GB2400176A

GB2400176A - Ultrasound probe with needle-guiding feature

Info

Publication number: GB2400176A
Application number: GB0307311A
Authority: GB
Inventors: Malcolm J Watson
Original assignee: NORTH GLASGOW UNIVERSITY HOSPI
Current assignee: NORTH GLASGOW UNIVERSITY HOSPI
Priority date: 2003-03-29
Filing date: 2003-03-29
Publication date: 2004-10-06
Anticipated expiration: 2023-03-29
Also published as: GB0307311D0; GB2400176B

Abstract

The ultrasound probe comprises a housing 12 with a guide 18 for aiding the insertion of a needle into a patient. In one embodiment, the guide is a channel 18 provided in the housing and located between ultrasound transducers 16a,b. A preferred embodiment provides a blind spot in the imaged area, allowing alignment of the guide and needle with a specified target. The probe has particular application to the safe administration of central neuroaxial blocks, e.g. epidurals, to the lumbar interspace. An alternative embodiment has a V-shaped notch 79 at one end of the probe housing 70.

Description

Ultrasound probe and application thereof

1 The present invention relates to the field of

2 ultrasonography, and in particular to an improved 3 ultrasound probe and application thereof.

Ultrasonography is used in a variety of medical diagnosis 6 and examination applications. These include the 7 detection of malignant and benign tumours, providing 8 images of foetuses for assessment of their development, 9 and monitoring blood flow within various vital organs and foetuses. A variety of ultrasonographic techniques have 11 been developed for such applications.

13 It is known to provide a patient with local anaesthetic 14 into the sub-arachnoid or epidural space region either directly or via a catheter. The purpose of such an 16 injection may be to provide analgesia to the patient.

17 Alternatively, the anaesthetic may be administered to 18 provide a sufficient loss of sensation in the patient to 19 enable particular types of surgical procedure to be carried out. Examples of such procedures are: 1 À Obstetric surgery, such as trial of forceps, caesarean 2 section (emergency or elective), manual removal of 3 retained products of conception, repair of third degree 4 perineal tear À Lower limb orthopaedic surgery, such as hip, knee or 6 ankle replacements 7 À Gynaecological surgery, such as hystectomy, oophectomy, 8 or pelvic clearance for neoplasm 9 À General surgery, such as panproctocolectomy, Hartmanns procedure, Mastectomy, Whipple's procedure 11 À Cardiothoracic surgery, such as coronary artery bypass 12 grafting, valve replacement, pneumonectomy, 13 pleurodiesis 14 À Transplant surgery, such as cardiac, hepatic, lung or renal transplants 17 This type of anaesthetic is referred to as a central 18 neuroaxial block.

In order to administer effectively the anaesthetic into 21 the epidural space, it is necessary to correctly identify 22 a safe lumbar interspace. At present, clinicians rely on 23 three main techniques to locate a lumbar interspace. The 24 first is based on an assumption that an imaginary line joining the iliac crests crosses close to the 4th lumbar 26 spine. However, this line may in fact cross higher or 27 lower than the 4th lumbar spine.

29 Secondly, medical students are taught that the spinal cord ends at Ll2. In actuality, it is known that the 31 position of the end of the spinal cord follows a normal 32 distribution, with the mean position at L12. It has been 1 shown that the spinal cord ends opposite the body of L3 in 2 1-3% of cases, with increased variance in women patients.

4 A further technique is a reliance on lack of paraesthesia in the region, a reliance which research has shown to be 6 misplaced.

8 Additional techniques include the inherently unreliable 9 manual detection by the anaesthetist, as well as x-ray imaging techniques, which are unsuitable for use on women 11 during pregnancy.

13 In addition to the inherent disadvantages of the above 14 techniques, further problems are created when attempting to locate the lumbar inter-space on certain groups of 16 patients. Difficult patients include patients with 17 anatomical abnormalities, which may be congenital (e.g. 18 scolosis) or acquired (e.g. surgical fusion of lumbar 19 spinous processes following lumbar disc prolapse).

21 Problems are also encountered with obese patients, where 22 excessive subcutaneous tissue prevents the palpitation of 23 subcutaneous landmarks.

Patients that have been subject to several previous 26 failed insertion attempts also pose problems for an 27 anaesthetist. A further example is in the case of a 28 patient that has a coagulopathy or thrombocytopenia. In 29 this situation it is important to insert the needle with minimal trauma, and to reduce the risk of bleeding 31 complications.

1 The present invention identifies the drawbacks of the 2 established techniques and procedures, and proposes to 3 utilise ultrasound to assist in the location and 4 identification of anatomical features.

6 It is an aim of at least one aspect of the invention to 7 provide apparatus to aid in the location of a target area 8 on a patient.

It is an aim of at least one aspect of the invention to 11 provide a method of locating target areas on a patient 12 with improved accuracy, speed, and effectiveness.

14 It is an aim of at least one aspect of the invention to provide method and apparatus for identifying a lumbar 16 interspace on a patient.

