Patent Publication Number: US-6221045-B1

Title: Angiographic injector system with automatic high/low pressure switching

Description:
This application is a continuation-in-part U.S. Ser. No. 08/946,667, filed Oct. 7, 1997, entitled Angiographic System with Automatic High/Low Pressure Switching, which is a file wrapper continuation application of U.S. Ser. No. 08/426,148 filed on Apr. 20, 1995, which applications are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to angiography and more specifically, the injector system used to inject a medical fluid such as radiographic contrast material into living organisms. 
     BACKGROUND OF THE INVENTION 
     One of the major systems in the human body is the circulatory system. Components of the circulatory system include the heart, blood vessels, and blood, all of which are vital for the transportation of materials between the external environment and the cells and tissues of the body. 
     The blood vessels are the network of passageways through which blood travels in a human or animal body. Specifically, the arteries carry oxygenated blood away from the left ventricle of the heart. The arteries are arranged in progressively decreasing diameter and pressure capability from the aorta, which carries the blood immediately out of the heart to other major arteries, to smaller arteries, to arterioles, and finally to capillaries, where exchange of nutrients and waste products between the blood and the cells and tissues of the body occur. Generally, veins carry oxygen depleted blood back to the right atrium of the heart using a progressively increasing diameter network of venules and veins. 
     Angiography is a procedure used in the diagnosis and treatment of cardiovascular conditions including abnormalities or restrictions in blood vessels. During angiography, a radiographic image of the heart or a vascular structure is obtained by injecting a radiographic contrast material through a catheter into a vein or artery. The injected contrast material can pass to vascular structures in fluid communication with the vein or artery in which the injection is made. X-rays are passed through the region of the body in which the contrast material was injected. The X-rays are absorbed by the contrast material, causing a radiographic outline or image of the blood vessel containing the contrast material. The x-ray images of the blood vessels filled with contrast material are usually recorded onto film or videotape and are displayed on a fluoroscope monitor. 
     Angiography provides an image of the cardiac or vascular structures in question. This image may be used solely for diagnostic purposes, or the image may be used during a procedure such as angioplasty where a balloon is inserted into the vascular system and inflated to open a stenosis caused by atherosclerotic plaque buildup. 
     Currently, during angiography, after a catheter is placed into a vein or artery (by direct insertion into the vessel or through a skin puncture site), the angiographic catheter is connected to either a manual or an automatic contrast injection mechanism. 
     A simple manual contrast injection system typically has a syringe and a catheter connection. The syringe includes a chamber with a plunger therein. Radiographic contrast material is suctioned into the chamber. Any air is removed by actuating the plunger while the catheter connection is facing upward so that any air, which floats on the radiographic contrast material, is ejected from the chamber. The catheter connection is then attached to a catheter that is positioned in a vein or artery in the patient. 
     The plunger is manually actuated to eject the radiographic contrast material from the chamber, through the catheter, and into a vein or artery. The user of the manual contrast injection system may adjust the rate and volume of injection by altering the manual actuation force applied to the plunger. 
     Often, more than one type of fluid injection is desired, such as a saline flush followed by the radiographic contrast material. One of the most common manual injection mechanisms used today includes a valve mechanism which controls which of the fluids will flow into the valving mechanism and out to the catheter within the patient. The valve mechanism can contain a plurality of manual valves that the user manually opens and closes to direct fluid flow to a particular fluid channel. When the user aspirates or injects contrast fluid into or out of the chamber, the fluid flows through the path of least resistance directed by the position of the valves. By changing the valve positions, one or more other fluids may be injected. 
     Manual injection systems are typically hand actuated. This allows user control over the quantity and pressure of the injection. However, generally, most manual systems can only inject the radiographic contrast material at maximum pressure that can be applied by the human hand (i.e., 150 p.s.i.). Also, the quantity of radiographic contrast material is typically limited to a maximum of about 12 cc. Moreover, there are no safety limits on these manual contrast injection systems which restrict or stop injections that are outside of predetermined parameters (such as rate or pressure) and there are no active sensors to detect air bubbles or other hazards. 
     Currently used motorized injection devices consist of a syringe connected to a linear actuator. The linear actuator is connected to a motor, which is controlled electronically. The operator enters into the electronic control a fixed volume of contrast material to be injected at a fixed rate of injection. Typically, the fixed rate of injection consists of a specified initial rate of flow increase and a final rate of injection until the entire volume of contrast material is injected. There is no interactive control between the operator and machine, except to start or stop the injection. Any change in flow rate must occur by stopping the machine and resetting the parameters. 
     The lack of ability to vary the rate of injection during injection can result in suboptimal quality of angiographic studies. This is because the optimal flow rate of injections can vary considerably between patients. In the cardiovascular system, the rate and volume of contrast injection is dependent on the volume and flow rate within the chamber or blood vessel being injected. In many or most cases, these parameters are not known precisely. Moreover, the optimal rate of injection can change rapidly, as the patient&#39;s condition changes in response to drugs, illness, or normal physiology. Consequently, the initial injection of contrast material may be insufficient in volume or flow rate to outline a desired structure on an x-ray image, necessitating another injection. Conversely, an excessive flow rate might injure the chamber or blood vessel being injected, cause the catheter to be displaced (from the jet of contrast material exiting the catheter tip), or lead to toxic effects from contrast overdose (such as abnormal heart rhythm). 
     At present, the operator can choose between two systems for injecting contrast material: a manual injection system which allows for a variable, operator interactive flow rate of limited flow rate and a preprogrammed motorized system without operator interactive feedback (other than the operator can start/stop the procedure). Accordingly, there is a need for improvement in the equipment and procedures used for performing diagnostic imaging studies. 
     SUMMARY OF THE INVENTION 
     The present invention is an angiographic injection system which includes both high pressure and low pressure systems. The high pressure system includes a motor driven injector pump which supplies radiographic contrast material under high pressure to a catheter. The low pressure system includes, for example, a pressure transducer for measuring blood pressure and a pump which is used to both for delivering saline solution to the patient and for aspirating waste fluid. In the present invention, a manifold is connected to the syringe pump, the low pressure system, the catheter which is inserted into the patient. A valve associated with the manifold is normally maintained in a first state which connects the low pressure system to the catheter through the manifold. When pressure from the syringe pump reaches a predetermined level, the valve switches to a second state which connects the syringe pump to the catheter, while disconnecting the low pressure system from the catheter. 
     It will be appreciated that while the invention is described with reference to an angiographic injector, the devices and methods disclosed herein are applicable for use in performing other diagnostic and interventional procedures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view illustrating a preferred embodiment of the angiographic injector system of the present invention. 
     FIGS. 2A-2G are diagrams illustrating operations of the system of FIG.  1 . 
     FIG. 3 is an electrical block diagram of the control system of the injector system of FIG.  1 . 
     FIG. 4 illustrates front panel controls and displays of a preferred embodiment of the injector system of the present invention. 
     FIGS. 5A and 5B are side and partial top perspective views of the remote control of the system of FIG.  1 . 
     FIG. 6 is a perspective view of a foot operated remote control. 
     FIGS. 7A-7D illustrate the operation of the inlet check valve and manifold during contrast fill, air purge, and patient inject operations. 
     FIGS. 8A-8C illustrate operation of the inlet check valve in greater detail. 
     FIG. 9 is a perspective view illustrating a preferred embodiment of a portion of the angiographic injector system of the present invention. 
     FIG. 10 is a side view of one embodiment of the shell of a manifold according to the invention. 
     FIG. 11 is a top view of the embodiment of the manifold shell of FIG.  10 . 
     FIG. 12 is a bottom view of the embodiment of the manifold shell of FIGS. 10 and 11. 
     FIG. 13 is a longitudinal cross section view of one embodiment of a manifold assembly according to the invention. 
     FIG. 13A is a longitudinal cross section view of one end of the manifold shell of FIG.  13 . 
     FIGS. 14A-C are longitudinal cross section views which sequentially illustrate the interaction of an elastomeric wiper and the inner surface of a manifold shell as the wiper moves from its low pressure position to its high pressure position. 
