X-ray diagnostic apparatus and control method thereof

According to one embodiment, an X-ray diagnostic apparatus includes an X-ray tube, an X-ray variable diaphragm, an X-ray detector, and processing circuitry. The X-ray tube irradiates X-rays. The X-ray variable diaphragm limits an irradiation region of the X-rays. The X-ray detector detects the X-rays that have passed through an object. The processing circuitry controls a movement of the X-ray tube, the X-ray detector, and an aperture of the X-ray variable diaphragm such that, when the irradiation region on the X-ray detector moves within an imaging range, a movement velocity of the irradiation region relative to the imaging range is maintained constant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of Japanese Patent Application No. 2020-194175, filed Nov. 24, 2020, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an X-ray diagnostic apparatus and a control method thereof.

BACKGROUND

In X-ray diagnostic apparatus, the area to be observed may cover a wide range, such as the gastrointestinal tract or lower limb blood vessels. For example, the X-ray diagnostic apparatus tracks the movement of the contrast medium as it moves within the imaging range from upstream to downstream. In this case, with the X-ray detector stopped, the user can observe the entire area to be observed by controlling the X-ray variable diaphragm to move the X-ray irradiation region for X-ray fluoroscopy.

However, the desired imaging range of the user may not fit into the size of the X-ray detector. In this case, in order to prevent the irradiation region from extending outside the X-ray detector, when the moving irradiation region reaches the downstream end of the X-ray detector, the user must suspend observation, move the X-ray detector to the downstream side, manipulate the X-ray variable diaphragm such that the irradiation region is positioned at the upstream end of the moved X-ray detector, and then resume observation of the region to be observed. In this case, the user is forced to suspend the observation and perform complicated positioning of the imaging system. Further, the user may lose sight of the observation target during the position adjustment. Furthermore, since the examination time becomes longer due to the position adjustment, the burden on the object increases. In addition, since the X-ray fluoroscopy is continued during the positioning process to support the user, the radiation dose of the object increases.

DETAILED DESCRIPTION

Hereinbelow, a description will be given of an X-ray diagnostic apparatus and a control method thereof according to embodiments of the present invention with reference to the drawings.

In general, according to one embodiment, an X-ray diagnostic apparatus includes an X-ray tube, an X-ray variable diaphragm, an X-ray detector, and processing circuitry. The X-ray tube irradiates X-rays. The X-ray variable diaphragm, limits an irradiation region of the X-rays. The X-ray detector detects the X-rays that have passed through an object. The processing circuitry controls a movement of the X-ray tube, the X-ray detector, and an aperture of the X-ray variable diaphragm such that, when the irradiation region on the X-ray detector moves within an imaging range, a movement velocity of the irradiation region relative to the imaging range is maintained constant.

FIG.1is a block diagram showing an example of an X-ray diagnostic apparatus10according to an embodiment. The X-ray diagnostic apparatus10according to embodiments can be anything that can perform fluoroscopy and imaging, and includes, for example, X-ray TV apparatuses and X-ray angiography apparatuses. In this embodiment, an example of a case where an X-ray TV apparatus is used as the X-ray diagnostic apparatus10is described.

The X-ray diagnostic apparatus10, as shown inFIG.1, includes an X-ray source11, a housing12that houses an X-ray variable diaphragm20and an X-ray detector13, a supporting post14, a supporting post driving mechanism15, a tabletop16, a bed17, and a console30. In this embodiment, the lateral direction of the tabletop16is defined as the x-axis, the normal direction of the tabletop16as the y-axis, and the longitudinal direction of the tabletop16as the z-axis (seeFIG.1).

The X-ray source11is, for example, an X-ray tube to which a voltage is applied by a high-voltage generator (not shown) to generate X-rays. The X-ray tube includes a vacuum tube that irradiates hot electrons from a cathode (filament) to an anode (target) by being applied a high voltage from the high-voltage generator.

The housing12is a housing made of metal, houses at least the X-ray variable diaphragm20, and may also house a region of interest filter (ROI filter). The X-ray source11and the housing12are supported at one end of the supporting post14as shown inFIG.1.

