WO2018195654A1

WO2018195654A1 - Mri coil apparatus and method

Info

Publication number: WO2018195654A1
Application number: PCT/CA2018/050469
Authority: WO
Inventors: Nibardo LOPEZ RIOS; Julien COHEN-ADAD
Original assignee: Polyvalor, Limited Partnership; Valorisation Hsj, Limited Partnership
Priority date: 2017-04-26
Filing date: 2018-04-19
Publication date: 2018-11-01

Abstract

An MRI coil apparatus having a housing defining an inner enclosure. A coil array has a wire loop array and a plurality of coil plates engaged with the wire loop array. The coil plates delimit a body part cavity to receive a body part. The coil array has displacement mechanisms extending into the inner enclosure to a connection with a corresponding coil plate. The displacement mechanisms displace the coil plates and the wire loop array to vary a size of the body part cavity between a retracted position and an engaged position. The coil plates in the engaged position abut the body part. A point of contact is formed between each coil plate and the body part upon the coil plate first abutting the body part. Each coil plate is pivotable about the point of contact to better conform the coil plate to a surface of the body part.

Description

MRI COIL APPARATUS AND METHOD

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US provisional patent application having serial number 62/490, 173 and filed April 26, 2017, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

[0002] The application relates generally to magnetic resonance imaging (MRI) systems and, more particularly, to an MRI coil apparatus.

BACKGROUND

[0003] It is often difficult to perform magnetic resonance (MR) imagining of pediatric patients (e.g. neonates and young infants). Receiving coils for such patients are not readily available, which often results in standard adult coils being used. The use of standard adult coils results in sub-optimal image quality.

SUMMARY

[0004] In one aspect, there is provided a magnetic resonance imaging (MRI) coil apparatus for imaging a body part, the MRI coil apparatus comprising: a housing defining an inner enclosure; and a coil array having a wire loop array and a plurality of coil plates engaged with the wire loop array within the inner enclosure, the coil plates arranged to delimit a body part cavity to receive the body part therein, the coil array having a plurality of displacement mechanisms each mounted to the housing and extending therefrom into the inner enclosure along a longitudinal axis to a connection with a corresponding coil plate, the displacement mechanisms being operable to displace the coil plates and the wire loop array along the longitudinal axis to vary a size of the body part cavity by displacing the coil plates toward the housing to a retracted position and away from the housing to an engaged position, the coil plates in the engaged position abutting the body part, a point of contact being formed between each coil plate and the body part upon the coil plate first abutting the body part, each coil plate being pivotable about the point of contact to better conform the coil plate to a surface of the body part.

[0005] In an embodiment, each displacement mechanism includes a biasing mechanism operable to actively apply a force to displace the coil plates toward the retracted position, and operable to passively bias the coil plates toward the engaged position.

[0006] In an embodiment, the biasing mechanism includes a closed pneumatic tube array in fluid communication with a plurality of collapsible bellows each connected to one of the coil plates, the biasing mechanism being operable to actively collapse the bellows and displace the coil plates to the retracted position upon a negative pressure being provided to the tube array, the bellows being passively expandable to displace the coil plates toward the engaged position upon the negative pressure being relieved in the tube array.

[0007] In an embodiment, the engaged position is the default position of the coil plates.

[0008] In an embodiment, the coil plates are spaced apart from another in the retracted position.

[0009] In an embodiment, each of the coil plates has peripheral edges, at least some of the peripheral edges of at least some of the coil plates abut against at least one of the peripheral edges of a neighbouring coil plate in the engaged position.

[0010] In an embodiment, the coil plates are free of overlap in both the retracted and engaged positions.

[0011] In an embodiment, at least one of the coil plates is displaced along the longitudinal axis of a corresponding displacement mechanism independently of another one of the coil plates.

[0012] In an embodiment, the displacement mechanisms are operable to simultaneously displace all the coil plates along the respective longitudinal axes. [0013] In an embodiment, the body part cavity delimited by the coil plates has a spherical shape, the displacement mechanisms being operable to displace the coil plates along substantially radial lines.