     FIG. 15 is a transverse cross section view through line  15 — 15  of FIG.  11 . 
     FIG. 16 is a transverse cross section view through line  16 — 16  of FIG.  12 . 
     FIG. 17 is a diagrammatic illustration of a temporal position of a manifold plunger between the low pressure position and the high pressure position. 
     FIG. 18 is a cross section view through line  18 — 18  of FIG.  11 . 
     FIG. 19 is a longitudinal cross section view of one embodiment of a manifold shell according to the invention. 
     FIG. 19A is a longitudinal cross section view of the embodiment of FIG. 19 with the plunger wipe view in cross section and at a different position within the manifold shell. 
     FIG. 20 is a perspective view of two different embodiments for an injection material temperature control device according to the invention. 
     FIG. 21 is a perspective view of embodiment of a remote control according to the invention. 
     FIG. 22 is a side view of the embodiment of a remote control of FIG.  21 . 
     FIG. 23 is a front view of the embodiment of a remote control of FIG.  21 . 
     FIG. 24 is a rear view of the embodiment of a remote control of FIG.  21 . 
     FIG. 25 is a top view of the embodiment of a remote control of FIG.  21 . 
     FIG. 26 is an exploded perspective view of an adjustable transducer holder according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A. application Ser. No. 08/426,149 
     FIG. 1 shows angiographic injector system  10  for injecting radiographic contrast material into a blood vessel under interactive physician control. System  10  includes main console  12 , hand held remote control  14 , syringe holder  16 , syringe body  18 , syringe plunger  20 , radiographic material reservoir (bottle)  22 , one-way valve  24 , manifold  26 , high pressure tube  28 , catheter  30 , patient medication port  32 , three-way stop-cock  34 , T-connector  36 , pressure transducer  38 , stop-cock  40 , tubing  42 , peristaltic pump  44 , saline check valve  46 , waste check valve  48 , saline bag  50 , waste bag  52 , and bag support rack  54 . 
     Console  12  houses the electrical controls for system  10 , together with the motors which drive piston  20  and peristaltic pump  44 . On the front surface of console  12 , user interface  54  provides control switches  56  and display  58  through which the user may enter control settings and monitor the operational state of system  10 . 
     Remote control  14  is connected to console  12  by cable  60  (although in other embodiments remote control  14  may be connected by a wireless connection such as an RF, infrared optic, or ultrasonic link). Remote control  14  is, in the embodiment shown in FIG. 1, a hand-held control which includes reset and saline push button switches  62  and  64 , respectively, and flow rate control lever or trigger  66 . By squeezing trigger  66 , the user can provide a command signal to console  12  to provide a continuously variable injection rate. 
     Syringe holder  16  projects from the left hand side of console  12 . Syringe holder  16  is preferably a clear material, and includes a half cylindrical back shell  68 , a half cylindrical front door  70  (which is shown in open position in FIG.  1 ), and reservoir holder  72 . 
     Syringe  18  is a transparent or translucent plastic cylinder having its open end  74  connected to console  12 . Closed end  76  of syringe  18  contains two ports: upper port  78  and lower port  80 . 
     Plunger  20  is movable within syringe body  18 . Plunger  20  is connected to, and driven by a motor located within console  12 . 
     Radiographic contrast material reservoir  22  is connected through one-way check valve  24  to upper port  78 . Radiographic contrast material is drawn from reservoir  22  through check valve  24  and upper port  78  into the pumping chamber defined by syringe body  18  and plunger  20 . Check valve  24  is preferably a weighted one-way valve which permits air to flow from syringe body  18  back into reservoir  22 , but will not permit radiographic contrast material to flow from syringe body  18  to reservoir  22 . This permits automatic purging of air from the system, as will be described in more detail later. 
     Lower port  80  of syringe body  18  is connected to manifold  26 . Manifold  26  includes a spring biased spool valve which normally connects transducer/saline port  82  and patient port  84 . When radiographic contrast material is to be injected, the pressure of the radiographic material causes the spool valve to change states so that lower port  80  is connected to patient port  84 . 
     High pressure tube  28  is a flexible tube which connects patient port  84  to catheter  30 . Three-way stop-cock  34  is located at the distal end of tube  28 . Rotatable luer lock connector  86  is connected to stop-cock  34  and mates with luer connector  88  at the proximal end of catheter  30 . Stopcock  34  either blocks flow between tube  28  and catheter  30 , permits flow, or connects medication port  32  to catheter  30 . 
     In addition to injecting radiographic material into a patient through catheter  30 , system  10  also permits other related functions to be performed. A device for delivering the patient medication (not shown in FIG. 1) may be connected to medication port  32  when medication is to be delivered through catheter  30  to the patient. 
     When catheter  30  is in place in the patient, and an injection of radiographic contrast material is not taking place, pressure transducer  38  monitors the blood pressure through the column of fluid which extends from catheter  30 , tube  28 , patient port  84 , manifold  26 , transducer/saline port  82 , tubing  90 , T-connector  36 , and tubing  92 . Transducer  38  has an associated stop-cock  40  which allows transducer  38  to be exposed to atmospheric pressure during calibration and also allows for removal/expulsion of trapped air so the dome chamber of transducer  38  can be flushed with saline. 
     Peristaltic pump  44  supplies saline solution from bag  50  through saline check valve  46 , tubing  42 , T-connector  36  and tubing  90  to saline port  82 . When peristaltic pump  44  is operating to supply saline solution, the saline solution is supplied through manifold  26  to patient port  84  and then through tube  28  to catheter  30 . 
     Peristaltic pump  44  also operates in an opposite direction to draw fluid from catheter  30  and through tube  28 , manifold  26 , tubing  90 , T-connector  36  and tubing  42  to waste check valve  48  and then into waste collection bag  52 . 
     In a preferred embodiment of the present invention, syringe body  18 , manifold  26 , tube  28 , catheter  30 , T-connector  36 , tubing  42 , check valves  46  and  48 , bags  50  and  52 , and tubing  90  and  92  are all disposable items. They must be installed in system  10  each time an angiography procedure is to be performed with a new patient. Once system  10  is set up with all the disposable items installed, door  70  is closed, and syringe body  18  filled with contrast material and purged of air, the user (typically a physician) enters into system  10  the safety parameters that will apply to the injection of radiographic contrast material. These safety parameters typically include the maximum amount of radiographic contrast material to be injected during any one injection, the maximum flow rate of the injection, the maximum pressure developed within syringe body  18 , and the maximum rise time or acceleration of the injection. To actuate an injection of contrast material, the user operates remote control  14  by squeezing trigger  66 . Within the preset safety parameters, system  10  causes the flow rate of the injection to increase as the force or distance of travel of trigger  66  is increased. 
     Typically, the user will meter the amount and rate of contrast material injected based upon continuous observation of the contrast outflow into the structure being injected using fluoroscopy or other imaging methods. System  10  allows the user to tailor the contrast injections to the needs of the patient, thereby maximizing the quality of the procedure, increasing the safety, and reducing the amount of contrast material required to perform the fluoroscopic examination. 
     FIGS. 2A-2G are diagrams illustrating fluid flow paths during seven different operations of system  10 . Those operational are contrast fill (FIG.  2 A), air purge (FIG.  2 B), patient inject (FIG.  2 C), patient pressure (FIG.  2 D), saline flush (FIG.  2 E), aspirate waste (FIG.  2 F), and medicate patient (FIG.  2 G). 
     The contrast fill operation illustrated in FIG. 2A involves the filling of syringe body  18  with radiographic contrast material from reservoir (contrast media supply)  22 . The contrast fill operation is performed during initial set up of system  10 , and may be repeated during operation of system  10  whenever syringe body  18  is running low on radiographic contrast material. 
     During initial set up of system  10 , plunger  20  is initially driven to its furthest forward position adjacent closed end  76  of syringe body  18 . This will expel to the atmosphere the majority of the air which is located within syringe body  18 . 
