WO2010042146A2 - Ultrasound brain scanning apparatus - Google Patents

Abstract

An ultrasound apparatus can be configured for remote (i.e., outside a typical modality) brain scanning of subjects. For example, in some embodiments according to the invention, emergency personnel in an ambulance or emergency room, can utilize the apparatus to provide brain scanning of a subject relatively soon after a debilitating event, such as a suspected stroke in the brain. In such embodiments, sometimes referred to herein as a "stroke helmet," multiple transducer arrays are connected to 3D ultrasound hardware/software, 3D ultrasound Doppler hardware/software, and a wireless communication device, all of which may be incorporated into the helmet. In some embodiments according to the invention, two of the transducers are positioned opposite respective temporal windows of the skull anterior and a third transducer is opposite the sub-occipital skull window. In some embodiments, the two skull anterior transducers are located on ear attachments of the helmet. More or fewer transducer arrays can be used.

Description

ULTRASOUND BRAIN SCANNING APPARATUS

CROSS REFERENCE TO RELATED APPLICATION The present Application claims priority to U.S. Provisional Patent Application Serial No.: 61/195,530, entitled Ultrasound Brain Scanning Apparatus filed in the U.S.P.T.O. on October 8, 2008, the entire contents of which are hereby incorporated herein by reference.

FIELD OF THE INVENTION The present invention relates to the field of ultrasound, and more specifically, to ultrasound scanning for the brain.

BACKGROUND

It will be understood that the ultrasound scanning described herein can be provided by methods, systems, and devices such as those described for example in U.S. Patent No. 4,694,434 to von Ramm et al. (Von Ramm) entitled Three Dimensional Imaging System and U.S. Patent No. 5,546,807 to Oxaal et al. (Oxaal) entitled High Speed volumetric Ultrasound Imaging System, the entire disclosures of which are incorporated herein by reference. Other references include the following:

Alexandrov, A. V., C. A. Molina, et al. (2004). "Ultrasound-enhanced systemic thrombolysis for acute ischemic stroke." New England Journal of

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Babikian, V. L. and L. R. Wechsler (1999). Transcranial Doppler ultrasonography. Boston, Buttenvorth-Heinemann.

Bogdahn, U., G. Becker, et al. (1998). Echoenhancers and transcranial color duplex sonography. Berlin; Boston, Blackwell Science. Fink, M. (1992). "Time-Reversal of Ultrasonic Fields.l. Basic Principles." IEEE

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Signals from Point Reflectors and Diffuse Scatterers - Basic Principles."

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35(6): 758-767. Fronheiser, M. P., E. D. Light, et al. (2006). "Real-time, 3-D ultrasound with multiple transducer arrays." IEEE Trans Ultrason Ferroelectr Freq

Control 53(1): 100-5. Gauss, R., Trahey, GE, Soo, MS (2001). Wavefront estimation in the human breast. Proc. SPIE, 172-181. Gorelick, P. B. and M. Alter (2002). The prevention of stroke. Boca Raton,

Parthenon Pub. Group. Hanley, D. and W. Hacke (2005). "Critical care and emergency medicine neurology in stroke." Stroke 36(2): 205-207. Hennerici, M., Ed. (2003). Imaging in Stroke. London, Remedica.

Holscher, T., W. G. Wilkening, et al. (2005). "Transcranial ultrasound angiography (tUSA): A new approach for contrast specific imaging of intracranial arteries." Ultrasound in Medicine and Biology 31(8): 1001-

1006. Hynynen, K. and J. Sun (1999). "Trans-skull ultrasound therapy: The feasibility of using image-derived skull thickness information to correct the phase distortion." Ieee Transactions on Ultrasonics Ferroelectrics and

Frequency Control 46(3): 752-755.

Ivancevich, N. M., J. J. Dahl, et al. (2006). "Phase Aberration Correction with a Real-Time 3D Ultrasound Scanner: Feasibility Study. " IEEE

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53(8): 1432-1439. Ivancevich, N. M., Pinton, G.F., Nicoletto, H.A. Bennett, E., Laskowitz, D.T., and

Smith, S.W. (2008). "Real-Time 3D Contrast-Enhanced Transcranial Ultrasound and Aberration Correction." Ultras. Med. Biol (in press).

