WO2010022153A1

WO2010022153A1 - Delivery device for intraocular brachytherapy

Info

Publication number: WO2010022153A1
Application number: PCT/US2009/054320
Authority: WO
Inventors: Jay Daulton
Original assignee: Neovista, Inc.
Priority date: 2008-08-20
Filing date: 2009-08-19
Publication date: 2010-02-25

Abstract

A device for delivering ionizing radiation is disclosed. The device includes an ionizing radiation source and a cannula sized for intraocular insertion into an eye and including a proximal end and a distal end for receiving the radiation source. A housing carries the proximal end of the cannula and has an internal bore having an inner surface that includes a first material. A piston is operably coupled to the radiation source and slidably disposed within the internal bore to move the radiation source between a retracted position within the housing and a treatment position within the cannula. The piston includes a contact surface that slidably interacts with the inner surface of the bore and the contact surface of the piston includes a second material, where the first and second materials are chosen such that the contact and inner surfaces slidably interact with sufficiently low friction to allow precision movement of the piston within the bore.

Description

DELIVERY DEVICE FOR INTRAOCULAR BRACHYTHERAPY

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of the filing date of Provisional Patent

Application USSN 61/090,359, fiied August 20, 2008, the entire contents of which are incorporated by reference herein.

BACKGROUND

[0002] The present subject matter described herein generally relates to a device for performing intraocular brachytherapy. The subject matter may be employed in the treatment of a variety of eye disorders, but is particularly suited for treatment of macular degeneration.

[0003] The slow, progressive loss of central vision is known as macular degeneration. Macular degeneration affects the macula, a small portion of the retina. The retina is a fine layer of light-sensing nerve ceils that covers the inside back portion of the eye. The macula is the central, posterior part of the retina and contains the largest concentration of photoreceptors. The macula is typically 5 to 6 mm in diameter, and its central portion is known as the fovea. While all parts of the retina contribute to sight, the macula provides the sharp, central vision that is required to see objects clearly and for daily activities including reading and driving.

[0004] Macular degeneration is commonly associated with aging (termed Age

Related Macular Degeneration or "AMD") although smokers and individuals with circulatory problems have an increased risk for developing the condition. AMD is the leading cause of blindness in people older than 50 years in developed countries. Between the ages of 52-64, approximately 2% of the population is affected. This rises to about 28% of the population over the age of 75. [0005] There are two forms of macular degeneration, which are known as "wet" and "dry" macular degeneration. Dry macular degeneration blurs the central vision slowly over time and rarely causes total loss of reading vision,

[0006] Wet macular degeneration is more severe than dry macular degeneration.

The loss of vision due to wet macular degeneration also develops much more quickly than dry macular degeneration. This form of the disease is generally characterized by neovascularization, which is the growth of unwanted new blood vessels beneath the macula (Choroidal Neo-Vascularization (CNV) endothelial cells). These choroidal blood vessels are fragile and leak fluid and blood, which causes separation of tissues and damages light sensitive celis in the retina. Individuals with this form of macular degeneration typically experience noticeable distortion of vision such as, for example, seeing straight lines as wavy, and seeing blank spots in their field of vision. While wet AMD comprises only about 20% of the total AMD cases, it is responsible for approximately 90% of vision loss attributable to AMD.

[0007] It has been proposed to provide a device that is particularly suitable for the localized delivery of ionizing radiation for the treatment of macular degeneration. See, U.S. Pub. 2002/0115902A1 to DeJuan, et al., which is incorporated herein by reference. An ionizing radiation-emitting source may be introduced into the eye and the CNV may be directly irradiated, in addition, U.S. App. 11/559,958, filed November 15, 2006, U.S. App. 11/228,030, filed September 15, 2005, U.S. App. 11/056,763, filed February 11 , 2005, U.S. App. 11/593,683, filed November 11 , 2006, U.S. App. 11/780,159, filed July 19, 2007, U.S. Patent No. 6,875,165, issued April 5, 2005, U.S. Patent No. 7,220,225, issued May 22, 2007, U.S. Patent No. 7,223,225, issued May 29, 2007, U.S. Patent No. 7,276,019, issued October 2, 2007, are all hereby incorporated by reference. The exposure of the new blood vessels formed during the wet form of macular degeneration to radiation is understood to provide sufficient disruption of the cellular structures of the new blood cell lesions to reverse, prevent, or reduce the progression of the macular degeneration disease process. Such therapy can potentially restore visual acuity, extend retention of visual acuity or slow the progressive loss of visual acuity. [0008] The present subject matter relates to advances in devices and methods for performing intraocular brachytherapy, in general, and for the treatment of macular degeneration with ionizing radiation, in particular.