FIG.2is a diagram showing an example of the X-ray variable diaphragm20.

The X-ray variable diaphragm20has an aperture25for restricting (narrowing) the irradiation region of X-rays. The X-ray variable diaphragm20allows X-rays to pass through the aperture25, while restricting X-rays through regions other than the aperture25. The variable diaphragm20includes diaphragm blades that include a plurality of blade elements, for example.

By independently moving these blade elements21-24parallel to the X-ray source11, the position of the aperture25can be moved parallel to the surface of the tabletop16and the size of the aperture25can be changed while the supporting post14remains stationary and the positions of the X-ray source11and the X-ray detector13are fixed. Therefore, it is possible to change the position and size of the irradiation region corresponding to the aperture25while keeping the positions of the X-ray source11and the X-ray detector13fixed. The number of blade elements of the diaphragm blades is not limited to four as shown inFIG.2, and for example, a multi-leaf collimator may be used as the diaphragm blades.

The X-ray detector13is supported at the other end of the supporting post14such that it is placed opposite the X-ray source11and the X-ray variable diaphragm20across the object placed on the tabletop16of the bed17. The X-ray detector13including a flat panel detector (FPD) detects X-rays irradiated to the X-ray detector13through the object, outputs image data of X-ray fluoroscopic images and X-ray radiographic images based on the detected X-rays, and provides the image data to the console30. The X-ray detector13may include an image intensifier, TV camera, and the like.

The supporting post14is a supporting member that supports the imaging system including the X-ray source11, the X-ray variable diaphragm20, and the X-ray detector13. The configuration of the X-ray variable diaphragm20will be described later usingFIG.2.

The supporting post driving mechanism15moves the supporting post14in a direction parallel to the surface of the tabletop16(for example, in the longitudinal or shortitudinal direction of the tabletop16) to move the X-ray source11, X-ray variable diaphragm20, and X-ray detector13as a single unit. The supporting post driving mechanism15may also raise and lower the bed17together with the tabletop16around the x-axis with the supporting post driving mechanism15as the center. The supporting post driving mechanism15has a motor as a drive source to move the imaging system along the direction parallel to the surface of the tabletop16and to raise and lower the bed17, and has electronic components to control the motor.

The tabletop16is provided on the top of the bed17, and the object is placed on the tabletop16. The bed17may also be provided with shoulder rests, footrests, side hand grips, and the like, for supporting the object. The tabletop16is moved along the longitudinal and shortitudinal directions of the tabletop16with respect to the bed17by the tabletop driving mechanism (not shown). The tabletop driving mechanism has a motor as a drive source to move the tabletop16and electronic components to control the motor.

The user may observe the object or perform a medical procedure on the object while checking the real-time X-ray fluoroscopic image acquired by X-ray imaging.

The console30is composed of, for example, a general personal computer or workstation, and has an input interface31, a display32, a memory33, a network connecting circuit34, and processing circuitry35. The console30may not be provided independently, and for example, some of the components31-35of the console may be provided in the bed17.

The input interface31includes a general input device such as a trackball, a switch button, a mouse, a keyboard, and a numeric keypad, and outputs signals corresponding to user operations to the processing circuitry35. The user can set the imaging conditions via the input interface31. The input interface31may also include an exposure switch that controls the on/off of exposure.

The input interface31may include a supporting post movement instruction lever311that directs the supporting post driving mechanism15to move the supporting post14in the longitudinal and shortitudinal directions of the tabletop16. The input interface31may also include a region movement instruction lever312that directs the direction (including orientation) of the movement of the irradiation region41with respect to the tabletop16.

The display32is composed of a general display output device such as a liquid crystal display and an OLED (Organic Light Emitting Diode) display, and displays various information such as fluoroscopic images generated by the processing circuitry35based on X-ray imaging.

The memory33includes a recording medium that can be read by the processor, such as a magnetic or optical recording medium or semiconductor memory. Some or all of the programs and data stored in the recording medium may be configured to be downloaded by communication via an electronic network.

