Probe for optical spectroscopy

A probe comprising a body portion and a tip portion. The body portion comprises: a first mounting portion comprising a plurality of first carriers, each first carrier being arranged to support an elongate first waveguide, the first carriers being disposed in an equiangular arrangement around a longitudinal axis of the body portion; a plurality of first waveguides, each first waveguide being supported in a respective one of the plurality of first carriers; and a body end fitting at which first ends of the first waveguides are supported in the equiangular arrangement around the longitudinal axis of the body portion such that the first waveguides can transmit electromagnetic radiation signals from an energy source to the body end fitting and/or transmit electromagnetic radiation signals from the body end fitting to a receiver. The tip portion comprises: a second mounting portion comprising a plurality of second carriers, each second carrier being arranged to support an elongate second waveguides, the second carriers being disposed in the equiangular arrangement around a longitudinal axis of the tip portion; a plurality of second waveguides, each second waveguides being supported in a respective one of the plurality of second carriers; and a tip end fitting at which first ends of the second waveguides are supported in the equiangular arrangement around the longitudinal axis of the tip portion; and an elongate conduit for piercing human tissue.

This application is a U.S. national phase application under 35 U.S.C. § 371 of International Application No. PCT/GB2018/050678, filed Mar. 15, 2018, which claims priority to U.K. Application No. 1704405.8, filed Mar. 20, 2017, the complete disclosures of which are incorporated herein by reference.

BACKGROUND

During medical examination of a tissue sample it can be beneficial to identify the tissue type and/or disease state thereof.

For example, when cancer is suspected, a patient may have a tumour removed or biopsied and sent for histopathology analyses. Conventional handling involves the tissue undergoing fixation, staining with dyes, mounting and then examination under a microscope for analysis. Typically, the time taken to prepare the specimen is of the order of one day. The pathologist will view the sample and classify the tissue as malignant or benign based on the shape, colour and other cell and tissue characteristics. The result of this manual analysis depends on the choice of stain, the quality of the tissue processing and staining, and ultimately on the quality of education, experience and expertise of the specific pathologist.

Probes have been devised which contain optical fibres to enable testing of subcutaneous tissue and/or fluid.

However, the present inventors have identified that known probes can be time consuming and/or expensive to manufacture.

SUMMARY

By way of a non-limiting overview, embodiments of the invention relate to a probe in which a body portion positions free ends of first waveguides in an equal angular spacing around the axis of the body, and a tip portion positions free ends of second waveguides in the same equal angular spacing around the axis of the tip portion. Thus, during manufacture of the tip, this enables the second waveguides to be randomly mounted in the second mounting portion and subsequently the second mounting portion can be rotated about its axis to align a particular one of the second waveguides with a particular one of the first waveguides. This can simply manufacture of the tip portion, reducing both time and cost.

According to a first aspect of the invention, there is provided a probe, the probe comprising:a body portion, the body portion comprising:a first mounting portion comprising a plurality of first carriers, each first carrier being arranged to support an elongate first waveguide, the first carriers being disposed in an equiangular arrangement around a longitudinal axis of the body portion;a plurality of first waveguides, each first waveguide being supported in a respective one of the plurality of first carriers; anda body end fitting at which first ends of the first waveguides are supported in the equiangular arrangement around the longitudinal axis of the body portion such that the first waveguides can transmit electromagnetic radiation signals from an energy source to the body end fitting and/or transmit electromagnetic radiation signals from the body end fitting to a receiver; anda tip portion arranged to be removably coupled to the body portion in a coaxial manner by one of more connectors, the tip portion comprising:a second mounting portion comprising a plurality of second carriers, each second carrier being arranged to support an elongate second waveguide, the second carriers being disposed in the equiangular arrangement around a longitudinal axis of the tip portion;a plurality of second waveguides, each second waveguides being supported in a respective one of the plurality of second carriers;a tip end fitting at which first ends of the second waveguides are supported in the equiangular arrangement around the longitudinal axis of the tip portion; andan elongate conduit for piercing human tissue, the elongate conduit having a first opening and a second opening, the first opening being coupled (directly or indirectly) to the second mounting portion with the second waveguides extending from the second mounting portion into the elongate conduit such that, when the tip portion is coupled to the body portion and the first waveguides are axially aligned with the second waveguides, the second waveguides can transmit electromagnetic radiation signals from the first waveguides to the second opening of the elongate conduit and/or transmit electromagnetic radiation signals from the second opening of the elongate conduit to the first waveguides.

