An X-ray diagnostic apparatus includes a first arm mounted with a first X-ray tube and a first X-ray detector, a second arm mounted with a second X-ray tube and a second X-ray detector, a bed having a table top capable of rising and falling on which a patient is placed, a first rotating mechanism that rotates the first arm, a first moving mechanism that subjects the first arm to parallel translation, and a control unit that controls the first rotating mechanism and the first moving mechanism on the basis of a position of the second arm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-062038, filed Mar. 5, 2004, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a biplane X-ray diagnostic apparatus that makes it possible to perform simultaneous imaging in two directions.

2. Description of the Related Art

A biplane X-ray diagnostic apparatus, which has been developed mainly for inspection of the circulatory system, includes two X-ray imaging systems, namely, a frontal X-ray imaging system for imaging a patient from the front thereof and a lateral X-ray imaging system for imaging the patient from the side thereof, in order to make it possible to image the patient from two directions simultaneously. The frontal X-ray imaging system has an X-ray tube and an X-ray detector that are attached to both ends of a C arm supported by, for example, a stand placed on a floor. Similarly, the lateral X-ray imaging system has an X-ray tube and an X-ray detector that are attached to both ends of an Ω arm suspended from a ceiling.

Since the C arm of the frontal X-ray imaging system has the stand fixed to the floor, the C arm is capable of turning (pivoting) around the stand but, basically, cannot move on the floor. On the other hand the Ω arm of the lateral X-ray imaging system is suspended from sliders engaged with rails provided on the ceiling to be movable longitudinal and lateral along the rails. In radioscopy and imaging, the C arm and the Ω arm are initially aligned such that a region of interest of a patient is located in image centers in both the frontal X-ray imaging system and the lateral X-ray imaging system. In other words, the C arm and the Ω arm are aligned such that the region of interest of the patient is located on an imaging center axis of the frontal X-ray imaging system and located on an imaging center axis of the lateral X-ray imaging system.

Even if the region of interest is positioned on the respective imaging center axis, the region of interest does not always coincide with a rotation center point of the C arm and a rotation center point of the Ω arm. In this case, when the C arm or the Ω arm is rotated, the region of interest deviates from the respective imaging center axes. Consequently, since the region of interest deviates from the image centers, it is necessary to perform positioning of the region of interest again.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to always position a region of interest in image centers regardless of rotation of arms in a biplane X-ray diagnostic apparatus.

An X-ray diagnostic apparatus according to a first aspect of the invention includes: a first arm mounted with a first X-ray tube and a first X-ray detector; a second arm mounted with a second X-ray tube and a second X-ray detector; a bed having a table top capable of rising and falling on which a patient is placed; a first rotating mechanism that rotates the first arm; a first moving mechanism that subjects the first arm to parallel translation; and a control unit that controls the first rotating mechanism and the first moving mechanism on the basis of a position of the second arm.

An X-ray diagnostic apparatus according to a second aspect of the invention includes: a first arm mounted with a first X-ray tube and a first X-ray detector; a second arm mounted with a second X-ray tube and a second X-ray detector; a bed having a table top on which a patient is placed; a first rotating mechanism that rotates the first arm; a first moving mechanism that subjects the first arm to parallel translation; and a control unit that controls the first moving mechanism in order to subject the first arm to parallel translation following the rotation of the first arm.

An X-ray diagnostic apparatus according to a third aspect of the invention includes: an arm mounted with an X-ray tube and an X-ray detector; a bed having a table top on which a patient is placed; a rotating mechanism that rotates the arm; a moving mechanism that subject the arm to parallel translation; and a control unit that controls the moving mechanism to subject the arm to parallel translation following the rotation of the arm such that a specific region of the patient is located on an imaging axis.

DETAILED DESCRIPTION OF THE INVENTION

An X-ray diagnostic apparatus according to an embodiment of the invention will be hereinafter explained with reference to the accompanying drawings.FIG. 1shows an external appearance of the X-ray diagnostic apparatus according to the embodiment.FIG. 2is a side view of the X-ray diagnostic apparatus andFIG. 3is a front view of the X-ray diagnostic apparatus. This X-ray diagnostic apparatus is applicable to a biplane system and includes a frontal X-ray imaging system (a first X-ray imaging system) and a lateral X-ray imaging system (a second X-ray imaging system) to be capable of imaging a patient placed on a table top18of a bed17from two directions simultaneously.

