U.S. patent number 3,880,138 [Application Number 05/434,847] was granted by the patent office on 1975-04-29 for method for injecting contrast media into the vascular system.
This patent grant is currently assigned to Lear Siegler Inc.. Invention is credited to George S. Rives, John A. Wootten.
United States Patent |
3,880,138 |
Wootten , et al. |
April 29, 1975 |
Method for injecting contrast media into the vascular system
Abstract
A method by which fluid is delivered sequentially at more than
one rate as desired. Such different flow rates and the duration of
time of each flow rate are independently preselected, after which
the piston is caused to be automatically sequentially advanced
within the syringe at the preselected rates of speed for the
preselected periods of time during one cycle of advancement of the
piston to obtain the desired different flow rates and duration of
time of each flow rate.
Inventors: |
Wootten; John A. (South Euclid,
OH), Rives; George S. (North Ridgeville, OH) |
Assignee: |
Lear Siegler Inc. (Elyria,
OH)
|
Family
ID: |
26992018 |
Appl.
No.: |
05/434,847 |
Filed: |
January 21, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
340226 |
Mar 12, 1973 |
3812843 |
|
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Current U.S.
Class: |
600/432;
128/DIG.1; 604/507 |
Current CPC
Class: |
A61M
5/14546 (20130101); A61M 5/44 (20130101); A61M
5/16854 (20130101); Y10S 128/01 (20130101); A61M
5/14566 (20130101) |
Current International
Class: |
A61M
5/145 (20060101); A61M 5/168 (20060101); A61b
006/00 (); A61m 005/00 (); A61m 005/20 () |
Field of
Search: |
;128/218A,DIG.1,2.5R,2A,236,2R,214R,214F ;222/59,76 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Medbery; Aldrich F.
Attorney, Agent or Firm: Donnelly, Maky, Renner &
Otto
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a division of applicants' copending U.S.
application Ser. No. 340,226, filed Mar. 12, 1973 and now U.S. Pat.
No. 3,812,843.
Claims
The embodiments of the invention in which an exclusive property or
privelege is claimed are defined as follows:
1. A method of injecting a fluid into the vascular system of a
mammal comprising the steps of filling a syringe with the desired
quantity of fluid to be injected, providing a bolus of said fluid
in the vascular system during one cycle by moving a motor driven
piston mounted for axial movement within the syringe for expelling
such bolus of fluid therefrom, and controlling the movements of
such piston to cause the piston to automatically sequentially
advance at more than one rate of speed of advance movement within
the syringe for different periods of time during such one cycle of
advance movement of such piston.
2. The method of claim 1 wherein controls are provided for
independently preselecting more than one rate of speed of
advancement of the piston within the syringe and the periods of
time of each advancement during such one cycle of advancement prior
to such advancement, further comprising the step of presetting such
controls to control the movements of such piston as aforesaid.
3. The method of claim 1 further comprising the step of stopping
and restarting the piston at selected times during such
advancement.
4. The method of claim 2 further comprising the step of
automatically actuating an X-ray machine after a time delay upon
completion of such sequential advancement of such piston.
5. The method of claim 4 further comprising the step of activating
the time delay for the X-ray machine whenever the piston reaches
the end of its stroke before the preselected time.
6. The method of claim 1 wherein there is a syringe cap and
associated seal on the outer end of the syringe, and prior to the
step of filling the syringe with the desired quantity of fluid the
piston is extended to expel any fluid therefrom and the syringe is
disassembled and sterilized, then reassembled except for the
syringe cap and associated seal, and the piston is retracted to the
desired fluid volume and the syringe is then pointed vertically
upwardly to permit the fluid to be poured into the syringe.
7. The method of claim 6 wherein after the syringe has been filled
with the desired quantity of fluid, the syringe cap and associated
seal are assembled on the outer end of the syringe.
8. The method of claim 1 wherein prior to filling the syringe with
the desired quantity of fluid the syringe is checked for current
leaks to ground.
9. The method of claim 1 wherein the piston is caused to
automatically sequentially advance first at a relatively slow rate
for a relatively long period of time and then at a relatively
faster rate for a much shorter period of time during such one cycle
of advancement of such piston, followed by automatic actuation of
an X-ray machine.
10. The method of claim 1 further comprising the step of
interrupting such automatic sequential advancement of the piston
during such one cycle of advancement of the piston, and controlling
the movements of the piston for the remaining portion of the
injection cycle.