Thus, a probe according to this aspect includes a conduit, such as a needle, via which electromagnetic radiation can be used for examining a tissue sample. The conduit is arranged and configured such that it may easily be inserted into human tissue and as such the probe can be used to test subcutaneous tissue and/or fluid. The probe can be coupled to a receiver that can be used to analyse the electromagnetic radiation returned from the sample through the conduit. The tip portion, which includes the elongate conduit and in use is likely to be contaminated by test tissue or test fluid, can be uncoupled from the body portion of the probe. As such, the tip portion can be discarded following a single use, but the body portion can be retained for subsequent use. Advantageously, the body portion mounting portion positions the free ends of the first waveguides in an equal angular spacing around the axis of the body; the tip portion mounting portion positions the free ends of the second waveguides in the same equal angular spacing around the axis of the tip portion. Thus, during manufacture of the tip, this enables the second waveguides to be randomly mounted in the second mounting portion and subsequently the second mounting portion can be rotated about its axis to align a particular one of the second waveguides with a particular one of the first waveguides. This can simply manufacture of the tip portion, reducing both time and cost.

According to a second aspect of the invention, there is provided a tip portion of a probe arranged to be removably coupled to a body portion in a coaxial manner by one of more connectors, the body portion comprising: a first mounting portion comprising a plurality of first carriers, each first carrier being arranged to support an elongate first waveguide, the first carriers being disposed in an equiangular arrangement around a longitudinal axis of the body portion; a plurality of first waveguides, each first waveguide being supported in a respective one of the plurality of first carriers; and a body end fitting at which first ends of the first waveguides are supported in the equiangular arrangement around the longitudinal axis of the body portion such that the first waveguides can transmit electromagnetic radiation signals from an energy source to the body end fitting and/or transmit electromagnetic radiation signals from the body end fitting to a receiver, the tip portion comprising:a second mounting portion comprising a plurality of second carriers, each second carrier being arranged to support an elongate second waveguides, the second carriers being disposed in the equiangular arrangement around a longitudinal axis of the tip portion;a plurality of second waveguides, each second waveguide being supported in a respective one of the plurality of second carriers;a tip end fitting at which first ends of the second waveguides are supported in the equiangular arrangement around the longitudinal axis of the tip portion; andan elongate conduit for piercing human tissue, the elongate conduit having a first opening and a second opening, the first opening being coupled (directly or indirectly) to the second mounting portion with the second waveguides extending from the second mounting portion into the elongate conduit such that, when the tip portion is coupled to the body portion and the first waveguides are axially aligned with the second waveguides, the second waveguides can transmit electromagnetic radiation signals from the first waveguides to the second opening of the elongate conduit and/or transmit electromagnetic radiation signals from the second opening of the elongate conduit to the first waveguides.

The following are options features of the first and second aspects.

The particular one of the first waveguides can be a first excitation waveguide arranged to transmit electromagnetic radiation signals from the energy source to the body end fitting.

The particular one of the second waveguides can be a second excitation waveguide arranged to transmit electromagnetic radiation signals from the first excitation waveguide to the second opening of the elongate conduit.

The remaining ones of the first and second waveguides can be collection waveguides. The second collection waveguides can each be arranged to transmit electromagnetic radiation signals from the second opening of the elongate conduit to the ends of the first collection waveguides at the body end fitting. The first collection waveguides can each be arranged to transmit electromagnetic radiation signals from the body end fitting to the receiver.

The tip portion and body portion can each define a cooperating keying formation arranged to permit the tip portion to be coupled to the body portion in just a single configuration.

The second mounting portion and the tip end fitting can be discrete portions of the tip that are coupled together during manufacture after the second mounting portion has been rotated about its axis to align the particular one of the second waveguides with the particular one of the first waveguides.