SUMMARY

[0009] The subject matter described herein is directed, in part, to a device for delivering ionizing radiation. Specifically, the device preferably includes an ionizing radiation source and a cannula sized for intraocular insertion into an eye and including a proximal end and a distal end for receiving the radiation source. A housing carries the proximal end of the cannula and defines an internal bore. The bore includes an inner surface comprised of a first material. A piston is operably coupled to the radiation source and slidably disposed within the internal bore to move the radiation source between a retracted position within the housing and a treatment position within the cannula. The piston includes a contact surface that slidably interacts with the inner surface of the bore. The contact surface of the piston is comprised of a second material. The first and second materials are chosen such that the contact and inner surfaces slidably interact with sufficiently low friction to allow precision movement of the piston within the bore. The device is particularly suitable for localized delivery of beta radiation for the treatment of macular degeneration.

BRIEF DESCRIPTION OF THE DRAWINGS

[00010] In the course of this description, reference will be made to the accompanying drawing, wherein:

[00011] Figure 1 is a perspective view of one embodiment of a radiation delivery device.

[00012] Figure 2 is a cross-sectional perspective view of one embodiment of a radiation delivery device.

[00013] Figure 3 is a partial cross-sectional perspective view of one embodiment of a radiation delivery device.

[00014] Figure 4 is another partial cross-sectional perspective view of one embodiment of a radiation delivery device. [00015] Figure 5 is an additional partial cross-sectional perspective view of one embodiment of a radiation delivery device.

[00016] Figure 6 is a further partial cross-sectionai perspective view of one embodiment of a radiation delivery device.

DETAILED DESCRIPTION

[00017] In accordance with one aspect of the subject matter disclosed herein, a device is provided that facilitates movement of a radiation source between a stored position and treatment position that is particularly but not exclusively suited for intraocular treatment of macular degeneration.

[00018] With reference to FiG. 1 , the device, generally designated 10, includes a radiation source wire (RSW) 12 terminating in a radiation source (not shown), a housing 14, which incorporates a movable piston 16, and a delivery cannula 18 for positioning at the treatment site. As will be discussed in more detail below, the piston 16 is operably coupled to the RSW 12 and slidably disposed within the housing 14 to move the radiation source between a retracted position in the housing 14, for shielding for example, and a treatment position in the cannula 18.

HOUSING

[00019] The radiation delivery device 10 is preferably, but not necessarily, handheld to facilitate control and positioning of the radiation source during use. As illustrated in FIG. 2, the housing 14 is generally elongated and sized for convenient holding by a physician. The housing 14 is generally hollow and includes has an internal bore 30 defining a generally elongated cylinder 20 for slidably receiving the piston 16. The illustrated housing 14 is closed at its proximal end by a rear hub or cover 22 and at its distal end by a removable cannula hub 24, to which the cannula 18 is mounted. The dimensions of the housing 14 may be selected as desired. For example, the housing may be sized and shaped for ergonomic convenience, if it is intended to be held by a physician. Alternatively, it may be sized or shaped for cooperation with other devices, such as robotic surgical instruments. If shaped for ergonomic finger or hand positioning, the distal end of the housing may have an hourglass or other suitable shape; however, other configurations or contours of the housing may also be used. Also, the length needs to be sufficient to accommodate retraction of the RSW 12 and radiation source into a shielded position within the housing.

