PORTABLE ULTRASOUND DEVICE AND ULTRASOUND IMAGING METHOD - Patent application

Abstract

A portable ultrasound device (109) for non-invasively imaging selected subcutaneous structures includes (a) a housing (110), and (b) a plurality of arrays (300A) of transducer elements (300). Each array (300A) is arranged in parallel, with each transducer element (300) including a transmit transducer (705) and a receive transducer (707), and is positioned within the housing (110) for sequentially transmitting ultrasonic energy within a predetermined frequency range toward a subject's body (100) and sequentially receiving echo signals within a predetermined frequency range from the subject's body (100). The multiple parallel arrays (300A) enable imaging of the subcutaneous structures (101, 101A) in multiple transverse and lateral planes. The ultrasound device (109) further includes (c) a controller (250) for operating the multiple arrays (300A) of transducer elements (300), the controller being in communication with a processor (350) for processing echo signals received from the multiple arrays (300A) of transducer elements (300), and (d) a screen (104) for displaying interpretable images (104A, 104B) of the subcutaneous structures (101, 101A) generated by the processor (350).

Description

[Technical field]

[0001] The present invention relates to a portable ultrasound device and a method of ultrasound imaging using the device. [Background technology]

[0002] Peripheral intravenous cannulation (PIVC; the placement of a vascular access device, usually a plastic cannula, inside a vein with the aid of an introducer needle) is the most commonly performed invasive medical procedure, with over 2 billion cannulas sold worldwide each year (Rickard et al. (2018) Lancet 392(10145):419-430). Over 70% of hospitalized patients require a cannula during their stay (Zingg and Pittet (2009) Int J Antimicrob Agents 34 Suppl 4:S38-42).

[0003] The vast majority of vascular access procedures using vascular access devices such as cannulas are performed without the aid of any visualization device and rely on what is observed through the patient's skin and the clinician's ability to feel the veins. Patients are most commonly first cannulated in the emergency department, which is also the entry point for most hospitalized patients. These are often inserted in a hasty manner that involves guesswork by feeling or seeing the vein, resulting in a suboptimal insertion location and method. Once the patient's condition is stabilized, these PIVCs often need to be removed and reinserted.

[0004] The position of the cannula can be decided by either the doctor or the nurse, but this varies between countries and hospitals. In Western Australian public hospitals, the majority of cannulas are placed by junior doctors (interns, resident medical officers and registrars) or trained clinical nurses.

[0005] If cannulation is deemed difficult or after repeated failures, the junior doctor will retry the insertion with the assistance of a senior doctor. If multiple standard attempts have failed, an appropriately trained, usually senior, doctor may use ultrasound to visualise the vein and guide further cannulation attempts. Ultrasound-assisted cannulation or venipuncture requires significant training and experience, but ultrasound equipment is available in only a few departments.

[0006] The main obstacle to successful implementation of ultrasound is the difficulty of using the technology.

[0007] First, end users require extensive training to adjust the ultrasound settings and properly position the hardware (probe) on the patient to obtain clear images in the first place, let alone interpret the images.

[0008] Second, it is difficult for end users, especially those who perform most of the cannulations (junior physicians or certified nurses), to objectively interpret conventional B-mode or color Doppler images and identify and differentiate the artery or vein of interest.

[0009] Third, the screen is typically on a separate cart-based system and is not aligned with the vessel location, presenting usability issues such as the end user having to view an adjacent screen while holding the imaging probe and attempting to insert the needle.

[0010] Literature reports that cannulation has an unacceptable 40% failure rate on the first attempt (Rickard et al. (2018) Lancet 392(10145):419-430; Cooke et al. (2018) PLoS One 13(2):e0193436; Keogh and Mathew (2019) Australian Commission on Safety and Quality in Health Care).

[0011] Patients with difficult venous access often require multiple cannulation attempts. These multiple attempts cause significant pain and distress to the patient, frustration for clinicians, and a significant waste of time and equipment. This causes delays in downstream testing and treatment. These delays also slow the flow of patients through the department, increasing emergency wait times.

[0012] Repeated cannulation attempts are also associated with higher infection rates, increased morbidity, and longer hospital stays, which translates into increased costs for health care services (Bahl et al. (2016) The American Journal of Emergency Medicine, 34(10):1950-1954; Fields et al. (2013) Journal of Vascular Access 15(6):514-518).

[0013] First-pass cannulation attempts in patients can fail for a number of reasons. Some may be related to patient anxiety and associated movement, many may be related to lack of skill or experience of the clinician, but most are due to the patient having difficulty accessing the vein, reducing identification of the vein by sight or feeling. As non-limiting examples, this may be the result of obesity, past or current chemotherapy, previous intravenous drug use, or renal and cardiac failure.

[0014] Other patients who may have difficulty cannulating include, but are not limited to, the very young and very elderly, as well as those with darker skin (Au et al. (2012) Am J Emerg Med 30(9):1950-1954; Bauman et al. (2009) Am J Emerg Med 27(2):135-140; Brannam et al. (2004) Acad Emerg Med 11(12):1361-1363; Chinnock et al. (2007) J Emerg Med 33(4):401-405). Obesity is the most common cause of difficult vascular access, with 28% of Australians and 13% of people worldwide being obese (World Health Organisation (2018)).

[0015] The foregoing discussion of the background art is intended only to facilitate understanding of the present invention. This discussion is not an acknowledgment or admission that any of the material referenced is or was part of common general knowledge as of the priority date of this specification. Summary of the Invention

[0016] The present invention provides a portable ultrasound device for imaging subcutaneous structures of a subject, for example to assist a physician in performing venipuncture or cannulation.

[0017] In one aspect, the present invention provides a portable ultrasound device for non-invasively imaging selected subcutaneous structures within a subject, the portable ultrasound device comprising: (a) a housing; (b) a plurality of arrays of transducer elements, each array arranged in parallel, each transducer element including a transmit transducer and a receive transducer, and positioned within the housing for sequentially transmitting ultrasonic energy within a predetermined frequency range toward a body of a subject, and sequentially receiving echo signals within the predetermined frequency range from the body of the subject after reflection of the ultrasonic energy, wherein the plurality of parallel arrays of transducer elements enable imaging of subcutaneous structures in multiple transverse and lateral planes; (c) a controller for operating the multiple arrays of transducer elements, the controller in communication with the processor for processing echo signals received from the multiple arrays of transducer elements; (d) a screen forming part of the housing for displaying an image of the subcutaneous structure, the processor being configured to process echo signals returned from the subcutaneous structure to selectively generate an interpretable image of the subcutaneous structure of interest on the screen; and Includes.

[0018] It will be understood that the subject may be a human patient or may be a veterinary subject, such as a domestic animal, livestock, or laboratory animal.

[0019] The portable ultrasound device is configured to facilitate operation by personnel without specific expertise in ultrasound imaging. Typically, an ultrasound operator would have to manually adjust the orientation of the probe and manually calibrate the operating field of view, gain level, contrast level, imaging depth or Doppler parameters all while interpreting an abstracted 2D grayscale image (or 2D color Doppler) acquired in a single scan line. The device is conveniently configured as described below, or the controller of the portable ultrasound device is conveniently programmed to take over one, several or all of these functions so that the user of the device does not have to do so. For example, the gain control can be fully automated without the user of the portable ultrasound device having to adjust the gain. The portable ultrasound device only needs to be provided with user functions that allow the device to be powered up and down and to select a preferred image mode, for example, between B-mode, color Doppler mode and schematic mode, which preferably allows the display of subcutaneous structures such as vascular structures. The user functions may include the ability to store images, as described below, if desired. Furthermore, in the embodiments of the portable ultrasound device described below, there is no need to manually adjust the orientation of the probe.

[0020] Preferably, the subcutaneous structure is a vascular structure, such as a vein or artery, however, the portable ultrasound device may alternatively or additionally be configured to enable imaging of other subcutaneous structures for neuroimaging and / or foreign body imaging.

[0021] A planar or linear array of transducer elements is preferred. The multiple arrays of transducer elements may include any convenient number of arrays, for example, four arrays. Preferably, the multiple arrays of transducer elements are spaced apart from one another by a distance ξ along the transverse axis selected to minimize interference and maximize the scan window. Most preferably, ξ is between 5 and 30 mm.