     Plunger  20  is then retracted, which creates a vacuum within syringe body  18  which draws contrast material from reservoir  22  through check valve  24  into syringe body  18  through upper port  78 . 
     The Contrast Fill operation typically will result in some air being drawn into or remaining within syringe body  18 . It is important, of course, to prevent air from being injected into the patient through catheter  30 . That is the purpose of the Air Purge operation shown in FIG.  2 B. Also, the location of two ports at different elevations allows for a greater amount of safety in preventing air bubbles in the injection. 
     During the Air Purge operation, plunger  20  travels forward to expel trapped air within syringe body  18 . The air, being lighter than the contrast material, gathers near the top of syringe body  18 . As plunger  20  moves forward, the air is expelled from syringe body  18  through upper port  78  and one-way valve  24 . In the embodiment illustrated in FIG. 2B, one-way valve  24  is a weighted one-way valve which allows flow of radiographic contrast material from reservoir  22  to upper port  78 , but will not allow radiographic contrast material to flow in the opposite direction from upper port  78  to reservoir  22 . Valve  24  will, however, allow air to flow from port  78  to reservoir  22 . As soon as radiographic contrast material begins flowing out of syringe body  18  through upper port  78  to valve  24 , valve  24  closes to prevent any further flow toward reservoir  22 . 
     Valve  24  can also, in alternative embodiments, can be a solenoid actuated or motor driven valve operated under control of the electric circuitry within console  12 . In either case, valve  24  is capable to withstanding the relatively high pressures to which it will be subjected during the inject operation. Preferably, valve  24  is capable of withstanding static fluid pressures up to about 1200 p.s.i. 
     FIG. 2C illustrates the Patient Inject operation. Plunger  20  travels forward under the interactive control of the user, who is controlling trigger  66  of remote control  14 . The movement of Plunger  20  creates hydraulic pressure to force contrast material out of syringe body  18  through lower port  80  and through manifold  26  and high pressure tube  28  into catheter  30 . As shown in FIG. 2C, syringe lower port  80  and patient port  84  are connected for fluid flow during the patient inject operation. 
     Manifold  26  contains a valve which controls the routing of fluid connections between patient port  84  and either syringe bottom port  80  or transducer/saline port  82 . In one embodiment of the present invention, manifold  26  includes a spool valve which is spring biased so that patient port  84  is normally connected to transducer/saline port  82  (as illustrated in FIGS.  2 A and  2 B). When the pressure at syringe bottom port  80  builds with the movement of plunger  20  forward, the bias force against the spool valve is overcome so that syringe bottom port  80  is connected to patient port  84 , and transducer/saline port  82  is disconnected the valve within manifold  26  protects pressure transducer  38  from being exposed to the high pressure generated by the patient inject operation. 
     The spool valve opens automatically during the patient inject operation in response to increase pressure exerted on it from the syringe lower port  80 . The spool valve closes and returns to its original position allowing for connection of patient port  84  to transducer  38  when a slight vacuum is applied by retraction of plunger  20  at the end of each Patient Inject operation In an alternative embodiment, the valve within manifold  26  is an electromechanical or motor driven valve which is actuated at appropriate times to connect either syringe lower port  80  or transducer/saline port  82  to patient port  84 . The actuator mechanism is controlled by console  12 . Once again in this alternative embodiment, the valve protects pressure transducer  38  from being exposed to high pressure. 
     FIG. 2D illustrates the Patient Pressure operation. System  10  allows for reading of the patient&#39;s blood pressure, which is monitored through catheter  30 . Patient blood pressure can be monitored through the use of pressure transducer  38  at any time except during the patient inject, saline flush, and waste aspirate operations. The pressure reading being produced by pressure transducer  38  may be normalized by manually opening stop-cock  40  and closing stop-cock  34  to expose pressure transducer  38  to atmospheric pressure. 
     During the Saline Flush operation illustrated in. FIG. 2E, saline solution is used to flush all of the internal lines, pressure transducer chamber  38 , tube  28 , and catheter  30 . As shown in FIG. 2E, peristaltic pump  44  is operating in a direction which causes saline solution to be drawn from bag  50  through check valve  46  and through tubing  42  to saline port  82 . Manifold  26  connects saline port  82  to patient port  84  so that saline solution is pumped out of patient port  84  and through tube  28  and catheter  30 . 
     During the Aspirate Waste operation, patient port  84  is again connected to saline port  82 . During this operation, peristaltic pump  44  is operating in the opposite direction from its rotation during the saline flush operation. As a result, patient fluids are aspirated from patient port  84  to saline port  82  and then through tubing  42  and check valve  48  into waste collection bag  52 . Peristaltic pump  44  acts as a valve pinching/occluding tubing  42  and preventing back flow to/from saline and waste containers  50  and  52  in conjunction with check valves  46  and  48 . 
     With catheter  30  in place within the patient, it may be desirable to supply patient medication. System  10  allows for that option by providing patient medication port  32 . As shown in FIG. 2G, when stop-cock  34  is open, a medication source connected to port  32  will be connected to patient port  84 , and thereby to catheter  30 . During the medicate patient operation, peristaltic pump  44  and plunger  20  are not moving. 
     FIG. 3 is an electrical block diagram of the control system which controls the operation of angiographic injector system  10 . The electrical control system includes digital computer  100 , which receives input signals from remote control  14  and front panel controls  56  through interface  102 , and provides signals to display  58  to display operation data, alerts, status information and operator prompts. 
     Computer  100  controls the motion of plunger  20  through a motor drive circuit which includes motor  104 , motor amplifier  106 , tachometer  108 , potentiometer  110 , a rectifier  112 , pressure sensing load cell  114 , and A/D converter  160 . 
     Motor amplifier  106  provides a Drive  1  signal to motor  104  in response to Control Voltage, Fwd/Rev, and/Brake signals from computer  100  and a speed feedback signal from tachometer  108  through rectifier  112 . The outputs of tachometer  108  and potentiometer  110  are supplied to computer  100  through A/D converter  116  as Speed Monitor and Position Monitor signals. These allow computer  100  to check motor speed, motor direction, and position (volume is a calculated value). 
     Pressure sensor  114  senses motor current or plunger force in order to measure the pressure being applied to the radiographic contrast material within syringe body  18 . This Pressure Monitor Signal is supplied through A/D converter  116  and interface  102  to computer  100 . 
     Peristaltic pump  44  is driven under the control of computer  100  through pump motor  120 , motor driver  122  and optical encoder  124 . Computer  100  provides Saline (Forward) and Waste (Reverse) drive signals to motor driver  122  to operate pump motor  120  in a forward direction for saline flush and a reverse direction for waste aspiration. Optical encoder  124  provides the Speed Direction Monitor signal to interface  102  which indicates both the speed and the direction of rotation of pump motor  120 . 
     FIG. 3 illustrates an embodiment of the control system in which valve motor  130  is used to actuate valves such as one-way valve  24  and the valve within manifold  26 . In this embodiment, computer  100  controls valve motor  130  through motor driver  132 , and monitors position through a Position Monitor feedback signal from potentiometer  134 . In this particular embodiment, valve motor  130  is a stepper motor. 
     Computer  100  monitors temperature of the contrast material based upon a Temp Monitor signal from temperature sensor  140 . Temperature sensor  140  is preferably positioned near syringe body  18 . If the temperature being sensed by temperature sensor  140  is too high, computer  100  will disable operation motor  104  to discontinue patient injection. If the temperature is too low, computer  100  provides a /Temp Enable drive signal to heater drive  150 , which energizes heater  152 . In one preferred embodiment, heater  152  is a resistive film heater which is positioned within syringe holder  116  adjacent to syringe body  18 . 
     Computer  100  also receives feedback signals from contrast bottle sensor  160 , forward limit sensor  162 , reverse limit sensor  164 , syringe missing sensor  166 , chamber open sensor  168 , no contrast bubble detector  170 , and air in line bubble detector  172 . 
