Ultrasound needle guide devices

Abstract

A needle guide device (20) is provided for guiding insertion of a needle (22) between vertebral bones into a spinal canal. A handheld housing (30) defines a distal skin-contact surface (34), a user handle (36), and a needle guide passage (24) between the distal skin¬ contact surface (34) and a proximal surface (38) of the user handle (36), through which the needle (22) is insertable along an axis (40) of the needle guide passage (24). Ultrasound transducers (32) are arranged in the handheld housing (30) radially outside the needle guide passage (24) at respective angular locations (42) around the axis (40), and oriented to emit and receive ultrasound energy through the distal skin-contact surface (34). Visual indicators (50), corresponding to the ultrasound transducers (32), are arranged on the user handle (36) at respective angular locations (44) around the axis (40) corresponding to the angular locations (42) of the ultrasound transducers (32), and indicate, for the corresponding ultrasound transducers (32), respectively, whether the received ultrasound energy was reflected by bone or soft tissue. Other embodiments are also described.

Description

[0001] ULTRASOUND NEEDLE GUIDE DEVICES

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] The present application claims priority from US Provisional Application 63 / 662,120, filed June 20, 2024, which is assigned to the assignee of the present application and incorporated herein by reference.

[0004] FIELD OF THE APPLICATION

[0005] The present invention relates generally to needle guide devices, and specifically to ultrasound needle guide devices for insertion of needles into a spinal canal.

[0006] BACKGROUND OF THE APPLICATION

[0007] Neuraxial anesthesia is a type of regional anesthesia, which is generally divided into spinal or epidural. It is administered by placing a needle in a specific point in the spinal canal. The challenge is to "hit the spot," since it is hidden to the anesthesiologist, which requires guesstimating the correct needle entry point and trajectory of the needle.

[0008] SUMMARY OF THE APPLICATION

[0009] Some embodiments of the present invention provide a needle guide device for guiding insertion of a needle between vertebral bones into a spinal canal, such as for neuraxial anesthesia or lumbar puncture. The needle guide device comprises a handheld housing, which is shaped so as to define a distal skin-contact surface, a user handle, and a needle guide passage between the distal skin-contact surface and a proximal surface of the user handle. The needle is insertable through the needle guide passage.

[0010] The needle guide device further comprises at least three ultrasound transducers, arranged in the handheld housing radially outside the needle guide passage at respective angular locations around an axis of the needle guide passage, and oriented to emit and receive ultrasound energy through the distal skin-contact surface. Visual indicators (e.g., lights), which correspond to the ultrasound transducers, respectively, are arranged on the user handle at respective angular locations around the axis corresponding to the angular locations of the respective ultrasound transducers.

[0011] Circuitry of the needle guide device is configured to repeatedly: drive the ultrasound transducers to emit and receive ultrasound energy, • analyze the ultrasound energy received by each of the ultrasound transducers to ascertain whether the received ultrasound energy was reflected by bone or soft tissue, and

[0012] • actuate the visual indicators to indicate, for the corresponding ultrasound transducers, respectively, whether the received ultrasound energy was reflected by bone or soft tissue.

[0013] These techniques enable the needle guide device to provide easily-understood and actionable feedback to the anesthesiologist on the needle guide device itself, without the need for additional hardware, or for the anesthesiologist to interpret ultrasound images or ultrasound graphs. Therefore, the needle guide device typically does not comprise a display screen, any external electrical cables, any data communication ports, or any antennas. The needle guide device is typically not configured to be wiredly or wirelessly coupled in data communication with any elements external to the handheld housing.

[0014] During use, the anesthesiologist, using the user handle, places the distal skin-contact surface of the handheld housing against skin of the patient at a target insertion site over a vertebral column. If the axis of the needle guide passage is both properly positioned in the skin and properly aligned, the needle guide passage will be properly aligned with a target space between vertebral bones and into the spinal canal. As a result, the axis of the needle guide passage will intersect only soft tissue between the skin and the spinal canal. Thus, all of the ultrasound transducers, which are positioned radially outside needle guide passage near the axis of the needle guide passage, will detect soft tissue. All of the visual indicators will indicate detection of soft tissue.

[0015] On the other hand, if the needle guide device is initially not properly positioned to guide the needle through soft tissue into the spinal canal, one or more of the ultrasound transducers detect bone of the vertebral bones surrounding the target space. This detection of bone is indicated by a first subset of the visual indicators corresponding to the subset of the ultrasound transducers that detected the bone. The remaining ultrasound transducers detect soft tissue, which is indicated by a corresponding second subset of the visual indicators. Using the user handle, the anesthesiologist adjusts a position of the handheld housing (a location on the skin and / or an orientation of the handheld housing with respect to the vertebral column), until all of the visual indicators indicate that the ultrasound energy received from the corresponding ultrasound transducers was reflected by soft tissue. The identification of the soft tissue in all radial directions from the axis indicates that the needle guide passage is properly oriented toward the target space between the vertebral bones.

[0016] Once the needle guide device is properly positioned, the anesthesiologist inserts the needle through the skin via the needle guide passage, such that the needle guide passage guides the needle through the target space between the vertebral bones and into the spinal canal.

[0017] The ultrasound transducers may thus serve as virtual needles, which sense whether the tissue directly ahead of each transducer is bone or soft tissue.

[0018] The needle guide device is generally suitable for any patient position and compatible with current anesthesia workflow. For example, the needle guide device may help address the challenges faced by anesthesiologists when administering epidural anesthesia to parturients, particularly overweight parturients, including manually finding the entrance point for needle insertion and the correct trajectory due to the disappearance of anatomical landmarks.

[0019] There is therefore provided, in accordance with an application of the present invention, a needle guide device for guiding insertion of a needle between vertebral bones into a spinal canal, the needle guide device including: a handheld housing, which is shaped so as to define (a) a distal skin-contact surface, (b) a user handle shaped so as to define a proximal surface, and (c) a needle guide passage between the distal skin-contact surface and the proximal surface, through which the needle is insertable along an axis of the needle guide passage; at least three ultrasound transducers, arranged in the handheld housing radially outside the needle guide passage at respective angular locations around the axis, and oriented to emit and receive ultrasound energy through the distal skin-contact surface; visual indicators, which correspond to the ultrasound transducers, respectively, and are arranged on the user handle at respective angular locations around the axis corresponding to the angular locations of the respective ultrasound transducers; and circuitry, which is configured to repeatedly: drive the ultrasound transducers to emit and receive ultrasound energy, analyze the ultrasound energy received by each of the ultrasound transducers to ascertain whether the received ultrasound energy was reflected by bone or soft tissue, and actuate the visual indicators to indicate, for the corresponding ultrasound transducers, respectively, whether the received ultrasound energy was reflected by bone or soft tissue.

[0020] For some applications, the visual indicators are arranged equidistantly from the axis.

[0021] For some applications, the ultrasound transducers are arranged equidistantly from the axis.

[0022] For some applications, the ultrasound transducers are arranged at an average of 0.5 - 2 cm from the axis.

