The present invention relates in general to magnetic resonance imaging and spectroscopy and devices related thereto, in particular to methods and devices used to enhance signal to noise ratio and obtain high-quality magnetic resonance spectra, and more particularly to devices that reduce the distance between a MR coil and a structure of interest inside a subject.
Magnetic resonance imaging (MRI) and spectroscopy (MRS) require high signal to noise ratio (SNR) to obtain high-quality magnetic resonance (MR) spectra and images. For a typical surface coil, signal drop-off inversely follows with distance squared, making difficult to achieve high SNR for MRI/MRS applications on anatomical regions that are not superficial. In some instances, internal coils have been utilized (intra-vascular/endorectal coils), but have limited applications and are often uncomfortable for patients. External surface coils for these non-superficial regions are designed using large coils to have best possible signal sensitivity at the required depths. There are multiple regions of clinical significance that are not suited for internal coil applications and would greatly benefit from improved SNR over what can be achieved using typical external surface coils. The diagnostic capability of MRI/MRS for external surface coil applications to internal organs/tissue of interest such as pancreas MRI could be improved.
Presently, to obtain MRI/MRS images or spectra from a structure that is located within a subject, a surface loop coil is used to produce maximum SNR at a particular depth of interest within a subject or sample. The size and geometry (square, circular, etc) of the loop coil is improved for that depth of interest. A second, so called “butterfly” coil element may be added on top of the loop coil and combined into a single channel using an improved combiner to increase the SNR at that depth of interest typically by 20-30% [1]. For that depth of interest, this technique is thought to increase the SNR for a single channel. To increase fields-of-view (FOV) in the long dimension additional inductively decoupled loop-butterfly elements are placed along the long axis and fed into separate receivers. Alternatively, a phased array of surface loop coils can be employed, but like the standard single surface coil, the SNR is ultimately limited by the distance between the surface coil or array and the depth of interest inside the body of the subject. Alternative approaches for internal structures include, as mentioned above, internal coils, such as endorectal [2] or intravascular [3]. Furthermore, internal coils have limited applications as the coils have to be very small to accommodate being inserted into the patient. This results in localized and inhomogeneous sensitivity maps. Internal coils are not a practical consideration for many internal structures such as the pancreas or kidneys. The use of endocrectal coils for prostate diagnosis also has complications of patient discomfort and significant tissue deformation [4].
U.S. Pat. No. 8,380,281 describes a compression device for enhancing normal/abnormal tissue contrast in MRI. The compression device has a fixed surface and a moveable member. The target tissue to be compressed is located between the fixed surface and the movable member. When the movable member is moved the target tissue is compressed between the fixed surface and the movable member. The compression device of this US patent is suitable for compression of an entire breast of the subject while the breast is disposed within a conventional MRI breast coil, which may result in a reduction of comfort to the subject. Furthermore, the “target” in U.S. Pat. No. 8,380,281 is the tissue (i.e. the breast) as opposed to a structure inside the body/breast of the subject. The devices and methods of U.S. Pat. No. 8,380,281 only work with target tissues that extend from the body, as such the devices and methods of this patent will not work for structures of interest inside a subject, for example, inside the abdomen. Furthermore, the device of U.S. Pat. No. 8,380,281 does not include a MR coil in the movable compression member.
In view of the foregoing, there is a need for devices or methods that will reduce the distance between the MR coil and a structure of interest inside a body of an object or subject thereby enabling improved SNR behavior from the MR coil. There is also a need that the device and method for reducing the distance between the MR coil and a structure of interest does not result in patient discomfort.
Presented herein are devices and methods that selectively press a portion of an area of a subject or object so as to bring a magnetic resonance (MR) coil closer to a structure of interest inside the subject or object by displacing tissue and/or organs that may be in between the devices of the present invention and the structure of interest. Bringing the MR coil closer to an internal structure of interest enables improved signal to noise ratio (SNR) behavior from the MR coil. Selectively pressing a smaller surface than the entire breast or abdomen, for example, will bring MR coils within the device closer to the desired internal structure inside the breast or abdomen, than could be achieved with a plate that compresses the entire breast or abdomen. That said, the pressing surface of the present invention, selectively presses or indents a surface area that is generally smaller than the surface area of the abdomen, breast, leg, neck of the subject.
