JPS6353814B2 - - Google Patents

Description

[Detailed description of the invention] This invention is a computerized tomography (hereinafter referred to as CT)
This invention relates to improvements in devices for supplying power to rotating elements, such as x-ray sources in scanning devices.

CT scanning technology has significantly improved doctors' ability to precisely diagnose a patient's internal structures. This CT scanning method involves irradiating a patient with X-rays from various directions, measuring the intensity of the X-rays exiting the patient with one or more X-ray detectors, and transmitting this intensity information to imaging electronics. It guides the user and reproduces the image. Many studies have shown that this image, when viewed by a doctor, provides much more detail than standard X-ray techniques and can therefore be used to diagnose a patient's condition with better results.

In a typical CT scanning device, an x-ray source rotates (orbits) around the patient while irradiating the patient, while one or more detectors simultaneously revolve with the x-ray source, or multiple detectors do not revolve. An array of vessels is formed. In both cases, a substantial amount of x-ray radiation shaping equipment rotates with the x-ray source. The device as well as the X-ray source must be supplied with electrical energy from a power source external to the rotating CT device.

One particular CT scanning unit includes an orbiting x-ray source that emits an x-ray beam in a diffuse manner, and all detection units, except for the calibration detector, are stationary with respect to the x-ray source and are aligned with the patient. A ring-shaped array of detectors is formed around it. As the x-ray source revolves, x-rays pass through the patient along a series of beam paths. When revolution occurs, various beam generation, shaping, and transmission functions must be performed for the orbiting device, requiring a large number of electrical signals to be supplied to the device.

To generate X-rays, it is necessary to generate a large potential difference of about 150 KV, and this voltage accelerates electrons emitted from the cathode of the X-ray tube toward the anode, generating X-rays. In general, filament voltages and X-ray focusing cup control voltages are required, so many high voltage inputs are required, and in order to supply these high voltages to an orbiting X-ray source, conventional
There was a design problem that required complex bonding techniques.

A number of low voltage control and energizing signals must also be sent to the orbiting device. For example, it is necessary to supply electrical power (at a lower voltage than the voltage supplied to the x-ray tube) to a motor that rotates the anode of the x-ray tube.

Current CT scanning units use slip rings to provide power from an external power source to the rotating x-ray source, and to couple signal devices and additional power sources to other components that rotate with the x-ray source. One such device is disclosed in US Pat. No. 4,093,859. In this patent, a stationary member is coupled to a structure supporting an x-ray source, and the structure rotates relative to the stationary member about an axis on two sets of bearings spaced apart from each other along an axis. . A slip ring is also provided at a point on the axis away from the orbital plane of the X-ray source.

If the slip ring needs to be immersed in an insulating fluid to prevent electrical discharge in its vicinity, the structure of the above patent does not provide a convenient form of enclosing the fluid to surround the slip ring in an envelope. In addition, in current CT scanning units, the space in which the patient is accommodated is shaped like a bucket with one end open and the other end (inlet) closed, so the patient is confined in a narrow space during X-ray irradiation. The disadvantage is that this condition causes a person to feel extremely anxious. In order to ameliorate the drawbacks of slip rings in conventional CT devices, the present invention provides an integrated compact slip ring structure with an insulating fluid for transmitting electrical energy to the orbiting component in a CT scanning unit. Provide something that can be immersed in.

In accordance with the invention, each portion of the gantry and rotating structure defines a cavity surrounding a patient receiving space and accommodating a slip ring, the cavity retaining an insulating fluid about the slip ring. .

Further, according to the present invention, the rotatable structure supported on the gantry by a bearing so as to be rotatable relative to the gantry has a closed hole for accommodating a part of the patient's body, and the rotatable structure has a closed hole at both ends. It is an open through-hole and is configured to alleviate the fear or anxiety of a patient undergoing an X-ray scan.

In a preferred version of the invention, means are provided for tilting the trajectory of the x-ray source with its air gap relative to the gantry, making it possible to select the scanning section for the patient.

Next, the present invention will be explained in more detail with reference to the accompanying drawings.