Jensen, J. A. and N. B. Svendsen (1992). "Calculation of pressure fields from arbitrarily shaped, apodized, and excited ultrasound transducers." IEEE

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262-267. Lee, W., S. F. Idriss, et al. (2004). "A miniaturized catheter 2-D array for realtime, 3-D intracardiac echo cardiography." Ieee Transactions on

Ultrasonics Ferroelectrics and Frequency Control 51(10): 1334-1346. Light, E. D., R. E. Davidsen, et al. (1998). "Progress in two-dimensional arrays for real-time volumetric imaging." Ultrasonic Imaging 20(1): 1-15. Liu, D. L. and R. C. Waag (1994). "Time-Shift Compensation of Ultrasonic Pulse

Focus Degradation Using Least-Mean-Square Error-Estimates of Arrival

Time." Journal of the Acoustical Society of America 95(1): 542-555. Marler, J. R., T. Brott, et al. (1995). "Tissue-PIasminogen Activator for Acute

Ischemic Stroke." New England Journal of Medicine 333(24): 1581-1587. Miller-Jones, M. (1980). Automated arrival time correction for ultrasonic cephalic imaging, Duke University. Ph.D. Pua, E. C, S. F. Idriss, et al. (2007). "Real-time three-dimensional transesophageal echocardiography for guiding interventional electrophysiology: Feasibility study." Ultrasonic Imaging 29(3): 182-194. Smith SW, C. K., Idriss SF, Ivancevich NM, Light ED, Wolf PD (2004).

"Feasibility Study: Real time 3D ultrasound imaging of the brain." Ultras.

Med. Biol 30: 1365-1371. Smith, S. W., H. E. Pavy, et al. (1991). "High speed ultrasound volumetric imaging system part I: transducer design and beam steering." IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 38(2):

100-108. Smith, S. W., von Ramm, O.T., Kisslo, J.A. and Thurstone, F.L., (1978). "Real

Time Ultrasound Tomography of the Adult Brain." Stroke 9(2): 117-122. Stathaki, T. (2008). Image fusion: algorithms and applications. Academic Press. Vignon, F., J. F. Aubry, et al. (2006). "Adaptive focusing for transcranial ultrasound imaging using dual arrays." Journal of the Acoustical Society of America 120(5): 2737-2745. von Ramm, O. T., S. W. Smith, et al. (1991). "High speed ultrasound volumetric imaging system part II: Parallel processing and display." IEEE

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Methods and systems for volume rendering using ultrasound data #6,544,178,

2003.

SUMMARY

In some embodiments according to the invention an ultrasound apparatus can be configured for remote (i.e., outside a typical modality) brain scanning of subjects. For example, in some embodiments according to the invention, emergency personnel in an ambulance or emergency room, can utilize the apparatus to provide brain scanning of a subject relatively soon after a debilitating event, such as a suspected stroke in the brain. In such embodiments, sometimes referred to herein as a "stroke helmet," multiple transducer arrays are connected to 3D ultrasound hardware/software, 3D ultrasound Doppler hardware/software, and a wireless communication device, all of which may be incorporated into the helmet. In some embodiments according to the invention, two of the transducers are positioned opposite respective temporal windows of the skull anterior and a third transducer is opposite the sub-occipital skull window. In some embodiments, the two skull anterior transducers are located on ear attachments of the helmet. More or fewer transducer arrays can be used.

