Abstract:
Devices and methods are provided for percutaneously treating atherosclerotic plaques within blood vessels. Atherosclerotic plaques cause significant morbidity and mortality by narrowing the arteries, which adversely affects blood flow, and by acting as a source for thrombi and emboli thus causing acute organ ischemia. Current treatments include open surgery with its inherent drawbacks, and stenting, which is less invasive but leaves the plaque material in the artery, which promotes restenosis. The present invention combines the advantages of both approaches. In general, the invention provides tools that enable percutaneously dissecting the plaque from the arterial wall and removing it from the body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 14/349,920, filed Apr. 4, 2014, which is a U.S. National Phase Application of International Application No. PCT/IB2012/002847, which has an international filing date of Oct. 4, 2012, and which claims priority to U.S. Provisional Application No. 61/542,091, filed Oct. 4, 2011, the disclosures of which are incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to devices and methods for percutaneously treating atherosclerotic plaques within blood vessels. 
       BACKGROUND OF INVENTION 
       [0003]    The normal human artery is composed of three main layers. The innermost layer lining the artery, in contact with the blood, is the intima. This is a single cell layer of endothelial cells, which among other functions regulates vascular tone, platelet activation and thrombus formation, monocyte adhesion and inflammation and vascular remodeling. The media—the middle layer, consists of several layers of smooth muscle cells and elastic fibers. The outermost layer is the adventitia, which is mainly composed of connective tissue containing small blood vessels and nerves. 
         [0004]    Atherosclerosis is one of the major causes of cardiovascular cerebrovascular and peripheral vascular morbidity and mortality. It is a disease of large and medium-sized muscular arteries, which is characterized by the formation of discrete lesions called atherosclerotic plaques, or atheromas, thought to be caused by injury to the endothelium. An atheroma is a buildup of lipids, cholesterol, calcium, and cellular debris within the intima of the vessel wall. Atherosclerotic buildup also results in vascular remodeling, acute and chronic luminal obstruction, abnormalities of blood flow and diminished oxygen supply to target organs. 
         [0005]    A complex and incompletely understood interaction is observed between the critical cellular elements of the atherosclerotic lesion. These cellular elements include endothelial cells, smooth muscle cells, platelets, and leukocytes. 
         [0006]    The presence of risk factors accelerates the rate of development of atherosclerosis. The main risk factors for the development and progression of atherosclerosis include hyperlipidemia and dyslipidemia, hypertension, cigarette habituation, air pollution, diabetes mellitus, older age, male sex, family history of premature CAD, obesity and physical inactivity. Additional risk factors associated with atherosclerosis include various metabolic diseases, autoimmune diseases, chronic kidney disease, and depression. 
         [0007]    Manifestations of atherosclerotic disease depend on the affected organs and the type of lesions. Chronically narrowed arteries give rise to symptoms of insufficient blood flow such as angina pectoris (chest pain during exertion), intermittent claudication (leg pain during exertion), and chronic leg ulcers. Acute events can occur as a result as of plaque rupture and thrombosis, which might totally clog the artery as in most cases of acute myocardial infarction (heart attack), or as a result of distal embolization of plaque fragments, as in many cases of stroke. 
         [0008]    Treatment of atherosclerosis depends on many factors including the location of symptomatic lesions, the severity of symptoms, and their dynamics. 
         [0009]    Acute obstruction events usually require acute intervention. For acute coronary events, treatment is urgent percutaneous angioplasty (balloon dilation of the obstructed artery) and stenting. Depending on the time from the beginning of symptoms, acute ischemic stroke is sometimes treated urgently by percutaneous mechanical removal of the obstruction or injection of compounds that lyse it (tPA, streptokinase), but in many such cases treatment will only focus on the prevention of future events. Acute limb ischemia is also treated by urgent revascularization, either percutaneous or surgical. 
         [0010]    The treatment of chronic obstruction is usually a combination of medical therapy and an interventional procedure. 
         [0011]    Medical treatment may include anti platelet agents such as Aspirin, anti-coagulants such as Coumadin, Statins, which decrease cholesterol levels and stabilize plaques, and more. 
         [0012]    Interventional procedures may be surgical or percutaneous and are aimed at revascularization of the target organs and removal of a potential source of emboli, if present. 
         [0013]    Surgical treatments include bypass surgery, more commonly used for coronary and lower limb arteries, and endarterectomy, which is used for limb and carotid arteries, and involves opening the artery and removing the plaque along with the intima. Obviously, the disadvantage of surgery is its highly invasive nature, the need for anesthesia, and the pain and stress involved which make it unsuitable for certain patients. 
         [0014]    Percutaneous procedures enable treating the lesions using long catheters inserted to the arteries at a distant point such as the groin arteries. The most common of these is placement of a stent, a metal structure which is inserted to the artery in a closed state and expanded within the lesion so as to keep the lumen patent. This can be done with or without balloon angioplasty (inflation of a balloon in the lesion to enlarge the lumen prior to or following stent placement). The main disadvantage of angioplasty and stenting is that the plaque remains in the artery. This has several deleterious consequences. First—in carotid stenting, many of the post stenting strokes are caused not during the procedure, but after it, and are probably related to plaque material squeezing through the cells of the stent and embolizing to the brain (a phenomenon known as the “mashed potato effect”). Second—in many cases the plaque encroaches on the stent and does not enable attainment of a normal vascular lumen. This in turn affects flow dynamics and shear stress, which may enhance atherogenesis and cause restenosis. Third—the plaque material itself contains many inflammatory and prothrombotic substances. This may be the reason for the high rate of restenosis experienced after stenting. 
         [0015]    In view of the disadvantages of surgery and of stenting, and for treating heavily calcified lesions, novel procedures have been developed that attempt to remove the plaque via a percutaneous route. This type of procedure is termed percutaneous atherectomy, and utilizes some form of ablation device that removes plaque from within the lumen. Examples of such devices based on mechanical grinding include the SILVERHAWK directional atherectomy device (Covidien), the ROTABLATOR rotational atherectomy device (Boston Scientific), the JETSTREAM NAVITUS (Pathway Medical Technologies). Other systems use different forms of energy for removing plaque material such as in laser atherectomy. 
         [0016]    The two major drawbacks of these devices are: 
         [0017]    (1) It is impossible to know exactly how much plaque to remove—too much will injure the artery with possible rupture or dissection in the wall, too little will leave a significant amount of atheroma. Angiography is not accurate enough for this purpose, ultrasound is being incorporated in such systems but will never allow as accurate a result as that achieved with endarterectomy. 
         [0018]    (2) Its fibrous cap having been removed, the atheroma with its deleterious contents is left exposed to the blood flow. 
         [0019]    Two other methods worthy of mention are subintimal angioplasty and remote endarterectomy. Although good results were reported with both methods, they require high technical proficiency, have a long learning curve, and have therefore not gained much acceptance in the medical community. 
         [0020]    Subintimal angioplasty (also known as the Bolia technique) is a percutaneous procedure developed for treating chronic total occlusions (CTOs), in which the obstruction of the lumen is complete, and the system cannot traverse the lesion. In these cases, a guidewire is directed into the subintimal space between the intima and the media of the arterial wall, and passed across the lesion until it re-enters the lumen beyond it. Angioplasty and stenting is then performed in this new artificial channel within the arterial wall. As the atheroma is still adjacent to the stent, the disadvantages mentioned above for regular stenting apply here as well. 
         [0021]    Remote endarterectomy is an open vascular procedure performed on the arteries of the thigh, and mainly used to remove long, severe plaques. The artery is surgically exposed and cut open, and the dissection plane between the intima and media is identified. Special tools for separating the plaque from the arterial wall are inserted around the “core” which is subsequently removed. This procedure is by definition a surgical one and the tools are not appropriate for percutaneous use. Results of this procedure are very good compared to other treatment modalities, and advantages include decreased morbidity and shorter hospital stays compared to surgery, preservation of bypass options, and decreased incidence of limb-threatening ischemia when a remote endarterectomy fails. 
         [0022]    It is clear from the above, that percutaneous procedures and devices enabling subintimal removal of atherosclerotic plaques could provide great advantages over current practice, by combining the accuracy of surgical endarterectomy with the benefits of minimally invasive procedures. The aim of the current invention is to describe such a solution, which will also be simple, safe, and effective. 
       SUMMARY OF INVENTION 
       [0023]    The invention includes various solutions to the removal of atherosclerotic plaque from arteries. The apparatus and methods include use of the natural dissection plane between the plaque and the media of the artery. 
         [0024]    Embodiments of the present invention include devices and methods removal of atherosclerotic plaque from arteries, in particular for percutaneous endarterectomy. 
         [0025]    One embodiment of the invention is a device for percutaneous endarterectomy including: a shaft configured to pass through the lumen of a catheter, having a distal end; and one or more expandable fingers having a proximal and distal end with the proximal end of the one or more fingers attached to the distal end of the shaft. In that embodiment, the fingers are configured to remove an atherosclerotic plaque by peeling the plaque at the subintimal space without performing an incision into the intimal space and without use of a blade. Furthermore, optionally, the finger may be configured so that radial force applied by the fingers decrease going from the proximal to the distal end of the tip relative to the plaque. 
         [0026]    The device may further include a catheter having a lumen and a distal end configured so that the shaft passes through the lumen of the catheter. 