[0014] In another aspect, there is provided a method of arranging a magnetic resonance imaging (MRI) coil apparatus to receive a body part, the method comprising: providing a plurality of displaceable coil plates disposed to define a body part cavity for receiving the body part therein, the coil plates being engaged with a wire loop array; and displacing the coil plates and the wire loop array to: increase a volume of the body part cavity when the coil plates and the wire loop array are displaced in a first direction along the longitudinal axis; and abut the coil plates against the body part when the coil plates and the wire loop array are displaced in a second direction opposite to the first direction, a point of contact being formed between each coil plate and the body part when the coil plate first abuts the body part, each coil plate being pivotable about the point of contact to better conform the coil plate to a surface of the body part.

[0015] In an embodiment, displacing the coil plates and the wire loop array along the first direction includes actively displacing the coil plates and the wire loop array in the first direction.

[0016] In an embodiment, actively displacing the coil plates and the wire loop array in the first direction includes applying a negative pressure to displace the coil plates.

[0017] In an embodiment, displacing the coil plates and the wire loop array in the second direction includes passively displacing the coil plates and the wire loop array to abut the coil plates against the body part.

[0018] In an embodiment, passively displacing the coil plates and the wire loop array in the first direction includes relieving the negative pressure.

[0019] In an embodiment, applying the negative pressure includes maintaining the negative pressure to maintain the increased volume of the body part cavity.

[0020] In an embodiment, displacing the coil plates and the wire loop array along the first direction includes spacing the coil plates apart from one another. [0021] In an embodiment, displacing the coil plates and the wire loop array in the second direction includes abutting peripheral edges of at least one coil plate against at least one of the peripheral edges of a neighbouring coil plate.

[0022] In an embodiment, displacing the coil plates and the wire loop array in the second direction includes simultaneously displacing all the coil plates.

[0023] In an embodiment, displacing the coil plates and the wire loop array in the second direction includes displacing at least one of the coil plates independently of another one of the coil plates.

[0024] In an embodiment, the method further includes imaging the body part of a non- sedated child patient, the body part being disposed in the body part cavity.

DESCRIPTION OF THE DRAWINGS

[0025] Reference is now made to the accompanying figures in which:

[0026] Fig. 1A is a perspective view of a magnetic resonance imaging (MRI) coil apparatus shown in a retracted position;

[0027] Fig. 1 B is a perspective view of the MRI coil apparatus of Fig. 1A shown in an engaged position;

[0028] Fig. 2A is a perspective view of a biasing mechanism of the MRI coil apparatus of Fig. 1A;

[0029] Fig. 2B is an enlarged perspective view of the biasing mechanism of Fig. 2A;

[0030] Fig. 3 is a perspective view of a pneumatic tube array of the biasing mechanism of Fig. 2A; and

[0031] Fig. 4 is a schematic view of a pivotable coil plate of the MRI coil apparatus of Fig. 1A.

DETAILED DESCRIPTION [0032] Figs. 1A and 1 B illustrate a magnetic resonance imaging (MRI) coil apparatus 10 used to generate images of a body part of a patient or imaging subject. The coil apparatus 10 can be used with a medical imaging device, such as an MRI machine, so as to generate images or scans of the body part of the animal or human for medical or research purposes.

[0033] The coil apparatus 10 of Figs. 1A and 1 B is used to image the body part of a human. In an alternate embodiment, the coil apparatus 10 is used to image a body part of a non-human animal. While the coil apparatus 10 is described herein as being used for imaging body parts, it can also be used to record neural activity using functional MRI or metabolic information using MR spectroscopy. Therefore, a non-limitative example of a procedure that can be performed using the coil apparatus 10 includes neuroimaging. Although shown and described herein as a being used to image the brain of a neonate, the coil apparatus 10 can also be used with other body parts, and with animals of different ages. Some non-limitative examples of body parts that can be imaged with the coil apparatus 10 include the neck, breasts, and limbs. As will be explained in greater detail below, the coil apparatus 10 is adaptable to receive other size-varying anatomy, and can accommodate a variety of organ shapes and sizes. The coil apparatus 10 has a housing 20 for accommodating the body part to be imaged, and a coil array 30.

