Method and system for guiding acquisition of cranial ultrasound data

Abstract

The invention provides a method for guiding acquisition of ultrasound data within a 3D field of view. The method starts with obtaining initial 2D B-mode ultrasound data of a cranial region of a subject from a reduced field of view at a first imaging position and determining whether a vessel of interest is located within the 3D field of view based on the initial 2D B-mode ultrasound data. If the vessel of interest is not located within the 3D field of view, generating guidance instructions based on the initial 2D B-mode ultrasound data, wherein the guidance instructions are adapted to instruct a second imaging position to obtain further ultrasound data. If the vessel of interest is located within the 3D field of view, obtaining 3D Doppler ultrasound data of the cranial region from the 3D field of view.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of ultrasound imaging, and more particularly to the field of cranial ultrasound imaging. BACKGROUND

[0002] Cerebrovascular hemodynamic measurements are used to diagnose and monitor a number of conditions in both adult and pediatric populations. Radiopaque CT tracer and MRI contrast techniques generally provide poor temporal resolution insufficient to assess hemodynamics, require extensive instrumentation and setup, and are expensive.

[0003] Transcranial Doppler (TCD) ultrasound technology can be used to monitor blood flow dynamics at the point of care in a non-invasive manner and at relatively low cost with excellent temporal resolution. TCD is capable of detecting and monitoring intracranial aneurysms, patent foramen ovale, vasospasm, stenosis, brain death, shunts, and microemboli in a non-radiative manner in both surgical and ambulance settings. Additionally, accurate TCD measurements enable non-invasive measurement of intracranial pressure (nICP), a key indicator of cerebrovascular status due to stroke, tumor growth, or due to head trauma. Other ICP monitoring methods are generally highly invasive, requiring surgical penetration of the skull to place parenchymal or ventricular sensors, and are therefore limited to severe cases where monitoring and / or cerebrospinal fluid (CSF) drainage is required. It has been suggested that management of TBI within the first few minutes of the point of injury greatly impacts patient prognosis, which is summarized in evidence-based pre-hospital and in-hospital TBI treatment guidelines such as those outlined in N. Badjatia et al., "Guidelines for Prehospital Management of Traumatic Brain Injury 2nd Edition," Prehosp. Emerg. Care, vol. 12, no. sup 1, pp. S1-S52, Jan. 2008.

[0004] Currently, consistent TCD measurements are difficult to obtain due to skull attenuation and aberration and the variability and tortuosity of the perforating cerebral vessels. As a result, TCD must be performed by users with a considerable level of professional training using single element transducers, as described in A.V. Alexandrov et al., "Practice Standards for Transcranial Doppler (TCD) Ultrasound. Part II. Clinical Indications and Expected Outcomes," J. Neuroimaging, vol. 22, no. 3, pp. 215-224, July 2012. This requirement for experienced operators significantly limits the scope of TCD as a clinical tool. In addition, experienced operators exhibit considerable inter-operator variability in their measurements.

[0005] If novice ultrasound users could operate the device in a consistent manner, TCD could be routinely performed in environments such as emergency rooms, rural medical centers, battlefields, and ambulances for continuous monitoring of a variety of conditions involving cerebral vessels, patient triage, and evidence-based treatment applications.

[0006] Accordingly, there is a need for a means of guiding the acquisition of cranial ultrasound data. SUMMARY

[0007] The invention is defined by the claims.

[0008] According to examples in accordance with an aspect of the invention, there is provided a computer implemented method for guiding the acquisition of ultrasound data within a 3D field of view, the method comprising:

[0009] obtaining initial 2D B-mode ultrasound data from a cranial region of a subject at a reduced field of view at a first imaging location;

[0010] determining whether a vessel of interest is located within the 3D field of view based on the initial 2D B-mode ultrasound data from the first imaging location; and

[0011] if the vessel of interest is not located within the 3D field of view:

[0012] generating guidance instructions based on the initial 2D B-mode ultrasound data, wherein the guidance instructions are adapted to instruct a second imaging location to obtain further ultrasound data; and

[0013] if the vessel of interest is located within the 3D field of view:

[0014] obtaining 3D Doppler ultrasound data from the cranial region of the 3D field of view.

[0015] This method provides guided acquisition of 3D color Doppler ultrasound data of vessels of interest in the cranial region.

[0016] By using 2D B-mode ultrasound data with a limited field of view to locate vessels of interest, the frame rate of ultrasound data can be greatly increased, thereby improving the accuracy of vessel localization.

[0017] In this embodiment, determining whether the blood vessel of interest is located within the 3D field of view includes:

[0018] Based on the initial 2D B-mode ultrasound data, anatomical features, such as bone structures, within the reduced field of view are identified; and

[0019] The probability that the blood vessel is located within the 3D field of view is determined based on the identified anatomical features.

[0020] The locations of typical vessels of interest in the cranial region are very close to other distinct anatomical features, such as bone structures. Therefore, by identifying such structures within ultrasound data, the location of the vessel of interest can be determined within a given probability. The probability that a vessel is located within the 3D field of view can be expressed in one of two ways: either confirming the presence of the vessel; or informing the user of its absence using additional instructions regarding a second imaging location, where such additional instructions can be based on comparative analysis of images from different modalities.

[0021] In another embodiment, determining the likelihood that the blood vessel is located within the 3D field of view based on the identified anatomical features includes obtaining 2D color Doppler ultrasound data from a reduced field of view at a first imaging location.

[0022] In this way, rapid Doppler images can be provided to confirm whether the vessel of interest is indeed within the probe's field of view. Structural information obtained from 2D B-mode image data can be used to acquire 2D color Doppler ultrasound from a reduced field of view to verify whether flow exists where it is expected.