11. A method of injecting a fluid into the vascular system of a
mammal comprising the steps of filling a syringe with the desired
quantity of fluid to be injected, such syringe including a motor
driven piston mounted for axial movement within the syringe for
expelling such fluid therefrom, and controlling the movements of
such piston to cause the piston to automatically sequentially
advance at more than one rate of speed of advance movement within
the syringe barrel for different volumes of each advancement during
one cycle of advance movement of such piston and providing controls
for independently preselecting more than one rate of speed of
advance movement of the piston within the syringe and volumes of
each advancement prior to such advancement, further comprising the
step of presetting such controls to control the movements of such
piston as aforesaid, such piston being caused to automatically
sequentially advance first at a relatively slow rate for a
relatively long period of time and then at a much faster rate for a
much shorter period of time, followed by actuation of an X-ray
machine.
Description
BACKGROUND OF THE INVENTION
This invention relates generally as indicated to an improved method
for injecting a contrast media into a person's vascular system.
It has become standard procedure to inject contrast media into the
vascular system to study and obtain information about the arterial
tree. Conventional practice has been to make multiple injections
and take a series of X-rays where visualization of a substantial
portion of the arterial tree is desired, particularly the entire
arterial tree of a lower extremity which is the most frequently
involved site of an obstruction. The primary objection to this
procedure is that it often requires the patient to be subjected to
multiple injections, and also increases the patient's exposure to
X-rays. The time required to carry out this procedure is also
oftentimes lengthy, and it involves the use of relatively expensive
equipment such as rapid film changers, moving table, and special
X-ray source.
Another objection to the procedure described above is that
visualization of the critical span is not always adequate,
necessitating a repeat of the procedure at another time after the
contrast media has disappeared from the system.
An improved arteriographic technique has been devised which
provides simultaneous visualization of the entire arterial tree of
a lower extremity during a single injection without the use of a
film changer. By this technique, a slow prolonged infusion,
typically 2 ml per second for 20 seconds, is made into the femoral
artery at the groin, immediately followed by a rapidly delivered
bolus, typically 20 ml per second for 2 seconds. On completion of
the injection, the low flow injection has reached the digital
vessels and the final bolus is localized in the distal aorta with
all vessels between being opacified, whereby a single X-ray
exposure may be taken from the aorta to the foot with the film
positioned under the area of interest.
Using this latter technique, peripheral arteriography of the lower
extremities can be accomplished without multiple X-ray exposures,
and without the need for such expensive equipment as rapid flim
changers, moving table top, or tedious flow measurement methods. A
single puncture is made in the femoral artery, followed by low flow
injection down the extremity, high flow retrograde into the aorta,
and a single X-ray exposure from the aorta to the foot. This not
only minimizes the time required for angiography of the
extremities, but also substantially contributes to more complete
opacification and renders exceptionally good filling and
visualization of the critical area.
This biphasic technique has previously been carried out on a
limited scale using hand injections. However, it has been found
that the results obtained by such hand injections were not always
consistent, and the final bolus could not always be delivered
retrograde into the aorta.
SUMMARY OF THE INVENTION
With the foregoing in mind, it is a principal object of this
invention to provide a method for obtaining much more consistent
results using the biphasic technique previously described.
Another object is to provide such a method by which fluid may be
delivered from the injector sequentially at two different rates or
at one rate as desired.
Still another object is to provide such a method which permits
independent selection of both the flow rates and duration of time
of each.
Yet another object is to provide such a method which provides for
sequential injection of fluid at such different flow rates and
times utilizing either manual or automatic controls.
To the accomplishment of the foregoing and related ends, the
invention, then, comprises the features hereinafter fully described
and particularly pointed out in the claims, the following
description and the annexed drawings setting forth in detail a
certain illustrative embodiment of the invention, this being
indicative, however, of but one of the various ways in which the
principles of the invention may be employed.
BRIEF DESCRIPTION OF THE DRAWINGS
In the annexed drawings:
FIG. 1 is a front elevation view of a preferred form of injection
apparatus constructed in accordance with this invention;
FIG. 2 is a fragmentary transverse section through the control
cabinet and syringe assembly of the apparatus of FIG. 1, taken on
the plane of the line 2--2 thereof;
FIG. 3 is a fragmentary isometric view on a somewhat reduced scale
of the control cabinet and syringe assembly illustrating the range
of movements of the syringe assembly relative to the control
cabinet;
FIG. 4 is a top plan view of the syringe assembly of FIG. 2 as seen
from the plane of the line 4--4 thereof;
FIG. 5 is a fragmentary enlarged longitudinal section through the
syringe assembly of FIG. 2, taken on the plane of the line
5--5;
FIG. 6 is an enlarged sectional view of the syringe piston seal of
FIG. 5;
FIG. 7 is a fragmentary transverse section through the syringe
assembly of FIG. 5 taken on the plane of the line 7--7;
FIG. 8 is a schematic diagram showing a control circuit for
controlling the operation of the injector apparatus of FIGS. 1
through 7; and
FIG. 9 is a schematic diagram showing a ground fault interrupter
circuit for providing protection against current leaks to
ground.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now in detail to the drawings and initially to FIGS. 1
and 2 thereof, for carrying out the method of the present
invention, there is shown a preferred form of injection apparatus 1
in accordance with this invention including a syringe assembly 2
and control assembly 3 for controlling the operation thereof in a
manner to be subsequently described. The syringe assembly 2 is
desirably connected to the control assembly by an elongated tube 4
which extends from one side of the syringe assembly box 5 into the
control cabinet 6 as clearly illustrated in FIG. 2.
