WO2010097726A1

WO2010097726A1 - A magnetic induction tomography system

Info

Publication number: WO2010097726A1
Application number: PCT/IB2010/050599
Authority: WO
Inventors: Ming Yan; Hui Liu; Hua Jin; Dayu Chen; Ron Kroon; Claudia Hannelore Igney; Marko Johannes Vauhkonen
Original assignee: Koninklijke Philips Electronics N.V.; Philips Intellectual Property & Standards Gmbh
Priority date: 2009-02-27
Filing date: 2010-02-10
Publication date: 2010-09-02

Abstract

The invention provides a magnetic induction tomography system (20) comprising: - an adaptive unit (21) arranged for detecting an electromagnetic signal from an object (30), wherein the adaptive unit (21) is adaptive to the shape of the object (30) for closely contacting the object (30); and - a main unit (23) for processing the electromagnetic signal received from the adaptive unit (21) through a connecting unit (22).

Description

A MAGNETIC INDUCTION TOMOGRAPHY SYSTEM

FIELD OF THE INVENTION

The invention relates to a magnetic induction tomography system.

BACKGROUND OF THE INVENTION

Magnetic induction tomography (MIT) is a non-invasive imaging approach and is suitable for biomedical applications. A MIT system comprises generator coils and sensor coils surrounding an object, so as to obtain the passive electrical properties of the object, i.e., conductivity σ , permittivity ε and permeability μ . In a MIT system, a sinusoidal electric current, normally ranging between a few kHz and several MHz, is applied to the generator coils for generating a varying magnetic field called the primary magnetic field. Due to the conducting object, the primary magnetic field produces eddy currents for generating a secondary magnetic field. The secondary magnetic fields induce voltages in the sensor coils for measurement, so that the set of electrical properties of the object can be measured.

Fig. 1 schematically shows a current MIT system. The generator coils and sensor coils of the MIT system are arranged in a cylindrical shape. When an object is placed in the cylindrically shaped MIT system, the MIT system may not be sufficiently sensitive to detect an electromagnetic signal of an object, and have difficulty to accurately measure electrical properties of the object. For example, the top of the head is very difficult to detect.

Based on the current MIT system, a quite large distance exists between the MIT system and an object, and a quite large space exists between adjacent coils, so that the sensitivity and accuracy of measuring the electrical properties of the object may be affected. Furthermore, during monitoring the wound status of an object by means of the current MIT system, unavoidable movement of the object may substantially impact the measurement of electrical properties.

SUMMARY OF THE INVENTION

An object of this invention is to provide an improved magnetic induction tomography system.

The magnetic induction tomography system comprises:

- an adaptive unit arranged for detecting an electromagnetic signal from an object, wherein the adaptive unit is adaptive to the shape of the object for closely contacting the object; and

- a main unit for processing the electromagnetic signal received from the adaptive unit through a connecting unit.

The advantage is that the adaptive unit can more closely detect an accurate electromagnetic signal by adapting to the shape of the object.

In an embodiment of the invention, the adaptive unit is helmet-shaped or strap- shaped.

The advantage is that the helmet shape can detect the electromagnetic signal of the top of a head, and the strap shape can detect electromagnetic signals of many separate parts of a body, for example, arm, leg, neck, abdomen etc. In another embodiment, the adaptive unit comprises a fixing means for fixing the adaptive unit on the object during detection of the electromagnetic signal.

Advantages: the fixing means can reduce the relative movement between the object and the adaptive unit, so that the adaptive unit can detect more accurate electromagnetic signals.

In a further embodiment, the adaptive unit comprises a set of coils, and the set of coils comprises generator coils for generating a primary magnetic field inducing an eddy current in an object, and sensor coils for sensing a primary and a secondary magnetic field generated as a result of the eddy current, and the set of coils seamlessly contact each other.

The advantage is that the coils contacting each other seamlessly can more sensitively detect more accurate electromagnetic signals.

The generator coils connect with a generator circuit and the sensor coils connect with a sensor circuit, and the generator circuit and the sensor circuit are included in the main unit.

The advantage is that accommodating the generator circuit and the sensor circuit in the main unit makes the adaptive unit very light.

Detailed explanations and other aspects of the invention will be given below.