     Contrast bottle sensor  160  is a miniature switch located within reservoir holder  72 . The state of the Contrast Bottle Present signal from sensor  160  indicates whether a reservoir  22  is in position within holder  72 . If reservoir  22  is not present, computer  100  will disable the fill operation. 
     Forward limit and reverse limit sensors  162  sense the end limit positions of plunger  20 . When plunger  20  reaches its forward limit position, no further forward movement of plunger  20  is permitted. Similarly, when reverse limit sensor  164  indicates that plunger  20  has reached its reverse limit position, no further reverse movements are permitted. 
     Syringe missing sensor  166  is a miniature switch or infrared emitter/detector which indicates when syringe body  18  is not in position within syringe holder  16 . If syringe body  18  is not in position, all movement functions are disabled except that plunger  20  can move to its reverse limit position (i.e., return to zero). 
     Chamber open sensor  168  is a miniature switch or infrared emitter/detector which senses when door  70  of syringe holder  16  is open. When the signal from sensor  168  indicates that door  70  is open, all movement functions are disabled. Only when door  70  is closed and locked may any movement be allowed. When door  70  is indicated as closed and sensor  166  indicates the syringe body  18  is in position, other normal functions of the system  10  can proceed. 
     Bubble detector  170  is positioned between reservoir  22  and top port  78 , and is preferably an infrared emitter/detector which senses air bubbles. If an air bubble is sensed in the flow path between reservoir  22  and top port  78  during a fill operation, the fill operation is disabled until a new reservoir is connected. 
     Bubble detector  172  is positioned to sense air bubbles in high pressure line  28 . It is preferably an infrared emitter/detector type of bubble detector. Any air bubble which is sensed in high pressure line  28  results in the disabling of all fluid push out functions, whether the fluid is saline solution from peristaltic pump  44  or contrast material from syringe body  18 . 
     The control system of FIG. 3 also includes the capability to provide a control signal to x-ray equipment through relay  180  which is controlled by computer  100 . In addition, computer  100  receives data from blood pressure transducer  38  and from an electrocardiograph (ECG) system, which is separate from injector system  10 . The Pressure and ECG signals are received through signal conditioners and A/D converter  190 , and are transferred to computer  100 . The ECG signal is used by computer  100  in one preferred embodiment, to synchronize operation of motor  104  (and thus the Patient Inject operation) with heart beats. 
     Blood flow to the heart occurs predominantly in diastole (when the heart is between contractions). Continuous injection of contrast material results in spillage of the contrast material into the aorta during systole (during contraction). By injecting primarily during diastole, contrast dosage can be reduced without impairing the completeness of the contrast injection into the coronary artery. 
     In a preferred embodiment, the injection of radiographic contrast material is synchronized to the coronary artery blood flow. The time periods of systole and diastole are determined using an electrocardiographic (ECG) electrical signal, arterial blood pressure waveform analysis, or other timing based on the heart rate. By controlling speed of motor  104 , speed and therefore movement of plunger  20 , the injection of contrast material is interrupted during the period of systole, which reduces or stops contrast injection during this time. In combination with remote control  14 , the operator can vary the rate of contrast injection into the coronary artery while computer  100  automatically pulses the contrast injection to the cardiac cycle. 
     The inertial forces of the moving contrast material and expansion of the containers and tubing holding the contrast material and transmitting it to the patient can cause a phase lag between movement of plunger  20  within syringe body  18  and movement of contrast material out of catheter  30  into the patient. To adjust to the phase lag between the plunger  20  movement and contrast expulsion into the patient, a variable time offset can be entered through control panel  54  such that the timing of the cardiac cycle can be offset by a selected time. Since the magnitude of the phase lag may be dependent on the frequency of the heart rate, an algorithm within computer  100  continuously and automatically adjusts the magnitude of the time offset, based on the instantaneous heart rate during the injection of contrast material. 
     FIG. 4 shows one embodiment of control panel  54  which illustrates the front panel control switches  56  and display  58  of one embodiment of the present invention. Front panel control switches  56  include Set Up/Fill/End switch  200 , Purge switch  202 , Aspirate switch  204 , Saline switch  206 , Enable OK switch  208 , Injection Volume Limit switches  210   a  and  210   b , Injection Flow Rate Limit switches  212   a  and  212   b , Injection Pressure Limit switches  214   a  and  214   b , Rise Time switches  216   a  and  216   b  OK switch  218 , Injection Range Toggle switch  220 , Large Injection OK switch  222 , and Stop switch  224 . 
     Set Up/Fill/End switch  200  is a momentary push button switch. When it is first activated, the user will be notified to place syringe  18  in syringe holder  16 . When syringe  18  has been placed in syringe holder  16  (which is indicated to computer  100  by sensor  166 ), the user will be instructed to close and lock the chamber (i.e., to close door  70 ). Plunger  20  is moved to its full forward position expelling all air within the syringe. Display  58  then indicates to the operator that contrast reservoir  22  should be connected. Once contrast reservoir  22  has been put in place, the operator is requested to depress OK switch  218 , at which time plunger  20  will retract at a set rate (preferably corresponding to a flow rate of 10 ml per second) to the maximum syringe volume. If the real speed (as indicated by feedback to computer  100  from A/D converter  116 ) is greater than the set speed, system  10  will stop. 
     Once plunger  20  is at its rearward most position, motor  104  is actuated to move plunger  20  forward to purge all air bubbles. Pressure sensor  114  provides an indication of when one-way valve  24  is closed and pressure is beginning to build up within syringe body  18 . Once the purge is completed, the total volume injected and the number of injections counter is reset. 
     The actuation of switch  200  also allows for Ml retraction and disengagement of plunger  20  from syringe body  18 . 
     Purge switch  202  is a protected momentary push button switch. When activated, Purge switch  202  causes plunger  20  to move forward to expel air through top port  78 . The forward movement of plunger  20  is limited and stopped when a predetermined pressure within syringe  18  is reached. This is sensed by pressure sensor  114 . The purge operation which is initiated by Purge switch  202  will expel air within syringe  20 . The user may also use Purge switch  202  to purge fluid through patient port  84  by depressing and holding Purge switch  202  continuously on. 
     Aspirate switch  204  is a momentary push button switch which causes computer  100  to activate pump motor  120  of peristaltic pump  44 . Pump motor  120  is operated to aspirate catheter  30  at a set speed, with the aspirated fluid being collected in waste bag  52 . All other motion functions are disengaged during aspiration. If the real speed of motor  120  is greater than a set speed, computer  100  will stop motor  120 . 
     Saline switch  206  is an alternate action switch. Pump motor  120  is activated in response to Saline switch  206  being pushed on, and saline solution from bag  50  is introduced into manifold  26  and catheter  30  at a set speed. If Saline switch  206  is not pushed a second time to stop the flow of saline solution within  10  seconds, computer  100  automatically stops pump motor  120 . If a time-out is reached, Saline switch  206  must be reset to its original state prior to initiating any further actions. 
     Enable OK switch  208  is a momentary push button switch. After the system has detected a disabling function at the end of an injection other than a limit, Enable OK switch  208  must be activated prior to activating OK switch  218  and initiating any further function. 
     Injection Volume Limit keys  210   a  and  210   b  are pushed to either increase or decrease the maximum injection volume that the system will inject during any one injection. Key  210   a  causes an increase in the maximum volume value, and key  210   b  causes a decrease. Once the maximum injection volume limit has been set, if the measured volume reaches the set value, computer  100  will stop motor  104  and will not restart until OK switch  218  has been depressed. If a large injection (i.e., greater than 10 ml) has been selected, OK switch  218  and Large Injection OK switch  220  must both be reset prior to initiating the large injection. 
     Injection Flow Rate Limit keys  212   a  and  212   b  allow the physician to select the maximum flow rate that the system can reach during any one injection. If the measured rate (which is determined by the feedback signals from tachometer  108  and potentiometer  110 ) reaches the set value, computer  100  will control motor  104  to limit the flow rate to the set value. 
     Injection Pressure Limit keys  214   a  and  214   b  allow the physician to select the maximum pressure that the system can reach during any one injection. If the measured pressure, as determined by pressure sensor  114 , reaches the set value, computer  100  will control motor  104  to limit the pressure to the injection pressure limit. The injection rate will also be limited as a result. 