Within the control cabinet 6 is a support 7 suitably attached to
the base plate 8 and having an opening therethrough in which the
tube 4 is slidably received, permitting both longitudinal and
rotational movement of the syringe assembly 2 relative to the
control assembly 3. A pair of spaced apart stop rods 9 paralleling
the tube 4 limits the extent to which the syringe assembly 2 may be
rotated in either direction for all longitudinal adjusted positions
of the syringe assembly, there being provided a stop screw 10 on
the distal end of the tube 4 which engages one or the other of the
stop rods 9 during rotation of the syringe assembly in opposite
directions to limit such rotation and protect the wiring harness 11
leading from the control assembly to the syringe assembly through
the hollow tube 4 against breakage. The stop screw 10 also limits
the maximum extent to which the syringe assembly 2 may be extended
relative to the control assembly 3 by engagement with the fixed
support 7. Preferably, the disposition of the stop rods 9, only one
of which is shown, is such that the syringe 12 of the syringe
assembly 2 may be tilted a maximum of +150.degree. and -150.degree.
from the vertical as illustrated in FIG. 3, and the syringe
assembly may also be extended from 0 to approximately 18 inches
from the control cabinet 6.
To secure the syringe assembly 2 in the desired longitudinal and
rotational adjusted positions, a lock knob 16 is provided on the
control cabinet 6. Tightening of the lock knob 16 causes the tube 4
to be clamped by a flexible collar 17 on the stationary support 7,
the lock knob being connected to the collar 17 by a threaded rod
18. Further adjustments of the position of the syringe assembly 2
will be permitted upon loosening the lock knob 16 and subsequently
retightening the same after the syringe assembly has been moved to
the desired adjusted position.
For ease of portability of the injector apparatus 1, the control
assembly 3 may be mounted on a mobile support stand 19 with a
triangular base 20 on which are mounted swivel casters 21 as shown
in FIG. 1 to permit the unit to be wheeled about. Each caster 21
desirably includes a separate lock 22 which when turned in one
direction locks the caster against rotation and when turned in the
opposite direction unlocks the caster.
Adjacent the upper end of the stand column 19 may be provided a
column adjustment handle 23 for raising and lowering of the control
assembly 3 and syringe assembly 2 attached thereto. The height of
the injector 1 is desirably adjustable from approximately 38 to 57
inches by rotation of the column adjustment handle 23 in opposite
directions, and a column lock nut 24 is desirably provided for
locking the control assembly and syringe assembly in the desired
vertical adjusted position.
As best seen in FIGS. 5 and 7, the syringe assembly 2 includes a
main support housing 28 to which is bolted a syringe housing 29 for
receipt of the barrel 30 of the syringe 12. The syringe barrel 30
has a radial outwardly projecting flange 31 intermediate the ends
of the barrel for accurately locating and clamping the barrel
within the syringe housing 29. A syringe hold-on nut 32 having
threaded engagement with the OD of the syringe housing 29
releasably retains the syringe barrel 30 within the syringe housing
29, and suitable plastic insulators 33 interposed between the
hold-on nut 32 and syringe barrel 30 and syringe barrel and syringe
housing 29 electrically isolate the syringe barrel from the various
other parts of the apparatus.
Axially extending into the syringe barrel 30 is a ball screw shaft
34 which has a push-pull screw 35 threaded into the forward end
thereof to facilitate positive attachment of a syringe piston 36 to
the ball screw shaft. The syringe piston 36 is shown screwed onto a
screw lock-on nut 37 which has a polygonal shaped recess 38 therein
of a shape corresponding to but slightly larger than the head 39 of
the push-pull screw 35 for receipt of such head within the recess.
The enlarged recess 38 within the screw lock-on nut 37 provides a
radial clearance with the push-pull screw 35 to accommodate any
misalignment between the syringe piston 36 and ball screw shaft 34
while still permitting positive pushing and pulling of the syringe
piston within the syringe barrel 30 during axial inward and outward
movement of the ball screw shaft. Making the nut recess 38 and
screw head 39 of a corresponding polygonal shape also permits
unscrewing of the syringe piston assembly 36 from the ball screw
shaft 34 for sterilization of the syringe piston assembly as
described hereafter.
