Patent Publication Number: US-2019175842-A1

Title: A needle arrangement

Description:
TECHNICAL FIELD 
     The invention relates to a needle arrangement for a medical application. Three different types of needle arrangements will be disclosed herein, namely a biopsy needle arrangement, an injection needle arrangement, and an aspiration needle arrangement. 
     BACKGROUND OF THE INVENTION 
     Within the field of medicine, needles for various purposes exist. For example, needle arrangements for injection, aspiration, and for taking biopsies are commonly used for different purposes. A common characteristic for these types of needle arrangements is that a needle of the needle arrangement is inserted into a body part (of a human) for performing, for example, an injection, an aspiration, or for collecting a biopsy sample. In connection with these types of invasive procedures there is always a risk of infection. 
     For example, when performing a trans rectal prostate biopsy (TRPB, which is the gold standard for diagnosis of prostate cancer, a biopsy needle is forwarded through the rectal wall and into the prostate. Normally, 8-12 biopsies are taken during the examination. A drawback with this method is a risk of infection due to intrusion of bacteria in the prostate during the medical procedure. In order to prevent infection antibiotics is often given by routine. With raising prevalence of multi-resistant bacteria, the number of infections risk to increase. Current studies show a sepsis rate of 1-5% after prostate biopsies. Another 5% suffers a milder infection treatable with per oral antibiotics (Lundström et al J Urol. 2014 October; 192 (4):1116-22). 
     Patients suffering sepsis after prostate biopsies normally require at least 2-3 days stay at the hospital receiving intravenous antibiotics. Some patients suffer long lasting troublesome infections and some lifelong morbidity. In an American study, the cost of sepsis was 5 900 US dollar per patient. In the US about 1 million biopsies are performed each year and approximately 3 million biopsies are performed yearly worldwide. 1.1 million persons are diagnosed with prostate cancer every year. 
     Lots of work has been made to prevent infections with for example rectal swabs and different antibiotics. However, there is still a need for improvements of needle arrangements, for example for application in the fields of biopsy sampling, such as prostate biopsy sampling, and in injection/aspiration applications, such as for amniocentesis and punctures. 
     SUMMARY OF THE INVENTION 
     In view of the above, it is an object of the present invention to provide a needle arrangement that provides a decreased risk of infections for the patient. Another object of the present invention is to lower the risk of infections due to an invasive procedure by a needle arrangement and to lower the general need for antibiotics, both in the precautionary and the treatment regimes. The needle arrangement, with different configurations that will be disclosed herein, is called a Forsvall needle and is configured with a Forsvall tip comprising a sealing member. 
     These and other objects of the inventive concept are at least partly met by the inventive concept as defined in the independent claim. Preferred embodiments are set out in the dependent claims. 
     According to a first aspect of the invention, a needle arrangement for a medical application is provided. The needle arrangement comprises: 
     an elongated needle sheath having a front end and a rear end, and 
     a needle comprising:
         an elongated portion adapted to be coaxially arranged inside the needle sheath, and   a sealing member being arranged to a front end of the elongated portion.       

     The needle arrangement is adapted to bet set in:
         a closed position, in which the sealing member is arranged to abut at least a portion of a front end surface of the needle sheath extending transverse the longitudinal axis of the needle thereby restricting intrusion of foreign matter in an area between the needle sheath and the needle, and   an open position, in which a longitudinal gap, extending in the longitudinal axis of the needle, is formed between the sealing member and the front end surface of the needle sheath.       

     In the context of this application, the following definitions apply. 
     The term coaxially arranged should be construed as sharing a common axis. The elongated portion is positioned inside the needle sheath and shares a common axis therewith. The common axis is referred to as the longitudinal axis. 
     The sealing member is arranged to abut at least a portion of the end surface of the needle sheath. Optimally, a perfect fit is achieved between the sealing member and the end surface. In reality, however, an interstice (i.e. a small gap) between the sealing member and the end surface may be present due to for example surface roughness or precision in fitting and/or manufacturing of the sealing member and/or the needle sheath. It should be noted that other structures, such as a coating, may be provided in the interface between the sealing member and the end surface, in which case the two parts are still defined as being abutting. 
     A gap may be present between the elongated portion of the needle and the needle sheath. Thus, there is a small distance between the needle and the needle sheath which provides an area referred to as a gap. 
     The term biopsy is conventionally referred to as ‘the act of taking a biopsy’, as well as ‘a biopsy’ being the sample itself. To facilitate the reading of this application, a biopsy will be referred to the procedure and biopsy sample will be referred to as the (tissue) sample being collected/obtained from the body during the biopsy. 
     Throughout the application, the term bacteria is used as an example of foreign matter, which should be construed in a broad sense as unwanted matter in the context of biopsy sampling. Other non-limiting examples of foreign matter are viruses and protozoa. 
     Details of the first aspect will now be disclosed. 
     A biopsy, injection, or aspiration process may comprise the step of entering multiple parts of the body with the needle arrangement, for example the biopsy needle arrangement, and thereby there is a risk that the needle arrangement, for example the biopsy needle arrangement, transports bacteria between different parts. A risk of infection is thus present when performing biopsies. 
     For example, a biopsy of the type TRPB involves a step of entering the rectum of the patient and with a biopsy needle arrangement pierce the wall of the rectum. With it, the biopsy needle arrangement may carry bacteria, in for example grooves/holes on the outer surface structure thereof or in gaps between structures of the arrangement, from the rectum into the space between the rectum and the prostate and further into the prostate. The bacteria may, if brought into the prostate, cause a very severe and potentially life threatening infection in the body. A conventional needle arrangement, such as a conventional biopsy needle arrangement, may have a gap between a needle and a needle sheath. The entrance of the gap typically faces forward in the direction of travel when the biopsy needle arrangement is inserted in the body. By that the gap is open towards the direction of travel in such a way it is particularly prone to collect and bring along bacteria. Bacteria may also be collected by the outer surface structure of the needle arrangement, for example the biopsy needle arrangement, which typically is made of stainless steel. 
     By that the sealing member, comprised in the inventive needle arrangement, for example a biopsy needle arrangement, is connected to the needle and is arranged to abut at least a portion of the end surface of the needle sheath, the sealing member is arranged to cover at least a part of the entrance to the gap provided between the elongated portion of the needle and the needle sheath. By covering the entrance facing the forward movement direction of the biopsy needle arrangement, the risk of collecting and bringing with bacteria is reduced. It is noted that a gap between the sealing member and the end surface of the needle sheath may be provided, however an entrance to such a gap is now directed in a direction being transversal to the longitudinal direction, i.e. transversal to the direction of movement, thereby contributing to a reduced risk of collecting bacteria. Moreover, a strong fit between the sealing member and the needle sheath may be achieved by forcing the sealing member and the needle sheath towards each other (by for example a spring mechanism) which contributes to a minimized interstice between the parts. The gap between the needle and the needle sheath cannot be minimized in such manner since that would create a frictional force between the parts which would counteract movement of the needle in relation to the needle sheath and thus the function of the needle arrangement, for example the biopsy needle arrangement. Hence, the risk of that bacteria is collected in the interstice between the sealing member and the needle sheath is reduced by the above mentioned factors, i.e. the repositioned entrance and the strong fit, when compared to the risk of collecting bacteria in a conventional needle arrangement, for example a conventional biopsy needle arrangement. 
     When the needle is arranged in the closed position, also referred to as a retracted portion, the sealing member abuts at least a portion of the end of the needle sheath. Notwithstanding the fact that there may always be an interstice between the two parts, as soon as the sealing member no longer abuts the end surface of the end of the needle sheath, the needle may be considered to be in the open position, also referred to as an extraction position. 
     Applications for the needle arrangement according to the invention include, for example, biopsy sampling, amniocentesis and punctures of various kinds. 
     A connection member may be arranged to the rear end of the needle sheath and adapted to connect to an actuator or to a syringe. 
     The actuator may be provided for actuating the needle out from the needle sheath. The actuator may be part of a system that comprises the needle arrangement provided for biopsy purposes, and further comprising arrangements for actuating retraction/extraction movements in the biopsy needle arrangement, tubes, and holders. 
     The syringe may be utilized in applications where the needle arrangement is used for injection or aspiration. The connection member may have various configurations depending on the actuator or syringe that it is adapated to connect to. Non-limiting examples of different configurations will be provided in the detailed description. 
     The connection member may comprise a biasing means arranged to bias the needle arrangement to be set in the closed position. The biasing means may comprise a spring mechanism. It is advantageous to have the needle arrangement set and maintained in the closed position when the needle is not in an active mode, i.e. when it is not set in the open position for sampling (when taking a biopsy), for injection, or for aspiration. 
     A needle arrangement adapted for an injection application or for an aspiration application may be configured such that a channel is provided between the front end and the rear end of the needle sheath. The cannel may extend along the longitudinal axis of the needle. The channel may be provided between the needle sheath and the needle or inside the needle. The connection member may be adapted to connect the needle arrangement to a syringe such that a fluid communication is allowed between the syringe and the longitudinal gap being formed when the needle arrangement is set in the open position. 