FIG. 1 shows a CT method 10 designed to examine internal structures of a patient. The system includes a scanning unit 12, a bed 16, a signal processor 20, and a display 22. The scanning unit 12 is housed in a housing 13.
, which covers the X-ray device and creates an attractive appearance for the device. Before CT scanning, the bed 16 and the patient lying on it are placed in the opening 14 of the housing 13.
The X-ray tube inside the unit is energized and the
A beam is emitted, thereby irradiating the patient.

The scanning unit 12 can be tilted about an axis 24 parallel to the floor, and this movement provides increased scanning freedom without changing the patient's position. The unit 12 is mounted on two support frames 23 and is adapted to rotate about an axis 24. This rotational movement is provided by an AC motor 25, a right-angle drive rod 26 and a rotary arm 27.

A series of x-ray detectors senses the intensity of the x-rays passing through the patient and generates electrical signals in response. These signals representative of patient density are sent from the scanning unit by electrical connection means 15 to a signal processor 20. A signal processor receives this signal and uses known CT processing techniques to generate signals representative of various densities across the cross-section of the patient and sends the signals to display 22 to form an image of the patient.

Figure 2 shows the CT X-ray source 30 and patient opening 14.
A detector array 32 provided around the is schematically shown. When the X-ray source 30 emits divergent X-rays, this collimator 3
4 and are shaped into a number of individual X-ray beams. As shown, one x-ray beam 33 is incident on one detector in the circular x-ray detector array 32 through the patient aperture. Each of the illustrated detectors is located on the opposite side of the patient aperture from the x-ray source 30, so that one of them detects the intensity of the x-rays after they have passed through the patient.

Although FIG. 2 shows only a limited number of detectors, so-called stationary detectors, the CT design provides for arrays of detectors completely surrounding the patient. Thus, the X-ray detector can remain stationary and the X-ray source can be revolved around the patient aperture to irradiate the patient from various positions. The detector is of known design and converts the x-rays into electrical signals that can be sent to signal processor 20 for CT display.

All CT reconstruction calculation methods require that X-rays illuminate a cross-section of the patient from a number of different locations to obtain intensity information from the X-rays emanating from the various locations. By obtaining this multi-point strength information,
A picture or image of density changes within a cross-section of the patient can be reproduced. To provide this multi-point irradiation, the invention includes a rotating structure that supports the x-ray tube 30 and is movable relative to the x-ray detector array 32.

Moving the x-ray source along a circular trajectory creates power supply problems associated with applying a high voltage potential difference to the x-ray tube.

Figures 3A and 3B show a new and advanced technology that facilitates sending a potential difference to an x-ray source to generate x-rays.
A CT device is shown. The illustrated CT apparatus includes a stationary gantry assembly 40, a rotating assembly 42, and an x-ray tube case 44. In operation, the rotating assembly 42 is rotated within the stationary gantry apparatus 40 about the axis 36 by the belt drive 48, thereby causing the x-ray source 44
As it moves in a circular orbit surrounding the aperture of the structure 42 about the axis 36, it illuminates the cross-section of the patient's portion of interest within the aperture from a number of positions. The rotating assembly includes a frame 50 attached to its annular portion by eight connecting members 43 (see FIG. 3) equally spaced around the patient aperture 14; It supports the wire tube case 44 and orbits around the patient opening 14. Patient opening 14
is a through hole with both ends open.

One feature of this invention is the provision of a high potential difference between the negative and positive poles of the x-ray tube, and in one embodiment, this potential difference is on the order of 150 KV. This potential difference is formed by both positive and negative inputs, each of about 75KV relative to ground. To deliver electrical energy to the x-ray tube, the stationary gantry 40 has positive and negative high voltage input terminals 46,4.
7, the positive voltage input terminal 46 shown in FIG. 3 receives a 75 KV pulsed voltage input from an external voltage source, and the negative high voltage input terminal (not shown in FIG. 3) receives approximately -
Accepts input voltage of 75KV.

