WO2010049483A1

WO2010049483A1 - Biopsy needle guidance system

Info

Publication number: WO2010049483A1
Application number: PCT/EP2009/064282
Authority: WO
Inventors: Åsmund ØVERBØ
Original assignee: Medinnova As
Priority date: 2008-10-30
Filing date: 2009-10-29
Publication date: 2010-05-06

Abstract

The present invention relates to a biopsy needle guidance system (5) for use with a medical imaging system (3) so as to perform an image assisted biopsy. The guidance system comprises a support plate (7), a moveable guide (8;30) and a needle support assembly (9) comprising a biopsy needle holder (20). Moreover, the needle support assembly comprises a fixing arrangement (21;36) for fixing the needle support assembly to an associated receiver unit (6), the associated receiver unit being attached to a patient intended for biopsy. In an embodiment, the fixing of the needle support assembly to the associated receiver unit is obtained by means of a hook and loop fastening means (38; 39).

Description

BIOPSY NEEDLE GUIDANCE SYSTEM

FIELD OF THE INVENTION

The present invention relates to a biopsy needle guidance system, in particular to a guidance system for use in connection with image assisted biopsy.

BACKGROUND OF THE INVENTION

In connection with the diagnosis and treatment of potential cancerous tumours or other suspected pathologic conditions it is often desirable to sample and test a portion of the tissue from the human or animal patient by taking a biopsy of the suspected tissue. Such a biopsy is often taken by use of a biopsy needle which minimizes the surgical intervention.

In order to improve the precision of biopsy sampling, biopsy needle guidance systems have been developed to assist the medical person with the procedure. The increased precision associated with guided biopsy sampling can potentially reduce the risk of complications associated with the procedure. For instance in lung biopsy sampling, the biopsy needle may create a tear in the pleura causing air leakage and collapse of the lung. A lung biopsy should therefore be a success the first time procedure performed. Biopsy guidance systems may also reduce the amount of radiation exposure to the patient and to the medical person performing the procedure by shortening the procedure time.

In one type of system, the biopsy needle guidance system is fixed to a frame which is attached to the table supporting the patient. An example of such a system can be found in the published European patent application EP 1 103 223 A2. An advantage of this type of systems is that the position of the biopsy needle is fixed to the image plane of the medical image system. A disadvantage of this type of system is however that if the patient moves, for instance during breathing, there is a high risk that the patient moves in relation to the biopsy guide. A movement of the patient may result in that the insertion site and insertion angle are changed which may cause the biopsy needle to miss the intended target. In another type of system, the biopsy needle guidance system is configured to be positioned directly on a patient at the area of the intended insertion site. An example of such a system can be found in the internationally published patent application WO 2006/081409 A2. An advantage of this type of systems is that it is ensured that the biopsy needle stays over the intended insertion site, even in case of patient movement. A disadvantage of this type of system is however that if the patient moves, there is a high risk that the patient moves away from the image plane of the imaging system. Another disadvantage of this type of system is that the surface of a patient is an unstable area which may change in shape during the respiration cycle causing variation in both insertion site and angle which may lead to the biopsy needle missing the intended target.

The inventor of the present invention has realized that an improved biopsy needle guidance system would be advantageous and have in consequence devised the present invention.

SUMMARY OF THE INVENTION

The inventor of the present invention has realized that in connection with performing image assisted biopsy it is important to ensure correct positioning both with respect to the image plane of the imaging apparatus and with respect to the insertion site and insertion angle.

It may therefore be seen as an object of the present invention to provide an alternative solution which solves the above-mentioned problems of the prior art. Moreover it may be seen as an objective of the present invention to provide a solution which is simple to use for the medical person in charge of the biopsy procedure and which is comfortable for the patient. To this end it would be advantageous to provide a biopsy needle guidance system which helps the medical person to focus on obtaining the biopsy itself which could reduce the time it takes to obtain the biopsy sample and could reduce the number of complications as well as the seriousness of complications if they arise. In general, the present invention seeks to provide an improved biopsy needle guidance system. Preferably, the invention alleviates, mitigates or eliminates one or more disadvantages of the prior art, singly or in any combination.