[0023] For some applications, the visual indicators and the ultrasound transducers are equally spaced around the axis.

[0024] For some applications, the needle guide device includes no more than ten ultrasound transducers.

[0025] For some applications: the user handle is shaped so as to define a generally cylindrical portion that is shaped so as to define the proximal surface and a longitudinal portion of the needle guide passage, and the visual indicators are arranged on the generally cylindrical portion around the axis.

[0026] For some applications, the circuitry is configured to actuate the visual indicators to have a first color indicating that the received ultrasound energy was reflected by the bone, and a second color, different from the first color, indicating that the received ultrasound energy was reflected by the soft tissue.

[0027] For some applications, the circuitry is configured to actuate the visual indicators to indicate, for the corresponding ultrasound transducers, respectively, whether the received ultrasound energy was reflected by bone or soft tissue, by: setting a first on / off status of the visual indicators to indicate that the received ultrasound energy was reflected by the bone, and setting a second on / off status of the visual indicators to indicate that the received ultrasound energy was reflected by the soft tissue, the second on / off status the opposite of the first on / off status. For some applications, the soft tissue is ligament, and the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers to ascertain whether the received ultrasound energy was reflected by bone or ligament.

[0028] For some applications, the circuitry is disposed within the handheld housing.

[0029] For some applications, the needle guide device does not include a display screen.

[0030] For some applications, the needle guide device does not include any external electrical cables.

[0031] For some applications, the needle guide device does not include any data communication ports.

[0032] For some applications, the needle guide device does not include any antennas.

[0033] For some applications, the needle guide device does not include any external electrical cables, any data communication ports, any antennas, or a display screen.

[0034] For some applications, the needle guide device is not configured to be wiredly or wirelessly coupled in data communication with any elements external to the handheld housing.

[0035] For some applications, the ultrasound transducers include respective annular phased array transducers.

[0036] For some applications, the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by measuring a nonlinear parameter of tissue.

[0037] For some applications, the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by calculating a one-dimensional value for each of the ultrasound transducers.

[0038] For some applications, the visual indicators include respective light sources.

[0039] For some applications, the circuitry is configured to actuate the light sources to emit light having a first color indicating that the received ultrasound energy was reflected by the bone, and a second color, different from the first color, indicating that the received ultrasound energy was reflected by the soft tissue.

[0040] For some applications: the ultrasound transducers are configured to emit the ultrasound energy at an emission amplitude and a fundamental frequency, and to measure a received amplitude of the received ultrasound energy at a harmonic frequency of the fundamental frequency, the harmonic frequency greater than the fundamental frequency, and the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by calculating a ratio of the received amplitude to the emission amplitude.

[0041] For some applications: each of the ultrasound transducers is configured to focus the emitted ultrasound at a plurality of different depths, and the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers at the plurality of different depths to ascertain whether the received ultrasound energy was reflected by bone or soft tissue.

[0042] For some applications, the harmonic frequency is a second harmonic frequency of the fundamental frequency.

[0043] For some applications, the ultrasound transducers include respective annular phased array transducers.

[0044] For some applications, the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by measuring a nonlinear parameter of tissue.

[0045] For some applications, the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis or define an angle of less than 7 degrees with the axis.

[0046] For some applications, the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that the respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis.

[0047] There is further provided, in accordance with an application of the present invention, a needle guide device for guiding insertion of a needle between vertebral bones into a spinal canal, the needle guide device including: a handheld housing, which is shaped so as to define (a) a distal skin-contact surface, (b) a user handle shaped so as to define a proximal surface, and (c) a needle guide passage between the distal skin-contact surface and the proximal surface, through which the needle is insertable along an axis of the needle guide passage; at least three ultrasound transducers, arranged in the handheld housing radially outside the needle guide passage at respective angular locations around the axis, and oriented to emit and receive ultrasound energy through the distal skin-contact surface, wherein the ultrasound transducers are configured to emit the ultrasound energy at an emission amplitude and a fundamental frequency, and to measure a received amplitude of the received ultrasound energy at a harmonic frequency of the fundamental frequency, the harmonic frequency greater than the fundamental frequency; one or more user outputs; and circuitry, which is configured to: drive the ultrasound transducers to emit and receive ultrasound energy, analyze the ultrasound energy received by each of the ultrasound transducers by calculating a ratio of the received amplitude to the emission amplitude, to ascertain whether the received ultrasound energy was reflected by bone or soft tissue, and actuate the one or more user outputs to indicate whether the ultrasound energy received by the ultrasound transducers was reflected by bone or soft tissue.

[0048] For some applications, the circuitry is configured to actuate the one or more user outputs to separately indicate for each of ultrasound transducers whether the ultrasound energy received by the ultrasound transducer was reflected by bone or soft tissue.

[0049] For some applications: each of the ultrasound transducers is configured to focus the emitted ultrasound at a plurality of different depths, and the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers at the plurality of different depths to ascertain whether the received ultrasound energy was reflected by bone or soft tissue.

[0050] For some applications, the harmonic frequency is a second harmonic frequency of the fundamental frequency.

[0051] For some applications, the ultrasound transducers include respective annular phased array transducers.

[0052] For some applications, the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by measuring a nonlinear parameter of tissue. For some applications, the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis or define an angle of less than 7 degrees with the axis.

[0053] For some applications, the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that the respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis.

[0054] There is still further provided, in accordance with an application of the present invention, a method for inserting a needle between vertebral bones into a spinal canal of a vertebral column of a patient, the method including: using a user handle of a handheld housing of a needle guide device, placing, against skin of the patient at a target insertion site over the vertebral column, a distal skin-contact surface of the handheld housing, the handheld housing shaped so as to define a needle guide passage between the distal skin-contact surface and a proximal surface defined by the user handle, wherein the needle guide device includes:

[0055] (i) at least three ultrasound transducers, which are (a) arranged in the handheld housing radially outside the needle guide passage at respective angular locations around an axis defined by the needle guide passage, and (b) oriented to emit and receive ultrasound energy through the distal skin-contact surface; and

[0056] (ii) visual indicators, which correspond to the ultrasound transducers, respectively, and are arranged on the user handle at respective angular locations around the axis corresponding to the angular locations of the respective ultrasound transducers; activating circuitry of the needle guide device to repeatedly: drive the ultrasound transducers to emit and receive ultrasound energy, analyze the ultrasound energy received by each of the ultrasound transducers to ascertain whether the received ultrasound energy was reflected by bone or soft tissue, and actuate the visual indicators to indicate, for the corresponding ultrasound transducers, respectively, whether the received ultrasound energy was reflected by bone or soft tissue; using the user handle, adjusting a position of the handheld housing until all of the visual indicators indicate that the ultrasound energy received from the corresponding ultrasound transducers was reflected by soft tissue; and inserting a needle through the skin via the needle guide passage, such that the needle guide passage guides the needle between the vertebral bones and into the spinal canal.

