Patent Application
20240099806
The present invention relates to ultrasound positioning and imaging used in device localization inside a target body structure of a patient, by means of the same probe.
For some advanced medical treatments, it might be relevant to use microrobots inserted in a target body part of a patient in order, for example, to deliver a very precise amount of drug to a very precise point. For safety purposes, this microrobot should be as autonomous as possible and most preferably controlled from outside the patient's body in a contactless manner. This micro-device thus needs a wireless localization system comprising an internal referential, in order to be tracked and precisely located while moving inside the target body part. This system should also be able, in order to enable a surgeon to be in full control of the situation, to offer a precise 3D visualization of the localization of said micro-robot inside the target body part.
There is a need for improving the tracking system and especially the localization for this kind of microrobots in correspondence to the anatomy of the target body part. The position of the microrobot with respect to anatomic features, such as functional areas, vessels or nerve, is of primary importance since it will define the path and target point of the robot, inside the target body part. A 3D imaging modality is thus necessary to envision these features and permit path planning. Moreover, the imaging modality and the microrobot positioning has to be perfectly co-registered with a precision better than 1 mm. It is thus important for the imaging system and the positioning system to be performed in the same internal referential, ideally through the same technique.
Additionally, regarding the specific case of the brain, even if the brain is encapsulated by the skull, it can move, distort, expand or dilate. The micro-robot itself might modify the surrounding anatomy while it moves through tissue. Tissue physiology such as blood flow might be impacted by the micro-robot and its action. Consequently, it would be ideal to provide a frequent refreshment of the images, along with the position of the microrobot, in order to have an up-to-date spatial information of the microrobot localized in the referential space. A commonly known wireless communication path between two elements is ultrasound communication. Such technique could be used for positioning the robot. A commonly known way to obtain reliable 3D body imagery is also ultrasound imaging. Both approaches could therefore be performed in alternance with a similar or identical apparatus.
There are several implementations for 3D ultrasound imaging, Brightness-mode, elastography or Doppler. One of the possibilities for highly precise imaging of the vascular network is ultrasound localization microscopy (ULM). The core idea of the ULM is generally known to be a very highly precise ultrasound imagery method based on the introduction of sparse punctual sources in the medium being imaged, to highlight specific parts. These sources are usually air microbubbles, more precisely millions of microbubbles, also called contrast agents. In order to obtain an ULM image of a target body structure like, for example, the brain vascular system, microbubbles are injected in the patient. Many 3D transcranial images are acquired. Microbubbles are localized and within a few minutes, a 3D ULM image is obtained. Thanks to these microbubbles, the vascular system is resolved under the diffraction barrier (the precision reaching a λ/10 precision). A super-resolved image is thus constructed by localizing each bubble center separately and accumulating their positions to recover the vessel's network, several times smaller than the wavelength. The use of microbubbles (with a diameter ranging from 1 to 3 μm), thanks to their high deformation, allows the imaging system to outperform accuracy limitations due to the classical wave diffraction theory which is around half of the wavelength and to bypass the usual compromise to be found between wave penetration (favorized in the low wave frequency range) and image resolution (favorized in the high wave frequency range). This enables to visualize details which remain invisible on images built by conventional echography, Doppler echography in particular. In particular regarding brain vascularization, this technology enables the creation of highly precise images enabling a precise 3D mapping of a patient's brain vascular system.
Approaches proposed in ULM can also be implemented for improving the positioning of the microrobot with ultrasound. Localization of microbubbles in ULM is not limited in resolution by the wavelength, but rather by the signal-to-noise ratio (SNR) linked to the detection of the microbubbles. A similar idea can be implemented for the localization of the robot, which could yield very high SNR and, hence, allow very precise localization. This precision could be well below 100 micrometers for frequencies that are capable of penetrating the skull (<3 MHz).
The present invention aims at solving the visualization and tracking precision issue in co-registering the ultrasound signals used either to acquire a 3D image of the target body part or to track the micro-device.
