Patent Application
20150338477
The present invention relates to magnetic-resonance-based interventional procedures and systems and, in particular, to an interventional needle device, a position of which is subject to tracking during an MRI-guided surgical or interventional procedure.
Metallic needles are commonly used in interventional applications due to their mechanical strength of resistance (characterized by a high Young's modulus and a low, less than 0.3, Poison's ratio) to compressive and bending forces. The metallic needles also exhibit a high degree of elasticity (i.e., possess a high yield strength) and are non-brittle (i.e., possess a high ultimate tensile strength). Examples of interventional applications include tumor (or other pathology) biopsy procedures; thermal-ablative (using radio-frequency, RF, or microwave sources) or cryo-ablative (using a cooling mechanism such as the Joule-Thompson effect, for example) procedures where a metallic needle, such as a cannula, is used to transport the ablation delivery device to the proximity of the targeted pathology; radiation treatment of pathologies, where the needles are used to bring radioactive seeds (or mechanically-soft enclosures, referred to as “catheters” in the Radiation Oncology nomenclature, into which the radioactive seeds can later be inserted) to the proximity of the targeted pathology; chemical ablative or therapeutic procedures, where therapeutic chemical or biological agents are delivered to the tumor; as well as neurovascular and cardiovascular interventions, in which catheters utilize metallic braids to enable remote (at a separation on the order of 1.5 meters) deflection and rotation during navigation within the vascular anatomy.
An MR-imaging (MRI) modality is often employed to detect the pathology because of the enhanced contrast-to-noise ratio (CNR) between soft tissues afforded by the MRI system, which can be used to enable improved navigation to the target and improved differentiation between the pathology and its surroundings. As a result, it may be beneficial to perform the interventional procedure while the patient is inside the bore of the MRI system. Advantages of performing the intervention inside the MRI system are particularly pronounced when the pathology is present within soft tissue, which can deform non-rigidly and non-uniformly (for example, to different degrees in different directions). Indeed, performing the intervention procedure on such deformable tissues outside the MRI system, based on the information obtained with the MRI system, is not straightforward, as the patient tends to move between the MR-imaging session and the intervention.
During the magnetic-resonance (MR) based interventional procedures, the position and orientation of a catheter or needle can be rather precisely tracked using MR-based tracking methods, such as active tracking using one-dimensional MRI profiles (MR Tracking), or tracking utilizing micro-coils which detect electrical fields induced by temporal changes in the magnetic-gradient fields. The presence of metal, such as found in the metallic needle, within the field of view of the MR tracking element affects the tracking quality by causing in-homogeneities in both the static and radio-frequency (RF) magnetic fields around the needles, a result of the strong paramagnetic and electrical conductivity properties of the metallic needle. Moreover, metallic needles that are long (for example, about 15 cm) act as radiofrequency (RF) antennae that operably couple to the tracking coils, thereby distorting the appearance of the tracking signals, so that spatial localization is complicated. As a result, tracking of metallic devices is presently limited to tracking of non-metallic objects (referred to as “hand-holders” or “device-holders”) that are attached to the proximal ends (the side which, in operation, is usually outside of the body) of the needles; the “device-holders”, however, cannot detect the bending of the needle shaft which occurs during insertion of the needle into human tissue and, as a result, they cannot facilitate accurate determination of the position of the needle's tip.