18 It is an aim of at least one aspect of the invention to 19 provide an improved method of aligning a needle or catheter with a lumbar interspace of a patient.

22 Further aims and objects of the invention will become 23 apparent from reading the following description.

According to a first aspect of the invention, there is 26 provided an ultrasound probe for identifying a target 27 area on a target object, the ultrasound probe comprising: 28 a housing, an array of ultrasound transducers, a guide 29 means, and means for positioning the guide means in relation to a target area on a target object.

32 Preferably, the target object is a human body.

1 More preferably the target object is the lumbar region of 2 a human body.

4 The array may be planar. The array may be a rectangular array.

7 Preferably, the array has a discontinuity provided 8 therein.

The array may comprise two spatially separated sub 11 arrays.

13 Preferably, the sub-arrays are separated such that an 14 image produced from the ultrasound probe has a discontinuity therein.

17 The discontinuity in the image may be a two-dimensional 18 area of the image.

The two-dimensional area of the image may contain no 21 image data.

23 Preferably, the guide means is a channel provided in the 24 housing.

26 The channel may correspond to the discontinuity in the 27 array produced from the ultrasound probe.

29 The channel may be aligned with the discontinuity in the array.

32 Preferably, the housing has an anterior face for locating 33 with respect to a surface of the target object, a 1 posterior face, and a pair of lateral edges, and the 2 channel is a recess formed in a lateral edge of the 3 housing, the recess extending through from the posterior 4 face to the anterior face.

6 The channel may be at least partially defined by an upper 7 side wall and a lower side wall, the upper side wall and 8 lower being inclined with respect to the normal to the 9 anterior face such that the channel has a first width at the posterior surface and a second width at the anterior 11 surface.

13 The first width at the posterior surface may be greater 14 than the second width at the anterior surface.

16 Optionally, the ultrasound probe as claimed in Claim 16 17 wherein the transducer array is displaced from the 18 posterior face of the housing, and an edge of a first 19 part of the array is arranged adjacent to the upper side wall of the channel, and an edge of a second part of the 21 array is arranged adjacent to the lower side wall of the 22 channel, such that the spatial separation between the 23 first part of the array and the second part of the array 24 is less than the width of the channel at the posterior face.

27 The transducer array may be arranged substantially 28 parallel to the anterior face of the housing.

Optionally, the transducer array comprises two sub-arrays 31 inclined with respect to one another such that axes 32 normal to the two sub-arrays intersect at a point in 33 space beyond the anterior face.

2 Preferably, at least one sub-array is inclined towards 3 the channel.

The channel may be further defined by an internal lateral 6 sidewall being parallel to the normal to the anterior 7 surface.

9 The guide means may further comprise a pair of guide members protruding from the housing.

12 Preferably, the guide means is adapted to receive a 13 needle.

The ultrasound probe is preferably further adapted to 16 communicate with image processing apparatus via a cable, 17 the cable protruding from a lateral edge of the housing.

19 According to a second aspect of the invention, there is provided apparatus for identifying a target area on a 21 patient, including: an ultrasound probe, the ultrasound 22 probe having an array of ultrasound transducers and means 23 for identifying a target area on a target object; the 24 ultrasound probe having guide means for locating in relation to a target area on a target object.

27 Preferably, the apparatus further comprises a display for 28 displaying an image produced in response to a signal from 29 the ultrasound probe.

31 More preferably, image enables identification of the 32 target area.

1 The image may display the location of the target area in 2 relation to the guide means.

4 According to a third aspect of the invention, there is provided a method of identifying a target area on a 6 target object, the method comprising the steps of: 7 positioning an ultrasound probe in relation to the target 8 object, the ultrasound probe having an array of 9 ultrasound transducers and a guide means; displaying an image of the target object; 11 identifying a target area from said image, and; 12 positioning the guide means in relation to said target 13 area.

Preferably, the target object is a human body.

17 More preferably, the target object is the lumbar region 18 of a human body.

The method may include the additional step of aligning 21 the guide means with the target area.

23 The method may include the additional step of: 24 positioning a needle with respect to the guide means, such that the needle is positioned with respect to the 26 target area.

28 The method may include the additional step of marking the 29 target area on the target object.

31 The method may include the additional step of: 32 displaying an image of the needle in relation to the 33 target object.

2 Preferably, the target area is a lumbar interspace of a 3 patient, and the guide means is positioned in relation to 4 said lumbar interspace.

6 The method may include the additional step of positioning 7 a needle with respect to the guide means, such that the 8 needle is positioned with respect to the lumbar 9 interspace.

11 The method may include the additional step of aligning 12 the guide means with the lumbar interspace.

14 The method may include the additional steps of: displaying an image of the needle in relation to the 16 target object; 17 directing the needle towards the target object.

19 The method may include the additional step of marking a target area corresponding to the lumbar interspace.

22 According to a fourth aspect of the invention, there is 23 provided a method for inserting a needle into a lumbar 24 interspace of a patient, the method comprising the steps of: 26 positioning an ultrasound probe in relation to the lumbar 27 region of the body of the patient, the ultrasound probe 28 having an array of ultrasound transducers and a guide 29 means; displaying an image of the lumbar region; 31 identifying a lumbar interspace from said image; 32 positioning the guide means in relation to said lumbar 33 interspace, and; 1 inserting a needle into the lumbar region of the patient 2 via the guide means.

