Patent Application
20250032091
The invention relates to the general field of ultrasonography, and more particularly to ultrasonographic probes comprising at least one piezoelectric transducer element with an oscillating & pivoting mount, with mechanical sectorial scanning functions. More specifically, some aspects of the invention relate to the precision of the transducer element's position. The invention applies not only to the probes, but also to ultrasound scanners with embedded probes, and implementation methods.
Professionals are aware that ultrasound scanners comprise an ultrasound emission and reception probe, designed to be placed on part of the body (in particular the human body) corresponding to the area of interest to be explored, and a central electronic system powered by a processor that applies algorithms, using a keyboard, display and visualization, adjustment and storage means, etc., to form an image from the echoes received by the probe following the ultrasound emissions. Such ultrasound scanners are used in a number of medical applications, including, but not limited to, cardiology and obstetrics, to acquire information for study, research, monitoring and diagnosis purposes. For sedentary use, the central system is typically mounted on a mobile cart and connected to the operating probe by cables. Such central systems are bulky and heavy, limiting the applications. For semi-nomadic use, portable ultrasound scanners, similar to laptop computers, were considered. Even lighter ultrasound scanners were then proposed for nomadic use in any location (e.g. U.S. Pat. No. 10,349,893, WO 2017009735), in which case the probe is controlled via wireless communication with a smartphone (i.e. a portable digital device able to run an application suitable for certain functions, not necessarily a phone, but also potentially a tablet or other device).
Professionals are aware that ultrasound probes are contained in a case used to handle and protect contents, with an external format suitable for the purpose, and housing at least one single or multiple piezoelectric transducer elements facing an acoustic window. Such transducers usually operate at a resonant frequency between 1 MHz and 30 MHz. It may be necessary to place a coupling fluid between the transducer element(s) and the acoustic window, particularly with mechanically-scanned probes. The transducer element transmits an ultrasound detection signal to an area of interest on the body for which an ultrasound image is required, which could be described as an ultrasound beam in a certain median direction. The transducer element picks up the echoes reflected by the impacted body tissues, interfaces or organs in the area of interest. The operator moves the probe relative to the body at different locations and angles to investigate the target organs. Such ultrasound probes may also include powering, processing, adjusting, controlling, monitoring, connecting and communicating components, etc.
Professionals are aware that the frequency must be adapted to the depth of the target area of interest, therefore either a broadband transducer element supporting several frequencies is provided, or several transducers corresponding to specific frequencies (e.g. U.S. Pat. No. 4,276,491), or several different low-band probes connected to the system.
The probe can be unidirectional or multidirectional depending on requirements and design, with sectorial scanning of the target area of interest. Although such scanning is mainly electronic, mechanical scanning is also feasible (e.g. FR 2516246, EP 0045265, EP 0079284). Depending on the set-up used, several transducer elements are secured, spaced on a pivoting mount (e.g. disc, wheel or drum), which is mechanically driven by a motor with oscillating and pivoting axes and possibly an intermediate motion transmission system (e.g. belt, pinions or connecting rod). The active transducer scans the sectors in the area facing the scanning zone.
When scanning alternating sectors, the transducer emits an ultrasound pulse towards the area to be scanned at each successive position, and in return picks up a line of echoes returned by the medium. The transducer picks up a set of around one hundred echo lines for each complete swept sector covering approximately 40° to 90°. The area of interest is visually reconstructed by juxtaposing these echo lines using an imaging algorithm. The successive to-and-fro scans swept several times per second produce an animated model of the area of interest.
Professionals are also aware that the drive motor for a transducer element can be a stepper motor (e.g. U.S. Pat. No. 7,635,335, EP 0476495), with inherent advantages such as simplicity, robustness, low cost, reliability, high torque at a low speed, and suitability for the environment of an ultrasound probe (EP 1744178). However, professionals are also aware that stepper motors bring the inevitable problem of angular offset between the actual position of the transducer element and its theoretical position (EP 0079284), caused by the angular inaccuracy of the motor and the inaccuracy induced by the motion transmission system, particularly during use. This angular inaccuracy, however slight, distorts the final image and/or the superposition of emitted and return images, which adversely affects the quality of the rendering. As a result, electronic scanning may be preferable to mechanical scanning, but the benefits of the latter are lost.
