X-ray or gamma ray systems or devices – Source support – Including movable source
Reexamination Certificate
2002-05-24
2004-09-14
Glick, Edward J. (Department: 2882)
X-ray or gamma ray systems or devices
Source support
Including movable source
C378S196000
Reexamination Certificate
active
06789941
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to medical diagnostic equipment, and, more particularly, to apparatuses for supporting and positioning x-ray and other medical imaging devices.
BACKGROUND
Angiography involves the use of x-rays or other electromagnetic waves to examine arteries, veins, organs, and the like. Typically, a contrast agent (e.g., x-ray dye) is applied to the features under observation, via a catheter passing through the skin or an injection, to differentiate them from surrounding regions of the body. For most angiographic procedures, the x-rays being applied to a patient must be precisely directed, in order to ensure that the proper area is examined. Since orienting patients with respect to stationary x-ray devices (which typically include an x-ray source and an x-ray receptor) has been found to be imprecise, many gantry-like mechanisms have been developed over the years for supporting and positioning x-ray devices.
In designing x-ray support apparatuses, the x-ray device should ideally be positionable for use anywhere around the periphery of a patient in three dimensions. More specifically, it is typically desirable to utilize spherical angulation, where x-rays can be directed from any loci on an imaginary sphere centered on the patient to an isocenter of the x-ray device (the isocenter is the point of intersection of an axis defined by the x-ray source and receptor and the axis of angulation, i.e., the axis of device rotation). Other factors to take into account include: maintaining the x-ray beam normal to the x-ray receptor; the size of the examination room, and the room's ability to accommodate large devices; unrestricted access to the patient, especially around the head area; minimizing control complexity and/or the need for computer image correction or manipulation; and, as always, cost.
Most current x-ray device support apparatuses utilize either a parallelogram-shaped construct or a combination of C-, U-, and/or L-shaped arms for x-ray device positioning and (ideally) spherical angulation. An example of the former is shown in U.S. Pat. No. 3,892,967 to Grady et al. (“Grady”). In Grady, an x-ray source
23
and receptor
22
are positioned with respect to a patient P by way of an angularly-adjustable, pivoting, rotating parallelogram
3
,
5
,
8
,
9
. This achieves 360° rotation coverage about the patient P, by virtue of the parallelogram being rotatable about shaft
2
, and 55° of head/foot tilt (the arms
8
,
9
can be moved in and out). Thus, the device basically moves in an unrestricted way on the surface of a sphere about the patient, and the x-ray image itself inherently always remains “upright” irrespective of the compound angles used. However, to cover from head to foot on a six feet tall patient, the “throat depth” (clearance) of the support apparatus has to be over six feet. This makes the support apparatus at least ten to twelve feet long, plus the patient tabletop has to travel at least six feet, which means it must be eight to nine feet long. Thus, the entire system is almost twenty feet long, necessitating a twenty-eight or thirty foot long room, which might cause architectural problems.
Because parallelogram-based devices are so bulky, various C-arm based devices have been developed over the years. However, large C-arms arc difficult to balance (a parallelogram can be an entirely mechanically-balanced device), since the entire mass of the C-shaped structure is offset to one side. Accordingly, these have primarily taken the form of a simple, light, balanced, C-shaped arm which holds the x-ray source at one end and the receptor at the other end. The C-shaped arm slides in a journal, and is positionable by way of one or more pivoting arms attached to the journal. Such devices can deliver most of the angular coverage of a parallelogram in a smaller space, but typically have several severe, inherent problems, such as the inability to carry heavy equipment without dangerous power-driven operation.
Furthermore, with existing C-arm based devices, as the axis of the x-ray beam approaches the horizontal, rotating the horizontal axis only serves to rotate the image, without changing the viewing angle. This results in zero image rotation with a vertical beam, and 100 percent rotation (only) at a horizontal beam. In between 0° and 90° the x-ray beam/positioner angular relationship is complex, and the two rotation axes interact. The result is a tilted image as viewed on the x-ray image screen. This effect can be compensated for by either mechanically rotating the x-ray receptor (and also the source collimator if a square x-ray field is utilized) according to a pre-programmed code, or by implementing an “image de-rotation” scheme where the image, as stored electronically, is manipulated by digital means. However, such systems are expensive, and can ultimately degrade the image.
There have been numerous variations in the design and construction of C-arm based x-ray gantries, but two main divisions are apparent: types where the horizontal C-arm axle comes at the patient from the left side, and types where the C-arm axle comes over the patient's head. In regards to the former, the achieved angle and tilting image problem is severe, plus the left side of the patient is obstructed. To solve that, putting the C-arm axle at the head of the patient gives good angular coverage, but the patient can only be imaged as far as the abdomen area, since otherwise the patient's head will hit the C-arm structure. The C-arm cannot be made larger in radius, as the center of rotation must be in the patient (isocentric operation is a requirement), and the floor and ceiling set bounds on the outer diameter of the C-arm, when the center of rotation is in the patient's body. Thus, “head end” mounting brings restricted coverage of the patient's length, especially below the abdomen.
U.S. Pat. No. 4,358,856 to Stivender et al. (“Stivender”), with reference to its
FIG. 2
, attempted to solve these problems by mounting a sliding, journal type C-arm
25
(with rotating axle construction) on a rotating, swinging, L-shaped member
10
, where the lower right part of the “L,” viewed as an alphabetical character, is attached to a bearing
14
centered under the isocenter
37
. While this design provided good angular coverage, it presented its own problems. More specifically, the height or structural width of the horizontal member of the L-shaped arm
10
on the floor
15
effectively “raised the floor,” requiring that the C-arm
25
have a smaller radius by about six inches. This is a critical shortcoming, as everything is much closer to the table and patient, due to the smaller “C” radius. Furthermore, swinging the L-shaped arm
10
: (i) rotates the image yet again on another axis (now a three way interaction); and (ii) is problematic in a clinical sense, as it sweeps out a 90° arc to the left of the patient's head, where various monitors would normally be placed, medical lines are attached to the patient, and where nurses typically stand. As a result, units such as those shown in Stivender are almost always left at the head end of the patient (i.e., the L-shaped arm is not moved), mimicking other existing devices where a large radius C- or U-shaped arm is permanently mounted at the head.
U.S. Pat. No. 4,653,083 to Rossi (“Rossi”), with reference to its
FIG. 1
, discloses a C-arm based x-ray gantry with: a floor-mounted stand
1
; an outer C-shaped track
8
attached to the stand; and an inner U-shaped arm
11
rotatably connected to a carriage
9
that slides along the outer track
8
. While this device provides good angular coverage, it is very difficult to balance, and, therefore, was never commercially produced. More specifically, because the outer track
8
, inner arm
11
, and table T are all offset to one side of the stand
1
, the stand has to be either provided with a large counterweight for balance, or the stand has to be particularly well secured to the floor. Furthermore, to balance the x-ray source X and receptor I, a counter
Glick Edward J.
Ho Allen C.
Holland & Bonzagni, P.C.
Holland, Esq. Donald S.
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