Needles made from non-ferromagnetic metals (i.e. from metals that are paramagnetic, but not ferromagnetic) can be tracked passively (based, for example, on the magnetic susceptibility of the metals, that is higher than that of the surrounding soft tissue). The disadvantage of this approach, however, is that high-resolution MRI sequences responsive to differences in magnetic susceptibility must be used, which requires far longer imaging times than those of active tracking (for example, about 60 seconds as compared to about 0.025 to 0.04 second to achieve comparable spatial accuracy). In addition, the accuracy of the needle's tip localization is lower (about 3 mm in passive tracking, as compared to about 0.5 mm in active tracking). When multiple needles are used, tracking of the individual paths of the individual needles with a passive approach becomes problematic, especially if different needles end up in proximity to one another or have their paths crossed. Passive tracking has an additional shortcoming in that the lengthy time required to accomplish the tracking procedure is not conducive to carrying out rapid (on the order of several seconds) MRI imaging of the immediate neighborhood of the needle's tip during navigation, using the instantaneous coordinates and orientation of the tip, a procedure which is possible to perform with the use of active tracking, since updates to this position are obtained several times per second. Yet another shortcoming of passive tracking is the inability to perform motion-compensated imaging. High-spatial-resolution MRI images typically require several minutes to acquire, which encompasses multiple cycles of physiological motion (human cardiac motion, typically at 1-2 cycles per second, includes non-rigid motion over about 1 to 2 cm, while respiratory motion, typically at 0.2-0.5 cycles/sec, includes non-rigid motion over about 2 to 3 cm). Since the duration of an MRI acquisition is longer than the physiological cycle, the anatomy is continuously moving while it is being imaging, which results in blurred (lower resolution) and even artifactual images. If a needle or catheter, equipped with active tracking micro-coils, is placed inside the anatomy, then this device can sense the instantaneous direction and magnitude of the motion. As a result, MRI imaging sequences can be constructed that interleave between active tracking and imaging segments, whereby the imaging segments are fed with the detected changes in position and shifted appropriately, so that the imaging sequence is performed in a static (non-moving) frame of reference relative to the anatomy, which results in MRI images with substantially reduced image blurring or image artifacts. Imaging of moving anatomy is commonly performed by utilizing sensors placed on the body surface or image-based navigators, but these methods cannot accurately correct for motion in cases where the anatomic motion is not of a rigid-body nature (i.e. it varies greatly with position), so they tend to over- or under-compensate for such motion, and they also can result in very lengthy scans. In such cases of physiological motion, the correction provided by the microcoils, since they are positioned far closer to the target tissues, provides a far better approximation of the magnitude and direction of motion at the target tissue, and thereby in images with better removal of motion artifacts.
Yet another approach to tracking of interventional needles using MRI methods is to replace the metallic needles entirely with a hard non-ferrous substance (such as a ceramic or a composite material, for example: fiber glass or carbon fiber). However, a lengthy needle of a small diameter (for example, at least 8 cm long by less than 2 mm thick), made of most of the composites or ceramic materials, is inflexible and exceeds its elastic limit when bent at an angle of a few degrees. Accordingly, such a needle is likely to break when used to push aside or cut-through soft tissue, which is unacceptable. Moreover, machining such needles is complicated, thereby limiting easily producible needle shapes. Finally, observing the entire length of the needle at once with an active tracking method is problematic, and an optimized approach may therefore require the detection of the needle tip actively, while the rest of the needle is passively detected.
It is appreciated, therefore, that there remains a need for a needle system and method for MR-based tacking of such a needle that overcome shortcomings of the related art and, in operation, facilitate the creation of conditions that help avoid distortions of the image provided by the MRI system on the one hand and yet are able to position the needle accurately with respect to a desired location in the tissue.
Embodiments of the invention provide a method for making a needle for an interventional device. Such method includes attaching a tubular distal needle segment, made of a non-metallic and either diamagnetic or paramagnetic material, to a distal end of the carrying portion of the needle made of metal. The ratio of a first value representing a length of the carrying portion and a second value representing a length of the tubular distal needle segment is at least 10. The method additionally includes adding a coil made of electrically conductive wire around the tubular distal needle segment; and providing an electrical output to the coil. In a specific implementation, the distal end of the carrying portion is dimensioned to ensure friction fit of the distal end inside the tubular needle element. The method further includes providing an electrically conducting member between the coil and the electrical output; and encasing at least the carrying portion of the needle in a plastic tubing to pass the electrically conducting member inside the tubing. Embodiments of the invention additionally provide a needle formed according to the above-identified method, and a system and method for MR-guided tracking of the needle guidance.