     In one embodiment of the needle arrangement adapted for an injection application, the connection member is arranged to connect to a tip of the syringe. The channel may be provided between the needle sheath and the needle. In a needle arrangement for an injection application, it is advantageous that the channel of the needle arrangement is provided between the needle and the needle sheath. In such a configuration, a flow of liquid may be present between the sealing member and a front end surface of the needle sheath. 
     Further, the biasing means may comprise a spring member that extends in parallel to the longitudinal axis of the needle and between the connection member and a part of the needle. The spring member may be arranged to be compressed when exerted to a liquid pressure during injection of a liquid by a thereto connected syringe, whereby the needle arrangement is set in the open position. In one embodiment, the spring member comprises a spring element that extends between an inner wall portion of the connection member and an end plate arranged to a back portion of the needle. Such a configuration may contribute to a compact needle arrangement. 
     A guiding mechanism may be provided. The purpose of the guiding mechanism is to guide the sealing member towards an aligned position relative the needle sheath while the needle arrangement is set towards the closed position. By aligned position is meant a predetermined relative position between the sealing member and the needle sheath that is desired for an application. 
     In one embodiment, the guiding mechanism may be provided by one or more guiding portion(s) of the needle. The one or more guiding portions are arranged to a front portion of the elongated portion for guiding the sealing member towards an aligned position relative the needle sheath while the needle arrangement is set from the open position to the closed position. 
     In one embodiment, the guiding portion comprises a plurality of flanges extending between the elongated portion of the needle and the needle sheath. 
     In one embodiment, the guiding portion comprises a conical portion formed around the longitudinal axis of the needle and being oriented with its base facing the sealing member. 
     In one embodiment, the guiding mechanism may be provided by the configuration of an interface between the sealing member and the needle sheath. 
     In one embodiment of the needle arrangement adapted for an aspiration application, the channel is provided inside the needle. Further, a rear end of the needle may be arranged to connect to a tip of the syringe. The connection member may comprise a syringe housing adapted to receive at least a part of a barrel of the syringe. The needle may be arranged to, when connected to the tip of the syringe, be forced forward along the longitudinal axis while the syringe is inserted to be received in the syringe housing, thereby setting the needle arrangement in the open position. 
     In one embodiment, the biasing means comprises a spring member, such as a helical spring element, extending in parallel with the longitudinal axis of the needle and between the connection member and a front portion of the barrel of the syringe when received in the syringe housing. An advantage with this configuration is that a user does not need to manually retract the needle into the needle sheath for ensuring a sealing between the sealing member and the needle sheath. 
     In one embodiment, the connection member comprises a locking mechanism, for example in the form of a locking element, for locking the barrel of the syringe when received in the syringe housing for lockingly setting of the needle arrangement in the open position. An advantage by this configuration is that a user does not need to actively hold the syringe in the inserted position. This freedom provides for a less complex aspiration process. 
     In one embodiment of the needle arrangement adapted for a biopsy application, a compartment may be provided in the elongated portion of the needle such that the compartment is exposed to a surrounding area when the needle arrangement is set in the open position. 
     Different embodiments which may be applied to a needle arrangement according to the invention, for example an injection needle arrangement, an aspiration needle arrangement, or a biopsy needle arrangement, will now be disclosed. 
     In one embodiment of the needle arrangement, the sealing member is arranged to abut the complete end surface of the needle sheath when the needle is arranged in the retraction position. The sealing member may be arranged to have the same cross-sectional shape and size as the needle sheath, so as to provide a smooth transition between the outer surfaces of the sealing member and the needle sheath when the needle is arranged in the retraction position. Such a smooth transition may contribute to a reduced risk of collecting bacteria in the biopsy needle arrangement. 
     In one embodiment of the needle arrangement, the distal outer surface of the sealing member is inclined relative to the longitudinal axis of the needle. As the needle arrangement, for example the biopsy needle arrangement, moves in the forward movement direction, being essentially the same as the longitudinal direction, the shape of the sealing member may be chosen to facilitate the movement. By having the distal outer surface shaped in an inclination relative the longitudinal axis of the needle, and hence relative the movement direction of the biopsy needle arrangement, a pointy tip may be provided that is facing in the forward movement direction. The needle arrangement, for example the biopsy needle arrangement, may thereby move more easily through the tissue and pierce, for example, the wall of the rectum easier. 
     In a preferred embodiment, the inclination angle between the distal outer surface and the longitudinal axis of the needle is in the interval of 30-60 degrees. A pointy tip obtained by an inclination with an inclination angle in this interval may facilitate the movement of the needle arrangement, for example the biopsy needle arrangement, through tissue. 
     In an embodiment of the needle arrangement, the end surface of the needle sheath is inclined relative to the longitudinal axis of the needle. The sealing member surface abutting at least a portion of the end surface of the needle sheath is in such an embodiment inclined in a corresponding manner. In other words, the inner surface of the sealing member and the end surface of the needle sheath are inclined relative to the longitudinal axis by the same inclination angle. 
     In another embodiment of the needle arrangement, the end surface of the needle sheath is arranged orthogonally to the longitudinal axis of the needle. The sealing member surface abutting at least a portion of the end surface of the needle sheath is in such an embodiment also arranged orthogonally. Such a configuration of the needle sheath arrangement allows for the needle to rotate in relation to the needle sheath. Such control and maneuverability of the needle in relation to the needle sheath may be desirable in some applications. Moreover, the interface area between the sealing member and the needle sheath is minimized thus minimizing the area in which bacteria may be collected and/or tissue may be clamped when the needle goes from being in an extraction position to a retraction position. 
     In one embodiment of the needle arrangement, a coating, such as a repellent coating or a smooth nanocoating, is provided on at least a distal outer surface of the sealing member. 
     The smooth nanocoating provides a smooth surface, having a low surface roughness, in which bacteria is less prone to be collected when compared to material used for conventional needle arrangement, for example conventional biopsy needle arrangements, such as stainless steel. The smooth nanocoating may provide an especially even surface, with a very low amount of microscopic grooves and holes. 
     The repellent coating may comprise a material that has a low affinity for the foreign matter. By, for example, having a material that repels proteins, a lower number of binding sites are presented to the binding protein structures of the bacteria. It should be noted that there are many ways for the skilled person to chemically alter the surface to prevent foreign matter from adhering. 
     In one embodiment of the needle arrangement, a heat coating is provided on at least a distal outer surface of the sealing member. By heat coating is meant a coating which may be heated up by providing a current through the heat coating or by radiation provided by an external energy source. The heat coating may for example be activated to produce heat by providing a current through the heat coating which in that case has a relatively high resistance. As another example, the heat coating may be heated by subjecting it to radiation from an external energy source, such as a laser source. 
     By heating sections of the needle arrangement, for example the biopsy needle arrangement, that is exposed to bacteria, the bacteria will be thermally eliminated. Eliminating or at least reducing the amount of bacteria on and/or in the needle arrangement, for example the biopsy needle arrangement, may lower or eliminate the risk of infections. 
     In one embodiment of the needle arrangement, where the heat coating is arranged to develop heat when a current is applied there through, the heat coating may be a heat nanocoating. When using such resistive heating, the voltage drop depends on, among other things, the thickness of the material. By using a heat nanocoating, heating occurs quickly. Such a feature may be an advantage when heat is desired at a precise moment. A heat nanocoating also ensures quick cooling, which contributes to a minimized time of exposing surrounding tissue for potentially damaging heat. 
     In one embodiment of the needle arrangement, the heat coating is provided in an interface between the sealing member and the needle sheath. Preferably, the heat coating is provided in the whole interface, i.e. in the whole gap between the sealing member and the needle sheath. Bacteria which may have been collected in this area may thereby be heated and thus eliminated or at least reduced in number. 
     In one embodiment of the needle arrangement, the heat coating is provided along an outer surface portion of the needle sheath. The heat coating may be arranged in connection to the distal end thereof. As bacteria may also be collected on and/or by the outer surface of the needle sheath, this section may advantageously be coated with heat coating. Preferably, the whole outer surface of the biopsy needle arrangement that enters an area that is sensitive for contamination, such as a prostate in TRPB, may be coated with the heat coating. 
     In one embodiment of the needle arrangement, the needle arrangement, for example the biopsy needle arrangement, comprises an electrically conductive section connected to the heat coating and arranged to provide a conductive path through the needle arrangement, for example the biopsy needle arrangement. The conductive section inside the needle arrangement, for example the biopsy needle arrangement, is arranged to provide current through a heat coating, preferably a heat nanocoating that is arranged to produce heat when subjected to a current. 
     In one embodiment, the electrically conductive section comprises one or several of the following materials: carbon fiber, metals, such as gold and silver. 
