Phototherapy Device and Method

1. Field of the Invention

The present invention pertains to a phototherapy device and method, and more particularly to a handpiece and method for advancing an optical fiber.

2. Description of the Related Art

Devices and methods for performing various types of laser surgery using optical fibers have become widespread. One relatively new application is myocardial revascularization which is used as an alternative to coronary artery bypass surgery. Trans-myocardial revascularization is a method for treating ischemic heart disease in which the heart muscle or myocardium does not receive an adequate blood supply. Trans-myocardial revascularization helps supplement the blood supply delivered to the heart by providing the heart muscle with direct access to blood within the ventricle chamber.

Lasers have been proposed in trans-myocardial laser revascularization to produce channels in the ventricle wall. The channels provide blood flow to the ischemic heart muscle. Optical fibers are useful for directing laser energy to the desired regions of the heart muscle. However, in order for lasers to be effective in trans-myocardial revascularization, the energy from the laser must be concentrated on a narrow region of the heart tissue. As tissue is ablated, if the optical fiber is held in a fixed position, the surface being cut moves away from the area of greatest laser energy concentration. Consequently, optical fibers are advanced in the cutting direction as the tissue is ablated in order to concentrate energy on the heart tissue. In other words, one may think of the optical fiber as ablating a channel through the heart tissue. If the laser energy is not concentrated on a sufficiently narrow region of the heart tissue, the laser begins to heat up regions of the heart tissue without ablating narrow regions of tissue. This can lead to blood coagulation and damage to the heart tissue.

Devices are known in the art for advancing optical fibers using electric motors. However, such devices are complicated and expensive.

Mechanical devices are also known in which optical fibers are advanced manually by the operator through a rack-and-pinion type of mechanism. However, such devices have the disadvantage that it is difficult to control the speed of the forward advancement since the speed depends on the operator moving a lever or some similar mechanical device.

Accordingly, it is an object of this invention to provide a mechanical device which advances an optical fiber in a phototherapy device at a substantially constant rate of speed.

It is another object of this invention to provide a phototherapy device which provides the operator with good control over the advancement of an optical fiber.

It is another object of this invention to provide a trans-myocardial laser revascularization device in which an optical fiber is advanced at substantially a constant rate of speed by a mechanical device which is easily controllable by the operator.

It is a further object of this invention to provide a trans-myocardial laser revascularization method.

The above and related objects of this invention are realized by providing a phototherapy handpiece having a drive assembly which mechanically advances an optical fiber attached to the phototherapy handpiece in the direction of the emitted radiation, at substantially a constant speed.

The drive assembly has a driving component, preferably a spring, which forces the optical fiber in the direction of the emitted radiation. However, since driving components such as springs alone do not generate a constant forward motion to an object attached to an end of the spring, the drive assembly also has a damping component that resists the motion produced by the driving component. Preferably, the damping component is a hydraulic cylinder. Such hydraulic cylinders produce a resisting force which increases with increasing speed. Consequently, the combination of the driving spring and the damping hydraulic cylinder yields a substantially constant speed advancement of the optical fiber in the direction of the emitted radiation.

The phototherapy handpiece preferably has a catch mechanism which holds the optical fiber in a retracted position. The operator of the phototherapy handpiece can release the catch mechanism at a desired moment. Upon releasing the catch mechanism, the driving component (the spring in the preferred embodiment) forces the optical fiber in the direction of the emitted radiation from the end of the optical fiber. The optical fiber advances at a substantially constant rate of speed due to the resistance of the damping component.

In the preferred embodiment, a mechanical limiter is set at a selectable position to stop the forward motion of the optical fiber at a preselected point. The mechanical limiter can be an annular ring which is attached to the outer surface of the phototherapy handpiece in the preferred embodiment. Preferably, the phototherapy handpiece is cylindrical and the mechanical limiter is attached to it by threads. The mechanical limiter can then be rotated to adjust its position.

The laser phototherapy light source is preferably turned on by the action of the catch mechanism as the operator releases the catch such that the optical fiber can move in the direction of radiation being emitted.