According to US 2003/0055338, while the probe comprises a stepper motor, a closed-loop optical servo device is installed to detect the position of the array of transducer elements. According to U.S. Pat. No. 4,773,268, the drum supporting the multiple transducer elements on the mount and the motor outlet pinion, itself fitted with a position encoder, are especially designed to prevent the slippage of the connecting belt. Either one or more encoders may be used indifferently (e.g. FR 2516246, EP 1838753, U.S. Pat. No. 6,645,151 with two encoders). FR 2409742 provides for additional optical equipment to generate signals indicating the position of the rotary transducer element and subsequently transmit signals to a servo controller. EP 0201137 provides for an optical encoder. According to FR 2479531, offsets arise between scans, therefore digital processing and a storage device are required.
CN109951129 describes a method for controlling a stepper motor, without a position sensor, comprising the following steps: observe the estimated position of the motor rotor at the target time as a function of the two-phase current and the two-phase voltage of the motor; compare the theoretical position of the motor rotor with the estimated position at the target time to determine compensation for position error for the motor rotor; compensate the position of the motor rotor based on position error. CN106571758 describes a stepper motor offset compensation method used for an ultrasound probe which is also equipped with a transducer. The method involves the following steps: acquire actual transducer position information by calculating the number of motor steps required for the transducer to reach its actual position; compare the actual position with the target position to obtain stepper motor offset data; compare the desynchronization data with a predefined threshold to determine within which threshold range the desynchronization data fall; determine the appropriate compensation mode for the desynchronization data as a function of the threshold range; compensate the data. With this set-up, the motor is used to compensate for the pre-calculated offset.
Furthermore, WO2019122665 describes a method used to determine the deployed position of an implantable medical device based on a three-dimensional image of an area of interest comprising the vascular structure in which a positioning point has been defined, including several steps: determine an artery centerline, place the device in an initial position with respect to the centerline, and simulate the final position of the device based on the loads applied by the walls of the vascular structure. With this set-up, the centerline is determined by placing points at different longitudinal positions along the vascular structure in order to minimize fluid travel time along said points between a point of entry into the vascular structure and a point of exit from the vascular structure, and travel time is minimized using a gradient descent algorithm. These points form the centerline.
Ultrasound scanners are required for mobile use, and more specifically embedded probes, which can be used for a wide range of purposes (in particular, working at several depths to observe different areas of interest), particularly in emergency situations. These scanners must be able to guide diagnostics, particularly in emergency situations, must be simple, lightweight and robust by design, reliable for the intended purpose, provide a simple, robust and effective means of reconstructing images for the practitioner's intended purpose, be cost-effective (in terms of manufacturing, use and maintenance), and be compatible with a standard smartphone, as carried by the operator. The smartphone must be able to both control the probe and receive, display, save and transmit the images obtained, using a specialist application if necessary, and provide an image of a suitable quality for the intended purpose, which will particularly help to compensate, to some extent, the image distortions caused by the very design of the probe.
In particular, an ultrasound probe with mechanical sectorial scanning is required, comprising a stepper motor and a motion transmission system, which reduces, more specifically minimizing and eliminating or almost eliminating, image shaking due to the offset between successive images. In particular, it is essential to reduce, more specifically minimize and eliminate or almost eliminate such image shaking, without any need for additional measuring equipment for errors caused by defects affecting mechanical parts of the probe.
To this end, with reference to an initial aspect, an implementation method is proposed for an ultrasound scanner comprising an ultrasound probe for exploring an area of interest on the human body, in which:
The process:
A stepper motor without an encoder is used in one set-up.
With this method, the effects of the defects affecting the mechanical probe equipment on the final image are harnessed and used to directly correct the image, so that these effects (image shaking) are reduced, more specifically minimized and eliminated or almost eliminated, without any need to use additional error measuring equipment.
According to one set-up, in order to measure the offset:
According to another set-up, in order to measure the offset:
According to a first set-up, in order to correct the offset, the angular offset is repeatedly calculated and, when the offset calculated in this way is considered to be reliable, the images returned to the imaging algorithm are corrected by applying an inverse rotation to the offset calculated in this way and considered to be reliable.
According to a second set-up, to correct the offset, the angular offset is repeatedly calculated, and when the calculated offset is considered to be reliable, it is permanently saved and the firing and movement scheduling pilot is instructed to time-shift the emissions with respect to the return movement, as a function of the reliable calculated offset.