[0057] For some applications, adjusting the position of the handheld housing includes: adjusting a location of the handheld housing on the skin, adjusting an orientation of the handheld housing with respect to the vertebral column, or adjusting the location of the handheld housing on the skin and the orientation of the handheld housing with respect to the vertebral column.

[0058] For some applications, inserting the needle through the skin including inserting the needle into the needle guide passage before adjusting the position of the handheld housing, and inserting the needle through the skin after adjusting the position of the handheld housing.

[0059] For some applications, inserting the needle through the skin including inserting the needle into the needle guide passage after adjusting the position of the handheld housing.

[0060] For some applications, the visual indicators are arranged equidistantly from the axis.

[0061] For some applications, the ultrasound transducers are arranged equidistantly from the axis.

[0062] For some applications, the ultrasound transducers are arranged at an average of 0.5 - 2 cm from the axis.

[0063] For some applications, the visual indicators and the ultrasound transducers are equally spaced around the axis.

[0064] For some applications, the needle guide device includes no more than ten ultrasound transducers.

[0065] For some applications: the user handle is shaped so as to define a generally cylindrical portion that is shaped so as to define the proximal surface and a longitudinal portion of the needle guide passage, and the visual indicators are arranged on the generally cylindrical portion around the axis.

[0066] For some applications, the visual indicators include respective light sources.

[0067] For some applications, the circuitry is configured to actuate the light sources to emit light having a first color indicating that the received ultrasound energy was reflected by the bone, and a second color, different from the first color, indicating that the received ultrasound energy was reflected by the soft tissue.

[0068] For some applications, the circuitry is configured to actuate the visual indicators to have a first color indicating that the received ultrasound energy was reflected by the bone, and a second color, different from the first color, indicating that the received ultrasound energy was reflected by the soft tissue.

[0069] For some applications, the circuitry is configured to actuate the visual indicators to indicate, for the corresponding ultrasound transducers, respectively, whether the received ultrasound energy was reflected by bone or soft tissue, by: setting a first on / off status of the visual indicators to indicate that the received ultrasound energy was reflected by the bone, and setting a second on / off status of the visual indicators to indicate that the received ultrasound energy was reflected by the soft tissue, the second on / off status the opposite of the first on / off status.

[0070] For some applications, the soft tissue is ligament, and the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers to ascertain whether the received ultrasound energy was reflected by bone or ligament.

[0071] For some applications, the circuitry is disposed within the handheld housing.

[0072] For some applications, the needle guide device does not include a display screen.

[0073] For some applications, the needle guide device does not include any external electrical cables.

[0074] For some applications, the needle guide device does not include any data communication ports.

[0075] For some applications, the needle guide device does not include any antennas. For some applications, the needle guide device does not include any external electrical cables, any data communication ports, any antennas, or a display screen.

[0076] For some applications, the needle guide device is not configured to be wiredly or wirelessly coupled in data communication with any elements external to the handheld housing.

[0077] For some applications, the ultrasound transducers include respective annular phased array transducers.

[0078] For some applications, the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by measuring a nonlinear parameter of tissue.

[0079] For some applications, the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by calculating a one-dimensional value for each of the ultrasound transducers.

[0080] For some applications: the ultrasound transducers are configured to emit the ultrasound energy at an emission amplitude and a fundamental frequency, and to measure a received amplitude of the received ultrasound energy at a harmonic frequency of the fundamental frequency, the harmonic frequency greater than the fundamental frequency, and the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by calculating a ratio of the received amplitude to the emission amplitude.

[0081] For some applications: each of the ultrasound transducers is configured to focus the emitted ultrasound at a plurality of different depths, and the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers at the plurality of different depths to ascertain whether the received ultrasound energy was reflected by bone or soft tissue.

[0082] For some applications, the harmonic frequency is a second harmonic frequency of the fundamental frequency.

[0083] For some applications, the ultrasound transducers include respective annular phased array transducers. For some applications, the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by measuring a nonlinear parameter of tissue.

[0084] For some applications, the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis or define an angle of less than 7 degrees with the axis.

[0085] For some applications, the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that the respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis.

[0086] There is additionally provided, in accordance with an application of the present invention, a method for inserting a needle between vertebral bones into a spinal canal of a vertebral column of a patient, the method including: using a user handle of a handheld housing of a needle guide device, placing, against skin of the patient at a target insertion site over the vertebral column, a distal skin-contact surface of the handheld housing, the handheld housing shaped so as to define a needle guide passage between the distal skin-contact surface and a proximal surface defined by the user handle, wherein the needle guide device includes:

[0087] (i) at least three ultrasound transducers, which are (a) arranged in the handheld housing radially outside the needle guide passage at respective angular locations around an axis defined by the needle guide passage, and (b) oriented to emit and receive ultrasound energy through the distal skin-contact surface, wherein the ultrasound transducers are configured to emit the ultrasound energy at an emission amplitude and a fundamental frequency, and to measure a received amplitude of the received ultrasound energy at a harmonic frequency of the fundamental frequency, the harmonic frequency greater than the fundamental frequency; and

[0088] (ii) one or more user outputs; activating circuitry of the needle guide device to repeatedly: drive the ultrasound transducers to emit and receive ultrasound energy, analyze the ultrasound energy received by each of the ultrasound transducers by calculating a ratio of the received amplitude to the emission amplitude, to ascertain whether the received ultrasound energy was reflected by bone or soft tissue, and actuate the one or more user outputs to indicate whether the ultrasound energy received by the ultrasound transducers was reflected by bone or soft tissue; using the user handle, adjusting a position of the handheld housing until the one or more user outputs indicate that the ultrasound energy received from all of the ultrasound transducers was reflected by soft tissue; and inserting a needle through the skin via the needle guide passage, such that the needle guide passage guides the needle between the vertebral bones and into the spinal canal.

[0089] For some applications: each of the ultrasound transducers is configured to focus the emitted ultrasound at a plurality of different depths, and the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers at the plurality of different depths to ascertain whether the received ultrasound energy was reflected by bone or soft tissue.

[0090] For some applications, the circuitry is configured to actuate the one or more user outputs to separately indicate for each of ultrasound transducers whether the ultrasound energy received by the ultrasound transducer was reflected by bone or soft tissue.

[0091] For some applications, the harmonic frequency is a second harmonic frequency of the fundamental frequency.

[0092] For some applications, the ultrasound transducers include respective annular phased array transducers.

[0093] For some applications, the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by measuring a nonlinear parameter of tissue.

[0094] For some applications, the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis or define an angle of less than 7 degrees with the axis.