To this end, in a first aspect, the invention relates to a biopsy needle guidance system for use with a medical imaging system, the system comprising :

- a support plate fixable to a reference frame of the medical imaging system;

- a moveable guide attached at a first end to the support plate;

- a needle support assembly attached at a second end to the moveable guide, the needle support assembly comprising a biopsy needle holder;

wherein the needle support assembly comprises a fixing arrangement for fixing the needle support assembly to an associated receiver unit, the associated receiver unit being suitable for attachment to a patient intended for biopsy.

The medical imaging modality may be any suitable imaging modality. Typically a computed tomography (CT) or magnetic resonance imaging (MRI) system is used.

The needle biopsy guidance system is to assist the medical practitioner to perform a biopsy of a patient. The biopsy may be conducted in any suitable manner preferred by the practitioner. Typically either a so-called "real-time" procedure is applied or a so-called "quick-check" procedure is applied. In the real-time procedure a time-resolved imaging modality is used, such as a continuous computed tomography (CCT) image system, rendering time-resolved guidance possible. Accurate insertion of the biopsy needle may thereby be ensured via supervision of the needle trajectory and the target area on a monitor. In the quick-check procedure, images are obtained prior to performing the biopsy to ensure that the needle is positioned correctly, and also possibly at intervals while the biopsy needle is inserted in the patient to ensure that the needle hits the intended area. However, imaging is not performed during the insertion itself. The biopsy needle guidance system comprises a support plate fixable to a reference frame of the medical imaging system. The biopsy needle is thereby mechanically coupled to the support plate through the moveable guide and the needle support assembly, a fixed reference between the biopsy needle and the image plane of the medical imaging system is ensured. By use of a moveable guide it is at the same time ensured that the needle support assembly can be positioned over the insertion site of the patient.

The needle support assembly comprises a fixing arrangement for fixing the needle support assembly to an associated receiver unit, the associated receiver unit being suitable for attachment to the patient intended for biopsy. The receiver unit is typically attached to the patient prior to positioning the patient onto the table. The receiver unit may conveniently be part of a belt or strap, a support unit, or any other suitable means, fixed to the patient in the vicinity of the insertion site.

From the mechanical coupling between the needle support assembly and the reference frame of the image system, it is ensured that the biopsy needle is fixed to the image plane of the medical image system during the entire procedure. From the fixing of the needle support assembly to the patient by means of the fixing arrangement, it is ensured that the biopsy needle stays over the intended insertion site and that the insertion angle remains constant during the entire procedure, even in case of patient movement. If the patient moves, the needle support assembly and thereby the needle itself, simply follows the patient's movement. In the present invention the biopsy needle is fixed to two fix-points: one being provided by the support plate; the other being provided by the attachment to the patient.

Further advantages of the system includes, but are not limited to, that the fixing arrangement is a simple solution which is convenient to use for the medical personal in charge of preparing the patient and for the medical personal in charge of performing the biopsy procedure. Moreover, the solution is comfortable for the patient since the receiver unit is convenient to wear, and the system is not disturbed by the respiration of the patient or smaller unintended movements. The patient may take his or her mind off the requirement that he or she should not move prior to and during the procedure, as is the case with the prior art solutions. Therefore the patient may easier relax in the inconvenient situation during the biopsy procedure.

In an advantageous embodiment the support plate is fixable to the reference frame of the medical imaging system by mounting it to the table for supporting the patient. The table for supporting the patient is mechanically coupled to a medical imaging apparatus and therefore by fixing the support plate to the table, the reference frame of the medical imaging system and the biopsy needle are mechanically coupled. The mounting may be by any suitable way of mounting, such as by a suitable fastening means to the table. The support plate may be a plate extending upwards from one side of the table or in the middle of the table between the legs or above the head of the patient, since this allows easy placement of the patient to the table. However in embodiments, the support plate may also be a frame extending partly or completely over the patient. The support plate may be fixed at a number of different areas on the table. A specific position may be used in dependence upon the intended biopsy site on the patient.

In an advantageous embodiment the moveable guide is freely moveable to position the needle support assembly in any given point within a three- dimensional (3D) region. A number of guide assemblies are known to the skilled person in order to assure this, such assemblies may be based on telescopic, rotational and/or sliding couplings. The 3D region needs to be sufficiently large to be able to position the biopsy needle within a given section of the patient. For example if the biopsy is taken in the lungs of the patient, the 3D region need to be sufficiently large cover the thorax of the patient.

