Note: Descriptions are shown in the official language in which they were submitted.
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Scintillation Camera Comprising At Least Three Fields of View
Field
The invention relates generally to scintillation cameras, and more
particularly to an improved
scintillation camera comprising at least three fields of view.
Background
In the human body, increased metabolic activity is associated with an increase
in emitted
radiation. In the field of nuclear medicine, increased metabolic activity
within a patient is
detected using a radiation detector such as a scintillation camera.
Scintillation cameras are well known in the art, and are used for medical
diagnostics. A
patient ingests, or inhales or is injected with a small quantity of a
radioactive isotope. The
radioactive isotope emits photons that are detected by a scintillation medium
in the
scintillation camera. The scintillation medium is commonly a sodium iodide
crystal, BGO
or other. The scintillation medium emits a small flash or scintillation of
light, in response to
stimulating radiation, such as from a patient. The intensity of the
scintillation of light is
1 S proportional to the energy of the stimulating photon, such as a gamma
photon. Note that the
relationship between the intensity of the scintillation of light and the gamma
photon is not
linear.
A conventional scintillation camera such as a gamma camera includes a detector
which
converts into electrical signals gamma rays emitted from a patient after
radioisotope has been
administered to the patient. The detector includes a scintillator and
photomultiplier tubes.
The gamma rays are directed to the scintillator which absorbs the radiation
and produces, in
response, a very small flash of light. An array of photodetectors, which are
placed in optical
communication with the scintillation crystal, converts these flashes into
electrical signals
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which are subsequently processed. The processing enables the camera to produce
an image
of the distribution of the radioisotope within the patient.
Gamma radiation is emitted in all directions and it is necessary to collimate
the radiation
before the radiation impinges on the crystal scintillator. This is
accomplished by a collimator
which is a sheet of absorbing material, usually lead, perforated by relatively
narrow channels.
The collimator is detachably secured to the detector head, allowing the
collimator to be
changed to enable the detector head to be used with the different energies of
isotope to suit
particular characteristics of the patient study. A collimator may vary
considerably in weight
to match the isotope or study type.
Scintillation cameras are used to take four basic types of pictures: spot
views, whole body
views, partial whole body views, SPECT views, and whole body SPECT views.
A spot view is an image of a part of a patient. The area of the spot view is
less than or equal
to the size of the field of view of the gamma camera. In order to be able to
achieve a full
range of spot views, a gamma camera must be positionable at any location
relative to a
patient.
One type of whole body view is a series of spot views fitted together such
that the whole
body of the patient may be viewed at one time. Another type of whole body view
is a
continuous scan of the whole body of the patient. A partial whole body view is
simply a
whole body view that covers only part of the body of the patient. In order to
be able to
achieve a whole body view, a gamma camera must be positionable at any location
relative
to a patient in an automated sequence of views.
The acronym "SPELT" stands for single photon emission computerized tomography.
A
SPELT view is a series of slice-like images of the patient. The slice-like
images are often,
but not necessarily, transversely oriented with respect to the patient. Each
slice-like image
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is made up of multiple views taken at different angles around the patient, the
data from the
various views being combined to form the slice-like image. In order to be able
to achieve a
SPECT view, a scintillation camera must be rotatable around a patient, with
the direction of
the detector head of the scintillation camera pointing in a series of known
and precise
directions such that reprojection of the data can be accurately undertaken.
A whole body SPECT view is a series of parallel slice-like transverse images
of a patient.
Typically, a whole body SPECT view consists of sixty four spaced apart SPECT
views. A
whole body SPECT view results from the simultaneous generation of whole body
and
SPECT image data. In order to be able to achieve a whole body SPECT view, a
scintillation
camera must be rotatable around a patient, with the direction of the detector
head of the
scintillation camera pointing in a series of known and precise directions such
that
reprojection of the data can be accurately undertaken.