[0034] The housing 20 forms the corpus of the coil apparatus 10 and provides structure thereto. The housing 20 defines an inner enclosure 21 in which the body part is received. In the embodiment of Figs. 1A and 1 B, the inner enclosure 21 has a substantially spherical shape and is centrally located within the housing 20. The inner enclosure 21 is sized and shaped to receive the head of the imaging subject. In embodiments where the coil apparatus 10 is used to image other body parts, the inner enclosure 21 has a different shape. For example, when the coil apparatus 10 is used to image a limb, the inner enclosure 21 has a substantially cylindrical shape. In another example, when the coil apparatus 10 is used to image a neck, the inner enclosure 21 is shaped substantially in a "U". The housing 20 shown in Figs. 1A and 1 B includes a base portion 24 for housing some components of the coil apparatus 10, and a semi- spherical top portion 26 mounted onto the base portion 24. Other configurations for the housing 20 are possible. In one alternate embodiment, the housing 20 includes a frame. [0035] The coil array 30 includes a wire loop array 31 to receive radio-frequency (RF) signals resulting from tissue being excited by the transmit volumetric coil of the imaging machine. Other components of the MRI system generate the image of the body part itself. The wire loop array 31 is made up of a plurality of wire loops 31A or coils which, in the embodiment of Figs. 1A and 1 B, are distributed in a soccer ball pattern within the inner enclosure 21. The wire loops 31 A are made of 16 AWG tinned copper wire, although other materials for the wire loops 31A are within the scope of the present disclosure (e.g. PCB, copper tape, etc.). Each wire loop 31A may be closed or open. The shape formed by each wire loop 31A in the wire loop array 31 may vary to adapt the wire loop array 31 to match the shape of the body part while also substantially covering the imaging region of interest of the body part. Some non-limitative examples of shapes for the wire loops 31A include circular, trapezoidal, and rectangular. As will be explained in greater detail below, each wire loop 31A and thus the wire loop array 31 is displaceable within the inner enclosure 21 to maximize their proximity to the body part to be imaged. The wire loop array 31 of Figs. 1A and 1 B is described herein as having receive-only functionality. In an alternate embodiment, the wire loop array 31 is capable of also providing transmit functionality. In such an embodiment, the wire loops 31 A are configured for both transmitting and receiving, for transmit-only, or for receive- only. The adjustable wire loop array 31 may therefore be an array of RF receive elements in which each RF wire loop 31 A separately detects the MRI signals. In an alternate embodiment, the wire loop array 31 includes other types of coil array elements, such as dipoles, patches, etc.

[0036] The coil array 30 is adjustable in size. The coil array 30 therefore allows the coil apparatus 10 to accommodate differently sized and shaped body parts. In an embodiment of the coil apparatus 10 used for imaging the brains of neonates, the overall diameter of the coil array 30 can be varied from about 8 cm to about 12.5 cm.

The coil array 30 adjusts in size and shape with a plurality of displaceable coil plates

32. The coil plates 32 are arranged with respect to one another to circumscribe a body part cavity 22, which is a subset of the inner enclosure 21 defined by the housing 20.

The body part of the patient is received in the body part cavity 22. Each coil plate 32 is engaged with the wire loop array 31. In the depicted embodiment, each coil plate 32 is mounted to a portion of one or more of the wire loops 31A. The wire loops 31A are mounted to an outer surface 32C of each coil plate 32 (see Fig. 2A). Therefore, the displacement of the coil plates 32 also causes the wire loops 31A, and thus the wire loop array 31 , to displace.