In an advantageous embodiment the biopsy needle holder is adapted for restricted movement in a two-dimensional (2D) imaging plane of the medical imaging system so that an insertion axis of the needle holder is restricted to rotational movement in the image plane. It is important that the biopsy needle is parallel with the image plane, since otherwise the needle tip may move out of sight in the recorded image during the biopsy procedure. By restricting the movement of the biopsy needle holder the medical person in charge of positioning the biopsy needle need not deal with this aspect and is consequently free to concentrate upon other aspects, such as to ensure that the needle is inserted to the correct depth. It is known to the skilled person how to restrict the movement of the biopsy needle holder while maintaining that the moveable guide is freely moveable in a given region. In an embodiment it may be achieved by mechanically coupling of the moveable guide, the needle support assembly and the biopsy needle holder. Various methods for achieving this are known to the skilled person. In an embodiment, this may be achieved by so-called parallelogram movement of the needle holder, possibly in combination with sliding movements with respect to the table of the imaging apparatus. If the imaging system gantry is angled with respect to the plane of the patient table, this angle may be accounted for by rotating the moveable guide in relation to the support plate.

In an advantageous embodiment the biopsy needle holder is adapted for receiving a disposable holder element. By using a disposable holder element the requirement relating to sterility of the biopsy system can be achieved, since not the entire biopsy needle assembly needs to be kept sterile, only the disposable holder element and the biopsy needle need to be sterile. Separation of the sterile area from the non-sterile area may further be emphasized by mounting a sterile drape between the needle support assembly and the sterile biopsy needle holder. The adhesive edge of the sterile drape may be glued to the skin under the fixing arrangement.

In an advantageous embodiment the biopsy needle holder is adapted for release and locking of the needle or needle part. In an embodiment the locking and release mechanism may be a so-called snap or quick mechanism, where the needle or needle holder or possible part of the needle holder can quickly and easily be detached and re-inserted. For example, if the biopsy is obtained by use of a coaxial needle, it may be possible to release the needle or the needle holder after placement of the coaxial needle to allow the patient to breathe freely. By detaching the needle, the needle is free to oscillate with the lung parenchyma during the respiration cycle and thereby reducing the risk of provoking a bleeding in the lung parenchyma around the needle tip.

In an advantageous embodiment, the fixing arrangement comprises a plate for attachment to the patient and a mechanical coupling interconnecting the plate and the needle support assembly. A plate may easily be incorporated into fastening means, such as a belt or strap, that may be fastened to a patient, or may be fastened to a patient by such means a gluing the plate to the body of the patient. . In a further embodiment the fixing of the needle support assembly to the associated receiver unit is obtained by means of a reusable fastening means. By use of a reusable fastening means it may be ensured that it may be easy to attach and release the needle support assembly to and from the patient. In an embodiment the reusable fastening means is a hook and loop fastener type fastening means, such as the type generally associated with the trademark Velcro. However other means may be used, such as push buttons, magnetic or adhesive devices or other locking means.

While, the biopsy needle guidance system may advantageously be operated manually. Advantageous embodiments may nevertheless be provided where, either one of, or both of, the moveable guide and the needle support assembly are automatically or semi-automatically operable. In this case the positioning of the needle over the intended insertion site, as well as the insertion into the body of the patient of the needle can be controlled at a distance. In an interesting semi-automatic embodiment, the adjustment of the angle of the needle within the image plane of the medical image system may be controlled at a distance.

Thereby, the medical person needs not to move in and out of the radiation region, and a faster biopsy procedure may be achieved.

In a second aspect, the invention further relates to medical imaging system comprising a biopsy needle guidance system according to the first aspect of the invention.

In a third aspect, the invention further relates to a method of performing a biopsy, the biopsy being performed using the biopsy needle guidance system according to the first aspect of the invention. The method comprising :

- attaching the receiver unit to a patient; - positioning the needle support assembly on an insertion site of a patient intended for biopsy such that the needle support assembly is positioned over a target biopsy site;

- attaching the fixing arrangement of the needle support system to the associated receiver unit attached to the patient;

- performing the biopsy.