[00020] The internal bore 30 of the cylinder 20 within the housing 14 is sized to receive the piston 16, movement of which advances and retracts the RSW 12 and associated radiation source. The internal bore 30 has an inner surface 32 that interacts with the surface of the piston 16, as the piston 16 slides within the bore 30. The inner surface 32 of the bore 30 is preferably comprised of a material that allows the piston 16 to slide with sufficiently low friction so that precision movement of the piston 16 within the bore may be achieved. Preferably, the material forming the inner surface of the bore 30 is highly durable, very low friction material such as an amorphous solid material and, more specifically, a glass or ceramic material or combination thereof. [00021] The housing 14 may have a separate case 28 that surrounds a cylinder 20, or the housing 14 and cylinder 20 may be made integrally of one-piece construction. The surface 32 of the bore 30, which is preferably of extremely durable, low friction material, may be separately coated or formed on the surface, or also of integral one- piece construction with the cylinder. If the housing is made separately, it may be of any suitable material including plastic or metal. The thickness or material of the housing also is preferably sufficient to block or shield radiation from the source when it is located in the retracted position within the housing.

CANNULA

[00022] The cannula 18 is used to direct or guide the radiation source to the treatment site of the eye. Preferably, the cannula 18 is sized to be suitable for insertion into a standard intraocular incision. In the embodiment illustrated in FlG. 3, the cannula 18 has an elongated small-diameter cylindrical shape (preferably 1.0 mm or less). The cannula 18 includes at least one interior iumen for receiving the RSW 12 and is closed at its distal end. Although the cannula 18 is depicted as cylindrical in shape, other shapes may be used as desired. Preferably, the distal end of the cannula 18 may be curved or bent at an angle to facilitate proper alignment of the radiation source at the treatment site, such as the macula of the human eye.

[00023] Preferably, the lumen of the cannula 18 is sized to receive the radiation source and allow easy low friction movement of it through the cannula 18. Typically, the diameter of the lumen is substantially uniform and may range from about 0.6 to about 1.0. The diameter of the cannula may taper towards the distal end to provide more precise placement of the radiation source. The length of the cannula 18 is of such suitable length as may be required, but typically no more than a few inches long for accessing the back of the eye. it is to be understood that that the diameter and length of the cannula 18 that enters the incision may vary depending on the particular procedure performed, the size of the incision made (which may be a standard vitrectomy incision) and the distance from the incision to the treatment site.

[00024] Because the cannula 18 is exposed to bodily fluids, the cannula 18 may be a disposable / "single-use" article or one that may be resterilized. The cannula 18 may be constructed from conventional materials such as stainless steel or rigid plastic; however, any other suitable material may be used that can withstand common sterilization techniques and passes radiation sufficiently to allow radiotherapy treatment from the radiation source to the target tissue.

CANNULA HUB

[00025] The illustrated cannula 18 is attached to the housing 14 by the cannula hub 24. The cannula hub 24 is preferably a selectively removable member that is attached to the cannula and can be disposed of after use. The illustrated cannula hub 24 includes an aperture or opening 40, into which the cannula 18 is inserted upon manufacture, As illustrated in Figure 3, the opening 40 is defined by a guide tube 42 positioned in the cannula hub 24. The cannula 18 may be bonded to the cannula hub 24 by epoxy adhesive but other methods of attachment including mechanical interfit may be used. Together, the guide tube 42 and cannula 18 define a passageway 44 through which the RSW 12 can be moved by movement of the piston 16. The guide tube 42 helps direct the RSW 12 into the cannula 18 during the RSW movement from the retracted position to the treatment position. When the cannula hub 24 is attached to the cylinder 20, the proximal end of the guide tube 42 extends into the housing 14. As iiiustrated in FIG. 3, the proximal end of the guide tube 42 may take the form of a funnel or other suitable shape to help direct the RSW 12 into the guide tube 42. [00026] To allow attachment and removal of the cannula hub 24 to and from the housing 14, preferably, the distal end of the housing 14 defines a fitting hub 46 as illustrated in FlG. 3. The fitting hub 46 engages a mating portion 48 defined on the cannula hub 24. Preferably, the fitting hub 46 and the mating portion 48 have corresponding threaded portions (threads not shown) that can be engaged by simple twisting motion and allow removable attachment of the cannula hub 24, so that it can be disposed of after use. However, other removable attachment means such as bayonet lock or other arrangements may be used. Preferably, the engagement between the cannula hub 24 and the distal end of the housing 14 is airtight to prevent the leakage of fluid. In the embodiment iiiustrated in FIG. 3, two methods of sealing the cannula hub 24 to the housing 14 are provided. First, an elastomeric O-ring seal 73 is located in a channel 75 in the cannula hub 24 to engage the outer surface of the fitting hub 46. In addition, an elastomeric flat seal ring 76 is positioned in a channel 78 defined in the cannula hub 24. The sea! ring 76 interacts with the end of the fitting hub 46. Both the O- ring seal 73 and the flat seal ring 76 are constructed from any suitable material to seal the cannula hub 24 to the housing 14.

