Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to alignment apparatus
in general and more particularly to detents for aligning and
mating collimator and a scintillation camera.
In the diagnosis of certain illnesses, radioactive
agents are administered to patients. These administered agents
have the characteristics of localizing to a greater or lesser
degree in certain tissues. For example, iodine 131 localizes
in thyroid glands. A presentation of the spatial distribution
; and concentration of administered iodine 131 in a thyroid gland
provides by scintillation scanning an image of the gland itself.
The image is useful in diagnosing the condition of the gland.
In a somewhat similar manner technetium, an element
obtained by the irradiation of molybdenum with deuterons, is an
element commonly utilized in brain studies. In studying the
effect of administered radiation on various organs, scintigrams
-~ are frequently generated using scintillator cameras.
In many of these cameras, a relatively large disc-
shaped scintillation crystal is positioned to be stimulated by
the radiation emitted from the patient. In most cameras a
collimator is interposed between the patient and the crystal
for absorbing unwanted radiation and permitting desired rays to
strike the crystal.
Depending upon the particular study, the administrator
must choose the appropriate collimator and perhaps exchange it
with the presently attached collimator. For example, if a
thyroid study or a static whole body study is to be performed,
typically a pin-hole type collimator will be selected. Con-
~- versely, if a brain study is to be performed, a parallel hole
type collimator of the appropriate dimensions will be selected.
Resulting collimator exchanges may be necessitated several times
~ day during the normal routine of hospital affairs.
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Historically, such collimator exchanges have been
troublesome. A collimator typically weighs between 100 and 300
pounds and additionally is quite bulky. One present method for
aligning the scintillator camera and the collimator includes
mounting the particular collimator on a cart with its face
downward and positioning the cart to directly underlie the
camera head. The cart is then maneuvered directly into fine
alignment, necessitating engagement of sturdy metal alignment -
pins in the camera head with corresponding tight fitting holes
in the collimator. Because of the relative bulk of the camera
and the collimator compared with the small alignment pins,
vision is obscured, and alignment is burdensome. Furthermore,
the collimator is heavy, and the repeated precise motion of the
collimator on its cart is a strenuous task for the involved
technician.
Another proposed method uses longer pins and thereby
facilitates visualization of the mounting. Such has proven an
undesirable alternative as generally the collimator requires
thinness in the region of the mounting pins.
Proposals have been suggested for x-ray apparatus
whereby spring biased balls are utilized as a detent. Such
proposals have not proven to be the solution as fine alignment
is still initially required, and the inherent problems remain.
Furthermore the proposals using such spring biased balls did
not contemplate mating two relatively heavy and massive members,
as is the case in certain radiation imaging systems, such as in
~ gamma camera systems.
`~ Still another proposed method requires storing the
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extra collimators in fixed relation to the detector to eliminate
one or more degrees of freedom during alignment: for example, in
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a ring stand having its axis fixed parallel to the detector
axis. The drawbacks here include: 1) the limitation placed on
utilization of valuable floor space, 2) the relatively complex
and sturdy mechanism to support a plurality of collimators,
3) the structure and unused collimators may interfere with a
study and, 4) a collimator cannot readily be used on another
camera.
The present invention overcomes the foregoing and
other drawbacks of the prior art by providing alignment apparatus ;
including a plunger coordinated with one of the mating members
and extending in the direction of alignment. The second mating
member has a recess coordinated therewith which is positioned
and configured to loosely receive the plunger for coarse align-
ment. To effect fine alignment, tight fitting fine alignment
apparatus coordinated with the members is urged into joinder
under constraints of the coarse alignment apparatus.
In a preferred embodiment, one member has a pair of
spaced plungers, each plunger having a circumscribing collar, or
sleeve, adjacent the member. The other mating member has a
pair of recesses spaced and positioned to loosely receive the
; rods and to tightly receive the collars. Each recess in the
second member includes an upper side portion tapered to an inward
perimeter from the surface, and a lower side portion extending
substantially untapered from the inward perimeter for precisely
receiving the tight fitting collar. The collar preferably
comprises a substantially cylindrical portion adjacent the first
member and a tapered remote portion, whereby the members are
urged into fine alignment by force against the respective tapered
surfaces.