The structure further includes a stationary gantry section 40 for accepting these high voltage inputs and delivering them to the x-ray tube.
It has positive and negative slip ring portions 56, 58 for transmission from the rotating assembly 42 to the rotating assembly 42. Each of the slip rings includes an annular conductor disposed concentrically with the shaft 36 and a brush that presses against the annular conductor and makes electrical contact therewith. In the illustrated embodiment of the invention, each concentric ring conductor is supported on a rotating structure 42 and each brush is supported on a structure mounted on a gantry 40. Conversely, each ring conductor is connected to the gantry 4.
It should be understood that the brushes may be mounted on the rotating assembly 42. The annular conductors of these slip ring sections are concentric with axis 36 and rotate with body 42. The first positive portion 56 has a slip ring coupled to the positive input terminal 46.
The second negative portion 58 includes four slip rings and is designed to accept one or more negative high voltage inputs. The purpose of providing multiple high voltage slip rings is to
It is possible to control the x-ray radiation using either multifocal inputs or grid voltage inputs.

The high voltage transmitted to rotating assembly 42 is further transmitted to two terminals 60, 62 attached to frame 50 via cable 120 (FIG. 4). A first terminal 60 accepts a positive voltage and a second terminal 62 accepts a negative voltage. These high voltages are transmitted from these terminals to the anode (positive) and cathode (negative) of the rotating x-ray tube.

The mechanical connection between the gantry 40 and the rotating assembly 42 includes a support member 52 mounted radially away from the patient aperture by suitable fasteners 54 such as bolts and nuts, such that it remains stationary. Gantry 40 is positioned relative to the patient, and support member 52 and rotating assembly 42 (as described below)
It becomes possible to tilt about axis 24 perpendicular to scan axis 36. If the support member 52 is tilted while the patient is held in a horizontal position, the x-rays will pass through the patient aperture in a direction other than vertically, increasing the freedom of CT scanning. For example, the support member 52 may be rotated about an axis perpendicular to the scanning axis 36.
When tilted by 20 degrees, the irradiation cross section of the patient will also be tilted by 20 degrees with respect to the vertical direction.

The geometries of frame 50 and x-ray tube case 44 are selected to provide good balance of rotating assembly 42 about scan axis 36. The width of the frame 50 is wider on the side 51 opposite the x-ray tube case to balance the weight of the x-ray tube case and the x-ray tube therein and to provide symmetrical mass distribution about the axis 36. .

The stationary gantry 40 has an annular bearing joint 64 (fourth
The rotary structure 42 is supported through the rotary structure 42 (FIG.), so that the structure 42 can freely orbit around the axis 36. A compact design of the device, such as locating the bearing 64 and the annular slip ring portion 58 described above in close proximity to each other along the axis of rotation 36, allows a single bearing to be sufficient to support the rotating assembly. By using such a single bearing compact design, the entire structure 42 and single bearing can be placed on the bed 1.
6 or can be tilted relatively large angles about axis 24 without disturbing the patient.

An annular encoder 66 is attached to the rotating structure 42 . This encoder 66 has a number of symbols arranged at equal intervals around its circumference and indicating the angular direction of the encoder 66, and as the ring rotates about the central axis, an optical encoder 67 is placed on the stationary gantry 40. Determine the position of the torus relative to . In this way, the precise position of the X-ray source can be determined at all times during patient irradiation. This position information is correlated with intensity information from the X-ray detector array and used for a known re-correction calculation.

Figures 5A, 5B and 5C show three types of X
The input arrangement for energizing the wire tube is shown. In either case, anode 7
0 and cathode 72 are coupled to a high voltage energization input, which is shown in large numbers.

In the single focus X-ray tube (Fig. 5A), the high voltage input is 3
One is necessary. That is, the first input 76 is the positive input to the anode of the x-ray tube, and in the preferred embodiment of the invention is the first positive portion 56 of the slip ring assembly.
The two negative inputs 78, 80 are used to energize the cathode 72 and are transmitted through the second portion 58 of the slip ring assembly in the preferred embodiment. Transformer 82 provides filament current to emit thermionic electrons 84 from the cathode and accelerate them toward high voltage anode 70 .