Therefore, in order that the radiation detector be capable of achieving the
above four basic
views, the support structure for the radiation detector must be capable of
positioning the
radiation detector in any position relative to the patient. Depending on the
type of study
being conducted, the configuration of the radiation detector is variable. The
two common
types of studies are planar imaging and cardiac imaging.
Planar imaging is used for bone scanning and various other types including
liver scanning.
In order to obtain optimum images, two cameras should be opposed one another.
In general,
these cameras should also be relatively large in order to obtain a large field
of view.
Cardiac imaging is used for obtaining images of the heart. In order to obtain
optimum
images, two detector heads and two collimators should be at substantially 90
degrees to one
another, with their fields of view close as possible.
In an attempt to provide the ability to produce both types of images with a
single scintillator
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machine, detectors of variable geometry were developed. These systems conduct
both planar
and cardiac imaging. However, the problem with these systems is that it is
difficult, if not
impossible, to position the heads to an exact same position where a prior
image was taken
from. This is primarily due to backlash in the mechanical structure of the
system. When the
computer conducts the reconstruction of the images, it does so with the
assumption that the
information it is writing into the pixels in the image display is in the
correct place. With the
presence of backlash, the computer is unknowingly writing information into the
wrong place,
which results in blurring of the image and loss of image resolution. This in
turn results in
images that are inaccurate. This also precludes any reproducability of the
study.
Also, these systems use two separate and distinct detectors to produce the 90
degree view.
This means that it further requires lead shielding between the detectors to
prevent any stray
radiation from getting into each of the detectors. With the lead shielding
between the
detectors, the detectors are prevented from being as close together as
possible in the 90
degree position; they are not as close as they would be without the shielding
between them.
1 S Since then, the fields of view of the detectors are not close, this leaves
open the risk of
cutting off views of the heart as cardiac imaging is conducted.
These systems also, generally, can not easily vary in size of support to
accommodate
different sizes of patients. In order to do accommodate either a larger or
smaller patient, the
entire scintillation camera is physically repositioned.
The use of three detectors is known, but usually, these systems use three
relatively little
detectors which don't image bones well. The smaller fields of view of the
detectors mean
they can not produce whole body images or images of the skeleton.
Even if the system did utilize relatively large detectors, systems using three
relatively large
detectors have disadvantages. The detectors are generally set at 60 degrees
from one another.
This results in the detectors wanting to slide over one another. As well, a 60
degree is not
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ideal for cardiac work. As mentioned above, the image should be taken at 90
degrees.
For this reason, it is beneficial to use a detector which comprises a rigid
structure comprising
two detector heads and two collimators fixed at 90 degrees to one another.
This detector is
optimum for cardiac work, but with it, then, the scintillation camera becomes
only a cardiac
camera. As mentioned above, 90 degree views are only useful for cardiac
studies and are not
really useful in other studies.
Therefore, there exists a need for a scintillation camera optimal for both
planar and cardiac
imaging that mitigates the disadvantages mentioned above.
Summary
An object of the invention is to provide an improved scintillation camera. The
invention is
directed to a scintillation camera with an improved three view detector
system. Preferably,
the camera is adapted to produce both optimized planar imaging and cardiac
imaging.
The present invention has many advantages including:
the need for lead shielding is eliminated, thereby allowing the two fields of
view to
1 S be as close together as possible;
designed for optimal cardiac imaging and eliminates the problems associated
with
backlash;
designed for optimum planar imaging and whole body imaging as well;
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increased sensitivity over current two headed designs;
design is flexible and versatile;
size of support diameter is adjustable while being able to maintain the
detectors in
the ideal positions relative to each other.
Other aspects and advantages of the invention, as well as the structure and
operation of
various embodiments of the invention, will become apparent to those ordinarily
skilled in
the art upon review of the following description of the invention in
conjunction with the
accompanying drawings.