One implementation of the invention provides a system adapted for use with a system for actively tracking of a position of a device within a magnetic resonance imaging (MRI) scanner. The system of the invention includes a fully-metallic filament extended along an axis and including proximal and distal ends, a first length, and extended along an axis, such filament having a substantially flat surface along the first length. The system additionally includes at least one MR receiver coil including at least one first loop that forms a first electrically-conductive trace disposed in a first plane parallel to the substantially flat surface such that a normal to the plane is transverse to the substantially flat surface. At least one coil has electrical terminals electrically extended towards the proximal end. In one embodiment, the at least one coil further includes at least one second loop that forms a second electrically-conductive trace disposed in a second plane parallel to the substantially flat surface and electrically connected to the at least one first loop, such as to define a length of the at least one coil as a sum of lengths of the first and second electrically-conductive traces, the first and second planes being different and parallel to one another. The needle may further contain a plastic sheath encasing at least the fully-metallic filament, wherein the first plastic portion and the plastic sheath are dimensioned to form a gap there between, and wherein an electrical extension of a terminal toward the proximal end is disposed in the gap.
The invention will be more fully understood by referring to the following Detailed Description in conjunction with the Drawings, of which:
Below, a discussion is presented of a device and an approach for using the device by which the “MRI-tracking” method can be implemented to track position(s) and orientation(s) of metallic objects while inside an MRI scanner. The problem of improving the navigation of the interventional device to the target and high-quality differentiation between the pathology and its surroundings with the use of the interventional device is solved by creating a composite interventional device that substantially maintains the mechanical properties of the conventional metallic needle while obviating the tracking and imaging artifacts caused by noise and interference attributed to the conventional needle being fully metallic.
The idea of the present invention stems from the realization that an interventional needle that constitutes a judiciously designed composite system (whether passive or active, in which case a portion of such composite system is structured to take part in the tracking process by generating an associated wave registrable with an appropriate detector, as opposed to a simple metallic needle) can substantially aid the process of not only tracking the needle-based composite system but also the process of repositioning/relocation of such system within the tissue.
For example, structuring an active composite system by juxtaposing a metallic object (such as a metallic needle) to be MRI-tracked with a radio-frequency (RF) coil the geometry of which has an RF radiation (“lobe”) pattern tunable to project this lobe away from the surface of the metallic object, causes the tracking MRI-signal to approach, in practice, the MRI-signal that is undistorted by the presence of the metallic body in the MRI scanner and that, otherwise, can only be obtained in the far-field with respect to the surface of the metallic object.
As another example, structuring a passive composite system as a metallic/non-metallic composite needle facilitates the MR-guided interventional procedure such as, for example, radiation brachytherapy treatment of cervical and prostate tumors because the non-metallic portion of the needle does not interfere with MR imaging. For example, a significant portion of the base of needle, close to the handle, may include traditional metallic materials that provide strength and stifthess to the passive composite needle system, while a distal tip includes non-metallic composite materials that do not compromise the mechanical properties of the needle. About the tip of the composite needle there may be disposed actively-tracked MRI receivers (such as coils, for example), which substantially aid in the tracking of the needle and its rotation.
As already alluded to above, active tracking a position of a metallic object (with emphasis on surgical or interventional devices, for example), is difficult when such active tracking is carried out with the use of Electromagnetic (EM) tracking methods (such as magnetic-field-based or electrical-voltage-based) or MRI-based tracking methods (such as, for example, “MR-tracking”, that is an MRI Radio Frequency-projection based method; or “Robin medical” , an MRI-gradient magnetic-induction based method). One of the problems encountered during such tracking is caused by the tendency of a metallic object to distort, in its proximity, the magnetic and electric fields. As the linearity of these fields is relied upon for determining the object's position(s), these positions are likely to be wrongly calculated. As a result, practical implementation of the tracking of a metallic device in the interventional setting requires the use of X-ray (ionizing) radiation.