Embodiments of the invention may be applied in a range of applications. An important application is biopsies in lung tissue or parenchyma. Another important application is biopsies of liver tissue, as an alternative to ultrasonic guided biopsies of the liver. However embodiments of the invention may advantageously be applied, but is not limited to, the following percutaneous interventions: - Percutaneous biopsies (core biopsy, fine needle aspiration) in abdomen and pelvis when ultrasound guiding is insufficient Percutaneous drainages in abdomen and pelvis

Preoperative needle localization of lesions, e.g. placing marking wires in pulmonary lesions - Liver interventions (radiofrequency ablation, cryotherapy, PTC/PTCD)

- Percutaneous gastrostomy Percutaneous nephrostomy

- Traumatological interventions, e.g., saeroilial joint and tibial head osteosynthesis - Paravertebral interventions, e.g., sympathieolysis, periradicular injections

- Vertebra plasty, nucleoplasty, neurolysis

In general the various aspects of the invention may be combined and coupled in any way possible within the scope of the invention. These and other aspects, features and/or advantages of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES Embodiments of the invention will be described, by way of example only, with reference to the drawings, in which

FIG. 1 schematically illustrates an overall view of a biopsy needle guidance system together with an imaging system, a patient and a medical practitioner;

FIGS. 2A to 2C schematically illustrate elements of a biopsy needle guidance system;

FIG. 3 shows a schematic illustration of an embodiment of a biopsy needle guidance system in accordance with the present invention;

FIG. 4 shows a photo of a first prototype of a biopsy needle guidance system;

FIG. 5 shows a computer generated image of a second prototype of a biopsy needle guidance system;

FIG. 6 shows CT images of a phantom in the form of a water melon with an artificial target inserted; and

FIG. 7 shows CT images of a phantom in the form of a water melon with an artificial target inserted, the water melon being covered by a pork rib section.

DESCRIPTION OF EMBODIMENTS

The present invention relates to a biopsy needle guidance system to assist the medical personal in connection with performing a biopsy procedure on a patient. In this connection reference is made to insertion site as being the area at the skin through which the needle is inserted into the body, and the biopsy site as being the region from which a biopsy is to be taken.

Embodiments are described in connection with a biopsy of the lungs with insertion from the front of the thorax. The invention is however not limited to be used in connection with this type of procedure. Embodiments of the invention may be used for biopsy of any body part as well as with insertion from the front, the side or the back of the body.

A general biopsy procedure is disclosed with reference to FIGS. 1 and 2. In the Figures same reference numerals are used to designate same or similar features in the drawings.

FIG. 1 illustrates a patient 1 positioned on a table 2, the table being part of a CT imaging system 3. A medical practitioner 4 in charge of the biopsy is handling the biopsy needle guidance system 5 in accordance with embodiments of the present invention.

FIGS. 2A to 2C schematically illustrate a part of the needle support assembly 9, the needle holder 20, as well as the fixing arrangement 21 and the receiver unit 6. FIG. 2A illustrates the situation prior to insertion, FIG. 2B illustrates the situation during preparation, whereas FIG. 2C illustrates the situation during insertion.

Prior to position the patient on the table, a receiver unit 6 is attached to the patient, e.g. by means of plate attached to a strap 10 that is fixed around the lower part of the thorax. If desired, the receiver unit may be attached after the patient has been positioned on the table. The patient is positioned so that the insertion site and biopsy site is positioned in the image plane 11 of the CT apparatus, or a plane parallel to the image plane if the patient is positioned outside the scanner and the patient inserted prior to obtaining the images. The image plane typically varies between 1 and 10 millimetres.

A first low dose image volume is recorded to localize the suspected area, and from this, the insertion site on the thorax is determined and a mark is made on the skin. A verification of estimated insertion point may then be done with a opaque marker at the insertion site from a new recorded image. The insertion path needs to be free of a rib and other specific aspects may also be taken into account. At this point in time, the biopsy needle guidance system need not be mounted onto the table or only a part of the system may be mounted. A lead apron may be placed over the patient to reduce secondary radiation. If the biopsy needle system is not already mounted, it is to be mounted now. If the gantry is angled, this should be accounted for when mounting the system. This may be obtained by proper rotation of the movable guide.

In the illustrated embodiment, the support plate 7 is fixed to the side of the table at an appropriate distance with respect to the insertion site; and the moveable guide 8 is attached to the support plate. The needle support assembly 9 is typically permanently attached to the moveable guide.

