　For tomosynthesis imaging, it is not necessary to blink multiple cold-cathode X-ray sources in a fixed direction one by one on an arc, straight line, or circumference. When the image from the irradiation from a certain direction serves as the basic information for synthesizing a tomographic image, and it is effective to spend more time for computer analysis than other images, irradiation in this direction should be performed first, and then By continuing the difference analysis by prioritizing the imaging in the vicinity (FIG. 5), the time until the final tomographic image synthesis is shortened and the image quality can be improved. In this way, according to the purpose, it is possible to blink the light in any order such as jumping, reciprocating, and repeating without being bound by a fixed order. As described above, the blinking may be performed sequentially along the arrangement order of the plurality of cold cathode X-ray sources, or the blinking may be performed sequentially in an order different from the arrangement order of the plurality of cold cathode X-ray sources.

In Fig. 5, it is not necessary that the blinking of the cold cathode X-ray source be performed once under the same conditions. If a higher X-ray dose is required for an image from irradiation from a particular direction, a large current can be set for irradiation in this direction. This can also be realized by repeating the irradiation (Fig. 6). In the example shown in FIG. 6, the X-ray dose of the cold cathode X-ray source G is 20 mAs, and the X-ray dose of the other cold cathode X-ray sources G is 10 mAs. The cold cathode X-ray source G may irradiate the X-ray dose of 20 mAs at a time, or may irradiate the X-ray dose of 10 mAs in two times. With a cold cathode X-ray source that does not mechanically move during imaging, the imaging time does not significantly increase even if the specific X-ray source is repeatedly irradiated. Such adjustment of the dose according to the irradiation direction is repeated in the same irradiation direction in order to correct a problem such as poor image quality found in the analysis of a certain image in addition to the case of being preset. The dose adjustment in the next irradiation direction can be performed dynamically in conjunction with image analysis by a computer.

The method of adjusting the irradiation conditions from each cold cathode X-ray source can affect not only the X-ray dose but also the X-ray energy, but the anode voltage of one X-ray tube is blinked or the energy level is changed. Up and down has already been done. In tomosynthesis in which a plurality of cold cathode X-ray sources are arranged, the anode voltage of each X-ray source is not dynamically adjusted, but different anode voltages are given to a specific X-ray source in advance, and the corresponding X-ray sources are provided. By flashing the current of X, it is possible to realize X-ray irradiation with different energies (FIG. 7). In the example shown in FIG. 7, the anode voltage is 40 keV in some cold cathode X-ray sources, while the anode voltage is 70 keV in the remaining cold cathode X-ray sources. In this case, the combination of X-ray energy and its irradiation direction is uniquely determined, but the order and number of times can be arbitrarily selected.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention. It goes without saying that it is included in the range.

Claims (11)

1. A plurality of cold cathode X-ray sources for irradiating the object with X-rays,
   The tomosynthesis device in which the plurality of cold cathode X-ray sources are two-dimensionally arranged on a predetermined plane.
2. The tomosynthesis device according to claim 1, wherein the plurality of cold cathode X-ray sources are arranged so as to surround the object to be photographed when viewed from a predetermined direction.
3. The tomosynthesis device according to claim 1 or 2, wherein at least two of the plurality of cold cathode X-ray sources have different distances from the object to be photographed.
4. The tomosynthesis device according to any one of claims 1 to 3, wherein the plurality of cold cathode X-ray sources are sequentially blinked.
5. The tomosynthesis device according to claim 4, wherein the plurality of cold cathode X-ray sources are sequentially blinked in accordance with the arrangement order of the plurality of cold cathode X-ray sources.
6. The tomosynthesis device according to claim 4, wherein the plurality of cold cathode X-ray sources are sequentially blinked in an order different from the arrangement order of the plurality of cold cathode X-ray sources.
7. The plurality of cold cathode X-ray sources includes first and second cold cathode X-ray sources,
   7. The energy of X-rays emitted by the first cold cathode X-ray source and the energy of X-rays emitted by the second cold cathode X-ray source are different from each other. Tomosynthesis device.
8. The tomosynthesis device according to claim 7, wherein an anode voltage previously given to the first cold cathode X-ray source and an anode voltage previously given to the second cold cathode X-ray source are different from each other.
9. A method for driving a tomosynthesis device, in which a plurality of cold cathode X-ray sources for irradiating an object with X-rays are two-dimensionally arranged on a predetermined plane,
   A method for driving a tomosynthesis device, which comprises sequentially blinking the plurality of cold cathode X-ray sources.
10. The method for driving a tomosynthesis device according to claim 9, wherein the plurality of cold cathode X-ray sources are sequentially blinked in the order of arrangement of the plurality of cold cathode X-ray sources.
11. The method of driving a tomosynthesis device according to claim 9, wherein the plurality of cold cathode X-ray sources are sequentially blinked in an order different from the arrangement order of the plurality of cold cathode X-ray sources.

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