Alternatively, or in addition, a portion of the (or the entire) metallic device is being substituted in practice with a portion made of a non-metallic material. Such substitutions, however, may cause problems in operation of the interventional device. For example, while proceedings of the Congenital and Structural Interventions Society's annual conference (Jun. 21-15, 2011) reported the use of a guide-wire (suited for clinical trials and MRI-guided interventions) with the shaft constructed of glass-fiber material, the lowered mechanical properties of such guide-wire were acknowledged to be inadequate for safety purposes, causing breakage while inside the tissue, and the need for MRI compatible equipment, especially guide-wires and catheters, was emphasized. (See also “Magnetic resonance-guided cardiac interventions with the use of magnetic resonance-compatible devices” by Tzifa et al., available at http://circinterventions.ahajournals.org/content/3/6/585.full, the contents of which are incorporated herein by reference). It is recognized, therefore, that translation of MR-guided interventions into subjects has been limited by the lack of MR-compatible and safe non-metallic equipment such as MR guide-wires with mechanical characteristics similar to standard guide-wires.
Another method for active-tracking is the use of an attachment (an external piece referred to as a device handle) to the devices. Each of the alternative and practically-used, at the moment, approaches enables positioning of the tracking sensor(s) at some distance from the metallic portion of the device, as a result of which the interference of the metallic portion of the device with the field of interest can be reduced. The “device handle” approach, however, is only practically suitable for rigid devices, since the bending of a non-rigid object at a point away from the handle cannot be known.
The use of so-called “passive tracking” of the metallic devices, which utilizes image artifacts that a metallic object creates to determine its position, is practically possible but such passive tracking is less accurate spatially, has a lower temporal resolution, and requires the exclusive use of the scanner for the localization of the object's position. Practice shows that passive tracking is also highly dependent on the method of imaging (and, in particular, on imaging sequence, spatial resolution, as well as shape and orientation of the object). Another shortcoming of the passive tracking methodology is the inability to practically implement imaging which is guided with respect to the instantaneous position of the device (“Guided Imaging ”, i.e. imaging at the tip of the device, which follows the position of the tip as it is displaced), which is a result of the fact that locating the position and orientation of the device tip requires an extensive amount of time, relative to the time in which the device remains at a single location, and that the accuracy of this localization is insufficient for purposes of accurately defining the imaging planes. Guided Imaging is known to aid the clinician in revising the insertion path of the device and can reduce the possibility of unwanted perforation and/or invasion of a critical biological structure, so that this deficiency is important clinically.
In one implementation, the device of invention addresses the unsolved-to-date need for a structurally-reliable, strong, stiff, sharp and otherwise medically preferred, fully-metallic interventional catheterization device (such as a catheter, guide-wire, or needle) that does not impede the ability of MRI-related measurement modalities to actively track the positiion of the device. Accordingly, the embodiment includes a fully-metallic catheter, needle, or quidewire equipped with an auxiliary MR RF receiver coil judiciously structured to enable accurate and quick tracking of the fuly-metallic catheter needle, or quide-wire inside the MRI system. This includes non-rigid devices, where tracking using an external attached “handle” was shown to be insufficiently accurate. The fact that the user of an MRI system equipped with an embodiment of the invention does not have to employ an exploratory tool such as, for example, a brachytherapy needle that is only partially made of metal, but can utilize a fully-metallic needle that is structurally and, in addition, by being actively tracked, operationally superior to any other alternative used today, secures operational advantages not realized by the related art up to date: unique (mechanical, elastic, thermal, etc.) properties of a metallic interventional device are preserved and optimized for performance of specific imaging tasks. Among such tasks there is a task of precise and accurate localization of devices placed around, or within, a patient during MRI diagnostic imaging or MRI-guided interventions (sensors, probes, guidewires, sheathes, catheters, needles, etc.). Finally, the fact that the embodiments of the invention make it possible to utilize previously rejected and/or viewed as operationally inappropriate fully-metallic interventional devices during the MRI procedure, makes the measurements of displacement of such objects (and its derivatives) as well as the related measurement of the surrounding anatomy possible.
