Patent Publication Number: US-2022211942-A1

Title: Adjustable Medium Diverter

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/871,704, filed May 11, 2020; which is a continuation of U.S. patent application Ser. No. 15/907,752, filed Feb. 28, 2018, issued as U.S. Pat. No. 10,835,670; which is a division of U.S. patent application Ser. No. 14/851,939, filed Sep. 11, 2015, issued as U.S. Pat. No. 10,010,673; which is a continuation-in part of U.S. patent application Ser. No. 13/839,771, filed on Mar. 15, 2013, issued as U.S. Pat. No. 9,320,846 for “Devices and Methods for Modulating Medium Delivery;” which claims the benefit of priority from U.S. Provisional Patent Application No. 61/694,137, filed Aug. 28, 2012 for “Devices and Methods for Modulating Medium Delivery;” and this application claims the benefit of priority from U.S. Provisional Patent Application No. 62/048,974, filed Sep. 11, 2014, for “Devices and Methods for Modulating Medium Delivery,” and U.S. Provisional Patent Application No. 62/082,260, filed Nov. 20, 2014, for “Devices and Methods for Modulating Medium Delivery”, the contents of all of these priority applications are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     There are numerous occasions in the diagnostic, prophylactic and treatment practice of medicine wherein an agent, medicant, or medium is preferably delivered to a specific site within the body, as opposed to a more general, systemic introduction. One such exemplary occasion is the delivery of contrast media to coronary vasculature in the diagnosis (i.e., angiography) and treatment (i.e., balloon angioplasty and stenting) of coronary vascular disease. 
     SUMMARY 
     In one aspect, a system for modulating delivery of a fluid medium to a selected site within a patient&#39;s body is disclosed. The system comprises a syringe for injecting the fluid medium, a delivery catheter comprising a conduit for delivering the fluid medium from outside of the body to the selected site within the body, and a flow diverter assembly disposed in a fluid medium flow path between the syringe and the delivery catheter. The syringe comprises a chamber for receiving the fluid medium therein. The flow diverter assembly is configured to simultaneously divert at least some of the fluid medium within the chamber of the syringe away from the delivery of the medium through the delivery catheter conduit during injecting with the syringe, and wherein the flow diverter assembly creates increasing medium fluid flow resistance with increasing pressure level of the fluid medium within the flow diverter assembly. 
     In another aspect, a method for modulating fluid delivery of a fluid medium to a selected site within a patient&#39;s body is disclosed. The method comprises injecting the fluid medium from a syringe through a fluid delivery catheter to deliver the fluid medium to the selected site, and simultaneously employing a flow diverter assembly disposed in a fluid medium flow path between the syringe and the delivery catheter. The flow diverter assembly resides outside the patient&#39;s body and is configured to divert at least some of the fluid medium within the syringe away from the delivery of medium to the delivery catheter conduit during injection of medium, and wherein the diverter assembly is configured to increase medium fluid flow resistance with an increase in pressure level of the fluid medium within the flow diverter assembly. 
     This summary is provided to introduce concepts in simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the disclosed or claimed subject matter and is not intended to describe each disclosed embodiment or every implementation of the disclosed or claimed subject matter. Specifically, features disclosed herein with respect to one embodiment may be equally applicable to another. Further, this summary is not intended to be used as an aid in determining the scope of the claimed subject matter. Many other novel advantages, features, and relationships will become apparent as this description proceeds. The figures and the description that follow more particularly exemplify illustrative embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosed subject matter will be further explained with reference to the attached figures, wherein like structure or system elements are referred to by like reference numerals throughout the several views. 
         FIG. 1  illustrates in graphic form, the exemplary pulsatile nature of left coronary artery blood flow and blood pressure. 
         FIG. 2  is a graphic representation of an exemplary blood flow rate profile for a left main coronary artery. 
         FIG. 3A  illustrates an exemplary coronary artery treatment system. 
         FIG. 3B  illustrates a distal portion of the exemplary treatment of  FIG. 3A . 
         FIG. 3C  illustrates a proximal portion of the exemplary treatment system of  FIG. 3A . 
         FIG. 4A  illustrates graphically an exemplary injection profile (flow rate) of agent for the treatment system of  FIG. 3 . 
         FIG. 4B  illustrates graphically an injection profile (flow rate) of agent for the treatment system of  FIG. 3 , identifying under-injection and over-injection volume areas of media for opacification purposes. 
         FIG. 4C  illustrates graphically an exemplary improved constant injection profile (flow rate) of agent for achieving opacification. 
         FIG. 4D  illustrates graphically the exemplary agent injection profile of  FIG. 4A  relative to the exemplary blood rate flow profile of  FIG. 2 . 
         FIG. 5A  illustrates an exemplary flow of injection in the distal portion of the exemplary treatment system of  FIG. 3B . 
         FIG. 5B  illustrates an alternative exemplary flow of injection in the distal portion of the exemplary treatment system of  FIG. 3B . 
         FIGS. 6A and 6B  illustrate an exemplary single chamber flow modulator, in different stages of flow control. 
         FIG. 6C  illustrates the single chamber flow modulator of  FIGS. 6A and 6B  disposed in the proximal portion of the treatment system of  FIG. 3 . 
         FIG. 7  sets forth exemplary fluid flow equations (laminar) that may be used in modeling a conduit fluid flow. 
         FIGS. 8A, 8B and 8C  illustrate an exemplary two-chamber flow modulator, in different stages of flow control. 
         FIGS. 9A, 9B and 9C  illustrate an exemplary two-chamber flow modulator with holding chamber, in different stages of flow control. 
         FIGS. 10A and 10B  illustrate a capacitance chamber flow modulator (bladder), in different stages of flow control. 
         FIGS. 11A and 11B  illustrate an exemplary flow modulator with constant force chamber, in different stages of flow control. 
         FIGS. 12A and 12B  illustrate an exemplary constant flow modulator, in different stages of flow control. 
         FIG. 13  illustrates graphically an exemplary agent injection profile (flow rate) synchronized with the exemplary blood flow rate profile of  FIG. 2 . 
         FIG. 14  illustrates exemplary schemas of synchronized agent delivery modulation systems. 
         FIG. 15  illustrates an exemplary synchronized agent delivery with direct modulation. 
         FIG. 16A  illustrates an exemplary synchronized agent delivery with indirect modulation, adjacent a distal portion of a treatment system therefor. 
         FIG. 16B  illustrates an exemplary synchronized agent delivery with indirect modulation (top view), adjacent a proximal portion of such a treatment system. 
         FIG. 16C  illustrates an exemplary synchronized agent delivery with indirect modulation (side view), adjacent a proximal portion of such a treatment system. 
         FIG. 16D  illustrates, in side sectional view, the brake mechanism of the exemplary synchronized agent delivery arrangement of  FIG. 16C . 
         FIGS. 17, 17A, 17B, 17C and 17D  illustrate exemplary delivery catheter distal constructions. 
         FIG. 18  illustrates an exemplary delivery catheter with distal disrupting structure. 
         FIG. 19  illustrates, in chart form, exemplary medium delivery modulation control factors and/or elements, the features of which may be combined, in part or in whole, to achieve the advantages of minimizing over-introduction of agent into a patient, pursuant to the teachings disclosed herein. 
         FIGS. 20-22  illustrate an exemplary constant force modulator system, in different stages of flow control. 
         FIGS. 23, 24A and 24B  illustrate an exemplary passive blood flow and medium flow valving mechanism operable as a function of a physical attribute in and/or around a medium delivery site. 
         FIGS. 25A and 25B  illustrate another exemplary arrangement for passive valve control of blood flow and medium flow adjacent a medium delivery site. 
         FIG. 26  illustrates an exemplary variable force delivery platform for use in a modulator system. 
         FIG. 27  illustrates a force pin selection guide for use in connection with a variable force delivery platform. 
         FIG. 28  illustrates an exemplary pin and its associated pin location slot, as used with a variable force delivery platform. 
         FIG. 29  illustrates an alternative exemplary variable force delivery platform for use in a modulator system. 
         FIG. 30  illustrates an exemplary flow diverter assembly. 
         FIG. 31  illustrates a switch plate for the flow divert assembly of  FIG. 30 . 
         FIG. 32  illustrates an exemplary flow restrictor assembly. 
         FIG. 33  illustrates an exemplary automatic flow diverter assembly. 
         FIG. 34  is an exploded perspective view of the automatic flow diverter assembly of  FIG. 33 . 
         FIG. 35  is a sectional view of a valve in the automatic flow diverter assembly of  FIGS. 33 and 34 . 
         FIG. 36  is an enlarged perspective view of a portion of  FIG. 35 . 
         FIG. 37  is a perspective view of an exemplary compression plate for the valve of the automatic flow diverter assembly shown in  FIGS. 33-36 . 
         FIG. 38  is a plan view of a proximal face of the compression plate of  FIG. 37 . 
         FIG. 39  is a side view, as taken along lines  39 - 39  in  FIG. 38 . 
         FIG. 40  is a sectional view, as taken along lines  40 - 40  in  FIG. 38 . 
         FIG. 41  is a sectional view, as taken along lines  41 - 41  in  FIG. 38 . 
         FIG. 42  is an exploded perspective view of an alternative automatic flow diverter assembly. 
         FIG. 43  is a side view of a movable diffuser and check valve O-ring thereon for the automatic flow diverter assembly of  FIG. 42 . 
         FIG. 44  illustrates graphically a typical injection profile (pressure) of agent with a treatment system of  FIG. 3 , and an injection profile (pressure) of agent for the treatment system of  FIG. 3  as modulated using a variable force delivery platform such as illustrated in  FIGS. 26-27 . 
         FIG. 45  illustrates graphically an injection profile (pressure) of agent for the treatment system of  FIG. 3  in a typical injection (P Typical ) and a pulsed medium injection profile (P Pulsatile I ). 
         FIG. 46  illustrates an enlarged view a segment of the pulsed injection profile P Pulsatile I  of  FIG. 45 . 
         FIG. 47  illustrates graphically an injection profile (pressure) of agent for the treatment system of  FIG. 3  in a typical injection (P Typical ) and an alternative pulsed medium injection profile (P Pulsatile II ). 
         FIG. 48  illustrates an enlarged view a segment of the pulsed injection profile P Pulsatile II  of  FIG. 47 . 
         FIG. 49  illustrates an exemplary arrangement for indirect application of pulsed pressure to medium being manually injected via a catheter. 
         FIG. 50  illustrates an exemplary arrangement for direct application of pulsed pressure to the medium being manually injected via a catheter. 
         FIGS. 51A, 51B and 51C  schematically illustrate alternate flow diversion configurations for agent flow from an injector through a catheter system. 
         FIG. 52  illustrates an exemplary medium management system. 
         FIG. 53  is a perspective view of an exemplary medium diversion reservoir. 
         FIG. 54  is a perspective exploded view of an exemplary medium diversion reservoir. 
         FIG. 55  is a cross-sectional view of the exemplary medium diversion reservoir in a first configuration, taken along line  55 - 55  of  FIG. 53 . 
         FIG. 56  is a cross-sectional view of the exemplary medium diversion reservoir in a second configuration, taken along line  55 - 55  of  FIG. 53 . 
         FIG. 57  illustrates another exemplary medium diversion reservoir. 
         FIG. 58  illustrates another exemplary medium management system. 
     
    
    
     While the above-identified figures set forth one or more embodiments of the disclosed subject matter, other embodiments are also contemplated, as noted in the disclosure. In all cases, this disclosure presents the disclosed subject matter by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of this disclosure. 
     The figures may not be drawn to scale. In particular, some features may be enlarged relative to other features for clarity. Moreover, where terms such as above, below, over, under, top, bottom, side, right, left, etc., are used, it is to be understood that they are used only for ease of understanding the description. It is contemplated that structures may be oriented otherwise. 
     DETAILED DESCRIPTION 
     This disclosure pertains to devices and methods used to control, transform or otherwise modulate the delivery of a substance, such as radiopaque contrast, to a delivery site. More specifically, it is the intention of the following devices and methods to modulate the delivery of media to a vessel, vascular bed, organ, or/and other corporeal structures so as optimize the delivery of media to the intended site, while reducing inadvertent introduction (or reflux) of the media to other vessels, vascular beds, organs, and/or other structures, including systemic introduction. 
     The terms medium (media), agent, substance, material, medicament, and the like, are used generically herein to describe a variety of fluidal materials that may comprise, at least in part, a substance used in the performance of a diagnostic, therapeutic or/and prophylactic medical procedure and such use is not intended to be limiting. 
     The description, as well as the inventive devices and methods described herein, may be used in modulating contrast media delivery to the coronary vasculature in prevention of toxic systemic effects of such an agent; although, one skilled in the art would recognize that there are many other applications wherein the controlled delivery of a media to a specific vessel/structure/organ/site of the body may also benefit from the devices and methods disclosed herein. For simplicity, these devices and methods may be described as they relate to contrast media delivery modulation. As such, they may be used in the prevention of Contrast Induced Nephropathy; however, it is not intended, nor should it be construed, so as to limit the use to this sole purpose. Exemplary other uses may include the delivery/injection/modulation of: cancer treatment agent to a tumor; thrombolytic to an occluded artery; occluding or sclerosing agent to a vascular malformation or diseased tissue; genetic agent to a muscular bed, neural cavity or organ; emulsion to the eye; bulking agent to musculature and/or sphincter; imaging agent to the lymphatic system; anti-biotics to an infected tissue; supplements in the dialysis of the kidney; to name but a few. 
     Exemplary Use—Prevention of Contrast Induced Nephropathy 
     Contrast Induced Nephropathy (CIN) is a form of kidney damage caused by the toxic effects of dyes (radiopaque contrast media) used, for example, by cardiologists to image the heart and its blood vessels during commonly performed heart procedures, such as angiography, angioplasty, and stenting. In general, the dye is toxic and is known to damage kidneys. Although most healthy patients tolerate some amount of the “toxicity,” patients with poor or non-functioning kidneys may suffer from rapidly declining health, poor quality of life, and significantly shortened life expectancy. Potential consequences of CIN include: irreversible damage to the kidneys; longer hospital stays; increased risk of heart disease; increased risk of long-term dialysis; and, ultimately a higher mortality risk. For patients who acquire CIN, their risk of dying remains higher than others without CIN, and this risk continues even after five years of their procedure. CIN has a significant economic burden on the healthcare system and currently there is no treatment available to reverse or improve damage to the kidneys, once a patient develops CIN. 
     To date, there have been attempts in reducing the toxic effects of contrast media on patients who undergo procedures involving dyes, especially those patients who are at high risk for developing CIN. Some of these efforts have been to: change the inherent toxicity (chemical/molecular nature) of the dyes; reduce the total amount of contrast agent injected (through injection management and/or dye concentration); remove media through coronary vasculature isolation and blood/contrast agent collection systems, to name a few. These methods and/or devices used in the control of the toxic effects of contrast agents have had their inherent compromises in effectively delivering a contrast media specifically to a target site while minimizing the systemic effects. As an example, changing the composition of a dye and/or injection concentration may help reduce a contrast agent&#39;s inherent toxicity at the expense of the contrast agent&#39;s ability to perform its intended function (e.g., visualization of vasculature). Conversely, the ability to “collect” contrast agent laden blood “downstream” from the visualization site may ensure visualization, but requires the complexity of placement and operation of a collection system. 
     Other attempts to manage the amount of contrast agent delivered to a patient have employed automated (versus manual, syringe injected) contrast media injection systems. Close monitoring and control of the total quantity of contrast agent injected may have a positive impact in the incidence of CIN. However, these injection systems are expensive (including capital equipment and disposables), cumbersome to use within a cath lab, and take additional time and expertise to set-up and operate properly. Improper use could negate any benefits seen by better management of the quantity of the contrast agent delivered to a patient, and the additional time required to set-up such a system may also add significant complexity to a procedure. 
     Exemplary Use—Coronary Blood Flow and Management of Agent Delivery 
     Many of the vascular structures and capillary beds of the human body perfuse with enriched, oxygenated blood as a result of the blood being pressurized by the cyclical driving force of the heart during contraction (systole) and decompression (diastole). Most vascular blood flows peak in the body in response to the heart&#39;s contractile phase. Because of the cyclical flow of blood in the vasculature, optimization of delivery of any contrast agent to a vascular delivery site may be enhanced through the coordination of an injection&#39;s pressure and flow to coincide more closely with that of the vascular site receiving the contrast agent. 
     Although similar flow principals may apply, the flow of coronary blood is unique in that the perfusion of the heart coronary arteries principally peak during the diastolic (relaxation) phase of the ventricular cycle. As seen in  FIG. 1 , the pressure of blood in the aorta (from the heart) peaks during ejection (b). However, the flow of blood into the coronary arteries (left coronary artery/left main, as an example) actually peaks after this, during the relaxation/decompression of the heart (i.e., during diastole (c)). Thus, blood flow through the coronary vasculature, in a normal functioning heart, peaks when aortic blood pressure has diminished. This phenomenon appears contra to what one would expect for arterial heart vessel filling. The flow of blood through the coronary vasculature is not necessarily, or completely, “driven” by a high pressure gradient in the aorta into the coronary arteries. In fact, normally the filling of the coronary arteries peaks when the pressure in the aorta is substantially lower than the peak systolic pressure. 
     It is believed that this phenomenon is derived from a backward travelling, “driving force” or “suction” force of blood that is generated by the relaxing of the myocardium (as well as myocardial microvasculature) during diastole—in essence, during the decompression of the heart. The decompression of the heart in diastole results in a driving wave caused by the relief of the myocardial compression. This force is actually created through a pressure gradient wherein the low pressure of the aorta is actually higher than the vacuum created in the coronary capillary beds—thus, a gradient created from the aorta to the microvasculature. Further description of this phenomenon may be found, for example, in “Evidence of a Dominant Backward-Propagating ‘Suction’ Wave Responsible for Diastolic Coronary Filling in Humans, Attenuated in Left Ventricular Hypertrophy” (Circulation. 2006; 113:1768-1778), which is incorporated by reference in its entirety herein. 
     A challenge in the delivery of contrast agent to the coronary arteries is the cyclical nature of the flow in the arteries (quantity and rate). As further seen in  FIG. 1 , the pulsatile blood in the arteries may change significantly in flow rate over a single cycle of the heart. In addition, the variation in flow rate transpires over a very short period of time—in many cases, this takes place in less than a second. 