The tip portion can comprise at least four, more preferably at least five, and even more preferably at least seven second waveguides, the diameter of each second waveguide being such that the second ends of the second waveguides are housed within the bore of the elongate conduit in a configuration in which the second excitation waveguide is central and surrounded by the second collection waveguides. The body portion can comprise an equal number of first waveguides.

The first mounting portion can be integrally formed with or can define the body end fitting.

Each waveguide can comprise optical fibre.

The conduit can comprise a hypodermic needle.

The energy source can comprise a light source, such as a laser.

The electromagnetic radiation can be within the range of ultraviolet to infrared.

In any embodiment of the invention including optical fibre, the fibre core can have a diameter of 300 μm or less, preferably 200 μm or less, and advantageously 150 μm or less.

The receiver can comprise a spectroscopic detector, such as a detector arranged to detect Raman spectra.

The body portion can house wave manipulation modules including lenses and filters. Thus, relatively expensive components of the probe such as the wave manipulation modules may be associated with the reusable portion of the probe.

In some embodiments, the tip portion does not comprise the elongate conduit.

According to a third aspect of the invention, there is provided an optical spectroscope including a probe according to the first aspect. The optical spectroscope may comprise a Raman or fluorescence spectroscope.

According to a fourth aspect of the invention, there is provided a method of assembling a tip portion of a probe according to the first aspect, the method comprising the steps of:providing a tip portion comprising a second mounting portion, a tip end fitting and an elongate conduit, the second mounting portion comprising a plurality of second carriers, each second carrier being arranged to support an elongate second waveguide, the second carriers being disposed in an equiangular arrangement around a longitudinal axis of the tip portion;mounting a plurality of second waveguides in the second mounting portion, each second waveguide being supported in a respective one of the plurality of second carriers such that first ends of the second waveguides are supported in the equiangular arrangement around the longitudinal axis of the tip portion at a tip end fitting and second ends of the second waveguides extend from the second mounting portion into a first opening of the elongate conduit;rotating the second mounting portion, such as around the longitudinal axis of the tip portion, to align a particular one of the second waveguides with a target position on the tip end fitting corresponding to the position of a first waveguide of a body portion such that, when the tip portion is coupled to the body portion and the second waveguides are axially aligned with the first waveguides, the second waveguides can transmit electromagnetic radiation signals from the first waveguides to the second opening of the elongate conduit and/or transmit electromagnetic radiation signals from the second opening of the elongate conduit to the first waveguides; andcoupling the second mounting portion to the second interface surface to inhibit further relative rotation between them about the axis of the tip portion.

Optional features of the first and second aspects can be applied to the fourth aspect in an analogous manner.

DETAILED DESCRIPTION

FIG.1shows a probe10according to a first embodiment of the present invention. The term “probe” is used in relation to embodiments of the invention to mean an instrument, such as a surgical instrument, which is suitable for, or arranged to be, at least partially inserted into human or animal tissue to enable a fluid or tissue sample to be tested in situ using electromagnetic radiation such as light.

The probe10according to embodiments of the invention enables subcutaneous tissue to be tested using spectroscopy, preferably Raman spectroscopy. As will be understood, when exciting optical energy of a single wavelength interacts with a molecule, the optical energy scattered by the molecule may contain small amounts of optical energy having wavelengths different from that of the incident exciting optical energy. This is known as the Raman effect. The wavelengths present in the scattered optical energy are characteristic of the structure of the molecule, and the intensity of this optical energy is dependent on the concentration of these molecules. Thus, the identities and concentrations of various molecules in a substance can be determined by illuminating the substance with energy of a single wavelength and then measuring the individual wavelengths, and their intensities, in the scattered optical energy. Raman spectroscopy provides a means for obtaining similar molecular vibrational spectra over optical fibres using visible or near infrared light that is transmitted by the optical fibres without significant absorption losses. In Raman spectroscopy, monochromatic light is directed to a sample and the spectrum of the light scattered from the sample is determined. It should however be noted that a probe according to embodiments of the invention may be used with any suitable receiver or detector, such as a spectroscopic detector arranged to measure fluorescence or elastic scattering.

