U.S. patent application number 09/863798 was filed with the patent office on 2002-04-25 for x-ray system.
Invention is credited to Baker, David E., Elliott, Douglas D., Loeffler, Peter E., Skillicorn, Brian, Solomon, Edward G..
Application Number | 20020048346 09/863798 |
Document ID | / |
Family ID | 22607733 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020048346 |
Kind Code |
A1 |
Solomon, Edward G. ; et
al. |
April 25, 2002 |
X-ray system
Abstract
An x-ray system comprising a scanning beam x-ray source
configured to projected at least one x-ray beam in a generally
upward direction. When the generated x-rays are scattered they are
scattered in a direction predominantly away from x-ray sensitive
areas of attending staff. The unscattered x-rays are subsequently
received at a detector and an image is reconstructed.
Inventors: |
Solomon, Edward G.; (Menlo
Park, CA) ; Elliott, Douglas D.; (Scotts Valley,
CA) ; Skillicorn, Brian; (Saratoga, CA) ;
Loeffler, Peter E.; (Los Gatos, CA) ; Baker, David
E.; (San Jose, CA) |
Correspondence
Address: |
LYON & LYON LLP
633 WEST FIFTH STREET
SUITE 4700
LOS ANGELES
CA
90071
US
|
Family ID: |
22607733 |
Appl. No.: |
09/863798 |
Filed: |
May 21, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09863798 |
May 21, 2001 |
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09167524 |
Oct 6, 1998 |
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Current U.S.
Class: |
378/197 ;
378/121; 378/196 |
Current CPC
Class: |
A61B 6/4441 20130101;
A61B 6/4021 20130101; G21K 1/025 20130101 |
Class at
Publication: |
378/197 ;
378/121; 378/196 |
International
Class: |
H05G 001/02 |
Claims
What is claimed is:
1. An x-ray system comprising: a scanning beam x-ray source, said
scanning beam x-ray source configured to project x-rays in an
upward direction; a detector, said detector arranged to receive at
least a portion of said x-rays, and a system axis extending from
said scanning beam x-ray source to said detector, said system axis
deviating not more than 45.degree. from vertical.
2. The x-ray system of claim 1, wherein said scanning beam x-ray
source further comprises: a charged particle gun, said charged
particle gun having a projection axis and a projection plane
perpendicular to said projection axis; a high voltage vessel
comprising a high voltage receptacle, said high voltage receptacle
having a receptacle axis; and said charged particle gun and said
high voltage vessel arranged such that said receptacle axis
intersects said projection plane, wherein an angle of the
intersection between said receptacle axis and said projection plane
is less than 75.degree., said angle being the smallest angle formed
by said intersection.
3. The x-ray system of claim 2, wherein said angle is less than
30.degree..
4. The x-ray system of claim 2, said scanning beam x-ray source
including two conducting cables disposed between said high-voltage
power cable receptacle and said charged particle gun, said
conducting cables configured to operate at approximated -100 kV,
and to provide a voltage differential of approximately 30 V to said
charged particle gun.
5. The x-ray system of claim 1, said scanning beam x-ray source
further comprising: a high-voltage vessel, said high-voltage vessel
having a high-voltage power cable receptacle configured to receive
a high-voltage power supply along a longitudinal axis of said
high-voltage power cable receptacle such that said longitudinal
axis of said high-voltage power cable receptacle and said x-ray
projection axis form an acute angle; and a gun electronics housed
within said high-voltage vessel.
6. The x-ray system of claim 5 wherein said x-ray projection axis
and said longitudinal axis of said high-voltage power supply
intersect.
7. The x-ray system of claim 5, said high-voltage vessel
comprising: a cylindrical chamber having a top surface, a bottom
surface, an interior surface, an outer surface, a wall and an
opening, said cylindrical chamber having a height which is less
than its diameter, and said cylindrical chamber configured to house
a gun electronics; and a tube having open ends, one end of said
tube attached to said outer surface of the chamber wall such that
the interior of said tube connects with the interior surface of
said cylindrical chamber, and said tube configured to hold said
high-voltage power cable receptacle.
8. The x-ray system of claim 5, said scanning beam x-ray source
including two conducting cables disposed between said high-voltage
power cable receptacle and said gun electronics, said conducting
cables configured to operate at approximated -100 kV, and to
provide a voltage differential of approximately 30 V to said gun
electronics.
