Patent Application
20150190280
The present invention relates to an irradiation method and apparatus, of particular but by no means exclusive application in ablating tissue, and especially soft tissue (such as the retina, vessel wall, trabecular meshwork, or other tissue), in a liquid environment.
Infrared sources, such as CO2, erbium-YAG and holmium:YAG lasers, have undergone trials, involving optical fiber delivery to a surgical target. Though adapted for use in intraocular surgery, problems include collateral, thermal damage to surrounding tissue and shock-wave effects.
UV lasers are widely accepted for use in corneal refractive surgery, such as photorefractive keratectomy (PRK) and laser intrastroma keratomileusis (LASIK), and provide good control of ablation depth and minimal damage to surrounding tissue. However, such systems are adapted for use in gaseous environments—that is, typically the atmosphere.
UV lasers at 266 nm have been extensively studied for use in tissue ablation in liquid environments; they are closely matched to the absorption peak of proteins in some target tissues and afford good control of ablation depth with minimal damage to surrounding tissue.
UV lasers at 213 nm have also been extensively studied for use in tissue ablation in liquid environments. They allow good control of ablation depth and minimal damage to surrounding tissue, but provide poor penetration in liquids. For example, the absorption coefficient (a) depends on the nature and contents of the liquid, which change according to disease and disease advancement, and liquid concentrations: both can be difficult to estimate clinically. For example, absorption coefficient differs from 0.05 to 6.9 cm−1 for 0.9% saline and BSS (Balanced Salt Solution, respectively.
In addition, in UV lasers are often controlled to deliver multiple pulses. However, each pulse produces a certain amount of tissue ablation, thereby changing the distance between illuminating probe and the tissue and the contents and nature of the surrounding liquid. This results in a continually changing surgical environment.
One existing approach is illustrated schematically in
The forward or distal end 22 of optical probe 12 is tapered to a distal tip 24, which is also the exit from which the ultraviolet light 14 is emitted from optical probe 12. In use, there is a liquid layer 26 of the liquid 18 between distal tip 24 and specimen 16, and hence there is also an interface 28 between liquid 18 and distal tip 24, corresponding essentially to distal tip 24.
In use, ultraviolet light 14 is applied to specimen 16 in order to ablate specimen 16 (that is, remove surface portions of specimen 16). This leads, however, to the irradiation of liquid 18 in liquid layer 26 between distal tip 24 and specimen 16, causing changes to its composition, temperature and absorption coefficient. The ablation of specimen 16 also progressively increases the distance between the optical probe 12 and specimen 16, and the material removed by ablation further alters the composition of liquid 18 and hence its absorption coefficient.
Thus, liquid layer 26 between the optical probe 12 and the specimen 16 constitutes a complicated and unpredictable boundary, requiring consideration of (and potentially allowance for) micro-irradiation effects, laser biophysics, laser chemistry, laser biochemistry and probe-specimen distance, precluding a constant operational environment.
According to a first broad aspect, the present invention provides an apparatus for irradiating a specimen (such as to ablate the specimen), the apparatus comprising:
Generally, the optical probe is adapted to be located when in use with the exit in contact with the specimen, in which case the material forward of the optical probe is the specimen.
Thus, the distance between optical probe and the surface (such as the specimen) affects, for example, ablation, so is thus advantageously controlled according to this aspect to be substantially constant. The present invention maintains the distance as effectively zero, which both is simpler to maintain and minimizes the effects of liquid—if used in a liquid environment—between probe and specimen (in those embodiments in which the surface is the specimen). It is expected that, although some liquid may be trapped between the probe and specimen, it will i) be minimal, and ii) be promptly evaporated during use, further reducing its quantity.
Thus, a generally gentle contact can be maintained between tip and specimen.
Although the apparatus is envisaged as principally for use for ablation, it could alternatively be incorporated into a fiberoptic laser endoscope and used to irradiate, for example, tumors (such as of the trachea, oesophagus or stomach). Such an endoscope typically comprises separate optical channels—terminating in the endoscope head—for imaging and specimen irradiation (according to this invention), respectively.
The optical probe could be, for example, solid or capillary, but is typically in the form of an optical fiber or an optical fiber bundle of optical fibers, such that the exit comprises the exit tip of the optical fiber or the exit tips of the optical fibers of the optical fiber bundle, respectively.
In one embodiment, the exit is at a distal tip of the optical probe and configured to emit the light in the longitudinal direction.
In one embodiment, the position detector comprises a force transducer coupled to the optical probe, wherein the force transducer is arranged to output a signal indicative of a force or a change in force between the optical probe and the surface, the feedback controller is adapted to output to the drive a control signal determined from the signal and the drive is adapted to receive the output signal and to control the position so as to maintain a substantially constant force between the optical probe and the surface (such as the specimen).
In another embodiment, the position detector comprises a probe adjacent to or coupled to the optical probe and having a force transducer, wherein the probe is arranged to contact the surface, in use, and output a signal indicative of a force or a change in force between the probe and the surface, the feedback controller is adapted to output to the drive a control signal determined from the signal and the drive is adapted to receive the output signal and to control the position so as to maintain a substantially constant force between the optical probe and the surface.
The apparatus may include a laser source for supplying the laser light. In applications in which the light is ultraviolet light, the laser source may comprise an ultraviolet laser source, or an infrared laser source and a mechanism for converting an output of the infrared laser source into ultraviolet light.