DESCRIPTION OF THE DRAWINGS The above and other objects and features of the present invention will become more apparent from the following detailed description considered in connection with the accompanying drawings, in which:

Fig. 1 schematically shows a current MIT system;

Fig. 2 schematically depicts a MIT (Magnetic Induction Tomography) system according to an embodiment of the invention;

Fig. 3 schematically depicts a helmet-shaped adaptive unit of the MIT system;

Fig. 4 schematically depicts a strap-shaped adaptive unit of the MIT system;

Fig. 5 schematically shows a helmet-shaped adaptive unit on a head;

Fig. 6 schematically shows a strap-shaped adaptive unit surrounding an object;

Fig. 7 schematically shows an embodiment of the fixing means according to the helmet- shaped adaptive unit;

Fig. 8 schematically shows another embodiment of the fixing means according to the helmet-shaped adaptive unit;

Fig. 9 schematically shows a helmet-shaped adaptive unit with a set of coils;

Fig. 10 schematically shows another embodiment of an adaptive unit according to the MIT system;

Fig. 11 schematically shows a B-B enlarged pluggable unit according to the adaptive unit of Fig. 10; Fig. 12 schematically shows an A-A cross section of the adaptive unit 21 of Fig. 10.

The same reference numerals are used to denote similar parts throughout the

Figures.

DETAILED DESCRIPTION

Fig. 2 schematically depicts a MIT (Magnetic Induction Tomography) system according to an embodiment of the invention. The MIT system 20 comprises an adaptive unit 21 for detecting an electromagnetic signal of an object, a connecting unit 22 for transmitting the electromagnetic signal from the adaptive unit 21 to a main unit 23, the main unit 23 being arranged to process the electromagnetic signal from the adaptive unit 21 to obtain electrical properties of the object. The adaptive unit 21 is adaptive to the shape of the object for closely contacting the object, so as to more sensitively detect an accurate electromagnetic signal. The object can be any part of a patient body, e.g. head, leg, arm, abdomen, neck etc.

Fig. 3 schematically depicts a helmet- shaped adaptive unit 21 of the MIT system 20.

Fig. 4 schematically depicts a strap-shaped adaptive unit 21 of the MIT system 20.

The helmet- shaped adaptive unit 21 is wearable on a head and contacts the head closely and in a stable manner, so as to sensitively detect an accurate electromagnetic signal from the head. Fig. 5 schematically shows a helmet-shaped adaptive unit 21 on a head. The strap-shaped adaptive unit 21 can be used to surround different parts of a body closely, e.g. arm, leg, abdomen, neck etc., so as to sensitively detect an accurate electromagnetic signal from different parts of a body. Fig. 6 schematically shows a strap-shaped adaptive unit 21 surrounding an object.

The adaptive unit 21 is fixable on the object. The adaptive unit 21 comprises a fixing means for fixing the adaptive unit 21 on the object during detection of an electromagnetic signal.

Fig. 7 schematically shows an embodiment of the fixing means according to the helmet-shaped adaptive unit. The fixing means comprises at least one air cushion strip 211 at an inner surface of the adaptive unit 21, and the air cushion strip 211 is to be filled with air for fixing the adaptive unit 21 on a head 30. If the fixing means comprises at least two air cushion strips 211, the fixing means may comprise an interval 212 located between two air cushion strips 211, so that a carotid 31 of the object 30 is accommodated at the interval to avoid the pressure from the air cushion strips. The air amount of the air cushion strips 211 can be adjusted in order to achieve comfortable pressure on the carotid 31. The air cushion strip 211 may not cover the whole inner surface of the helmet-shaped adaptive unit 21 in order to avoid a patient feeling uncomfortable and blocking of the bi-lateral external carotid circulation.

Fig. 8 schematically shows another embodiment of the fixing means according to the helmet-shaped adaptive unit. The fixing means comprises a sticky layer 213 at the inner surface of the adaptive unit 21, which is to be stuck to a cover 214, and the sticky layer 213 may include several pieces of sticky material spread over different locations of the inner surface of the helmet. The cover 214 may be provided to surround a patient's head, and the cover can be a headgear, a bandage, or a wound dressing. The cover 214 may comprise at least one adhesive belt for sticking to a head 30. The outer surface of the cover 214 also comprises sticky material for sticking to the sticky layer 213, enabling the sticky layer 213 to be fixed to the helmet-shaped adaptive unit 21. The sticky layer 213 may be also an adhesive bandage to stick to a head directly, and the sticky layer can be removed from the helmet-shaped adaptive unit 21 for one-off usage.