     In one embodiment, the smooth nanocoating, the repellent coating and/or the heat nanocoating comprises one or several of the following materials: metals, carbon and carbon fibers, polyethylene glycol, PEG, (L-lysine)-[g]-poly(ethylene glycol), PLL-PEG or oxides such as titanium dioxide, silicon dioxide, and niobium petoxide. 
     It is noted that a particular nanocoating, or other material, may fulfil the characteristics of a combination of one or more of a smooth nanocoating and a heat nanocoating. In other words, the needle arrangement, for example the biopsy needle arrangement, may be provided with a single coating that provides the function of both a smooth nanocoating and a heat nanocoating. 
     In one embodiment, the complete outer surface of a distal portion of the needle arrangement, for example the biopsy needle arrangement, is provided with a coating, for example a smooth nanocoating, a repellent coating, a heat coating, or a combination thereof, wherein the distal portion corresponds to the portion that is to be inserted in a region of the body, for example a biopsy region. By biopsy region is meant for example the organ that the biopsy is to be sampled from. For a prostate biopsy, the biopsy region is the prostate region. 
     In one embodiment, the biopsy needle arrangement is configured for prostate biopsy. 
     In summary, the sealing member of the needle arrangement, for example the biopsy needle arrangement, contributes to lowering the number of bacteria that is collected and brought with the needle arrangement, for example the biopsy needle arrangement, from for example an area in the rectum, through the wall of the rectum and into the prostate. Surface treatment, such as coatings, and/or heat elements may be applied to an outer surface (portion) of the needle arrangement, for example the biopsy needle arrangement to (further) lower the risk that bacteria is collected. 
     The needle arrangement, or parts thereof, may be provided as a disposable article or as a non-disposable article. 
     A further scope of applicability of the present invention will become apparent from the detailed description given below. It is to be understood that this invention is not limited to the particular component parts of the arrangements and systems described as such arrangements and systems vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It must be noted that, as used in the specification and the appended claim, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, reference to “a unit” or “the unit” may include several devices, and the like. Furthermore, the words “comprising”, “including”, “containing” and similar wordings does not exclude other elements or steps. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other aspects of the present invention will now be described in more detail, with reference to appended drawings showing embodiments of the invention. The figures should not be considered limiting the invention to the specific embodiment; instead they are used for explaining and understanding the invention. 
       As illustrated in the figures, the sizes of layers and regions, such as gaps between structures, are exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of embodiments of the present invention. Like reference numerals refer to like elements throughout. 
         FIG. 1  is a schematic view of a conventional biopsy needle arrangement. 
         FIG. 2  is a perspective view of a biopsy needle arrangement according to an embodiment. 
         FIG. 3  is a cross-sectional view taken along the longitudinal axis of a biopsy needle arrangement according to an embodiment. 
         FIG. 4 a    is a cross-sectional view taken along the longitudinal axis of a biopsy needle arrangement, when the needle is in a retraction position. 
         FIG. 4 b    is a cross-sectional view taken along the longitudinal axis of a biopsy needle arrangement, when the needle is in an extraction position. 
         FIGS. 5 a - c    are perspective views of a biopsy needle arrangement in different configurations during a process of collecting a tissue sample. 
         FIG. 6  is a cross-sectional view taken along the longitudinal axis of a biopsy needle arrangement being provided with a coating. 
         FIGS. 7 a - b    are cross-sectional views taken along the longitudinal axis of a biopsy needle arrangement, wherein the needle comprises a conductive section. 
         FIGS. 8   a - c  are cross-sectional views taken along the longitudinal axis of a biopsy needle arrangement showing shapes of the sealing member according to different embodiments. 
         FIG. 9  is a cross-sectional view taken along the longitudinal axis of a biopsy needle arrangement according to an embodiment. 
         FIG. 10  illustrates a needle arrangement according to an embodiment of the invention. 
         FIG. 11  illustrates a connection member of a needle arrangement. 
         FIG. 12  illustrates a needle arrangement with a syringe connected thereto, and a close-up of a connection member of the needle arrangement. 
         FIGS. 13 a -13 d    illustrate different configurations of a part of a needle arrangement for providing a guiding mechanism. 
         FIG. 14  illustrates a needle arrangement according to an embodiment of the invention. 
         FIG. 15  illustrates the needle arrangement in  FIG. 14  with a syringe inserted therein. 
     
    
    
     Note that figures are not to scale for purposes of clarity. 
     DETAILED DESCRIPTION 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and to fully convey the scope of the invention to the skilled person. 
     Embodiments of the present invention relate, in general, to the field of prostate biopsy, to injection applications, and to aspiration applications. 
     Preferred embodiments which will be disclosed relate to a biopsy needle arrangement, to an injection needle arrangement, and to an aspiration needle arrangement. 
     First, an embodiment relating to a biopsy needle arrangement will be described with reference to  FIGS. 1-5   c.    
     A preferred embodiment relates to the biopsy of the prostate, however, it should be appreciated that the invention is as such equally applicable to performing biopsy on other organs or parts of the male, female and/or an animal body. However, for the sake of clarity and simplicity, most embodiments outlined in this specification are related to prostate biopsy only. 
       FIG. 1  is a schematic view of a conventional, so called tru-cut biopsy needle arrangement  10 . The biopsy needle arrangement  10  may be part of a system for performing biopsy of any type, including prostate biopsies. The system may further comprise arrangements for actuating retraction/extraction movements in the biopsy needle arrangement, tubes, and holders. 
     The biopsy needle arrangement  10  comprises a needle  12  which is arranged inside a needle sheath  14 . The biopsy needle arrangement  10  further comprises a compartment  16 , for housing a biopsy sample (not illustrated). The needle  12  is movable relative to the needle sheath  14  along the longitudinal axis  18  of the biopsy needle arrangement  10 . The biopsy needle arrangement  10  is arranged to be moved in the longitudinal direction, i.e. along the longitudinal axis  18 . In order to facilitate movement of the biopsy needle arrangement  10  through tissue when the biopsy needle arrangement  10  is inserted into the body, the distal end of the needle sheath  14  and the elongated portion  12  may be inclined relative to the longitudinal axis  18 . 
     The needle  12  and the elongated needle sheath  14  may be connected to springs for actuating movement of the needle  12  and the needle sheath  14  in relation to each other. The movement of the needle  12  and the needle sheath  14  may be independently controlled. 
     When performing, for example, a TRPB, an ultrasound device is inserted into the rectum of the patient in order to visualize the prostate and provide guidance through a canal for the biopsy needle arrangement  10 . The biopsy needle arrangement  10  is then pierced through the wall of the rectum and into the prostate. The biopsy needle arrangement  10  normally penetrates the prostate by up to 6 cm. 
     The needle sheath  14  and the needle  12  may be arranged to be actuated in a forward directed movement in two steps. Firstly, the needle  12  is actuated out from the needle sheath  14  to an extraction position, exposing the compartment  16 . Surrounding tissue is collected inside the exposed compartment  16 . Closely after, normally within milliseconds, the needle sheath  14  is actuated forward thereby making the needle  12  revert to a retraction position. The compartment  16  now contains the collected biopsy sample. The biopsy needle arrangement  10  may then be pulled out of the prostate and the biopsy sample may be obtained from the compartment  16 . Normally around 8-12 samples are extracted during one examination, however anything from 1 to more than 20 biopsies can be obtained. 
     The gap  11  between the needle sheath  14  and the needle  12  is exposed to the surroundings by a gap entrance which faces in the direction of travel. Bacteria are prone to be collected in the gap, especially during the travel in a forward direction through tissue while passing for example faeces with bacteria lining the inside of the rectal wall. The conventional biopsy needle arrangement  10  may thus collect and bring bacteria along with it when traveling through tissue which may increase the risk of post-examination infections. 
     The conventional biopsy needle arrangement  10  is typical made in stainless steel. Due to the surface roughness of such materials, bacteria may be collected and brought with the biopsy needle arrangement  10  on the outer surface of the needle sheath  14  and of the needle  12 , respectively. 
       FIG. 2  is a perspective view of a needle arrangement  100  according to an embodiment relating to a biopsy needle arrangement. The biopsy needle arrangement  100  comprises a needle  202  and an elongated needle sheath  104 . The biopsy needle arrangement  100  may typically be 20 or 25 cm long. The biopsy needle arrangement, or any needle arrangement according to an embodiment, may of course be of any length suitable the application. The length and dimensions of the biopsy needle arrangements and its components (needle/needle sheath thickness, compartment dimension, etc.) may vary between different applications. 
     The needle  202  comprises an elongated portion  102  and a sealing member  204 . The elongated portion  102  forms a compartment  106  for housing a collected tissue sample (not illustrated). The compartment  106  may be 1-3 cm long. In a preferred embodiment, the compartment  106  is situated close to the sealing member  204 , such as at a distance of 1-7 mm. 
     The sealing member  204  may be an integral part of the elongated portion  102 . The sealing member  204  may alternatively be attached to the elongated portion  102  using, for example, screwing, welding or gluing. 