[0022] The array of transducer elements preferably includes at least one Doppler transducer array. Preferably, the parallel transducer arrays are placed at an insonation angle Φ where 10<Φ<60 to ensure that the Doppler effect is captured and not nullified. Such an angular configuration can eliminate the need for an operator to manually adjust the operational field of view and imaging angle.

[0023] Multiple parallel transducer arrays provide the ability to image subcutaneous structures in multiple transverse and lateral planes to display their lateral location to a selected depth, e.g., 2-3 cm, below the skin surface within the contact area where the ultrasound device contacts the subject's skin. Simultaneous transverse and lateral imaging effectively gives the images a "3D" appearance, making them easier for personnel with or without ultrasound imaging training to interpret and use for effective cannulation.

[0024] The linear array may be single and affixed to a mobile track device, allowing the transducer array to be moved along the length of the vessel while being used to sense multiple ultrasound images for processing. The movement of the array on the track allows imaging in multiple planes, allowing the combined lateral and transverse imaging described above. For example, rather than having, for example, four crystal arrays in fixed positions, a single movable array can achieve the same multi-planar function.

[0025] The linear transducer may be single and may oscillate about a fixed point while sensing multiple ultrasound images for processing.

[0026] The controller of the ultrasound device controls the operation of the multiple arrays of transducer elements to selectively transmit ultrasonic energy to locate subcutaneous structures and display on the screen after processing of received echo signals by the processor. Where vascular structures are involved, and vascular structures such as veins are described below for illustrative purposes, candidate subcutaneous vascular structures are conveniently located in both transverse and lateral directions. This may include transmitting ultrasonic energy to a selected depth where the candidate vascular structures are located, from less than 1 cm into the subject's body, with a dead zone of about 5 mm, up to a few centimeters, for example up to about 5 cm for a relatively narrow frequency range of 3-8 MHz. Transmission of ultrasonic energy to deeper depths is prevented to avoid receiving echo signals that do not reflect vascular structures and are not useful in preparing a cannulation procedure with a vascular access device such as a cannula or needle. This may include or include processing the echo signals to remove noise signals that do not reflect candidate vascular structures. The processor enables the path of the venous structures to be updated and displayed on the screen as the portable ultrasound device moves over the skin surface. The image quality is adequate to locate appropriate cannulation points to assist in venipuncture.

[0027] In a preferred embodiment, the one-dimensional locations (as x-axis coordinates) of veins and arteries are identified across a single transducer through several possible methods described below. This process is advantageously performed in real time for multiple transducers in an array, and the x-axis location for each vein or artery location can be stored and interpolated between transducers to create the vein or artery path.

[0028] Advantageously, when subcutaneous vasculature is of interest, the processor is programmed with instructions to distinguish between arterial and venous vasculature. In one embodiment, the first algorithm enables such a distinction, optionally a time-domain based algorithm based on pulsatility measurements. Veins are typically much less pulsatile than arteries, if at all. Suitable pulsatility metrics for measurement and input into such an algorithm may include pulsatility index (i.e., (systolic-diastolic) / mean blood flow velocity in a vessel), dicrotic ridge, velocity reflex index (VRI), viscoelastic index (VEI) and / or resistivity index.

[0029] In another embodiment, the processor may be programmed with instructions to use the energy signal or energy signature to identify and distinguish between arterial and venous structures and to determine the location of veins below the contact area of ​​the ultrasound device. The energy signal is preferably determined from a frequency domain representation of the raw signal determined by a Fast Fourier Transform (FFT) of the continuously acquired current signal, or more preferably from a power spectral density (PSD) calculated from the sampled signal. This energy signature is preferably the amplitude of the dominant signal frequencies, or alternatively the sum of the amplitudes of the dominant frequencies, or the sum of the squares of the other amplitudes. More preferably, the energy is the area under the FFT or PSD distribution. Alternatively, the energy may be the ratio of the amplitude to the area under the distribution, or the ratio of the sum of the amplitudes (or the sum of the squares of the amplitudes) to the area under the distribution.

[0030] The processor can also be programmed with instructions to distinguish between veins and arteries due to inherent differences in the measured Doppler shift. If venous blood flow is toward the transducer, but the opposite occurs in arteries, the frequency shift can be either positive (venous) or negative (arterial). If venous flow is away from the transducer and arterial flow is toward the transducer, the opposite is true. According to the directionality inferred from the Doppler shift, the processor can determine a pseudo-negative magnitude for arteries, which is also usually larger than the absolute magnitude for veins. Thus, veins and arteries can be distinguished.

[0031] The processor can also determine the depth of subcutaneous structures below the skin. For example, in the case of vascular structures, for a given vessel diameter, which can be calculated by the processor using a method as described below, a characteristic curve can be inferred relating the magnitude of energy to the vessel depth for different vessel diameters. This depth can be visualized numerically as a value of a few millimeters or centimeters below the skin, or through color weighting by depth magnitude, or through other visual representations such as a 3D perception of shallowness or depth, all of which can be conveniently displayed on a screen. Thus, the processor can calculate the depth without requiring a B-mode cross-sectional image reconstruction.

[0032] Alternatively, the processor may be programmed in the instructions to perform B-mode imaging for each transducer element. As described below, structural metrics (such as diameter or dimensions, compressibility, and other curvilinear characteristics) may be calculated and used to distinguish between arteries and veins. Machine learning techniques, including, for example, the use of convolutional neural networks, may be used to classify and identify veins and arteries according to a training data set provided by a population of ultrasound users. In B-mode or color Doppler representations, the depth of the vessels may be measured directly and displayed on the screen of the ultrasound device.

[0033] In another embodiment of the algorithm for distinguishing between arteries and veins, B-mode and color Doppler images can be acquired and automated computer vision techniques can be used to identify flow away from or towards the transducer (or flow away from the heart representing arteries and flow towards the heart representing veins). Color Doppler represents flow towards the transducer (usually venous) as shades of blue whose intensity represents the magnitude of velocity, and flow away from the transducer (usually arterial) as shades of red. Thus, arteries and veins can be distinguished by automated computer vision techniques that distinguish between colors. In B-mode or color Doppler representations, the depth of the vessels can be measured and displayed directly.

[0034] Advantageously, once the energy signal is captured, the algorithm, as embodied in the instructions programmed into the processor, recognises that the peaks of the energy signal or energy signature form part of a parabolic or Gaussian-like distribution, and that the beginning and end points of such distributions can be used to estimate the subcutaneous dimensions or diameters of structures, particularly in the lateral direction.

[0035] Ultrasound data may be acquired by a processor for processing both with and without mechanical compression of the subcutaneous blood vessels due to the housing of the ultrasound device exerting an external force on the skin. Different vessel wall properties of veins (which are compressible but not muscular and not elastic) and arteries (which are muscular and elastic) can be exploited to measure changes during compression and distinguish between arteries and veins.

[0036] In one embodiment of the compression method, the peak energy signal (determined from either the FFT or the PSD) is altered by compression. In particular, the positive peaks (representing venous flow as it flows towards the transducer) are flattened by compression, whereas the negative peaks (representing arterial flow as it flows away from the transducer) only show a decrease in magnitude while maintaining their directionality (negative peaks represent flow away from the transducer). The drop (towards zero) of the characteristic venous peak and the linear decrease in arterial size are calculated, preferably by absolute value measurement, or more preferably by characteristic curve analysis to distinguish between arteries and veins. Alternatively, the diameter of the vessel can be determined from the energy curve as described above, so that the change in diameter from before to after compression can be calculated to estimate the change in size due to compression. Compared to arteries, a large deformation (e.g. equivalent to 90-100% of the original diameter) is expected for veins. Preferably, the method is applicable to subcutaneous structures, i.e. veins or arteries, up to a depth of 5 cm, most preferably up to a depth of 2-3 cm. The elasticity of the vessel can also be determined.

[0037] In another embodiment of the compression method using B-mode or color Doppler, automatic feature edge recognition can be used to identify circular or elliptical objects and measure the maximum vertical chord length of these objects. Circular or elliptical objects can be identified as veins or arteries because the reduction in maximum vertical chord length is greatest for veins compared to arteries (e.g., equivalent to 90-100% of the original diameter).