[0023] In one embodiment, determining the likelihood of whether a vessel of interest is located within the 3D field of view includes applying a convolutional neural network to the initial 2D B-mode ultrasound data.

[0024] In another embodiment, the convolutional neural network is trained using 2D duplex color Doppler data.

[0025] Duplex color Doppler data comprises 2D Doppler images superimposed on B-mode images. Therefore, the location of blood vessels (as shown in the Doppler images) can be indicated in relation to structural features (as shown in the B-mode data). By training a network using these images, the network can infer the presence of blood vessels of interest based solely on the B-mode data.

[0026] In an embodiment, the ultrasound data is obtained using an ultrasound probe, and the method further includes:

[0027] Determine the orientation of the ultrasound probe at the first imaging position; and

[0028] Based on the orientation of the ultrasound probe and the initial 2D B-mode ultrasound data, probe manipulation instructions are generated, wherein the probe manipulation instructions are adapted to indicate how the ultrasound probe should be adjusted to reach the second imaging position.

[0029] In this way, instructions can be given to the user or automated system on how to manipulate the probe to achieve the optimal view of the blood vessel of interest.

[0030] In another embodiment, determining the orientation of the ultrasound probe includes:

[0031] Obtain tracking data related to the orientation of the probe; and

[0032] The second convolutional neural network is applied to the tracking data.

[0033] Neural networks can be trained to recognize the difference between the current orientation and the previous correct orientation and generate guidance accordingly.

[0034] In an embodiment, if the blood vessel of interest is located within the 3D field of view, the method further includes:

[0035] Measure the bone structure within the 3D field of view;

[0036] Generate a kernel for spatial filtering of the bone structure; and

[0037] The kernel is applied to the 3D Doppler ultrasound data.

[0038] In this way, interference from structures other than the structure of interest within the field of view can be reduced or removed.

[0039] In an embodiment, the method further includes:

[0040] Periodically acquire additional 2D B-mode ultrasound data;

[0041] The additional 2D B-mode ultrasound data is compared with the initial 2D B-mode ultrasound data; and

[0042] The movement of the blood vessel of interest is determined based on the comparison.

[0043] In this way, the movement of blood vessels of interest over time can be monitored and corrected (e.g., due to object movement).

[0044] In another embodiment, the ultrasound data is obtained using an ultrasound probe, and the method further includes determining the movement of the ultrasound probe based on the comparison.

[0045] In this way, the movement of the probe of interest over time can be monitored and corrected (e.g., due to user movement).

[0046] According to an example of one aspect of the invention, a medical system suitable for guiding the acquisition of ultrasound data within a 3D field of view is provided, the system comprising:

[0047] Processor, wherein the processor is adapted to:

[0048] Initial 2dB mode ultrasound data of the cranial region of the object from a narrowed field of view at the first imaging position are obtained;

[0049] Based on the initial 2D B-mode ultrasound data from the first imaging location, it is determined whether the vessel of interest is located within the 3D field of view; and

[0050] If the vessel of interest is not located within the 3D field of view, then:

[0051] A guiding instruction is generated based on the initial 2D B-mode ultrasound data, wherein the guiding instruction is adapted to instruct a second imaging position to obtain additional ultrasound data; and

[0052] If the vessel of interest is located within the 3D field of view, then:

[0053] 3D Doppler ultrasound data of the cranial region from the 3D field of view are obtained.

[0054] In one embodiment, the system further includes an ultrasound probe in communication with the processor, wherein the ultrasound transducer is adapted to acquire 2D ultrasound data and 3D ultrasound data, and wherein the processor is adapted to: activate the ultrasound probe in a 2D B-mode ultrasound acquisition mode with a limited field of view; and switch the ultrasound probe to a 3D color Doppler ultrasound acquisition mode with a full field of view if the vessel of interest is located within a full 3D field of view.

[0055] In another embodiment, the system further includes a probe tracker adapted to generate tracking data relating to the orientation of the ultrasound probe, wherein the processor is further adapted to determine the orientation of the probe based on the tracking data.

[0056] In another embodiment, the probe tracker includes one or more of the following:

[0057] Optical trackers; and

[0058] Motion tracker.

[0059] In one embodiment, the system further includes a probe holder adapted to receive the ultrasound probe and hold the ultrasound probe in a given imaging position, wherein the probe holder is adapted to selectively lock the ultrasound probe in the given imaging position.

[0060] These and other aspects of the invention will be apparent and illustrated with reference to one or more embodiments described below. Attached Figure Description

[0061] To better understand the invention and to more clearly illustrate how it can be practiced, reference will now be made to the accompanying drawings by way of example only, in which:

[0062] Figure 1 An ultrasound diagnostic imaging system is shown to explain general operation;

[0063] Figure 2 The method of the present invention is shown;

[0064] Figure 3A and Figure 3B An example of the spatial relationship between blood vessels and structures of interest within the skull of an object is shown. Detailed Implementation

[0065] The invention will be described with reference to the accompanying drawings.

[0066] It should be understood that while the detailed description and specific examples indicate exemplary embodiments of the apparatus, system, and method, they are for illustrative purposes only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, system, and method of the invention will be better understood from the following description, claims, and drawings. It should be understood that these drawings are merely schematic and not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to indicate the same or similar parts.