The probe10generally comprises an elongate conduit12which is arranged to pierce human tissue, a two part wave coupling18,20,22a,22b,24a,24barranged to transmit electromagnetic radiation from an energy source (not shown) into the conduit12and/or transmit electromagnetic radiation from the conduit12to a receiver (not shown), a carriage16for moving second waveguides22b,24bof the wave coupling between a deployed condition and retracted condition and a pressure modifier16arranged in fluid communication with the conduit12, the pressure modifier16being operable to change the pressure within the conduit12.

The elongate conduit12has a first opening12aand a second opening12b. The openings12a,12bare spaced from one another at opposite ends of the conduit12. The conduit12is hollow so as to define a fluid passageway between the openings12a,12bsuch that the openings12a,12bare in exclusive fluid communication with one another via the conduit12. A proximal end of the conduit12is connected to the body of a syringe14so as to provide a fluid-tight coupling therewith via the first opening12a. A distal end of the conduit12defines a tip which is arranged and configured to enable the conduit to pierce human tissue or the like. For example, the conduit tip may define a sharp point such as that of a hypodermic needle; alternatively, it may be arranged to fit inside a disposable needle arranged to pierce tissue or the like. The second opening12ais located at the tip of the conduit12. The conduit12is formed of a resilient material such as steel. The conduit12may have an outer diameter which is less than 2 mm, 1.5 mm or less than 1 mm. Preferably, the conduit has an outer diameter which is equal to or less than 0.95 mm. In some embodiments the conduit may comprise a conventional hypodermic needle, such as a 20 gauge needle. The conduit12may have any suitable length, such as less than or equal to: 300 mm, 200 mm or 100 mm.

The wave coupling18,20,22a,22b,24a,24bin the illustrated embodiment is an optical coupling and comprises a plurality of first optical fibres22a,24ain a body portion of the probe10which are arranged to be aligned for signal communication with a plurality of second optical fibres22b,24bin a tip portion of the probe10. Laser light may be transmitted from a laser (not shown) into an excitation fibre22aof the first optical fibres22a,24aand then via a first light manipulation module18. Light exiting the first light manipulation module18passes across a body/tip interface17(seeFIG.1b) to an excitation fibre22bof the second optical fibres, via which the manipulated laser light may be directed into the conduit to a sample to be tested, such as tissue or fluid. A plurality of second collection fibres24b(only one is shown for clarity) collect light from the sample and transmit the light back across the body/tip interface17to a second light manipulation module20arranged to manipulate the light returned from the sample and pass the output light to a plurality of first collection fibres24avia which light exiting the second light manipulation stage20may be transmitted to a receiver, such as a spectrometer.

As will be appreciated, the exact configuration of the wave coupling according to embodiments of the invention will depend on factors such as the type of electromagnetic radiation used, the target sample and the type of receiver used. In embodiments of the invention the wave coupling may comprise any suitable waveguides and manipulation modules.

In the illustrated embodiment, the set of second optical fibres consists of a single excitation optical fibre22band six collection optical fibres24b, which can be connected to one another to improve the stiffness of the second waveguides22b,24b. The close proximity of the optical fibres22b,24bforming the second waveguides22b,24bmay provide for particularly efficient collection of light from the sample, such as Raman scattered light. While only a single excitation optical fibre22band six collection optical fibres24bare provided, there may in other embodiments be a plurality of either. The second waveguides22b,24b, or components thereof, may be clad with a metal coating or jacket to improve the stiffness of the second waveguides22b,24b. The tip22c,24cof each optical fibre may be configured to provide a substantial overlap between the illuminating cone and the collection cones.

In the illustrated embodiment, the optional carriage16for moving the second optical fibres22b,24bbetween the deployed and retracted conditions comprises a plunger16of the syringe14. The plunger16is conventional in that it has a body16bhaving a piston seal16aat one end which is contained within the barrel15of the syringe14and an enlarged base16cwhich protrudes from the barrel15of the syringe14and may be used to actuate the plunger16. The light manipulation modules18,20are mounted on the plunger body16bon the body side of the coupling interface17. Consequently, movement of the plunger16causes corresponding movement of the second optical fibres22b,24b.