9. The x-ray system of claim 1, further comprising a gantry having
two ends, said gantry configured to support said detector and said
scanning beam x-ray source each on an end, and said gantry
configured to facilitate movement of said scanning beam x-ray
source.
10. The x-ray system of claim 9, further comprising: an angulation
mechanism connected to said gantry, said angulation mechanism
comprising an actuator, said actuator configured to move gantry
about an angulation axis.
11. The x-ray system of claim 9, further comprising a rotation
mechanism connected to said gantry, said rotation mechanism
configured to cause said gantry to rotate about a radial axis.
12. The x-ray system of claim 1, said scanning beam x-ray source
further comprising: a high-voltage vessel; and a high-voltage power
cable receptacle connected to said high-voltage vessel, said
high-voltage power cable receptacle configured to receive a
high-voltage power supply along a longitudinal axis of said
high-voltage power cable receptacle such that said longitudinal
axis and said x-ray projection axis form an acute angle.
13. The x-ray system of claim 1, said scanning beam x-ray source
further comprising: a gun electronics coupled to said charged
particle gun, said gun electronics configured to receive power from
a source other than a transformer; a high-voltage vessel, said
high-voltage vessel housing said gun electronics, and said
high-voltage vessel configured to receive a high-voltage power
supply cable along a first axis such that said first axis and said
x-ray projection axis form an acute angle; a vacuum chamber, said
vacuum chamber attached to said high-voltage vessel; a first focus
coil, said first focus coil mounted to said high-voltage vessel and
surrounding a first portion of said vacuum chamber; a second focus
coil, said second focus coil attached to said focus coil and
surrounding a second portion of said vacuum chamber; and a charged
particle target, said charged particle target mounted to said
vacuum chamber.
14. The x-ray system of claim 1, further comprising an object
table, said object table located approximately above said scanning
beam x-ray source and below said detector.
15. An x-ray system comprising: a scanning beam x-ray source, said
scanning beam x-ray source generating x-rays; a detector, said
detector arranged to receive at least a portion of said x-rays; an
object table, said object table disposed above said scanning beam
x-ray source.
16. An x-ray system comprising: a scanning beam x-ray source, said
scanning beam x-ray source comprising an x-ray projection axis, and
said x-ray projection axis being within 45.degree. of a vertically
upward direction; an object table, said object table located
approximately above said scanning beam x-ray source; and a scanning
beam x-ray source support structure, said scanning beam x-ray
source support structure configured to allow spherical movement of
said scanning beam x-ray source about said object table.
17. A method for generating an x-ray image comprising: projecting a
plurality of x-rays from an x-ray source; passing a first portion
of said plurality of x-rays through an x-ray table and toward a
target body; scattering a second portion of said plurality of
x-rays off said x-ray table and away from attending staff; and
detecting said first portion of said plurality of x-rays at a
detector, said x-rays having passed through said x-ray table and
subsequently through said target body.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention pertains to the field of x-ray imaging
systems, including among other things, diagnostic x-ray imaging
systems.
[0003] 2. Background
[0004] Real-time x-ray imaging is increasingly being utilized by
medical procedures as therapeutic technologies advance. For
example, many electro-physiologic cardiac procedures, peripheral
vascular procedures, PTCA procedures (percutaneous transluminal
catheter angioplasty), urological procedures, and orthopedic
procedures benefit from the use of real-time x-ray imaging.
[0005] A number of real-time x-ray imaging systems are known. These
include fluoroscope-based systems where x-rays are projected into
an object to be imaged and shadows caused by relatively x-ray
opaque matter within the object are detected on the fluoroscope
located on the opposite side of the object from the x-ray source.
Reverse-geometry x-ray imaging systems are also known. In such
systems, an x-ray tube is employed to generate x-ray radiation.
Within the x-ray tube, high-energy charged particles are generated
and focused on a small spot on the relatively large target of the
tube, inducing x-ray radiation emission from that spot. The charged
particles are deflected (electromagnetically or electrostatically)
in a raster scan pattern or otherwise over the target. A small
x-ray detector is placed at a distance from the target of the x-ray
tube. The detector typically converts x-rays that strike it into an
electrical signal in proportion to the detected x-ray
intensity.