     Rise Time keys  216   a  and  216   b  allow the physician to select the rise time that the system will allow while changing flow rate during any one injection. Computer  100  controls motor  104  to limit the rise time to the set value. 
     In alternative embodiments, keys  210   a - 210   b ,  212   a - 212   b ,  214   a - 214   b , and  216   a - 216   b  can be replaced by other devices for selecting numerical values. These include selector dials, numerical keypads, and touch screens. 
     OK switch  218  is a momentary push button switch which resets functions and hardware sensors. In response to OK switch  218  being activated, computer  100  controls display  58  to ask the operator to acknowledge that the correct function has been selected. Activation of OK switch  218  causes the status to be set to Ready. 
     Injection Range switch  220  is a toggle switch. Depending on whether switch  220  is in the “small” or “large” position, it selects either a high or a low injection volume range for the next injection. 
     Large Injection OK switch  222  is a momentary push button switch. When the large injection range has been selected by injection range switch  220 , the Large Injection OK button  222  must be activated to enable OK switch  218 . OK switch  218  must be activated prior to each injection. On large volume injections, the user is required to verify the volume selected by activating first Large Injection OK switch  222  and then OK switch  218 . 
     Stop switch  224  is a momentary push button switch. When stop switch  224  is pushed, it disables all functions. Display  58  remains active. 
     Display panel  58  includes Set-Up display  250 , Status display  252 , Alerts display  254 , Limits display  256 , total number of injections display  260 , total volume injection display  262 , flow rate display  264 , injection volume display  266 , injection volume limit display  268 , injection rate limit display  270 , pressure limit display  272 , rise time minimum display  274 , large injection display  276 , and real time clock display  278 . 
     Set-Up display  250  contains a series of messages which are displayed as the operator goes through the set up procedure. The display of messages in set up display  250  are initiated by the actuation of set up switch  200  as described previously. 
     Status display  252  provides a flashing indication of one of several different operating conditions. In the embodiment shown in FIG. 4, these status conditions which can be displayed include “Ready”, “Set-Up”, “Injecting”, “Filling”, “Flushing”, and “Aspirating”. 
     Alerts display  254  and Limits display  256  notify the operator of conditions in which system  10  has encountered a critical control parameter and will disable operation, or has reached an upper or lower limit and will continue to function in a limited fashion, or has reached an upper or lower limit and will continue to operate. 
     Total number of injections display  260  displays the total number of injections (cumulative) given for the current patient case. The cumulative total volume injected during the current patient case is displayed by total volume display  262 . 
     Displays  264  and  266  provide information on the current or last injection. Display  264  shows digital value of the real time flow rate to the patient during injection. Once the injection is completed, the value displayed on display  264  represents the peak flow rate reached during that injection. Display  266  shows the digital value of the volume injected during the most recent injection. 
     Display  268  displays the digital value of the maximum injection volume selected by operation of switches  210   a  and  210   b . Similarly, display  270  shows the digital value of the maximum flow rate that the system will allow, as selected by switches  212   a  and  212   b.    
     Display  272  shows the digital value of the maximum pressure that the system will allow to be developed in syringe  18 . The pressure limit is selected by switches  214   a  and  214   b.    
     Display  274  displays the minimum rise time that the system will allow while changing flow rate. The minimum rise time is selected through switches  216   a  and  216   b.    
     Large injection display  276  provides a clear indication when the large injection scale has been selected by the operator. 
     Real-time clock display  278  shows the current time in hours, minutes, and seconds. 
     FIGS. 5A and 5B show remote control  14  which includes main housing  300 , which is designed to conform to the users hand. Trigger  66  is movable with respect to housing  300 , and the position of trigger  66  generates a command signal which is a function of trigger position. In one embodiment, trigger  66  is linked to a potentiometer within housing  300 . The command signal controls the injunction flow rate or speed. The flow rate is directly proportional to trigger position. 
     Reset switch  62  is a momentary push button switch whose function is identical to that of OK switch  218 . Alternatively, Reset switch  62  may also be labeled “OK”. 
     Saline switch  64  on remote control  14  is an alternate action push button switch which is pushed to turn on and pushed again to turn off. The function of Saline switch  62  is the same as that of Saline switch  206  on front panel  54 . 
     As illustrated in another embodiment of the present invention, an alternative remote control  14 ′ in the form of a foot pedal is used instead of the hand held remote control  14  illustrated in FIG.  1  and in FIGS. 5A and 5B. Foot pedal remote control  14 ′ includes foot operated speed pedal or trigger  66 ′ for providing a command signal, as well as Reset or OK switch  62 ′ and Saline switch  64 ′. Covers  310  and  312  protect switches  62 ′ and  64 ′ so that they can only be actuated by hand and not accidentally by foot. Foot pedal remote control  14 ′ is connected to console  12  by cable  60 ′, but could alternatively be connected by a wireless link. 
     FIGS. 7A-7D and FIGS. 8A-8C illustrate the construction and operation of one way valve  24  and manifold  26  during Contrast Fill, Air Purge and Patient Injection operation. 
     FIGS. 7A and 8A illustrate one way or check valve  24 , manifold  26 , syringe body  18 , and plunger  20  during a Contrast Fill operation. Inlet check valve of one way valve  24  includes weighted ball  350  which is positioned at its lower seated position within valve chamber  352  in FIGS. 7A and 7B. Contrast material is being drawn into syringe body  18  by the rearward movement of plunger  20 . The contrast material flows through passages  354  around ball  350  and into upper port  78 . 
     Manifold  26  contains spring loaded spool valve  360 , which includes spool body  362 , shaft  364 , O-rings  366 ,  368  and  370 , bias spring  372 , and retainer  374 . As shown in FIG. 7A, during the Contrast Fill operation, bias spring  372  urges spool body  362  to its right-most position toward syringe body  18 . In this position, spool body  362  blocks lower port  80  of syringe body  18  while connecting transducer saline port  82  to patient port  84  through diagonal passage  376 . O-rings  366  and  368  on the one hand, and O-ring  370  on the other hand, are positioned on the opposite sides of diagonal passage  376  to provide a fluid seal. 
     FIGS. 7B and 8B illustrate the Air Purge operation. Syringe body  18  has been filled with contrast fluid, but also contains trapped air. Plunger  20  is driven forward to force the air out of syringe body  18  through upper port  78  and through check valve  24 . The force of the air may cause a slight lifting of ball  350  in check valve  20 . Ball  350 , however, is sufficiently heavy that the air being forced out of syringe body  18  and back toward reservoir  22  cannot lift ball  350  into its uppermost seated position where it would block the flow of air out of syringe body  18 . 
     During the Air Purge operation, spool valve  360  is in the same position as in FIG.  7 A. Diagonal passage  376  connects transducer saline port  82  with patient port  84 . As a result pressure monitoring by pressure transducer  38  can be performed during the Air Purge (as well as the Contrast Fill) operation. 
     FIGS. 7C and 8C illustrate the state of manifold  26  and check valve  24  at the end of the Air Purge operation and at the beginning of a Patient Inject operation. 
     In FIG. 7C, all air has been expelled from syringe body  18 . Ball  350  may float on the radiographic contrast material, so that when all air has been removed and the radiographic contrast material begins to flow out of syringe body  18  and through upper port  78  to valve chamber  352 , ball  350  is moved upwards to its upper seated position. Ball  350  blocks any continued upward flow of radiographic contrast material, as is illustrated in FIGS. 7C and 8C. 
     In the state which is illustrated in FIG. 7C, the pressure within syringe body  18 , and specifically the pressure in lower port  80  has not yet reached a level at which the bias force of spring  372  has been overcome. As a result, spool body  362  has not yet moved to the left and diagonal passage  376  continues to connect transducer saline port  82  with patient port  84 . 