While the examples of the embodiment disclosed below discuss embodiments of a interventional needle, it is appreciated that other interventional devices such as, for example, guide-wires and catheters structured in a fashion similar to that disclosed in this application have also been considered and are within the scope of the present invention.
Referring to
An example 200 of a substantially flat, thin, and containing four metallic loops RF receiver coil (such as any of the coils 110, 120) is shown in
While an embodiment of the substantially flat coil can be generally structured as a conventional, structurally continuous multi-loop spiral (the multiple inner loops of which encircle progressively smaller areas, for example, and in which the multiple loops are defined in the same plane), according to a specific embodiment of the invention the example of which is shown in
The MRI images of the coils 110, 120 of
According to a related implementation, an MRI-tracking sequence was created and used with the Siemens MRI system. The MRI-tracking system included additional software features which aid in the tracking of these needles. The features improve the ability to detect the position of the RF receiver microcoil, since placement of the coils on a metallic surface results in a received RF signal which is commonly noisier that when such coils are attached to non-conductive and non-metallic surfaces. Specifically, these added features reduce the dephasing of the signal due to the inhomogeneous magnetic field and improve the ability to perform peak detection in the presence of a noisy RF signal. Among these algorithmic features there was program code for performing the MRI-imaging with a very short “time-to-echo” (TE) duration. The TE duration is defined as the time interval between the MRI excitation pulse and the reception of the signal by the receiver of the system. Short TEs are useful in maximizing the detected MR signal because MRI spins close to the metal surface are in an inhomogeneous static magnetic field, B0, and are therefore readily dephased (i.e. rapidly lose phase coherence between all the spins that are part of the signal).
Additional processing features of the specific implementation included the ability to remove noise from the time-domain traces (“MRI free induction decay” signals), using a combination of signal averaging as well as the use of noise-peak removal algorithms.
Results of conventionally-implemented MRI-tracking are shown as signals received by the receiver of the MRI-system in
In contradistinction to the averaging procedure relied on by the methods of related art, in the embodiment of the invention a time domain noise-peak removal algorithm is used. The noise-based peak manifests as a false-peak on an MRI-trace. The false-peak removal algorithm allows the use of a lower-level signal averaging to detect the true position of the tracking micro-coil. Accordingly, it preserves the degree of temporal resolution of the MRI tracking procedure, which would be reduced if extensive signal-averaging were carried out as required by algorithms of the related art.
According to the false-peak removal algorithm of the invention, a noise-free Free Induction Decay (FID), a decaying curve representing the MRI tracking signal in a time domain and substantially devoid of sharp peaks, is assumed. The presence of sharp peaks is attributed, therefore, to the presence of noise. In reference to
The implementation of the algorithm of
To illustrate clear advantages of the application of a false-peak removal algorithm of the invention over the approaches of the related art, the data shown in
In reference to
The calculated spatial distribution of the radio-frequency magnetic field (B1− field), measured in Tesla in the axial plane is shown in
For comparison,
The comparison of the magnetic field distributions of
In implementing embodiments of the present invention, the ability of the MRI-system to actively track metallic brachytherapy needles equipped with a flat RF-receiver coil-on-a-flexible-substrate was demonstrated. Modification of a commercial brachytherapy needle to implement an embodiment of the invention includes reducing its diameter at the specific points on the shaft which are to be tracked, to facilitate the juxtaposition between the RF-coil-carrying circuit board to the needle, thus enabling active MRI-based tracking of the needle without increasing the diameter of the needle. The diagram illustrating such needle 1500 with three slots 1510, 1512, 1514 (that are used for attaching three printed circuit coils) is presented in
The second body portion 1614 is tubular, with the ratio of inner diameter, ID114, to the outer diameter, OD114 of about ID114/OD114=½. In one example, ID114 is about 0.020″ while the OD114 is about 0.039″. The first body portion 1610 is shaped as a solid metallic (e.g., tungsten alloy) cylinder with the OD110 of about 0.054″, with the exception of the distal end 1610b that is appropriately machined to remove a part of the solid cylinder and create a cross-sectional profile substantially matching the ID114. Accordingly, a portion of about 1.25″ of the distal end 1610a of the needle has a cross-section, formed in a plane substantially perpendicular to an axis 1618 of the portion 110, which has a dimension of OD114 less applicable machining tolerances to ensure friction fit between the first and second body portions.