4 The method may include the additional step of aligning the guide means with the lumbar interspace.

7 The method may include the additional step of: 8 displaying an image of the needle in relation to the 9 target object.

11 The method may include the additional step of marking a 12 target area corresponding to the lumbar interspace.

14 It will now be described, by way of example only, various embodiments of the invention with reference to the 16 following drawings of which; 18 Figure 1 shows a plan view of the probe according to the 19 embodiments of the invention; 21 Figure 2 shows a perspective view of the probe of Figure 22 1; 24 Figure 3 shows an example of how the probe of Figures 1 and 2 may be held by an operator; 27 Figure 4 shows an example of how the probe of Figures 1 28 and 2 may be positioned on a patient; Figure 5 shows a schematic overview of a system in 31 accordance with an embodiment of the invention; 1 Figure 6 shows an example of an image produced by the 2 probe of Figures 1 and 2; 4 Figure 7 shows a perspective view of a probe in accordance with an alternative embodiment of the 6 invention) 8 Figure 8 shows an example of how the probe of Figure 7 9 may be held by a users 11 Figure 9 shows an example of how the probe of Figure 7 12 may be positioned on a patient; 14 Figure 10 shows a probe in accordance with a further embodiment of the invention; 17 Figure 11 shows a probe in accordance with a further 18 alternative embodiment of the invention; Figure 12a shows a probe and transducer array 21 configuration in accordance with a particular embodiment 22 of the invention; 24 Figure 12b shows a probe and transducer array configuration in accordance with a particular embodiment 26 of the invention; 28 Figure 13 shows a plan view of a probe and transducer 29 array configuration in accordance with an alternative embodiment of the invention; 1 Figure 14 shows a probe and transducer array 2 configuration in cross-section in accordance with an 3 embodiment of the invention) Figure 15 shows a probe and transducer array 6 configuration in cross-section in accordance with an 7 alternative embodiment of the invention; 9 Figure 16 shows a perspective view of a probe housing in accordance with an embodiment of the invention.

12 Referring firstly to Figures 1 and 2, the drawings show 13 an ultrasonic probe generally depicted at 10. The 14 ultrasound probe comprises a housing 12 which is substantially cuboidal in shape. The housing has 16 posterior and anterior planar faces 13a and 13b 17 respectively. In this embodiment, the thickness of the 18 housing is significantly less than the length and width 19 of the planar surfaces 13a and 13b, such that the overall shape of the probe housing is approximately "slab-like".

22 Provided on the exterior of the housing is a cable 14 for 23 transmitting control signals and detection signals to and 24 from the probe. A cable support 15 is provided to supplement the integral strength of the cable and housing 26 assembly. The cable protrudes from a lateral face of the 27 housing so as not to restrict access to the posterior 28 face and channel 18 by the user.

Figures 1 and 2 also show that the housing encloses an 31 array of ultrasound transducers. This array is shown in 32 two spatially separated sub-arrays 16a and 16b. The 33 array is configured such that it is two-dimensional with 1 an elongated longitudinal axis and a narrow transverse 2 axis. The division of the array into two sub-arrays 16a 3 and 16b causes a central gap within the overall two- 4 dimensional array.

6 The probe housing is provided with a channel 18 extending 7 from the posterior planar face 13a through to the 8 anterior planar face 13b. The channel is cut away from a 9 lateral edge of the probe housing, and is substantially rectangular in shape. The channel corresponds to the gap 11 provided between the sub-arrays of transducers 16a and 12 16b.

14 Figures 3 and 4 show how the ultrasound probe 10 may be held against the body of the patient during use. Figure 16 4 shows the orientation of the probe with respect to the 17 patient's body. The anterior plane 13b is placed flat 18 against the lumbar region of the patient's back. The 19 patient is placed in a sitting position, with the lumbar spine flexed. The probe is covered with a sterile sheath 21 (not shown) and a gel is placed between the sterile 22 sheath and the patient's back in order to improve 23 acoustic contact between the probe and the patient's 24 skin. The gel also enables the operator to manoeuvre the probe on the patient's back more effectively. An 26 estimate of the appropriate level of probe position can 27 be obtained by counting interspinous spaces from the 28 continuous echogenic signal of the sacrum or skull.

Figure 3 shows how the probe may be held by an operator 31 by pressing the index finger and thumb against the 32 posterior planar surface 13a, with the anterior planar 1 surface 13b against the back. The lateral edge of the 2 probe is oriented in the saggital plane of the patient.

4 The probe is held in position by the operator's hand.

The flat design allows the probe to be securely held, 6 with the ulnar borders of the hand, and the middle, ring, 7 and little fingers pressed on the patient's back. The 8 shape of the probe enables the operator to keep their 9 fingers clear of the channel 18.

