WO2015066280A1

WO2015066280A1 - Ventriculostomy guidance device

Info

Publication number: WO2015066280A1
Application number: PCT/US2014/063079
Authority: WO
Inventors: Kirby Gannett VOSBURGH; Phillip Jason WHITE
Original assignee: Brigham And Women's Hospital, Inc.
Priority date: 2013-10-30
Filing date: 2014-10-30
Publication date: 2015-05-07

Abstract

A system is provided for guiding a medical instrument relative to a subject's anatomy using ultrasound-guided imaging. The system includes a support frame configured to be positioned on the subject's anatomy, the support frame defining an entry location for the medical instrument, and at least one ultrasound transducer coupled to the support frame and arranged such that the at least one ultrasound transducer is operable to transmit ultrasound energy to the subject's anatomy and receive echo signals therefrom. The system also includes a processor in communication with the at least one ultrasound transducer and configured to receive the echo signals and generate a trajectory that extends from the entry location to a desired region of the subject's anatomy.

Description

VENTRICULOSTOMY GUIDANCE DEVICE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on, claims priority to, and incorporates herein by reference in its entirety U.S. Provisional Application Serial No. 61/897,315 filed October 30, 2013 , and entitled "VENTRICULOSTOMY GUIDANCE DEVICE."

BACKGROUND OF THE INVENTION

[0002] The field of the invention is systems and devices for interventional medicine. More particularly, the system described herein supports a guided intracranial instrument insertion without the disadvantages of known technologies.

[0003] Extra Ventricular Drains ("EVD"} are often placed to relieve intracranial pressure in patients with subarachnoid hemorrhage and head trauma. The procedure is generally performed freehand. Published studies have reported rates of initial EVD catheter misplacement as high as 100%. Further studies have estimated the mean distance error from optimal placement for these free-hand procedures to be ~16 mm, with typically 2 passes needed for placement, and nearly one quarter of catheter tip placements outside of the ventricular space. While it is based on survey of practicing neurosurgeons and residents, the paper of O'Neill et al. ("A survey of ventriculostomy placement and intracranial pressure monitor placement practices," Surgical Neurology 2008; 70:268-73} is the most comprehensive study, with over 900 returned questionnaires. It is notable that all practitioners, including experienced, active neurosurgeons, report frequently requiring more than one attempt to complete a successful ventriculostomy, and many had observed peers make multiple attempts. While immediately observable brain injury, such as blood on the stylet, occurs in less than 2% of cases, significant injuries, including functional deficits, are observed in many cases; the data are spotty and inconsistent, but 10-15% is a rough average.

[0004] There are several image-guidance systems commercially available to assist and improve the accuracy of brain targeting. However, despite their performance (error ~5 mm] and clear patient benefit, they are not commonly used. According to the O'Neill et al. survey, only a few percent of the 934 American neurosurgeon respondents used such a system on a regular basis. This low rate appears to be due to two factors: 1} the equipment is expensive and cumbersome to use, thus greatly extending the time required, and 2} current practice is "good enough." Simple alignment fixtures, such as the Ghajar approach, ("A guide for ventricular catheter placement (technical note}." J Neurosurg 1985; 63(6} 985-986} may also be used to improve accuracy for ventricles of normal shape and location. However, this is performed without cannula trajectory monitoring and direct confirmation of placement, and less than 5% of neurosurgeons and none of the 100 reporting residents reported using such a guide. In addition, a hybrid approach has been recently demonstrated (Patil,V et al. "Accuracy of an electromagnetic tracking system for image guided placement of external ventricular drain," American Association of Neurological Surgeons 2010, Philadelphia, PA} in which a pre-procedure CT-based model is registered to the skull and a "GPS-like" display guides a stylet to its target. However, this device also requires extensive setup and the availability of a pre-procedure CT.

[0005] Therefore, given these shortcomings, it would be desirable to have a system that will not require pre-procedure images of the ventricles or independent systems for head tracking. It would also be desirable to have a system that will be a stand-alone system, requiring minimal training, and with performance and ease of use intended to promote adoption and increase the potential for becoming a standard of care.

