DESCRIPTION

Fly wheel electrode

The invention relates to the field of tomography imaging. In particular, the invention relates to an examination apparatus having a fly wheel electrode, to an electrode for being used in said examination apparatus, a method of examination of an object of interest, a computer-readable medium, a program element, and a computer chip.

Future computed tomography systems will provide increased temporal resolution and larger detector coverage per rotation, and therefore will require increased instantaneous electrical power. Larger detectors will allow driving the tube with less total energy throughput per patient and the X-ray tube will be "on" for shorter scan times, but with increased instantaneous power. As a result, for rotating a computed tomography system, the main power supply and power transfer from the stationary gantry to the rotating part of the computed tomography system will become more elaborate and expensive when designed for a full peak power rating. Increasing energy per exposure in an X-ray tube being mounted on a rotating part of a computed tomography system results in serious problems in view of a power transfer from a stationary part of the computed tomography system having included the power supply for supplying power to the gantry rotor as rotating part of the computed tomography system having included the X-ray tube to be supplied with the power.

On the other hand, within a time interval between two exposures, there is no need to transfer power from a gantry as a stationary part to a rotary part on a peak level of the power.

It is desirable to reduce the peak level of power to be supplied from the mains supply and a stationary part to a rotary part of a computed tomography system.

The invention provides an examination apparatus, an electrode, a method of examining an object of interest with an examination apparatus, a computer-readable medium, a program element, and a computer chip with the features according to independent claims. It should be noted that the following described exemplary embodiments of the invention apply also for the method of examination of an object of interest, the computer-readable medium, the electrode, the program element, and the computer chip.

According to an exemplary embodiment of the present invention, an examination apparatus for examination of an object of interest may be provided, the examination apparatus comprising an X-ray tube having at least one rotatable electrode, an electrical machine adapted for being operated as a generator, wherein the rotatable electrode is coupled with the electrical machine such that a kinetic energy of the rotating electrode can be converted into electrical energy by means of the electrical machine, using the rotatable electrode as a fly wheel for storing the kinetic energy. Therefore, the examination apparatus may be adapted for temporary storing of energy as kinetic energy of a rotating electrode being used as fly wheel, thereby smoothing the instantaneous level of transferred energy. When attached to a suitable generator dynamo/motor system, this construction drives the electrode, if the coils are powered, or retrieves electric energy, while breaking the electrode. This constitutes an electro-mechanical energy storage device comparable to a fly wheel.

According to another exemplary embodiment of the present invention, the examination apparatus further comprises a high- voltage circuit adapted for providing electrical power to the electrode of the X-ray tube.

Therefore, the X-ray tube may be provided with a high- voltage being necessary for generating X-ray radiation.

According to another exemplary embodiment of the present invention, the examination apparatus further comprises a first power supply, wherein the electrical machine is also adapted for being operated as a motor, wherein the first power supply is adapted for providing the electrical machine with power when being operated as a motor.

Therefore, the rotatable electrode can be driven for increasing the X-ray power and lifetime of the electrode and for storing electrical energy therein as kinetic energy depending on the inertia and the rotation speed of the rotating electrode.

According to another exemplary embodiment of the present invention, the examination apparatus further comprises a switch adapted for alternatively connecting the first power supply with the electrical machine when being operated as a motor and the electrical machine when being operated as a generator with the high- voltage circuit.

Therefore, it may be possible to change between two states, namely the first state when driving the rotatable electrode to be fed with power for accelerating it and storing kinetic energy therein, and the second state when retrieving the stored kinetic energy by means of reconverting the kinetic energy into electrical energy by means of the electrical machine when being operated as a generator for feeding the high- voltage circuit with the retrieved energy from the rotating electrode. According to another exemplary embodiment of the present invention, the examination apparatus further comprises a second power supply adapted for supplying power to the high- voltage circuit.

Therefore, it may be possible to supply power to the high- voltage circuit additionally from the retrieved power from the rotating electrode. According to another exemplary embodiment of the present invention, the second power supply is mounted on a stationary part or gantry of the examination apparatus.

According to another exemplary embodiment of the present invention, the X-ray tube is mounted on a rotating part of the examination apparatus. According to another exemplary embodiment of the present invention, the second power supply and the high- voltage circuit are coupled by means of an inverter /transformer / diode / capacitor - network.

Therefore, the moved mass of the power supply may be kept stationary on a gantry, whereas the radiation source may be moved for maintaining the basic function of a computed tomography instrument, and the mass of the moved parts may be kept low.

