RU2845310C1 - Veterinary orthopaedic mri radio-frequency coil switching unit - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to orthopaedic MRI for examination of standing horse extremities, namely to switching unit of radio-frequency coil of tomograph. Switching unit of the radio-frequency coil of a veterinary orthopaedic MRI, made with a preamplifier mounted on the mobile magnet of the tomographic scanner and including a radio-frequency coil carrying a connection cable providing its electrical connection with the preamplifier. At that, the preamplifier is mounted on the magnet yoke bridge opposite to its pole gap working zone with the switching connector turning towards the radio-frequency coil, wherein the input of the cable connector into the housing of the radio-frequency coil is made through its upper face facing the preliminary amplifier, and the connection of the radio-frequency coil to the preliminary amplifier is made using a multi-pin connector.

EFFECT: use of this invention will allow to prevent damage and failure of tomography devices in direct contact with the examined extremity of a horse due to the destruction of the wire connection between them when examining a standing horse due to its spontaneous movements uncontrolled by the tomography operator.

1 cl, 3 dwg

Description

The invention relates to orthopedic MRI for examining horse limbs in a standing position, namely to a switching unit for a radiofrequency coil of the tomograph.

Orthopedic magnetic resonance imaging of a horse in a standing position allows obtaining detailed images of the horse's limb sections under study in projections of any spatial orientation with a wide range of specific MR contrast. The use of the method provides highly informative diagnostics of horse limb pathologies, which is several times more valuable in its diagnostic value than the results of X-ray and ultrasound examinations, especially in the early stages of diseases.

The main task in organizing an examination on orthopedic MRI is the need for a long-term and motionless placement of the examined section of the horse's limb in the working area of the magnetic system of the tomograph during the examination. Due to the fact that even a drug-sedated, standing horse is rarely motionless during the scanning process, there is a need for a technical solution that makes the examination safe for both the horse and the equipment used in the examination.

The magnetic system in veterinary orthopedic MRI, to which class the equipment in question belongs, is most often manufactured using a low-field permanent magnet with opposite magnetic poles located on a U-shaped steel yoke and an induced field B ₀ , the direction vector of which is orthogonal to the horse's limb standing in the interpolar working zone of the magnet. The mobile design of the magnet provides the possibility of its controlled movement to adjust the position of the magnet's working zone relative to the examined limb of a standing horse without its rearrangement.

One of the delicate devices of the tomograph, which are in direct contact with the horse's limb being examined and in close proximity to the tomograph equipment to which they are connected, are radio frequency coils (RF coils), which are highly sensitive antennas involved in the processes of radio frequency excitation and subsequent detection of radio frequency components of nuclear magnetic resonance signals, using which tomographic images of the organ being examined are reconstructed.

Typically, orthopaedic MRI of standing equine limbs uses a set of RF coils of different sizes, each with a cable connector with a male connector on the end of the cable that provides electrical communication with RF coil signal processing and transmission devices that carry a female connector, such as the preamplifier (PA) of the scanner's radiofrequency system.

When preparing to examine a horse using orthopedic MRI, the limb being examined with a detachable RF coil installed on it is placed in the working area of the tomograph's mobile magnet, after which the RF coil is connected.

In the practice of medical MRI, the most commonly used method of connecting the RF coil to the devices of the tomograph radiofrequency system, designed to process and transmit the RF coil signal, is its switching using devices for mutual mechanical fixation of the connector parts, excluding accidental breakage of the connection. When examining an animal under deep anesthesia, such a switching method is acceptable, since in this case the animal is motionless. However, when using an RF coil with a fixed connection for examining a horse standing in the magnet of an orthopedic MRI, uncontrolled by the operator, amplitude movements of the horse with the examined limb lead either to breakage of the detachable connector of the RF coil with the PU, or to breakage of its cable connector. Also, when using a fixed connection of the coil with the amplifier, damage to the coil itself is possible, the mechanical strength of which is not infinite. The destruction of the connection between the RF coil and the control unit, which are critical elements of the tomograph, leads to the shutdown of the MRI room for repair work and to a repeat examination after the system is restored to working order.

