Patent Application
20240345196
This application claims priority to Korean Patent Application No. 10-2023-0047268 (filed on Apr. 11, 2023), which is hereby incorporated by reference in its entirety.
The present disclosure relates to a magnetic resonance imaging (MRI) vibration measurement device.
Since the temporal resolution of magnetic resonance imaging (MRI) images is low, MRI images are sensitive to movement, image distortion and image artifacts due to movement of a patient or mechanical vibrations of an MRI system are present in the MRI images, and thus re-scanning or duplicate scanning is frequently required.
Particularly, the human brain is a soft and complex biomaterial, and because of various physiological dynamics, the human brain is regularly moved and deformed. Therefore, while the heart contracts and relaxes during a heartbeat cycle, a periodic change in arterial blood pressure is transmitted through blood vessels to cause local movement and deformation of the brain.
In addition, a diffusion tensor imaging technique used in brain disease research is sensitive to even minute movement in a brain image region during MRI scans, and is affected not only by patient movement but also by mechanical vibrations of an MRI scanner. Accordingly, inaccurate quantitative indicators (fractional anisotropy (FA), radial diffusivity (RD), axial diffusivity (AD), and mean diffusivity (MD)) of diffusion tensor metrics are extracted due to image distortion and a decrease in signal-to-noise ratio, and thus an accurate diagnosis of a brain disease is not performed.
For such reasons, there is a problem that image quality obtained by an MRI device is degraded, and re-scanning is required.
Conventionally, in a process of performing an MRI device and acquiring an image, vibrations have not been detected, and the magnitude and direction of the vibrations have not been detected. Accordingly, there is a difficulty in obtaining quantitative data required to reduce or remove the vibrations.
The removal of the difficulty of the conventional technology is one problem to be solved by the present disclosure. That is, the present disclosure is directed to providing a device capable of measuring vibrations which occur in a process of driving an MRI device.
According to an aspect of the present disclosure, there is provided a magnetic resonance imaging (MRI) vibration measurement device for measuring vibrations of an object inserted into the bore of an MRI scanner. The MRI vibration measurement device including a human phantom inserted into the MRI scanner in a direction (z-axis (head-to-foot direction); a light source which emits light; a mirror structure which emits the light to the human phantom and provides light reflected by the human phantom; a fiber-optic sensor which measures the reflected light to detect z-axis direction vibration of the human phantom, and a vibration sensor part, which is disposed in the human phantom holding apparatus, detects vibrations in x-axis and y-axis directions. The x-, y- and z-axis directions are orthogonal.
The human phantom may have any one shape of a spherical shape and a cylindrical shape, and the human phantom may be formed of any one material of glass and high density polyethylene (HDPE).
The human phantom holding apparatus may further include a phantom fixing member for firmly holding the human phantom, and the phantom fixing member may be formed of a polyethylene plastic material which is a non-magnetic material and externally expose at least a portion of the human phantom.
The vibration sensor part may be formed of a non-magnetic material and include at least one vibration sensor for measuring vibrations in two directions (an x-axis and a y-axis) which are perpendicular to each other and form 90 degrees with respect to the direction (z-axis) in which the human phantom is inserted into the MRI scanner and a vibration sensor for measuring vibrations on the z-axis.
The MRI vibration measurement device may include a light source which emits light, a mirror structure which emits the light to the human phantom and provides light reflected by the human phantom, and a sensor which measures the reflected light to detect the z-axis direction vibration of the human phantom.
The mirror structure may include a support shaft inserted into the MRI scanner along the z-axis (head-to-foot direction), a mirror which is positioned on an end portion of the support shaft, and reflects the light to the human phantom, a counter weight positioned on an end portion of the support shaft opposite to the mirror, and a holding leg part which fixes the mirror structure to a bottom.
According to another aspect of the present disclosure, there is provided a magnetic resonance imaging (MRI) vibration measurement device for measuring vibrations of an object inserted into the bore of an MRI scanner, the MRI vibration measurement device with a human phantom holding apparatus including a human phantom inserted into the MRI scanner, and a vibration sensor part disposed in the human phantom holding apparatus and formed of a non-magnetic material, wherein the vibration sensor part includes at least two accelerometer sensors for measuring vibrations in x-axis and y-axis directions which are perpendicular to each other and also are orthogonal to the z-axis direction in which the human phantom is inserted into the MRI scanner.