[0038] In another embodiment of both compression methods described, the compressibility of the vein, either by energy drop or chord length reduction, can be used to indicate the structural integrity of the vein, with greater resistance to compression indicating greater stiffness (structural integrity). Additionally, the recovery of the structure after compression can be used to determine the degree of plastic deformation, which can then be used to determine elasticity. Selecting a structurally stable vein through inferences of both stiffness and elasticity is a critical factor for cannulation as well as success during cannulation (no dislodgement, no extravasation).

[0039] In another embodiment, if both the diameter and the path of a vascular structure are available to the processor, the processor can be programmed with instructions to create a three-dimensional structure of that vascular structure. The path data can be used as a centerline, and the point-by-point diameter data can be used to create ideal circular cross sections with constant diameter for energy-based algorithmic approaches, or specific vascular cross sections of the subject (for B-mode or color Doppler approaches) that may or may not be circular. These cross sections can then be lofted along the vascular path to create a three-dimensional structure with triangular surfaces created by algorithms such as marching cubes.

[0040] The processor preferably includes a graphics processor which assists in providing the necessary image quality in that it provides sufficient information to identify candidate vascular structures without simplifying to a simple schematic that provides too little information to assist in cannulation.

[0041] The processing of echo signals received during an ultrasound examination involves many complex calculations, and the wide range of ultrasound examinations that medical ultrasound equipment is required to perform usually makes such equipment non-portable. In a preferred embodiment, this complexity is reduced, but still present, since the procedure is limited to locating candidate vascular structures for cannulation. To that end, the processor, preferably housed within the housing, may include a processing unit that is located outside the housing but is capable of communicating with the portable ultrasound device via a wired or wireless network, thereby enabling the display of candidate vascular structures on a screen that forms part of the housing of the portable ultrasound device.

[0042] Most preferably, the processor is included within the housing of the device, so that processing, including a processing unit located outside the housing, can be performed using a cloud-based system such as Amazon AWS, whereby data is wirelessly transmitted, processed, and returned to the device. Preferably, trivial and junk signals are automatically filtered out, and the Doppler frequencies of non-trivial signals are calculated and temporarily stored in a sampling memory. The temporary sampling memory is preferably less than 8 GB, more preferably less than 6 GB, or most preferably less than 4 GB or 2 GB. Wireless communication from the portable ultrasound device to the processing unit or storage device can be by, for example, reversible USB-C, Bluetooth 5.0, or wireless Internet in the form of standard WiFi, dual band, Wi-Fi Direct, or hotspot. For remote use where wireless Internet is not present, in one embodiment, the portable ultrasound device may have standard GSM or CDMA or HSPA or EVDO or LTE network technology paired with a single SIM (nano SIM).

[0043] The housing of the portable ultrasound device is advantageously provided with a transducer array base. In this embodiment, the housing base may include a plurality of arrays of transducer elements padded with a backing layer and a matching layer. The transducer array base, or other housing base, may include at least one sensor selected from the group consisting of, for example, a temperature sensor, a heart rate sensor, a cardiovascular sound sensor, a bowel sound sensor, a sweat analyte sensor, a skin stiffness sensor, and a skin microbiome sensor.

[0044] Advantageously, the multiple arrays of transducer elements are first arranged to direct ultrasonic energy within a predetermined frequency range at an insonation angle Φ to a subcutaneous region of interest of the subject's body as commanded by a controller, preferably including or in communication with a processing block for an analog front end (AFE), a beamformer with front end processing, and a back end processing block. The AFE can be implemented in single chip format with 2, 4, 8, 16, 32 etc. fully integrated chips per channel or in a multi-chip solution per channel. The AFE block can be implemented by a field programmable gate array (FPGA) or ASIC, which is advantageously implemented using a chip(s). An FPGA-based controller that can store and generate pre-programmed digital signals including ultrasonic oscillation settings is optional.

[0045] The beamformer includes two parts, the transmit beamformer has the function of initiating a scan line and generating a time digital pulse string to the transducer elements. The digital pulse string is internally converted to a high voltage pulse for the transducer elements so that they transmit ultrasonic energy within a predetermined frequency range. The receive beamformer has the function of receiving echo signals within a predetermined frequency range from the AFE and collating the data into a representative scan line through filtering, windowing, summing and demodulation. The two beamformers are time synchronized and continuously communicate timing, position and control data to each other. The receive beamformer is also preferably implemented by an FPGA for portable ultrasound devices.

[0046] The back-end processing block preferably includes B-mode, Doppler (preferably pulsed wave Doppler, or most preferably continuous wave Doppler) and color flow processing capabilities that the user of the portable ultrasound device can toggle between. B-mode receives demodulated and compressed scanlines and uses interpolation and grayscale mapping to form a 2D grayscale image from the scanlines generated by the receive beamformer. In this case, the back-end processing block preferably produces images that are ready for use by non-specialized staff when performing cannulation. This may include the use of enhancement techniques such as frame smoothing and / or edge detection.

[0047] Desirably, the screen forming part of the portable ultrasound device is a color display unit, non-limiting examples include LCD, LED, OLED, AMOLED, or transflective with or without memory of pixel display. The screen is preferably compatible with touch screen function and is preferably flat. Subcutaneous, preferably vascular, structures are conveniently displayed on the screen (including 1280x720 pixels, preferably less than 720x480 pixels, more preferably less than 640x360 pixels, and most preferably less than 215x180 pixels) in real time and in a manner that does not require the user of the portable ultrasound device to interpret only the ultrasound image. This is different from the range of operations conventionally performed by ultrasound operators, such as manually adjusting the orientation of the ultrasound probe, manually calibrating the operating field of view, setting gain levels, setting contrast levels, and setting imaging depth or Doppler parameters, all while interpreting an abstracted 2D grayscale (or 2D color Doppler) taken in a single scan line.

[0048] The screen, or the display unit of which it forms part, has one or more of the following properties: preferably lightweight, preferably hydrophobic, preferably oleophobic, and preferably chemically resistant to allow easy sterilization.

[0049] The screen, advantageously with the assistance of a processor, desirably provides an indication of the correct position for inserting a vascular access device in the form of a cannula or similar device. To that end, the on-screen representation(s) may display information including one or more of the depth of the imaged subcutaneous structure and the position of the needle tip inserted into the tissue. The on-screen representation(s) may indicate one or more of the caliber of the imaged subcutaneous structure, e.g., vascular structure, and the position of the needle tip inserted into the tissue. In processing and software indication embodiments such as these, an algorithm may advantageously automatically recognize when a cannula is inserted into a vein and represent that insertion both relative to a single transducer or as a schematic representation of a path segment. For example, in embodiments including a rough venous pathway representation determined from a peak energy signature (either determined from an FFT or PSD), the original peak may become a valley, or alternatively, a "valley-like" shape, such as a square or triangular depression in the energy signature, indicating that the tip of the cannula has interrupted the flow resulting in an interruption in the energy from the flow.

[0050] In another embodiment where B-mode or color Doppler techniques are used, image enhancement techniques can be used to enhance the intensity and acoustic reflection from the needle tip both in the tissue and in the vein, and a bright spot may be depicted to indicate the cannula tip in depth. In this embodiment, the location of the cannula tip within the vein can be used to create a schematic venous pathway representation showing the segment of the vein to which the cannula is directed.

[0051] The processor may be programmed with instructions to calculate a recommended optimal needle gauge and / or insertion angle for accessing a subcutaneous structure, e.g., a vascular structure, imaged by the vascular access device. The processor may be provided with instructions to select a vascular access device (cannula type) based on selected parameters, which may include, for example, the group of vessel diameter, venous pathway length, and intended flow rates for both venous flow or infusion of fluids such as medications.

[0052] As previously mentioned, the path of the vasculature can be determined through interpolation between multiple transducer elements. In embodiments with a rough vein path representation determined from the peak energy signature (either determined from the FFT or PSD), vein diameter can be determined based on characteristic energy-position curve features.

[0053] Automatic feature recognition methods can be used in B-mode or Doppler ultrasound embodiments to automatically determine circular or elliptical objects in the field of view, and the vessel diameter or ellipticity can be automatically calculated by the processor. Based on the vessel diameter or ellipticity, the size of the cannula may be determined by the processor and displayed on the screen.

[0054] The processor can be programmed with instructions for determining blood flow or velocity within the vasculature using the ultrasound data processed by the processor. If the fluid flow rate through the cannula needs to ideally match the venous blood flow rate, the processor is conveniently programmed with instructions for selecting and displaying a recommended cannula depending on the blood flow rate.

