The present invention relates generally to medical imaging systems for medical treatment and/or diagnostic purposes. More particularly, the present invention relates to an apparatus for immobilizing an anatomical feature, especially a wrist, during medical imaging and image analysis.
Osteoporosis is a bone disease that affects a large portion of the population, especially post-menopausal women, which leads to increased risk of fracture. The disease is characterized by decreased bone mineral density and deteriorated bone microarchitecture. Clinical research studies have shown that bone microarchitecture makes a significant contribution to fracture risk and that changes in bone microarchitecture in response to therapeutic treatment can be detected much earlier than changes in bone mineral density. While commercially available x-ray devices can monitor changes in bone mineral density, non-invasive imaging devices to quantify bone microarchitecture would be very useful.
Characterization of bone microarchitecture requires visualization and quantification of the network of trabecular bone such as found at the end of the long bone in the wrist. The imaging system must be capable of acquiring volumetric data sets with 3D voxel size on the order of 100 microns, the same scale size as trabecular bone structure.
Magnetic Resonance Imaging (MRI) has been shown to be capable of achieving this resolution when imaging appendages such as the wrist. A special pulse sequence and image processing algorithm are required for data acquisition and data processing, respectively. The scan time to acquire a 3D volumetric set of data is in the range of 5-15 minutes.
To create an MR image of the wrist, an RF (Radio Frequency) coil tuned according to the field strength of the magnet must be placed in close proximity to the wrist.
During the image scanning process, movement of the wrist must be minimized to prevent blurring and other motion-related image artifacts, which degrade image quality and measurement accuracy. Since the voxel size is so small, even a small amount of patient movement can degrade a scan or necessitate a study to be repeated.
However, due to the inherent flexibility of the wrist joint that couples the hand to the arm, it is difficult to immobilize the wrist itself. While a close-fitting wrist coil is desirable for generating high quality MRI images, attempts to immobilize the joint, for example, by inserting pads between the wrist and the inner wall of the coil housing have been found to be inadequate. Efforts to use a separate immobilization device, such as a vacuum fixation bag, have failed to provide consistent and adequate immobilization. In addition, exam set up and patient positioning using such a device are cumbersome and time consuming.
Furthermore, under many circumstances, serial exams for the same patient with respect to the same anatomical feature (such as the wrist) are important for monitoring disease regression or progression during the course of treatment, which may run over the course of months or years. Accordingly, precise and consistent registration at different time between the wrist and the RF coil as well as between the RF coil and the MR scanner is critical for studying and controlling the treatment. However, for the known systems, each time when the equipment is set up to scan the wrist, the resultant image may not be consistent with the previous images in terms of angle and orientation.
Thus, it is desirable to provide an apparatus for immobilizing and stabilizing the wrist during a medical imaging process, so as to obtain a high quality, high-resolution volumetric image of the wrist.
Thus, it is also desirable to provide an apparatus for precisely and consistently registering the wrist, RF coil and MR scanner with one another during a medical imaging process, so as to ensure that serial exams on the same patient are recorded at precisely the same anatomic location even if the exams are performed at different time (for, example, months or years apart).
Thus, it is also desirable to provide an apparatus for maximizing patient comfort during the exam with medical imaging, which further reduces the likelihood of voluntary or involuntary patient movement during the scan.
Thus, it is also desirable to provide an apparatus for streamlining the patient setup procedure during a medical imaging process in order to minimize the total time required to set up and perform the exam.
As described herein, the various exemplary embodiments of the present invention overcome one or more of the above or other disadvantages known in the art.
An aspect of the present invention relates to an apparatus for immobilizing an anatomical feature during a medical imaging process of the anatomical feature. The apparatus includes a housing, which has a central opening to accommodate the anatomical feature. The apparatus further includes a coil member fixedly mounted in the housing. The coil member processes an RF signal. The apparatus further includes a first support member disposed at a side of the housing and a second support member disposed at an opposite side of the housing. The first and second support members are fixed with respect to the housing.