         [0027]    This embodiment of the invention may have various other features including but not limited to one or more of the following: a) the one or more fingers are connected to each other by one or more spokes; b) a distal end of the one or more expandable fingers, when expanded, are substantially parallel to the shaft; c) the one or more fingers are self-expanding; d) the one or more fingers include a plurality of fingers to surround the shaft; e) the one or more fingers include a substantially cylindrical formation when expanded; f) the one or more fingers include a substantially conical formation when expanded; g) the one or more fingers are elongated and form a ribbon-shaped configuration; h) the one or more fingers are each connected to a spoke, each spoke is connected to a rod and the shaft includes a lumen through which the rod may pass; i) the one or more fingers have a guidewire for passing a guidewire therethrough; j) the one or more fingers are held in a position relative to the shaft by a spoke; k) the one or more fingers are held in a position substantially parallel to the shaft; l) the one or more fingers are substantially straight; m) the one or more fingers are substantially curved; n) the one or more fingers have a bent end; o) the one or more fingers have a transverse cross-section with a leading end and an trailing end, wherein the leading end is smaller than the trailing end; p) the one or more fingers has a longitudinal length and a cross-section size of the one or more fingers along the longitudinal length varies; q) the one or more fingers may have the same or different cross-sectional shapes; r) the one or more fingers include a loop; s) the one or more fingers are petal-shaped; and/or t) the one or more fingers include a plurality of fingers surrounding the shaft and the plurality of fingers, when expanded, are spaced apart from each other. The fingers may also be rotatable. 
         [0028]    Another embodiment of the invention is a device for percutaneous endarterectomy including: a rod; a shaft having a lumen and a distal end for passing over the rod; a catheter having a lumen and a distal end for passing over the shaft; one or more expandable and rotatable fingers having a proximal and distal end with the proximal end of the one or more fingers attached to the distal end of the shaft, having an exterior surface facing the artery and an interior surface facing the rod; and one or more spokes connecting the rod to the one or more expandable fingers on the interior surface whereby the fingers are controllable by the rod through the one or more spokes, whereby the fingers are configured to remove an atherosclerotic plaque by peeling the plaque at the subintimal space without performing an incision into the subintimal space and without use of a blade, whereby the distal end of the expandable fingers when expanded is parallel to the shaft, and whereby the fingers are configured to be advanced forwards and/or backwards. 
         [0029]    In one embodiment, the fingers are configured so that radial force applied by the fingers decrease going from the proximal to the distal end of the tip relative to the plaque. In another embodiment, the fingers further include a centerline running longitudinally from the distal end of the fingers to the proximal end of the fingers. Optionally, the fingers also further include a marker at the distal end of the centerline. The fingers may be radially expandable. 
         [0030]    Two or more rows of spokes may connect the rod to the one or more fingers. In one embodiment, the two or more rows of spokes are parallel to each other. In another embodiment, the two or more rows of spokes create a parallelogram configuration with two sides of the parallelogram formed by the rows of spokes, one side formed by the shaft and the other side formed by the one or more fingers. 
         [0031]    In any of these embodiments, the distal tip of the fingers may be sharp and the distal end of the fingers is sufficient to find the edge of the plaque without cutting the media or adventitia. Alternatively, in any of these embodiments, the distal end of the fingers is blunt and sufficient to find the edge of the plaque without cutting the media or adventitia. 
         [0032]    The device for percutaneous endarterectomy of the invention may further include additional components such as e.g. a dissector, cutting tool and/or rotatably mounted jets. 
         [0033]    The dissector may include expandable loops configured to separate the plaque from the arterial wall around its circumference and along its whole length. In one embodiment, the dissector is configured for passing through the lumen of a catheter. In another embodiment, a cutting tool located at the tip of the dissector tool. The dissector tool may also include one or more jets. 
         [0034]    In addition, when jets are included the device includes monitoring of pressure. Thus, in one embodiment, the fluid pressure of liquid injected by the one or more jets and the net volume of liquid injected is monitored. In another embodiment, the pressure inside the catheter is monitored. In yet another embodiment, the pressure inside the artery is monitored. 
         [0035]    In one embodiment, the device includes a cutting tool. A suitable cutting tool is a cutting tool having one or more deployable angled blades at the tip of the cutting tool. In one embodiment, the cutting tool is configured so that the deployable angled blades excise the plaque. 
         [0036]    In addition to the cutting tool, the device may also include a funnel shaped catheter tip. This funnel shaped catheter tip may be advanced around the plaque to collect plaque after cutting. 
         [0037]    In another embodiment, the devices also include one or more rotatably mounted jets. In one embodiment, the jets are configured to sever the plaque from the vascular walls. 
         [0038]    The devices may also contain a balloon and/or cage configured to separate the plaque. 
         [0039]    Another embodiment of the invention is a device for percutaneous endarterectomy including: a shaft; a catheter having a lumen and a distal end for passing over the shaft; one or more expandable and rotatable retrograde fingers having a proximal and distal end with the proximal end of the one or more fingers attached to the distal end of the shaft wherein the distal end of the fingers faces the proximal end of the catheter; a slideable sheath positioned on the distal end of the catheter configured to cover the one or more rotatable fingers, wherein the fingers are configured to remove an atherosclerotic plaque by peeling the plaque at the subintimal space without performing an incision into the subintimal space and without use of a blade. This device may be configured so that sliding of the sheath expands the fingers. In one embodiment, the fingers remove the plaque by a backward motion. 
         [0040]    The devices of the invention may be used in methods of percutaneous endarterectomy. Thus, other embodiments of the invention are method of percutaneous endarterectomy which use of the devices of the invention, whereby an atherosclerotic plaque is removed by peeling the plaque at the subintimal space without performing an incision into the subintimal space and without use of a blade. 
         [0041]    Another embodiment of the invention is a method of percutaneous endarterectomy including: accessing an artery having an atherosclerotic plaque nearby the plaque with a device including: a shaft configured to pass through the lumen of a catheter, having a distal end, and one or more expandable fingers having a proximal and distal end with the proximal end of the one or more fingers attached to the distal end of the shaft, wherein the fingers are configured to remove an atherosclerotic plaque by peeling the plaque at the subintimal space without performing an incision into the subintimal space and without use of a blade, wherein the distal end of the expandable fingers when expanded is substantially parallel to the shaft; peeling the plaque at the subintimal space without performing an incision into the subintimal space and without use of a blade; and separating the plaque from the arterial wall around its circumference and along its length. 
         [0042]    The method may further include cutting the intima connecting the distal part of the plaque to the arterial wall and optionally local treatment of the exposed media after cutting by instillation of endothelial progenitor cells, stem cells, other cells, or substances. In one embodiment of the method, the step of cutting comprises use of a dissection tool having one or more deployable angled blades. Via use of the angled blades, the step of cutting my include cutting the intima and excises the plaque without leaving an intimal flap. The method may further include removal of the cut plaque (via e.g. use of a funnel shaped catheter tip) and removal of the device. The step of separating the plaque may include use of a dissector. The method may optionally include the step of locating the plaque prior to peeling. In one embodiment, step of locating includes moving the fingers of the device along the subintimal space to locate the plaque. 
         [0043]    Another embodiment of the invention is a device for entry into subintimal space having: a rotatable shaft having a metal strip attached to the distal tip of the shaft, wherein the distal end of the metal strip curves; one or more inclined blades attached to the distal end of the metal strip; a removable sheath for sliding over the rotatable shaft and for covering the one or more inclined blades; a catheter having a lumen and a distal end for passing over the shaft; and one or more balloons disposed towards the distal end of the catheter; wherein the device is configured so that rotation of the shaft rotates the blades which in turn cuts through the intima, wherein the sheath is configured to be removable during use of the device. 
         [0044]    Yet another embodiment of the invention is a device for percutaneous endarterectomy including: a catheter having a lumen; one or more guidewires for threading through the subintimal space, wherein the guidewires pass through the lumen of the catheter; an expandable separator device comprising a hollow cylinder folded onto an elongated member, wherein the separator when deployed assumes a cylindrical shape with an overlap of both ends over the slit. In one embodiment, the expansion of the separator device separates the plaque from the arterial wall. The device may also further include a cutting tool. 
         [0045]    In certain embodiments, the devices of the invention include a grinder. The grinder may be mounted on the distal end of the catheter. Alternatively, the grinder may be deployable through the lumen of the catheter. 
         [0046]    Yet another embodiment of the invention is a device for percutaneous endarterectomy including: a catheter having a lumen and a distal end; one or more guidewires for threading through the subintimal space, wherein the guidewires pass through the lumen of the catheter; a shaft having a distal end passing through the catheter lumen; one or more expandable loop shaped wings having a distal edge and a distal tip, wherein the loop shaped wings are attached to the shaft; a removable cap on the distal end of the catheter, whereby the device is configured so that removal of the cap causes expansion of the wings. The cap may include a tip and a shaft, such that the shaft of the cap passes through the catheter lumen. The device may also include a web covering the one or more wings. In one embodiment, the web is configured to be an emboli protection device. Additionally, the device may further include a cutting tool. In one embodiment, the one or more wings are configured to anchor the distal intima and to thereby enable cutting without leaving an intimal flap. 
         [0047]    Yet another embodiment of the invention is a device for inserting one or more guidewires into a subintimal space of an artery including: a catheter having a lumen, a distal end and a tip at the distal end; a pushing element at the tip of said catheter; a balloon proximal to said pushing element; and one or more guidewire catheters adjacent and parallel to said catheter, said guidewire catheter passing over balloon and configured to assume an orientation essentially parallel to longitudinal axis of distal catheter or up to approximately 5 degrees outward of said axis. The pushing element may be a balloon or include an expandable metal element. In one embodiment, the balloon is moveable relative to said catheter. 