     The biopsy needle arrangement  100  is shown with the needle  202  being in an extraction position, i.e. the needle arrangement  100  is set an open position. 
     The needle  202  may be arranged in a retraction position, i.e. in a closed position, by that the needle sheath  104  is forwarded to encompass the elongated portion  102  of the needle  202 , wherein the sealing member  204  of the needle  202  abuts at least a portion of the end surface  206  of the needle sheath  104 . 
     The end surface  206  is the area of the needle sheath  104  that is facing forward in the longitudinal direction of the biopsy needle arrangement  100 , and towards the sealing member  204 . By forward is meant in the direction of travel that the biopsy needle arrangement  100  is intended to travel when entering a part of the body for taking a sample. By backwards is meant the opposite direction to forward, also along the longitudinal axis  18 . In other words, when entering a part of the body for taking a biopsy sample, the biopsy needle arrangement  100  travels in a forward direction and when being retracted through the tissue the biopsy needle arrangement  100  travels in a backward direction. This definition of forward and backward directions is applicable to other embodiments of a needle arrangement exemplified herein as well. 
     By that the sealing member  204  and the end surface  206  abuts when the needle  202  is in the retraction position, a gap entrance  110  to a longitudinal gap between the needle sheath  104  and the elongated portion  102  of the needle  202  is at least partly blocked by the sealing member  204  so that intrusion of foreign matter is prevented, or at least restricted. The sealing member  204  in the shown embodiment is arranged to cover the whole gap entrance  110  around the elongated portion  102  of the needle  202 , but it is understood that even closing a part of the gap entrance  110  may contribute to a lowered risk for collecting bacteria. For example, the sealing member  204  may be arranged to cover a quarter or half of the edge of the gap entrance  110 . 
     The sealing member  204  may have a different cross-sectional shape than that of the elongated portion  102  and/or of the needle sheath  104 . 
     The biopsy needle arrangement  100  is in  FIG. 2  shown to have a circular cross-sectional geometry but various other geometrical forms are possible. Non-limiting examples include rectangular and oval cross-sectional shapes. 
       FIG. 3  illustrates a part of a biopsy needle arrangement  100  according to an embodiment. The biopsy needle arrangement  100  comprises a needle sheath  104  and a needle  202  coaxially arranged inside the needle sheath  104 . The needle  202  is here arranged in a retraction position, i.e. the needle arrangement  100  is set in a closed position. A longitudinal gap  112  is present between the elongated portion  102  of the needle  202  to allow the needle  202 , in particular the elongated portion  102  thereof, to easily move in relation to the needle sheath  104 , i.e. without too much friction between the elongated portion  102  and the needle sheath  104 . Optimally, the elongated portion  102  of the needle  202  is well fitted inside the needle sheath  104 . In order to assist reading, however, the distances between the two parts are exaggerated in the figures. 
     Due to, for example, surface roughness, and/or lack of position preciseness or manufacturing precision, a transversal interstice  300  may be present between the sealing member  204  and the end surface  206  of needle sheath  104  when the sealing member  204  abuts the end surface  206 . However, since the transversal interstice  300  is directed in a transversal direction, and thus the entrance of the transversal interstice  300  is not facing directly in the longitudinal direction, hence in the forward direction, as is the case of the entrance to the longitudinal gap  112  between the needle  102  and the needle sheath  104 , the risk that bacteria is collected through the entrance of the transversal interstice  300  is lowered. Moreover, a strong fit between the sealing member  204  and the needle sheath  104  may be achieved by forcing the sealing member  204  and the needle sheath  104  towards each other which contributes to a minimized interstice  300  between the parts. The longitudinal gap  112  between the needle  102  and the needle sheath  104  cannot be minimized in such manner since that would create a frictional force between the parts which would counteract movement of the needle  104  in relation to the needle sheath  104  and thus the function of the biopsy needle arrangement  100 . Hence, the risk of that bacteria is collected in the interstice  300  between the sealing member  204  and the needle sheath  104  is reduced by the above mentioned factors, i.e. the repositioned entrance of the interstice  300  and the strong fit between the sealing member  204  and the needle sheath  104 , when compared to the risk of collecting bacteria in a conventional biopsy needle arrangement. 
     Additionally, a labyrinth effect is achieved since the transversal interstice  300  and the longitudinal gap  112  are not arranged in the same direction, further increasing the prevention of bacteria reaching the inside of the biopsy needle arrangement  100 , in particular the compartment  106  provided therein. 
     The transversal interstice  300  may be minimized by a biasing means, such as a spring mechanism, arranged to actuate the needle sheath  104  forward towards the inner surface of the sealing member  204  such that the needle sheath  104  and the sealing member  204  are forced together. The biasing means may thus be arranged to bias the needle arrangement  100  to be set in the closed position. The biasing means, such as the spring mechanism, may be part of the biopsy needle arrangement  100 . 
     In order to cover the gap entrance  110 , the radial extension b of the sealing member  204  should be greater than the inner radial extension a of the needle sheath  104 . In other words, in an embodiment where the cross-section of the sealing member  204  and of the needle sheath  104  is circular, the outer diameter of the sealing member  204  should be greater than the inner diameter  104  of the tubular needle sheath  104 . 
     The radial extension b may be chosen such that the sealing member  204  completely covers the end surface  206  of the needle sheath  104 . In  FIG. 3 , the radial extension b is equal to the outer radial extension c of the needle sheath  104 . In this case, a smooth transition between the radial outer surface of the sealing member  204  and the radial outer surface of the needle sheath  104  is achieved. Such a smooth transition may contribute to a reduced risk of collecting bacteria in the biopsy needle arrangement  100 , for example by reducing bacteria adhering to the end surface  206 . 
     It is noted that the radial extension b of the sealing member  204  may in other embodiments be greater than the radial extension c of the needle sheath  104 . 
     The sealing member  204  may be arranged to extend past the end surface  206  in the longitudinal direction and along the outer surface of the needle sheath  104 . In such an embodiment, a second longitudinal gap will be present between the needle sheath  104  and the sealing member  204 . An entrance to the second longitudinal gap will be facing away from the direction of forward movement of the biopsy needle arrangement  100  and thus there will still be a lowered risk of collecting bacteria through such an entrance when compared to conventional biopsy needle arrangements. 
       FIGS. 4 a  and 4 b    are each a schematic view of the biopsy needle arrangement  100  according to an embodiment. The needle  202  is arranged in a retraction position. 
     The inner surface of the sealing member  204  may be inclined relative to the longitudinal axis  18 . In a preferred embodiment, an inclination angle α is in the interval 30-60 degrees, relative to the longitudinal axis  18 . 
     The inclination angle γ of the end surface  206  relative to the longitudinal axis  18  is equal to the inner surface inclination angle α of the sealing member  204 . 
     The distal outer surface of the sealing member  204  is also inclined. The inclination angle β of the distal surface may differ from the inner surface inclination angle α. The distal surface inclination angle β is in the illustrated embodiment equal to the inner surface inclination angle α. Other distal surface inclination angles are possible, such as 0-90 degrees. 
     The inclination angles and shape of the sealing member  204  and the needle sheath  104  may affect the deviation angle and force needed to move the biopsy needle arrangement  100  through tissue. 
       FIG. 5  is a perspective view of a biopsy needle arrangement  100  according to an embodiment. A process of performing a TRPB biopsy with a biopsy needle arrangement  100  according to this embodiment will now be disclosed. 
       FIG. 5 a    shows the biopsy needle arrangement  100  with the needle  202  arranged in a retraction position, i.e. the needle arrangement  100  is set in the closed position. The sealing member  204  effectively closes the gap  110  in accordance with above disclosed embodiments. The biopsy needle arrangement  100  may be inserted through a canal in the rectum of the patient, guided by an ultra sound device. The biopsy needle arrangement  100  is inserted by movement in a direction along the longitudinal direction of the biopsy needle arrangement  100  and with the sealing member  204  facing forward in the travel direction during insertion. 
     The biopsy needle arrangement  100  may be put against the rectum wall and aimed towards the prostate of the patient. The biopsy needle arrangement  100  may then be pushed through the wall and into the prostate. The biopsy needle arrangement  100  may be arranged to penetrate the prostate by up to 6 cm. The biopsy needle may also penetrate further into the prostate. 
     As illustrated in  FIG. 5 b   , while in a desired position, the needle  202  may be actuated forward in relation to the needle sheath  104 . The actuation may be achieved by a spring element or the like which may be part of the biopsy needle arrangement  100 . The needle  202  may thus be moved further into the prostate. In this extraction position, i.e. when the needle arrangement  100  is set in this open position, the compartment  106  of the needle  202  is exposed by that a gap, extending in the longitudinal axis of the needle, is formed between the sealing member  204  and the end surface  206  of the needle sheath  104 . A prostate biopsy sample may be collected in the compartment  106  of the needle  202 . 
