US3674009A - Angiographic injector with pump motor starting control - Google Patents

Abstract

The angiographic injector disclosed herein employs a pump motor which is gradually and progressively energized to prevent whipping of the catheter tip. The energization of the motor is varied as a function of a control signal voltage which rises relatively gradually, the motor being energized from an a.c. source through a triggerable semiconductor current switching device whose firing angle is varied as a function of the amplitude of the control signal voltage.

Description

United States Patent Williamson 1451 July 4, 1972 [$4] ANGIOGRAPHIC INJECTOR WITH PUMP MOTOR STARTING CONTROL [72] Inventor: Donald E. Williamson, Miami, Fla.

[73] Assignee: Coulis Corporation, Miami, Fla.

[22] Filed: July 13, 1970 [21] Appl.No.: 54,430

[52] 0.5. CI. ..l28/2 A, 128/218 A, 128/01, 318/599 51 Int. Cl. ..A61b 5/02 [58] measures ..128/2 A,2R,2.05 F,2.05 R,

128/218 A, DIG. 1, 13; 318/599, 684, 227, 345; 331/111; 328/185; 307/263, 265, 301, 315

[56] References Cited UN lTED STATES PATENTS 3,415,419 12/1968 Jewett et al ..128/2l8 A 3,573,580 4/1971 Shinozaki ..3 18/227 3,156,236 11/1964 Williamson. .l28/2.05 R 3,192,449 6/1965 Brockett.. ..307/315 3,571,696 3/1971 Liska ..307I301 3,447,055 5/1969 Mason ..3 18/345 3 ,192,462 6/1965 James ..318/345 Primary Examiner-William E. Kamm Attorney-Kemvay, Jenney & Hildreth [57] ABSTRACT The angiographic injector disclosed herein employs a pump motor which is gradually and progressively energized to prevent whipping of the catheter tip. The energization of the motor is varied as a function of a control signal voltage which rises relatively gradually, the motor being energized from an a.c. source through a triggerable semiconductor current switching device whose firing angle is varied as a function of the amplitude of the control signal voltage.

2 Claims, 3 Drawing Figures PATENTEUJUL 41m 3. 674.009

SHEET 1 or 2 oo m JJ mod 20 4:: E P E i c958 E glL FIG.|

INVENTOR DONALD E.WHiJAMSON BY WHM ATTORNEYS RIO INVENTOR DONALD E. WILLIAMSON B ATTORNEYS ANGIOGRAPIIIC INJECTOR WITH PUMP MOTOR STARTING CONTROL BACKGROUND OF THE INVENTION This invention relates to an angiographic injector and more particularly to such an injector providing an injection pressure which rises relatively gradually thereby to prevent whipping of the catheter tip.

Angiographic injectors are employed in studying the functioning of a patients arterial system. The purpose of the injector is to introduce, through a long, thin, hollow catheter, materials which are radio-opaque, that is, which will provide contrast for X-ray photography. Typically, the catheter is introduced into the arterial system through a vessel which passes relatively close to the patientss skin so as to minimize the insertion wound. The catheter is then threaded by the surgeon to that part of the arterial system under study. Typically, it is desirable that the injection of material be relatively precisely controlled in time so that synchronization of the injection with the X-ray photography or with the patient's heart heat can be provided. Accordingly, in certain circumstances it may be necessary to employ relatively high injection pressures. In various applications, however, a rapid onset of a relatively high injection pressure will cause the tip of the catheter to whip, that is, to move violently sideways in an oscillatory motion which continues for the duration of the injection. This motion is objectionable and may itself cause injury.

According to one aspect of the present invention, it has been found that the occurrence of this whipping motion can be eliminated by a relatively gradual application of pressure, even though relatively high pressures are ultimately reached. This progressive application of the pressure causes the tip of the catheter to move relatively slowly against the wall of the cavity or vessel in which it is positioned and to then be held there as the pressure increases.