     FIG. 7D illustrates the patient inject operation. Plunger  20  is moving forward, and inlet check valve  24  is closed. The pressure at lower port  80  has become sufficiently high to overcome the bias force of spring  372 . Spool body  362  has been driven to the left so that lower port  80  is connected to patient port  84 . At the same time spool body  362  blocks transducer/saline port  82 . 
     By virtue of the operation of spool valve  360 , the high pressure generated by movement of plunger  20  and syringe body  18  is directly connected to patient port  84 , while saline port  82  and pressure transducer  38  are protected from the high pressure. The pressure to actuate may be variable and determined after manufacture by increasing or decreasing the syringe preload. 
     B. Detailed Description of the Present Invention 
     FIG. 9 illustrates another embodiment for an injector system  400  according to the invention. According to this embodiment, system  400  includes a main console  401 , syringe holder  410 , syringe body  411 , syringe plunger  412 , radiographic material reservoir  413 , one-way valve  414 , lower port  415 , lower port tube  416 , manifold assembly  417 , patient tube  418 , three-way stopcock  419 , catheter  420  and transducer  430 . Tubing  431  is similar to tubing  42  of the previously described embodiments and provides for saline flush or waste removal. In addition, the previously described peristaltic pump, saline check valve, waste check valve, saline bag, waste bag, bag support rack, counsel and remote control previously described can be used in the present embodiment. 
     Lower port  415  of syringe body  411  is connected to manifold assembly  417  through high pressure port  432  optionally using lower port tube  416 . Manifold assembly  417  includes a spring bias spool valve as described below. The spring bias spool valve can be manually operated by handle  435 . During low pressure operation, manifold assembly  417  provides a fluiditic connection from low pressure port  434  to patient port  433 . During high pressure operation, manifold assembly  417  provides a fluiditic connection from high pressure port  432  to patient port  433 . Hence, during a patient inject operation, the pressure of injection of the radiographic material causes the spool valve in manifold assembly  417  to change from the low pressure position to the high pressure position such that lower port  415  is in fluid flow communication with patient port  433 . 
     In some embodiments, the spring bias spool valve which controls routing of fluid flow through manifold assembly  417 , can be manually operated by pulling or pushing handle  435 . According to the illustrated embodiment, moving handle  435  away from manifold assembly  417  changes fluid flow from the low pressure path (i.e., low pressure port  434  to patient port  433 ) to the high pressure path (i.e., high pressure port  432  to patient port  433 ). 
     Patient tube  418  can be a flexible tube which connects patient port  433  to catheter  420 . A three-way stopcock  419  can be located at the distal end of patient tube  418 . Rotatable lure lock connector  421  mates with lure connector  422  at the proximal end of catheter  420 . Stopcock  419  either permits or blocks flow between patient tube  418  and catheter  420 , or connects medication port  423  to catheter  420 . As described earlier, a device for delivering patient medication may be connected to medication port  423 . 
     When catheter  420  is in place in the patient, and an injection of radiographic contrast material is not taking place, i.e., low pressure operation, pressure transducer  430  monitors the blood pressure through the column of fluid which passes through catheter  420 , patient tube  418 , patient port  433 , manifold assembly  417 , low pressure port  434 , low pressure tube  436 , and dome chamber  438 . Transducer connector  440  couples a first end of low pressure tube  436  to transducer  430  and low pressure connector  441  couples a second end of low pressure tube  436  to low pressure port. As illustrated in FIG. 9, flush tube  431  can mount to transducer  430  through flush tube connector  442 . In some embodiments, system  400  can also include a transducer holder  600  (discussed below) for adjustable positioning of transducer  430 . When a peristaltic pump, discussed earlier, is operating to supply saline solution through flush tube  431 , the solution is supplied through manifold assembly  417  to patient port  433  and then through patient tube  418  to catheter  420 . It will be appreciated that aspiration applied at low pressure port  434  can draw blood from the patient through patient tube  418 , manifold assembly  417 , low pressure port  34  and into flush tube  431 . 
     In the present embodiment, preferably, syringe body  411 , manifold assembly  417 , patient tube  418 , catheter  420 , stopcock  423 , low pressure tube  436 , transducer dome chamber  438 , flush tube  431  and previously described check valves, fluid containers and waste containers are all disposable items. They should be installed in system  400  each time a new procedure is to be performed with a new patient. Once system  400  is set up with all the disposable items installed, the operator enters into the console  401  of system  400 , the limiting safety parameters that will apply to the patient injection of radiographic contrast material. 
     FIGS. 10-18 illustrate preferred embodiments of a manifold assembly  417 . FIG. 10 is a side view of one embodiment of the shell (body)  450  of manifold assembly  417 ; FIG. 11 is a top view of manifold shell  450 ; FIG. 12 is a bottom view of manifold shell  450 ; and FIG. 13 is a longitudinal cross section view of manifold assembly  417 . These figures all illustrate high pressure port  432 , patient port  433  and low pressure port  434 . 
     FIG. 13 illustrates that manifold handle  435  has a shaft  456  that passes through opening  452  of manifold cap  453  . Manifold cap  453  has threads  454  for securing cap  453  to first end  491  of manifold shell  450  through manifold shell threads  451 . In the illustrated embodiment, cap  453  includes a hollow protuberance  455  through which handle shaft  456  passes into manifold  450 . Manifold plunger assembly  490  includes, manifold shaft  458 , manifold wiper  460 , O-ring  461  and valve sensor trigger  462 . Protuberance  455  of manifold cap  453  stops travel of manifold plunger assembly  490  to the left (relative to the orientation of FIG. 13) during high pressure operation. Spring  463  is mounted over handle shaft  456  between manifold cap  453  and valve sensor trigger  462  to maintain a fluiditic connection between low pressure port  434  and patient port  433 . 
     Within manifold assembly  417 , handle shaft  456  is rigidly fixed to a first end  457  of manifold shaft  458  using, for example, threads. Manifold wiper  460  is mounted at the second end  459  of manifold shaft  458 . In the illustrated embodiment, manifold shaft  458  has a hollow core that is open at first end  457  and second end  459 . The hollow core provides for release of air that would otherwise be trapped inside the hollow region of manifold wiper  460  during assembly. In the illustrated embodiment, wiper  460  includes a thickened tip  497  which provides reinforcement of the wall of wiper  460  to reduce the chance of rupture of wiper  497  into the hollow core of manifold shaft  458 . Preferably, manifold wiper  460  is manufactured from an elastomeric thermoset material, for example, ethylene propylene diene monomer (EPDM) silicon, nitrile, polyisoprene, etc. The resistance to compression set of the thermoset material provides for maintaining a fluid tight seal between the outer perimeter of manifold wiper  460  and the inner surface  464  of manifold shell  450 . 
     A valve sensor trigger  462  is mounted at the first end  457  of manifold shaft  458 . The position of the valve sensor trigger  462  is detected by the valve state sensor  425  (FIG. 9) to indicate the state of the fluiditic connections within manifold assembly  417 . In one embodiment, the valve state sensor trigger  462  can be manufactured from stainless steel for use with an inductive type valve state sensor  425 . 
     FIG. 13A illustrates a longitudinal cross section view of the second end  492  of manifold shell  450  of FIG.  13 . As illustrated in FIG. 13A, the inner surface  464  of shell  450  near high pressure port  432  is cone shaped  493 . This cone shaped end  493  provides a gradual transition from high pressure port  432  to inner surface  464  which can facilitate removal of trapped air at this junction during initial flushing of the system by minimizing adverse turbulent flow. In addition, the cone shaped end can eliminate regions of fluid stagnation during injection. In addition, the external configuration of the cone tip protrudes slightly and is wedge shaped to form an annular ring  494  for an air tight pressure fit with the inner surface  495  of lumen  496  of low port tube  416 . 
     Referring to FIGS. 10-17, the structure of manifold shell  450  at the junction between the inner surface  464  of manifold shell  450  and the fluid channel  466  of patient port  433  and the fluid channel  467  of low pressure port  434  will be described. 