[0006] In known embodiments of reverse geometry diagnostic x-ray
imaging system the x-ray source is located above the patient. When
these x-ray imaging systems are activated radiation is projected
from the x-ray scanning tube, in a generally downward direction. As
such, the radiation scatter off of the patient and the x-ray table
supporting the patient is generally in an upward direction. Since
the scattered radiation is directed predominantly in an upward
direction, the attending staff often absorbs the radiation in the
most sensitive portions of the body, namely the head and neck.
Furthermore, since patients usually lie face up on the x-ray table,
when a woman is imaged, her breast tissue, which is more sensitive
than other tissue types, is subjected to the direct radiation from
the x-ray source.
[0007] Thus, there is a need for an x-ray imaging system that
minimize x-ray absorption risks to the patient and the attendant
staff.
SUMMARY OF THE INVENTION
[0008] The present invention comprises an x-ray imaging system
wherein the x-ray source is oriented such that extraneous x-rays
scatter predominantly in a direction away from the attending
staff's x-ray sensitive areas. According to a preferred embodiment
of the invention, the x-ray system comprises an x-ray source and a
detector, the x-ray source configured to project x-rays in a
generally upward direction.
[0009] The invention also comprises the method of generating an
x-ray image wherein the extraneous x-rays are scattered
predominantly in a direction away from the x-ray sensitive areas of
the attending staff. According to an embodiment, the method
comprises the acts of projecting a plurality of x-rays from an
x-ray source, passing a first portion of the x-rays through an
object table and toward an object to be imaged, scattering a second
portion of the x-rays off the object table, and away from attending
staff, and detecting the first portion of x-rays at a detector.
[0010] These and other objects, advantages, and aspects of the
present invention will become apparent to those of ordinary skill
in the art from a consideration of the drawings, description, and
claims of the invention contained herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Preferred embodiments of the present invention are
illustrated by way of example, and not by way of limitation, in the
figures of the accompanying drawings and in which, like reference
numerals refer to similar elements and in which:
[0012] FIG. 1 is a block diagram showing the basic components of an
x-ray imaging system;
[0013] FIG. 2 is a side-view of a preferred x-ray imaging
system;
[0014] FIG. 3A is a perspective view of a preferred x-ray imaging
system shown rotated according to one embodiment; FIG. 3B is a
perspective view of a rotator mechanism according to one embodiment
of a preferred x-ray imaging system oriented for ease in
description;
[0015] FIG. 3C is a perspective view of an angulation mechanism
according to one embodiment of a preferred x-ray imaging system;
FIG. 4 is a perspective view of a preferred high-voltage
vessel;
[0016] FIG. 5 is an exploded view of a preferred high-voltage
vessel with components associated therewith;
[0017] FIG. 6 is an exploded view of a preferred charged particle
gun electronics;
[0018] FIG. 7 is a second exploded view of a preferred high-voltage
vessel with components associated therewith;
[0019] FIG. 8 is an exploded view of a preferred x-ray source;
[0020] FIG. 9 is a perspective view of the x-ray source of FIG. 8
mounted on a gantry; and
[0021] FIG. 10 is a block diagram of a preferred imaging
system.
DETAILED DESCRIPTION
[0022] FIG. 1 depicts the basic components of a reverse geometry
x-ray imaging system.
[0023] The x-ray source 100 preferably comprises an x-ray tube and
a high-voltage charged particle source. The high-voltage charged
particle source is preferably connected to an adjustable
high-voltage power supply capable of generating approximately -70
kV to -120 kV.
[0024] According to a preferred embodiment, the high-voltage power
supply provides a DC output to the x-ray imaging system. At this
voltage level, x-ray source 100 produces a spectrum of x-rays
ranging to 120 keV. X-ray source 100 is an example of a scanning
beam x-ray source in which charged particles are scanned across a
target assembly. X-ray source 100 includes deflection coils 104
under the control of a scan generator 108.