[0055] A 3D representation may be provided by the processor and displayed on the screen for both vascular structure and hemodynamic fields, such as, but not limited to, one or more of flow, velocity, pressure, shear stress, turbulence, congestion, pulsatility or stenosis. Measurements such as these may be represented as time dependent, for example in the form of averaged graphs or real-time displays of the magnitude of calculated hemodynamic parameters overlaid on the reconstructed 3D structure. Calculated hemodynamic parameters such as shear stress or turbulence may indicate interruptions in flow due to the insertion of a vascular access device, such as a cannula. Parameters such as these may be monitored to facilitate the cannulation process, by determining, for example and not by way of limitation, when to recommend replacement of the vascular access device, and / or to assess the effectiveness of flushing the vein with saline, keeping the vein open, and otherwise managing the patency of the vein.

[0056] The portable ultrasound device can be used to determine the vascular structure or vessel that is most suitable for the selected drug infusion. In general, larger vessels, such as those with better flow in the antecubital fossa of the forearm, are more suitable for iron or potassium infusion. Vessels such as these tend to pass through the infusion therapy and experience less irritation and damage compared to smaller, more superficial vessels, which have a much slower flow. The processor can process the structural characteristics of the vessels and the measured hemodynamic parameters to determine the vessel that is best suited for delivery of the selected infusate.

[0057] Mechanical indication for cannulation may also be provided when the portable ultrasound device housing is provided with a base plate with a needle guide to guide the placement of the cannula. The needle guide may include a notch, preferably a triangular or rectangular extrusion cut into the front face of the base, but most preferably a spherical cut. To limit movement of the needle along the insertion face, the notch is preferably less than 3 mm in size, more preferably less than 1.5 mm in size.

[0058] The screen, or the display unit of which it forms a part, may be hinged or flexed to move between a viewing position at an acute angle to the housing and a position in which the screen can be flattened on the housing of the device, thereby reducing the volume consumed while allowing desirable ergonomics for the user during use. This is particularly useful in paramedical, agricultural, military or other technical field applications where equipment space is limited. The portable ultrasound device may be configurable to allow the image to be displayed on another device, such as a computer or smartphone screen. However, this is not required and no additional device is required to display the image, as the screen is provided as part of the housing of the portable ultrasound device of the present invention.

[0059] The base of the housing of the portable ultrasound device is conveniently placed in contact with the patient's skin, so that the base has a contact area with the patient's skin. The base preferably has a curved shape, and is optionally concave away from the skin surface, allowing it to be conveniently placed near an extremity, for example an upper extremity, such as a forearm, of a human subject. The base of the portable ultrasound device is preferably 150 cm 2 Less than 60cm, preferably 2 More preferably, the surface area of ​​the base is less than 50, 45, 40 or 35 cm 2 Less than 30cm, most preferably 2 or 25cm 2 is less than.

[0060] Portable ultrasound devices are also advantageously lightweight, with the device preferably massing no more than 400g, preferably less than 350g, more preferably less than 200g, and most preferably less than 100g or even less than 75g.

[0061] Preferably, the portable ultrasound device includes memory for storing images and other data such as patient and location data, as needed. Preferably, an internal device storage (conveniently microSDXC) of less than 512 GB capacity, more preferably less than 256 GB or 128 GB capacity is installed. When full, the storage can be simply deleted or transferred to a reference backup drive by the means described above. Instead of or in addition to the device's on-board storage, the storage may be communicated remotely between the portable ultrasound device implemented as described above and the storage device. Data communicated in this manner may be encrypted depending on the application.

[0062] Data obtained from or using the portable ultrasound device can be securely transmitted to a cloud-based or other system operated by the community organization that utilizes it, which may store electronic medical records or information for insurance purposes. In an advantageous embodiment, the portable ultrasound device can be used for pathology collection or blood sampling applications, as blood test results can be automatically tracked and updated from the time of collection.

[0063] A handheld ultrasound scanner, conveniently in the form of a cylindrical pipe, can be connected to the housing of the portable ultrasound device, for example, via a USB port provided on the housing. The scanner desirably has Doppler capabilities (preferably pulsed wave Doppler or most preferably continuous wave Doppler) and therefore has the ability to image subcutaneous structures, especially vascular structures, when the base of the device is too large for the surface of the skin of the subject to be imaged, for example, neonatal, pediatric, or medium to small sized animals, including but not limited to dogs, cats, rodents, birds or rabbits. The scanner can also be useful when imaging is required within tight corners, grooves or localized areas of physiological interest within the subject. Preferably, the scanner is 35 cm or less in diameter. 3 less than 25 or 20 cm 3Volume less than 15cm, most preferably 3 Preferably, the skin contact base of the scanner is less than 1 cm 2 An area of ​​less than 0.75 cm is preferred 2 or 0.6 cm 2 and most preferably an area of ​​less than 0.5 cm 2 Preferably, at least one of the processing, storage and display of images is performed using a portable ultrasound device housing that serves as a base unit for an attached handheld scanner.

[0064] The portable ultrasound device may include a tracking device reader, such as a QR code or barcode, that allows for scanning of the tracking device containing pertinent data, such as standard electronic patient data, including, but not limited to, one or more of: patient ID, age, sex, major patient history, ultrasound imaging location, ultrasound imaging time, and reason for ultrasound imaging. For example, barcodes are commonly used to store such data in hospitals, clinics, medical collection or blood collection centers, and other clinical or non-clinical settings.

[0065] Conveniently, the housing also contains a power source, such as a rechargeable battery, for powering the portable ultrasound device. Connection to other power sources is possible. The housing may also contain a DC / DC converter to step up the battery voltage, for example up to a voltage of 200 volts, to enable the controller to excite the transducer elements to transmit ultrasonic energy.

[0066] In another aspect, the present invention provides a method for imaging a subcutaneous structure of a subject, the method comprising: non-invasively transmitting ultrasound energy within a predetermined frequency range into a body of a subject via a plurality of arrays of transducer elements included in a portable ultrasound device applied to a location on or proximate to the body of the subject, each array of the plurality of arrays of transducer elements being arranged in parallel, each transducer element including a transmit transducer and a receive transducer, the plurality of parallel arrays of transducer elements enabling imaging of subcutaneous structures in a plurality of transverse and lateral planes; receiving echo signals within a predetermined frequency range from the subject's body after transmitting ultrasonic energy; processing the received echo signals by a processor; generating an image representing a subcutaneous structure of the subject on a screen forming part of the portable ultrasound device; Includes.

[0067] As mentioned above, the portable ultrasound device is conveniently contacted with a subject, more particularly an extremity such as the forearm of a human patient. Advantageously, the user deploys and secures the portable ultrasound device in place with the releasable fastening means without having to manually hold it in place. The releasable fastening means may be a single or multiple use strap, band or belt, preferably made of common medical materials such as textile or silicone. Preferably, the textile material is compatible with standard sterilization and cleaning mechanisms, although it may be disposable. Hypoallergenic non-latex based materials are suitable for disposable fastening means.

[0068] In another embodiment of the fastening attachment method, the straps can be in the form of a sleeve, wrap, or cuff that is attached to the device and contacts a larger surface area of ​​the limb.

[0069] The fastening means desirably allows for adjustment of the fastening force, for example by an adjustable clasp. As with commonly used tourniquets, the fastening force is advantageously selected to increase intravascular pressure, thereby engorging the vessel, improving visibility and reducing blood flow velocity to a pre-programmed extent as extracted by a digital processing algorithm.

[0070] The portable ultrasound device is then positioned near the user and optionally fastened to assist in identifying the optimal location of the vascular structure, typically a vein, for cannulation. As mentioned above, the base plate of the portable ultrasound device is conveniently provided with a needle guide that guides the placement of the cannula by aligning the image of the selected vein with the needle guide. The needle guide may include a notch that is aligned between the notch and the image of the selected vein. This feature facilitates selection of the correct orientation of the portable ultrasound device without guesswork or excessive manual adjustments.

[0071] The user can then proceed to insert the needle or cannula, aided by the needle guide and images displayed on the screen, which serve to guide the user to the optimal spot for cannulation.