The syringe15defines a pressure modifier arranged in exclusive fluid communication with the first opening12aof the conduit12, the pressure modifier being operable to change the pressure at the first opening12aof the conduit12. Thus, a probe10according to such an embodiment includes a pressure modifier which can be used to modify the pressure within the conduit12to draw fluid or cells into the conduit12or expel fluid from the conduit12. In embodiments where a tip, or other portion, of the second optical fibres22b,24bare arranged to be moved to the second opening12b, it is advantageous to be able to expel fluid, such as saline solution, from the conduit12because this may clear the passageway between the tip of the second optical fibres22b,24band the target tissue of subcutaneous tissue and/or fluid that may inhibit the passage of electromagnetic radiation. In some embodiments the optical coupling between the probe and tissue may also be improved. In embodiments where fluid is to be tested (as described in more detail with reference toFIG.4), it is advantageous to be able to draw the test fluid into the conduit12. Thus, the probe10according to the illustrated embodiment conveniently makes use of a syringe plunger16to act as the pressure modifier and carriage. The tip portion of the syringe15provides a convenient structure to which to attach the conduit.

In other embodiments which include a carriage for moving one or more portions of the wave coupling, the carriage may be any suitable part arranged to move relative to the conduit of the probe and should the embodiment also include a pressure modifier, the carriage need not also serve as the pressure modifier. For example, the plunger16of the illustrated embodiment may include an opening, or one way valve, through the piston seal16asuch that the plunger can be depressed without forcing fluid into the conduit12. Although the plunger of such an embodiment may affect the pressure within the conduit12, it is not arranged to modify the pressure in the conduit such that a substantial quantity of fluid can be drawn into, or purged from, the conduit and thus is not considered to be a pressure modifier as disclosed herein. A substantial quantity in embodiments of the invention may be at least 5%, 10%, 20%, 30%, 40%, 50%, 75% or 100% of the volume of the conduit chamber12d.

In other embodiments which include a pressure modifier arranged to change the pressure within the conduit12, the pressure modifier may be any suitable part arranged to increase or decrease the pressure at an opening of the probe12. Should an embodiment include a carriage and a pressure modifier, the pressure modifier need not also serve as the carriage. For example, the optical coupling may be coupled to the syringe body of the illustrated embodiment and the plunger16may move relative to both the syringe body and optical coupling as is the case with the embodiment described with reference toFIG.4. In some embodiments the pressure modifier may comprise a pump.

Referring additionally toFIG.3, the light manipulation modules18,20are shown in more detail. For clarity, as withFIG.1c, only a single collection path24a,24bis shown.

The excitation or input optical fibre22a, which in this embodiment is arranged to be coupled to a laser light source, directs laser light into a gradient index (GRIN) input lens18a. The input lens18acollimates the laser light to generate a collimated beam. The collimated beam is then passed through a short wavelength pass filter18bthat rejects Raman and photoluminescence emission generated within the input optical fibre22a. The filtered light is then passed to a GRIN focussing lens18c. The focussing lens18cfocusses the filtered light into the excitation optical fibre22bwhich transmits the filtered light into the conduit12to the target sample.

Light from the sample is collected and collimated by a GRIN collecting lens20cand directed to a long wavelength pass filter20bthat rejects the laser excitation light. Stokes shifted wavelengths are transmitted by the filter20b. The filtered light is then focussed by a GRIN output lens20ainto the output optical fibre24awhich is arranged to be coupled to a receiver, such as a spectrometer for generating a Raman spectrum.

In other embodiments, any suitable electromagnetic radiation may be used as the excitation signal. It should be also noted that, while GRIN lenses have been described, any suitable lens type may be used in the optical coupling of other embodiments.