According to another exemplary embodiment of the present invention, the switch is mounted on the rotating part of the examination apparatus.

Therefore, the retrieved energy may be kept on the rotary part of the computed tomography system without needing a further transfer of energy between the rotary part and the stationary part or needing only a significantly reduced power rating of the transmission between stationary and rotary part.

According to another exemplary embodiment of the present invention, the electrical machine comprises a cylindrical rotor body.

According to another exemplary embodiment of the present invention, the electrical machine comprises a stationary coil system.

Therefore, it is possible to drive the rotor body of the electrical machine with respect to the stationary coil system for driving the rotatable electrode.

According to an exemplary embodiment, the cylindrical rotor or disk- shaped body is provided within the vacuum part of the X-ray tube, and the stationary coil system is provided outside the vacuum part of the X-ray tube.

Therefore, the border between the vacuum part and the non- vacuum part can be provided between the cylindrical rotor body and the stationary coil system of the electrical machine to keep the coil system outside the vacuum.

According to another exemplary embodiment of the present invention, the rotor body comprises a magnetic coupling to the stationary coil system.

Therefore, the driving force can be optimized for driving the rotor body within the X-ray tube.

According to another exemplary embodiment of the present invention, the examination apparatus comprises a multiple tube arrangement. Therefore, a computed tomography system may be provided with a plurality of exposure systems for reducing the total examination time of an object of interest. This may be of importance if examining a human body.

According to another exemplary embodiment of the present invention, the electrode is an anode.

The anode is usually the electrode having the higher material consummation and heating so that rotating the anode will increase power rating and lifetime of an X-ray tube.

According to another exemplary embodiment of the present invention, an electrode is adapted for being used in an X-ray tube of the above examination apparatus to be used as a fly wheel for storing kinetic energy.

According to another exemplary embodiment of the present invention, a method for examination of an object of interest with an examination apparatus comprises the steps of driving an electrical machine being adapted for being operated as a generator by rotating an electrode within an X-ray tube, the electrode being coupled with the electrical machine, and converting kinetic energy of the rotating electrode into electrical energy by means of the electrical machine when being operated as a generator, using the rotatable electrode as a fly wheel for storing the kinetic energy.

According to another exemplary embodiment of the present invention, the method further comprises the step of supplying power to the electrical machine by means of a first power supply.

According to another exemplary embodiment of the present invention, the method comprises the step of providing the electrode of the X-ray tube with a high- voltage. According to another exemplary embodiment of the present invention, the method further comprises the steps of connecting the first power supply with the electrical machine when being operated as a motor, and connecting the electrical machine when being operated as a generator with a high- voltage circuit.

According to another exemplary embodiment of the present invention, the method comprises the step of supplying power to the high- voltage circuit by means of second power supply.

According to another exemplary embodiment of the present invention, a computer-readable medium, in which a computer program of examination of an object of interest is stored, when executed by a processor, is adapted to carry out the steps of the above method.

According to another exemplary embodiment of the present invention, a program element of examination of an object of interest, when being executed by a processor, is adapted to carry out the steps of the above method.

According to another exemplary embodiment of the present invention, a computer chip, in which a computer program of examination of an object of interest is stored, when executed by processor, is adapted to carry out the steps of the above method.

It may be seen as the gist of an exemplary embodiment of the present invention to temporary storing energy on a gantry rotor, and that a rotatably mounted electrode of an X-ray tube may be used as an energy storage for buffering the energy for driving the X-ray tube on the rotary part of the examination apparatus to avoid high peak transfer of power, in particular for the exposure times of the X-ray tube, by retrieving the stored energy of the rotating electrode, converting the energy and feeding tube current and high voltage to the X-ray tube at a time of exposure. These and other aspects of the present invention will become apparent from and elucidated with reference to the embodiments described hereinafter.

Exemplary embodiments of the present invention will be described in the following with reference to the following drawings.

Fig. 1 shows a schematic representation of a tube of an X-ray tube according to an exemplary embodiment of the present invention.

Fig. 2 shows a simplified schematic representation of a circuit of an examination apparatus according to an exemplary embodiment of the present invention. Fig. 3 shows a schematic representation of a circuit of an examination apparatus according to another exemplary embodiment of the present invention.