       FIG. 2  illustrates an example of a blood flow pattern that may be found within a left main coronary artery of a human heart. The illustrated profile of blood flow rate (Q Blood , or blood volume flow rate) represents about four cycles of the heart over a period of time that is less than four seconds. The average flow rate of blood (e.g., mean Q Blood ) in this example averages about 3.7 ml/sec over a single cycle of the heart, and may vary significantly during each cycle from about 1.3 ml/sec to about 6.5 ml/sec. In this example, the left main is approximately 4.4 mm diametrically and has a length about 5 mm before it bifurcates into the left anterior descending artery and the left circumflex artery. It should be noted that this is only an example and any physiological, anatomical, or fluid flow characteristics described may vary significantly between patients, as well as within the same patient. These variations may occur as a function of age, vascular and/or coronary disease, vascularity and collateralization of the heart, metabolism, blood pressure, patient activity, stress level, functional status of various patients&#39; organs, patient weight, vasodilatory and/or constrictive medicants, and chemical or biochemical mediators, to name but a few of the involved variables. Therefore, the example is intended to help elucidate the disclosure of the devices and methods herein, and is not intended to limit their use. 
     In further illustrating the inventive devices and methods herein, an example of a use of the system will involve the delivery of contrast agent to the left arterial system of the heart during the performance of a treatment procedure (e.g., stent delivery). However, this exemplary use should not, in any way, limit the use of the devices and methods described. 
     Referring to  FIG. 3A , a catheter, therapy, or treatment system  10  is shown that may be used in the treatment of an occlusion in a coronary vessel.  FIG. 3B  further highlights the distal portion of the catheter system, proximate a left coronary artery ostium. As seen in  FIG. 3B , the system  10  includes a system delivery catheter  12  (e.g., guide catheter) and occlusion treatment devices (e.g., balloon catheter  14  with stent  16  and guide wire  18 ). The distal end of the guide catheter  12  is placed proximate an opening  20  (ostium) of the aorta  22  to the left coronary artery  24  (left main), off of the aortic root  26 . The system  10  may be placed by percutaneous advancement of the system  10  from the femoral artery (not shown) to the aortic root  26 .  FIG. 3C  further illustrates a proximal portion of such an arterial occlusion treatment system  10  (including a balloon catheter with stent, guide wire, connectors, etc.) shown in  FIGS. 3A and 3B . Typically, there is a guide catheter connector  28  that may have a Tuoy-Borst compression fitting  30  attached to a proximal portion of the connector  28 . The treatment devices may be passed axially through an outlet of the connector  30  and into a primary lumen  32  of the connector  28 , and then into the guide catheter  12 . The fitting  30  of the connector  28  may be adjusted so as to allow passage of the treatment devices through connector  28 , but resist back flow of fluid out of the guide catheter  12  and connector  28 . In addition, the connector  28  may have a secondary lumen  34  displaced laterally of, and in communication with, primary lumen  32 . Secondary lumen  34  may terminate in luer-fitting  36 . A manifold assembly  38  with multiple ports (e.g., ports  38   a ,  38   b ) may be attached to luer fitting  36 . These additional ports of the manifold  38  may be used to infuse various media through the guide catheter  12  (e.g., within a flow conduit defined by an inner lumen of the guide catheter, and the outer proximities of any treatment system components  14 ,  16 ,  18  therein). Such infusions may include, for example, radiopaque contrast, medicaments, or saline for flushing the guide catheter  12 . 
     The treatment system  10  described in  FIGS. 3A-3C  may be comprised of components that may be used in such a procedure, such as a 6 F guide catheter having an approximate length of 100 cm and an inner diameter of approximately 0.070 inch. Further, the treatment devices (e.g., balloon catheter, stent, guide wire, etc.) might have an outer diameter of 3.2 F proximally and 2.7 F distally. The delivery of the treatment devices may be accomplished by passing the balloon catheter through the guide catheter and over a guide wire of 0.014 inch in diameter. The injection of contrast agent for the visual assessment of the vasculature may be performed by activating an injection device  40  (such as an injector or syringe), as seen in  FIG. 3C . In this case, the contrast agent may pass from the injection device  40 , through a tubing connector  42  (i.e., between injection device  40  and manifold  38 ), the manifold  38 , the guide catheter connector  28 , and ultimately through the co-axial conduit defined between the guide catheter inner diameter and the treatment catheter system (e.g., balloon catheter) outer diameter. 
     This example is illustrative of a treatment procedure and should not be limited to the various assemblies that may be deployed for any given procedure, or by any specific physician. The various infusions of the given example may be introduced through the manifold connections by numerous means, to include manual injection (i.e., syringe), automatic injection with an injection machine, or a “gravity fed” injection arrangement. How perfusions/infusions of various substances may be administered may depend on the medium and the intended therapy. In  FIG. 3C , a syringe is shown connected to the manifold with a tubing connector, providing means to hand-inject contrast medium through the manifold and to the distal outlet of the guide catheter. Conversely, a power injector may be attached to the manifold to perform the injection, as an alternative configuration. 
     Moreover, the example described is illustrative of a treatment procedure comprising a “guide catheter” in conjunction with a treatment system. However, there are a multitude of constructions of conduits that may be capable of delivering, or otherwise mediating the delivery, of substance from a proximal portion of a system (outside of a body) to an intended corporeal site. And thus, reference to a “guide catheter” or “catheter” in the example could be described as a tube, delivery catheter, or any other conduit used in mediating the delivery of a substance; and as such, should not be limited to the various assemblies for the exemplary procedure. 
       FIG. 4A  illustrates an exemplary hand-injection flow rate profile (Q Agent ) of contrast media that may be delivered through a catheter treatment system such as described above. In the example of  FIG. 4A , flow rate (Q Agent ) is described. However, it should be apparent to those skilled in the art that a pressure profile could have been used to describe the concepts herein since there is a direct relationship between the flow rate (Q) and the pressure drop (dP or ΔP) over a conduit. 
     In the example of  FIG. 4A , an injection profile of Q Agent , as delivered to the distal tip of the guide catheter, represents approximately 10-12 ml of contrast media injected over approximately 3-4 seconds. This may be a fairly typical hand-injection for illuminating the left coronary vasculature over 2 to 5 cycles of the heart (while performing a stenting procedure); although, such injections may vary significantly (e.g., from 3 ml to 30 ml over periods of 1 to 8 seconds). It should be noted that some clinical investigators (and injector manufacturers) have suggested using around 5 ml/second flow rate of agent (Q Agent ) for a left heart injection. However, these recommendations may have been derived solely on the optimization of vessel opacification, with little regard for over-use of contrast media. Over-injection may result in unnecessary delivery of contrast media systemically. It is the objective of at least some of the embodiments herein to modulate systemic contrast induction, and therefore minimize “over-injection” (injection that is greater than necessary for the contrast agent to effectively perform its opacification function). 
     In a coronary angiography procedure, a hand-injection is normally administered with increasing pressure, and thus volume, until contrast media is “seen” filling the coronary vasculature radiographically. At this point, the administration continues for about 3 seconds until the quantity of contrast media (e.g., approximately 10 ml) within the injector is used. For an automatic injector, typically the pressure or volume may be set (e.g., 5 ml/sec) and then the operator may activate the automatic injector with a hand-held actuator for several cycles of the heart. 
     The exemplary injection profile Q Agent  shown in  FIG. 4A  reveals an increasing injection (flow rate, which is directly related to pressure). V i  on the graph of  FIG. 4A  represents a minimum level of injection flow rate that may be necessary for the operator to “see” vascularity as a result of visualizing the contrast medium. In essence, V i  is an injection rate of media that may be delivered to a vessel, or organ, wherein V i  is a level known, or believed to be, an acceptable concentration of the substance to provide its intended function. In this case, V i  is the level of delivery wherein the concentration of contrast media injected to the left main is of sufficient quantity to opacity the vasculature, on the average, over several cycles of the heart. V i , as shown in this example, is approximately 3.0 ml/second. That is to say, with an injection of a constant 3.0 ml/second of contrast media the operator may effectively visualize the vasculature, while not over-injecting contrast media. In this exemplary context, an injection meaningfully less than V i  will not provide adequate opacification. The exemplary injection of profile Q Agent  in  FIG. 4A  results in a total volume of approximately 11 ml of contrast media delivered. 
     Referring to  FIG. 4B , various areas are shown which may have (by definition of V i ) injection flows that are either insufficient to opacity the vessel appropriately (areas A and B), or are of a magnitude greater than is necessary for opacification, and may thus result in the over-delivering of contrast agent (area C). That is to say, if the injection had been controlled in the delivery of the contrast agent to obtain V i  (identified as a rectangle within the injection rate profile Q Agent  of  FIG. 4B ), approximately 3 ml less of contrast (25% to 30%) might have been used to achieve the same result (e.g., to sufficiently visualize the artery over the same period of time). Therefore, an injection flow rate profile Q Improved  shown in  FIG. 4C  may outline an “improved” constant flow rate of injection for V i  (i.e., wherein the injection flow rate may be held at a constant rate sufficient for visualization). 
     As a practical matter, and in further illustration of the complexity in efficiently delivering contrast agent into the dynamic environment of a coronary artery, some operators of the injector (a syringe, for example) may try to mimic a rapid injection so as to minimize the area of A in  FIG. 4B  through a rapid increase of pressure (and commensurate volume flow rate) with an injection. When sufficient opacification is “seen” radiographically, the operator may then decrease the pressure (and volume flow rate) of the injection. This technique may be helpful in reducing the area of A (quickly reaching V i ); however, the operator may “over-shoot” the delivery rate required to the vessel for opacification (i.e., V i ) and thus increase the amount of over-injection which may be seen by area C in  FIG. 4B . It should be noted that a 10 cc (ml) syringe may be capable of injecting at 100 psi or more. This pressure of injection from the syringe could generate flows as high as 4.0 ml/second in the exemplary system described above; whereas, only 75 to 85 psi may be needed to inject 3.0 ml/second, as an example. 
       FIG. 4D  illustrates the exemplary flow of blood in the left main (e.g., left main  24  of  FIG. 2 ), noted as blood flow rate profile Q Blood  super-imposed with an exemplary profile of an injection flow rate of contrast (e.g., profile Q Agent  of  FIGS. 4A and 4B ) over-laying the blood flow pattern. In this example, we have additionally assumed that the start of the injection begins at about the same time as systole (compression of the heart with lower blood flow rates). However, from a practical point of view, timing of the beginning of an injection may happen at any time during the heart cycle since it may be difficult to synchronize injections with the vessel blood flow. As can be seen in  FIG. 4D , an injection at a constant V i  flow rate (or, as described by Q Improved  in  FIG. 4C ), although notably better than no modulation (e.g., Q Agent ) may still result in over-injecting contrast media (at times) since the blood flow rate (e.g., Q Blood ) is less than the rate of injection (e.g., V i  or Q Improved ). In this case, the areas D in  FIG. 4D  may indicate such over-injection, where contrast may be injected into the aorta (as an example) rather than into the left main artery. 
     In describing this example further, the arrows in  FIGS. 5A and 5B  illustrate flows Q Blood  (arrow  50 ) and Q Agent  (arrows  52 ) during injection of contrast agent during different phases of the heart cycle. When the injection of contrast medium is greater than the blood flow in the vessel  24  ( FIG. 5A ) there will be a tendency for the contrast media to flow to the least path of resistance. In this case, some of the contrast media may flow to the aorta  22  and, consequently, systemically. Conversely, when the blood flow (Q Blood ) in the vessel is greater than the injection flow (Q Agent ), the flow of contrast media may preferentially pass into the vessel  24  ( FIG. 5B ). In other words, the injection flow rate (Q Agent ) illustrated by arrow  52  in  FIG. 5B  will follow the blood flow rate (Q Blood ) illustrated by arrow  50 . 
     Various embodiments of the inventive devices and methods will now be described in further detail. Many of these embodiments may control, transform or otherwise modulate a pattern of medium, agent, substance, medicament, or fluidal material delivery to a vessel, vascular bed, organ, or/and other corporeal structures so as optimize the delivery of media to the intended site, while reducing inadvertent introduction (or reflux) of the media to other vessels, vascular beds, organs, and/or other structures, including systemic introduction. Some of these embodiments may modulate an injection, such as the example shown in  FIG. 4A , by controlling the flow rate profile of an injection to attain a profile designed to reduce inefficient agent use (e.g., areas A, B and/or C in exemplary injection profile Q Agent  of  FIG. 4B ), and to obtain an “improved” injection profile Q Improved  in  FIG. 4C . 
     Exemplary Modulation Devices and Methods 
     Some of the “modulators” in the following examples may be located at various locations proximate the proximal portion of the therapy system  10 , as described in  FIGS. 3A-3C . For example, a modulation controlling mechanism may be positioned on the injection device outlet, between the injector  40  and the manifold  38 , between the manifold  38  and the guide connector  28 , as well as between the guide connector  28  and the guide catheter  12 . Some other embodiments may also include directly controlling the performance of the injection device  40 . The placement of the modulator may also be highly dependent on the diagnostic, prophylactic or therapeutic procedure to be performed and, as such, the positioning should not be limited by the examples used herein. 
     In addition to locations described above, some inventive embodiments of fluid modulators may alternatively be positioned in, and/or around, and/or proximate the distal portion of the guide catheter/delivery catheter  12 . 
     Furthermore, some embodiments of control devices disclosed herein may advantageously receive a sensor signal so as to coordinate a valving, controlling, or otherwise modulating function on an injection agent before the agent enters an intended target injection site. 
     One exemplary embodiment of a modulation device  55  is shown in  FIG. 6A . Device  55  may be positioned within the exemplary system  10  of  FIG. 3C , as shown in  FIG. 6C . As such, an “injection” port  56   a  of modulator  55  has a connector  56  coupled by tubing  42   a  to injection device  40 , and an outlet port  58   a  of the modulator  55  has a connector  58  coupled by tubing  42   b  to manifold  38 .  FIG. 6A  shows the exemplary modulator  55  comprising a body  60  having three ports thereon. One of these ports (the “Injection” port  56   a ) receives an injection of agent from injection device  40 . A “To Guide” port (outlet port  58   a ) delivers agent from device  55  to the manifold  38 , and subsequently through the guide  12 . An “Overflow” port (outlet port  58   b ) is activated upon over pressurization by the injector  40  to the modulator  55 , so as to release excessive agent out of the system  10  (i.e., out of device  55 ). 
     An example of how such a modulator may function may be determined by the injection parameters (i.e., pressure, volume, flow rate, etc.) intended to improve the delivery of the agent. For example, V i  of  FIG. 4  (with the exemplary treatment system use as described for and by  FIG. 3 ) may be approximately 3.0 ml/second. Using various flow equations for flow within a conduit (assuming some amount of laminar flow), such as those shown in  FIG. 7 , an injection pressure level (from the injector, for example) may be derived to provide an agent flow rate delivered from the distal end of the guide catheter. With a set-up and dimensions as described, a pressure of 75 psi (at or around the proximal portion of the guide catheter) may sufficiently produce about 3.0 ml/second of Q Agent  delivered to the distal tip of the guide catheter positioned at the ostium to the left main. This example is intended to be illustrative for the purpose of description and, as such, should not be restrictive or limiting in the scope of the devices and methods described and disclosed herein. For example, if the treatment device (e.g., balloon catheter  14 , stent  16 , and wire  18 ) described above were to have a different construction (than previously described), such as a proximal and a distal outer dimension of 2.7 F, only 43 psi may be necessary to produce approximately 3.0 ml/second of Q Agent . Alternatively, utilizing a guide catheter (e.g., delivery catheter  12 ) with different inner diameter dimensions might be used in producing a medium flow rate of about 3.0 ml/second, at a lower pressure differential. For example, the guide catheter could be larger (0.076 inch inner diameter/6.5 F outer diameter) in corporeal areas less critical in the performance of the treatment (e.g., descending aorta), while providing advantages of a smaller treatment system (e.g., guide catheter having 0.70 inch inner diameter/6 F outer diameter) in proximity of the treatment region (for example, 30 centimeters of the guide catheter  12  distal portion). Advantageously, agent flow rate of approximately 3.0 ml/second may be accomplished at about 50 psi, while not sacrificing the benefit of a smaller treatment system within the coronary vasculature. In summary, therefore, it is not the intention per se to describe all possibilities of various constructions of treatment systems and improvements thereto, but rather it is to provide examples of how one might construct exemplary devices for use in such exemplary treatment systems as described herein. 
     Referring to  FIG. 6A , injection of agent from an injection device (as indicated by flow arrow  62 ) may enter a chamber  64  of modulator body  60  having a spring-loaded plunger  66  therein. The plunger  66  in this example (and in others to follow) may be in sealing, but sliding, relationship with the chamber  64 —such as one might find in a syringe. Compression spring  68  (providing, e.g., spring constant k 1 ) may be positioned within the side of the chamber  64  opposing the force of injection and configured so as to resist movement of the plunger  66  against the force applied by filling the chamber with agent from the injector. As the agent injection pressure increases in chamber  64 , the plunger  66  may move against the compression spring  68 . The force generated by the spring  68  against the pressure of injection will be defined by the spring&#39;s spring constant (k) and the distance (L) the spring has been compressed, or otherwise displaced from its equilibrium (Hooke&#39;s Law, F=−k*L).  FIG. 6A  shows a displacement of the spring  68  (at plunger  66 ) within the chamber  64  of a distance greater than L 1 . In this example, displacement of the spring/plunger equal to, or greater than, L 1  may allow passage of the pressurized agent to flow through an orifice in the chamber  64  and then through the “To Guide” port  58   a  at a minimum, threshold pressure (such as indicated by flow arrow  70 ). In the example described above, we have hypothetically selected a pressure of about 75 psi to produce the intended flow of agent. That is to say, when the force within the chamber  64  is equal to 75 psi/(cross-sectional area of the plunger/chamber), the force derived from the compression of the spring  68  over a distance L 1  should be about equivalent. The spring  68  used in producing such a force would have a spring constant (k) to optimally produce an equivalent force over the displaced length. This modulator construction may advantageously produce an injection flow profile of agent that allows flow to the guide at some intended flow rate that may be radiologically visible (i.e., V i ). In our example, V i  may be 3.0 ml/second. 
     Furthermore, as an injection of agent into the modulator  55  is increased in pressure, the plunger  66  of  FIG. 6B  may continue compression of the spring  68  along the longitudinal axis of the chamber  64  so as to expose a second orifice in the chamber  64  (e.g., to the “Overflow” port  58   b ) at L 2  wherein the highly pressured agent may be diverted away from introduction into the guide  12  (such as indicated by flow arrow  72  in  FIG. 6B ). For example, it may be determined that an acceptable working range of a modulator may be 75 psi to 80 psi, to produce controlled injections with flows in the above example of about 3.0 ml/second to about 3.1 ml/second. The displacements of the spring  68  with spring constant k 1  at L 1  and L 2  could define these operating pressures/flow rates. An injection greater than 80 psi will result in the excessive injection being bled-off into the “Overflow” port  58   b , and not introduced systemically. Moreover, if the injection should fall below 75 psi, no agent will pass into the system (the plunger would be moved within the chamber by the spring such that both orifices of the chamber would close due to insufficient pressure). The exemplary modulator described may advantageously produce an improved injection flow profile, reducing inefficient agent use as illustrated as areas A, B and/or C in exemplary injection Q Agent  profile of  FIG. 4B , and resembling (within a working range), an “improved” injection profile Q Improved  of  FIG. 4C . 