[0025] High-energy charged particles 112 generated within vacuum
chamber 158 by gun 111 are scanned across a target 120 preferably
in a predetermined stepping pattern. For example, the predetermined
stepping pattern may be a raster scan pattern, a serpentine (or "S"
shaped) pattern, a spiral pattern, a random pattern, or such other
pattern as may be useful to the task at hand. An apparatus that can
be used in an embodiment of the invention for generating and moving
charged particles across target 120 is disclosed in commonly owned
U.S. Pat. No. 5,644,612, which is incorporated herein by reference
in its entirety. Charged particles 112 pass through vacuum chamber
158 and strike target 120 at focal spot 124. X-rays 128 are emitted
in all directions (although the term "x-rays" are used herein, it
is for illustration purposes only --other forms of radiation can be
employed according to the present invention.) For simplicity only a
portion of the x-rays 128 are shown. To optimize system performance
of a presently preferred embodiment, a x-rays are generated that
diverge in a manner that just covers the detector 136. This is
preferably accomplished by placing a collimating element between
the target 120 of the x-ray source 100 and the detector 136, and
more preferably between object 132 and x-ray source 100. According
to one embodiment, the x-rays 148, after passing through
collimation grid 144, only diverge slightly from axis 150.
[0026] The presently preferred configuration for the collimating
element is a grid of x-ray transmissive conical apertures 140.
Collimation grid 144 is designed to permit passage to only those
x-rays whose axes are in a path (e.g. axis 150) that directly
intersects the detector 136. Collimation grid 144 preferably does
not move with respect to the detector 136 while the system is in
operation. Thus, as charged particles 112 are scanned across target
120, at any given moment there is only a single beam of x-rays 148
which pass through object 132 to detector 136. According to one
embodiment, detector 136 has a face having an active area, wherein
the area is broken into individual segments 160. Each segment is a
detector which, when combined, form a detector array, simply
referred to as detector 136. A collimation grid 144, useful in an
embodiment of the invention, is disclosed in commonly owned U.S.
patent application Ser. No. 08/660,229, which is incorporated
herein by reference in its entirety.
[0027] The output of detector 136 is processed by an image
reconstruction system 156 and displayed by a video display device
154 which is preferably attached to a workstation 152. The video
display device 154 allows attending staff to view the x-ray
images.
[0028] FIG. 10 depicts a block diagram of an embodiment of the
image reconstruction system 156. The image reconstruction system
156 comprises a PCI interface 1010, which connects to control
workstation 152. A detection module 1020 comprises the components
of detector 136 and receives x-ray transmissiveness information.
Image reconstruction chassis 1005 comprises an interface module
1030, one or more plane reconstruction modules 1040, an image
selection module 1050 and an image preprocessor 1060. The various
components on the image reconstruction chassis 1005 are
interconnected via one or more busses 1100, which also include
control lines. PCI interface 1010 and detection module 1020 are
coupled to interface module 1030, whereas image preprocessor 1060
is coupled to video post processor 1070. Video post processor 1070
is coupled to display monitors 1080.
[0029] Details of the preferred embodiments of the components
depicted with reference to FIG. 10 are described in detail in
copending U.S. patent application Ser. Nos. [not yet assigned]
(attorney docket 221/259), [not yet assigned] (attorney docket
232/010), [not yet assigned] (attorney docket 221/260) and [not yet
assigned] (attorney docket 221/262), all of which are incorporated
herein by reference in their entirety.
[0030] According to an embodiment, information about the x-rays 148
detected at the detector 136 is fed back to scan generator 108.
Accordingly, the workstation 152 and the scan generator 108 are
coupled.
[0031] Details of preferred elements depicted in FIG. 1, as well as
elements related to the same, are described in further detail in
copending U.S. patent application Ser. Nos. [not yet assigned]
(attorney docket 232/011), [not yet assigned] (attorney docket
221/261), [not yet assigned] (attorney docket 219/143), and [not
yet assigned] (attorney docket 232/012) filed on the same day
herewith, all of which are incorporated herein by reference in
their entirety.
[0032] FIG. 2 is a side view of a preferred x-ray imaging system
200. X-ray imaging system 200 comprises an x-ray source 204
connected to one end of a curved gantry 208. At a second end of
curved gantry 208 is attached a detector 212. According to one
embodiment, the curved gantry 208 is attached to a base support
216. The gantry 208 is preferably capable of movement of a
generally spherical rotation.