         [0048]    This device for inserting one or more guidewires into a subintimal space of an artery may be used in a method for inserting one or more guidewires into subintimal space including identifying a lesion, bringing the device proximate to lesion, inflating proximal balloon, applying tension by the pushing element, and pushing guidewire forward into subintimal space. The method may further include one or more of (a) application of suction on the area between the proximal and distal balloon prior to the pushing the guidewire into subintimal space and (b) verification of guidewire insertion into subintimal space by use of angiography. 
         [0049]    In another embodiment, this device for inserting one or more guidewires into a subintimal space of an artery may be used in a method for removal of a plaque including inserting one or more guidewires using the device and rotating the one or more guidewires around the plaque, first forward until the one or more guidewires re-enter the lumen and then backwards to remove the plaque. 
         [0050]    Additional features, advantages, and embodiments of the invention are set forth or apparent from consideration of the following detailed description, drawings and claims. Moreover, it is to be understood that both the foregoing summary of the invention and the following detailed description are exemplary and intended to provide further explanation without limiting the scope of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0051]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and together with the detailed description serve to explain the principles of the invention. In the drawings: 
           [0052]      FIGS. 1A-B  show two different common structures of the edge of an atherosclerotic plaque in an artery. 
           [0053]      FIGS. 2A-F  show embodiments of edger tools in accordance with the principles of the invention. 
           [0054]      FIGS. 3A-3E  show stages of use of an edger tool in accordance with the principles of one embodiment of the invention. 
           [0055]      FIGS. 4A-B  show the angiographic appearance of successful and failed edging. 
           [0056]      FIGS. 5A-C  show embodiments of dissector tools in accordance with the principles of the invention 
           [0057]      FIGS. 6A-B  show use of one embodiment dissector tool in accordance with the principles of the invention. 
           [0058]      FIGS. 7A-E  show embodiments of a distal intimal cutting tool in accordance with the principles of the invention. 
           [0059]      FIG. 8  shows use of one embodiment of a distal intimal cutting tool in accordance with the principles of the invention. 
           [0060]      FIGS. 9A-B  show cross-sectional views of two different embodiments of anchoring balloons for guiding catheter in accordance with the principles of the invention. 
           [0061]    FIGS.  10 AA,  10 BB,  10 CC and  10 A-F show various overall shapes of a distal end of a fingered shaft (edger) from both side and end views in accordance with the principles of the invention. 
           [0062]      FIGS. 10G-K  show various cross-sectional shapes of a finger of the fingered shaft (edger) in accordance with the principles of the invention. 
           [0063]      FIG. 11  shows use of a fingered shaft (edger) in accordance with the principles of the invention. 
           [0064]      FIG. 12  shows use of a fingered shaft (edger) with saline jet in accordance with the principles of the invention. 
           [0065]      FIG. 13A-C  show cross-sectional view of the finger and showing a saline jet exiting finger of the fingered shaft in accordance with the principles of the invention. 
           [0066]      FIG. 14  shows use of edging and dissection tool employing saline jet and no fingers in accordance with the principles of the invention. 
           [0067]      FIG. 15  shows an alternative embodiment of an edger tool finger in accordance with the principles of the invention. 
           [0068]      FIG. 16A-B  show an embodiment of a combined edger and dissector tool in accordance with the principles of the invention. 
           [0069]      FIG. 17  shows an embodiment of a cutting tool in accordance with the principles of the invention. 
           [0070]      FIG. 18A-C  show an embodiment of a dissector tool in three dimensional and longitudinal sections. 
           [0071]      FIG. 18D-F  show longitudinal sections of alternative embodiments of dissector tools. 
           [0072]      FIG. 19A-B  show alternative embodiments of distal intimal cutting tools. 
           [0073]      FIG. 20A-D  show various embodiments of a distal tip of dissector tool loops. 
           [0074]      FIG. 21A-B  show an embodiment of a medial plaque remover device. 
           [0075]      FIG. 22A-F  shows stages of use of a medial plaque remover device. 
           [0076]      FIG. 23  shows an embodiment of a medial plaque remover device in its inflated position. 
           [0077]      FIG. 24  shows a different embodiment of a medial plaque remover device in its inflated position. 
           [0078]      FIGS. 25A-C  show an embodiment of a metal medial plaque remover device from different views. 
           [0079]      FIG. 26A-C  show embodiments of subintimal wire insertion devices. 
           [0080]      FIG. 27A-C  show additional embodiments of subintimal wire insertion devices. 
           [0081]      FIG. 28  shows an embodiment of a media treatment catheter device. 
           [0082]      FIG. 29  shows an embodiment of a distal intima cutting tool. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0083]    The invention includes various solutions to the removal of atherosclerotic plaque from arteries. This invention includes methods and devices for performing percutaneous endarterectomy (i.e. removal of atherosclerotic plaques from arteries via a e.g. a catheter). The devices and methods may release plaque at its edge and peel away the plaque naturally, preferably, for example, along the subintimal space. All may be preferably based on the same principle of utilizing the natural dissection plane, which in the subintimal space, exists between the plaque and the media of the artery, for removing the plaque with a percutaneous tool. 
         [0084]    As known to those skilled in the art, the subintimal space is a potential space where a false lumen could form if blood flow were to enter it through an intimal tear and cause an arterial dissection. 
         [0085]    It is the same space used for passing the guidewire and creating an artificial extraluminal route in subintimal angioplasty procedures (the Bolia technique), and where the plaque is usually separated from the arterial wall in open endarterectomy operations. A recent article reports a case in which an occluded artery was endarterectomised two months after a subintimal angioplasty was performed on it, and histological cuts demonstrated that “the subintimal track had been formed between the internal elastic lamina and the atherosclerotic plaque at most levels.” Scholtes et al., “Subintimal Angioplasty Track of the Superficial Femoral Artery: A Histological Analysis”,  Circ Cardiovasc Interv.;  2012; 5:e6-e.8. It is therefore thought that subintimal angioplasty is not a random extraluminal revascularization procedure but creates subintimal passage in the form of a dissection between the atherosclerotic plaque and the media of the artery.” Scholtes et al. 
         [0086]    In this invention, the plane between the media and intima is utilized because it may be the pathway of least resistance around the plaque. As such, the guidewire in subintimal angioplasty procedures usually finds its way into the subintimal space quite naturally. The current invention describes additional ways in which to enter this space. 
         [0087]      FIGS. 1A-B  show two different common structures of the edge of an atherosclerotic plaque in an artery. With reference to  FIG. 1A  the artery comprises normal media  10  and normal intima  11 . The atherosclerotic plaque  12  in the artery is shown in both  FIG. 1A  and  FIG. 1B .  FIG. 1B  also illustrates the atherosclerotic (thickened) intima  13 . 
         [0088]    Two general directions are described, which differ in the aspect from which the plaque is approached: its edge or the medial aspect. 
         [0089]    “Plaque&#39;s edge,” as used herein refers to the border of the occluding lesion, whether proximal or distal. In some cases, as shown in  FIG. 1A , the lesion may have a distinct, abrupt border between a normal or essentially normal area and a stenotic area, wherein an actual “step” in thickness of the intima is present. In other cases, this border may be less distinct, with a gradual transition or tapering between the stenotic and patent areas of the artery ( FIG. 1B ). In such cases, the “edge” would be a location initially chosen by the physician, from which the stenosis is deemed of no clinical significance. 
         [0090]    “Medial aspect” refers to an approach to the plaque beginning with passage of a device in the subintimal space throughout the length of the lesion. 
         [0091]    All the described procedures and tools are preferably used after deployment of an embolic protection device in the artery. Alternatively, by way of example, the treated area may be isolated by inflating balloons at one or both of its ends. 
         [0092]    The tools and methods described herein may be used with slight modifications either in an antegrade or in a retrograde fashion. Antegrade use refers to advancement around the plaque while the device is being pushed forward. This has the advantage of not necessitating traversing of the lesion before initiation of treatment; hence, it is appropriate for the treatment of CTO lesions (Chronic Total Occlusions). The disadvantage is that pushing the device forward may be more difficult technically than pulling it. Retrograde use refers to advancement around the plaque while the device is being pulled backward. This requires that the device be passed through the lesion prior to initiation of treatment. Only then can it be deployed and pulled back. The main disadvantage is that the lumen through some lesions may be so stenotic as to prevent passage of the catheter, in which case this approach cannot be used. On the other hand, this approach may be more suitable for lesions at bifurcations. 
         [0093]    After placing the treatment catheter at the vicinity of the lesion, demonstrating it, optionally placing any of the many available embolization protection devices, and anchoring the treatment catheter, treatment may follow these stages: 
         [0094]    1. Access into the subintimal space. This entails passage of an instrument into the subintimal space (“SIS”), and in some cases initial separation of the plaque, a process herein referred to as “edging,” which may be performed using an “edger” tool. Such separation is intended to enable further separation of the plaque from the arterial wall, herein referred to as “dissection.” 
         [0095]    2. Dissection of the plaque. This entails separation of the plaque from the arterial wall around its circumference and along its whole length. Dissection may be performed using a specialized “dissector” tool, or in some embodiments with the edger tool. 
         [0096]    3. Distal cutting. After the plaque was separated all around, the intima connecting the distal part of the plaque to the arterial wall may be cut. 
         [0097]    4. Closure. A device enclosing the plaque is generally closed so as to contain the plaque and its fragments. 