[0072] A consumable acoustically conductive patch may be applied to the base of a portable ultrasound device prior to use. Preferably, the consumable double-sided acoustically conductive patch is conveniently attached to the base of the portable ultrasound device by a medically compatible removable adhesive or double-sided adhesive tape. The adhesive-attached end of the consumable patch is conveniently attached to the base of the device. A portion of the consumable patch can be peeled away to expose a medically sterile gel contained within the patch, intended to reduce airborne ultrasound conduction, which is normally a source of signal noise and signal loss, while maintaining a sterile field necessary for venipuncture. Preferably, the volume of sterile gel within such a preferred patch is 120 cm. 3More preferably, the volume of gel in such preferred patches is less than 110 cm 3 or 100cm 3 Less than 90cm, but most preferably 3 is less than.

[0073] A consumable conductive patch, preferably including an external sterile gel pocket, fits the form factor of the portable ultrasound device and may be provided in the form of, for example, a custom sleeve, envelope or pocket. Such a patch may conveniently have a medically compatible removable adhesive applied thereto and may cover the portable ultrasound device. The external sterile gel pocket may conveniently be exposed by a peeling means as described above.

[0074] The portable ultrasound device and imaging method described above does not require any dedicated needles or syringes for cannulation, allowing the use of any conventional vascular access device, such as any form of catheter.

[0075] The described portable ultrasound device is self-contained, conveniently handheld, low-cost and simple in construction. In contrast to conventional ultrasound equipment, the portable ultrasound device of the present invention can be easily positioned in the correct orientation to determine subcutaneous structures, e.g., for cannulation, and does not require complex adjustments by the physician or modular and separate system components consisting of a scanning probe, a processing unit and a monitor. The major components, including the transducer elements, processor and circuitry, and a screen, are packaged in a single housing. The portable ultrasound device is conveniently lightweight and can be used to assist in cannulation and other ultrasound imaging of subcutaneous structures by a wide range of personnel, including medical personnel and paramedical personnel without formal specialized training, such as, but not limited to, registered nurses, laboratory phlebotomists, therapists and researchers.

[0076] Further features of the portable ultrasound device and subcutaneous imaging method of the present invention are described in more detail in the following description of a preferred, non-limiting embodiment thereof. This description is included for the purpose of illustrating the present invention only. It should not be understood as a limitation of the broad overview, disclosure or description of the invention as set forth above. The description is made with reference to the accompanying drawings. [Brief description of the drawings]

[0077] [Figure 1] 1 shows a diagrammatic representation of a portable ultrasound device of one embodiment of the present invention in contact with the forearm of a human patient. [Diagram 2] FIG. 2 is a block diagram of the portable ultrasound device of FIG. 1. [Figure 3a] 2 shows a side cross-sectional view of a housing of the portable ultrasound device of FIG. 1. [Figure 3b] 1A-1C show top and side views of the transducer base of the portable ultrasound device of FIG. 1 and the arrangement of transmitter and receiver crystal arrays forming the transducer element array. [Figure 4] FIG. 2 is a flow diagram of one embodiment of a method for imaging subcutaneous structures of the present invention. [Diagram 5] 2 shows a schematic diagram of transducer elements within the base of the portable ultrasound device of FIG. 1. [Figure 6] 5 shows the output of the method of FIG. 4 on an integrated display. [Figure 7a] 2 is a schematic diagram of the base of the portable ultrasound device of FIG. 1 in contact with a conductive material on the skin of a patient. [Figure 7b] FIG. 7b is a schematic diagram of the various components of the single transducer element shown in FIG. 7a that are involved in scanning a blood vessel. [Figure 8] FIG. 2 is a schematic diagram illustrating converting an amplitude versus time signal into amplitude versus frequency data by a Fast Fourier Transform (FFT) according to one embodiment of a method of the present invention. [Figure 9] FIG. 2 is a schematic diagram illustrating differentiation of arterial and venous structures by an energy signal based algorithm, according to one embodiment of the method of the present invention. [Figure 10] 1(a) and (b) are schematic diagrams illustrating the determination of the depth of a vascular structure by an energy signal-based algorithm, according to one embodiment of the method of the present invention. [Figure 11] 1 is a schematic diagram illustrating vascular structure characterization by B-mode imaging, according to one embodiment of the method of the present invention. [Figure 12] 1 is a schematic diagram showing vascular structure characteristics by B-mode and color Doppler imaging according to one embodiment of the method of the present invention. [Figure 13] FIG. 2 is a schematic diagram illustrating the estimation of blood vessel diameter based on an energy signal according to an embodiment of the method of the present invention. [Figure 14] 1 is a schematic diagram illustrating vascular structure characteristics from ultrasound imaging using a compression method, according to an embodiment of the present invention;

[0078] FIG. 1 shows a self-contained portable ultrasound device 109 that is used to detect subcutaneous structures, here peripheral veins 101 at a depth of 2-3 cm below the skin of a patient's forearm 100, by continuous transmission and reception of ultrasound energy for the purpose of assisting in cannulation. The subcutaneous structures may be at a shallower depth, e.g., 5 mm, as determined by the dead zone of the portable ultrasound device 109. The portable ultrasound device 109 is self-contained, handheld, low-cost, and of simple construction, and excludes excess circuitry required for whole-body imaging that is not required for vascular imaging to reduce size and processing requirements. The portable ultrasound device 109 can be used by personnel (usually junior doctors and nurses) who do not have expertise in ultrasound imaging and who perform the majority of the cannulations.

[0079] In contrast to conventional complex ultrasound equipment systems, such as those used for whole body imaging, the portable ultrasound device 109 does not include multiple user controls or require modular and separate system components consisting of a scanning probe, an external processing unit and a monitor along with the requirement to fine-tune several ultrasound equipment parameters (such as gain) as understood for conventional ultrasound imaging equipment in the medical ultrasound imaging field, but rather all major components including the ultrasound transducer elements 102, the processor 350 including the controller 250 and processor blocks 208-210, the power supply (FIG. 2: 202) and the integrated display unit 103 with screen 104 are packaged on-board the portable ultrasound device 109 within a single housing 110, making it easier to use than current options.

[0080] Digital processing algorithms can abstract and interpret the ultrasound images by simplifying conventional B-mode or color Doppler (preferably pulsed wave Doppler or most preferably continuous wave Doppler), providing a two-dimensional image of the vein 101 candidate for cannulation on a screen 104 that forms part of the housing 108 and is easier to view than a conventional adjacently located screen. Rather than reconstructing the raw signals (amplitude and frequency) into a grayscale image (B-mode) with mapping of the corresponding signal receiving transducer crystal positions, the raw signals (and corresponding positions) are simply processed by frequency domain signal processing and differentiation methods, for example by pulsatility metrics as described above. A pulsatility index defined as (systolic minus diastolic) divided by the mean blood flow velocity in the vessel can be used in this embodiment, although other metrics are available as described below.

[0081] Frequency domain signal processing and differentiation methods have been shown to require less computation for B-mode image reconstruction and less storage (both temporary and permanent), simplifying hardware requirements, although the user may choose to visualize and store raw images (B-mode) of subcutaneous structures if desired using the display mode switch 106.

[0082] The integrated display unit 103, screen 104, power switch 105, and display mode switch 106 represent a simple user interface dedicated to the primary functions of the portable ultrasound device 109. The configuration of the controller 250 for the portable ultrasound device 109 and the processor blocks 208-210 of the processor 350 does not require the user to be provided with the ability to access additional features (such as gain) or adjust the field of view for gain or contrast adjustment. If adjustment of such settings is required, such adjustments can be made by an authorized user, such as a maintenance engineer or repairman. This does not typically occur or need not occur during a cannulation procedure.

[0083] 2, 3, 4, 5, 6 and 8, in summary, the portable ultrasound device 109, through the selection of the transmission signals by the controller 250 and the processing of the received echo signals by the processor 350 and its associated processor blocks 208-210, can locate the peripheral vein 101 in the lateral direction 308, 309 (as shown in FIG. 3b) and at various selected depths from 5 mm to 2-3 cm, up to 7-15 centimeters in the case of exceptional central vessels, and the dedicated processor performs the signal processing 203, 205, 206 and the digital processing block 208 to display a simplified longitudinal representation 104A of the peripheral vein 101, which can then be shown in real time on the screen 104 of the integrated display unit 103, with the path of the vein 101 being updated and displayed as the portable ultrasound device 109 moves over the skin surface of the patient's forearm 100.