DETAILED DESCRIPTION OF EMBODIMENTS ACCORDING TO THE

INVENTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

As will be appreciated by those of skill in the art, the present invention may be embodied as methods and/or systems. Accordingly, the present invention may take the form of hardware embodiments, software embodiments or embodiments that combine software and hardware aspects. Moreover, the components of ultrasound systems according to the present invention, including those described herein, may be packaged as a single unit or packaged separately and interconnected to provide embodiments of methods and systems according to the present invention. The present invention is disclosed using block diagram illustrations. It will be understood that blocks of diagram illustrations, and combinations of blocks, can be implemented by computer program instructions. These program instructions may be provided to a processor circuit(s), such as a Digital Signal Processor (DSP) circuit, within an ultrasound system according to the present invention, such that the instructions which execute on the processor circuit(s) create means for implementing the functions specified in the block or blocks. The computer program instructions may be executed by the processor circuit(s) to cause a series of operational steps to be performed by the processor circuit(s) to produce a computer implemented process such that the instructions which execute on the processor circuit(s) provide steps for implementing the functions specified in the block or blocks.

Accordingly, the blocks support combinations of means for performing the specified functions, combinations of steps for performing the specified functions and program instructions for performing the specified functions. It will also be understood that each block, and combinations of blocks, can be implemented by special purpose hardware-based systems which perform the specified functions or steps, or combinations of special purpose hardware and computer instructions.

It will be understood that when an element is referred to as being "connected to," "coupled to" or "responsive to" (and/or variants thereof) another element, it can be directly connected, coupled or responsive to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected to," "directly coupled to" or "directly responsive to" (and/or variants thereof) another element, there are no intervening elements present. Like numbers refer to like elements throughout. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items and may be abbreviated as ¹V".

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising" (and/or variants thereof), when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. In contrast, the term "consisting of (and/or variants thereof) when used in this specification, specifies the stated number of features, integers, steps, operations, elements, and/or components, and precludes additional features, integers, steps, operations, elements, and/or components.

As used herein, the term "real time" is defined to include time intervals that may be perceived by a user as having little or substantially no delay associated therewith. For example, when a volume rendering using an acquired ultrasound dataset is described as being performed in real time, a time interval between acquiring the ultrasound dataset and displaying the volume rendering based thereon may be in a range of less than 1 second to reduce a time lag between an adjustment and a display that shows the adjustment. For example, some systems may typically operate with time intervals of about 0.10 seconds. Time intervals of more than one second may also be used.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present application, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It will be understood that the term "cushion" includes any arrangement where the patient's head can be placed thereon and made relatively secure for the purposes of diagnostic ultrasound imaging in the remote applications described herein. For example, the cushion may be any open platform that is suitable for placing the patient's head thereon while also allowing for access by the ultrasound transducers described herein. Some embodiments according to the invention provide an ultrasound apparatus configured for remote (i.e., outside a typical modality) brain scanning of subjects. For example, in some embodiments according to the invention, as illustrated for example in Figure 3, emergency personnel in an ambulance or emergency room, can utilize the apparatus to provide brain scanning of a subject relatively soon after a debilitating event, such as a suspected stroke in the brain. In such embodiments, sometimes referred to herein as a "stroke helmet," multiple transducer arrays are connected to 3D ultrasound hardware/software, 3D ultrasound Doppler hardware/software, and a wireless communication device, all of which may be incorporated into the helmet. In some embodiments according to the invention, two of the transducers are positioned opposite respective temporal windows of the skull anterior and a third transducer is opposite the sub-occipital skull window. In some embodiments, the two skull anterior transducers are located on ear attachments of the helmet. More or fewer transducer arrays can be used.