In order to find a solution to this problem, the applicant studied the state of the art.

An MR magnetic system for an animal limb is known from source JPH0236842A (published 06.02.1990, A61B5/055; G01R33/20; G01R33/38; A61B5/055; G01R33/38). The system contains a detachable radiofrequency coil. The coil body is covered with a cover made of soft material. A connecting pin protrudes from one end surface of the open coil, and a hole into which the connecting pin is inserted is formed on the other end surface. After the horse stands in a given position, the coil closes around the horse's leg.

When the horse is placed in the fixing frame, the upper part of the magnet yoke is level with the floor surface to prevent the horse's hooves from falling into the technological opening of the magnet in the floor. In this state, when the horse's hoof is placed in a predetermined position by the position of the radio frequency coil on the floor, which is the center of the working area of the study, a detachable radio frequency coil is mounted around the hoof, and then the magnet yoke is slowly raised to a predetermined height and scanning is performed. After the diagnosis is completed, the magnet yoke is lowered to the floor surface level, the radio frequency coil is removed from the horse's limb and the horse is taken out of the fixing frame.

It should be noted that the radio frequency coil consists of two parts, which are connected to the coil body in such a way that after closing they form a resonant circuit of the radio frequency coil. The plug of the coil connector protrudes from one end surface of the open coil, and the socket of the connector into which the plug is inserted is mounted in the opposite end surface of the open coil.

A device for conducting studies of a limb of a large animal, in particular a horse, based on the nuclear magnetic resonance effect is known from patent US6567683B1 (published on 20.05.2003, IPC A61B5/055; G01R33/465; A61B5/05;). The device includes a magnetic unit with a U-shaped magnet. The size and geometry of the magnet are adapted to the shape of a large animal. A special support has been developed for placing the limb being studied on it. The support is adapted for placement in the magnet. It is preferable to use resistive pole coils for the magnetic unit, but superconducting pole coils or permanent magnetic poles can also be used. The radio frequency unit is intended for radio frequency irradiation of the limb and/or for receiving nuclear magnetic resonance signals from the limb.

Patent US10989774 B2 (published on 27.04.2021, IPC A61B5/055; G01R33/38; G01R33/3815;) discloses an invention that relates to a vertically movable magnet for an MRI system intended for examining equine limbs in a standing position. The equine MRI system includes a positioning system that is configured to move a magnetic field assembly. The magnetic field assembly includes a magnet. The magnet may be made in the form of a single cylindrical structure or made from a plurality of individual magnetic segments. The magnet has an opening located along the longitudinal axis XX′ and configured to receive the body part being examined.

According to the invention, the magnetic unit may also include a transmitting coil mounted above the open circular surface of the gradient coil. In this case, the geometry of the transmitting coil may correspond to the geometry of the interpolar gap and the poles of the magnet and may not be circular in shape. Alternatively, the transmitting function may be performed by a radiofrequency coil fixed to the examined part of the body and operating in the transmitting/receiving mode. The transmitting coil is configured to form a radiofrequency field in the working zone of the interpolar gap of the magnet, where the examined part of the patient's body is located.

The patent CA2471244A1 (published on 26.06.2003, IPC A61B5/055; G01N24/00; G01R33/28; G01R33/38) discloses the Hallmarq Standing Equine MRI (sMRI) system for scanning a leg or other limb of an animal using a magnetic resonance imaging device. The system includes a detachable RF coil, which is made with a housing consisting of two rigid halves of a cylinder, with a hinged connection at one end and a detachable connector with a lever lock at the other. The coil is heavy and large in size. The RF coil is connected to a pass-through panel secured to the side cheek of the magnet yoke with a cable of the electronics module of the radio frequency path of the tomograph connected to it using a bayonet connector with a rotary mutual fixation of the connector parts after connection.

The disadvantages of the known solution are the breaks of the RF coil cable during amplitude movements of the horse's limb under study. The input of the connecting cable into the sMRI RF coil design is made from the side, which leads to an increase in the overall dimensions of the coil in width and the rotation of the coil by the cable around the vertical axis during movements of the horse's limb. The connecting cable of the RF coil is made long and lies on the floor under the horse's feet, which leads to its damage. The RF coil connection unit is not protected from the ingress of physiological fluids of the animal.