[0084] The portable ultrasound device 109 allows for the differentiation of peripheral veins from arteries. In one embodiment, the digital processing block 208 includes the execution of algorithms embodied in electronic instructions that allow for such differentiation through measurements of pulsatility. Veins are typically much less pulsatile than arteries, if at all. Suitable pulsatility metrics for measurement here and input into such algorithms include pulsatility index as described above determined from velocity waveforms (if determined in the time domain) or high amplitude at low frequencies (if determined in the frequency domain after a fast Fourier transform (FFT) as shown diagrammatically in FIG. 8). The digital processing block 208, in an embodiment, can prevent any representation of arteries appearing on the screen 104 of the integrated display unit 103.

[0085] 2 depicts a system block diagram of a portable ultrasound device 109. The device 109 is provided with functionality to control and process the transmission and reception of ultrasound waves from the transducer crystal array 102, and the display or storage of imaging data. Excess circuitry required for whole body imaging, but not specifically required for vascular imaging, is purposely omitted from the system to reduce size and processing requirements and ease of use of the portable ultrasound device 109.

[0086] 2 shows a field programmable gate array 205 in a controller block 250, which acts as a microcontroller for the portable ultrasound device 109, storing and generating pre-programmed digital signals containing ultrasound oscillation settings, and then converting the digital signals to analog signals using a digital-to-analog converter (DAC) 204, where noise 203 is filtered. In this embodiment, the filtered signal is sent to an ultrasonic waveform generator 201, which generates and sends a prime signal to a diplexer 200 for frequency domain multiplexing. It will be understood that the FPGA 205 can be replaced with a chip-based controller, such as an ASIC chip-based controller, or other acceptable alternatives.

[0087] In this embodiment, the ultrasonic waveform generator 201 may be powered by a high voltage power supply 202 that may be toggled on or off using the user interface 105. The array of transducer elements 102 thus transmits and receives ultrasonic signals to and from the subject, respectively, at a predetermined frequency, for example in the range of 3-8 MHz, with 7 MHz chosen here (this compares with the wide frequency range of 2-18 MHz for typical diagnostic ultrasound scanners, see "Application of Ultrasound in Medicine" at www.ncbi.nlm.nih.gov>pmc>articles>PMC3564184).

[0088] The received signal from the transducer crystal array 102 is amplified using a low noise amplifier 207, filtered 203, and returned as a digital signal to the FPGA microcontroller 205 using an analog to digital converter (ADC) 206. The received signal is processed on-board the portable ultrasound device 109 by a processor block 210 using digital instructions or algorithms described below. Due to the complexity of the calculations, parallel processing is performed in the processor block 210.

[0089] While on-board processing by the processor 350 is most preferred, it is possible to perform the processing using a cloud-based system such as that provided by Amazon AWS, thereby reducing processing constraints on the portable ultrasound device 109 by wirelessly transmitting the data to the device 109, processing it, and returning it. In this example, trivial and junk signals are automatically filtered out, and the Doppler frequencies of non-trivial signals are calculated and stored in the temporary sampling memory 209.

[0090] The digital processing block 208 executes instructions in a manner described below to convert the raw signal into a simplified vein representation 104 A for display on the screen 104 of the integrated display unit 103 .

[0091] A display mode switch 106 is toggled to switch between a simplified venous representation 104A or a conventional B-mode or color Doppler image.

[0092] Data related to the ultrasound imaging process of the portable ultrasound device 109 is stored in the device memory 211 or transferred to another device 212 via reversible USB-C, Bluetooth 5.0, or wireless internet in the form of standard WiFi, dual band, Wi-Fi Direct or hotspot.

[0093] 3a and 3b show an ultrasonic transducer crystal array 102 disposed in a base 102A of a housing 110 of a portable ultrasonic device 109 for transmitting and sensing reflected waves of a pulsed ultrasonic signal. In this case, the base 102A is composed of individual transducer elements 300 padded with a backing layer 302 and a matching layer 301. The transducer elements 300 are such that at least one emitter or transmitter crystal 705 and one receiver crystal 707 per transducer element 300 are separated by a bulkhead 706 having acoustically insulating properties, although other configurations of the transmitter crystals 705 and receiver crystals 707 are possible. The transducer elements 300 can include piezoelectric materials such as PZT, or films, PVDF, PMN-PT, PMN-XX, PIN-PMT-XX, where XX represents some derivative of the material, such as silicon, metal, CMUT, MEMS, NEMS, etc. The transducer elements 300 are advantageously selected from the group consisting of capacitive micromachined ultrasonic transducers (CMUTs), piezoelectric micromachined ultrasonic transducers (PMUTs), and similar configurations that use semiconductor technology to fabricate the transducer elements 300 across the transducer crystal array 102.

[0094] The transducer element 300 is connected to an electronics package 303 that also includes an on-board battery. In this example, the electronics package 303 is surrounded by a heat exchange and dissipation mechanism 305, which is surrounded by an acoustic insulation layer 304.

[0095] The portable ultrasound device 109 includes multiple linear transducer arrays 300A, here four arrays, oriented parallel to one another as shown in FIG. 3b and carried by the housing 110 of the device 109. The multiple parallel transducer arrays 300A provide the ability to image the vein 101 in multiple cross-sectional planes to display the external location of the blood vessel on the screen 104.

[0096] The parallel transducer arrays 300A are placed at an insonation angle Φ, as shown in FIG. 3b, where 10<Φ<60, to ensure that the Doppler effect is captured and not nullified. This angular configuration is fixed, eliminating the need for the user to manually adjust the operational field of view and imaging angle. In this example, the parallel transducer arrays 300A are separated along the horizontal axis 309 by a distance ξ selected to minimize interference and maximize the scanning window 708. As mentioned above, ξ may be in the range of 5-30 mm. In this embodiment, a spacing of 15 mm is provided between each parallel array 300. This covers a region of interest of 45 mm. Spacing greater than 30 mm would make the portable ultrasound device 109 larger than desired for use in cannulation procedures.

[0097] 4 shows a flow diagram of the ultrasound signal acquisition mode used to image the vein 101 for cannulation. The FPGA microcontroller 205 applies pulses continuously throughout the operation, resulting in continuous wave operation (step 400) starting from the emitter crystal 705 of the first transducer array at the boundary (T(y=0) at position x=0), shown in FIG. 5 at 503 of the first transducer 500. The reflected ultrasound, when received by the receiver crystal 707, is converted to a voltametric signal (step 401) and then filtered (step 402) to remove trivial signals that enter the sampling memory 403.

[0098] The Doppler frequency and corresponding coordinates are temporarily stored in a sampling memory (step 403), and then a fast Fourier transform (FFT) is applied to determine the received frequency and calculate the frequency shift (Doppler shift). This Doppler shift can help distinguish between the vein 101 and the artery 101A based on the energy signal determined from the frequency shift, with the positive waveform 505 representing flow towards the transducer receiving crystal 707 (i.e. blood flow in the vein or vice versa) (step 404). This characteristic can be referred to as the venous signature of the vein 101, which is stored and / or displayed on the screen 104 as the venous pathway 104A (step 405).

[0099] The Doppler shift can also be used to calculate blood flow or velocity according to the following formula: v = (frequency shift * speed of sound) / (2 * transducer frequency * (cosine (ultrasonic irradiation angle Φ)) Flow rate = velocity * cross-sectional area, Cross-sectional area is 0.25*pi*diameter 2 , the diameter can be calculated, for example, as described below with reference to FIG.

[0100] The next transducer crystal 705 is pulsed and the process of steps 402-406 is repeated until the nth crystal on the first transducer 502 is reached as shown in FIG. 5. As the first transducer 500 cycles, an inter-transducer cycle begins (step 407) until the nth transducer 501 is reached. The outward coordinates x, y of each vein signature 104A for each transducer element 300, 501, 502 are reconstructed in real time in the outward direction on the screen 104 and connected by vein blueprint lines to form an image 104A of the vein 101 as shown in FIG. 6 (step 408). This image 104A can be continuously updated on the easily viewable screen 104 as the portable ultrasound device 109 is operated by the user.