[0095] For some applications, the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that the respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis. The present invention will be more fully understood from the following detailed description of embodiments thereof, taken together with the drawings, in which:

[0096] BRIEF DESCRIPTION OF THE DRAWINGS

[0097] Figs. 1A-E are schematic illustrations of a needle guide device for guiding insertion of a needle between vertebral bones into a spinal canal, in accordance with an application of the present invention;

[0098] Fig. 2 is a schematic illustration of the needle guide device of Figs. 1A-E and a needle inserted into a needle guide passage of the needle guide device, in accordance with an application of the present invention;

[0099] Fig. 3 is a schematic illustration of a portion of a method for inserting the needle of Fig. 2 between vertebral bones into a spinal canal of a vertebral column of a patient, in accordance with an application of the present invention;

[0100] Figs. 4A-C are schematic illustrations of additional portions of the method of Fig. 3, in accordance with an application of the present invention; and

[0101] Fig. 5 is a schematic illustration of an annular phased array transducer of the needle guide device of Figs. 1A-E, in accordance with an application of the present invention.

[0102] DETAILED DESCRIPTION OF APPLICATIONS

[0103] Figs. 1A-E are schematic illustrations of a needle guide device 20 for guiding insertion of a needle between vertebral bones into a spinal canal, in accordance with an application of the present invention. Fig. ID is a cross-sectional view of needle guide device 20 taken along line ID — ID of Fig. 1C.

[0104] Reference is also made to Fig. 2, which is a schematic illustration of needle guide device 20 and a needle 22 inserted into a needle guide passage 24 of the needle guide device, in accordance with an application of the present invention. Needle 22 is typically not an element of needle guide device 20. Needle 22 may comprise a needle suitable for neuraxial anesthesia, such as an epidural needle or a spinal needle; a needle for lumbar puncture, such as a lumbar puncture needle; or any other needle known in the art.

[0105] Needle guide device 20 comprises a handheld housing 30, at least three ultrasound transducers 32 (shown highly schematically in Fig. ID), one or more user outputs 46, and circuitry 48 (shown highly schematically in Fig. ID). Circuitry 48 typically comprises one or more processors and memory configured in hardware and / or software to perform the operations described herein.

[0106] For example, handheld housing 30 may comprise at least four, at least five, or at least six ultrasound transducers 32, and / or no more than 20 ultrasound transducers 32, such as no more than 15 or no more than ten ultrasound transducers 32.

[0107] Typically, ultrasound transducers 32 comprise respective piezoelectric transducers. Optionally, ultrasound transducers 32 comprise respective annular phased array transducers 132, such as described hereinbelow with reference to Fig. 5. Alternatively, ultrasound transducers 32 may comprise other types of transducers known in the ultrasound art, such as linear array transducers.

[0108] Typically, circuitry 48 is disposed within the handheld housing 30.

[0109] Handheld housing 30 is shaped so as to define:

[0110] • a distal skin-contact surface 34 (labeled in Figs. ID and 2), which may comprise a soft or hard material,

[0111] • a user handle 36 shaped so as to define a proximal surface 38, and

[0112] • needle guide passage 24 between distal skin-contact surface 34 and proximal surface 38, through which needle 22 is insertable along an axis 40 of needle guide passage 24 (labeled in several figures, and perhaps best seen in Fig. ID).

[0113] Needle guide passage 24 is shaped so as to guide needle 22 through distal skincontact surface 34 along axis 40.

[0114] As labeled in Figs. ID and IE, ultrasound transducers 32 are arranged in handheld housing 30 radially outside needle guide passage 24 at respective angular locations 42 around axis 40, and oriented to emit and receive ultrasound energy through distal skincontact surface 34.

[0115] For some applications, the one or more user outputs 46 comprise visual indicators 50, which correspond to ultrasound transducers 32, respectively, and are arranged on user handle 36 at respective angular locations 44 around axis 40 corresponding to angular locations 42 of respective ultrasound transducers 32.

[0116] Alternatively, for some applications, visual indicators 50 are arranged at respective angular locations around a point or axis other than axis 40, in which case the respective angular locations do not correspond to angular locations 42 of respective ultrasound transducers 32 (configuration not shown). In these applications, visual indicators 50 may be arranged on user handle 36, or on a separate element of needle guide device 20, such as a display screen, that is wiredly or wireless coupled to user handle 36.

[0117] For some applications, circuitry 48 is configured to repeatedly:

[0118] • drive ultrasound transducers 32 to emit and receive ultrasound energy,

[0119] • analyze the ultrasound energy received by each of ultrasound transducers 32 to ascertain whether the received ultrasound energy was reflected by bone or soft tissue, and

[0120] • actuate visual indicators 50 to indicate, for the corresponding ultrasound transducers 32, respectively, whether the received ultrasound energy was reflected by bone or soft tissue.

[0121] Typically, circuitry 48 is configured to effectively provide real-time feedback. For example, circuitry 48 may repeat the actions described above at a rate of at least once per second, such as least five times, e.g., at least 10 times or at least 100 times, per second.

[0122] For some applications, the soft tissue is ligament, and circuitry 48 is configured to analyze the ultrasound energy received by each of ultrasound transducers 32 to ascertain whether the received ultrasound energy was reflected by bone or ligament.

[0123] For some applications, circuitry 48 is configured to analyze the ultrasound energy received by each of ultrasound transducers 32 by measuring a nonlinear parameter of tissue.

[0124] For some applications, circuitry 48 is configured to analyze the ultrasound energy received by each of ultrasound transducers 32 by calculating a one-dimensional value for each of ultrasound transducers 32.

[0125] For some applications, circuitry 48 is configured to analyze the ultrasound energy using A-mode, as is known in the ultrasound art. Typically, each of ultrasound transducers 32 is configured to focus the emitted ultrasound at a plurality of different depths, and circuitry 48 is configured to analyze the ultrasound energy received by each of ultrasound transducers 32 at the plurality of different depths to ascertain whether the received ultrasound energy was reflected by bone or soft tissue.

[0126] Reference is still made to Figs. 1A-E and 2. For some applications, visual indicators

[0127] 50 are arranged equidistantly from axis 40, such as shown in the figures. Alternatively, visual indicators 50 are arranged at different distances from axis 40, such as in a generally elliptical arrangement, and / or along a perimeter of user handle 36.

[0128] For some applications, ultrasound transducers 32 are arranged equidistantly from axis 40, such as shown in the figures. Alternatively, ultrasound transducers 32 are arranged at different distances from axis 40, such as in a generally elliptical arrangement.

[0129] For some applications, ultrasound transducers 32 are arranged at an average of at least 0.5 cm from axis 40, no more than 2 cm from axis 40, and / or 0.5 - 2 cm from axis 40.

[0130] For some applications, as best seen in Fig. ID, ultrasound transducers 32 are oriented with respect to axis 40 of needle guide passage 24 such that respective propagation directions of the ultrasound energy emitted by ultrasound transducers 32 are parallel with axis 40 or define an angle of less than 15 degrees, e.g., less than 10 degrees, such as less than 7 degrees with axis 40.

[0131] Reference is still made to Figs. 1A-E and 2. Typically, visual indicators 50 and ultrasound transducers 32 are equally spaced around axis 40, i.e., uniformly distributed with a constant angular offset between adjacent visual indicators 50 and between adjacent ultrasound transducers 32.