To maintain a fluid-tight sliding seal between the syringe piston
35 and wall 40 of the syringe barrel 30, the syringe piston may be
provided with an annular external groove 41 containing a Teflon
slipper seal 42, with an O-ring 43 between the slipper seal 42 and
bottom of the groove 41 which acts as a spring for maintaining the
slipper seal in sealing contact with the syringe barrel wall as
clearly shown in FIG. 6.
Threadedly received in the outer end of the syringe barrel 30 is a
see-through syringe cap 45 having a central longitudinal passage 46
therethrough permitting expulsion of the fluid from the syringe
during longitudinal movement of the syringe piston 36 within the
syringe barrel 30 in the direction of the syringe cap. An O-ring 47
is confined between the syringe cap 46 and an internal shoulder 48
on the syringe barrel to provide a fluid seal therebetween.
The inner end of the ball screw shaft 34 is received in a
longitudinally extending generally channel-shape raceway 49 in the
main housing 28 and is retained against rotation by a pair of ball
bearing assemblies 500 disposed on opposite sides of the screw
shaft and connected thereto by a dowel pin 51 extending through the
center of the ball screw shaft and ball bearings. Such ball
bearings 50 absorb any rotational forces applied to the ball screw
shaft 34 and support the inner end of the ball screw shaft for
axial movement in either direction along the raceway 49.
Axial movement of the ball screw shaft 34 is obtained by rotation
of a ball screw nut 55 having threaded engagement with the ball
screw shaft and driven by a gear 56 suitably journaled within a
gear box 57 between the main support housing 28 and the syringe
housing 29 which provides a cover for the gear box.
Rotation of the main gear 56 may be accurately controlled by an
electric motor 58, preferably a DC motor, with suitable motor
mounts 59 being provided for direct attachment of the motor 58 to
the main support housing 28. A suitable clutch mechanism 60 is
desirably used to transmit power from the drive motor 58 to the
main gear 56 to protect the motor against overload and the various
other parts of the syringe against damage in the event that the
syringe piston 36 bottoms out with the motor still running or
limits the pressure build up within the syringe barrel 30 due to
fluid blockage or other reason.
As seen in FIG. 5, the clutch mechanism 60 may comprise a drive
pinion 61 with driven clutch face 62 freely rotatable on the outer
end of the motor shaft 63 and retained in place by a thrust washer
64 and screw 65 attached to the free end of the motor shaft. A
clutch disc 66 keyed to the motor shaft 63 for rotation therewith
is maintained in driving engagement with the driven clutch face 62
by a clutch spring 67 as long as the force required to transmit
axial motion to the ball screw shaft 34 and syringe piston 36 does
not exceed a predetermined level. The clutch spring 67 is confined
between the clutch disc 66 and a clutch spring retainer 68 retained
on the motor shaft by a snap ring 69 or the like.
The axial location of the syringe piston 36 within the syringe
barrel 30 is indicated by a syringe piston position indicating rod
70 attached to the inner end of the ball screw shaft 34. The
position indicating rod 70 may be secured in place by a set screw
71 threaded into a recess in the inner end of the ball screw shaft.
The sheet metal cover 5 which surrounds the syringe assembly 2 has
a longitudinally extending slot 72 in the top panel thereof for
receipt of the upper end of the position indicator rod making it
visible to the operator. A piston position indicator sight glass 73
is shown covering the longitudinally extending slot 72 and retained
in place by a pair of mounting brackets 74 suitably fastened to the
cover 5 at opposite ends of the slot. As clearly shown in FIGS. 3
and 4, the sight glass 73 may have suitable indicia thereon and the
sides of the longitudinal slot may have a calibrated scale to
indicate the actual volume of contrast agent in the syringe 12 from
0 to 120cc indicated by the position of the indicator rod 70 with
respect to the calibrated scale. A pair of limit switches 75, 76
mounted in spaced apart relation on the main support housing 28
adjacent the raceway 49 are engaged by the position indicator rod
70 when the syringe piston 36 reaches either end of its stroke to
shut off the motor 58.
The main support housing 28, in addition to providing a gear box 57
and raceway 49 for the ball screw shaft 34 and support for the
syringe drive motor 58 and limit switches 75, 76 therefor, also
contains a recess 78 for receipt of one end of the tube 4 which
connects the syringe assembly 2 to the control assembly 3. As
cleary shown in FIG. 7, the connecting tube 4 is retained in place
within the recess 78 in the main support housing 28 by a bolt 79. A
mounting ring 80 surrounding the connecting tube 4 is attached to
the main support housing 28 by suitable fasteners to secure the
sheet metal cover 5 to the main support housing. A weight 81 is
also suitably attached to the main support housing 28 or motor 58
to locate the center of gravity of the syringe assembly 2 closely
adjacent the axis of the tube 4 to facilitate tilting of the
syringe assembly to any desired position as previously
described.