RADIATION SOURCE

[00027] The radiation source for the RSW 12 may be any suitable ionizing radiation emitting material, which may be a radioactive isotope, such as a beta radiation emitting isotope or gamma radiation emitting isotope, or an x-ray emitter such as a miniature x-ray generator, for carrying out a radiotherapy treatment of the target tissue associated, for example, with macular degeneration. Such is described, for example, in U.S. Patent No. 7,220,225 to DeJuan, fully incorporated by reference herein. [00028] Preferably, but not exclusively, the radiation source is an essentially beta emitting material, such as a Strontium/Yttrium 90 (Sr-90/Y-90) beta emitting isotope. The radiation source may typically have a source activity of approximately 11 mCi and a location of about 1-3 mm from the target tissue (preferably about 2-2.8 mm), the treatment duration is relatively short, approximately 3-5 minutes. When delivering ionizing radiation, the device 10 preferably provides radiation to a target site at a dose rate of from approximately 4 to 10 Gy/min; with a preferred target dose of between approximately 10 and 40 Gy, with the target dose more preferably being approximately 24 Gy for neovascularized tissue.

[00029] The preferred embodiment of the radiation source includes a cylindrical aluminum insert that is doped with the Sr-90/Y-90 isotope in accordance with conventional techniques and preferably resides inside a sealed stainless steel canister. The stainless steel canister may be mounted to a solid or braided wire made of stainless steel or other suitable material to form the RSW 12. The RSW 12 may further include a relatively flexible distal or leading strand and relatively stiffer proximal strand. Specifically, the flexibility of the leading strand is such as to allow unimpeded mechanical transport of the RSW 12 though the cannula 18 and around a radius of curvature from about 4 to 8 mm. Examples of suitable RSW 12 are described in more detail in the U.S. patent applications serial Nos. 11/056,763, filed February 11 , 2005 and 11/593,683, filed November 7, 2006, all of which are hereby incorporated herein by reference.

RADIATION BARRIERS

[00030] For added safety, the device 10 typically includes a radiation barrier to provide a physician, patient and others in the operating area with protection from the radiation source. In the retracted position, the radiation source is preferably stored within a shielding zone in the housing 14. The shielding zone may be a separate shield 50 constructed of conventional materials suitable for shielding the radiation from the particular radiation material being utilized and/or alone or in combination with other radiation (such as radiation known as brehmsstrahiung). The shield may, for example, be of tungsten steel or lead. However, any other suitable materials or combination of materials that can shield radiation may be used. In the embodiment illustrated in FIG. 3, the shield 50 is generally located at or near the distal end of the housing 40 and, more specifically, may be attached to the distal end of the cylinder 20. The thickness of the shield 50 is sized to sufficiently block the radiation from the device 10 such that those in the general area of the device 10 are sufficiently protected from the radiation, in one embodiment, the shield may be a solid cylindrical piece that is positioned in the internal compartment of the housing 40. As illustrated in FIG. 3, the shield 50 defines a passageway 52 through which the RSW 12 can be moved. The passageway 52 is preferably sized to receive the RSW 12 and allow easy, preferably very low friction movement of the RSW 12 by the piston 16.

[00031] As discussed previously, the housing 14 includes a passageway 44 through which the RSW 12 can be moved. The passageway 44 is preferably defined by the guide tube 42 and cannula 18. When the RSW 12 is in the retracted position, preferably a radiation barrier 43 closes or otherwise limits the escape of radiation through the passageway. Radiation barrier 43 may include an elastomeric or other suitable radiation portal seal gasket 45 to affect a seal to the inside of the fitting hub 46, to minimize unintended radiation emission.

PISTON

[00032] As noted above, the housing 14 includes a piston 16 for moving the radiation source between the retracted and treatment positions. The piston 16 is slidably disposed within the internal bore 30 of cylinder 20 and is operably coupled to the radiation source via the RSW 12.