     An alternative embodiment of a controlling device  75  may be of the construction as shown in  FIGS. 8A-8C . In essence, a single chamber device such as illustrated in  FIG. 6  may be replaced by a double chamber configuration so as to provide greater fidelity in the selection of modulator working pressures/flow rates. 
     As shown in  FIG. 8A , there may be two separate tanks or chambers with two compression springs (having spring constants of K 1  and K 2 ). Medium from the injection device may be delivered to the device  75  as in device  55  of  FIG. 6C  (as illustrated by flow arrow  62 ), or any of the alternative locations described herein. Fluid flow from the injector enters chamber  1  (tank  76 ) and compresses plunger/spring  78  of chamber  1  until an intended pressure (and commensurate flow rate) is obtained. When the intended pressure/flow is obtained (i.e., V i  at 75 psi of the previous example), the flow of medium passes via an orifice in chamber  1  and out the “To Guide” port  80 , as shown in  FIG. 8B  (such as indicated by flow arrow  82 ). Chamber  2  (tank  84 ) is in fluid communication with port  80  and may also be pressurized by the injection. Fluid flow from the injector (via port  80 ) enters chamber  2  and compresses plunger/spring  86  until another compression level is reached within chamber  2 , at which point plunger/spring  86  in chamber  2  will compress to a point that the passage of fluid is allowed, via an orifice in chamber  2 , into port  88  (the “Overflow” port). As shown in  FIG. 8C , the “decompression” of chamber  2  acts as a “relief valve” and reduces the pressure of the fluid going to the “To Guide” port  82  if the pressure in chamber  2  exceeds an upper-end threshold (i.e., 80 psi in the example of  FIG. 6 ). Any additional pressure/volume will be bled-out of the system via port  88  (such as indicated by flow arrow  90  in  FIG. 8C ) and not introduced through the guide. In operation, the use of a device such as device  75  with an agent injection system may likewise produce an “improved” injection agent flow profile, reducing inefficient agent use as illustrated as areas A, B and/or C in exemplary injection profile Q Agent  of  FIG. 4B , and resembling (within a working range) the “improved” injection profile Q Improved  of  FIG. 4C . 
     Advantageously, an alternative modulator design, as shown in  FIGS. 9A-9C , might also accommodate cessation of injection from the injection device without fully ceasing the injection of medium to the guide. For example in a modulator  95  having two chambers or tanks  96  and  98  such as shown in  FIG. 9A , tank  2  might include a compression spring with a lower spring constant than the compression spring in tank  1 , but allow more filling of the tank  2  (i.e., greater compression length of its spring), while providing flow to the guide at an intended rate. In essence, tank  2  might act as a “holding tank” of the injection. 
     In further viewing  FIG. 9A , the modulator  95  may comprise two tanks  96  and  98  with two compression springs  100  and  102  (with spring constants of K 1  and K 2  respectively). Medium from the injection device may be delivered to the device as in the device of  FIG. 6B  (as again illustrated by flow arrow  62 ), or any of the alternative locations described. Fluid flow from the injector enters chamber  1  and compresses plunger and spring  100  of chamber  1  until an intended pressure (and commensurate flow) is obtained. When the intended pressure/flow rate is obtained, the flow of medium passes out of chamber  1  via an orifice and into chamber  2  via channel  104 , and then out the “To Guide” port  106 , as shown in  FIG. 9B  (as illustrated by flow arrow  108  in  FIG. 9B ). In essence, chamber  1  provides chamber  2  with a pressurized flow of a value equal to, or greater than, some intended limit (i.e., a minimum threshold, such as 75 psi). If chamber  2  should pressurize with fluid greater than an upper threshold of some working pressure (for example, 80 psi) spring  102  of chamber  2  may compress to a point to allow passage of fluid out of chamber  2  via another orifice and into port  110  (the “Overflow” port) with any additional pressure/volume bled-out of the system, and not introduced through the guide (as illustrated by flow arrow  112  in  FIG. 9B ). Again, an injection system equipped with a device such as device  95  may aid in producing an “improved” agent injection profile similar to profile Q Improved  in  FIG. 4C . 
     Although the previous example describes using device  95  as simultaneously injecting a medium while delivering the medium to/through the guide catheter, the device  95  may also be employed to deliver the medium in a “sequential” fashion. For example, to “sequentially” inject a medium (i.e., fill a chamber with a medium to be delivered, but allow time before release of the injection), or avoid an interruption in the delivery of a medium, the device  95  of  FIG. 9C  may advantageously continue to deliver medium to the “To Guide” port  106  as spring  102  decompresses. As shown, the cessation of the injection  62  at a minimum level (as illustrated at  113  in  FIG. 9C ) may result in the cessation of medium delivered via channel  104  from chamber  1  (as illustrated at  114  in  FIG. 9C ) to chamber  2  since spring  100  has sufficiently decompressed so as to occlude the orifice in chamber  1  into channel  104 , thus stopping the flow of medium from chamber  1  to chamber  2 . 
     In this example, tank  2  may “bleed-out” the medium contained within tank  2  while no additional medium is injected into the device  95 . The device  95  of  FIGS. 9A-9C  might also have a “relief” mechanism or one-way valving type system (such as valve  107  in  FIG. 9C ) attached to the “To Guide” port to assure that a minimum pressure is maintained as chamber  2  decompresses (i.e., a relief valve that only operates above the intended pressure of, say 75 psi and only allows flow to the guide if minimum pressure is maintained). Conversely, the spring of chamber  2  may also be designed to “close” the orifice to the “To Guide” port if a minimum level of pressure is not maintained.  FIGS. 9A-9C  also illustrate knurled-knob bolts  100   a  and  102   a  threadably extending from tanks  1  and  2 , and attached to springs  100  and  102 , so as to provide a mechanism for independently adjusting the forces delivered by their respective plungers. 
     An alternative example of a regulator that could be used for sequential or/and simultaneous injection may be seen in  FIGS. 10A and 10B . In this exemplary embodiment, a pressure chamber is filled with a quantity of medium to be delivered. The pressure and volume of the medium to be injected to a guide may be determined when it is introduced into the chamber, or conversely the chamber may be designed to provide/apply pressure upon the medium within the chamber after its introduction.  FIGS. 10A and 10B  illustrates such a modulator  115  that comprises a compartment (medium chamber  116 ) defined for a medium to be injected, another compartment (gaseous chamber  118 ) for receiving a gaseous medium (e.g., air), and a deformable bladder  120  sealingly separating the compartments  116  and  118 . As seen in the example, a valve  122  may be used to facilitate the flow of gas in and out of compartment  118  (e.g., to seal the gaseous compartment  118 ). The medium to be delivered can be introduced into the chamber  116  of the modulator  115  with the gaseous compartment valve  122  closed. During introduction of medium, the start of which is shown in  FIG. 10A  (fluid filling from the injector as indicated by flow arrow  62 ), the bladder  120  may deform into the gaseous compartment  118  until the medium obtains an intended pressure for the delivery of the medium to the guide catheter. Not shown in  FIG. 10  are the valve mechanisms (such as those found on the manifold  38 , for example, of  FIG. 3C ) to allow the passage of medium, and retention of medium within the modulator  115 , until an injection to the guide is warranted. The medium may be released from the chamber  116  by opening, or otherwise activating, a valve (not shown) between the medium chamber  116  and the guide.  FIG. 10B  illustrates releasing of the medium from the chamber  116  to the guide catheter (as indicated by flow arrow  124 ). 
     Conversely, the chamber  116  of  FIG. 10A  might be filled with injection medium first; and, then pressurized to an intended delivery pressure by introduction of gas into the gaseous compartment  118 , thus applying pressure to the medium through the bladder  120 . 
     Although the previous description of device  115  may be illustrated as “sequential” delivery, device  115  may be designed to act as a “capacitor” during simultaneous delivery. In this case, there may be another port (a “To Guide” port configured on the medium chamber  116 , not shown), to allow delivery from the device  115  during injection. 
     A modulator  115 , such as example devices of  FIGS. 10A and 10B , may advantageously provide a flow profile that resembles the injection Q Improved  of  FIG. 4C , at least as it pertains to areas A and C of  FIG. 4B , since the injection may be delivered quickly to a V i  flow rate, accommodating a quick ramp up and a fairly even flow rate for a short period of time. With respect to area B of  FIG. 4B , chamber  116  of  FIGS. 10A and 10B  may decompress (while delivering flow) to a level that is below an “improved” working range. To compensate for this, a mechanism (such as a one-way value; e.g., valve  117  in  FIG. 10B ) may be disposed between the chamber and the guide to assure that the medium flow rate delivered meets the intended limits (e.g., minimal flow rate) for the injection, or terminates the flow. 
     An alternative construction of a modulator may include a chamber constructed with a constant force spring, as shown in  FIGS. 11A and 11B . Such a spring, by design, may deliver a constant force on a member (such as a plunger) over its working range (displacement). A modulator  125  of this type may include a conical spring ( 126  as shown in  FIG. 11A ) as an example of such a spring that can be made to have a constant force delivered over different compression lengths (displacements from equilibrium). The spring  126  may have variable pitches, with a larger pitch in its larger outer coils and a smaller pitch in its smaller inner coils, thus collapsing/expanding the coils at the same force during compression/decompression. Similar to the other devices described herein, the alteration of an injection&#39;s pressure and flow may be performed while delivering media to a delivery site, as well as performed by more than one step/sequence in delivery. 
     Using such a constant force injection modulator  125  as described, one might inject a quantity of medium into a chamber  128  of modulator  125  (as indicated by flow arrow  62 ), leading to compression of conical spring  126 , as seen in  FIG. 11B . Once a desired volume of medium has be received within chamber  128 , injection may be stopped and/or back flow of medium from chamber  128  to the injector prevented (such as by manipulation of a valve—not shown), as further illustrated at  129  in  FIG. 11B . Upon actuation, or otherwise release, of medium from the chamber  128  (such as opening of a valve to the guide—not shown) a plunger  130  may drive (as urged by compressed spring  126 ) the medium from the chamber  128  with constant pressure (and commensurate volume flow rate) toward the guide via an orifice in chamber  128  leading to the “To Guide” port  132 . It might be advantageous with this modulating system  125  to allow “space” within the chamber  128  for the plunger  130  to close the “To Guide” orifice once a desired volume has been delivered. 
     An alternative construction (not shown) for the modulation system  125  of  FIGS. 11A and 11B  might also include mechanically driving a displacement/plunger element at a constant force within/upon a chamber so as to achieve a constant pressure upon the chamber and drive agent at a constant flow rate to the delivery catheter. Such a chamber might have a construction as shown in  FIG. 11A . An alternative embodiment for simply providing constant force on a plunger in a chamber might include the placement of a weight upon a vertically-mounted plunger element within the chamber. For example, a syringe-type chamber might be vertically situated with the displacement actuator/element located above (further away from the center of the earth), and the outlet port located below (closer to the center of the earth). After filling the chamber with medium, various weights may be placed upon the displacement element so as to create the intended constant force upon the plunger (e.g., using gravity upon a mass in deriving a constant force). When an injection is needed, the medium may be released (or otherwise actuated to be released) from the chamber by opening a valve (such as a stopcock). The opening of the valve thus allows the medium to exit the chamber as a result of the force placed on the medium from the weight upon the plunger. The measure of the weight might be, for example, similar to the force determined for the constant force modulator  125  described above. 
     An alternative use of regulator  125  of  FIG. 11  might be employing the regulator during the simultaneous injection and delivery of medium to/through the delivery catheter. With this application, injecting medium into chamber  128  with constant force spring  126  may provide a “pre-loaded” resistance to filling of the chamber. Once a pre-set level of pressure is achieved, regulator  125  may allow injectate to pass into chamber  128  and out of the chamber through the “To Guide” port  132 . Additional filling of chamber  128  may take place during injection of medium if the injection pressure is greater than the pre-set spring resistance (and assuming sufficient resistance to delivery in the delivery catheter). In addition to filling, the chamber  128  may “discharge” medium (a reduction in volume) at a constant pressure (approximately the pre-set level of pressure) if/when the pressure from the injector is less than the pre-set resistance by constant force spring  126 . With this exemplary simultaneous modulation, regulator  125  may act as a “capacitor” (i.e., having the ability to store and discharge a pressurized volume of medium) so as to “level-out” or “smooth-out” the pressure/flow profile of a medium directed to the catheter during injection. 
     Further to the description of modulator  125 , and other media modulators described herein, manual injection (such as a syringe) during delivery media to an injection site might have varied pressures/flows passing to the modulator. Not only might the flows/pressures to the modulator be varied, but it is conceivable (depending on the system construction) that the flow of injection medium might, at times, return into the injector (syringe). As an example, it is possible that an administrator of a syringe might release the pressure placed upon the plunger. Depending on this reduced force, it is possible that the pressure/fluid stored into chamber  128  may be diverted back to the syringe—a function of the “least path of resistance” to the flow from the capacitance chamber  128 . 
     Advantageously, a modulator having a constant force chamber of such construction may be configured to improve a medium injection flow/pressure profile delivered to a delivery catheter.  FIGS. 20 to 22  illustrate such an alternative system configuration/construction, and its method of use, which may provide an improved pressure/flow delivery profile. A modulator system  325  of  FIG. 20  includes a manifold  326  having several elements attached to the manifold  326  to include: a reservoir or vial  328  of medium (i.e., contrast agent), a constant force chamber  330 , an injector  332  (e.g., syringe), a delivery catheter  334 , and a 4-way stopcock  336 . These elements may be configured so as to be in fluid communication with one another, at times, via suitable tubular members T. Valves A (manifold to catheter), B (medium vial to manifold), C (constant force chamber to manifold), and D (injector to manifold) may allow for opening and closing such fluid communications between the manifold  326  and different elements of  328 ,  330   332 ,  334  and  336  of modulator  325 . Note that 4-way stopcock  336  may provide the valving functions of valves C and D in lieu of separate valves/attachments. Of further note, the constant force chamber  330  may be configured, as illustrated, to accommodate a weighted force element (discussed previously) or a coiled constant force element, so as to deliver a constant force upon medium in a chamber therein with a displaceable plunger or surface. These are but two examples of how one might configure a constant force chamber and, as such, are to be illustrative but not limiting in the various configurations to construct a constant force apparatus. 
     In the exemplary method of performing an injection modulation, contrast agent from vial  328  is drawn into the syringe  332  by closing valve A (to prevent flow between the manifold  326  and the delivery catheter  334 ), opening valve B (to permit flow between the medium vial and the manifold  326 ), closing valve C (to prevent flow between from the constant force chamber  330  and the manifold  326 ), and opening valve D (to permit flow between the manifold  326  and the syringe  332 ), as represented in  FIG. 21 . The syringe  332  may be filled with injectate medium by drawing on a plunger  338  of the syringe  332 , as represented in  FIG. 21  by arrow  339 , to thus draw medium from vial  328  into syringe  332 . Valve B (between medium vial  328  and manifold  326 ) may be closed when sufficient medium has been drawn into syringe  332 . 
     Whether a construction having a weighted force element acting upon a plunger (such as illustrated by weight system  330   a ), a construction employing a constant force spring acting on a plunger (such as illustrated by constant spring force  330   b ), or an alternative constant force contrivance, a load is determined to be deployed upon the constant force chamber  330  (and its fluid contents) sufficient in regulating medium flow to be delivered by the delivery catheter  334 . For the sake of elucidation only, say a pressure of 50 psi is wanted at the manifold  326  (e.g., into the proximal port of the delivery catheter  334 ) to create an improved medium delivery flow through the catheter  334 . Constant force chamber  330  may be configured so as to generate approximately 50 psi upon a fluid within, entering, or exiting, the constant force chamber  330  when valve C is opened (i.e., open to permit flow from constant force chamber  330  into the modular system  325 ). 
     When an injection of medium to an injection site is warranted, valves A (to catheter  334 ), C (to chamber  330 ) and D (to syringe  332 ) may be opened and the plunger  338  of the syringe  332  depressed (in direction of arrow  340  in  FIG. 22 ). As the plunger  338  of the syringe  332  is quickly depressed, the fluid ejected from the syringe  332  will want to travel towards the least path of resistance, simultaneously driving fluid to the catheter  334  (as represented in  FIG. 22  by medium flow arrows  342 ) while passing into the constant force chamber  330 . Rapid introduction of medium by the syringe  332  will allow the pressure within the manifold apparatus to quickly obtain 50 psi, and allow for filling the constant chamber force  330  with medium (via flow of arrow  344 ) when pressure is greater than 50 psi. Thus, constant force chamber  330  acts as a capacitor as it takes on more medium at, or above, a pressure of approximately 50 psi; while, also allowing the delivery of medium to the catheter  334  at approximately 50 psi (via flow arrows  342 ). In essence, the flow delivery profile of the modulator  325  may reduce the “wasted” contrast due to ramping-up pressure/flow (area A of  FIG. 4B ); as well as, reduce the “wasted” contrast from over-injecting into the delivery catheter (area C of  FIG. 4B ) by maintaining a more constant pressure within the manifold. 
     In the example shown in  FIGS. 20 to 22 , once the operator has filled the constant force chamber  330  with contrast medium to some degree, the constant force chamber  330  may continue to discharge the wanted 50 psi to the delivery catheter  334  even if the injection flow is diminished, thus facilitating a “smooth” injection to the delivery catheter  334 . 
     When it is determined that sufficient medium has been delivered by the syringe  332 , releasing the plunger  338  (e.g., allowing the plunger  338  on the syringe  332  to negatively displace with no loading) may allow a rapid drop-off of pressure from the manifold  326  as the pressure within the constant force chamber  330  may be dissipated by discharging flow away from the delivery catheter  334  and into the syringe  332  (e.g., least path of resistance—represented by the phantom arrows  346  in  FIG. 22 ). Thus, the rapid decrease in pressure delivered to the delivery catheter  334  may act to reduce the “wasted” contrast as typically seen at the tail end of an injection (e.g., area B of  FIG. 4B ). It is also possible to facilitate the rapid termination of the injection by closing valve A (manifold to catheter) before, during, or quickly after an injection is terminated by the syringe  332 . The termination of the medium injection also may be enhanced by including other mechanisms (such as a one-way valve) so as to quickly shut-off delivery to the catheter  334  when there is insufficient pressure (e.g., when a selected low pressure threshold is reached). Such a one-way valve could be placed at various locations within the modulator system  325 , including its residing between the manifold  326  and the delivery catheter  334 , along the tubular connector therebetween, such as illustrated by valve  317  in  FIG. 22 . 