Conversely, the methods and compression-type devices such as that of U.S. Pat. No. 8,380,281 do not selectively press (i.e. does not displace tissue out of the way) a portion of the breast, but rather it compresses an entire breast.
In one embodiment, the present invention provides for a magnetic resonance (MR) apparatus. The MR apparatus of the present invention, in one embodiment, includes a tissue pressing surface and one or more MR coil elements coupled to the tissue pressing surface, the pressing surface being configured and sized to selectively press a portion of an exterior tissue of a subject when a physical force is applied to the pressing surface thereby reducing a distance between the one or more MR coil elements and a structure of interest located inside the subject.
In another embodiment of the MR apparatus of the present invention, the MR apparatus includes a top surface opposite to the tissue pressing surface, and wherein the one or more MR coil elements are housed in between the tissue pressing surface and the top surface.
In another embodiment of the MR apparatus of the present invention, the MR apparatus further includes one or more secondary devices capable of mating to the pressing surface, each secondary device having one or more additional MR coil elements.
In another embodiment of the MR apparatus of the present invention, the MR apparatus includes one secondary device, and the one secondary device has a periphery larger than a periphery of the pressing surface.
In another embodiment of the MR apparatus of the present invention, the MR apparatus includes more than one secondary device and the more than one secondary devices are capable of mating to the pressing surface around a periphery of the pressing surface.
In another embodiment of the MR apparatus of the present invention, the MR apparatus further includes a member coupling having an end attached to the pressing surface and a free end.
In another embodiment of the MR apparatus of the present invention, the pressing surface includes a member coupling having an end attached to the pressing surface and a free end, and at least one of the one or more secondary devices includes an engaging means for receiving the free end of the member coupling.
In another embodiment of the MR apparatus of the present invention, the engaging means has a channel extending through the at least one of the one or more secondary devices.
In another embodiment of the MR apparatus of the present invention, the pressing surface includes a member coupling having an end attached to the top surface and a free end, the MR apparatus includes two or more secondary devices, and the two or more secondary devices are modular pieces that fit together to create an engaging means for receiving the free end of the member coupling.
In another embodiment of the MR apparatus of the present invention, the member coupling includes a hollow interior configured to house electronic components of the one or more coil elements coupled to the pressing surface.
In another embodiment of the MR apparatus of the present invention, the MR apparatus further includes a means for applying a physical force to the pressing surface.
In another embodiment of the MR apparatus of the present invention, the means for applying physical force is capable of attachment to the free end of the member coupling.
In another embodiment of the MR apparatus of the present invention, the MR apparatus further includes a driving means operatively linked to the means for applying physical force.
In another embodiment of the MR apparatus of the present invention, the subject has limbs and the means for applying a physical force to the pressing surface includes limb support configured to receive the limbs of the subject.
In another embodiment of the MR apparatus of the present invention, the subject is an animal and the one or more secondary devices are sized to cover a torso of the animal.
In another embodiment of the MR apparatus of the present invention, the one or more coil elements of the pressing surface and the additional one or more coil elements of the secondary devices include MR signal receiving coils, RF transmitting coils, gradient coils or any combination thereof.
In another embodiment of the MR apparatus of the present invention, the additional one or more coil elements of the one or more secondary devices are laid out within the secondary devices so as to reduce electromagnetic coupling with the one or more coil elements of the pressing surface when the one or more secondary devices is/are mated to the indenting substrate.
In another embodiment of the MR apparatus of the present invention, the subject is a human and the MR apparatus further includes a means for use by the human subject to apply a physical force to the pressing surface, and wherein the means for applying physical force is capable of attaching or coupling to the pressing surface.
In another embodiment of the MR apparatus of the present invention, the means for use by the human subject to apply physical force to the pressing surface includes limb support configured to receive limbs of the human.