[0101] Still referring to step 404, alternatively, the processor blocks 208-210 can be programmed with instructions to use the energy signature 504 to distinguish between arterial and venous structures and to determine the location of the vein 101 below the contact area between the patient's skin and the ultrasound transducer 705, 707. The energy signature 504 may be determined from a frequency domain representation 405 of the raw signal determined by a Fast Fourier Transform (FFT) of the continuously acquired current signal 404 as shown by FIG. 8, as shown diagrammatically in FIG. 9, or more preferably from a power spectral density (PSD) calculated from the sampled signal. This energy signature is preferably the amplitude (Amp) of the dominant signal frequencies, or alternatively the sum of the amplitudes of the dominant frequencies, or the sum of the squares of the amplitudes of other frequencies. More preferably, the energy is the area under the FFT or PSD distribution. Alternatively, the energy may be the ratio of the amplitude to the area under the distribution, or the ratio of the sum of the amplitudes (or the sum of the squares of the amplitudes) to the area under the distribution.

[0102] 9, as described above, the positive waveform 505 acquired for each of the receiver crystals 510 and 707 and the receiver crystals in the transducer element array 300A represents points along the vein 101, with the points having positions that may remain the same or may vary, as shown in the energy-position trace or waveform 504 and the waveform 507 as shown in FIG. 10 for the artery 101A. The point 505A, or the peak of the waveform 505, represents the approximate center of the vein 101 at a given point where the maximum energy is typically in the center of a healthy vasculature. As shown in FIG. 10, the negative waveform 507 represents points along the artery 101A, with the point 507A, or the peak of the waveform 507, represents the approximate center of the artery 101A at a given point where the maximum energy is typically in the center of a healthy vasculature. The processor 350 displays these points on the screen 104, so that the path of the vein 101 is shown as a line 104A.

[0103] The processor 350 may use the difference between the positive waveform 505 (vein 101) and the negative waveform 507 (artery 101A) to enable differentiation between the vein 101 and the artery 101A. The venous path is shown as line 104A and the arterial path is shown as line 104B.

[0104] The processor 350 also estimates the depth of the vein 101 below the skin by executing the above-described energy signature-based instructions, as schematically shown also by FIG. 10. For the vessel diameters d1 - d4 calculated using the method described below, a characteristic curve can be inferred that correlates the energy magnitude for different vessel diameters d1 - d4 (d1 < d2 < d3 < d4), as shown in FIG. 10(b), where larger vessels have higher magnitude energy signatures, with the vessel structure or the depth of the vein 101. This depth can be determined as a value of several millimeters or centimeters below the skin, or through color weighting by depth magnitude, or through other visual representations such as 3D perception of shallowness or depth, and can be displayed on the screen 104. Thus, the processor 350 enables the calculation of the depth of the vein 101 or artery 101A below the skin without requiring B-mode cross-sectional image reconstruction.

[0105] Instead of the above approach, as schematically shown in FIG. 11, B-mode imaging can be performed for each of the transducers 510, 707 in the array. Structural metrics (such as diameter, compression ratio (as indicated), and other curve features) can be calculated by the processor 350 and used to distinguish the artery 101A from the vein 101 in the state where the paths of the vein 101 and artery 101A are displayed on the screen 104 as respective lines 104A, 104B. For this purpose, machine learning techniques, including for example the use of convolutional neural networks, can be used to classify and identify veins and arteries according to a training dataset provided by an experienced ultrasound user population. In B-mode or color Doppler representation, the depth of the vascular structure can be directly measured and displayed on the screen 104 of the ultrasound device 109.

[0106] In another embodiment of an algorithm for distinguishing arteries or veins, as shown diagrammatically in FIG. 12, B-mode and color Doppler images 510 are acquired and automated computer vision techniques are used to identify flow away from or toward the transducer 510, 707 (or flow away from the heart representing the artery 101A and flow toward the heart representing the vein 101). Color Doppler represents the (usually venous) flow toward the transducer as shades of blue 515 whose intensity represents the magnitude of velocity, and the (usually arterial) flow away from the transducer as shades of red 520. Thus, the artery 101A and vein 101 can be easily distinguished by automated computer vision techniques that distinguish between colors. In the B-mode or color Doppler representation, the path and depth of the blood vessels can be directly measured and displayed on the screen 104 of the ultrasound machine 109 as venous path 104A and arterial path 104B.

[0107] Advantageously, the processor 350 recognizes that in an energy signal based algorithm such as described with reference to Figures 9, 10 and 13, the peaks of the energy signature form part of a parabolic or Gaussian-like distribution, and the start 530 and end 535 of such distributions can be used to estimate the diameter d of the vein 101, particularly in the lateral direction. As shown in Figure 13, the method of determining the start 530 or end 535 involves the processor 350 calculating the slope at every point along the energy curve 520, calculated by taking the ratio of the energy change between successive data points to the change in position. The start 530 may be identified, for example, when the slope increases rapidly from a low value (e.g., between -0.25 and 0.25) to a large value (e.g., between 0.75 and 1). Conversely, the end 535 may be identified as a change in slope from a large negative value (e.g., between -0.75 and -1) to a low value (e.g., between -0.25 and 0.25). Compared to structural analysis of B-mode cross-sectional images, which require either manual measurement of diameter or automatic feature recognition (through artificial intelligence constraints or machine learning methods) for diameter measurement, the energy curve method as described above allows for a more efficient and more objective way of determining diameter. Furthermore, automatic diameter calculation does not require a training data set (with labels), although machine learning models can be trained to optimize the identification of start points 530 and end points 535.

[0108] In another embodiment of a method for distinguishing between an artery or a vein, ultrasound data is acquired by the ultrasound device 109 both with and without mechanical compression of the subcutaneous blood vessels by applying an external force to the housing on the skin. This method is illustrated in Figure 14. The different vessel wall properties of veins (which are compressible but not muscular and are inelastic) and arteries (which are muscular and less compressible and more elastic than veins) can be exploited to distinguish between arteries and veins by measuring the changes during compression.

[0109] In one embodiment of the compression method, the peak energy signature (determined from either the FFT or the PSD) changes with compression, as shown diagrammatically in FIG. 14. In particular, the positive peak 101C (representing the flow of the vein 101 as it flows towards those of the receiver crystals 510, 707 and the transducer array 300A) flattens out with compression, while the negative peak 101D (representing the flow of the artery 101A as it flows away from the transducer) only shows a decrease in magnitude while maintaining its directionality (the negative peak represents the flow away from the transducer). The drop (towards zero) of the characteristic venous peak 101C and the linear decrease in the magnitude of the artery 101D are calculated, preferably by absolute value measurement, or more preferably by characteristic curve analysis to distinguish between arteries and veins. Alternatively, the diameter d of the vasculature can be determined from the energy waveform 504 as described above, so that the change in the diameter from before compression to after compression, i.e., from u1 to u2 and v1 to v2, can be calculated to estimate the change in size due to compression of the vasculature. Compared to arteries, larger deformations are expected in veins (e.g., equivalent to 90-100% of the original diameter). This method also results in the display of a venous pathway 104A and an arterial pathway 104B on the screen 104 of the ultrasound device 109.

[0110] In another embodiment of the compression method utilizing B-mode or color Doppler mode, automatic feature edge recognition can be used to identify circular or elliptical objects and measure their maximum vertical chord length. Circular or elliptical objects can be identified as arteries or veins, respectively, because the reduction in maximum vertical chord length is greatest for veins compared to arteries (e.g., equivalent to 90-100% of the original diameter).

[0111] In another embodiment of both compression methods described, the compressibility of the vein, either by energy drop or chord length reduction, can be used to indicate the structural integrity of the vein 101, with greater resistance to compression indicating greater stiffness (structural integrity). Additionally, the recovery of the structure after compression can be used to determine the degree of plastic deformation, which can then be used to determine elasticity. Selecting a structurally stable vein through inferences of both stiffness and elasticity is a critical factor for cannulation as well as success during cannulation (no dislodgement, no extravasation).

[0112] As mentioned above, the automatic feature recognition method can be used in B-mode or Doppler ultrasound embodiments to automatically determine circular or elliptical objects in the field of view, and the diameter or ellipticity of the vessel can be automatically calculated by the processor. Based on the diameter or ellipticity of the vessel, the size of the cannula may be determined by the processor and displayed on the screen. For example, if the vein diameter of an adult is greater than 1.3 mm, the algorithm most preferably recommends a green cannula (18G, 1.3 mm diameter), a pink cannula (20G, 1.1 mm diameter), or a blue cannula (22G, 0.9 mm diameter). Orange (14G, 2.1 mm diameter) or gray (16G, 1.8 mm diameter) may also be recommended for larger veins (greater than 1.8 mm), but these are all recommended at very high infusion flow rates (240 mL / min for orange and 180 mL / min for gray) for trauma, resuscitation, rapid blood transfusion, rapid fluid replacement, or surgery.

