WO2012096562A1

WO2012096562A1 - System and method for training ultrasound guided needle placement in the field of medical application

Info

Publication number: WO2012096562A1
Application number: PCT/NL2011/050018
Authority: WO
Inventors: Mark Vogt; Koen TERRA
Original assignee: Erasmus University Medical Center Rotterdam
Priority date: 2011-01-12
Filing date: 2011-01-12
Publication date: 2012-07-19

Abstract

A training system is providing for training medical practitioners to train ultrasound guided needle handling and placement. Ultrasound guided regional anaesthesia involves selective application of a drug locally in a specific body region. The training system comprises a set of phantom modules, each comprising a matrix of a matrix material, and at least part of the phantom modules comprising a target structure within the matrix. During training, a trainer assembles exercise by selecting modules and placing them together in a container in a selected order, and closes cover to press the modules together so that no ultrasound reflections will arise at the boundaries between modules. The matrix material is at least partly ultrasound transmissive. The target structure and the matrix material having mutually different ultrasound transmission properties that give rise to ultrasound reflection at the targets. The trainee then tries to reach a target structure with a needle, while viewing an ultrasound image of the modules/.

Description

Title: System and method for training ultrasound guided needle placement in the field of medical application.

The invention

The invention relates to a system and method for training medical employees in ultrasound guided needle handling.

Background

Ultrasound guided regional anaesthesia involves selective application of a drug locally in a specific body region. This is done by moving the tip of an injection needle through a patient's body at a desired angle toward the specific body region, often at a depth a several centimetres underneath the skin. Ultrasound imaging is used during movement to help the anaesthesiologist guide the tip of the needle to the body volume, while avoiding body structures that should be left intact. Such an intervention requires considerable skills from the anaesthesiologist, both in terms of ability to interpret ultrasound images for this context and dexterity to guide needle movement in order to get a visualization of the relation between needle tip and the specific body volume. Therefore training tools have been developed to help

anaesthesiologist train these skills. Known training tools for training ultrasound guided regional anaesthesia comprise a simulated body part, called a phantom, with a structure like a tube that simulates a target region.

Realistic training models for anaesthesia are available from Blue Phantom (R) and CIRS (R). A training tool of this type has been described in an article by Brian A. Pollard, titled "A New Model for Learning Ultrasound-Guided Needle to Target Localization", published in Regional Anesthesia and Pain Medicine, Vol 33, No 4 (July-August), 2008: pp 360-362.

In the known phantoms a structure is incorporated in an opaque matrix that allows transmission of ultrasound waves much like human tissue. Several phantoms including different structures may be used to provide different exercises of the skills to interpret ultrasound images showing the structures and the needle and to guide the needle. Existing phantoms are minimalistic or complex. However, predictability increases after a small amount of exercises. Therefore in practice an extensive training program would require an excessive number of different phantoms.

Summary

An object of the invention is to provide for an ultrasound guided regional anaesthesia training system that makes it possible to provide an extensive training program without requiring an excessive number of different phantoms.

According to the invention the training system comprises a set of phantom modules, each comprising a matrix of at least partly ultrasound transmissive material, and at least part comprising a target structure within the matrix with ultrasound transmission properties that differ from those of the matrix (e.g. different speeds of sound), so that ultrasound reflections arise at the target structures. Furthermore, the training system comprises a container. The phantom modules each have a rectangular block shape of the same size, or more generally any shape that allows a volume filling stack of modules to be formed in the container. The container has a size wherein a predetermined number of phantom modules can be fitted (the number being greater than one, the modules preferably being stacked at least two deep from a needle entry surface). The container has means to press the phantom modules together. Thus, air between the phantom modules is expelled to prevent reflections on boundaries between modules, which makes the modules suitable to create useful exercises. These means for pressing the modules together may comprise a hinged cover that is pressed against the stack of phantom modules in the container when the cover is rotated to a closed position around a hinge. In an embodiment, the cover comprises an at least partly ultrasound transmissive layer. In other embodiments a cover may be used that is clamped to the container, with screws and/or clips for example, to press the modules together. The cover may be weighted to press the modules together without clamps, or the weight of the cover may selected so high that it exerts sufficient pressure. Use of a set of phantom modules makes it possible to assemble stacks of phantom modules in different compositions, so as to provide different training exercises. The use of a container with means to press the modules together makes it possible to prevent, or at least reduce, ultrasound reflections from boundaries between the phantom modules by expelling the air from between the different modules, so that the stack acts as a single phantom for ultrasound reflections.