Another aspect of the present invention relates to a system for performing an MRI imaging of an anatomical feature of a patient. The system includes an apparatus for immobilizing the anatomical feature during the MRI imaging. The apparatus includes a housing, which includes a central opening configured to accommodate the anatomical feature. The apparatus includes a coil member fixedly mounted in the housing, the coil member processing an RF signal. The apparatus further includes a first support member disposed at a side of the housing and a second support member disposed at an opposite side of the housing. The apparatus further includes a base member. The housing, the first support member and the second support member are fixedly mounted on a common side of the base member. The system further includes an MR scanner. The scanner includes, inter alia, a table for supporting the patient. The system further includes a means for releasably locking the base member of the apparatus to the table of the MR scanner.
It is contemplated that the teaching of the description set forth below is applicable to all types of medical imaging systems, including but not limited to MRI systems. The present invention is therefore not intended to be limited to any particular MRI apparatus or configuration described in the exemplary embodiments of the present invention.
As shown, the apparatus 100 includes a housing 102 and coil member 104 (shown in dashed lines) fixedly mounted in the housing 102. The coil member 104 processes an RF signal, for example, in response to a magnetic filed generated during medical imaging. The coil member 104 can be a receive-only coil or a transmit/receive coil. The housing 102 defines a central opening 106 for accommodating an anatomical feature, such as a wrist W, as shown in
The housing 102 includes an upper portion 108 and an opposite lower portion 109, releasably fixable to each other through a locking means, which will be described later with reference to
The coil member 104 includes an upper portion 110 fixed in the upper portion 108 of the housing 102, and a lower portion 111 fixed in the lower portion 109 of the housing 102.
The apparatus 100 further includes a first support member 112 disposed at one side of the housing 102. The first support member 112 is adapted to support a forearm F associated with the wrist W, as best seen in
The apparatus 100 further includes a second support member 116 disposed at another side of the housing 102, longitudinally opposite to the first support member 112. The second support member 116 is adapted to support a hand H associated with the wrist W, which is shown in
The housing 102, the first support member 112 and the second support member 116 are constructed to substantially aligned along an axis X-X′, which can be defined with respect to the wrist W, the forearm F and the hand H.
The apparatus 100 further includes a base member 120, on which the housing 102, the first support member 112 and the second support member 116 are fixedly mounted. For example, the base member 120 can be a piece of solid material, such as a metal or plastic plate. The base member 120 provides a common structure for mounting the housing 102, the first support member 112 and the second support member 116, thereby providing a structurally integral apparatus for immobilizing the forearm F, the wrist W and the hand H. In addition, the common base member 120 provides positional rigidity between the housing 102 and the first support member 112 and between the housing 102 and the second support member 116. Thus, for each time the wrist W is being scanned, the wrist W can be maintained at positions satisfactorily consistent with one another.
The first support member 112 can be lined with a removable pad (not shown) to provide additional patient comfort or to better support smaller arms. A pedestal 122 can be provided between the first support member 112 and the base member 120, for adjusting the vertical position of the first support member 112 with respect to the central opening 106, which would allow a patient to place his/her forearm and wrist in a comfortable position. Accordingly, undesirable movement of the forearm and wrist due to the patient's uncomfortable feeling can be avoided. The first support member 112 can be attached to the pedestal 122, which is in turn fixed to the base member 120. For example, the pedestal 122 can match the height of the first support member 112 nearest to the coil member 104 to the height of the bottom of the central opening 106 in the lower portion 109 of the housing 102. Optionally, the longitudinal location of the pedestal 122 can be adjusted along the axis X-X′, to accommodate different lengths of the arms. Optionally, a locking mechanism, such as a ratchet, can be used to fix the location of the pedestal 122 after it has been placed in a desired position, to eventually fix the pedestal 122 as well as the first support member 112 with respect to the base member 120.
A rail 124 can be provided for slidably adjusting the longitudinal position of the second support member 116 with respect to the central opening 106, which would allow a patient to place his/her wrist and hand in a comfortable position. Accordingly, undesirable movement of the hand and wrist due to the patient's uncomfortable feeling can be avoided. A locking mechanism, such as a ratchet, can be provided to fix the second support member 116 with respect to the rail 124.