Surrounding the syringe barrel 30 is a thermostatically controlled
syringe blanket 85 for heating the contrast media from room
temperature to 96.degree. to 100.degree.F and maintaining such
temperature within twenty minutes after filling the syringe and
turning on the main power. Both the blanket and thermostat 85 are
desirably molded in rubber and insulated from the syringe 12.
The syringe is also electrically insulated from the syringe housing
29 by the plastic spacers 33 previously described, and the injector
apparatus 1 has a ground clip 86 which is connected to the ground
pin on the power cord 87. A ground fault interrupter circuit to be
later described is also desirably provided to remove the power from
the motor and controls and provide a signal or alarm whenever there
is a current leakage to ground exceeding 0.5 milliamps.
Both the main support housing 28 and syringe housing 29 are
desirably made of aluminum for reduced weight, whereas the syringe
barrel 30 is desirably made of a non-corrosive high strength
material such as stainless steel. The see-through syringe cap 45 is
desirably made of polycarbonate and the syringe piston 36 of
delrin, both autoclavable to 250.degree.F for sterilization.
The various parts of the syringe 12 are disassembled to permit
sterilization thereof. Before disassembling the syringe, the
syringe piston 36 is desirably moved to the 0cc position as
indicated by the volume indicator rod 70. Then the large nut 32
holding the syringe to the syringe housing 29 may be removed to
permit the see-through syringe cap 45 and syringe barrel 30 to be
pulled out of the syringe housing. Next the see-through syringe cap
45 may be unscrewed from the syringe barrel 30 and the O-ring 47
removed, after which the syringe piston assembly 36 may be
unscrewed from the ball screw shaft 34, leaving the cap seal 42, 43
on the syringe piston.
After the various syringe parts have been sterilized, the syringe
piston 36 is screwed back onto the ball screw shaft 34 and the
syringe barrel 30 is pushed into place and retained therein by
screwing the large nut 32 back on to firmly clamp the radial flange
31 on the syringe barrel in place adjacent the end of the syringe
housing 29.
Next the syringe piston 36 is retracted until the indicator reading
corresponds to the desired volume of contrast media with which the
syringe is to be filled. Then the lock knob 16 on the control
cabinet 6 is loosened to permit the syringe assembly 2 to be
rotated until the syringe 12 is pointing vertically upward so that
the contrast media may be poured directly into the syringe barrel,
keeping the fluid level below the O-ring groove 48.
Before filling the syringe barrel, the O-ring 47 is inserted into
the O-ring groove 48 and afterwards the see-through cap 45 is
screwed into the barrel until it bottoms against the O-ring. Next
one end of a catheter may be connected to the luer loc fitting on
the see-through syringe cap 45 and the other end inserted into an
empty contrast media bottle to permit the syringe piston 36 to be
moved slightly forward to express any trapped air from the syringe
or catheter. Finally, the lock knob 16 is loosened and the syringe
assembly 2 rotated until the tip of the syringe 12 is pointing down
from the horizontal at a maximum angle from the horizontal of
approximately 60.degree..
Suitable controls are provided on the control panel 88 which permit
selection of two different flow rates for two different periods of
time. Separate control knobs are provided for selecting each rate
of flow in cubic centimeters per second and the time of each flow
rate in seconds. The first slow inject flow control knob 89 permits
a selection of a flow rate of anywhere from 0.3 to 10cc per second
for a period of time anywhere from off to 25 seconds as determined
by the setting of a second control knob or dial 90. The first rapid
inject flow control knob 91 permits the selection of a flow control
rate of anywhere from 5 to 40cc per second for a period of time
anywhere from off to 6 seconds as determined by still another
control knob 92. The product of the flow rate and time for each of
the slow and rapid inject phases will determine the volume of fluid
injected during each phase of injection.
An additional control knob 93 may also be provided on the control
panel 88 for selecting a delay period, for example, from 0 to 2
seconds after completion of the entire injection phase for
triggering the X-ray exposure. An X-ray cable connector 94 is shown
for connecting the control box to an X-ray machine.
Also provided on the control panel 88 are a lighted on-off power
switch 95 which includes a 20 amp circuit breaker, a manual loading
and unloading switch 96, and a lighted armed/unarmed selector
switch 97. The manual loading or unloading switch 96 is used to
fill or empty the syringe 12 when the armed/unarmed switch 97 is in
the unarmed position. When the armed/unarmed switch 97 is in the
armed position, the unit may be operated by a remote control or
hand trigger switch 98 to inject contrast media into a patient
either manually or automatically as described hereafter.