In the illustrated embodiment, the tips22c,24cof the second optical fibres22b,24bare closer to the second opening12bof the conduit12when the second optical fibres22b,24bare in the deployed condition than when second optical fibres22b,24bare in the retracted condition. Thus, the probe10enables the position the tips22c,24cof the second optical fibres22b,24bto be varied. As such, the tips22c,24cmay be stowed within the conduit12during insertion of the conduit12into human tissue or the like, so as to reduce the likelihood of the tips22c,24cbeing damaged or coming into contact with subcutaneous fluid or tissue which may otherwise impair the wave transmitting efficiency of the wave coupling. Once the conduit12has been inserted to a measurement depth, the second optical fibres22b,24bcan be moved to the deployed condition for testing. When in the deployed condition, the tips22c,24cof the second optical fibres22b,24bmay be in contact with the tissue sample.

As shown inFIGS.1band1c, the tips22c,24cof the second optical fibres22b,24bare spaced from second opening12bof the conduit12when the second optical fibres22b,24bare in the retracted condition. For example, the tip22c,24cmay be spaced from the second opening12bby at least: one tenth of; one eighth of; one quarter of; a half of; three quarters of; or the entire length of the conduit12. Thus, a probe10according to such an embodiment enables the tip22c,24cof the second optical fibres22b,24bto be spaced from the second opening12bof the conduit12. Increasing this spacing can provide a more efficient buffer between the second opening12band the tip22c,24cof the second optical fibres22b,24b. However, there may be a trade-off between providing a suitable buffer spacing and enabling the tip22c,24cto easily reach a target location, such as the second opening12bof the conduit12. In embodiments which include a pressure modifier, it may be desirable for the tips22c,24cof the second optical fibres22b,24bto be spaced from the second opening12bof the conduit12by less than one quarter of the length of the conduit12so as to limit the volume of fluid that is displaced as the second optical fibres22b,24bmoves between the retracted and deployed configurations.

Referring additionally toFIGS.2ato2c, the tips22c,24cof the second optical fibres22b,24bare positioned at the second opening12bof the conduit12when the second optical fibres22b,24bare in the deployed condition. This enables the conduit12to be inserted into tissue to a required measurement depth and the tips22c,24cof the second optical fibres22b,24bbrought close to the tissue to be sampled. This may improve the testing accuracy of the probe10relative to an embodiment where the tips22c,24cof the element22b,24bare significantly spaced from the target tissue because the wave coupling of the probe10transmits the electromagnetic radiation substantially all of the way to and from the target tissue. Arranging the probe such that the tip22c,24cof the second optical fibres contacts the tissue sample when in the deployed condition may advantageously remove the need for a lens at the tip and/or remove the need for setting a focal distance.

FIG.4shows the disposable tip of the probe10in more detail. The probe10has a body portion70and a tip portion80that are arranged to be removably coupled to one another. Thus, the tip portion80may be disposed following a single use, but the body portion70can be reusable.

The body portion70, of which only a part is shown inFIG.4, houses the light manipulation modules (not shown) described with reference toFIG.3. The light manipulation modules are arranged to be removably coupled to the second optical fibres22b,24bthat are associated with the removable tip portion80. The term “associated” is used to mean that second optical fibres22b,24bare part of the tip portion80rather than part of the body portion70, such that following uncoupling of the portions70,80, the second optical fibres22b,24bremain coupled to the tip portion80.

The tip portion80is arranged to be removably coupled to the body70by any suitable connectors; for example, one or more retention clips92such as flexible hooks or barbed structures arranged to mechanically engage with receiving apertures in the body, screw fittings, interference fit features or a magnetic coupling.

The set of first optical fibres22a,24amust be connected to and aligned with the set of second optical fibres22b,24bfor the device10to function.

The tip portion80comprises a cylindrical mounting portion82which includes, in this embodiment, seven carrier holes arranged in an equiangular arrangement around the longitudinal axis A of the tip portion80. Thus, the central axis of each carrier hole is separated from the central axes of adjacent carrier holes by around 51.4°. The first end of each second optical fibre is provided with a ferrule84arranged to project from an axial face of the mounting portion82when the fibre is mounted within one of the carrier holes. When the second optical fibres are mounted within the carrier holes, the second ends of the optical fibres extend from the mounting portion82into a conical tip86arranged to guide the fibres into the bore of the needle12. The conical tip86can be secured to the mounting portion82by any suitable means, such as bonding or by way of a mechanical fixing.

