1 . A tubular guidewire assembly comprising:
a tubular guidewire member having a distal end, a proximal end and a lumen defined therein; an occlusive balloon proximate the distal end and fluidly connected to the lumen; and an extended crimpable section proximate the proximal end and fluidly connected to the lumen, the extended crimpable section adapted to be selectively sealed at one of a plurality of separate locations to form an airtight seal of the tubular guidewire assembly.
2 . The tubular guidewire assembly of claim 1 wherein the guidewire assembly has an effective length of at least 40 cm and an outer diameter of less than 0.060 inches, the extended sealable section has an effective length of at least 1 cm and an outer diameter of less than 0.050 inches and the occlusive device is deflated in less than two minutes.
3 . The tubular guidewire assembly of claim 1 wherein the guidewire assembly has an effective length of at least 100 cm and an outer diameter of less than 0.018 inches, and the extended crimpable section has an effective length of at least 5 cm and an outer diameter of less than 0.012 inches.
4 . The tubular guidewire assembly of claim 1 wherein the crimpable section is dimensioned such that an effective outer diameter of the crimpable section after crimping is no greater than an outer diameter of the guidewire member of the guidewire assembly.
5 . The tubular guidewire assembly of claim 1 wherein the extended crimpable section has a length sufficient to permit a plurality of crimps and a plurality of corresponding cuts along the crimpable section and has a diameter that is small than a diameter of the main body of the guidewire.
6 . The tubular guidewire assembly of claim 1 wherein the tubular guidewire member includes a main body formed of a stainless steel hypotube.
7 The tubular guidewire assembly of claim 6 wherein the extended crimpable section is collinearly attached to the proximal end of the stainless steel hypotube and is formed of a stainless steel hypotube having a diameter small than the stainless steel hypotube of the main body.
8 . The tubular guidewire assembly of claim 6 wherein the tubular guidewire member further includes a distal portion formed of a Ni—Ti alloy.
9 . The tubular guidewire assembly of claim 8 wherein the distal portion includes a tapered portion.
10 . The tubular guidewire assembly of claim 9 wherein the tapered portion has an inner diameter of less than 0.05 inches and an outer diameter that decreases in ranges from at least 0.012 inches to less than 0.008 inches.
11 . The tubular guidewire assembly of claim 8 wherein the distal portion includes a platinum markerband proximal to the occlusive balloon.
12 . The tubular guidewire assembly claim 8 further comprising a flexible coil tip attached to distal portion distal to the occlusion balloon.
13 . The tubular guidewire assembly of claim 1 wherein the occlusive balloon is capable of repeated inflation and deflation during a vascular procedure in between which the proximal end of the guidewire assembly is free of mechanical connections and obstructions and functions as a conventional exchange guidewire.
14 . The tubular guidewire assembly of claim 1 wherein the lumen has an inner diameter of at least 0.002 inches such that passive deflation of the occlusive balloon is accomplished in less than one minute.
15 . The tubular guidewire assembly of claim 1 wherein the crimpable section is formed of a material dimensioned such that the crimpable section has sufficient strength in terms of high tensile and kink resistance to permit catheter devices to repeatedly pass over the crimpable section yet, when severed, the crimpable section does not penetrate a standard surgical glove when gripped within less than one inch of a proximate end of the crimpable section.
16 . The tubular guidewire assembly of claim 1 wherein the occlusion balloon is preinflated to prestretch balloon so balloon expansion is relatively linear with pressure.
17 . The tubular guidewire assembly of claim 1 wherein the extended crimpable section is weakened at a plurality of score locations along the extended crimpable section to aid in severing the crimpable section at the score locations.
18 . The tubular guidewire assembly of claim 1 wherein the tubular guidewire member and the extended crimpable section are formed of a continuous stainless steel tube having a second wire wound therearound except for along the crimpable section.
19 . The tubular guidewire assembly of claim 1 wherein the tubular guidewire member comprises a braided polyimide hypotube having a tapered core rod positioned therein.
20 . The tubular guidewire assembly of claim 19 wherein at least a proximal portion of the tapered core rod is tubular having a lumen defined therein and extending proximal a proximate end of the polyimide hypotube to define the extended crimpable section.
21 . The tubular guidewire assembly claim 1 further comprising a pair of coil sections positioned along a distal portion of the guidewire member that are longitudinally spaced apart and adjacent to at least one hole in the guidewire member that provides fluid access between the lumen and the occlusive balloon, with at least a portion of the balloon being bonded to at least a portion of each of the coil sections.
 The present invention is related to two co-pending applications that are commonly assigned to the assignee of the present invention and filed concurrently herewith, the first of which is entitled “Guidewire Occlusion System Utilizing Repeatably Inflatable Gas-Filled Occlusive Device,” Ser. No. 09/______ (Attorney Docket No. 2856.02US01), and the second of which is entitled “Gas Inflation System for Guidewire Having Occlusive Device,” Ser. No. 09/______ (Attorney Docket No. 2856.04US01), a copy of each of which is attached and the disclosure of both which are incorporated by reference.