[00033] The piston 16 is of such suitable size as may be required to be received by the cylinder 20, but typically the diameter of the piston 16 is no more than an inch or fraction thereof. As mentioned above, to ensure smooth and relatively easy movement (i.e. little or almost no friction) of the piston 16 through the cylinder 20, the piston 16 includes a contact surface 34 that slidably interacts with inner surface 32 of the bore 30. Preferably, the contact surface 34 (best seen in FIG. 4) is constructed of highly durable, very low friction material such as a carbon material and more specifically, graphite. Preferably, the contact surface 34 allows the piston 16 and cylinder 20 to slidably interact with sufficiently low friction to allow precision movement of the piston 16 within the bore 30. The contact surface 34 of the piston 16, may be separately coated or formed on the surface of the piston 16, or also of integral one-piece construction with the piston 16.

[00034] To obtain sufficiently low friction and allow for precision movement of the radiation source, the materials of the surfaces preferably have very similar static and dynamic coefficients of friction. This can significantly reduce, if not eliminate, the frictional forces that may initially hold the piston 16 in place or inhibit the piston 16 during movement. As discussed above, preferably one of the surfaces is constructed of an amorphous soiid material such as glass and the other surface of a carbon material such as graphite. A preferred piston/cylinder combination including a glass cylinder and a graphite piston is available from Airpot Corporation of Norwalk, Conneticut. [00035] The combination of the graphite contact surface 34 on piston 16 and the glass inner surface 32 of the cylinder 20 has been found to substantially reduce the static and dynamic forces that typically bind a conventional piston in place and which requires a substantial initial force to induce movement. The described glass cylinder/graphite piston combination may, of course, be reversed. In other words, the cylinder can be comprised of graphite and the piston member can be comprised of glass. Also, other combinations of materials presently known or later discovered that generate little or no static friction may be used in the piston assembly of the present disclosure.

[00036] The piston 16 is operably coupled to the radiation source via the RSW 12. In the embodiment illustrated in FIG. 4, the piston 16 includes a central aperture 36, through which the RSW 12 extends. The RSW 12 may be fixedly or removably connected to the piston 16. The RSW 12 may be fixedly attached to the piston 16 by known means such as, for example, adhesives or mechanical interfit. Preferably the RSW 12 is removably secured to the piston 16 by means such as, for example, the RSW 12 and piston 16 having corresponding threaded portions (threads not shown) that allow removable attachment of the RSW 12, so that the device 10 can be used after resteriiizing. [00037] The piston 16 divides internal bore 30 into a first chamber 54 disposed between rear hub 22 and piston 16 and a second chamber 56 disposed between shield 50 and piston 16. By appropriately introducing pressurized fluid, such as air or hydraulic fluid, into the first chamber the piston 16 can be precisely forced to siidably translate and therefore move longitudinally along an axis. As a result, the RSW 12 can be advanced between the retracted position and the treatment position and intermediate positions.

[00038] Fluid may be introduced into and released from first chamber 54 via a port 60 disposed through rear hub 22. Fluid under pressure may be introduced into and released from second chamber 56 via a port. Depending on the application, conventional hydraulic or pneumatic hoses can be in fluid communication with ports 60 and 62. In the illustrated embodiment, an end cap 64 is mounted on the proximal end of the housing 40 and more specifically to rear hub 22. End cap 64 defines an extension 66 with which a standard air compressor or other fluid source may communicate. [00039] When fluid is introduced into first chamber 54 through fluid port 60 and under sufficient pressure to overcome any small counteracting forces, piston 16 is driven toward cannula hub 24. Any fluid in second chamber 56 is displaced through fluid port 62. Thus, extension of piston 16 and coupled RSW 12 is preferably controlled by the selective introduction of pressurized fluid into the hollow cylinder 20. [00040] The piston 16 and radiation source may be biased to normally reside in the retracted position. In the illustrated embodiment, the piston 16 is biased by a spring force; however, other biasing force devices or systems (e.g. compressed gas) may be used. This biasing force helps maintain the radiation source within the radiation shielding zone during non-use. Preferably, the piston 16 and thus the RSW 12 can only move when pressurized fluid is introduced into the cylinder 20 and overcome the biasing force as described above. Otherwise, the piston 16 and RSW 12 are biased to normally reside in the retracted position.