11 Figure 5 shows schematically an arrangement of the 12 apparatus in accordance with an embodiment of the 13 invention. The system includes an ultrasound probe 10, a 14 processing module 52 and a display 54. The ultrasound probe 10 is of the type shown in Figures 1 or 2, and 16 communicates with the processing module 52 via cable 14.

17 The processing module processes a detection signal from 18 the ultrasound probe, and creates an image on display 52.

The operator 56 views the image on the display, and 21 controls the position of the probe with respect to the 22 patient. This causes the detection signal to change, and 23 thus the image displayed on the display 54 as the probe 24 is held over a different part of the lumbar region.

26 Typically the ultrasound transducers will be operated at 27 a frequency in the range of 400kHz to 2000kHz, chosen to 28 allow maximal tissue penetration. This is lower than the 29 frequency ranges typically used in ultrasonographic diagnosis applications. The range of 400kHz to 2000kHz 31 also allows optimal differentiation of bone and soft 32 tissue, in contrast to the requirements of established 33 ultrasound techniques. However, in certain applications, 1 frequencies of up to 5000kHz (the frequency normally used 2 for muscular skeletal imaging) may be useful.

4 The shape of the probe and the arrangement of the array of ultrasound transducers causes an image to be formed 6 with a shadow or "blind-spot". This corresponds to the 7 aperture between the sub-arrays 16a and 16b, and the 8 channel 18 formed in the housing.

An example image is shown in Figure 6. The probe 10 is 11 shown, pressed against contact with the skin 61 of the 12 patient via gel 62. The linear array 16, split into two 13 sub-arrays 16a, 16b produces an image of region 63. The 14 image shows spinous processes 64 differentiated from soft tissue 65. The image allows the operator to identify the 16 target area, which in this case is a lumbar interspace 17 66.

19 The spatial separation of the sub-arrays 16a, 16b causes a discontinuity in the image, shown as shadow 67. In 21 use, the shadow 67, and hence the channel 18, is aligned 22 with the lumbar interspace 66.

24 The correspondence of the shadow 67 in the image with the channel 18 allows the operator to use the channel as a 26 guide for the subsequent insertion of a needle.

28 In use, the operator positions a tuohy needle centrally 29 within the channel 18, and inserts the needle into the patient. The needle is aligned with a lumbar interspace 31 66, and passes safely through this gap into the epidural 32 space. The needle is then used to administer the 33 anaesthetic to the patient.

2 With the above-described system, the operator inserts the 3 needle into the patient while visually monitoring the 4 position of the probe and needle via the display. The needle may be guided with the index finger and thumb of 6 the probe-supporting hand. Alternatively, the operator 7 may guide the needle with one hand (the dominant hand) 8 while holding the probe with the other.

The arrangement described allows the point of skin entry 11 to be directed accurately towards the required 12 interspace, without the need for multiple insertions.

13 The arrangement also allows the recordal of data 14 pertaining to anatomical parameters of the interspinous space. This includes the measurement of depth of the 16 sub-arachnoid space and epidural space. This provides 17 valuable information to aid administration of the block.

19 It will be appreciated that the above-described technique could be used for placing alignment marks onto the skin 21 for information purposes, or for later administration of 22 anaesthetic.

24 Referring now to Figure 7, an ultrasound probe in accordance with an alternative embodiment of the 26 invention is shown. The probe, generally depicted at 70, 27 comprises a housing 72 of substantially cuboidal shape.

28 The housing includes a posterior face 73a, an anterior 29 face 73b, inferior face 73c, and lateral faces 73d, 73e.

A cable 14 is provided for communicating with other 31 equipment, and a cable support 15 protrudes from an 32 aperture in lateral face 73d.

1 The inferior face 73c is provided with a pair of 2 protruding guide members 79. The anterior edges of the 3 guide members lie flush with the anterior face 73b, and 4 the guide members extend part way across the depth of the housing from the anterior face 73b to the posterior face 6 73b. The outer faces of the guide members protrude 7 orthogonally from the inferior face and are parallel to 8 one another. The inner edges are angled away from the 9 outer edges such that an inverted v-notch is formed between the guide members 79.

12 The ultrasound probe includes an array of ultrasound 13 transducers 76. The array is two-dimensional, with a 14 long axis lying parallel to the anterior face 73b. The transverse axis of the array 76 is relatively narrow, 16 such that the probe produces a vertically orientated, 17 narrow rectangular image. The probe is also provided 18 with an acoustic lens (not shown), for focusing and/or 19 directing the ultrasound waves.

21 Figures 8 and 9 show how the probe of Figure 7 may be 22 held against the body of the patient during use. Figure 23 9 shows the orientation of the probe with respect to the 24 patient's body. The anterior plane 73b is placed flat against the lumbar region of the patient's back. The 26 patient is placed in a sitting position, with the lumbar 27 spine flexed. As before, the probe is covered with a 28 sterile sheath (not shown) and a gel is placed between 29 the sterile sheath and the patient's back in order to improve acoustic contact between the probe and the 31 patient's skin. The gel also enables the operator to 32 manoeuvre the probe on the patient's back more 33 effectively.