The frontal X-ray imaging system has an X-ray tube (a first X-ray tube)11and an X-ray detector (a first X-ray detector)12. The lateral X-ray imaging system has an X-ray tube (a second X-ray tube)21and an X-ray detector (a second X-ray detector)22. As the X-ray detectors12and22, a combination of an image intensifier and a TV camera or a flat panel detector (FPD) is adopted.

The X-ray tube11is attached to one end of a C arm13. The X-ray detector12is attached to the other end of the C arm13so as to be approachably and separably with respect to a rotation center point RC1(in a direction of an arrow F). Reference sign CA1denotes an imaging center axis of the frontal X-ray imaging system connecting a focal point of the X-ray tube11and a center of an image reception area of the X-ray detector12. The X-ray tube12is attached to one end of an Ω arm23. The X-ray detector22is attached to the other end of the Ω arm23so as to be approachably and separably with respect to a rotation center point RC2(in a direction of an arrow M). Reference sign CA2denotes an imaging center point of the lateral X-ray imaging system connecting a focal point of the X-ray tube21and a center of an image reception area of the X-ray detector22.

The C arm13of the frontal X-ray imaging system is supported by a stand15fixed on a floor via an arm holder14. The arm holder14holds the C arm13to be slidingly rotatable in a direction of an arrow A. The stand15holds the arm holder14to be axially rotatable in a direction of an arrow B. The stand15is capable of pivoting (turning) in a direction of an arrow C. The stand15holds the arm holder14to be movable in a vertical direction (capable of rising and falling) in a direction of an arrow D. With such a structure, it is possible to incline an imaging angle of the frontal X-ray photographing system arbitrarily in the directions of the arrows A and B. An intersection of a rotation axis of the arrow A and a rotation axis of the arrow B is referred to as a rotation center point RC1. It is possible to retract the frontal X-ray imaging system and the C arm13from an imaging position by causing the stand15to turn in the direction of the arrow C. In addition, it is possible to move the C arm13to an arbitrary height by causing the stand15to rise and fall in the direction of the arrow D. In addition, the above-mentioned enforcement form is applicable also to a system without the arrow D.

The Ω arm23of the lateral X-ray imaging system is suspended from a slider base25via an arm holder24. The arm holder24holds the Ω arm23to be slidingly rotatable in a direction of an arrow G. The slider base25holds the arm holder24to be axially rotatable in a direction of an arrow H. The Ω arm23holds the X-ray tube21and the X-ray detector22to be capable of rising and falling in a direction of an arrow K. An intersection of a rotation axis of the arrow G and a rotation axis of the arrow H is referred to as a rotation center point RC2. The slider base25is engaged with a traveling rail26provided on a ceiling surface to be movable longitudinal and lateral in directions of arrows I and J.

The bed17supports the table top18to be capable of rising and falling in a vertical direction N and to be slidable in a direction O parallel to a long axis direction Z thereof and a direction P parallel to a lateral axis direction X thereof.

The movements in the directions A to D, F to N, and O and P of the movable sections can be operated individually by manual operation buttons37on an operator's console36that is set near the bed17(seeFIG. 4). The manual operation buttons37correspond to the movable sections that move in the directions A to O. The operator's console36includes an ROI fixing function button38that switches ON and OFF of an automatic control function (an ROI fixing function) for fixing the region of interest ROI in an image center and an ROI coordinate storage button39for storing coordinates of the region of interest in addition to the manual operation buttons37. A movable section control unit30is connected to the operator's console36.

Concerning the frontal X-ray imaging system, drive systems51,53,55,57, and61, which correspond to the respective movements in the directions A, B, C, D, and F, are connected to the movable section control unit30together with sensors52,54,56,58, and62therefor. Similarly, concerning the lateral X-ray imaging system, drive systems71,73,75,77,79, and83, which correspond to the respective movements in the directions G, H, I, J, K, and M, are connected to the movable section control unit30together with sensors72,74,76,78,80, and84therefor. Concerning the bed, drive systems91,93, and95, which correspond to the respective movements in the directions N, O, and P, are connected to the movable section control unit30together with sensors92,94, and96therefor. In accordance with an instruction of an operator inputted via the manual operation buttons37of the operator's console36, the movable section control unit30outputs a drive signal to a drive system corresponding to a movable section to which the instruction is sent and inputs a sensor output signal. In the case of manual operation, the movable section control unit30outputs a brake or clutch release signal.