The method according to this invention includes a
multi-step sequence of initially establishing a vertical axis
about a first coarse point of alignment between the two mating
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members, then angularly displacing a member into coarse rota-
tional alignment, and then maneuvering the members into fine
alignment under the constraints of course alignment.
One feature of the detent according to the invention
is that the plunger making primary contact with its mating
recess has an extended length greater than the other plunger.
The added length enhances viewing of the process for facilitating
alignment, and the retractable nature of the plunger retains use
of the desirably shallow recess.
Another feature of the invention is spring actuated
plungers of sufficient strength such that an audible indication
is generated when coarse alignment is achieved, i.e. when the
plunger initially is received by the respective recess.
As will be apparent from the foregoing summary, it is
a general feature of the present invention to provide novel and
improved aligning and detent apparatus in radiation imaging
systems. A more specific feature of the invention is to provide
alignment apparatus and method for initially coarse aligning
the system and then fine aligning the system, while using
standard positioning servomechanisms.
Other features and advantages w'll become apparent
rom the following detailed description of tIle inYention when
referring to the accompan~ dra~ings~
FIGURE 1 depicts one rad;ation imaging s~stem featuring
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the invention;
FI~URFI 2a is a cross-sectional cut-awa~ vi~w of a
preferred detent assembly u~ed ~n th~s invention;
FIGURE 2~ dep~cts a pxeferred collar assembly shown in
the detent of FIGURE 2~;
:
FIGURES 3a-3d de~ct ~tages of alignment showl~ the
relationship of the mem~zrs and alignment apparatus.
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Referring now to FIGURE 1, a radiation detector
assembly is shown generally at 1 comprising a collimator 4,
detents 6 and 8, detector head 3, and support means 11. Colli-
mator 4 is shown cradled in cart 5 positioned under the detector
head 3 to which it is normally affixed. Detent assemblies 6
and 8 are provided for aligning the collimator 4 with the
detector head 3, as will be explained.
During a particular aligning and mounting process, the
collimator 4 resides face down on cart 5 positioned underneath
the overhanging detector head 3. The head is adjustably mounted
on stand 11 and is lowered therealong during the alignment
process until the head 3 engages the collimator ~.
, After mounting of the collimator 4 on the head 3, the
head and collimator are positioned adjacent the patient or other
subject under study for data generation and processing. Elec- ,"
trical signals from the head 3 are conducted to circuitry con-
;~ tained within a console shown generally at 12. After processing, ~ ;~
the signals provide an image on a monitor oscilloscope 14 depict-
ing the distribution of an isotope in the subject under investi-
gation. A duplicate image may be produced on a camera oscillo-
~` scope, not shown, which is viewed and photographed by a camera 16.
..... .
Console 12 circuitry processes the data and generates
~ analog signals in a manner now well known in the art. Assuming
;` that the analog signals represent photopeak events, they are
,~
digitized. ~he digital signals may be fed to an offline computer
for analysis and diagnosis. The digital information may alter-
natively be fed to a built-in digital data processor 18. This
processor utilizes the digital information to generate either a
variable width profile histogram of counts versus hori20ntal
distance or a histogram of counts versus time. Such histograms
are displayed on a monitor 20. The digital information may also
be fed to a tape recording storage console shown generally at 22
for later use. The digital information is reconstructed to
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analog to produce the images displayed on the monitar oscillo-
scope 14 arld recorded by the camera 16.
Referring now to FIGURE 2a, there is shown in detail
a preferred embodiment of one of the detent assemblies 6 or 8
secured in coordination with the first member. A plunger assembly
comprises a rod 24, such as a dowel, slidably secured within
chamber 25 through a sleeve such as collar 26. First and second
springs 28 and 30 respectively are serially connected to the rod
24 for urging it into its fully extended position in the direc-
tion of alignment. A snap ring 23 is affixed to the rod 24
against which spxing 30 interacts. As rod 24 is depressed
inwardly, spacer 32 compresses springs 28 and 30. As will sub-
sequently be e~plained in greater detail, springs 28 and 30 are
preferably of sufficient strength to force a collision between
; the partially compressed rod 24 and its corresponding mating mem-
ber to produce an audible indication thereof, which will be an
indication of coarse alignment. The collar 26 retains the snap
ring 23 during travel of the rod 24 and the collar is secured
to the first mating member by an inset screw 34. r
~ 20 The collar or sleeve 26 as shown in FIGURE 2a is repro-
,-~ duced in FIGURE 2b for better understanding of the preferred
detent embodiment. A portion 29 of the collar 26 is adapted to
be inserted into the first mating member while a second portion
31 is secured adjacent the mating edge of the first member. In
the preferred embodiment portion 31 is comprised of an upper
cylindrical portion 31a adjacent the mating surface of the first
member and a lower beveled portion 31b remote from the mating
surface. As will henceforth be explained beveled portion 31b
facilitates fine alignment by guiding the mating members into
engagement and minimizes collision shock.