Fig. 4 shows a simplified schematic representation of an examination apparatus having a multiple tube arrangement according to another exemplary embodiment of the present invention. Fig. 5 shows a schematic representation of a tube of an examination apparatus according to another exemplary embodiment of the present invention.

Fig. 6 shows a flow chart of an exemplary embodiment of the method according to the present invention.

Detailed description of exemplary embodiments

The illustration of the drawings is schematically. In different drawings, similar or identical elements are provided with the same reference numerals. Fig. 1 shows a simplified tube of an X-ray tube according to an exemplary embodiment of the present invention. The tube of Fig. 1 comprises a housing in which a rotatable electrode 111 is located. The housing comprises a metal frame 119 and ceramics insulators or bushings 118 for contacting the rotatable electrode 111 and the counter electrode 115.

According to an exemplary embodiment of the present invention, the rotating electrode

111 is provided as an anode and the counter electrode 115 is provided as a cathode. The rotating anode may be provided with a graphite backed body. Within the tube 110 there may be provided a rotor 151 for rotating the rotatable electrode 111.

The rotatable electrode 111 is coupled with the rotor 151, which is part of an electrical machine 150. The rotor 151 is provided within the vacuum tube and may be provided as a cylindrical rotor body, whereas the stator 155 of the electrical machine 150 is provided outside the vacuum tube and may be provided as a stationary coil system. Eddy currents induce a torque in the rotor body and speed up the anode to about

10.000 r.p.m. and more.

Fig. 2 shows a simplified representation of a circuit of an examination apparatus according to an exemplary embodiment of the present invention. The circuit of the examination apparatus comprises a stationary part 101 and a rotating part 102. The stationary part may be provided on a gantry, and the rotating part may be provided on a gantry rotor. The stationary part of the circuit of Fig.

2 includes a power supply 130 which may be provided with a three phase rectified voltage. However, also a different number of phases may be applied to the power supply 130, like a single phase system. The power supply 130 may include a converter adapted for providing an alternating current the form of which may be of a sinus, a

square, a saw tooth, a triangle, or any other alternating form. The rotating part 102 includes a high- voltage circuit 120 including a rectifier and a buffer capacitor serving also as a smoothing capacitor. It should be noted that also any other form of high- voltage may be supplied. The rotating part further includes an X-ray tube 110 including a rotatable electrode 111 and a counter electrode 115. According to an exemplary embodiment, the rotatable electrode 111 may be provided as an anode and the counter electrode may be provided as a cathode.

The stationary part 101 and the rotating part 102 may be coupled by means of a capacitor 140. It should be noted that also any other coupling means may be provided like contact system or a contact-free system like a transformer. The transmission may be a low-frequency transmission, a high-frequency transmission or an ultrahigh- frequency transmission.

Fig. 3 shows a simplified schematic representation of a circuit of an examination apparatus according to a further exemplary embodiment of the present invention.

The circuit of the embodiment shown in Fig. 3 constitutes of a stationary part 101 and a rotating part 102 similar to tat of Fig. 2. The stationary part may include a power supply 130 having a three phase power supply with a rectifier and a converter for generating an alternating current. The power supply may be also of another form as already outlines with respect to Fig. 2. The rotating part 102 may include a high- voltage circuit 120 and an X-ray tube 110. The X-ray tube may be provided with a rotatable electrode 111 and a counter electrode 115. The rotatable electrode 111 may be provided as an anode and the counter electrode 115 may be provided as a cathode. The rotatable electrode may be coupled with an electrical machine 150 being operable as a motor and a generator.

The stationary part 101 and the rotating part 102 may be coupled with a capacitor 140, wherein the coupling between the stationary part 101 and the rotating part 102 may be also of another kind as already outlined with respect to Fig. 2.

The examination apparatus 100 of Fig. 3 may be also provided with a further power supply 160 adapted for providing the electrical machine 150 with power when being operated as a motor.

The examination apparatus 100 of Fig. 3 may be also provided with a switch 180 adapted for alternatively connecting the power supply 160 with the electrical machine 150 when being operated as a motor, and the electrical machine 150 when being operated as a generator with the high- voltage circuit 120.

The switch 180 may be provided on the rotating part 102 of the examination apparatus 100. It should be noted that the switch 180 may also be provided on the stationary part of the examination apparatus.