[0132] Reference is still made to Figs. 1A-E and 2. For some applications, user handle 36 is shaped so as to define a generally cylindrical portion 54 that is shaped so as to define proximal surface 38 and a longitudinal portion of needle guide passage 24. For some of these applications, visual indicators 50 are arranged on generally cylindrical portion 54 around axis 40. For example, each of visual indicators 50 may include a portion that faces proximally and a portion that faces laterally (away from axis 40), in order to facilitate viewing of visual indicators 50 by the anesthesiologist from different directions during use.

[0133] For some applications, circuitry 48 is configured to actuate visual indicators 50 to have a first color indicating that the received ultrasound energy was reflected by the bone, and a second color, different from the first color, indicating that the received ultrasound energy was reflected by the soft tissue. By way of example and not limitation, the first color may, for example, by red, and the second color may, for example, be green.

[0134] For some applications, visual indicators 50 comprise respective light sources 60 (e.g., comprising LEDs). For some of these applications, circuitry 48 is configured to actuate light sources 60 to emit light having the first color indicating that the received ultrasound energy was reflected by the bone, and the second color indicating that the received ultrasound energy was reflected by the soft tissue.

[0135] Alternatively or additionally, for some applications, circuitry 48 is configured to actuate light sources 60 to flash at a first rate indicating that the received ultrasound energy was reflected by the bone, and at a second rate, different from the first rate, indicating that the received ultrasound energy was reflected by the soft tissue.

[0136] For some applications, circuitry 48 is configured to actuate visual indicators 50 (e.g., light sources 60) to indicate, for the corresponding ultrasound transducers 32, respectively, whether the received ultrasound energy was reflected by bone or soft tissue, by:

[0137] • setting a first on / off status of visual indicators 50 to indicate that the received ultrasound energy was reflected by the bone, and

[0138] • setting a second on / off status of visual indicators 50 to indicate that the received ultrasound energy was reflected by the soft tissue, the second on / off status the opposite of the first on / off status.

[0139] In some of the configurations described hereinabove, the one or more user outputs 46 comprise visual indicators 50 (e.g., light sources 60), which correspond to ultrasound transducers 32, respectively, and are arranged on user handle 36 at respective angular locations 44 around axis 40 corresponding to angular locations 42 of respective ultrasound transducers 32. These techniques enable needle guide device 20 to provide easily- understood and actionable feedback to the anesthesiologist on the needle guide device itself, without the need for additional hardware, or for the anesthesiologist to interpret ultrasound images or ultrasound graphs.

[0140] Therefore, needle guide device 20 typically does not comprise a display screen, any external electrical cables, any data communication ports, or any antennas. Needle guide device 20 is typically not configured to be wiredly or wirelessly coupled in data communication with any elements external to handheld housing 30.

[0141] Reference is made to Figs. 1A and IB. Optionally, needle guide device 20 comprises a distal protective cover 62, which removably covers and protects at least a portion of distal skin-contact surface 34, and / or a proximal protective cover 64, which removably covers and protects at least a portion of proximal surface 38 of user handle 36, such as shown in Fig. 1A. As shown in Fig. IB, these covers are removed before use of needle guide device 20.

[0142] Reference is now made to Figs. 3 and 4A-C, which are schematic illustrations of a method for inserting needle 22 between vertebral bones 70 into a spinal canal 72 of a vertebral column 74 of a patient, in accordance with an application of the present invention.

[0143] As shown in Figs. 3 and 4A, an anesthesiologist, using user handle 36 of handheld housing 30, places distal skin-contact surface 34 of handheld housing 30 against skin 76 of the patient at a target insertion site 78 over vertebral column 74.

[0144] Before or after placing distal skin-contact surface 34 against skin 76, the anesthesiologist activates circuitry 48 of needle guide device 20 to repeatedly:

[0145] • drive ultrasound transducers 32 to emit and receive ultrasound energy 80 (schematically illustrated by lines 80 in Figs. 4A and 4B),

[0146] • analyze the ultrasound energy 80 received by each of ultrasound transducers 32 to ascertain whether the received ultrasound energy 80 was reflected by bone 82 or soft tissue 84, and

[0147] • actuate visual indicators 50 to indicate, for the corresponding ultrasound transducers 32, respectively, whether the received ultrasound energy 80 was reflected by bone 82 or soft tissue 84.

[0148] In the exemplary use shown in Fig. 4A, needle guide device 20 is initially not properly positioned to guide needle 22 into spinal canal 72, such that needle guide passage 24 is not properly oriented toward a target space 86 between vertebral bones 70. Therefore, one or more of ultrasound transducers 32 detect bone 82 of vertebral bones 70 surrounding target space 86. This detection of bone 82 is indicated by a first subset 50A of visual indicators 50 corresponding to the subset of ultrasound transducers 32 that detect bone 82 (for example, in configurations in which visual indicators 50 comprise respective light sources 60, circuitry 48 may activate first subset 50A to emit red light). The remaining ultrasound transducers 32 detect soft tissue 84; this detection of soft tissue 84 is indicated by a corresponding second subset 50B of visual indicators 50 (for example, in configurations in which visual indicators 50 comprise respective light sources 60, circuitry 48 may activate second subset 50B to emit green light). As shown in Fig. 4B, using user handle 36, the anesthesiologist adjusts a position of handheld housing 30 until all of visual indicators 50 indicate that the ultrasound energy 80 received from the corresponding ultrasound transducers 32 was reflected by soft tissue 84. The identification of soft tissue 84 in all radial directions from axis 40 indicates that needle guide passage 24 is properly oriented toward target space 86 between vertebral bones 70. The anesthesiologist repeatedly adjusts the position of handheld housing 30 until an appropriate location on skin 76 and orientation of axis 40 is achieved.

[0149] The anesthesiologist performs the above-mentioned adjustment of the position of handheld housing 30 by adjusting, as appropriate, a location of handheld housing 30 on skin 76, as indicated schematically in Fig. 4B by an arrow 88, and / or adjusting an orientation of handheld housing 30 with respect to vertebral column 74, as indicated by an arrow 90. This adjustment of the position of handheld housing 30 changes the trajectory of axis 40 of needle guide passage 24, and thus of the needle 22, when it is subsequently inserted through needle guide passage 24 and into the patient, as described below with reference to Fig. 4C.

[0150] As shown in Fig. 4C, the anesthesiologist inserts needle 22 through skin 76 via needle guide passage 24, such that needle guide passage 24 guides needle 22 through target space 86 between vertebral bones 70 and into spinal canal 72 (depending on the procedure, either into an epidural space 92, as shown in Fig. 4C or an intrathecal (subarachnoid) space 94 (insertion not shown in Fig. 4C)). Needle 22 may be inserted into needle guide passage 24 before adjusting the position of handheld housing 30 (before or after placing distal skincontact surface 34 against skin 76), or after adjusting the position of handheld housing 30.