[0033] An x-ray table 220 (also referred to as an "object table"),
preferably having one or more x-ray transparent areas, supports an
object for which an x-ray image is desired. According to an
embodiment of the x-ray table 220, the x-ray table 220 can be a
substantially flat table, having no dips or valleys. However,
according to another embodiment it may include one or more dips or
valleys so as to more approximately curve to the shape of the
object to be imaged. The x-ray source 204, is preferably located at
the end of the gantry that is capable of movement in the lower
hemisphere.
[0034] According to one embodiment, cabinet 218 supports a control
workstation and display device (e.g., control workstation 152 and
monitor 154).
[0035] When the system is operated, the electron gun generates a
charged particle beam which strikes the target and generates x-ray
photons. The x-ray photons preferably pass through a collimator
forming an x-ray beam. The x-ray beam has an axis that is
preferably substantially aligned with the center of the active area
of x-ray detector. The x-ray beam has a beam vector 205 which is
defined by the x-ray beam axis in the direction of the x-ray
detector assembly as shown in FIG. 2. The majority of the x-ray
photons in the x-ray beam first pass through the table 220 and the
object under investigation before striking the x-ray detector.
[0036] FIGS. 3A-C depict, in greater detail, embodiments of
mechanisms that facilitate the spherical motion of the gantry
208.
[0037] In FIG. 3A, gantry 208 is depicted rotated about a
rotational pivot axis 304. The rotation angle depicted in FIG. 3A
is only illustrative of the degree of rotation of the gantry 208.
However, according to an embodiment, the gantry is configured to
rotate to approximately 45.degree. of vertically upward direction.
Rotator mechanism 308, depicted in further detail in FIG. 3B and
described below, supports gantry 208 and provides a force to drive
gantry 208 about axis 304. In addition, a hydraulic support arm 312
further supports the load and rotation of gantry 208 as it is
rotated about axis 304 by rotator mechanism 308.
[0038] According to a preferred embodiment, gantry 208 is further
configured to slide along a curved path concentric with a curve
following the shape of gantry 208. System axis 316, formed between
x-ray source 204 and detector 212, and pivot axis 304 intersect at
point 324. Angulation axis 320 is perpendicular to system axis 316
and pivot axis 304. Angulation mechanism 328 provides support and
force to slide gantry 208 such that gantry 208 slides in a circular
or curved path about angulation axis 320. According to one
embodiment, angulation mechanism 328 comprises bearing rails 332
and two drive belts 336. According to one embodiment, the bearing
rails 332 also provide support for gantry 208. System vector 317 is
defined by system axis 316 in the direction of the x-ray detector
212.
[0039] An enlarged view of the circled area 330 of angulation
mechanism 328 is depicted in FIG. 3C. Angulation mechanism 328
further comprises an electromechanical actuator 340 and belt drives
344. Electro-mechanical actuator 340 rotates a drive wheel 348.
Drive wheel 348 is connected via the belt drives 344 to roller 352
around which drive belts 336 are connected with tension. A control
signal (not shown) is received by angulation mechanism 328 which,
in turn, causes actuator 340 to begin to rotate drive wheel 348 and
consequently drive belts 336 begin to move. As drive belts 336
move, they carry gantry 208 along the path formed by bearing rails
332, or in other words, in a curved path about angulation axis
320.
[0040] Turning to FIG. 3B, it depicts in further detail rotation
mechanism 308. Rotation mechanism 308 is connected to gantry 208
via a rotational support member 356 (FIG. 3A) that is connected to
bearing rails 332 (FIG. 3A). The rotational support member 356
provides not only structural support between the gantry and base
support 216, but also, in conjunction with a hydraulic support arm
312, rotational assistance to rotation mechanism 308. An
electromechanical rotator actuator 360 provides force to rotate
gantry 208 about rotational pivot axis 304. As the rotator actuator
360 is actuated, internal gears (not shown) within the actuator 360
turn. While the internal gears turn; teeth 368 on rotational drive
gear 364 engage the internal gears of the actuator 360 and rotate
rotational drive gear 364 about axis 304. Rotational drive gear 364
is connected to gantry 208 through rotational support member 356,
so when rotational drive gear 364 turns so does gantry 208.
[0041] FIG. 4 depicts high-voltage vessel 400. High-voltage vessel
400 houses charged particle gun electronics (not shown) that is
employed to control the charged particle gun (e.g., gun 111).