[0067] This invention provides a method for guiding the acquisition of ultrasound data within a 3D field of view. The method begins by acquiring initial 2dB mode ultrasound data of a cranial region of an object from a first imaging position (within a reduced field of view compared to the 3D field of view), and determining whether a vessel of interest is located within the 3D field of view based on the initial 2dB mode ultrasound data acquired within the reduced field of view. If the vessel of interest is not located within the 3D field of view, a guidance instruction is generated based on the initial 2dB mode ultrasound data, wherein the guidance instruction is adapted to instruct a second imaging position to acquire additional ultrasound data. If the vessel of interest is located within the 3D field of view, 3D Doppler ultrasound data of the cranial region from the 3D field of view is acquired.

[0068] First refer to Figure 1 The present invention describes the general operation of an exemplary ultrasound system, and focuses on the system’s signal processing capabilities, as the present invention relates to the processing of signals measured by a transducer array.

[0069] The system includes an array transducer probe 4 with a transducer array 6 for emitting ultrasonic waves and receiving echo information. The transducer array 6 may include: a CMUT transducer; a piezoelectric transducer formed of a material such as PZT or PVDF; or any other suitable transducer technology. In this example, the transducer array 6 is a two-dimensional array of transducers 8 capable of scanning a two-dimensional plane or a three-dimensional volume of a region of interest. In another example, the transducer array may be a one-dimensional array.

[0070] The transducer array 6 is coupled to a microwave beamformer 12, which controls the signal reception performed by the transducer elements. The microwave beamformer is capable of performing at least partial beamforming on the signals received by the subarrays of transducers (often referred to as “groups” or “patchworks”), as described in U.S. Patents US 5,997,479 (Savord et al.), US 6,013,032 (Savord), and US 6,623,432 (Powers et al.).

[0071] It should be noted that the microwave beamformer is entirely optional. Additionally, the system includes a transmit / receive (T / R) switch 16, which is coupled to the microwave beamformer 12 and switches the array between transmit and receive modes, and protects the main beamformer 20 from high-energy transmitted signals when the microwave beamformer is not used and the main system beamformer directly operates the transducer array. The transmission of the ultrasonic beam from the transducer array 6 is guided by a transducer controller 18, which is coupled to the microwave beamformer via the T / R switch 16 and to the main transmit beamformer (not shown), which can receive input from user operation via a user interface or control panel 38. The controller 18 may include transmit circuitry arranged to drive the transducer elements of the array 6 during transmit mode (directly or via the microwave beamformer).

[0072] In a typical line-by-line imaging sequence, the beamforming system within the probe can operate as follows. During transmission, a beamformer (which may be a microwave beamformer or a main system beamformer, depending on the implementation) activates the transducer array or sub-apertures of the transducer array. The sub-apertures can be one-dimensional transducer rows or two-dimensional transducer patches within a larger array. In transmission mode, the focusing and steering of the ultrasonic beam generated by the array or its sub-apertures are controlled as described below.

[0073] Upon receiving the backscattered echo signal from the object, the received signal is subjected to receive beamforming (as described below) to align the received signal, and, in the case of a sub-aperture, the sub-aperture is then shifted, for example, through a transducer element. The shifted sub-aperture is then activated and the process is repeated until all transducer elements of the transducer array are activated.

[0074] For each row (or each sub-aperture), the total received signal for the associated row used to form the final ultrasound image will be the sum of the voltage signals measured by the transducer elements of the given sub-aperture during the reception period. Following the beamforming process below, the resulting row signals are typically referred to as radio frequency (RF) data. Each row signal (RF dataset) generated from the individual sub-apertures then undergoes additional processing to generate the row of the final ultrasound image. The amplitude variation of the row signal over time will contribute to the brightness variation of the ultrasound image with depth, where high amplitude peaks will correspond to bright pixels (or sets of pixels) in the final image. Peaks appearing near the beginning of the row signal will represent echoes from shallow structures, while peaks appearing gradually later in the row signal will represent echoes from structures of increasing depth within the object.

[0075] One of the functions controlled by the transducer controller 18 is the direction of beam steering and focusing. The beam can be steered straight forward (perpendicular to) the transducer array, or steered at different angles to obtain a wider field of view. Therefore, the controller 18 enables the steering of the beam within a narrowed field of view in a 3D volume corresponding to the 3D field of view. The steering and focusing of the transmitted beam can be controlled based on the actuation time of the transducer elements.

[0076] In general ultrasound data acquisition, two methods can be distinguished: plane wave imaging and beam steering imaging. The difference between these two methods lies in the presence of beamforming in the transmit mode (beam steering imaging) and / or receive mode (plane wave imaging and beam steering imaging).

[0077] First, let's look at the focusing function. By simultaneously activating all transducer elements, the transducer array generates a plane wave, which diverges as it travels across an object. In this case, the ultrasound beam remains unfocused. By introducing a location-dependent time delay into the transducer activation, the wavefront of the beam can be converged to the desired point, called the focal zone. The focal zone is defined as the point where the lateral beamwidth is less than half the width of the emitted beam. In this way, the lateral resolution of the final ultrasound image is improved.

[0078] For example, if a time delay causes the transducer elements to activate sequentially from the outermost element and terminate activation at one or more central elements of the transducer array, a focal zone will be formed at a given distance from the probe, aligned with the central element(s). The distance between the focal zone and the probe will vary depending on the time delay between each subsequent round of transducer element activation. After the beam passes through the focal zone, it will begin to diverge, forming a far-field imaging region. It should be noted that for focal zones located close to the transducer array, the ultrasonic beam will diverge rapidly in the far field, resulting in beamwidth artifacts in the final image. Typically, the near field between the transducer array and the focal zone shows little detail due to significant overlap in the ultrasonic beam. Therefore, changing the position of the focal zone can cause a significant change in the quality of the final image.

[0079] It should be noted that in emission mode, only one focus can be defined unless the ultrasound image is divided into multiple focal zones (each of which may have a different emission focus).