Preferably, the sizes of the container and the phantom modules are selected to allow the phantom modules to be stacked at least two high in the container. More preferably the sizes allow the phantom modules to be arranged in rows and/or columns of at least two wide. This allows composition of different training examples for a wide range of exercises.

Preferably, the set of phantom modules comprises phantom modules containing different shapes such as spherical ultrasound target structures, different phantom modules containing spherical structures of mutually different diameter. In a further embodiment, the set of phantom modules comprises further phantom modules containing cylindrically shaped structures (hollow and/or solid), different further phantom modules containing cylinders of mutually different diameter and/or length. Hollow structures may be used to practice injecting liquid for example. In another embodiment, the set of phantom modules comprises further phantom modules containing target structures with U-shaped cross- section, different further phantom modules containing structures with U-shaped cross-section of mutually different diameter and/or length. The set of phantom modules may also comprise homogeneous modules without target structures, i.e. phantom modules entirely made of the same matrix material. Such a set of phantom modules makes it possible to compose phantoms to train different skills and/or different levels of skill.

The container may have a cover with layer of ultrasound

transmissive material. In an embodiment an optically opaque layer may be used. This hides the phantom modules from sight, while allowing ultrasound imaging. In this way trainees are kept from seeing the phantom modules during the exercise. In an embodiment, the phantom modules themselves may be optically transparent. This helps the selection modules prior to the exercise.

Brief description of the drawing

These and other objects and advantages will become apparent from a description of exemplary embodiments, using the following figures.

Figure 1 shows a training system for ultrasound guided needle handling.

Figure 2 shows a set of blocks

Figure 3a,b show examples of target structures in the blocks Detailed description of exemplary embodiments

Figure 1 shows a training system for ultrasound guided needle handling. The system comprises an ultrasound probe 10, an ultrasound imaging system 12, a set of phantom modules 14, a container 16 and a needle 18. Container 16 and the phantom modules 14 in it are shown in cross-section. Part of phantom modules 14 are made of a matrix material that contains target structures 14a. Target structures 14a are shown by dashed lines to indicate an exemplary position and size of the targets inside the phantom modules 14; they need not be optically visible from outside the phantom modules.

Container 16 has internal dimensions that correspond to an integer multiple of dimensions of phantom modules 14. In an embodiment, phantom modules 14 are cubes, all phantom modules 14 having the same size. Each cubic phantom module 14 may have a height of 50 mm for example, or more generally a height in a range from 10-100 mm. The height of container 16 preferably is sufficient to stack phantom modules 14 at least two layers high. In an embodiment the internal dimensions of container 16 provide for at least two layers of at least two times two phantom modules 14 each. In a simple embodiment it may suffice to provide for a single layer of phantom modules 14.

The matrix material of phantom modules 14 is at least partially ultrasound-transmissive. The matrix material may be a resilient ultrasound transmissive matrix material such as soft silicone rubber, but it should be appreciated that alternatively other resilient transmissive materials may be used. Preferably, electrically isolating material is used, with at most sufficiently low electrical conductivity to allow electric currents to be passed through a needle in the matrix material without more than 10 percent leakage to the matrix material. This makes it possible to perform detection using electric current through the needle. The material of target structures 14a has ultrasound transmission properties (e.g. an ultrasound transmission speed) that differ from those (e.g. the ultrasound transmission speed) of the matrix material of phantom modules 14, so that ultrasound reflections arise at the interface between phantom modules 14 and target structures 14a. Target structures 14a may be hyper- echoic or hypo-echoic in relation to the matrix material of phantom module 14. In an embodiment target structures 14a may simply be hollow spaces in the matrix material of phantom modules 14. Preferably a material is used that offers more resistance to a needle than the matrix material. This provides for touch feedback to the user. In an embodiment the material of the target structures 14 may be electrically conductive, an electrically conductive part may be provided in a target structure 14. This makes it possible use electrical detection to detect that a needle has reached the target.