SUMMARY OF THE INVENTION

[0006] The present invention overcomes the aforementioned drawbacks by providing a low cost, easily used system for guiding a medical instrument relative to a subject's anatomy for use in trans-cranial procedures. The system includes a support frame configured to be positioned on the subject's anatomy. The support frame defines an entry location for a medical instrument. The system also includes an instrument guide coupled to the support frame. The instrument guide includes an annular portion coupled on one end to the entry location for the medical instrument. The instrument guide is configured to receive the medical instrument such that the medical instrument can be guided to this entry location. The system also includes at least one ultrasound transducer movably coupled to the instrument guide and arranged such that the at least one ultrasound transducer is operable to transmit ultrasound energy to the subject's anatomy and receive echo signals therefrom. The system also includes a processor in communication with the at least one ultrasound transducer and configured to receive the echo signals and identify therefrom a trajectory that extends from the entry location to a desired region of the subject's anatomy.

[0007] The foregoing and other aspects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention, however, and reference is made therefore to the claims and herein for interpreting the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is an example of a system for performing trans-cranial procedures using ultrasound imaging guidance, in accordance with the present invention.

[0009] FIGS. 2A and 2B illustrate an example of a mode of operation for the system, in accordance with the present invention.

[0010] FIG. 3 is another example of a system for use in accordance with the present invention.

[0011] FIG. 4 is another example of a system for use in accordance with the present invention.

[0012] FIG. 5 is another example of a system design for use in accordance with the present invention.

[0013] FIG. 6 is another example of a system design for use in accordance with the present invention.

[0014] FIG.7 is a block diagram illustrating an example of controlling a system for performing trans-cranial procedures using ultrasound imaging guidance, in accordance with the present invention.

[0015] FIG. 8A is a MRI image of a patient with a ID ultrasound device applied at the right temporal acoustic window.

[0016] FIG. 8B is a ID brightness-mode display from intracranial ultrasound signal traces.

DETAILED DESCRIPTION OF THE INVENTION

[0017] A system for guiding an interventional medical procedure is provided.

The system generally includes a frame that can be positioned on a subject's anatomy. The frame also supports one or more ultrasound transducers that are configured to determine an entry location on the subject's anatomy and a trajectory along which a medical device or instrument is to be guided.

[0018] The present disclosure provides an approach that utilizes transcutaneous ultrasound imaging (e.g., imaging through an intact skull] in combination with a system that may be easily positioned on the head to optimize the placement of interventional instrumentation, such as an extra- ventricular drain ("EVD"}. Traditional ultrasound techniques for brain imaging require a burr hole in the skull, which must be enlarged so the ultrasound transducer may touch the dura, thereby bypassing the skull and attaining good acoustic contact with the brain. In contrast, the system described herein does not require a burr hole, and will likely provide more positioning flexibility for difficult cases, such as patients having displaced or distorted ventricles, when the need for guidance is most apparent. The approach is based on development of systems to perform trans-cranial focused ultrasound therapy, wherein new methods for transmitting ultrasound through the skull, including a new shear-mode technique for trans-cranial imaging, may be implemented. While the definition of intricate structures remains challenging, the ventricles can be readily distinguished and characterized through these signals, as will be described below.

[0019] Shown in FIG. 1 is one embodiment of a system 100 that is designed to minimize complexity and, as such, increase safety while performing trans-cranial procedures, such as a ventriculostomy, using ultrasound imaging guidance. The system 100 generally includes a support frame 102, and an ultrasound transducer assembly 104 and instrument guide 106 coupled to the support frame 102. The system 100 is configured to be positioned on a portion of a subject's anatomy, for example on a subject's head. Furthermore, the system 100 may be fastened, secured, or otherwise affixed to subject in any number of ways and may be configured with the ability for repositioning while in use.

[0020] The support frame 102 generally may include a planar surface and may be detachably coupled to or positioned against the surface of a target anatomy, such as a skull's outer convexity. In one aspect, the system 100 may be mounted in direct contact with a scalp rather than a skull bone. This design aspect obviates the requirement for an extended skin incision to expose a skull surface. The support frame 102 is also configured such that when it is positioned against the scalp or skull surface, ultrasound signals can be projected from the ultrasound transducers 105 through the skull bone into a desired region in an intracranial space so as to provide, for example, ventricle- localizing data.