In another embodiment of the MR apparatus of the present invention, the one or more coil elements of the pressing surface includes MR signal receiving coils, RF transmitting coil, gradient coils or any combination thereof.
In another embodiment of the MR apparatus of the present invention, the tissue pressing surface is made of a substantially rigid material.
In another embodiment of the MR apparatus of the present invention, the pressing surface has a relatively thin profile.
In another embodiment of the MR apparatus of the present invention, the subject is an animal, and the pressing surface is sized to cover an abdominal portion, a chest portion of, a neck portion or a limb of the animal.
In another embodiment of the MR apparatus of the present invention, the subject is an animal and the structure of interest is an organ or a tumor. In one aspect of this embodiment the subject is a human.
In another embodiment of the MR apparatus of the present invention, the subject is a vertebrate and the structure of interest includes an organ of a skeletal system, endocrine system, urogenital apparatus, digestive apparatus, respiratory apparatus, circulatory system or nervous system, synovial fluid, blood and/or lymph of the vertebrate.
In another embodiment of the MR apparatus of the present invention, the subject is a mammal, and the structure of interest is inside a breast of the mammal.
In another embodiment of the MR apparatus of the present invention, the subject is a human and the pressing surface is configured to press a breast of the human in the prone position.
In another embodiment of the MR apparatus of the present invention, the subject is a MR phantom and the exterior tissue is an exterior surface of the phantom.
In another embodiment of the MR apparatus of the present invention, the subject is a plant, and the exterior tissue is an epidermis of the plant.
In another embodiment of the MR apparatus of the present invention, the subject is an animal, and the exterior tissue is an epidermis of the animal.
In another embodiment of the MR apparatus of the present invention, the subject is an organ or a tissue biopsy.
In another embodiment of the MR apparatus of the present invention, the subject is a vertebrate, and the pressing surface includes a convex curved portion configured to accommodate an inferior curved costal margin of a rib cage of the subject, or configured to accommodate a curvature formed by a pubic bone and both superior pubic rami, or formed to fit inferior to an abdominal pannus over the pubic bone.
In another embodiment of the MR apparatus of the present invention, the pressing surface comprises a substantially rigid material having a thin profile, the pressing surface comprising a first wing region, a tail region, a head region, and a second wing region, the first wing region and second wing region extending longitudinally away from a midline connecting the head and tail regions, the head region being defined by a convex shape and the tail region being defined by a concave shape.
In another embodiment of the MR apparatus of the present invention, the one or more MR coil elements contour the periphery of the pressing surface.
In another embodiment of the MR apparatus of the present invention, the first and second wing regions curve from the midline such that the subject contacting side of the MR apparatus is capable of approximately conform to the shape of the exterior tissue of the subject.
In another embodiment of the MR apparatus of the present invention, the one or more MR coil elements are coated with a suitable coating, and the combination of each of said one or more MR coil elements with the coating constitutes the pressing surface.
In another embodiment, the present invention is a method of recording magnetic resonance (MR) signals from a structure of interest inside a subject. The method, in one embodiment, includes: (a) providing a MR apparatus having a tissue pressing surface and one or more MR signal receiving coils coupled to the tissue pressing surface, the tissue pressing surface being configured and sized to selectively press a portion of an exterior tissue of a subject; (b) positioning the pressing surface in contact with a portion of the subject's exterior tissue that is relatively near to where the structure of interest is located inside the subject; (c) exposing the portion of the subject's exterior tissue to an MR system having a Larmor frequency; (d) stimulating the structure of interest at the Larmor frequency of the MR system; and (e) receiving MR signals from the stimulated structure of interest with the one or more MR receiving coils of the MR apparatus.
In one embodiment of the method of recording MR signals from the structure of interest inside the subject, prior to step (d) the method further includes the step of applying physical force to the pressing surface thereby selectively pressing the portion of the subject's exterior tissue and reducing a distance between the one or more MR signal receiving coils of the MR apparatus and the structure of interest inside the subject.