[0113] Calculated hemodynamic parameters such as shear stress or turbulence may indicate interruption of flow due to the insertion of a vascular access device, e.g., a cannula. Parameters such as these may be monitored to expedite the cannulation process by determining, by way of example and not limitation, a recommended time for replacement of the vascular access device, and / or to evaluate the effectiveness of flushing the vein with saline to keep the vein 101 open. For example, the processor 350 may calculate and display the blood flow rate on the screen 104 and use this information to manage the cannulation. The procedure may show stasis on the screen 104, which may occur around the cannula tip when a recirculation (stasis) zone is formed, for example, at 10 mL / h saline flow, thus blocking the tip and reducing the patency of the device. Preferably, 20 mL / h indicates a reduction in stasis and a vein patency score may be calculated. Most preferably, 30-40 mL / h saline has been shown to be most effective for a wider range of venous flow rates and peripheral vein sizes. However, based on the patient's needs, as determined by factors such as hydration, difficulty in access, or bruising, a greater flow load of more than 40 mL / h may be displayed on the screen 104 of the ultrasound machine 109.

[0114] The use of the portable ultrasound device 109 is described below.

[0115] As a user moves the portable ultrasound device 109 above the skin of a patient's forearm 100 to find a venous pathway (determined as vein 101 through use of the device 109), the user aims to align the simplified longitudinal representation 104A of the vein 101 obtained with the notch on the base 102A (preferably using other procedural data or recommendations as described above).

[0116] 7 shows an example in which a disposable double-sided acoustically conductive patch 701 is attached by a user to the base 102A of the device 109, preferably with a medically compatible removable adhesive or double-sided sticky tape. The adhesive-attached end of the acoustically conductive patch 701 is attached to the base 102A of the portable ultrasound device 109. The opposite end of the acoustically conductive patch 701 can be peeled back to expose a medically sterile gel contained within the patch 701, intended to reduce airborne ultrasound conduction, which is normally a source of signal noise and signal loss, while maintaining a sterile field required for cannulation.

[0117] Referring again to FIG. 1, once aligned, the user deploys the releasable fastening means 107 to secure the portable ultrasound device 109 in place on the patient's forearm 100. The fastening means 107 can be a single or multiple use strap or band or belt, which can be made of common medical materials such as fabric or silicone, with an adjustable clasp to adjust the fastening force. The fastening force can be similar to that produced by commonly used tourniquets and can be required to increase intravascular pressure, engorging the vessel, improving visibility, and reducing blood flow velocity to a pre-programmed extent as extracted by the digital processing algorithm 208.

[0118] The user can then conveniently advance the needle or cannula to be inserted through the insertion notch 310 and into the base 102A of the portable ultrasound device 109 without having to hold it in place. Thus, the simplified longitudinal representation 104A of the peripheral vein 101 generated by the processor 350, and in particular the processor blocks 208-210 as described above, guides the operator to the optimal spot for needle insertion with respect to the imaged pathway 104A of the peripheral vein 101, to the benefit of both the user and the patient.

[0119] The described portable ultrasound device 109 is self-contained, conveniently handheld, low-cost, and simple in construction. In contrast to conventional ultrasound equipment, the portable ultrasound device of the present invention does not require modular and separate system components consisting of a scanning probe, a processing unit, and a monitor. The major components, including the transducer elements, the processor and circuitry, and the screen, are packaged in a single housing. The portable ultrasound device 109 is conveniently lightweight and can be used to assist in venipuncture or cannulation and other ultrasound imaging of subcutaneous structures by a wide range of personnel, including medical personnel and paramedical personnel without formal specialized training, such as, but not limited to, registered nurses, laboratory phlebotomists, therapists, and researchers.

[0120] It will be understood that modifications and variations may be made to the portable ultrasound device and method for ultrasound imaging of subcutaneous structures that may be apparent to one of ordinary skill in the art in view of this disclosure, and such modifications and variations are deemed to be within the scope of the present invention.

Claims

1. 1. A portable ultrasound device for non-invasively imaging selected subcutaneous structures within a subject, comprising: (a) a housing; (b) a plurality of arrays of transducer elements arranged in parallel at an oblique angle, each array including a transmit transducer and a receive transducer, positioned within the housing for sequentially transmitting ultrasonic energy within a predetermined frequency range toward a body of a subject and sequentially receiving echo signals within a predetermined frequency range from the body of the subject after reflection of the ultrasonic energy, the plurality of arrays enabling imaging of subcutaneous structures in a plurality of transverse and lateral planes; (c) a controller for operating the multiple arrays of transducer elements in a continuous wave Doppler mode, the controller in communication with a processor for processing echo signals received from the multiple arrays of transducer elements; (d) a screen for displaying an image of the subcutaneous structure, the screen forming part of the housing, the processor being configured to process echo signals returning from the subcutaneous structure to selectively generate an interpretable image of the subcutaneous structure of the subject; and 13. An ultrasound device comprising:

2. The ultrasound device of claim 1 , wherein the subcutaneous structure is a vascular structure, optionally a vein.

3. 3. The ultrasound device of claim 1 or 2, wherein the multiple arrays of transducer elements are spaced apart from one another by a distance ξ along a transverse axis selected to minimize interference and maximize a scan window, optionally ξ being between 5 mm and 30 mm.

4. 10. The ultrasound device of claim 1, wherein the multiple arrays are positioned at an insonation angle Φ where 10<Φ<60.

5. 5. The ultrasound device of claim 4, wherein the screen, with the assistance of the processor, provides an indication of the correct location for insertion of a cannula or similar device, and one or more representations on the screen optionally display information including one or more of the depth of the imaged subcutaneous structure and the location of a needle tip inserted into the tissue.

6. 6. The ultrasound device of claim 5, wherein a 3D representation is provided for both vascular structure and hemodynamic fields, optionally for one or more of velocity, pressure, shear stress, turbulence, congestion, pulsatility and stenosis.

7. 7. The ultrasound device of claim 6, wherein the processor is programmed with instructions to distinguish between arterial and venous vasculature based on a power spectral density (PSD) calculated from optionally sampled ultrasound signals.

8. 5. The ultrasound device of claim 4, wherein the processor determines at least one of a depth and a dimension of a subcutaneous structure below a contact area of ​​the ultrasound device with the subject's body based on processing of sampled ultrasound signals.

9. 1. A method for imaging a subcutaneous structure in a subject, comprising: non-invasively and continuously transmitting ultrasound energy within a predetermined frequency range into the body of the subject in a continuous wave Doppler mode via a plurality of arrays of transducer elements included in a portable ultrasound device applied to a location on or proximate to the body of the subject, wherein each array of transducer elements is arranged in parallel at an oblique angle, each transducer element including a transmit transducer and a receive transducer, the plurality of arrays of transducer elements enabling imaging of subcutaneous structures in a plurality of transverse and lateral planes; receiving echo signals within a predetermined frequency range from the subject's body after transmitting ultrasonic energy; processing the received echo signals by a processor; generating an image representing a subcutaneous structure of the subject on a screen forming part of the portable ultrasound device; A method comprising:

10. 10. The method of claim 9, wherein the processor distinguishes between arterial and venous vasculature based on a power spectral density (PSD) calculated from an optionally sampled ultrasound signal.

11. The method of claim 10 , wherein the processor distinguishes between arterial and venous structures based on pulsatile measurements.

12. The method of claim 10 , wherein the processor distinguishes between arterial and venous structures based on processing of an energy signal determined from a Fast Fourier Transform (FFT) of a sampled ultrasound signal.

13. 13. The method of any one of claims 10 to 12, wherein the processor determines a depth and location of subcutaneous structures below a contact area of ​​the ultrasound device with the subject's body based on processing of the sampled ultrasound signals.

14. The method of claim 13 , wherein the processor processes the sampled ultrasound signals by compression of the subcutaneous structures.

15. The method of claim 12 , wherein the processor calculates an optimal needle gauge and / or insertion angle for accessing the imaged subcutaneous structures, and optionally vascular structures, with the vascular access device.

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