     As illustrated in  FIG. 5 c   , the needle sheath  104  may be actuated forward so as to encompass at least a part of the elongated portion  102  of the needle  202  and thus close the compartment  106 . It may take a shorter or a longer amount of time for the needle sheath  104  to move forward. 
     The movement needle sheath  104 , is restricted when impinging against the inner surface of the sealing member  204 . In order to reduce possible damage of the sealing member  204 , the biopsy needle arrangement  100 , or a system that the biopsy needle arrangement  100  is part of, may be provided with a breaking mechanism so as to reduce the collision force. 
     The reader is reminded that the gap between the elongated portion  102  of the needle  202  and the needle sheath  104  is exaggerated for illustrative purposes. 
     A schematic view of an embodiment of the biopsy needle arrangement  100  is illustrated in  FIG. 6 . Here, the needle  202  is arranged in a retraction position. That is, the needle arrangement  100  is set in a closed position. 
     When the biopsy needle arrangement  100  is moved from the rectum to the prostate, bacteria may get stuck in small grooves of the surface structure of the sealing member  204 . This is the case with for example the material stainless steel which is conventionally used in this type of constructions. 
     In order to alleviate this effect, the sealing member  204  may partly, or completely, be coated in a coating  600 . The coating  600  may be a repellent coating or a smooth nanocoating. 
     The term repellent is defined as surface structure that chemically lowers the adherence of bacteria when compared to conventionally used surface structures. For example, a surface structure that is hydrophobic lowers the adherence to the hydrophilic binding structures of bacteria. Non-limiting examples of the repellant coating are: metals, polymere brushes and/or zwitter ionic groups, such as PEG and PLL-PEG. 
     The term smooth is defined as an evenness of a surface structure, wherein the surface evenness contributes to that bacteria is less prone to adhere thereto when compared to conventionally used materials. 
     Non-limiting examples of the smooth nanocoating are: metals and Au. 
     The coating  600  may extend in the interface between the sealing member  204  and the needle sheath  104 . This may be achieved by coating the end surface  206  of the needle sheath  104  and the inner surface of the sealing member  204  abutting the end surface  206  or provided on just one of the two. The interface between the inner surface of the sealing member  204  and the needle sheath  104  may take many different other forms in order to, for example, strengthen the labyrinth effect. For example, the inner surface of the sealing member  204  may form a conical recess in which the needle sheath  104 , shaped in a corresponding manner, may be received. 
     The coating  600  may be provided on the outer surface of the needle sheath  104 . The coating  600  may be provided on a part of the outer surface of the needle sheath  104 , preferably at least the part that is inserted into the prostate. In a preferred embodiment, 6 cm of the needle sheath  104  as measured in the longitudinal direction and from the distal end is coated in coating  600 . The distance 6 cm coincides with the distance of which the prostate is penetrated by the biopsy needle arrangement  100  in some applications. 
     In one embodiment, the coating  600  is provided along the whole outer surface of the needle sheath  104 . This may be beneficial from a manufacturer perspective in that it may be less complex to coat the entire outer surface instead of a part thereof. 
     The application of coating  600  may be preceded by for example processing the material of the needle sheath  104  through, for example, electrochemical polishing. Another embodiment of the biopsy needle arrangement  100  is illustrated in  FIG. 7 a    and  FIG. 7 b   . The needle  202  illustrated in  FIG. 7 a    is arranged in a retraction position. 
     A conductive section  700  is comprised in the biopsy needle arrangement  100 . By conductive is meant electrically conductive in the context of this application. 
     The conductive section  700  runs inside the elongated portion  102  and forms an inner section of the elongated portion  102 . The conductive section  700  may alternatively run along an outer surface of the elongated portion  102  of the needle  202 . 
     The sealing member  204  is provided with a heat coating  702 . 
     Non-limiting examples of the heat coating are: metals, carbon and carbon fibers. The conductive section  700  is conductively connected to the heat coating  702 . The heat coating  702  may be a heat nanocoating. The heat nanocoating may also form a smooth nanocoating, and vice versa. 
     The heat coating  702  may also be arranged in the interface between the sealing member  204  and the needle sheath  104 . This may be achieved by coating the end surface  206  of the needle sheath  104  and/or the inner surface of the sealing member  204  which is arranged to abut the end surface  206 . 
     As illustrated, the heat coating  702  also extends on and along the outer surface of the needle sheath  104 . The heat coating may be provided on parts of the needle sheath  104 , preferably at least the part that is inserted into the prostate. In a preferred embodiment, 6 cm of the outer surface of the needle sheath  104  along the longitudinal extension and as measured from the distal end is covered by the heat coating  702 . The distance 6 cm coincides with the distance of which the prostate is penetrated by the biopsy needle arrangement  100  in some applications. 
     In one embodiment, the heat coating  702  is provided along the whole outer surface of the needle sheath  104 . This may be beneficial from a manufacturer perspective in that it may be less complex to coat the entire outer surface instead of a part thereof. 
     The heat coating  702  may be connected to a circuit (not illustrated) arranged in the biopsy needle arrangement  100  or in connection thereto. The heat coating  702  may be of a resistive material. By providing a current through the conductive section  700  of the biopsy needle arrangement  100 , the current will flow also through the heat coating  702 . By running a current through the heat coating  702 , the material heats up. The heat coating  702  is preferably heated to at least 100 degrees Celsius, in order to eliminate any bacteria collected on the surface structure. 
     In one embodiment, the sealing member  204  comprises a connecting conductive section  706  arranged to conductively connect the conductive section  700  and the heat coating  702  of the sealing member  204 . 
     The biopsy needle arrangement  100  may be constructed such that the current is disconnected when the needle  202  is arranged in the extraction position, as seen in  FIG. 7   b.    
     In a preferred embodiment, current is provided to the heat coating  702  of the sealing member  204  through the conductive section  700 . The connecting section  706  bridges the connection between the conductive section  700  and the heat coating  702  of the sealing member  204 . The skilled person appreciates that there may be other ways to connect the conductive section  700  with the heat coating  702  of the sealing member  204 . For example, the sealing member may be of a conductive material, thereby in itself bridging the current from the conductive section  700  to the heat coating  702  of the sealing member  204 . 
     Furthermore, the heat coating  702  of the needle sheath  104  provides a closed path for the current to return from the sealing member  204  back to a conductive return section (not shown in figures). It is appreciated that the conductive return section may be arranged differently in different configurations of the biopsy needle arrangement  100 . 
     As can be seen in  FIG. 7 b   , as soon as the needle  102  is arranged in an extracted position, the connection between the heat coating  702  of the needle sheath  104  and the heat coating  702  of the sealing member  204  may be disconnected. When the needle  102  is arranged in the extracted position, no current can flow through the biopsy needle  100 . 
     In an embodiment, the conductive return section is connected to the power supply or to ground. In a preferred embodiment, the return section is placed inside the needle sheath  104 , with a conductive bridge connecting the heat coating  702  with the return section through the need sheath  104  as is shown in  FIG. 7 a - b   . The skilled person realizes that for the purpose of this embodiment, the return section may be placed on the outer surface of the needle sheath  104 . 
     In order to reduce the risk that the biopsy sample becomes heat damaged, the sample is preferably kept below 41 degrees Celsius. For that purpose, part of the needle  202  may be made in an insulating material, thus forming an insulating portion  704 . Specifically, the portion of the needle  202  forming the compartment  106  may be made in an insulating material. The insulating portion  704  may protect a biopsy sample in the compartment  106  from the heat developed in the heat coating  702 . Insulating material may also be arranged as a part of the needle sheath  104 . Specifically, an insulating material may be arranged in connection to the compartment  106  in order to protect a biopsy sample collected therein from heat. Non-limiting examples of insulating materials are: Kevlar, COP, PEEK and LCP. 
     In one preferred embodiment, the parts of the biopsy needle arrangement  100  not forming the disclosed conducting sections or the heat coating  702  are made of an insulating material. 
     In a preferred embodiment the heat coating  702  is formed by a nanocoating, being a thin coating. The term nanocoating is in the context of this application defined as a coating having a thickness of about 10-1000 nanometers. In the preferred embodiment, the thickness is about 100-400 nanometer. Such a thin heat coating  702  contributes to a quick heating and cooling process, with the effect of thermally eliminating bacteria on the surface of the heat coating with a lowered risk of damaging surrounding tissue. 
     It is appreciated that the concept of providing a coating  600  and the concept of providing a heat coating  702  may be applied to a needle arrangement according to any embodiment, not only a biopsy needle arrangement. Specifically, these coating concepts may be applied to an injection needle arrangement or to an aspiration needle arrangement according to embodiments. The skilled person may, by the above description of the coating concepts applied to a biopsy needle arrangement, translate the concepts to applications on other needle arrangements, such as an injection needle arrangement or an aspiration needle arrangement. 