         [0098]    5. Removal. The device with the plaque in it is removed from the artery. 
         [0099]    6. Medial surface treatment. Optionally, treatment may be applied that enhances arterial healing and attenuates thrombogenicity and platelet adhesion to the exposed medial surface. Such treatment may consist of re-endothelialization therapy by e.g. instillation of endothelial progenitor cells, stem cells, or other cells or substances. Typically, such treatment will be applied using a specially designed balloon catheter system which keeps the cells/substance in contact with the arterial wall while at the same time allowing continuous blood flow through the treated area. 
         [0100]    The tools and methods described herein are aimed at removal of the plaque as a whole, preferably in one piece. For example, the exemplary devices and methods described herein provide for release of the plaque, preferably at its edge, and peeling of the plaque. A different approach is to use a grinder/macerator tool, which can also be used along with certain aspects and embodiments of the current invention. However, such a tool adds complexity, cost, and danger to the system, and in addition, grinding the plaque releases various deleterious thrombogenic and inflammatory substances into the blood stream, hence the preference for removal of the plaque without disintegrating it. 
         [0101]    Most preferred embodiments of the invention are based on the approach of attacking the plaque from its edge. In particular, the devices and methods of the invention provide for release of the plaque, such as through scraping and peeling of the plaque. Preferably, this is done without making a cut into the intima and/or media. Without radial cutting, grinding or abrading the plaque as the primary removal technique, the plaque may be scraped or edged away from the vessel wall to be peeled away along the natural dissection plane. In one embodiment, a device, utilizing, for example, fingers or projections, approaches the plaque from inside the vessel to contact and/or engage the plaque with a scraping action, for example, to find the way into the subintimal space. With the scraping action, the plaque/intima layer separates because the plaque/intima is naturally peeled away. The methods and devices of the invention do not rely e.g. on radial cutting, grinding, or abrasion and as such are much more gentle. 
         [0102]    In a preferred embodiment, an edger tool is provided including a tubular member from which end extend several elongated radially expandable “fingers.” An example of such tool based on an umbrella like mechanism is shown in  FIG. 2A-2E .  FIG. 2A  is a three-dimensional depiction of edger  20  which is passed through catheter  30 . It includes of shaft  24  from which extend fingers  21 . Rod  25  extends through shaft  24  and is connected to each finger  21  by spoke  26 . At centerlines  22  of fingers  21  near their edge may be additionally installed radiopaque marker  23 . A longitudinal section of edger  20  in its open position is shown in  FIG. 2B  and in its closed position in  2 C. Fingers  21  may be formed of an elastic material and pre-shaped in the open position, such that when pushed out of guiding catheter  30  and in the absence of pulling resistance by rod  25 , the edger will open. In such case, release of rod  25  controls the degree of finger  21  radial expansion and open diameter. Alternatively, finger  21  radial expansion may depend on pushing rod  25  forward. In any case, following radial expansion, fingers  21  assume a position essentially parallel to that of shaft  24  longitudinal axis ( FIG. 2B ). 
         [0103]    A slightly different example of edger tool is shown in  FIG. 2D-2F . This tool is similar to edger  20  but has additional spokes intended to maintain the fingers&#39; parallel position. More particularly,  FIG. 2D  is a 3D depiction of edger  40  which is passed through catheter  30 . It includes shaft  44  from which extend fingers  41 . Rod  45  extends through shaft  44  and is connected to each finger  41  by inner spoke  46  and a more distal outer spoke  47 . Inner spoke  46  and outer spoke  47  are of the same length, and the distances between their connection points on finger  41  and on rod  45  are also equal, such that they form a parallelogram. At centerlines  42  of fingers  41  near their edge may be additionally installed radiopaque marker  43 . A longitudinal section of edger  40  in its open position is shown in  FIG. 2E  and in its closed position in  2 F. Fingers  41  may be formed of an elastic material and pre-shaped in the open position, such that when pushed out of guiding catheter  30  and in the absence of pulling resistance by rod  45 , the edger will open. In such case, release of rod  45  controls the degree of finger  41  radial expansion and open diameter. Alternatively, finger  41  radial expansion may depend on pushing rod  45  forward. In any case, following radial expansion, fingers  41  assume a position essentially parallel to that of shaft  44  longitudinal axis ( FIG. 2E ), which is maintained at any opening diameter due to the parallelogram design. 
         [0104]    In one embodiment, the fingers  41  are of the same length. The fingers are designed so that radial force applied by the fingers decrease going from the proximal to the distal end of the tip (relative to the plaque). Thus, in one embodiment, the fingers deliver more force on the proximal end of the finger and less force on the distal end. In one embodiment, the tips of fingers are parallel to the shaft so that they do not cut the artery and so they are substantially in the direction of the dissection plane. The fingers are also so configured that they are more rigid towards the distal end and more flexible to the distal end. Furthermore, the edges of the fingers may be blunt or rounded. Thus, in one embodiment, the radius at the end of the fingers is not sharp, rather it is blunt and sufficient to find the edge of the plaque without cutting the intima. The fingers, in this configuration, may be used to remove the plaque in a forward motion. In one embodiment, the longitudinal sections of the fingers are parallel. It is thought that less force on the distal end results in a device that provides for a more gentle removal of the plaque and the ability to find the natural separation of the plaque. The embodiments shown and described herein are exemplary. For example, the force differences can be achieved in a variety of ways including structurally (via e.g. use of structural features such as struts and guidewires or a changing cross-section) or functionally (via e.g. use of a different materials). 
         [0105]    Fingers  41  as shown in  FIG. 2A  have a thin configuration that may be flat or curved as desired in accordance with the principles of the invention. Although other configurations may be used in accordance with the principles of the invention, for example, the lateral and transverse cross-sections of finger  41  may vary, and, further may vary, for example, as discussed in other embodiments described herein. Finger cross-sections also are shown in  FIGS. 10G-K . 
         [0106]    In another embodiment, the fingers may be sharp and the fingers are configured to find the edge of the plaque without radially cutting the intima. In another embodiment, due to the lateral positioning of the edger relative to the plaque, the fingers, may be relatively blunt, sharp or otherwise in accordance with the principles of the invention to accomplish the scraping and/or edging of the plaque so it may be removed along its natural dissection line. The fingers of the edger tools in accordance with the principles of the invention may be caused to probe along the arterial wall to find the edge and/or natural line/plane of dissection of the plaque. In one embodiment, the fingers press gently against the arterial wall and gently scrape the plaque to find the edge and/or natural separation.  FIG. 2A-3E  show the stages of edger  40  use. More particularly  FIG. 3A  shows longitudinal section of artery having inner diameter  15  with media  10  and plaque  12  at a distance  14  from tip of catheter  30 , which is anchored by balloon  31 .  FIG. 3B  shows edger  40  in its closed position passed through catheter  30 .  FIG. 3C  further shows edger  40  in its open position.  FIG. 3D  shows the above with edger  40  being advanced towards plaque  12 .  FIG. 3E  further shows fingers  41  separating between media  10  and plaque  12 . The distal portions of the fingers may also be substantially parallel to the central axis of the device e.g. pushing rod 
         [0107]    In use, guiding catheter  30  is brought to the vicinity of the target lesion  12  which is then demonstrated angiographically. If possible, an embolization protection device is deployed. The guiding catheter has a balloon  31  around its tip, which is inflated to anchor the catheter with its tip at a distance  14  from the plaque&#39;s edge, typically approximately 0.5-1 cm in a large (approximately 6-8 mm) artery, but possibly as short as approximately 1-5 mm in a small or medium (approximately 2-6 mm) artery ( FIG. 3A ). Arterial diameter  15  at the plaque edge is measured angiographically and an edger tool is chosen having an open diameter at least approximately 10% larger than arterial diameter  15 . Edger  40  is deployed through guiding catheter  30  ( FIG. 3B ) and expanded such that its fingers are slightly pressed against the arterial wall ( FIG. 3C ). This can be verified angiographically. Edger  40  is then rotated along its longitudinal axis and advanced towards lesion  12  ( FIG. 3D ). This separates the edge of plaque  12  from media  10 , such that fingers  41  are in the SIS ( FIG. 3E ). The normal medial layer of the arterial wall has much higher axial flexibility (ultimate stretch greater than about 1.5) compared with the normal intimal layer, and these differences are exaggerated when comparing normal media to atherosclerotic intima in which both axial and circumferential flexibility are reduced (ultimate axial stretch of about 1.1-1.2). Calcified plaque elements are essentially rigid with an ultimate stretch of approximately 1.02 (See Holzapfel AG et al., “Anisotropic Mechanical Properties of Tissue Components in Human Atherosclerotic Plaques”  Journal of Biomechanical Engineering,  2004, 126; 657-665). These differences in mechanical properties aid in the process of separation between the layers by the edger tool, which applies both circumferential and axial forces on all layers. The different response of each layer to these forces creates shear forces between the layers, which lead to their separation. 
         [0108]    Optionally, verification of proper “edging” can be done angiographically, as seen in  FIG. 4A-4B .  FIG. 4A  shows a schematic of an angiogram in case of successful edging. Edger  20  is shown through catheter  30  with radiopaque marker at the tip of finger  21 . Filling defect  33  is seen between contrast material  32  and finger  21 .  FIG. 4B  shows a schematic of an angiogram in case of unsuccessful edging. Edger  20  is shown through catheter  30  with radiopaque marker at the tip of finger  21 . No filling defect  33  is seen between contrast material  32  and finger  21 . As shown in  FIG. 4A , the correctly positioned fingers are demonstrated external to the edge of the plaque, which is seen as a filling defect, whereas in  FIG. 4B , the fingers are internal to the plaque edge, which means the edging was not successful. 