[0080] Furthermore, upon receiving an echo signal from within the object, the reverse process described above can be executed to perform receiver focusing. In other words, the incoming signal can be received by the transducer elements and undergoes an electronic time delay before being transmitted to the system for signal processing. The simplest example of this is called delay-summation beamforming. The receiver focusing of the transducer array can be dynamically adjusted according to time.

[0081] Now consider the function of beam steering. By correctly applying a time delay to the transducer elements, a desired angle can be assigned to the ultrasonic beam as it leaves the transducer array. For example, by activating the transducers on the first side of the transducer array and then sequentially ending the remaining transducers on the opposite side of the array, the beamfront will form an angle toward the second side. The magnitude of the steering angle relative to the normal of the transducer array depends on the magnitude of the time delay between subsequent transducer element activations.

[0082] Furthermore, it is possible to focus a steered beam, where the total time delay applied to each transducer element is the sum of the focusing time delay and the steerable time delay. In this case, the transducer array is called a phased array.

[0083] When a DC bias voltage is required for the activated CMUT transducer, the transducer controller 18 can be coupled to control the DC bias control 45 for the transducer array. The DC bias control 45 sets one or more DC bias voltages applied to the CMUT transducer elements.

[0084] For each transducer element in the transducer array, an analog ultrasonic signal, typically referred to as channel data, enters the system through a receiving channel. In the receiving channel, a microwave beamformer 12 generates a partially beamformed signal based on the channel data. This partially beamformed signal is then passed to a main receiving beamformer 20, where the partially beamformed signals from individual transducer patches are combined into a fully beamformed signal (referred to as radio frequency (RF) data). The beamforming performed at each stage can be performed as described above, or may include additional functionality. For example, the main beamformer 20 may have 128 channels, each receiving partially beamformed signals from patches of dozens or hundreds of transducer elements. In this way, signals received by thousands of transducers in the transducer array can be effectively contributed to a single beamformed signal.

[0085] The beamformed received signal is coupled to signal processor 22. Signal processor 22 can process the received echo signal in various ways, such as bandpass filtering; decimation; I and Q component separation; and harmonic signal separation, which separates linear and nonlinear signals, thereby enabling the identification of nonlinear (higher harmonics of the fundamental frequency) echo signals returning from tissue and microbubbles. The signal processor can also perform additional signal enhancement, such as speckle reduction, signal recombination, and noise cancellation. The bandpass filter in the signal processor can be a tracking filter; as the echo signal is received from increasingly deeper depths, the passband of the tracking filter slides from higher to lower frequency bands, thereby suppressing higher-frequency noise from greater depths (which typically lacks anatomical information).

[0086] The beamformer used for transmission and the beamformer used for reception are implemented in different hardware and are capable of different functions. Of course, the design of the receiver beamformer must take into account the characteristics of the transmission beamformer. For simplicity, in... Figure 1 Only receiver beamformers 12 and 20 are shown in the diagram. Throughout the system, there will also be a transmit chain, which includes a transmit microwave beamformer and a main transmit beamformer.

[0087] The function of microwave beamformer 12 is to provide an initial combination of signals in order to reduce the number of analog signal paths. This is typically performed in the analog domain.

[0088] The final beamforming is performed in the main beamformer 20, and is typically done after digitization.

[0089] The transmit and receive channels use the same transducer array 6 with a fixed frequency band. However, the bandwidth occupied by the transmit pulse can vary depending on the transmit beamforming used. The receive channel can capture the entire transducer bandwidth (this is the classic approach), or it can use bandpass processing so that it only extracts the bandwidth containing the desired information (e.g., harmonics of the main harmonic).

[0090] The RF signal (representing the acquired ultrasound data) can then be coupled to a B-mode (i.e., brightness mode or 2D imaging mode) processor 26 and / or a Doppler processor 28. The B-mode processor 26 performs amplitude detection on the received ultrasound signal to image structures in the body (e.g., organs, tissues, and blood vessels). In the case of line-by-line imaging, each line (beam) is represented by an associated RF signal whose amplitude is used to generate brightness values ​​to be assigned to pixels in the B-mode image. The exact location of a pixel within the image is determined by measuring its position along the associated amplitude of the RF signal and the number of lines (beams) of the RF signal. As described in U.S. Patent 6283919 (Roundhill et al.) and U.S. Patent 6458083 (Jago et al.), B-mode images of such structures can be formed in a harmonic imaging mode or a fundamental imaging mode, or a combination of both. The Doppler processor 28 processes signals that differ temporally due to tissue movement and blood flow for the detection of moving material (e.g., blood cell flow in the image field). Doppler processor 28 typically includes a wall filter whose parameters are set to allow or reject echoes returning from a selected type of material in the body.

[0091] The structural and motion signals generated by the B-mode processor and / or Doppler processor can be coupled to the scan converter 32 and the multiplane reformer 44. The scan converter 32 arranges the echo signals in the desired image format according to the spatial relationships at which the echo signals are received. In other words, the scan converter is used to transform RF data from a cylindrical coordinate system to a Cartesian coordinate system suitable for displaying ultrasound images on the image display 40. In the case of B-mode imaging, the brightness of a pixel at a given coordinate is proportional to the amplitude of the RF signal received from that location. For example, the scan converter can arrange the echo signals into a two-dimensional (2D) fan-shaped format or a pyramidal three-dimensional (3D) image. The scan converter can overlay colors on the B-mode structural image corresponding to the motion at various points in the image field, where Doppler-estimated velocities produce the given colors. The combined B-mode structural image and color Doppler image depict tissue motion and blood flow within the structural image field. As described in U.S. Patent 6,443,896 (Detmer), a multiplane reformer converts echoes received from points in a common plane of a volumetric region of the body into an ultrasound image of that plane. As described in U.S. Patent 4,653,0885 (Entrekin et al.), a volume plotter 42 converts echo signals from a 3D dataset into a 3D image of a projection as seen from a given reference point.

