Abstract:
A micro-catheter delivery system that includes radio-opaque marker bands optimized for the purpose of length reference to assist the operating physician to estimate the length of a tortuous lesion and to anticipate foreshortening of stents with multiple sizes. The radio-opaque maker bands are positioned at the distal end of a stent delivery catheter at a certain intervals acts like a ruler. In another embodiment, a stent delivery system includes a stent delivery wire with one or more radio-opaque markers distanced from the stent distal end for indicating the non-restrained length of the stent when discharged from the delivery catheter.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 U.S.C. §111(a) continuation of PCT international application number PCT/US2013/057630 filed on Aug. 30, 2013, incorporated herein by reference in its entirety, which claims priority to, and the benefit of, U.S. provisional patent application Ser. No. 61/700,741 filed on Sep. 13, 2012, incorporated herein by reference in its entirety, and U.S. provisional patent application Ser. No. 61/700,300 filed on Sep. 12, 2012, incorporated herein by reference in its entirety. Priority is claimed to each of the foregoing applications. 
     The above-referenced PCT international application was published as PCT International Publication No. WO 2014/042900 on Mar. 20, 2014, which publication is incorporated herein by reference in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     INCORPORATION-BY-REFERENCE OF COMPUTER PROGRAM APPENDIX 
     Not Applicable 
     NOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION 
     A portion of the material in this patent document is subject to copyright protection under the copyright laws of the United States and of other countries. The owner of the copyright rights has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office publicly available file or records, but otherwise reserves all copyright rights whatsoever. The copyright owner does not hereby waive any of its rights to have this patent document maintained in secrecy, including without limitation its rights pursuant to 37 C.F.R. §1.14. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains generally to endovascular delivery systems and methods, and more particularly to systems and methods for delivery of expandable stents. 
     2. Description of Related Art 
     Current endovascular procedures use a metallic expandable stent to expand a lesion or to cover a target lesion. There is an increase in the use of stents due to advancements in biomaterial technology. For example, intracranial aneurysms had been treated only by endovascular coiling or open-surgical clipping until recently; but now those aneurysms can also be treated by using a stent that reduces the blood flow into the target aneurysm and induces complete thrombosis. In order to successfully treat an aneurysm with a stent, it is crucial to cover the aneurysm lesion completely with the stent. Any uncovered area in the aneurysm neck may make the stent procedure ineffective. Therefore, if an uncovered area occurs, an additional stent may need to be placed to completely cover across the aneurysm lesion. This applies not only to aneurysms, but also to stenotic/narrowing lesions. An atherosclerotic plaque covered by a stent should bridge the proximal to the distal normal arterial segment. Thus, the capacity to accurately place a stent across the lesion is a critically important element in endovascular stenting procedure. 
     There are generally two different types of stents: a laser-cut stent and a braided stent. There are pros and cons for each type of the stent. The most significant limitation of a braided stent is a phenomenon called “foreshortening,” which is defined as the change in the length of the stent from a constrained (i.e. compressed) state to an unconstrained (i.e. expanded) state. Although the degree of foreshortening is most significant in a braided stent, it may occur in a micro-machined or laser-cut stent as well. The degree of foreshortening with certain kinds of braided stents can be as large as 100%. This foreshortening poses a challenge to the treating physicians to place a stent very accurately. 
     Referring to  FIG. 1 , a stent is generally delivered to a target lesion via a catheter and delivery wire  12 . When a braided stent is squeezed in a delivery catheter, the stent becomes longer (elongated stent  10   b ). Once the stent is being pushed out of the delivery catheter, the stent expands in the target vessel and it becomes shorter (foreshortened stent  10   a ). This foreshortening phenomenon must be taken into account when a braided stent needs to be placed in a lesion with high accuracy. A physician must therefore anticipate the degree of foreshortening during the stent placement, which requires a certain amount of training and clinical experiences. Nevertheless, it is virtually impossible to achieve 100% accuracy as long as the procedure depends on “anticipation” or “experience.” 
     Another challenge for the accurate stent placement is tortuous anatomy. It is difficult to control the position of delivery catheter and also to anticipate the shape and position of a stent in a curvy target lesion. Endovascular stenting procedures are performed under a 2-dimensional fluoroscopic X-ray imaging guidance. Even with the use of multiple angle fluoroscopic images (for example, bi-plane digital subtraction angiography machine), there is an intrinsic challenge in making a real time estimate on the length of a lesion in a tortuous 3-dimensional anatomy projected onto a 2-dimensional fluoroscopic view. 
     BRIEF SUMMARY OF THE INVENTION 
     One aspect of the invention is a micro-catheter delivery system that includes radio-opaque marker bands optimized for the purpose of length reference (i.e. position indicator) to assist the operating physician to estimate the length of a tortuous lesion and to anticipate foreshortening of stents with multiple sizes. In order to accommodate to various anatomies and various stent sizes, the radio-opaque maker bands positioned at the distal end of a stent delivery catheter at certain intervals acts like a ruler, which can be used as a reference of length of the lesion, even in a 2-dimensional projection image. 
     In another aspect, a stent delivery system is provided that includes a stent delivery wire with one or more radio-opaque markers distanced from the stent distal end for indicating the non-restrained length of the stent when discharged from the delivery catheter. 
     Further aspects of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only: 
         FIG. 1  is an image of an exemplary prior art stent and delivery wire, with the stent shown in an expanded, elongate configuration, and another stent in a non-constrained configuration. 
         FIG. 2  is a schematic diagram that illustrates an exemplary micro-catheter for precision stent placement in accordance with the present invention. 
         FIG. 3  is a schematic diagram that shows a stent delivery system comprising a stent delivery wire configured for precise stent delivery to a target treatment location within the body. 
         FIG. 4  is an exemplary radiographic image that shows a micro-catheter comprising multiple radio-opaque maker bands at 10 mm intervals in use within tissue in accordance with the present invention. 
         FIG. 5  is a radiographic image of an expanded stent and stent delivery wire with radio-opaque markers in accordance with the present invention. 
         FIG. 6  is a schematic diagram of a brain artery (e.g. left internal carotid artery) and a brain aneurysm as the target treatment anatomy. 
         FIG. 7  is a schematic diagram of the micro-catheter of  FIG. 2  with radio-opaque markers navigated into the brain artery of  FIG. 6 . 
         FIG. 8  is a schematic diagram of a braided aneurysm stent inserted into the micro-catheter of  FIG. 7 . 
         FIG. 9  is a schematic diagram of the micro-catheter of  FIG. 8  being pulled back as the stent is being pushed out of the distal end. 
         FIG. 10  is a schematic diagram of the stent of  FIG. 9  completely extracted from the micro-catheter for completion of the stent placement. 
         FIG. 11  is a schematic diagram of a stent delivery micro-catheter navigated into the brain artery of  FIG. 6 . 
         FIG. 12  is a schematic diagram of a braided aneurysm stent inserted into the micro-catheter of  FIG. 11  over a delivery wire. 
         FIG. 13  is a schematic diagram of the micro-catheter of  FIG. 12  being pulled back as the stent and delivery wire assembly are being pushed out of the distal end. 
         FIG. 14  is a schematic diagram of the stent and delivery wire assembly of  FIG. 13  completely extracted from the micro-catheter for completion of the stent placement. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 2  illustrates an exemplary micro-catheter  20  for precision stent placement in accordance with the present invention. Micro-catheter  20  comprises a flexible tubular catheter body  28  having an internal passage stemming from distal end  22  to proximal end  24  (at connector  26 ) for delivery of stents or other instruments/devices to a target location within the body. Starting from the distal end  22  of the catheter body  28 , the catheter  20  comprises a plurality (e.g. six) of radio-opaque markers  30  at spaced apart intervals (e.g. 10 mm). The markers  30  act as a ruler to help the physician determine length and location with respect to an internal lumen or vessel. 
     Markers  30  may comprise any radio opaque material for visibility within the body under x-ray (e.g. radiographic or fluoroscopic imaging). In one embodiment, markers  30  comprise thin-walled tubes placed at spaced-apart locations on catheter body  28 , and are typically made from a high density material such as a metal (e.g. platinum, gold or tantalum) for visibility under an x-ray fluoroscope. Markers  30  may be embedded with, or adhered to an outside surface of, catheter body  28 . Markers  30  may also comprise a radio-opaque coating deposited on the catheter body. 
     The radio-opaque markers  30  may be of various quantity, sizes and intervals from the distal end  22  of the catheter body. For example, catheter  20  may comprise a plurality of radio-opaque markers  30  spaced-apart at 5 mm intervals along a distal segment spanning 3 cm-5 cm to provide reference for an operator placing a braided stent. The interval of the radio-opaque markers may range from every 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm or more. The length of the radio-opaque marker segment  30  may be 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, and 10 mm or more to provide sufficient visibility under an x-ray fluoroscope. Each radio-opaque marker  30  may be shaped similarly, or may be variably shaped, e.g. the 5 mm marker (from distal end  22  may comprise one band, the 10 mm marker may comprise 3 bands, the 15 mm marker may comprise 4 bands, and so on. 
     In one embodiment, the stent delivery catheter  20  may comprise multiple radio-opaque marker bands  30  spaced apart in a 40 mm distal segment  22  at 5 mm intervals, and may be configured for delivery of a 20 mm long braided stent. The stent would generally elongate in the delivery catheter  20  more than twice as much as its unconstrained length. Since the elongated stent in the delivery catheter  20  could not be helpful as a guide to anticipate where the 20 mm long stent ends (when unconstrained), the use of the array of radio-opaque markers  30  would indicate the 20 mm point from the catheter tip, enabling better stent positioning. 
       FIG. 3  shows a stent delivery system  50  comprising a stent delivery wire  40  configured with a proximal end  46  and a distal end  42  for supporting stent  38  for delivery to a target treatment location within the body. The stent  38 /delivery wire  40  assembly is delivered through micro catheter  20  (which may comprise radio-opaque markers  30  as shown in  FIG. 2 ) to the target treatment location in the vessel. Once the stent is completely pushed out from the distal end  22  of the delivery catheter  20 , it is detached from the delivery wire  40  and is positioned at the target location/lesion permanently. 
     As shown in  FIG. 3 , delivery wire  40  comprises a radio-opaque marker  44  a set length L SE  from the distal end  42  of the delivery wire. L SE  indicates the true, expanded length of the stent  38 , i.e. from distal end  34  to proximal end  36 . As mentioned previously, stents, and particularly braided stents, are significantly elongated when crimped in a delivery catheter. Radio-opaque marker  44  may comprise a ring or coating of size, shape and composition similar to marker  30  described above for  FIG. 2 . While delivery wire  40  is typically metallic, it is generally made of stainless steel or Nitinol, and the distal end  42  of the delivery wire is generally very thin so as not to generally be very radio-opaque. Marker  44  generally comprises radio-opaque metal, such as a platinum band, that is welded or bonded on wire  40 . 
     Without the system of the present invention, it is difficult to anticipate where the proximal end  36  of the stent lands in relation to the target anatomy. Using system  50  of the present invention, the physician may use the radio-opaque marker  44  on the delivery wire  40  to give an indication where the proximal end  36  of the unconstrained stent  38  would land after delivery through the micro catheter  20 , and thus start extraction of the distal end  34  of stent  38  at the appropriate distance from the target anatomy. For example, a 20 mm long braided stent  38  is crimped and mounted on delivery wire  40  having a radio-opaque marker positioned on the wire at a point that indicates L SE =20 mm from the distal tip  34  of the stent  38  (which may or may not correspond to the distance from distal end  42  of the wire  40 ). With this marker  44 , the operator can easily anticipate where the proximal end  36  of the stent would land in the tortuous vessel, and select a delivery location of the stent  38  (generally starting at the distal end  22  of the micro-catheter) that corresponds to the desired treatment location (e.g. the aneurysm  52 ). 
       FIG. 4  shows an exemplary radiographic image of the catheter  20  comprising multiple radio-opaque maker bands  30  at 10 mm intervals in use within tissue in accordance with the present invention. As seen in  FIG. 4 , the markers  30  are clearly delineated, and provide valuable visualization as a position indicator when placed in a tortuous anatomy. 
       FIG. 5  shows a radiographic image of an expanded stent  38  and stent delivery wire  40  with radio-opaque markers for illustrating expanded and compressed lengths. The image shows a braided stent  38  after it is delivered, but still attached to the delivery wire  40 . The left-most arrowhead shows a maker on the delivery wire  40  that corresponds to the distal end  36  of the stent  38 . The middle arrow indicates an additional radio-opaque marker  44  that represents the unconstrained length (or location of proximal end  36  when unconstrained) of the stent  38 . The double arrowheads  48  correspond to the location of the proximal end  36  of the stent  38  when crimped and constrained in the catheter  20  or delivery sheath. The marker  44  therefore guides the treating physician to better anticipate where the proximal end  36  of the stent lands. 
       FIG. 6  illustrates a schematic diagram of a brain artery  54  (e.g. left internal carotid artery) and a brain aneurysm  52  as the target treatment anatomy.  FIG. 7  through  FIG. 10  show a first embodiment of the invention of a stent delivery procedure using the micro-catheter  20  illustrated in  FIG. 2 .  FIG. 11  through  FIG. 14  show a second embodiment of the invention of a stent delivery procedure using the stent delivery system  50  illustrated in  FIG. 3 . 
       FIG. 7  illustrates a schematic diagram of the micro-catheter  20  with radio-opaque markers  30  navigated into the brain artery  54  and is placed across the aneurysm  52  neck. The general strategy is to cover the aneurysm  52  neck with a stent. As shown in  FIG. 7 , the distal end  22  of the micro-catheter  20  is delivered past the target location  52  and is placed at a location corresponding to the desired extraction of the stent  38  (e.g. where the distal end  34  of the stent will be located at distal end  22 ). 
       FIG. 8  illustrates a schematic diagram of a braided aneurysm stent  38  (e.g. 30 mm length) inserted into the micro-catheter  20 . In general, stents are very radio-opaque so that the entire length is clearly visible even if it is in a micro-catheter  20 . Due to the significant elongation, the 30 mm stent is much longer than the true length. This elongation on top of the tortuous anatomy sometimes poses a challenge to the physician for accurate placement. The multiple radio-opaque markers  30  at known intervals on the micro-catheter  20  allow the physician to ignore the elongation and simply use the 30 mm point marker (e.g. 3 rd  marker from distal end  22  at 10 mm spacing) as a reference. If the stent  38  lands in the vessel  54  as projected, it will span the neck of the aneurism  52 . 
       FIG. 9  illustrates a schematic diagram of the micro-catheter  20  being pulled back as stent  38  is being pushed out of the distal end  22 . Distal end  34  of the stent lands at the location of the distal end  22  at extraction, while proximal end  36  is still within the micro-catheter  20  as distal end  22  of the micro-catheter is pulled back to the location of the aneurysm  52 . Due to the stent elongation effect in the micro-catheter  20 , the remaining length of the stent  38  in the micro-catheter is significantly different from the length that the stent  38  covers within the artery  54 . 
       FIG. 10  illustrates a schematic diagram of the stent  38  completely extracted from the micro-catheter  20  for completion of the stent placement. The proximal end  36  of the stent  38  lands well beyond the aneurysm  52  neck to fully cover or occlude the target lesion. 
       FIG. 11  illustrates a schematic diagram of a stent delivery micro-catheter  20  navigated into the brain artery and placed across the aneurysm neck. In this configuration, delivery micro-catheter  20  does not have radio-opaque markers  30  as shown in  FIG. 2 . However, it is contemplated that markers  30  may also be employed. As with the previous procedure described in  FIG. 7  through  FIG. 10 , the desired treatment plan is to cover the aneurysm neck  52  with a stent (e.g. 30 mm length). 
       FIG. 12  illustrates a schematic diagram of a braided aneurysm stent  38  (e.g. 30 mm) inserted into the micro-catheter  20  over a delivery wire  40  so that the distal end  42  of the delivery wire is at or past the distal opening  22  of the micro-catheter  20 . In general, stents are very radio-opaque so that the entire length is clearly visible even it is in a micro-catheter  20 . Due to the significant elongation, the 30 mm stent  38  is much longer than the true length. This elongation on top of the tortuous anatomy sometimes poses a challenge to the physician for accurate placement. The radio-opaque marker  44  at known distance L SE  on the delivery wire  40  allows the physician to ignore the elongation and simply use the point marker  44  (e.g. 30 mm from the distal end  34  of the stent  38  when positioned on the delivery wire  40 ) as a reference. Having the radio-opaque marker  44  that indicates the unconstrained length of the stent  38 , the physician can simply navigate the stent delivery system (e.g. distal end  22  of micro-catheter  20 ) to the point where the desired stent placement starts in light of the radio-opaque marker  44  that indicates where the proximal end  36  of the stent  38  should land. 
       FIG. 13  illustrates a schematic diagram of the micro-catheter  20  being pulled back as stent  38  and delivery wire  40  are being pushed out of the distal end  22 . Distal end  34  of the stent  38  lands at the location of the distal end  22  at extraction, while proximal end  36  is still within the micro-catheter  20  as distal end  22  of the micro-catheter is pulled back to the location of the aneurysm  52 . Due to the stent elongation effect in the micro-catheter  20 , the remaining length of the stent  38  in the micro-catheter is significantly different from the length that the stent  38  covers within the artery  54 . Nevertheless, the physician can use the radio-opaque marker  44  as a predicted stent  38  ending point. 
       FIG. 14  illustrates a schematic diagram of the stent  38  and delivery wire  40  assembly completely extracted from the micro-catheter  20  for completion of the stent placement. The proximal end  36  of the stent  38  lands well beyond the aneurysm  52  neck at the projected marker location  44  on the delivery wire  40  to fully cover or occlude the target lesion  52 . 
     While the above examples are illustrated with use of a braided stent because of its associated substantial foreshortening, it is appreciated that the systems and methods of the present invention may be used with stents fabricated via any method, including micro-machined metal stents fabricated with laser-machining, photo-etching, electroforming, and micro-electro-discharge machining, and polymeric stents fabricated using injection, compression, or fused deposition molding processes. 
     It is appreciated that the length of the stent  38  while in a completely unconstrained state may be different than (e.g. smaller) the length of the stent when “unconstrained” in the lumen  54  outside of delivery micro-catheter  20 . For example, a stent may be sized to have a diameter that compresses against the inner wall of the lumen  54 . Thus, the lumen  54  may have a constraining effect on the stent  38  that causes it to be slightly larger than when in completely free state outside the body. Thus, length L SE  of the marker location in  FIG. 3 , and the incremental spacing between markers  30  in micro catheter  20  of  FIG. 2 , may have dimensions that are larger than the unconstrained length of the stent  38 . 
     From the discussion above it will be appreciated that the invention can be embodied in various ways, including the following: 
     1. An apparatus for precision delivery of a stent within a lumen of the body, comprising: a delivery wire having a proximal end and a distal end; wherein the distal end of the delivery wire is configured to support an expandable stent in a compressed, elongated configuration; wherein the delivery wire comprises a radio-opaque marker disposed at a predetermined distance from the distal end of the delivery wire; and wherein the predetermined distance corresponds to a length of the stent when the stent is in a shortened, unconstrained state. 
     2. An apparatus as in any of the previous embodiments: wherein the predetermined distance corresponds to a length of a braided stent in a shortened, unconstrained state; and wherein the length of the braided stent in a shortened, unconstrained state is smaller than the length of the braided stent when in a constrained state within a catheter. 
     3. An apparatus as in any of the previous embodiments: wherein the predetermined distance corresponds to a length of a micro-machined stent in a shortened, unconstrained state; and wherein the length of the micro-machined stent in a shortened, unconstrained state is smaller than the length of the braided stent when in a constrained state within a catheter. 
     4. An apparatus as in any of the previous embodiments: wherein the delivery wire and stent are configured to be delivered through a catheter in the compressed, elongated configuration to a treatment location within the lumen. 
     5. An apparatus as in any of the previous embodiments; wherein the treatment location comprises an aneurysm within a cerebral blood vessel; and wherein the stent is configured to span across the aneurysm when disposed at the treatment location in the unconstrained state. 
     6. An apparatus for precision delivery of a stent within a lumen of the body, comprising: a micro-catheter having a proximal end and a distal end; wherein the micro-catheter is configured to house an expandable stent in a compressed, elongated configuration for delivery to a treatment location within the lumen; and wherein the micro-catheter comprises three or more radio-opaque markers disposed at spaced-apart intervals from the distal end of the micro-catheter. 
     7. An apparatus as in any of the previous embodiments, wherein the spaced-apart marker intervals correspond to a length of the stent when the stent is in a shortened, unconstrained state. 
     8. An apparatus as in any of the previous embodiments, wherein the spaced-apart marker intervals form a ruler visible under radiographic imaging. 
     9. An apparatus as in any of the previous embodiments: wherein the spaced-apart intervals correspond to a length of a braided stent in a shortened, unconstrained state; and wherein the length of the braided stent in a shortened, unconstrained state is smaller than the length of the braided stent when in a constrained state within the micro-catheter. 
     10. An apparatus as in any of the previous embodiments: wherein the predetermined distance corresponds to a length of a micro-machined stent in a shortened, unconstrained state; and wherein the length of the micro-machined stent in a shortened, unconstrained state is smaller than the length of the braided stent when in a constrained state within the micro-catheter. 
     11. An apparatus as in any of the previous embodiments: wherein the micro-catheter is sized to allow delivery of the stent through the micro-catheter in the compressed, elongated configuration to the treatment location within the lumen. 
     12. An apparatus as in any of the previous embodiments: wherein the treatment location comprises an aneurysm within a cerebral blood vessel; and wherein the stent is configured to span across the aneurysm when disposed at the treatment location in the unconstrained state. 
     13. A system for precision delivery of a stent within a lumen of the body, comprising: a delivery wire having a proximal end and a distal end; wherein the distal end of the delivery wire is configured to support an expandable stent in a compressed, elongated configuration; a micro-catheter having a proximal end and a distal end; wherein the micro-catheter is configured to house the expandable stent while in the compressed, elongated configuration on the delivery wire for delivery to a treatment location within the lumen; wherein the delivery wire comprises a radio-opaque marker disposed at a predetermined distance from the distal end of the delivery wire; and wherein the predetermined distance corresponds to a length of the stent when the stent is in a shortened, unconstrained state. 
     14. A system as in any of the previous embodiments: wherein the predetermined distance corresponds to a length of a braided stent in a shortened, unconstrained state; and wherein the length of the braided stent in a shortened, unconstrained state is smaller than the length of the braided stent when in a constrained state within the micro-catheter. 
     15. A system as in any of the previous embodiments: wherein the predetermined distance corresponds to a length of a micro-machined stent in a shortened, unconstrained state; and wherein the length of the micro-machined stent in a shortened, unconstrained state is smaller than the length of the braided stent when in a constrained state within the micro-catheter. 
     16. A system as in any of the previous embodiments: wherein the treatment location comprises an aneurysm within a cerebral blood vessel; and wherein the stent is configured to span across the aneurysm when disposed at the treatment location in the unconstrained state. 
     17. A system as in any of the previous embodiments, wherein the micro-catheter comprises a plurality of radio-opaque markers disposed at spaced-apart intervals from the distal end of the micro-catheter to form a ruler visible under radiographic imaging. 
     18. A method for precision delivery of a stent within a lumen of the body, comprising: positioning a distal end of a micro-catheter to a treatment location within the lumen; delivering an expandable stent in a compressed, elongated configuration on a distal end of a delivery wire through the micro-catheter to the distal end of the micro-catheter; wherein the delivery wire comprises a radio-opaque marker disposed at a predetermined distance from the distal end of the delivery wire; and wherein the predetermined distance corresponds to a length of the stent when the stent is in a shortened, unconstrained state; locating the distal end of the micro-catheter at a delivery location corresponding to the radio-opaque marker and the treatment location; and extracting the stent from the distal end of the micro-catheter at the delivery location. 
     19. A method as in any of the previous embodiments: wherein the predetermined distance corresponds to a length of a braided stent in a shortened, unconstrained state; and wherein the length of the braided stent in a shortened, unconstrained state is smaller than the length of the braided stent when in a constrained state within the micro-catheter. 
     20. A method as in any of the previous embodiments: wherein the treatment location comprises an aneurysm within a cerebral blood vessel; and wherein the delivery location is selected such that the stent spans across the aneurysm when disposed at the treatment location in the unconstrained state. 
     21. A method for precision delivery of a stent within a lumen of the body, comprising: positioning a distal end of a micro-catheter to a treatment location within the lumen; delivering an expandable stent in a compressed, elongated configuration through the micro-catheter to the distal end of the micro-catheter; wherein the micro-catheter comprises three or more radio-opaque markers disposed at spaced-apart intervals from the distal end of the micro-catheter; and locating the distal end of the micro-catheter at a delivery location corresponding to the radio-opaque marker and the treatment location; and extracting the stent from the distal end of the micro-catheter at the delivery location. 
     22. A method as in any of the previous embodiments, wherein the spaced-apart marker intervals correspond to a length of the stent when the stent is in a shortened, unconstrained state. 
     23. A method as in any of the previous embodiments, wherein the spaced-apart marker intervals form a ruler visible under radiographic imaging. 
     24. A method as in any of the previous embodiments: wherein the spaced-apart intervals correspond to a length of a braided stent in a shortened, unconstrained state; and wherein the length of the braided stent in a shortened, unconstrained state is smaller than the length of the braided stent when in a constrained state within the micro-catheter. 
     25. A method as in any of the previous embodiments: wherein the spaced-apart intervals corresponds to a length of a micro-machined stent in a shortened, unconstrained state; and wherein the length of the micro-machined stent in a shortened, unconstrained state is smaller than the length of the braided stent when in a constrained state within the micro-catheter. 
     26. A method as in any of the previous embodiments: wherein the micro-catheter is sized to allow delivery of the stent through the micro-catheter in the compressed, elongated configuration to the treatment location within the lumen. 
     27. A method as in any of the previous embodiments: wherein the treatment location comprises an aneurysm within a cerebral blood vessel; and wherein the delivery location is selected such that the stent spans across the aneurysm when disposed at the treatment location in the unconstrained state. 
     Although the description herein contains many details, these should not be construed as limiting the scope of the disclosure but as merely providing illustrations of some of the presently preferred embodiments. Therefore, it will be appreciated that the scope of the disclosure fully encompasses other embodiments which may become obvious to those skilled in the art. 
     In the claims, reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the disclosed embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed as a “means plus function” element unless the element is expressly recited using the phrase “means for”. No claim element herein is to be construed as a “step plus function” element unless the element is expressly recited using the phrase “step for”.