EP4314852A1

EP4314852A1 - High q-factor multi-loop gap resonator mlgr together with a tuning system

Info

Publication number: EP4314852A1
Application number: EP21728331.6A
Authority: EP
Inventors: Miko aj BARANOWSKI; Pawe MALINOWSKI; Tomasz Czechowski; Piotr Szczepanik
Original assignee: "novilet" Spolka Z OO
Current assignee: "novilet" Spolka Z OO
Priority date: 2021-03-30
Filing date: 2021-03-30
Publication date: 2024-02-07
Also published as: WO2022211645A1

Abstract

An multi-loop gap resonator MLGR for EPR spectroscopy and imaging applications is housed in a segmented housing and equipped with two coupled and independently driven tuning and adjusting systems, the motor (1) of the adjusting system and the motor (2) of the tuning system being located on the front plate of the first segment (25) of the resonator housing. The adjusting of the resonator is achieved by adjusting the distance of the adjusting loop (21) from the first petals (10) and the second petals (9), while the tuning of the resonance frequency is achieved by mutually changing the orientation of the first petals (10) and the second petals (9) of the MLGR resonator.

Description

High Q-factor multi-loop gap resonator MLGR together with a tuning system

The present invention is related to a high Q-factor multi-loop gap resonator MLGR together with a tuning system for use in spectroscopy and Electron Paramagnetic Resonance EPR imaging, especially in the study of biological objects. The proposed solution is based on the solution disclosed in the Polish Patent Application No. P.431384 dated 2019/10/04.

Electron Paramagnetic Resonance EPR imaging, which is a highly sensitive technique for detecting the partial pressure of oxygen, can also provide data on the spatial distribution and pharmacokinetics of free radicals in tissues. The finding of oxygen in tissues represents very important information for the treatment of cancer in oncological therapy. Due to the fact that free radicals in tissues occur in low concentrations and their lifetimes are very short, it is assumed that at this stage of research a radical with a sufficiently long lifetime and appropriate concentration should be externally introduced, whose EPR linewidth is highly dependent on the partial pressure of oxygen in its surroundings. Due to the depth of penetration of electromagnetic radiation into living matter and the potential heating effect on the test object, standard EPR spectrometers operating at microwave frequencies are unsuitable for performing EPR imaging. For this reason, lower frequencies in the radio frequency RF range are used in practice, which entails a significant reduction in the signal-to-noise ratio S/N. The reduction in S/N is due to the reduction in resonance frequency, which results in a reduction in the value of the magnetic field in the area for which the test is performed. The value of the magnetic field significantly determines the value of magnetisation, which has a major influence on the intensity of the recorded signal and consequently is responsible for the decrease in S/N. In addition, as the resonance frequency decreases, the quality factor (Q) of the resonator decreases, which further decreases the S/N, and, in practice, introduces limits related to the practical choice of the resonance frequency, especially in EPR scanning.

Continuous wave CW, rapid switch and pulsed techniques methods are currently used to image living objects in laboratory conditions. The usefulness of pulsed methods is limited by the very short spin-spin T₂ relaxation time for most radicals. The associated significant broadening of the resonance line width makes these methods unsuitable for EPR imaging. An additional problem is the shortening of the relaxation time T₂ due to the presence of a field gradient, which at significant gradients causes a free induction signal decay FID occurring in the spectrometer dead time. This effect makes it difficult, if not impossible, to perform the measurement. In order to significantly reduce the dead-time effect of the scanner, the use of Frank or Chu sequences has been proposed, which allow imaging to be performed. This method can only be used for radicals with long relaxation times. Images generated by this method are characterised by low spatial resolution, especially for larger objects.

The use of methods based on continuous wave CW and rapid switch RS techniques, on the other hand, does not have similar limitations. In both techniques it is required that the resonator registers the whole band of signal transmission, however, in case of CW technique the transmission band is very narrow, whereas in case of RS or pulsed technique the signal has very wide transmission band of the order of several or a dozen MHz’s It should be noted, however, that even lowering the scanning speed in the (RS) technique makes it possible to reduce the signal transmission bandwidth, due to the linear dependence of both values.

The quality factor (Q) of the resonator defines the bandwidth of the signal that can be correctly detected. The higher the quality factor, the lower the frequency bandwidth. It is important that the bandwidth of the resonator is of the order of, but not less than, the signal bandwidth. In this case the signal detection will be most effective.