     Depending upon the circumstances, it may be desired to change, from procedure to procedure (or even during a single procedure), the load provided by the constant force chamber  330 . When the constant force chamber  330  is configured to accommodate a weighted force element (such as weight system  330   a ), this may be accomplished by changing the amount of weight being applied to the plunger. When the constant force chamber is configured as a coiled constant force element (such as illustrated by constant spring force  330   b ), the load may be modified by changing the coiled constant spring element. However, these approaches may be cumbersome and require a stockpile of alternate components (e.g., sets of weights or springs) to achieve varied loads. A constant force element that may be varied (e.g., the ability to change the constant force delivered) with a platform capable of varying the constant force, such as  402 , may be of value. 
     As illustrated in  FIG. 26 , a variable force delivery platform  402  for use in a modulation system such as modulation system  325  is provided to act upon a plunger  404  which in turn presents a load to the medium via a force surface within a plunger chamber  406  filled with medium. The chamber  406  thus may act as the pressure chamber within the constant force chamber  330  (such as illustrated in  FIG. 22 ) that may be connected by tubular member T to valve C on stopcock  336 . 
     The platform  402  may include a constant force spring  408 , such as the coiled constant spring element illustrated in  FIG. 26 , which is operably connected at a free end  410  of the spring  408  to a first end  412  of a pivotable lever  414 . A portion of the lever  414 , adjacent a second end  416  thereof, may be operably engaged with a free end  418  of the plunger  404 . The spring  408  may be coupled to the lever  414  so as to provide a constant spring force, such as illustrated by force arrow  420 , upon the lever  414  adjacent its first end  412 . 
     The lever  414  may be pivotally coupled to a housing or other support structure as at pivot point  425  in  FIG. 26 . Thus, the lever  414  may pivot about point  425  due to the application of force  420  adjacent its first end  412  and a corresponding, yet opposite, force  430  being imparted adjacent the second end  416  of the lever  414 . The force  430  may be applied via the lever  414  and plunger  404  to the medium in the chamber  406 , and is defined by the spring force of the spring  408  as it is transferred via the lever  414  to the plunger  404 . The force transfer is dependent upon the pivoting of the lever  414  about its pivot point  425 . 
     The amount of constant force thus applied to the medium in the chamber  406  can be modified by changing the position of the pivot point  425  relative to the lever  414 . In other words, by moving the pivot point  425  toward or away from the spring  408 , the effective pivotable length of the lever  414  between the spring  408  and pivot point  425  is changed. The amount of force  420  applied to the lever adjacent its first end  412  does not change, but movement of the pivot point  425  will alter the amount of force  430  applied at the second end  416  of the lever  414 . 
     This lever and pivot point arrangement is schematically illustrated in  FIG. 26  as a fulcrum  442 , which as illustrated, is mounted on suitable supporting structure of the constant force chamber  330 . Leaving all other things equal, movement of the fulcrum  442  and its associated pivot point (e.g., from left to right and vice versa, as seen in  FIG. 26 ) will change the force  430  relative to the plunger  404 . This optional directional movement of the fulcrum  442  is illustrated by arrow  444  in  FIG. 26 . When the fulcrum  442  is moved toward the first end  412  of the lever  414 , the effective lever arm distance between the spring  408  and the pivot point  425  is shortened, thus lowering the force  430  applied to the plunger  404 . Alternatively, when the fulcrum  442  is moved away from the spring  408  (and toward the second end  416  of the lever  414 ), the effective lever arm distance between the spring  408  and pivot point  425  is lengthened, resulting in a greater force  430  applied to the plunger  404 . Accordingly, the constant force applied to the medium in the chamber  406  can be changed simply by changing the location of the pivot point  425  relative to the length of the lever  414 , and in this example, that is accomplished by movement of the fulcrum  442  along its possible travel movement trail represented by arrow  444 . Advantageously, this may allow for incremental adjustment of the constant force applied to the medium in the chamber  406 . 
     In one example, the position of the fulcrum  442  is determined by placement of a “pin” along a “pin slot” having a discrete number of pin locations. Each pin location relative to the pivoting lever  414  thereby defines the fulcrum  442  position, which in turn defines a pre-established load to be placed on the medium in the medium chamber  406  depending upon the force of the constant force spring  408 . An exemplary pin location slot  450  is illustrated at  FIGS. 27 and 28 . The slot  450  may be further defined by a connected line of circular pin receiving holes  452  (illustrated in  FIG. 27  as “pin receiving holes”  452   a  to  452   s , as viewed from left to right). The desired constant force is selected by inserting a pin (such as shown as pin  454  in  FIG. 28 ) into a selected pin receiving hole  452  of the slot  450 . The amount of force that will be applied to the plunger  404  may be determined by which pin receiving hole is selected. Selecting a pin receiving hole adjacent a first end  456  of the slot  450  will result in less force being applied to the plunger  404 , while selecting a pin receiving hole at a second end  458  of the slot  450  will result in a greater force being applied to the plunger  404 . By way of example, in a left main coronary artery setting, for effective medium modulation, less force will be required when a larger guide catheter is deployed. For a six French or a seven French guide catheter, placing the pin  454  in the pin receiving hole  452   s  may provide sufficient constant force on the medium in chamber  406  to deliver a medium at a desired rate. However, when a seven French guide catheter is used with a treatment (“Rx”) catheter, more constant force may be required to deliver a medium, and thus the most appropriate location for the pin  454  is in pin hole  452   r . In a further example, if a five French catheter is being deployed which includes a “Rx” catheter, the pin  454  may be placed in pin hole  452   a  to provide a greater constant force for the medium being supplied by the constant force chamber  330  into the modulator system  325 . 
     Other exemplary constant force “pin” settings for use with different catheter configurations may be seen in  FIG. 27 . The settings shown are exemplary of a situation wherein one might expect approximately 2 ml/sec of medium delivered with a constant force chamber  330  of approximately 50 psi, as an example. In the context of the example of  FIG. 27 , these terms may generally mean as follows: “Guide” means a coronary guide catheter, “Diag.” means a coronary diagnostic catheter, “Rx” means a coronary treatment catheter, and “OTW” means an over-the-wire coronary treatment catheter. 
     An exemplary constant force chamber  330  having the slot  450  and its associated pin  454  for manipulating the fulcrum  442 , and its associated pivot point  425 , is illustrated in  FIG. 28 . Other arrangements for moving the fulcrum  442  along or about lever  414  and defining their relative positions are also contemplated, such as rack and pinion movement, magnetic couplings, and other like contrivances that may provide the ability to vary a constant force delivered to a pressure chamber  406  thru plunger  404 . 
       FIG. 29  illustrates an alternate variable force delivery platform  502 , where instead of a constant spring  408 , a weight system  508  is employed to define a constant force such as illustrated by force arrow  520 . The force from the weight system  508  is transferred to the lever  514  at  510  by suitable means, such as a cable and pulley arrangement as shown. Other than the source of the constant force being a weight system instead of a constant spring, the platform  502  operates in a similar matter to the platform  402  described above. Like elements and features are shown in  FIG. 29 , indexed upwardly by 100 using reference numerals similar to those illustrated in  FIG. 26 . 
     An alternative embodiment in the modulation of flow through a device to control injections may be found in  FIGS. 12A and 12B , which illustrate a constant flow rate modulator  135  that may advantageously modulate the flow rate delivered to the guide (or any other delivery device), versus the constant force of modulator system  325 . A modulator such as this might be useful for delivering a constant flow rate of a medium to a target site, independent of using different conduit configurations. For example, the resistance to flow of a medium through an angiographic catheter (for diagnostic visualization of an artery) may be different than the treatment system described previously. And, as such, the pressure required to drive constant agent flow through an angiographic catheter typically may be lower than the pressure necessary to drive similar agent flow through the treatment system. Advantageously, a physician may be able to perform an angiographic assessment (with an angiographic catheter) of an artery, as well as a treatment (with a treatment system) with the same modulator delivering similar constant flows of agent. An arrangement as shown in  FIGS. 12A and 12B  may allow a physician to switch between both agent delivery systems with the same modulator  135 . This is in comparison to say, the constant force of modulator system  325 , wherein the weight, the constant force coil, or the constant force contrivance may require adjustment of the force to accommodate different system considerations (e.g., guide catheter, treatment catheter, etc.). 
     Referring to  FIG. 12A , the injection device provides an injection (see flow arrow  62 ) into a chamber  136  of the modulator  135 . The injection acts upon plunger  138  (that is sealably and movably disposed within chamber  136 , and biased in opposition to initial injection medium pressure by variable force spring  139 ) with a force derived from the pressure of the medium over the area of the plunger  138 . The flow of medium is directed out of chamber  136  along an injection flow path  140 , by-passing the plunger  138 , and then re-establishing flow within the chamber  136 , via an orifice  142 , on the guide side of the plunger  138 . Depending on the pressure that the medium experiences on the guide side of the modulator  135 , the spring-engaged plunger  138  will be driven (by the force of that pressure) to a location along the orifice  142  passing through the wall of the chamber  136 . The placement of the plunger  138  (and its associated spring  139 , and the bias force of spring  139 ) and its relationship to the orifice  142  may partially restrict the flow of the medium into the guide portion (i.e., guide catheter side) of the chamber  136 . As an example, the orifice is held completely open in the drawing of  FIG. 12A , suggesting the pressure of the injection may be nearly the pressure in the guide portion of the chamber  136 , with the modulator “opening the flow” of the orifice  142  as much as possible to allow greater flow. The differential of pressure, and thus the forces acting upon both sides of the plunger may be nearly the same in  FIG. 12A . An example of this scenario may be when there is relatively high resistance to medium flow in the delivery guide (e.g., when in use with a treatment system). 
     Conversely,  FIG. 12B  shows the orifice  142  partially occluding the flow from the injection flow path  140  into the guide portion of the chamber  136 . In this case, there may be less resistance (i.e., medium flows more readily) from the guide or delivery catheter and the differential in pressures within the two sides of the chamber  136  have increased. In other words, the injection path has been restricted (driven by the pressure differentials) to drive the fluid in a delivery catheter having less resistance (and, therefore requiring less pressure) in delivering an equivalent flow rate (such as when in use with an angiographic catheter). In both cases presented, the flow rate of medium to/though the delivery catheter may be the same; however, it is the modulator that may be configured to adapt/change resistance to flow in order to accommodate constant flows (delivery of medium with different systemic resistances). 
     The example of the flow modulator of  FIGS. 12A and 12B  illustrates a chamber with a single, graduated orifice in performing the constant flow rate modulation function. However, such a function could be performed with a multitude of orifices, as well as with different cross-sectional areas of the orifice(s) to accomplish the same intended function. In addition, other forms of variable pressure restrictors (having constant flow rate modulation) may accomplish the intended function. As such, these alternatives are considered within the scope of the disclosed devices and processes. 
     It should be also noted that the exemplary descriptions have assumed that the ancillary tubings/connections/channels within and/or between system components/devices, are relatively large and may have negligible “resistive” impact on the overall flows/pressures modulated by the devices. For example, the pressure drop created by the lumen of the channel between chambers  1  and  2  of  FIGS. 9A-9C , or within the connective tubings and/or connectors of  FIGS. 6A-6C  should be minimal. If not, design changes could be made to accommodate for the additional resistances created with such connections without deviating from the scope of the disclosed devices and processes. 
     Although the various constructions of modulating devices have been described as having chambers with springs therein, it is clear that any passive and/or active biasing or valving mechanisms (or any combination thereof) might also be used to produce similar functions, including apparatuses being significantly smaller than the devices illustrated. For example, hydraulic valves, release valves, one-way valves may perform functions so as to activate or otherwise modulate flow (i.e., allow flow) upon a known/determined flow rate and/or pressure, as well as deactivate (stop or limit flow) once a known/determined flow rate and/or pressure condition has been obtained. Furthermore, passive devices such as fluid flow restrictions (i.e., tubular members) and/or diffusers may also be utilized in modulating the flow. These restrictive devices may not necessarily define an “on-off” (e.g., digitally “there is” or “there isn&#39;t” flow based on pressure) restriction, but rather act to affect the flow rate in the catheter based on restrictions to flow in the total system. It is within the scope of the devices and methods described herein to include such alternative devices, or devices in combination, to produce similar injection modulation effects. 
     As an example of passive devices that may alter, or modify, the flow of fluid delivered through a catheter, a review of the resistance to flow of the embodiment in  FIG. 6  may be seen in  FIG. 51A  (noting that Q=ΔP/R; where Q=fluid flow through a system, ΔP=pressure differential across the systems and R=Resistance to fluid flow in the system; see e.g.,  FIG. 7 ). In the example shown in  FIG. 51A , an injection from a syringe passes into a chamber  64  with pressure P I  and flow Q I . There is initially resistance to flow (R 1  of the modulator device  55  “valve”) in the chamber  64  from the spring constant k 1  of the spring  68 . Once the resistance is overcome (say, for example, by injecting over 30 psi), flow is allowed to pass to the catheter through orifice  58   a  (“To Guide”), at a pressure of P 2  and flow of Q 2 . This pressure/flow might be considered a minimum threshold of delivering flow to the catheter system. Upon increased pressurization from the injection (e.g., from P I ), additional resistance R 2  to flow will be created by the spring  68  in the modulator device  55  (in addition to the resistance R c  of the catheter/system). Once resistance R 2  is overcome through increased pressurization/flow (say, for example, 50 psi), fluid flow will be allowed to flow out of the “overflow” orifice  58   b  (see, e.g.,  FIG. 6B ) at a pressure of P o  and flow of Q o . This might be considered a maximum threshold of pressure at which the medium may be injected into the guide (e.g., any pressurization above this will result in bleeding or diverting medium out of the system). It should be noted that when the pressure at P 2 , for example, is high enough to allow flow (e.g., minimum threshold) to the guide, but less than the amount of pressure to overcome R 2  (e.g., maximum threshold), the flow of fluid to guide (and out of the catheter) will vary as a result of the pressure. As well as, when the pressurization exceeds the pressure at which the resistance of R 2  has been overcome, overflow Q o  from the system will continue to increase with pressurization. As shown in  FIG. 51A , the flow exits the catheter system at a pressure P e  and a flow of Q c . 
     Looking at  FIG. 51A , it is possible to alter the flow delivered to the catheter (or guide) system without using the resistance of R 1  (derived from the valve from the modulator device  55 ). The flow diagram of this example may be seen in  FIG. 51B , wherein the pressure (P I ) and flow (Q I ) may be directly delivered to the catheter and an overflow path, in parallel. In this example, Q I  may be split (based on different resistances between the two parallel pathways depending on the amount of flow one might want to direct to the catheter system. As an example, if a flow rate of 3 ml/sec were the maximum one wanted to deliver to the catheter, and the catheter system had a resistance of R C  and possible maximum pressure and flow of (i.e., depending on the syringe, individual strength of the operator, convenience, etc.) P I  of about 60 psi and Q I  of about 5 ml/sec, one could design the constant resistance R O  of the overflow, or diverting, fluid pathway (e.g., tubular member) to allow 3 ml/sec delivered to the guide at about 60 psi P I . This embodiment allows for a simple solution for diverting flow, while modifying the delivered medium, so as not to exceed some approximate injection threshold amount that results in excess contrast being delivered. It should be noted in this configuration that there would be a constant “bleeding” off of the injection, irrespective of the injection pressure. Moreover, it is also possible the resistance of the “overflow” (R O ) may be created by alternative constructs, such as: resistance as a result of a tubular diameter or length dimension; resistance created by flowing through a restrictor, resistor, diffuser, filter medium, etc.; resistance created by alteration in the normal fluid path (pinching of the line in a discrete fashion); resistance created by a combination of any, or all, of the above (for example). To this end, overflow resistance R O  of the above example could simply be a “tube” having sufficient resistance (e.g., diameter/length), or the placement of a resistance, such as a narrowing in a tube (e.g., pinching) to establish sufficient resistance. 
     An alternative embodiment of diverting flow can be seen in  FIG. 51C .  FIG. 51C  illustrates a flow pattern wherein the initial flow of Q I  is directly injected to the catheter system, and upon reaching a minimum pressure (e.g., a pressure P 1  and associated flow rate Q 1 ), a “check valve” may be employed to start diverting the fluid away from the catheter system. In this case, the check valve resistance (R CV ) is in addition to, and prior, to the arrangement illustrated in the overflow tubing resistance (R O ). In  FIG. 51C , the fluid pressure and flow rate exiting the check valve are represented as P CV  and Q CV . One advantage of this configuration (versus the arrangement illustrated in  FIG. 51B ) is that this configuration may allow less fluid to be discharged, since it diverts at a higher pressure point.  FIG. 30  shows an exemplary device capable of producing the fluid flows as described. 
     As has been described, one means for producing an operative medium flow rate is to “strip off,” “bleed off,” or otherwise divert some of the medium flow coming from the syringe away from the catheter system.  FIGS. 30 and 31  illustrate one exemplary arrangement for doing so. In this arrangement, syringe  332  may be fluidly coupled to medium reservoir  328  by suitable tubular members T 1 , T 2  and T 3 , and via manifold  326 . For use, syringe  332  may be loaded with medium from medium reservoir  328  and then valve B on manifold  326  is manipulated to prohibit the flow of medium back to reservoir  328  via tubular member T 1 . 
     A flow diverter assembly  550  may be positioned in the medium flow path between the syringe  332  and the catheter  334 . As can be seen in  FIG. 30  the flow diverter assembly  550  may be coupled to a four way stopcock  552  allowing the assembly  550  to be selectively active or inactive in the flow of the medium, if desired. For example, when the syringe  332  is being loaded with medium from the medium reservoir  328 , the stopcock  552  may be positioned to permit medium flow between tubular members T 2  and T 3 , but not to tubular member T 4  (disposed between the stopcock  552  and the flow diverter assembly  550 ). When the stopcock  552  is positioned to allow flow into tubular member T 4 , medium flow may pass into the flow diverter assembly  550  upon pressurization from the syringe  332 . Like the exemplary agent flow schematic in  FIG. 51C , the flow diverter assembly  550  includes a check valve  554  aligned to prevent the flow of medium into the flow diverter assembly  550  until a certain medium pressure threshold is reached (e.g., 20 psi). Once the threshold pressured is exceeded, the check valve  554  may permit fluid flow into the flow diverter assembly  550 . After traversing check valve  554 , medium flow may pass distally therefrom via tubular member T 5  to a medium reservoir, which may be reservoir  328 , as shown. When the pressure of the medium reaching the check valve  554  from the syringe  332  is lower than the threshold pressure, the check valve  554  seats itself so as to prevent back flow (i.e., medium flow out of the flow diverter assembly  550  via tubular member T 4 ). 