In one embodiment of the method of recording MR signals from a structure of interest inside a subject, the MR apparatus further includes one or more transmitting coils capable of transmitting signals at the Larmor frequency of the MR system, and wherein the stimulation of the structure of interest is done with the transmitting coils of the MR apparatus.
In another embodiment of the method of recording MR signals from a structure of interest inside a subject, the MR apparatus further includes one or more gradient coils, and wherein the method further includes performing variations in a main magnetic field (Bo) of the MR system with the gradient coils.
In another embodiment of the method of recording MR signals from a structure of interest inside a subject, the MR apparatus is the MR apparatus of any one of embodiments of the present invention.
In another embodiment, the present invention is a method of transmitting signals at the Larmor frequency of a magnetic resonance (MR) system to a structure of interest inside a subject. In one embodiment, the method of transmitting signals at the Larmor frequency of a magnetic resonance (MR) system to a structure of interest inside a subject includes: (a) providing a MR apparatus having a tissue pressing surface and one or more transmitting coils coupled to the tissue pressing surface, the tissue pressing surface being configured and sized to selectively press a portion of an exterior tissue of a subject; (b) positioning the pressing surface in contact with a portion of the subject's exterior tissue that is relatively near to where the structure of interest is located inside the subject; (c) exposing the portion of the subject's exterior tissue to an MR system having a Larmor frequency; and (d) transmitting the signal at the Larmor frequency with the one or more transmitting coils thereby stimulating the structure of interest.
In one embodiment of the method of transmitting signals at the Larmor frequency of the MR system to the structure of interest of the present invention, prior to step (c) the method further includes the step of applying physical force to the pressing surface thereby selectively pressing the portion of the exterior tissue and reducing a distance between the one or more transmitting coils and the structure of interest.
In one embodiment of the method of transmitting signals at the Larmor frequency of a MR system to a structure of interest inside a subject of the present invention, the MR apparatus further includes MR signal receiving coils, and wherein the method further includes the step of receiving MR signals from the stimulated structure of interest with the one or more MR signal receiving coils of the MR apparatus.
In another embodiment of the method of transmitting signals at the Larmor frequency of a MR system to a structure of interest inside a subject of the present invention, the MR apparatus further includes one or more gradient coils, and wherein the method further includes performing variations in a main magnetic field (Bo) of the MR system with the gradient coils.
In another embodiment of the method of transmitting signals at the Larmor frequency of a MR system to a structure of interest inside a subject of the present invention, the MR apparatus is the MR apparatus of any one of embodiments of the present invention.
In one embodiment of the method of recording MR signals or transmitting MR signals of the previous embodiments, the subject is a human and the step of applying the physical force includes: (i) having the subject produce an inhalation stroke; (ii) applying the physical force to the pressing surface during the inhalation stroke; (iii) holding the pressing surface for a sufficient amount of time while the subject keeps the inhalation stroke; (iv) having the subject exhale and release the pressing surface; and (v) repeating sub-steps (i)-(v) as necessary.
In yet another embodiment, the present invention is a use of a magnetic resonance (MR) apparatus having one or more MR coil elements and a tissue pressing surface to record, transmit or to record and transmit MR signals form a structure of interest inside a subject. In one aspect of this embodiment, the MR apparatus is the MR apparatus of any of the embodiments of the present invention.
In a further embodiment, the present invention is a magnetic resonance (MR) apparatus. The MR apparatus, in one embodiment, includes a surface having one or more MR coil elements, the surface comprising a first wing region, a tail region, a head region, and a second wing region, the first wing region and second wing region extending longitudinally away from a midline connecting the head and tail regions, the head region being defined by a convex shape and the tail region being defined by a concave shape.
In one embodiment of the MR apparatus of the previous embodiment, the one or more MR coil elements contour a periphery of the indenting substrate.
In another embodiment of the MR apparatus of the previous two embodiments, the first and second wing regions curve from the midline such that the subject contacting side of the MR apparatus is capable of approximately conforming to the shape of the exterior tissue of the subject or body part.