The network connecting circuit34may include a network card having a predetermined printed circuit board, and implements various protocols for information communication according to the form of the network. The network connecting circuit34connects the X-ray diagnostic apparatus10to other devices according to these various protocols. An electrical connection via an electronic network or the like can be applied to this connection. The term “electronic network” refers to all information and communication networks using telecommunications technology, including wireless or wired hospital LAN (Local Area Network), internet networks, telephone communication networks, optical fiber communication networks, cable communication networks, and satellite communication networks.

The processing circuitry35includes a processor that executes the processing for automatic fluoroscopy of the imaging range wider than the width of the X-ray detector while moving the X-ray irradiation region at a constant velocity relative to the object by reading and executing the programs stored in the memory33.

FIG.3is a schematic block diagram showing an example of functions realized by the processing circuitry35. As shown inFIG.3, the processor of the processing circuitry35realizes a setting function351, an interlock controlling function352, and an image generating function353. Each of these functions is stored in the memory33in the form of a program.

The setting function351, based on the user's instruction via the region movement instruction lever312of the input interface31, sets the imaging range having a width larger than the width of the X-ray detector13in a predetermined direction parallel to the surface of the tabletop16(hereinafter referred to as the “set direction of movement”), the size of the irradiation region of X-rays, and the direction of movement of the irradiation region in the imaging range as the set direction of movement.

The interlock controlling function352enables the irradiation region to move at a constant velocity in the set direction of movement relative to the surface of the tabletop16. For this purpose, the interlock controlling function352controls the diaphragm driving circuit26and the supporting post driving circuit27according to the positional relationship between the irradiation region and the X-ray detector13. The diaphragm driving circuit26and the supporting post driving circuit27are controlled such that the movement of the aperture25of the X-ray variable diaphragm20in the set direction of movement made by the diaphragm driving circuit26and the movement of the supporting post14in the set direction of movement made by the supporting post driving circuit27of the supporting post driving mechanism15are linked (interlocked).

The diaphragm driving circuit26determines the size of the aperture25of the X-ray variable diaphragm20according to the size of the set irradiation region. Further, the diaphragm driving circuit26is controlled by the interlock controlling function352to move the position of the aperture25parallel to the surface of the tabletop16according to the set direction of movement.

FIG.4is an explanatory diagram showing an example of a relationship between the aperture25and the irradiation region41.FIG.4shows an example where the set direction of movement is positive in the z direction.

By moving the aperture25in the set direction of movement, the X-ray flux40can be moved. Therefore, even if the X-ray source11and the X-ray detector13remain stationary, the irradiation region41on the X-ray detector13can be moved from the upstream end13uto the downstream end13dof the X-ray detector13in the set direction of movement by moving the aperture25in the set direction of movement (seeFIG.4).

FIG.5Ais a side view for explaining an example of how the supporting post14moves along the longitudinal direction of the tabletop16, andFIG.5Bis a top view thereof.

The supporting post driving circuit27is controlled by the interlock controlling function352to move the supporting post14parallel to the surface of the tabletop16according to the set direction of movement, thereby moving the X-ray source11, the housing12, and the X-ray detector13as a single unit in the set direction of movement. As the X-ray source11moves, the X-ray flux40moves along the set direction of movement with respect to the surface of the tabletop16.

Additionally, the interlock controlling function352may further interlock the movement of the tabletop16in the set direction of movement by the tabletop driving circuit28of the tabletop driving mechanism (not shown) with these movements.

The image generating function353generates an X-ray fluoroscopic image corresponding to the irradiation region41in real time and displays it on the display32.

FIG.6Ais an explanatory diagram showing an example of a fluoroscopic image display area42on the display32, andFIG.6Bis another example thereof.

The image generating function353causes the fluoroscopic image corresponding to the irradiation region41to be displayed on the fluoroscopic image display area42on the display32. The fluoroscopic image display area42may be set to occupy most of the display area on the display32(seeFIG.6A). In this case, since the fluoroscopic image corresponding to the irradiation region41can be enlarged, the user is able to observe the observation target in detail. The fluoroscopic image display area42may be a region corresponding to the position of the irradiation region41on the X-ray detector13. In this case, the entire display area of the display32may be made to correspond to the entire detection surface of the X-ray detector13(seeFIG.6B). In this case, the user can easily and intuitively grasp the position of the current irradiation region41on the X-ray detector13. These display methods can also be switched according to the user's instructions.