In addition to the manual operation control function, in order to realize an ROI fixing function for fixing a region of interest in an image center, the movable section control unit30includes a position calculating unit31, an ROI coordinate calculating unit32, an ROI coordinate storing unit33, a corrected distance calculating unit34, and a magnification ratio calculating unit35. The position calculating unit31calculates coordinates of a position of a focal point of the X-ray tube11on the basis of outputs of the sensors52,54,56, and58that detect angles and positions of the movable sections, which move in the directions A, B, C, and D, of the frontal X-ray imaging system. Similarly, the position calculating unit31calculates coordinates of a position of a center point of the X-ray detector12on the basis of outputs of the sensors52,54,56,58, and62that detect angles and positions of the movable sections, which move in the directions A, B, C, D, and F, of the frontal X-ray imaging system. Moreover, the position calculating unit31obtains a linear equation of the imaging center axis CA1connecting the calculated focal point of the X-ray tube11and the calculated center point of the X-ray detector12.

Similarly, concerning the lateral X-ray imaging system, the position calculating unit31calculates coordinates of a position of a focal point of the X-ray tube21on the basis of outputs of the sensors72,74,76,78, and80that detect angles and positions of the movable sections, which move in the directions G, H, I, J, and K, of the lateral X-ray imaging system. The position calculating unit31also calculates coordinates of a position of a center point of the X-ray detector22on the basis of outputs of the sensors72,74,76,78,80, and84that detect angles and positions of the movable sections, which move in the directions G, H, I, J, K, and M, of the lateral X-ray imaging system. The position calculating unit31obtains a linear equation of the imaging center axis CA2connecting the calculated focal point of the X-ray tube21and the calculated center point of the X-ray detector22.

The ROI coordinate calculating unit32calculates coordinates of an intersection of the imaging center axis CA1and the imaging center axis CA2at a point when the ROI coordinate storage button39is pressed by an operator as ROI coordinate. The operator operates the arms13and23and the table top18manually to press the ROI coordinate storage button39in a state in which a region of interest substantially coincides with a center of an image formed by the frontal X-ray imaging system and also substantially coincides with a center of an image formed by the lateral X-ray imaging system. In this state, a position of the region of interest coincides with the intersection IC of the imaging center axis CA1and the imaging center axis CA2(seeFIG. 5). The calculated ROI coordinates are stored in the ROI coordinate storage unit33. Note that, although the ROI coordinate storage button39is pressed in the example described above, instead of this, it is also possible that an automatic storage mode is provided to cause the ROI coordinate calculating unit32to automatically calculate and store ROI coordinates, for example, with first imaging as a trigger.

In many cases, the intersection IC coincides with the region of interest but deviates from the rotation center points RC1and RC2. Therefore, when the arms13and23are rotated (in the directions A, B, G, and H) from the initial state, as shown inFIG. 6, the intersection IC of the imaging center axis CA1and the imaging center axis CA2deviates from the region of interest. As a result, the region of interest deviates from the image center. The corrected distance calculating unit34for calculating moving directions and distances of the C arm13and the Ω arm23are provided such that, even if the C arm13and the Ω arm23are rotated form the initial state, the intersection IC of the imaging center axes CA1and CA2is substantially fixed in the region of interest following the rotation as shown inFIG. 7. Note that, the table top18may be moved instead of the movement of the C arm13and the Ω arm23or together with the movements of the C arm13and the Ω arm23such that the region of interest substantially coincides with the intersection IC of the imaging center axes CA1and CA2.