In another embodiment, the present invention is a magnetic resonance (MR) apparatus, the MR apparatus including a tissue pressing surface and one or more MR coil elements coupled to the pressing surface, the pressing surface being configured and sized to selectively press a portion of an exterior tissue of a body part an animal when a physical force is applied to the pressing surface thereby reducing a distance between the one or more MR coil elements coupled to the surface and a structure of interest located inside the subject, wherein the size of the portion ranges between about 1/20 to about ⅔ of the exterior tissue of the body part.
In one embodiment the body part is an abdomen, and the size of the portion ranges between 1/20 to about ⅔ of the exterior tissue of the abdomen.
In another embodiment the body part is a breast, and the size of the portion ranges between 1/20 to about ½ of the exterior tissue of the breast.
The present invention, in yet another embodiment, provides for a magnetic resonance (MR) apparatus, as substantially described herein with reference to and as illustrated by the accompanying drawings.
The present invention, in yet a further embodiment, provides for a method of recording or transmitting a magnetic resonance (MR) signal from or to a structure of interest inside a subject as substantially described herein with reference to and as illustrated by the accompanying drawings.
The following figures illustrate various aspects and preferred and alternative embodiments of the invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Also, unless indicated otherwise, except within the claims, the use of “or” includes “and” and vice versa. Non-limiting terms are not to be construed as limiting unless expressly stated or the context clearly indicates otherwise (for example “including”, “having” and “comprising” typically indicate “including without limitation”). Singular forms including in the claims such as “a”, “an” and “the” include the plural reference unless expressly stated otherwise. In order to aid in the understanding and preparation of the within invention, the following illustrative, non-limiting, examples are provided. The priority document is incorporated by reference to this document.
“Exterior tissue” refers in this document to an outermost layer of a subject or the outmost layer of a body part. The “exterior tissue” may depend on the nature of the subject or body part. In the case of an animal or plant, the exterior tissue will be the skin of the animal or the epidermis of a plant and it will not include endothelium, or the tissue lining the inside cavities, tracts and lumen of the animal or plant; in the case of a body part or body section (i.e. the abdomen, breast, neck, limb and so forth) “exterior tissue” will be the skin covering the body part or body section; in the case of an ex vivo organ or tissue biopsy obtained from an animal or plant, the “exterior tissue” will be the layer of cells lining the exterior of the organ or biopsy; and in the case of a MR phantom, the “exterior tissue” refers to the outermost layer of the MR phantom. Preferably, the exterior tissue is an indentable tissue.
“Pressing” or “press” refers in this document to the pressing of a surface or substrate onto a portion of exterior tissue of a region or part of a subject or object, such that the surface penetrates, including indents, into the subject or object but without breaking or piercing the exterior tissue, or without leaving a permanent mark or permanent dent on the exterior tissue. The size of the portion of exterior tissue may depend on the region or part of the subject or object, and it may range from about 1/20 to about ⅔, but less than 1/20 and more than ⅔ may also be possible. For example, “pressing a portion of the abdomen” refers to pressing a surface onto a portion of the abdomen (the anterior portion of the body of a vertebrate between the thorax and the pelvis), and not to the entire abdomen, for example, pressing on 1/20, 1/10, ¼, ⅓, ½, ⅔ and so forth of the abdomen area and including any area there in between; and “pressing a breast” refers to pressing a surface onto a relatively small portion of the breast, but not the entire breast, for example pressing on 1/20, 1/10, ¼, ⅓, ½ and so forth of the breast's area including any area there in between. The smaller the portion being pressed the deeper the press. “Pressing” is not the same as “compression,” which refers to the non-selective pressing of a surface onto a relatively large tissue portion of or the entire region or part of a subject so as to reduce a volume of the tissue portion being compressed.