In another particular embodiment, the exit is located to emit the light laterally from the optical probe so as to irradiate the specimen when located beside the optical probe. The probe may be adapted to direct the light to exit the exit by reflecting the light towards the exit (such as with a mirror located in the probe, which may operate conventionally or by total internal reflection).
According to a second broad aspect, the present invention provides an endoscope comprising the apparatus described above.
According to a third broad aspect, the present invention provides an ablation apparatus comprising the apparatus described above.
According to a fourth broad aspect, the present invention provides a method of irradiating a specimen (such as to ablate the specimen), the method comprising:
In one embodiment, the method includes driving the optical probe to maintain a position of the exit against the surface.
The method may include employing a feedback controller to control the drive according to the signal.
In another particular embodiment, the method includes emitting the light laterally from the optical probe and thereby irradiating the specimen located beside the optical probe. The method may include directing the light to exit the exit by reflecting the light towards the exit (such as with a mirror located in the probe, which may operate conventionally or by total internal reflection).
According to a fifth broad aspect, the present invention provides a method of ablating a specimen, comprising the method described above.
It should be noted that any of the various features of each of the above aspects of the invention, and of the various features of the embodiments described below, can be combined as suitable and desired.
In order that the invention may be more clearly ascertained, embodiments will now be described, by way of example, with reference to the accompanying drawing, in which:
System 30 also includes a pair of mirrors 34a,34b that reflect the infrared light into a harmonic generator 36 that emits the infrared light as well as light at harmonic wavelengths 532 nm, 266 nm and 213 nm. Harmonic generator 36 comprises BBO crystals for generation of the second harmonic and CLBO crystals for generation of the fourth (266 nm) and fifth (213 nm) harmonics.
System 30 includes a dispersing prism 38 that receives the light emitted by the harmonic generator 36 and emits it dispersed according to wavelength, and first and second beam blocks 40 and 42 located to receive and block from further transmission the 1064 nm and 532 nm wavelength beams of light.
System 30 also includes moveable third and fourth beam blocks 44 and 46, and partially reflective mirrors 48 and 50. Third and fourth beam blocks 44 and 46 are locatable respectively in the optical paths of the 266 nm and 213 nm wavelength beams of light. A drive mechanism (not shown) allows third and fourth beam blocks 44 and 46 separately to be controlled to selectively pass or block each of these beams of light, and—when passed—these 266 nm and 213 nm wavelength beams impinge partially reflective mirrors 48 and 50, respectively.
Light at 266 nm and 213 nm closely matches absorption peaks of proteins in specimens of the type described below, but in other applications different wavelengths may be preferable and hence employed as necessary and suitable.
System 30 includes a hollow glass taper 52 for concentrating the beam, towards the larger (or entrance) end of which partially reflective mirrors 48 and 50 direct the reflected component of the 266 nm and 213 nm wavelength beam(s). Taper 52 is coupled at its distal or narrow end to the proximal end of an optical probe 54 (comprising an optical fiber, as described below) and thus launches the beam into the proximal end 56 of optical probe 54. The distal end of optical probe 54 is locatable against a specimen (in this example, an intraocular specimen, such as a portion 58 of is the retina of an eyeball 60).
It should be noted that, in system 30 (and other embodiments of the present invention) light may be transmitted by any suitable mechanism or medium. For example, some or all of the optical paths referred to above or shown in
Thus, system 30 can be employed to irradiate and ablate specimen 58 with an ablating beam of wavelength 266 nm or 213 nm, or with components of wavelength 266 nm and of wavelength 213 nm.
System 30 includes a rotatable prism 62 located in the optical path between dispersing prism 38 and partially reflective mirror 50, which is rotatably adjustable so that the path of the 213 nm beam can be finely adjusted.
System 30 also includes a second laser source in the form of HeNe laser source 64, which emits visible light with a wavelength of 633 nm. Additional mirror pair 66a, 66b direct light from HeNe laser source 64 through partially reflective mirrors 48 and 50 (and hence into the same optical path as that of the ablating light) onto the specimen 58. This visible light allows, in effect, the visualisation of the location of incidence of the ablating beam (which, being in the ultraviolet, is invisible to the naked eye).
In use, distal tip 74 is located against specimen 58 (as is described in greater detail below). In use, optical probe 70 ablates a hole in the specimen of approximately 60 μm diameter, and from 40 to 400 μm depth depending on whether the optical probe 70 is not advanced or is advanced, respectably, between pulses.
Referring again to
Thus, once optical probe 70 has been located as desired against the specimen 58, such that distal tip 74 exerts a gentle force against specimen 58, this feedback control mechanism—comprising transducer 78, feedback controller 84 and drive 86—is activated and holds distal tip 74 against the specimen 58 so that the original gentle force is maintained.
It will also be appreciated that the feedback control mechanism of
Referring to
These embodiments would typically be preferred when the specimen or target tissue is adjacent to normal tissue, and it is desired to protect the normal tissue.
Mirror 126 may be provided in any suitable way, such as by providing optical probe 120 with an oblique distal tip with a silvered surface, or an internal, mirrored surface.
In each of the embodiments of
Modifications within the scope of the invention may be readily effected by those skilled in the art. It is to be understood, therefore, that this invention is not limited to the particular embodiments described by way of example hereinabove.
In the claims that follow and in the preceding description of the invention, except where the context requires otherwise owing to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, that is, to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.
Further, any reference herein to prior art is not intended to imply that such prior art forms or formed a part of the common general knowledge in Australia or any other country.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012903038 | Jul 2012 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2013/000771 | 7/11/2013 | WO | 00 |