Currently, for CW and RS methods used in EPR scanning, the quality factor (Q) of the resonator is not matched in terms of signal bandwidth, i.e. the signal bandwidth is much narrower than the resonator bandwidth. For optimal signal detection the quality factor (Q) of the resonator should be as large as possible in order not to influence the shape of the detected signal. Furthermore, the resonator must be made of materials which do not influence the magnetic field distribution. For detection (meeting the condition of resonance for a given frequency) an alternating magnetic field generated by external coils is used. Such a field in a standard resonator generates eddy currents which disturb the signal by generating indeterminate magnetic fields. A very important factor is also the difficulty of tuning the resonance conditions, which is particularly evident when studying living objects. It turns out that the resonator is susceptible to objects placed inside it, which in particular causes changes in the resonance frequency. The above effect can change the resonance conditions so much that the resonance falls outside the available range of the transmitter and receiver system of the scanner, making imaging impossible.

These limitations are eliminated by the new resonator design for small animal EPR spectroscopy and imaging applications proposed in this solution.

The purpose of the invention is to provide a high Q-factor resonator together with a tuning system for use in spectroscopy and EPR imaging of small animals.

The essence of a multi-loop gap resonator according to the invention, situated in a segmented housing and provided with two coupled and independently driven tuning and adjusting systems, is that the two motors of the adjusting system and the tuning system are located on the front plate of the first segment of the resonator housing, the motor shaft of the adjusting system being connected via a coupling to a drive screw which is connected to a positioning carriage located on the positioning element, which in turn is connected by means of fastening rods to the positioning arrangement of the adjusting loop, while the positioning element is further connected to a connecting element which is connected to the first supporting element of the petals of the MLGR resonator, while this element is connected to the fifth segment of the housing of the MLGR resonator, wherein the first petals of the resonator are mounted on the first resonator petals supporting element, and its second petals are located on the supporting element fitted to the mounting ring, supporting element is mounted to the third segment of the resonator housing by means of the first and second bearing assembly, the mounting ring, in turn, is driven by a belt and drive wheel mounted on a drive shaft which, at one end, is seated in a support bearing located in the fifth segment of the resonator housing, while at the other end, by means of a second coupling, is connected to the drive shaft of the motor of the tuning system, and furthermore a shield is mounted on the third, fourth and fifth segments of the resonator housing, the high frequency signal being fed to the resonator via a transmission line input/output, embedded in the shell of the second segment of the resonator housing, transmission line input/output is connected via a cable to the adjusting loop. It is preferably when:

- the petals are made of solid and/or perforated and/or scratched and/or parallel wires and/or are sputtered, or when

- the petals are arranged on elements of different radii, or when

- the petals are situated helically and/or linearly and/or circularly on the supporting element, or when

- the petals thickness is between 10 nm and 1 cm or when

- the petals are placed coaxially, or when

- the petals are placed on elements of equal radii, or when

- the number of petals is between 1 and 10000 or when

- the petals are of different or equal dimensions, or when

- the petals are made of multiple loops joined at their ends, or when

- the shield is made of uniform material, or of multiple loops, or of perforated or scratched material, coils or parallel wires, or when

- the shield is cylindrical or of variable geometry, or when

- the shield coils are cut and joined, or when

- the number of shields with different geometries is between 1 and 10000, or when

- the number breaks in the shield is between 1 and 10000, or when

- the shield is at most equal to the length of the resonator, or when

- the screen is at least equal to the length of the resonator.

The essence of the method of adjusting the multi-loop gap resonator according to the invention is that the adjusting is achieved by adjusting the distance of the adjusting loop to the first and second petals of the resonator.

It is preferably when the adjusting is performed by inductive coupling, by predetermining the distance of the adjusting loop from the first and second petals of the resonator, and adjusting the adjustment with trimmers connected to the resonator via the transmission line input/output.

It is also preferably when the adjusting is carried out by:

- magnetic or electrical coupling, or

- a variable geometry loop, or - the adjustment is made by means of a movable loop;

- an additional antenna performing rotational or progressive movements, or

- a loop and external capacities, or

- an antenna and external capacities.

A further essence of the method of adjusting the multi-loop gap resonator according to the invention is that the adjustment is achieved by means of a mutual change in the orientation of the first and second petals of the resonator.

It is preferably when the change in the resonance frequency is achieved by rotating the second petals relative to the first petals of the resonator.

The invention will be described in more detail on the basis of an exemplary construction of the resonator shown in Fig.l and Fig.2, which present, in two perpendicular views, elements enabling the resonator to be tuned to resonance conditions. The recorded signal is further processed in a transceiver or other electronic system.

An example 3D image of the marker distribution using the proposed solution is shown in Fig. 3.