     In one embodiment, the flow diverter assembly  550 , upon reaching a threshold pressure, may divert approximately 40% of the medium flow from the syringe  332 , thereby allowing 60% of that flow to reach the catheter  334 . For example, upon reaching a threshold pressure delivered to check valve  554  of flow diverter assembly  550  from syringe  332 , the flow rate delivered from the syringe  332  could be 5 ml/sec.; however, the desired flow rate to the catheter  334  at this pressure may be 3 ml/second. In this case, flow diverter assembly  550  may be designed (i.e., length, diameter, configuration or other restrictive type structures) so as to allow a medium flow rate of 2 ml/sec. to “bleed off” (or, otherwise be diverted through tube T 5 ) from the total amount of medium delivered to the catheter  334 . In one regard, this flow diversion arrangement can be considered to form flow resistors disposed in parallel, with one form of resistor being the catheter  334  itself, and the other form of resistor being the flow diverter assembly  550  (see again, e.g.,  FIG. 51C ). It should be noted that a change in the “catheter resistance” (e.g., change in the delivery catheter system) may require changing the resistances imposed by flow diverter assembly  550  to achieve similar diversion of flow (e.g., 2 ml/second). 
     In one embodiment, the flow diverter assembly  550  may include a mechanism that allows for selection and changing of a level of flow resistance and/or variation in the amount of medium flow allowed through the flow diverter assembly  550 . Advantageously, a variable flow diverter assembly  550  which is capable of changing resistance may allow a user to switch medium delivery systems (i.e., a diagnostic catheter to a guide catheter with a treatment device) without having to change-out or replace the flow diverter assembly  550 . In an exemplary embodiment, changing the level of flow resistance of the fluid medium through the flow diverter assembly  550  comprises changing an effective size of at least a portion of the fluid medium flow path through the flow diverter assembly  550 . In simplified form,  FIG. 31  illustrates a switch plate  560  that is movable between three positions relative to a base  562  of the flow diverter assembly  550  to allow for manual selection of a level of flow resistance of the fluid medium through the flow diverter assembly  550  to provide greater medium fluid flow resistance with higher pressure of injection. The switch plate  560  has an elongated opening  563  therein that may be sized to receive flexible and deformable tubular member T 5  therethrough. As illustrated in  FIG. 31 , the opening  563  may be larger in a first area  564 , with a diminished dimension in at least one other direction  565  in a second area  566 , and with a further diminished dimension in at least one other direction  567  in a third area  568 . The tubular member T 5  extending out of the flow diverter assembly  550  and toward the reservoir  328  may extend through opening  563  on the switch plate  560 . The switch plate  560  may be movable relative to the base  562  in direction of arrows  570 . Switch plate  560  essentially acts as a sliding pinch valve relative to tubular member T 5 . Accordingly, when the switch plate  560  is aligned with the tubular member T 5  in the first area  564  of the opening  563 , the greatest amount of flow may be allowed through tubular member T 5  by the flow diverter assembly  550  (or, conversely, the least amount of flow to the catheter  334 ). In one embodiment, this may provide a bleed off of medium flow rate suitable for use with a 6 French guide catheter (or equivalent flow restrictive structure). When the switch plate  560  is moved to align tubular member T 5  within the second area  566  of the opening  563 , the tubular member T 5  may be pinched (or otherwise restricted in cross-section), thereby restricting the amount of medium that may flow therethrough, and back to the reservoir  328  (i.e., the flow in T 5  may be more restricted in this configuration than when the tubular member T 5  is aligned within the first area  564  of the opening  563 ). In one embodiment, this may provide a bleed off of medium flow rate suitable for use with a 6 French guide catheter with a coronary treatment catheter therein, or with a 5 French coronary diagnostic catheter, wherein a greater amount of flow may be directed toward the catheter  334 . When the switch plate  560  is moved to align tubular member T 5  within the third area  568  of the opening  563 , tubular member T 5  may be further pinched or restricted in cross-section, thereby allowing even less flow of medium therethrough (e.g., through tubular member T 5 ) than either of the previous two positions of the switch plate  560 . In one embodiment, this may provide a bleed off of medium flow rate suitable for use with a 4 French diagnostic catheter. 
     The flow diverter assembly  550  need not include merely discrete alternate variable flow settings via a mechanism such as movable switch plate  560 . Instead, the flow diverter assembly  550  could have a mechanism or design that allows variable flow settings including two, three (as shown in  FIG. 31 ) or more selected flow rates for flow diversion from the syringe  332  to the reservoir  328 . In one embodiment, flow diverter assembly  550 , tubular member T 4  and stopcock  552  are configured as one self-contained component (such as illustrated by component  572  in  FIG. 30 ) that can simply be inserted into the medium flow path between the syringe  332  and the catheter  334 . 
     Another means for achieving restriction of the driving medium flow rate from the syringe  332  is to dispose a flow restrictor in line somewhere between the syringe  332  and the catheter  334 . Such a flow restrictor would take the form of, for example, a tubular member constrained in size to restrict flow therethrough, a flexible tubular member pinching mechanism, or a check valve. 
     One in-line flow restrictor arrangement is illustrated, for example, in  FIG. 32 . In this embodiment, flow restrictor assembly  550   a  is disposed distally of the manifold  326  and may be similar in configuration to flow diverter assembly  550  of  FIG. 30 . As shown, no check valve may be provided therein, or in association with the medium flow therethrough; however, a check valve could also be provided. Flow restrictor assembly  550   a  of  FIG. 32  is aligned in series along the medium flow path between the syringe  332  and the catheter  334 . In one embodiment, the flow restrictor assembly  550   a  may include a switch plate  560   a  which is movable relative to a body  562   a , in the same manner as described above with respect to switch plate  560  and base  562 . Accordingly, tubular member T 6  extends from the flow restrictor assembly  550   a  and is selectively pinched by manipulation of the switch plate  560   a  in order to selectively restrict medium flow distally from the flow restrictor assembly  550   a , and toward the catheter  334 . This arrangement could provide an in-line flow resistor along the medium flow path between the syringe  332  and the catheter  334 . In one desired arrangement, a minimum flow rate of 2.5 ml/second delivered to the catheter may be necessary to attain the desired opacity of the medium in the vasculature. 
     While the medium flow rate modulation schemes illustrated and discussed above with respect to  FIGS. 30-32  provide additional means for inhibiting the introduction of excess medium into the patient over, and during, an injection profile of such medium, they may be constrained by design to preselected flow diversion or restriction relations of the overall flow of medium from the syringe to the catheter (e.g., splitting that flow into a 40%-60% relation, as an example). Although the flow diverter assembly  550  illustrated in  FIG. 30  does allow preselected variations in the flow rate of medium through the flow diverter assembly  550  (by means of the manipulation of switch plate  560 ), such variations are achieved by manual manipulation of the switch plate  560 . The flow diverter assembly  550  of  FIG. 30  may not automatically compensate for different pressures or injection flow rates introduced by the syringe operator, as may be seen with the exemplary constant flow modulator  135  illustrated in  FIGS. 12A and 12B . 
       FIGS. 33-37  illustrate an alternative flow diverter assembly  575  that may compensate for a user injecting short (e.g., one second), hard “puffs” of medium (e.g., during catheter navigation) versus long (e.g., two seconds or longer), sustained injections (e.g., during vascular visualization/assessment). Advantageously, diverter assembly  575  may also allow an operator to change the injection delivery system (i.e., guide catheter, stent delivery system, angiographic catheter, etc.) while automatically adjusting the flow of the medium to be sufficient for opacification (likening the function of the constant flow modulator of  FIG. 12 ). The flow diverter assembly  575  may change the resistance to flow rate depending upon changes in the pressure applied to the medium by an operator via the syringe. As resistance is modified to the diverted medium flow rate, the un-diverted flow rate (i.e., the flow rate to the catheter  334 ) likewise is modified. This arrangement may be useful for minimizing the amount of medium diverted when a syringe operator is attempting to introduce a quick “puff” of medium into the patient. By using a very fast syringe squeeze for that purpose, the operator will tend to achieve opacity in this arrangement more readily than, for example, the arrangement of the flow diverter assembly  550  of  FIG. 30 . Therefore, flow diverter assembly  575  may be able to reduce the size of area A in  FIG. 4B , as compared to flow diverter assembly  550  of  FIG. 30 . With a long, sustained injection, flow diverter assembly  575  may act similarly as the flow diverter assembly  550  of  FIG. 30 , in diverting flow away from introduction to the catheter  334 . 
     The flow diverter assembly  575  may be disposed in the medium flow path between the syringe  332  and the catheter  334 , as seen in  FIG. 33 . In one embodiment, the flow diverter assembly  575  may be positioned between the syringe  332  and the manifold  326 , fluidly coupled thereto by tubular members  578  and  580 , respectively. Tubular members  578  and  580  may be connected to the fittings of a four way stopcock  582 , which in turn is connected by a further tubular member  584  to a valve  586 . The stopcock  582  is disposed between the syringe  332  and the delivery catheter  334  in the fluid medium flow path. The stopcock  582  is operably connected to the syringe  332  such that manipulating the stopcock  582  allows a user to selectively activate and inactivate the flow diverter assembly  575 . Valve  586  is operably connected to stopcock  582 . In one embodiment, the stopcock  582  and valve  586  may be separate components, coupled via the tubular member  584 . In another embodiment, the stopcock  582 , tubular member  584  and valve  586  are configured as one self-contained component that can simply be inserted into the medium flow path between the syringe  332  and the catheter  334 . In either configuration, another tubular member  588  extends from the valve  586  to a medium overflow and/or re-use reservoir  328 . In one embodiment, the medium reservoir  328  may also serve as the supply reservoir for loading the syringe  332  with medium. In that arrangement (as illustrated in  FIG. 33 ), syringe  332  is fluidly coupled to medium reservoir  328  by tubular members  590 ,  580  and  578 , coupling those components together via a fluid coupling element or assembly. In an exemplary embodiment, the fluid coupling element or assembly includes manifold  326  and stopcock  582 . The manifold has a manifold lumen therethrough and includes a first medium port fluidly coupled to the flow diverter assembly  575 , a second medium port fluidly coupled to the medium reservoir  328 , and a third medium port fluidly coupled to the delivery catheter  334 . When the syringe  332  is being loaded with medium from the medium reservoir  328 , the stopcock  582  may be positioned to permit medium flow between tubular members  580  and  578 , but not to tubular member  584  disposed between the stopcock  582  and the valve  586 . Once the syringe  332  is loaded with medium from medium reservoir  328 , then valve B on manifold  326  may be manipulated to prohibit flow back to medium reservoir  328  via tubular member  590 , and the stopcock  582  may be positioned to allow flow through the tubular members  578 ,  584 ,  580  and manifold  326 . 
     One embodiment of the flow diverter assembly  575  is illustrated in  FIG. 34 , with the components of the valve  586  shown in exploded axial relation relative to the stopcock  582  thereof.  FIG. 35  is a sectional view of the assembled components of the valve  586  and the stopcock  582  illustrated in  FIG. 34 , while  FIG. 36  is an enlarged sectional view of a portion of  FIG. 35 . The valve  586  includes a diffuser  592  which may be at least partially received within a tubular diverter arm  594  of the stopcock  582 . The movable diffuser  592  is activated to move with pressure, and the diverter arm  594  is capable of increasing or decreasing a medium flow resistance through the diverter arm  594 . The diffuser  592  comprises a radial shoulder  602 , and the valve  586  comprises a deformable O-ring  596  disposed between the radial shoulder  602  and a face  608  of a valve compression plate  604 . The valve  586  includes a deformable and resilient O-ring  596  that extends over a cylindrical extension  598  of the diffuser  592 , until it is seated against a radially extending face  600  on a radial shoulder  602  of the diffuser  592 . A generally disc-shaped valve compression plate  604  has a central cylindrical bore  606  therethrough which is larger than the outer diameter of the cylindrical extension  598  of the diffuser  592 . The compression plate  604  (as shown in  FIG. 35  as being disposed over the extension  598 ) has a first face  608  that abuts the O-ring  596 . The diffuser  592 , O-ring  596  and compression plate  604  are all retained on the diverter arm  594  of the stopcock  582  by a valve housing  610 . In an exemplary embodiment, the valve housing  610  is attached to the diverter arm  594 , and the valve housing  610  and the diverter arm  594  define an internal chamber  616  therein, the internal chamber  616  having longitudinal axis therethrough. The valve housing  610  is sealably coupled to a distal end  612  of the diverter arm  594 , as at area  614 , to form a single component serving as flow diverter assembly  575 . The valve housing  610  has a first internal chamber  616  for receiving the compression plate  604 , O-ring  596  and a portion of the diffuser  592 , including radial shoulder  602 . The first internal chamber  616  includes a radially extending face  618  that abuts in generally planer engagement with a face  620  of the compression plate  604 . The first internal chamber  616  also includes a cylindrical socket  616   a  sized to receive a cylindrical projection  604   a  of the compression plate  604  therein. The valve housing  610  has a second internal chamber  622  which receives a portion of the cylindrical extension  598  of the diverter  592  therein. The second chamber  622  is in fluid communication with the first internal chamber  616  (via the bore  606  in the compression plate  604 ), and with a fitting  624  on the valve housing  610 . The fitting  624  is configured for fluid connection to tubular member  588  (e.g., see  FIG. 33 ). 
     As with the flow diverter arrangement illustrated in  FIG. 30 , a portion of the injected medium flow from the syringe  332  may be diverted away, in this case by the flow diverter assembly  575 . In an exemplary embodiment, the flow diverter assembly  575  is configured to divert at least some of the fluid medium within the chamber of the syringe  332  to the medium reservoir  328  when a threshold pressure level of the fluid medium within the flow diverter assembly  575  is reached. The diverted medium flows through a first cylindrical flow channel  650 , past an annular check valve seat  652  and into a second larger (in diameter and thus cross-sectional area) cylindrical flow channel  654 , all still within an internal chamber  616  of the diverter arm  594  of the stopcock  582  (as illustrated by flow arrows  655  in  FIGS. 35 and 36 ). The valve  586  further comprises a deformable o-ring disposed between an end of the diffuser  592  and the annular check valve seat  652 . The annular check valve seat  652 , when abutted by the diffuser  592 , limits such flow until sufficient pressure (e.g., a flow diversion threshold pressure level) is exerted by the injected medium to move the diffuser  592  off of the annular check valve seat  652  (thereby overcoming the bias exerted by the O-ring  596  on the diffuser  592 ). Medium flow continues away from the stopcock  582  through flow channel  654  and around a cylindrical portion  656  of the diffuser  592 , along a generally tubular flow path. As medium flow exits the flow channel  654 , it may enter the first internal chamber  616  of the valve housing  610 , and encounter a ramped, radially extending face  658  of the shoulder  602  of diffuser  592 . An outer circumferential edge  660  of the shoulder  602  has a smaller circumference than an opposed inner circumference of the first internal chamber  616 , so flow may continue past the shoulder  602  between its circumferential edge  660  and an inner wall of the first chamber  616  (see, e.g., along a generally tubular flow path as illustrated by flow arrows  655  in  FIG. 36 ). Medium flow may then continue past the O-ring  596  and encounter the compression plate  604 . The face  608  of the compression plate  604  may have one or more grooves radially extending therein, between its inner opening  606  and outer circumferential face  662 . 
       FIGS. 37-41  illustrate an exemplary compression plate  604 , with grooves  664   a ,  664   b  and  664   c  therein. While a plurality of such grooves are illustrated in  FIGS. 37-41 , one groove or some other form of surface discontinuity may suffice to permit fluid flow across the proximal face  608  of the compression plate  604 . In the embodiment illustrated in  FIGS. 37-41  of the compression plate  604 , groove  664   a  extends radially outwardly across the proximal face  608  of the compression plate  604 , from the inner opening or bore  606  therein to its outer circumferential face  662 . The groove  664   a  also becomes wider as it radiates outwardly (so that is it wider at the outer circumferential face  662  than at the inner opening  606 ), with its groove edges  665   a  defined by radial lines extending from a central axis of the compression plate  604 . In one embodiment, the arc defined by the groove  664   a  is 40 degrees of the circumference of the compression plate  604 . The groove  664   b  likewise extends radially outwardly from the bore  606  of the compression plate  604  to its outer circumferential face  662  across the proximal face  608  of the compression plate  604 . The groove  664   b  also becomes wider as it radiates outwardly (so that is it wider at the outer circumferential face  662  than at the inner opening  606 ), with its groove edges  665   b  defined by radial lines extending from a central axis of the compression plate  604 . Groove  664   b  may be larger than the groove  664   a  in one embodiment, with the arc defined thereby being 60 degrees of the circumference of the compression plate  604 . Groove  664   c  is disposed, in the illustrated embodiment, entirely within  664   b  and is defined by a pair of parallel groove edges  665   c  extending between the bore  606  and the outer circumferential face  662 . The groove  664   c  defines a deeper groove channel  666  within the groove channel already formed by the groove  664   b . In one exemplary embodiment, as illustrated in  FIG. 38 , centerlines for each of the grooves may be collinear. 
     Viewing  FIG. 35  and  FIG. 36  again, medium introduced from the stopcock  582  and through the first chamber  616  adjacent the O-ring  596  may flow radially inwardly (between the O-ring  596  and the compression plate  604 ) via the grooves  664   a ,  664   b  and  664   c  and into the bore  606  which, as noted above, may have a circumference larger than the outer diameter of the distal extension  598  of the diffuser  592 . Medium can thus flow along a generally tubular flow path through the compression plate  604  (via its bore  606 ) and around the portion  598  of the diffuser  592  and into the second internal chamber  622  of the valve housing  610  (see, e.g., flow arrows  655  in  FIG. 36 ). From there, medium can further flow into the tubular member  588  connected to the fitting  624  on the valve housing  610 . The medium pressure acting on the compression plate  604  urges its face  620  against opposed radially extending face  618  of the first internal chamber  616 , thus creating a barrier to flow by medium past the compression plate  604 , except through the bore  606  (e.g., passing along grooves  664   a ,  664   b  and/or  664   c  on face  608  of compression plate  604 ). 
     As the pressure is increased in the medium within the flow diverter assembly  575 , greater fluid pressure is exerted against the face  658  of the diffuser  592 , thereby urging the diffuser  592  against the O-ring  596  and an end of the valve housing  610 . This in turn compresses the O-ring  596  against the face  608  of the compression plate  604  and into flow channels defined by each groove thereon, to reduce the effective channel size of the grooves and thereby inhibit the flow of medium across the proximal face  608  of the compression plate  604 . As the pressure acting on the face  658  of the diffuser  592  increases, the O-ring  596  is further compressed and further inhibits the flow of medium past the compression plate  604 . For instance, with respect to the stepped grooves  664   b  and  664   c , the O-ring  596  may first deform to inhibit flow through shallower groove  664   b . Further deformation of the O-ring  596  may cause it to then inhibit flow through deeper groove  664   c , progressively. Likewise, as pressure is lessened, the pressure exerted by the diffuser  592  on the O-ring  596  is lessened and more medium is allowed to flow between the O-ring  596  and the compression plate  604  through the flow channels defined by the grooves. The diffuser  592  thus “floats” within the flow diverter assembly  575  in direction of arrows  666  ( FIG. 35 ) and forms a floating valve element that may change the amount of medium flow allowed, depending upon the pressure of the medium flow entering the valve  586 . The diffuser  592  is received within the internal chamber  616 , the diffuser  592  being movable along the longitudinal axis of the internal chamber  616 . The diffuser  592 , in combination with the deforming O-ring  596 , and face  608  of the compression plate  604 , may form a deforming valve that is pressure compensating for medium flow through the flow diverter assembly  575 . This arrangement may allow a syringe operator to vary the type of injection of medium using the syringe  332  (e.g., short puff versus a long, sustained injection), but still attain flow diversion characteristics that serve to minimize the amount of excess introduction of medium into the patient. 