2 Figure 9 shows how the probe may be held by an operator 3 by pressing the index finger and thumb against the 4 posterior face 73a, with the anterior face 73b against the back. The lateral edges of the probe are oriented in 6 the sagittal plane of the patient.

8 The probe is held in position by the operator's hand. In 9 comparison to the embodiment of Figures 1 to 4, the probe 70 has greater depth, and thus has a different holding 11 position. The design allows the probe to be securely 12 held, with the ulnar borders of the hand, and the middle, 13 ring, and little fingers pressed on the patient's back.

14 The index finger and thumb are curled around the probe and allow it to be held firmly.

17 As before, an arrangement of apparatus as shown in Figure 18 5 will be used, with ultrasound probe 70 analogous to 19 ultrasound probe 10. The ultrasonic waves are directed inferiorly and anteriorly from the probe 70, such that an 21 image is captured of a region of the patient's lumbar 22 region that lies beneath the guide members 79, and 23 surrounding target region 81 of Figure 8. The image 24 produced will be such that the point of skin entry lies at the lower region of the vertically orientated image.

27 In use, the operator positions a tuohy needle between the 28 guide members 79, and inserts the needle into the skin.

29 The image displayed to the operator includes the needle, and the interspinous space anterior from the probe. The 31 operator is able to alter the caudal and cranial 32 orientation of the needle as required such that the 33 needle is directed safely into the epidural space. The 1 needle is then used to administer the anaesthetic to the 2 patient.

4 The needle may be guided with the thumb and index finger of the probeholding hand. Alternatively, the operator 6 may guide the needle with one hand (the dominant hand) 7 while holding the probe with the other.

9 This arrangement allows the needle to be aligned and inserted under real-time guidance, and also allows the 11 recordal of data pertaining to anatomical parameters of 12 the interspinous space.

14 A further embodiment of the invention is shown in Figure 10, which shows an ultrasound probe generally depicted at 16 100. This embodiment is similar to the embodiment of 17 Figures 1 and 2. As before, the probe includes a housing 18 102, which is substantially cuboidal in shape. The 19 housing has posterior and anterior planar faces 103a and 103b respectively. As before, the depth between the 21 anterior and posterior planar faces of the housing is 22 significantly less than the length and width of the 23 planar surfaces 103a and 103b, such that the overall 24 shape of the probe housing is approximately "slab-like".

26 In addition, the housing 102 encloses a pair of sub 27 arrays 106a, 106b.

29 Ultrasound probe 100 differs in that channel 108 is provided in a central region of the housing. The image 31 produced by the probe 100 will contain a shadow, by 32 virtue of the gap between the sub-arrays of transducers.

33 Indeed, the image will be substantially identical to that 1 produced by probe 10. However, the enclosed channel 108 2 provides the user with an improved guide for the 3 insertion of a needle, and greater integral strength in 4 the housing. Supplementary guide markings, shown as partial cross-hairs 109, may also be provided on the 6 housing.

8 A further alternative embodiment is shown in Figure 11.

9 In this example, the probe 110 itself is of the type shown in Figure 10. However, the probe is provided with 11 a needle support structure 111. The support structure 12 includes a support block 113 extending outwardly from the 13 posterior face of the probe 110. An bore 114 extends 14 through the support block and the main probe housing 112 through to the anterior face. The bore is oriented 16 orthogonally to the planar faces of the housing.

18 Within the bore is an internal sterile sheath 115. The 19 sheath provides direct support to a needle 116, and provides a degree of resistance to movement of the 21 needle.

23 In use, the operator identifies the lumbar interspace in 24 the manner described above. The needle 116 can be positioned in the sheath 115 before or during the 26 location process. This allows the operator align the 27 needle easily, without requiring potentially awkward 28 handling by the probe supporting hand, and avoiding the 29 need to use two hands.

31 When the needle is successfully aligned, it can be 32 inserted into the skin.

1 Figure 12a shows a plan view of an ultrasound probe 120 2 comprising a housing 12 that is substantially cuboidal in 3 shape. The face shown is the posterior face 13b, which 4 is approximately square in plan view. The probe comprises a rectangular array of transducers 16 6 comprising sub-arrays 16a and 16b. The rectangular sub 7 arrays 16a and 16b are elongated, such that they are 8 relatively long in the direction 121, compared to the 9 lateral direction 122.

11 This orientation of transducers functions to produce an 12 elongated rectangular image. When the probe is held 13 against the patients back such that the lateral edges of 14 the probe are orientated in the sagittal plane of the patient, this rectangular image is aligned with the 16 spine. Consequently, the image produced views a 17 relatively large length of the spine, but does not image 18 much of the patient's tissue on either side of the spine.