[0037] In the embodiment of Figs. 1A and 1 B, each coil plate 32 is a plastic structure which supports one or more of the wire loops 31A and other electronic components (e.g. a preamplifier, circuitry, etc.). Each coil plate 32 defines an inner plate surface 32A opposite to the outer surface 32C. The inner plate surface abuts against the body part. The plate surface 32A is shaped to substantially match a shape of the portion of the body part against which it will abut. For example, in the depicted embodiment, each plate surface 32A has a curvature similar to that of the curved portion of the head against which it will abut. Each coil plate 32 is independent of the other coil plates 32. Stated differently, each coil plate 32 is mechanically decoupled from the other coil plates 32 so that its displacement can be controlled independently of the displacement of another coil plate 32. This allows the coil plates 32 to collectively better adapt to the portion of the body part against which each of them will abut to thereby be brought closer to the body part to be imaged.

[0038] The coil array 30 also includes multiple displacement mechanisms 33 used to displace the coil plates 32. Each displacement mechanism 33 is mounted to one of the coil plates 32 to displace the coil plate 32 and the associated wire loop 31A toward and away from the body part in the inner enclosure 21. The displacement of the coil plates 32 by the displacement mechanisms 33 adjusts the size of the body part cavity 22. Each displacement mechanism 33 includes any component that is responsible for moving a corresponding coil plate 32, such as an actuator. In the depicted embodiment, and as will be described in greater detail below, each displacement mechanism 33 is pneumatically controlled. Each displacement mechanism 33 extends along a longitudinal axis 35 between a first end 36A mounted to the housing 20, and an opposed second end 36B mounted to the coil plate 32.

[0039] The displacement mechanisms 33 operate to displace the coil plates 32 along the longitudinal axes 35 to vary a size of the body part cavity 22. This is achieved by displacing the coil plates 32 toward the housing 20 to a retracted position, as shown in Fig. 1A, and by displacing the coil plates 32 away from the housing 20 to an engaged position, as shown in Fig. 1 B. In the retracted position, the body part cavity 22 defined by the coil plates 32 has its largest volume. In the engaged position, the coil plates 32 engage the body part by abutting against the body part.

[0040] Still referring to Figs. 1A and 1 B, each coil plate 32 and wire loop 31 A is linearly displaceable by the corresponding displacement mechanism 33 in a direction R1 in order to abut against the body part in the engaged position. In the illustrated embodiment, the displacement mechanisms 33 operate to simultaneously displace the coil plates 32 inwardly with respect to the stationary housing 20. In an alternate embodiment, the displacement mechanisms 33 stagger the displacement of the coil plates 32. When the coil plates 32 are displaced in direction R1 , the body part cavity 22 decreases in volume and the coil plates 32 close in around the body part, as shown in Fig. 1 B. In the engaged position shown in Fig. 1 B, the coil apparatus 10 is in a "closed" position and the coil plates 32 collectively form a shape corresponding to that of the body part. In Fig. 1 B, the coil plates 32 collectively form a spherical shape corresponding to the shape of the head of the imaging subject. In this "closed" engaged position, the peripheral edges 32D of each of the coil plates 32 abut against at least one of the peripheral edges 32D of a neighbouring coil plate 32. The abutted coil plates 32 are free of overlap, and do not overlap one another. When multiple coil plates 32 are abutted against the body part, they act to constrain the motion of the body part. Restraining the motion of the body part may help image non-sedated pediatric imaging subjects.

[0041] The displacement mechanisms 33 are also operable to displace each coil plate 32 and wire loop 31A toward the housing 20 and into the retracted position, as shown in Fig. 1A. Each coil plate 32 and wire loop 31A is therefore also displaceable in a direction R2 toward the housing 20. The direction R2 is opposite to the direction R1. When the coil plates 32 are displaced in direction R2, the body part cavity 22 increases in volume to receive therein the body part. In the retracted position shown in Fig. 1A, the coil plates 32 are spaced from one another. The spaced-apart coil plates 32 are free of overlap, and do not overlap one another. In the retracted position shown in Fig. 1A, the coil apparatus 10 is in an "open" position. In the illustrated embodiment where the coil apparatus 10 is used to image a spherical head, the directions R1 ,R2 substantially correspond to a radial line of the head. The directions R1 ,R2 are also substantially parallel to the longitudinal axes 35 of the displacement mechanisms 33. The coil plates 32 are therefore displaced in a "radial" direction in the illustrated embodiment.