     Different examples of configurations of the sealing member will now be disclosed with reference to  FIGS. 8 a   - 8   c.  These examples will be provided based on the above disclosed biopsy needle arrangement  100 , however it is appreciated that configurations may be applied to other embodied needle arrangements as well, such as an injection needle arrangement or an aspiration needle arrangement. 
     As illustrated in  FIGS. 8 a   - 8   c,  the skilled person appreciates that the sealing member  204  may have many different shapes and forms. For example, the embodiment shown in  FIG. 8 b    has an arrowhead configuration enabling better precision of the movement of the biopsy needle arrangement  100 . Different shapes/forms of the sealing member  204  may be desired in different applications, for example between different biopsy techniques. 
       FIG. 8 c    illustrates a sealing member  204  with a distal outer surface angle that is inclined in an opposite direction relative to the inclination angle of the needle sheath  104 . This configuration may provide a better precision, with low deviation, of the biopsy needle arrangement  100  when the needle  202  and the needle sheath  104 , respectively, is actuated into the tissue. 
     Another example of a biopsy needle arrangement  100  is illustrated in  FIG. 9 . The biopsy needle arrangement  100  comprises a needle  202  and a needle sheath  104 . A heat coating  702  is provided with the corresponding form and function as disclosed above in connection to  FIG. 7 a    and  FIG. 7 b   . The heat coating  702  may be heated by providing a current through the heat coating  702 . The current may be provided through a conductive portion  700  that is arranged to run inside or along the needle  202  and that is conductively connected to the heat coating  702 . A conductive return section is also provided for providing a return path for the current, at least when the needle  202  is arranged in a retraction position. 
     An embodiment may be provided with a combination of the features of  FIG. 7  and  FIG. 9 . In this embodiment, the current flowing through the needle sheath  104  is not disconnected while the needle  202  is in an extracted position. This concept is also applicable to other embodied needle arrangements such as an injection needle arrangement or an aspiration needle arrangement. 
     The conductive return section may be placed outside of the biopsy needle arrangement, for example it may comprise a conductive plate on the hip of the patient. In this case, the current is led through the conductive section  700 , through the heat coating  702  and further through the tissue of the patient reaching the conductive plate, thereby completing the circuitry. 
     Examples of Configurations of a Biopsy Needle Arrangement 
     A1. A biopsy needle arrangement for obtaining a tissue sample, the biopsy needle arrangement comprising: an elongated needle sheath, a needle comprising an elongated portion coaxially arranged inside the needle sheath and movable between an extraction position and a retraction position in relation to the needle sheath, wherein the needle further comprises a sealing member arranged at a distal end of the elongated portion, the sealing member being arranged to abut at least a portion of an end surface of the needle sheath extending transverse the longitudinal axis of the needle when the needle is arranged in the retraction position, thereby restricting intrusion of foreign matter in an area between the needle sheath and the needle. 
     A2. The biopsy needle arrangement according to the example A1, wherein the sealing member is arranged to abut the complete end surface of the needle sheath when the needle is arranged in the retraction position. 
     A3. The biopsy needle arrangement according to any of the previous examples A1-A2, wherein a distal outer surface of the sealing member is inclined relative to the longitudinal axis of the needle. 
     A4. The biopsy needle arrangement according to example A3 wherein an inclination angle between the distal outer surface and the longitudinal axis of the needle is in the interval of 30-60 degrees. 
     A5. The biopsy needle arrangement according to any of the previous examples A1-A4, wherein the end surface of the needle sheath is inclined relative to the longitudinal axis of the needle. 
     A6. The biopsy needle arrangement according to any of the previous examples A1-A5, wherein the end surface of the needle sheath is arranged orthogonally to the longitudinal axis of the needle. 
     A7. The biopsy needle arrangement according to any of the previous examples A1-A6, wherein a coating, such as a smooth nanocoating or a repellent coating, is provided on at least a distal outer surface of the sealing member. 
     A8. The biopsy needle arrangement according to any one or the examples A1-A7, wherein a heat coating is provided on at least a distal outer surface of the sealing member. 
     A9. The biopsy needle arrangement according to the example A8, wherein the heat coating is a heat nanocoating. 
     A10. The biopsy needle arrangement according to any of the examples A8-A9, wherein the heat coating is provided in the interface between the sealing member and the needle sheath. 
     A11. The biopsy needle arrangement according to any of examples A8-A10, wherein the heat coating is provided along an outer surface portion of the needle sheath in connection to the distal end thereof. 
     A12. The biopsy needle arrangement according to any of the examples A8-A11, further comprising a conductive section connected to the heat coating and arranged to provide a conductive path through the biopsy needle arrangement. 
     A13. The biopsy needle arrangement according to the example A12, wherein the electrically conductive section comprises one or several of the following materials: carbon fiber, metals, such as gold and silver. 
     A14. The biopsy needle arrangement according to any of the previous examples A1-A13, wherein the arrangement is configured for prostate biopsy. 
     A15. A system comprising a biopsy needle arrangement according to any of the previous examples A1-A14. 
     An embodiment relating to an injection needle arrangement will be now be disclosed with reference to  FIGS. 10-12 . 
     Up to here, the geometry and function of various types of biopsy needle arrangements are presented and discussed. In the following, an embodiment relating to an injection needle arrangement will be disclosed. 
       FIG. 10  is a perspective view of an injection needle arrangement  1000  comprising a sealing member  1003 , a needle sheath  1002 , and a connection member  1004 . An elongated portion (not shown in  FIG. 10 ) of a needle is coaxially arranged inside the needle sheath  1002 . The needle is movable relative to the needle sheath  1002  along a longitudinal axis  1001  of the needle. The needle sheath  1002  is arranged to sheath the elongated portion of the needle. The needle further comprises the sealing member  1003  which is arranged to a front end of the elongated portion of the needle. 
     The needle sheath  1002  has a front end and a rear end, and is arranged to cover the entire length of the elongated portion of the needle when the needle arrangement is set in a closed position, as in  FIG. 10 . By closed position is meant that the sealing member  1003  is arranged to abut at least a portion of a front end surface of the needle sheath  1002  extending transverse the longitudinal axis  1001  of the needle. As disclosed in previous embodiments, intrusion of foreign matter is thus restricted in an area between the needle sheath  1002  and the needle. As shown in  FIG. 10 , the rear end of the needle sheath  1002  is connected to the connection member  1004  which is adapted to connect to the tip of a syringe. The connection member  1004  comprises a circumferential flange  1005  arranged at a rear end of the connection member  1004 . The connection member  1004  is by its front end arranged to the rear end of the needle sheath  1002 . 
     The connection member  1004  will now be disclosed in detail with further reference to  FIG. 11 .  FIG. 11  is a close-up perspective cross-sectional view of the connection member  1004  of the injection needle arrangement  1000  shown in  FIG. 10 .  FIG. 11  illustrates a part of the needle  1102  arranged inside the needle sheath  1002 . A channel  1105  is provided between the needle  1102  and the inner surface of the needle sheath  1002 . The channel  1105  extends along the longitudinal axis  1001  of the needle  1102  between the front end to the rear end of the needle sheath  1002 . The channel  1105  is formed by a gap between an outer surface of the needle  1102  and an inner surface of the needle sheath  1002 . 
     It is advantageous to have a needle arrangement of any embodiment set and maintained in the closed position when the needle arrangement is not in an active mode, i.e. when it is not set in the open position for sampling (when taking a biopsy), for injection, or for aspiration. For this purpose, a biasing means may be provided. The biasing means may be arranged to bias the needle arrangement to be set in the closed position so as to ensure a tight sealing between the sealing member and the needle sheath. 
     Returning to  FIG. 11 , the connection member  1004  comprises such a biasing means in the form of a helical spring element  1104 . The helical spring element  1104  extends parallel to the longitudinal axis  1001  between an inner wall portion  1106  of the connection member  1004  and an end plate  1103  being part of the needle  1102 . That is, the helical spring element  1104  is arranged to be compressed in a direction extending at least partly along the longitudinal axis  1001 . The compression axis may for example extend in parallel or be common with the longitudinal axis  1001 . The end plate  1103  is arranged to, and connected to, a back portion of the needle  1102 . The dimensions and characteristics of the needle  1102 , the connection member  1004 , and the helical spring element  1106  is chosen such that the helical spring element  1106  is at least slightly compressed when arranged between the connection member  1004  and the end plate  1103 . Thus, the helical spring element  1106  applies a force on the end plate  1103 , and thus also on the rest of the needle  1102 , in a backward direction. The sealing member  1003  (seen in  FIG. 10 ) is thus forced backwards towards the needle sheath  1002 , which in turn is forced in the opposite direction (forwards) by the helical spring element  1104 . The helical spring element  1104  thus provides a biasing of the needle arrangement  1000  to be set in the closed position. 
     The injection needle arrangement  1000  may also be set in an open position, which is illustrated in  FIG. 12 . When the needle arrangement  1000  is set in the open position, a gap  1204  is formed between the sealing member  1003  and the front end surface of the needle sheath  1002 . The gap  1204  is formed by that the relative position of the needle  1102  and the needle sheath  1002  is adjusted such that a front portion of the elongated portion of the needle  1102  is extracted from the needle sheath  1002 . 