[0021] The ultrasound transducer assembly 104 includes one or more ultrasound transducers 105 arranged such that the location of an anatomical target in the subject, such as a ventricle, can be determined. The ultrasound transducers 105 are also arranged such that a trajectory for a medical device or instrument, such as a catheter or cannula, suitable to reach the anatomical target may be determined and tracked. Coupled to each ultrasound transducer 105 is a guide 108 that extends from an upper surface of the transducer 105. Each guide 108 may be used to modify the orientation of the respective transducer 105, thereby modifying a propagation axis of that ultrasound transducer 105 with respect to a subject. In this manner, the ultrasound transducers 105 may be used to identify locations of anatomical targets relative to the instrument guide 106 and base plate 102 such that the medical instrument can be effectively directed to a desired target.

[0022] The instrument guide 106 is preferably an annular structure, such as a tube or lumen, and sized to receive a medical device or instrument, such as a catheter or cannula, or any other interventional instrument or tool. The instrument guide 106 may be configured to provide access to an entry location on the anatomy of a subject, as well as guidance for a medical device or instrument from the entry location to a desired point or region within the subject's anatomy. In this manner, the instrument guide 106 defines a trajectory along which a medical instrument can be introduced into the body of a subject.

[0023] In some configurations, the medical device or instrument received by the instrument guide 106 (not shown in FIG. 1} may be designed to include echogenic features that can facilitate or enhance monitoring during a trans-cranial procedure. This may include tailoring the physical characteristics of the medical device or instrument in a manner that would generate specific ultrasound signatures or readily identifiable ultrasound signals. For example, the medical device or instrument may include textured, patterned, indented, angled, or otherwise irregular surfaces, including, for example, one or more dimples, notches, divots, knurls, ridges, nubs, and the like, or may include materials that are capable of enhancing echogenicity. In some designs, such echogenic features may be configured generally near the tip of the medical device or instrument, although other suitable locations can also be possible.

[0024] Mechanical linkages 112 movably couple the guides 108 to the instrument guide 106. In some aspects, the mechanical linkages 112 may be coupled on one end to an annular support 110, which is slidably coupled to the instrument guide 106, and on the other end is coupled to the guides 108. In this configuration, manipulation of guides 108 can adjust the orientation of the transducers 105, but may also allow for a related adjustment in the orientation of other ultrasound transducers 105. Specifically, this can occur via the mechanical linkages 112 when the annular support 110 is moved along the instrument guide 106. In this manner, movement of the medical device or instrument, by way of insertion and guidance of the medical device or instrument through instrument guide 106, can be actively monitored.

[0025] In the embodiment shown in FIG. 1, system 100 includes an ultrasound transducer assembly 104 composed of three single-channel (1-D] transducers 105 movably coupled to the instrument guide 106 via mechanical linkages 112, as described above. The instrument guide 106 may be positioned such that the principal axis 114 of system 100 is substantially aligned with the direction of travel of a medical device or instrument, defining an instrument trajectory 116. The transducers 105 may be oriented such that their respective 1-D propagation vectors can be adjusted to sweep across and monitor their respective two-dimensional regions of interest. As such, the transducers 105 may be configured to adjust from an orientation axis 118, which is aligned substantially parallel to the principal axis 114, to a tilted axis 120, by sweeping over an angle, φ, 122, either manually , or using motors, which may or may not be precision motors. In some aspects, the orientation or angulation of transducers 105 may be correlated or synchronized with the movement of the medical device or instrument in order to maintain view of specific portions of the device or instrument, such as echogenic features configured therein.

[0026] The transducers 105 may be mechanically coupled to support frame 102 such that a positioning cam (not shown in FIG. 1} may allow for accurate and precise angulations of the transducers 105, with pivot points near the scalp contact. In some configurations, the transducers 105 may have apertures that are weakly geometrically focused (e.g. F-number between 4.0 and 6.0], or planar apertures having an active area of, for example, 3 cm². In addition, the transducers 105 may operate at a center frequencies between, for example, 0.5 and 1.0 MHz with fractional bandwidths approaching 60%. Moreover, the transducers 105 may be commercially procured or assembled in-house with silver-electroded PZT piezoceramic elements encased in polymethyl methacrylate (PMMA] housing and backed by tungsten-impregnated polymer.

[0027] It is envisioned that additional features and elements not explicitly shown in FIG. 1 may also be included into system 100. For instance, standoff layers (not shown] may be designed and incorporated into system 100 in a manner that facilitates acoustical coupling between the transducers 105 and the subject's anatomy, as well as allows for the varied positioning of the transducers 105. Specifically, the optional standoff layers may be preferably composed of materials with appropriate ultrasound transmission properties, such as polyvinyl alcohol cryogel (PVA-C}. Additionally, potentiometers (not shown in FIG. 1} may also be incorporated for electronically encode positions.