The transducers can be connected to the scanner hardware, which can be incorporated, for example, into the helmet wall. The scanner may produce multiple real time 3D scans from the transducers. The 3D scans can then be wirelessly transmitted to a physician, who may then use the 3D ultrasound scans to diagnose the subject, such as in cases where an acute ischemic stroke is suspected. In some embodiments, the controls of the scanner can be manipulated remotely including selection of scan angle and Doppler beam direction, as described in Oxaal. After diagnosis the Doppler beam can be steered onto an occluded vessel to promote thrombolysis and recanalization of the vessel. Multiple intersecting hyperthermia beams and HIFU beams can also originate from the three transducers through the skull acoustic windows. In some embodiments, as illustrated for example in Figure 8, an apparatus can include a cushion including multiple matrix array transducers connected to the hardware of a 3D ultrasound scanner and 3D ultrasound Doppler hardware and a wireless communication device all of which may be incorporated into the cushion. The transducers can include a first matrix array transducer which is on the cushion, but protrudes from a surface of the cushion (which may be, in appearance, similar to an upholstery button). The angle of the cushion and the angle of the first matrix array transducer is configured to be adjustable to allow accesses to the sub-occipital acoustic window at the base of the patient's skull. Second and third matrix transducer can be on strap and may also protrude from the strap like a button. The strap (which may be adjustable) cooperates with the cushion and is configured to be placed at least partially around the head of the patient and positioned so that the second and third transducers are located opposite the temporal windows of the skull near to the ear. In some embodiments, the strap can include a flexible circuit board. The transducers are connected to the scanner hardware which is incorporated into the cushion. By incorporating the scanner into the cushion the need for long, heavy expensive transducer cables and connectors may be reduced. The short cables may also increase the ultrasound signal to noise ratio. In some embodiments the transducers may by affixed to the scalp through a disposable adhesive patch as is used for ECG lead attachments.

In some embodiments, the scanner does not include a monitor for viewing images. The scanner can produce multiple real time 3D scans from the 3 transducers. The 3D scans are wirelessly communicated (for example via cell phone or wireless internet technology) to the physician who can use the 3D ultrasound scans to diagnose the patient, such as in cases where acute ischemic stroke is suspected. The controls of the scanner can be manipulated remotely including selection of scan angle and Doppler beam direction. After diagnosis the Doppler beam can be steered onto an occluded vessel to promote thrombolysis and recanalization of the vessel. Multiple intersecting hyperthermia beams and HIFU beams can also originate from the three transducers through the skull acoustic windows. Skull correction algorithms can be used to correct the phase aberrations of the skull to narrow the ultrasound beams and improve beam aiming accuracy.

In other embodiments, the cushion can be an inflatable cushion with multiple pockets. In other embodiments, the hardware is integrated into a bed or patient gurney or stretcher.

In some embodiments, as illustrated for example in Figure 9, the cushion can include a recess therein into which the patient's head may be, at least partially, inserted. A first transducer can protrude from a surface of the recess and be positioned to allow accesses to the sub-occipital acoustic window at the base of the patient's skull. Second and third matrix transducer can be on a strap and may also protrude from the strap like a button. The strap (which may be adjustable) cooperates with the cushion and is configured to be placed at least partially around the head of the patient and positioned so that the second and third transducers are located opposite the temporal windows of the skull near to the ear. In some embodiments, the strap can include a flexible circuit board. The transducers are connected to the scanner hardware which can be incorporated into the cushion.

In some embodiments, the strap described above may be replaced by a more rigid member which can be hinged at one side of the recess and configured to open/close to allow the patient's head to be inserted/removed from the recess. In other embodiments, a movable visor type structure may cooperate with the cushion and recess. For example, the visor may be hinged at sides of the recess and be configured to extend over the top of the patient's head and at least partially cover the head when in a "closed" position. Further, the second and third transducers can be included on the interior side surfaces of the visor and be configured to align opposite the temporal windows of the skull near to the ear in the closed position. In the "open" position, the visor would allow the patient's head to be inserted and removed.

In some embodiments, the second and third transducers are mounted on opposing interior walls of the recess so that when the patient's head is inserted, the second and third transducers are aligned opposite the temporal windows of the skull anterior to the ear.

It will be understood that other systems can be combined with the embodiments described herein to provide complete imaging systems. For example, the cushion can be integrated with EEG, MRI, MEG, and/or CT, systems. What follows are examples of measurements/studies regarding operations an ultrasound brain helmet to produce multiple simultaneous real-time three-dimensional (3D) scans of the cerebral vasculature from temporal and suboccipital acoustic windows of the skull. These examples are only for the purpose of illustration and are not intended to limit embodiments according to the invention. The transducer hardware and software of the Volumetrics Medical Imaging (Durham, NC, USA) real-time 3D scanner were modified to support dual 2.5 MHz matrix arrays of 256 transmit elements and 128 receive elements which produce two simultaneous 64° pyramidal scans. The real-time display format consists of two coronal B-mode images merged into a 128° sector, two simultaneous parasagittal images merged into a 128° x 64°C-mode plane and a simultaneous 64° axial image. Real-time 3D color Doppler scans from a skull phantom with latex blood vessel were obtained after contrast agent injection as a proof of concept. The long-term goal is to produce real-time 3D ultrasound images of the cerebral vasculature from a portable unit capable of internet transmission thus enabling interactive 3D imaging, remote diagnosis and earlier therapeutic intervention.