Among the several objects of the present invention may be noted the provision of an angiographic injector in which injection pressure builds up relatively gradually; the provision of such an injector in which the rate of pressure build-up may be controlled and adjusted; the provision of such an injector in which the ultimate pressure level is readily adjustable; the provision of such an injector which prevents catheter whipping; the provision of such apparatus which is highly reliable and which is relatively simple and inexpensive. Other objects and features will be in part apparent and in part pointed out hereinafter.

SUMMARY OF THE INVENTION The angiographic injector of the present invention employs an electric motor to pump radiosopaque material through a catheter which is adapted to be inserted into a patient's vascular system. Whipping of the tip of the catheter is prevented by gradually and progressively energizing the motor at the start of an injection cycle. The motor is connected to an 21.0. power source through a triggerable semiconductor current switching device so that the energization of the motor is variable as a function of the phase angle of triggering of the switching device. A control signal voltage is generated which rises gradually over a plurality of cycles of the ac. source frequency, starting at a preselectable time. Further, means are provided for repetitively triggering the switching device at a phase angle which varies as a function of the amplitude of the control signal voltage, the phase angle being progressively advanced. Accordingly, the motor is progressively energized and whipping of the catheter tip is prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a somewhat diagrammatic illustration of an angiographic injector according to the present invention;

FIG. 2 is a schematic circuit diagram of motor control apparatus employed in the FIG. 1 injector; and

FIG. 3 is a graphical representation of various waveforms occurring in the circuit of FIG. 2.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, there is indicated at 11 generally, the mechanical injector assembly employed in the illustrative embodiment of apparatus constructed in accordance with the present invention. This assembly may, for example, be essentially the same as that disclosed in my earlier U.S. Pat. No. 3,156,236. For the purposes of the present invention it may be briefly noted that this assembly comprises a piston pump I3, an electric motor 15 for driving the pump, and a low friction ball-nut assembly 17 for converting the rotary motion of motor 15 to a linear motion suitable for operating the piston of the pump. The pump 13 provides radio-opaque contrast material to an elongate catheter 14 for injection into a patients vascular system in conventional manner.

As is disclosed in the aforementioned patent, motor 15 is preferably of the permanent split capacitor type, although other motors adaptable to this kind of operation can be used. At speeds substantially below synchronous speed, the permanent split type of motor provides a substantially constant output torque for a given level of energization. Thus, the injection pressure may be controlled as a predictable and controllable function of energization of the motor 15. While an electric motor has been illustrated as a preferred means of providing an electrically controllable force, an electrically operated clutch or solenoid may also be used as a force control, e.g. in conjunction with a separate mechanical or hydraulic power source. Thus, as used herein, the term motor means should be understood in its broad sense to include such equivalents.

In accordance with the present invention, the energization of motor 15 is controlled by means of a substantially conventional solid-state motor power controller 19. Motor control I9 is of the type which employs a tn'ggerable semiconductor eurrent-switching device, e.g. a silicon-controlled rectifier (SCR) or a triac. Such power controls are known in the art and, accordingly, are not described in detail herein. As is understood in the art, the level of energization of motor 15 can be controlled as a function of the phase angle of firing of the triggersble current-switching device. Triggering pulses suitable for firing such a current-switching device are applied to the motor controller 19 through a pulse transfonner TI from a programmable firing-angle control 21. As will be described in greater detail hereinafter, control 21 includes a switch S1 whose operation controls the duration of an injection cycle and a variable resistance R8 for controlling the rate at which pressure is built up in the injector pump 13. Control 2| may also include various timers and reversing switches (not shown) for controlling the operation of motor 15 as is conventional in this art.

In the firing angle control 21 illustrated in FIG. 2, ac. power is applied to a bridge rectifier DI through the switch S1. The pulsating dc. voltage provided by the bridge D1 is applied, through a pair of dropping resistors RI and R2, to a Zener diode D2 so as to provide, between a pair of leads L3 and L4, a clipped waveform substantially as illustrated at A in FIG. 3.