Preferably the structures in phantom modules 14 lie at a distance from the surface of phantom modules 14. However, in an embodiment a surface of the target structure in some phantom modules 14 may lie abutting to the surface of phantom modules 14.

In an embodiment, the matrix material is the same in all phantom modules 14, having identical ultrasound transmission properties. In an embodiment a plurality of different subsets of phantom modules 14 is used, with matrix materials that have different ultrasound attenuation properties, but the same speed of sound, so that no ultrasound reflections need occur between modules. The option to replace phantom modules by modules with matrix material having higher attenuation makes it possible to create more difficult exercises.

During learning a student may be given a task that involves identification of structures in ultrasound images of phantom modules 14 in container 16, such as counting objects structures at least a predetermined size, or tasks to move the tip of needle 18 through one or more of phantom modules 14 in container 16, while viewing the ultrasound based. Prior to a learning exercise, a teacher selects a subset of phantom modules 14 and clamps them in a stack of phantom modules 14 in container 16.

The height of the stack of phantom modules in container 16 need not be larger than typical needle penetration depth, i.e. maximum ultrasound path length through the human body. Typically, more than 100 mm is not needed, but of course a deeper stack may be used. Needle 18 may have a length of 150 mm for example. The dimensions of phantom modules 14 preferably provide for at least two layers of phantom modules 14 within the depth of the stack, to enable the teacher to use variable combinations of phantom modules, for example to make exercises more difficult by placing structures deeper under the surface, or by adding obstructing structures above a target structure.

Although an embodiment has been shown wherein phantom modules 14 are cubes, it should be appreciated that other shapes may be used, as long as the shapes allow for stacking without unintended spaces between the phantom modules. Phantom modules 14 that have a non-square, rectangular cross-section in at least one direction may be used for example. It is preferred that a shape is used that leads only to boundaries that are parallel to or perpendicular to the surface of the stack. This minimizes the risk of disturbing reflections. Furthermore, not all phantom modules 14 need have the same size. For example, in one embodiment phantom modules 14 of mutually different height may be used. Thus for example, a stack of phantom modules 14 with layers of different height may be realized, each layer containing phantom modules 14 of the particular height of the layer. Thus, different distances from the surface of the stack to structures in the stack may be realized. Furthermore stacks of more than two layers may be used. In this way, structures with a larger range of height variations may be provided and/or more obstructing structures may be provided. In an embodiment, variation of the thicknesses of different layers of a three layer stack may be used to realize different distances from the surface of the stack to the middle layer within a stack of constant height. Although an embodiment has been described wherein the matrix material of all phantom modules 14 is the same, it should be appreciated that it suffices that the ultrasound transmission properties of the matrix material of the phantom modules 14 at the ultrasound frequencies used by ultrasound probe 10 is the same.

Figure 2 shows an embodiment of container 16, comprising sidewalls

20, a lid 22, a hinge 24 connecting lid 22 to sidewalls 20, an optional cover sheet 26 in lid 22 and an optional ramp 28. In operation the teacher opens lid 22, places selected phantom modules in container 16, fitting between sidewalls 20 and presses phantom modules in container 16 together by means of lid 22. Use of a lid that operates to press phantom modules 14 together has the effect that it presses out air between the phantom modules that could result in reflections at the boundaries between phantom modules 14, which could lead to effects that differ from real use.