[0042] The wire loops 31A of the wire loop array 31 are displaced towards and away from the housing 20 when the coil plates 32 are displaced. The wire loops 31A are therefore positioned and shaped to expand and contract, and to cover imaging regions of interest. In the depicted embodiment, portions of each wire loop 31A overlap portions of adjacent wire loops 31 A. These overlapping portions change in size as the wire loops 31 A are displaced toward and away from the housing 20. The extent and shape of the overlapping portions of the wire loops 31A may vary to prevent large gaps from forming between the wire loops 31A when the wire loop array 31 is expanded.

[0043] Still referring to Figs. 1A and 1 B, the displacement of the coil plates 32 and the wire loops 31 A by the displacement mechanisms 33 is both "active" and "passive". The active displacement of the coil plates 32 and the wire loops 31 A involves the positive provision or application of a force by the displacement mechanisms 33. This active force is usually provided from a source that is external to the displacement mechanisms 33. In contrast, the passive displacement of the coil plates 32 and the wire loops 31 A involves the application of a force by displacement mechanisms 33 that may be provided by the inherent resiliency or recoil of the displacement mechanisms 33 in response to the absence of the active force. This is more clearly understood by referring to Figs. 2A and 2B.

[0044] Each displacement mechanisms 33 in the embodiment of Figs. 2A and 2B includes a biasing mechanism 37. Each biasing mechanism 37 is operable to actively and passively displace the corresponding coil plate 32 and wire loop 31A. Each biasing mechanism 37 is operable to actively apply a force to displace the coil plate 32 toward the retracted position, and is also operable to passively bias or urge the coil plates 32 toward the engaged position to abut against the body part. Many configurations of the biasing mechanism 37 which achieve such functionality are within the scope of the present disclosure, and one of these is now described in greater detail. [0045] In the depicted embodiment, the biasing mechanism 37 includes a closed pneumatic tube array 38 (see also Figs. 1 and 3). The closed tube array 38 includes multiple flexible tubes 38A in fluid communication with a vacuum source 38B (see Fig. 1A), and in fluid communication with multiple collapsible bellows 39. The tube array 38 may also include valves, conduits, seals, or other components to fluidly connect the vacuum source 38B to the bellows 39, and to provide an air-tight pneumatic system. Each bellow 39 is an accordion-like, flexible tube having flexible folds or gussets that expand and contract. The desired behavior of the bellows 39 can be achieved by a selection of parameters including, but not limited to, stiffness, flexibility, compressibility, memory, and travel. Each bellow 39 extends into the inner enclosure 21 , and one end of each bellow 39 is mounted to the housing 20 while the other end is mounted to one of the coil plates 32. Each bellow 39 defines a substantially airtight cavity which can be expanded and contracted in a direction parallel to the longitudinal axis 35.

[0046] The biasing mechanism 37 in the depicted embodiment is operable to actively collapse the bellows 39 and displace the coil plates 32 in the direction R2 toward the retracted position when a negative pressure is provided to the tube array 38. A "negative pressure" is a pressure within the tube array 38 and bellows 39 which is less than the pressure of the surrounding environment. By providing the bellows 39 with a negative pressure, the pressure of the surrounding environment applies a force against the bellows 39 causing them to collapse unto themselves. The negative pressure in the depicted embodiment is supplied by the vacuum source 38B that is separate from the bellows 39. The vacuum source 38 is shown as a hand pump in Fig. 1A. Operation of the hand pump functions to evacuate air from the tube array 38 and from the bellows 39, thereby creating a negative pressure within the bellows 39. The bellows 39 respond to the greater pressure of their surroundings by collapsing unto themselves. A check valve may be provided to hold the negative pressure in the bellows 39 and the flexible tubes 38A so as to keep the bellows 39 collapsed while the body part is placed in the body part cavity 22, and so as to maintain the coil plates 32 in the retracted position.