[0028] An illustration of one mode of operation for system 100 is shown in FIGS.

2A and 2B. Specifically, a coordinated angulation of the transducers 105 in a direction away from the principal axis 114 of system 100 is shown. For instance, the transducers 105 are angulated by adjusting the orientation of guides 108, either by directly manipulating the guides 108 or by way of displacement of the annular support 110 along the instrument guide 106. By design, the three scanning planes of the transducers 105 can intersect at a line coincident with a point 200 on the instrument trajectory 116.

[0029] In some aspects, system 100 can also be configured such that an additional angulated steering direction can be provided to all three single-channel (1-D] transducers 105. For instance, in addition to angulation in the plane of the trajectory 116, the transducers 105 can be configured to have freedom of motion to angulate (either manually or by using motors] "out-of-plane." The advantages of this design include the availability of added spatial information.

[0030] The system 100 of FIG. 1 may also be configured such that the single- channel (1-D] transducers 105 in the transducer assembly 104 are oriented such that their imaging planes are orthogonal to each other. It is also noted, however, that this orthogonal scan plane orientation can be achieved with any number of transducers 105 and not just three. The advantages of this design include ease of user interpretation and the potential for mechanical and electronic simplicity.

[0031] In some configurations, the coupling of the transducers 105 to the frame

102 may define the entry point for a medical device or instrument on the skull and the instrument trajectory 116. It is possible in this configuration that the arrangement of the instrument trajectory 116 does not enable hitting the target based on the initial positioning of the system 100. If that is the case, the operator can move the system 100 until it registers. Alternatively, the support frame 102 can have an adjustment capability to tilt the axis of the instrument guide 106 and the instrument trajectory 116 so that the entry point can still be used, but with a tilted instrument trajectory 116. This approach may require tilting of the transducers 105, which may require more complex linkages or mechanical controls. In one configuration, the transducers 105 can be capable of moving vertically relative to the plate 102 while keeping the linkage point fixed so the arc displacement still stays in geometric synch.

[0032] In another embodiment of the current invention, illustrated in FIG. 3, a variation of system 100 includes a transducer assembly 104 composed of multiple- channel (2-D] transducer arrays 302 instead of single-channel (ID] transducers 105. This embodiment allows for electronic scanning of the respective 2-D regions-of- interest of the transducers 302. The advantages of this design include the lack of moving parts (the transducers 302 are stationary with respect to the frame 102 but angulated toward the instrument trajectory 116 and improved scanning speed relative to the 1-D transducer configuration in FIG. 2.

[0033] In yet another embodiment of the current invention, illustrated in FIG. 4, a variation of system 100 includes more single-channel (1-D] transducers 105 than are utilized in the configuration of the transducer assembly 104 shown in FIG. 1. The advantages of this design include the additional spatial information that is available without repositioning system 100.

[0034] In yet another embodiment of the current invention, illustrated in FIG. 5, a variation of system 100 includes a transducer assembly 104 that includes a substantially hemispherical cap 502, on which a plurality of single-channel (1-D] transducers 105 are arranged in different rows such that each transducer 105 extends radially from the instrument guide 106 insertion point 504. Electronic selection of the transducers 105 may variably control the 1-D projection and the depth of scan, and thus may not necessitate electronically phased steering. The advantages of this design include the lack of moving parts (the transducers 105 are stationary with respect to the support frame 102} and improved scanning speed relative to the transducer assembly 104 configuration illustrated in FIG. 1. [0035] In yet another embodiment of the current invention, illustrated in FIG. 6, a variation of system 100 includes a transducer assembly 104 that includes two multiple- channel (2-D] transducer arrays 602. The two transducers 602 are mounted on the frame 102 diametrically opposite each other and oriented to scan in planes that cut across the instrument trajectory 116. The planes are selected by manual or via motor- driven angulation of the transducers 602 away and toward the instrument trajectory 116. The advantage of this design includes a full volumetric scan of the entire region-of- interest.