[0151] For some applications, needle guide device 20 implements a loss of resistance technique. Needle guide device 20 alerts the anesthesiologist when the tip of needle 22 enters epidural space 92. For example, needle guide device 20 may detect the entrance into epidural space 92 by tracking changes in the speed of movement of needle 22 (typically acceleration) as the needle enters epidural space 92 (the needle accelerates because of the sudden drop of resistance in the epidural space). For example, needle guide device 20 may detect the increase in speed using a combination of the nonlinear parameter (P), described hereinbelow, and optical tracking of dark (e.g., black) stripes on the needle.

[0152] For some applications, needle guide device 20 is configured to output a depth of epidural space 92. For example, needle guide device 20 may use Equation 2, described hereinbelow, which includes x as the distance from the transducer (sensor), and therefore provides the depth as a byproduct due to the difference in the nonlinear parameter (P).

[0153] Reference is now made to Fig. 5, which is a schematic illustration of one of ultrasound transducers 32, in accordance with an application of the present invention. In this application of the present invention, ultrasound transducers 32 comprise respective annular phased array transducers 132.

[0154] For some applications, annular phased array transducers 132 are configured to emit the ultrasound energy at an emission amplitude and a fundamental frequency, and to measure a received amplitude of the received ultrasound energy at a harmonic frequency of the fundamental frequency, the harmonic frequency greater than the fundamental frequency (e.g., at a second harmonic frequency of the fundamental frequency). Circuitry 48 is configured to analyze the ultrasound energy received by each of annular phased array transducers 132 by calculating a ratio of circuitry 48 may be configured to use the finite amplitude method (FAM) based on harmonic generation, which comprises sending a sinusoidal ultrasonic wave through the tissue and measuring the amplitude of a harmonic wave (e.g., second harmonic wave) that is generated due to nonlinearity of the tissue.

[0155] Typically, each of annular phased array transducers 132 is configured to focus the emitted ultrasound at a plurality of different depths, and circuitry 48 is configured to analyze the ultrasound energy received by each of annular phased array transducers 132 at the plurality of different depths to ascertain whether the received ultrasound energy was reflected by bone or soft tissue. For example, annular phased array transducers 132 may be configured to adjust their focal length (and thus depth of focus) by changing the phase and amplitude of the signal for each ring of elements, for example using spherical focusing.

[0156] Typically, circuitry 48 is configured to analyze the ultrasound energy received by each of ultrasound transducers 32 by measuring a nonlinear parameter (P) of tissue. The nonlinear parameter (P) is a dimensionless quantity that characterizes the degree of nonlinearity in a material. It is related to the displacement amplitudes of the fundamental and second-order harmonic frequency components of the ultrasonic wave propagating through the material.

[0157] For example, the acoustic nonlinear parameter (P) for a specific point may be expressed as: Equation 1 where:

[0158] • A1is the amplitude of the fundamental frequency (first harmonic);

[0159] •2is the amplitude of the second harmonic;

[0160] • k is the wave number of the fundamental frequency, given by k = where c0is c0 the speed of sound in the medium.

[0161] For example, the acoustic nonlinear parameter (P) for a row of points at a distance x from a transducer (sensor) may be expressed as:

[0162] Equation 2 where:

[0163] • A1is the amplitude of the fundamental frequency (first harmonic) at distance x

[0164] • d2is the amplitude of the second harmonic at distance x

[0165] • c0is the speed of sound in the medium;

[0166] • f is the frequency of the fundamental harmonic; and

[0167] • x is the distance from the sensor (or the sound source) where the amplitudes A1and 2 are measured.

[0168] Different types of biological tissue have different P values. In particular, the P value of bone tissue is higher than that of soft tissue (e.g., ligament tissue), because of differences in their microstructure and composition. For example, the P value (measured using the second harmonic) of bone tissue may range from 0.5 to 2.5, while the P value of ligament tissue (measured using the second harmonic) may range from 0.1 to 0.5.

[0169] The annular phased array transducers 132 and techniques for using them to detect tissue type, described with reference to Fig. 5, may be implemented in needle guide device 20, described hereinabove with reference to Figs. 1A-4C. Reference is made to Figs. 1A-5. For some applications, the one or more user outputs 46 comprise visual indicators 50, which correspond to ultrasound transducers 32, respectively, and are arranged on user handle 36 at respective angular locations 44 around axis 40 corresponding to angular locations 42 of respective ultrasound transducers 32, such as described hereinabove with reference to Figs. 1A-4C. Alternatively or additionally, the one or more user outputs 46 may comprise audio (e.g., voice) indicators, or a display screen, either of which may be an element of handheld housing 30, or provided separately from handheld housing 30 and coupled thereto either wiredly or wirelessly.

[0170] It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.

Claims

CLAIMS1. A needle guide device for guiding insertion of a needle between vertebral bones into a spinal canal, the needle guide device comprising: a handheld housing, which is shaped so as to define (a) a distal skin-contact surface, (b) a user handle shaped so as to define a proximal surface, and (c) a needle guide passage between the distal skin-contact surface and the proximal surface, through which the needle is insertable along an axis of the needle guide passage; at least three ultrasound transducers, arranged in the handheld housing radially outside the needle guide passage at respective angular locations around the axis, and oriented to emit and receive ultrasound energy through the distal skin-contact surface; visual indicators, which correspond to the ultrasound transducers, respectively, and are arranged on the user handle at respective angular locations around the axis corresponding to the angular locations of the respective ultrasound transducers; and circuitry, which is configured to repeatedly: drive the ultrasound transducers to emit and receive ultrasound energy, analyze the ultrasound energy received by each of the ultrasound transducers to ascertain whether the received ultrasound energy was reflected by bone or soft tissue, and actuate the visual indicators to indicate, for the corresponding ultrasound transducers, respectively, whether the received ultrasound energy was reflected by bone or soft tissue.

2. The needle guide device according to claim 1, wherein the visual indicators are arranged equidistantly from the axis.

3. The needle guide device according to claim 1, wherein the ultrasound transducers are arranged equidistantly from the axis.

4. The needle guide device according to claim 1, wherein the ultrasound transducers are arranged at an average of 0.5 - 2 cm from the axis.

5. The needle guide device according to claim 1, wherein the visual indicators and the ultrasound transducers are equally spaced around the axis.

6. The needle guide device according to claim 1, wherein the needle guide device comprises no more than ten ultrasound transducers.

7. The needle guide device according to claim 1, wherein the user handle is shaped so as to define a generally cylindrical portion that is shaped so as to define the proximal surface and a longitudinal portion of the needle guide passage, and wherein the visual indicators are arranged on the generally cylindrical portion around the axis.

8. The needle guide device according to claim 1, wherein the circuitry is configured to actuate the visual indicators to have a first color indicating that the received ultrasound energy was reflected by the bone, and a second color, different from the first color, indicating that the received ultrasound energy was reflected by the soft tissue.

9. The needle guide device according to claim 1, wherein the circuitry is configured to actuate the visual indicators to indicate, for the corresponding ultrasound transducers, respectively, whether the received ultrasound energy was reflected by bone or soft tissue, by: setting a first on / off status of the visual indicators to indicate that the received ultrasound energy was reflected by the bone, and setting a second on / off status of the visual indicators to indicate that the received ultrasound energy was reflected by the soft tissue, the second on / off status the opposite of the first on / off status.