[0047] The bellows 39 are passively expanded to displace the coil plates 32 and the wire loops 31A toward the engaged position when the negative pressure is removed from the tube array 38. By removing or relieving the negative pressure from the bellows 39, the pressure of the surrounding environment no longer acts to collapse the bellows 39. The bellows 39 are therefore free to passively expand due to the inherent resiliency of the flexible folds of the bellow 39 and/or their inherent desire to expand. The passive expansion of the bellows 39 causes the coil plates 32 mounted thereto and the wire loops 31A to be gently pushed in the direction R1 toward the engaged position. The negative pressure in the depicted embodiment is removed by opening a valve in the airtight tube array 38 to allow air to enter the flexible tubes 38A and the bellows 39. This allows the pressure of the bellows 39 to equalize with the pressure of the surrounding environment. The default configuration of the bellows 39 is their expanded configuration in the engaged position.

[0048] The bellows 39 of Figs. 2A and 2B therefore avoid actively pushing the coil plates 32 against the imaging subject's head. Instead, the compressible bellows 39 act like springs and naturally and passively press on the imaging subject's head with a small force. The application of a smaller, gentle force by the coil plates 32 against the head of a neonate may increase the comfort and safety of the imaging procedure. Active force is applied on the bellows 39 only to collapse them, and thus to withdraw the coil plates 32 into the retracted position.

[0049] The coil apparatus 10 is therefore operated as follows, with reference to Figs. 2A and 2B. To place the imaging subject's head inside the housing 20, a negative pressure is actively supplied to the tube array 38 and the bellows 39 to collapse the bellows 39, and to withdraw the coil plates 32 to the retracted position and increase the size of body part cavity 22. Once the head of the imaging subject is placed within the body part cavity 22, the negative pressure is relieved from the bellows 39 causing them to passively expand and displace the coil plates 32 to the engaged position to shrink the body part cavity 22 until the coil plates 32 abut against the head and conform to its shape. It will be appreciated that although the bellows 39 are deployed simultaneously in the depicted embodiment, the movement of each bellow 39 occurs independently of the other bellows 39. Each bellow 39 is therefore free to expand or contract independently of the other bellows 39 so that the coil plates 32 are able to better accommodate the shape of the head of the imaging subject. [0050] Referring to Fig. 3, the housing 20 has a spherical body 28 that serves as a structural member for components of the coil apparatus 10, and defines a spherical inner enclosure 21. Each bellow 39 is mounted at one of its ends to the body 28. The flexible tubes 38A of the closed tube array 38 connect all the bellows 39 to the vacuum source 38B to create an air-tight pneumatic system. Wiring, electronic components, and other circuitry are positioned within openings 29 in the body 28, on the outer surface 32C of the coil plates 32.

[0051] Referring to Fig. 4, each coil plate 32 is pivotable when its inner plate surface 32A abuts against the body part 12. This allows the coil plate 32 to better conform to the shape of the body part 12. In many instances, but not necessarily all, the shape of the plate surface 32A will not immediately correspond to the shape of the portion of the body part 12 when the plate surface 32A first abuts against the portion of the body part 12. Fig. 4 shows the coil plate 32 and its plate surface 32A at the moment it contacts the body part 12. As can be seen, only a portion 32B of the plate surface 32A abuts against the body part 12. The portion 32B defines one or multiple points of contact 40 with the body part 12 when the coil plate 32 first abuts the body part 12. The bellow 39 continues to expand and displace the coil plate 32 until the coil plate 32 assumes its final position against the body part 12, which is designated as 32'. The coil plate 32' and its plate surface 32A' more closely correspond to the surface of the body part 12 than the coil plate 32 when it initially contacts the body part 12.