     FIGS. 14A-C are longitudinal cross section views which illustrate the interaction of an elastomeric manifold wiper  460   a  and the inner surface  464   a  of a manifold shell  450   a  as the wiper  460   a  moves from its low pressure position (FIG. 14A) to its high pressure position (FIG.  14 C. As illustrated in FIG. 14B as wiper  460   a  moves within the inner surface  464   a  of manifold shell  450   a  past fluid channel  466   a  of patient port  433   a , the elastomeric material of wiper  460   a  tends to “extrude” (illustrated as  465 ) into the fluid flow channel  466   a  of patient port  433   a . The same event can occur as wiper  460   a  passes over fluid flow channel  467   a  of low pressure port  434   a  (FIG.  14 C). A potential problem with extrusion of wiper  460   a  into fluid flow channels,  466   a  or  467   a , is that the extruded portion  465  of manifold wiper  460   a  can prevent proper functioning of manifold assembly  417  by causing plunger assembly  490  to stick in a position wherein wiper  460  blocks fluid channels  466   a  or  467   a . In addition, the extruded portion  465  can be broken or “nibbled” off during passage of wiper  460   a  past fluid channels  466   a  or  467   a . In a preferred embodiment, manifold assembly  417  is constructed to reduce the amount of extrusion and reduce the likelihood of sticking or nibbling of manifold wiper  460  as it moves past fluid channels  466  and  467 . 
     FIG. 11 is a top view of manifold shell  450  looking down into fluid flow channel  466  of patient port  433 . FIG. 15 is a transverse cross section view through line  15  of FIG.  11 . FIG. 12 is a bottom end view of manifold shell  450  looking into fluid channel  467  of low pressure port  434 . FIG. 16 is a transverse cross section view through line  16 — 16  of the low pressure port of FIG.  12 . Referring to patient port  433  in FIGS. 11 and 15, at the location where fluid channel  466  communicates with the inner surface  464  of manifold shell  450 , the fluid channel  466  is bifurcated by a “fillet”  468  to form a multipartate opening. As illustrated best in FIG. 15, fillet  468  permits fluid flow through elongate openings  469   a  and  469   b  of shell  450  into fluid channel  466  but also constrains expansion of manifold wiper  460  to reduce the amount of extrusion into fluid channel  466 . Preferably, fillet  468  reduces the likelihood of extrusion of manifold wiper  460  into fluid channel  466 , but does not cause an increase in cavitation or an appreciable increase in resistance to the flow of fluid passing into fluid channel  466 . It will be appreciated that openings  469   a  and  469   b  are not limited to any particular shape as a result of the fillet. Moreover, while FIGS. 11 and 15 show a single fillet creating two openings, additional fillets forming more than two openings are envisioned within the scope of the invention. In the illustrated embodiment, the opening is bipartate and the longitudinal dimension of the fillet is oriented parallel to the longitudinal dimension of the manifold shell  450 . Also, in one embodiment, the fillet is about 0.030 inch wide, the longitudinal dimension of openings  469   a  and  469   b  is about 0.080 inch and the width of openings  469   a  and  469   b  is about 0.030 inch. 
     Referring now to FIGS. 12 and 16, for the reasons discussed above, a similar fillet  470  can be present in fluid flow channel  467  of low pressure port  434 , bifurcating channel  467  into openings  471   a  and  471   b.    
     FIG. 17 diagrammatically illustrates a temporal position of manifold wiper  460   a  at a position after which the pressure at high pressure port  432   a  has become sufficient to overcome: (1) the bias force of spring  463  (FIG.  13 ); (2) the friction force between manifold wiper  460   a  and manifold inner surface  464   a ; (3) the pressure induced friction force between seal ring  460   b  and manifold inner surface  464   a . In the illustration, manifold wiper  460   a  has not moved completely to the left to the fully open high pressure position. Just after seal ring  460   c  has blocked the fluid connection between patient port  433   a  and low pressure port  434   a , the pressurized fluid entering high pressure port  432   a  can flow up fluid channel  466   a , at arrow  472 , which reduces the pressure at high pressure port  432   a  because there is, as yet, little flow resistance or pressure build up in fluid channel  466   a.    
     This reduction in pressure simultaneously reduces the pressure induced force on the seal face  460   d  and pressure induced friction force between seal ring  460   b  and manifold inner surface  464   a . Without being limited to a single theory, it is believed that as the forces pushing and holding the plunger assembly  490  to the left are simultaneously reduced, the force of spring  463  must also decline due to the laws of physics. Thus, spring  463  must expand, which pushes plunger assembly  490  to the right. Once manifold wiper  460   a  moves far enough to the right to seal off the fluid outflow through fluid flow channel  466   a , the pressure at high pressure port  432   a  will increase again to overcome the bias force of spring  463  allowing wiper  460   a  to move enough to the left to allow fluid to once again rush out at arrow  472 . The repeated occurrence of the movement of wiper  460   a  back and forth at the point where fluid is just beginning to move up fluid channel  466   a  at arrow  472  results in an oscillation of the plunger. This oscillation can produce a pulsation in the fluid flow which causes uncontrolled variable flow rates. 
     Referring to FIGS. 11,  13  and  18 , in a preferred embodiment of the invention, manifold assembly  417  is constructed, in part, to reduce or eliminate the occurrence of this oscillation. FIG. 18 is a transverse sectional view taken at line  18 — 18  of FIG.  11 . Referring to FIGS. 11 and 18, within patient port  433 , there is located an outer oscillation reduction port  473 . The port  473  leads into an oscillation reduction channel  474  that extends from patient port  433 , through manifold shell  450  to communicate with the inner surface  464  of manifold shell  450  at inner oscillation reduction port  475  (FIGS.  13  and  18 ). Referring to FIG. 13, during use, as the pressure at high pressure port  432  becomes sufficiently high to overcome the previously described counter forces, manifold wiper  460  moves to the left. As wiper  460  moves sufficiently to the left to expose inner port  475  of oscillation reduction channel  474 , fluid is forced up oscillation reduction channel  474 . The resistance to fluid flow from the combination of inner port  475  and oscillation reduction channel  474  is sufficient to maintain the pressure within the inner surface  464  of manifold assembly  417  to prevent oscillation. This maintained pressure also maintains the pressure induced force on seal face  460   d . As a result, plunger assembly  490  is moved fully to the left without oscillation. Thus, oscillation ports  473  and  475  and oscillation channel  474  maintain the force balance between the biasing spring  463  and the pressure induced force of the fluid on wiper  460 . 
     Referring to FIGS. 19 and 19A, in some embodiments, the elastomeric material of manifold wiper  460  can be configured to form a plurality of ridges,  485   a ,  485   b  and  485   c . These ridges contact inner surface  464  of manifold shell  450 . In one aspect, the intervening valleys  486   a  and  486   b  between ridges  485   a - 485   c , help reduce the amount of friction between the elastomeric surface of wiper  460  and inner surface  464  while ridges  485   a  and  485   c  maintain a fluid tight seal. In the illustrated embodiment, ridge  485   b  acts to eliminate the presence of air between ridges  485   a  and  485   c . As seen in the cross section view of FIG. 19A, the inner surface  498  of wiper  460  includes circumferential protrusions  499   a  and  499   b . The pressure of these protrusions against manifold shaft  458  causes formation of ridges  485   a  and  485   c . Ridge  485   b  is formed by the presence of shim  500  on manifold shaft  458 . It will be appreciated that ridge  485   b  could be configured to create a greater friction force against outer surface  464  by placement of a circumferential protrusion similar to protrusions  499   a  and  499   b.    
     Referring to FIGS. 19 and 19A, it is believed that the area within valleys  486   a  and  486   b  can trap air which, when wiper  460  moves past fluid flow channel  466 , could be forced into patient port  433 , out patient tubing  418  and ultimately into the patient. The ill effects of air entering the patient&#39;s vascular system are well known. Hence, to reduce the chance of air entering the patient, manifold shell  450  can include projections  487   a  and  487   b  that substantially fill the valleys  486   a  and  486   b  between ridges  485   a - 485   c  when manifold wiper  460  is in the low pressure position, i.e., closest to high pressure port  432 . As illustrated in FIG. 19A, the interdigitation of ridges  485   a-c  with protuberances  487   a-b  reduces dead air space and the air present in valleys  486   a - 486   b  thus reducing the chance for air to move into patient port  433  as wiper  460  is moved from the low pressure position. 