FIGURES 3a-3d show an alignment sequence depicting the
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relationship between the mating members and the preferred embodi-
ment of the detent assembly of FIGURE 2. Although only a single
detent assembly is shown in FIGURES 3a-3d, the preferred embodi-
ment utilizes a pair of detent assemblies as will be apparent
during description of the alignment process.
FIGURE 3a shows a preferred configuration of an
accepting means 32 for the plunger assembly. Recess 32 positioned
in coordination with the other mating member is configured such
that rod 24 is loosely captured thereby to define coarse align-
ment between those points. Recess 32 is also configured to
receive collar 26 in tight fitting engagement to effect fine
alignment. It is seen that the preferred embodiment recess 32
comprises three portions, an upper beveled portion 32a extending
from the mating surface to an inward perimeter. Surface 32b '~
extends from the inward perimeter substantially untapered and
is of a configuration to receive portion 31a of the collar
assembly 26. Recess 32 is further comprised of a cavity 32c
substantially centered in the bottom boundary having its primary
function during fabrication and not alignment.
For convenience it is assumed that the first member
to be mated is a detector head 3, and the second member to be
mated is a collimator 4 underlying head 3 as shown in FIGURE 1.
FIGURES 3 accordingly depict a preferred sequence wherein the
detector head 3 is lowered substantially vertically along stand
11 to the underlying collimator 4 positioned on a cart 5. As
the detector head 3 is lowered, the technician performing the
aligning and mounting task visually observes the relative posi-
tion of the rod 24 and the recess 32. If the detector head is
lowered so as to cause sufficient retraction of the rod 24, an
audible indication will be generated when the rod 24 slips into
recess 32 into coarse alignment. That is, rod 24 slips from
surface 32a and impacts the bottom boundary of the recess with
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the force stored in the compressed springs 28,30. This step is
exemplified in FIGURE 3b wherein the rod 24 has slipped from
the beveled side 32a of the recess and is traveling towards the
bottom boundary thereof.
FIGURE 3c depicts the stage of coarse alignment
between the two specific points as the rod 24 has been captured
by the recess 32. The first member and collar 26 have been
brought adjacent the second member. In this coarse alignment
configuration, the lower tapered portion 31b of the collar
assembly 26 resides against the upper tapered portion 32a of
the recess. After slight additional manipulation, the two mem-
bers to be mated are brought into fine alignment as shown in
FIGURE 3d. Typically, weight of the detector head 3 generates
sufficient force in the direction fransverse to alignment to
urge the members into fine alignment with little additional
` manipulation of the collimator. r
; FIGURE 3d depicts fine alignment between the first
and second mating members. The lower boundary portion 32b of
the recess 32 fully and precisely receives the upper contoured
portion 31a of the collar 26. The collar portion 31b must be
received by recess portion 32b in tight fitting joinder to assure
accurate alignment. The two members are thus in a contiguous
and abutting relationship and are positioned to be fastened to-
gether.
;~ It will be understood that the above specifically
,
i described embodiment is a preferred embodiment and is not to be
construed in a limiting fashion. As will be apparent from sub- -
sequent description, apparatus according to the preferred embodi-
ment incorporates another alignment plunger assembly and corre-
sponding recess 32 which are diametrically spaced therefrom and
coordinated with the second mating member as depicted in FIGURE 1.
The first coarsely aligned plunger assembly establishes an axis
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of rotation so that the second plunger assembly will function as
a rotational detent. ~his will be explained in detail subse-
quently with respect to the method of this invention.
Although the plunger assemblies are herein depicted as
physically part of the mating members, it is understood that
they may be associated with apparatus in fixed physical rela-
tionship to the particular member, such as the collimator cart 5.