Based on the fixing means, the helmet-shaped adaptive unit 21 can be fixed on a head for detecting an electromagnetic signal with less movement relative to the head.

In a third embodiment of the fixing means according to the helmet-shaped adaptive unit 21, the fixing means may comprise a first fixing means (e.g. belt) extending from a side of the helmet-shaped adaptive unit 21 and a second fixing means extending from an opposite side of the helmet-shaped adaptive unit for coupling with the first fixing means to fix the adaptive unit 21 on a head, for example, by tying the first fixing means with the second fixing means, sticking the first fixing means to the second fixing means, clasping together the first fixing means and the second fixing means.

In an embodiment of the strap-shaped adaptive unit 21, similarly, the fixing means may comprise an air cushion as mentioned in the first embodiment of the helmet-shaped adaptive unit 21.

In another embodiment of a strap-shaped adaptive unit 21, similarly, the fixing means may comprise a sticky layer as mentioned in the second embodiment of the helmet-shaped adaptive unit 21.

In a third embodiment of a strap-shaped adaptive unit 21, similarly, the fixing means may comprise a first fixing means extending from an end of the adaptive unit 21 and a second fixing means extending from another end of the adaptive unit 21 for coupling with the first fixing means to fix the adaptive unit 21 to a part of body, for example, by tying the first fixing means with the second fixing means, sticking the first fixing means to the second fixing means, clasping together the first fixing means and the second fixing means. Furthermore, the fixing means may comprise an elastic element for fixing the adaptive unit 21 to an object through elasticity forces.

Based on the fixing means, the adaptive unit 21 can be fixed on an object, so as to decrease relative movement between the object and the adaptive unit 21, and thus decrease the effect of the relative movement on the electromagnetic signal.

The adaptive unit 21 comprises a set of generator coils for generating a primary magnetic field inducing an eddy current in an object, and a set of sensor coils for sensing the primary magnetic field and a secondary magnetic field generated as a result of the eddy current. Fig. 9 schematically shows a helmet-shaped adaptive unit 21 with a set of coils. The set of coils 215 comprises generator coils and sensor coils. The set of coils 215 may be substantially seamless, so that the adaptive unit 21 is more sensitive to detect more accurate electromagnetic signals, for example the cross section of each coil is hexagonal for establishing seamless contact between adjacent coils. The cross section of each coil can also be any other polygon for establishing substantially seamless contact between adjacent coils.

The generator coils connect with a generator circuit to generate the primary magnetic field, and the sensor coils connect with a sensor circuit for sensing the primary magnetic field and the secondary magnetic field. The generator circuit and the sensor circuit can be stored in the adaptive unit 21 or the main unit 23.

If the generator circuit and the sensor circuit are included in the main unit 23, the generator coils and the sensor coils are connected to the generator circuit and the sensor circuit, respectively, by the connecting unit 22, so as to excite the generator coil to generate the primary magnetic field and control the sensor coils to sense the primary magnetic field and the secondary magnetic field, and transmit an electromagnetic signal to the main unit 23. In Fig. 2, the connecting unit 22 is used for connecting the generator coils and the sensor coils to the generator circuit and the sensor circuit in the main unit 23, respectively. Based on this embodiment, the adaptive unit 21 is very light. When the MIT system 20 is put in non-work status, the adaptive unit 21 disconnects from the connecting unit 22, so that the object can move conveniently, wearing the adaptive unit 21. When the MIT system is put in work status, the adaptive unit 21 connects with the connecting unit 22.

If the generator circuit and sensor circuit are included in the adaptive unit 21, the generator coils and the sensor coils are connected to, respectively, the generator circuit and the sensor circuit by conductive lines, so as to excite the generator coil to generate the primary magnetic field and control the sensor coils to sense the primary magnetic field and the secondary magnetic field. The adaptive unit 21 is connected to the main unit 23 by the connecting unit 22 for transmitting an electromagnetic signal to the main unit 23, so that the main unit 23 can process the electromagnetic signal to obtain electrical properties of the object.

Fig. 10 schematically shows another embodiment of adaptive unit 21 according to the MIT system 20. The adaptive unit 21 and the main unit 23 comprise a pluggable unit 218 for connecting with the connecting unit 22, so as to interconnect the adaptive unit 21 and the main unit 23. Fig. 11 schematically shows a B-B enlarged pluggable unit 218 according to the adaptive unit 21 of Fig. 10.