The power supply 130 and the power supply 160 may be provided on the stationary part 101 of the examination apparatus 100. It should be noted that either the power supply 130 or the power supply 160 or both power supplies 130 and 160 may be also provided on the rotating part 102 of the examination apparatus 100. With an arrangement as shown in Fig. 3 it is possible to store kinetic energy by driving the electrical machine 150 by a power supply 160 to accelerate the rotatable electrode 111. The rotatable electrode 111 acts as a fly wheel due to the inertia and the rotation speed. When needing power for feeding the tube 110 with high- voltage for an exposure process, the kinetic energy stored in the rotating electrode 111 may be retrieved by driving the electrical machine 150 by means of the rotating electrode 111 acting as the fly wheel, thereby retrieving kinetic energy to be converted to electrical energy by means of the electrical machine acting as a generator. In this case, the switch 180 connects the electrical motor 150 acting as the generator with the high- voltage circuit 120 for providing the X-ray tube 110 with energy in form of high- voltage. Between two subsequent exposure times, the switch 180 connects the power supply 160 with the electrical machine 150 acting as a motor for driving again the rotatable electrode 111 for storing kinetic energy again using the rotatable electrode 111 as a fly wheel until the next exposure period. It should be noted that the term "high voltage" is used for any voltage being suitable for driving the X-ray tube. A control element 190 may control the timing of any of the elements of the examination apparatus 100, in particular the power supply 130, the power supply

160, the high-voltage circuit 120, the switch 180, and/or the electrical machine 150 acting as a motor or as a generator.

The motor Fig. 4 shows a simplified schematic representation of an examination apparatus according to an exemplary embodiment of the present invention. The examination apparatus 100 may be provided with a multiple tube arrangement, wherein the rotating part 102 of the examination apparatus 100 may be provided with a plurality of X-ray tubes 110, for example two X-ray tube electrodes 110. It should be noted that the rotating part 102 of the examination apparatus may be also provided with any other number of X-ray tubes other than two. Thus, a faster examination of the object of interest 107 is possible due to the multiple tube arrangement. This may be of importance when examining moving organs of a human body.

Fig. 5 shows an exemplary embodiment of an X-ray tube for being used in an examination apparatus according to an exemplary embodiment of the present invention.

The X-ray tube 110 includes a rotatable electrode 111 being coupled to a cylindrical rotor body 151, which is a part of the electrical machine 150. The cylindrical rotor body 151 may be provided within the tube under vacuum. The electrical machine 150 may be provided with a stationary coil system 155. The stationary coil system 155 may be provided outside the tube in a non-vacuum area. According to an exemplary embodiment of the invention, the cylindrical rotor body 151 comprises a magnetic coupling to the stationary coil system 155. Opposite to the rotatable electrode 111 there is provided a counter electrode 115. The rotatable electrode may be an anode and the counter electrode 115 may be a cathode. The cathode may be located on the rotational axis of the cylindrical rotor body 151 and the rotatable anode 111 coupled thereto, or may be offset to the axis of rotation.

Fig. 6 shows a flow chart of an exemplary embodiment of the method for operating the examination apparatus according to the present invention.

During operation, two different operation modes are possible, one of which is a generator operation mode including the steps Sl to drive an electrical machine adapted for being operated as a generator by rotating an electrode within an X-

ray tube, the electrode being coupled with the electrical machine, and step S2 to convert a kinetic energy of the rotating electrode into electrical energy by means of the electrical machine when being operated as a generator, using the rotatable electrode as a fly wheel for storing the kinetic energy. According to another exemplary embodiment of the present invention, there is provided an operation mode as a motor operation mode including step S3 to supply power to the electrical machine by means of a first power supply.

According to a further exemplary embodiment of the present invention, the generator operation mode includes step S4 to provide the electrode of the X-ray tube with a high- voltage.

According to a further exemplary embodiment of the present invention, the motor operation mode includes the step S5 to connect the first power supply with the electrical machine when being operated as a motor, and the generator operation mode includes the step S6 to connect the electrical machine when being operated as a generator with a high- voltage circuit.

According to another exemplary embodiment of the present invention, the generator operation mode further includes step S7 to supply power to the high- voltage circuit by means of a second power supply.

It should be noted that the method of the present invention is not limited to the above steps and may also include further steps for driving the examination apparatus.

The method which is represented by the flow-chart of Fig. 6 may also be implemented as a computer program of examination of an object of interest stored on a computer-readable medium, which when executed by a processor is adapted to carry out the above steps. The method represented by the flow chart of Fig. 6 may also be implemented in a program element of examination of an object of interest.

It should be noted that the term "comprising" does not exclude other elements or steps and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.