Further, the relative position of the extending plungers between
the mating members may be reversed; i.e., the plunger assemblies
may extend from the collimator surface toward the camera head.
` Still further, one plunger assembly and its recess may be
reversed with one plunger assembly on one member and the other
plunger assembly on the other member. Yet further the tight
fitting means for effecting fine alignment need not circumvent
the plunger, as the collar or other protrusion and its receiving
part may be spaced from the plunger/recess combination in a
~' known relationship. All such configurations and combinations
thereof providing a first coarse alignment position and a second
; fine alignment position are understood to be within the scope of
this invention.
The method of aligning two members according to this
invention is best illustrated when referring to the detent
assemblies 6 and 8 in FIGURE 1 in combination with the sequence
of FIGURES 3a-3d. For facilitating understanding of the method
of alignment according to this invention, the first member will
again be described as the camera head 3, and the second member
will be described as the collimator 4 in FIGURE 1. However it
is understood that other mating apparatus in the radiation imag-
ing art may suitably utilize techniques herein described, and
that such members need not necessarily be initially in the over-
lying positional relationship of FIGURE 1.
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The detent assembly shown in FIGURE 3a is initially
considered to represent one of the detent assemblies shown in
FIGURE 1, such as detent 6. In a preferred embodiment, one of
the plungers extends a length greater than the other of the
plungers from the head 3, and the plunger having the longer
length is selected initially. The head 3 is initially lowered -
towards the collimator until the rod 24 begins to depress,
usually in a position proximate to the recess 32 but in somewhat
misalignment. By choosing the long detent for initial gross
alignment, the technician readily observes the relati~e positions
of the rod 24 and the recess 32 during lowering of the head and
maneuvers the collimator on its cart into rough alignment as ~ ;
shown in FIGURE 3b. The plunger 24 during coarse alignment
fully extends to the bottom boundary of the recess 32 as shown in
FIGURE 3c. Such coarse alignment establishes by way of the
plunger 24 a vertical axis for horizontal rotational displace-
ment of the members for subsequently aligning the diametrically
opposed detent.
During lowering of the head 3 into coarse alignment,
the diametrically opposed plunger assembly is compressed in a
manner similar to that of the first plunger assembly. To show
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this, the sequence of FIGURES 3 is considered to represent the
diametrically opposed detent during coarse alignment. The
relative distance between the members as shown in FIGURE 3a
during coarse alignment is exaggerated. FIGURE 3b represents
the result of the step of angularly displacing the two members
in the right-to-left direction about the vertical axis provided
by the first plunger assembly.
FIGURE 3b thus represents coarse rotational and linear
alignment of the system immediately following the audible click
produced by rod 24 forcefully contacting the bottom of the
recess, or by the snap r-ing 23 striking the collar 26.
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FIGURE 3c depicts the subsequent steps of bringing
the two members into closer proximity such that the beveled
surfaces of the collar contacts the recess. In this position,
the technician needs at most only slight jockeying of the cart
and collimator to bring the head into fine alignment, as the
beveled surfaces provide a force vector tending to align the
members as the head is further lowered toward the collimator.
It thus is apparent that a novel and improved method
; of alignment has been described wherein initially a vertical ~ -~
axis is established between the two mating members at points of
coarse alignment, and then the members are angularly displaced
such that a diagonally opposed detent assembly and recess is
also brought into coarse alignment. An audible clicking sound
! iS generated by a spring loaded plunger snapping into the bottom
of the recess. The second phase or fine alignment phase is
then readily effected by slight pressure in the direction of
~; alignment, such as by continued lowering of the camera head.
It will be appreciated that when modifying the struc-
tural relationship of the detent assemblies as above suggested,
20 the specific step accordi~g to the method will also be modified.
For example, if the collar or tight fitting means is spaced from
the plunger assembly, after initially coarse aligning the first
plunger assembly, the step of angularly displacing the members
may substantially simultaneously effect coarse alignment and
fine alignment.
Although the invention has been described in its pre-
ferred form with a certain degree of particularity, it is under-
stood that the present disclosure of the preferred form has been
only by way of example. Numerous changes in the details of con-
struction and the combination and arrangement of parts, espec-
ially in the relative detent assembly locations, may be altered
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without departing from the spirit ~nd scope of the invention as
hereinafter claimed.
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