Optional cover sheet 26 may be used to cover the phantom modules 14 in container 16 from view for the student and to act as an artificial skin. Cover sheet 26 may be made of soft silicone rubber for example, with a thickness in a range of 1-10 mm and preferably in a range 3 - 5 mm. In an embodiment, a cover sheet of material with the same ultrasound transmission properties as the matrix material of phantom modules 14 is use (the same speed of sound). Thus additional ultrasound reflections between cover sheet 26 and phantom modules 14 are avoided. However, it may be acceptable to have a reflection near the surface due to use of different materials in cover sheet 26 and phantom modules 14.

Lid 22 may comprise an open frame, with stiff ribs to press down on phantom modules 14 and with room for cover sheet 26 between the ribs.

Optional ramp 28 has an inclined slope at an angle to the top surface of the stack of phantom modules. Ramp 28 serves as an armrest for students during practice to move needle 18. One or more of the sidewalls 20 may comprise a cover sheet similar to that of lid 22. This makes it possible to perform exercises wherein

ultrasound imaging is performed from the side.

Figure 3a shows examples of target structures 30 in the phantom modules. Different structures are provided in different phantom modules. One or more phantom modules 32 may contain no structure. Other phantom modules 34 may each contain a cylindrical structure, different phantom modules 34 containing cylinders of different diameter and/or length. Further phantom modules 36 may each contain a spherical structure, different phantom modules 34 containing spheres of different diameter.

Figure 3b shows phantom modules 38 with more advanced examples of target structures 30, such structures with as U shaped profiles or rings.

Phantom modules 14 may either be optically transparent or be provided with labels that allow a teacher to identify individual phantom modules 14 and the orientation of the structures within phantom modules 14. A list with information about the properties of the individual phantom modules 14 may be provided. A student may act as his or her own teacher by assembling successive stacks of phantom modules 14.

In principle a teacher may select phantom modules at will and place them in container 16 to realize a training exercise. In an embodiment, a program of training exercises is defined, which defines a predetermined series of stacks of phantom modules 14, or a series of sets of stacks corresponding to a same level of difficulty. During learning a teacher may assemble stacks from the series of the program, or from the successive sets of the series, each time once an exercise using the previous stack has been performed. More

complicated learning routes may be supported by using a program that provides for selection of successive stacks to be assembled dependent on the student's performance at a previous step or steps. A computer program product may be provided with a program of instructions that, when executed by a programmable computer, will cause the computer to select successive stacks to be assembled dependent on input about student performance.

The program may use stacks with predefined combinations of phantom modules, and rules indicating the stack to be selected dependent on the state of progress of the student. Alternatively sets of predefined

combinations of phantom modules may be used and rules to select such a set dependent on the state of progress of the student, after which a stack may be selected randomly from the set. In another embodiment stacks may be selected according to rules that indicate respective types of phantom modules to be selected (empty, with spheres, with cylinders, etc. the type optionally defining a range of diameters etc) and the positions of the phantom modules of the indicated type in the stack. In this case the phantom modules may be selected randomly for subsets of phantom modules of the same type.

In an embodiment, ultrasound imaging system 12 may be used to compare the selection of the stack of phantom modules according to the program with the actual stack. This may be used to generate an alarm signal if the wrong stack was created, or it may be used when the state of learning of the student is updated.

The learning program may also provide for rules to update the state of progress of the student dependent on the performance of the student, so that the state can be used to select new stacks. The updates may be performed by the teacher dependent on whether the teacher determines that the task set in an exercise was accomplished. In an embodiment the state may be updated using an automated verification whether the task was accomplished using measurements by ultrasound imaging system 12 of the path followed by the tip of the needle and a comparison with the known position of structures in rhea stack of phantom modules. Optionally needle 18 may also be adapted to perform position measurements for this purpose.