The tip portion80further comprises a tip end fitting88, via which the tip portion80is arranged to be coupled to the body portion70. The end fitting88includes one or more holes which together are sized to receive the tip ferrules84when the end fitting88is coaxially coupled to the mounting portion82. Ferrules84are inserted into standard ceramic mating sleeves to provide alignment of the waveguides. In this condition, the first ends of the second optical fibres are supported in the equiangular arrangement at the tip end fitting88.

Similarly, the body portion70comprises a mounting portion72comprising a plurality of carrier holes73, each first carrier being arranged to support a first optical fibre (not shown). The first carrier holes are disposed in the same equiangular arrangement around the longitudinal axis A.

The body portion70also comprises a body end fitting74at which sockets76located at first end regions of the first optical fibres are supported in the equiangular arrangement around the longitudinal axis A. The sockets76are arranged to receive the ferrules84.

In the illustrated embodiment, the body end fitting74is provided with a keying surface78arranged to engage with corresponding keying surfaces on the mounting portion72and tip end fitting88to permit the tip portion80to be coupled to the body portion70in a single orientation. In other embodiments, any suitable arrangement can be provided to control the coupling orientation, such as male and female keying formations, magnetic poles, guide channels and rails, pin and socket arrangements and the like. In some embodiments, a marking may be provided to indicate the coupling orientation.

Various types of standard ferrules are available. Typically these could be 1 mm diameter stainless steel or 2.5 mm Ceramic. However, in other embodiments the ferrules may have any suitable size and be formed of any suitable material, such as a ceramic material, plastics material or stainless steel. The fibre may be inserted into the ferrule and cemented with an epoxy or adhesive, or connectors may also use crimped ferrules that do not require cement.

Referring additionally toFIG.5, it is preferred that the tip portion80has least four and preferably at least six second optical fibres22b,24b. The body portion70can comprise an equal number of first optical fibres22a,24a. A greater number of optical fibres increases light collection resulting in increased signal intensity and hence improved analytical performance. The diameter of each second optical fibres22b,24bis such that the tips of the second optical fibres22b,24bare housed within the bore of the needle12in a configuration in which the second excitation optical fibre22ais central and surrounded by the second collection optical fibres22b. This configuration enables the optical fibres to illuminate the sampling region evenly and in its entirety, so that scattered light is returned to all of the collection fibres24b. This configuration can also avoid the collection of unwanted signal generated in the fibres themselves.

The tip portion80is arranged such that the orientation of the mounting portion82can be altered to control distribution of the fibres carrying laser light towards the sample and returning scattered light to the spectrometer. For example, this can be to ensure the central fibre22bcarries excitation laser light, and other fibres24breturn scattered light. Once the correct orientation is selected, the orientation of the mounting portion82is locked in place relative to the end fitting88to maintain this distribution.

As this alignment can be performed after the second fibres22b,24bhave been mounted, ordering of the second fibres22b,24bin the tip is unimportant during construction, thus greatly lowering the complexity and cost of construction.

Referring additionally toFIG.6, a method of manufacturing a tip portion80according to an embodiment of the invention is illustrated generally at90.

At step92the ferrules84on the ends of the fibres22b24bprotruding from the needle12are installed in carriers of the mounting portion82.

At step94, the central fibre22bwithin the bore of the needle12can be identified using a microscope to view the needle end and an illumination source on each of the ferrules in turn until the central fibre22bis identified.

At step96, once identified, this fibre's ferrule84is placed in a known positioned hole in the end fitting88, normally but not limited to, the hole next to the key formation.

At step98, the mounting portion82is affixed to the end fitting88to maintain the orientation against the key. This keyed fibre is then used to maintain alignment with the fibre leading to the laser in the body portion70so that when the tip portion80is removed and replaced as an assembly, the excitation fibre remains in a constant position.

In any embodiment of the invention, the electromagnetic radiation may be within the range of ultraviolet to infrared.

In any embodiment of the invention including optical fibre, the fibre may have a diameter of 300 μm or less, preferably 200 μm or less and advantageously 150 μm or less.

Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims. The word “comprising” can mean “including” or “consisting of” and therefore does not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.