[0092] 2D or 3D ultrasound images are coupled from the scan converter 32, multiplane reformer 44, and volume plotter 42 to the image processor 30 for further analysis, enhancement, buffering, and temporary storage for display on the image display 40. The image processor can be adapted to remove some imaging artifacts from the final ultrasound image, such as acoustic shadowing caused by strong attenuators or refraction; post-enhancement caused by weak attenuators; and reverberation artifacts at locations adjacent to highly reflective tissue interfaces. Additionally, the image processor can be adapted to perform certain speckle reduction functions to improve the contrast of the final ultrasound image.

[0093] In addition to their use in imaging, the blood flow values ​​generated by the Doppler processor 28 and the tissue structure information generated by the B-mode processor 26 can also be coupled to the quantization processor 34. Besides structural measurements (e.g., organ size and gestational age), the quantization processor also generates measurements of different flow conditions (e.g., blood flow volumetric velocity). The quantization processor can receive input from the user control panel 38 (e.g., points to be measured in the anatomical structures of the image).

[0094] Output data from the quantization processor can be coupled to the graphics processor 36 for reproducing the image along with measurement graphics and values ​​on the display 40 and for outputting audio signals from the display device 40. The graphics processor 36 can also generate graphic overlays for display alongside ultrasound images. These overlays can include standard identification information (e.g., patient name), the date and time of the image, imaging parameters, etc. For this purpose, the graphics processor receives input (e.g., patient name) from the user interface 38. The user interface is also coupled to the transmission controller 18 to control the generation of ultrasound signals from the transducer array 6 and thus control the images generated by the transducer array and the ultrasound system. The transmission control function of the controller 18 is only one of the functions performed. The controller 18 also considers the operating mode (given by the user) and the corresponding required transmitter and bandpass configurations in the receiver analog-to-digital converter. The controller 18 can be a state machine with fixed states.

[0095] The user interface is also coupled to a multiplane reformer 44 for selecting and controlling planes of multiple multiplane reformatted (MPR) images, which can be used to perform quantization measurements in the image field of the MPR image.

[0096] The method described herein can be executed on a processing unit. Such a processing unit can be located in an ultrasound system (e.g., as referenced above). Figure 1Within the system described. For example, the image processor 30 described above can perform some or all of the method steps detailed below. Alternatively, the processing unit can be located in any suitable system adapted to receive object-related input (e.g., a monitoring system).

[0097] Figure 2 A method 100 for guiding the acquisition of ultrasound data within a 3D field of view is shown.

[0098] The method begins at step 110: obtaining initial 2D B-mode ultrasound data of the cranial region of the object from a reduced field of view at a first imaging location, wherein the imaging location is within a 3D field of view.

[0099] The proposed method can be implemented as an image-guided routine that relies on initial 2D B-mode ultrasound data to initially locate the ultrasound probe before switching to a 3D color Doppler or power Doppler imaging routine to locate the vessel of interest and quantify blood flow. In this way, the high frame rates available in 2D B-mode imaging allow for accurate probe localization, and robust flow quantification, acquiring flow data (which often takes longer in 3D Doppler techniques), allows the user to obtain accurate measurements of the vessel of interest.

[0100] In other words, this method provides a means to rapidly determine the accuracy of the ultrasound probe position for transcranial vascular imaging using high frame rate 2D B-mode imaging (instead of using full 3D Doppler imaging) during the localization phase.

[0101] In other words, by using 2D B-mode imaging, it is possible to use 3D Doppler imaging to quickly orient the ultrasound probe for subsequent flow monitoring.

[0102] In step 120, it is determined whether the vessel of interest is located within the 3D field of view based on the initial 2D B-mode ultrasound data from the first imaging location.

[0103] The operation of determining whether a vessel of interest is located within the 3D field of view from the first imaging position can be performed in a variety of ways.

[0104] For example, determining whether a vessel of interest is located within the 3D field of view may include having the processor 30 (in a non-limiting example) identify anatomical features (e.g., bone structures) within the reduced field of view based on initial 2D B-mode ultrasound data, and determining the likelihood that the vessel is located within the 3D field of view based on the identified anatomical features. Such anatomical feature identification can be performed by comparing the B-mode ultrasound data of the acquired 2D ultrasound images with a database of other image modalities depicting the bone and vascular structures of the skull. The processor 30 may have means of accessing such a database and is adapted to apply a convolutional neural network to the initial 2D B-mode ultrasound data. Alternatively, the anatomical feature identification step can be performed at a location different from the physical location of the processor 30 (e.g., in the cloud).

[0105] Magnetic resonance angiography, CT angiography, digital subtraction angiography, and nuclear imaging of the brain and head provided a 3D atlas of other imaging modalities depicting the human cerebral vascular system. As a result, the locations of known major cerebral vessels (e.g., the MCA) were consistently localized relative to the bone structures in the skull.

[0106] In other words, the likelihood that a vessel of interest is located within the field of view of an ultrasound probe can be determined based on the identification of bone structures within the field of view.

[0107] The following is for reference. Figure 3A and Figure 3B Examples of the localization of blood vessels of interest relative to structures within the skull are discussed.

[0108] Determining the likelihood that a blood vessel is located within a 3D field of view based on the identified anatomical features may include obtaining 2D color Doppler ultrasound data from a reduced field of view at a first imaging location.