The term “pressing surface” refers in this document to a material-carrying MR coil which is used to apply a physical force to a portion of an exterior tissue of a subject or object so as to bring the MR coil being carried by the material relatively closer to a target located under the exterior tissue or object (i.e. inside the subject or object). At the same time the MR coil may transmit or receive MR signal data from, or deliver gradient fields to, the target and the rest of the body. “Pressing surface” excludes inserting or implanting the MR coil under the exterior tissue or inside the body of the subject or object. The material may be a shell or pad carrying the MR coil(s) or the material may be a coating on an MR coil.
“Subject” refers in this document to subjects, objects and to any matter or body from which an MR signal can be recorded. Examples of subjects include living objects, such as plants, human and non-human animals, as well as phantoms designed for MR experiments (MR phantoms). The term “subject” also includes samples obtained or extracted from the subject, such as organs and/or biopsies.
“Structure” refers to any matter or body inside the subject from which a MR signal can be recorded. Examples of structures may include the organs of an animal (pancreas, stomach, liver, intestines, kidneys, prostate, uterus, bladder, and so forth). “Structure” may also be used to refer to a mass inside a subject such as a tumor, or to fluids, such as blood, lymphatic and synovial fluids. Preferably, the structure may be located generally near tissue capable of being pressed, such as the abdomen or the breast of an animal. Structure of interest may be a structure or an exploratory area of imaging below the exterior tissue.
Presented herein is an MR apparatus having an exterior tissue pressing surface carrying one or more MR coil elements.
Referring to
In the embodiment illustrated in
In another embodiment of the present invention, the MR apparatus may also include one or more secondary devices having one or more additional coil elements. The secondary device may be used to provide coverage for portions of the subject that are not covered by the pressing surface.
The one or more secondary devices may be fixed to the pressing device, or the one or more secondary devices may be capable of attachment or detachment from the pressing device.
When two or more secondary devices are provided, the secondary devices may be made into modular pieces or modules that fit together or interlock such as to create an engaging means to receive the pedestal or member coupling.
The MR apparatus of the present invention may also be provided with a device for applying physical force to the pressing surface. The device for applying physical force may take the form of arm rests located on the surface of the pressing device or pressing substrate that is not in contact with the exterior tissue of the subject, i.e. the top side.
If one secondary device is to be used, as shown in
The pressing surface and, if one is provided, the coupling members, may be made of a substantially rigid, non-ferromagnetic material.
The MR coil elements coupled to the pressing surface or to the secondary device may be any type of suitable coils for MR. The MR coils may be radio frequency (RF) transmitting coils, MR signal receiving coils, gradient coils or any combination thereof.
The pressing surface of the MR apparatus of the present invention may take any suitable shape for pressing or even indenting an exterior tissue of a subject. The design of the pressing surface may take into account the relationship between anatomical morphing capabilities of a tissue to be pressed or indented and the performance of the coil elements enabled by the pressing surface. When the subject is an animal (including humans), the design may also take into account comfort to the subject.
Although the above description refers to a pressing surface, it should be understood that the MR apparatus of the present invention may also acquire or transmit MR signals from/to a structure of interest without a pressing step. That is, the pressing surface of the MR apparatus of the present invention is suitable for pressing, but it may just be positioned on the exterior tissue of the subject and rest on the exterior tissue of the subject.
The pressing surface or tissue contacting surface or the MR apparatus of the present invention may be sized to cover a portion of a body or body part. The size of the pressing surface or tissue contacting surface may depend on body or body part to be analyzed with the MR apparatus and/or the structure of interest within the body or body part. For example, in the case of the abdomen the size of the pressing surface or tissue contacting surface may range from about 1 cm in diameter to about 20 cm in diameter; for breasts, the pressing surface or contacting surface may range from about 1 cm in diameter to about 10 cm in diameter.