Brief Description of the Drawings
The invention will be described with reference to the accompanying drawings,
wherein:
FIG. 1 is a perspective view of a scintillator in accordance with the
invention;
FIG. 2 is a perspective view illustrating the base in further detail with the
cameras removed;
FIG. 3 is a perspective view of the mounting means for one camera;
FIG. 4 is a front elevation view of a scintillator in accordance with the
invention;
FIG. S is a front elevation view of a scintillator with the cameras removed;
FIG. 6 is a side elevation view of a scintillator illustrating the counter
weight for one camera;
FIG. 7 illustrates one camera in detail;
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FIG. 8 illustrates a second camera in detail;
FIG 9. illustrates a positioner for a camera;
FIG 10. is a front elevation view of another embodiment in accordance with the
invention;
FIG. 11 illustrates a patient support;
FIG. 12 is a perspective view of the scintillation camera of FIG. 1, including
the detached
patient support and engaged patient support, with the stretcher removed; and
FIG. 13 is a side view of a portion of the patient support apparatus.
Similar references are used in different figures to denote similar components.
Detailed Description
Referring to FIGS. 1 to 13, scintillator 500 is illustrated. Nuclear cameras 5
and 300 are
supported and positioned relative to a patient by a support structure 10.
Nuclear cameras are
heavy, usually weighing approximately three to four thousand pounds. Thus, the
support
structure 10 should be strong and stable in order to be able to position the
cameras 5 and 300
safely and accurately. The support structure 10 includes a base 15, an annular
support 20, an
elongate support 25, and a guide 30.
The base 15 includes a frame 35. The frame 35 includes twelve lengths of
square steel tubing
welded together in the shape of a rectangular parallelepiped. The frame 35 has
a front square
section 37 and a rear square section 38. In the illustrated embodiment, the
frame 35 is
approximately five feet wide, five feet high, and two feet deep. The frame 35
also includes
eight triangular corner braces 40 welded to the front square section 37, that
is, each corner
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of the front square section 37 has two corner braces 40, one towards the front
of the front
square section 37, and one towards the rear of the front square section 37. In
the illustrated
embodiment, the corner braces 40 are in the shape of equilateral right angle
triangles.
Attached to the underside of the frame 35 are two horizontal legs 45. Attached
to each leg
45 are two feet 50. An alternative to the use of feet 50 is to attach the base
15 to a floor by
way of bolts set into the floor. The legs 45 extend beyond the frame 35 so as
to position the
feet 50 wider apart to increase the stability of the base 15. The feet 50 are
adjustable so that
the base 15 may be levelled. Thus constructed, the base 15 is strong, stable,
rigid, and
capable of supporting heavy loads.
The annular support 20 is vertically oriented, having an inner surface 55
defining an orifice
60, an outer surface 65, a front surface 70, and a rear surface 75. The
annular support 20 is
constructed of a ductile iron casting capable of supporting heavy loads. In
the illustrated
embodiment, the annular support 20 has an outside diameter of about fifty two
inches. The
annular support 20 is supported by upper rollers 80 and lower rollers 85 which
are mounted
1 S on the base 15. The upper rollers 80 and lower rollers 85 roll on the
outer surface 65, thus
enabling the annular support 20 to rotate relative to the base 15 in the plane
defined by the
annular support 20. Each of the upper rollers 80 and lower rollers 85 are
mounted onto a pair
of comer braces 40 by way of axles with deep groove bearings. The bearings
should be low
friction and be able to withstand heavy loads. The axles of the upper rollers
80 are radially
adjustable relative to the annular support 20, so that the normal force
exerted by the upper
rollers 80 on the outer surface 60 is adjustable. The curved surfaces of the
upper rollers 80
and lower rollers 85 (i.e. the surfaces that contact the outer surface 60)
should be tough so
as to be able to withstand the pressures exerted by the annular support 20,
and should have
a fairly high coefficient of friction so as to roll consistently relative to
the annular support
20.
Attached to each pair of corner braces 40 is a stabilizing arm (not shown)
oriented
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perpendicularly to the plane of the annular support 20. A pair of small
stabilizing rollers (not
shown) are mounted onto each stabilizing arm. Each pair of stabilizing rollers
is positioned
such that one stabilizing roller rolls on the front surface 70, and the other
stabilizing roller
rolls on the rear surface 75. The stabilizing rollers maintain the annular
support 20 in the
vertical plane.