Fig. 12 schematically shows an A-A cross section of the adaptive unit 21 of Fig. 10. The adaptive unit 21 comprises an outer surface 217, an inner surface 216, and a set of coils 215 (generator coils and sensor coils) positioned between the outer surface 217 and the inner surface 216.

In the main unit 23 of the MIT system 20, the electrical properties of an object can be measured in a way similar to a standard measurement procedure according to the secondary magnetic field/electromagnetic signal. For example, a difference image for reflecting electrical properties can be obtained with the following Equation (1). In Equation (1), Δσ j_s the change of the conductivity of an object, J is the Jacobian matrix, ^a is the regularization parameter, R is the regularization matrix, V ^m is the actual measurement and V ° is the reference measurement

Δσ = (J^TW^TWJ + aR^T Ry^l(J^TW^TW(V_m - V₀))

(D

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim or in the description. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by units of hardware comprising several distinct elements and by units of a programmed computer. In the system claims enumerating several units, several of these units can be embodied by one and the same item of hardware or software. The usage of the words first, second and third, et cetera, does not indicate any ordering. These words are to be interpreted as names.

Claims

CLAIMS:

1. A magnetic induction tomography system (20) comprising:

- an adaptive unit (21) arranged for detecting an electromagnetic signal from an object (30), wherein the adaptive unit (21) is adaptive to the shape of the object (30) for closely contacting the object (30); and

- a main unit (23) for processing the electromagnetic signal received from the adaptive unit (21) through a connecting unit (22).

2. A system as claimed in claim 1, wherein the adaptive unit (21) is helmet-shaped or strap- shaped.

3. A system as claimed in claim 2, wherein the adaptive unit (21) is fixable on the object (30).

4. A system as claimed in claim 3, wherein the adaptive unit (21) comprises a fixing means for fixing the adaptive unit (21) on the object (30) during detection of the electromagnetic signal.

5. A system as claimed in claim 4, wherein the fixing means comprises at least one air cushion strip (211) at an inner surface (216) of the adaptive unit (21), and the air cushion strip (211) is to be filled with air for fixing the adaptive unit (21) on the object (30).

6. A system as claimed in claim 5, wherein the fixing means comprises an interval (212) located between two air cushion strips (211), so that a carotid of the object (30) is accommodated at the interval to avoid pressure from the air cushion strips, if the fixing means comprises at least two air cushion strips (211) and the adaptive unit (21) is helmet-shaped.

7. A system as claimed in claim 4, wherein the fixing means comprises a sticky layer (213) at the inner surface (216) of the adaptive unit (21), which is to be to stuck to the object (30).

8. A system as claimed in claim 7, wherein the sticky layer (213) sticks to a cover (214) fixed on the object (30), and the cover 214 is a headgear, a bandage, or a wound dressing.

9. A system as claimed in claim 4, wherein the fixing means comprises a first fixing means extending from a side/end of the adaptive unit (21) and a second fixing means extending from an opposite side/end of the adaptive unit (21) for coupling with the first fixing means to fix the adaptive unit (21) on the object (30).

10. A system as claimed in claim 9, wherein the first fixing means is tied to, stuck to, or clasped together with the second fixing means.

11. A system as claimed in claim 4, wherein the fixing means comprises an elastic element for fixing the adaptive unit (21) to the object (30) through elasticity forces.

12. A system as claimed in claim 1, wherein the adaptive unit (21) comprises a set of coils (215), and the set of coils (215) comprises generator coils for generating a primary magnetic field inducing an eddy current in an object, and sensor coils for sensing the primary magnetic field and a secondary magnetic field generated as a result of the eddy current.

13. A system as claimed in claim 12, wherein the set of coils (215) contact each other seamlessly.

14. A system as claimed in claim 12, wherein the generator coils connect with a generator circuit and the sensor coils connect with a sensor circuit, and the generator circuit and the sensor circuit are included in the main unit (23).

15. A system as claimed in claim 14, wherein the generator coils and sensor coils connect with the generator circuit and the sensor circuit, respectively, if the adaptive unit (21) is put in work status; the generator coils and sensor coils disconnect from the generator circuit and the sensor circuit, respectively, if the adaptive unit (21) is put in non-work status.