The arrangement of the various parts of the biopsy system at this instance is illustrated in FIG. 2A.

The needle support assembly is positioned such that the needle canal 22 of the needle holder is properly positioned over the insertion site 23, 24. This position is locked by fixing the needle support assembly, or more specifically the fixing arrangement 21, to the associated receiver unit 6 attached to the patient. The arrangement of the various parts of the biopsy system at this instance is illustrated in FIG. 2B.

A non sterile test needle may be placed in the needle holder. The patient is asked to breath maximally in or out, and a new CT image is recorded while the patient holds his or hers breath. The test needle is of a metal, and will therefore cast a shadow or core artefact through the recorded image to indicate the insertion path 24. It is ensured that the shadow runs through the intended biopsy site. If this is not the case, the orientation of the needle holder assembly is repositioned and the above mentioned procedure is repeated.

The insertion site is sterilized, e.g. by washing the area by use of a proper sterilization agent, such as a solution of chlorhexidine, and surrounding the insertion site with sterile tape. During the sterilisation of the skin, the needle support assembly may temporarily be removed from the intended insertion site and be exactly repositioned afterwards. This may be obtained by positioning the needle assembly holder as shown in FIG. 2A and reposition the needle assembly holder as shown in as shown in FIG. 2B and 2C afterwards. This may be obtained by means of a hinge.

A sterile needle holder 25 as well as a sterile biopsy needle 28 is mounted in the needle holder assembly. In connection with the sterilization procedure a sterile drape 200 is typically used to physically separate the sterile side 26 from the non- sterile side 27. The patient is locally anaesthetized, and optionally the insertion path is checked by a new CT recording to test that the needle shadow passes through the biopsy region.

Finally, the biopsy is performed. The biopsy is often conducted while the patient breathes maximally in or out making use of either the "real-time" method or the "quick-check" method for guidance. The biopsy procedure may however be performed during any part of the respiration cycle if this is desired by the physician or the patient. The arrangement of the various parts of the biopsy system at this instance is illustrated in FIG. 2C.

The biopsy needle system may further comprise an elastic band 29 or other means to provide a bias force towards the body of the patient. For example, in situations where the insertion site is at the side of the body, it may be convenient to drag the needle assembly holder towards the insertion side

The biopsy needle holder 20 may be adapted for release and locking of the needle or needle part. In an embodiment this may be obtained by using a semi-open canal in the needle holder, and where the needle or needle part, e.g. an insertion tube, may be released and locked by means of a pin or other fixing means that is operated by a spring biased release button.

FIG. 3 shows a schematic illustration of an embodiment of a biopsy needle guidance system in accordance with the present invention. Elements are illustrated in terms of their functionality. A specific embodiment is within the capability of the skilled person to design.

FIG. 3 schematically illustrates elements of an embodiment of a biopsy needle guidance system. The system comprises a support plate 7 that may be fixed to the side of the patient table by appropriate fixing means (not shown). The system further comprises a moveable guide 30 attached at a first end to the support plate and a needle support assembly 9 attached to the moveable guide at a second end. The needle support assembly comprises the biopsy needle holder 20.

The moveable guide ensures that needle support assembly can be freely positioned in any given point within a three-dimensional region. This may e.g. be ensured from the ability to rotate around a horizontal axis as well as around a vertical axis in either of the two joints 31, 32 combined with a telescopic action of the element 33 attached between the two joints 31, 32.

The biopsy needle holder may be adapted for restricted movement in a plane parallel to the two-dimensional imaging plane 11 of the medical imaging system so that an insertion axis of the needle holder is restricted to rotational movement in the image plane. This may in an embodiment be achieved by restricting the movement of the needle support assembly so that a plane at one end of the moveable guide 34, a plane at another end of the moveable guide 35 and the image plane 11 of the medical imaging system are parallel at all times. Such movement is also referred to as parallelogram movement of the needle holder assembly.

The system further comprises a fixing arrangement, here in the form of a distance rod 36 and an attachment plate 21. The attachment plate may at one end be provided with a grip 37 for easy handling of the plate. The fixing arrangement further comprises an associated receiver unit 6, the associated receiver unit suitable for attachment to a patient intended for biopsy, e.g. by means of a strap 10, as described above.

The biopsy needle holder 20 may be adapted for receiving a disposable holder element, such as a biopsy needle holder element as sold by the company CIVCO Medical Solutions.