         [0109]    At this stage of the procedure, a dissector tool is introduced over the edger tool through the guiding catheter. An example of a dissector made of looped metal (such as nitinol) wires is shown in  FIG. 5A-5C . More particularly,  FIG. 5A  shows dissector  50  made of wire loops  51 , which may or may not be connected to each other by connector  52 . The distal most part of each loop is at its centerline  53 .  FIG. 5B  shows a similar dissector wherein each loop  51  is braided with the adjacent loop  51 .  FIG. 5C  shows a possible more intricate pattern of braiding in which several loops are interlaced with each other. 
         [0110]    The number of loops  51  in dissector  50  may vary between 2-8 but is typically 3-5. Loops may be completely separate as in  5 A, or every two adjacent wires may be connected to each other by a connector  52 . The braiding may be a simple one, involving only each two adjacent wires as in  FIG. 5B , or more intricate including several loops as shown in  FIG. 5C . Alternatively, such dissector may be formed of laser cut metal sheets or tube. 
         [0111]      FIG. 6A-6B  show use of dissector  50 . More particularly,  FIG. 6A  is a three dimensional depiction of dissector  50 , which is seen coming out of catheter  30 , with its loop centerlines  53  over edger  20  finger centerlines  22 .  FIG. 6B  shows a longitudinal section of an artery with plaque  12 , and catheter  30  anchored by balloon  31 . Dissector  50  is seen coming out of catheter  30  and being inserted into the SIS over edger fingers  21 . 
         [0112]    In use, as the dissector is pushed forward out of the guiding catheter ( FIG. 6A ), the user can rotate it to bring the centers of the loops  53  in line with the edger finger centerlines  21  . Thus, the edger serves as a guide for the dissector into the SIS ( FIG. 6B ). Once the dissector loops pass the edger fingers, the edger can be retracted and removed. Optionally, the interior of guiding catheter  30  may be shaped with grooves that help align the edger and dissector tools. 
         [0113]    The dissector is then advanced in the SIS under angiographic monitoring until it reaches the end of the lesion. Advancement of the dissector is achieved by a combination of forward push and rotation. The dissector loops will tend to expand as it is pushed forward, pressing against the flexible media and away from the more rigid plaque, which aids in the separation process. 
         [0114]    Once dissector  50  passes lesion  12 , dissector loop ends  53  might tear through intima  11  and enter the lumen without any action on behalf of the user. Such automatic re-entry may be enhanced by pre-shaping the dissector&#39;s nitinol loops with a curve towards the center of the lumen. However, this type of unintended re-entry carries a high chance of producing an intimal flap, which in turn might cause an arterial dissection, a dangerous complication of endarterectomy, which can lead to clogging of the artery, thrombosis, aneurysm or perforation. If an intimal flap is observed or suspected, it can be treated by placement of a stent over the transition area between the endarterctomized artery and untreated intima. In the current embodiment, in order to prevent the above, the dissector loops are shaped with an outward curve to reduce their tendency for re-entry. An intima cutting tool is provided as part of the dissector To enable smooth re-entry. Such tool  60  is shown in  FIG. 7A-7E . 
         [0115]    More particularly,  FIGS. 7A &amp; 7B  are three-dimensional depictions of intimal cutting tool  60  including blade  61  and guard  62 , slideably held together by holder  63 .  FIG. 7A  shows the closed position of cutting tool  60  whereas  FIG. 7B  shows the open position of cutting tool  60 .  FIG. 7C  is an end view and  FIG. 7D  a side view of cutting tool  60 .  FIG. 7E  shows typical assembly of cutting tool  60  over centerline  53  of loop  51  of dissector  50 .  FIG. 8  shows use of cutting tool  60  in a longitudinal section of an artery with media  10 , plaque  12  separated by dissector  50 , with cutting tool  60  over it, cutting through intima  11 . A close-up view of the re-entry area is shown, with blade  61  sliding over guard  62  and loop centerline  53  of dissector  50 , bending towards the lumen, and cutting through intima  11 , creating an incision in intima  11  having an angle  64  with longitudinal axis of artery. 
         [0116]    Intimal cutting tool  60  may be include two parallel metal strips, a blade  61 , and a guard  62 , held together by holder  63 . Blade  61  has a sharp tip and side, whereas guard  62  has a rounded tip and blunt sides. Blade  61  is also pre-shaped with an arch, such that when slid forward over the guard, its sharp area is exposed and it arches to the direction of the guard. The cutting tool is typically attached to one of the dissector loop centerlines  53  ( FIG. 7E ). In use, when the dissector passes the lesion, the blade  61  is deployed ( FIG. 8 ), penetrating through the intima in a sharp angle  64 . The whole dissector is then rotated along its longitudinal axis such that the intima is cut all around the lumen, without leaving an intimal flap. The blade is retracted. 
         [0117]    The entire intimal core is now completely separated from the arterial wall. The dissector is pulled backwards. This causes the loops to lengthen and the dissector&#39;s diameter to decrease, compressing the intimal core, and holding on to it. This enables removal of the complete core with the dissector. 
         [0118]    The above was a general description of a preferred embodiment. Specific modifications of each stage and tool may be employed to improve performance of the invention. Following are some such modifications. 
         [0119]    The anchoring balloon of the guiding catheter may be formed as several separate balloons ( FIG. 9A ), or having several conduits through it ( FIG. 9B ), to allow continuous blood flow across the treatment area during the procedure. This may be essential when the procedure is performed in areas that cannot tolerate cessation of blood flow, for example in case of treating a carotid artery when contralateral circulation is insufficient. Of course, in such a case, a distal protection device would be crucial.  FIG. 9A  shows catheter  30  surrounded by split balloons  34 , and  FIG. 9B  shows a balloon having conduits  35  through it. 
         [0120]    In a different embodiment of the edger tool, referring generally to FIGS.  10 AA,  10 BB and  10 CC, the tool may include an elongated member from which end at least one “finger” (FIGS.  10 AA &amp;  10 BB) but preferably three “fingers” (FIG.  10 CC) or more “fingers” project retrogradely. Radial expansion of these fingers may be achieved by their being made of a shape memory alloy such as nitinol, or by other means or ways such as an inflatable balloon. Limitation of the radial expansion of the fingers for example by a slideable external sheath enables control over the degree of contact with the arterial wall and force applied to it. In one embodiment, the edger tool complete with the sheath is deployed through the guiding catheter which is anchored by the balloon. The sheath may function to only open and close the tool. The fingers are designed so that radial force applied by the fingers decrease going from the proximal to the distal end (relative to the plaque). In one embodiment, the fingers are parallel so that they do not cut the artery and so the fingers extend substantially in the direction of the dissection plane. The fingers are also so configured that they are more rigid towards the distal end and more flexible to the distal end. In another embodiment, the edges of the fingers may be sharp and the fingers configured to find the edge of the plaque without radially cutting the intima. 
         [0121]    This “retrograde edger” tool is inserted through the guiding catheter placed proximal to the lesion. This tool is intended to be pulled back. It is passed beyond the lesion, deployed, then pulled back. The guiding catheter is used as a “base station”. The guiding catheter is in place for passing any kind of tool and does not need to be part of the various devices. The edger is passed through the lesion until after its distal edge as seen on angiography. The sheath is withdrawn to allow radial expansion of fingers, which contact the arterial wall. The guiding catheter is away from the tool (see  FIG. 11 ) 
         [0122]    More particularly, FIGS.  10 AA and  10 BB show an “edger” tool generally shown by reference number  70 . Edger tool  70  includes an elongated member  71  with a distal end  72  terminating in a distal tip  73 . From elongated member  71  extends one finger  74  that extends retrogradely. For example, as shown, distal tip  73  may extend in one direction and a finger distal tip  78  may extend in another direction, preferably, retrogradely relative to a direction of distal tip  73 . The relative positioning and direction of distal tips  73  and  78  may vary depending upon the positioning of finger  74  radially and/or relative to shaft  71 . Finger  74  may move relatively freely and independently of shaft  71 , in the embodiment shown, and may expand in a generally radial direction. In the illustrated embodiment, finger  74  is self-expanding. Radial expansion of finger  74  may be controlled by the intrinsic capabilities of the materials from which it is made and/or by external factors. For example, a slideable external sheath  75 , enables control over the radial expansion of finger  74  and thereby the degree of contact with the arterial wall and force applied to it. FIGS.  10 AA,  10 BB and  10 CC show the edger together with the sheath, which may be part of the edger device. Sheath  75  is a generally elongated hollow tube with a lumen passing through it. A distal end of guiding catheter  75  may include a side opening  76  and an open end  77 . When distal end  72  of edger tool  70  is positioned in the distal end of sheath  75 , edger tool  70  may be positioned as desired relative to sheath  75  to control positioning and radial expansion of finger  74 . For example, in FIG.  10 AA, finger  74  is positioned substantially away from side opening  76  and thereby is confined by sheath  75  so that finger  74  extends substantially alongside shaft  71 . FIG.  10 BB shows another position of edger tool  70  in sheath  75  where finger  74  is substantially disposed in side opening  76  as such finger  74  may be free to self-expand radially away from shaft  71 . Typically, during delivery, sheath  75  is positioned relative to edger  70 , such that open end  77  is proximate to finger distal tip  78 , holding finger  74  essentially alongside shaft  71 —“closed position.” Edger  70  can then be passed through the lesion and deployed distal to it by sliding sheath  75  distally, bringing open end  77  over distal end  72 —“open position”. Sliding open end  77  back over finger  74  will gradually bring it adjacent to shaft  71 , thus controlling its angle of opening. 