A lighted safe/unsafe ground fault interrupter switch 99 and
associated circuit detects current leaks to ground above .5
milliamps, and automatically moves from the safe to unsafe position
when the power switch 95 is on to remove power from the control and
syringe assemblies. A ground fault interrupter push to test switch
100 is also provided for checking the operation of the ground fault
interrupter circuit. Correct operation of the ground fault
interrupter circuit is indicated during a test when the unsafe
light comes on and an audible alarm sounds. To turn the unsafe
light off and stop the audible alarm after completion of a test
merely requires pushing the safe/unsafe switch 99 to the safe
position.
With the armed/unarmed switch 97 in the armed position, depressing
and releasing the automatic position on the hand trigger switch 98
will cause the injector apparatus 1 to automatically sequentially
inject the two different flow rates selected on the flow and rapid
inject flow rate and time control dials 89, 90 and 91, 92,
respectively. However, the injection may be stopped at any time
during the automatic injection phase by depressing and releasing
the manual position on the hand trigger switch 98. Alternatively,
the entire injection phase will remain under the direct control of
the operator by pressing the manual position on the hand trigger
switch. Releasing the manual position on the hand trigger switch at
any time will immediately stop the injection.
Having thus described the various parts of the injector apparatus,
a brief description of its operation will be set forth.
OPERATION
To operate the injector apparatus 1, the control assembly 3 should
first be raised to the desired height by loosening the stand lock
knob 24 and rotating the stand adjustment handle 23 to raise or
lower the control and syringe assemblies 3, 2 to the desired
height, after which the lock knob may be tightened to hold such
assemblies in the desired vertical adjusted position. The power
cord 87 should then be plugged into a suitable power source and the
lighted main power switch 95 turned on, followed by a testing of
the ground fault interrupter circuit as previously described. If
the ground fault interrupter circuit checks out properly, the
safe/unsafe switch 99 should be pushed to the safe position to turn
off the unsafe light and stop the audible alarm which should have
gone on when the test switch 100 was depressed to indicate a
correct operation of the ground fault interrupter circuit.
The load/unload switch 96 should then be held in the unload
position until the syringe piston 36 is at the 0cc position to
facilitate disassembly and sterilization of the syringe as
previously described. After sterilization, the syringe piston 36
and syringe barrel 30 should be reassembled and with the
armed/unarmed switch 97 in the unarmed position the load/unload
switch 96 moved to the load position to retract the syringe piston
to the desired volume of contrast media as shown on the indicator
rod 70. Then the cabinet lock knob 16 should be loosened to permit
the syringe assembly 2 to be rotated until the syringe 12 extends
vertically upward and with O-ring 47 in place the contrast media
may be poured into the syringe barrel, keeping the fluid level
below the O-ring groove 48. After filling, the syringe cap 45
should be threaded into position in the upper end of the syringe
barrel 30.
Next one end of a catheter may be connected to the syringe cap 45
and the other end inserted into an empty contrast media bottle so
that the unload switch 96 may be depressed to express any trapped
air in the syringe or catheter.
Thereafter the cabinet lock knob 16 should be loosened to permit
the syringe 12 to be rotated until its tip is pointing down from
the horizontal. The syringe assembly 2 may also be extended
horizontally from the control assembly 3 to the extent desired,
followed by a tightening of the cabinet lock knob to lock the
syringe in the desired position.
Next both the slow inject control knobs 89 and 90 and rapid inject
control knobs 91 and 92 should be set to the desired flow rates and
periods of time for each flow rate, and the X-ray delay control
knob 93 should also be set to the desired time delay for the X-ray
exposure after completion of the entire injection phase. The X-ray
cable 94 should also be properly connected both to the control
assembly 3 and to the X-ray machine.
The injector apparatus 1 is now ready to be used to inject contrast
media or other fluid into the patient after the catheter needle has
been properly inserted. The injection phase is under the control of
the hand trigger switch 98 as soon as the armed/unarmed selector
switch 97 is moved to the armed position, whereby movement of the
hand trigger switch either to the automatic or manual positions
will cause the contrast media to be injected into the patient. When
the hand trigger switch 98 is depressed in the automatic direction,
the switch may be released and the injector apparatus will still
continue to inject the fluid into the patient in accordance with
the programmed flow rates and times. However, such procedure may be
interrupted at any time by depressing the hand trigger switch 98 in
the manual direction and releasing it. Moving the hand trigger
switch 98 in the manual direction requires the operator to continue
to press the switch during manual injection since releasing the
trigger switch after pushing it in the manual direction will
immediately stop the injection.