List of reference numbers in the individual figures

1 - Motor of the adjusting system together with the shaft

2 - Motor of the tuning system together with the shaft

3 - Second coupling

4 - First coupling

5 - Drive shaft

6 - Driving screw of the adjusting system

7 - Positioning carriage

8 - Shield

9 - Second petals of the resonator

10 - First petals of the resonator

11 - Supporting element of the second petals of the resonator

12 - Supporting element of the first petals of the resonator

13 - First bearing 14 - Second bearing

15 - Transmission line input/output

16 - Cable

17 - Second segment of the resonator housing

18 - Drive wheel

19 - Belt

20 - Third bearing

21 - Adjusting loop

22 - Fastening rods

22a - Positioning arrangement for the adjusting loop

23 - Connecting element

24 - Positioning element

25 - First segment of the resonator housing

26 - Third segment of the resonator housing 26a - Fourth segment of the resonator housing 26b - Fifth segment of the resonator housing

27 - Mounting ring

The test sample is placed inside an MLGR resonator, which consists of two cut petals of different diameters mounted inside a shield. Preferably, the cylindrical shield is used and the resonator petals are in the shape of an intersected cylinder, the mounting of which is shown in Fig. 1 and Fig. 2. The adjustment of the resonator can be achieved by a adjusting loop which, by adjusting the distance from the resonator petals, adjusts the inductive coupling.

Alternatively, the adjustment can be achieved by initially determining the distance of the adjusting loop from the resonator petals and then fine-tuning with trimmers connected to the transmission line input/output. The position of the adjusting loop is determined by mechanisms 22a, 22, 24, 7, 6 and 4, which are set in motion by motor 1 of the adjusting system together with the shaft (Fig.l).

The motor 1 of the adjusting system together with the shaft, which constitutes the drive for the adjusting system, is connected to the resonator housing, while its shaft is connected via a second coupling 3 to the driving screw 6 of the adjusting system, which is housed in a plain bearing. The driving screw 6 drives the positioning arrangement 22a of the adjusting loop 21 through the elements; the positioning carriage 7 and the positioning element 24, providing freedom of movement and proper stiffening of the system. The positioning arrangement 22a is connected to the sliding element by means of the fastening rods 22. The connecting element 23 connects the positioning element 24 to the supporting element 12 of the first cylindrical resonator petals, which element is anchored in the fifth segment 26b of the resonator housing. Tuning is accomplished by mutually changing the angle of the first petals 10 and the second petals 9 of the resonator. The second petals 9 are mounted on the supporting element 11 , one end of which is fixedly attached to the mounting ring 27 - fixed through the first bearing 13 and the second bearing 14 to the third member 26 of the resonator housing. The drive transmission of the mounting ring 27 is realized by means of the belt 19 and the drive wheel 18, which is fixed to the drive shaft 5. The drive shaft 5 is seated in the third bearing 20. The transmission of motion of the drive shaft 5 is implemented by means of the second coupling 3 directly cooperating with the shaft of the motor 2 of the tuning system - built into the first segment 25 of the resonator housing. The shield 8 is mounted on the third 26, fourth 26a and fifth 26b segment of the resonator housing. The high- frequency signal is fed to the resonator via the transmission line input/output 15, embedded in the shell of the second segment 17 of the resonator housing and connected via the cable 16, to the adjusting loop 21.

On the other hand, if the resonance frequency needs to be tuned, it is changed by mutual rotation of the first petals 10 and the second petals 9 of the resonator.

The sample is placed in a resonator which is placed in an area of a multicomponent magnetic field suitable for use in spectroscopy or EPR imaging, followed by a procedure to adjust and tune the resonator so that the signal can be detected and further analysed in the receiving system.

Once the sample is positioned between the first petals 10 of the resonator, the position of the adjusting loop 21 is changed - via the positioning arrangement 22a of the adjusting loop, the fastening rods 22, the positioning element 24, the positioning carriage 7, the driving screw 6 of the adjusting system and the first coupling 4 of the motor 1 - until an optimum matching of the resonator is achieved. Changing the position of the adjusting loop 21 is performed by changing the position of the positioning arrangement 22a of the adjusting loop - via the fastening rods 22, permanently mounted in the positioning carriage 7. The positioning carriage 7 is moved by a screw driven by the motor 1.

In order to change the resonance frequency, rotation of the second petals 9 relative to the first petals 10 of the resonator is performed - until the resonance condition is obtained at the expected resonance frequency. The above adjustment is accomplished by rotating the supporting element 12 of the petals 9 - by means of rotating the mounting ring 27, to which the supporting element 12 is attached. The rotation of the mounting ring 27 is carried out by means of the rotation of the drive wheel 18 transmitted through the belt 19. In turn, the drive wheel 18 is rotated by means of the drive shaft 5, which is driven by the motor 2 of the tuning system together with the shaft and the second coupling 3.