[0036] In yet another embodiment, the system 100 may also include a system controller 710 that controls operation of system 100, with and/or without manual assistance or input from a human operator, as shown in FIG. 7. The system controller 710 generally includes a processor 712 configured to communicate with a multichannel transmitter 714 and a multi-channel receiver 716. Multi-channel transmitter 714 receives driving signals from processor 712 and, in turn, directs an ultrasound transducer 105 to generate ultrasound energy. Multi-channel receiver 716 receives acoustic signals during and/or after sonications and relays these signals to processor 712 for processing. In one embodiment of the present invention, ultrasound driving signals may be transmitted in a manner consistent with a longitudinal mode and/or a shear wave mode. Although for the sake of clarity FIG. 7 only shows one communication between multi-channel transmitter 714, multi-channel receiver 716 and a single transducer 105, it is implicit that additional communications are possible and/or necessary when the system 100 is configured to include multiple transducer 105 in the ultrasound transducer assembly 104.

[0037] Processor 712 may be designed to process acoustic signals and construct any number of images of, for example, a subject anatomy or a location of a medical instrument with respect to the subject anatomy in ID, 2D or 3D, as desired. By way of example, acoustic signals from a far surface of a skull or skull base may be used as a reference, allowing the production of an accurate and real-time dynamic visual image of a medical instrument tip location. Using geometric and time-of-flight analysis, the magnitude and direction of the medical instrument tip shifts may be determined.

[0038] Processor 712 may also be configured to communicate with a memory

720 for storing and retrieving data, and may be able to relay data via an output 718. Output 718 may be designed to take any desired shape or form, including a visualization system for displaying images of, for example, a subject anatomy or a medical device or instrument, or any other interventional devices, about or within the subject anatomy. In one aspect, a visualization system may receive a real-time feed of the encoded A-mode ultrasound signals, although other visualization schemes may be possible. For example, a likely strategy may involve a translucent rendering of "scan planes" showing the ventricle surfaces and a position of a medical device or instrument, such as a cannula or catheter.

[0039] System controller 710 may also include a position controller 722 which is in communication with processor 712. Position controller 722 may be configured to control the positioning and/or orientation of transducers 105 in the ultrasound transducer assembly 104 or a medical device or instrument, such as a cannula or catheter, by directing, for example, servos or motors (not shown in FIG. 1} during operation of system 100. Although for the sake of figure clarity FIG. 7 only shows one communication of the position controller 722 with a single transducer 105, it is implicit that additional communications are also possible between position controller 722 and other transducers 105, or any other device, configured with system 100 in accordance with the present invention.

[0040] During operation, system controller 710 may adjust the driving signals in response to the acoustic signals received by the multi-channel receiver 716. For example, the phase and/or amplitude of the driving signals may be adjusted so that ultrasound energy is more efficiently transmitted through, for example, a skull of subject and into the target volume-of-interest (VOI}. Furthermore, the acoustic signals may also be analyzed to determine whether and how the extent of a focal region should be adjusted. In one aspect, the actuation signal may include repeated pulses of high- voltage bursts with inter-burst periodicity tuned to match the fundamental operating frequency of the transducers (for example ±180 V, PRP=100-200 ms, Duty cycle = 0.0015-0.0030% based on/_c=l MHz}.

[0041] Backscattered ultrasound signals may be processed by processor 712 to isolate and accentuate signals arising from a VOI containing, for example, a ventricle to be catheterized. A standard method for producing ultrasound A-mode signals may be implemented (viz., time windowing, transducer PSF cross-correlation, time-gain compensation, nonlinear compression, rectification, demodulation, and noise rejection], including temporal and spectral filters appropriate to the operating conditions (i.e., with consideration of the ultrasound interaction characteristics of periosteal, skull, and intracranial tissues}. Position encoded A-mode data may be supplied to a visualization engine for further processing and display.

[0042] Turning now to FIG. 8A, an example of a pre-operative MRI image of a patient having illustrated thereon an example of a trajectory towards a ventricle is shown. The line corresponds to the approximate trajectory of an ultrasound signal, demonstrating the lateral interface of the right lateral ventricle to be at a distance of approximately 7.0 cm from the ultrasound transducer aperture. A representative A- mode ultrasound signal acquired along this line is shown in FIG. 8B, demonstrating a prominent peak (arrow] at the expected location of the lateral ventricle boundary.