This invention thus relates to a micro-device tracking and visualization system configured to monitor a target body part of a patient and localizing a micro-device inside said target body part, the tracking system comprising:
The tracking system according to the invention may comprises one or several of the following features, taken separately from each other or combined with each other:
The invention also relates to a micro-device tracking and localization method implemented by means of the tracking system according to any one of the preceding features, wherein the method may enable, at the same time:
The method may include following steps taken separately from each other or combined with each other:
As can be seen on
In order to be able to work at the micro-device 16 scale, and obtain a precise enough visualization of the micro-device 16 while it is moving inside the target body part 10, it is essential to rely on a very precise remote tracking system, like the tracking system 18 according to the present invention. This remote paradigm imposes high constraints on the volume and energy used by the embedded tracker. In this perspective, a tracking system must answer several strong requirements: sub-millimetric position accuracy, depth from 100 mm and more, real time update (from 20 Hz), non-invasiveness, minimal and at best micro size, at best energetically passive and not harming human body.
In order to achieve this visualization, the tracking system 18 comprises:
In the embodiment illustrated on
The at least one probe 22 is brought into contact with the securing body part 24. In some embodiments (not represented), the probe 22 is manually handled around the securing body part 24. It is commonly known that, for technical reasons, some gel is spread on the body part 24 and the at least one probe 22. It is nevertheless considered that the at least one probe 22 is brought into contact with the securing body part 24. In some alternative embodiments, the probes 22 are secured to the body part 24 for example by means of a helmet or an elastic holder, as can be seen on
Each probe 22 is in constant communication with the control unit 20 on one hand and with the at least one tracker 26 fixed to the micro-device 16 on the other hand. Each probe 22 comprises at least one ultrasound transducer, for example a piezo-electric transducer.
In the current application, the term “transducer” is used synonymously as “emitter” and the term “sensor” is used synonymously as “receptor”.
This transducer sends ultrasounds to the tracker 26 on the micro-device 16 inside the target body part 10 (as can be seen on
In some alternative embodiment, the tracker 26 can be an active tracker, actively emitting signals to the probes 22. In those cases, each probe 22 comprises at least one ultrasound sensor and the tracker 26 comprises at least one ultrasound transducer, for example a piezo-electric transducer. The global functioning of the system remains the same, with the ultrasound waves being emitted by the tracker 26 and travelling up to the securing part 24, towards the probes 22.
As already mentioned, in some embodiments, the tracker 26 when being a passive tracker, can comprise at least one encapsulated gas pocket 27 attached to the micro-device 16. This solution is inspired from the principle of ultrasound contrast agents. In this embodiment, each encapsulated gas pocket 27 forms as a very ultrasound reflective object. These encapsulated gas pocket 27 have a large acoustic impedance compared to tissue. This gives them the ability to scatter efficiently the incident ultrasound waves sent by the probes 22 and therefore improve locally the contrast. As object localization precision depends on the signal-to-noise ratio, it allows to track micro-devices 16 smaller than the wavelength deeply inside the target brain part 10, especially the brain, in a non-invasively way. Regarding this embodiment, the tracker 26 comprises several encapsulated gas pockets 27 which are separated by more than half of the detection wavelength are combined to build a full 3D orientation and localization tracker 26. At least two encapsulated gas pocket 27 are needed to obtain the orientation of the micro-device 16.
The control unit 20 further comprises a memory 28 which stores an internal referential R. This internal referential R is defined with reference to the absolute position of each probe 22 with regards to the target body part 10.
The memory 28 further stores at least one ultrasound image 29 of the target body part 10. The ultrasound image 29 can be ULM images or B-mode images, or a Doppler images or an elastography image. All those ultrasound images 29 can be implemented with the same ultrasound probe. The internal referential R enables the co-registration of the ultrasound tracking of the tracker 26 with the ultrasound image 29 acquisition. In some embodiments, the memory also stores at least one pre-established image of the securing body part 24 on which each probe 22 is secured. In those cases, the control unit 20 aligns the at least two images within the internal referential R to precisely position the target body part with respect to each probe 22. In any case, the control unit 20 is able to precisely locate any point of the target body part 10 inside the internal referential R.
The information sensed by each probe 22 is then, in real time, sent to the control unit 20 and the control unit 20 is thus able to localize, in real time, the at least one tracker 26 inside the target body part 10, with regards to the internal referential R.