19 If the position of the probe strays laterally to the left or the right of the spine, the spinal processes will 21 disappear from the image. The size of the transducer 22 array 16 is, for example, lam by 5cm. 24 In this example, the transducer array 16 is placed towards one lateral

edge of the probe housing. This 26 provides a large flat area 123 to enable the operator to 27 firmly hold the probe against the patient. The channel 28 18 provided in the housing extends to a point just beyond 29 halfway through the transducer width, to enable the internal lateral casing edge 124 to be used for a guide 31 against which the needle can slide.

1 Figure 12b shows an alternative embodiment, generally 2 shown at 120', in which the probe housing 12 is formed to 3 a greater width. The transducer array 16 is placed 4 centrally within the housing 12. As in the embodiment of Figure 12a, the channel 18 extends just beyond the centre 6 of the transducers. This example provides a surface for 7 holding by the operator on both sides of the transducer 8 array 16; this allows an operator to use two hands, or 9 either hand, to firmly hold the probe against the patient.

12 Figure 13 shows an embodiment, generally shown at 130, 13 similar to that of Figure 12a. However, in this case the 14 transducer array 16 is not split into two distinct sub arrays. Rather, the transducer array 16 has a cut out 16 portion 131 at one lateral edge. This cut out in the 17 transducer array is a rectangular recess formed in the 18 lateral edge, and corresponds to the channel 18 formed in 19 the housing.

21 This arrangement has the advantage that the images formed 22 by the arrays are not entirely distinct. Although there 23 is a discontinuity or shadow formed in the image, the 24 image also has a continuous aspect. This may require less processing since it is not necessary to mesh two 26 distinct images formed from two distinct sub-arrays.

28 Figure 14 shows an example of a possible cross-section of 29 the probe. The Figure shows a cross-section at a line taken through the channel, parallel to a lateral edge of 31 the probe. The upper and lower sidewalls 141a, 141b 32 defining the channel 18 are bevelled such that the 33 channel 18 formed has a width narrower at the anterior 1 face 13a than at the posterior face 13b. This 2 arrangement provides improved accuracy of alignment with 3 the target area.

As shown in the Figure, the transducer sub-arrays 16a, 6 16b are placed close to the anterior face 13a of the 7 probe housing and displaced from the posterior face 13b.

8 The edge of the sub-arrays 16a, 16b is placed close to 9 the upper side wall channel defining edges, such that the spatial separation between sub-arrays is minimised. This 11 causes a smaller discontinuity or shadow 142 in the image 12 formed.

14 The sidewalls 141a, 141b of the channel 18 are graded such that during insertion of the needle, caudal or 16 cranial movement of the proximal part of the needle can 17 be applied. The arrangement allows the needle to be 18 manoeuvred in a relatively large area, as indicated by 19 the dotted lines 143.

21 The lateral sidewall (161, Figure 16) of the channel 18 22 is perpendicular to the anterior and posterior faces 13.

23 This allows the lateral sidewall to be used as a guide 24 during the insertion of the needle, while maintaining the needle within the sagittal plane of the patient.

27 Figure 15 shows an alternative embodiment of the 28 invention having inclined transducer sub-arrays 16a, 16b.

29 In this example, the arrays are planar, and are inclined to the plane of the anterior face 13a. The sub-arrays 31 16a, 16b are inclined towards one another such that the 32 areas imaged by each sub-array overlap in area 154, 33 indicated by the dotted lines.

2 However, the spatial separation of the sub-arrays and the 3 angle of inclination are chosen such that the images only 4 overlap beyond a particular depth below the patient's skin. This results in a discontinuity or shadow 152 6 being formed close to the surface of the tissue imaged, 7 and aligned with the space between the arrays and the 8 channel 18 in the probe housing.

In this arrangement, the discontinuity or shadow 152 in 11 the image does not extend infinitely due to the 12 converting nature of the images formed from each sub 13 array 16a, 16b. This is in contrast to the arrangements 14 shown in Figure 14, which have parallel imaging from each sub-array.

17 In use, the operator will align the image discontinuity 18 or shadow 152 with the lumbar interspace, and gradually 19 insert the needle into the patient. After the needle has passed a short distance into the patient's tissue, it 21 emerges from beyond the shadow 152, and into the imaged 22 region 154. The operator can therefore see the exact 23 position of the needle and manoeuvre it if necessary to 24 provide exact alignment with the target area. As with the embodiment of Figure 14, the ability to apply caudal 26 or cranial movement is enhanced by the grading of the 27 channel walls.

29 This particular arrangement may require encoding of the ultrasound pulses from each transducer sub-array in order 31 that the overlapping images in region 152 can be 32 disentangled.

1 Figure 16 shows a perspective view of the probe housing 2 with inclined channel sidewalls, similar to the 3 embodiments of Figures 14 and 15.

The preferred embodiments of the present invention 6 utilise "linear" transducer arrays. That is, the 7 transducer arrays are planar, rather than curvilinear.

8 This enables easy interpretation of the image by 9 anaesthetists, without extensive training in ultrasonography. However, it will be appreciated that 11 other forms of array, such as curvilinear arrays, may be 12 used within the scope of the invention.

14 It will be evident that various modifications and improvements could be made to the above-described 16 apparatus and methods within the scope of the invention.