10. The needle guide device according to claim 1, wherein the soft tissue is ligament, and wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers to ascertain whether the received ultrasound energy was reflected by bone or ligament.

11. The needle guide device according to claim 1, wherein the circuitry is disposed within the handheld housing.

12. The needle guide device according to claim 1, wherein the needle guide device does not comprise a display screen.

13. The needle guide device according to claim 1, wherein the needle guide device does not comprise any external electrical cables.

14. The needle guide device according to claim 1, wherein the needle guide device does not comprise any data communication ports.

15. The needle guide device according to claim 1, wherein the needle guide device does not comprise any antennas.

16. The needle guide device according to claim 1, wherein the needle guide device does not comprise any external electrical cables, any data communication ports, any antennas, or a display screen.

17. The needle guide device according to claim 1, wherein the needle guide device is not configured to be wiredly or wirelessly coupled in data communication with any elements external to the handheld housing.

18. The needle guide device according to claim 1, wherein the ultrasound transducers comprise respective annular phased array transducers.

19. The needle guide device according to claim 1, wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by measuring a nonlinear parameter of tissue.

20. The needle guide device according to claim 1, wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by calculating a one-dimensional value for each of the ultrasound transducers.

21. The needle guide device according to any one of claims 1-20, wherein the visual indicators comprise respective light sources.

22. The needle guide device according to claim 21, wherein the circuitry is configured to actuate the light sources to emit light having a first color indicating that the received ultrasound energy was reflected by the bone, and a second color, different from the first color, indicating that the received ultrasound energy was reflected by the soft tissue.

23. The needle guide device according to any one of claims 1-20, wherein the ultrasound transducers are configured to emit the ultrasound energy at an emission amplitude and a fundamental frequency, and to measure a received amplitude of the received ultrasound energy at a harmonic frequency of the fundamental frequency, the harmonic frequency greater than the fundamental frequency, and wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by calculating a ratio of the received amplitude to the emission amplitude.

24. The needle guide device according to claim 23,wherein each of the ultrasound transducers is configured to focus the emitted ultrasound at a plurality of different depths, and wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers at the plurality of different depths to ascertain whether the received ultrasound energy was reflected by bone or soft tissue.

25. The needle guide device according to claim 23, wherein the harmonic frequency is a second harmonic frequency of the fundamental frequency.

26. The needle guide device according to claim 23, wherein the ultrasound transducers comprise respective annular phased array transducers.

27. The needle guide device according to claim 23, wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by measuring a nonlinear parameter of tissue.

28. The needle guide device according to any one of claims 1-20, wherein the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis or define an angle of less than 7 degrees with the axis.

29. The needle guide device according to claim 28, wherein the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that the respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis.

30. A needle guide device for guiding insertion of a needle between vertebral bones into a spinal canal, the needle guide device comprising: a handheld housing, which is shaped so as to define (a) a distal skin-contact surface, (b) a user handle shaped so as to define a proximal surface, and (c) a needle guide passage between the distal skin-contact surface and the proximal surface, through which the needle is insertable along an axis of the needle guide passage; at least three ultrasound transducers, arranged in the handheld housing radially outside the needle guide passage at respective angular locations around the axis, and oriented to emit and receive ultrasound energy through the distal skin-contact surface, wherein the ultrasound transducers are configured to emit the ultrasound energy at an emission amplitude and a fundamental frequency, and to measure a received amplitude ofthe received ultrasound energy at a harmonic frequency of the fundamental frequency, the harmonic frequency greater than the fundamental frequency; one or more user outputs; and circuitry, which is configured to: drive the ultrasound transducers to emit and receive ultrasound energy, analyze the ultrasound energy received by each of the ultrasound transducers by calculating a ratio of the received amplitude to the emission amplitude, to ascertain whether the received ultrasound energy was reflected by bone or soft tissue, and actuate the one or more user outputs to indicate whether the ultrasound energy received by the ultrasound transducers was reflected by bone or soft tissue.

31. The needle guide device according to claim 30, wherein the circuitry is configured to actuate the one or more user outputs to separately indicate for each of ultrasound transducers whether the ultrasound energy received by the ultrasound transducer was reflected by bone or soft tissue.

32. The needle guide device according to claim 30, wherein each of the ultrasound transducers is configured to focus the emitted ultrasound at a plurality of different depths, and wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers at the plurality of different depths to ascertain whether the received ultrasound energy was reflected by bone or soft tissue.

33. The needle guide device according to claim 30, wherein the harmonic frequency is a second harmonic frequency of the fundamental frequency.

34. The needle guide device according to claim 30, wherein the ultrasound transducers comprise respective annular phased array transducers.

35. The needle guide device according to claim 30, wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by measuring a nonlinear parameter of tissue.

36. The needle guide device according to claim 30, wherein the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis or define an angle of less than 7 degrees with the axis.

37. The needle guide device according to claim 36, wherein the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that the respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis.

38. A method for inserting a needle between vertebral bones into a spinal canal of a vertebral column of a patient, the method comprising: using a user handle of a handheld housing of a needle guide device, placing, against skin of the patient at a target insertion site over the vertebral column, a distal skin-contact surface of the handheld housing, the handheld housing shaped so as to define a needle guide passage between the distal skin-contact surface and a proximal surface defined by the user handle, wherein the needle guide device includes:(i) at least three ultrasound transducers, which are (a) arranged in the handheld housing radially outside the needle guide passage at respective angular locations around an axis defined by the needle guide passage, and (b) oriented to emit and receive ultrasound energy through the distal skin-contact surface; and(ii) visual indicators, which correspond to the ultrasound transducers, respectively, and are arranged on the user handle at respective angular locations around the axis corresponding to the angular locations of the respective ultrasound transducers; activating circuitry of the needle guide device to repeatedly: drive the ultrasound transducers to emit and receive ultrasound energy, analyze the ultrasound energy received by each of the ultrasound transducers to ascertain whether the received ultrasound energy was reflected by bone or soft tissue, and actuate the visual indicators to indicate, for the corresponding ultrasound transducers, respectively, whether the received ultrasound energy was reflected by bone or soft tissue; using the user handle, adjusting a position of the handheld housing until all of the visual indicators indicate that the ultrasound energy received from the corresponding ultrasound transducers was reflected by soft tissue; and inserting a needle through the skin via the needle guide passage, such that the needle guide passage guides the needle between the vertebral bones and into the spinal canal.

39. The method according to claim 38, wherein adjusting the position of the handheld housing comprises: adjusting a location of the handheld housing on the skin, adjusting an orientation of the handheld housing with respect to the vertebral column, or adjusting the location of the handheld housing on the skin and the orientation of the handheld housing with respect to the vertebral column.