[0109] 2D color Doppler ultrasound data will show any movement (i.e., blood flow) within the narrowed field of view. The direction of the blood flow relative to the imaging plane, as well as the size and velocity of the blood flow, can be used to determine whether the vessel of interest is actually shown.

[0110] Determining whether a vessel of interest is located within the 3D field of view can involve applying a convolutional neural network (CNN) to the initial 2D B-mode ultrasound data. For example, a CNN can be used with any suitable image recognition technique to identify bone structures within the field of view and determine the likelihood of a vessel occupying the field of view based on the identified structures. The CNN can be trained using 2D duplex color Doppler data, which is a combination of color Doppler data and B-mode data. This means that the location of the blood flow area (shown in Doppler data) relative to the structures (shown in B-mode data) can be learned.

[0111] If it is determined in step 120 that the vessel of interest is not located within the 3D field of view, the method proceeds to step 130.

[0112] In step 130, a guidance instruction is generated based on the initial 2D B-mode ultrasound data, wherein the guidance instruction is adapted to indicate a second imaging position to obtain additional ultrasound data. The method then returns to step 110, where the additional ultrasound data is used instead of the initial ultrasound data.

[0113] The guiding instructions may vary depending on the implementation of the method and system. For example, ultrasound data can be acquired using an ultrasound probe. There are many implementations of ultrasound probes that can be used to collect ultrasound data as described above. For example, an ultrasound probe may include: a linear transducer array; multiple linear transducer arrays; or a 2D transducer array.

[0114] Guidance instructions provided to the user can be delivered indirectly. In other words, the system can analyze initial ultrasound data and generate guidance signals using a guidance unit separate from the ultrasound probe. For example, in the case of generating visual guidance signals, arrows instructing the user to move the ultrasound probe can be displayed on the screen (image display 40). The screen can also be the same as the screen of the patient monitoring system.

[0115] Alternatively, the unit for providing guidance to the user can be included within the ultrasound probe itself. For example, the ultrasound probe may be adapted to generate one or more of the following to guide the user to a second imaging position: auditory commands; visual commands; electronic control signals; and tactile commands.

[0116] In the case of visual feedback, the ultrasound probe can be equipped with one or more LEDs that provide the user with visual signals regarding how the probe should be moved. In the case of auditory commands, one or more speakers can be provided to provide auditory commands to the user. In the case of haptic feedback, the ultrasound probe can be equipped with one or more vibration modules that are deactivated to provide haptic commands that can be interpreted by the user. In the example of electronic command signals, feedback can be provided to a remote digital display unit (e.g., a monitor), which then presents the command to the user in an appropriate format.

[0117] A convolutional neural network can be used to generate guidance commands. This network is trained with a prior set of initial ultrasound data and the movements required to reach the correct imaging position. In this way, the convolutional neural network can learn to make the probe move more efficiently from the initial imaging position to the second imaging position.

[0118] It should be noted that user guidance information can indicate any number of additional imaging locations. For example, based on initial 2dB mode ultrasound data, it can be determined that the vessel of interest can be imaged from several different imaging locations. In this case, user guidance instructions can be generated for each of the alternative imaging locations and presented to the user, who can then select one of the alternative imaging locations to move the ultrasound probe there. Additionally, the system can store this alternative imaging location for future users who require future imaging.

[0119] If the vessel of interest is determined to be within the 3D field of view in step 120, the method proceeds to step 140.

[0120] In step 140, a 3D field of view is used to acquire 3D Doppler ultrasound data from the cranial region. In other words, once the initial 2D B-mode ultrasound data has confirmed that the vessel of interest is within the 3D field of view, the controller 18, which is also coupled to the processor 30, switches the imaging mode to the desired 3D Doppler imaging mode.

[0121] Then, (e.g., Doppler processor 28) 3D Doppler ultrasound data can be used to analyze blood flow within the vessel of interest.

[0122] Additionally, if the vessel of interest is determined to be located within the 3D field of view, the method may further include, for example, using processor 30 to measure bone structures within the 3D field of view, generating a kernel for spatial filtering of the bone structures, and applying the kernel to the 3D Doppler ultrasound data.

[0123] In other words, a specially generated kernel can be used to filter out structures within the field of view that may disrupt 3D Doppler ultrasound data related to the vessel of interest and cause interference in the final image.

[0124] The above method can be used in ultrasound systems (e.g., as referenced above). Figure 1 Execution occurs within the system described. Although the individual functional units of the system... Figure 1 While described and illustrated as individual elements, their exact implementation may be achieved with a smaller number of hardware components, each performing a few units of function. However, this method can also be employed on any device capable of receiving ultrasound data. For example, an ultrasound probe can be used to acquire ultrasound data, which can then be provided to a separate patient monitor to perform the method described above. The data can be provided via any suitable communication means.

[0125] In the case of directly obtaining ultrasound data using an ultrasound probe, the method may further include: determining the orientation of the ultrasound probe at a first imaging position, and generating probe manipulation commands based on the orientation of the ultrasound probe and initial 2D B-mode ultrasound data.

[0126] The probe manipulation commands can be adapted to indicate how the ultrasound probe should be adjusted to achieve the second imaging position. Probe manipulation commands can be transmitted in a manner similar to the guidance commands described above.

[0127] Additionally, the method may include periodically acquiring extra 2D B-mode ultrasound data, particularly in 3D Doppler imaging mode. This extra 2D B-mode ultrasound data can be compared with the initial 2D B-mode ultrasound data to determine the movement of the vessel of interest within the field of view. Furthermore, the movement of the ultrasound probe can also be determined in this manner.