On completion of the injection, the X-ray machine will be
automatically triggered after a time delay of from 0 to 2 seconds
as determined by the setting of the X-ray delay control knob 93. By
then the earliest delivered contrast media has reached the digital
vessels, while the final bolus is in the distal aorta with all
vessels in between opacified. The X-ray source is desirably
elevated maximally, preferably to 6 feet, and the X-ray film is
positioned along the entire length under study, with appropriate
filters. A single, long film holder is preferred, but multiple,
overlapping film holders may also be used.
THE CONTROL CIRCUIT
FIG. 8 is a schematic diagram of the primary control circuit 105
for controlling the operation of the injection apparatus 1
previously described. Included in the circuit is the circuit
breaker and on-off switch 95 which must be depressed to energize
the circuit. A light 106 signals that the power is on, and the
circuit breaker 107 protects the circuit against an overload. The
power to the circuit passes through a differential transformer 108
which produces a signal in the transformer core 109 whenever the
current through the two coils 110, 111 is different, as when there
is a current leakage to ground. This signal is picked up by the
output coil 112 of a ground fault interrupter amplifier circuit
115, schematically illustrated in FIG. 9, which amplifies the
signal to energize a relay R1, causing the safe/unsafe switch 99 to
open thereby removing the power from the motor and controls. When
this occurs, a second relay R2 is deenergized causing the
associated switch S2 to close which lights the unsafe light 116 and
sounds a buzzer or alarm 117. Such a ground fault interrupter
circuit 115 is desirably sufficiently sensitive to detect current
leaks to ground above 0.5 milliamps.
The ground fault interrupter test switch 100 is connected to a
suitable resistor 118 for simulating a current leakage when the
test switch 100 is depressed to check the operation of the fault
interrupter circuit 115. Correct operation of the ground fault
interrupter circuit 115 is indicated when, upon pushing the test
switch 100, the unsafe light 116 goes on and the buzzer or alarm
117 sounds.
To reactivate the primary control circuit 105 upon release of the
test switch 100, the operator need only depress the ground fault
interrupter switch 99 to energize the relay R2 which opens the
portion of the circuit including the unsafe light 116 and buzzer
117 causing them to be turned off.
When the primary control circuit 105 is energized, power is
supplied to the heater 85 surrounding the syringe barrel 30 which
is controlled by the thermostat 120 to heat the contrast media from
room temperature to approximately 96.degree. to 100.degree.F and
maintain the contrast media at that temperature.
The armed/unarmed selector switch 97 may be moved between the
unarmed position shown in FIG. 6 in which operation of the syringe
drive motor 58 may be manually controlled by the loading and
unloading switch 96 and the armed position in which such motor may
be controlled by the hand trigger switch 98. When the armed/unarmed
selector switch 97 is in the unarmed position shown, the hand
trigger switch 98 is taken out of the primary control circuit and
the load/unload switch 96 is in the circuit permitting manual
operation of the syringe drive motor 58 in opposite directions by
moving the load/unload switch to the load and unload positions for
respectively filling or emptying the syringe 12.
When the load/unload switch 96 is moved to the unload position, the
relay R3 is activated which closes the associated motor contacts C3
causing the motor to extend the syringe piston 36 for unloading the
syringe. Movement of the load/unload switch 96 to the load position
activates another relay R4 which closes its respective motor
contacts C4 causing the direction of rotation of the motor 58 to be
reversed to retract the syringe piston 36 for loading the
syringe.
The speed of the drive motor 58 when under the control of the
load/unload switch 96 is desirably greater during operation in the
loading direction than in the unloading direction and is controlled
by the amount of resistance in the SCR firing circuit. A field
relay FR in the load/unload circuit activates its associated
contacts CF1 when the load/unload switch is moved either to the
load or unload positions to supply current to the motor field
circuit. A manual relay MR switches between the two motor speeds
for loading and unloading the syringe. When the switch 96 is moved
to the unload position, the manual relay MR is energized, causing
the associated contact CM1 to be opened, whereby the speed of the
motor 58 is controlled by the resistor 125 for unloading the
syringe, whereas when the switch 96 is moved to the load position,
the manual relay MR is not energized, causing the associated
contact CM1 to be closed, whereby the speed of the motor is
controlled by the resistor 126 for loading the syringe.
Since the speed of the syringe piston 36 need not be adjustable
during the manual load and unload modes, fixed resistors 125, 126
may be used to control the speed of the motor during such modes.
Preferably, such resistors 125, 126 are selected so that when the
load/unload switch 96 is moved to the load position the syringe
piston will be retracted to fill the syringe at a rate of
approximately 6cc per second and when the switch 96 is moved to the
unload position the syringe will be extended to empty the syringe
at a rate of approximately 1.3cc per second. Separate limit
switches 75 and 76 are provided in the unload and load circuits,
respectively, for opening their respective contacts when the
syringe piston 36 reaches the respective ends of its stroke.