For example, when the Ω arm23of the lateral X-ray imaging system is slidingly rotated in the direction G from the initial state by operation of the manual operation buttons37as shown inFIG. 6, the corrected distance calculating unit34calculates a moving direction (a rising and falling direction) K of the Ω arm23for correcting the deviation of the image center due to the rotation in the direction G and a moving distance thereof. The moving direction of the Ω arm23is a direction parallel to the imaging center axis CA1of the C arm13and is, typically, the vertical direction. The corrected distance is calculated as a distance between the stored coordinate point of the region of interest (the intersection IC of the imaging center axes CA1and CA2) and an intersection of the rotated imaging center axis CA2and the imaging center axis CA1. In addition, the corrected distance is calculated on the basis of a rotation angle of the imaging center axis CA2. A rising and falling direction N and a corrected distance of the table top18may be calculated instead of calculating the moving direction (the rising and falling direction) K and the corrected distance of the Ω arm23.

The Ω arm23is subjected to parallel translation by the calculated moving distance along the calculated moving direction K. The moving direction K and the moving distance of the Ω arm23are calculated repeatedly and the Ω arm23is subjected to parallel translation repeatedly every time the Ω arm23rotates a predetermined angle, for example, rotates once. Consequently, the Ω arm23is subjected to parallel translation following the rotation of the Ω arm23. Even if the Ω arm23is rotated arbitrarily, the region of interest is always fixed in the image center.

Similarly, a moving direction K and a moving distance of the C arm13are calculated such that the intersection of the imaging center axis CA2and the imaging center axis CA1is fixed to the region of interest when the C arm13is rotated. The C arm13is subjected to parallel translation in accordance with the calculated moving direction K and the calculated moving distance. The moving direction K and the moving distance of the C arm13are calculated repeatedly and the C arm13is subjected to parallel translation repeatedly every time the C arm13rotates a predetermined angle, for example, rotates once. Consequently, the C arm13is subjected to parallel translation following the rotation of the C arm13. Even if the C arm13is rotated arbitrarily, the region of interest is always fixed in the image center.

In this way, even if the region of interest deviates from the rotation center points RC1and RC2of the arms13and23, it is possible to always locate the region of interest in the respective image centers by moving the arms13and23in directions corresponding to rotations thereof and by distances corresponding to rotation angles thereof following the rotations.

Here, an imaging magnification ratio is given as a ratio of a distance from the focal points of the X-ray tubes11and21to the X-ray detectors12and22with respect to a distance from the focal points of the X-ray tubes11and21to the region of interest. In a state in which the region of interest deviates from the rotation center points RC1and RC2of the arms13and23, the arms13and23are rotated around the rotation center points RC1and RC2and positional deviation following the rotations of the arms13and23is eliminated by parallel translation of the arms13and23. Thus, the imaging magnification ratio changes from that in the initial state. The magnification ratio calculating unit35calculates an imaging magnification ratio in the initial state of the frontal X-ray imaging system from the position in the initial state of the X-ray tube11, the position of the region of interest (the intersection IC), and the position in the initial state of the X-ray detector12and holds the imaging magnification ratio.

The magnification ratio calculating unit35calculates an imaging magnification ratio after correction movement of the frontal X-ray imaging system from a position of the X-ray tube11after rotation and correction movement of the C arm13, the position of the region of interest (the intersection IC), and the position in the initial state of the X-ray detector12. The magnification ratio calculating unit35calculates a moving direction and a distance of the arm stand15with respect to the direction of the arrow D or F that are necessary for making the imaging magnification ratio after correction movement of the frontal X-ray imaging system identical with the imaging magnification ratio in the initial state. By moving the arm stand15in accordance with the calculated moving direction and distance, it is possible to maintain the imaging magnification ratio after the rotation of the C arm13at the imaging magnification ratio in the initial state. In addition, by maintaining the imaging magnification ratio, it is possible to realize an advantage that the X-ray tube11and the X-ray detector12are prevented from approaching the patient excessively.

Similarly, in the lateral X-ray imaging system, the magnification ratio calculating unit35calculates an imaging magnification ratio after correction movement of the lateral X-ray imaging system from a position of the X-ray tube21after rotation and correction movement of the Ω arm23, the position of the region of interest (the intersection IC), the position in the initial state of the X-ray detector22. The magnification ratio calculating unit35calculates moving directions and distances of the X-ray tube21and the X-ray detector22with respect to the direction of the arrow M and a moving direction and a distance of the slider base25with respect to the direction of the arrow I or J that are necessary for making the imaging magnification ratio after the correction movement of the lateral X-ray imaging system identical with the imaging magnification ratio in the initial state. By moving the X-ray tube21, the X-ray detector22, and the slider base25in accordance with the calculated moving directions and distances, respectively, it is possible to maintain an imaging magnification ratio after the rotation of the Ω arm23at the imaging magnification ratio in the initial state. In addition, by maintaining the imaging magnification ratio, it is possible to realize an advantage that the X-ray tube21and the X-ray detector22are prevented from approaching the patient excessively.