As shown in Fig. IA, the 3D ultrasound system scans a full 64° pyramid using a matrix (checkerboard) array transducer at up to 30 volumes per s. Figure IA shows a schematic of the matrix phased array transducer producing a pyramidal scan and displaying two simultaneous orthogonal B-mode images, corresponding to axial and coronal image planes, as well as two C-mode planes, corresponding to parasagittal image planes. Real-time display options in our 3D scanner also include 3D volume rendering, 3D color flow imaging and a steerable 3D ultrasound beam (red) to be used for spectral Doppler measurements of cerebral blood flow or therapeutic applications such as ultrasound enhanced thrombolysis (Alexandrov et al. 2004). Figure IB is a photograph of the VMI matrix array probe which is used for real-time 3D scanning in both cardiac as well as transcranial applications.

Fig. 2 A shows an illustrative axial image of the Circle of Willis (CW), the ipsilateral middle cerebral artery (MCA) and contralateral skull from a normal subject. By manipulating the thickness and orientation of the simultaneous coronal slice from the real-time 3D scan, as shown, in Fig. 2B, a coronal view of that same MCA demonstrating patency as the vessel makes its tortuous path toward the outer surface of the brain. Figure 2C shows the off-line 3D-rendered view of the contralateral skull and cerebral vasculature from the same subject, a 3D ultrasound angiogram. This view can be tilted and rotated to examine the vasculature from any perspective. In like manner, for another subject scanned from the suboccipital window, Fig. 2D shows the color Doppler 3D rendering of the vertebral arteries (VA) joining to form the basilar artery (BA).

Figure 3 is a diagram that illustrates some embodiments of a brain helmet including three matrix array transducers (T1-T3) mounted in a helmet to produce three simultaneous 3D ultrasound scans of the brain through the temporal and suboccipital windows of the skull. In the first experiment of our feasibility study, a brain scan of a human subject, who had given informed consent per the IRB approved protocol (Ivancevich 2008), was generated, using two simultaneous Volumetrics 3D scanners running asynchronously. The video output of the two displays was fed into a video screen splitter (Microimage, Boyeitown, PA, USA) so that the image planes from two simultaneous 3D scans could be viewed on a single television monitor. As shown in Fig. 4A through D, the combination of a temporal scan and a suboccipital scan yielded useful 3D images in operation. After a Definity contrast injection, a matrix transducer probe on the temporal acoustic window produced color Doppler data from the cerebral vessels of the Circle of Willis in axial (Fig. 4A) and coronal (Fig. 4B) image planes. Simultaneously, a second matrix array on the suboccipital window produced the coronal and parasagittal image planes of Fig. 4C and Fig. 4D, yielding views of a vertebral artery (VA) and the atlas loop (AtL) in Fig. 4C and of the foramen magnum (FM) in Fig. 4D. In Fig. 4A through D, the green horizontal lines indicate the positions of the simultaneous C-mode planes which were not shown on the split screen video display.

The 3D scanner was modified for synchronous operation of multiple matrix arrays. In this project, we relied on our previous experience developing multiple 3D intra-cardiac echo (3D-ICE) catheters wherein we had modified the 3D scanner to switch between two 3 D-ICE catheters in one second at the push of a button (Fronheiser et al. 2006). In normal operation, the scanner includes 512 transmitters and 256 receive channels with 16: 1 receive-mode parallel processing to generate 4096 B-mode image lines in the pyramidal scan. Matrix array designs for multiple simultaneous transducers were simulated for a steering angle of (0°, 0°) using the Field II ultrasound simulation software (Jensen and Svendsen 1992) yielding the axisymmetric beam plots shown in Fig. 5. For each design, as a measure of image quality, the relative peak pressure (a surrogate of image sensitivity), the 6 dB beam width (equivalent to transducer lateral resolution) and the grating lobe amplitude (a surrogate of image clutter), were calculated.