         [0123]    As discussed above, edger tool may include one or more fingers.  FIG. 10C  shows an exemplary embodiment of an edger tool  79  with  3  fingers  74   a,    74   b,  and  74   c.  This embodiment operates similarly to that described with respect to FIGS.  10 AA and  10 BB. With three fingers or more, edger tool  79  is kept centered in the arterial lumen by force of the fingers pressing against the arterial wall all around edger  79 . This is in contrast to one finger, which may cause edger  70  to be pushed against the arterial wall opposite finger  75 . Two fingers might cause the lumen&#39;s cross-sectional area to decrease as the artery is expanded radially at only two points on its circumference. 
         [0124]    The fingers in accordance with the principles of the invention may include different configurations. For example, the fingers may have an overall shape and cross-section with specific profiles that enhance their ability to dissect the plaque from the arterial wall as shown in  FIGS. 10A-10F  and  FIGS. 10G-10K . With references to  FIGS. 10A-K , the fingers are flexible elongated fingers as shown. The fingers are configured to scrape and peel, but preferably are not sufficiently sharp to cut the plaque and/or intima. Furthermore, the distal tips of the fingers point towards the proximal end of the apparatus. Thus, these fingers are used for removing the plaque in a backwards motion. The shape, configuration and/or radius at the finger is not sharp as for cutting, rather it is blunt or sufficient to find the edge of the plaque through scraping without cutting the intima. The fingers are designed so that radial force applied by the fingers decrease going from the proximal to the distal end of the tip (relative to the plaque). Thus, in one embodiment, the fingers deliver more force on the proximal end of the finger and less force on the distal end. Alternatively, the force may change along the fingers in a non-linear manner, for example such that it is maximal at a certain distance along the fingers. In one embodiment, the tips of fingers are parallel to the shaft, thereby approximately parallel to how it engages the artery, so that the fingers do not cut the artery. The fingers preferably extend substantially along or in the direction of the dissection plane. The fingers are also so configured that they are more rigid towards the distal end and more flexible to the proximal end. Furthermore, the edges of the fingers may be relatively blunt, rounded, and/or curved so at to scrape along the plaque to find the edge and/or the separation of the plaque/layer. In one embodiment, the fingers are generally parallel to each other along their longitudinal sections. Preferably, the distal end results in a device that provides for a more gentle removal of the plaque. The embodiments shown are exemplary. As discussed above, the force differences can be achieved through structure (via e.g. use of structural features such as struts and guidewires or changing cross-section) or function (via e.g. use of a different materials). The device can be used in the methods described herein, including, being scraped along the plaque to find the edge and/or the natural separation of the plaque. 
         [0125]      FIGS. 10A-B  illustrate a configuration of fingers  80   a,  where each finger  80   a  is generally straight upon radial expansion. This shape will easily “dig” under plaques on the arterial wall, as its straight edge is pointed towards them. However, it is more prone to puncture the arterial wall than are shapes described in  FIGS. 10C-F .  FIG. 10A  shows an end view of a distal end of an embodiment of an edger tool having three (3) fingers and  FIG. 10B  shows a side view of the edger tool in  FIG. 10A . Fingers  80   a  are spaced radially equal distances apart on a main shaft as shown in  FIG. 10A . Fingers  80   a,  when fully deployed, are at an acute angle relative to a longitudinal axis of the shaft. Referring now to  FIGS. 10C and 10D , three fingers are positioned on the elongated shaft similar to fingers  74  in  FIGS. 10A-10B , however, fingers  80   b  have a different shape, they are configured in a curved shape. Thus, the part applying the most force on the arterial wall is not the tip but the curvature of finger  80   b.  This reduces the risk of arterial injury. Referring now to  FIGS. 10E-10F , three fingers  80   c,  are positioned on the elongated shaft similar to fingers  80   a,    80   b,  in  FIGS. 10A-10D , however, fingers  80   c,  are configured in a bent shape. This combines the benefits of both fingers  80   a  and  80   b:  the bend provides for a slightly sharper tool touching the arterial wall compared with the curved  80   b,  thus improving its edging capability, while at the same time preventing penetration of the tip into the arterial wall. As discussed above, one or more fingers may be used, and the placement and configuration of each finger may vary. Moreover, the placement and configuration of fingers may differ from each other on the same edger tool. 
         [0126]      FIGS. 10G-10K  illustrate alternative embodiments for cross-sections of a hypothetical finger, embodiments of which are described herein. The cross-section is taken transversely across a distal end of a finger on an edger tool, with the direction of advancement to the left. The cross-section of the finger may vary along its length.  FIGS. 10G ,  10 H,  10 J are symmetrical. They differ in their profiles. 
         [0127]    The edging action includes dissecting and wedging actions. “Dissecting” refers to the initial penetration between the layers, and “wedging” refers to their separation. The wedging action is mainly dependent upon the tool&#39;s wedge angle  82 . Increasing this angle for a given length will increase the forces separating the plaque from the media. This will also increase the torque required to rotate the tool, therefore selection of specific tool wedge angle may be done by the physician during the procedure.  FIG. 10G  shows a cross-section of fingers having a small wedge angle, which will allow for low torque dissecting, but will be limited in the wedging action.  FIG. 10H  shows a cross-section of fingers having a larger wedge angle, which will require higher torque for the dissecting action, but will apply larger wedging forces.  FIG. 10J  depicts a finger cross-sectional shaping that is designed to reduce the required torque for the edging action. It does so by changing the wedge angle along the tool, so that a deeper penetration is achieved before the larger angled part of the finger induces the separating forces.  FIG. 10I and 10K , both having an asymmetrical cross-sectional shaping, are examples of possible design solutions that utilize finger shaping to exert forces on the fingers, directing them towards the separation plane. 
         [0128]    The retrograde edger tool is rotated around its axis and simultaneously retracted so that the finger edges perform a spiral movement on the arterial wall. This movement gradually separates the plaque edge from the arterial wall ( FIG. 11 ). 
         [0129]    More particularly,  FIG. 11  shows retrograde edger tool  70  in action. Artery with media  10  is seen in longitudinal section, plaque  12  is shown in 3D for demonstration purposes. Edger  70  has been deployed by pushing sheath  75  distally, after being passed through guiding catheter  30  and plaque  12 . Edger  70  is in the fully open position, and is being rotated and pulled back thereby scraping, pealing and lifting the edge of the plaque. This is done, preferably, without cutting or damaging the artery. 
         [0130]    As an adjunct to the above, a jet of saline or other biocompatible fluid may be used to assist in the dissection, shown, for example, in  FIGS. 12-14 . 
         [0131]      FIG. 12  shows guiding catheter  30  in artery with media  10  seen in longitudinal section, plaque  12  in three-dimensional. Jet edger tool  100  deployed with sheath  110  positioned such that fingers  101  are at fully open position. Open end  111  has nozzle  112  emitting jet  115 . Fingers  101  have nozzles  102  emitting jet  105 . Suction tube  120  removes excess fluids. Jets  115  and  105  aid in edging the plaque while edger  100  is rotated and pulled proximally. 
         [0132]    Suction of excess fluid out of the blood vessel to prevent an undesirable increase in pressure may be performed through suction tube  120  as shown in  FIG. 12 . Suction may be used in combination with any of the embodiments described herein. Suction may be controlled either by keeping the net volume of injected fluid below a certain threshold, or by keeping the pressure in the vessel below a certain threshold. 
         [0133]    Such a jet may be directed towards the arterial wall through the above-mentioned fingers as shown in  FIG. 13A . 
         [0134]    The jet may be constant or intermittent, fixed or pulsatile. The jet may form a cross-sectional shape that is circular, elliptical or any other shape as shown for example in  FIGS. 13A-C .  FIG. 13A  shows cross-section through artery and finger, depicting media  10  and plaque  12  being separated by finger  101 , while nozzle  102  emits jet  105 .  FIG. 13B  shows circular nozzle  116   a  emitting jet  105  having circular cross-section  117   a.    FIG. 13C  shows elliptical nozzle  116   b  emitting jet  105  having elliptical cross-section  117   b.  A jet with an elliptical cross-section may be more effective in dissection than a jet with a circular cross-section when directed at the arterial wall with its longitudinal axis parallel to the arterial longitudinal axis. 
         [0135]    Such a saline jet can be used instead of the fingers as shown in  FIG. 14 .  FIG. 14  shows artery with media  10  seen in longitudinal section, plaque  12  in three dimensions. Guiding catheter  30  has balloon  31  inflated. Balloon  140  is placed and inflated distally. Jet edger tool  131  has nozzle  132  emitting jet  135 . Suction tube  120  removes excess fluids. Jet  135  edges and dissects the plaque while edger  100  is rotated. In this embodiment, both edging and dissection may be performed by jet only, while the treated area is isolated between the two balloons. Alternatively, a similar jet edger tool may be used in anterograde fashion, when passage through the lesion is not possible, for example on a lower limb. Distal isolation may be achieved by external compression of the limb. Mixing contrast material with the jet fluid can enable angiographic visualization of the progression of subintimal dissection. 