[0128] New guidance commands can be generated based on detected movement to ensure that the probe is kept in the correct position when acquiring 3D Doppler ultrasound data.

[0129] The above methods can utilize the fast 2D generalized Hough transform (described in DHBallard's "Generalizing the Hough transform to detect arbitrary shapes" (Pattern Recognit., Vol. 13, No. 2, pp. 111-122, January 1981)) and / or template matching techniques (described in Yuhai Li, Jian Liu, Jinwen Tian and Hongbo Xu's "Afast rotated template matching based on point feature" (2005, Vol. 6043, pp. 60431-6043–7)).

[0130] Figure 3A An example 200 illustrates the spatial relationship between cerebral blood vessels 210 and bone structures (e.g., the pterygopalatine fossa 220 (in this example, the pterygopalatine fossa 220 is adjacent to the vessel of interest), the occipital floor 230, and the clivus 240 of the frontal bone) within the subject's head during ultrasound examination. Here, the middle cerebral artery is the vessel of interest 210, which is very close to the clivus 240, the occipital floor 230, and the pterygopalatine fossa 220 (which are visible in the B-mode image). Figure 3B The pterygopalatine fossa 220 and the vicinity of the vessel of interest are shown in the magnetic resonance (MR) angiography image.

[0131] For example, the above method can be implemented as follows.

[0132] The user (e.g., a clinician) places the ultrasound probe on the patient's temporal bone. In this example, the user can indicate the blood vessel they wish to locate via a user interface. Guidance instructions can then be generated based on the user's selection.

[0133] The user can then coarsely manipulate the ultrasound probe (e.g., by performing millimeter translations and small-angle connections) until the selected vessel of interest is determined to be within the field of view. During this stage, the ultrasound probe operates in 2D B-mode imaging, meaning that probe-guided feedback to the user should have a high update rate (e.g., >10 Hz).

[0134] Once the probe is identified as being aimed at a blood vessel, the user can be guided to fix the probe in place. When the optimal probe position / orientation is determined, the imaging system can automatically switch to 3D Doppler mode imaging and automatically place the initial position of the Doppler window based on the expected location of the blood vessel of interest.

[0135] As discussed above, the described methods can be implemented on a processor in any medical system. Referring to an example ultrasound system, the methods described above can be implemented in a compact ultrasound system capable of operating in a combination of at least B-mode imaging and color Doppler imaging (and additionally, power Doppler and / or M-mode imaging). Since the vessels of interest located in the cranial region of the subject are typically situated near the bone structures that generate the echo, the ultrasound system can drive multiple planar acquisitions (e.g., the X-plane or multiple height planes) for model training.

[0136] An ultrasound system may include a transcranial ultrasound probe, which is a compact matrix ultrasound probe that can be manipulated by the user along the surface of the head in front of the ears to acquire volumetric data of the cranial region of the subject.

[0137] If the vessel of interest is found to be outside the probe's field of view, the user can receive guidance instructions on how to manipulate the probe to achieve the desired view.

[0138] In this example, a convolutional neural network can be trained to provide the user with probe guidance in the form of differential poses (i.e., the translations and / or angularities required to position the probe in the optimal orientation for vascular blood flow imaging). In this case, initial 2D B-mode ultrasound data (or additionally duplex 2D color or power Doppler ultrasound data and / or multiplanar 2D B-mode ultrasound data) are taken as input to the network. The convolutional neural network can then output the differential poses (e.g., probe movements with 5 degrees of freedom) required to orient the probe for imaging the vessel of interest.

[0139] This convolutional neural network can be trained in several ways. For example, real-world data can be prospectively obtained from multiple objects. In one example, a series of objects (e.g., 25 objects) can undergo bilateral TCD scans using an ultrasound probe with optical tracking markers rigidly fixed to the probe body and the patient's head to track probe movement during the scan. The vessel of interest is imaged by an experienced TCD sonographer according to standard care, while the tracking and duplex color Doppler images are saved to memory. Data acquisition can be terminated when the vessel of interest is within the field of view. For each frame of the ultrasound imaging, the pose difference relative to the pose in the final frame can be calculated. In other words, for each 2D ultrasound image, the motion required to maneuver the probe to the center of the probe position when the vessel of interest is within the probe's 3D field of view is measured and used as real-world data in model training.

[0140] During training, the network can be used to generate guidance commands based on incoming 2D B-mode ultrasound data that can be provided to the user for probe manipulation.

[0141] During ultrasound data acquisition, the probe or blood vessel may move. Therefore, the system can be adapted to provide rapid, flow-independent determination of probe or blood vessel movement.

[0142] For example, at periodic intervals (default and / or user-modified), the system can compare live 2D B-mode images with a set of navigation 2D B-mode images acquired after successful vessel localization. These images can be acquired in a conventional 2D manner or in a multi-planar manner (e.g., the X-plane or multiple height planes). By iteratively comparing the live images with a set of height planes acquired after successful vessel localization, image cross-correlation can be used for image matching during probe reconfiguration.

[0143] Additionally, the probe can be equipped with a motion sensor. Tracking the probe's movement during the probe manipulation phase can be combined with 2D / B mode ultrasound data to determine a coarse directional movement. Furthermore, if it is determined that the vessel of interest has been lost from the field of view, gyroscope recordings during the motion phase can be used to guide the probe back to its original orientation when the vessel of interest was located.

[0144] The described methods and systems can be used to guide users manipulating ultrasonic probes or automated systems. The ultrasonic probe can be mounted in a device that selectively rigidly secures the probe to the head of an object. Such a device can allow one or more degrees of freedom for the probe and can be provided with a locking mechanism.