Each camera 5 and 300 is mounted to the annular support 20 by mounting means.
The
mounting means can be of any type known in the art. The elongate support 25
includes a
pair of support arms 100, each of which extends through an aperture in the
annular support
20. The nuclear camera 5 is rotatably attached to one end of the pair of
support arms 100,
such that the nuclear camera 5 faces the front surface 70. A counter weight
105 is attached
to the other end of the pair of support arms 100, such that the counterweight
105 faces the
rear surface 75.
The counter weight 1 OS includes a pair of parallel counter weight members
110, 111 each
of which is pivotally attached to one of the support arms 100. A first weight
1 OS is attached
to one end of the pair of counter weight members 110, and a second weight 120
is attached
to the other counter weight members 111. A pair of counter weight links 121
and 122
connect the counter weight members 110 and 111 to the annular support 20. Each
counter
weight link 121, 122 is pivotally attached at one end to its corresponding
counter weight
member 110, 111. Each counter weight link 121, and 122 is pivotally attached
at its other
end to the annular support 20. The counter weight links 121, 122 are attached
to the
counterweight members 110 using bolts and tapered roller bearings. Each
counter weight
link 121, 122 is pivotable relative to the annular support 20 in a plane
perpendicular to and
fixed relative to the annular support 20.
The guide 30 attaches the elongate support 25 to the annular support 20, and
controls the
position of the elongate support 25, and hence the scintillation camera S,
relative to the
annular support 20. A pair of parallel brackets 125 is rigidly attached to the
annular support
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20. A parallel pair of rigid links 130 is pivotally attached at support arm
pivot points 135 to
the support arms 100. The pair of links 130 is also pivotally attached at
bracket pivot points
140 to the brackets 125. At the support arm pivot points 135 and bracket pivot
points 140 are
tapered roller bearings mounted with bolts. Each link 130 is pivotable
relative to the annular
5 support 20 in a plane perpendicular to and fixed relative to the annular
support 20. Thus, as
the annular support 20 rotates relative to the base 15, the respective planes
in which each link
130 and each support arm 100 can move remain fixed relative to the annular
support 20.
A pair of linear tracks 145 (only one shown for simplicity )are rigidly
attached to the front
surface 70 of the annular support 20. The tracks 145 are oriented such that
they are parallel
10 to the respective planes in which each link 130 and each support arm 100
can move. A pair
of rigid sliding arms 150 (not shown in FIG. 1 ) include camera ends 155 and
straight ends
160. Each camera end 155 is pivotally attached to one of the support arms 100
at the point
of attachment of the scintillation camera 5. Each straight end 160 includes a
pair of spaced
apart cam followers or guides 165 slidable within the corresponding track 145.
Thus,
1 S movement of the scintillation camera S relative to the annular support 20
(i.e. we are not
concerned, at this point, with rotational movement of the scintillation camera
S relative to
the elongate support 25) is linear and parallel to the plane of the annular
support 20. Note
that if the camera ends 155 were pivotally attached to the support arms 100
between the
nuclear camera S and the annular support 20, the movement of the nuclear
camera 5 relative
to the annular support 20 would not be linear.
Movement of the scintillation cameras 5 and 300 relative to the annular
support 20 is
effected by actuators 170. Each actuator 170 includes a fixed end 175
pivotally attached to
the annular support 20, and a movable end 180 pivotally attached to the
elongate support 25.
Each actuator 170 is extendable and retractable, and is thus able to move the
elongate support
25 relative to the annular support 20.
Movement of the annular support 20 relative to the base 15 is effected by a
drive unit 185.
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The drive unit 185 includes a quarter horsepower permanent magnet DC motor and
a
gearbox to reduce the speed of the output shaft of the drive unit 185.