The human phantom may have any one shape of a spherical shape and a cylindrical shape, and the human phantom may be formed of any one material of glass and high density polyethylene (HDPE).
The human phantom structure may further include a phantom fixing apparatus for firmly holding the human phantom, and the phantom fixing member may be formed of a polyethylene plastic material which is a non-magnetic material and externally expose at least a portion of the human phantom.
The vibration sensor part may further include an accelerometer sensor which is formed of a non-magnetic material and measures vibrations on the z-axis (head-to-foot direction).
The above and other objects, features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing exemplary embodiments thereof in detail with reference to the accompanying drawings, in which:
Hereinafter, present embodiments will be described with reference to the accompanying drawings.
An MRI technology is a medical imaging technology used for acquiring an image of an anatomical structure and a physiological process of a human body positioned in an MRI scanner. The MRI system which generates an MRI image includes a magnet, a gradient coil, and a radio frequency (RF) coil and noninvasively generates an image of the inside of an object using a magnetic field, a dynamic magnetic field, and an RF energy. However, MR images of an object are degraded due to mechanical vibrations of the MRI device frequently.
In the first embodiment of the MRI vibration measurement device, the human phantom holding apparatus including the human phantom 100 is fixedly positioned on a bed. As one embodiment, the human phantom structure may include the human phantom 100 and a phantom fixing member (not shown) which firmly holds the human phantom 100 to the bed. As illustrated in the drawing, the human phantom structure may be positioned in a head coil for generating a high resolution MR image of the human head.
The human phantom 100 is designed based on a Korean standard human head shape. As one embodiment, as illustrated in
An inner portion of the spherical human phantom is filled with 2000 mL of a nickel chloride hydrate solution, and an inner portion of the cylindrical human phantom is filled with 1180 mL of the nickel chloride hydrate solution.
The phantom fixing apparatus (not shown) firmly holds the human phantom 100 to the bed. As one embodiment, the phantom fixing apparatus firmly holds the human phantom 100 so that a portion of the human phantom 100 is exposed, and light reflected by a mirror 210 (see
The phantom fixing apparatus is formed of a non-magnetic material. As described above, the human phantom is positioned in the MRI scanner. Accordingly, when the phantom holding apparatus includes a magnetic material, the phantom fixing apparatus may be moved into the MRI scanner by a strong magnetic field force. Thus, it may damage the MRI scanner. In order to prevent this damage, the phantom holding apparatus is formed of the non-magnetic material.
In one embodiment, the mirror structure 200 includes a support shaft 220 inserted into the bore of the MRI scanner along the z-axis, the mirror 210 which is positioned on an end portion of the support shaft 220 and reflects the light provided by the light source to the human phantom, a counter weight 230 which is positioned on an opposite end portion of the support shaft 220, and a fixing leg part 240 which firmly supports the mirror structure 200 to a bottom.
The mirror 210 is positioned on one side end portion of the support shaft 220, and the counter weight 230 is positioned on the other side end portion thereof. A connecting part C may be positioned at an intermediate portion of the support shaft 220, and a connecting shaft connected to the support shaft 220 and the fixing leg part 240 may be connected to the connecting part C.
The connecting part C may move between one side end portion and the other side end portion along the support shaft 220 to adjust a position at which the mirror 210 is inserted into the MRI scanner. The counter weight 230 formed on the opposite end portion of the support shaft 220 may also be moved between one side end portion and the other side end portion of the support shaft 220 to balance a weight. The connecting shaft fastened to the fixing leg part 240 is connected to the connecting part C. Accordingly, the mirror structure 200 may be firmly held to the fixing leg part 240 without shaking.
