to provide a needle device , a multilumen stylet in form of an insert 200 inside a cannula having a hollow shaft 100 is used . the insert 200 is typically made with well defined lumen at positions that define the distance between fibers 300 that can be inserted in these lumen . according to the invention , the insert 200 has at least one lumen or channel 260 that can contain at least one fiber 300 . the insert of the needle device may be moved forward after the needle device has been inserted in a body . therefore , it is very easy for the surgeon to work with it . the shape is typically like a syringe with an operating mechanism at for example one side of the cylinder of the syringe . the surgeon can introduce the needle into a tissue like a normal injection needle and after insertion push , with one finger , a lever 510 of the operating mechanism 500 . by pushing the lever 510 , a second lever 520 translates the movement to the insert 200 so that the insert slides from a position with its distal end inside the hollow shaft forward over the length of a cannula pocket at the distal end of the hollow shaft to a second position outside the distal end of the hollow shaft . in this second position of the insert , optical measurements may be performed . by loosening the lever 510 , the insert may be retract automatically to the not protruding first position . in this way it is possible to measure at different locations , i . e . at different locations in depth by pushing the needle outwardly , without retracting the needle in total . this is a huge advantage during the measurements . to push the insert 200 forward a number of constructions are possible . for instance a motorized , most likely electromagnetically , drive or a manually , most likely hand , drive can be implemented . both could , for example , drive a screw spindle , cam profile , wedge or lever configuration . in a preferred embodiment , for simplicity and easy manufacturing , a lever construction as shown in fig1 and 2 may be used . a first lever 510 comprises a pivot 512 arranged at the housing 600 of the needle device . a second lever 520 comprising a first pivot 522 and a second pivot 524 is arranged between the first lever 510 and the insert 200 , to translate the pivotal movement ( arrow a ) of the first lever in a direction to the housing , into a translational movement ( arrow b ) of the insert in a direction to the distal end of the needle device . the insert comprises a slider 250 which is adapted to firstly be connected with the second pivot 524 of the second lever 520 , and to secondly be guided within the housing 600 . as shown in fig1 , bearings 530 are provided between the housing 600 and the slider 250 . such a lever construction has a very low friction which is an advantage above the other possible constructions . the lever construction provides the surgeon also with a good “ feel ” during the measurement . it is important that the surgeon obtains clear feedback , in this case by feeling with his fingertip during the measurement whether the insert is moved forward . this feel can be adjusted , to the wishes of the surgeon , by adjusting the pre - load ( spring 550 ) of the first lever 510 . it is noted that the spring 550 may also be arranged at other position appropriate to finally retract the distal end portion of the insert 200 into the hollow shaft 100 . additionally a switch 540 is provided that may trigger the measurement due to a pushing of the first lever 510 . fig3 illustrates a first embodiment of a distal tip portion of a needle devide according to the invention , as a plain view as well as a section side view . the needle comprises a hollow shaft 100 and an elongated insert 200 . the shaft 100 is formed with a bevel 110 and the insert 200 is formed with a front surface 210 . as can be seen in fig3 , the bevel 110 is formed with an angle which is different to the angle of the second bevel 210 . the insert 200 further includes channels 260 having open ends at the front surface 210 of the insert . within the channels 260 , optical fibers 300 with front surfaces 310 are arranged . fig4 shows a second embodiment of a distal end portion of a needle device according to the invention . also in this embodiment , the shaft 100 has facets 120 formed at the sides of the bevel so that the facets are orientated to the front as well as the side of the tip . the insert 200 of this embodiment has a blunt distal tip , i . e . the front surface of the insert 200 includes a bevelled portion 210 and a blunt portion 240 . it will be understood that a contact with tissue will differ due to the different distal tip of the insert , when the insert with a distal end portion according to the first embodiment will be pushed out of the hollow shaft , and when the insert with a distal end portion according to the second embodiment will be pushed out of the hollow shaft 100 . a third embodiment of a distal end portion of the insert 200 is shown in fig5 . here , the front surface of the insert 200 comprises a blunt portion 240 as a distal tip , followed ( in a direction from distal to proximal ) by a bevelled portion 220 , a stepped portion 230 and a further bevelled portion 220 . by the stepped portion 230 , a surface oriented in an axial direction of the insert and a surface transverse to the axial direction is formed . in this embodiment , channels 260 are located so that both channels ends at a surface transverse to the axial direction , one of the channels ends at the blunt portion 240 and the other one of the channels ends at the transverse surface of the stepped portion 230 . further depicted in fig5 , are the position of the distal end portion of the insert 200 inside the hollow shaft , i . e . proximal to the bevel of the hollow shaft , and the position of the distal end portion of the insert outside the hollow shaft , i . e . distal to the bevel of the hollow shaft . assuming that tissue will be in close contact with the bevel of the hollow shaft , when the hollow shaft is introduced into the tissue , the two transverse surfaces of the front surface of the insert , and thus the end surfaces of fibers located within the channels 260 , can be pressed in reliably in contact with the tissue , thus ensuring good optical measurements . the insert may be produced in mass production . producing straight cut fibers may be done in batches . assembling fibers in the multilumen may be well controlled making these needles compatible with mass production . furthermore , because of this way of assembling , a rather low cost needle may be assured . as illustrated in fig6 , the needle with hollow shaft 100 and insert including at least one fiber may be connected to an optical console 400 . the optical console comprises a light source 410 enabling light to be provided via one or more of the fibers to the tip of the insert at the distal end of the needle device . the scattered light is collected by one or more fiber and is guided towards at least one detector 420 . the amount of reflected light measured at the “ detection ” fiber , is determined by the absorption and scattering properties of the probed structure ( e . g . tissue ). the data may be processed by a processing unit 440 using a dedicated algorithm . for diffuse reflectance measurements , either the light source or the detector or a combination of both must provide wavelength selectivity . for instance , light can be coupled out of the distal tip through at least one fiber , which serves as a source , and the wavelength is swept from e . g . 