As a demonstration of image quality, for each design, we also show the experimental C-scan images of a 12 mm cyst phantom (contrast =- _40 dB). In its original configuration, as described by Light et al. (1998), the 2.5 MHz Volumetrics matrix array (lamda H2O = _ 0.6 mm) was configured in a sparse periodic vernier pattern shown in Fig. 5 A with 256 transmit (Tx) elements (spacing = 0.35 mm) and 256 receive (Rx) ele-ments (spacing _ =0.7 mm). The simulations yielded a pulse- echo sensitivity, which we assign to 0 dB, _-6 dB beamwidth _ =3.9 mm at a depth of 70 mm, and a grating lobe amplitude -45 dB resulting in the associated C-scan image. In a later design, shown in Fig. 5B, every available element in the array was used in transmit mode resulting in 440 transmit elements and 256 receive elements yielding a sensitivity improvement of _-4.7 dB relative to that of Fig. 5 A, -6 dB beamwidth _ =3.4 mm at a depth of 70 mm, but an increased grating lobe amplitude of -24 dB, resulting in the associated C-scan image of the cyst. This design was used in the transcranial human study of Ivancevich et al. (2008).

For a brain helmet configuration of two simultaneous 3D transducers, the image quality trade-offs of a number of matrix array designs were analyzed including the use of multiplexer circuits to switch between transducers. In one embodiment, , based on criteria of cost, simplicity and sensitivity, we allocated 256 transmitters and 128 receivers to each matrix array in the pattern shown in Fig. 5C yielding a relative sensitivity of _-6 dB, _-6 dB beamwidth _ =5.5 mm at a depth of 70 mm, a grating lobe amplitude of _-60 dB and associated C-scan image of the cyst. A comparison of the C-scans shows the enlarged speckle size associated with increased beam width but good cyst contrast for the brain helmet design. Having chosen the transducer design, we fabricated a new transducer coupling system wherein the circuitry of 512 transmitters and 256 receivers, which normally are connected to two ITT Cannon connectors (Model DLM6-360), were rewired into four of these connectors for the two matrix arrays. To complete our hardware developments, we adapted a Transcranial Doppler Fixation System (Spencer Technologies, Seattle, WA, USA), which is conventionally used for one-dimensional (ID) spectral Doppler, to mount our two simultaneous matrix array probes. We then constructed a skull phantom by using a polymer casting of a human skull (3B Scientific, Hamburg, Germany) filled with degassed water. The skull adequately mimics the compact bone of the temporal window. We fixed a plastic mesh in the sagittal plane to mimic the midline falx structure and we suspended a latex tube (3 mm inner diameter) into a Ushaped loop lying in the coronal plane within the skull. The completed skull phantom with the transcranial transducer fixation system, latex vessel and the two matrix arrays are shown in the photograph of Fig. 6. We next modified the scanner software to produce dual pyramidal scans. In normal operation, a 64° pyramidal scan includes 64 x 64=_ 4096 image lines. Previously, we have developed 90° and 120° pyramidal scans for our 3D intra-cardiac catheters (Lee et al. 2004) and 3D endoscopes (Pua et al. 2007). In this case, we developed a 64x 64 =_ 4096 line pyramidal scan of 64° x 128°. Under software control, we can enable or disable individual array elements on each image line, so we split this pyramidal scan between the two matrix arrays by enabling only the elements of array no.l during the first 2048 image lines and enabling only the elements of array no. 2 during the second 2048 image lines. Thus we created two independent pyramidal scans each of roughly 64°. Note that the scan line spacing was doubled in the elevation direction. All other features of the 3D scanner, including Doppler capabilities, were unchanged. As of yet, we have not customized the display features of the 3D scanner for the brain helmet so that the simultaneous display planes now included: (1) a 128° elevation (coronal plane) sector scan which consisted of adjacent 64° elevation planes from the dual transducers; (2) C-scan planes of adjustable orientation and depth, which consisted of adjacent parasagittal planes from the dual transducers; and (3) a 64° azimuth sector scan selected from one of the dual transducers.