According to one option offered by the invention, with this process, on the one hand, probe movement is sensed, and on the other hand:
According to one set-up:
According to one set-up, n is equal to three, and the frequencies are equal to or close to 3.5 MHz, 5 MHz and 7.5 MHz respectively.
According to one set-up:
Depending on the set-up used, the angular offset of the lines associated with the operation of the drive system is calculated from either the portable digital device or the probe; and/or the angular offset thus calculated is compensated from either the portable digital device or the probe.
According to a second aspect, an ultrasound scanner suitable for implementation using the method described is proposed, comprising:
According to one feature, the stepper motor has no encoder.
According to one set-up, the carrier supports n transducer elements, each with its own frequency, to allow for n examination depths, and a control system is adapted to instruct the stepper motor to move the carrier and bring the transducer element corresponding to the selected frequency to its operating position.
According to one set-up, n is equal to three, and the frequencies are equal to or close to 3.5 MHz, 5 MHz and 7.5 MHz respectively.
According to one set-up, the ultrasound scanner:
According to one set-up, the probe in the ultrasound scanner comprises:
Either the wet compartment only houses the transducer element (rotary drum) and the rest of the drive system, including the stepper motor, is housed in the dry compartment, with a dynamic seal (e.g. on the shaft) separating the two compartments, or the entire drive unit, transducer carrier (rotary drum) and the rest of the drive unit (including the stepper motor) is housed in the wet compartment, in which case no dynamic seal is required to separate the two compartments, and the electrical connections to the stepper motor are sealed.
According to one set-up, the drive system for the ultrasound scanner includes a motion transmission system between the stepper motor and the transducer element carrier, such as a toothed belt interlocking with notches on a rotary pinion at the stepper motor outlet and the notches on a rotary pinion at the transducer element carrier inlet.
According to the set-up, the portable digital device and the probe are arranged to ensure that:
The following description refers to the drawings shown in the figures. The terms used are to be understood and interpreted in light of the scope of the invention and the state of the art presented above.
The invention presents two aspects, on the one hand, an ultrasound scanner 1 and, on the other hand, implementation resources for such an ultrasound scanner 1, comprising an ultrasound probe 2 for exploring an area of interest ZI on the human body C, comprising equipment 3a for communication with a separate computer. In the set-up under consideration, the computer is a portable digital device 4, capable of running an application suitable for the execution of a functionality, such as a smartphone or tablet, and with communications capabilities 3b. Once communications capabilities 3a and 3b are installed to communicate with each other, they can particularly operate via the WI-FI or Bluetooth protocol or the Internet protocol. This specific arrangement ensures that probe 2 is portable.
As professionals are well aware, probe 2 has a rigid, outer casing 5, with an ergonomic shape for easy handling by the operator. For example, this shape bulges towards the two ends and narrows in the middle to form a manual grip. Housing 5 features a removable cover providing access to an inner housing space 6, comprising a dry compartment 6a where the cover is located, and a wet compartment 6b located at the opposite end and forming a contact zone 7 with a human body contact zone C for exploring the area of interest ZI. The two compartments 6a and 6b are separated from each other by a watertight partition 6c.
In the specific set-up shown in schematic view
In this same specific set-up (
Part 8a of drive system 8 for one transducer element 9 housed in dry compartment 6a comprises a stepper motor which, according to one feature, is not equipped with an encoder unlike many conventional professional set-ups. One pilot 13 is associated with stepper motor 8a. Drive system part 8b housed in the wet compartment 6b comprises a fixed carrier for transducer element 9, such as a drum 8b, which can rotate thanks to stepper motor 8a, via a motion transmission system 8c, such as a toothed belt interlocking with the notches of a rotating pinion at the outlet of stepper motor 8a and the notches of a rotating pinion at the inlet of drum 8b. Such gears are used to minimize the angular offset caused by the movement of stepper motor 8a and drum 8b, which cannot, however, be completely eliminated on a permanent basis.