Alternatively, other
types of motors could be used, such as hydraulic or pneumatic motors. The
output shaft of
the drive unit 185 is coupled, by means of a toothed timing belt 195 and two
pulley wheels
(not shown), to the axle of a drive roller 190, which is simply one of the
lower rollers 85,
thus driving the drive roller 190. Power is then transferred from the drive
roller 190 to the
annular support 20 by friction between the drive roller 190 and the outer
surface 65 of the
annular support 20.
The cameras 5 and 300 used for detection will now be described.
A detector head 305 of the nuclear camera 300 is supported between the two
support arms
100. The detector head 305 includes a casing 310 in which is contained a
scintillation crystal
and photomultiplier tubes. Attached to the underside of the casing 310 is a
collimator plate
315. The collimator plate 315 is made of lead perforated by narrow channels,
and includes
a collimator support 325 extending from the two edges of the collimator plate
adjacent the
support arms 310. The collimator plate 315 provides a first field of view 275.
The
collimator plate 315 is attached to the casing 310 by way of bolts 311. By
removing the
bolts 311, the collimator plate 315 can be removed from the casing 310 and
replaced by
another collimator plate 315. A particular design and weight of collimator is
selected
depending on the isotope being used or the type of study being conducted.
Thus, the
collimator plate 315 must be changed from time to time. Since the collimator
plates 315
vary considerably in weight from one to another, the location centre of
gravity of the detector
head 3 05 is dependent upon the weight of the collimator plate 315 attached to
the casing 310.
Since the angle of the detector head 305 relative to the patient must be
adjusted by an
operator of the nuclear camera 300, the detector head 305 must be rotatable
relative to the
arms 100. If the centre of gravity of the detector head 305 is positioned
approximately on
the axis of rotation of the detector head relative to the support arms 100,
then the detector
head 305 will be balanced, and the angle of the detector head 305 relative to
the support arms
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100 will be adjustable by hand. However, changing the collimator plates moves
the centre
of gravity of the detector head. Since collimator plates 315 are so heavy, it
becomes
inconvenient or impossible to adjust the angle of the detector head 305 by
hand. The
positioner 320 enables the operator to adjust the position of the centre of
gravity of the
detector head 305 to be approximately aligned with the point of rotation of
the detector head
305, which passes through the support arms 100.
In a similar fashion, detector head 400 of the nuclear camera 5 is supported
between the two
support arms 100. The detector head 400 includes a casing 410 which is a L
shaped rigid
structure. As illustrated, the casing allows two collimator plates 255 and 260
to be attached
to the underside of the casing 410. The collimator plates 255 and 260 are at
90 degrees to
one another. Each collimator plate 255 and 260 provides a second and third
field of view
280 and 285 respectively. Each collimator plate 255 and 260 includes a
scintillation crystal
and photomultiplier tubes and operates in a similar fashion as camera 300.
The collimator plates 255 and 260 define an apex 290 at their meeting point.
It is seen that
camera 300 is diametrically opposed from camera 5 along the annular support.
With the detector head 400 comprising a single rigid structure 410 with two
collimators 255
and 260 fixed together at 90 degrees, no stray radiation can enter the other
collimator. This
eliminates the requirement for lead shielding between them. And without the
lead shielding,
the fields of view 280 and 285 of the camera 5 are closer together, resulting
in minimized
risk of cutting off views of the heart as during operation. Also the rigid
structure also allows
the camera 5 to be repositioned easily to an original position. This allows
reproducability
of studies.
The camera 5 is of an ideal geometry for cardiac studies. And with the camera
300, the three
fields of view are of an ideal geometry for other organ work, especially brain
and liver
studies.
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Each of cameras 5 and 300 are preferably supported by the support arms by a
positioner 320.