In one implementation, for example, the distal end 1610b is dimensioned as a solid cylinder that is substantially co-axial with the proximal end 1610a. In another implementation, the distal end 1610b is shaped as a cut cylinder, truncated with a plane parallel to the axis 1618 at least on one side of the axis 1618. The examples of so-formatted distal end 1610b are shown schematically in
The second tubular portion 1614 carries a plurality (as shown—two) microcoils 1630, 1632 wrapped around it and connected by respective electrically conductive leads 1640, 1642 with the connector-plugs 1644 and through the connector-lugs—with external circuitry (not shown). As compared with
Modifications to, and variations of, the illustrated embodiments may be made without departing from the inventive concepts disclosed herein. For example, in a related embodiment the first portion 1610 may contain at least one lumen segment extending there through and fluidly connecting the hollow of the second portion 1614 with the proximal end 1610b.
Referring now to
The methods employed in tracking the needle 1600 included specific active tracking sequences that facilitate minimization of errors in determining the absolute position of the device by comparing the actively-detected position with that determined from high-resolution MRI images, that facilitates, in practice, more frequent update of empirical data representing the position of the needle, and that provide real-time input to a clinician enabling him to precisely advance the needle in the biological tissue.
In reference to
This tracking interface 2110 (illustrated in more detail in
With the zero-phase-reference scheme, a reference frequency offset is provided by the excitation without a spatial encoding gradient. The X, Y, and Z positions are determined by subtracting the location of the reference-frequency peak from the peak location provided by the Fourier-transformed signal of the each of the directionally encoded profiles. With the Hadamard scheme, the positions are calculated by taking the linear combinations of the peak positions computed from each excitation.
Irrespective of the excitation method used (whether the zero phase reference or Hadamard), the signal profile obtained in association with each pulse excitation depends on the orientation of the coil with respect to the frequency encoding direction utilized in this specific excitation. As a result, the following centroid algorithm is used to find the position of the microcoil: (1) the location Lmax of the maximum signal intensity is found; (2) a window W of twice the length of the microcoil, with the window center at Lmax is set; (3) The location of the coil LC is calculated to be the centroid of the signal intensity profile within the window:
where S(l) is the signal intensity at location l.
The orientation of the needle device 2000 of
The MR tracking sequence and reconstruction method are currently implemented on the Siemens MRI acquisition and reconstruction engine, but they can be implemented on stand-alone modules as well.
In further reference to
A tangible non-transitory computer-readable memory 2158 may be provided to store instructions for execution by the programmable electronic circuitry 2140 to control the pulse generator 2144 and the switch matrix 2156. For example, the memory 2158 may be used to store programs defining different sets of pulse parameters and microcoil combinations. Other information relating to operation of the system 2100 may also be stored. The memory 2158 may include any form of computer-readable media such as random access memory (RAM), read only memory (ROM), electronically programmable memory (EPROM or EEPROM), flash memory, or any combination thereof.