In the specific set-up (
The specific set-up shown in schematic view
Stepper motor 8a is instructed to mechanically drive drum 8b to scan alternating sectors from a reference position, at a sweep angle between 40° and 90° which can be adjusted if required. In addition, transducer element 9 is able to emit ultrasound pulses towards the area of interest ZI corresponding to several successive firing operations, controlled by one firing and movement scheduling pilot 14 in probe 2. Transducer element 9 is also able to pick up several echo lines LEA, LER when receiving the pulses. This arrangement ensures that transducer element 9 is brought to the reference position facing the acoustic window by stepper motor 8a, and is then rotated by stepper motor 8a, over a certain distance in one direction and then in the other, to scan both emissions and echoes. The axis of transducer element 9 continues to face the acoustic window. The scan of emission echoes is symbolized in
According to a specific, but non-limiting set-up, drum 8b supports n transducer elements 9, each with its own frequency, allowing for n examination depths P of the area of interest ZI. Frequency can be adjusted on the fly between series of images. Pilot 13 for stepper motor 8a can be controlled for this purpose from smartphone 4, instructing stepper motor 8a to move drum 8b in order to bring transducer element 9 corresponding to the selected frequency to the reference position. This arrangement allows different depths P to be explored with the same probe 2, without any need for several probes or to replace these probes. This specific arrangement is particularly flexible and versatile thanks to the portable design of probe 2 made possible by combining probe 2 with smartphone 4 to form ultrasound scanner 2. For example, in one set-up, n is equal to three, and the frequencies are equal or close to 3.5 MHz, 5 MHz and 7.5 MHz respectively. If ultrasound scanner 1 thus comprises three transducer elements 9a, 9b, 9c, the latter are arranged on drum 8b with angular spacing designed to minimize the total angular excursion of drum 8b between the most distant transducer elements (e.g. 9a and 9b according to
Dry compartment 6a contains electronic unit 10 for probe 2 in addition to stepper motor 8a, and, if applicable, power supply unit 11, and at least one and generally several ports 12. This electronic unit comprises:
Smartphone 4, or equivalent, can run an application suitable for the execution of a functionality, i.e. software or an application which can apply the AFI imaging algorithm to visually reconstruct the area of interest ZI by juxtaposing the image points in the echo lines LEA and LER and an animated model of the area of interest ZI is produced based on the successive to-and-fro scans of transducer element 9. In addition, as professionals are generally aware, smartphone 4, or equivalent, also includes, in particular, screen 27, control device 28, MEM memory, and one or more ports. Smartphone 4, or equivalent, is designed to be able to parameterize and control probe 2. In addition, smartphone 4, or equivalent, is designed to be able to apply the AFI imaging algorithm. Finally, smartphone 4, or equivalent, is primarily configured to display the images obtained by and received from probe 2 on screen 27, and transmit the images obtained by and received from probe 2 to an external storage platform. Schematic view
According to plans, ultrasound scanner 1 will be capable of analyzing the image points along an arc at a given depth P of the area of interest ZI for two series of successive emission LEA and return LER echo lines, in order to determine the angular offset of the image points in the two successive arcs AA and AR (
In order to reduce, more specifically minimize and eliminate or almost eliminate, this image shaking, the plan is to analyze the image points, using the indicated resources, in order to determine the angular offset of the image points in the emission LEA and return LER echo lines, and to calculate the angular offset for these echo lines LEA and LER, and subsequently to correct offset as a function of the calculated angular offset, using an offset corrector. The operating procedure for probe 2 therefore ensures that the image points along an arc AA and AR are analyzed, at a given depth P of the area of interest ZI for two series of successive emission echo lines LEA and return echo lines LER, to determine the angular offset of the image points for the two successive arcs and calculate the angular offset of the emission echo lines and return echo lines. This offset is associated with the operation of drive system 8. The offset is then corrected by approximating the successive emission and return images, particularly by superimposing or almost superimposing the images, incorporating the calculated offset for the operation of drive system 8. In this way, the effects caused by defects affecting the mechanical drive system 8 for probe 2 on the final image are harnessed and used to directly correct the image, so that the effects of the defects affecting the mechanical drive system 8, i.e. image shaking, are reduced, more specifically minimized and eliminated or almost eliminated, without any need to use additional error measuring equipment.
The process is symbolically illustrated in
The lower right-hand part of
The upper right-hand part of
The arrows F1, F2, F3 and F4 in
One possible way to measure the offset is described below. The following procedure may be used in an optimal situation in which the imaged area of interest ZI is high-contrast and stationary relative to the tip of probe 2:
By implementing a gradient descent algorithm and minimizing the distance between the points on the emission arc curve AA and the return arc curve AR, it may not be possible to perfectly superimpose or almost perfectly superimpose the emission images and the successive return images, but they can be approximated in all events (compared to a situation where the invention process is not implemented), and in particular they will be subject to best approximation, i.e. to the extent of the minimization obtained. For this reason, if we fail to eliminate or almost eliminate the shaking in the final image, we will reduce it, and more specifically minimize it, to ensure that the image is acceptable to a practitioner.