Further, high-voltage vessel 400 is also configured to receive a
high-voltage power supply line (not shown), which operates at a
voltage potential between -70 and -120 kV. According to a preferred
embodiment, high-voltage vessel 400 is also configured to receive
fiber optic control lines (not shown) that are used to control the
charged particle gun electronics.
[0042] Because high-voltage vessel 400 receives a high-voltage
power supply line and the high-voltage vessel itself has a voltage
potential at ground, the interior surface of high-voltage vessel
400 is polished and free from irregularities which may cause
electrostatic discharge between the high-voltage vessel 400 and any
object within the high-voltage vessel 400 that is maintained at a
high-voltage (e.g., gun electronics). Additionally, sharp edges on
the interior surface of the high-voltage vessel 400 are preferably
chamfered or rounded to minimize electrostatic discharge. To
further protect against electrostatic discharge, high-voltage
vessel 400 is sealably enclosed and designed to hold a
non-conducting medium to prevent such electrostatic discharge.
According to a preferred embodiment, the non-conducting medium is
sulfur-hexafluoride (SF.sub.6) gas. The SF.sub.6 is preferably
maintained in high-voltage vessel 400 at a pressure of 4 atm.
[0043] According to a preferred embodiment, high-voltage vessel 400
comprises a cylindrical chamber 404, which is larger in diameter
than in height. The cylindrical chamber 404 has a chamber wall 408,
an inner surface 412, an outer surface 416, a top surface 420 and a
bottom surface 424. The top surface 420 of cylindrical chamber 404
preferably is connected to a washer-shaped plate 428 that creates
an inner lip and an outer lip 432, with reference to the chamber
wall 408. Circumferentially arranged about the outer lip 432 of
plate 428 are a number of apertures 436 though which fasteners may
pass. Additionally, along the inner most circumference of plate 428
is a mounting ring 440 comprising a number of evenly distributed
apertures 444. The apertures 444 are designed to receive fasteners
that will connect the high-voltage vessel 400 to the vacuum chamber
(e.g., vacuum chamber 158).
[0044] The bottom surface 424 of cylindrical chamber 404 is
preferably configured to receive a chamber cover (not shown). A
number of evenly distributed cover apertures 448 are
circumferentially arranged about the bottom surface 424 and allow
the chamber cover to be sealably attached to the cylindrical
chamber 404. When attached to bottom surface 424 of cylindrical
chamber 404, the chamber cover is preferably flush with the inner
surface 412 of the cylindrical chamber 404. Additionally,
cylindrical chamber 404 preferably has smoothly chamfered interior
edges 452.
[0045] In the broader spirit of the invention, the high-voltage
vessel 400 is not limited to having a cylindrical chamber, such as
cylindrical chamber 404, rather, high-voltage vessel comprises any
suitable chamber configured to house a gun electronics. In this
regard, the high-voltage vessel 400 can comprise, for example, a
hemispherical chamber or an elliptical chamber.
[0046] High-voltage vessel 400 preferably comprises a sleeve or
tube 456, attached to the outer surface 416 of the chamber wall 408
and which creates an opening between the interior of the tube 456
and the inner surface 412 of cylindrical chamber 404. According to
an embodiment, the tube 456 has an elliptical shape about a
longitudinal axis and a slight elbow near one end.
[0047] In an embodiment, the tube 456 and the cylindrical chamber
404 are arranged such that the longitudinal axis of tube 456 form
an angle .phi. with a plane that is perpendicular, or substantially
perpendicular to the longitudinal axis of cylindrical chamber 404.
Angle .phi. is the smallest angle formed by the intersection
between the longitudinal axis of tube 456 and the plane
perpendicular to the longitudinal axis of cylindrical chamber 404.
According to an embodiment, angle .phi. is less than 75 degrees,
and in an alternate embodiment, angle .phi. is less than 30
degrees.
[0048] In an alternate embodiment, the longitudinal axis of the
tube 456 preferably passes through the cylindrical chamber 404 to
the inner surface 412 of chamber wall 408 such that the
longitudinal axis of the tube 456 and the longitudinal axis of the
cylindrical chamber 404 form an acute angle, as measured,
generally, between the longitudinal axis of the tube 456 and a
projection direction of a charged particle gun. In another
embodiment the angle is substantially perpendicular, that is
between approximately 60 and 120.degree.. Finally, it should be
noted that the longitudinal axis of the tube 456 and the
longitudinal axis of the cylindrical chamber 404 do not have to be
coaxial.