As described above, since the mirror structure 200 is used in the MRI scanner in which a strong magnetic field is formed, when a magnetic material is included, the mirror structure 200 is moved by the strong magnetic field force and has a risk of damaging the MRI system. Accordingly, at least the mirror 210 and the support shaft 220 of the mirror structure 200 are formed of non-magnetic materials. Preferably, the mirror 210, the support shaft 220, the counter weight 230, the connecting part C, and the fixing leg part 240 of the mirror structure 200 may be formed of non-magnetic materials.
A sensor 300 capable of measuring x-direction and y-direction vibrations may be disposed in the phantom with human body structures 100 inserted into the MRI scanner. As an example, the sensor 300 may be an optic-fiber accelerometer sensor, and as illustrated in the drawings, the single sensor 300 may detect both x-direction and y-direction accelerations. In an embodiment which is not illustrated, a sensor may be provided as a plurality of sensors including a sensor which measures both an x-direction acceleration and a sensor which measures a y-direction acceleration simultaneously.
The mirror 210 reflects light provided by the light source 400 and provides the reflected light to the human phantom 100. The light provided to an exposed surface of the human phantom 100 may be reflected by the human phantom 100 and provided to the mirror again. Vibrations of the MRI system during MRI scanning cause the movement of the human phantom 100, and thus the light reflected by the human phantom 100 is also vibrated.
As one embodiment, the mirror 210 also provides the light reflected by the human phantom 100 to an optical detector positioned outside the MRI scanner. The optical sensor may detect the light reflected by the human phantom 100 while the human phantom 100 vibrates, and measures z-axis direction vibrations of the human phantom 100.
As another example, light reflected by the human phantom 100 while the human phantom vibrates may be provided to an optical sensor positioned in the mirror structure 200. The optical sensor positioned in the mirror structure 200 may detect the light reflected by the human phantom 100 while the human phantom 100 vibrates in order to detect z-axis direction vibrations of the human phantom 100.
Hereinafter, an MRI vibration measurement device according to a second embodiment will be described. However, the same or similar components to those of the above-described embodiment may be omitted for the sake of simple and clear description.
The human phantom 100 is positioned in the human phantom holding apparatus and fixed to a bed. The sensors 300 which measure vibrations of the human phantom 100 may be attached to the human phantom structure. As one embodiment, the sensors 300 may include a sensor which measures an acceleration in the x-direction, a sensor which measures an acceleration in the y-direction, and an accelerometer sensor which measures an acceleration in the z-direction. Among them, sensors which measure accelerations in any two directions may be implemented as one sensor.
The sensors may be made of injection control pressure (ICP) shear accelerometer sensors in which interference and noise due to a strong magnetic field of 1.5 tesla or more and also electromagnetic waves which are formed in the MRI scanner. The sensors have a length of 10 mm, sensitivities of 102.7 and 101.1 mV/g, and output biases of 10.8 and 10.9 VDC.
As described above, the sensor 300 which measures vibrations of the human phantom 100 is positioned and operated in an MRI scanner in which a strong magnetic field is formed. Since the sensor may be moved by the magnetic field and damage the MRI device in the case of the sensor 300 including a magnetic material, the sensor 300 may be formed of a non-magnetic material to prevent damage to the MRI device and the sensor.
A cylindrical phantom (a diameter of 100 mm and a length of 230 mm) was designed and constructed, based on a shape of a Korean standard human head and neck. device mirror fixing stand capable of firmly holding the phantom was designed and formed using a non-magnetic plastic. In addition, a phantom holding apparatus formed of an insulating plastic net which is a non-magnetic material was formed to tightly fix the phantom to a bed.
X-axis and y-axis direction vibrations were measured using a first vibration measurement sensor capable of detecting x-axis and y-axis vibrations, and z-axis direction vibrations were measured using a second vibration measurement sensor capable of detecting z-axis vibrations simultaneously.
According to the present disclosure, there is an advantage of measuring and quantifying vibrations occurring when an MRI device is operated.
Although the present disclosure has been described to facilitate understanding of the present disclosure with reference to embodiments illustrated in the accompanying drawings, the embodiments are only exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other example embodiments may be made from the embodiments of the present disclosure. Therefore, the scope of the present disclosure should be defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2023-0047268 | Apr 2023 | KR | national |