This situation may not be optimal as described above, because the area of interest imaged has high contrast, and is moving uniformly perpendicular to the tip of probe 2, and not stationary. Indeed, most of the time, practitioners move the ultrasound probe 2 to search for the area of interest ZI, and this movement introduces additional offset in successive images which must not be taken into account, as it is simply the consequence of moving ultrasound probe 2, and is not linked to the mechanical play previously discussed and which we aim to correct. In this case, the gradient descent algorithm can be successively applied to an emission arc and a return arc to obtain an initial offset d1, and then to this same return arc and the subsequent emission arc to obtain a second offset d2. If dj is the systematic offset associated with mechanical play and dm the offset associated with probe 2 movement, we obtain:
It may be that the situation is neither optimal as described above nor even sub-optimal as just mentioned, because the area of interest imaged has low contrast or the motion is not uniform and perpendicular to the tip of probe 2. In this case, several optional strategies can be adopted to improve results. One potential strategy is to randomly vary the depth P of the measurement arc to increase the chances of analyzing a higher-contrast area of interest ZI. Another potential strategy is to take around 10 images per second, allowing about 10 offsets per second to be evaluated. Given that the damage caused by the mechanical play to be corrected is mainly constant or changing very slowly, primarily as a function of wear or thermal variations, a high number of offset values can be measured and a correction only applied if a clear trend emerges, for example never more than one correction per hour or per day.
Several possible, but non-limiting, offset correction methods are now described. According to a first set-up, offset is corrected by repeatedly calculating angular offset, then, when the offset calculated in this way is considered to be reliable, correcting the return images produced by the AFI imaging algorithm by applying an inverse rotation of the offset calculated in this way and considered to be reliable. The term “reliable offset” means that repetitive calculations of the offset lead to values with a low degree of variation, as the degree of variation can be adjusted at the discretion of the probe 2 manufacturer according to the required level of performance. This initial set-up provides a sort of instant remedial correction.
Considering a second set-up, designed for future preventive corrections, as described previously, angular offset is repeatedly calculated until the calculated offset is considered to be reliable, particularly if a new probe is first used after assembly. However, once this offset has been saved on a permanent basis, firing and movement scheduling pilot 14 is instructed to time-shift emissions as a function of return movements, and according to the offset thus calculated and considered to be reliable. This second set-up is shown in
The method and the ultrasound scanner 1 described for the invention are compatible with another operating procedure if practitioners move probe 2, and subsequently stabilize the probe in relation to an area of interest ZI, given that the relative displacement of probe 2 over the area of interest ZI can be determined using the algorithm implemented or by any other means, such as, for example, a movement sensor associated with probe 2. Indeed, if probe 2 is moving, practitioners generally aim to obtain a fluid image with a fast refresh rate (e.g. 10 frames per second) and normal spatial resolution. On the other hand, if probe 2 is stabilized in an area of interest ZI, practitioners generally prefer a high-resolution image, to the detriment of the refresh rate. With this approach, the return lines are deliberately and temporarily offset by a ½ step to ensure that they fit exactly between the emission lines. This artificially doubles the number of lines in an image, but at half the refresh rate (e.g. 5 frames per second). The image reconstruction algorithm adapts to this new arrangement of emission and return echo lines. The angular offset measurement algorithm also adapts to this new arrangement in order to continue detecting probe movements. If the algorithm detects probe movement again, it switches back to fast refresh/normal resolution mode. Thus, thanks to this option offered by the invention, with the process, on the one hand, probe 2 movement is detected, and on the other hand:
Depending on the set-up, probe 2 movement is detected by either the algorithm or a movement sensor integrated in probe 2.
Several set-up variants are possible for calculating the angular offset of the lines associated with the operation of the drive system, and for compensating the angular offset calculated in this way. For example, the angular offset can be calculated using either portable digital device 4 or probe 2 and, alternatively or cumulatively, the calculated angular offset can be compensated from either portable digital device 4 or probe 2. Consequently, portable digital device 4 and probe 2 are arranged accordingly, so that:
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2105473 | May 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2022/000051 | 5/25/2022 | WO |