Operation
The MR apparatus of the present invention may be used in methods for recording a MR signal from a structure of interest inside a subject, and/or to transmit a Larmor frequency signal to a structure of interest inside a subject. In one embodiment, a method may begin by providing a MR apparatus of the present invention having one or more MR signal receiving coils and/or one or more coils capable of transmitting a Larmor frequency, and a tissue pressing surface. The design of the MR apparatus to be provided may depend on the structure of interest and the subject. For example, when the structure of interest is inside the abdomen, then an MR apparatus of
With reference to
While the physical force is applied, the structure of interested may be stimulated at the Larmor frequency of the MR system. Stimulation at the Larmor frequency may be done with the transmitting coils of the MR apparatus of the present invention. The MR signals from the stimulated structure of interest may then be received by the MR signal receiving coils of the MR apparatus of the present invention.
Different inhale/exhale indentation conditions may be used to improve pressure depth. In one embodiment, the pressing may be carried out as follows:
i) inhale with pressing of the MR apparatus;
ii) holding the press while transmitting a signal at the Larmor frequency to the structure of interest and receiving MR signal from the structure stimulated with the Larmor frequency; and
iii) exhale and release the press.
Another condition may be:
i) inhale ii) press and hold press, iii) exhale and hold breath while holding press, iv) stop holding breath and release press.
Although the pressing surface of the present invention may be used for pressing the exterior tissue of a subject to bring the MR coils relatively closer to a structure of interest, the MR apparatus of the present invention may also be operated without a pressing step. As shown in
The embodiments of the MR apparatus of the present invention provide the following, non-limiting advantages:
1. Using a pressing surface to reduce the distance between MR coil elements and a target of interest inside a body enables improved SNR behaviour from the coil elements. There may also be a parallel MRI benefit (improved g factor) with pressing or even indenting relative to the same coil un-pressed.
2. Reduce patient discomfort by having the patient control the pressing force.
3. House all electronic components required for the coils within the pressing surface.
4. Pressing surface rigid enough to not deform under the physical force applied by the subject.
5. Safely enclose the components and cables to a level suitable for human REB protocol testing or clinical imaging.
6. Maintain a narrow or thin profile to sit nicely posterior to the larger housing of the secondary device.
7. The narrow or thin profile of the pressing surface enables the secondary device being positioned relatively closer to the subject.
8. Have a variable depth sliding connection with the larger housing of the secondary device.
By limiting the dimensions of the pressing surface to substantially less than the size of the subject, object, or the part thereof for which the MR apparatus of the present invention is designed, the tissue pressed into has a space around the pressing surface, into which to move. This tends to decrease a compression of the tissues, which is an advantage for comfort of the patient and reduces a force required for a particular penetration depth. While some minimal amount of compression may be inevitable with the present invention depending on the tissue being pressed, substantial compression of the tissue is not necessary for the MR coils to approach the structure of interest.
These Examples are described solely for purposes of illustration and are not intended to limit the scope of the invention. Changes in form and substitution of equivalents are contemplated as circumstances may suggest or render expedient.
Pressing a subject's exterior tissue to reduce the distance between a structure of interest inside the subject and a MR coil, results in improved MRS/MRI performance. To investigate the viability and performance improvements of this approach, a computational simulation of a viable coil design under the described conditions was conducted. Using a human torso sized phantom with an anatomically placed pancreatic tissue region, a 14Ch coil design was simulated based on 0 cm, 2 cm and 4 cm indentation into the torso model (
Relative SNR performance for two different axial slices is shown in
An RF coil array design was segmented into a portion (i.e. the pressing device) that will press the abdominal tissue to provide high signal sensitivity to an abdominal structure, such as the pancreas, and a larger portion to sit above (anterior) for providing signal coverage over the entire torso (i.e. the secondary device). This large portion may be used to improve parallel imaging performance of the array. To design the pressing portion of the RF coil array, we had to determine the shape and orientation that will provide the best pressing or indenting structure to design the RF coil in. This presents a relationship between anatomical morphing capabilities of the abdominal region and the coil performance properties enabled by the associated pressing device.