The firing angle control employs a relaxation oscillator which comprises a unijunction transistor ()2. The base-one circuit of this transistor is connected to the primary winding of pulse transformer T1, as illustrated. The base-two terminal of unijunction transistor 02 is connected, through a load resistor R3, to the junction between dropping resistors RI and R2. This intermediate connection of the unijunction transistor somewhat spoils the regulation to transistor 02 provided by the Zener diode D2, with regard to the operation of the relaxation oscillator, in a manner tending to compensate for the effect of line voltage variation upon the operation of the motor 15.

The relaxation oscillator also comprises a timing capacitor C2 which receives charging current from two sources, a resistor R4 which is connected to the positive supply lead L3 and the emitter output terminal of a Darlington pair amplifier Ql. The collectors of the Darlington pair are connected to the positive supply lead through a common load resistor R5 As is understood by those skilled in the art, the unijunction transistor 02 is a form of voltage breakdown device and when the voltage on capacitor C2 reaches the firing threshold which is determined by the transistors intrinsic standoff ratio, the transistor fires, discharging the timing capacitor and delivering a pulse to the primary winding of transformer Tl.

A voltage divider comprising a pair of resistors R6 and R10 and a potentiometer R9 is connected across the supply leads L3 and L4 for providing a voltage which is a preselectable por tion of the total pulsating dc. voltage. A current which is proportional to this preselected voltage portion is applied, through the variable resistance R8, to a capacitor C1. As is described hereinafter, the rate of charging of capacitor C1 determines the rate at which pressure builds up in the injector. The voltage on capacitor C1 is applied, through a currentlirniting resistor R7, to the input terminal of the Darlington pair amplifier Q1.

The operation of this apparatus is substantially as follows. It is assumed initially that switch St is open and has been open long enough so that the timing capacitors Cl and C2 are substantially discharged. Upon closing the switch S], the ac. supply voltage is applied to the motor and motor power controller but no current flows through the motor circuit until triggering pulses are applied to the motor power controller 19. Since the capacitor C1 is initially discharged, substantially the only current available to charge capacitor C2 during the first ac half-cycle will be that provided through resistor R4. Accordingly, the voltage on capacitor C2 will reach the firing potential of the unijunction transistor Q2 only toward the end of each ac half-cycle and thus the level of energization of motor will be relatively low.

Gradually, however, the voltage on capacitor C1 will rise, turning on the Darlington pair and causing it to provide a component of charging current to the capacitor C2 during a portion of each half cycle. The value of this component is determined essentially by the value of resistor R5, the Darlington amplifier being operated in saturation. This added component of charging current is provided, during each half cycle, until the voltage on capacitor C2 substantially reaches the level of the voltage on capacitor C1, the base-emitter offset voltages being ignored, since at this point the Darlington pair turns off. From this point on until the unijunction transistor fires, the charging current is provided substantially only by the resistor R4. The waveform generated across capacitor C2 is represented at B in FIG. 3 and it can be seen that this waveform has a break or knee at a point which varies from cycle to cycle as capacitor C1 charges. From FIG. 3 it can further be seen that, as capacitor C1 charges, the unijunction transistor ()2 reaches its firing point, designated E earlier in each a.c. half-cycle. Accordingly, the motor power controller 19 is progressively fired at earlier phase angles. As the energization of the motor 15 is thus gradually and progressively increased, following the closing of switch S1, it can also be seen that the pressure in the injector will gradually and progressively rise starting from the initiation of an injection cycle. After the unijunction transistor fires in each half cycle, it is kept in conduction for the rest of the half cycle by current provided through the Darlington pair 01 and then turned off at the end of the half cycle when the pulsating voltage provided by the bridge rectifier Dl drops to zero. In this way, the charging of capacitor C2 starts from a repeatable starting point for each half cycle.