Next, an example of the operation of the X-ray diagnostic apparatus10of embodiments will be described.

FIG.7is an explanatory diagram showing an example of a relationship between the X-ray detector13and the imaging range50.

As described above, the setting function351sets, based on instructions by the user through the input interface31, the imaging range50having a width larger than the width of the X-ray detector13in the set direction of movement, the size of the X-ray irradiation region41, and the direction of movement of the irradiation region41in the imaging range50.

FIG.7shows an example where the set direction of movement is positive (from head to foot) in the z-axis direction (body axis direction). In the following, an example is shown where the width of the imaging range50is equal to the width of the irradiation region41in the direction orthogonal to the set direction of movement. In this case, the irradiation region41does not need to be moved in the direction orthogonal to the set direction of movement, and the entire range of the imaging range50can be fluoroscopically imaged by moving the irradiation region41in the set direction of movement. The upstream end13uand the downstream end13dof the X-ray detector13are defined by setting the set direction of movement.

FIG.8is an explanatory diagram showing an example of how to move the irradiation region41. Hereinafter, the method starting in a state where the upper end of the irradiation region41matches the upstream end13uof the X-ray detector13will be described.

First, the interlock controlling function352starts moving the aperture25of the X-ray variable diaphragm20at a constant velocity vc such that the supporting post14is not moved and the irradiation region41is moved at a constant velocity vf. The movement velocity vc of the aperture25is defined as the velocity of the aperture25relative to the housing12, for example. The movement velocity vf of the irradiation region41may be defined as the velocity on the top surface of the tabletop16, on the object, or on the X-ray detector13.

Next, when the lower end of the irradiation region41reaches the downstream end13dof the X-ray detector13(see the upper center ofFIG.8), in order to move the X-ray detector13to the next region adjacent to the downstream side of the current region, the interlock controlling function352moves the X-ray detector13(i.e., supporting post14) at a velocity vd by the width of the X-ray detector13in the set direction of movement, and also moves the aperture25at a velocity vc such that the upstream end13uof the moved X-ray detector13coincides with the upper edge of the irradiation region41(see the upper right ofFIG.8). At this time, the direction of the velocity vc (negative in the z-axis direction) is opposite to the set direction of movement, and it is preferable that the movement of the X-ray detector13and the movement of the aperture25are performed concurrently. The moving velocity vd of the X-ray detector13may be defined as the velocity of the X-ray detector13relative to the tabletop16.

Next, the interlock controlling function352starts to move the aperture25of the X-ray variable diaphragm20at the constant velocity vc again such that the irradiation region41is moved at the constant velocity of while the supporting post14remains stationary (see the lower part ofFIG.8).

When the lower end of the irradiation region41reaches the downstream end13dof the X-ray detector13, and the user manually adjusts the position of the imaging system, the user has to constantly check on whether the current irradiation region41extends beyond the X-ray detector13or not. Also, the user further needs to suspend observation so as to adjust the position of the imaging system by operating the supporting post movement instruction lever311and the position of the irradiation region by operating the region movement instruction lever312.

According to the method shown inFIG.8, even when imaging range50is wider than the width of X-ray detector13, the user only needs to indicate the direction of movement of the irradiation region41via the region movement instruction lever312, without operating the supporting post movement instruction lever311, and then the interlock controlling function352automatically moves the irradiation region41relative to the object, whereby the user can observe the fluoroscopic images through the entire imaging range50smoothly. Further, according to the method shown inFIG.8, the user is not only free from the burden of manipulations, but also does not need to check on whether the current irradiation region41protrudes from the X-ray detector13or not. In addition, the imaging range50can be observed in a much shorter time compared with the case of manually adjusting the position of the imaging system, thus the exposure dose of the object can be reduced.