[00041] In the embodiment illustrated in FIG. 4, the spring force is supplied by a spring 70. Preferably, only one spring needs to be used; however, a plurality of springs may also be used, in this embodiment, the spring 70 is a constant force spring that is rotatably mounted on shaft 72 in the rear hub 22. The distal end of spring 70 is secured to an attachment hub 74 of the piston 16. A constant force spring of the type illustrated is a roll or coil of prestressed material such as plastic or metal which exerts a nearly constant restraining force to resist uncoiling. Thus, the spring 70 helps return the piston 16 and RSW 12 to their retracted positions after they have been moved to the treatment position by the introduction of pressurized fluid into the cylinder 20. The use of a constant force biasing system allows the force that moves the piston 16 to the treatment position to be potentially more controllable and limited in contrast to a structure where the force must increase to overcome the changing force, e.g., of a compressed spring which is the result of the classic spring force equation F=Kx, where F is the force, K is the spring constant and x is the distance compressed or extended. [00042] To help return the piston 16 and RSW 12 to the retracted position, a vacuum source may be in communication with the first chamber 54 to remove the fluid and assist in retracting the piston 16 along with the spring force.

RSW POSITION SENSOR

[00043] To sense whether the radiation source is in one of the retracted or treatment positions, the device 10 preferably includes a position sensor. The position sensor may be either of the Hall-effect or Giant Magnetoresistance (GMR) type that senses the strength of a magnetic field; however, other suitable sensors may be used. [00044] The illustrated example position sensor includes a magnet 80 and at least one sensing device. As shown in FIG. 2, the magnet 80 is fixed to the distal end of the piston 16; however, the magnet 80 can also be fixed to any other location on the piston 16 provided that it acts on the sensing device, or the parts may be reversed. In the illustrated embodiment, the sensing device 82 is positioned within a ring 86 mounted on the distal end of the exterior of the cylinder 20. As best seen in FIG. 2, the ring 86 typically spans at least a portion of the space between the cylinder 20 and the outer case 28 of the housing 14. The sensing device 82 is fixed in place relative to the housing 14 while the magnet 80 moves with the piston 16, as it is slidably translated within the cylinder 20. The sensing device 82 picks up variations in the magnetic flux generated by the movement of the magnet 80 through the cylinder 20 and sends a corresponding feedback voltage signal to a controller, such as via wires (not shown) passing through the housing 14 and a port 23 in the rear hub 22. [00045] When the piston 16 is in a retracted position, such as shown in FiG. 2, the magnet 80 acts only weakly on the sensing device 82, which, as a result, sends a low voltage to the controller. When the piston 16 moves toward the distal end of the housing 14 and reaches the treatment position, as shown in FIG. 5, the influence of the magnet 80 on sensing device 82 is increased as compared to that of the retracted position, and the voltage increases, resulting in a different signal.

[00046] Preferably, an additional sensing device 84 can be included that is positioned within a ring 88 mounted on the proximal end of the exterior of the cylinder 20. The feedback voltage of sensing device 84 in each position is the opposite of the voltage of sensing device 82. Thus, for sensing device 84, the voltage is high when the piston 16 is in the retracted position and low when the piston 16 is in the treatment position. Additional sensing devices can be added to sense the position of the piston 16 at different locations. As illustrated in FIGS. 2 and 5, preferably, the device 10 includes sensing device 82 to sense when the piston 16 is fully in the treatment position and sensing device 84 to sense when the piston 16 is fully in the retracted position.