[0052] The coil plate 32' is therefore pivoted in comparison to the coil plate 32, and with respect to the longitudinal axis 35 of the bellow 39. As the bellow 39 continues to expand and displace the coil plate 32 after the portion 32B first enters into contact with the body part 12, the passive force of expansion of the bellow 39 will cause the coil plate 32 to pivot about the point of contact 40 until the coil plate 32 assumes its final position against the body part 12, which is designated as 32'. The coil plate 32 is therefore caused to pivot along a pivot direction P by the expansion of the bellow 39 until it achieves its final position as coil plate 32'. In the depicted embodiment, the flexible tube and folds of the bellow 39 help the coil plate 32 to pivot. Depending on the extent of the pivot of the coil plate 32, the bellow 39 may bend as well. Each coil plate 32 therefore has a relative freedom to pivot about its movement axis to better adapt to the specific portion of the body part 12. The coil plates 32 can therefore be finely adjusted to the shape of the body part 12 because each coil plate 32 has the possibility to be displaced along the longitudinal axis 35, but also to pivot with respect thereto. This helps to position the wire loops 31 A associated with the coil plate 32 over the imaging region of interest of the body part 12. The pivotable coil plate 32 contrasts with some conventional coil-support devices which do not pivot, and therefore do not conform well to the local surface of the body part. It will be appreciated that all the coil plates 32 do not necessarily undergo pivoting. For example, where a coil plate 32 substantially conforms to the shape of the portion of the body part 12 against which it abuts at the moment of contact, it may not undergo any pivoting movement.

[0053] Referring to Figs. 1A and 1 B, there is also disclosed a method of arranging the MRI coil apparatus 10 to receive the body part 12. The method includes displacing the coil plates 32 and the wire loop array 31 to increase a volume of the body part cavity 22 when the coil plates 32 and the wire loop array 31 are displaced in a first direction R2 along the longitudinal axis 35. Displacing the coil plates 32 also includes, subsequently or separately to displacing the coil plates 32 in the first direction R2, abutting the coil plates 32 against the body part 12 when the coil plates 32 and the wire loop array 31 are displaced in a second direction R1 opposite to the first direction R2. The point of contact 40 is formed between each coil plate 32 and the body part 12 when the coil plate 32 first abuts the body part 12. Each coil plate 32 is pivotable about the point of contact 40 to better conform the coil plate 32 to a surface of the body part 12. The method may also include imaging the body part 12 of a non-sedated child patient, the body part 12 being disposed in the body part cavity 22.

[0054] The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the disclosure. Still other modifications which fall within the scope will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.

Claims

1. A magnetic resonance imaging (MRI) coil apparatus for imaging a body part, the MRI coil apparatus comprising:

a housing defining an inner enclosure; and

a coil array having a wire loop array and a plurality of coil plates engaged with the wire loop array within the inner enclosure, the coil plates arranged to delimit a body part cavity to receive the body part therein, the coil array having a plurality of displacement mechanisms each mounted to the housing and extending therefrom into the inner enclosure along a longitudinal axis to a connection with a corresponding coil plate, the displacement mechanisms being operable to displace the coil plates and the wire loop array along the longitudinal axis to vary a size of the body part cavity by displacing the coil plates toward the housing to a retracted position and away from the housing to an engaged position, the coil plates in the engaged position abutting the body part, a point of contact being formed between each coil plate and the body part upon the coil plate first abutting the body part, each coil plate being pivotable about the point of contact to better conform the coil plate to a surface of the body part.

2. The MRI coil apparatus as defined in claim 1 , wherein each displacement mechanism includes a biasing mechanism operable to actively apply a force to displace the coil plates toward the retracted position, and operable to passively bias the coil plates toward the engaged position.