The invention also encompasses a trans-myocardial laser revascularization method. According to the trans-myocardial laser revascularization method of this invention, the operator performs work on a phototherapy handpiece, such as by compressing a spring which serves as the drive component in the preferred embodiment. This step can be thought of as loading the phototherapy handpiece. The operator places a distal portion of the phototherapy handpiece in contact with a region of the patient's body. The operator then releases the catch mechanism on the optical fiber drive assembly which permits the optical fiber to move at a substantially constant speed in the direction of the emitted radiation.

These and other objects and advantages of the present invention will be apparent from the detailed description, the accompanying drawings, and the claims.

FIG. 1 is a cross-sectional view of the trans-myocardial laser revascularization device according to a first preferred embodiment of the invention, with the catch mechanism holding the drive assembly in the loaded position;

FIG. 2 is a cross-sectional view of the trans-myocardial laser revascularization device according to the first preferred embodiment of the invention in which the catch mechanism is in a released position;

FIG. 3 is a schematic illustration of the laser revascularization device according to the first preferred embodiment of the invention;

FIG. 4 is a cross-sectional view of a second preferred embodiment of the trans-myocardial laser revascularization device in a loaded position; and

FIG. 5 is a cross-sectional view of the trans-myocardial laser revascularization device according to the second preferred embodiment of the invention with the catch mechanism in a released position.

The trans-myocardial laser revascularization device according to the present invention is designated generally by the reference numeral 10 in FIGS. 1 and 2. The trans-myocardial laser revascularization device 10 has a phototherapy handpiece 12, an optical fiber 14 attached to the phototherapy handpiece 12, and a laser phototherapy light source 15 (see FIG. 3). The optical fiber 14 is attached to the phototherapy handpiece 12 near the distal end 16 of the optical fiber. The proximal end 17 of the optical fiber 14, shown in FIG. 3, is attached to a laser phototherapy light source 15 such that light from the laser is directed into the optical fiber (see FIG. 3). Suitable phototherapy light sources are excimer lasers such as xenon-chloride lasers, or holmium-yttrium-aluminum garnet (Ho:YAG) lasers. The optical fiber 14 may be a single fiber, or a fiber bundle. The term "optical fiber" is used in its general sense in this invention to encompass both a single fiber and a fiber bundle.

As one may best view in FIGS. 1 and 2, the phototherapy handpiece 12 has a handpiece body 18 which defines an interior region. The handpiece body 18 has a portion known as a foot 20. The foot 20 has an outer surface 22 with a much greater surface area than the light emitting end 24 of the optical fiber 14. The large surface area of the outer surface 22 of the foot 20 permits the reduction of applied pressure when the surface 22 of the phototherapy handpiece 12 is brought into contact with portions of the patient's body. A suitable material for the handpiece body 18 is polycarbonate or stainless steel.

The phototherapy handpiece 12 also has a drive assembly 26, a mechanical limiter 28 and a catch mechanism 30. For the first preferred embodiment, the drive assembly 26 has a connecting member 32 attached to an optical fiber attachment portion 34. The connecting member 32 is forced in a distal direction by a driving component 36. In a preferred embodiment, the driving component 36 is a spring which the operator compresses to store energy as potential energy from the work done on the spring while compressing it. However, the invention is not limited to having a spring as the driving component 36. One skilled in the art would recognize that there are numerous embodiments in which one may select a driving component which stores work done as potential energy which in turn can be reconverted back into kinetic energy. Such alternate driving components include, but are not limited to, compressed air cylinders, gravimetric weights, or electromechanical solenoids. The drive assembly 26 also has a damping component 38. In the first preferred embodiment, the damping component 38 has an end 40 with a fixed position relative to the handpiece body 18. The end 40 of the damping component 38 defines a region of contact between the drive assembly 26 and the handpiece body 18 such that the end 40 of the damping component 38 remains substantially fixed relative to the handpiece body 18 as the connecting member 32 and optical fiber connecting portion 34 move.