CANNULA HUB LOCK /SENSOR

[00047] As described above, the cannula 18 can be selectively removed from the housing 14 (for example, via the cannula hub 24). For safety purposes, preferably, the cannula 18 is not removable from the housing 14 unless the radiation source is in the retracted position. Preferably, a lock associated with the housing 14 prevents the removal of the cannula 18 when the radiation source is not in the retracted position. In the embodiment illustrated in FIG. 5, the lock employs a piston movably disposed within the housing 14; however, any other suitable lock mechanism may be used. As illustrated, the lock is located at or near the distal end of the housing 14. [00048] Specifically, the piston 90 is disposed within a cavity 96 of a casing 94 which defines an entry passageway 98 and exit passageway 100. An elongated member 92 is attached to the distal end piston 90. In use, pressurized fluid is introduced through the entry passageway 98 into the cavity 96 and displaces the piston 90. As a result, a portion of the elongated member 92 is advanced through the exit passageway 100 and into a pocket 102 defined in the cannula hub 24. The interaction between the pocket 102 and elongated member 92 prevents the removal of the cannula hub 24 by restricting the twisting motion required to remove the hub 24. Preferably, a biasing member, such as a spring 104 is positioned in the cavity to bias the piston 90 and elongated member 92 to the retracted position when the pressurized fluid is not being introduced into the cavity; however, other means of returning the piston may be used, for example, a vacuum. The pressurized fluid is preferably the same fluid that is used to advance the piston 16 and the radiation source. Preferably, an air passageway is defined typically by a tube disposed between the case 28 and the cylinder 20 of the housing 14. The tube may run up through the housing 14 and a port 23 in the rear hub 22 for connection to a control device (not shown). Thus, the tube is in fluid communication with the fluid source and the entry passageway 98 of the piston assembly.

[00049] To assess whether the cannula 18 is properly attached to the housing 14, the device 10 may include a cannula sensor assembly that preferably includes a target 110 and target sensor 112 that is adapted to sense the target 110 to determine when the cannula hub 24 is properly attached to the housing 14. The target 110 and target sensor 112 may be disposed at any location in the device 10 where the target sensor 112 can sense the target 110 when the cannula hub is attached. For example, the target 110 may be disposed in the cannula hub 24 and the target sensor 112 in the housing 14, as shown in FIG. 6; however, of course the placement of the target 110 and target sensor 112 may be reversed. The wires for such sensor may through the housing 14 and a port 23 and into the rear hub 22 for connection to a control device (not shown).

[00050] The target 110 is preferably a magnet or any magnetized material that can be oriented in any direction. The magnet is preferably attached to the cannula hub 24 by adhesive or any other suitable attachment means. The target sensor 112 is positioned adjacent to the magnet 110; however, the target sensor 112 is preferably positioned in the distai end of the housing 14 as depicted in FIG. 6. The target sensor 112 may be a Hall-effect or GMR type that senses the strength of a magnetic field from the target 110. The target sensor 112 detects the attachment of the cannula hub 24 to the housing by sensing the change in magnetic force when the target 110 moves toward the target sensor 112. Preferably, the target sensor 112 sends a corresponding signal to a controller (not shown) to notify the user that the cannula hub 24 and ultimately the cannula 18 is properly attached to the housing 14. The controller may iimit further operation or function, or generate an alarm, in the event the cannula is not sensed as being properly attached. Alternatively, the target sensor 112 may be a proximity sensor that detects the proximity of the cannula hub 24 and ultimately the target 110 to the housing 14 without using a magnet.

USE SENSOR

[00051] In order to enhance patient safety, the device 10 preferably further includes a detector for determining prior use of the cannula 18. The detector typically comprises a first surface associated with one of the cannula 18 and housing 14 that interacts with a second surface associated with the other of the cannula and housing. When the two surfaces interact, at least one of the surfaces is irreversibly altered in a detectable manner.

[00052] In the embodiment illustrated in FIG. 3, the first surface is what is commonly referred to as an RFID chip 114 encoded to identify a new cannula hub 24 or other relevant values. The RFID chip 114 can be preprogrammed or programmable as is well understood in the art. The chip may be placed in a container, for example, a disk, in order to contain and protect the RFID chip 114. The RFID chip 114 is positioned within the cannula hub 24 such that it can interact with the second surface when the piston is advanced to its final position.

[00053] The second surface is an altering device, such as a magnet 80, that is associated with the movable piston 16 in the housing. Once the piston 16 is advanced to fully deploy the radiation source, the magnetic field of the magnet 80 interacts with the RFID chip 114 and permanently alters the encoding of the RFiD chip 114. The magnet 80 may be the same magnet as is used for the position sensor; however, an additional magnet may also be used. This alteration of the encoding allows the user to detect, using a standard RFID reader that the cannula hub 24 has already been used. Therefore, before each use of the removable cannula hub 24, the user can place a cannula hub 24 near an RFID reader and determine whether or not the particular cannula hub 24 has already been used. A signal may be transmitted, to provide such indication, via wires that run up through the housing 14 and a port 23 and into the rear hub 22 for connection to a control device (not shown),