18 For example, the above description is written in the 19 context of administering anaesthetic to patients.

However, the methods and apparatus apply equally to the 21 location or identification of particular anatomical 22 features of a patient for any purpose. The techniques 23 apply to the alignment of catheters, as well as the 24 direct injection methods described.

26 In addition, alternative ultrasound probe shapes and 27 housings could be utilized. In particular, various array 28 configurations could be used within the scope of the 29 invention. For example, the probe could incorporate acoustic lenses for focussing and directing the 31 ultrasound waves so that an image is produced of the 32 required area. Alternatively, the array could be 33 inclined with respect to the anterior face of the housing 1 in order to direct the ultrasound waves to a particular 2 area. It will also be possible to use curvilinear arrays 3 of ultrasound transducers.

The present invention in one of its aspects provides an 6 improved ultrasound probe, suitable for use in 7 identification and/or location of anatomical features, 8 and alignment with those features. Used in conjunction 9 with appropriate supplementary apparatus, the probe provides an image to the operator for assisting with 11 location, identification and alignment.

13 The apparatus is simple and easy to use, and provides 14 images that are interpretable by an operator quickly and accurately. In particular, the operator need not be a 16 specialized radiologist. An anaesthetist or clinician 17 with other areas of expertise is able to interpret the 18 images with minimal supplementary training.

Furthermore, the use of ultrasonography is feasible in 21 everyday practice. Little preparation is required and 22 portable machines are commonplace.

24 The invention has particular application in locating useable lumbar interspaces for epidural or sub 26 arachnoidal injection. The invention allows these spaces 27 to be located with improved accuracy and confidence. The 28 use of the guidance techniques described is likely to 29 increase patients willingness to undergo regional anaesthetic, where this is appropriate.

32 The invention enables the formation of images of the 33 lumbar spine without utilising ionising radiation or

1 strong magnetic fields, which have inherent

2 impracticalities. Neither such technique would be 3 appropriate before lumbar puncture or spinal anaesthetic, 4 and in pregnant patients, could be harmful.

6 The invention may reduce the need to subject a patient to 7 general anaesthetic, which may not be suitable in a 8 variety of cases. Obese patients pose the additional 9 difficulty that the spine may not be palpable, whilst elderly patients may have an increased propensity for 11 fusion of spinal processes, and thus a higher likelihood 12 of bone strikes.

14 Further modifications may be made without departing from the scope of the invention herein intended.

Claims

1 Claims 3 1. An ultrasound probe for identifying a target area on 4 a

target object, the ultrasound probe comprising: a housing, an array of ultrasound transducers, a guide 6 means, and means for positioning the guide means in 7 relation to a target area on a target object.

9 2. The ultrasound probe as claimed in Claim 1 wherein the target object is a human body.

12 3. The ultrasound probe as claimed in Claim 2 wherein 13 the target object is the lumbar region of a human 14 body.

16 4. The ultrasound probe as claimed in any preceding 17 Claim wherein the array is planar.

19 5. The ultrasound probe as claimed in any preceding Claim wherein the array is a rectangular array.

22 6. The ultrasound probe as claimed in any preceding 23 Claim wherein the array has a discontinuity provided 24 therein.

26 7. The ultrasound probe as claimed in Claim 6 wherein 27 the array comprises two spatially separated sub 28 arrays.

8. The ultrasound probe as claimed in Claim 7 wherein 31 the sub-arrays are separated such that an image 32 produced from the ultrasound probe has a 33 discontinuity therein.

2 9. The ultrasound probe as claimed in Claim 8 wherein 3 the discontinuity in the image is a two-dimensional 4 area of the image.

6 10. The ultrasound probe as claimed in Claim 9 wherein 7 the two-dimensional area of the image contains no 8 image data.

11. The ultrasound probe as claimed in any preceding 11 Claim wherein the guide means is a channel provided 12 in the housing.

14 12. The ultrasound probe as claimed in Claim 11 wherein the channel corresponds to the discontinuity in the 16 array produced from the ultrasound probe.

18 13. The ultrasound probe as claimed in Claim 12 wherein 19 the channel is aligned with the discontinuity in the array.

22 14. The ultrasound probe as claimed in any of Claims 11 23 to 13 wherein the housing has an anterior face for 24 locating with respect to a surface of the target object, a posterior face, and a pair of lateral 26 edges, and the channel is a recess formed in a 27 lateral edge of the housing, the recess extending 28 through from the posterior face to the anterior 29 face.

31 15. The ultrasound probe as claimed in Claim 14 wherein 32 the channel is at least partially defined by an 33 upper side wall and a lower side wall, the upper 1 side wall and lower being inclined with respect to 2 the normal to the anterior face such that the 3 channel has a first width at the posterior surface 4 and a second width at the anterior surface.

6 16. The ultrasound probed as claimed in Claim 15 wherein 7 the first width at the posterior surface is greater 8 than the second width at the anterior surface.