40. The method according to claim 38, wherein inserting the needle through the skin comprising inserting the needle into the needle guide passage before adjusting the position of the handheld housing, and inserting the needle through the skin after adjusting the position of the handheld housing.

41. The method according to claim 38, wherein inserting the needle through the skin comprising inserting the needle into the needle guide passage after adjusting the position of the handheld housing.

42. The method according to claim 38, wherein the visual indicators are arranged equidistantly from the axis.

43. The method according to claim 38, wherein the ultrasound transducers are arranged equidistantly from the axis.

44. The method according to claim 38, wherein the ultrasound transducers are arranged at an average of 0.5 - 2 cm from the axis.

45. The method according to claim 38, wherein the visual indicators and the ultrasound transducers are equally spaced around the axis.

46. The method according to claim 38, wherein the needle guide device comprises no more than ten ultrasound transducers.

47. The method according to claim 38, wherein the user handle is shaped so as to define a generally cylindrical portion that is shaped so as to define the proximal surface and a longitudinal portion of the needle guide passage, and wherein the visual indicators are arranged on the generally cylindrical portion around the axis.

48. The method according to claim 38, wherein the visual indicators comprise respective light sources.

49. The method according to claim 48, wherein the circuitry is configured to actuate the light sources to emit light having a first color indicating that the received ultrasound energy was reflected by the bone, and a second color, different from the first color, indicating that the received ultrasound energy was reflected by the soft tissue.

50. The method according to claim 38, wherein the circuitry is configured to actuate the visual indicators to have a first color indicating that the received ultrasound energy was reflected by the bone, and a second color, different from the first color, indicating that the received ultrasound energy was reflected by the soft tissue.

51. The method according to claim 38, wherein the circuitry is configured to actuate the visual indicators to indicate, for the corresponding ultrasound transducers, respectively, whether the received ultrasound energy was reflected by bone or soft tissue, by: setting a first on / off status of the visual indicators to indicate that the received ultrasound energy was reflected by the bone, and setting a second on / off status of the visual indicators to indicate that the received ultrasound energy was reflected by the soft tissue, the second on / off status the opposite of the first on / off status.

52. The method according to claim 38, wherein the soft tissue is ligament, and wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers to ascertain whether the received ultrasound energy was reflected by bone or ligament.

53. The method according to claim 38, wherein the circuitry is disposed within the handheld housing.

54. The method according to claim 38, wherein the needle guide device does not comprise a display screen.

55. The method according to claim 38, wherein the needle guide device does not comprise any external electrical cables.

56. The method according to claim 38, wherein the needle guide device does not comprise any data communication ports.

57. The method according to claim 38, wherein the needle guide device does not comprise any antennas.

58. The method according to claim 38, wherein the needle guide device does not comprise any external electrical cables, any data communication ports, any antennas, or a display screen.

59. The method according to claim 38, wherein the needle guide device is not configured to be wiredly or wirelessly coupled in data communication with any elements external to the handheld housing.

60. The method according to claim 38, wherein the ultrasound transducers comprise respective annular phased array transducers.

61. The method according to claim 38, wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by measuring a nonlinear parameter of tissue.

62. The method according to claim 38, wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by calculating a onedimensional value for each of the ultrasound transducers.

63. The method according to claim 38, wherein the ultrasound transducers are configured to emit the ultrasound energy at an emission amplitude and a fundamental frequency, and to measure a received amplitude of the received ultrasound energy at a harmonic frequency of the fundamental frequency, the harmonic frequency greater than the fundamental frequency, and wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by calculating a ratio of the received amplitude to the emission amplitude.

64. The method according to claim 63, wherein each of the ultrasound transducers is configured to focus the emitted ultrasound at a plurality of different depths, and wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers at the plurality of different depths to ascertain whether the received ultrasound energy was reflected by bone or soft tissue.

65. The method according to claim 63, wherein the harmonic frequency is a second harmonic frequency of the fundamental frequency.

66. The method according to claim 63, wherein the ultrasound transducers comprise respective annular phased array transducers.

67. The method according to claim 63, wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by measuring a nonlinear parameter of tissue.

68. The method according to claim 38, wherein the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis or define an angle of less than 7 degrees with the axis.

69. The method according to claim 68, wherein the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that the respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis.

70. A method for inserting a needle between vertebral bones into a spinal canal of a vertebral column of a patient, the method comprising: using a user handle of a handheld housing of a needle guide device, placing, against skin of the patient at a target insertion site over the vertebral column, a distal skin-contact surface of the handheld housing, the handheld housing shaped so as to define a needle guide passage between the distal skin-contact surface and a proximal surface defined by the user handle, wherein the needle guide device includes:(i) at least three ultrasound transducers, which are (a) arranged in the handheld housing radially outside the needle guide passage at respective angular locations around an axis defined by the needle guide passage, and (b) oriented to emit and receive ultrasound energy through the distal skin-contact surface, wherein the ultrasound transducers are configured to emit the ultrasound energy at an emission amplitude and a fundamental frequency, and to measure a received amplitude of the received ultrasound energy at a harmonic frequency of the fundamental frequency, the harmonic frequency greater than the fundamental frequency; and(ii) one or more user outputs;activating circuitry of the needle guide device to repeatedly: drive the ultrasound transducers to emit and receive ultrasound energy, analyze the ultrasound energy received by each of the ultrasound transducers by calculating a ratio of the received amplitude to the emission amplitude, to ascertain whether the received ultrasound energy was reflected by bone or soft tissue, and actuate the one or more user outputs to indicate whether the ultrasound energy received by the ultrasound transducers was reflected by bone or soft tissue; using the user handle, adjusting a position of the handheld housing until the one or more user outputs indicate that the ultrasound energy received from all of the ultrasound transducers was reflected by soft tissue; and inserting a needle through the skin via the needle guide passage, such that the needle guide passage guides the needle between the vertebral bones and into the spinal canal.

71. The method according to claim 70, wherein each of the ultrasound transducers is configured to focus the emitted ultrasound at a plurality of different depths, and wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers at the plurality of different depths to ascertain whether the received ultrasound energy was reflected by bone or soft tissue.

72. The method according to claim 70, wherein the circuitry is configured to actuate the one or more user outputs to separately indicate for each of ultrasound transducers whether the ultrasound energy received by the ultrasound transducer was reflected by bone or soft tissue.

73. The method according to claim 70, wherein the harmonic frequency is a second harmonic frequency of the fundamental frequency.

74. The method according to claim 70, wherein the ultrasound transducers comprise respective annular phased array transducers.

75. The method according to claim 70, wherein the circuitry is configured to analyze the ultrasound energy received by each of the ultrasound transducers by measuring a nonlinear parameter of tissue.

76. The method according to claim 70, wherein the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that respective propagationdirections of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis or define an angle of less than 7 degrees with the axis.

77. The method according to claim 76, wherein the ultrasound transducers are oriented with respect to the axis of the needle guide passage such that the respective propagation directions of the ultrasound energy emitted by the ultrasound transducers are parallel with the axis.

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