FIELD OF THE INVENTION
 The present invention relates generally to the field of vascular medical devices. More specifically, the present invention relates to a guidewire with a repeatably inflatable gas-filled occlusive device for use with a guidewire occlusion system in vascular procedures.
BACKGROUND OF THE INVENTION
 Arterial disease involves damage that happens to the arteries in the body. Diseased vessels can become plugged with thrombus, plaque, or grumous material that may ultimately lead to a condition known as ischemia. Ischemia refers to a substantial reduction or loss of blood flow to the heart muscle or any other tissue that is being supplied by the artery and can lead to permanent damage of the affected region. While arterial disease is most commonly associated with the formation of hard plaque and coronary artery disease in the heart, similar damage can happen to many other vessels in the body, such as the peripheral vessels, cerebral vessels, due to the build up of hard plaque or softer thrombus or grumous material within the lumen of an artery or vein.
 A variety of vascular medical devices and procedures have been developed to treat diseased vessels. The current standard procedures include bypass surgery (where a new blood vessel is grafted around the narrowed or blocked artery) and several different types of non-surgical interventional vascular medical procedures, including: angioplasty (where a balloon on a catheter is inflated inside the narrowed or blocked portion of the artery in an attempt to push back the plaque or thrombotic material), stenting (where a metal mesh tube is expanded against the narrowed or blocked portion of the artery to hold back the plaque or thrombotic material) and debulking techniques in the form of atheroectomy (where some type of high speed or high power mechanism is used to dislodge the hardened plaque) or thrombectomy (where some type of mechanism or infused fluid is used to dislodge grumous thrombotic material). In each of these vascular medical procedures, a very flexible guidewire is routed through the patient's vascular system to a desired treatment location and then a catheter that includes a device on the distal end appropriate for the given procedure is tracked along the guidewire to the treatment location.
 Although interventional vascular procedures avoid many of the complications involved in surgery, there is a possibility of complications if some of the plaque, thrombus or other material breaks free and flows downstream in the artery, potentially causing a stroke, a myocardial infarction (heart attack) or other tissue death. One solution to this potential complication is to use some kind of occlusive device to block or screen the blood flowing downstream of the treatment location. Examples of catheter arrangements that use a pair of balloons as occlusive devices to create an isolated space in the blood vessel are described in U.S. Pat. Nos. 4,573,966, 4,636,195, 5,059,178, 5,320,604, 5,833,644, 5,925,016, 6,022,336 and 6,176,844. Examples of catheter arrangements that use a single balloon as an occlusive device either upstream or downstream of the treatment location are described in U.S. Pat. Nos. 5,171,221, 5,195,955, 5,135,482, 5,380,284, 5,688,234, 5,713,917, 5,775,327, 5,792,179, 5,807,330, 5,833,650, 5,843,022, 6,021,340, 6,159,195 and 6,248,121. An example of a catheter arrangement that uses a mechanically-expanded occlusion device is shown in U.S. Pat. No. 6,231,588. Occlusive balloons also have been used on non-over-the-wire catheters without any guidewire internal to the catheter as described, for example, in U.S. Pat. Nos. 4,838,268 and 5,209,727.
 The use of an occlusive device as part of a vascular procedure is becoming more common in debulking procedures performed on heart bypass vessels. Most heart bypass vessels are harvested and transplanted from the saphenous vein located along the inside of the patient's leg. The saphenous vein is a long, straight vein that has a capacity more than adequate to support the blood flow needs of the heart. Once transplanted, the saphenous vein is subject to arterial disease caused by plaque or thrombotic materials build up in the grafted arterial lumen. Unfortunately, the standard interventional vascular treatments for debulking are only moderately successful when employed to treat saphenous vein coronary bypass grafts. The complication rate for a standard balloon angioplasty procedure in a saphenous vein coronary bypass graft is higher than in a native vessel with the complications including embolization, “no-reflow” phenomena, and procedural related myocardial infarction. Atheroectomy methods including directional, rotational and laser devices are also associated with a high degree of embolization resulting in a greater likelihood of infarction. The use of stents for saphenous vein coronary bypass grafts has produced mixed results. Stents provide for less restenosis but they do not eliminate the risk of embolization and infarction.