500 - 1600 nm , while the light detected by at least one detection fiber is sent to a broadband detector . alternatively , broadband light may be provided by at least one source fiber , while the light detected by at least one detection fiber is sent to a wavelength - selective detector , e . g . a spectrometer . for a detailed discussion on diffuse reflectance measurements see r . nachabe , b . h . w . hendriks , a . e . desjardins , m . van der voort , m . b . van der mark , and h . j . c . m . sterenborg , “ estimation of lipid and water concentrations in scattering media with diffuse optical spectroscopy from 900 to 1600 nm ”, j . biomed . opt . 15 , 037015 ( 2010 ). for fluorescence measurements the console must be capable of providing excitation light to at least one source fiber while detecting tissue - generated fluorescence through one or more detection fibers . the excitation light source may be a laser ( e . g . a semiconductor laser ), a light - emitting diode ( led ) or a filtered light source , such as a filtered mercury lamp . in general , the wavelengths emitted by the excitation light source are shorter than the range of wavelengths of the fluorescence that is to be detected . it is preferable to filter out the excitation light using a detection filter in order to avoid possible overload of the detector by the excitation light . a wavelength - selective detector , e . g . a spectrometer , is required when multiple fluorescent entities are present that need to be distinguished from each other . in case fluorescence measurements are to be combined with diffuse reflectance measurements , the excitation light for measuring fluorescence may be provided to the same source fiber as the light for diffuse reflectance . this may be accomplished by , e . g ., using a fiber switch , or a beam splitter or dichroic beam combiner with focusing optics . alternatively , separate fibers may be used for providing fluorescence excitation light and light for diffuse reflectance measurements . although diffuse reflectance spectroscopy is described above to extract tissue properties also other optical methods may be envisioned like diffuse optical tomography by employing a plurality of optical fibers , differential path length spectroscopy , raman spectroscopy . furthermore , the system may also be employed when contrast agents are used instead of only looking at autofluorescence . in accordance with the invention an algorithm may be utilized to derive optical tissue properties such as the scattering coefficient and absorption coefficient of different tissue chromophores : e . g . hemoglobin , oxygenated haemoglobin , water , fat etc . these properties are different between normal healthy tissue and diseased ( cancerous ) tissue . the main absorbing constituents in normal tissue dominating the absorption in the visible and near - infrared range are blood ( i . e . hemoglobin ), water and fat . in fig7 the absorption coefficient of these chromophores as a function of the wavelength are presented . note that blood dominates the absorption in the visible range , while water and fat dominate in the near infrared range . the total absorption coefficient is a linear combination of the absorption coefficients of for instance blood , water and fat ( hence for each component the value of that shown in fig7 multiplied by its volume fraction ). by fitting the model to the measurement while using the power law for scattering ( see r . nachabe , b . h . w . hendriks , a . e . desjardins , m . van der voort , m . b . van der mark , and h . j . c . m . sterenborg , “ estimation of lipid and water concentrations in scattering media with diffuse optical spectroscopy from 900 to 1600 nm ”, j . biomed . opt . 15 , 037015 ( 2010 )) we may determine the volume fractions of the blood , water and fat as well as the scattering coefficient . with this method we may now translate the measured spectra in physiological parameters that may be used to discriminate different tissues . another way to discriminate differences in spectra is by making use of a principal components analysis . this method allows classification of differences in spectra and thus allows discrimination between tissues . it is also possible to extract features from the spectra . how to extract the intrinsic fluorescence from the measured fluorescence may be found for instance in zhang et al ., optics letters 25 ( 2000 ) p1451 . the needles device according to the invention may be used in minimally invasive needle interventions such as low - back pain interventions or taking biopsies in the field of cancer diagnosis or in case where tissue characterization around the needle is required . while the invention has been illustrated and described in detail in the drawings and foregoing description , such illustration and description are to be considered illustrative or exemplary and , not restrictive ; the invention is not limited to the disclosed embodiments . other variations to the disclosed embodiments may be understood and effected by those skilled in the art in practicing the claimed invention , from a study of the drawings , the disclosure , and the appended claims . in the claims , the word “ comprising ” does not exclude other elements or steps , and the indefinite article “ a ” or “ an ” does not exclude a plurality . a single processor or other unit may fulfill the functions of several items recited in the claims . the mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage . a computer program may be stored / distributed on a suitable medium , such as an optical storage medium or a solid - state medium supplied together with or as part of other hardware , but may also be distributed in other forms , such as via the internet or other wired or wireless telecommunication systems . any reference signs in the claims should not be construed as limiting the scope .
a needle device according to the invention comprises a hollow shaft , an elongated insert and an operating means . the hollow shaft has a first distal end portion with a bevel , the elongated insert has a second distal end portion and is movably arranged within the hollow shaft , and the operating means is shiftable between a first condition and a second condition . furthermore , the operating means is interconnected with the elongated insert , so that the second distal end portion is located within the hollow shaft and proximally to the bevel , when the operating means is in the first condition , and that the second distal end portion is located outside the hollow shaft and distally to the bevel , when the operating means is in the second condition .