     In general, the adjustment may be achieved by moving the needle forward out from the needle sheath, or by moving the needle sheath backward to expose the needle, or by a combination of these adjustments. In the illustrated embodiment of the injection needle arrangement  1000 , however, the adjustment is achieved mainly by a forward movement of the needle  1102  which will now be disclosed in detail. 
     In  FIG. 12 , a conventional syringe  1200  is connected to the connection member  1004  of the injection needle arrangement  1000 . The syringe  1200  comprises a barrel  1201  formed by a hollow cylindrical tube and a plunger  1203  which can be pulled (for aspiration) or pushed (for injection) along the longitudinal axis  1001  of the needle  1102 . An end plunger plate  1206  is attached to the front side of the plunger  1203  facing the needle arrangement  1000 . The end plunger plate  1206  is arranged to provide a sealing against the barrel  1201 . 
     The syringe  1200  is here of a conventional Luer lock type in which a tip  1202  of the syringe  1200  comprises an inner tip  1207  and an outer tip  1208 . The inner surface of the outer tip  1208  is threaded for allowing the syringe  1200  to be screwed on a fitting such as the flange  1005  of the connection member  1004 . In  FIG. 12 , the syringe  1200  is fitted on the connection member  1004  and the inner tip  1207  is located partly inside the connection member  1004 . The connection member  1004  is arranged such that a sealed fitting is provided between the syringe  1200  and the connection member  1004 . 
     The circumferential flange  1005  extends in a transverse direction to the longitudinal axis  1001 . The circumferential flange  1005  may have a different cross-sectional shape than that of the rest of the connection member  1004 . The injection needle arrangement  1000  shown in  FIG. 10  comprises a connection member  1004  with a circumferential flange  1005  having a circular cross-sectional geometry but various other geometrical forms are possible. Non-limiting examples include rectangular and oval cross-sectional shapes. The circumferential flange, of any shape, may extend along the whole circumference a sub-portion thereof. 
       FIG. 12  illustrates the needle arrangement  1000  in an active mode, i.e. during injection by the syringe  1200 . The plunger  1203  is pushed in a forward direction  1205 , thus forcing a liquid located in the syringe in a forward direction  1209 , along the longitudinal axis  1001 , out from the syringe  1200  through the inner tip  1207  and into an inner space of the connection member  1004 . The liquid exerts a pressure on the end plate  1103  of the needle  1102 , which moves in a forward direction along the longitudinal axis  1001  whereby the helical spring element  1104  is compressed. The needle  1102  is thereby moved forwards in relation to the needle sheath  1002 , thus exposing a front part of the elongated portion of the needle  1102 . A longitudinal gap  1204  is formed which extends along the longitudinal axis  1001  of the needle  1102 . The distance d between the sealing member  1003  and the needle sheath  1002 , i.e. the length of the longitudinal gap  1204 , may be 0.1-1 mm, but may be outside this range depending on embodiment. 
     When the needle arrangement  1000  is set in this open position, the liquid pushed out from the syringe  1200  is allowed to travel between the syringe  1200  and the gap  1204  through the channel  1105  provided between the needle  1102  and the needle sheath  1002 . A fluid communication is thus allowed between the syringe  1200  and the gap  1204 . At the front end of the needle sheath  1002 , the channel  1105  is open towards a surrounding area to which the liquid may be injected. The injection needle arrangement  1000 , with the syringe  1200  connected thereto, may be (at least partly) inserted into a tissue. When in place, the plunger  1203  is pushed thus setting the injection needle arrangement  1000  in the open position. The liquid of the syringe  1200  is thus injected into the tissue via the channel  1105 . When the plunger  1203  is no longer pushed, or when reaching the front end of the barrel  1201 , the liquid pressure will decrease whereby the forward force on the end plate  1103  also decreases. The helical spring element  1104  will thereby decompress from its compressed state and force the end plate  1103 , and thus also the rest of the needle  1102 , backwards. The injection needle arrangement  1000  is thereby set in the closed position and the needle arrangement  1000  may be retracted from the tissue in a sealed state providing a lowered risk of infection when compared to conventional injection needle arrangements. 
     The helical spring element  1104  is chosen such that the force required for compression corresponds to the force exerted by the liquid pressure in order to provide the above disclosed function of setting the needle arrangement  1000  in the open position. The configuration of the helical spring element  1104 , or of an alternative biasing means, may of course vary between applications. The ability to design the needle arrangement  1000  in view of these characteristics is considered to be knowledge of the skilled person without the need for a more detailed explanation here. 
     It is appreciated that other types of biasing means may be used. Non-limiting examples include wave springs, spring mechanisms based on compression of air or gas, gas springs, volute springs, machined springs, and spring mechanism based on compression of an elastic material. 
     Moreover, the skilled person realizes that other types of syringes may be used and that the needle arrangement may be adapted for connection to those different types of syringes. For example, a slip tip syringe may be used which is fitted by a press fit. The connection is in in that case held together by friction between the syringe and a connection member of the needle arrangement. 
     In a needle arrangement, such as the one disclosed above, for an injection application, it is advantageous that the channel of the needle arrangement is provided between the needle and the needle sheath. In such a configuration, a flow of liquid may be present between the sealing member and a front end surface of the needle sheath. Specifically, when the liquid pressure decreases the sealing member will move towards and eventually abut the front end surface of the needle sheath. During this movement the liquid flow, i.e. flow of liquid from the syringe to the surroundings via the channel, also decreases but will be present throughout the movement. An advantage with the flow of liquid is that it counteracts that surrounding tissue is clamped between the sealing member and the front end surface of the needle sheath when the needle arrangement is set in the closed position. This advantage contributes to an optimal sealing. This is especially an advantage during procedures where multiple insertions with the same needle are performed in the tissue since a strong sealing may be kept throughout the procedure. 
     Different examples of a guiding portion for providing a guiding mechanism will now be disclosed with reference to  FIGS. 13 a   - 13   b.  It is appreciated that these configurations may be applied to needle arrangements of any embodiment, i.e. to a biopsy needle arrangement, to an injection needle arrangement, or to an aspiration needle arrangement. 
       FIGS. 13 a - b    is each a close-up perspective cross-sectional view of a front portion of a needle arrangement. The needle arrangement may be any one of the herein disclosed needle arrangement embodiments. The needle arrangement comprises a needle  1102  having a sealing member  1003  and an elongated portion. The elongated portion is adapted to be coaxially placed inside a needle sheath  1002  of the needle arrangement. These components have been disclosed in detail in connection to previously disclosed embodiments. 
     The needle  1102  further comprises, in each of the illustrated embodiments, one or more guiding portions for providing a guiding mechanism. The purpose of the guiding mechanism is to guide the sealing member  1003  towards an aligned position relative the needle sheath  1002  while the needle arrangement is set towards the closed position. By aligned position is meant a predetermined relative position between the sealing member  1003  and the needle sheath  1002  that is desired for an application. In a preferred embodiment where the sealing member  1003  is arranged to have the same cross-sectional shape and size as the needle sheath  1002  to provide a smooth transition between the outer surfaces of the sealing member  1003  and the needle sheath  1002 , when the needle  1102  is arranged in the closed position. In such an embodiment, the aligned position may be the relative position between the sealing member  1003  and the needle sheath  1002  that provides the desired smooth transition. A smooth transition may contribute to a reduced risk of collecting bacteria in the needle arrangement. 
     Different examples of how the guiding portion may be formed will now be disclosed in detail. 
     In  FIG. 13 a   , the guiding portion is formed by a plurality of flanges  1301   a,    1301   b  that extend between the elongated portion of the needle  1102  and an inner wall of the needle sheath  1002 . The flanges  1301   a,    1301   b  may extend from a back end surface  1303  of the sealing member  1003  and along, for example, 1-3 mm of the elongated portion of the needle  1102 . The flanges  1301   a,    1301   b  preferably extend at least the length being the maximum length of the gap, between the sealing member  1003  and the front end of the needle sheath  1002 , when the needle arrangement is set in the open position, in order to avoid any surrounding tissue to be caught by the back ends of the flanges  1301   a,    1301   b.    
     The plurality of flanges  1301   a,    1301   b  may form an integral part of the needle  1102 . Each of the flanges  1301   a,    1301   b  may be formed with a decreasing width at a back end portion thereof. Thus, an inclined surface is provided for facilitating the guiding towards the aligned position. 
     In  FIG. 13 b   , the guiding portion is formed by a conical portion  1302 . The conical portion  1302  is formed around a longitudinal axis  1001  of the needle  1102 . The conical portion  1302  is oriented with its base facing the sealing member  1003 . In the illustrated embodiment, the conical portion  1302  is connected to the sealing member  1003 . The conical shape of the conical portion  1302  facilitates the guiding towards the aligned position. 