[0049] At one end of tube 456 a number of fastener apertures 464
are disposed about the outer edge 460. The fastener apertures 464
are configured to engage fasteners which secure a high-voltage feed
through (not shown) to the high-voltage vessel 400. High-voltage
vessel 400 preferably comprises a tube support 466 disposed between
the outer lip 432 of the cylindrical chamber 404 and above the tube
456.
[0050] FIG. 5 is an exploded view of a high-voltage vessel 400 and
the components associated therewith. For example, high-voltage
vessel 400 houses charged particle gun electronics 504, which is
connected to the charged particle gun (not shown). A vessel cover
508 sealably encloses gun electronics 504 within the cylindrical
chamber 404.
[0051] High-voltage mount 512 attaches to tube 456 at end 460.
According to one embodiment, high-voltage mount 512 comprises a
high-voltage receptacle 524 having a feedthrough end 525, which
preferably receives one end of a -120 kV power supply line 516, a
fiber optic receptacle 520, which preferably receives fiber optic
control lines, and a high-voltage feedthrough 528, which shields
the interior of tube 456 from the end of high-voltage power supply
line 516. A receptacle vector 527 is defined by the longitudinal
axis of the high voltage receptacle 524 and the direction of
insertion of the high voltage cable 516 into the high voltage
receptacle 524. In a presently preferred embodiment, the angle
between the system vector 317 and the receptacle vector 527 is
approximately an acute angle.
[0052] When enclosed, high-voltage vessel 400 preferably does not
allow gas to flow from the interior of the high-voltage vessel 400
out and vise-versa. A sealant or gasket may be disposed between the
cover 508 and the bottom surface 424 of the cylindrical chamber
404, and the mount 512 and the end 460 of the tube 456. Fiber optic
receptacle 520 is preferably sealed with or comprised of an epoxy
resin, or an equivalent gasket.
[0053] FIG. 6 depicts an exploded view of gun electronics 504.
According to one embodiment, the gun electronics 504 comprises an
end cap 608, a ring housing 612 and a printed circuit board 620.
The ring housing 612 mounts to the end cap 608. Disposed between
the ring housing 612 and the end cap 608 is the printed circuit
board 620. The printed circuit board 620 has on it control
electronics to control charged particle gun. According to another
embodiment, the gun electronics 504 further comprises a mechanical
ring housing 614 and, on top of the mechanical ring housing 614, a
second printed circuit board 618. The mechanical ring housing 614
and the second printed circuit board 620 are disposed between the
end plate 608 and the first printed circuit board 620. Further, a
fiber optic and power cable connector 628 is mounted to a side of
mechanical ring housing 614, and an electronics cover 624 is
connected to the bottom surface of ring housing 612. The
electronics cover 624, the ring housing 612 and the mechanical ring
housing 614 each contain a number of openings 636 through which gas
and heat may pass. Preferably, if high-voltage vessel 400 is filled
with SF.sub.6 gas, then the gas freely flows through the openings
636. In a preferred embodiment, a charged particle gun (not shown)
is mounted to end plate 608 via a gun sleeve 632. When the x-ray
source is activated, the gun is capable of projecting charged
particles along the longitudinal axis of the charged particle gun
and towards the target (not shown) that is above the end plate
608.
[0054] FIG. 7 is a perspective exploded view that depicts the
interconnections between high-voltage vessel 400 and its associated
components. According to an embodiment, once the high-voltage
vessel 400 is assembled, two conducting cables (not depicted in
FIG. 7) run between the high-voltage receptacle 528 and gun
electronics 504 (FIG. 5). Since the gun electronics 504 does not
include a power transformer to power the electronics circuits
enclosed therein, power is provided by the two conducting cables,
which have a voltage differential of approximately 30 V. The gun
electronics 504 is maintained at approximately -100 kV during
operation of the x-ray source. In addition to the two conducting
cables, fiber optic cables (not shown) are also run between
connector 628 and fiber optic cable receptacle 520.