The positioner can be of any type to allow for this rotational movement. One
such positoner
is described. 'The positioner 320 attaches the detector head 305 to the
support arms 100 and
includes a pair of rigid elongate detector head links 330 for aligning the
centre of gravity of
the detector head 305 relative to the support arms 100. Each detector head
link 330 is
rotatable relative to the support arms 310 in a plane substantially parallel
to its adjacent
support arm 100. Each detector head link 330 includes an arm end 335 rotatably
attached
to the adjacent support arm 100 by way of an arm axle 340, which allows each
camera to be
rotatably positioned in any desired angle relative to the patient. Each
detector head link 330
also includes a head end 345 rotatably attached to the detector head 305 by
way of a head
axle 350.
The positioner 320 also includes a pair of locks 355 for selectively
preventing rotation of the
detector head 305 relative to the detector head links 330. Each lock 355
includes the
collimator support 325 extending from the detector head 305 from the
collimator plate 315.
Each lock 355 also includes a block 360 for supporting the detector head link
330 on the
collimator support 325. Each block 360 includes a pair of pins 365 located
either side of the
head axle 350.
In operation, each lock 355 supports the head end 345 of one of the detector
head links 330
on the corresponding collimator support 325. Thus, the distance between the
head axle 350
and the collimator support 325 remains constant, and rotation of the detector
head 305
relative to the detector head link 330 is prevented.
If a heavier collimator plate 315 is installed, shorter pins 365 are
installed, thus reducing the
distance between the head axle 350 and the collimator support 325, and
aligning the centre
of gravity of the detector head 305 with the axis of rotation of the detector
head 305, which
passes through the arm axles 340.
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If a lighter collimator plate 315 is installed, longer pins 365 are installed,
thus increasing the
distance between the head axle 350 and the collimator support 325, and
aligning the centre
of gravity of the detector head 305 with the axis of rotation of the detector
head 305, which
passes through the arm axles 340.
Once the locks 355 are in place, the detector head 305 will be balanced, and
the detector head
305 can be rotated manually by the operator. Once the detector head 305 has
been rotated
to the desired position relative to the support arms 100, a brake 370 can be
implemented to
selectively prevent rotation of the detector head link about the arm axle 340.
In a preferred embodiment, the camera 5 and camera 300 are not mechanically
joined
together; each camera is mounted to the annular support by its own mounting
means. This
allows for the system to increase/decrease in size depending on the size of
the patient.
Adjustments to the cameras do not affect the relative position of each camera
and each field
of view, only the relative distance between them. Since camera 5 is of a rigid
construction,
the fields of view 280 and 285 will always be maintained at a constant angle,
which is
preferably 90 degrees. As well, camera 300 will always be maintained at a
position
diametrically opposed the camera 5.
In a preferred embodiment, camera 300 is of a rectangular shape.
Also, in another preferred embodiment, the fields of view 275, 280 and 285 are
in alignment
with one another. With industry standard sizes, it is possible to provide
optimum geometry
for this configuration. While the cameras can be of any size, the camera 5
ideally is either
15 feet by 10.5 feet or 15 feet by 20 feet and the camera 300 is ideally 15
feet by 20 feet.
The invention also allows for complete flexibility in configuration choices
and the ability to
upgrade. For example, a scintillation camera could include only a single
detector, such as
detector 300. The scintillation camera could be upgraded to include the use of
a second
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detector head, such as detector 400.
In an alternative embodiment, the camera 300 could be identical to camera 5,
providing for
a four field of view configuration. This would be very useful for brain
studies since a very
high sensitivity, high resolution image would result. The camera 5 could
comprise a circular
5 or square shape as well.
The sizes of the cameras are variable.
In another alternative embodiment, the camera 5 could be rotated about
supporting arms 100
and arm axles 340 so collimator plates 255 and 260 face out rather than down
as seen in
Figure 10. This configuration is useful for performing bi-plane angiography of
the heart
10 where the heart is examined in two directions simultaneously.
The support structure 10 of the illustrated embodiment is designed to operate
with an
apparatus for supporting and positioning a patient, such apparatus including a
detached
patient support 205 or bed, an engaged patient support 210 or pallet receiver,
and a cylinder
support or cylinder 212.