Since the charging current provided to capacitor Cl is variable as a function of the setting of rheostat R8, the rate at which pressure increases following initiation can be adjusted by varying the setting of this rheostat. If only a predetermined rate of rise is needed, a fixed resistance may be used in place of rheostat R8.

In view of the foregoing, it may be seen that several objects of the present invention are achieved and other advantageous results have been attained. 4

As various changes could be made in the above construction without departing from the scope of the invention, it should be understood that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: 1. An angiographic injector comprising: a catheter adapted to be inserted into a patients vascular system; a pump for propelling radio-opaque material through said catheter; an electric motor for driving said pump; at least one semiconductor current control device; means for connecting said motor means to an electric power source through said current control device so that the energization of said motor means is controllably variable; means for generating a control signal having an amplitude which varies in accordance with a predetermined gradual time function having a preselectable time constant, starting at a controllable point in time, said generating means including means for adjusting said time constant; means for varying the conduction of said current control device as a function of said control signal to progressively energize said motor means and thereby prevent whipping of the catheter tip. 2. An angiographic injector comprising: a catheter adapted to be inserted into a patients vascular system; a pump for propelling radio-opaque material through said catheter; an electric motor for driving said pump; at least one triggerable semiconductor current switching device; means for connecting said motor to an ac power source through said current switching device so that the energization of said motor is variable as a function of the phase angle of triggering of said switching device relative to the phasing of the source power; a first capacitor; means for applying a preselectable d.c. charging current to said first capacitor when said motor is energized thereby to generate a control signal voltage which changes gradually over a plurality of cycles of said a.c. source, said charging current applying means including means for manually adjusting the value of said charging current; a timing capacitor; means for applying a first charging current component to said timing capacitor; means for applying a second charging current component to said timing capacitor when the timing capacitor voltage is below said control signal voltage; and a voltage breakdown device interconnected with said timing capacitor to generate a pulse for firing said triggerable semiconductor current switching device within each half cycle of the source a.c. when the voltage on said timing capacitor reaches a predetermined value, the phase angle of firing being progressively advanced relative to the phasing of the source power, whereby said motor is progressively energized and whipping of the catheter tip is prevented.

Claims (2)

1. An angiographic injector comprising: a catheter adapted to be inserted into a patient''s vascular system; a pump for propelling radio-opaque material through said catheter; an electric motor for driving said pump; at least one semiconductor current control device; means for connecting said motor means to an electric power source through said current control device so that the energization of said motor means is controllably variable; means for generating a control signal having an amplitude which varies in accordance with a predetermined gradual time function having a preselectable time constant, starting at a controllable point in time, said generating means including means for adjusting said time constant; means for varying the conduction of said current control device as a function of said control signal to progressively energize said motor means and thereby prevent whipping of the catheter tip.

2. An angiographic injector comprising: a catheter adapted to be inserted into a patient''s vascular system; a pump for propelling radio-opaque material through said catheter; an electric motor for driving said pump; at least one triggerable semiconductor current switching device; means for connecting said motor to an a.c. power source through said current switching device so that the energization of said motor is variable as a function of the phase angle of triggering of said switching device relative to the phasing of the source power; a first capacitor; means for applying a preselectable d.c. charging current to said first capacitor when said motor is energized thereby to generate a control signal voltage which changes gradually over a plurality of cycles of said a.c. source, said charging current applying means including means for manualLy adjusting the value of said charging current; a timing capacitor; means for applying a first charging current component to said timing capacitor; means for applying a second charging current component to said timing capacitor when the timing capacitor voltage is below said control signal voltage; and a voltage breakdown device interconnected with said timing capacitor to generate a pulse for firing said triggerable semiconductor current switching device within each half cycle of the source a.c. when the voltage on said timing capacitor reaches a predetermined value, the phase angle of firing being progressively advanced relative to the phasing of the source power, whereby said motor is progressively energized and whipping of the catheter tip is prevented.

Images