[0055] FIG. 8 is an exploded view of a preferred embodiment of the
x-ray source 800. According to the preferred embodiment, the x-ray
source 800 comprises a high-voltage vessel 400, a charged particle
gun, a first focus coil, a second focus coil, deflection coils, a
deflection insulator, a target and a vacuum chamber. In one
embodiment, the x-ray source is stacked, from the bottom up, such
that the high-voltage vessel 400 receives an electron gun 804. A
first focus coil 808 is positioned above the electron gun 804. A
second focus coil 812 is mounted on top of the first focus coil
808. A deflection insulator 820 is received by openings within the
first focus coil 808, the second focus coil 812 and the deflection
coils 816. The deflection insulator 820 is attached to the electron
gun 804. A vacuum chamber 822 is attached to an end of the
deflection insulator 820, and a target 826 is placed over the
vacuum chamber 822. A cradle 828 wraps around approximately
three-quarters of the x-ray source 800 and extends between the top
surface of high-voltage vessel 400 and approximately midway along
the vacuum chamber 822. Finally, the high-voltage power cable 516
is received by high-voltage vessel 400 at high-voltage receptacle
524.
[0056] The currents flowing within first focus coil 808 and second
focus coil 812 cause the charge particles 112 to be brought into
focus at focal spot 124. Further, deflection coils 816 cause the
charged particles 112 to track a particular scan pattern across
target 826.
[0057] FIG. 9 is a perspective view of the x-ray source 800 mounted
at one end of gantry 208. According to a preferred embodiment,
x-ray source 800 is mounted on the lower end of gantry 208. To
provide further support to x-ray source 800 as it rests on one end
of gantry 208, cradle 828 is attached to gantry 208 via support
arms 904. Fiber optic communication and control cables 908 are
received into fiber optic cable receptacle 520. Both the fiber
optic cables 908 and the high-voltage power supply line 516 are
strung along the interior of gantry 208.
[0058] According to an embodiment, the high-voltage power supply
line 516 is received into a high-voltage receptacle 524 on high
voltage vessel 400 such that the longitudinal axis of the high
voltage receptacle 524 forms an angle .theta. with a projection
plane defined by the projection axis of the charged particle gun.
In an embodiment, the projection plane is defined as a plane
perpendicular or substantially perpendicular to the projection axis
of the charged particle gun and angle .theta. is the smallest angle
formed by the intersection of the longitudinal axis of the high
voltage receptacle 524 with the projection plane. In one
embodiment, angle .theta. is less than 75 degrees, and in another
embodiment, angle .theta. is less than 30 degrees.
[0059] In an alternate embodiment, the high-voltage power supply
line 516 is received into high-voltage receptacle 524 on
high-voltage vessel 400 such that the longitudinal axis of the
high-voltage receptacle 524 forms an acute angle with the
projection axis 316 of the charged particle gun, as measured
between the high-voltage receptacle 524 and the charged particle
gun with reference to the projection direction of the charged
particle gun. Alternatively, the angle is substantially
perpendicular, between approximately 60.degree. and 120.degree..
Finally, it should be noted that the longitudinal axis of the
high-voltage receptacle 524 does not need to intersect the
projection axis of the charged particle gun.
[0060] According to an embodiment of the innovative configuration
and assembly of the x-ray system described herein, the x-ray source
is compact enough to fit below, rather than above, the patient and
the x-ray table. Consequently, when the x-ray system is activated
and radiation is emitted, the x-ray scatter is predominantly
downward, rather than upward. As a result, the risk of exposure to
harmful x-rays is reduced to the attending staff, as well as
depending on the procedure being performed, to the x-ray sensitive
tissues of the patient. Additionally, the positioning of the x-ray
source is highly adjustable, allowing movement in a spherical
pattern about the x-ray table or patient. For example, according to
an embodiment, the x-ray source is capable of movement about a
target object such that the system axis can vary at least between
0.degree. and 45.degree. from a vertically upward direction. In an
embodiment, the system axis is the axis extending from the x-ray
source to the detector.
[0061] In the foregoing specification, the invention has been
described with reference to specific embodiments thereof. It will
be evident, however, that various modifications and changes may be
made thereto without departing from the broader spirit and scope of
the invention. The specification and drawings are, accordingly, to
be regarded in an illustrative, rather than a restrictive
sense.
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