15 The detached patient support 205 includes rigid patient frame 21 S
supported by four casters
220. Mounted near the top of the patient frame 215 are first support wheels
225 for
supporting a stretcher 227 having a flat lower surface and two parallel sides
upon which a
patient is lying. Two parallel, spaced apart side rails 230 are rigidly
attached to the patient
frame 215. The first support wheels 225 and the side rails 230 are arranged to
enable the
stretcher 227 to roll lengthwise on the detached patient support 205. Thus, if
the patient
support 205 faces the front surface 70 such that the patient support is
central and
perpendicular relative to the annular support 20, the stretcher 227 is movable
on the first
patient support wheels 225 substantially along the axis of the annular support
20. A gear box
and motor unit 237 driving at least one of the first patient support wheels
225 moves the
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stretcher 227 as described. A 0.125 horsepower permanent magnet DC motor has
been found
to be adequate.
The detached patient support 205 can be used both for transporting a patient
to and from the
scintillator S00 and support structure 10 therefor, and for supporting and
positioning a patient
relative to the base 15 during operation of the scintillation cameras 5 and
300 and support
structure 10. To ensure that the detached patient support 205 remains
stationary during
operation of the scintillation cameras 5 and 300, four brakes 233 can be
lowered. Thus
lowered, the brakes 233 ensure that the detached patient support remains
stationary relative
to the floor.
The engaged patient support 210 includes a second rigid frame or rigid base
frame 234 and
second support wheels 235. The second support wheels 235 are positioned such
that the
stretcher 227 rolled along the first support wheels 225 can roll onto the
second support
wheels 235 until the stretcher 227 is either fully or partially supported by
the second support
wheels 235. The engaged patient support 210 also includes four transverse
wheels 240.
The cylinder 212 is rigidly mounted to the annular support 20. The cylinder
212 is aligned
with the orifice 60 of the annular support 20 such that the cylinder is
coaxial with the annular
support 20. The cylinder 212 includes a smooth inner surface 244 upon which
rest the
transverse wheels 240 of the engaged patient support 210. Thus, the
arrangement is such that
the patient remains stationary substantially along the axis of the annular
support 20 as the
annular support 20 rotates relative to the base 15, regardless of whether the
board or stretcher
is supported by the first support wheels 225, the second support wheels 235,
or both.
The engaged patient support 210 also includes a stabilizer 245. The stabilizer
245 includes
outside wheels 250 to maintain the engaged patient support 210 horizontal,
that is, to stop
the engaged patient support from tipping relative to the cylinder 212. The
outside wheels
250 roll on the outside surface 243 of the cylinder 212. The stabilizer 245
also includes end
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wheels 255 to prevent the engaged patient support 210 from moving in a
direction parallel
to the axis of the cylinder 212. The end wheels 255 roll on the ends 244 of
the cylinder 212.
The previously described embodiments of the present invention have many
advantages
including:
eliminating the need for lead shielding between the collimators at 90 degrees
to one
another, thereby allowing the fields of view to be a close together as
possible;
ensuring cardiac studies are done accurately by using a fixed geometry which
eliminates backlash and accomplishes reproducability;
allowing for accurate bone work and whole body views to be taken since three
fields
of view are provided;
increasing the sensitivity from only using two heads ;
permitting both optimum cardiac and other studies to be conducted with the
same
machine;
allowing flexibility and the ability to upgrade in the field; and
adjusting the size of diameter of the annular support to accommodate all
patients
while being able to maintain the cameras in the right positions relative to
each other.
While the invention has been described according to what is presently
considered to be the
most practical and preferred embodiments, it must be understood that the
invention is not
limited to the disclosed embodiments. Those ordinarily skilled in the art will
understand that
various modifications and equivalent structures and functions may be made
without
CA 02326025 2000-11-16
1g
departing from the spirit and scope of the invention as defined in the claims.
Therefore, the
invention as defined in the claims must be accorded the broadest possible
interpretation so
as to encompass all such modifications and equivalent structures and
functions.