 In order to overcome the shortcomings of these standard non-surgical interventional treatments in treating saphenous vein coronary bypass graft occlusion, embolic protection methods utilizing a protective device distal to the lesion have been developed. The protective device is typically a filter or balloon. Use of a protective device in conjunction with an atheroectomy or thrombectomy device is intended to prevent emboli from migrating beyond the protective device and allow the embolic particles to be removed, thereby subsequently reducing the risk of myocardial infarction. When the occlusive device is a balloon, the balloon is inserted and inflated at a point distal to the treatment site or lesion site. Therapy is then performed at the treatment site and the balloon acts to block all blood flow which prevents emboli from traveling beyond the balloon. Following treatment, some form of particle removal device must be used to remove the dislodged emboli prior to balloon deflation. U.S. Pat. No. 5,843,022 uses a balloon to occlude the vessel distal to a lesion or blockage site. The occlusion is treated with a high pressure water jet, and the fluid and entrained emboli are subsequently removed via an extraction tube. U.S. Pat. No. 6,135,991 describes the use of a balloon to occlude the vessel allowing blood flow and pressure to prevent the migration of emboli proximally from the treatment device. There are various designs that have included an occlusive balloon on the end of a guidewire. U.S. Pat. Nos. 5,520,645, 5,779,688 and 5,908,405 describe guidewires having removable occlusion balloons on a distal end. U.S. Pat. No. 4,573,470 describes a guidewire having an occlusion balloon where the guidewire is bonded inside the catheter as an integral unit. U.S. Pat. Nos. 5,059,176, 5,167,239, 5,520,645, 5,779,688 and 6,050,972 describe various guidewires with balloons at the distal end in which a valve arrangement is used to inflate and/or deflate the balloon. U.S. Pat. No. 5,908,405 describes an arrangement with a removable balloon member that can be repeatedly inserted into and withdrawn from a guidewire. U.S. Pat. No. 5,776,100 describes a guidewire with an occlusive balloon adhesively bonded to the distal end with an adapter on the proximal end to provide inflation fluid for the occlusive balloon.
 Except in the case of the cerebral anatomy where there are redundant arteries supplying blood to the same tissue, one of the problems with using an occlusive device in the arteries is that tissue downstream of the occlusive device can be damaged due to the lack of blood flow. Consequently, an occlusive device that completely blocks the artery can only be deployed for a relatively short period of time. To overcome this disadvantage, most of the recent development in relation to occlusive devices has focused on devices that screen the blood through a filter arrangement. U.S. Pat. Nos. 5,827,324, 5,938,672, 5,997,558, 6,080,170, 6,171,328, 6,203,561 and 6,245,089 describe various examples of filter arrangements that are to be deployed on the distal end of a catheter system. While a filter arrangement is theoretically a better solution than an occlusive device, in practice such filter arrangements often become plugged, effectively turning the filter into an occlusive device. The filter arrangements also are mechanically and operationally more complicated than an occlusive balloon device in terms of deployment and extraction.
 As is the case in almost all angioplasty devices or stenting catheter devices where a balloon is used to expand the blood vessel or stent, most catheter balloon occlusive devices as well as most guidewire balloon occlusive devices utilize a liquid fluid such as saline or saline mixed with a radiopaque marker for fluoroscopic visualization (i.e., contrast) as the inflation medium for the balloon. Generally, a liquid fluid medium for expanding vascular balloons has been preferred because the expansion characteristics of a liquid are more uniform and predictable, and because a liquid medium is easier to work with and more familiar to the doctors. In the case of angioplasty balloons, for example, high-pressure requirements (up to 20 atmospheres) necessitate that the inflation fluid be an incompressible fluid for safety reasons. While having numerous advantages, liquid fluids do not lend themselves to rapid deflation of an occlusive balloon because of the high resistance to movement of the liquid in a long small diameter tube. In the context of angioplasty procedures, the balloon catheter has a much larger lumen than a guidewire. Consequently, rapid deflation is possible. In the context of a guidewire, however, liquid filled occlusion balloons typically cannot be deflated in less than a minute and, depending upon the length of the guidewire, can take up to several minutes to deflate. Consequently, it is not practical to shorten the period of total blockage of a vessel by repeatedly deflating and then re-inflating a liquid filled occlusive balloon at the end of a guidewire.
 Gas-filled balloons have been used for intra-aortic occlusion devices where rapid inflation and deflation of the occlusion device is required. Examples of such intra-aortic occlusion devices are shown in U.S. Pat. Nos. 4,646,719, 4,733,652, 5,865,721, 6,146,372, 6,245,008 and 6,241,706. While effective for use as an intra-aortic occlusion device, these devices are not designed for use as a guidewire as there is no ability to track a catheter over the intra-aortic occlusion device.
 An early catheter balloon device that utilized a gas as an inflation medium and provided a volume limited syringe injection system is described in U.S. Pat. No. 4,865,587. More recently, a gas filled occlusion balloon on a guidewire is described as one of the alternate embodiments in U.S. Pat. No. 6,217,567. The only suggestion for how the guidewire of the alternate embodiment is sealed is a valve type arrangement similar to the valve arrangement used in a liquid fluid embodiment. A similar gas filled occlusion balloon has been described with respect to the Aegis Vortex system developed by Kensey Nash Corporation. In both U.S. Pat. No. 6,217,567 and the Aegis Vortex™ system, the gas filled occlusive balloon is used for distal protection to minimize the risk of embolization while treating a blocked saphenous vein coronary bypass graft. Once deployed, the occlusive balloon retains emboli dislodged by the atheroectomy treatment process until such time as the emboli can be aspirated from the vessel. No specific apparatus are shown or described for how the gas is to be introduced into the device or how the balloon is deflated.
 Although the use of occlusive devices has become more common for distal embolization protection in vascular procedures, particularly for treating a blocked saphenous vein coronary bypass graft, all of the existing approaches have significant drawbacks that can limit their effectiveness. Liquid filled occlusive balloons can remain in place too long and take too long to deflate, increasing the risk of damages downstream of the occlusion. Occlusive filters are designed to address this problem, but suffer from blockage problems and can be complicated to deploy and retrieve and may allow small embolic particles to migrate downstream. Existing gas-filled occlusive balloons solve some of the problems of liquid filled occlusive balloons, but typically have utilized complicated valve and connection arrangements. It would be desirable to provide for an occlusive device that was effective, simple, quick to deploy and deflate, and that could overcome the limitations of the existing approaches.
SUMMARY OF THE INVENTION
 The present invention is a tubular guidewire assembly having an extended crimpable section proximate a proximal end that is adapted to removably connect to a gas inflation/evacuation system and a sealing system. The extended crimpable section can be selectively sealed at one of a plurality of separate locations to form an airtight seal of the tubular guidewire assembly. Each time a deflation of the occlusive device is desired to reestablish blood flow to a vessel downstream of the occlusive device, the extended crimpable section preferably is cut distal to the location of the last seal to quickly deflate the occlusive device.
 The advantage of the guidewire assembly of the present invention is that the occlusive device can be repeatably inflated and deflated a plurality of times during a vascular procedure in between which the proximal end of the guidewire is free of mechanical connections and obstructions and functions as a conventional exchange guidewire for one or more over-the-wire catheters. Alternatively, the guidewire assembly of the present invention can be shorter in length for use with rapid exchange catheter systems. Unlike existing liquid filled occlusive devices, the present invention is capable of repeated and quick inflation and deflation which allows an operator to deploy the gas-filled occlusive device numerous times during a procedure for shorter periods of time, thereby reducing the risk of potential damage to downstream tissue. Unlike other gas-filled occlusive devices, the present invention is simple and permits the guidewire to be used as a conventional exchange guidewire. There are no complicated mechanical arrangements or valve systems internal to the guidewire that increase the cost, complexity and potential for failure of the system.
 In a preferred embodiment, the extended crimpable section has a sufficient length to permit a plurality of crimps and cuts along the crimpable section and has a diameter that is smaller than a diameter of the main body of the guidewire. A crimping mechanism preferably is used to crimp the crimpable section of the guidewire to seal the guidewire a plurality of times. Each time a deflation of the occlusive device is desired to reestablish blood flow to the vessel downstream of the occlusive device, the crimpable section is cut distal to the location of the last crimp so as to quickly deflate the occlusive device. Preferably, the extended crimpable section of the guidewire is dimensioned and the crimping mechanism is arranged such that an effective outer diameter of the crimpable section at the location of a seal is no greater than the outer diameter of a main body of the guidewire assembly when the crimpable section is sealed.
 In one embodiment for coronary vascular procedures, the guidewire assembly preferably has an effective length of at least 40 cm and more preferably at least 100 cm and an outer diameter of less than 0.060 inches and more preferably less than 0.018 inches, the extended sealable section has an effective length of at least 1 cm and more preferably at least 5 cm and an outer diameter of less than 0.050 inches and more preferably less than 0.012 inches, and the occlusive device is deflated in less than two minutes and more preferably less than one minute. This embodiment is particularly adapted to provide distal embolization protection in atheroectomy procedures, such as those involving a blocked saphenous vein coronary bypass graft. Alternatively, the guidewire assembly may be configured and dimensioned for use in peripheral vascular procedures or neural vascular procedures.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 is a schematic diagram of a guidewire occlusion system in accordance with the present invention operating in an evacuation mode.
 FIG. 2 is a schematic diagram of the embodiment shown in FIG. 1 operating in an inflation mode.
 FIGS. 3 a and 3 b are side views of the guidewire assembly shown in FIG. 1.
 FIGS. 4 a and 4 b are cross-sectional views of the proximal portion of the guidewire assembly of FIG. 3 a.
 FIGS. 5 - 7 are perspective views of alternate embodiments of the inflation/deflation system.
 FIG. 8 is an exploded view of the gas inflation/evacuation system of the alternate embodiment shown in FIG. 7.
 FIG. 9 is a perspective view of the crimping mechanism of the alternate embodiment shown in FIG. 7.
 FIGS. 10 and 11 are side views of the distal portion of the guidewire assembly.
 FIG. 12 is an end view of the handheld apparatus for the sealing system in accordance with one embodiment of the present invention.
 FIGS. 13 and 14 are two sectional views of the sealing system of FIG. 12.
 FIGS. 15 and 16 are perspective views of alternate embodiments of the guidewire assembly shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Referring now to FIGS. 1 - 2 , the overall operation of a guidewire occlusion system 20 will be described. The guidewire occlusion system 20 includes the guidewire assembly of the present invention 22 , a sealing system 60 and a gas inflation/evacuation system 80 .
 Guidewire assembly 22 is a tubular member that includes a proximal portion 24 and a distal portion 26 . As used in the present invention, the terms proximal and distal will be used with reference to an operator of the device, such that a distal portion of the device of the guidewire assembly 22 , for example, is the portion first inserted into a blood vessel and the proximal portion remains exterior to the patient and is therefore closer to the operator of the device. An extended crimpable section 28 is provided proximate the proximal portion 24 of guidewire assembly 22 . In accordance with the present invention, the crimpable section 28 is comprised of a tubular segment having an outer diameter smaller than an outer diameter of a main body portion 30 of guidewire assembly 22 . Although the diameter of the crimpable section could be any size consistent with effective use as a guidewire, it will be understood that the smaller diameter allows for less force to be used in sealing the crimpable section and provides a crimped seal that is not too large when crimped. An occlusive balloon 32 is located along the distal portion 26 of guidewire assembly 22 with channels or holes 35 allowing for fluid communication between lumen 34 and balloon 32 . The occlusive balloon 32 is fluidly connected via a lumen 34 to a proximal end 36 of proximal portion 24 of guidewire assembly 22 . In a preferred embodiment, a flexible tip 38 is positioned at the distal end 40 of distal portion 26 of the guidewire assembly 22 . Preferably, distal portion 26 of guidewire assembly 22 includes a tapered portion 42 to increase the flexibility and transition properties of the distal portion 26 of guidewire assembly 22 .
 Preferably, sealing system 60 is implemented as part of a handheld apparatus that also includes gas inflation/evacuation system 80 . Alternatively, sealing system 60 may be a component completely separate from the gas inflation/evacuation system 80 . Alternatively, other handheld and/or separate arrangements could be utilized for crimping and inflating the guidewire assembly 22 . Sealing system 60 includes a first aperture 62 into which the proximal end 36 of the proximal portion 24 of guidewire assembly 22 is insertable so as to operably position at least a portion of crimpable section 28 in relation to sealing system 60 . Sealing system 60 further includes a second aperture 64 that is fluidly connectable to gas inflation/evacuation system 80 . In a preferred embodiment, sealing system 60 includes a crimping mechanism 66 and a sealing mechanism 68 . A passageway 70 is defined from first aperture 62 to second aperture 64 and having a passage through both crimping mechanism 66 and sealing mechanism 68 . Preferably, at least a portion of the crimpable section 28 is inserted into first aperture 62 a sufficient distance to engage crimping mechanism 66 and sealing mechanism 68 .
 In a preferred embodiment of the crimping mechanism 66 as shown in FIGS. 12 - 14 , the crimping mechanism 66 comprises a handle 72 that actuates a pivotable cam arrangement 74 that crimps and then severs the crimpable section 28 between a pair of rollers 76 , 78 . Preferably, the sealing mechanism 68 is a rotatable hemostatis valve positioned proximal to the crimping mechanism 66 along passageway 70 . Preferably, crimping mechanism 66 and sealing mechanism 68 are arranged coaxial with each other along a straight portion of passageway 70 . In this embodiment, when the proximal end 36 of proximal portion 24 of guidewire assembly 22 is inserted into first aperture 62 until the proximal end 36 engages the hemostatis valve of sealing mechanism 68 , the crimpable section 28 is properly positioned relative to the crimping mechanism 66 .
 It will be seen that the relative distance between the engaging portions of sealing mechanism 68 and crimping mechanism 66 in this embodiment effectively defines the relative distances between a plurality of locations along sealing section 28 at which an airtight seal can be created as shown in FIGS. 1 - 2 . To permit multiple inflations and deflations of the occlusive balloon 32 of the guidewire assembly 22 , the length of the extended crimpable section 28 should be greater than at least twice the distance between crimping mechanism 66 and sealing mechanism 68 .
 The gas inflation/evacuation system 80 is connected via conduit 82 to the second aperture 64 of the sealing system 60 . The gas inflation/evacuation system 80 preferably includes a valve arrangement 84 that selectively couples one of an evacuation system 86 and an inflation system 88 to the conduit 82 . The evacuation system 86 is used to evacuate air from the guidewire assembly 22 , passageway 70 and conduit 82 . The inflation system 88 contains a volume of a biocompatible gas sufficient to inflate the occlusive balloon 32 a plurality of times. Optionally, a pressure gauge 90 can be associated with the inflation system 88 .
 Preferably, the gas is a biocompatible gas such as carbon dioxide. Other biocompatible gasses that may be utilized with the present invention include: oxygen, nitrogen, and nitrous oxide. While non-biocompatible gasses could be used, biocompatible gasses that are soluble in blood are preferred so as not to cause air embolization in the event of a leak in the system. Preferably, the biocompatible gas also has a good driving gradient in addition to being soluble, in that the biocompatible gas will effectively go into a solution, in this case blood, better than ambient air. Although not preferred, low viscosity biocompatible liquids or foams may also be used for inflation provided the surface tension of the fluid was sufficient to permit the rapid inflation and deflation contemplated by the present invention.
 It will be understood that if the guidewire assembly 22 , including the occlusion balloon 32 could be verified as capable of repeated inflations and deflations without any leakage or bursting of the balloon, then the evacuation portion of the inflation/evacuation system 80 would not be necessary as the evacuation portion of the inflation/evacuation system 80 is intended for safety purposes to insure that air within the guidewire assembly 22 and sealing system 60 is not introduced into the blood stream in the event of a failure, leakage or bursting of any component. For a more detailed description of the preferred embodiment of the sealing system 60 and the gas inflation/evacuation system, reference is made to the previously identified co-pending applications entitled “Guidewire Occlusion System Utilizing Repeatably Inflatable Gas-Filled Occlusive Device,” and “Gas Inflation System for Guidewire Having Occlusive Device.”
 In a preferred embodiment shown in FIGS. 3 a , 3 b , 4 a , and 4 b , the main body portion 30 of the guidewire assembly 22 is formed of a primary stainless steel hypotube having an outer diameter of 0.013 inches and an inner diameter of 0.007 inches. To accomplish passive deflation in the desired time of less than one minute when the crimpable section 28 is cut, it is preferable that the main body portion 30 have an inner diameter of at least 0.002 inches. The crimpable section 28 of guidewire 22 is comprised of a crimp tube also formed of stainless steel and having an outer diameter of 0.009 inches to 0.115 inches and an inner diameter of at least 0.002 inches and preferably about 0.005 inches. The crimpable section 28 is preferably secured to the proximal portion 24 by a laser weld 44 of sufficient strength. Alternatively, the sealable section 28 may be formed by center grinding or reducing the outer diameter of a portion of the proximal portion 24 of the main body 30 of guidewire assembly 22 . Still other embodiments may also enable the sealable section to be a modified, treated or otherwise indicated portion of the proximal portion 24 of the main body 30 of guidewire assembly 22 that is suitable for the particular sealing technique to be used. As shown in FIG. 4 a , in one embodiment the distal end of the crimpable section 28 is preferably center ground and press fit within a chamfered proximal end of the main body portion 30 . Alternatively as shown in FIG. 4 b , a chamfered crimp arrangement or a separate joining/crimping tube or similar tubular joining arrangements could be used. Preferably, a protective polymer coating 56 of polytetraflourene (PTFE) or a hydrophilic coating is applied by any of a number of known techniques such that the coating 56 surrounds the main body portion 30 . The protective polymer coating 56 is preferably about 0.0004+/−0.0003 inches thick such that the effective outer diameter of the main body portion 30 of guidewire assembly 22 is 0.014 inches.
 In this embodiment, the crimpable section 28 can be made of any material that when deformed and severed retains that deformation so as to form an airtight seal. When crimped and severed, it is preferable that the crimpable section 28 not present a sharp, rigid point that is capable of piercing a gloved hand. It has been found that as long as the preferred embodiment is not gripped within less than one inch of the proximate end 36 of the crimpable section 28 , the severed proximate end 36 of crimpable section 28 does not penetrate a standard surgical glove. In addition, the crimpable section 28 must have sufficient strength in terms of high tensile and kink resistance to permit catheter devices to repeatedly pass over the crimpable section 28 .
 In this embodiment, the main body portion 30 is preferably secured to the distal portion 26 using a Ni—Ti, or stainless steel sleeve 46 , laser welded to the main body portion 30 at laser weld 48 and crimped to the distal portion 26 at crimp 50 . The distal portion 26 is preferably formed of a Ni—Ti alloy having an inner diameter of 0.045 inches and an outer diameter that ranges from 0.014 inches to 0.0075 inches to form tapered portion 42 , preferably formed by a center-less grinding process. Preferably, the distal portion includes a pair of coil sections, proximal tip coil 52 and distal tip coil 54 that are longitudinally spaced apart and adjacent to the holes 35 and that assist in providing a better surface for bonding the balloon 32 to the distal portion 26 . FIGS. 10 and 11 provide detailed views of this embodiment. This arrangement also tends to increase the visibility of the location of balloon 32 under fluoroscopy as the balloon 32 filled with a biocompatible gas will be radiotranslucent when compared to the two coils 52 and 54 . Alternatively, a platinum markerband could be located around the distal portion 26 just proximal to the occlusive balloon 32 to serve as a radiopaque/MRI marker. The flexible tip 38 is a coiled tip attached to distal portion 26 distal to occlusion balloon 32 , preferably by a crimp 54 . Alternatively, a sleeve could be welded to the tip 38 and the tapered portion 42 could then be inserted into this sleeve and crimped.
 Alternatively, any number of other alloys or polymer materials and attachment techniques could be used in the construction of the guidewire assembly 22 , provided the materials offered the flexibility and torque characteristics required for a guidewire and the attachment techniques were sufficiently strong enough and capable of making an airtight seal. These materials include, but are not limited to, a tubular guidewire of all Ni—Ti, 17-7 stainless steel, 304 stainless steel, cobalt superalloys, or other polymer, braided or alloy materials. The attachment techniques for constructing guidewire assembly 22 include, but are not limited to: welding, mechanical fits, adhesives, sleeve arrangements or any combination thereof.
 The balloon 32 may be made of any number of expandable polymer or rubber materials. Preferably, the occlusion balloon is preinflated to prestretch the balloon so balloon expansion is more linear with pressure. Preferably, the pressure supplied by gas system 80 is designed to stay well within elastic limits of balloon 32 . A two layer balloon arrangement, adding gas and/or liquid between balloon layers may be used in an alternate embodiment to increase visibility of the distal end of the guidewire assembly 22 under fluoroscopy.
 In practice, medical personnel gain entry to the vessel lumen prior to use of the guidewire occlusion system 20 . The proximal portion 24 of guidewire assembly 22 is inserted into first aperture 62 and connected via sealing mechanism 68 . The distal portion 26 of guidewire assembly 22 is inserted into the vessel lumen and occlusive balloon 32 is inserted to a point distal to the vessel occlusion. Valve arrangement 84 is set for evacuation. First syringe plunger 92 of evacuation system 86 is slidably withdrawn removing any air from guidewire assembly 22 . Valve arrangement 84 is then set for inflation. Second syringe plunger 94 of inflation system 88 is slidably advanced inserting a volume of an inert gas into guidewire assembly 22 . The inert gas inflates occlusive balloon 32 as shown in FIG. 2. During inflation, the medical personnel monitor pressure gauge 90 to insure that the inflation pressure does not exceed the burst rating of the occlusive balloon 32 and to gauge the relative size of the occlusive balloon 32 as it is inflated. Following inflation of occlusive balloon 32 , crimping mechanism 66 is employed to crimp the crimpable section 28 of guidewire assembly 22 thereby sealing the guidewire assembly 22 to maintain the occlusive balloon 32 in an inflated state. Sealing mechanism 68 is released and the proximate portion 24 is removed from first aperture 62 , as shown in FIG. 3, such that the proximal portion 24 of the guidewire assembly 22 is free of mechanical or other obstructions and functions as a conventional guidewire. When the medical personnel decide to deflate the occlusive balloon 32 , the crimpable section 28 is cut using a medical scissor or the like distal to the existing crimp in the crimpable section 28 . When the medical personnel deem reinflation of the occlusive balloon 32 to be necessary, proximal portion 24 is reinserted into first aperture 62 . Sealing mechanism 68 is then activated and the evacuation/inflation process can be repeated. It will be understood that a crimping handle 72 may also be provided with a separate severing arrangement to cut the crimpable section 28 . Alternatively, crimpable section 28 may be scored or otherwise weakened in selected locations to assist in crimping or severing, including severing by repeated bending back and forth at one of the scored locations. In another embodiment, the sealable section 28 could be broken off rather than sheared by using a brittle metal for the sealable section that aided in the severing of sealable section 28 .
 FIG. 9 shows an embodiment of the sealing system 60 . Sealing system 60 is preferably comprised of sealing mechanism 68 and crimping mechanism 66 . Crimping mechanism 66 is comprised of crimp body 126 , handle 72 , handle return 128 and crimp aperture 130 . Sealing mechanism 68 is comprised of sealing body 132 and sealing aperture 134 . Sealing system 60 has sealing bore 136 fluidly interconnecting crimp aperture 130 and sealing aperture 134 .
 Depending on the sealing method specified in the embodiment, different deflation techniques can be utilized. For the preferred embodiment, the crimpable section 28 is of sufficient length to allow deflation through the shearing of the crimpable section 28 distal to the sealant material 158 located in the proximal end of the crimpable section 28 . By having sufficient length of the crimpable section 28 , the guidewire assembly 22 can be coupled to the gas inflation/evacuation system 80 multiple times allowing the occlusive balloon 32 to be inflated and deflated multiple times.
 In practice, medical personnel gain access to the blood vessel lumen through which the guidewire assembly 22 will travel. The guidewire occlusion system 20 is removed from biocompatible packaging 174 . Flexible tip 38 is inserted and is manipulated to a point beyond the vessel occlusion. Valve arrangement 84 is adjusted to the evacuation position and first syringe plunger 92 is slidably withdrawn to remove any gas present in the guidewire assembly 22 . Valve arrangement 84 is adjusted to the inflation position and second syringe plunger 94 is slidably inserted causing occlusive balloon 32 to inflate.
 Following inflation of occlusive balloon 32 , handle 72 on the crimping mechanism 66 is depressed causing roller 76 and roller 78 to crimp and preferably sever the crimpable section 28 of guidewire assembly 22 . In this embodiment, severing of the sealable section 28 serves as an immediate verification of the creation of an effective seal. Sealing mechanism 68 can be released and guidewire assembly 22 can be completely removed from the sealing system 60 allowing the occlusive balloon 32 to remain inflated while occlusive substance treatment occurs. Following treatment, the crimpable section 28 can be sheared or broken off resulting in the deflation of the occlusive balloon 32 . If occlusive treatment is complete, guidewire assembly 22 can be removed from the vessel lumen. If additional treatment is required, crimpable section 28 can be reattached to sealing system 60 through first aperture 62 . Sealing mechanism 68 can be retightened and the evacuation/inflation process can be repeated.
 In a preferred embodiment of the present invention, the guidewire occlusion system 20 is utilized as the guidewire for an atheroectomy or thrombectomy procedure of the type described in U.S. Pat. Nos. 5,370,609 or 5,496,267, the disclosure of each of which is hereby incorporated by reference. In each of these embodiments, the guidewire occlusion system 20 is introduced into the patient, the occlusion balloon 32 is inflated, and then the atheroectomy or thrombectomy catheter arrangement is slid over the proximal end 36 of the guidewire assembly 22 and advanced until it is proximate and proximal to the location of the occlusion balloon. The procedure is performed for a time period consistent with the desired maximum length for blockage of the particular vessel, at which time the crimpable section 28 of the guidewire assembly 22 may be severed to deflate the balloon 32 , thereby reestablishing blood flow within the vessel. Depending upon the nature of the procedure, the catheter arrangement may be removed from the vessel or left in place. Preferably, an evacuation of any debris or other plaque material dislodged by the therapy is accomplished before deflation of the balloon 32 and the balloon 32 is reinflated prior to reinitiation of the procedure.
 It will be understood that because gas is used as the inflation medium instead of liquid, the wall thickness and therefore the strength of tubular members of the guidewire assembly 22 can be increased to effectively match the strength and flexibility of an ideal solid guidewire. Strength increase is dramatic as a result because strength of the tube is governed by the equation (R(o)**4−R(i)**4), such that an increase in wall thickness effectively quadruples the increase in strength of the guidewire assembly.
 Rapid inflation and deflation of an occlusive balloon is the key to a successful occlusion device. The viscosity of the inflation fluid and resistance through the evacuation/inflation lumens dictate the effective speed of inflation and deflation. By lowering the viscosity of the inflation fluid, the present invention is able to increase the amount of resistance through the evacuation/inflation lumen that can be overcome. This results in being able to use a smaller inner diameter tube for the evacuation/inflation lumen which allows for a significant increase in the structural robustness of the guidewire, while maintaining the desired inflation and deflation properties. The increase in allowable resistance also allows for the use of longer guidewires, specifically guidewires that are a more typical exchange length. With typical high viscosity inflation fluids used to inflate liquid occlusion balloons, for example, it is not practical to develop an exchange length guidewire because of the long deflation times associated with evacuation the high viscosity inflation fluid through a much longer lumen.
 Another embodiment, as shown in FIG. 15, for constructing the guidewire assembly 22 includes a continuous stainless steel tube of 0.007 inch outer diameter by 0.004 inch inner diameter, having a second wire of 0.003 inch wound around except for along the sealable section 28 . The distal portion distal of the occlusive balloon 32 could be pinched in a taper to provide the desired flexible tip 38 . A second unwrapped portion could be provided at the distal portion 26 along with one or more apertures in the stainless steel tube over which the occlusive balloon 32 would be adhesively secured. This embodiment would be less expensive by avoiding the use of Ni—Ti alloy and eliminating the need for laser welding or other attachment techniques along the guidewire assembly 22 .
 Another embodiment, as shown in FIG. 16, for constructing the guidewire assembly 22 includes a braided polyimide hypotube having a Ni—Ti core rod positioned therein. The Ni—Ti core rod provides stiffness to the guidewire assembly 22 , but is much less expensive than a Ni—Ti tube. Alternatively, the polymer outer hypotube could include composite carbon fiber reinforcement to increase the strength of the hypotube. Numerous arrangements for securing the rod within the hypotube, including a flexible tip 38 and securing the occlusive balloon 32 to the hypotube are available with respect to this embodiment.
 The present invention may be embodied in other specific forms without departing from the essential attributes thereof; therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.