The plate 21 of the fixing arrangement may be a provided with one part of a loop and hook type fastener at the bottom face 38 and the associated receiver unit 6 may be provided with the other part of the loop and hook type fastener at the top face 39, such that a reusable fastening means for convenient and firm fastening is obtained.

FIG. 4 shows a photo of a first prototype of a biopsy needle guidance system in accordance with embodiments of the present invention. The photo shows a support plate 7. The prototype further has a two-part moveable guide 8; one part 40 attached to the support plate 7 and a second part 41 attached to the needle support assembly 9. In the embodiment of the prototype, the first part 40 of the moveable guide is tube-formed and provides sliding movement along a sliding axis 42 parallel with the tube by means of two distance arms 46 attached at one end to the first part 40 and at another end to the support plate. Also rotational movement 43 around the sliding axis 42 can be obtained by means of a rotational joint 47 between the first part and the second part of the moveable guide. The second part 41 of the moveable guide is made of three metallic rods 44 each attached at the two ends to plates 34, 35 by means of universal joints 45. The mechanical coupling of the rods 44 to the plates ensures parallelogram movement of the two plates 34 and 35. Also the fixing arrangement 21 for fixing the needle support assembly to a patient is shown.

FIG. 5 shows a computer generated image of a second prototype of a biopsy needle guidance system in accordance with embodiments of the present invention. The Figure shows a zoom of an embodiment of the needle support assembly 9. The needle support assembly is generally similar to the other embodiments disclosed herein. Only two aspects of this embodiment are therefore pointed out. A first aspect relates to a rotational joint 50 in the needle support assembly. The joint 50 ensures rotation of the biopsy needle holder 20 around an axis 57 which is close to or coincident with the exit point 51 of the needle. In this way, rotation around the axis 57 does not change or only changes slightly the position of the needle tip 51. Also is shown a locking mechanism 52 which allows to lock a given angle of the needle 28 with respect to the axis 57. Rotation around the axis 57 corresponds to rotation of the needle in the 2D imaging plane of the medical imaging system. The second aspect relates to the fixing arrangement 53 for fixing the needle support assembly to a receiver unit 54. The fixing arrangement comprises a rod which is terminated by a ball. The ball fits into a receiver cup 55 attached to the receiving unit 54. The receiver cup may be opened and locked by means of wings 56, the position of which controls whether or not the cup fits tightly around the ball so as to lock and release the fixing arrangement. The receiver unit 54 may be attached to a strap or glued directly onto the skin of the patient.

The prototype as shown in FIG. 4 has been tested by experiments on a phantom and an experimental animal (pig).

CT images obtained during the phantom experiments are shown in FIGS. 6 and 7.

FIG. 6 shows CT images of a phantom in the form of a water melon 60 with a target 61 inserted. The target is in the form of a piece of a plastic tube inserted into a depth of approximately 12 to 15 cm. The soft texture of water melon mimics the soft tissue of the lungs. The experiments were carried out on a Siemens CT scanner model Emotion 6 by use of different needle sizes. As an example, tests were performed by use of a Chiba needle 22G (0.7 mm), with and without a 19G (1.1 mm) leading cannula of 40 mm lengths. FIG. 6A shows an image prior to insertion of the biopsy needle, whereas FIG, 6B shows an image with the biopsy needle 28 inserted. In FIG. 6A, the needle holder 20 and the needle 28 can be seen in the top of the image. The direction 24 of the needle can be extended, e.g. by dedicated software means or simply by drawing a line on the image, thereby indicating the insertion path 24 to ensure that the target 61 is hit when the needle is inserted. In FIG. 6B, the needle is inserted into the melon. Even though the needle is not inserted to the complete depth of the target 61, it is clear that the target would be hit if the needle is inserted further.

FIG. 7 shows CT images of a phantom in the form of a water melon 60 covered by a pork rib section 70, again with a plastic tube target 61 inserted, thereby testing the biopsy needle guidance system under conditions which resembles taking a lung tissue biopsy of the lung through the thorax. Similar to FIG. 6A and 6B, FIG. 7A shows the needle holder 20 and the needle 28 in the top of the image prior to insertion of the needle. Again, the direction 24 of the needle is extended to ensure that the needle does not hit a rib when the needle is inserted. In FIG. 7B, the needle is inserted into the melon, through the pork rib section. Only a small part of the needle can be seen. This is due to a slight misalignment of the insertion path with respect to the imaging plane of the imaging system. Nevertheless, the target is hit by the needle.