FIG. 5B is a bifocal x-ray tube in which three negative high voltage inputs 86, 87, 88 are transmitted to the x-ray tube cathode 72. By controlling the voltage developed on the primary side of transformer 82, high voltage inputs 86, 87, 88 can be controlled to provide a means of x-ray control not available with single focus tubes.

An x-ray tube with a control grid is shown in FIG. 5C. This X-ray tube has one high voltage positive input 76 and three high voltage negative inputs, two inputs 90, 91 carrying the voltage appearing on the secondary side of the transformer 82, and a third
The input 92 of is used to maintain the control voltage of the grid 94 within the x-ray tube. By controlling this grid potential, it is possible to control electrons to the anode, which is impossible with a single focus tube.

The description of FIGS. 5A-5C shows that when using monofocal, bifocal, and grid-controlled x-ray tubes, it is necessary to handle multiple high voltage negative inputs. The second negative portion 58 of the slip ring assembly (FIG. 3) includes a plurality of slip rings for this purpose. CT in recommended practice
It is equipped with four slip rings to increase the degree of freedom in scanning design. The voltages applied to these slip rings are several thousand volts below ground potential, but each value differs by a relatively small amount. For example, in a single focus x-ray tube configuration, the only requirement for voltage division to the two inputs 78, 80 is that the filament current can be applied to the x-ray tube cathode.

FIG. 4 is a more detailed sectional view of the slip ring structure of FIG. 3B, and FIG. 3B shows the X-ray tube case 44.
and rotating assembly 42 mounted on bearings 64 within stationary gantry 40, FIG. 4 shows further details thereof.

In FIG. 4, the first slip ring structure 5
6 is the one that sends a positive high voltage to the X-ray tube, and the second
The slip ring assembly 58 includes four individual slip rings and, as previously described, delivers a high negative voltage to the x-ray tube. Both the first and second slip ring assemblies are immersed in an oil bath within the cavity 112. This oil is applied to the control circuit and the
Prevent electrical discharges that could destroy the tube.

Preferably, the portion surrounding this gap on the stationary gantry 40 side is constructed of aluminum, and the portion on the rotating structure 42 side is constructed of plastic. The use of such lightweight materials makes it easy to rotate the device, and the use of plastic for the rotating parts allows the device to be rotated more easily with a belt drive.

The four elastic packing materials 114-117 prevent leakage of dielectric fluids, such as oil, from the voids. This material is mounted on a non-rotating gantry 40,
It is pressed against the rotating structure by a spring member 118. The spring member brings the packing material into fluid-tight contact with the rotating portion of the rotating assembly as it rotates relative to the stationary gantry.

The transmission path for the positive high voltage signal is clearly shown in FIG. Applied to high voltage input terminal 46 (usually
The high voltage (of 75 KV) is transmitted to the slip ring section 56 and further via a high voltage cable to a second high voltage terminal 60 mounted on the rotating assembly for delivery to the anode section of the x-ray tube. This high voltage passes through a brush that is pressed against the slip ring by a spring to ensure contact. Slip ring and X
One example of a cable used for high voltage transmission to and from a radiation tube is a federal cable, which is well known in the field of X-ray CT scanning. This cable 120 passes through an aperture drilled in the rotating structure.

The second portion 58 of the slip ring assembly includes four rotating slip rings 122-125 that transmit four negative high voltages to the x-ray tube. Details of the second portion of this slip ring assembly are shown in Figure 4A. As shown, each rotating slip ring contacts a pressure brush 127 that is connected to electrical contacts within the case 126. Since the illustrated embodiment uses a single focus tube, the negative high voltage input is 12
Only two of 8,129 are needed, and the remaining two can be used for other X-ray tubes.

A number of low voltage slip rings 13 are located remotely from this high voltage slip spring assembly for transmitting low voltage electrical signals from a stationary gantry to a rotating assembly.
There are 0 to 135. Since these slip rings carry low voltages, there is no need to immerse them in oil to ensure electrical insulation. For convenience of explanation, only six slip rings are shown in the diagram, but some commercial
In the recommended embodiment of the CT unit, 16 units are used. Three of the low voltage inputs power electric motors located within rotating assembly 42 for rotating and cooling the anode of the x-ray tube. Three additional low-voltage slip rings are used as a common potential or ground potential, and four others are used as general AC power inputs, which are mounted on the structure 42 and provide a number of connections to be energized with an AC signal. Used to operate electromagnets.