[0145] Those skilled in the art, through studying the accompanying drawings, disclosure, and claims, will be able to understand and implement variations of the disclosed embodiments when practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude multiple. A single processor or other unit can implement the functions of several items recited in the claims. Although certain measures are recited in dissimilar dependent claims, this does not indicate that combinations of these measures cannot be advantageously used. If a computer program has been discussed above, it can be stored / distributed on a suitable medium, such as an optical storage medium or solid-state medium supplied together with or as part of other hardware, but it can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems. If the term "suitable" is used in the claims or description, it should be noted that the term "suitable" is intended to be equivalent to the term "configured as." No reference numerals in the claims should be construed as limiting the scope.

Claims

1. A method for guiding the acquisition of ultrasound data within a 3D field of view by a computer, the method comprising: Initial 2D B-mode ultrasound data of the cranial region of the object from a reduced field of view at a first imaging position within the 3D field of view are obtained. Based on the initial 2D B-mode ultrasound data from the first imaging location, it is determined whether the vessel of interest is located within the 3D field of view; and If the vessel of interest is not located within the 3D field of view, then: A guidance command is generated based on the initial 2D B-mode ultrasound data, wherein the guidance command is adapted to instruct a second imaging position to obtain additional ultrasound data, wherein the second imaging position is a position within the 3D field of view that differs from the first imaging position; and If the vessel of interest is located within the 3D field of view, then: 3D Doppler ultrasound data of the cranial region from the 3D field of view are obtained.

2. The computer-implemented method as described in claim 1, wherein, Determining whether a blood vessel of interest is located within the 3D field of view includes: Anatomical features within the reduced field of view are identified based on the initial 2D B-mode ultrasound data; and The probability that the blood vessel is located within the 3D field of view is determined based on the identified anatomical features.

3. The computer-implemented method as described in claim 2, wherein, Determining the likelihood that the blood vessel is located within the 3D field of view based on the identified anatomical features includes obtaining 2D color Doppler ultrasound data from a reduced field of view at a first imaging location.

4. The computer-implemented method according to any one of claims 1 to 3, wherein, Determining whether a vessel of interest is located within the 3D field of view involves applying a convolutional neural network to the initial 2D B-mode ultrasound data.

5. The computer-implemented method as described in claim 4, wherein, The convolutional neural network is trained using 2D duplex color Doppler data.

6. The computer-implemented method according to any one of claims 1 to 5, wherein, The ultrasound data is obtained using an ultrasound probe, and the method further includes: Determine the orientation of the ultrasound probe at the first imaging position; and Based on the orientation of the ultrasound probe and the initial 2D B-mode ultrasound data, probe manipulation instructions are generated, wherein the probe manipulation instructions are adapted to indicate how the ultrasound probe should be adjusted to reach the second imaging position.

7. The computer-implemented method as described in claim 6, wherein, Determining the orientation of the ultrasound probe includes: Obtain tracking data related to the orientation of the probe; and The second convolutional neural network is applied to the tracking data.

8. The computer-implemented method according to any one of claims 1 to 7, wherein, If the vessel of interest is located within the 3D field of view, the method further includes: Measure the bone structure within the 3D field of view; Generate a kernel for spatial filtering of the bone structure; and The kernel is applied to the 3D Doppler ultrasound data.

9. The computer-implemented method according to any one of claims 1 to 8, wherein, The method further includes: Periodically acquire additional 2D B-mode ultrasound data; The additional 2D B-mode ultrasound data is compared with the initial 2D B-mode ultrasound data; and The movement of the blood vessel of interest is determined based on the comparison.

10. The computer-implemented method as described in claim 9, wherein, The ultrasound data is obtained using an ultrasound probe, and the method further includes determining the movement of the ultrasound probe based on the comparison.

11. The computer-implemented method as described in claim 2, wherein, The anatomical features include bone structure.

12. A medical system suitable for guiding the acquisition of ultrasound data within a 3D field of view, the system comprising: Processor, wherein the processor is adapted to: Initial 2D B-mode ultrasound data of the cranial region of the object from a reduced field of view at a first imaging position within the 3D field of view are obtained. Based on the initial 2D B-mode ultrasound data from the first imaging location, it is determined whether the vessel of interest is located within the 3D field of view; and If the vessel of interest is not located within the 3D field of view, then: A guidance command is generated based on the initial 2D B-mode ultrasound data, wherein the guidance command is adapted to instruct a second imaging position to obtain additional ultrasound data, wherein the second imaging position is a position within the 3D field of view that differs from the first imaging position; and If the vessel of interest is located within the 3D field of view, then: 3D Doppler ultrasound data of the cranial region from the 3D field of view are obtained.

13. The system of claim 12, wherein, The system also includes an ultrasound probe in communication with the processor, wherein the ultrasound probe is adapted to acquire 2D ultrasound data and 3D ultrasound data, and wherein the processor is adapted to: activate the ultrasound probe in a 2D B-mode ultrasound acquisition mode with a limited field of view; and switch the ultrasound probe to a 3D color Doppler ultrasound acquisition mode with a full field of view if the vessel of interest is located within a full 3D field of view.

14. The system of claim 13, wherein, The system also includes a probe tracker adapted to generate tracking data relating to the orientation of the ultrasound probe, and wherein the processor is further adapted to determine the orientation of the probe based on the tracking data.

15. The system of claim 14, wherein, The probe tracker includes one or more of the following: Optical trackers; and Motion tracker.

16. The system according to any one of claims 13 to 15, wherein, The system also includes a probe holder adapted to receive the ultrasound probe and hold the ultrasound probe in a given imaging position, wherein the probe holder is adapted to selectively lock the ultrasound probe in the given imaging position.

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