The studied analogues do not solve the described problem of protecting equipment from breakdowns associated with spontaneous movements of the horse being examined.

The system described in CA2471244A1 is accepted as the closest equivalent.

The present invention solves the problem of maintaining the integrity of the tomograph equipment in direct contact with the horse in all situations associated with uncontrolled movement of the animal at the workplace. In this case, the integrity of the equipment in the proposed technical solution should be understood as maintaining the technical (operational) state of the connection of the RF coil with the PU mounted on the mobile magnet of the orthopedic MRI when conducting an examination of a standing sedated horse on it.

As a result of solving the specified problem, a technical result is achieved, consisting in preventing damage and failure of tomograph devices that are in direct contact with the horse's limb being examined due to the destruction of the wire connection between them during examination of a standing horse due to its spontaneous movements that are not controlled by the operator.

The achievement of the specified technical result is ensured by the proposed RF coil switching unit with the PU, located on the mobile magnet of the orthopedic MRI and including the RF coil carrying a connecting cable that ensures its electrical connection with the PU, while:

– the PU is mounted on the jumper of the magnet yoke opposite the working area of its interpolar gap with the switching connector turned towards the radio frequency coil;

– the cable connector is inserted into the RF coil housing through its upper edge facing the control unit;

– the connection of the RF coil with the PU is made using a multi-contact connector without a device for mutual fixation of its parts.

Mounting the PU in the center of the upper edge of the magnet yoke bridge opposite the interpolar gap with the switching connector turned toward the RF coil located in the working area of the magnet gap eliminates the possibility of applying a lateral breaking force to their detachable connection, since the standard laying of the RF coil cable connector is performed along the mating/disconnecting axis of the connector and coincides with the possible direction of applying force to the connector when the coil is removed from the PU due to the movement of the horse's limb.

The introduction of the cable connector into the RF coil housing through the upper edge of the housing facing the control unit allows for additional shortening of the RF coil connecting cable, eliminates the possibility of laying the cable on the floor and increasing the overall dimensions of the RF coil, as well as the possibility of unwanted rotation of the coil by the cable around the vertical axis when placing the limb with it in the working area of the magnet interpolar gap.

The connection of the RF coil with the PU using a multi-contact connector ensures the assembly strength of the closure of the connector parts due to the sum of the friction forces in several contact pairs, as well as high reliability of the connection due to the duplication of the connection of the same-name signal communication lines by additional contact pairs.

At the same time, the use of a multi-contact connector without locking mechanisms for the mutual fixation of its parts when switching the RF coil with the PU allows freely, without violating the integrity of the equipment, to break the connection during amplitude movements of the horse's limb being examined with the coil fixed to it, without causing damage to the components of the switching unit. The proposed solution is further described in detail with references to the explanatory materials provided.

Fig. 1 – RF coil switching unit of orthopedic MRI;

Fig. 2 – Arrangement of the elements of the RF coil switching unit of the orthopedic MRI during examination of the horse’s hoof;

Fig. 3 – RF coil of orthopedic MRI.

Fig. 1 shows a switching unit of the RF coil (Fig. 3) of the orthopedic MRI, which includes an RF coil (1) carrying a connecting cable (2) with a plug (3) of the connecting connector mounted on its end, providing its electrical connection with the devices for processing and transmitting the signal of the RF coil (1) of the radio frequency system of the tomograph, in particular with the PU module (4), located in the center of the upper edge of the jumper (5) of the yoke of the mobile magnet (6).

Unlike the closest analogue, in the proposed technical solution the PU (4) is mounted in the centre of the upper edge of the jumper (5) of the yoke of the magnet (6) opposite its interpolar working gap, and the socket (7) of the RF coil (1) switching connector on the side edge of the PU (4) housing faces the RF coil (1). At the same time, the input of the connecting cable (2) into the coil (1) housing, facing the PU (4) in the working position, is made on its upper edge, which makes it possible to additionally shorten the connecting cable (2), eliminates an increase in the overall dimensions of the coil (1) and its rotation by cable (2) around the vertical axis when placing the horse limb (8) under study in the working area of the interpolar gap of the magnet (6). The detachable connection of the RF coil (1) with the PU (4) is made using a multi-contact connector without using locking devices for fixing the detachable connection after switching its parts. The RF coil switching module, PU and mobile magnet are protected by a sealed cover to prevent contact with the animal's physiological fluids.