The remaining five slip rings are attached to the rotating structure and are used to control the state of three switches that operate the shutter, filter, and collimator. The functions of these three components must be linked to the generation of X-rays during the CT display process. One of these remaining five inputs transmits a frequency proportional to the reference intensity from the rotating assembly 42 to the stationary display 20, and two of the remaining four inputs are used to provide synchronization and clock signals. The remaining two slip rings are used to send and receive digital data to a control panel that controls and monitors the status of the three switches.

Although there are 16 slip-rings, I only mentioned the function of 15 inputs, so in this design, one of the 16 slip-rings has no role, but is kept for future design changes.

Although the above-described embodiments have been described with respect to specific detailed structures, it is obvious to those skilled in the art that various modifications can be made without departing from the technical scope of the invention as described in the claims.

[Brief explanation of drawings]

Fig. 1 is a diagram schematically showing the elements constituting the CT scanner, Fig. 2 is a diagram schematically showing the X-ray source arranged to irradiate a cross section of the patient, and Fig. 3A is a diagram schematically showing the elements of the CT scanner. The front view of Figure 3B is the front view of Figure 3A.
FIG. 4 is an enlarged sectional view of a part of the scanner shown in FIG. 3B, FIG. 4A is an enlarged sectional view of a part of the cross section of FIG. 4, and FIGS.
Figure C is a schematic diagram showing wiring for high voltage excitation of an X-ray tube for CT. 14... Opening part, 30... X-ray source, 36... First shaft, 40... Gantry, 42... Rotating structure,
46, 47...Input means, 56, 58...Slip ring, 112...Gap, 122-125...
Annular conductor, 127...Brush.

Claims (1)

Claims: 1. a gantry; having an opening defining an aperture for receiving a portion of a patient and rotatable relative to the gantry about a first axis passing through the aperture;
a rotatable structure supported on said gantry by bearings; an X-ray source disposed on said structure so as to follow a path around said aperture when said structure rotates; a plurality of slip rings including an annular conductor and a brush concentric with the shaft, one of the annular conductor and brush of each slip ring being supported by the rotatable structure and electrically connected to the X-ray source; a slip ring connected to the annular conductor and the brush of each of the slip rings, the other of which is supported by the gantry; input means mounted on the gantry for applying a high voltage electrical input to the x-ray source through the slip ring; rotating the structure; the slip ring is housed in a gap surrounding the aperture adjacent the passageway, the gap being defined by portions of the gantry and the rotatable structure; and contains an insulating fluid therein such that the slip ring is completely immersed during rotation of the structure, and the rotatable structure is configured to define a through opening for patient reception. A computerized tomography scanner characterized by having a circular shape. 2. The bearing comprises an annular bearing surrounding the aperture adjacent to the path, and the rotatable structure is arranged to intersect the first axis with the slip ring and the annular bearing by means of a tilting means. and tilting the path about a second axis to scan multiple cross-sections of the patient without changing the patient's position. A computerized tomography scanner device according to scope 1. 3. A computerized tomography scanner according to claim 2, wherein said second axis is an axis extending substantially perpendicular to said first axis. 4 The gap has an annular shape concentric with the first axis, and in order to keep the gap fluid-tight, a sealant is supported on the gantry and pressed into contact with the surface of the rotatable structure. A computerized tomographic scanner apparatus according to any one of claims 1 to 3, characterized in that: 5. The computer according to claim 1, wherein the brush of each slip ring is pressed by a spring so as to come into contact with the annular conductor of the slip ring. Mechanical tomography scanner device. 6. Claims 1 to 6, characterized in that the electrical connection from the annular conductor of the slip ring and the brush supported by the rotatable structure to the X-ray source is a cable connection. The computerized tomography scanner device according to any one of Item 5. 7. A computerized tomographic scanner apparatus according to any one of claims 1 to 6, wherein the insulating fluid contained in the void is comprised of oil.