The damping component 38 supplies a damping force on the connecting member 32 and optical fiber connecting portion 34 with a strength that depends on the speed of the connecting member 32 and directed so as to oppose the motion of the connecting member 32 and optical connecting portion 34. In the preferred embodiment, the damping component 38 is a hydraulic cylinder. However, other types of damping components may be used for the damping component 38 without departing from the scope and spirit of the invention. Such alternative damping components include, but are not limited to air-damped dashpots or turbines.

The catch mechanism 30 is similar to a trigger mechanism and it is pivotally attached at a point 42 in the first preferred embodiment. The catch mechanism 30 has a first position, as one may see illustrated in FIG. 1, which holds the drive assembly in a higher potential energy state, for example, so that spring 36 is compressed. FIG. 2 shows a second position of the catch mechanism 30 in which the catch mechanism 30 is rotated about the pivot point 42. In the second position of the catch mechanism 30 the connecting member 32 and optical fiber attachment portion 34 are free to move without being constrained by the catch mechanism 30. Although the preferred embodiment uses a catch mechanism 30 with a trigger-like structure, other catch mechanisms may be used without departing from the scope and spirit of the invention. Such alternative structures include, but are not limited to, magnetic latches, solenoids, or springloaded detent mechanisms.

If one uses a solenoid catch release instead of the trigger-like catch mechanism 30 of the preferred embodiment, the light source 15 may transmit a signal to activate the solenoid which releases the catch. One may obtain coordination of fiber motion with light emission by causing the signal to coincide with the onset of light emission.

The mechanical limiter 28 is preferably adjustable to set an end 44 of the mechanical limiter 28 to a selectable position. In the first preferred embodiment, the mechanical limiter 28 is connected to the handpiece body 18 by conventional threading 46.

The catch mechanism 30 includes a switch 31, which turns the laser phototherapy light source 15 on when the catch mechanism 30 is changed from the first to the second position.

In operation, the user adjusts the mechanical limiter 28 such that the mechanical limiter end 44 is at a desired position to stop the progression of the optical fiber 14 such that the light emitting end 24 of the optical fiber 14 will be at a pre-selected position relative to the surface 22 of the foot 20. In a preferred embodiment, the mechanical limiter 28 is adjusted by rotating it about an axis 45. The operator performs work on the driving component 36 to store potential energy in the driving component 36. In the preferred embodiment, this is done by compressing the spring 36. The driving component 36 is held in the higher potential energy state by the catch mechanism 30, which one may consider as being a "loaded" position.

The operator of the trans-myocardial laser revascularization device 10 places the surface 22 of the foot 20 in contact with a selectable portion of the patient's body, for example, with a selectable portion of the patient's heart. The large area of the surface 22 helps spread the applied force over a greater area, thus decreasing the applied pressure. This helps prevent tissue damage. When the trans-myocardial laser revascularization device 10 is in position, the operator selects a desired time to initiate phototherapy by pulling the trigger-like catch mechanism 30. By pulling the catch mechanism 30 such that the catch mechanism 30 moves from the first position to the second position, the laser phototherapy light source 15 turns on and the optical fiber 14 becomes free to move under the influence of the driving assembly 26 such that the light emitting surface 24 moves in the direction of the light emission as time progresses.

The force of the spring 36 is opposed by the hydraulic cylinder 38 to produce a substantially constant speed progression of the light emitting surface 24 in the direction of the emission of light. The desired speed of progression of the light-emitting surface 24 of the optical fiber 14 can be selected by selecting appropriate combinations of driving components 36 and damping components 38. For example, one may select springs having various spring constants and hydraulic cylinders with various damping characteristics.

After the operator pulls the trigger-like catch mechanism 30, the optical fiber 14 then moves at a substantially constant speed until it reaches the mechanical limiter 28. The progression of the optical fiber 14 is then stopped by the mechanical limiter 28.

