Surgery – Instruments – Light application
Reexamination Certificate
1999-09-07
2001-08-07
Nasser, Robert L. (Department: 3736)
Surgery
Instruments
Light application
C606S007000, C606S013000
Reexamination Certificate
active
06270492
ABSTRACT:
BACKGROUND OF THE INVENTION
The technical field of this invention is phototherapy and, in particular, methods and devices which employ optical fibers or other flexible light waveguides to deliver radiation to a targeted biological site.
Fiber optic phototherapy is a increasing popular modality for the diagnosis and/or treatment of a wide variety of diseases. For example, in surgery, infrared laser radiation will often be delivered to a surgical site via a hand-held instrument incorporating an optically transmissive fiber in order to coagulate blood or cauterize tissue. Similar fiber optic delivery systems have been proposed for endoscopic or catheter-based instruments to deliver therapeutic radiation to a body lumen or cavity. U.S. Pat. No. 4, 336,809 (Clark) and U.S. Reissue Patent No. RE 34,544 (Spears) disclose that hematoporphyrin dyes and the like selectively accumulate in tumorous tissue and such accumulations can be detected by a characteristic fluorescence under irradiation with blue light. These patents further teach that cancerous tissue that has taken up the dye can be preferentially destroyed by radiation (typically high intensity red light) that is absorbed by the dye molecules during phototherapy.
Others have proposed the use of fiber-delivered radiation to treat artherosclerotic disease. For example, U.S. Pat. No. 4,878,492 (Sinofsky et al.) discloses the used of infrared radiation to heat blood vessel walls during balloon angioplasty in order to fuse the endothelial lining of the blood vessel and seal the surface. Another application of fiber-delivered radiation is disclosed in U.S. Pat. No. 5,053,033 (Clarke) which teaches that restenosis following angioplasty can be inhibited by application of UV radiation to the angioplasty site to kill smooth muscle cells which would otherwise proliferate in response to angioplasty-induced injuries to blood vessel walls.
Nonetheless, a number of problems limit the expanded use of fiber-optic phototherapy. Typically, an optical fiber emits light from only its end face. Thus, the emitted light tends to be focused or at best divergent in a conical pattern and, therefore, exposes only a small region directly in front of the fiber's distal end. The small exposure area limits the power available for phototherapy since overheating of the target tissue must often be avoided.
Although “sideways-emitting” fibers have been proposed to permit greater flexibility in phototherapy, this approach still does not allow uniform irradiation of large volumes of tissue and can also be ill-suited for applications where circumferential uniformity is desired. Because sideways-emitting fibers expose limited regions, they do little to alleviate the problem of “hot spots” which limit the intensity of radiation which can be delivered via the fiber to the treatment site.
Others have proposed diffusive tips for optical fibers to enlarge the region which can be irradiated and/or reduce the potential for overexposure. However, diffusive tips have not been satisfactory for many therapeutic purposes because of their complexity of manufacture and/or because the radiation may not be scattered uniformly enough to alleviate the problem of “hot spots.” Prior art diffusive tip structures have not be capable of delivering high power radiation, e.g., on the order of ten watts or more, to facilitate photocoagulation therapy or the like.
There exists a need for better apparatus for fiber-optic phototherapy. In particular, diffusive fiber tip assemblies which can provide circumferential (or large angle) exposure regions in radial directions (e.g., sideways) relative to the fiber axis without hot spots would satisfy a long-felt need in the art. Moreover, diffusive assemblies which illuminate or irradiate an azimuthal angle of less than 360° would meet a particularly important need in the field of minimally-invasive, phototherapeutic surgery. In addition, diffusive fiber tip assemblies which can extend the longitudinal extent of irradiation and provide greater flexibility during use would likewise satisfy a need in phototherapy.
In addition, there exists a need for controlling or reduced unwanted heating effects during phototherapy. Typically, light can be delivered to the site of the desired phototherapeutic reaction by inserting a fiber-optic cable into a patient and maneuvering it to the site of the desired photochemical reaction. The position of the fiber's tip can be monitored by including a metallic structure at the tip and monitoring the position of the metallic structure, either visually or by x-ray fluoroscopy. Additionally, metallic structures are sometimes used to reflect light and to thereby control the illumination field within the patient.
When illuminated by light, these metallic structures absorb a small, yet significant amount of optical energy and reradiate it as heat. Since the metallic structures of phototherapeutic instruments are generally in contact with or proximate to surrounding tissue, the rise in temperature of these structures can inflict heat-induced tissue damage on surrounding tissue or melt catheters in the vicinity of the fiber's tip.
Accordingly, there exists a need for better methods and apparatuses for preventing the metallic structure in phototherapeutic devices from being heated excessively by incident light during use.
SUMMARY OF THE INVENTION
Methods and apparatus are disclosed for diffusing radiation from a optical fiber to provide a larger exposure area for phototherapy. The methods and apparatus are particularly useful as part of a fiber optic-based medical laser system. The present invention can further provide substantially uniform energy distribution to a major portion of the exposure area. The invention is especially useful in constructing and implementing circumferential and/or sideways-emitting diffusive tip assemblies for optical fibers to direct laser radiation in a radially outward pattern relative to the fiber's axis. As used herein the term “optical fiber” is intended to encompass optically transmissive waveguides of various shapes and sizes.
In one aspect of the invention, an optical transmissive fiber tip structure is disclosed having a radiation-scattering particles and a reflective end. As radiation propagates through the fiber tip, the radiation is scattered. Each time the radiation encounters a scatterer particle, it is deflected until some of the radiation exceeds the critical angle for internal reflection and exits the tip Radiation which is not emitted during this initial pass through the tip is reflected by at least one end surface and returned through the tip. During this second pass, the remaining radiation (or at least a major portion of this returning radiation) again encounters the scatterers which provide further radial diffusion of the radiation.
In one embodiment, a diffusive tip assembly is disclosed for diffusing radiation from an optical fiber. The tip assembly includes a light transmissive, tubular housing alignable with, and adapted to receive, the distal end of the fiber and serve as a waveguide for light propagating through the fiber. The assembly further includes a reflective end cap and a light scattering medium disposed therein such that light propagating through said fiber enters the scattering medium and a portion of the light escapes outward through the housing, and another portion passes through the scattering medium and is reflected by the end cap for retransmission through said scattering medium.
The reflective surfaces of the apparatus can also be modified to effect non-cylindrical or non-spherical exposure patterns. Reflective structures are disclosed which control the azimuthal extent of the light emitted from the tip. These techniques and structures permit, for example, 270 degrees, 180 degrees or even smaller angles of azimuthal exposure. The term “large angle exposure” is used herein to describe partially cylindrical (or partially spherical) exposure patterns having a azimuthal angle of more than about 90 degrees.
In another aspect of the invention, the amo
CardioFocus, Inc.
Engellenner Thomas J.
Nasser Robert L.
Nutter & McClennen & Fish LLP
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