X-ray or gamma ray systems or devices – Source – Electron tube
Reexamination Certificate
2002-10-11
2003-10-28
Dunn, Drew A. (Department: 2882)
X-ray or gamma ray systems or devices
Source
Electron tube
C378S119000, C313S231710
Reexamination Certificate
active
06639970
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates generally to multi-slice computed tomography (CT) imaging systems, and more particularly, to an apparatus and method of generating x-rays within an imaging tube.
There is a continuous effort to increase computed tomography (CT) imaging system scanning capabilities. This is especially true in CT imaging systems. Customers desire the ability to perform longer scans at high power levels. The increase in scan time at high power levels allows physicians to gather CT images and constructions in a matter of seconds rather than several minutes as with previous CT imaging systems. Although the increase in imaging speed provides improved imaging capability, it causes new constraints and requirements for the functionality of the CT imaging systems.
Referring now to
FIG. 1
, a cross-sectional view of a traditional CT tube assembly
10
is shown. CT imaging systems include a gantry that rotates at various speeds in order to create a 360° image. The gantry contains the CT tube assembly
10
, which composes a large portion of the rotating gantry mass. The CT tube assembly
10
generates x-rays across a vacuum gap
12
between a cathode
14
and an anode
16
. In order to generate the x-rays, a large voltage potential is created across the vacuum gap
12
allowing electrons, in the form of an electron beam, to be emitted from the cathode
14
to a target
18
of the anode
16
. In releasing of the electrons, a filament contained within the cathode
14
is heated to incandescence by passing an electric current therein. The electrons are accelerated by the high voltage potential and impinge on the target
18
, whereby they are abruptly slowed down, directed at an impingement angle &agr; of approximately 90°, to emit x-rays through CT tube window
19
. The high voltage potential produces a large amount of thermal energy not only across the vacuum gap
12
but also in the anode
14
.
The anode
14
, as with other traditional style CT tube anodes, uses a store-now/dissipate-later approach to thermal management. In order to accommodate this approach the anode
14
is required to have a large mass and a large diameter target. The electron beam impacts the target
18
, near a rim
20
, essentially normal to the target face
22
. The target
18
is rotated about a center axis
24
at approximately 180 Hz or 10,000 rpm to distribute load of the electron beam around a track region
26
of the target
18
. Thermal energy generated in the track region
26
is transferred through the target
18
to a thermal storage material, such as graphite, which brazed to a back surface of the target
18
. As the anode
14
rotates, thermal energy stored on the back surface of the target
18
dissipates during each revolution of the anode
14
, thereby cooling the anode
14
.
Traditionally, in order to increase performance of a CT imaging system, thereby increasing the amount and frequency of electron emission for a given duration of time, the diameter and mass of the target is increased. By increasing the diameter and mass of the target, thermal energy storage and radiating surface area of the target is increased for increased cooling.
Increasing the diameter and rotational speeds of the target is limited due to size, mass, and material strength of the target. The stated limitations in combination with a large amount of rotationally induced stress in the target, from instantaneous power being applied over very short durations on the target, also limit linear velocity of the track. Size of the target is also further limited by space constraints in a CT imaging system. An example of a space constraint, is the desire for good angulation capability, in that in cardiac or similar applications the CT system needs to be mobile and position flexible. Other space constraints exist and are commonly known in the art.
Additionally, faster scanning increases the mechanical loads on an entire CT tube, especially anode bearings, thus degrading CT tube component performance. Hence, in order to minimize mechanical loads the ability to increase the mass of the target is limited, which conflicts with the thermal performance of the X-ray tube. Faster scanning in increasing anode surfaces can cause subcooled nucleate boiling further decreasing scanning quality.
There is a continuous desire to perform CT scans at increased rates, thus requiring more instantaneous power to be applied on the target over very short durations potentially causing increased thermal energy. It would therefore be desirable to provide an apparatus and method of generating x-rays within an x-ray tube that provides increased scanning speed without increased thermal energy.
SUMMARY OF INVENTION
The present invention provides an apparatus and methods of converting electrons into x-rays within an imaging tube. An imaging tube is provided including a cathode and an anode. The cathode includes an emission surface, which emits a plurality of electrons along an emission axis. The anode includes a body having a track on a peripheral section of the body. The plurality of electrons are directed to impinge on the track at an impingement angle approximately equal to or between 15° and 25° relative to the emission axis and are converted into x-rays. A method of generating x-rays within the imaging tube is also provided.
One of several advantages of the present invention is that it provides an apparatus for emitting x-rays from an imaging tube with increased speed due to the ability to rotate the anode at increased speeds over traditional rotating anodes speeds.
Another advantage of the present invention is that due to mechanical and thermal operation of the imaging tube the present invention minimizes heat generated within the imaging tube as well as providing cooling of the anode while operating at the increased rotational speeds.
Furthermore, the present invention provides a smaller size anode, thus, reducing space requirements of the anode and increasing versatility as to application use of the imaging tube.
REFERENCES:
patent: 4166231 (1979-08-01), Braun
patent: 4894852 (1990-01-01), Das Gupta
patent: 6341157 (2002-01-01), Sakabe
patent: 6542576 (2003-04-01), Mattson
Dunn Drew A.
GE Medical Systems Global Technology Co. LLC
Kiknadze Irakli
Vogel Peter J.
LandOfFree
Low angle high speed image tube does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Low angle high speed image tube, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low angle high speed image tube will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3138603