To investigate potential pressing surfaces or devices, a variety of shapes, sizes, orientations and depths of paddles were tested on a group of volunteers. These paddles were made using balsa wood, as shown in
Due to the position of the pancreas, the paddle was designed to be as close as possible to the rib cage. Also, it may be desirable for the pad face to be given a slight superior angle, pointing it superiorly towards the pancreatic region. This angle can be seen in
Different inhale/exhale indentation conditions were tested to improve depth of pressure. Also considered was the order of operations (exhale then indent, vs. indent then exhale) to see if pancreas position or orientation changed. Two of the sample patient datasets are shown in
1. Equipment and Subject
MRI system: Siemens 3T Verio.
Human volunteer: 100 kg healthy adult male.
A variety of shapes, sizes and thicknesses of pressing pads shown in
2. Imaging Sequence
T1 FLASH (Axial)—80 slices (interleaved contrast), FOV 289 mm×360 mm (165×256), 5 mm slice, TR=3.95 ms, TE=1.19 ms and 2.14 ms. [Note that the sequence is numbered based on system tracker]:
2) Inhale with press (axial)
3) Inhale without press (axial)
4) Exhale with press (axial)
5) Exhale without press (axial)
6) Press and then inhale (axial)
7) Inhale with press (sagittal)
8) Inhale without press (sagittal)
Changed Geometry of Indenting Substrate
10) Inhale with press (axial)
12) Inhale without press (axial)
13) Inhale with press (sagittal)
14) Inhale without press (sagittal)
3. Results
Exemplary images of the sequences are displayed in
The benefits of pressing with inhale are clearly demonstrated in
The benefits of pressing are seen in
In conclusion, using the pressing pad of the present invention reduces the distance between the pressing pad and the structure of interest inside the body of a subject. In the case of the pancreas, the reduction in distance may be augmented by having the subject inhale prior to pressing.
A printed circuit board (PCB) was engineered to optimally fill the pressing device space. The pressing device was designed to be a 5-channel coil based on the footprint of the pressing surface of the pressing device and the information gathered regarding pancreas region size and expected distance from the pressing surface. Also created a coil layout (secondary device) for an 8 channel array to provide coverage for the remainder of the torso. This pancreas coil design may be placed anterior to the patient. For parallel imaging purposes, an additional posterior coil is desirable. The standard Original Equipment Manufactured (OEM) posterior spine array coil available on the intended MRI system may provide adequate coverage for the torso.
As part of the PCB layout process, multiple iterations of the trace layouts were created to reduce electromagnetic coupling, layout of cable locations, and improve SNR performance. Cable routing and mechanical design are also considered to improve clinical usability. The trace layout iterations are shown for the 8-channel PCB in
The final PCB's are laid out in computer aided design (CAD) to allow future modifications and potential production engineering.
Construction of the 5-channel pressing device array was completed within the mechanical housing, after performance optimization, trouble shooting, investigating cable layout and decoupling. The populated pressing device, with cables for phantom testing is shown in
Phantom Design and Results
A phantom design that mimics a torso of a human had to represent human torso dimensions, in addition to being capable of quick and reproducible conditions between the pressed and non-pressed state. To achieve this, and with reference to
First, we investigated the noise properties of the constructed 5 channel indentation coil shown in
Phantom Performance Discussion and Summary
First, we consider the SNR gain from adding the 5Ch pressing device coil array without applying any pressure. This gain in SNR is relative to if the 6 Channel Siemens Body Matrix was used only. From the 10 cm deep coronal and central axial slice data shown in
The mechanical housing for the pedestal portion of the MR apparatus forms a variable separation connection between the 5 channel pressing device and the 8 channel outer device. The rectangular shape allows for two potential pressing device orientations, pointing superior or inferior along the patient's body. This design feature was included for developing this pressing device as both pressing assisted pancreas and prostate array coil.
In Examples 2 and 3 shaped pads were used to study the benefit of pressing. In this example, an MR apparatus of the present invention was used to study the advantages of the MR apparatus of the present invention in improving the signal to noise ratio in MR images.
The MR apparatus with RF coil elements shown in
Various modifications may be made in this invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/CA2015/051041 | 10/16/2015 | WO | 00 |
Number | Date | Country | |
---|---|---|---|
62065424 | Oct 2014 | US |