         [0136]    The tools described herein may be used under direct vision by endoscopy or other visualization method, as can optionally be done with all the edger and dissection tools described herein. 
         [0137]    An alternative embodiment of the edger tool pertains to the structure of the fingers. As shown in  FIG. 15 , the fingers can be made of looped metal wires, or a laser cut metal tube or sheet.  FIG. 15  shows wire  150  bent at point  151 , with both ends returning to the base  152 . Alternatively, the edger fingers can be made of metal tubes through which are passed metal wires.  FIG. 16A  shows such metal tube  160 , compressed at its distal tip  161 , and metal wire  162  extending therethrough.  16 B is the same finger with wire loop slightly more distally extended. This structure can enable combining both edger and dissector into one tool, such that after edging is performed, the wire loops  162  can be extended into the SIS from the edges  161  of the fingers  160 . 
         [0138]    An alternative approach to entering the SIS is based on an intentional cut of the intima, proximal to the lesion. This can be done using a specialized tool with a blade of predetermined depth. This is shown in  FIG. 17 : catheter  30  with balloon  31  in artery with media  10  and normal intima  11  proximal to lesion  12 . Proximal intima cutting tool  170  includes a metal strip having elongated shaft  171 , which curves into a radial part  172  oriented circumferentially from which a distally inclined blade  173  of height  174  protrudes radially. Sheath  175 , which covers the tool before deployment, is retracted to enable its expansion and contact with intima  11 . Rotation of proximal intimal cutter  170  several times cuts a thin incision through the intima. The tool  170  is covered by sheath  175  and removed. This can later be followed by deployment of radially expansive dissector tool, which when expanded radially and advanced distally, find its way into the incision, and enters the SIS or an adjacent dissection plane within the media. 
         [0139]    Another aspect of the invention is a dissector tool. Dissection and advancement of the dissector may be aided by vibration that may be applied to the tool, and/or saline jet dissection as previously described. 
         [0140]    An example of a tool intended for separating the rest of the plaque from the arterial wall is shown in  FIGS. 18A and 18B . This embodiment includes a cylindrical bag, which is rolled up or folded into a ring. The ring is mounted on an elongated member. The bag has longitudinal inflatable strips in it that can be inflated through the external edge of the elongated member. The tool is placed in the artery via the guiding catheter. The ring is inserted between the plaque and media of the artery, preferably over the edger tool. Inflation of the longitudinal strips causes the bag to open and lengthen while dissecting between the plaque and media. This and additional similar embodiments are depicted in  FIG. 18   c  in side view. 
         [0141]    More particularly, in  FIGS. 18A-B , dissection tool is shown generally at  180 .  FIG. 18A  is a three-dimensional view of the device while  FIG. 18B  is a longitudinal section through the artery and device.  FIG. 18A  shows inflatable dissection tool  180  which has longitudinal inflatable strips  183  configured in a funnel shape when inflated. The ends of the strips face inwards. The inflatable dissection tool further includes longitudinal bag  181  which is surrounded by the longitudinal inflatable strips  183  and folded bag  182  which is towards the distal end of the tool  189 . The folded bag  182  may be integral with longitudinal bag  181 .  FIG. 18B  shows media  10 , plaque  12 , already slightly separated at edge by edger tool. With reference  FIG. 18B , Inflatable dissection tool  180  is depicted with its longitudinal bag  181  in the lumen and the folded bag part  182  in the SIS. Once the longitudinal strips are inflated, the device unfolds while dissecting further between the layers. 
         [0142]      FIGS. 18C-F  show alternate embodiments of a distal end of dissection tools as described above with reference to  FIGS. 18A-B .  FIG. 18C  shows dissection tool  180  described above.  FIG. 18D  shows another aspect of a dissection tool  180   a.  This device is identical to  180  except the direction of folds is inwards instead of outwards. Compared to  180   a,  tool  180  has the advantage of pushing the media outwards, whereas tool  180   a  pushes the intima inwards towards the plaque, which causes more resistance.  FIG. 18E  shows another aspect of a dissection tool  180   b.  This tool is folded as a harmonica fashion instead of being rolled.  FIG. 18F  shows another aspect of a dissection tool  180   c.  Both  180   b  and  180   c  encounter less resistance to unfolding than do  180  and  180   a,  however, the method of making the folds is simpler in the rolled up devices  180  and  180   a.  Importantly, devices  180  and  180   a  can be made of braided stents instead of a polymer bag. Instead of using inflation, they can be unfolded for example by pushing the folded ring forward at several points with wires extending proximally through the guiding catheter. 
         [0143]    With regard to the distal intimal cutting tool, there are several additional embodiments. The distal intimal cutting tool  60  previously described may be inserted through a specialized groove located in the wall of the guiding catheter ( FIG. 19A-B ).  19 A shows cross-section of multi-lumen guiding catheter  190  with catheter main lumen  191  and cutting tool groove  192 .  FIG. 19B  shows a longitudinal section of the artery with cutting tool  60  extending from groove, inserted between media  10  and dissector tool  50 , and cutting intima  11  at plaque edge. Alternatively, the cutting tool may be inserted through lumen  191  over or instead of dissector. 
         [0144]    Another approach to cutting the intima at the edge of the lesion is based on the shape memory properties of the nitinol wires including dissector  200 , shown in  FIG. 20A-D .  FIG. 20A  shows dissector  200  having one or more dissector tip  201  at the distal end and loopwires  202 , which is identical to dissector  50 , apart from having been thermally treated to assume a thermally dependent conformation change. At normal body temperature, the dissector has a slight outward angulation of tip  201 .  FIG. 20B  shows dissector after being heated/cooled—the angulation changes towards the interior of the lumen.  FIGS. 20C-D  show same in arterial longitudinal section. This change in angulation inwards can cause re-entry of the loops into the lumen. Alternatively, a needle may be extended from the edge of one of the loops, and after its entry into the lumen, a guide wire can be passed through it. 
         [0145]    In some embodiments of the cutting tool, there are multiple tools on the dissector, each slideably attached to a loop&#39;s centerline. This allows for cutting around the whole intima with partial rotation of the dissector. After cutting and blade retraction, the cutting tools can be pushed forward such that they bend towards the center of the lumen and form a wall that assists in holding the plaque as it is pulled back and removed. 
         [0146]    Medial Aspect: 
         [0147]    This approach is based on threading a guidewire through the subintimal space from one end of the plaque to the other, then using a tool, which expands along this space, thus peeling the plaque from the arterial wall. This is intended to peel the plaque, which includes the intima, while leaving the media and adventitia intact. Sometimes, especially if the plaque involves the media, some medial layers might be peeled as well. However, this should not pose a major problem, as it often occurs during surgical endarterectomy, and does not cause any complications. 
         [0148]    An embodiment of this approach is shown in  FIGS. 21-23 . A guidewire is introduced into the subintimal space and advanced along the lesion and beyond its far end, then back into the lumen. A separator device such as that shown in  FIG. 23  (in its deployed state) is introduced over the wire (in its folded, non-deployed state). This tool includes a hollow cylinder with a longitudinal slit, folded onto an elongated member. When deployed, it assumes its cylindrical shape with an overlap of both ends over the slit. 
         [0149]    This can be achieved for example by an inflatable balloon constructed of multiple longitudinal chambers having a trapezoid cross-section and connected to each other side by side. As the balloon is inflated, it dissects around the plaque, separating it from the arterial wall and encompassing the dissected plaque. 
         [0150]    More particularly, with reference to  FIG. 21A , a three-dimensional view of artery with deployed device  210  is depicted. Guidewire  211  inside device catheter  212  is seen intraluminally, then passes via intima  11  into subintimal space (“SIS”)  214 , and is again seen intraluminally  213  distal to lesion.  FIG. 21B  is a cross-section of device  210 , folded balloon  215 , catheter  212 , and bilateral longitudinal radiopaque markers. The device may optionally have one or more longitudinal markers  216 . 
         [0151]    With reference to  FIGS. 22A-F , the stages of this procedure are depicted.  FIG. 22A and 22B  are longitudinal and transverse views of non-deployed device  210  passed over guidewire  211  in SIS, traversing lesion  12 .  FIG. 22C and 22D  are longitudinal and transverse views of device  210  partially deployed.  FIG. 22E and 22F  are longitudinal and transverse views of device  210  at full deployment, encompassing lesion  12 .  FIG. 23  is a three-dimensional view of the deployed device  210  with catheter  212 . 
         [0152]    Prior to deployment, angiography can be used to ascertain the device is at the optimal orientation for deployment. Radiopaque markers  216  must be demonstrated parallel to each other at the medial border of the plaque. During deployment, the markers may be seen moving across the lumen to encompass the lesion. 
         [0153]    After the device is fully deployed, a distal intimal cutting tool  60  can be used to free the connecting intima. Such tool  60  may either be integral with the dissector  210 , or a separate tool used in combination with  210 . 
         [0154]    Alternatively, a similar device  220  may be formed of transverse longitudinal strips, each having a slight curvature, such that when inflated the device assumes a flat shape, with only slight radius of curvature. This increases the tendency of the dissector to inflate within the SIS without encroaching on the arterial lumen.  FIG. 24  is a 3D view of the flat device  220  with catheter  222 . 
         [0155]    A different embodiment shown in  FIGS. 25A-C  is based on a nitinol device composed of multiple arched wires stemming off both sides of a central longitudinal spine. A sheath covers those “ribs” holding them flatly adjacent to the spine. When the sheath is removed, the ribs dissect around the plaque and form a cage encircling it. 