Movement of the armed/unarmed switch 97 to the armed position
removes the load/unload switch 96 from the primary control circuit
and readies the circuit for the injection phase through actuation
of the hand trigger or remote control switch 98. The position of
the armed/unarmed switch 97 may readily be indicated by providing
indicator lights 127 and 128 in the respective armed and unarmed
circuits. Current is continuously supplied to the motor field
windings when the injector apparatus is in the armed mode to avoid
any time lag in building up the magnetic field during the normal
injection phase, whereas during the unarmed mode, the motor field
is only turned on when the field relay FR is energized by movement
of the load/unload switch 96 to either of the load or unload
positions.
During the armed mode, the two manual motor speed resistors 125 and
126 are removed from the primary control circuit and the hand
trigger or remote control switch 98 is operative to control the
movement of the syringe piston 36 in the injection direction only.
The hand trigger switch 98 desirably includes both an automatic
position 130 and an off/manual position 131. When the switch 98 is
moved to the automatic position 130, the relay R6 is activated
causing the associated contacts C6, C6 to close, and such contacts
C6, C6 will remain closed even though the hand trigger switch 98 is
released to cause automatic sequential injection of the fluid as
determined by the settings of the slow and rapid inject control
knobs 89, 90 and 91, 92. However, the injection may be stopped at
any time during the automatic injection phase by moving the switch
98 to the off/manual position 131 and releasing the switch. When
the switch 98 is moved to the off/manual position, it activates the
jog relay R7 which opens the contact C7 in the automatic control
circuit, deenergizing the relay R6 and opening the associated
contacts C6, C6 whereby when the switch 98 is then released, the
injector motor will stop. Movement of the switch 98 to the off or
manual position also causes the jog relay R7 to close another
contact C7' for manual operation of the injector during the armed
mode. Releasing the switch 98 from the manual position will
automatically stop the injection.
When the hand trigger switch 98 is moved either to the automatic or
manual positions 130 or 131, a relay LR is energized which closes
its associated contact CL for controlling the speed of the drive
motor during slow injection as determined by the setting of the
potentiometer control knob 89. A time delay relay T1 is energized
at the end of its timing cycle as set by the slow inject time
potentiometer control knob 90 to open the contact CT1 associated
with the slow inject potentiometer control knob 89 and close the
contact CT1' associated with the rapid inject potentiometer control
knob 91 for automatically switching from slow inject to rapid
inject at the end of the slow inject time. The time delay relay T1
also closes a switch CT1" for actuating a second time delay relay
T2 at the end of its timing as set by the rapid inject time control
knob 92. When the time delay relay T2 is energized, it closes the
contact CT2 for activating the X-ray time delay relay T3 after a
delay of from 0 to 2 seconds as set on the X-ray delay control knob
93. If the syringe piston 36 reaches the end of its stroke during
the armed mode before the relay T3 is activated, the limit switch
132 will be tripped, stopping the drive motor 58 and activating the
X-ray time delay relay T3 as previously described. The relay
contacts C3', C4' on the motor provide dynamic braking when both
contacts are closed by creating a magnetic field which brakes the
motor, as well known in the art. the art.
Although a single drive motor 58 is shown, it will be apparent that
two different speed drive motors may be used for the slow and rapid
modes of injection, respectively. Alternatively, two different gear
boxes may be used in conjunction with a single drive motor, with
clutches to switch the motor from one gear box to the other for
slow and rapid injection.
Conventional feedback controls such as disclosed in U.S. Pat. Nos.
3,623,474 and 3,631,847 may also be provided for measuring and
controlling the speed of the syringe piston throughout the period
of injection to obtain predictable, controlled flow rates under
varying conditions. Alternatively, various other control systems
may be used to accomplish substantially the same results,
including, for example, an optical feedback to monitor the motor
speed; a highly regulated DC power supply wherein the voltage
supplied to the motor is monitored and fed back to control the
power supply; or an open loop frequency control system utilizing an
RC circuit with a variable resistance and a unijunction transistor
to create a variable frequency pulse to operate the motor.
From the foregoing, it will now be apparent that the method and
apparatus of the present invention minimize the time required for
angiography of the extremities, reduce the amount of apparatus, and
substantially contribute to more complete opacification and
visualization. Such a method and apparatus also make X-ray exposure
minimal with fewer injections and smaller volumes of contrast
media. The injector apparatus may also be used for other
arteriographic procedures as well, including conventional
angiography, by using either the slow inject or rapid inject modes
separately. The controls for the mode not used are simply set at
"0".
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