     In one embodiment such as illustrated in  FIGS. 34-36 , the diffuser  592  of the valve  586  is formed of a material that may deform at its end, adjacent annular check valve seat  652 , to serve as a check valve and prevent fluid flow from the flow diverter assembly  575  back into the main flow line between the syringe  332  and the catheter. In an alternative embodiment, such as illustrated in  FIGS. 42 and 43 , a flow diverter assembly  575   a  is essentially the same in configuration and function as the flow diverter assembly  575  described above, except for the diffuser in valve  586   a . As seen in  FIGS. 42 and 43 , a modified diffuser  592   a  may include a O-ring support shank  592   b  formed to receive and retain a deformable and resilient O-ring  592   c  thereon. The O-ring  592   c  is thus provided between the end of the diffuser  592   a  and the annular check valve seat  652  (e.g., see  FIG. 35 ) to provide the check valve function, described previously. 
     As may be appreciated, the shapes of the grooves or discontinuities on the face  608  of the compression plate  604  and the compressibility of the O-ring  596  must be compatible to attain the desired flow control characteristics between those components, when the O-ring  596  is compressed against the face  608  of the compression plate  604  by movement of the diffuser  592 . Changes in the material forming the O-ring  596  (either being more or less deformable) relative to the same compression plate  604  configuration will change the rate of flow modification depending upon pressure changes in the fluid medium in the valve  586 . In addition, while a deformable O-ring in conjunction with a radial face having surface discontinuities is illustrated as one embodiment for forming a pressure compensating valve in a flow diverter assembly  575 , other variable flow mechanisms may also suffice. For example, a disc that expands dependent upon pressure over an array of medium flow holes, to progressively cover more holes as more pressure from the medium is applied to the disc or to a related component, will likewise suffice to serve as a flow constrictor. In many cases, full exclusion of medium flow past the compression plate  604  may not be indicated. Valve  586  may allow some medium flow therethrough, at all applied fluid pressures, once a minimum pressure threshold is exceeded (such as, again, e.g., 20 psi). 
     It is anticipated that valve  586  may be configured to be adjustable by an operator. For example, medium flow through the valve  586  may be changed by modifying the size of the flow channel  654 , such as by modifying the diameter of the portion  656  of the diffuser  592  by enlargement/reduction (i.e., mechanically, inflatably, etc.) thereby changing the effective cross-sectional area of the generally tubular flow path along the diffuser  592 . This is but one way that the valve  586  may be configured so as to be adjustable, and should not be construed so as to limit the scope of the invention. The capability of adjusting the valve may allow an operator the ability to make changes mid-procedure (e.g., changing out a diagnostic catheter for a treatment system), as seen, for example, in diverters described in  FIGS. 33-43 . 
       FIGS. 52-57  illustrate another medium management system  825  that may include, as shown in the illustrated embodiment, flow diverter assembly  575  and a diversion reservoir  827 . In this embodiment, tubular member  588   a  extends from the valve  586  of the flow diverter assembly  575  to a medium diversion reservoir  827 , and tubular member  588   b  extends from diversion reservoir  827  to medium reservoir  328 . Medium from the medium reservoir  328  is permitted to flow away from the medium reservoir  328  and through diversion reservoir  827  via tubular members  588   b  and  588   a , as well as via tubular member  590 . In the illustrated arrangement (see e.g.,  FIG. 52 ), syringe  332  may be fluidly coupled to medium reservoir  328  by tubular members  588   b ,  590 ,  580  and  578 , coupling those components together by a manifold  326  and through stopcock  582 . When the syringe  332  is being loaded with medium from medium reservoir  328 , the stopcock  332  may be positioned to permit medium flow between tubular members  580  and  578 , but not to tubular member  584  disposed between the stopcock  582  and the valve  586  of the flow diverter assembly  575 . Drawing back the syringe  332  may pull medium from the medium reservoir  328  through tubular member  588   b , and/or diversion reservoir  827 , and through tubular member  590 . Medium from the medium reservoir  328  may then be further drawn, into and toward, syringe  332  through tubular members  580  and  578 . Once the syringe  332  is loaded with medium from medium reservoir  328 , valve B on manifold  326  may then be manipulated to prohibit flow back to medium reservoir  328  via tubular member  590  (and such flow may be further inhibited by a check valve disposed between diversion reservoir  827  and medium reservoir  328 ), and the stopcock  582  may be positioned to allow flow through the tubular members  578 ,  584 ,  580  and manifold  326 . 
     As noted above with respect to exemplary modulator systems illustrated in  FIGS. 33-43 , a portion of the injected medium flow from the syringe  332  may be diverted away from the medium flow path to catheter  334  by the flow diverter assembly  575 . In the modulation/reservoir system  825  illustrated in  FIGS. 52-57 , such diverted medium flow passing through the flow diverter assembly  575  flows into the diversion reservoir  827 , as opposed to flowing directly into the medium reservoir  328  or some other outflow/overflow reservoir/chamber. Advantageously, the diversion reservoir  827  provides means for collecting overflow medium diverted by the flow diverter assembly  575 , for possible re-use as the syringe  332  may be again activated to pull medium into the system (e.g., for introduction into the patient via catheter  334 ). The use of such a diversion reservoir in this manner, with an associated check valve preventing back flow of medium into the medium reservoir  328 , allows for capture and re-use of medium that is already introduced into the system (e.g., in the diversion reservoir  827 ) while preserving the integrity of the medium disposed within medium reservoir  328  in its original form. 
     One embodiment of the diversion reservoir  827  is illustrated in  FIGS. 53-56 .  FIG. 53  shows an assembled view of diversion reservoir  827  along with its associated tubular members  588   a  and  590 .  FIG. 54  is an exploded view of the assembly of  FIG. 53 . The system  825  further comprises a second supply conduit  590  in fluid communication with the supply conduit  588   b  and the diversion conduit  588   a , wherein the second supply conduit  590  is fluidly coupled to the fluid medium flow path. Tubular members  588   a  and  590  are sealably connected to a first end cap or manifold  835  on diversion reservoir  827 , as further shown in  FIG. 55 , which is a sectional view taken through lines  55 - 55  in  FIG. 53 . A first end of a through-tube  837  is sealably connected to an interior side of first end cap  835 , as at  838 . Through-tube  837  includes an inner conduit  839  extending therethrough. Inner conduit  839  is in fluid communication with the interiors of tubular members  588   a  and  590  via their adjacent couplings in the first end cap  835 , as illustrated in  FIG. 55 . A second end of through-tube  837  is sealably connected to a check valve assembly  841 , as at  842 , and the inner conduit  839  is in fluid communication with the check valve assembly  841 . The check valve assembly  841  is, in turn, in fluid communication with the tubular member  588   b . As seen in  FIG. 55 , the check valve assembly  841  includes a moveable valve plate  843  (or other suitable structure allowing one way flow through the valve) which is operable to permit flow from the medium reservoir  328  via tubular conduit  588   b  into the inner conduit  839  of through-tube  837 , but to inhibit flow in reverse thereof. This arrangement may allow flow of medium from fluid reservoir  328  via tubular conduit  588   b , inner conduit  839  of through-tube  837 , and tubular conduit  590  to the syringe  332 . Moreover, medium flow diverted by flow diverter assembly  575  may also be permitted to flow via tubular member  588   a  into inner conduit  839  of through-tube  837 , but inhibited from flowing back to the medium reservoir  328  by check valve assembly  841 . A second end cap  844  on diversion reservoir  827  is secured about the check valve assembly  841 . 
     The diversion reservoir  827  is designed to accommodate such back flow of medium from the flow diverter assembly  575 , to collect and hold such medium and then, if desired, urge such collected medium back into the system for use in delivering additional medium to the patient via injection catheter  334 . To accomplish this end, diversion reservoir  827  may include an elastic expansion tube  845  disposed about through-tube  837 . As seen in  FIGS. 55 and 56 , expansion tube  845  extends along a portion of a length of through-tube  837 . In one embodiment, expansion tube  845  is formed of silicone material sealably secured adjacent each end thereof about the through-tube  837  by first and second retention washers  847  and  849 , respectively, or by other suitable sealable and mechanical fastening arrangements. An outer surface of the through-tube  837  may include interference elements such as surface features or an annular interference rim  837   a  (see  FIG. 55 ) to further facilitate the sealing of the expansion tube  845  to the through-tube  837  via the retention washer  847  and  849 . 
     A housing tubular outer shell  855  may be connected between the first end cap  835  and second end cap  844 , thereby covering the expansion tube  845  and other diversion reservoir components therein. The shell  855  may serve to protect the components of the diversion reservoir  827  therein, limit the extent of inflation or expansion of expansion tube  845 , and/or (if the shell  855  is either transparent or translucent) allow observation of the condition (e.g., expanded state) of expansion tube  845  therein. 
       FIG. 56  illustrates the diversion reservoir  827  in perspective sectional view (again, as taken along lines  55 - 55  in  FIG. 53 ) with the expansion tube  845  shown in an exemplary stretched and expanded state, as opposed to its relaxed state shown in  FIG. 55 . The expansion tube  845  of the diversion reservoir  827  receives medium flow from the flow diverter assembly  575 , via tubular member  588   a . This medium flow, as illustrated by flow arrows  857  in  FIG. 56 , flows from tubular member  588   a  into the inner conduit  839  of through-tube  837  adjacent the first end of through-tube  837 . Flow out of the through-tube  837  is inhibited at its second end by the check valve assembly  841 . However, the supply conduit through-tube  837  may have one or more apertures  859  therethrough which allows an interior of the expansion tube  845  to be in fluid communication with the inner conduit  839  and reservoir chamber  860 . Medium from the flow diverter assembly  575  can thus flow through apertures  859  and into a medium reservoir or chamber  860  defined by the expansion tube  845 . This medium chamber  860  is defined between the inner surface of expansion tube  845  and the outer surface of through-tube  837 , whereby the expansion tube  845  forms an elastic bladder disposed around the supply conduit  837 , with the walls of expansion tube  845  capable of imparting a force on the fluid medium within the chamber  860 . A surface within chamber  860  is capable of imparting a variable or constant force on the fluid medium within the chamber  860 , and the surface is defined at least in part by a wall of the elastic bladder of expansion tube  845 . The medium chamber  860  thus receives and collects the diverted portion of the flow of medium from the flow diverter assembly  575 . The diversion reservoir  827  comprises a variable or constant force biasing member disposed relative to at least one surface within the reservoir chamber  860  to urge the surface against the fluid medium within the reservoir chamber  860 . The expandable wall of the expansion tube  845  thus defines a surface within the medium chamber  860  capable of imparting a force (variable or constant) on the fluid medium within the medium chamber  860 . In one embodiment, the second end cap  844  includes an aperture  861  therethrough to permit the escape of gas within the cover  855  and thereby readily permit expansion of the expansion tube  845  therein. 
     In use, as the pressure of medium within the flow diverter assembly  575  increases enough to allow flow therethrough, medium flows from the valve  586  via the tubular member  588   a  to the diversion reservoir  827 . Medium then flows within the diversion reservoir  827  as illustrated by arrows  857  into medium chamber  860 , thereby stretching the walls of the expansion tube  845  and expanding chamber  860  to accommodate the diverted medium flow. Accordingly, as the medium pressure provided via syringe  332  increases in the system, the flow diverter assembly  575  diverts medium so that the flow to the patient increases as less flow is diverted by the flow diverter assembly  575  into the diversion reservoir  827 . The medium contained in the chamber  860  may be available for further infusion into the patient via the modulation/reservoir system  825 . As an example, an operator may activate valve B to allow medium flow from the chamber  860  of the diversion reservoir  827  into the syringe  332  (which is being withdrawn to draw such fluid therein). If the fluid needed is greater than the volume retained within the chamber  860 , the force of check valve  843  is overcome and further medium is withdrawn from the medium reservoir  328 . Once a sufficient amount of medium has been withdrawn from the chamber  860  and/or reservoir chamber  328 , valve B may be closed and the modulation/reservoir system  825  may be again in condition for delivery of medium via injection catheter  334 , by activation of injection syringe  332  by an operator. As long as the stopcock  582  is disposed to allow flow into tubular members  580  and  584 , the flow modulator assembly  575  may automatically activate to divert excess medium, thereby ultimately reducing the amount of medium introduced into the patient via injection catheter  334  (e.g., thus introducing no more medium than necessary to attain operative opacity). Again, as the pressure is increased in the modulator  575 , the flow to the patient is actually decreased by operation of the flow diverter assembly  575 . The process can be repeated by an operator as many times as deemed necessary to complete the procedure desired. Use of the modulation/reservoir system  825  in this manner may achieve the advantageous reduction of introduction of unnecessary medium into the patient while achieving the necessary amount and flow of medium in the patient for diagnostic or treatment means (e.g., for opacity). In addition, the diversion reservoir  827  may allow re-use of the diverted outflow of medium. 
     The diversion reservoir illustrated in  FIGS. 53-56  presents one form of such a reservoir. Alternative forms are contemplated as well. For example, an alternative form of elastic bladder or elastic surface may be provided that functionally allows the receipt of medium overflow from the flow diverter assembly  575  into an expansion chamber, and then further allows the flow of medium from the medium reservoir  328  through the diversion reservoir  827  and into the modulation/reservoir system  825  for use. An alternative means of placing force on the medium within the chamber in the diversion reservoir  827  may be attained by a bias plunger, such as illustrated schematically in  FIG. 57 . The diverted portion of the fluid medium flows through a diversion conduit  588   a  away from the flow diverter assembly  575 . The system  825  comprises a medium reservoir  328  containing a supply source of fluid medium for the system  825  and a supply conduit  588   b  through the reservoir chamber  834  that fluidly connects the medium reservoir  328  and the diverter conduit  588   a . The supply conduit  588   b  comprises a check valve  841   a  to prevent the flow of fluid medium from the supply conduit  588   b  into the medium reservoir  328 . Diversion reservoir  827   a  includes a plunger  828  slidably disposed in housing  826  and moveable in a linear fashion relative to the housing  826 , as illustrated by movement line  830 . Thus, the surface  832  is movable in a linear direction relative to the fluid medium within the reservoir chamber  834 . A proximal face or surface  832  of the plunger  828  thus defines a portion of a chamber  834  within the housing  826  for diverted medium that is received therein via the tubular member  588   a.    
     Like the diversion reservoir  827  illustrated in  FIGS. 53-56 , diversion reservoir  827   a  may include a first end cap  835   a  that acts as a manifold for medium flow. Tubular member  588   a  is connected to first end cap  835   a , as is tubular member  590 . Chamber  834  is in fluid communication with the interiors of tubular members  588   a  and  590 , such as via manifold  836  within the first end cap  835   a , as seen in  FIG. 57 . A through-tube  837   a  is also in fluid communication with the manifold  836 , and extends through the housing  826  of the diversion reservoir  827   a  to a check valve  841   a . Check valve  841   a  permits medium flow from medium reservoir  328  via tubular member  588   b  into through-tube  837   a  but prevents backflow. Medium from the medium reservoir  328  can then flow from the diversion reservoir  827   a  into the syringe  332  via tubular member  590 . 
     When medium is diverted by the flow diverter assembly  575  into the diversion reservoir  827   a , medium flows as illustrated by flow arrows  857   a  from tubular member  588   a , through manifold  836 , and into the chamber  834 . The diversion reservoir  827   a  comprises a variable or constant force biasing member disposed relative to at least one surface  832  within the reservoir chamber  834  to urge the surface  832  against the fluid medium within the reservoir chamber  834 . In an exemplary embodiment, surface  832  is planar. The face  832  of the plunger  828  is biased toward the manifold chamber  836 , and thus defines a moveable surface  832  for the chamber  834  that can move away and expand chamber  834  as more medium is introduced therein, when the bias of the force acting against it is overcome. This bias may be in the form of a constant or variable force acting on the plunger  828  within the housing  826 , as illustrated schematically by force arrows  838 , and such force may be achieved by suitable means such as springs, weight distribution, linear actuator, etc. The use of a linearly moving plunger  828  (as its movement is illustrated by arrows  830 ) may permit more ready measurement of how much medium has actually been diverted by the flow diverter assembly  575  and thereby, by derivation, how much medium has actually been delivered to a patient by the injection catheter  334 . The plunger  838  thus provides a linear expansion element (surface  832 ) that serves to apply force to the overflow medium collected for possible re-use in the chamber  834 . 
     The diversion reservoir  827   a  operates in a similar manner to the diversion reservoir  827 , discussed above, by providing an expandable chamber for medium diverted by the flow diverter/modulating assembly  575 , wherein the chamber (e.g., chamber  834 ,  860 ) has at least one surface acting upon it to urge the medium therein back to the flow diverter assembly  575  for possible re-use. Likewise, medium which has been diverted by the flow diverter assembly  575  into the diversion reservoir chamber  834  is not permitted to flow back to the medium reservoir  328 , via check valve  841   a . In alternative embodiments for modulation/reservoir systems, the diversion reservoir is configured so that flow through it to the medium reservoir is not permitted or necessary. One such arrangement is illustrated in  FIG. 58 , in connection with a modulation/reservoir system  825   a . In these arrangements, there may be no necessity for a through-tube arrangement through the diversion reservoir. The diversion reservoir simply provides an expandable chamber therein for retaining and re-using medium diverted from the flow diverter assembly  575 . Such diversion reservoirs  827   b  may employ a bladder form of chamber or a constant or variable force resistance form of chamber, such as those illustrated and discussed herein, where at least one surface therein is capable of imparting a force on the fluid medium within the chamber.  FIG. 58  illustrates an arrangement where the medium reservoir chamber  328  is connected via tubular member  588   c  to a T-connector  840  disposed between a diversion reservoir  827   b  (without a through-tube) and the flow diverter assembly  575 . The T-connector  840  connects at its first end to the tubular members  590  and  588   a , and at its second end to tubular member  588   d  that leads to the diversion reservoir  827   b . A side fitting of the T-connector  840  leads via tubular member  588   c  to the medium reservoir  328 . A check valve  841   b  is disposed between the T-connector  840  and the medium chamber  328  to prevent back flow of medium from the flow diverter assembly  575  and/or diversion reservoir  827   b  into the medium container  328 . In operation, the configuration illustrated in  FIG. 58  may be similar to that described above with respect to  FIG. 52 . As the pressure of medium within the flow diverter assembly  575  increases enough to allow flow therethrough, medium flows from the valve  586  via tubular member  588   a  to the T-connector  840 . Medium may then flow from the T-connector  840  via tubular member  588   d  to the diversion reservoir  827   b . Medium flowing into the diversion reservoir  827   b  expands the expandable chamber therein to accommodate the diverted medium flow. Accordingly, as the medium pressure provided via syringe  332  decreases in the system, the flow diverter assembly  575  diverts medium so that the flow to the patient decreases as more flow is diverted by the flow diverter assembly  575  into the diversion reservoir  827   b.    