[00054] In an alternative embodiment, the first surface in the cannula hub 24 is a plate constructed of material such as ceramic. The plate is at least partially covered in a conductive coating, for example, goid. The plate is positioned to interact with the second surface, for example, at least two pins located near the distal end of the housing. When the cannula hub 24 is attached, the pins of the second surface contact the conductive coating and then contact the ceramic plate of the first surface. As the cannula hub 24 is being attached, a control system picks up a high conductivity signal when the pins contact the coating. Then, once the cannula hub 24 is fully attached to the housing the ceramic plate will break due to the pins being advanced through the plate and thus the high conductivity signal is eliminated. Preferably, the plate is positioned under a plug in the cannula hub 24 that can be pierced by the pins but that also can then contain the broken ceramic plate. In a further alternative embodiment, the first surface positioned in the cannula hub 24 to interact with the two pins would consist of at least two materials. A highly conductive material, for example, gold, would be coated with a less conductive material, for example, silicone. As the cannula hub is being attached to the housing, the second surface pins would register two different conductivity signals as it passed through the silicone and then interact with the gold. During a reattachment of the cannula hub, the sensor tips wouid pick up different conductivity signals because the silicone would be displaced during the first attachment.

[00055] The foregoing description of the subject matter is merely illustrative thereof, and it is understood that variations and modifications can be effected without departing from the scope or spirit of the subject matter as set forth in the following claims. For example, although the present subject matter is described in detail in connection with ophthalmic surgical procedures, particularly in connection with the treatment of AMD, the present invention is not limited to use on the eye. Rather, the present invention may be used on other areas of the body to treat various conditions such as, for example, the prevention of restenosis.

Claims

1. A radiation delivery device comprising: a radiation source; a cannula sized for intraocular insertion into an eye and including a proximal end and a distal end for receiving the radiation source; a housing carrying the proximal end of the cannula, the housing defining an internal bore, the bore including an inner surface comprised of a first material; a piston operably coupled to the radiation source and slidabiy disposed within the internal bore to move the radiation source between a retracted position within the housing and a treatment position within the cannula; the piston including a contact surface that slidabiy interacts with the inner surface of the bore, and wherein the contact surface of the piston is comprised of a second materia!; the first and second materials slidabiy interacting with sufficiently low friction to allow precision movement of the piston within the bore,

2. The radiation delivery device of claim 1 wherein the first material is comprised of a glass or ceramic material or combination thereof.

3. The radiation delivery device of claim 2 wherein the second material is comprised of carbon

4. The radiation delivery device of claim 1 wherein the housing includes a shielding zone for shielding the radiation source in the retracted position.

5. The radiation delivery device of claim 1 wherein the housing includes a position sensor for sensing when the radiation source is in one of the retracted position or treatment position.

6. The radiation delivery device of claim 5 wherein the housing includes a second position sensor for sensing when the radiation source is in one of the retracted position or treatment position,

7. The radiation delivery device of claim 1 wherein the piston is biased to normally reside in the retracted position.

8. The radiation delivery device of claim 7 wherein the piston is biased by a spring force.

9. The radiation delivery device of claim 1 wherein the cannula is selectively removable.

10. The radiation delivery device of claim 9 wherein the cannula is not removable from the housing unless the radiation source is in the retracted position.

11. The radiation delivery device of claim 10 wherein a lock mechanism associated with the housing prevents the removal of the cannula.

12. The radiation delivery device of ciaim 9 further including a detector for determining prior use of the cannula.

13. The radiation delivery device of claim 12 wherein the detector comprises a first surface associated with one of the cannula and housing that interacts with a second surface associated with the other of the cannula and housing; whereby when the surfaces interact, at least one of the surfaces is irreversibly altered in a detectable manner.

14. The radiation delivery device of claim 9 wherein a target is associated with one of the cannula and housing and a target sensor is associated with the other of the cannula and housing, whereby the target sensor is adapted to sense the target to determine when the cannula is carried by the housing.

15. The radiation delivery device of claim 1 wherein the housing defines a passageway that allows movement of the radiation source to the treatment position, and the radiation delivery device further comprises a radiation barrier that limits the escape of radiation through the passageway when the radiation source is in the retracted position.