         [0156]    More particularly,  FIG. 25A  shows device  230  at 3D.  FIG. 25B  shows a side view of device  230  shown in  FIG. 25A .  FIG. 25C  shows and end view of device  230  in  FIG. 25A . Ribs  232  extend laterally from spine  231   
         [0157]    The above described devices  210 ,  220  and  230 , which dissect and contain the plaque, may have a predetermined shape such that their distal end is closed. This allows for containment of the dissected plaque inside such structure, which prevents debris from embolizing. Alternatively, the distal end only or both ends may be closed for example by a wire traversing that end in a “purse-string,” which wire can be tightened by pulling on such wire. 
         [0158]    Inflating a balloon or deploying a nitinol web at the open end are additional ways for closing the aperture. 
         [0159]    Removal of the freed plaque from the body can be achieved in several ways. If the volume of plaque is not very large, it may be possible to remove the plaque as is within the containment structure through the introducing sheath and outside of the artery. However, in some cases the plaque will be too large for such removal, and will need to be ground into small pieces. 
         [0160]    Grinding the plaque can be done by a grinder mounted on a catheter, with a suction catheter as part of the same tool or used in conjunction with it. If the proximal end of the containment structure holding the plaque has been closed, it will need to be penetrated by such catheter to contact the plaque. 
         [0161]    A useful addition to the above is a modification for preventing clogging of the grinder device. 
         [0162]    In cases where the freed plaque was not contained in a bag or chamber, balloons should have been inflated on both sides of the work area to isolate it. Grinding and aspiration of the plaque can take place in this isolated area, followed by rinsing of the space with saline to ensure removal of all debris. 
         [0163]    In some embodiments, after plaque removal, the treatment area is isolated between balloons and flushed with isotonic fluid in rapidly changing directions and pressure, in order to wash away any residual loosely adherent plaque, intima, or medial tissue. Alternatively or in addition, a fogarty catheter may be passed over the treated in a gentle manner. Other methods of ensuring removal of residuals include angiography, IVUS, or visual inspection. 
         [0164]    Following completion of the percutaneous atherectomy using the methods and devices described above, the next stage of treatment begins.  FIG. 28  shows device  400  situated across area  500  where lesion was removed. Device  400  is a multilumen catheter intended for isolation of the treated area and delivery of medial layer therapy. Catheter  400  has lumen  401  for blood flow across isolated area  501 . Lumen  402  inflates proximal balloon  412 , lumen  403  inflates distal balloon  413 . Lumen  404  serves for inflow of therapy and lumen  405  for outflow. 
         [0165]    In use, proximal balloon  412  and distal balloon  413  are inflated. Blood passes freely through the blood flow lumen. Treatment may be delivered according to the specific protocol—e.g. perfusion with saline or blood, and instillation of the treating agent—usually endothelial progenitor cells. The treatment continues for the required duration. The area is flushed with saline and refilled with the patient&#39;s blood, the balloons are deflated, and catheter  400  removed. 
         [0166]    Another aspect of the current invention includes devices for insertion of guidewires into the SIS. Such a device intended for non-CTO lesions is shown in  FIGS. 26A-B  and includes a multilumen catheter, proximal and distal balloons, a suction lumen, and a catheter for passing a guidewire extending across the periphery of the proximal balloon.  FIG. 26A  is a longitudinal section through artery and device  250  showing device catheter  251 , proximal balloon lumen  252 , distal balloon lumen  253 , suction lumen  254 , guidewire catheter  255 , guidewire  256 , proximal balloon  257 , distal balloon  258 .  FIG. 26B  is a front view of same device. In use, device  250  is brought proximate to the plaque edge such that distal balloon  253  is within lesion. Proximal balloon  257  is inflated, followed by distal balloon inflation. Inflation of the balloons produces a force pushing the plaque distally and normal artery proximally, as well as an outward force on the arterial wall proximal to the lesion. These forces apply tension on transition zone  259  between “normal” intima  10  proximal to the lesion and plaque  12 . The pushing force between the plaque and proximal artery may be increased by making distal balloon  253  moveable forward relative to guidewire catheter  255 . The guidewire catheter is compressed against the arterial wall by the proximal balloon, and assumes an angle up to approximately  5  degrees outwards of the longitudinal arterial axis, leading the guidewire towards transition zone  259 . Optionally, suction may be applied to the suction lumen, reducing the pressure in the area between the balloons and pulling the plaque away from the arterial wall towards the center of the lumen. The combination of increased tension in transition zone  259 , exact direction of the guidewire towards transition zone  259 , and pulling of plaque  12  away from arterial wall  10 , facilitates entry of guidewire  256  through transition zone  259  into SIS. 
         [0167]    In another embodiment, a similar device  270  is provided for insertion of multiple guidewire around the lesion.  FIG. 26C  shows device  270  having device catheter  271  in front view with four guidewire catheters  275   a - d  leading four guidewires  276   a - d  into the SIS in the same manner described for device  250 . 
         [0168]    For CTO lesion or other lesions where a balloon cannot be inflated to within the lesion, a similar device is provided which uses an umbrella-like contraption instead of the distal balloon.  FIG. 27A  illustrates this device in an artery&#39;s longitudinal section. With reference to  FIG. 27A , device catheter  291  is shown having proximal balloon lumen  292  and umbrella and suction lumen  293 . The umbrella  294  is shown passing through the lumen of the device catheter  291 . Guidewire catheter  295  containing guidewire  296  also passes the lumen of the device catheter  291 . Umbrella  294  has umbrella distal end  298   FIG. 27B  shows a front view of the catheter device and  27 C a front view of the umbrella device. In use, device  290  is brought proximate to the plaque edge. Proximal balloon  297  is inflated, followed by deployment of umbrella  294 . Inflation of the proximal balloon and pushing umbrella  294  forward produces a force pushing the plaque distally and normal artery proximally, as well as an outward force on the arterial wall proximal to the lesion. These forces apply tension on transition zone  299  between “normal” intima  10  proximal to the lesion and plaque  12 . The guidewire catheter is compressed against the arterial wall by the proximal balloon, and assumes an angle up to approximately 5 degrees outwards of the longitudinal arterial axis, leading the guidewire towards transition zone  299 . Optionally, suction may be applied to the suction lumen, reducing the pressure in the area between the proximal balloon  297  and plaque and pulling the plaque away from the arterial wall towards the center of the lumen. The combination of increased tension in transition zone  299 , exact direction of the guidewire towards transition zone  299 , and pulling of plaque  12  away from arterial wall  10 , facilitates entry of guidewire  296  through transition zone  299  into SIS. 
         [0169]    In yet another embodiment, a device based on the edger tool  20  can be used to deliver guidewires to the SIS. One or more guidewire catheters are attached to fingers  21  of edger, such that when edger fingers enter SIS or are proximate to it, pushing forward the guidewires will result in their entry to the SIS. Multiple such guidewires in the SIS can be used as a dissection means for short plaques or as a lead for insertion of a dissector too. 
         [0170]    Another embodiment of the invention is described in  FIG. 29 . This embodiment involves use of an anvil-like tool, which is placed distal to the lesion in order to assist with the distal intimal cutting stage. More particularly,  FIG. 29  shows a longitudinal section of artery with media  10 , plaque  12 , guiding catheter  30  anchored by balloon  31 . Anvil  600  is a cylindrical tool including body  601  continuous with elongated shaft  602 , and several wings  603  each with distal tip  604  and distal edge  605 . Wings  603  are formed such that when deployed, wings  603  flare outwards and distal edges  605  form an essentially continuous circumferential line around the inside of the lumen of the artery. Wings  605  may optionally be covered by web  606 . Also provided is cap  610  including body  611  and elongated shaft  612 . Body  611  is cylindrical and continuous with elongated shaft  612 . Cap  610  can be pulled to cover Anvil  600 , which folding wings  603  towards the elongated shaft  602 . 
         [0171]    Elongated shaft  612  is threaded through elongated shaft  602 , and both parts are passed through the guiding catheter  30 , optionally over guidewire  620 . 
         [0172]    In use, anvil  600  is passed through guiding catheter  30  and inside lesion  12 , and deployed distal to it by pushing cap  610  distally, such that anvil distal edges  605  press against the arterial wall and cause it to bulge outwards slightly. Web  606  of anvil  600  may then act as an emboli protection device. Edging or proximal intimal cutting is then performed in a manner similar to that described for previous embodiments, and dissection tool  50  is passed in guiding catheter  30  over elongated shaft  602  and through SIS until it reaches the distal plaque edge. At this point, pushing dissection tool  50  forward will cut intima between anvil distal edges  605  and loop centerlines  53 . Cap  610  can then be pulled back to slightly close anvil  600  and dissector  50  to enable removal of all instruments together. 
         [0173]    Using the anvil tool enables anchoring of the intima to the media during distal cutting, thus preventing or reducing the risk of creation of an intimal flap. 
         [0174]    It is clear to anyone familiar with the art that the above described devices and methods can be used in any other organ in the body that has an elongated lumen such as the gastrointestinal tract, pulmonary system, urinary system etc. 
         [0175]    Potential alternative applications of the above include but are not limited to biopsies, removal of tumors or pathological tissues. 
         [0176]    Although the foregoing description is directed to the preferred embodiments of the invention, it is noted that other variations and modifications will be apparent to those skilled in the art, and may be made departing from the spirit or scope of the invention. Moreover, features described in connection with one embodiment of the invention may be used in conjunction with other embodiments, even if not explicitly stated above. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive.