WO2001024683A2

WO2001024683A2 - Interventional injury sizing tool for radiation therapy

Info

Publication number: WO2001024683A2
Application number: PCT/US2000/027440
Authority: WO
Inventors: Thomas K. Brooks; Richard M. Griffith
Original assignee: Novoste Corporation
Priority date: 1999-10-04
Filing date: 2000-10-04
Publication date: 2001-04-12
Also published as: AU1191801A; WO2001024683A3

Abstract

An interventional measuring tool for assisting with the accurate and precise determination of the effective radiation source length that will deliver the prescribed radiation or brachytherapy dosage to a targeted site within a patient. The interventional measuring or sizing tool (10) includes an elongated wire (11) having a proximal section (12), a distal section (16), and an intermediate section (14) therebetween, and two or more radiopaque markers (18) affixed to the distal section (16) of said elongated wire (11), the radiopaque markers (18) spaced at predetermined distances that indicate to the user the effective lenth of the radiation source that will provide for effective radiation dosing of the targeted tissue being treated.

Description

INTERVENTIONAL INJURY SIZING TOOL FOR VASCULAR AND NON-VASCULAR APPLICATIONS

INVENTORS: Thomas K. Brooks

Richard M. Griffith

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser. No. 60/157, 496, filed October 4, 1999.

FIELD OF THE INVENTION

The present invention generally relates to an elongated wire being capable of navigating the vascular system or intraluminal passageways of a patient and having radiopaque markers strategically placed along the distal end of the wire for use as a tool to accurately measure the injury length of a vessel or other intraluminal passageway that has been subjected to an interventional procedure, such as balloon angioplasty, atherectomy or stent placement, and to accurately position a catheter or other such device within a vessel or intraluminal passageway.

BACKGROUND OF THE INVENTION

Intraluminal passageways, vascular and non-vascular alike, can experience stenosis, the narrowing or stricture of human passageways. For example, partial and complete blockage of vessels can be attributed to fatty and fibrous substances deposited in the vessel walls Such blockages may be treated using any one of a number of devices and procedures that have the objective to eliminate or at least reduce the blockage and increase the cross-luminal diameter, thus increasing blood flow The most common of such procedures is percutaneous transluminal coronary angioplasty (PTCA), which is more commonly referred to as balloon angioplasty In this procedure, a balloon catheter is introduced into the vessel, the umnflated balloon at the distal end of the balloon catheter is positioned at the stenotic site, and the balloon is inflated Inflation of the balloon disrupts and compresses the plaque and fibrous tissue against the vessel wall and stretches the vessel wall, resulting in enlargement of the intraluminal passageway and increased blood flow The balloon is then deflated and the balloon catheter is removed from the patient Other such devices or procedures used to reduce a blockage or enlarge an intraluminal passageway include atherectomy devices, which physically remove the plaque, hot or cold lasers, which vaponze the plaque, and stents, which expand and maintain open the lumens The walls of the treated lumens most likely are injured during use of the above-identified devices and procedures A.s a result of the injury, a healing response, known as restenosis, is initiated by the human body and an overgrowth of tissue due to increased cell proliferation renarrows the lumen, negating the progress made by the interventional procedure

Applying radiation therapy directly to the injured tissue has shown promise in reducing the incidence of restenosis by inhibiting the cell proliferation that follows interventional procedures for the reopening of intraluminal passageways Methods and apparatus for such intraluminal radiation treatment are disclosed in U S Patent Nos 5, 683, 345, 5, 899, 882, and 6, 013, 020 and pendmg patent applications Serial Nos 09/304, 752, filed May 4, 1999, 09/469, 510, filed December 22, 1999, 09/522, 759, filed March 10, 2000, and 09/616, 260 filed July 14, 2000 With improper technique, however, a phenomenon labeled as "Geographic Miss" has been observed and may hinder the effectiveness of the radiation therapy if not eliminated Geographic Miss occurs when the interventional injury length, or the tissue subjected to an interventional procedure, as descnbed above (balloon angioplasty, stent placement, atherectomy, etc.), is not adequately covered by radiation during the radiation therapy procedure. When inadequate radiation coverage is administered, the unexposed or underexposed injury length will not benefit from the therapeutic effects of intraluminal radiation and may become restenotic as if no radiation was administered.

Geographic Miss is most commonly a result of ( 1 ) incorrect positioning of the catheter and/or radiation source relative to the injury site; and/or (2) delivering less than the effective radiation source length. The effective radiation source length is at least as long as the injury length but may be required to extend beyond the edge of the injury to compensate for "edge effect", which is defined as the situation where the proximal and distal ends of the injury length are underdosed due to the decaying dose rate that has been associated with the proximal and distal edges of the radiation source.

The length of an injury created during an interventional procedure is very difficult to determine. For example, a 20 mm balloon does not necessarily create a 20 mm injury site. Balloon lengths are often longer than specified, and balloons lengthen as the inflation pressures increase. Multiple balloon inflations while repositioning the balloon catheter along the stenotic site may also result in long injury lengths greater than that of the balloon. Length assessment can further be hindered by vessel foreshortening, heart movement, and the use of flawed or crude methodologies. An inaccurate length assessment correlates to an ineffective radiation source length, resulting in Geographic Miss. To optimize the effectiveness of radiation therapy for the prevention and treatment of restenosis, the occurrence of Geographic Miss must be eliminated. Thus, there is a great need for a technique and/or tool for accurately and precisely measuring the interventional injury length, which has become a crucial element in determining the corresponding effective radiation source length.

It is among the general object of the present invention to provide a measuring or sizing tool and a method of use that would ultimately assist in the assessment of the effective radiation source length of a specific injury length through the measurement of that injury length.

SUMMARY OF THE INVENTION

The main objectiv e of the invention is to assist with the accurate and precise determination of the effective radiation source length that will deliver the prescribed radiation or brachytherapy dosage to a targeted site within a patient. This is accomplished by an interventional measuπng tool that comprises an elongated wire having a proximal section, a distal section, and an intermediate section therebetween, and two oi more radiopaque markers affixed to the distal section of said elongated wire, said radiopaque markers spaced at predetermined distances that indicate to the user the effective length of the radiation source that will provide for effective radiation dosing of the targeted tissue being treated. The wire may have sufficient stiffness and flexibility to navigate the vascular system of a patient In one embodiment, the first and second radiopaque markers are spaced about 30 mm apart λ thu d ladiopaque marker may be added and spaced about 40 mm horn the first radiopaque marker, and a fourth radiopaque marker may be added and spaced about 60 mm fiom the first radiopaque marker Additionally, the wire may comprise a handle along its proximal section for easier manipulation and positioning of the wire within the body of a patient, and the handle may comprise a clip for gripping the distal end of said elongated wire for manageability when said tool is not in use

Othei objectiv es will become more apparent upon reference to the following detailed description and drawing

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a segmented plan view of the interventional injury sizing tool according to the present invention. DETAILED DESCRIPTION OF INVENTION

As shown in Figure 1 , the interventional injury sizing tool 10 of the present invention is an elongated flexible solid w ire 1 1 having a proximal portion 12 of a uniform ι diameter, a distal portion 16 of a smaller uniform diameter, and a tapered intermediate portion 14 that facilitates the transition from the larger diameter proximal portion 12 to the smaller diameter distal portion 16 Two or more radiopaque markers 18 are attached to the distal portion 16 of the wire 1 1 One of said maikers 1 8 is attached to the distal tip of the distal portion 16 and the additional 0 maikeis 18 are spaced at predetermined distances from said distal tip marker 18 to Li LJtt a iriLJsiii ing tool foi accurately sizing a v ascular or other intraluminal injury to determine the radiation source length for effective radiation treatment of the injured tissue

5 The interventional injury sizing tool 10 is used to measure the length of intraluminal injuries l esulting horn interventional procedures, such as balloon angioplasty, atherectomy, and stent placement Therefore, it is designed to be maneuverable w ithin the asculai system and othei intraluminal passageways for the alignment of injured tissue with the distal radiopaque maikers 18, as can be readily v isible via 0 fluoroscopy The larger diameter proximal portion 12 and the tapered intermediate poition 14 pi ov ide the needed stiffness to advance the wire 1 1 through the vascular system or other intraluminal passageways of a patient without damaging the luminal oi cjthetei walls, depending on whether it is being inserted directly into the intraluminal passage ay or through a catheter When inserted into a catheter that is ι housing a guidewire oi 014 inch diameter, the injury sizing tool 10 , however, preferably does not create a catheter stiffness greater than 1 2 times that of the catheter housing only the guidewire The distal portion 16 of the wire 1 1 is more flexible than the proximal portion 12 so as to be capable of navigating the tortuousity of the human anatomv Most preferably, the injury sizing tool 10 must be capable of

30 navigating intraluminal passageways without kinking when placed through bends of no less than 025 inch radius The tapered intermediate section 14 provides a smooth transition between the stiffer proximal section 12 and the flexible distal section 16

The dimensions of the injury sizing tool 10 are directlv related to the dimensions of the catheter with which the sizing tool 10 is inserted and the dimensions of the radioactive source to be used to irradiate injured tissue The length of the injury sizing tool 10 is longer than the catheter so that when in place it extends outside the proximal end of the catheter for purposes of manipulation by the user The proximal section 12 υt the mjuiy sizing tool 10 has an outer diameter that is at least oi somewhat larger than that of the radiation source to be used for radiation treatment, and the distal section 16 of the injury sizing tool 10 has a diameter smaller than that of the pioximal section 12 to increase its flexibility The intermediate section 14 is initially the diameter of the proximal section 12 and tapers down to the smaller diameter of the flexible distal section 16 For example, if the radiation source has an outei diametei ol 025 inch and the diametei of the cathetei lumen tor receiving the radiation source is slightly larger than the radiation source, then the proximal section diameter would be at least 025 inch and the distal section 16 may have a diameter of approximately 008 inch The proximal section 12 of the wire 1 1 is the longest, preferably making up approximately seventy percent of the wire length, the intermediate section 14 of the wire 1 1 is the shortest, preferably making up four to six pei cent of the entite wne 1 1 and the distal section 16 of the wire 1 1 is longer than the lntei mediate section 14 but shorter than the proximal section 12, preferably making up appioximately twenty-one to twenty three percent of the wire length Foi example, a wire 1 1 having a length of 61 4 ± 0 1 inches could have a proximal section 12 of 44 05 ± 0 l inches in length, an intermediate section 14 of 3 55 ± 25 inches in length and a distal section 16 of 13 8 ± 0 1 inches

1 he elongated wn e 1 1 can be of any metal, such as stainless steel or nitinol, oi polvmer as long as it provides the πght amount of flexibility and pushabihty to deliver it through the vasculature of a patient To create the desired amount of stiffness at the proximal end 12 in combination with the desired amount of flexibility at the distal end 16, the material may vary along the length of the wire 1 1 For easier advancement, the wire 1 1 can be coated with a mateπal having a low coefficient of friction s

Radiopaque markers 18 that are readily visible under fluoroscopy are permanently affixed to the distal portion 16 of the elongated wire 1 1 Once the injury sizing tool 10 is fully inserted into the intraluminal passageway, the proximal end of the most distal ladiopaque marker 18 is aligned with the distal end of the injured site, and the

10 injury length is assessed using the set distances between the proximal end of the most distal ladiopaque marker 18 and the distal ends of the more proximal radiopaque markers 1 8 The radiopaque markers 18 may be spaced at equal or varied distances along the distal portion 16 of the injury sizing tool 10 It is preferable, however, that the radiopaque markers 1 8 are spaced at distances that correspond to the different

I radiation source lengths available for treatment Radiation source lengths of 30 mm, 40 mm, and 60 mm will provide effective treatment for most coronary arteries having undergone interventional restructuπng Thus, an injury sizing tool 10 specifically designed for coronary applications may have a first radiopaque marker 18 at its distal tip a second ladiopaque markei 18 proximally spaced 30 mm from the first

20 ladiopaque markei 1 8. a third radiopaque markei 18 proximally spaced 40 mm from the fust ladiopaque marker 18 and 10 mm from the second radiopaque marker 18, and a fourth radiopaque marker 18 proximally spaced 60 mm from the first radiopaque marker 18, 30 mm from the second radiopaque marker 18, and 20 mm horn the third radiopaque marker 18 For peripheral vessels, which tend to have longei injuiv lengths, the injury sizing tool 10 may have additional radiopaque maikei s 18 spaced at 80 mm and 120 mm from the first radiopaque maiker 18 at the distal tip of the distal portion 16

The radiopaque markers 18 of the injury sizing tool 10 are of the same length as the 30 radiopaque markeis on either end of the radiation source, such as the radiopaque markei seeds positioned on each end of a series of radiation source seeds as referenced herein by the disclosures of U S Patent Nos 5, 683, 345, issued November 4, 1997 and 5, 899, 882 issued May 4, 1999 After being delivered through the radiation source lumen of a catheter, the radiation source seeds and two marker seeds are maintained in an end to end configuration with the most distal marker seed abutting a distal wall that impedes the forward motion of the radiation source seeds The interventional injury sizing tool 10 is properly positioned within the catheter when the tool's distal tip, which happens to be the distal tip of the first and most distal ladiopaque marker 18, maintains contact with the distal wall in the same way as does the radiation source during radiation treatment Having the radiopaque markers 18 equal in length to that of the radiopaque segments of the radiation source and having the distances between the most distal radiopaque marker 18 and each of the additional radiopaque markers 18 equal to the different radiation source lengths, the injury sizing tool 10, if positioned properly, projects via fluoroscopy a preview of where the radiation source and its radiopaque segments will reside during radiation therapy This preview is extremely important in determining the proper placement of the catheter with respect to the injury and determining the effective radiation train length that will adequately treat the entire injured area

Radiopaque markers 18 may also be of the same diameter as the radiation source and its radiopaque markei sections Positioning an injury sizing tool 10 having radiopaque markers 1 8 of both the same length and diameter as the radiation marker sections of the radiation source has the advantage of simulating the movement of the radiation source through the catheter to its placement at the distal end of the catheter.

If the injury sizing tool 10 cannot be advanced to the injury site then it stands to reason that the radiation source most likely would also be incapable of being fully advanced Such an important discovery prevents unnecessary exposure to radiation that would most definitely be encountered by the patient and personnel during a failed attempt to deliv ei the radiation souices to the distal end of the cathetei When sizing the radiopaque markeis 18, consideration should also be given to the need that the radiopaque markers 18 be of a diameter that allows for easy removal of the injury sizing tool 10 without significant displacement of the distal portion of the catheter, preferably no more than one millimeter deflection when the catheter is placed in a bend of no less than 25 inch in radius Any more deflection and the catheter is no longer withm proper position to provide effective radiation treatment

The radiopaque markers 18 may have a slightly larger outer diameter than the distal portion 16 of wire 1 1 , or the distal portion 16 may be undercut where the radiopaque markers 18 are permanently affixed, creating a uniform diameter along the entire length of the distal portion 16 of the wire 1 1 When the radiopaque markers 18 are of a larger diameter than the distal portion 16 of the wire 1 1 , non-radiopaque sections of l ϋ the same outer diameter as the radiopaque markers 1 8 may reside in between the ladiopaque markers 18 to create a uniform diameter from the distal tip to the proximal end of the most proximal radiopaque marker 18 The radiopaque markers 18 can be bands oi coils made of any radiopaque material, such as gold, platinum, or platinum indium oi platinum tungsten alloys Although the radiopaque markers 1 8 could be

1 s adhered to the wire 1 1 in a number of ways, such as with the use of epoxy or other adhesives, the radiopaque markers 18 are preferably welded to the distal end 16 of the wire 1 1 to create a strong and lasting bond

In addition to the ladiopaque marker bands or coils 18, the injury sizing tool 10 may 20 hav e one or moie proximal depth markeis (not shown ) on the proximal wire portion 12 that gives the physician an indication of the working length of the catheter and vvheie it is within the intraluminal passageway

A handle (not shown) mav be securely attached to the proximal end of the wire 1 1 for 2s easiei manipulation and positioning of the injury sizing tool 10 Additionally, a clip or slot mav be integrated into the handle to securely grip the distal end of the injury sizing tool 10 when not in use and outside the catheter The clip will make it easier to maintain the elongated injury sizing tool 10 in a coiled or other manageable position during shipping and handling

30 The main focus of the interventional injury sizing tool 10 is to provide a device that can accurately and precisely measure the length of an injured site to deliver the effective radiation source length and eliminate the occurrence of Geographic Miss. The interventional injury sizing tool 10, however, has additional built in features for contributing to the overall improvement of the radiation therapy procedure. The interventional injury sizing tool 10 can be inserted directly into the intraluminal passageway, directly into the radiation source lumen of a radiation delivery catheter prepositioned with the intraluminal passageway, or indirectly into the intraluminal passageway by being preinserted into the radiation source lumen of a radiation delivery catheter and carried to the injury site by placement of the catheter. The built in design features come into play when the injury sizing tool 10 is being used in conjunction with a catheter.

With respect to U.S. Patent Nos. 5, 683. 345, issued November 4, 1997 and 5, 899, 882 issued May 4, 1999, as referenced herein, the radiation sources may be a series of individual seeds. A series of steps are completed to deliver non-radioactive seeds to the distal end of the catheter as a trial run to determine the patency of the radiation source lumen of the catheter in use. By inserting the injury sizing tool 10 within the radiation source lumen of the catheter, either before or after the catheter is placed within the intraluminal passageway, the dummy run is no longer needed. Since the markers I S are of the same diameter as the radiation sources, successful placement oi^' the injury sizing tool 10 within the catheter^'s source lumen assures the physician that the lumen is patent and indicates successful placement of the radiation sources.

Furthermore, an advantage of pre-inserting the injury sizing tool 10 within the catheter prior to packaging is that it maintains the source lumen open during shipping and handling of the catheter and prevents the source lumens from becoming kinked or collapsed.

Typically, a radiation delivery catheter will be advanced over a prepositioned guidewire and through a prepositioned guide catheter to the intraluminal injury for treatment. A hemostasis valve, such as a Touhy Bourst valve, is clamped to the guide cathetei and is tightened down around the guide catheter and radiation delivery catheter until the space between the two is closed off preventing back flow of blood from escaping the proximal end of the guide catheter Overaggressive tightening of the hemostasis valve will constrict the delivery catheter's source lumen, reducing it to a diameter smaller than the radiation sources and either crushing the radiation sources or obstiucting their pathway To prevent extreme tightening of the hemostasis valve, an injury sizing tool 10 having a proximal portion 12 of a larger diameter than the radiation source is inserted into the radiation source lumen of the delivery catheter, if not already prepackaged that way The hemostasis valve cannot constrict the catheter's radiation source lumen to a diameter less than that of the proximal portion 12 of the injury sizing tool 10, thus, there will be space for the radiation source to tiavel its pathway without being crushed or without being hindered by a crimped or collapsed radiation source lumen

The interventional injury sizing tool 10 of the present invention can be used in conjunction with any catheter, radiation source, and radiation delivery system to assess the tieatment length and position needed for effective radiation treatment

Claims

WHAT IS CLAIMED

1 An interventional measuring tool for assisting w ith the accurate determination of the effective radiation source length that will deliv er the prescribed s radiation dosage to the injured site being treated, comprising

an elongated wire having a proximal section, a distal section, and an intermediate section therebetween,

0 two or more radiopaque markers disposed on the distal section of said elongated wire, said radiopaque markers spaced at predetermined distances that indicate to the user the effective length of the radiation source foi effective radiation dosing of the injured tissue being treated

s 2 The interventional measuring tool of Claim 1 wherein said elongated wn e has sufficient stiffness and flexibility to navigate the vascular system of a patient

3 The interventional measuring tool of Claim 1 comprising four 0 ladiopaque markers, the fust radiopaque marker being the most distal, the second iadiopaque marker being proximal spaced about 30 mm from said first radiopaque mai kei . the thu d iadiopaque mai ker being proximally spaced about 40 mm from said first ladiopaque mai kei , and the fourth radiopaque marker proximally spaced about 60 mm from said first radiopaque marker s

4 The interventional measuring tool of Claim 1 comprising a handle at the proximal section of said elongated wire

5 The handle of Claim 4 comprising a clip foi gripping the distal end of 0 said elongated wire foi manageability when said tool is not in use