FIG.9is an explanatory diagram showing an example of how to move the irradiation region41at a constant velocity vf0.

In the method shown inFIG.9, the movement of the X-ray detector13is started before the lower end of the irradiation region41reaches the downstream end13dof the X-ray detector13, whereby the irradiation region41can move at the constant velocity vf0in the entire imaging range50.

Specifically, when the position of the lower end of the irradiation region41on the X-ray detector13is upstream from the downstream end13dof the X-ray detector13more than the predetermined distance D, the interlock controlling function352does not move the supporting post14, but moves the aperture25of the X-ray variable diaphragm20at the constant velocity vc such that the irradiation region41moves at the constant velocity vf0(see upper left ofFIG.9).

The speed of the constant velocity vf0of the irradiation region41may be set by the user or automatically set according to the size of the irradiation region41.

When the position of the irradiation region41on the X-ray detector13is reached within the predetermined distance D from the downstream end13d(see upper center ofFIG.9), the interlock controlling function352moves the aperture25at velocity vc and concurrently moves the X-ray detector13at velocity vd such that the velocity vf0of the irradiation region41is maintained (see upper right ofFIG.9). More specifically, the interlock controlling function352controls the velocity vc of the aperture25and the velocity vd of the X-ray detector13in conjunction with each other, depending on their positions, such that the velocity vf0of the irradiation region41is maintained.

At this time, the interlock controlling function352may also control the speed and orientation of the velocity vc of the aperture25as well as the speed and orientation of the velocity vd of the X-ray detector13, such that the timing when the X-ray detector13completes the movement to the next region and the timing when the upper end of the irradiation region41matches the upstream end13uof the X-ray detector13after moving to the next region are simultaneous (see lower left ofFIG.9). When the X-ray detector13finishes moving to the next region, the supporting post14is stopped and the aperture25is moved at the constant velocity vc such that the irradiation region41is moved at the constant velocity vf0(see lower right ofFIG.9).

The method shown inFIG.9has the same effect as the method shown inFIG.8. Further, the method shown inFIG.9allows fluoroscopic observation of the entire imaging range50to be performed while the moving velocity vf0of the irradiation region41remains constant.

In addition, compared to the method shown inFIG.8, the method shown inFIG.9does not require the time from when the lower end of the irradiation region41reaches the downstream end13dof the X-ray detector13until the fluoroscopy of the next region is resumed. Therefore, the method shown inFIG.9can further shorten the inspection time than the method shown inFIG.8, and can significantly reduce the exposure dose of the object.

The method shown inFIG.9can start the movement of the X-ray detector13before the lower end of the irradiation region41reaches the downstream end13dof the X-ray detector13and control the movement of the X-ray detector13in conjunction with the movement of the aperture25, and thus, the velocity of the irradiation region41can be easily maintained at the constant velocity vf0even during the acceleration period immediately after the X-ray detector13starts to move.

FIG.10is a flowchart showing an example of a procedure of a process for performing automatic fluoroscopy of the imaging range50wider than the width of the X-ray detector13while moving the X-ray irradiation region41at the constant velocity vf0relative to the object by the processor of the processing circuitry35. InFIG.10, reference numerals with numbers attached to S indicates each step of the flowchart. The procedure shown inFIG.10corresponds to the method shown inFIG.9.

First, in step S1, the setting function351sets the size of the imaging range50and irradiation region41based on the instructions given by the user through the input interface31.

Next, in step S2, the setting function351sets the direction of movement of the irradiation region41in the imaging range50based on the instructions given by the user via the region movement instruction lever312of the input interface31.

When the fluoroscopy of the imaging range50is started (step S3), in step S4, the interlock controlling function352moves the aperture25of the X-ray variable diaphragm20at the constant velocity vc such that the irradiation region41moves at the constant velocity vf0(see upper left ofFIG.9).

Next, in step S5, the interlock controlling function352determines whether the position on the X-ray detector13of the lower end of the irradiation region41is within the predetermined distance D from the downstream end13dof the X-ray detector13.

When the lower end of the irradiation region41on the X-ray detector13is more upstream than the predetermined distance D from the downstream end13dof the X-ray detector13, the procedure returns to step S4.

Meanwhile, when the lower end of the irradiation region41on the X-ray detector13is within the predetermined distance D from the downstream end13dof the X-ray detector13, in step S6, the interlock controlling function352interlocks the movement of the aperture25and the movement of the X-ray detector13such that the irradiation region41moves maintaining the constant velocity vf0(see upper right ofFIG.9).

Until the X-ray detector13reaches the next area adjacent to the downstream side (NO in step S7), the process in step S6is repeated. When the X-ray detector13reaches the next area adjacent to the downstream side (YES in step S7), the procedure returns to step S4. When the lower end of the irradiation region41reaches the lower end of the imaging range50, the procedures come to an end.

In the above manner, by the method shown inFIG.9is executed, an automatic fluoroscopy of the imaging range50, which is wider than the width of the X-ray detector13, can be performed while moving the X-ray irradiation region41at the constant velocity vf0relative to the object. Therefore, the user can observe the fluoroscopic images of the imaging range50smoothly at the constant velocity from the beginning to the end.

FIG.11is a diagram for explaining an example of a case where the size of the irradiation region41changes.

The size of the irradiation region41is uniquely determined by the size of the aperture25and the source-to-image distance (SID). Therefore, when the size of the aperture25is the same, the irradiation region41becomes larger as the Source to image Distance (SID) becomes longer, as shown inFIG.11. Also, when the movement velocity vc of the aperture25is constant, the movement velocity of the irradiation region41becomes faster as the SID becomes longer. Therefore, when the SID is changed during fluoroscopy of imaging range50, the moving velocity of irradiation region41will change, and the user may have difficulty observing the observation target.

Therefore, the interlock controlling function352is preferably designed to move the irradiation region41at the constant velocity vf0even when the size of the irradiation region41is changed during fluoroscopy of the imaging range50. It is recommended to control the movement velocity vc of the aperture25and the movement velocity vd of the X-ray detector13according to the size of the irradiation region41such that the irradiation region41moves at the constant velocity vf0even when the size of the irradiation region41is changed during fluoroscopy of the imaging range50.

When the enlarged display method shown inFIG.6Ais adopted, the smaller the irradiation region41is, the finer the observation image becomes. However, when the irradiation region41is small, it is easy to lose sight of the observation target if the velocity of the irradiation region41is fast. Meanwhile, when the irradiation region41is large, it is difficult to find the observation target if the movement velocity of the irradiation region41is slow, which makes operation difficult. Therefore, the interlock controlling function352is preferably designed such that the smaller the irradiation region41set by the setting function351is, the slower the constant velocity vf0of irradiation region41becomes.

According to at least one of the above-described embodiments, the imaging range wider than the width of the X-ray detector can be automatically fluoroscoped while moving the X-ray irradiation region at a constant velocity relative to the object.

The processing circuitry in the above-described embodiments is an example of the processing circuitry described in the claims. In addition, the term “processor” used in the explanation in the above-described embodiments, for instance, refers to circuitry such as dedicated or general purpose CPUs (Central Processing Units), dedicated or general-purpose GPUs (Graphics Processing Units), or ASICs (Application Specific Integrated Circuits), programmable logic devices including SPLDs (Simple Programmable Logic Devices), CPLDs (Complex Programmable Logic Devices), and FPGAs (Field Programmable Gate Arrays), and the like. The processor implements various types of functions by reading out and executing programs stored in the memory circuitry.

In addition, instead of storing programs in the memory circuitry, the programs may be directly incorporated into the circuitry of the processor. In this case, the processor implements each function by reading out and executing each program incorporated in its own circuitry. Moreover, although in the above-described embodiments an example is shown in which the processing circuitry configured of a single processor implements every function, the processing circuitry may be configured by combining plural processors independent of each other so that each processor implements each function of the processing circuitry by executing the corresponding program. When a plurality of processors is provided for the processing circuitry, the memory medium for storing programs may be individually provided for each processor, or one memory circuitry may collectively store programs corresponding to all the functions of the processors.