An insulated case 128 can be further provided between the second support member 116 and the base member 120. The second support member 116 is attached on the insulated case 128. The case 128 may optionally receive electronic components such as preamps (not shown) for processing signals from the coil member 104. The electric cable (not shown) carrying signals between the coil member 104 and an external MR scanner (as shown schematically in
The apparatus 100 further includes a first pair of extensions 132 and 132′ (not shown), associated with the first support member 112. The first pair of extensions 132 and 132′ are disposed at either side of the first support member 112, for applying a cloth strap around the forearm F to avoid movement of the forearm F. For example, the first pair of extensions 132 and 132′ each include a longitudinally extending rail 134 attached to struts 136 vertically extending from the base member 120. In this way, the cloth strap looping around the rails may be drawn firmly over the top of the patient's forearm to prevent movement of the forearm during a scan. Optionally, the cloth strap can be provided with Velcro® surfaces.
The apparatus 100 further includes a second pair of extensions 138 and 138′, associated with the second support member 116. The second pair of extensions 138 and 138′ are disposed at either side of the second support member 116, for applying a cloth strap around the hand H to avoid movement of the hand H. For example, the second pair of extensions 138 and 138′ each include a longitudinally extending rail 140 attached to struts 142 vertically extending from the base member 120. In this way, the cloth strap looping around the rails may be drawn firmly over the top of the patient's hand to prevent movement of the hand during a scan. Optionally, the cloth strap can be provided with Velcro® surfaces. The cooperation of the second support member 116 and the cloth strap on top of the hand provides robust mechanical registration and significantly restricts both translational and rotational movement of the patient's wrist with respect to the axis X-X′.
The base plate 120 is firmed attached a patient table (as shown schematically in
100351 Using a mechanical means to repeatably fix the position of the base plate 120 with respect to the isocenter of the MR scanner ensures, that any spatial non-uniformity, in the magnetic field strength away from isocenter that might influence image quality or affect quantitative outputs of the post-processing software, is repeatable from scan to scan.
Except for the cable port 130, the coil member 104, the housing 102, the first support member 112 and the second support member 116 are disposed to be symmetric about the center line X-X′, which enables the same system to be used for imaging either the left or right wrist.
For the purpose of clarity of use,
In the shown embodiment, the locking means includes a pair of levers 150 and a pair of receptacles 152, the levers engaging the receptacles, respectively. The levers 150 are disposed on one of the upper portion 108 and lower portion 109; and the receptacles 152 are disposed on the other of the upper portion 108 and the lower portion 109.
In order to assist the MR technical to accurately examine the position of the patient's wrist, a reference marker 158 is further provided. For example, the reference marker 158 can be a fiducial reference marker provided on an upper surface 160 of the lower portion 109 of the housing 102, as shown in.
When the upper portion 108 of the housing 102 is removed, the reference marker 158 is exposed, adjacent to the center of the exposed upper surface 160 of the lower portion 109.
In operation, the forearm F rests in the first support member 112 and the wrist W rests in the lower portion 109 of the housing 102. The technician ensures that the patient's ulnar styloid process (the bony protuberance on the upper-outside part of the wrist, not indicated) is positioned next to the fiducial reference marker 158. Thus, every time when the upper portion 108 of the housing 102 is removed, the reference marker 158 is revealed to assist the technician to properly position the patient's wrist as well as forearm and hand.
For the MRI imaging system 200, the apparatus 100 immobilizes the patient's wrist to allow the scanner 300 and coil member 104, in cooperation, to acquire high quality images for diagnostic and treatment purposes.
In the system 200, the positioning of the wrist only relies on the alignment of the patient's ulnar styloid process with the fiducial marking, which ensures consistent and repeatable positioning of the wrist anatomy.
Only by securing the patient's arm and hand using fixtures that are rigidly attached to the coil, is mechanical registration achieved and even small motion of the wrist substantially eliminated. Integration of the immobilization apparatus with the coil into a single mechanical structure maintains proper and repeatable registration of the wrist to the coil, significantly attenuates patient potion, and ensures high image quality and measurement accuracy.
While there have shown and described and pointed out fundamental novel features of the invention as applied to various specific embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the apparatus illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/US09/65474 | 11/23/2009 | WO | 00 | 5/24/2011 |
Number | Date | Country | |
---|---|---|---|
61117341 | Nov 2008 | US |