A power source 2162 delivers operating power to the components of the system 2100. The power source 2162 may include a rechargeable or non-rechargeable battery or an isolated power generation circuit to produce the operating power.
It is appreciated that embodiment(s) of the invention enable rapid advancing of needles in interventional procedures and real-time visualization of the needle tip with respect to the internal patient anatomy. The tracking data representing location and trajectory of the needle can be overlaid on pre-acquired MR image(s) and used to control the MRI imaging location and orientation thereby further improving real-time navigational guidance. The latter is of particular importance in a situation where advancing the needle may result in a dynamic displacement of the tissue or change/rupture of the tissue boundaries. When used in conjunction with the embodiment of the invention, multi-channel MR-tracking receivers (which can be configured as part of an MRI scanner) allow simultaneous tracking of a multiplicity of needles configured according to the invention—for example, an array of such needles optionally closely spaced from one another. When used in conjunction with a plastic enclosure (such as the plastic tubing 1910 of
References throughout this specification to “one embodiment,” “an embodiment,” “a related embodiment,” or similar language mean that a particular feature, structure, or characteristic described in connection with the referred to “embodiment” is included in at least one embodiment of the present invention. Thus, appearances of these phrases and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. It is to be understood that no portion of disclosure, taken on its own and in possible connection with a figure, is intended to provide a complete description of all features of the invention.
Also, features of the invention are described with reference to corresponding drawings, in which like numbers represent the same or similar elements wherever possible. In the drawings, the depicted structural elements are generally not to scale, and certain components are enlarged relative to the other components for purposes of emphasis and understanding. It is to be understood that no single drawing is intended to support a complete description of all features of the invention. In other words, a given drawing is generally descriptive of only some, and generally not all, features of the invention. A given drawing and an associated portion of the disclosure containing a description referencing such drawing do not, generally, contain all elements of a particular view or all features that can be presented is this view, for purposes of simplifying the given drawing and discussion, and to direct the discussion to particular elements that are featured in this drawing. A skilled artisan will recognize that the invention may possibly be practiced without one or more of the specific features, elements, components, structures, details, or characteristics, or with the use of other methods, components, materials, and so forth. Therefore, although a particular detail of an embodiment of the invention may not be necessarily shown in each and every drawing describing such embodiment, the presence of this detail in the drawing may be implied unless the context of the description requires otherwise. In other instances, well known structures, details, materials, or operations may be not shown in a given drawing or described in detail to avoid obscuring aspects of an embodiment of the invention that are being discussed. Furthermore, the described single features, structures, or characteristics of the invention may be combined in any suitable manner in one or more further embodiments.
The invention as recited in claims appended to this disclosure is intended to be assessed in light of the disclosure as a whole.
Modifications to, and variations of, the illustrated embodiments may be made without departing from the inventive concepts disclosed herein. Disclosed aspects, or portions of these aspects, may be combined in ways not listed above. Accordingly, the invention should not be viewed as being limited to the disclosed embodiment(s).
The present application relates to and claims priority from each and every one of U.S. provisional applications Nos. 61/750,473 (attorney docket no. 129319.00165) filed on Jan. 9, 2013 and titled “Metallic Needle Insertion and Tracking systems for MRI”; 61/779,037 (attorney docket no. 129319.00168) filed on Mar. 13, 2013 and titled “Tracking System for MRI”; 61/847,321 (attorney docket no. 129319.00192) filed on Jul. 17, 2013 and titled “Active MRI-based positional tracking of metallic objects”; and 61/875,367 (attorney docket no. 129319.00193) filed on Sep. 9, 2013 and titled “Active MRI-based positional tracking of metallic objects”. The disclosure of each of the above-identified patent applications is incorporated herein by reference in its entirety
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2014/010656 | 1/8/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61750473 | Jan 2013 | US | |
| 61779037 | Mar 2013 | US | |
| 61847321 | Jul 2013 | US | |
| 61875367 | Sep 2013 | US |