As already mentioned, the memory 28 is configured to store at least one ultrasound image 29 of the target body structure 10, like for example the image illustrated on
In order to reach the desired co-registration, the at least one probe 22 displays two working modes:
In some embodiments, the memory 28 of the control unit 20 can store several ultrasound images 29 of the target body part 10. The memory 28 can thus store a succession of ultrasound image 29 of the target body structure 10. In some embodiments, in order to reduce storage energy, each new ultrasound image 29 replaces the prior one inside the memory 28. In order to increase the precision and accuracy of the mapping of the target body part 10 during its monitoring by the system 18, the ultrasound image acquisition is done in real time. Depending on the ultrasound technique, the ultrasound image 29 acquisition can last several minutes. It nevertheless considered to be real time acquisition. This provides a real time mapping of the target body part 10 and enables to take quick structure changes into consideration. This real time mapping occurs in that a new ultrasound image 29 acquisition is launched, by the control unit 20, as soon the prior ultrasound image 29 acquisition is terminated, each new ultrasound image 29 thus replacing the prior one as soon its acquisition is terminated. One example could be that the first ultrasound image 29 is an ULM image, further replaced by a Doppler image, which is quicker to acquire.
The control unit 20 is also designed to display, on a screen 30, each acquired and/or stored ultrasound image 29. This is illustrated on
By combining the real time ultrasound information obtained from each probe 22 regarding the at least one tracker 26 and the information of the stored ultrasound image 29, the control unit 20 is able to display, in real time, the localization of the at least one tracker 26 on said ultrasound image 29. This enables the surgeon to know, precisely, where the micro-device 16 is.
The control unit 20 further may include a user interface 32 enabling, for example, an operator to indicate, to the micro-device 16 which precise point to reach inside the target body part 10. This user interface may also allow an operator to direct said micro-device 16 in a contactless manner.
The improvement of the micro-device 16 visualization by means of an ultrasound super-resolution technique (like for example the ULM technique) enables a surgeon to precisely monitor the micro-device in a far deeper part of any target body part 10, as for example the brain. Using classic ultrasound imagery enables, for a wave frequency of 1 MHz to obtain an image resolution of 0.75 mm. Using super-resolution imaging technology enables, for the same frequency, a resolution of 0.15 mm. The super-resolution imaging technology further enables the visualization of little veins which are not visualizable on classic ultrasound imagery. This can help a surgeon to remotely navigate the micro-device 16 around those veins and thus, avoiding to damage or hurt one of those veins and cause internal bleeding.
The micro-device 16 can for example be actuated by either an external engine (for example an external coil, see document PCT/US2019/059096) or an internal engine. It is therefore able to move inside the human body, in any sort of biological medium. The control could be achieved directly with a joystick or through a more complex controller (like a phantom haptic controller) manipulated by a user. The control could also be achieved automatically by following a pre-set pathway. The control signals could be either sent wirelessly or using wires connected to the microdevice.
Using super-resolution ultrasound technology for the tracking further enables the localization of the micro-device 16 to reach a precision better than half the size of the wavelength of the ultrasound used to perform the localization. More particularly, when using ULM technology, one can reach a precision of λ/10 regarding localization and λ/5 regarding visualization.
The ultrasound image 29 thus allows the surgeon to visualize the micro-device 16 and the precise point to be reached by said micro-device 16. Thus, the surgeon can:
The tracking system 18 according to the invention thus enables to implement a micro-device 16 tracking and localization method, wherein the method enables:
The method further allows:
If the same probes 22 are used to acquire the ultrasound image 29 and to track the tracker 26, the method thus enables the system 18 to alternate between:
In order to, for example, inform the surgeon that the drug has been well delivered or to allow a precise monitoring of the target point the micro-device 16 has to reach inside the target body part 10, the micro-device can be designed to drop, at least one contrast agent inside the target body part 10. The contrast agent dropping can be induced by the surgeon or can be pre-programmed. This contrast agent might, for example, be a micro-bubble. When the at least one contrast agent is dropped inside the target body part 10, it can be sensed by each probe 22 and the control unit 20 is thus able to localize and display, on the ultrasound image 29, said at least one contrast agent, this visualization adds to the precision of the system 18.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20306554.5 | Dec 2020 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/085202 | 12/10/2021 | WO |