The operation of the device is shown in the following example of an orthopedic MRI examination of a horse's hoof (Fig. 2).

In order to conduct an examination of the horse's hoof, the mobile magnet (6) is moved away from the workstation, on which the horse's limb (8) to be examined is placed, onto which a special detachable coil (1) for examining the hoof is installed. The coil (1) for the hoof has an internal volume repeating the conical shape of the horse's hoof and, after the coil (1) is closed around the hoof, rests together with it under its own weight on the floor of the workstation. The body of the RF coil (1) is turned by the connecting cable (2) towards the PU (4), mounted in the center of the upper edge of the jumper (5) of the yoke of the magnet (6). After this, the magnet (6) is moved to the limb (8) to place the hoof to be examined in the working area of the magnet (6), after which the plug (3) of the cable connector (2) of the RF coil (1) is inserted into the socket (7) of the connector on the side edge of the PU (4). The physical location of the horse's hoof with the coil (4) installed on it in the working area of the magnet (6) is limited by the geometry of the narrow tunnel of the interpolar gap, allowing the limb (8) with the coil (1) to move either in the direction of the PU (4) or away from it. Thus, the RF coil (1) switching unit using a multi-contact connector with a free connection to the PU (4) without using devices for mutual fixation of the connector parts clearly excludes the connector's destruction when the examined limb (8) of the horse moves in the working area of the tomograph.

In case of unpredictable movements of the horse's limb under examination with the coil placed on it, only a force coaxial with the direction of the connector connection and cable laying can be applied to the connector of the connection with the PU, which will only lead to the plug falling out of the connector socket, without any damage to it. This event does not irreversibly violate the conditions for conducting the examination, since the horse's limb must still be returned to the working area of the magnet, after which the connection of the RF coil with the PU is restored and the examination continues. The application by the horse of a lateral force that breaks the connector in the working area of the interpolar gap of the magnet is impossible due to the small width of the magnet gap and, therefore, the limitation of the horse's movement of the limb to the side.

To improve the protection of the RF coil connecting cable from breaking at the point of its entry into the coil housing, the cable is inserted into it through the upper edge of the housing, which in addition to protecting the cable reduces the overall width of the coil, eliminates the characteristic rotation of the coil by the cable around the vertical axis when the cable is inserted into the housing from the side, and, when placing the coil in a narrow interpolar gap of the magnet, makes the operation of mounting and connecting the RF coil easily performed by the tomograph operator. Also, a positive consequence of the proposed solution is the ability to shorten the RF coil connecting cable, which eliminates its sagging and getting under the horse's hoof, and also improves the resonant characteristics of the coil connected to the PU with a high-impedance input gain stage.

Thus, the claimed invention ensures long-term operability and integrity of the equipment in direct contact with a standing sedated horse, the structural and functional combination of which is a switching unit of the RF coil of a veterinary orthopedic MRI. The combined features of the proposed solution eliminate the possibility of damage to the equipment of the switching unit of the RF coil due to spontaneous movements of the horse. The use of the invention guarantees a productive completion of the examination of the horse regardless of the anxiety of its behavior, reduces the average time of its implementation and improves the quality of diagnostics.

Claims (1)

A switching unit for a radiofrequency coil of a veterinary orthopedic MRI, made with a pre-amplifier placed on a mobile magnet of the tomograph and including a radiofrequency coil carrying a connecting cable that ensures its electrical connection with the pre-amplifier, characterized in that the pre-amplifier is mounted on a jumper of the magnet yoke opposite the working area of its interpolar gap with a rotation of the switching connector towards the radiofrequency coil, wherein the input of the cable connector into the body of the radiofrequency coil is made through its upper edge facing the pre-amplifier, and the connection of the radiofrequency coil to the pre-amplifier is made using a multi-contact connector.