An imaging control unit40controls generation of an X-ray from the X-ray tube11and generation of an X-ray from the X-ray tube21to thereby control irradiation of the X-rays on a patient. It is possible to control the generation of the X-rays by applying a high voltage to the X-ray tube11from a high voltage control unit of the frontal X-ray imaging system and applying a high voltage to the X-ray tube21from a high voltage control unit of the lateral X-ray imaging system. The imaging control unit40controls collection of signals from the X-ray detectors12and22in synchronization with the irradiation of the X-rays on the patient.

Position data of the X-ray tube11of the frontal X-ray imaging system, position data of the X-ray detector12of the frontal X-ray imaging system, position data of the X-ray tube21of the lateral X-ray imaging system, and position data of the X-ray detector22of the lateral X-ray imaging system are instantaneously supplied to the imaging control unit40from the movable section control unit30together with data of the position of the region of interest (the position of the intersection IC in the initial state). In addition, a signal for identifying whether the C arm13is moving or stopped and a signal for identifying whether the Ω arm23is moving or stopped are supplied to the imaging control unit40from the movable section control unit30together with the position data.

Usually, when X-ray radioscopy and imaging are performed at a certain angle, radioscopy for obtaining a desired angle is often performed. This radioscopy causes useless radiation exposure that is not directly related to diagnosis and treatment. An image generating unit41is provided to solve the problem.

In a period instructed by the operator or at appropriate time, instead of the X-ray radioscopy and photographing involving X-ray irradiation, the image generating unit41performs dummy imaging without irradiation of an X-ray. In other words, the image generating unit41calculates an imaging direction and a magnification ratio of the frontal X-ray imaging system with respect to the region of interest on the basis of the data of the region of interest (the position of the intersection IC in the initial state), the position data of the X-ray tube11of the frontal X-ray imaging system, and the position data of the X-ray detector12of the frontal X-ray imaging system and subjects three-dimensional image data (also referred to as volume data) concerning the patient acquired by the X-ray diagnostic apparatus or other image diagnostic apparatuses like an X-ray CT apparatus in advance, which is stored in a 3D image storing unit42, to projection processing in accordance with the calculated imaging direction and magnification ratio to thereby generate projected image data (dummy image data) that is substantially equivalent to an image obtained by actually generating an X-ray from the X-ray tube11and imaging the patient with the X-ray detector12. Similarly, concerning the lateral X-ray imaging system, the image generating unit41calculates an imaging direction and a magnification ratio of the lateral X-ray imaging system with respect to the region of interest on the basis of the data of the region of interest, the position data of the X-ray tube21of the lateral X-ray imaging system, and the position data of the X-ray detector22of the lateral X-ray imaging system and subjects the three-dimensional image data stored in the 3D image storing unit42to projection processing in accordance with the calculated imaging direction and magnification ratio to thereby generate projected image data (dummy image data) that is substantially equivalent to an image obtained by actually generating an X-ray from the X-ray tube21and imaging the patient with the X-ray detector22. Note that two-dimensional image data may be used instead of the three-dimensional image data.

Projected image data of the frontal X-ray imaging system, which is generated from the three-dimensional image data, is sent to an image display unit43together with projected image data of the lateral X-ray imaging system, which is generated from the same three-dimensional image data, and displayed on the image display unit43.

As described above, in this embodiment, even if the arms13and23are rotated, it is possible to always maintain the region of interest of the patient in the image center. In addition, even if the arms13and23are rotating or moving, since projected images corresponding to photographing directions and magnification ratios at every moment are generated and displayed, it is possible to find angles suitable for the arms13and23under a guidance of images.

Note that, although the biplane X-ray diagnostic apparatus is described in the above explanation, the same explanation is applied to a single plane X-ray diagnostic apparatus as well.