[0043] In summary, external ventricular drains ("EVD"} are often placed to relieve intracranial pressure due to cerebrospinal fluid excess generally caused by subarachnoid hemorrhage or traumatic brain injury. Errors in placement are a chronic, albeit low level, concern in neurosurgical practice. While reported data are limited and inconsistent, the rate of catheter misplacement is high. In practice, most EVD catheters are inserted "free-hand" at the bedside, resulting in reported rates of initial catheter misplacement as high as 50%.

[0044] To reduce the resultant damage to brain tissue, four approaches have been evaluated in the past two decades: a] mechanical guides for the cannula, b] neurosurgical instrument tracking and anatomic registration systems, c] direct CT guidance, and d] ultrasound guidance using a probe inserted through an access hole in the skull to contact the dura. These have not been widely adopted due to: performance and flexibility challenges (a], cost and complexity (b,c], or need for an additional "burr hole" in the skull (d}. There is general agreement that existent technical approaches to improve EVD guidance are too complex and time intensive to justify their use.

[0045] Therefore, the present disclosure describes various embodiments of a system for use in interventional procedures. Specifically, the approach of the present disclosure aims to facilitate, for example, correct placement of medical instrumentation under a range of clinical conditions, offering superior accuracy without the deficiencies of prior techniques. For instance, capabilities afforded by the system, as described herein, can be used to assist a clinician in placing, say, a cannula in the correct position and orientation during an EVD procedure by way of ultrasound information generated using integral ultrasound transducers therein. [0046] Further advantages afforded by the present disclosure include enabling a clinician or other health care professional to be confident about the particulars of a subject's anatomy via characteristic ultrasound signals or signatures obtained using a system, as described, as well as the medical procedure in progress. For example, if say ventricles appear "normal" on ultrasound images obtained using a system, as described, a clinician may be inclined to continue performing the intervention undertaken. By contrast, if anatomical features are not found normal, a clinician may be informed and inclined to pursue other procedures or protocols, such as reviewing recent radiologic examinations to better localize a desired target, or proceed freehand, or use a "full- deck" needle guidance, for example, using the Brainlab system.

[0047] The present invention has been described in terms of one or more preferred embodiments, and it should be appreciated that many equivalents, alternatives, variations, and modifications, aside from those expressly stated, are possible and within the scope of the invention.

Claims

CLAIMS What is claimed is:

1. An ultrasound system for guiding a medical instrument relative to a subject's anatomy, comprising:

a support frame configured to be positioned on the subject's anatomy, the support frame defining an entry location for a medical instrument;

an instrument guide coupled to the support frame and having an annular portion coupled on one end to the entry location for the medical instrument and configured to receive the medical instrument such that the medical instrument can be guided to the entry location;

at least one ultrasound transducer movably coupled to the instrument guide and arranged such that the at least one ultrasound transducer is operable to transmit ultrasound energy to the subject's anatomy and receive echo signals therefrom; and a processor in communication with the at least one ultrasound transducer and configured to receive the echo signals and identify therefrom a trajectory that extends from the entry location to a desired region of the subject's anatomy.

2. The system of claim 1, further comprising at least one mechanical linkage movably coupling the at least one ultrasound transducer to the instrument guide.

3. The system of claim 2, further comprising an annular support slidably coupled to an outer surface of the instrument guide, wherein the at least one mechanical linkage is coupled on one end to the annular support and coupled on another end to the at least one ultrasound transducer.

4. The system of claim 1, wherein the at least one ultrasound transducer is configured to transmit ultrasound energy along a propagation axis in a different scanning plane.

5. The system of claim 4, wherein the support frame is configured such that the different scanning planes of at least two of the transducers are orthogonal.

6. The system of claim 4, wherein the at least one ultrasound transducer is coupled to the instrument guide such that the propagation axis of the at least one ultrasound transducer extends radially from the entry location.

7. The system of claim 1, wherein the support frame is configured to be detachably coupled to the subject's anatomy.

8. The system of claim 1 further comprising a controller in communication with the at least one ultrasound transducer, the controller configured to direct the at least one ultrasound transducer to transmit ultrasound energy through a bone.

9. The system of claim 8, wherein the controller is configured to direct the at least one ultrasound transducer to transmit the ultrasound energy through a skull bone.

10. The system of claim 1, wherein the at least one ultrasound transducer comprises at least one ultrasound transducer array that is capable of performing synchronized ultrasound beam steering.