Claims

1. A high Q-factor multi-loop gap resonator MLGR for spectroscopy and EPR imaging applications, encapsulated in a segmented housing and equipped with two coupled and independently driven tuning and matching systems, characterised in that a motor (1) of an adjusting system and a motor (2) of a tuning system are located on a frontal plate of a first segment (25) of the MLGR resonator housing, wherein a shaft of the motor (1) being connected via a first coupling (4) to a driving screw (6) which is connected to a positioning carriage (7) located on a positioning element (24), which in turn is connected via the fastening rods (22) to a positioning arrangement (22a) of an adjusting loop (21), while the positioning element (24) is further connected to a connecting element (23), which is connected to a first supporting element (12) of the petals of the MLGR resonator, while this element is connected to a fifth segment (26b) of the MLGR resonator housing, wherein the first petals (10) of the MLGR resonator are mounted on the first supporting element (12) of the petals of the MLGR resonator, while its second petals (9) are located on a supporting element (11) fixed on a mounting ring (27), the supporting element (11) is fixed to a third segment (26) of the MLGR resonator housing by means of a first bearing assembly (13) and a second bearing assembly (14), in turn, the mounting ring (27) is driven by means of a belt (19) and a drive wheel (18), seated on a drive shaft (5), which at one end is seated in a supporting bearing (20) located in a fifth segment (26b) of the MLGR resonator housing, and at the other end, via a second coupling (3), is connected to the drive shaft of the motor (2), and furthermore a shield (8) is fixed on the third, fourth and fifth segments (26, 26a and 26b) of the MLGR resonator housing, wherein the high frequency signal is fed to the resonator via the transmission line input/output (15), embedded in the shell of the second segment (17) of the MLGR resonator housing and connected via the cable (16), to the adjusting loop (21).

2. A multi-loop resonator according to claim 1, characterised in that:

- the petals (9, 10) are made of solid and/or perforated and/or scratched and/or parallel wires and/or are sputtered;

- the petals (9, 10) are arranged on elements of different radii; - the petals (9, 10) are positioned helically and/or linearly and/or circularly on the supporting element;

- the petals (9, 10) thicknesses range from 10 nm to 1cm;

- the petals (9, 10) are placed coaxially;

- the petals (9, 10) are placed on elements of equal radii;

- the number of petals (9, 10) ranges from 1 to 10000;

- the petals (9, 10) have different or equal dimensions;

- the petals (9, 10) are made of multiple loops joined at their ends;

- the shield (8) is made of uniform material or of multiple loops or of perforated or scratched material, coils or parallel wires;

- the shield (8) is cylindrical or of variable geometry;

- the coils of the shield (8) are cut and connected;

- the number of shields (8) with different geometries ranges from 1 to 10000;

- the number of breaks in the shield (8) ranges from 1 to 10000;

- the shield (8) is at most equal to the length of the resonator;

- the shield (8) is at least equal to the length of the resonator.

3. A method of adjusting a high Q-factor multi-loop gap resonator MLGR equipped with a dual adjusting/tuning system for use in spectroscopy and EPR imaging, characterised in that the adjustment is achieved by adjusting the distance of the adjusting loop (21) to the first petals (10) and the second petals (9) of the MLGR resonator.

4. The method according to claim 3, characterised in that the adjustment is performed by inductive coupling by initially determining the distance of the adjusting loop (21) from the first petals (10) and the second petals (9) of the resonator and tuning the adjusting with trimmers connected to the resonator via the transmission line input/output (15).

5. The method according to claim 3 or 4, characterised in that:

- the adjustment is performed by means of magnetic or electrical coupling;

- the adjustment is performed using a variable geometry loop;

- the adjustment is performed by means of a movable loop;

- the adjustment is performed by means of an additional antenna with rotary or ' progressive movement; - the adjustment is performed using a loop and external capacitance;

- the adjustment is performed by means of an antenna and external capacitance.

6. A method of tuning the frequency of a high Q-factor multi-loop gap resonator MLGR equipped with a dual adjusting/tuning system for use in spectroscopy and EPR imaging, characterised in that the change of the resonance frequency is achieved by mutually changing the orientation of the first petals (10) and the second petals (9) of the MLGR resonator.

7. The method according to claim 6, characterised in that the change of the resonance frequency is obtained by rotation of the second petals (9) with respect to the first petals (10).