     In operation, the configuration illustrated in  FIG. 58  may be similar to that described above with respect to  FIG. 52 . As the pressure of medium within the flow diverter assembly  575  increases enough to allow flow therethrough, medium flows from the valve  586  via tubular member  588   a  to the T-connector  840 . Medium may then flow from the T-connector  840  via tubular member  588   d  to the diversion reservoir  827   b . Medium flowing into the diversion reservoir  827   b  expands the expandable chamber therein to accommodate the diverted medium flow. Accordingly, as the medium pressure provided via syringe  332  decreases in the system, the flow diverter assembly  575  diverts medium so that the flow to the patient decreases as more flow is diverted by the flow diverter assembly  575  into the diversion reservoir  827   b.    
     The medium contained in the expandable chamber within the diversion reservoir  827   b  may be available for further infusion into the patient via the modulation/reservoir system  825   a . To do so, an operator activates valve B to allow medium flow from the chamber within the diversion reservoir  827   b  into the syringe  332  (which is being withdrawn to draw such fluid therein). If the fluid needed is greater than the volume retained in the chamber reservoir  827   b , the force of check valve  841   b  is overcome and further medium is then withdrawn from the medium reservoir  328 . Once a sufficient amount of medium has been withdrawn from the chamber within the diversion reservoir  827   b  and/or reservoir chamber  328 , valve B is again closed and the modulation system  825   a  is again in condition for delivery of medium via injection catheter  334 , by activation of injection syringe  332  by an operator. As long as the stopcock is disposed to allow flow into tubular members  580  and  584 , the flow diverter assembly  575  will then again be automatically activated to divert excess medium when a threshold pressure for activation of the flow diverter assembly  575  is attained, thereby ultimately reducing the amount of medium introduced into the patient via injection catheter  334 . Again, as pressure is increasing going into flow diverter system  575 , the flow through the diverter  575  is relatively decreasing (thus, flow to the patient may be relatively increasing by operation of the flow diverter assembly  575 ). The process can be repeated by an operator as many times as deemed necessary to complete the procedure desired. Use of the modulation/reservoir system  825   a  in this manner achieves the advantageous reduction of introduction of unnecessary medium into the patient while achieving the necessary amount and flow of medium in the patient for the desired diagnostic or treatment process. Furthermore, the modulating/reservoir assembly may advantageously allow an operator to change out the injection delivery system (i.e., guide catheter, diagnostic catheter, treatment tools, etc.) without changing the flow modulator. Moreover, the diversion reservoir may allow simplistic re-use of the diverted medium. 
     Exemplary Modulation Devices and Methods with Synchronization 
     In addition to modulating injections by reducing inefficient agent use (as illustrated as areas A, B and/or C in exemplary injection profile Q Agent  of  FIG. 4B ), modulation may also advantageously include delivering medium to a vessel in greater quantity when there is greater blood flow, and in lesser quantity when the blood flow is diminished. It is an objective of at least some embodiments described herein to pattern the injection of medium into a vessel to coincide roughly with the pattern of blood flow in that vessel. By way of example,  FIG. 13  illustrates an exemplary injection profile delivered by an inventive injection system in which the injection profile coincides roughly with the blood flow within the vessel of  FIG. 2 . In this case, an average of about 2.8 ml/second of agent (e.g., average of Q Agent ) may be used to fill the vessel in sufficient quantity (e.g., to perform its opacification function) while not forcing the vessel to fully fill with agent, or otherwise displacing all of the normal blood flow. Thus, the dotted-line in  FIG. 13  highlights the profile produced by the injection system in filling the vessel with medium of about 65% to 85% of the normal blood flow, for example. The amount needed for medium concentration (e.g., within in the blood) may vary depending on the agent and the intended function, and it is possible that such concentrations could be provided at as low as 1% of the blood flow rate and at as great as 99% of the blood flow rate without deviating from the intent of the modulation devices and methods described herein. 
     Synchronized delivery of agent may reduce the risk of “over-filling” the vessels outside of the target vasculature. In addition, such an injection flow rate profile may provide sufficient agent concentration within the vessel for opacification during lower flow. Over-injecting the coronary vasculature (for diagnostic or therapeutic purposes) may be seen arteriographically as “blow back” or reflux, and loads the body with unnecessary agent(s). Examples of synchronization embodiments may involve sensors and controllers utilized to modulate the injection of medium into the target site. Such sensors/controllers might include an EKG (and/or inputs from an EKG) to initiate activation and deactivation, or modulation, of an injector to deliver medium to a vessel as a function of the pulsatile flow of blood in the vessel. Other embodiments may include sensors positioned into, upon, and/or proximate, an injection delivery catheter so as to infer or deduce a parameter of blood flow (pressure, flow rate, temperature, velocity, patient respiration, pH, pO 2 , etc.) in an effort to coordinate the injection of medium with the flow of blood in the vessel. 
     Although synchronized delivery will be further elucidated below, coordinating an injection of medium with the flow of blood in a vessel in a varied, or “pulsatile” fashion may not be the only means of using varied flow to reduce the amount of medium delivered to the patient, without compromising vascular opacity. Medium injection may also be reduced through pulsatile flow control methods/devices without synchronization. In this regard, pulsatile flow of medium may be generated by applying rapidly changing pressure (in amplitude over time) to drive a medium delivered to a patient. In this case, the peak amplitude of the pressure wave may be sufficient, or nearly sufficient, to achieve adequate opacity. In a sense, this may be akin to an electrical model of alternating current (AC) versus direct current (DC) in the application of medium to the patient. The pressure applied to the medium for the patient may be varied in amplitude over many cycles during each “pump” of the heart in a coronary artery application. The pressure may be “pulsed” in a variety of wave forms of design, such as: sinusoidal, symmetrical, and asymmetrical, as examples. As well as, the design of the wave may change and/or alternate in frequency, amplitude or wave size. As previously discussed, graphic illustrations of blood flow and injection agent flow have been illustrated relative to flow rates (e.g.,  FIGS. 2, 4A, 4B, 4C, 4D and 13 ). However, given the direct relationship of flow (Q) and pressure (P) in our model(s), graphical representation of pressure may also be utilized in characterizing injection medium modulation techniques. Optimization of delivery of medium (such as contrast agent) to a vascular delivery site may be enhanced by control of the medium injection pressure and flow rate. 
       FIG. 44  illustrates an example of a medium injection pressure profile that may be found within a left main coronary artery of a human heart—this may be a typical profile of injection pressure P Typical  illustrating an injection profile made by a doctor with a syringe extending over approximately 3.5 seconds, without any modulization modification pursuant to the disclosure herein. This profile may be similar to the injection profile illustrated in  FIG. 4A ; however,  FIG. 44  graphically represents a pressure (P) profile, whereas  FIG. 4A  depicts a flow rate (Q), over time.  FIG. 44  also illustrates an exemplary medium injection pressure profile P Modified  for a medium injection using a modulation system such as disclosed herein by modulation system  325  including a variable force delivery platform  402  (such as illustrated in  FIGS. 26-27 ). As seen in  FIG. 44 , the peak injection pressure along the modulation pressure profile P Modified  may be 60 percent less than the typical peak injection pressure without modulation. 
       FIG. 45  illustrates an exemplary pulsatile medium injection profile P Pulsatile I , again over a typical 3.5 second injection of medium into a patient. The medium injection profile P Pulsatile I  of  FIG. 45  may allow the attainment of full pressure of a typical injection to be realized, but do so at spaced intervals of medium pressurization. In the example illustrated in  FIG. 45 , the “duty cycle” (time between waves) for the pulsatile pressure profile P Pulsatile I  may be 0.25 seconds. This is more fully illustrated in  FIG. 46 , which is an enlarged segment of a portion of the pressure profile P Pulsatile I . In  FIG. 46 , the portion of each 0.25 second duty cycle where pressure is applied to attain the peak pressure is 0.15 seconds, whereas the portion of each duty cycle where the pressure is not applied at peak is 0.10 seconds, resulting in a 60% “on”/40% “off” pressurization duty cycle, as an example of pulsatile injection. It is clear that there are a variety of wave shapes, peaks, troughs, duty cycles, etc. that one may use to accomplish a reduction in medium injection without compromising function (e.g., opacification). This is merely one example in the use of a pulsatile injection to modulate the delivery of a medium. 
       FIGS. 47 and 48  illustrate an alternative medium injection pressure profile P Pulsatile II  that illustrates an injection pressure profile similar to  FIG. 45  but using a different duty cycle for the pulsed medium pressurization. In this case, the duty cycle is 0.125 seconds, resulting in a higher frequency of pulsation but still attaining a pressure P about that of a typical injection P Typical .  FIG. 48  illustrates an enlarged view, showing the exemplary 60/40 duty cycle ratio between peaks and valleys of the pulsed flow profile P Pulsatile II . Establishing a pulsatile pressure profile for a medium injection (such as profiles P Pulsatile I  or P Pulsatile II ) may not depend on the peak pressure being applied (such as pressure P in  FIGS. 44, 45 and 47 ). Pulsation of medium injection pressure could be applied to the medium at any desired pressure so as to reduce the reduce the amount of medium injected without opacity compromise 
     As discussed above with alternative embodiments, modulation of medium delivery to a patient may be achieved in parallel, or in series.  FIG. 49  illustrates schematically an arrangement whereby pulsatile medium pressure modulation may be achieved in a “parallel” arrangement (whereby the catheter  334  provides one level of medium flow resistance, and a flow diverter assembly which may include a medium reservoir  700  may, in combination with other diverter elements such as those described above, provide a second resistance to medium flow between the syringe  332  and the catheter  334 ). One means for modulating the pressure at the catheter is to modulate the bleed off medium pressure via manipulation of reservoir  700 . In effect, this is achieved by creating a negative pulse on the diverted flow path, like employing a variable resistor thereon. This may be done, for example, by modulating the volume in the reservoir  700 , such as by means of a movable piston, solenoid or membrane, which then has the consequence of changing the frequency of medium pressure applied to the patient via the catheter  334 . The volume in the reservoir  700  may be modulated by mechanical forces created by mechanical devices, thereby creating waves or pulses on the medium in the reservoir  700 . Such devices can be controlled by a controller  705  coupled to the reservoir  700 , either wired or wirelessly via control connection  710 . The controller  705  may be located outside the sterile surgical field relative to the patient. Alternatively, a mechanical device may be, by design, formed to define a pulsatile action on the medium in the reservoir  700  without requiring a controller  705 . The pulsing of the diverted medium flow in an arrangement such as illustrated in  FIG. 49  may be attained by modulating the volume in the reservoir  700 , or also by opening and closing a diverter flow path  715  extending between the reservoir and the main flow path between the syringe  332  and the catheter  334 . In either instance, using mechanical or controller driven means to achieve such pulsatile activity relative to the medium in the diverted portion of the medium flow results in likewise reduced medium flow to the patient via the catheter  334 , as illustrated again by the exemplary medium pressure profiles P Pulsatile I  ( FIG. 45 ) and P Pulsatile II  ( FIG. 47 ). Although these examples describe two ways of achieving a “pulsatile” pressure, there are a myriad of means to effect similar waves and these are not outside the scope of this disclosure. 
     Moreover, with pulsatile forces acting on a medium in the diverted portion of the medium flow path, the syringe operator may not necessarily feel the immediate effects of such pulsation (i.e., by tactile sensation when manually manipulating the syringe). To the operator, the manipulation of the syringe may not feel or function any differently than a typical medium injection pressure profile, such as illustrated P Typical  in  FIGS. 44, 45 and 47 . 
     As noted above, the pressure profile for medium applied to the patient via the catheter  334  may also be achieved by a pulsatile effect applied to the medium directly (i.e., in series with medium flow to the catheter  334 ). In this example, a pulsatile generator  720  may be disposed along the medium flow line extending between the syringe  332  and the catheter  334 . The pulsatile generator  720  may be designed to create a positive pulse on the medium flowing therethrough to the catheter  334  in order to vary the pressure of the medium to follow a medium pressure profile, such as illustrated by profile P Pulsatile I  ( FIG. 45 ) or P Pulsatile II  ( FIG. 47 ). Pulsing of pressure on the medium by the pulsatile generator  720  may be achieved by repetitive pinching of a medium flow line passing through or adjacent, the pulsatile generator  720 , or by other suitable mechanical flow pulsing means. Alternatively, the pulsatile generator  720  may be incorporated directly into the syringe  332  so that the fluid flow exiting the syringe  332  is already being delivered in a pulsed state relative to its pressure profile. In either case, the pulsatile generator (whether in line or incorporated into or adjacent the syringe), may be controlled by a controller  705  disposed outside of the sterile surgical field. The controller  705  may be coupled, either wired or wirelessly, via control connection  710  to the pulsatile generator  720 , whether the generator is disposed in line or in the syringe  332 . It is also conceivable that the pulsatile generator  720  acts independently of any controller. 
     In many cases of pulsatile flow of medium, the objective is to reduce the amount of medium delivered to the patient, yet still provide sufficient medium to achieve operative function. In the case of contrast delivery, functionality may be determined through opacification of the vasculature upon injection. The advantage of employing a pulsed medium pressure profile such as those illustrated in  FIGS. 45 and 47  is that the volume of medium necessary for achieving opacity may be reduced. Also, medium modulation via medium pressure/flow pulsation may not be dependent on the size or form of catheter configurations being deployed in the patient, and thus may provide the ability to further reduce the introduction of excess medium across all such catheter configurations and procedures. Furthermore, the effect of “pulsating” the flow of medium delivered to a site may provide better “mixing” of agent with the blood and this action, in and of itself, may reduce medium use similar to the “mixing” effect described by the device in  FIG. 18   
     Continuing with “synchronizing” an injection with the flow of blood in a vessel,  FIG. 14  illustrates exemplary schemas for a synchronized medium injection modulation system. As shown, one or more signal sensors  150  may each receive a signal representing, deducing, or inferring, the status of at least one parameter of flow at the target injection site such as the left coronary arteries of the heart. A controller  152  may receive the signal(s) from the sensor(s)  150  and then directly, or indirectly, activate modulated delivery of medium though the delivery catheter system  154 . As can be seen in  FIG. 14 , valving (or otherwise modulating mechanisms) may be positioned near the proximal portion of the delivery system  154  (e.g., in proximity of the delivery catheter proximal portion, outside of the body, as at proximal valving  156 ), and/or may be placed in, around, and/or in proximity of the distal portion of the delivery catheter (e.g., inside of the body, as at distal valving  158 ), with such valving being actuated by the controller  152 . Further, one or more of the sensor signals may be from a sensor located externally of the body such as an EKG, and/or one or more of the sensor signals may be derived from a sensor within the body (such as a pressure sensor placed in, about and/or in proximity to the distal portion of the catheter). 
     Direct control of modulation may include, for example, activating the injection device directly to synchronize dispensing of medium through the injection delivery catheter to produce the injection flow rate (e.g., Q Agent ) profile as shown in exemplary  FIG. 13 . In this example, a signal from a sensor  150  (such as, for example, an EKG signal) is used by the controller  152  to directly actuate the injector pump  160  so as to increase/decrease the injector output to produce a medium agent injection flow rate (e.g., Q Agent ) profile as shown in  FIG. 13 . An example of such a system may be found in  FIG. 15 . As can be seen, an EKG signal of the patient&#39;s heart rate is received from an EKG sensor  150  by the controller  152 . The controller  152  may selectively signal a start for increasing flow rate at some time interval after the QRS complex of the EKG, and a start for decreasing flow delivery before and/or during the QRS complex, for example. Thus, the controller  152  of  FIG. 15  may then activate/deactivate the pump  160  operably coupled to injector  162  to varying degrees to provide dispensing of medium from the injector  162  when an operator has signaled to the controller  152  that an injection is warranted. The activation/deactivation of the injector pump  160  may be capable of producing an exemplary injection profile (Q Agent ) as described by  FIG. 13 . 
     Indirect control of modulation may include, for example, valving (or otherwise modulating) an injection dispensed from an injection device. As described previously in the various schemas of  FIG. 14 , indirect valving (or otherwise controlling mechanisms) may be proximally or distally positioned within, about, and/or upon the agent delivery system  154 . An example of an indirect modulation control may be found in  FIGS. 16A-16D . In this example, a sensor  165  is deployed distally on a delivery catheter  166  (as seen in  FIG. 16A ) and a modulating device (of  FIG. 16B ) is provided proximally (i.e., positioned proximally as shown for modulator  168  of  FIG. 16C , for example). The sensor  165  of  FIG. 16A  is an exemplary pressure sensor positioned on the distal tip of the delivery catheter  166 . As described previously, this is only one example of the various sensors that may be used in obtaining a signal to synchronize the delivery of medium with the blood flow rate. Moreover,  FIG. 16A  illustrates the positioning of the sensor  165  upon the distal tip of the delivery catheter  166 . The exemplary positioning of the sensor  165  in  FIG. 16A  should not be limited to that shown in order to perform the functions described herein, since there may be a multitude of sensor types (and commensurate signals) positioned at various locations on (i.e., as a function of respiration), through (i.e., as a function of imaging) and within the body (i.e., as a function of a variable proximate a target delivery site). Clearly, even the placement of a distal pressure sensor in exemplary  FIG. 16A  could take many forms, such as: a pressure wire alongside the catheter; a lumen within the catheter body for pressure measurement; a pressure sensor deployed within the distal tip of the catheter; a pressure sensor deployed distally of the distal tip of the catheter and into the target vessel, to name but a few. 
     Referring to  FIG. 16B , modulating device  168  may comprise an inlet port  170  (from the injection device) and an outlet port  172  (to the delivery catheter  166 ). The flow of injection fluid may pass through the injection port  170  and into a fluid chamber  174  within a body or housing  176  of the modulator  168 . The modulator  168  may have a plurality of vane/plates  178  attached to a cylindrical hub  180  disposed within the fluid chamber  174 . The vanes  178  and hub  180  may be formed to define a “pinwheel” structure of vane-hub that is capable of rotating freely (relative to fluid chamber  174  and body  176  of modulator  168 ) upon the injection of medium into the fluid chamber  174  through the injection port  170 . The hub  180  may be designed to preferentially rotate in one direction. For example,  FIG. 16B  illustrates the preferential flow of fluid and rotation of the vane-hub, in a clockwise direction, via flow arrows  182 . From the fluid chamber  174 , injection fluid may flow out of the modulator  168  via the outlet port  172 . 