     FIG. 20, illustrates two different embodiments of temperature control device  555  for the fluid in reservoir  413  ( 22 ). The temperature control device  555  provides for heating or cooling of the injection material prior to passing into syringe  411 . In one embodiment, the temperature control device  555  can be a jacket,  556 , that sufficiently covers reservoir bottle  413  to effect the temperature of the material in the reservoir. In an alternative embodiment, the temperature control device can be a tubular heating element or heat exchanger  557  that warms the contrast material as it passes through the tubing  557  before entering syringe  411 . 
     FIGS. 21-25 show a preferred embodiment of a remote control device  550  which includes a main housing  501 , which is designed to conform to the user&#39;s hand. Trigger  502  is moveable with respect to housing  501 , and the position of trigger  502  generates a command signal which is a function of trigger position. The flow rate of contrast material during the patient inject operation is directly proportional to trigger position. 
     FIG. 21 is a perspective view of remote control  550 . In use, remote control  550  is preferably held in the user&#39;s hand such that the operation buttons, for example,  503  and  504 , on face panel  505 , can be readily actuated by the user&#39;s thumb. Trigger  502  can be operated by pulling trigger  502  toward housing  501  with one or more of the user&#39;s fingers. Referring to the orientation of remote control  550  in the figures, it will be appreciated that there is an upper end  506  and a lower end  507 . Referring to the top view of FIG. 25, housing  500  includes a slot  508  that guides the lateral travel of trigger  502  through guide pin  509 . Also, as trigger  502  is pulled, the forward and backward travel of trigger  502  is limited. Backwall  510  of slot  508  limits backward travel and forward wall  511  of slot  508  limits forward travel. As illustrated in FIG. 25, slot  508  can be in the form of an “L”  512 . The “L” configuration of slot  508  provides for guide pin  509  to rest within the short arm of the L when not in use, and requires lateral movement of trigger  502  to dislodge guide pin  509  from the short arm before trigger  502  can be pulled towards housing  501 . This feature of remote control  500  helps prevent against accidental patient injection without an affirmative lateral movement of trigger  502  by the operator. 
     The bottom end  507  of trigger  502  can mount with housing  501  through a pivot arrangement, for example, a spring hinge or a flexible material which provides for repeated pulling of handle  502  towards housing  501  and return to the forward position when the operator releases trigger  502 . 
     A maximum and minimum fluid discharge rate is set by the operator for the remote control prior to operation. The rate of fluid discharge can be varied by the operator and is directly proportional to the trigger position. That is, in one embodiment, the farther back that trigger  502  is pulled toward housing  501 , the greater the fluid discharge rate up to the preset maximum. 
     Referring to FIGS. 21 and 24, face panel  505  can include an indicator light  520  which illuminates when the system is armed and ready for use. Other control functions can be operated at the face panel. For example, in one embodiment, operation button  504  provides for a saline flush through the low pressure side of the system, and operation button  503  provides a “spritz” function through the high pressure side of the system. It will be appreciated that other functions can be remotely controlled through operation buttons installed at the face panel  505 . 
     As stated above, in one embodiment, face panel  505  includes an operation button  503  providing a “spritz” function. According to this embodiment, activation of operation button  503  will cause injection of a predetermined volume of contrast media at the operator&#39;s discretion. This function may be particularly useful when determining position of catheter in a heart, peripheral vessel or other anatomical location in the body. In one embodiment, activation of the spritz button will inject a volume of contrast media that is a percentage of the preset injection volume. For example, activation of a spritz button could inject 10% of the injection during small hunting procedures. 
     In some embodiments, an angiographic injector system according to the invention can include a transducer holder  600  for selective positioning of transducer  430  relative to the patient&#39;s heart line. As illustrated in FIGS. 9 and 26, transducer holder  600  includes a mounting shaft  601 , for mounting transducer holder  600  to console  401 , and adjustment shaft  602  for slidable adjustment of transducer  430  in transducer carrier  603 . Movement of transducer carrier  603  along adjustment shaft  602  is limited at a first end by mounting shaft  601  and at a second end by adjustment shaft cap  604 . Depressing adjustment sleeve  606  allows transducer carrier  603  to be moved freely along adjustment shaft  602 . 
     In the illustrated embodiment, transducer carrier  603  includes two sites,  613  and  614  for mounting transducer  430 . These sites are configured to conform to the shape of transducer  430  or transducer dome  438  for a snug fit regardless of the rotational orientation of adjustment shaft  602 . 
     Referring to FIG. 26, spring  605  and adjustment sleeve  606  are located within chamber  608  of carrier  603 . Adjustment sleeve  606  includes a channel  607  which fits around adjustment shaft  602 . Adjustment shaft  602  also passes through channel  610  of transducer carrier  603 . In use, when adjustment sleeve  606  is depressed towards end  611  of transducer carrier  603  such that channel  607  and channel  610  are in axial alignment, transducer carrier  603  can be slidably moved along adjustment shaft  602 . Upon release of pressure on adjustment sleeve  606  channel  607  of adjustment sleeve  606  is biased out of axial alignment with channel  610  creating a friction force which holds transducer carrier  603  in position. 
     In addition to slidable adjustment of carrier  603  along adjustment shaft  602 , shaft  602  can be rotated 360° around an axis  612  through mounting shaft  601 . Thus, between rotational adjustment and slidable adjustment, transducer  430 , mounted in transducer carrier  603 , can be positioned at the optimum location for monitoring a patient&#39;s blood pressure. 
     In one preferred embodiment, when the volume of contrast material in syringe  411  is less than the injection volume as determined by the microprocessor, the injector system will prevent subsequent injection operations or automatically refill syringe  411 . In auto mode or manual mode, syringe  411  can be refilled maximally or to some lesser volume entered by the operator at console  401 . In automatic mode, subsequent to completion of an injection, computer  100  compares the volume of contrast material remaining in syringe  411  with the injection volume preset in the computer by the operator. If the preset injection volume is greater than the volume of contrast material available in syringe  411 , computer  100  prevents subsequent patient injection operations. Provided contrast reservoir  413  (or  22 ) is in place, computer  100  can energize the motor drive circuitry to automatically retract plunger  412  at a set rate, preferably corresponding to a flow rate of about 3 ml per second, to load syringe  411  with contrast material to maximum or other preset volume. Once syringe  411  is filled as indicated by the reverse limit feedback signal from sensor  164 , motor  104  moves plunger  412  forward to purge air from the syringe out one-way valve  414  at a rate of about 3 ml per second. 
     It has also been discovered that by using multiple speeds for retracting of plunger  412  during syringe refill, an air forming bubble within syringe  411  can be reduced more readily. For example, assume a situation where syringe  411  is to be maximally filled. According to this example, the computer controlled retraction of plunger  412  occurs slowly at a rate of about 2 ml per second until filled with about 40 ml of media. This slower rate facilitates a forming air bubble to break free from the surface of plunger  412  at the meniscus. Subsequently, a faster rate of about 3 ml per second is used to complete the filling procedure and the bubble released from plunger  412  will tend to float away from the plunger toward one-way valve  414 . In addition, angulation of syringe  411  at about 10-200, preferably about 150 from horizontal facilitates release or movement of an air bubble to one-way valve  14 . 
     In conclusion, the injector system of the present invention provides interactive control of the delivery of radiographic contrast material to a catheter through a user actuated proportional control. The several embodiments disclosed herein enhance the safety and efficiency of the injector system as well as providing for the user to adjust the parameters for injection of contrast material interactively as needed and as the patient&#39;s condition changes. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, syringe holder  16  and  410  may take other forms, such as an end loaded cylinder. Similarly, manifolds  26  and  417  can take other configurations and can incorporate, for example, a part of syringe ports  78  and  80 .