FIGS. 1 and 2 provide schematic illustrations of the surgical effect produced by the trans-myocardial laser revascularization device according to this invention. In FIG. 1, the surgical region of the patient is represented generally by reference numeral 48 at a time before the catch mechanism 30 has been released. FIG. 1 illustrates the light-emitting end 24 of the optical fiber 14 at a time it is pressed into the region 49 before it has cut into the surgical region of the patient 48. As laser energy is emitted from the light-emitting surface 24 of the optical fiber 14, it cuts into the surgical region of the patient 52, as is illustrated in FIG. 2. The surgical energy from the laser is more efficiently and accurately deposited at a specific region by maintaining the light-emitting surface 24 close to the incision point 50 of the surgical region 52 at a time after releasing the catch mechanism 30. If the incision point 50 is allowed to be cut back too far without advancing the optical fiber 14 in the direction of the emitted laser energy, the energy becomes too disperse to cut the tissue and begins to heat and damage the tissue.

A second preferred embodiment of the invention is illustrated in FIGS. 4 and 5, and generally represented by reference numeral 100. The trans-myocardial laser revascularization device 100 according to the second preferred embodiment has a photo-therapy handpiece 112, an optical fiber 114, and a laser photo-therapy light source (not shown in FIGS. 4 and 5). The optical fiber 114 may be a single fiber, or a fiber bundle. The optical fiber 114 has a distal end 116.

The photo-therapy handpiece 112 has a handpiece body 118 which defines a foot 120 having a surface 122. The surface 122 of the foot 120 has a much greater area than the light emitting surface 124 of the optical fiber 114.

The photo-therapy handpiece 112 has an optical fiber drive assembly 126. The second preferred embodiment may include a mechanical limiter 128. A catch mechanism 130 has a first position, as illustrated in FIG. 4, to hold the optical fiber drive assembly 126 in a "loaded" position. The catch mechanism 130 is movably attached to the handpiece body 118 such that it has a second position, as illustrated in FIG. 5, in which it leaves the motion of the optical fiber 114 unimpeded.

In the second preferred embodiment, the optical fiber drive assembly 126 has an optical fiber attachment portion 134 disposed in the interior region of the handpiece body 118. Preferably, the optical fiber attachment portion 134 is a flange which is bonded to the optical fiber 114. The optical fiber drive assembly 126 has a driving component 136 which is preferably a spring, although other drive components can be employed as described above. The spring is preferably in contact with the optical fiber attachment portion 134 at one end, and in contact with the handpiece body 118 at an opposing end. Preferably, a pair of damping components 138 are in contact with the optical fiber attachment portion 134 at one end, and are in contact with the handpiece body 118 at an opposing end 140. In this embodiment, damping components 138 are hydraulic cylinders although other damping components may be employed as described above.

The top surface 129 of the damping component 138 provides a mechanical limiter 128 in one preferred embodiment. In another preferred embodiment of the limiter 129 the damping component 138 has a piston 129 which is stopped by the opposing end 140 of the damping component 138.

The catch mechanism 130 is preferably pivotally attached at a point 142. The handpiece body 118 defines orifices 148 and 150 to permit the optical fiber 114 to pass therethrough. The optical fiber 114 has a radio-opaque marker 152 at the distal end 116 of the optical fiber 114 in a preferred embodiment. Gold and iridium are suitable materials for radio-opaque marker 152.

The operation of the trans-myocardial laser revascularization device 100 according to the second preferred embodiment of the invention is very similar to the operation of the device according to the first embodiment. However, in the second preferred embodiment, the optical fiber 114 enters the handpiece body 118 at the orifice 150 and protrudes through the center of the foot 120. Fiducial markers 154 can be placed on the fiber at the orifice 150, or at other suitable location, to provide visual assurance that fiber motion is attained when the catch mechanism 130 is released. Similar markings can be used with the first embodiment also.

Although the specification describes the trans-myocardial laser revascularization device and method, and the photo-therapy handpiece in detail according to the preferred embodiments, those who are skilled in the art will readily appreciate that many modifications of the preferred embodiments are possible without departing from the novel teachings and advantages of this invention. One such modification would apply the device to excimer laser angioplasty. All such modifications are intended to be included within the scope of this invention as defined in the following claims.