In an embodiment the training system comprises an electrical detector device, electrically coupled to needle 18. The electrical detector device serves to detect contact with a target structure 14. In this embodiment at least part of the target structures is made of electrically conductive material (or contain a conductive part) and the matrix material is electrically isolating. The electrical detector device is configured to apply a voltage to and to detect whether the voltage results in a current through the needle that exceeds a threshold value and to generate a signal such as a sound signal and/or a light signal if the current exceeds the threshold.

The electrical detector device may comprise a voltage source, a signal generator and a current detector coupled to the voltage source and the signal generator for this purpose. Any type of resistance measuring device may be used. In one embodiment needle 18 may comprise two conductors running to the tip of the needle, isolated from one another. In this case a voltage may be applied between the conductors. Thus current arises when the needle tip contacts a target structure 14, or a conductive part of it. In another

embodiment a terminal of the electrical detector device may be coupled to one or more target structures, for example through (thin) electrical conductors that run from the target structures to the outside of the modules. In this case the voltage may be applied between the electrical conductors of the modules and the needle. An output of the electrical detector device may be fed to the computer that executes the learning program, the program being configured to select combinations of modules for new exercises dependent on the detection (e.g. the time needed to reach an intended target, detection of contact with not intended targets). Although an embodiment with targets of electrically conductive material and electrically isolating matrix material has been described, it should be appreciated that slightly conductive matrix material and slightly resistive target material may be used, as far as this does not affect detection.

Claims

1. A training system for training ultrasound guided needle handling and placement, the system comprising

- a set of contiguously stackable phantom modules, each comprising a matrix of a matrix material, and at least part of the phantom modules comprising a target structure within the matrix of the phantom module, the target structure and the matrix material having mutually different ultrasound transmission properties that give rise to ultrasound reflection at the targets, the matrix material being at least partly ultrasound transmissive;

- a container with a size that allows a plurality of the phantom modules to be fitted within the container;

- a cover of the container configured to press the phantom modules together in the container.

2. A training system according to claim 1, wherein the size of the container and the phantom modules allows the phantom modules to be fitted in the container stacked at least two high between a bottom and a top of the container.

3. A training system according to any one of the preceding claims, wherein the size of the container and the phantom modules allows a plurality of the phantom modules to be fitted in the container placed side by side in a plane parallel to the bottom of the container.

4. A training system according to claim any one of the preceding claims, wherein the cover is hingedly coupled to a wall of the container, and configured to press against the stack of phantom modules in the container when the cover is rotated to a closed position.

5. A training system according to any one of the preceding claims, wherein the cover comprises a layer of at least partly ultrasound transmissive material, said layer lying over the phantom modules in the container when the cover is in a closed position it presses the phantom modules together in the container..

6. A training system according to claim 5, wherein the ultrasound transmissive layer is optically opaque.

7. A training system according to any one of the preceding claims, wherein the phantom modules in the set are all blocks with the surfaces of each block at right angles to each other, all phantom modules in the set having the same size.

8. A training system according to any one of the preceding claims, wherein the set of phantom modules comprises phantom modules with target structures of mutually different shapes and sizes.

9. A training system according claim 8, wherein the set of phantom modules comprises phantom modules containing spherical target structures, different phantom modules containing spherical structures of mutually different diameter.

10. A training system according to any one of the preceding claims, wherein the set of phantom modules comprises phantom modules containing cylindrically shaped target structures, different phantom modules containing cylinders of mutually different diameter and/or length.

11. A training system according to any one of the preceding claims, wherein the set of phantom modules comprises phantom modules wherein the target structures are hollow spaces in the matrix.

12. A training system according to any one of the preceding claims, comprising an electrical detector device, electrically coupled to a needle to supply electric current through the needle, at least part of the target structures comprising electrically conductive material.

13. A training system according to any one of the preceding claims, wherein the matrix of the phantom modules is optically transparent.

14. A training system according to any one of the preceding claims, wherein the set of phantom modules comprises a phantom module with a homogeneous matrix without target structures.

15. A training system according to any one of the preceding claims, comprising an ultrasound probe and an ultrasound processing system.