     One advantage of a vane-hub modulator design of this type is that it may be easy to measure, or otherwise identify, the total volume of injection fluid delivered through the modulating device  168  (over time) since the volume of fluid passing through the device  168  during one rotation of the vane/hub may be easily determined, and the number of rotations simply counted by a counting mechanism. Alternatively, each “cell” of fluid between adjacent vanes  178  may be readily counted by a counting mechanism. The counting mechanism is not shown in the illustrations, but it may comprise a magnetic, mechanical, ultrasonic, infrared or similar measurement device capable of identifying the number of times a vane  178  and/or some other element of the vane-hub has passed within its field of measurement, or by determining the number of times the axis of the hub  180  has rotated. The output of such a counting device may be utilized to determine and display (in real-time) the total volume of medium used during a procedure. Advantageously, in the management of medium injected, an operator/physician may readily see the amount of medium used (as determined by the counting device and presented by a suitable display or indicative output). The determination of the volume (via calculations/conversions based on, for example, counted rotations) may be performed as part of the counting device, or may be performed by a display device. In addition to providing volume measurements, the counting mechanism/signal/display may incorporate various algorithms to alert an operator/physician before, or at a point which, a maximum volume of agent has been administered (i.e., operator determined value, Maximum Acceptable Contrast Dose, GURM ratio, etc.). 
     Continuing with the description of the exemplary modulation device  168  shown in  FIGS. 16B-16C , a vane-hub modulator may comprise two components. One component  186  may be situated adjacent a controller/actuator  185  and may comprise the input port  170 , the output port  172  and the fluid chamber  174  with rotating vane/hub  178 / 180 . This component of the system, which may come into contact with fluids, may be disposable if so desired. A second component  188  comprising the controller/actuator  185 , brake mechanism  191 , sensor signal  190  receiver, and the like may be used to clutch, brake, or otherwise inhibit the rotation of the vane-hub so as to provide resistance to rotation. The resistance induced to the rotation may be coordinated with a signal  190  from sensor  165  of  FIG. 16A , so as to modulate an injection from an injector to produce an agent fluid flow (Q Agent ) profile as described, for example, in  FIG. 13 . 
     The braking, or clutching of the modulator  168  of  FIG. 16C  may be performed through a variety of means, to include, for example, mechanical, hydromechanical, electromechanical, electromagnetic, chemomechanical, etc.  FIG. 16C  illustrates one such means  191  for braking the shaft  192  of the vane-hub, using electromagnetic means. The exemplary braking structure  191  is further detailed in  FIG. 16D , wherein the longitudinal shaft  192  of the hub  180  is coupled to a hysteresis plate/disc  194  positioned within a magnetic field  196 . When electricity is applied to the magnetic coil  196 , a magnetic flux is transferred to the hysteresis disk  194  (as it passes through the field) causing a magnetic “drag” on the disc  194 . The drag, or braking, applied to the hysteresis plate  194  (and thus the shaft  192  of the vane-hub) may be increased/decreased with increasing/decreasing voltage applied to the magnetic field to modulate the flow of medium as intended. When electrical current is removed, the connected disc/shaft may rotate freely about an axis of shaft  192 . In the example of  FIG. 13 , the maximum flow rate of agent (Q Agent ) is approximately 5.2 ml/second. Therefore, in producing profile of Q Agent  of  FIG. 13 , one might set the injection of medium into the modulator  168  at a constant rate of 5.2 ml/second. Upon modulating, braking mechanism  191  of  FIG. 16D  may increase the drag (reduce the flow rate) of the agent as needed to produce the flow profile of Q Agent  of  FIG. 13 . 
       FIGS. 16B and 16C  describe one of numerous means to regulate the flow profile of injection agent thru a modulator, and as such, are intended to illustrate the modulation monitoring and control concepts disclosed herein without limitation. Of course, such means may be employed with various signals and sensors (such as shown in  FIG. 16A ) to “synchronize” the flow of injection medium with corporeal medium flow. Therefore, the example of  FIG. 16  is but one example how one might use a modulator device to perform synchronization. 
     Previous embodiments of “synchronized” delivery described herein may include active sensing and subsequent modulating of the delivery of a medium. However, delivery of a medium to a delivery site may be also modulated by passively valving the medium delivery as a function of a physical attribute in and/or around the delivery site; such as pressure, for example. Referring to  FIG. 23 , a delivery catheter  260  may be placed to deliver a medium to a delivery site, such as the left main  24  of the coronary vasculature. In this setting, there are continuously changing pressures within the left main  24  as well as the aorta  22 , as previously described. A valving mechanism  262  may be deployed within, on or in proximity of the distal portion of the delivery catheter  260 . 
       FIGS. 24A and 24B  illustrate in more detail the distal portion of the catheter  260  with a passive valving mechanism  262  present. As shown in  FIGS. 24A and 24B , the valving mechanism may include a blood flow bypass lumen  264 , allowing some blood flow alongside medium delivery lumen  266  of the catheter  260 . A passive valve gate  268  is disposed to limit blood flow through bypass lumen  264  and medium flow through medium lumen  266 , as a function of pressure differential around the delivery site. As shown in the  FIG. 24A , when the pressure within the left main  24  (e.g., P LM ) is less than the pressure in the aorta  22  (e.g., P AO ), the valve gate  268  of delivery catheter  260  may allow the injection of medium to the delivery site (as illustrated by medium flow arrows  269   a  in  FIG. 24A ). Conversely, as shown in  FIG. 24B , as the pressure differential between the left main  24  and the aorta changes  22 , with the left main  24  increasing in pressure with respect to the aorta  22  (e.g., slowing of blood flow into the left main  24 ), the passive valve gate  268  may act to hinder, or reduce, the delivery of medium to the delivery site (as illustrated by the medium flow arrow  269   b  in  FIG. 24B ). Thus, the device of  FIGS. 23, 24A and 24B  provides an arrangement that may allow “synchronized” delivery of medium to the coronary vasculature as a function of a passive valve mechanism. 
       FIGS. 25A and 25B  illustrate another embodiment of passively valving the distal portion of a catheter so as to improve the efficiency of delivery of medium to a delivery site.  FIG. 25A  illustrates a delivery catheter  270  that may be placed in a sealing relationship (partial or total) with a coronary artery  25  such as, for example, as at catheter/artery interface  272 . With such use, there may be a concern that blood flow from the aorta  22  is restricted from perfusing the occluded artery  25 . However, as shown in  FIG. 25A , distal portion of delivery catheter  270  may have a valve  274  and orifice(s)  276  disposed distally of the valve  274  so as to provide perfusion from the aorta  22 , through the catheter  270 , and distal to the delivery catheter (i.e., into the artery  25 ) when medium injection is not taking place. In this instance, valve  274  is closed, allowing blood to flow into orifice(s)  276 , through the distal portion of the catheter  270 , and past the catheter/artery interface  272 . The valve  274  thus acts to allow blood flow distally, as illustrated by blood flow arrows  278  in  FIG. 25A  (while inhibiting the flow of medium past valve  274 ). Conversely, as shown in  FIG. 25B , when delivery of medium is warranted, valve  274  may be deployed so as to reduce perfusion from the aorta  22  and allow medium delivery to the delivery site. In this instance, valve  274  is open, allowing medium to flow past valve  274 , through the distal portion of the catheter  270 , and past the coronary/artery interface  272 . The valve  274  thus acts to allow medium flow distally, as illustrated by medium flow arrows  279  in  FIG. 25B  (while inhibiting the flow of blood past valve  274 ). 
     There are many forms wherein the passive distal valving of a delivery catheter may be employed to further enhance the efficiency and/or effectiveness of medium delivery to a delivery site. The previous examples are illustrative of the inventions, and should not be interpreted as limiting in their scope. 
     In addition to the various embodiments described herein to effect more efficient delivery of medium to a target site, the modulation of an injection may be further enhanced with various delivery catheter tip configurations, thus advantageously changing the flow characteristics in, around and/or proximate the delivery site. For example,  FIGS. 17A-17D  illustrate four embodiments that may be employed to perform such a function. As previously described by  FIGS. 5A and 5B , it is clear that at least one of the challenges associated with the delivery of medium may involve the location of the delivery catheter tip and the pressure differentials surrounding the tip.  FIGS. 5A and 5B  illustrate a catheter delivery tip within the aorta  22 , at the ostium  20  to the left main  24 . This “catheter tip” placement may be common since physicians may be hesitant in delivering the tip of the catheter into the left main due to concerns of injuring/disrupting the vessel wall and/or causing spasms (and thus acute occlusion) within the left arterial system. If the delivery catheter is positioned as such, there may be little “driving force” (e.g., pressure differential) to preferentially deliver the medium from the delivery catheter tip into the ostium, versus into the aorta (and, thus systemically).  FIGS. 17A-17D  show various embodiments that may preferentially modulate the environment surrounding and/or proximate the delivery catheter tip in order to enhance the delivery of agent into the ostium. In many regards, these embodiments may also act to isolate/control the environment surrounding the delivery catheter distal delivery portion so as to accommodate more efficient delivery of a substance. 
     For example,  FIG. 17A  illustrates a delivery device  210  that may have a balloon inflated around its distal portion  212  so as to increase the pressure within the aorta  22  (at least during injection), and further “drive” the injection medium into the ostium  20 . The embodiment of  FIG. 17B  illustrates a conical member  222 , surrounding the catheter delivery tip of delivery device  220 , which may act to capture/isolate medium, and/or increase flow resistance (when deployed) for the medium to flow to the aorta  22 ; and thus, preferentially “drive” the medium into the left main  24 . P AO  and P LM  of  FIG. 17B  designate areas of pressure within the aorta (e.g. P AO ) and the left main (e.g., P LM ) solely for the purpose of identification. The conical member  222  may also be expandable; as well as the expansion of  222  could further be in response to the pressure gradient between P AO  and P LM . 
     The alternative exemplary embodiment described by  FIG. 17C  shows a delivery device  230  that includes a coaxial member or sleeve  232  surrounding a distal catheter delivery portion  234  and may, in essence, act to artificially “extend” the left main  24  into the aorta  22 . Thus, upon injection of medium, the flow of the medium is subjected to greater resistance to flow along the path to the aorta  22  (via the sleeve  232 ) than would be present flowing to the ostium  20 . In some ways, the coaxial nature of the coaxial  232  member may also advantageously function as a distal “reservoir” of medium, acting to store and then release medium from the temporary reservoir structure in response to the cyclical pressure changes seen, for example, by the left main  24 . 
       FIG. 17D  illustrates another embodiment in the modulation of the flow parameters surrounding the delivery catheter distal portion. As shown, a delivery device  240  has a delivery catheter tip with a coaxially expandable sheath  242  surrounding a distal portion of the catheter. When expanded, the sheath  242  could partially engage the ostium  20 , as at  244  for example. The expansion of the sheath  242  may be actuated by the flow of injected medium through at least one or more orifices  246  along the distal portion of the catheter. The expanded sheath  242 , when deployed, may create greater resistance to flow (for agent) along the path to the opening  20  of the aorta  22 , than along the path into the left main  24 , as indicated by the flow arrows in  FIG. 17D . 
     There are many variations to the structures and configurations exemplified in  FIGS. 17A-17D  which may modulate, or otherwise control or isolate, the pressure and/or flow environment surrounding a distal portion of the delivery catheter.  FIGS. 17A-17D  are illustrative of embodiments that advantageously modulate the flow characteristics in, around and/or proximate the delivery site and, as such, should not be viewed as limiting the scope of the structures and methods for achieving such flow characteristics. 
     In addition to the various disclosed arrangements and processes that may act to modulate the environ of flow characteristics in, around and/or proximate the delivery site, other delivery catheter distal tip designs might advantageously “mix” the medium with the blood. The applicants have found that in at least some medium delivery scenarios (i.e., agent, target site, flow parameters) it may be necessary for the injected medium to travel a distance from the distal tip of the catheter before the medium may be sufficiently “mixed” with the blood flow (e.g., homogenous concentration of the medium within the blood). In the example described by  FIGS. 5A and 5B , it is possible that an injected agent may not reach a homogenous concentration within the blood flow for some distance distally along the left main and/or arterial supply from the ostium. As an example, if it were to take approximately 2 cm to 3 cm for the medium to mix with the blood, then this distance along the vessel may not be “well opacified.” In this situation, an operator of an injector may continue to increase the medium delivery in order to obtain greater opacification of the vessel. A delivery catheter having a distal tip construction as shown, for example, in  FIG. 18  may be able to more readily mix the medium exiting the catheter with the blood flowing by the catheter, and therefore may advantageously reduce the amount of medium necessary to see the opacification of the artery. 
     The example of  FIG. 18  shows a delivery catheter  250  having ribbed undulations  252  along the inner surface of its distal tip  254  so as to provide a flow pattern resembling a vortex  256  of the medium exiting the catheter  250 . The disrupted medium flow pattern may more readily mix the medium and blood. Although  FIG. 18  illustrates ribbed undulations along the inner surface of the delivery catheter, it is clear that there may be other structures and configurations that may perform the same function (such as: structures along the inner and/or outer diameters of the delivery catheter; structures deployed within the blood, distal to the catheter tip, to agitate/disrupt the blood/medium flow; structures such as orifices placed along the distal portion of the catheter to allow medium/blood mixing within the delivery catheter; etc.). In connection with the notion of mixing the medium and blood,  FIG. 18  is only intended to illustrate an exemplary arrangement and process for doing so. 
     Note that “tip” of the catheter as used may be synonymous with the “distal portion,” or any other portion of the catheter that may reside within the patient&#39;s body (e.g., distal of the proximal portion of the delivery catheter) and might play a role in the delivery of an agent to an intended target site. 
     In summarizing many of the embodiments described herein, there are numerous occasions in the diagnostic, prophylactic and treatment practice of medicine wherein an agent, substance, material, medicant, or medium is preferably delivered to a specific site within the body. Some of the examples described herein have advantageously comprised delivery control attributes that may derived from one or more of the modulating elements/functions illustrated in  FIG. 19  (i.e., injection device type, regulation type, sequential versus direct delivery, synchronization with corporeal flow, activation/deactivation at pump versus after pump, flow environ manipulation).  FIG. 19  attempts to summarize some of the described elements/functions with reference to illustrative FIGS. of this disclosure and/or their descriptions. As importantly, the various elements/functions in media delivery modulation are not, per se, mutually exclusive since one or more of these elements/functions may be used in combination to derive control attributes desired. As such, the various elements/functions identified in  FIG. 19  may be selected (e.g., “mix-and-matched”) to produce a modulator that optimally performs an intended purpose. For example, one might consider a variety of attributes in performance of medium modulating function, such as: target site location, target site access, fluid dynamics proximate the target site, agent to be delivered (e.g., quantity, viscosity, toxicity), injection frequency, concentration of agent within target site, target site isolation, ease of use of modulator, complexity in administration, cost of the system, and cost of agent, to name a few. 
       FIG. 19  can be considered a general summary for guiding the reader in identifying an exemplary function/element. Therefore,  FIG. 19  is not, per se, inclusive of all the figures and descriptions within this disclosure that may contain a particular function/element; nor, is  FIG. 19  inclusive of all embodiments disclosed herein. It is contemplated that the disclosed features, systems and schemes for modulation may be combined in a myriad of combinations and sub combinations to achieve operative introduction of medium (e.g., opacity) without excessive introduction thereof, in addition to those specifically shown and described. 
     Many of the examples of systems illustrated have involved the delivery of a cardiovascular contrast agent. However, there are many other applications wherein the controlled delivery of a substance to a specific structure/organ/site of the body may also benefit from the devices and methods disclosed herein. Due to the variety of medical applications, as well as the diversity of means to modulate (for example, elements/functions of  FIG. 19 ) there may be a multitude of mechanisms employed to produce a modulator for its unique and intended purpose. An example of how one might go about employing various elements/functions in the construction of a modulator device is further described below, as it pertains to a non-cardiovascular procedure of lymphography. 
     Lymphography employs the delivery of an imaging agent to the lymphatic system wherein an agent is injected, and subsequently radiograph(s) taken, in the visualization of metastatic cancer cells. Procedurally (and after identifying the lymphatic), a needle/catheter may be inserted into a lymphatic channel/vessel in the foot (near the base of the first metatarsal) and a contrast medium (such as Ethiodol) may injected into the body at a very slow rate (approximately 60 to 90 minutes). The total quantity of injection might be 6-7 ml. The patient typically remains on his or her back during the procedure. Once the injection is complete, radiographs may be taken. Of note, the “flow” of fluid in the lymphatic system is consistently slow, as compared to the high flow and variability of the coronary arteries. Moreover, the lymphatic channel/vessels may be very sensitive (e.g., rupture) to over-pressurization. 
     Given the description of the lymphatic example (and referring to  FIG. 19 ), one might construct a modulator with elements/functions that satisfy the following attributes: long delivery time; small volume delivered; constant flow rate; sensitivity to over-pressurization; sufficiently portable/movable to accommodate patient during the delivery; and, equal to or less expensive than using an automated injector. Given these attributes one might consider a manually-loaded injector device to deliver the medium sequentially (delayed) wherein the device may be filled with an amount of fluid to be delivered (e.g., 6 ml) first, and upon release of the injection, may deliver the medium over an extended period of time (e.g., 90 minutes). An element in regulation might include a device with constant flow rate (i.e., constant flow rate irrespective of variable pressures), or a regulator element that functions with constant pressure differentials (i.e., irrespective of variable flow rates). Because of the high sensitivity to pressures in the lymphatic, the latter alternative might be more amenable in accommodating high pressure “spikes” (for example, if the delivery catheter were to occlude during the delivery). Viewing  FIG. 19 , elements of corporeal flow synchronization, flow activation (via signal), and distal environ alternation may be less important, and therefore those features may not be included in the exemplary device construction. Ultimately, a multi-component, sequential delivery device as illustrated and described in  FIGS. 9A-9C  may simply modulate the delivery of a controlled amount of agent, without the risk of rupturing the lymphatic channels/vessels due to over-pressurization. The sequential delivery allows for filling a precise amount of fluid to be delivered, and once the lymphatic vessel is accessed, may continue to deliver the medium over time. 
     Clearly, the lymphatic medium delivery is but one additional, non-cardiovascular example and it is intended to help further illustrate how the various elements and components disclosed herein may be used in a variety of ways to satisfy a multitude of clinical applications in the delivery of a fluidal substance. Moreover, it is anticipated that the systems described herein may be formed and/or constructed of materials generally recognized to be suitable for medical use, and may include disposable materials, or reusable materials, or a combination of both in the construction of components of the system. 
     It should be understood that the medium delivery modulation devices and methods described herein are not limited to the particular, representative embodiments as described, since variations may be made to these embodiments without departing from the scope and spirit of the disclosure. Likewise, terminology employed in the description of embodiments is not intended to be limiting and is used merely for the purpose of conveyance of the concept. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art of which the disclosed devices and methods pertain. In addition, any feature disclosed with respect to one embodiment may be incorporated in another embodiment, and vice-versa.