Figure 7 shows the results of a real-time 3D scan with color Doppler of the skull phantom with dual simultaneous matrix array transducers positioned on the temporal acoustic windows after a contrast agent injection of agitated tap water into the loop of the latex tube. Figure 7A shows the blood vessel loop simultaneously imaged in the elevation coronal) plane from both sides of the skull so that the flow, which is away from the left transducer, is shown in blue and the flow, which is toward the right transducer, is shown in red. Due to the widening U-shape of the loop, flow does not reverse directions within the field of view. Each image includes the contralateral skull. Note also that the left transducer shows reduced signal-to-noise ratio compared with the right transducer due to RF interference in the coupler for the left transducer. Figure 7B shows the simultaneous tilted C-scan (parasagittal) plane cutting across the vessel loop in both scans to produce short axis images of flow in the vessel from the left transducer (blue) and the right transducer (red). The dotted yellow line in Fig. 7 A shows the plane of that tilted C-scan. Note that the tilted C-scan cuts the vessel loop twice for the right transducer (red). Figure 7C shows the simultaneous axial slice through the vessel loop for the left transducer. This slice orientation is determined by the white cursor arrow in Fig. 7A. Finally, after a quick track ball adjustment of that cursor, the display of Fig. 7D appears, showing the axial slice through the vessel loop from the right transducer (red). This slice orientation is determined by the yellow arrow in Fig. 7A.

In some embodiments, dual simultaneous in vivo 3D scans from both temporal windows may provide additional diagnostic information compared with the single temporal 3D scan of Fig. 2. In particular, the contralateral MCA may not be visible from the temporal scan of Fig 2 A through C. This problem may be addressed by the dual simultaneous temporal 3D scans, since each MCA would be scanned from the ipsilateral side in one of the two scans. It will be understood that, in a real-time 3D scan, precise positioning and aiming of the matrix array may not be as important as in conventional ID and 2D transcranial Doppler, since an entire volume of the brain will be scanned and stored. Thus, the display planes may be selected interactively at any desired orientation either in real time or in playback mode by the members of a remote stroke team. Accordingly, issues related to positioning over the acoustic windows of the skull by medical personnel of limited training such as in an ambulance environment may be addressed by embodiments described herein.

In some embodiments, sufficient quality of the 3D ultrasound brain scans may be provided to reliably differentiate normal cerebral vasculature from that of an ischemic or hemorrhagic stroke, utilizing, for example, recent progress in phase aberration correction of the skull bone (Ivancevich 2008) and other approaches (Fink 1992; Hynynen and Sun 1999). In some embodiments where transducers are positioned over the temporal windows, each transducer can act as a phase correction beacon for the opposing transducer. The use of an external transducer as a phase correction beacon is discussed, for example, in Miller- Jones (1980) and Vignon et al. (2006). Also encouraging is the recent development of improved transcranial phase inversion harmonic imaging to reduce the blooming artifact of contrast agents (Holscher et al. 2005).

In some embodiments, as illustrated, for example, in Figure 3, the real-time 3D scanner is substantially miniaturized for use in a helmet apparatus. In some embodiments, an appropriately sized ultrasound system may be provided by technology such as the Siemens P-10, which is a 2D phased array scanner approximately the size of a personal digital assistant (PDA), or the GE Voluson i, which is a real-time mechanical 3D fetal scanner the size of a laptop computer. In some embodiments, the thickness of the matrix arrays provides a low profile to fit within a helmet configuration. In some embodiments, arrays for 3D catheter and endoscope applications may be used to provide arrays on multilayer flexible circuits of polyimide measuring about two millimeters in total thickness (Lee et al. 2004). In some embodiments, as illustrated for example in Figure 3, wireless hardware/software can provide for wireless transmission of images via, for example, cell phone or internet using webcam technology from the scanner (located for example at a remote hospital, from an ambulance, and/or the patient's home or location of the event) to a neurologic team at a stroke center. The stroke team would select the imaging planes within a volume of data, thus enabling interactive 3D imaging, remote diagnosis and earlier therapeutic intervention. In some embodiments the 3D scanner can transmit streaming video output of the display over the internet using a video capture card (such as a ViewCast Osprey 100, Piano, TX, USA) with sufficient image quality. In some embodiments, an ambulance-based ECG telemedicine system may be used as the basis for the apparatus described herein.