       FIG. 13 c    and  FIG. 13 d    illustrate alternative embodiments of a needle arrangement for providing the guiding mechanism. In these embodiments, the interface between the sealing member  1003  and the needle sheath  1002  is configured to provide the guiding mechanism. 
     In  FIG. 13 c   , a back surface  1305  of the sealing member  1003  is inclined forwards in view of the longitudinal axis  1001  of the needle  1102 . The front end surface  1306  of the needle sheath  1002  is inclined in a corresponding manner. A preferred inclination angle may be in the interval of 30-60 degrees relative the longitudinal axis  1001 . 
     In  FIG. 13 d   , a back surface  1307  of the sealing member  1003  is inclined backwards in view of the longitudinal axis  1001  of the needle  1102 . The front end surface  1308  of the needle sheath  1306  is inclined in a corresponding manner. A preferred inclination angle may be in the interval of 30-60 degrees relative the longitudinal axis  1001 . 
     An embodiment relating to an aspiration needle arrangement will be now be disclosed with reference to  FIGS. 14-15 . 
     An aspiration needle arrangement  1400  is illustrated. As for the above disclosed needle arrangements, the aspiration needle arrangement  1400  comprises a needle sheath  1402  and a needle  1406 . The needle  1406  comprises an elongated portion, adapted to be coaxially arranged inside the needle sheath  1402 , and a sealing member  1403 . The aspiration needle arrangement  1400  is arranged to be set in an open position and a closed position in the same manner as disclosed for above disclosed embodiments. In  FIG. 14 , the needle arrangement  1400  is set in the closed position. In  FIG. 15 , the needle arrangement  1400  is set in the open position. 
     The aspiration needle arrangement  1400  further comprises a connection member in the form of a syringe housing  1401  arranged at a rear end of the needle sheath  1402 . The syringe housing  1401  is adapted to receive a syringe  1500 , specifically (at least a part of) a barrel  1501  of the syringe  1500 . It is appreciated that the syringe housing  1401  may have different forms for different applications. The syringe housing  1401  may preferably be made of a transparent material, such as a transparent plastic material, for allowing inspection of a syringe  1500  inserted therein during an aspiration process. 
     A channel  1405  is provided between a front end and the rear end of the needle sheath  1402 . The channel  1405  extends along a longitudinal axis  1404  of the needle  1406 . The channel  1405  is provided inside the needle  1406 . In other embodiments of the aspiration needle arrangement, a channel may instead be provided between the needle  1406  and the needle sheath  1402 . 
     The channel  1405  is provided for allowing a fluid communication between the syringe  1500  and a gap  1506  being formed when the needle arrangement  1400  is set in the open position, as illustrated in  FIG. 15 . The syringe housing  1401  is adapted to receive the syringe  1500  so as to allow a connection between a tip  1502  of the syringe  1500  to the needle  1406  for allowing a fluid connection therebetween. The needle  1406  may be provided with an appropriate connection configuration for enabling connecting of the tip  1502  thereto. Non-limiting examples of such connection configurations are a threaded connection and a slip tip configuration. These configurations are possible to achieve for the skilled person without the need for further details herein. 
     In order to allow a fluid connection between the channel  1405  and the surrounding area at a front end of the needle arrangement  1400 , one or a plurality of apertures  1504  are provided in the elongated portion of the needle  1406 . Each of the apertures  1504  connects the inner channel  1405  of the needle  1406  with the area outside the needle  1406 . Hence, a fluid connection between the surrounding area at the front end of the needle arrangement  1400  and the syringe  1500  is provided, when the syringe  1500  is connected to the needle arrangement  1400  and to the needle  1406  thereof. 
     The syringe housing  1401  comprises a biasing means in the form of a helical spring element  1407 . The biasing means is arranged to bias the needle arrangement  1400  to be set in the closed position. In this embodiment, the biasing towards the closed position is achieved when the syringe  1500  is received in the syringe housing  1401 . The helical spring element  1407  extends at least partly along the longitudinal axis  1404  of the needle  1406 , meaning that the helical spring element  1407  is arranged to be compressed in a direction extending at least partly along the longitudinal axis  1404 . A compression axis of the helical spring element  1407  may for example extend in parallel or be common with the longitudinal axis  1404 . 
     The helical spring element  1407  is located to extend between an inner wall of a front end of the syringe housing  1401  and an outer wall of a front portion of the barrel  1501  when the syringe  1500  is inserted into the syringe housing  1401 , as illustrated in  FIG. 15 . Further, the needle  1406  is arranged such that, when the tip  1502  of the syringe  1500  is connected thereto, the needle  1406  may be forced along the longitudinal axis  1404  of the needle  1406  while the syringe  1500  is inserted into the syringe housing  1401 . In other words, the length of the needle  1406  is chosen such as it is, when the syringe has been partly inserted into the syringe housing  1401  and connected to the needle  1406 , moved forwards together with the syringe  1500  moving forwards. A front portion of the elongated portion of the needle  1406  is thus moved forwards in relation to the needle sheath  1402  whereby a longitudinal gap  1506  is provided between the sealing member  1403  and the needle sheath  1402 . In other words, the injection needle  1400  is set from the closed position to the open position. In the open position, a fluid connection between the syringe  1500  and the area surrounding the front portion of the elongated portion of the needle  1406  is allowed. In the open position, aspiration by the syringe  1500  is enabled by retraction of a plunger  1503  of the syringe  1500 , thereby inducing a retraction force for aspirating a body liquid, such as blood, to the syringe  1500  via the apertures  1504  and the channel  1405 . 
     It is appreciated that the apertures may be shaped and/or have a different size depending on embodiment. For example, for aspiration of viscous liquids, such as synovial fluid, the apertures may preferably be of a relatively large size. 
     As illustrated in  FIG. 15 , where the syringe  1500  is fully received in the syringe housing  1401 , the helical spring element  1407  is arranged in a compressed mode. This configuration provides the function of a biasing towards the closed position of the needle arrangement  1400  since the syringe  1400  is forced backwards by the helical spring element  1407  when released. The needle  1406  is thereby also retracted into the needle sheath  1402  due to the connection between the needle  1406  and the syringe  1500 . An advantage with this configuration is that a user does not need to manually retract the needle  1406  into the needle sheath  1402  for ensuring a sealing between the sealing member  1403  and the needle sheath  1402 . 
     When compressed, the helical spring element  1407  thus applies a backward force on the inserted syringe  1500 . A counteracting force needs to be applied to the syringe  1500  in order for it to stay inserted in the syringe housing  1401 . For this purpose, a locking element may be provided. In the illustrated embodiment, the locking element comprises a locking pin  1409  that is arranged on a back end flange  1408  of the syringe housing  1401 . The locking pin  1409  is arranged to be moved between an unlocking position and a locking position. While the syringe  1500  is inserted into the syringe housing  1401 , the locking pin  1409  is set in an unlocking position. In  FIG. 15 , the locking pin  1409  that is illustrated in continuous lines is set in the unlocking position. When the syringe  1500  is fully inserted in the syringe housing  1401 , the locking pin  1409  may be moved to the locking position by pushing the locking pin  1409  such that the locking pin  1409  is moved inwards (according to the arrow in  FIG. 15 ) toward a longitudinal central axis of the syringe housing  1401 . The locking pin  1409  may be movable between the unlocking position and the locking position with a similar mechanism as an ink cartridge is moved in a retractable pen, i.e. with a spring-loaded mechanism. In FIG.  15 , the locking pin  1409  that is illustrated in broken lines is set in the locking position. In the locking position, the locking pin  1409  abuts the inserted syringe  1500  by abutting the plunger  1503 . Thus, the locking pin  1409  counteracts the retracting force applied by the helical spring element  1407  on the syringe  1500 . The needle arrangement  1400  is thereby lockingly set in the open position. An advantage by this configuration is that a user does not need to actively hold the syringe  1500  in the inserted position. This freedom provides for a less complex aspiration process. 
     It is appreciated that the locking mechanism provided by the locking element may be achieved in various other ways. For example, a locking mechanism similar to the mechanism of a retractable pen may be provided. In such an embodiment, the connecting member may comprise a spring-loaded mechanism which provides a lockingly setting of the needle arrangement in the open position when the syringe is inserted and pushed towards the spring mechanism. When performing a second pushing of the inserted syringe towards the spring mechanism and releasing, similar to a clicking of a button of a retractable pen, the spring mechanism is arranged to again bias the needle arrangement towards the closed position. 
     The skilled person realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. 
     For example, heating of the heat coating may be electrically induced through diathermy and the use of high-frequency electromagnetic waves, such as ultra sound, short-wave radio frequencies and microwaves. 
     The heating of the heat coating  702  may also be performed by focusing a laser on the coating, in which case the surrounding material, the needle  202  and/or the needle sheath  104  may be of a transparent material, such as a transparent plastic. The laser may be situated inside or outside the biopsy needle arrangement  100 . 
     Variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.