17. The ultrasound probe as claimed in Claim 16 wherein 11 the transducer array is displaced from the posterior 12 face of the housing, and an edge of a first part of 13 the array is arranged adjacent to the upper side 14 wall of the channel, and an edge of a second part of the array is arranged adjacent to the lower side 16 wall of the channel, such that the spatial 17 separation between the first part of the array and 18 the second part of the array is less than the width 19 of the channel at the posterior face.

21 18. The ultrasound probe as claimed in any of claims 14 22 to 17 wherein the transducer array is arranged 23 substantially parallel to the anterior face of the 24 housing.

26 19. The ultrasound probe as claimed in any of Claims 1 27 to 17 wherein the transducer array comprises two 28 sub-arrays inclined with respect to one another such 29 that axes normal to the two sub-arrays intersect at a point in space beyond the anterior face.

1 20. The ultrasound probe as claimed in Claim 19 wherein 2 at least one sub-array is inclined towards the 3 channel.

21. The ultrasound probe as claimed in any of Claims 11 6 to 20 wherein the channel is further defined by an 7 internal lateral side wall being parallel to the 8 normal to the anterior surface.

22. The ultrasound probe as claimed in any preceding 11 Claim wherein the guide means further comprises a 12 pair of guide members protruding from the housing.

14 23. The ultrasound probe as claimed in any preceding Claim wherein the guide means is adapted to receive 16 a needle.

18 24. The ultrasound probe as claimed in any preceding 19 Claim, further adapted to communicate with image processing apparatus via a cable, the cable 21 protruding from a lateral edge of the housing.

23 25. Apparatus for identifying a target area on a 24 patient, including: an ultrasound probe, the ultrasound probe having an array of ultrasound 26 transducers and means for identifying a target area 27 on a target object; the ultrasound probe having 28 guide means for locating in relation to a target 29 area on a target object.

31 26. Apparatus as claimed in Claim 25 further comprising 32 a display for displaying an image produced in 33 response to a signal from the ultrasound probe.

2 27. Apparatus as claimed in Claim 26 wherein the image 3 enables identification of the target area.

28. Apparatus as claimed in Claim 25 or Claim 26 wherein 6 the image displays the location of the target area 7 in relation to the guide means.

9 29. A method of identifying a target area on a target object, the method comprising the steps of: 11 positioning an ultrasound probe in relation to the 12 target object, the ultrasound probe having an array 13 of ultrasound transducers and a guide means; 14 displaying an image of the target object) identifying a target area from said image, and; 16 positioning the guide means in relation to said 17 target area.

19 30. The method as claimed in Claim 29 wherein the target object is a human body.

22 31. The method as claimed in Claim 30 wherein the target 23 object is the lumbar region of a human body.

32. The method as claimed in any of Claims 29 to 31 26 wherein the method includes the additional step of 27 aligning the guide means with the target area.

29 33. The method as claimed in any of Claims 29 to 32 wherein the method includes the additional step of: 31 positioning a needle with respect to the guide 32 means, such that the needle is positioned with 33 respect to the target area.

2 34. The method as claimed in any of Claims 29 to 33 3 wherein the method includes the additional step of 4 marking the target area on the target object.

6 35. The method as claimed in Claims 33 or Claim 34 7 wherein the method includes the additional step of: 8 displaying an image of the needle in relation to the 9 target object.

11 36. The method as claimed in any of Claims 29 to 35 12 wherein the target area is a lumbar interspace of a 13 patient, and the guide means is positioned in 14 relation to said lumbar interspace.

16 37. The method as claimed in any of Claims 29 to 36 17 wherein the method includes the additional step of 18 positioning a needle with respect to the guide 19 means, such that the needle is positioned with respect to the lumbar interspace.

22 38. The method as claimed in Claim 36 or Claim 37 23 wherein the method includes the additional step of 24 aligning the guide means with the lumbar interspace.

26 39. The method as claimed in Claim 37 or Claim 38 27 wherein the method includes the additional steps of: 28 displaying an image of the needle in relation to the 29 target object; directing the needle towards the target object.

32 40. The method as claimed in any of Claims 29 to 39 33 wherein the method includes the additional step of 1 marking a target area corresponding to the lumbar 2 interspace.

4 41. A method for inserting a needle into a lumbar interspace of a patient, the method comprising the 6 steps of: 7 positioning an ultrasound probe in relation to the 8 lumbar region of the body of the patient, the 9 ultrasound probe having an array of ultrasound transducers and a guide means; 11 displaying an image of the lumbar region; 12 identifying a lumbar interspace from said image; 13 positioning the guide means in relation to said 14 lumbar interspace, and; inserting a needle into the lumbar region of the 16 patient via the guide means.

18 42. The method as claimed in Claim 41 wherein the method 19 includes the additional step of aligning the guide means with the lumbar interspace.

22 43. The method as claimed in Claim 41 or Claim 42 23 wherein the method includes the additional step of: 24 displaying an image of the needle in relation to the target object.

27 44. The method as claimed in any of Claims 41 to 43 28 wherein the method includes the additional step of 29 marking a target area corresponding to the lumbar interspace.