In some embodiments, simultaneous axial and coronal slices from both transducers can be displayed in real time in standard orientations rather than as shown in Fig. 6 A through C. Additionally, in some embodiments, 3D rendering color Doppler scans can be displayed in real time. In some embodiments according to the invention, 3D scans from multiple transducers can be combined (sometimes referred to as "fused") to provide a single 3D image for examination by the neurosonologist (Stathaki 2008). In some embodiments, as shown for example by the double arrow in Fig. 2C and D, 3D ultrasound image fusion can be provided by connecting the posterior cerebral artery of Fig. 2C obtained from the temporal skull window with the basilar artery of Fig. 2D obtained from the suboccipital window.

In the specification, there have been disclosed embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation. The following claims are provided to ensure that the present application meets all statutory requirements as a priority application in all jurisdictions and shall not be construed as setting forth the entire scope of the present invention.

Claims

WHAT IS CLAIMED: 1. An apparatus comprising: a cushion configured to receive a patient's head; a first ultrasound transducer configured on the cushion to be opposite the sub- occipital skull window of the patient's skull when located on the cushion; and second and third ultrasound transducers coupled to cushion and configured to be positioned opposite respective temporal windows of the patient's skull anterior when located on the cushion.

2. An apparatus according to Claim 1 further comprising: an adjustable strap coupled to the cushion, wherein the second and third ultrasound transducers are on an interior surface of the strap and configured to face the temporal windows of the patient's skull anterior.

3. An apparatus according to Claim 1 wherein the cushion includes a recess therein configured to receive the patient's skull and wherein the first ultrasound transducer is positioned in the recess to be opposite the sub-occipital skull window of the patient's skull when inserted therein.

4. An apparatus according to Claim 1 further comprising: a movable visor coupled to the cushion, wherein the second and third ultrasound transducers are on an interior surface of the moveable visor and configured to face the temporal windows of the patient's skull anterior when the moveable visor is lowered over the patient's skull.

5. An apparatus according to Claim 1 wherein the cushion comprises an inflatable cushion.

6. An ultrasound system comprising: a helmet having an interior surface configured to receive a patient's skull and at least partially enclosing the patient's skull when inserted; a first ultrasound transducer on the interior surface configured to be opposite the sub-occipital skull window of the patient's skull when inserted; second and third ultrasound transducers on the interior surface and configured to be positioned opposite respective temporal windows of the patient's skull anterior when inserted; and a real-time 3D ultrasound scanner in the helmet and coupled to the transducers, wherein the real-time 3D ultrasound scanner is configured to provide real-time 3D image data of the patient's brain.

7. An ultrasound system according to Claim 6 further comprising: a wireless communications interface, coupled to the real-time 3D ultrasound scanner, and configured to transmit real-time 3D image data of the patient's brain to a remote location and configured to receive commands for the real-time 3D ultrasound scanner from the remote location.

8. An ultrasound system according to Claim 6 wherein the helmet further comprises: a first ultrasound transducer on an interior surface of the helmet and configured to be opposite the sub-occipital skull window of the patient's skull when inserted in the helmet; and second and third ultrasound transducers on the interior surface of the helmet and configured to be positioned opposite respective temporal windows of the patient's skull anterior when inserted therein.

9. An ultrasound system according to Claim 8 further comprising: a movable visor coupled to the helmet, wherein the second and third ultrasound transducers are on an interior surface of the moveable visor and configured to face the temporal windows of the patient's skull anterior when the moveable visor is lowered over the patient's skull.