Moreover, experiments were conducted where liver biopsies and lung biopsies were obtained on anesthetised pigs. Prior to obtaining performing the CT guided biopsies, an artificial target in the form of a small amount of barium (0,03 ml diluted BaSO₄) was inserted into the pig liver and into the pig lung. The animal was imaged using a Siemens Artis ZeeGoo imaging system. The animal experiments were performed by first mounting the needle guide and aligning it with the imaging plane. A biopsy needle guide (19G) was mounted in the guide and positioned to hit the target. A new CT image was acquired to confirm that the location and the angle were appropriate. The needle (22G) was introduced to a predetermined depth based on the image, and an image was acquired to determine the positioning of the needle tip. In the liver experiment was the target hit, whereas in the lung experiment was the needle tip slightly away from the target centre by 3 mm. The respirator was turned off for a short interval during imaging to simulate a patient breath hold.

The experiments proved a high accuracy in positioning a cannula in both the phantom and in living tissue of an anesthetized animal, as well as ease of use which is of aid to the medical practitioner during the biopsy procedure.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

1. A biopsy needle guidance system for use with a medical imaging system, the system comprising :

- a support plate fixable to a reference frame of the medical imaging system;

- a moveable guide attached at a first end to the support plate;

2. The biopsy needle guidance system according to claim 1, wherein the support plate is fixable to the reference frame of the medical imaging system by mounting to a table for supporting a patient.

3. The biopsy needle guidance system according to any of the preceding claims, wherein the moveable guide is freely moveable to position the needle support assembly in any given point within a three-dimensional region.

4. The biopsy needle guidance system according to any of the preceding claims, wherein the biopsy needle holder is adapted for restricted movement in a two- dimensional imaging plane of the medical imaging system so that an insertion axis of the needle holder is restricted to rotational movement in the image plane.

5. The biopsy needle guidance system according to claim 4, wherein the moveable guide, the needle support assembly and the biopsy needle holder is mechanically coupled so as to provide the restricted movement of the biopsy needle holder.

6. The biopsy needle guidance system according to claim 5, wherein the mechanically coupling restricts the movement of the biopsy needle holder to parallelogram movements.

7. The biopsy needle guidance system according to any of the preceding claims, wherein the biopsy needle holder is adapted for receiving a disposable holder element.

8. The biopsy needle guidance system according to any of the preceding claims, wherein the biopsy needle holder is adapted for locking and release of the needle or needle holder.

9. The biopsy needle guidance system according to any of the preceding claims, wherein the fixing arrangement comprises a plate for attachment to the patient and a mechanical coupling interconnecting the plate and the needle support assembly.

10. The biopsy needle guidance system according to any of the preceding claims, wherein the fixing of the needle support assembly to the associated receiver unit is obtained by means of a reusable fastening means.

11. The biopsy needle guidance system according to claim 10, wherein the reusable fastening means is a hook and loop fastener type fastening means.

12. The biopsy needle guidance system according to any of the preceding claims, wherein the medical imaging modality is a computed tomography or magnetic resonance imaging modality.

13. The biopsy needle guidance system according to any of the preceding claims, wherein the moveable guide or the needle support assembly are automatically or semi-automatically operable.

14. A medical imaging system comprising : - a support plate fixable to a reference frame of the medical imaging system;

- a moveable guide attached at a first end to the support plate;

15. A method of performing a biopsy, the biopsy being performed using the biopsy needle system according to claim 1, the method comprising :

- attaching the receiver unit to a patient;

- positioning the needle support assembly on an insertion site of a patient intended for biopsy such that the needle support assembly is positioned over a target biopsy site;

- performing the biopsy.

16. The method according to claim 15, wherein the attachment between the fixing arrangement and the associated receiver unit is obtained by a hook and loop fastener type fastening means.

17. The method according to claim 15 or 16, wherein the biopsy is assisted by a medical imagining.

18. The method according to any of the claims 15-17, wherein the biopsy is performed in lung tissue.

19. The method according to any of the claims 15-17, wherein the biopsy is performed in liver tissue.