3. The MRI coil apparatus as defined in claim 2, wherein the biasing mechanism includes a closed pneumatic tube array in fluid communication with a plurality of collapsible bellows each connected to one of the coil plates, the biasing mechanism being operable to actively collapse the bellows and displace the coil plates to the retracted position upon a negative pressure being provided to the tube array, the bellows being passively expandable to displace the coil plates toward the engaged position upon the negative pressure being relieved in the tube array.

4. The MRI coil apparatus as defined in any one of claims 1 to 3, wherein the engaged position is the default position of the coil plates.

5. The MRI coil apparatus as defined in any one of claims 1 to 4, wherein the coil plates are spaced apart from another in the retracted position.

6. The MRI coil apparatus as defined in any one of claims 1 to 5, wherein each of the coil plates has peripheral edges, at least some of the peripheral edges of at least some of the coil plates abut against at least one of the peripheral edges of a neighbouring coil plate in the engaged position.

7. The MRI coil apparatus as defined in any one of claims 1 to 6, wherein the coil plates are free of overlap in both the retracted and engaged positions.

8. The MRI coil apparatus as defined in any one of claims 1 to 7, wherein at least one of the coil plates is displaced along the longitudinal axis of a corresponding displacement mechanism independently of another one of the coil plates.

9. The MRI coil apparatus as defined in any one of claims 1 to 8, wherein the displacement mechanisms are operable to simultaneously displace all the coil plates along the respective longitudinal axes.

10. The MRI coil apparatus as defined in any one of claims 1 to 9, wherein the body part cavity delimited by the coil plates has a spherical shape, the displacement mechanisms being operable to displace the coil plates along substantially radial lines.

1 1. A method of arranging a magnetic resonance imaging (MRI) coil apparatus to receive a body part, the method comprising:

providing a plurality of displaceable coil plates disposed to define a body part cavity for receiving the body part therein, the coil plates being engaged with a wire loop array; and

displacing the coil plates and the wire loop array to: increase a volume of the body part cavity when the coil plates and the wire loop array are displaced in a first direction along the longitudinal axis; and

abut the coil plates against the body part when the coil plates and the wire loop array are displaced in a second direction opposite to the first direction, a point of contact being formed between each coil plate and the body part when the coil plate first abuts the body part, each coil plate being pivotable about the point of contact to better conform the coil plate to a surface of the body part.

12. The method as defined in claim 1 1 , wherein displacing the coil plates and the wire loop array along the first direction includes actively displacing the coil plates and the wire loop array in the first direction.

13. The method as defined in claim 12, wherein actively displacing the coil plates and the wire loop array in the first direction includes applying a negative pressure to displace the coil plates.

14. The method as defined in claim 13, wherein displacing the coil plates and the wire loop array in the second direction includes passively displacing the coil plates and the wire loop array to abut the coil plates against the body part.

15. The method as defined in claim 14, wherein passively displacing the coil plates and the wire loop array in the first direction includes relieving the negative pressure.

16. The method as defined in any one of claims 13 to 15, wherein applying the negative pressure includes maintaining the negative pressure to maintain the increased volume of the body part cavity.

17. The method as defined in any one of claims 1 1 to 16, wherein displacing the coil plates and the wire loop array along the first direction includes spacing the coil plates apart from one another.

18. The method as defined in any one of claims 1 1 to 17, wherein displacing the coil plates and the wire loop array in the second direction includes abutting peripheral edges of at least one coil plate against at least one of the peripheral edges of a neighbouring coil plate.

19. The method as defined in any one of claims 1 1 to 18, wherein displacing the coil plates and the wire loop array in the second direction includes simultaneously displacing all the coil plates.

20. The method as defined in any one of claims 11 to 19, wherein displacing the coil plates and the wire loop array in the second direction includes displacing at least one of the coil plates independently of another one of the coil plates.

21. The method as defined in any one of claims 1 1 to 20, further comprising imaging the body part of a non-sedated child patient, the body part being disposed in the body part cavity.